chapter 8 texas a&m university · em or english saddles, and special riding equipment is...

CHAPTER 8TEXAS A&M UNIVERSITY

College of EngineeringBioengineering Program

College Station, Texas 77843-3120

Principal Investigators:

William A Hyman (409) 845-5532Gerald E. Miller (409) 845-5532

101

102 NSF 1993 Engineering Senior Design Projects to Aid the Disabled

Horsemanship: Equipment for TherapeuticHorsemanship

Designer: Laura KleenClient Coordinator: Jean Green

Texas A&M University 6 EQUEST Therapeutic Horsemanship (Dallas)Supervising Professors: Drs. W.A. Hyman, G.E. Miller, 1. W. Evans*

Bioengineering Program*Department of Animal Science

Texas A&M UniversityCollege Station, TX 77843-3120

INTRODUCTIONA series of designs are available to facilitate horsebackriding by individuals with a variety of disabilities as aconsequence of this design project. These designs arein use at the Texas A&M Therapeutic Riding Programand at EQUEST. The designs are a Biding Surcingle, aPortable Mounting Block, and prototype designs forAmputee Saddles. The Biding Surcingle (Figure 8.1)consists of a padded leather form with three leathercovered rope handles. This form is attached to thehorse by a western riding style girth and latigos. Thissurcingle is tightened into place over a riding pad to

provide extra cushion for the rider. The MountingBlock (Figure 8.2) consists of a ramp and platformbuilt on an axle and a set of wheels. The bottom partof the ramp can be flipped back in order to attach atongue and hitch, allowing the mounting block to bemoved as a street legal trailer. A set of steps is alsoprovided to allow a helper to assist mounting from theopposite side of the horse. The Amputee Saddledesigns are mockups for use by rider’s missing one orboth lower extremities.

Figure 8.1. Surcingle.

Chapter 8: Texas A&M University 103

Figure 8.2. Mounting Block.

SUMMARY OF IMPACTTherapeutic riding programs have been initiatedthroughout the world as a new form of physical ther-apy. The horse is used as a treatment modality muchas therapy balls, bolsters and other equipment areused in the physical therapy clinic setting. Individualswho have benefited from therapeutic riding includethose who are visually, hearing or speech impaired;those with learning disabilities; and those who are se-riously emotionally disturbed, mentally retarded ormulti-handicapped. The basis for the beneficial effectof horsemanship varies with the needs of the rider.Physically, the horse’s motion imparts a smooth andrhythmic input to the rider. This movement, coupledwith the warmth of the horse, is thought to be usefulin reducing high muscle tone and promoting relaxa-tion in rider’s with spastic cerebral palsy. Riding canhelp to decrease fear of movement and reduce hyper-tonicity, while also requiring controlled contraction,joint stability, weight shifting and postural and equi-librium responses. The horse can also elicit a strongemotional response in many riders, and correspondingdesire to reach riding goals. Much of the basis forthese observations is presently anecdotal. One of theobjectives of the association between Texas A&M and

EQUEST is to investigate these benefits in a more rig-orous manner.

Equipment used in most therapeutic riding should notinterfere with the rider’s balance, movement or contactwith the horse. Some riders do not have enoughstrength in their leg adductor muscles to sit securely ina regular saddle. Riders with spastic Cl’ must nothave their leg’s forced into position in the saddle inorder to avoid undesirable muscle reflexes, althoughafter mounting the warmth of the horse reduces thesereflexes. Riders with postural problems may also beexcessively challenged by standard equipment. Forthis reason, many riders should not use normal west-em or English saddles, and special riding equipment istherefore required. The completed surcingle and pre-liminary amputee saddle designs address these typesof needs.

Mounting the horse can also present significant prob-lems to the rider and their attendant. Permanentramps and platforms can be provided at fixed loca-tions. However in some settings, and for specialevents, a portable and road worthy system is desir-


able. The portable mounting block described here ad-dresses this problem.

