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TRANSCRIPT
SCHOOL OF INDUSTRIAL AND
INFORMATION ENGINEERING
Master of Science in Biomedical Engineering
Designing of a hand rehabilitation
robotic device for the post-stroke
patients with flaccidity
supervisor: prof. Carlo Albino FRIGO
Paweł Leszek Michalec
893315
Academic Year 18/19
1
Table of Contents
Summary .........................................................................................................................2
Sommario ........................................................................................................................ 7
1. Introduction ........................................................................................................... 13
1.1. Stroke ............................................................................................................... 13
1.2. Defining the scope of thesis ............................................................................. 15
1.3. Outline ............................................................................................................. 16
2. Theory section ........................................................................................................ 17
2.1. Natural and flaccid paralysis hand motion ..................................................... 17
2.2. Hand rehabilitation devices ............................................................................ 19
3. Method section ....................................................................................................... 25
3.1. Project assumptions ........................................................................................ 25
3.2. Concept ........................................................................................................... 28
3.3. Data collecting, calculations, and element selection ..................................... 32
3.4. Prototype ......................................................................................................... 46
3.5. Control ............................................................................................................ 50
3.6. Analysis of the prototype ................................................................................. 52
4. Discussion .............................................................................................................. 57
5. Conclusion .............................................................................................................. 59
References ..................................................................................................................... 61
2
Summary
Prolonged lifetime brings a big number of various diseases and health cases in old
age. One of the major problems is the stroke, that has a huge impact on people quality
of life. Almost 70% of the post-stroke patients suffer from some disabilities connected
to it. Stroke, occurs whenever there is a blood or a clot blocking the blood flow
to the brain, what leads to death of the brain cells. It can cause some minor
disabilities, partial paralyze, and leads even to death.
The major treatment after the stroke is rehabilitation. It starts in the very first
days of hospitalization to recover as many muscles function as it is possible.
In the first weeks after the stroke, the patient suffers from the flaccidity,
that is caused by the muscles weakness. Later, antagonist muscles start to voluntary
tense, what leads to the spasticity.
At the beginning, rehabilitation focuses on stabilization of the hip
and shoulder joint. In the next step, therapy tries to recover functionality of the limbs
during everyday tasks. Physiotherapists help patients to function independently.
The ability of grasping and moving objects is essential for the normal life,
however, rehabilitation of the hand is not always sufficient, what leads to poor
recovery of it. The aim of this thesis is to design a robotic device for a hand
rehabilitation of the post-stroke patients suffering from flaccidity.
Due to the complexity of the subject, first the theoretical studies about stroke
and flaccidity were done. They gave better look on the difference between the affected
and the healthy hand movement. A hand has 21 degrees of freedom (DoF) thanks
to the big number of joint and muscles. The importance of the hand is also visible
in the big size of the area of the brain, that represents a hand motions and sensation.
The advantage of the robotic rehabilitation is huge compared to the traditional
one. It gives feedback of the recovery process, what can be used in the future
development of guidelines for rehabilitation. Moreover, the time of each training can
be extended, while maintaining a low cost of it.
All the robotic system may use 2 types of a control. The Continuous Passive
Motion (CPM) is used in almost all types of the robots. The device constantly moves
affected joints between established range of motion. However, the muscles of the
hand of the patient do not work during this type of exercise. This technique helps
with restoring proper nerve signal flow, nevertheless there is only small recovery
occurring.
The second type of the control is an active system. The robot follows intentions
of the patient, so the movement is not influenced by the robot. Whenever, there
is a need of help, the robot starts to move. The signal can be process in different ways.
It can use strain gauges, force sensors or biological signals like surface
electromyography (sEMG).
3
Analysis of existing rehabilitation robots was made. Gloreha, that uses
hydraulic system connected to the soft glove, achieves the movement of all the fingers
by pulling and pushing them from the dorsal side of the hand. There was reported
better blood flow and increased of a grip strength of the patient that were using this
robot. However, this robot is limited only to flexion and extension of the fingers
to the grip position with no division to specific finger joint.
The next robot, Amadeo, has 5 DoF and it has a shape of a board on which
there are 5 sliders. Physiotherapist connects the arm of the patient to the board,
and each finger to the slider. Thanks to the device, patient may achieve grip and
extension position. It works with kids and adults. However, not all the range of finger
motion is covered by this robot.
Hand of Hope is a glove shaped robot, that uses electric micro motors
to achieve movement. The electromyography (EMG) and electroencephalography
(EEG) signals are used to activate motors. This device has 4 different modes
of training: CPM, EMG triggered movement, EMG based movement, and active
system. Unfortunately, this robot has only 5 DoF and it is limited to the gripping
movement.
The highest prospecting soft actuator robot, developed by Polygerinos, uses
material, that change its shape by fluid flow. Thanks to that, the patient can execute
very complex tasks. Nevertheless, not many researches of using this robot was made.
All the devices improve grip strength, but usually they are not handy
and transportable. They strongly simplify the movement of the fingers, and only some
of them, the patient can wear without supervision of physiotherapist. It seems
the soft glove made by Polygerinos gives the most complex movement and meets
the biggest number of assumptions for the rehabilitation device. However, this
research also proves, there is not enough products to help patient to fully recover
their ability of hand movement after the stroke.
Based on the given knowledge, guidelines of the project were identified.
The major assumption is to design the robot, that can be used at home. Because
of the high occupancy of physiotherapists, the traditional rehabilitation may not be
enough to recover the hand motion. Home therapy brings, economic advantages
and rehabilitation progress because of the higher involvement of the patient
in the therapy.
However, it is crucial to make device save to use by the patient without
supervision of the physiotherapist. Moreover, if it is too expensive it will not be
borrowed or bought by the patient. It has to be transportable and simple, to make
the post-stroke patients able to use it safely. The last technical factor is to use
the source of the energy, that is accessible at home. The power should be focused
on the electricity.
An executed movement of the device should replicate kinematic movement
of the fingers, what will lead to proper recovery. Even with lower number of DoF,
compared to the biological hand, the movement can still be healthy for the patient,
4
as all the rehabilitation robots works. Also the position of the joints of the device
should be the same as the position of the biological joints. Otherwise the patient
could be injured.
The range of motion should cover all the possible movements of the hand,
and the device should use a force of 15 N, that is not exceed during daily living
activities. The frequency of the task execution should oscillate around 30 cycles
per minute.
The control should give a possibility of choosing between active and passive
system, as this is a norm for the rehabilitation robots.
With necessary background, a concept of the device was created and the 3D
model was designed. The designed device is aimed at rehabilitation of flexion
and extension movement of the metacarpophalangeal joint (MP joint)
and the proximal interphalangeal joint (PIP joint) of 4 fingers: index, middle, ring,
and pinkie. The design was focused on using the device at home without supervision
of physiotherapist.
The patient puts the affected hand inside the ABS 3D printed wrist holder, that
has a soft glove with 2 C-rings on each finger. C-rings are placed between the MP
and the PIP joint and between the PIP and the distal interphalangeal (DIP) joint.
Each C-ring is connected to the motor and the spring by wire. The motors pulls
the wires and position each joint in the extension position. From the bottom,
whenever the motors release wires, springs pull the fingers to the flexion position.
A direction of the movement of the wires is changed by the wheel systems placed
on the wrist holder and the frame. Thanks to them, the motor and the spring system
was placed on the front of the device. The concept with listed elements is shown
in figures 0.1 and 0.2.
Figure 0.1 - wearable part of a device [38]
5
Figure 0.2 - interior of the device with open side cover [38]
The motor system is placed inside the motor box. Moreover, the motor box
contains a power board, a microcontroller, an electric lock, and the Wheatstone
bridges. The wires are attached to the plate with strain gauges on it. The strain gauge
collects information of the occurring tension on the wire, and sends the signal
to the microcontroller. Based on this signal, control was made. The concept with
listed elements is shown in figure 0.3.
Figure 0.3 - interior of the motor box [38]
6
The whole interior of the device is fixed to the telescopic slides, that can be
slide out from the frame for easier installation of the hand. The magnetic sensors
where used to check if everything is in the right position before a training starts.
The force on each joint was measured. The maximal force, that can be created
by the springs was set. For the MP joint it was 27 N and for the PIP joint it was 18 N.
The distance of the movement between end positions was 50 mm and 100mm. Based
on that springs, Vanel U.092.080.0500.IX and T.087.070.0380.A, were selected.
Next, servo motors were selected. Needed torque to overcome the springs
and additional 15 N was calculated. This value was taken as a maximal force created
during everyday life activities. Chosen servo motors were Hitec HS-5645MG
for the MP joint and Hitec HS805 for the PIP joint.
The minimal thickness of 3D printed elements was calculated. All thicknesses
of the sections of the wrist holder were set at 5 mm. The dimension of the aluminum
alloy shaft of the wheel system was 6mm and the wires dimension 1,07 mm.
The used force sensors were 5 kg Micro load cells by Phidgets with dedicated
Wheatstone Bridges 1046-0B. The magnetic sensors were Schmersal BNS 250.
Everything was connected to the microcontroller STM32F411E Discovery. The device
starts by clicking RobotShop Rocker Switch. The power supply for all the 5V
instrumentation was Botland PMT 5V50W1AA. Moreover, because of the movement
of the interior part, e-chain Igus 0.26m E2i.10.06.018.0 + E2.100.06.12PZ.A1
was used.
In the last part, the prototype, that was based on the 3D model, was built
and ran with dedicated software to primary validate functionality of the robot.
However, the prototype was designed only for 1 finger control, what is enough
to validate functionality of it. Moreover, no telescopic slides were used. They do not
affect the functionality of the robot.
The created software sends the pulse width modulation (PWM) signal
to the motors, collects data from the strain gauges and runs the device in 4 different
modes: passive, active, resistive, and test. The test mode was created to manually
control motors and to collect data for calibration and analysis of the functionality.
Moreover, there were created 4 tasks to execute. The application was created
in C# language.
To properly run the device all the task position were found. Next, the change
of voltage of strain gauges was analysis, and based on it, the influence of the spring
was found and the thresholds set. At the end, all the created functions of the program
were validated with a positive result. The software gives a possibility of using 3 modes
of the training.
The biggest advantage of the designed robot, comparing to other existing
solutions, is the possibility of using it at home. Even if it does not cover the whole
range of hand motion, it still provides possibility of separate movement of the MP
and the PIP joint.
7
The closed palm design does not allow using the device as a portable glove
in everyday life activities. Moreover, there is no thumb rehabilitation, what should
be added in the future development.
The prototype demonstrated the functionality of the device and gave a good
prospect for the future development and use of the robot as an additional tool
in the traditional rehabilitation.
Sommario
Il prolungamento della durata della vita comporta il verificarsi di numerosi disturbi
e patologie in età avanzata. Uno dei maggiori problemi è l'ictus, che ha un impatto
enorme sulla qualità della vita delle persone.
Circa il 70% dei pazienti che hanno subito ictus soffre di alcune disabilità
ad esso collegate. L’Ictus può verificarsiquando un coagulo di sangue blocca il flusso
sanguigno al cervello, determinando la morte delle cellule cerebrali e causando
alcune disabilità minori, paralisi parziali e persino la morte.
Il trattamento principale dopo l'ictus è la riabilitazione. Essa comincia nei
primissimi giorni di ricovero in ospedale per recuperare quante più funzioni
muscolari possibile. Nelle prime settimane dopo l'ictus, il paziente soffre di flaccidità,
causata dalla debolezza muscolare. Successivamente, i muscoli antagonisti iniziano
a contrarsi volontariamente, portando alla spasticità.
Inizialmente, la riabilitazione si concentra sulla stabilizzazione dell'anca e della
spalla. Il passaggio successivo della terapia è volta a ripristinare la funzionalità degli
arti durante le attività quotidiane. I fisioterapisti aiutano i pazienti a muoversi
in modo indipendente.
La capacità di afferrare e spostare oggetti è essenziale per la vita ordinaria,
tuttavia, la riabilitazione della mano non è sempre sufficiente e comporta uno scarso
recupero delle sue funzionalità. L’obiettivodella presente tesi è progettare
un dispositivo robotico per la riabilitazione della mano dei pazienti che hanno subito
ictus e che soffrono di flaccidità.
Data la complessità dell’argomento, in primo luogo è stato condotto uno studio
teoretico sull’ictus e sulla problematica della flaccidità. Uno degli aspetti evidenziati
è la differenza tra il movimento della mano colpita dalla patologia e quella sana.
La mano possiede 21 gradi di libertà (GdL) permessi dal gran numero di articolazioni
e muscoli. L'importanza della mano si rispecchia anche nelle grandi dimensioni
dell'area del cervello dedicata al suo movimento e percezione tattile.
