study of legs' sensorymotor asymmetry using a lower-limb rehabilitation robot

Study of leg’s sensorimotor asymmetry using alower-limb rehabilitation robot :

The LegoPress

Chouaieb Nemri

[email protected]

https://www.linkedin.com/in/nemri

Department of Electrical and Control Engineering Robotic Systems LaboratoryENSEEIHT EPFL

September, 2014

Chouaieb Nemri (ENSEEIHT – EPFL - LSRO)Study of leg’s sensorimotor asymmetry using a lower-limb rehabilitation robot :September, 2014 1 / 34

Outline

1 IntroductionThe LegoPressFlexCOM

2 Study of sensorimotor asymmetryPrevious studiesStudy of lower-limb sensorimotor asymmetry

3 Control design and implementationLeg weight compensationPosition MatchingElastic MatchingEffort Matching

4 ResultsPreliminary observations

5 Conclusion


Introduction The LegoPress

Outline





5 Conclusion



Overview

Simple and cost-effective lower-limb rehabilitation device.

Figure: CAD view of the legopress

Adjustable sitting position - 2 separate motorized axes.



Axis elements

Figure: CAD view of one axis

Figure: schematic view of the axis elements



Force transducer

Precise force monitoring can be done by means of force sensorspositioned at the pedal level.

Figure: CAD view of the force sensor


Introduction FlexCOM

Outline





5 Conclusion


Introduction FlexCOM

PC-based motion control solution

PC-based open architecture with minimum time development

Adapted to different type of robots: serial (cartesian or not) orparallel.

Microsoft windows : Standard development software - standard PCIinput/output.

Real time capabilities guaranteed with RTX extension.


Study of sensorimotor asymmetry Previous studies

Outline





5 Conclusion



Previous studies

Movement, an essential way we have to interact with the world.

Sensorimotor asymmetry has been shown in upper limbs for righthanded people.

Findings are strongly supported by the following dual-linear model

Figure: Dual-linear model of sensori-motor feedback loops of each limb

Quantifiying asymmetries in the lower limbs.



Previous studies

Movement, an essential way we have to interact with the world.Sensorimotor asymmetry has been shown in upper limbs for righthanded people.

Findings are strongly supported by the following dual-linear model





Previous studies

Movement, an essential way we have to interact with the world.Sensorimotor asymmetry has been shown in upper limbs for righthanded people.Findings are strongly supported by the following dual-linear model




Study of sensorimotor asymmetry Study of lower-limb sensorimotor asymmetry

Outline





5 Conclusion



Objectives

The study aims to assess and understand lower-limb asymmetriessensorimotor origins.

To this end, an experimental protocol featuring postion and/or effortmatching tasks has been designed.



Experimental set up

The LegoPress

Reference position : 90 degree knee flexion

Target position : 120 degree knee flexion

Target force : 20% of the maximum voluntary exertion (MVE)



Experimental tasks and conditions

Position and/or effort reference is performed by the reference leg andthence, participants are asked to perform matching with the same oropposite leg.

Different Matching conditions



Experimental tasks and conditions

18 possible combinations


Control design and implementation Leg weight compensation

Outline





5 Conclusion


Control design and implementation Leg weight compensation

Leg weight compensation

The horizontal effort is measured every 20 mm along our experimentsuseful portion of the axis range (10 mm to 290 mm).

4th Polynomial regression has been used to identify the model

Figure: 2nd degree polynomial regression is insufficient


Control design and implementation Position Matching

Outline





5 Conclusion



Position matchingAdmittance control

Admittance control : Pedals move proportionally to the activelyapplied force magnitude.

Figure: Block diagram of the admittance controller




A deadzone has been introduced to overcome model’s imperfections(threshold = 10% of passive forces)




The controller laws can be descibed as follows:



Position matching algorithmAdmittance control


Control design and implementation Elastic Matching

Outline





5 Conclusion



Choice of control paradigm

Proportional position controller

Unaccurate restoring force

Admittance based spring behaviour

Unstable behaviour for low stiffnesses



Impedance based spring

Block diagram of the controller

The controller equations are the following



Elastic matching algorithm


Control design and implementation Effort Matching

Outline





5 Conclusion



Effort matching

During effort matching tasks, the pedals are simply position-controlled

The pedals are fixed in the 120 degree knee extension position.



Effort matching algorithm


Results Preliminary observations

Outline





5 Conclusion


Results Preliminary observations

Preliminary observations

Data has not been fully processed

In ipsilateral condition, position matching is more accurate with theleft leg.

No overshoot (resp. undershoot) trends when the right (resp. left)limb is matching the opposite limb’s reference.

Analysed data is not sufficient enough to make us draw soundconclusions.


Conclusion

Conclusion

An experimental protocol featuring position and/or effort matchinghas been designed in order to assess sensorimotor lower-limbasymmetry.

We run the experiments with 6 right-legged and one left-legged youngunimpaired participants.

During position tasks, the matching pedal is admittance controlled.While during elastic matching, the controller behaves as animpedance.

Future work, will focus on processing and thoroughly analysingthecollected data.


Appendix References

References I

J. Olivier. M. Jeannaret. M. Bouri. and H. BleulerThe LegoPress : A rehabilitation assessment and performance device -Mechanical Design and Control.LSRO -EPFL adfa, p. 1, 2011. Springer-Verlag Berlin Heidelberg 2011

M. Bouri. and R. ClavelA windows PC-based robot controller - An open architecture.ISR, Tokyo, Japan, November 29 - December 01, 2005

D. .E.Adamo. and B.J. MartinPosition sense asymmetry.Exp Brain Res DOI 10.1007/s00221-008-1560-0

D. .E.Adamo. S.Scotland and B.J. Martinasymmetry in grasp force matching and sense of effort.Exp Brain Res (2012) 217:273-285 DOI 10.1007/s00221-011-2991-6


Appendix References

Acknowledgements

Questions?


study of legs' sensorymotor asymmetry using a lower-limb rehabilitation robot

Engineering

cad view

schematic view

open architecture

different type of robots

serial cartesian

microsoft windows

real time capabilities

rtx extension