TECHNICAL DESCRIPTIONSurcingle.. The surcingle designed here is a replace-ment for another surcingle that had a single, hardhandle. This handle allowed only one hand position.In addition, it had frequently injured riders who losttheir balance and fell forward into it. Some riders hadalso deliberately banged their heads on it during selfabusive behavior. Other special purpose surcingle(e.g. bareback riding, lounging, vaulting) did not ad-dress the goals of the new design, which are to not in-terfere with the rider’s legs, to provide multiple softhandles that are at an easy grip height, to not slip sideto side when the horse moved, and to provide a ringfor an over rein that is used to keep the horses headup, and prevent the rider from feeling that they aregoing to be pitched forward. The leather form wasapproximately 7” wide and 2’ feet long. It is paddedwith artificial sheep skin to protect the horse. Threehandles, each 6” long and 4” wide, are attached to theform. The handles are made from manila rope cov-ered in thin leather. An 0 ring is sewn onto either sidein order to attach the latigos and girth. Two latigos areused so that the surcingle is adjustable from eitherside. Future modifications to the surcingle may in-clude the addition of detachable and adjustable stir-rups. This will allow beginning use of stirrups with-out requiring a saddle. The surcingle was initiallytested by the designer who is an experienced rider.The handles are at a comfortable height and allowedvarious hand positions. There is no interference withthe rider’s legs and sideways slippage was no morethan l/2”. Actual fabrication of the surcingle was by asaddle maker at a cost of $110 for materials and labor.

Mounting Block.. The requirements for the mountingblock are (1) portability, (2) able to hold up to 650 lbs(three adults and wheelchair), (3) as light as possible,(4) 3’ high platform large enough to maneuver awheelchair, (5) a 12’ ramp , (6) a 3’ railing on bothramp and platform, and (7) 3’ auxiliary steps. The unitis built on a 1500 LB axle and two 14” wheels. Theramp’s bottom is 4’ by 5’ and is attached to the remain-ing 8’ (by 6’ wide) of ramp by a pipe hinge. The plat-form is made of treated 2” by 6” pine and is 5’ by 6’ and

3’ high from the ground. There is a 1” square tubeacross the back of the platform which serves as awheelchair stop. The detachable hitch is 48” wide and42” long. A standard ball hitch is attached to a piece ofheavy pipe. Three-inch channel iron braces on eachside of the tongue, which is attached with 8 bolts to theplatform frame. A 3’ railing runs the length of the up-per ramp and platform. The platform is stabilized inuse by heavy duty jack stands in each comer. Thesejacks also allow use on uneven ground.

To haul the mounting block, the bottom portion of theramp is flipped up and the hitch attached. The front isthen raised with the jacks so that a vehicle can bebacked into place. All jacks are then raised.

Rear lights are provided on the platform for use intrailering. The light-weight separate-steps for use onthe opposite side of the horse, are constructed from anangle iron framework and 2” by 6” steps, with a handrail and 3’ by 4’ platform. The steps can be loaded ontothe mounting block for transport.

Professional assistance was required to construct thisproject and to assure that it could be legally hauled asa trailer. The total cost for parts and equipment rentalwas $1052. The labor was donated.

Amputee Saddles.. The basis for the saddle designs isan adaptation of the side saddle, where the saddle treeis altered to provide leg support. Padded outgrowthin the front and rear of the saddle and on the side ofthe missing limb is proposed to provide front to backstability. Straps with quick release buckles are used atthe top and lower part of the thigh for additional helpin staying in the saddle. This provides side to sidestability that is normally provided by the rider’sweight being carried in the heels. In the case of an ac-cident, the buckles allow a quick, manual release of theleg from the saddle. A modified saddle tree wouldalso be required, and weight balancing should beprovided. A sketch of these modifications is shown inFigure 8.3.


FR

STRAPS

Figure 8.3. Sketch of Amputee Saddle Design. x


Exercise Therapy: Equipment for Pediatric ExerciseTherapy

Designers: Matt Collier and Kenneth WhitleyClient Coordinator: Greta Cheery

United Cerebral Palsy of Greater HoustonSupervising Professors: Drs. W.A. Hyman, G.E. Miller

Bioengineering ProgramTexas A&M University

College Station, TX 77843-3120

INTRODUCTIONTwo exercise devices are described which are pediatricversions of common equipment. One is the pediatrack(Figure 8.4), which is similar to a scaled down andsimplified Nordictrac. It provides for a skiing typemotion, with fixed arm positions, for use by children3-6 years old. Two plastic adjustable skates providethe foot contact, and a pulley-cable system forces theskates to move in opposite directions on a wood guideand base. The second device is a pediatric stepper(Figure 8.5). This device is a low and variable resis-tance, low impact machine designed for use by youngchildren in developing leg muscles. These devices arebeing used in the physical therapy department at theclinics of the United Cerebral Palsy of Greater Hous-ton.

Figure 8.4. Pediatrack.