Il vantaggio della riabilitazione robotica è enorme rispetto a quello tradizionale: essa
fornisce feedback sul processo di recupero, i quali possono essere utili
nel futuro sviluppo di linee guida per la riabilitazione. Inoltre, la durata di ciascun
allenamento può essere prolungata, pur mantenendo un costo contenuto.
Tutti i sistemi robotici possono utilizzare due tipi di controllo. Il movimento
passivo continuo (CPM) è utilizzato in quasi tutti i robot. Il dispositivo muove
costantemente le articolazioni interessate nel range di movimento stabilito. Tuttavia,
8
i muscoli della mano del paziente non lavorano durante questo tipo di esercizio.
Questa tecnica aiuta a ripristinare il corretto flusso del segnale nervoso, mail
recupero che ne consegue è basso.
Il secondo tipo di controllo è il sistema attivo. Il robot segue le intenzioni
del paziente, quindi il movimento non è stabilito dal robot. Ogni volta che c'è bisogno
di aiuto, il robot inizia a muoversi. Il segnale può essere elaborato in diversi modi.
Possono essere utilizzati estensimetri, sensori di forza o segnali biologici come
l'elettromiografia di superficie (sEMG).
È stata effettuata l'analisi dei robot per la riabilitazione attualmente esistenti.
Gloreha, che utilizza un sistema idraulico collegato ad un guanto, permette
il movimento di tutte le dita tirandole e spingendole verso il lato dorsale della mano.
I pazienti che hanno utilizzato questo robot hanno riportato un miglioramento
del flusso sanguino e della forza di presa. Tuttavia, questo robot si limita solo
alla flessione e all'estensione delle dita nella posizione di presa senza suddividere
il movimento per ogni articolazione specifica delle dita.
Il secondo robot, Amadeo, possiede 5 GdL ed è costituito da una piattaforma
in cui vi sono 5 cursori. Il fisioterapista collega il braccio del paziente alla piattaforma
e ogni dito a ciascun cursore. Grazie al dispositivo, il paziente può effettuare
la posizione di presa ed estensione.
Il robot può essere utilizzatosia con bambini che con adulti. Purtroppo, anche
in questo caso l’ampiezza del movimento delle dita è limitata.
Hand of Hope è un guanto robotico che utilizza micro-motori elettrici per
effettuareil movimento. I segnali ottenuti dall’elettromiografia (EMG)
e dall'elettroencefalografia (EEG) vengono utilizzati per attivare i motori. Questo
dispositivo ha quattro diverse modalità di allenamento: CPM, movimento attivato
da EMG, movimento basato su EMG e sistema attivo. Sfortunatamente, questo robot
ha solo 5 GdL ed è limitato al movimento di presa.
Il robot ad attuatori flessibilipiù promettente è stato sviluppato da Polygerinos,
caratterizzato dall’utilizzo di un materiale che cambia forma grazie al flusso
di un fluido che scorre al suo interno. Grazie a questo meccanismo il paziente può
eseguire compiti molto complessi. Eppure, non sono ancora stati effettuati sufficienti
studi sui risultati dell’utilizzo di questo dispositivo.
Tutti questi dispositivi migliorano la forza di presa, ma non sono di semplice
utilizzoo trasportabili, semplificano eccessivamente il movimento delle dita e solo
alcuni di essi possono essere indossati dal paziente senza la supervisione
del fisioterapista. Sembra che il guanto flessibile realizzato da Polygerinos permetta
il movimento più realistico e soddisfi il maggior numero di requisiti per i dispositivi
di riabilitazione. Questa ricerca dimostra che non ci sono abbastanza dispositivi
in commercio per aiutare il paziente a recuperare completamente la propria capacità
di movimento della mano a seguito di un ictus.
Sulla base delle conoscenze ottenute, sono state definite le linee guida
del progetto. Il requisito principale è la possibilità dell’uso domestico del robot.
9
La riabilitazione tradizionale potrebbe non essere sufficiente per recuperare
il movimento della mano, a causa delle tempistiche ospedaliere. La terapia
domiciliare porta vantaggi economici e progressi nella riabilitazione grazie
al maggiore coinvolgimento del paziente nella terapia.
Per l’utilizzo domestico è fondamentale rendere sicuro il dispositivo
per il paziente senza la supervisione del fisioterapista. Deve essere trasportabile
e semplice, per consentire ai pazienti post-ictus di utilizzarlo in sicurezza.
Un ulteriore requisito tecnico riguarda la fonte di energia impiegata, che deve essere
accessibile da casa, come ad esempio l’energia elettrica.
Ogni movimento eseguito del robot dovrebbe replicare la cinematica fisiologica
delle dita per ottenere un corretto recupero. Anche se con un numero di GdL inferiore
rispetto a quelli permessi da una mano in salute, il movimento può ancora portare
beneficio al paziente, come dimostrano i robot attualmente disponibile. Le posizioni
articolari assunte dal dispositivo dovrebbero rispecchiare quelle fisiologiche, per non
recare danno al paziente.
Il dispositivo dovrebbeincludere tutti i possibili movimenti della mano,
impiegando una forza massima di 15 N, da non superare durante le attività
quotidiane. La frequenza di esecuzione delle attività dovrebbe oscillare intorno
a 30 cicli al minuto.
Come è di norma per i robot di riabilitazione, dovrebbe essere data
la possibilità di scelta tra sistema di controllo attivo o passivo.
Alla luce delle conoscenze necessarie sono state definite le specifiche
di progetto del dispositivo e un corrispondente modello 3D. Il robot è finalizzato
alla riabilitazione della flessione e del movimento di estensione dell'articolazione
metacarpo-falangea (articolazione MP) e dell'articolazione interfalangea prossimale
(articolazione PIP) di 4 dita: indice, medio, anello e mignolo. Il design
si è concentrato sull'utilizzo del dispositivo in casa senza la supervisione
del fisioterapista.
Il paziente posiziona la mano interessata all'interno del supporto per il polso
realizzato in ABS tramite stampante 3D, dotato di un guanto flessibile con 2 anelli a C
su ciascun dito. Gli anelli a C sono posizionati tra l’articolazione MP e l'articolazione
PIP e tra la PIP e l'articolazione interfalangea distale (DIP). Ogni anello a C
è collegato al motore e alla molla tramite uncavo. I motori tirano i cavi e posizionano
ciascuna articolazione nella posizione di estensione. Ogni volta che i motori rilasciano
i cavi, le molle posizionate in basso tirano le dita nella posizione di flessione.
La direzione del movimento dei cavi viene modificata dai sistemi di ruote posizionati
sul supporto del polso e sul telaio. In tal modo è stato possibile posizionare motore
e il sistema a molla sulla parte anteriore del dispositivo. Il disegno del prototipo
con l’elenco dei diversi elementi è mostrato nelle figure 0.1 e 0.2.
10
Figura 0.1 - parte indossabile del dispositivo [38]
Figura 0.2 - interno del dispositivo con coperchio laterale aperto [38]
Il sistema motorizzato è localizzato dentro la scatola motore, la quale dotato
di una scheda di potenza, un microcontrollore, una serratura elettrica e dei ponti
di Wheatstone. I cavi sono fissati alla piastra con degli estensimetri. L'estensimetro
trasduce la tensione del cavo in un segnale elettrico utilizzato dal microcontrollore.
Il controllo è stato effettuato sulla base di questo segnale. Il disegno del prototipo
con l’elenco dei diversi elementi è mostrato nella figura 0.3.
11
Figura 0.3 - interno della scatola motore [38]
L’interno del dispositivo è fissato alle guide telescopiche, che possono essere
estratte dal telaio per facilitare l'inserimento della mano. I sensori magnetici hanno
lo scopo di verificare la corretta posizione prima dell'inizio di un allenamento.
Le molle Vanel U.092.080.0500.IX e T.087.070.0380.A. sono state
selezionate in base alle misure di forza su ogni articolazione e alla forza massima
impostata. Per l'articolazione MP si è ottenuto 27 N e per l'articolazione PIP, 18 N.
L’ampiezza del movimento risultante è data dalla differenza tra le posizioni finali
di 50 mm e 100 mm.
Successivamente, i servo motori sono stati selezionati calcolando la coppia
necessaria per vincere la forzadalle molle con 15 N aggiuntivi. Questo valore è stato
preso come forza massima impiegata durante le attività della vita quotidiana.
I servomotori scelti per le articolazioni MP e PIP sono Hitec HS-5645MG e Hitec
HS805 rispettivamente.
Lo spessore delle sezioni del supporto per polso stampato 3D è stato fissato
a 5 mm. La dimensione dell'albero in lega di alluminiodel sistema a ruotaè di 6 mm
e la lunghezza dei cavidi 1,07 mm.
I sensori di forza utilizzati sono celle di carico Micro da 5 kg di Phidgets
con ponti di Wheatstone 1046-0B. I sensori magnetici sono iSchmersal BNS 250.
Gli elementi sono collegati al microcontrollore STM32F411E Discovery.
Il dispositivo si avvia attivando l’interruttore RobotShop Rocker. Per tutta
la strumentazione a 5v è stato utilizzato l’alimentatore Botland PMT 5V50W1AA.
12
Inoltre, per evitare movimenti all’interno del dispositivo è stata utilizzata
la e-chain Igus 0,26m E2i.10.06.018.0 + E2.100.06.12PZ.A1.
In fine, il prototipobasato sul modello 3D è stato realizzato e gestito con
un software creato appositamente per la convalida primaria della funzionalità
del robot, per la quale è stato sufficiente progettare il prototipo solamente
per il controllo di un dito. Non sono state utilizzate guide telescopiche poiché
non influiscono sulla funzionalità del robot.
Il software creato invia il segnale di Pulse Width Modulation (PWM) ai motori,
raccoglie i dati dagli estensimetri e permette il funzionamento del dispositivo
in 4 diverse modalità: passivo, attivo, resistivo e test. La modalità test è stata creata
per poter controllare manualmente i motori e per raccogliere dati per la calibrazione
e l'analisi della funzionalità. In totale sono state create 4 attività da eseguire.
Per la programmazione è stato impiegato il linguaggio C#.
Per eseguire correttamente il dispositivo sono state calcolate tutte le posizioni
dell'attività. Successivamente, è stata analizzata la variazione di tensione degli
estensimetri e, sulla base di quest’ultima, è stata calcolata l’azione della molla e sono
state fissate le soglie. In fine, tutte le funzioni create del programma sono state
validate ottenendo un risultato positivo. Il software offre la possibilità di utilizzare
3 modalità di allenamento.
Il più grande vantaggio del robot progettato, rispetto ad altre soluzioni
esistenti, è la possibilità di utilizzarlo comodamente in casa. Anche se non copre
l'intera gamma di movimenti possibili della mano, offre comunque la possibilità
di un movimento separato dell’articolazione MP e dell'articolazione PIP.
Il design a palmo chiuso non consente tuttavia l'utilizzo del dispositivo come
guanto portatile nelle attività quotidiane e la riabilitazione del pollice non è permessa.
Il prototipo ha dimostrato la piena funzionalità del dispositivo e ha fornito una buona
prospettiva per il futuro sviluppo e l’utilizzo del robot come strumento aggiuntivo
nella riabilitazione tradizionale.
13
1. Introduction
1.1. Stroke
The progress of medicine has a huge influence on people's health and length of their
life. In Europe the life expectancy at birth is 80,6 years (data from 2015), while
in 1990 it was 75 years. Because of expanding of the life time, there is more and more
people over 65 years old. In the World in 2016 the group of elderly was 19,2%
of population, and now it keeps increasing. However, due to the populations ageing,
the number of various diseases and health cases affecting them also increases [1,2].
In recent years in Europe smaller percentage of people having a stroke was
observed. However, with increasing number of older people, the number of strokes
is higher and keeps growing through the years. Chart 1.1 shows an increasing number
of discharges of post-stroke patients from the hospitals over 20 years. These numbers
were growing through the years [1,3].
Chart 1.1 - Rates of hospital discharges for stroke (1990 - 2010) in Europe and Europe Union [3]
In 2015 the number of recorded stroke incidences in Europe was 1 555 365.
In this group female were majority - around 56,5%. The forecasts predicts that
the number of recorded stroke incidence will increase by 34% before 2035 [3].
Data shows that at the end of 2015 there were almost 1200 post-stroke people
per 100 000 people living in Europe. In each country the percentage of post-stroke
people who get a health care was different. This numbers are between 10% to 80%.
Moreover, rehabilitation care in Europe is not everywhere developed properly, while
it is one of the main processes, which helps to recover correct functionality
of the body [1].