SUMMARY OF IMPACTThe design requirements are presented as the need forsmaller and lower resistance versions or variants onwell-known exercise equipment that was too difficultfor the clients of the UCPGH to use in their exercisetherapy programs. Although both aimed at the lower

extremity, these two devices complement each otherby exercising the muscles of the legs in different ways,and by requiring different directions of motion andcoordination. These devices are currently in use witha variety of children and judged by the therapists to beeffective.

Figure 8.5. Stepper.

TECHNICAL DESCRIPTIONPediatrack.. The base is constructed of 2” thick pine.Two + ” deep grooves + ” apart provide guides for theskates with a 2’ range of motion. Two + ” deep holesare present to hold the pulley’s mount shafts. Theskates used are Tyco No. 57 Roller Skates. Plasticcoated $- ” diameter steel cable is run through eachskate above the front axle and secured with U clamps.Two 5” diameter by $ ” nylon roller bearings sheavesare used in the pulley system. The arm railings are 16”in height and are constructed of 5 ” PVC pipe. Aschematic of the system is shown in Figure 8.6. Thetotal cost of the device was about $50.

Chapter 8: Texas A&M Universitv 107

Stepper.. The stepper is made of pie with metal rein-forcement and bracing. It has a 2’ by 10” base with twovertical sides 1 f ’ tall with a horizontal top. The stepsare hinged at one end using metal door hinges. Eachstep is suspended from the top piece at their center bytwo springs. The two springs are fastened to the stepat two different points to distribute the spring load.The springs can be changed or their rest positionmoved to alter the resistance. A pulley is also sus-pended from the horizontal top piece. A metal cordstretches from one step, over the pulley, to the otherstep. This assures an alternating stepping motion.

-

The length of the cord can be changed to adjust theheight of the steps. The top surface of each step is cov-ered with non-slip bathtub strips. To use the stepperthe child stands with one foot on the free end of eachstep. As weight is put on one foot, that step goesdown and the other step is raised. Shifting weight tothe other foot, the corresponding step goes downwhile the other step again is raised. The exercise con-tinues in this fashion. This device was built for ap-proximately $20.

1”OD xM ” dp

1”OD steel Pullev Mount Base

dia. thru

_I (2ea.)l/8” thick aluminum

J

Figure 8.6. Pediatrack Components.


Foot Steps: Responsive Foot Steps for Pediatric GaitTherapy

Designer: Chris SellersClient Coordinator: Greta Cheery




INTRODUCTIONThis project is specified as a series of foot step targetsthat would produce audible feedback when steppedon by a subject, used at United Cerebral Palsy ofGreater Houston as part of gait training for childrenwith cerebral palsy. The system consists of a xylo-phone circuit encased in a metal box, pressure sensi-tive switches inside circular pads, amplified speakers,and connecting wires. Each pad is individually placedon the floor. When a pad is stepped on by the subject,an internal switch closure produces a correspondingtone from the xylophone circuit. The pads are easilyrelocated, and the whole assembly is easily moved orstored.

Figure 8.7. Foot Step System.

SUMMARY OF IMPACTMany children with cerebral palsy do not have com-plete muscle control of their legs. Thus, ambulatorytherapy is a common treatment modality. This treat-ment, when applied to young children, is significantlyimproved if mentally stimulating feedback is alsoprovided for the child as the exercise is performed.This improves motivation to perform the exercise, and

increases the duration over which exercise will bemaintained. The system described here provides vari-able musical auditory feedback as each step is taken,thus meeting this goal. The system is in current use atthe UCPGH.

TECHNICAL DESCRIPTIONThe foot steps are designed for children with CP whoare between the ages of two and five. The primary re-quirements are: (1) the system had to produce pleasantauditory feedback for each successful step, (2) the padshad to be movable, (3) the pads had to be visually at-tractive to stimulate targeting, and (4) the system hadto be portable for transport to outreach centers and forstorage. The system has four main components: thexylophone circuit inside the metal enclosure, the footswitches, the connecting wires, and the speakers. Thefront of the box contains connectors for the switches.The back of the box has a connector for the speakers.The xylophone circuit has 11 pins plus battery, andspeaker connections. Pins 1-5 and 7-11 produce indi-vidual sounds, while pin 6 is the common ground.Zip wire is used to run from the box to the switchpads. This wire can be easily taped quite flat to thefloor, thereby eliminating it as a trip hazard or im-pediment to walking in the area. The switch pads usenormally open pressure sensitive switches, manufac-tured by TapeSwitch. These switches close at 2.5pounds of force. The switches are enclosed in a largertarget mat. The design of appropriate switch mats is akey component of the project, as they had to be lowforce and low profile to prevent tripping, yet easilymovable. The latter requirement precluded the use ofa walkway surface with embedded switches. Externalself-amplified speakers are used for strength and clar-ity of tone. A schematic of the xylophone circuit isshown in Figure 8.8. The system was tested for reli-ability of switch closure and durability before being


deployed at UCP. The system cost approximately$150.

speakerspeaker batterybattery

Ixylophone cktxylophone ckt

J

11s4 -s4 - 1111 - s9- s9s3 -s3 - IAIAI”I” 22s2 -s2 - nn

77 - s8- s8sl -sl - QQ 22”” d -d - - s7- s7

QQ AA”” .. 11 - s6- s677 E;E;

u’u’ - s5- s5soSO 77 Q _Q _ - sl- sl66

s=sounds=sound groundground

Figure 8.8. Circuit Diagram for Foot Step System.


Multisurface Walkway: A Multisurface Walkway forChildren

Designers: Lindy JordanClient Coordinator: Greta Cheery




INTRODUCTIONPediatric physical therapy at the clinic of the UnitedCerebral Palsy of Greater Houston includes a varietyof mobility objectives, each requiring separate items ofequipment, yet forming an integrated whole with re-spect to the spectrum of therapy required. Describedhere is one of several mobility projects, a multisurfacewalkway. This walkway provides four different typesof surfaces, on four separate units that can be attachedto each other in a variety of configurations. This pro-vides a controlled environment for the development ofwalking skills.

Figure 8.9. Multisurface Walkway.

SUMMARY OF IMPACTMany children with cerebral palsy lack the muscle de-velopment and coordination required to stabilizewhen moving from one type of walking surface toanother, and for walking easily and confidently on avariety of textures. This walkway provides four dif-ferent surfaces, with the required transition from oneto another. The surfaces vary from very soft, to me-

dium soft, to smooth hard and rough hard. These rep-resent such normal environmental surfaces as softmud or sand, grass, tile or concrete. The walkway in-cludes removable hand rails for additional support asrequired. The sections of the walkway can be ar-ranged in a variety of patterns. This system is cur-rently in use at UCP and has been found to be benefi-cial and to meet the objectives of the therapists inworking with their clients.

TECHNICAL DESCRIPTIONThe primary design requirements for the walkway are:(1) it had to be mobile so that it could be transportedfrom indoor storage to outdoor patio use (limitedspace prevented continuous deployment), (2) it couldnot exceed twelve feet in length because of storage re-quirements, and (3) the surfaces had to be reasonablyrealistic and present a challenge to the children usingit. The sections are of three shapes. Two are 18” by 36”rectangles. One is a 18” by 30” by 30” L shape. An-other is a 18” by 36” by 36” curved shape. Dimen-sioned diagrams for each part are given in Figure 8.10.Each piece consists of a support base made from ply-wood and 2” by 4” lumber. To transition to the surfacefrom the ground a two-step unit with approximately9” treads with 2- ” risers is provided. A ramp unitapproximately 23” inches long is also provided. Thefour surface materials are tile, sponge, indoor/outdoorcarpet, and flex stone, each attached to the plywoodsurface with an appropriate adhesive. Support railsfor both sides of each unit are made from $ ” schedule40 PVC pipe. They are set at a height of 21”, and at-tached to the surfaces through holes. Each unit alsohas rollers to facilitate moving them. The units can beconnected to each other using door hinges with re-movable hinge pins. The total cost of the system is$150.


(two> 1

30”I

12” / 1 ”

30”

Figure 8.10. Dimensions of Units for Multisurface Walkway.


Crawlway: An Adjustable Transparent Crawl Rampfor ChildrenDesigner: Anne Marie Chard

Client Coordinator: Greta CheeryUnited Cerebral Palsy of Greater Houston

Supervising Professors: Drs. W.A. Hyman, G.E. MillerBioengineering ProgramTexas A&M University


INTRODUCTIONIn order to provide visual stimulation during crawl-ing, the therapists at United Cerebral Palsy of GreaterHouston requested a transparent surfaced, adjustableangle, ramp with an underlying mirror. The resultantdevice (Figure 8.11) allows the children to see them-selves while crawling, thus adding enjoyment to thecrawling task.