14
Stroke is one of the major cause of the death and the biggest cause of disability
of adults. There can be distinguish two most common types of stroke. First one
is ischaemic stroke which covers 85% of all strokes incidence and have place when
blood flow is blocked by a clot and it does not go to the brain. Haemorrhagic stroke
occurs when there is a burst of blood vessel. Both types lead to death of the brain
cells, hence depending on the time of the stroke it can lead to small disabilities which
may be fully recovered, or to paralysis or even to death. More than 2/3 post-stroke
patients suffer from some disabilities [1,4].
When the stroke occurs, the opposite side of the body to the side of a brain
where stroke took place is paralyzed. Paralysis can affect up to the half of the body.
Moreover, stroke can cause lower motor functionality, problems with speaking
and understanding, loss of vision or delusions. It is important to make an immediate
diagnosis because any delay brings a bigger damage of a brain. Patient with diagnosis
of stroke are immediately transferred for a surgical treatment to remove a cause
of the stroke - blood or a clot. After successful surgery the patient stays on a drug
therapy to decrease probability of another stroke. The rehabilitation process
is initiated in the first few days [4,5].
The rehabilitation process helps patients to fully or partly recover of their
motor functionality, which is necessary in almost all daily activities.
Early mobilization benefits the patients. There is a focus on lower limb to make able
the patient to walk safety. Moreover, it is important to protect the shoulder.
Because of the flaccidity, muscle tone is lower and the shoulder joint is not stable.
Then minor paresis are under care. With a proper rehabilitation process some stages
of recovery can be distinguished [5,8].
In the first period after stroke, flaccid paralysis occurs, that means there
is a lack of voluntary movements, hence a patient cannot contract the muscles.
Flaccid paralysis take place due to the nerve damage, which affects a proper signal
connection in the way brain-muscles. Subsequently muscles loss occurs.
The antagonist muscles stay tensed. This unbalance situation, after few months,
leads to the second stage [8].
During the second stage, in some muscles redevelopment of limb synergies
begins, what leads to a small spasticity, pain, and uncontrollable muscle movements.
Also a small voluntary movements occur. Between 25% to 43% of patients suffer
spasticity in the first year after stroke. Due to the time, there is an increase
of the spasticity [8].
Post stroke hand, during a wrist drop exercise, acts differently than a healthy
hand. For a flaccidity, a flexion is exacerbated while in spasticity involuntary
extension occurs. Difference in behavior of the wrist during the wrist drop for spastic
and flaccid paresis is shown in figure 1.2.
15
Figure 1.2 - Wrist drop (B) - flaccid paresis (C) - spastic paresis [28]
However, with a proper rehabilitation care, effects of stroke can decrease
or fully disappear and increase control over the muscles. With time the complex
movements may be performed up to full recovery. Nowadays the rehabilitation
process is a golden standard to treat post-stroke patients [8,9].
1.2. Defining the scope of thesis
The most common post stroke issue is motor impairment. Almost 80% of patient
who had a stroke suffer from it. A patient who needs an acute rehabilitation in 32%
during first 3 months suffer from upper limb spasticity. Only a small group
of patients fully recover their upper limb functionality. That leads to the problems
in daily life activities which very often requires use of hands [9,10].
The researches show that the fastest recovery process happens in first 4 weeks.
In next 3-6 months the progress slows down. Rehabilitation acts positively
on mechanism of plasticity and brings short and long term gains in motor control.
Passive mobilization activates a motor network and promotes motor recovery.
Moreover, in the hemiparesis stage the immobilized bones of joints have a tendency
to decrease their density what may lead to pain or fracture [11,12,13,16].
It is important to perform rehabilitation in all post-stroke stages and focus on
all joints and muscles not to lead to any complications. However, 4 physiotherapists
from Poland, in the interview for the purpose of this paper, have said that the hand
rehabilitation is very often overlooked because of the lack of time with individual
patient and long recovery process with no visible results in the short period of time.
Physiotherapists are more focused on the lower limb rehabilitation and recovery
of the shoulder and elbow joint which have a bigger impact on a daily life activities
than precise movement of the wrist and fingers.
Robotic therapy brings a lot of advantages. There are highly repetitive,
the training may be more intense and more frequent, what decreases load of work
16
of physiotherapist. Also the movement of any task is finished and precise.
Moreover, it gives recovery data from the session which can be analyzed and used
in the future studies. Although the robots are used worldwide, it is not clearly
understood what are exact advantages of this kind of therapy in post-stroke care.
Nowadays the golden standard is to use robots therapy in parallel to the conventional
therapy, what seems to give the highest progress [9,17].
Home-based rehabilitation is also an expected way of treatment.
From the economic point of view it reduces the cost of rehabilitation process
by decreasing time spent in the health care institution. From the rehabilitation point
of view it brings to the patient an additional motivation while spending time
with family. Patients are more satisfied with this kind of therapy. However,
there are some issues with safety of the patient and lack of specific equipment
in the home environment. Also the researches in the area of potential hazard
or negative effects of home-based rehabilitation are limited [9].
Researches already showed that home-based therapy combined with regular
rehabilitation care, increases patients independence. Cochrane Collaboration review
showed that there is a bigger improvement in actives of daily living (ADL) for home
rehabilitated patients than treated in the conventional way [18].
This work will try to solve a problem of insufficient help in post-stroke patients
life and possibility of higher progress in hand recovery. The goal is to design
and preliminary test a robotic device for recovery of precision movements
of the fingers for post-stroke patients with flaccidity. The device should
be transportable and useable in home environment without direct supervision
of physiotherapist. The device should support the rehabilitation process in the first
4 weeks after stroke when there is the biggest impact on recovery process.
1.3. Outline
The purpose of this work is to design a hand rehabilitation robotic device
for the post-stroke patients with flaccidity, which can be used in home environment.
This system can give better outcome of rehabilitation therapy and a bigger amount
of training hours. This device could enable patients with acute stroke, flaccid
paralysis, muscle weakness and spine injuries, to perform rehabilitation task which
will lead to faster recovery of the hand motion and higher skills in the daily life
activities. This device will be inexpensive to be lent beyond the clinic or bought
by patient for personal use. Moreover, it will be safe to use by a patient without direct
supervision of the medical care staff.
This paper compares already existing solutions of the robotic devices
for a hand rehabilitation and lists their advantages and limitations. Thesis shows
the design of the hand rehabilitation robotic device with all necessary calculation
and assumption. Moreover, the paper explains control strategy for the rehabilitation
tasks and also describes future direction in which the project can go.
17
For the purpose of the thesis, two prototypes were built and the analyze
of the tasks execution by the robotic device was made.
2. Theory section
2.1. Natural and flaccid paralysis hand motion
The hand is composed from 27 bones divided into 3 types called: carpals, metacarpals
and phalanges. 8 carpals create a wrist and give a various of possible movement
to the hand. Palm, the middle part of the hand between wrist and fingers, is built
from 5 metacarpals. Fourteen phalanges are divided into proximal, medial and distal
and build human's fingers. There are 3 of them in each finger and 2 in the thumb.
This bones construction gives 21 degrees of freedom (DOF) to the hand. There are
4 DOF in each finger. Metacarpophalangeal joint (MP) has 2 DOF and proximal
interphalangeal joint (PIP) and distal interphalangeal joint (DIP) have 1 DOF.
The thumb has only interphalangeal and metacarpophalangeal joint with 1 DOF.
The palm joint of the thumb has 3 DOF. The anatomy of the hand is shown in
figure 2.1 [24, 25].
Figure 2.1 - Bones and joints of the hand and the wrist [26]
18
The normal adult hand has following ranges of motion. In MP joints
the adduction / abduction movement ranges from -20° to 20° and bending motion
from 20° to 90°. In PIP joints the bending motion is from 0° to 110° and in DIP joints
from 0° to 70° [24].
There are mainly 2 groups of muscles: extrinsic and intrinsic muscles.
Extrinsic muscles lie in the forearm narrowing into tendons and go to ligamentous
or bony part of the hand. Extrinsic muscles mostly assist in flexion-extension of the
wrist and finger, while intrinsic muscles are responsible for adduction-abduction and
cooperate with the extrinsic muscles to produce the opposition patterns like
in spherical grasp [25, 26].
Big number of joints and muscles in a hand obviously gives a possibility
of a large number of patterns of movement. Flexor and extensor muscles along
the proximal-distal axis gives some main flexion and extension patterns in fingers
and the attachments provides independent movements of fingers. From the other
hand a thumb is more versatile. It is due to the flexion-extension rotary plane
of the carpometacarpal joint. Besides that, another major fact is a big area
in the brain responsible for the hand control and sensation. The area representing
the hand is almost equal to the area covered by movement of arms, trunk, and legs.
Almost equally big is the area responsible for sensing of the hands.
This representation of the hand in brain shows how advanced and how important this
system is [26].
There are some main prehension movements distinguished in a hand
functionality, for example fixation movement. While grabbing an object the forces
from the muscles are equalized by the object itself, but when the hand is empty
or the object is delicate the hand maintains a position by co-contraction of groups
of muscles opposite to each other. Post-stroke patient cannot maintain this position,
and this is a big issue in the ADL [26].
After stroke due to actual denervation or disruption of signal in CNS
the muscle tonus may result in a flaccidity or paralysis. The bundles of muscles may
be affected only partly, but even while stimulating, this muscles may not sustain
the movement. However, acquisition and retrieval of information are similar
in the healthy brain and in the post-stroke one. The flaccidity of muscle groups causes
lower tension on antagonist muscle groups and leads to plastic reorganization which
catabolize antagonist muscle groups and increase weakness and flaccidity [11, 27].
Moreover, flaccidity creates a problem of joint instability. In the highest risk
is the glenohumeral joint which is placed in human shoulders. It is important
to stabilize and train the shoulder in order to prevent joint luxation and not cause any
injury [27].
When the flaccid side of the body in not loaded it becomes affected by
spasticity, which distorts or prevents the recovery of normal movement of the limb.
In fact muscles tension increases abnormally as a consequence of any stretch applied
19
to the muscle, what leads to resistance to movements imposed by external forces
and also to movements produced by the agonist muscles [27].
2.2. Hand rehabilitation devices
Traditional rehabilitation therapy for upper limb recovery have some limitation.
First of all this kind of therapy has to be individual with physiotherapist what is more
expensive and brings a problem of availability. Also there are no proper guidelines
for recovery of hand and therapists do not have feedback of the recovery process,
what leads to lower effectiveness of the therapy [24].
Compared to the traditional therapy, robotic rehabilitation units have a lot
to offer. They give a feedback of the recovery process and data about motion.
Moreover, the moves are repetitive and precise. Also they decrease the costs
of a therapy and occupancy of therapists. However, a lot of researches and proper
guidelines must be done [24].
The basic principal of the rehabilitation process with use of robotic devices
is application of the Continuous Passive Motion (CPM) what leads to restoring
of the motor functions of the affected limb. This technique is based on having
a passive constrained limb, while joints are constantly moved by a robot between
established range of motion [24].
The other idea is to use a robot as an active mechanism. The exercise thus will
be actively produced by the patient and the mechanism gives some constant
resistance to the movement of a joint while moving. Combining these two kind of
exercises, CPM and active system, gives the best results in recovery of the movement
and proprioception of a joint [29, 30].
The robotic devices should meet some criteria and follow specific guidelines.
The movement provided by robot should be healthy and safe for a patient. The finger
should move on its kinematic biological trajectory. The length between joints
of the device and patient's joints should be accurate, not to create an external torque
on the bones, what can lead to fracture. The force does not necessarily need
to be as high as a grasping force of the patient, however it should be high enough
to maintain the rehabilitation tasks. The frequency of movement should be around 30
cycles/minute for a single task to make a device effective. The wearable part
of the robot should be as light as possible and comfortable to the patient. It does not
have to be made from soft materials, although it is advisable.
Most of the hand movement are coordinate action between fingers and wrist.
It is recommended that the robot reproduces some of these movements,
and the rehabilitation tasks are not only focused on a single finger or just a wrist, but
covers both movements in the same time. This treatment can train a complex
movement as writing or using a fork. It would improve faster recovery of the patients
quality of life [31].
20
The robotic rehabilitation devices should meet all guidelines mentioned above.
It is important to support recovery process with a proper device not to make any kind
of harm to patient and to make this process effective.
There are already some robotic rehabilitation devices for upper limb recovery
used in the health care. One of these projects is Gloreha which was invented
and started in Lumezzane in Italy by a group of Small and Medium Enterprises
(SMEs) in industrial area. Gloreha is a soft exoskeleton in the shape of glove, which
is mounted on the dorsal side of the hand and strapped around the wrist.
This solution leaves the palm side open, hence the patient can grab objects during
task executing.
Gloreha motor functions are achieved by hydraulic system connected
to the fingers by wires. The hydraulic system is placed in the transportable box.
This solution gives an individual passive mobilization of each finger. The whole
device is connected to the computer and controlled by a software. The example
of Gloreha is shown in figure 2.1 [19].
Figure 2.2 - Gloreha robot Source: http://trends.medicalexpo.com/idrogenet/project-74722-415129.html
The studies made by the group of Luciano Bissolotti showed that after ten
sessions of treatment on the post-stroke patients the spasticity was decreased
in the area of the hand. There was also better blood flow in the region that was
moving. However, this research had a small sample size and no control group, what
could lead to some not controlled study bias. The further study should be done [19].
Clinical results showed that after 10 session Gloreha treatment the patients
that were up to 3 weeks after stroke, increased their grip strength by 113,29% while
control group had increased it by 13,87% in the same period. Also there was small
21
difference in pinch trial in benefit for Gloreha. Moreover, this treatment significantly
improved coordination of mono and bi-manual tasks. Also the patients in the chronic
phase after 1 week of sessions had visible decrease of spasticity [20].
However, despites of its advantages there are some crucial problems with this
device. First of all the movement is simple, there is only flexion and extension
of the fingers without division into metacarpophalangeal, proximal interphalangeal,
and distal interphalangeal joint. Also there is no abduction and adduction control.
Moreover, the whole equipment is big and expensive. There is no possibility to use
it at home, but only in the rehabilitation centers.
Another robotic device for upper limb rehabilitation is Amadeo. It is a device
with 5 degrees of freedom with possibility of moving each finger. Fingers
are connected to the slider by a rotational joint what allows to do a gripping
movement. However, not all the workspace of the finger is covered by this solution.
The wrist is fixed by straps. This device is universal and can be equipped by adults
and children as well as it can be used for right and left hand rehabilitation.
The example of the Amadeo robot is shown in figure 2.2 [21].
Figure 2.3 - Amadeo robot Source: https://products.iisartonline.org/productinfo.php?go=33
Amadeo can be use for passive and active rehabilitation. Active rehabilitation
may work with surface electromyography (sEMG) signal taken from the extensor
and flexor muscles of the forearm. Device is connected to the screen where data
22
is shown in conjunction with rehabilitation progress. Moreover, the software
has games which increase patients motivation [21].
The clinical use proves that using Amadeo improves gripping and pinching
of the affected arm and increases its strength. However, the patient needs
an assistance of the physiotherapist to connect fingers to the joints and electrodes
to the muscles. The machine is also big what reduces its use to the rehabilitation
centers. Once again the movement is limited to the grasp. There is no abduction
and adduction movements and no joint specify movements [22].
University of technology in Hong Kong created manipulator called Hand
of Hope (HOH). It is a devise which works on neuromuscular rehabilitation
of the hand. It is a biofeedback device using EMG and EEG signal to activate a desire
movement of the patient's hand. Signals are projected on the screen so the patient
can see responses and the training session is engaging. The hand in the hand brace
is placed on the dorsal side leaving the palm free. The device has 5 degrees of freedom
and uses electric micro motors to initiate movement. The device, with a hand in it,
is placed on the special pad to constrain a hand (figure 2.3) [23,24].
Figure 2.4 - Hand of Hope
Source: https://products.iisartonline.org
The training session of HOH can be done in 4 different modes. First mode
is the CPM movement, which is basic for this kind of devices,. Second and third
are based on the EMG signal. Either EMG signal can be a trigger for CPM movement,
or the movement occurs while EMG signal occurs. The last type of training
is a completely independent movement of patient's fingers while device works
23
as an active mechanism, which creates a torque to resist the movement of the fingers
and strengthen muscles [24].
HOH helps to post-stroke patients initiate and maintain voluntary movements
and motor learning by biofeedback. It has various number of possible training modes.
The whole device is small and transportable, however, it needs an assist of medical
care to install electrodes on the surface of forearm. Also there is a need to have a set
for each hand, right or left. Moreover, it is limited only to a gripping with
no abduction and adduction movement. The instrument is portable, so the patient
can wear it to support simple grasping movement in daily activities [23, 24].
Maref in Korea developed Reliver RL-100 instrument for hand rehabilitation.
It is a soft hand device which works with gas chambers which moves fingers
and wrist. It is used for fingers and wrist paralysis training. It improves brain
plasticity and acts on blood vessels. The device is comfortable to wear for patient
and its movement is soft. With this instrument it is possible to maintain abduction
and adduction movement of the fingers as well as flexion and extension, however
range of motion in each movement is limited. Moreover, device is complex
and it needs outer gas source to work. There was no research found proving benefits
of this device [24].
Figure 2.5 - Reliver RL-100
Source: https://cn.diytrade.com/china/pd/6407902/气动式手康复装置.html
Panagiotis Polygerinos from Harvard University developed robotic hand that
uses a soft actuator, a thin rectangular bladder from elastomeric fiber-reinforced
material, that can be bended, extended, and twisted. While the fluid is injected
24
the actuator starts to extend, bend or twist as is shown in figure 2.6. This actuators
have low resistance while not pressurized what gives a free, unloaded movement
of a hand. Meanwhile, when it is pressurized it produces a force to move an individual
finger [31].
Figure 2.6 - Soft actuator (A) - exploded view of unpressurized segments (B) - pressurized view with
combination of motions [31]
Each actuator is adjusted to individual finger and covers all 3 joints. This gives
precise control over the finger movement. There is a tube which goes from one end
of the actuator and injects or outlets pressure from it. It works in closed loop control.
The glove is wear only on one side and leaves a palm free, what can be use
with catching objects. Moreover, all the pumps and controllers are mounted
in a small box which can be placed next to the patient. The intention of movement is
taken from the signal from the force sensors placed on the dorsal side of the fingers.
There are 4 sensors which are placed between each joint. The scheme of the glove (A)
and example of the possible training task (B) is shown in figure 2.7 [31].
Figure 2.7 - Soft rehabilitation glove (A) - scheme (B) - example of motion [31]
25
This glove gives a complex movement which is similar to a biological
movement of the hand. It gives a possibility to perform very challenging tasks like
finger opposition movement with a thumb. This complex movement may highly
increase a recovery process of the hand [24, 31].
The position of the joints is read from GUI system and the glove
is personalized to the individual patient. This gives a healthy movement of the joints.
Moreover, there is no high weight placed on the hand, the glove weight less than 0,5
kg. All other elements are placed in the box. These parameters and also the open
palm design gives an extra freedom which leads to a possibility of using this glove
as a portable device in daily life activities. However, the box may be annoying
for the patient to move around. Also this glove does not have a good feedback
of finger position. Moreover, there is not many research done with the use of this
rehabilitation glove, hence its effectiveness is unknown [24, 31].
All listed devices improve grip of the post-stroke patients, however only two
of them are handy and transportable. The soft glove made by Polygerinos and Reliver
RL-100. Moreover, there is no data about using them at home while this process gives
a big profit to recovery. Also almost all devices strongly simplify the movement
of the fingers, only Polygerinos's soft glove gives the complex movement close
to the biological one. The other have no division into metacarpophalangeal, proximal
interphalangeal and distal interphalangeal joint movement and no abduction
and adduction movement. In some devices the range of the movement is limited what
decrease efficiency of use. Most of the precision movement of the hand are due
to coordinate action between fingers and wrist and in all the previous examples
the wrist was fixated and motionless, hence there is no rehabilitation process on it.
From all the listed devices, it seems, soft glove made by Polygerinos gives
the most complex movement and meets the most of assumptions for the robotic hand
rehabilitation. However, it still needs a bigger number of researches on the use
on patients to have an objective comparison. Also there is no feedback from this
product, so physiotherapist may not follow the telemedicine progress of the patient
when the rehabilitation is done.
This research shows there is still not enough products to help post-stroke
patients in full recovery of their hand motor function. Moreover, it proves that even
existing solutions need further improvement. Also the process of hand rehabilitation
needs more accurate guidelines for future robotic devices.
3. Method section
3.1. Project assumptions
From the knowledge of previous chapters some requirements for future projects were
made. The projects should meet them in number as high as possible. The hand
robotic device is aimed to support rehabilitation process of the post-stroke patient
in a stage of flaccid paralysis or weak spasticity.
26
Because of the high occupancy of physiotherapists, their time with patients
is limited, hence the rehabilitation process may be negligence. A conversation
with some therapists explained that a traditional rehabilitation is mostly focused
on walking, position stabilization, and shoulder stabilization first, while hand
recovery stays as a minor problem. A perfect solution to problem of insufficient
rehabilitation could be a robotic device. From already existing devices one can find
few main ways of designing this types of robots.
The robot can be stationary, what means that it is used in the rehabilitation
center. Mostly this kind of robots need support of physiotherapist. Very often the help
is only limited to setting up the device or putting some elements on patient's hand,
while the rehabilitation tasks are done individually by patient. Hence, it leads only
to small decrease of work load on the health care stuff as long as they still need
to supervise the patient. Moreover, the patient has to stay in the rehabilitation center
or arrive to it.
Home therapy brings both, economic advantages and rehabilitation progress.
It is cheaper for patient or a health found, if patient stays at home instead of spending
a time in the rehabilitation center. Because of spending time at home, patient has
higher motivation to perform rehabilitation what gives better results in the recovery
process. The other idea is to use the device at patient's home with telemedicine
support. In this case physiotherapist develops patient's training and explains how
to use the device. The rehabilitation is done at patient's home and the results
are saved and send to rehabilitation center. Thanks to this the supervisor can see
patient's progress. Home rehabilitation gives benefits to both, the patient
and the physiotherapist.
However, while rehabilitation is done at home there are some important issues
to be solved. First of all there is a safety factor which is crucial as long as patient uses
the device on his own without supervision. It is significant to make a device safe
and free from all possible failures leading to occurring danger for patient's health.
Secondly, there is an economic factor. If the device is too expensive, patient may not
afford it or rehabilitation center would not want to lend it. The third factor is size
of the device. It is important to make the rehabilitation device compact
and transportable. If it is too big, there can be problems with delivery to the patient's
house and placing it there. It would also make transport more expensive. The last
thing is to design this device as a home device. It has to use technologies and source
of energy which are common in houses, and if it use any other technology it should
be delivered with a device. Gas and fluid driven devices require pumps which are not
commonly use at home. Use of this kind of technologies may be problematic
for the patient. Moreover, that could lead to another problem which is a noise created
by it. Loud work could make it unusable in home environment. Another solution
is a use of electric elements instead of gas or fluid ones. Electricity is a norm
for all houses. Moreover, electric motors and cylinders are very quiet what would not
be disturbing for people around.
27
To achieve a healthy movement in hand rehabilitation, a trained movement
should replicate kinematic movement of the fingers. The perfect solution would have
21 degrees of freedom, however by decreasing number of DOF the movement may
still be healthy and effective during rehabilitation as long as it tracks kinematic
motion of biological hand. Nevertheless, lower number of DOF decrease complexity
of movement which can be achieved by the device.
The length of joints of the device should be in the same position and work
in the same plane as the biological ones. Any deviation may harm patient or make
some pathological changes in motion. Moreover, joints of patients with flaccid hand
are not well attached, so there is a risk of prolapse. There should be a compressive
force acting on joints. Patients that suffer from flaccidity may not feel properly their
fingers because of low stress in the joints, which is due to slow fluid flow. External
forces may give them a sensation of fingers and provides better nutrition
in the fingers, what is necessary to rebuild muscle tissue and increase effectiveness
of a recovery process [14, 27].
The grasping force of the healthy hand can achieve high values, however
in daily living activities this force does not exceed 15N. Moreover, people
with flaccidity have their grasping force reduced or cannot strain their muscles.
The actuators do not need to generate the maximum grasping force, it is enough
if they cover usable force of daily living activities. Moreover, device should not affect
natural movement of fingers, cause injuries, or discomfort to the patient who wears
it [31].
There is an increase in efficiency of training when it is repeated few time
per day in blocks of 20 minutes. Moreover, the series of extending or flexing task
should occur with a frequency of 30 cycles per minute [11, 31].
A wearable part of a robot should not be heavier than 0,5 kg. However,
it is important to have it as light as possible to not fatigue patient by wearing a device
itself. Besides, it is advisable to use soft materials, which give comfort to the patient
while wearing it. Moreover, soft materials weight less than conventional materials.
The patients can have some limitations in their body movement what can
be inconvenient while setting up a device with no additional help. As long as
a devices may be used at home this help may not be accessible. Some patient may
have clenched hand because of occurring spasticity, while the others may have totally
flaccid hand. Hence, device should be design in the way to be easy to set up for
patient with different types of limitation and with use of one hand.