SUMMARY OF IMPACTAs with many projects developed for the therapists atUCP, the objective here is to combine an exerciseregimen with stimulating feedback to the child to in-crease their motivation and extended compliance withthe therapy task. In this case, the system provides ahighly attractive and versatile device that includes theparticular feedback of seeing oneself in a mirror. Thismakes the crawling endeavor highly amusing. Thisdevice is in daily use with children up to three yearsold in the physical therapy program at UCP.

TECHNICAL DESCRIPTIONThe ramp consists of a plywood base which supports awooden frame constructed from two-by-fours. Theouter dimensions of the frame are 3’ by 6’. The bottomof the frame is hinged at one end so that the frame canbe raised or lowered at the other end. There are handholds in the bottom of the free end so that the therapist

can more easily control raising or lowering, and toprotect the user’s hands from inadvertent dropping ofthe frame. All of the wooden surfaces are finely fin-ished and painted. The ramp is held in the up positionby two metal bars which are rotated from a horizontalto a vertical position to support the raised surface. Inthe up position the ends of the bars fit into PVC endcaps mounted to wooden blocks. In the down positionclasps are provided to secure the frame to the base.This is helpful if the unit is tipped to the side formoving or storage.

A Plexiglas mirror is enclosed in the bottom frame andrests flat on the plywood base, secured by molding.Plexiglas was chosen for breakage resistance. The topof the frame, where the children crawl, is surfacedwith 3/8” transparent Plexiglas. A wooden cross bracehelps support the Plexiglas at the midpoint of theframe. This system is more than strong enough tosupport the weight of the intended users. A warninglabel is provided which reads “WARNING: 50 poundweight limit” to discourage adults from stepping onthe ramp. However, even if persons weighing signifi-cantly more than 50 pounds were to do so, it wouldonly result in cracking the Plexiglas, without present-ing a significant risk of injury. A 9” tall PVC railingwas provided so that children will not crawl off thesides or end of the ramp. An additional lower rail hassince been added since 9” proved to allow too large agap.


Figure 8.11. Transparent Surface Crawlway.


Door Opener: A Wheelchair Triggered Door Openerfor a Private Home

Designer: John LaughlinClient Coordinator: Beth Roberts

Franklyn Independent School DistrictSupervising Professors: Drs. W.A. Hyman, G.E. Miller



INTRODUCTIONThe design described here is a wheelchair triggeredfront door opener for a private home. The device isdesigned for a fourteen-year-old girl with musculardystrophy who is confined to a wheelchair, and whoreceives her schooling at home. Limited upper ex-tremity ability precluded the use of touch switches.Therefore floor mats which could be rolled over wereselected as the triggers. It was also required that theswing arm not interfere with normal manual use of thedoor.

Figure 8.12. Installed Door Opener.

SUMMARY OF IMPACTBeing wheelchair dependent, and receiving herschooling at home, has presented challenges with re-spect to developing this client’s sense of autonomy.The ability to exit from and return to her home by her-self can therefore be a significant milestone that in-creases the scope of her everyday world, and reducesher dependence on family members. This system wasinstalled at her home and is in daily use. It comple-ments other projects completed for this client, which

have included custom switches for operating herschool computer.

TECHNICAL DESCRIPTIONThis project consists of two main parts: the controlelectronics, and the swing arm and motor assembly.The control electronics begins with two pressure sen-sitive floor mats wired in parallel. When either mat istripped, a mechanical timing relay is triggered. A 555timer circuit is used to debounce the signal from therelay. The output from the 555 was set for approxi-mately 6s so that the input from the back wheelswould be ignored. The output is inverted using atransistor configuration, and then used as the clocksource for a 7473 JK flip flop. Each clock pulse affectsthe state of the door opener as shown in Figure 8.13.Magnetic door contact switches are used to determinewhether the door is open or closed. The signal fromthe open position and the Q output from the flip flopare NANDed together, as are the closed positionswitch and the Q output. The output from the NANDgates are fed into a current sink that operates two re-lays controlling the power to the motor, and its direc-tion. Induced back EMF from the motor proved to bea significant design problem. Capacitors are used atall of the Vcc terminals to filter out this source of noise.All wires were shielded, and all relays are isolatedfrom the logic circuit with optical isolators. The tran-sistor invertor is used to keep the clock input of the JKflip flop at ground potential. The system is alsoequipped with a reset button that brings it to theclosed door state. An on/off button is provided forthe motor power. The motor and the control electron-ics are powered from a standard 120-V, plug-in sourcein the house. The motor drives a swing arm thatpushes on the unlatched door from the push side ofthe door. The door end of the push arm is equippedwith rollers. With this configuration, manual use ofthe door pushes it away from the swing arm and


therefore the swing arm is uninvolved in manual use. swing arm can be easily detached from the motorIf the system were to fail in the door open position the Shaft.

opening

1 1 1 0 1 opening

Figure 8.13. Logic Table for Door Opener.

Figure 8.14. Schematic for Door Opener.


Exercise Table: A Customized Exercise TableDesigner: Anne Marie Chard

Client Coordinator: Beth RobertsFranklin independent School District



INTRODUCTIONThis project involved the design of a customized exer-cise table for a 12-year-old girl who suffered fromoxygen deprivation during her birth. She is able tostand with support and can walk with moderate assis-tance. She cannot talk or feed herself. A multi-purpose rehabilitative exercise program was pre-scribed; the table described here is designed to meetthe objectives of this program, which include strengthand range of motion for various joints and musclegroups. The therapy is carried out by therapists andthe child’s mother. The finished device is shown inFigure 8.15.

Figure 8.15. Exercise Table.

SUMMARY OF IMPACTThis exercise table is currently being used to increasethe child’s flexibility and build strength. The angleadjustment of the top allows a variety of sitting posi-tions, with variable flexion at the hip. A partially sup-ported standing position is also provided. Therabandexercise bands can be attached to the table edge at sev-eral points to provide active exercise. The table canalso be changed as the child grows. It is expected thatuse of this table will provide a measurable improve-ment in body flexibility and strength.

TECHNICAL DESCRIPTIONThe initial design process required discussions withthe therapist with respect to what positions and mo-tions had to be accommodated in the design. Themetal frame is made from square iron tubing, weldedas necessary. The legs telescope so that the height ofthe table can be adjusted from 30” to 37”. The table is24” tall without the lower legs. The legs at one endhave polyurethane locking wheels, with ball bearingsto facilitate movement of the table. The other legshave height adjustable gliders to allow for leveling.The metal frame supports the upper wooden portionof the table. The metal portion is finished with Rust-Fix, primer and paint. The wood + ” plywood top issupported by a wood frame which is constructed oftwo-by-fours. All exposed wood is smoothly sanded,with rounded edges and finished with polyurethanevarnish. The frame is attached to the base with screws.One end of the top can be raised and lowered, andfixed at angles of approximately 20,40,60 and 80 de-grees. Bent aluminum tubing supports the top withself locking stainless steel pins used to fix it at the de-sired angle. Slots are provided for attaching Thera-bands with accompanying handles. Hand holds areprovided to facilitate lifting the top. A hand stop wasadded to provide protection when the top is lowered.The other end of the top is composed of several sec-tions that can be arranged in a variety of ways. Thesesections rest in a groove cut into the side beams andare held in place by locking bolts. Figure 8.16 showsthe three major arrangements of the sections. In “A”this portion of the top is continuous and flat. In “B”the user’s legs can hang over the end with the backeither raised or flat. In “C” there is a space for the userto stand, with the angled portion either flat for a hori-zontal work surface or raised for an easel-like surface.The pads are made from 1” thick-covered foam. Theyare sufficiently flexible to conform to the various posi-tions and uses of the top. The top is secured withstraps and snaps. A removable seat belt is also pro-


vided. The total cost of the system was approximately$280.

Usage A

Usage B

Usage C

Figure 6.16. Various Arrangements of Top of the Exercise Table.


Laser Pointers: Second-Generation Head-MountedLaser Pointers

Designers: Shem Isukh, Orlesia DurenFort Worth State School, Texas Department of MHMR; and




INTRODUCTIONA variety of non-verbal individuals can use ahead-mounted light pointer as a communication de-vice. Older versions of this technology used incandes-cent lights that have drawbacks associated with powerconsumption, heat, and focusing. Texas A&M haspreviously reported on the adaptation of laser pointersfor head-mounted use. These provide a bright andsharply focused spot over a wide range of distances.This allows close pointing, as on a communicationboard, as well as distant pointing and activation of la-ser light sensitive ESU receivers such as those reportedby us in 1992. The laser unit we have used was a cyl-inder approximately + ” in diameter and l$ ” long.This was attached by coiled wire to a batterypack/power supply. Although rugged and quite ef-fective, this unit was slightly heavy for some applica-tions. It was therefore desired to design a new devicein which the laser diode could be separated from thedriver circuit, so that only the diode, lens and heat sinkwould have to be head mounted. Two such designsare presented. Each maintains the Class II output re-quired for maximum safety.