Besides mechanical factors, there are guidelines about control and data
collecting. There are few ideas of the control. Robot can execute a task itself with
a passive patient's hand inside. However, this is very limiting solution with low
effectiveness. The other solution is to create a system for active exercises. Whenever
the task is executed correctly, robot stays passive, but if there are any errors of the
trajectory or patient cannot perform the movement, the robot switches to the passive
mode and gives a push till the proper movement occurs. Next control system adds
28
some constant resistance, during task executing, to improve and strengthen
the movement.
Moreover, data can be collected from finger motions by EMG,
or any other signal from which it is possible to read a desired movement. In this case
the most important factor is accuracy and time of data processing, rather than a way
of collecting it.
It is recommended that robot can process some additional data which can
be useful for physiotherapists and patient in seeing the progress of the therapy.
This kind of feedback increases effectiveness of recovery process. Patient have extra
motivation because all progresses are measured.
Not all the guidelines are obligatory to meet, however the high number
of them is advisable. With all this information in mind, the concept device was
designed and built.
3.2. Concept
A main aspect of designing robotic device for hand rehabilitation of post-stroke
patients is possibility of using it in home environment. It is due to the fact, there
is a lack of this kind instrumentation. It can be a great additional help in the
rehabilitation therapies. The concept of the device is shown in figures 3.1 - 3.3.
Figure 3.1 - interior of the device with open side cover [38]
29
Figure 3.2 - interior of the motor box [38]
Figure 3.3 - wearable part of the device [38]
The rehabilitation robot uses a soft material glove (1) which is worn by the
patient. There is only an upper and a side part of the glove what gives possibility
of wearing it without necessity of sliding a hand inside it. This task could be
problematic for the patients with flaccidity. On the glove there is 3D-printed wrist
holder (2) made from polycarbonate which has high stiffness and strength, what gives
the possibility of lowering a mass of elements while good mechanical properties
are still achieved. Nowadays, 3D printing brings good quality and low production cost
30
of elements, what can be crucial, as an economic factor, in home use devices.
The wrist holder main function is keeping the hand steady in a natural position
during the training. The hand is fixed inside the wrist holder by two velcro fasteners
(3) placed under the wrist and around the palm.
On the fingers, just above proximal interphalangeal and distal interphalangeal
joints there are placed 3D printed C-rings (4) which are also fasten by velcro.
The C-shape of them makes the setting up process easier for patient. The C-rings can
be applied from the side on the fingers. To each ring two wires (5) are attached,
one from the dorsal side and the other one from the palmar side of the hand.
Moreover, the wires from motors to distal C-rings go through the proximal C-rings.
This is due to applying the force in the same direction for different position
of the hand. The wires transport force to the C-rings which act on fingers flexion
and extension. Some part of the force compresses joints. The robot uses biological
joints of patient to achieve movement of fingers. Thanks to this solution some small
compressive force is created. Acting on the joints attachment prevents prolapse
of them.
The upper wires go through the wrist holder on the top of the hand
and connect to the motor system (6) inside the motor box (7). The bottom wires go
to the palm side through the wheel system (9) on the wrist holder to the spring
system (8). The way of the wires is defined by different types of wheel systems.
On the top of the wrist holder there is the tenon (10) with a lock hole
in the middle of the surface. After sliding the tenon inside the dock (11), the lock (12)
stops further movement of the hand in the operating position. This system can be
used to change the glove between right and left hand. Also, in some cases it can be
used by the patient with a high level disability to install the device on the hand.
The motor box covers all electric and moving parts from the patient. Besides
the motor system, inside the box there is the electric lock (13), microcontroller (14),
Wheatstone bridges (15) and power board (16).
The frame (17) is build from aluminum profiles which are stiff and light while
the price of them is low. The rehabilitation process takes place inside the frame.
The size of the device should be as small as possible to transport it and place it
on a table or a desk. The interior of the device is hanged on the telescopic slides (18)
so it can be slide out from the frame. However, to maintain proper work during
sliding in and out the cables must be routed. For this task E-chain (19) was used.
Device should be connected to the computer by USB wire and ran
with a dedicated software. The results will show on the screen. Moreover, patient can
play games while executing tasks. This help with their bigger involvement into
rehabilitation process. The software can offer telemedicine and can send results
to physiotherapist for proper care over patient. However, the whole system is ran
from the microcontroller inside the device. Outer computer only receives data
and trigger tasks and actions.
31
The device should be connected to the regular electric socket and transform
the voltage to 5 V to power all the motors and sensors. This is why the power board is
used. It converts high voltage into lower, used by instruments.
When the patient wants to install the hand inside the device, the electric lock
opens and the interior of the device slides out from the frame. There is an easy access
to the wrist holder. Patient pulls up the lock (20) on the spring system to release
springs and remove tension from the wires. Spring system is presented in figure 3.4.
Next, patient slides in the hand to the wrist holder and straps it. Afterwards patient
installs two C-rings on each finger and straps them. Now the springs inside the spring
system can be pushed back to their operating position. The sensor (21) informs
if the springs are in the right position. In the end the patient slides back the telescopic
slide to the box and the lock gets blocked. After proper installation information
from the second sensor (22) occurs. The device is ready to use. The installation
position is shown in figure 3.5.
Figure 3.4 - 1: the spring system; 2: interior of the spring system, by unlocking, truck releases and moves on the rails. The springs are not stretched anymore [38]
32
Figure 3.5 - Device in installation position [38]
The task execution is achieved thanks to cooperation between motors
and springs. From the top, the servo motors can rotate by 180 degrees and pull
the wire. On each wire there is a plate with strain gauge (23) which collects
information about tension on the wire. From the bottom, wires go from C-ring
to spring system and each goes to the individual spring. The spring causes a tension
from the other side keeping the finger in stable position. Moreover, whenever motor
moves and slacks upper wire, the spring pulls it back. In that way all the wires
are tight in any moment.
When the rehabilitation exercises are finished, the lock opens and patient can
slide out the wrist holder and free patient's hand the same way as in the installation
process.
To verify the concept, a first prototype was made. It uses the same principle
of working. Two wires go to each C-ring, from the top a motor is placed,
and from the bottom a spring. However, there was no calculation or element selection
made, the prototype was built to prove the idea of working.
3.3. Data collecting, calculations, and element selection
The first step of designing was to prepare a hand model. From the research
the dimensions of the hand were found and presented [32]. A model of the hand
was downloaded from the GrabCAD library [33]. Figure 3.6 shows schematic view
of dimensions and their naming. Figure 3.7 presents the model of the hand used
in designing of robotic device.
33
Figure 3.6 - Schematic view of the measured dimensions [32]
Figure 3.7 - Model of a human left hand from GrabCAD [33]
All dimensions were compared to research results and presented in table 3.8.
The difference in dimensions were small and they were oscillating around 3%
for 50th percentile of male's left hand. Only the difference in dimension of breadth
of first joint of digit 1 was bigger (6%). The results were good for further use
and the hand was chosen as a model around which the rehabilitation device
was designed.
34
Dimension name Research value (mm) Model value (mm) Difference (%)
Hand length 192,98 196,84 2
Palm length 110,89 112,42 1
Hand breadth at thumb 101,95 104,32 2
Hand breadth at metacarpal 86,25 87,33 1
Fingertip to root digit 1 56,51 54,95 3
Fingertip to root digit 2 73,18 72,41 1
Fingertip to root digit 3 79,58 79,25 0
Fingertip to root digit 4 72,88 71,50 2
Fingertip to root digit 5 59,43 59,68 0
Breadth of first joint of digit 1 21,50 22,81 6
Breadth of first joint of digit 2 19,75 19,93 1
Breadth of first joint of digit 3 19,64 19,75 1
Breadth of first joint of digit 4 18,38 18,37 0
Breadth of first joint of digit 5 16,58 16,14 3
First joint to root digit 2 47,07 46,57 1
First joint to root digit 3 52,13 53,45 3
First joint to root digit 4 46,39 46,15 1
First joint to root digit 5 35,20 34,16 3
Second joint to root digit 1 22,74 22,65 0
Second joint to root digit 2 23,90 23,36 2
Second joint to root digit 3 25,86 26,28 2
Second joint to root digit 4 22,43 21,85 3
Second joint to root digit 5 17,87 18,17 2
Table 3.8 - Comparison of dimensions of the left hand for 50th percentile and 3D model [32]
Further, a range of motion was established. The maximum range of motions
for the MP (metacarpophalangeal) joints are from 0° to 90°. In the presented
solution abduction and adduction movements were neglected. The PIP (proximal
interphalangeal) joints move from 0° to 110°, however in the solution the range of
their motion may not occur fully. The PIP joints may bend to 90° whenever the MP
joints are bend to 90°. In other positions the range of motion of the PIP joints is
higher. It is due to design of the device. The DIP (distal interphalangeal) joints
movement was also neglected due to lower importance of use compared to other kind
of movements. Both end positions are shown in figure 3.9.
35
Figure 3.9 - 1: hand in full stretch; 2: hand in a grip position [38]
Strength of the fingers was roughly estimated experimentally. To this task the
first prototype was used. A hand scale was mounted to the finger at the end of the
wire. By flexing the finger, the hand scale showed created force in kilograms. The
measurement was made for each finger and each joint. All the results are shown in
table 3.10.
36
Finger Force on MP joint [N] Force on PIP joint [N]
Index 32 21
Middle 36 24
Ring 29 20
Pinkie 27 18
Table 3.10 - Fingers joints force [38]
Nevertheless, the weight is a very poor sensor with large measurement error,
the result may be used as a guide value of magnitude of force needed to flex finger.
The force of the spring should not create maximal value of the finger force
not to cause any injury to the patient. Moreover, patient with flaccid hand can create
only a small tension in their muscles, hence the force should be only a part
of the maximal force. However, due to the strength of the grip, results may be various
between different patients. It should be optimized in clinic trials.
The maximal value of force created by the springs was set at 27 N for the MP
joints and 18 N for the PIP joint. These numbers correspond to the pinkie finger
strength, which is the lowest from all the fingers.
Next, the length of movement of wires was measured on a prototype
for the MP and the PIP joint of the middle finger where the wire has the longest way
to travel between the two end positions. For the MP joint required length was 91 mm.
The PIP joint movement was 46 mm. However, to have some extra length the values
were set accordingly at 50 mm for the PIP joint and 100 mm for the MP joint.
The spring has to create a minimal force enough to hold the finger stably.
In the full extension, force of the spring cannot exceed the maximal strength
of the finger. It is important not to cause a harm to the patient by creating too high
force.
For the PIP joint movement the spring Vanel U.092.080.0500.IX was selected.
Its elongation is from 50 mm to 199 mm. The maximal force created by it is 20 N.
However, the force in working area values between 11,2 N to 19 N.
The MP joint spring is Vanel T.087.070.0380.A. This spring is shorter
and elongations goes from 38 mm to 148,5mm. Its maximal force is 22 N
and the force in the working area oscillates between 9,9 N to 21,3 N.
As it was mentioned before, the device is fully electric. To produce the action
of wire movements electric motors are used. Rotation of the motors takes less place
than linear movement, hence the servo motors are used. They create
a high torque while maintaining small dimensions thanks to the internal gear.
As an arm of a servo motor rotates by 180°, to cover full range of motion
of the finer, the length of arm has to be equal, or bigger, than a half of the way
of movement between the end positions. The lengths of arms are 𝑅1 = 50 𝑚𝑚 for the
37
PIP joint and 𝑅2 = 25 𝑚𝑚 for the MP joint. The scheme of servo motor arms is shown
in figure 3.11.
Figure 3.11 - Scheme of servo motors arms [38]
Servo motor has to create a force higher than the maximal force of the spring,
to spread it easily. Moreover, the small resistance from the finger may occur, that
is why servo motor torque has to be big enough to move all the load. Required force
was set at 15 N more than the minimal force needed to overcome springs. 15 N
is the maximal force created during daily life activities. By knowing length of the arm
and needed force, torque created by servo motor on the MP and the PIP joint
was calculated.
𝑀 = (𝐹𝑠𝑝𝑟𝑖𝑛𝑔 + 15 𝑁) ∙ 𝑅 (3.1)
𝑀1 = 19 𝑁 + 15 𝑁 ∙ 50 𝑚𝑚 = 1700 𝑁𝑚𝑚 ≈ 17,33 𝑘𝑔/𝑐𝑚
𝑀2 = 21,3 𝑁 + 15 𝑁 ∙ 25 𝑚𝑚 = 907,5 𝑁𝑚𝑚 ≈ 9,25 𝑘𝑔/𝑐𝑚
For the MP joint movement, Hitec HS805 servo motors, 1 for each finger,
was chosen. The maximum torque of them is 19,8 kg/cm. The operating voltage range
is from 4,8V to 6.0V. The weight is 152 grams.