Figure 8.17. A Laser Pointer.

I

Figure 8.18. Another Laser Pointer.

SUMMARY OF IMPACTThe new designs are an improvement over our origi-nal model, which has been one of the single mostpopular devices we have designed, resulting in theconstruction of multiple units following the prototype.The subsequent units were provided at cost. The ad-vantage of the new unit is that the head-mounted por-tion of the unit is much lighter and smaller. Thiseliminates some problems with excess weight causingglass-mounted units to slip. Construction of the newunits is somewhat more labor intensive since more as-sembly is required.

TECHNICAL DESCRIPTIONTwo approaches were taken, one using a pre-builtdriver circuit, and one in which the driver circuit wasconstructed at the component level. Use of the pre-built driver circuit (Meredith Instruments LDP-214)was straightforward, involving soldering a three-leadwire between the diode and the circuit board that wasmounted in a remote box with the battery and powersupply purpose (Figure 8.19). The diode (VLD151)was mounted in a collimating lens intended for this

Chanter 8: Texas A&M Universitv 119

(Figure 8.20). This approach cost about $100, roughlyequally divided between the diode, the lens and thedrive circuit. The component level design is shown inFigure 8.21 using a TOLD 9200 diode and appropriatecollimating lens. In terms of parts cost this approachsaved about $30 since the drive circuit was built forabout $5. In addition the component level design isrepairable if necessary.

LASER DIODE IWHITEBLUE, LDP-214

Y E L L O W ,

PHOTODIODE RED BLACK+-

4V TO 13V I

Figure 8.19. Board to Diode Wiring for Laser Pointer.

HousingRetaining

$%

LaserDiode Assembly

Figure 8.20. Screw Housing Collimating Lens for LaserPointer.

Switchr .125A FLJSE+=9v

Laser diode Laser diode

TOLD 9200LASER DIODE

Figure 8.21. Component Level Design and Push-On Collimating Lens for Laser Pointer.


Laser Keyboard: Laser Pointer-Operated MusicalKeyboard

Client Coordinator: Kathy MoodyUnited Cerebral Palsy of Greater Houston



INTRODUCTIONA variety of non-verbal individuals use ahead-mounted light pointer as a communication de-vice. Texas A&M has previously reported on the ad-aptation of laser pointers for such use, including a re-port on a second-generation unit in this volume.Head-mounted laser pointers provide a bright andsharply focused spot over a wide range of distances.This allows close pointing as on a communicationboard, as well as distant pointing and activation of la-ser light sensitive ESU receivers such as those reportedby us in 1992. The device described here is a modifiedelectronic musical keyboard where the keys have beenparalleled with a light sensitive circuit. In the currentversion (Figure 8.22), the light receivers are mountedin an attached accessory unit that does not interferewith manual use of the keyboard.

Figure 8.22. Laser Activated Musical Keyboard.

SUMMARY OF IMPACTThe provision of a musical keyboard for use by clientswith limited extremity function has proven to be valu-able in two ways. One is that it serves as an attractivetraining device for familiarization with the use of thehead-mounted pointer. Secondly, it provides a rec-

reational outlet for individuals with limited motor andverbal skills. It can also be useful in integration of theindividual with disabilities into activities involvingother children. In particular, at UCPGH, an effort ismade to involve siblings in activities of the client beingserved in order to build on family relationships.

TECHNICAL DESCRIPTIONThe light sensitive portion of the circuit consists of aphoto transistor and potentiometer. When the laserbeam is incident on the phototransistor, its resistancedrops enough to create a closed circuit that parallels anindividual key input (Figure 8.23). A circuit of thiskind is provided for each key that will be played. Inthe current version, this is a sub-set of the keys pro-vided on the basic unit. The potentiometer is used toadjust the light sensitivity of each receiver. Howeverthe system works best if high incident light levels areavoided such as by shading from overhead roomlights. The attachment of the circuits to each key re-quired finding locations in the base unit where indi-vidual attachments could be made without interferingwith normal use of the keys. Although co~ections

directly to the circuit board were possible, in the unitbeing modified, it was found that it was easier to makeall connections at a ribbon cable junction where thekey inputs were connected to other parts of the origi-nal circuit. A second version of the system is beingdeveloped in which the receiver unit is a separate itemthat can be detached from the main keyboard by aplug. This will improve positioning of the receiver,and increase the utility of the base unit. Alternativedesigns with a pulsed input and frequency sensitivereceiver were considered in order to eliminate sensi-tivity to extraneous light sources. However for theprototype system this was rejected as unnecessarilycomplex. It would also not be compatible with ourexisting pointers. For some users, it might also be de-sirable to have time-delayed receivers so that the inci-dent beam would have to be maintained for a prede-


termined period before the key closed. This wouldavoid inadvertent key activation during searching.This type of design was previously used in some ofour ESU receivers. However this approach was also

rejected for the first model of the keyboard because ofits increased complexity and cost, and its uncertainneed.