The second type of servo motors, used on the PIP joints, is Hitec HS-5645MG,
and the torque in 5V is 11 kg/cm. It weights 110 grams. Four motors were used.
Nylon was chosen as the material for the wires because it shows a low
elongation properties and low thermal effect on its length. It is important to have
38
a material with low elongation to precisely control position of the finger. Nylon's
tensile strength is 𝑘𝑡 = 80 𝑀𝑃𝑎 [34]. The maximal force working on the wires is
43,1 N, and it is generated by Hitec HS-5645MG servo motor. The wire works
on tensile. The minimal diameter d of nylon string was calculated.
𝜎 =𝐹
𝑆≤𝑘𝑡𝑋𝑡
(3.2)
where: 𝜎 - tensile stress
F - force of tensile
𝑠 = 𝜋𝑑2
4 - surface area
𝑋𝑡 = 1,5 - safety factor
𝑑 ≥ 4 ∙ 𝐹
𝜋 ∙ 𝑘𝑡
𝑑 ≥ 4 ∙ 43,1 𝑁
𝜋 ∙ 80 𝑀𝑃𝑎
𝑑 ≥ 1,02 [𝑚𝑚]
The chosen wire is a guitar string, size .042, what is around 1,07 mm
of diameter.
To measure the tension and to have a feedback from the device, strain gauges
were used and attached to the wires. Selected strain gauges are 5 kg Micro load cell
by Phidgets, which cover the maximal force occurring on the wires, 43,1 N. The device
uses 8 sensors to control all the motors. To amplify signal Phidgets 1046-0B
Wheatstone Bridges were used. These W-bridges are fully compatible with the chosen
strain gauges and has 4 inputs to control independently 4 sensors in the same time.
To collect signals from all the strain gauges, two W-bridges were used.
For all 3D printed elements ABS material was selected, which is one
of the most common used materials for 3D printing nowadays. Elements printed
from ABS are tough and durable, while mass and the cost of them is low. Moreover,
it withstands long time period without big structural changes, what prevent element
against failure.
The wrist holder is the most loaded 3D printed element in the device. It has a
shape of a half ring with extended side of it as It is shown in figure 3.12. It has to hold
steady the wrist during training session without failure or deformation. To calculate
thickness of it, it was divided for 3 segments and the moment of inertia for each
segment was calculated. This is due to complex shape of it, and normalized inertia
moment cannot be used in this case.
39
Figure 3.12 - auxiliary drawing; d, e, f - distance from section coordinate system to main coordinate system; g - thickness of wrist holder [38]
𝐼𝑥 = 𝐼𝑢 + 𝐴𝑢 ∙ 𝑃𝑢2
𝑢
(3.3)
𝐼𝑥 𝑠𝑞𝑢𝑎𝑟𝑒 =𝑏 ∙ 3
3
(3.4)
𝐼𝑥 𝑎𝑙𝑓 𝑐𝑖𝑟𝑐𝑙𝑒 =𝜋 ∙ 𝑅4
8 (3.5)
𝐼1 =𝜋 ∙ (17,5 + 𝑔 − 17,5)4
8=𝜋 ∙ 𝑔4
8
𝐼2 =35 ∙ 𝑔3
3
𝐼3 =20 ∙ 𝑔3
3
𝐼𝑥 = 𝐼1 + 𝐴1 ∙ 𝑃12 + 𝐼2 + 𝐴2 ∙ 𝑃2
2 + 𝐼3 + 𝐴3 ∙ 𝑃32
40
where: 𝑃1 = 𝑃2 = 𝑃3 = 6;
𝐴1 =𝜋 ∙ (35 + 𝑔)2
2−𝜋 ∙ 352
2=𝜋 ∙ (70𝑔 + 𝑔2)
2
𝐴2 = 35 ∙ 𝑔
𝐴3 = 20 ∙ 𝑔
𝐼𝑥 =𝜋𝑔4
8+
55𝑔3
3+ 18𝜋𝑔2 + (1260𝜋 + 1980)𝑔
Next, there was derived equation to calculate a minimal thickness of the wrist
holder.
𝑊𝑥 =𝐼𝑥𝑦∗
(3.6)
Where: 𝑦∗ = 𝑔 + 17,5;
𝜎 =𝑀𝑏
𝑊𝑥≤𝑘𝑏𝑋
(3.7)
Where: 𝑀𝑏 - bending moment, 𝑘𝑏 - flexural strength, X = 3 - safety factor
The research shows that for a healthy man the torque of wrist during flexion
goes up to 15 Nm = 15000 Nmm [35]. This value was set as a minimal value that
the wrist holder has to withstand. The flexural strength was set at 30 MPa. This value
is lower than a nominal value for ABS, because the element is 3D printed.
This process has an impact on the material properties of created elements.
Because the value of flexural strength strongly depends on the quality of 3D printing,
the safety factor was set at 3 to ensure no failure even when quality of a part is lower.
𝐼𝑥 −𝑋 ∙ 𝑀𝑏
𝑘𝑏∙ 𝑦∗ ≥ 0
𝜋𝑔4
8+
55𝑔3
3+ 18𝜋𝑔2 + (1260𝜋 + 1980)𝑔 −
3 ∙ 15000
30∙ 𝑔 + 17,5 ≥ 0
𝜋𝑔4
8+
55𝑔3
3+ 18𝜋𝑔2 + 1260𝜋 + 480 𝑔 − 26000 ≥ 0
𝑔 ≈ 4,98 [𝑚𝑚]
The designed thickness was set at 5 mm.
Next, the thickness of tenon was calculated. The force that tenon
has to withstand is a weight of the arm. For the male, the weight is around 4,3 kg
[36]. However, there is a possibility that the user may lean on the arm and create
bigger pressure. The final value was set at 300 N. The tenon in the dock is stretched.
41
The weakest segment of it, is the base. The length of the base was set at 10 mm. The
thickness was calculated. Figure 3.13 presents auxiliary drawing for the calculations.
Figure 3.13 - auxiliary drawing; b - thickness of tenon [38]
𝐹
𝐴≤𝑘𝑡𝑋
(3.8)
where 𝐴 = 10 𝑚𝑚 ∙ 𝑏
𝑏 ≥𝑋 ∙ 𝐹
10 𝑚𝑚 ∙ 𝑘𝑡
𝑏 ≥3 ∙ 140𝑁
10𝑚𝑚 ∙ 28,5 𝑀𝑃𝑎
𝑏 ≥ 3,2 𝑚𝑚
The value of thickness was set at 5 mm as the rest of the wrist holder.
This change was made to reduce a chance of failing of this segment.
The shaft of the wheel system was made from aluminum alloy 3.3315, which
has good mechanical properties and low weight. This alloy was used for all other
metallic elements. The most loaded shaft is the one on the dock (figure 3.14).
42
Figure 3.14 - Wheel system on the dock [38]
A calculation of the highest loaded profile was made. The maximal force F
is a sum of two forces from each pair of wheels. However, this is just a theoretical
force caused by motors in a hypothetical situation when wheels does not rotate
and motors pull the shaft. The real value of load should be significantly lower.
Each pair of wheels was treated as one. Scheme of the shaft is shown in figure 3.15.
Based on that calculations and diagrams were made.
𝐹 = 43,1 𝑁 + 38,3 𝑁 = 81,4 𝑁
Figure 3.15 - Scheme of the shaft with diagram of shear and moment [38]
43
𝑆 = 0 𝑎𝑛𝑑 𝑀 = 0 (3.9)
𝑆 = 𝑅𝑎 − 4 ∙ 𝐹 + 𝑅𝑏
𝑀𝑎 = −14,5 ∙ 𝐹 − 33,5 ∙ 𝐹 − 52,5 ∙ 𝐹 − 72,5 ∙ 𝐹 + 93 ∙ 𝑅𝑏 = 93 ∙ 𝑅𝑏 − 173 ∙ 𝐹
𝑅𝑏 =
173
93𝐹 ≈ 151,5 𝑁
𝑅𝑎 =199
93𝐹 ≈ 174,2 𝑁
1) 0 ≤ 𝑥 < 14,5
𝑀1 = 𝑅𝑎 ∙ 𝑥
𝑆1 = 𝑅𝑎
2) 14,5 ≤ 𝑥 < 33,5
𝑀2 = 𝑅𝑎 ∙ 𝑥 − 𝐹(𝑥 − 14,5)
𝑆2 = 𝑅𝑎 − 𝐹
3) 33,5 ≤ 𝑥 < 52,5
𝑀3 = 𝑅𝑎 ∙ 𝑥 − 𝐹(𝑥 − 14,5) − 𝐹(𝑥 − 32,5)
𝑆3 = 𝑅𝑎 − 2 ∙ 𝐹
4) 52,5 ≤ 𝑥 < 72,5
𝑀4 = 𝑅𝑎 ∙ 𝑥 − 𝐹(𝑥 − 14,5) − 𝐹(𝑥 − 32,5) − 𝐹(𝑥 − 52,5)
𝑆4 = 𝑅𝑎 − 3 ∙ 𝐹
5) 72,5 ≤ 𝑥 < 93
𝑀5 = 𝑅𝑎 ∙ 𝑥 − 𝐹(𝑥 − 14,5) − 𝐹(𝑥 − 32,5) − 𝐹(𝑥 − 52,5)− 𝐹(𝑥 − 72,5)
𝑆5 = 𝑅𝑎 − 4 ∙ 𝐹
The maximal value of the torque occurs for 𝑥 = 52,5 𝑚𝑚 , and has a value
of 𝑀𝑚𝑎𝑥 ≈ 4505 𝑁𝑚𝑚. Next, the minimal diameter of the shaft was calculated.
𝜎𝑏 =𝑀𝑏
𝑊𝑧≤ 𝑘𝑏 (3.10)
where: 𝑊𝑧 =𝜋𝑑3
16
𝑑 ≥ 16 ∙ 𝑀𝑚𝑎𝑥
𝜋 ∙ 𝑘𝑏
3
For the 3.3315 aluminum alloy tensile strength is 𝑅𝑒 = 230 𝑀𝑃𝑎. The value
of flexural strength is 𝑘𝑏 = 0,6 ∙ 𝑅𝑒 = 138 𝑀𝑃𝑎.
44
𝑑 ≥ 16 ∙ 4505 𝑁𝑚𝑚
𝜋 ∙ 138 𝑀𝑃𝑎
3
𝑑 ≥ 5,5 𝑚𝑚
The final diameter was set at 6 mm. However, there is also shear stress acting
on the shaft. To check if the diameter is big enough to withstand loads the Huber's
equation (3.11) was used. Shear in the position of maximal moment is S = 70 N.
𝜎𝑟𝑒𝑑 = 𝜎2 + 3(𝜏2) (3.11)
𝜎𝑟𝑒𝑑 = 𝑀𝑚𝑎𝑥
𝑊𝑧
2
+ 3((𝑆
𝐴)2) ≤ 𝑘𝑟𝑒𝑑
where: 𝐴 = 𝜋𝑑2; 𝑘𝑟𝑒𝑑 = 0,55 ∙ 𝑅𝑒 ≈ 126 𝑀𝑃𝑎
𝜎𝑟𝑒𝑑 = (4505 𝑁𝑚𝑚)
𝜋 ∙ (6 𝑚𝑚)3
16
2
+ 3((70 𝑁
𝜋 ∙ (6 𝑚𝑚)2)2) = 106 𝑀𝑃𝑎 ≤ 126 𝑀𝑃𝑎
The 6 mm shaft is big enough to stand all the occurring loads.
The telescopic slides were used to slide out the interior of the device from
the frame. By designing a complete device the length of movement of 300 mm was
chosen. The sliders were used to have a possibility to install the hand inside the wrist
holder with not limited access to it by the frame. The load capacity of the sliders has
to be big enough to support the weight of the arm and the weight of the components
of the device. The total mass should be lower than 10 kg, however the safety factor
was set at 3. To execute this task Kipp K0540 telescopic slides with load capacity
of 35 kg and range of 300 mm were selected. Moreover, the spring module locates
at the bottom of the device, the second pair of sliders was used to support it. In this
case, because of the low mass of the spring module, Kipp K0536 was selected.
This is the smallest telescopic slide available with 300 mm range of extension.
The load capacity of it is 15 kg.
Before any movement of motors start, there is a need to check if all
the elements are in the working positions. For this task inductive safety sensors were
used. The selected sensors are Schmersal BNS 250 with 2 mm detecting range. One
sensor is attached to the frame and the other one to the motor box. Whenever user
moves back the interior part of the device to the working position, the signal
from the sensor is send to the electric lock, Junson JS-303, and closes it.
The second sensor is attached to the spring module. Before device initiates its
work, the spring module has to be in its working position and the locker has to be
45
closed. When both sensors send a positive signal, the motor may start moving.
However, if there is a break in signal sending from the sensors, the whole device stops
immediately.
To start the device, 5 V RobotShop Rocker Switch has to be clicked, what sends
a power to all electric elements.
The system is controlled by microcontroller STM32F411E Discovery. It works
on 5 V voltage. It has an USB exit, so after connecting it to the computer there is
communication between the software and the device. It has 180 MHz processor,
which is enough to run PWM signal for 8 motors. Each motor needs only 5 Hz PWM
signal to run properly.
Because the device is connected to the 240 V AC, there is a need to use power
board to convert the input voltage to 5V DC on output, as all listed electrical elements
use it. Each motor needs 800 mA of current, for 8 motors it is 6,4 A. All other electric
devices use less than 1 A of current. That leads to selecting a power board that can
stand around 7,5 A current. Selected power board is Botland PMT 5V50W1AA which
converts 240 V AC to 5 V DC and have the output current of 10 A. This is fair reserve
to use the device safety and not to cause any high heating.
There is a need to use an electric chain for cables to maintain a smooth
movement of the sliders when the interior of the device is slide in and out. There are
3 cables which goes into the motor box. First one transfers 240 V AC from the electric
socket to the power board. This cable has 12 mm diameter. Second one, a 5 V DC,
goes from the power board to the Rocker Switch. It's diameter is 2,1 mm. The third
one is an USB cable also 2,1mm diameter. The interior of the e-chain has to fit all the
cables. The selected e-chain is Igus 0.26m E2i.10.06.018.0 + E2.100.06.12PZ.A1.
The travel range of it is 310 mm, what is 10 mm more than the range of the telescopic
slides.
The frame is build from 20 mm aluminum square profiles V-Slot 2020. These
are the smallest normalized aluminum profiles available on the market. They have
fast connection system based on the T-slots. The telescopic slides, that carries the rest
of the elements are connected to the frame. The frame is covered with ABS plates
to protect interior of the device from the dust. Moreover, there is no access
to the moving elements, hence no harm to the user should be done.
The locker of the spring module and the wrist holder is indexing plunger
Elesa-Ganter GN 817-4-6-B.
To safely place the device on the table leveling feet Elesa-Ganter
LX.25-SW13-M6x24 were used. They have rubber endings which keeps the device
motionless on the surface of the table.
The whole device weights 8,2 kg and has a cuboid shape of dimensions:
344 mm width, 383 mm height, and 401 mm length.
The 3D model of the rehabilitation device was designed in SolidWorks.
Figures 3.16 and 3.17 show model of the device with all selected elements marked and
listed.
46
Figure 3.16 - Scheme with listed elements [38]
Figure 3.17 - Scheme with listed elements that are inside the motor box [38]
3.4. Prototype
The first prototype was made to validate the basic concept of work, and to measure
the forces needed for the finger movement. The second prototype, was based
47
on the designed 3D model and it uses the same or similar elements,
as in the model. However, this prototype works only with one finger, what
is representative for all the fingers. The device was made to analys the precision
of the movement and functionality of the code in all 3 types of control loop.
The aluminum frame was built as in the 3D model. Nevertheless, it is 80mm
more narrow compare to 3D modeled. This change was done because the prototype
works only with 1 finger, hence there are only two motors. Moreover, the telescopic
slides were not used. It does not affect the work of the instrument. All the parts were
fixed to the frame. The wrist holder was made from the wrist brace and attached to
the metal plate. Wrist brace was used to orientate and hold the hand in one position.
The C-rings were glued to the glove's index finger and connected to the wires made
from a guitar nylon string. Just above and below the wrist brace, there are 2 plates
with wheels on it to change direction of the wire. That gives the possibility of placing
both motors in front of the device. On the top, the wires go to the Phidgets strain
gauges, and next to the servo motors. In this prototype, both motors were
Hitec HS805. To have similar force on the MP joint as in calculations, in both motors
50 mm reaction arms were used. Because of the high current, that motors need,
a separate power source was created. It converts 230V from the electric socket to 5V
on the output. The motors and the microcontroller is connected to the power supply.
The W-Bridge and second input of microcontroller is connected to the computer.
The program collects data from the W-bridge and sends it back to the
microcontroller. The control wire of the motor was connected to the microcontroller
STM32F411E Discovery. On the bottom of the device there are 2 springs. Because
of high cost of production single spring, instead of the Vanel springs other, less
expensive, springs were used. They were validated experimentally. For this use, the
force created by them is from 8 N to 19 N, what is similar to the original values of
Vanel springs.
Besides the prototype, a mechanical flaccid finger was made. It uses hinges
as the PIP and the MP joint. Moreover, it has mechanical limitations, that make
the finger move as a biological one. The finger was fixed to the frame, and placed
inside the glove. The device was tested with it inside to imitate a flaccid finger.
The prototype with mounted mechanical flaccid finger inside is shown
in figures 3.18 - 3.20.
48
Figure 3.18 - The prototype with mechanical flaccid finger [38]
Figure 3.19 - Top view of the prototype. To remove mechanical finger, demount first plate from the left [38]
49
Figure 3.20 - Close up to the working area [38]
This prototype gives a better look on how modeled device functions, and shows
if there are any problems with it. The prototype with elements description is shown
in figure 3.21.
Figure 3.21 - The prototype with elements listed [38]
50
3.5. Control
The program that provides reading of voltage from the strain gauges was created.
Thanks to the W-Bridge with microcontroller inside, the task was to communicate
the computer with the W-Bridge and to collect information from two ports, that
are connected to the strain gauges. The program uses Phidget22 library and it is
based on the guideline from the official website.
The servo motors use pulse width modulation (PWM) signal of value 3V
and frequency of 50 Hz to control their position. The STM microcontroller provides
this kind of voltage on PE5 and PA2 ports. Positions of the motors have the PWM
pulse duration between 0,9 ms to 2,1 ms. This values match both end positions
of the servo motor.
The control system of the rehabilitation device uses signal from the strain
gauges and the programmed information about the task, that has to be achieved.
There are three main modes of task execution:
passive - if the patient is unable to move the fingers, the robot device moves
them repetitively without any involvement of the patient.
active - whenever the patient moves the fingers correctly, the device follows
the movement. If there is any longer pause in the movement, the robotic
device switches to passive mode. However, if the user starts the proper
movement, device switches back to the active mode.
resistive - the device keeps the constant resistance to the movement.
The patient needs to overcome it during the movement.
All three modes were programmed based on the signal from the strain gauges
and saturation of the PWM signal. The passive mode executes the task, by rotating
the motor till reaching the setpoint, which is set depending on the given task.
However, if the signal from the strain gauges is higher than the safety threshold, the
motors stop and go to the starting position. The values of maximal force were tested
and verified.
The active mode follows the movement of the user by keeping the value from
the sensor on the same level dependent on the position of the spring. In each
position, the spring creates different force according to Hooke's law. This mean that
the threshold in the task execution was set individually for each position. However, if
the position of the motor does not change during a short period of time the control
switches to the passive mode. This time period was set at 2 sec. Moreover, if the user
starts to move the finger in the wrong direction, the motor does not allow for it. At
the moment, the patient starts to move the finger properly, the value on the strain
gauge changes, and the motor switches back to the active mode. The value change
depending on the direction of the movement and the spring extension.
The resistive mode keeps the value of the strain gauge on the set level, taking
into account the spring extension. The value of the resistance may be set between
0,1 kg and 0,9 kg. This is due to the minimal force created by the spring. However,
51
in the prototype the resistance was set permanently. The way the resistive mode
works is similar to the active mode. Only the thresholds are shifted.
Because of the lack of encoders, the motor position is known indirectly from
the saturation of PWM signal. In each move, saturation changes by the known value
of the step. Based on that, the control of the position for each mode was made, while
the strain gauges signal was a trigger for further movement and the safety threshold.
During running the program, a menu window with possible modes of training
to choose appears. After clicking each button, a choice of different tasks is given:
1) flexing the finger to the grip position
2) full extension of the finger
3) flexing the MP joint to 90° position
4) flexing the PIP joint to 90° position.
Moreover, a test mode was created. This mode is used to control the motors
manually and save the reading from the strain gauges in each position. Thanks to
that, setup of thresholds and steps was done. In the prototype there is no temperature
compensation, the test mode may be used when the prototype is placed in a different
environment, to reset the values of thresholds. A different temperature can have
an impact on the strain gauge reading.
The whole control system was programmed in C# language in Microsoft Visual
Studio. The prototype was ran and controlled from the computer. Microcontroller
collects information about saturation of the PWM signal from the computer and
controls both motors. The interface of written application is shown in figure 3.22.
Figure 3.22 - The interface of the application [38]
When the program starts, it rotates the motors till the tense on the wires
occurs, what is the starting position. At the beginning, there is no tense, so the user
may easily install a glove. By clicking the task button, the program starts to execute it
in the chosen mode. Until the task is not finished or an error occurs, other tasks
52
cannot be chosen. After successfully executing a task, a message box pops up. Next,
another task can be chosen. The MP and the PIP joint exercise first moves the finger
to the extension position, and next the task is executed.
Lower buttons are locked unless the test button is clicked. In the test mode,
user can move each joint up and down manually. In each position data from the
strain gauges is saved in the file. Moreover, tasks buttons still work, but now, the data
is collected while the motors are moving.
If there is a high tense on the wire, motors go to the installation position
and the error message box pops up.
After clicking the exit button, motors moves to the installation position.
3.6. Analysis of the prototype
Firstly, calibration of all variables was done. This task was achieved in the test mode.
At the beginning, exact positions for each tasks were found manually. The saturations
for each position were listed in table 3.23.
Motor MP Motor PIP
Grip 1,95 1,72
Extenion 2,46 1,27
MP joint 90° 2,01 1,72
PIP joint 90° 2,46 1,45
Table 3.23 - Saturation in ms. The PWM signal has frequency of 50 Hz, what is 20 ms [38]
Further, the step value was found. The movement suppose to take around 2s.
The value of the PWM signal change in each step was set at 0,02 ms. However,
because of a fast change of saturation in the microcontroller, the motor was moving
very fast. To solve this problem, a delay was added to the loop of program. After few
trials, the delay of 100 ms was found that matches the best and gives a smooth
movement of motors and set the task executing time around 2 s.
After setting the motors, the voltage values of the strain gauges for each
position were found. The values of position between grip and extension position were
used to find a pattern of voltage change caused by the springs. In the first trial,
the change was measured in static positions, which means that the motor was
stopped in some position and data was taken. The value changes for both strain
gauges caused by the springs are shown on chart 3.24 and 3.25
53
Chart 3.24 - Behavior of the MP spring; static test [38]
Chart 3.25 - Behavior of the PIP spring; static test [38]
There can be noticed a linear trend of the characteristics. It should be pointed
out, that in both the charts the value of voltage increases while the spring is extended.
However, it has some deviation. One of the reasons is, while flexing the finger,
the wire from the springs and from the motors transfers the loads in different angle
to the finger. In some positions, bigger amount of the force compresses joints than
in others. That leads to not perfectly linear characteristic. Moreover, some errors
of the reader occurs. Mostly, the error oscillates between ±0,02 mV. Based
on the charts, impact of the springs in each step was found.
Next, few values of threshold for the active mode was set. However, with its
low value motors were not stable, and there was a lot of twitches. With higher value,
there was some resistance, that was used later in the resistive mode. In the next step,
a safety value was set. Whenever any strain gauge sends a value higher than the safety
-0,039-0,038-0,037-0,036-0,035-0,034-0,033-0,032-0,031
-0,03
1,95 2,06 2,12 2,19 2,26 2,33 2,39 2,46
Vo
ltag
e in
mV
Saturation in ms
MP joint
0,0670
0,0680
0,0690
0,0700
0,0710
0,0720
1,72 1,68 1,61 1,54 1,48 1,41 1,34 1,27
Vo
ltag
e in
mV
Saturation in ms
PIP joint
54
value, the program switches to the error mode, and releases motors and informs
about the error occurring. All the values of voltage are listed in table 3.26.
MP Voltage PIP voltage
Grip -0,031 0,069
Extension -0,029 0,072
Spring step 0,0009 0,0015
Active threshold 0,002 0,002
Resistive threshold 0,005 0,005
Safety threshold (grip) 0,01 0,01
Table 3.26 - Voltage variables in mV [38]
A difference in voltage between MP and PIP strain gauge does not correspond
to different load, but to starting value of measurement. The measured value is not
important. The control works based on the change of the value of voltage.
Finally, a test of all the movements and modes was done. First, on the
mechanical flaccid finger, then on the healthy person finger. The range of motion
goes to 90° for the MP joint, and around 60° for the PIP joint. A low value of flexing
the PIP joint is caused by big dimensions of the C-rings, that are bigger than
in the 3D model. During flexing, both C-rings obstruct to each other and prevent
further movement.