CIRCUIT CONSTRUCTED BETWEENTHESE POINTS

/

f

CASIO KEYBOARD CONTROL PANEL

9 REPRESENTS KEYBOARD SWITCH WHICH ACTIVATES NOTE UPON CLOSURE

10K POTENTIOMETERI

EACH KEYBOARD SWITCH IS JUMPED AT EXPOSEDSOLDER JOINTS (SEE EXAMPLE) BY PHOTOCELL

&C ADMmM SULFIDE CELL

CIRCUIT. THE POTENTIOMETER IS TUNED TOTHRESHOLD AT AMBIENT LIGHT CONDITIONS.

(ARCHER--276-118)

Figure 8.23. Schematic of Individual Key Circuit.


Three-Wheel Bicycle: A Three-Wheel Bicycle for aChild with Cerebral Palsy

Designer: Erik Manse11Client Coordinator: Kathy Mennis

Texas Children’s Hospital (Houston)Supervising Professors: Drs. W.A. Hyman, G.E. Miller



INTRODUCTIONA three-wheel bicycle was designed for a child withrelatively mild cerebral palsy. He is nine years oldand has adequate leg strength to walk with the aid of abrace on his left leg. The custom bicycle was re-quested by his physical therapist after unsuccessfulattempts with a normal two-wheel bicycle with train-ing wheels. The latter was not sufficiently stable forthe client, and had the social stigma of training wheels.The new design, shown in Figure 8.24, uses standardfront and middle bicycle parts. An additional framewith two wheels is attached at the rear. With a uni-form painted finish this unit has a favorable appear-ance and can be safely ridden by the client. A stan-dard bicycle safety helmet was supplied with the bi-cycle.

SUMMARY OF IMPACTThe client attends public school and interacts well withother children. It was felt by the therapist, and by theuser, that the bicycle should appear as normal as pos-sible so that the child could fit in well with his friends,and have a bicycle that was attractive to them as well.It was not desired that the bicycle have any specialsupports or aids since the balance and posture re-quired to ride would serve therapeutic goals. Earlyuse demonstrated that some initial difficulty withkeeping the feet on the pedals could be mastered,thereby contributing to further motor skill develop-ment by exercising the flexor muscles in the legs. Thefirst demonstration of the bicycle was a great success,and it is currently being enjoyed by the client.

TECHNICAL DESCRIPTIONThe bicycle was designed for a particular individual,but could be used by others with similar disabilitiesand abilities. The primary design requirements were:(1) good stability, especially given the motor and bal-ance impairments of the user, (2) separate rear axlesfor stable maneuverability, and (3) the appearance of arecreational bicycle suitable for nine-year-old boy.Stability was obtained by using a 24” wheel base forthe rear wheels. This is much more stable than train-ing wheels because of the distance between the wheelsand the fact that the outer wheels are always in contactwith the ground. The wheel structure is also muchmore rigid and durable than training wheels. Theneed for separate rear axles was discovered during aprototype design. It was found that a solid driven rearaxle made the bicycle very difficult to turn, and gave ita tendency to tip over. A differential type rear axlewas considered and a prototype tested using a pur-chased differential. This approach caused consider-able difficulty in mounting all of the rear end compo-nents. Development of this approach was thereforesuspended in favor of testing what ultimately turnedout to be the final design. In the final design only theright rear wheel is driven, while the left rear wheelcoasts. This does not produce a noticeable tendency toveer left, and slight steering corrections maintainstraight line travel. Rigorous testing was conductedby having a variety of small adults ride the bicycleunder varying speeds, turns and surface conditions.These tests provided assurance that the bicycle pro-vided a high degree of stability. A standard bicyclehelmet was provided with the bicycle. The final costof the bicycle was $200, most of which were for parts,welding and finishing.


Figure 8.24. Three-Wheel Bicycle.

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