This test was not fully successful. In some position, the active mode was
activated without finger movement. Moreover, in the active and resistive mode the
required force to start movement was not always constant. All other modes worked
sufficiently.
The unsatisfying results of the device functionary were caused by the incorrect
data measurement. The signal was taken during static test, while during dynamic
movement the tension on the wires is different. Hence, the program was rearranged.
In the second measurement, the voltage values of the strain gauges were save
during movement of motors. This test was repeated several times to see the
measurement repeatability. Despite the threshold estimation, by repeating this test
for different values of the step and time delay, the smoothest movement was
identified. The results are shown on charts 3.27 - 3.32.
55
Chart 3.27 - Behavior of the MP spring; dynamic test A:
MP step = 0,02 ms; PIP step = 0,02 ms; time delay = 100 ms [38]
Chart 3.28 - Behavior of the PIP spring; dynamic test A:
MP step = 0,02 ms; PIP step = 0,02 ms; time delay = 100 ms [38]
Chart 3.29 - Behavior of the MP spring; dynamic test B:
MP step = 0,02 ms; PIP step = 0,02 ms; time delay = 50 ms [38]
-0,050
-0,040
-0,030
-0,020
-0,010
-
2,0
1
2,1
9
2,3
7
2,3
5
2,1
7
1,9
9
2,1
2
2,3
0
2,4
1
2,2
4
2,0
6
2,0
8
2,2
6
2,4
4
2,2
8
2,1
0
2,0
3
2,2
1
2,3
9
2,3
3
2,1
5
2,1
7
2,3
5
2,3
7
2,1
9
2,0
1
Vo
ltag
e in
mV
Saturation in ms
MP joint
0,065 0,066 0,067 0,068 0,069 0,070 0,071 0,072 0,073
1,6
1
1,4
3
1,3
6
1,5
4
1,5
0
1,3
2
1,3
0
1,4
8
1,5
4
1,3
6
1,4
3
1,6
1
1,5
9
1,4
1
1,3
9
1,5
7
1,4
5
1,2
7
1,3
4
1,5
2
Vo
ltag
e in
mV
Saturation in ms
PIP joint
-0,045 -0,040 -0,035 -0,030 -0,025 -0,020 -0,015 -0,010 -0,005
-
2,0
1
2,1
7
2,3
3
2,4
1
2,2
6
2,1
0
2,0
1
2,1
7
2,3
3
2,4
1
2,2
6
2,1
0
2,0
1
2,1
7
2,3
3
2,4
1
2,2
6
2,1
0
2,0
1
2,1
7
2,3
3
2,4
1
2,2
6
2,1
0
1,9
9
Vo
ltag
e in
mV
Saturation in ms
MP joint
56
Chart 3.30 - Behavior of the PIP spring; dynamic test B:
MP step = 0,02 ms; PIP step = 0,02 ms; time delay = 50 ms [38]
Chart 3.31 - Behavior of the MP spring; dynamic test C:
MP step = 0,014 ms; PIP step = 0,02 ms; time delay = 100 ms [38]
Chart 3.32 - Behavior of the PIP spring; dynamic test C:
MP step = 0,014 ms; PIP step = 0,02 ms; time delay = 100 ms [38]
0,065 0,066 0,067 0,068 0,069 0,070 0,071 0,072 0,073
1,6
1
1,4
5
1,3
0
1,3
0
1,4
5
1,6
1
1,6
1
1,4
5
1,3
0
1,3
0
1,4
5
1,6
1
1,6
1
1,4
5
1,3
0
1,3
0
1,4
5
1,6
1
1,6
1
1,4
5
1,3
0
1,3
0
1,4
5
1,6
1
Vo
ltag
e in
mV
Saturation in ms
PIP joint
-0,040
-0,035
-0,030
-0,025
-0,020
-0,015
-0,010
-0,005
-
2,0
1
2,1
2
2,2
4
2,3
5
2,3
9
2,2
8
2,1
7
2,0
6
2,0
6
2,1
7
2,2
8
2,3
9
2,3
5
2,2
4
2,1
2
2,0
1
2,1
0
2,2
1
2,3
3
2,4
4
2,4
1
2,3
0
2,1
9
Vo
ltag
e in
mV
Saturation in ms
MP joint
0,066
0,067
0,068
0,069
0,070
0,071
0,072
0,073
1,6
2
1,5
2
1,4
3
1,3
3
1,2
9
1,3
8
1,4
8
1,5
7
1,6
2
1,5
2
1,4
3
1,3
3
1,2
9
1,3
8
1,4
8
1,5
7
1,6
2
1,5
2
1,4
3
1,3
3
1,2
9
1,3
8
1,4
8
1,5
7
Vo
ltag
e in
mV
Saturation in ms
PIP joint
57
By comparing the test A (MP step = 0,02 ms; PIP step = 0,02 ms;
time delay = 100 ms) to the test B (MP step = 0,02 ms; PIP step = 0,02 ms;
time delay = 50 ms) it is noticeable the smoother effect of the spring on the MP joint
during faster movement. In this test, the slope is more stable and has smaller
distortion in the bottom part of the chart, that shows flexion. Moreover, during
flexion it was expected to have constantly decreasing voltage. In the test A and B, this
assumption was not met.
In the test C (MP step = 0,014 ms; PIP step = 0,02 ms; time delay = 100 ms),
the voltage during extension was constantly increasing and during flexion decreasing
as it was anticipated. Moreover, from all the tests, for the MP joint, the highest
repeatedly has the test C. In all listed examples there is a drop of the voltage before
flexion occurs. It is due to short pause between another task, hence no motor
movement affected the measurement.
In all the tests, data from the PIP joint shows a small jump at the end of the
extension. For the test B, there is a drop of the voltage in the mentioned area. In all
the tests the data is constant between each repetition. However, the smoothest
voltage change is in the test C.
Based on this results, the prototype was recalibrate to use data from the test C.
Moreover, the program was changed to save and use collected data instead of
previously chosen constant spring step. All listed thresholds stayed untouched.
With new calibration, all modes worked properly and all the tasks were
achieved. However, there were some motor twitching while moving. It is probably
caused by occurring high torque. The device was noisy, when the motors were loaded.
Moreover, as expected there was a force compressing joints together. This force did
not give an unpleasant sensation to the user.
The wrist holder, made from the wrist brace, did not stabilized the hand
in one position. There was a possibility of small rotation of the hand. It was caused
by the soft material from which the brace was made. However, in the 3D model
it should not be a problem, because there is used 3D printed ABS wrist holder, which
should keep the hand fixed.
The device can be easily placed on the table and training may be done
in a sitting position. Because of the flaccidity which occurs in the whole limb, there
could be a need for using some arm support for the patient.
4. Discussion
By comparing existing solutions of the hand rehabilitation robotic devices, it was
discovered that this area of device is new and still needs further improvements.
Thanks to researches and analysis of existing solutions, the guide for designing
of rehabilitation devices was delineated. Accordingly, a 3D model of a hand
rehabilitation robotic device for a home usage was designed. Based on it,
58
the prototype was built, tested, and analyzed. This process has permitted to get
a better look on pros and cons of the presented solution.
The biggest advantage of the tested device, comparing to other solutions, is the
possibility of using the device at home. From the beginning, the design was focused
on potential condition of usage. The developed instrument is cheap and easy to set
up, so it can be bought by the patient or lent from the rehabilitation center. This gives
an opportunity to train the affected limb for longer time compared to conventional
therapy, where the time with physiotherapist is limited.
The patient does not feel weight of the device, because his hand hangs inside it.
It is very important for the patient to relax his arm. However, this leads to the
limitation, that the device is not portable. The concept does not have an open palm
design, what does not leave a place for the future improvement of the device
as a portable one. Moreover, the device may use a software which can provide
entertaining games, however the limitation of not using the device during a regular
day activity will not be replaced by the games.
In contrast to other solutions, this device moves two joints, MP and PIP.
The skipped DIP joint does not have as important function as the other two
in everyday activities. However, as in many solution, there is no abduction
and adduction movement. There is no thumb leading and the wrist is fixated inside
the wrist holder.
The device loads the joints by compressing them together. Patients
with flaccidity very often do not feel their fingers well and compressing the joints
together might produce a better fluids flow in the fingers and restore sensation of
touch. However, this compressive force is different in different position, because of a
linear behavior of springs.
From one hand, the device does not allow to achieve a full range of motion
of the hand, mostly, because some parts of it are moving on the proximal side
of the hand. However, because of separate movements of fingers and joint, the area
of motion may be bigger than in most of existing solutions.
The device is small and light, which is good for transportation. However, it
has to be extended with a different sizes of gloves for different patients, and different
sets depending on which hand is affected, left or right.
The device uses only electric elements, which are possible to use at home.
Moreover, the device offers 3 types of task executing: active, passive, and resistive.
The rehabilitation may be more specific for individual patient.
The motors work loudly, what can be annoying for some patients. However,
with shorter arm of rotation, this noise should disappear. The prototype proved
working of the concept and opens a path to future analysis.
The studies were only limited to the test on the healthy person and the model
of the flaccid finger. There is a need of expanding them to post-stroke patients.
Moreover, there was only basic safety test and theoretical analysis of safety done
on it.
59
The system should be expanded with a software, that can collect data
and analyze it. Moreover, there should be a possibility of connecting the patient
and physiotherapist account, so that a telemedicine scheme can be implemented.
Telemedicine could lead to better feedback than in traditional rehabilitation. The
software may be expanded by regular games and VR system, what could lead to
higher involvement in the rehabilitation process. The thumb system should be added
to rehabilitation.
All mentioned improvements are possible to be added in the future works.
5. Conclusion
The main objective of this thesis was to design the robotic device for a hand
rehabilitation of the post-stroke patients. The device should be useable at home
without direct supervision of physiotherapist.
In the first part of the work, the aftermaths of stroke were presented. It was
proven that the hand rehabilitation is very often neglected, what leads to spasticity,
while the proper rehabilitated flaccidity in the first 4 weeks may increase recovery
of normal functioning of the hand. Next, the healthy hand movement was discussed
and compared to flaccid one. It is worth reminding, that post-stroke patient very
often struggle with joint instability, which is consequence of low tension
in the muscles. This aspect was taken into consideration in the designing process.
Some existing solutions of the robotic device for a hand rehabilitation were
presented and deeply analyzed. Almost all listed devices had a common issue
of strongly simplified movement of the fingers. Only the solution developed
by Polygerinos recreates movement of the fingers similar to the biological one.
All the devices help in a grip strength recovery, but only two of them, in theory, could
be used at home. Unfortunately, no research have been done yet in this area of usage.
Next, the guidelines for designing of a robotic device were defined. This part
helps to understand how the rehabilitation device should work, to give the best effect
on recovery process. Firstly, the main focus was put on creating a device that could be
used by the patient at home. Then, some mechanical factors as a range of motion,
frequency of movement, and forces acting on the finger were characterized.
With all collected knowledge, the concept of the rehabilitation device was
created and a first prototype was built. This prototype was used to verify work
of the concept. The concept was verified with a positive results and the 3D model
of the device was designed. The device has a shape of the box, that can be placed
on a table. Interior of the device has a glove with wires connected, that are pulled
by the servo motors and the springs. By controlling movements of the motors, fingers
are forced to flex and extend. For data collection, strain gauges were used.
All necessary calculations were done and proper element selection was made.
Based on the designed model, a prototype was built. It is limited to two joints
on the index finger, what is enough to test the control system and the task execution
of the prototype. For checking the control, three modes of control were created:
60
passive, active and resistive. For the motor control the PWM signal generator was set.
Moreover, a program to read values of the strain gauges was created.
The last task was to test and study the work of the device, and verify the quality
of task execution. Firstly, the device was calibrated, starting from the range
of movement. Then thresholds of strain gauges were set. After full calibration,
all modes were tested with use of the mechanical flaccid finger and a healthy hand.
The results of this work were satisfying. The aim of this thesis was to cover
the niche in home-use devices for rehabilitation. However, further researches
in the area of rehabilitation devices should take into account moving rehabilitation
process from the rehabilitation centers to the patients home. Nevertheless,
the created device is not free of defects, however with future development it can
be improved.
From all the listed examples the soft glove made by Polygerinos seems to have
the biggest potential to become major device used in the hand rehabilitation.
However, solution presented in this work, thanks to the adaptation to home
environment and a possibility of giving proper feedback of recovery process, can
be a great alternative for the traditional rehabilitation and represent a meaningful
step in the future design of the robotic rehabilitation devices, by showing potential
of a home therapy.
61
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