Flex2Play An ankle strengthening device with virtual reality interface for children with cerebral palsy

Flex2PlayAn ankle strengthening device with virtualreality interface for children with cerebral palsy

October 26, 2011BME 401 Senior DesignMentor: Jack Engsberg, PhDAmanda Meppelink(Presenter), Kelly Hill, Liz Phillips1The NeedA strength training device thatis safe for in-home userequires minimal setup or user trainingis affordableis portablemotivates patient participation

Overview Alternatives Analysis of Designs Chosen Design Our ApproachCP is non-progressive disorder that impairs motor function including gait kinematics and muscle strength

2The ScopeTo design an at-home ankle strengthening device Flex2Play that motivates participation by interfacing therapy with a WiiMote which controls online video games

Overview Alternatives Analysis of Designs Chosen Design Our Approach3Design SpecificationsFull range of motion30 from neutral in DF-50 from neutral in PFProgressive Resistance35 Nm DF torque101 Nm PF torqueAvailable in at least 15% incrementsAffordable $200 targetPortable 8 ft3Virtual Reality Interface2010 BME401 Group Wii Controlled Gaming for Therapy

Overview Alternatives Analysis of Designs Chosen Design Our Approach

20 Dorsiflexion0 Neutral50 Plantarflexion

Plantarflexion=F*d*sin()F=101Nm/(0.28m*sin(90))F=361NDorsiflexion=F*d*sin()F=35Nm/(0.28m*sin(90))F=125N4AlternativesOverview Alternatives Analysis of Designs Chosen Design Our ApproachXXXXEccentric vs Concentric eccentric not ideal b/c external driving force would be moving foot not playing game

5Springs

Overview Alternatives Analysis of Designs Chosen Design Our ApproachLeft: TorsionMiddle: CompressionRight: Extension

Replace springs for one that withstand larger torqueTorsion: Rotary force, internal rod to stabilize, RH wound DF, LH wound PFCompression: Resist load when compressed, DF top, PF bottomExtension: Pull components back to neutral, DF top, PF bottom6PulleysOverview Alternatives Analysis of Designs Chosen Design Our Approach

Use free weights to provide resistanceIn plantarflexion, pulley used to alter direction of forceDF just hang free weightsVary number weights to increase force7LeversConsist of fulcrum, load, and effortMagnitude of effort based on distance from fulcrumOverview Alternatives Analysis of Designs Chosen Design Our Approach

PF --- lever arm frontDF --- lever arm back8MagnetismUse permanent magnet, electromagnet, or combination of bothOverview Alternatives Analysis of Designs Chosen Design Our Approach

Strap into boot with magnets on top and bottom. Rotate around axle aligned with ankle. Frame more magnets positioned to repel boot through entire ROM.Change force by adding or removing magnets.Permanent force drops off exponentially w/ distance. Pairs diminish effect of each other.Electro connect with variable resistor. Strength proportional to current.9MotorsAC MotorIdeal for fixed speed applicationsDC Brushed MotorDC Brushless MotorSpeed controlled by adjusting amount of electrical current

Overview Alternatives Analysis of Designs Chosen Design Our Approach

Side ViewFront ViewStyles of Motors linear, rotary, servo (positive feedback control system)We want rotary servo motor.DC Brushed brushes transfer electrical current from power source to rotating coils.10Elastic BandsElastic bands provide resistive forcetan = extra thinyellow = thinred = mediumblue = extra heavyblack = special heavysilver = super heavygold = max

Overview Alternatives Analysis of Designs Chosen Design Our ApproachDescribe set-upVary band to create different resistances11Criterion for Pugh ChartEssentialCost, Safety, Strength Range, Range of Motion, Ability to Interface with WiiHigh ImportanceDurability, Train Both PF and DFImportantSize, Weight, Ease of Setup, Ease of UseOtherStrength Resolution, Train with Knee Extended, Train More than One DOF

Overview Alternatives Analysis of Designs Chosen Design Our ApproachEssential (10) cost, safety, strength range, range of motion, ability to interface with Wii specified in scopeHigh importance (9) durability, train both DF and PFImportant (8) physical dimensions, weight, ease of setup, ease of useOther strength resolution (7), train with knee extended (5), train more than one DOF (3)DOF consider ability to have inversion/eversion too, but PF and DF main focus, study showed those have much larger contribution to gait12Pugh Chart

Overview Alternatives Analysis of Designs Chosen Design Our ApproachWorst gravitational and magnetism mechanisms scored lowest (700 or lower)Springs and motors did relatively well (scored in 800s)

13Springs Pugh ResultsHigh scoreCost ($1-$24)SafetyStrength RangeLow scoreStrength ResolutionMore than One Degree of FreedomOverview Alternatives Analysis of Designs Chosen Design Our Approach

Cheap costExtension less safe come unattached under compressionTorsion not enough strengthROM a little limitedPoor strength resolution --- each spring one torque value --- ease of use14Motor Pugh ResultsHigh ScoreStrength RangeRange of MotionTrain Both PF and DFLow ScoreVery Expensive ($122-$966)SafetyDurabilityOverview Alternatives Analysis of Designs Chosen Design Our Approach

Very expensiveLess durableLess safe overheatGreat for training both PF and DF, ROM, strength resolution except AC15Chosen Design: Elastic Bands

Overview Alternatives Analysis of Designs Chosen Design Our Approach

Left: Iso ViewTop Right: Top ViewBottom Right: Back ViewFoot stabilization orthotic must be removed and foot placed in neutral position, footplate will be optimized to achieve this, some kids with CP so severe wont be able to do this need to improve ROM in clinical setting before using Flex2PlayWhy this structure chosen minimize size, no interference with Wii, saferKey features TheraBand connections, pivot joint (full ROM), WiiMote to sideNo compressive forces16Flex2PlayOverview Alternatives Analysis of Designs Chosen Design Our Approach

LimitationsDoes not reach maximum PF force valueVariability among patientsResistance forces quantified in clinical studies purpose to assist therapist in creating training regimensSpecs based on 35yrd old healthy malePossible for band to reach max DF force value (125N)With single band can not reach max PF force value (351N) can put more than one onVariability among patients depend if tie band at desired length. Looked into it. Not part of our scope.Solutions skype with therapist while training, come from therapist in already set lengths17Design ScheduleOverview Alternatives Analysis of Designs Chosen Design Our Approach

18Team ResponsibilitiesOverview Alternatives Analysis of Designs Chosen Design Our ApproachLiz ExpressiveFinal PresentationWeb DesignerResearch on Alternative IdeasKelly AnalyticalPreliminary PresentationWeekly ReportsResearch on Alternative IdeasDesignSafeMeet weekly with mentorWrite and revise reportsConduct background researchProvide feedback to group Amanda DriverProgress PresentationSchedule ManagerResearch on Chosen Design19Works CitedAisen, ML, et al. "Cerebral Palsy: Clinical Care and Neurological Rehabilitation." Lancet Neurology 10.9 (2011): 844-52.Boley, B. L. (1997). Overview of Motor Types Tutorial. Retrieved October 23, 2011, from http://www.oddparts.com/acsi/motortut.htmCompression Springs. 23 October 2011. .Dynetic Systems. (n.d.). Brushless vs Brushed. Retrieved October 23, 2011, from Dynetic Systems: http://www.dynetic.com/brushless%20vs%20brushed.htmPinneger, Gavin J and Andrew G. Cresswell. "Residual force enhancement after lengthening is present during submaximal plantar flexion and dorsiflexion actions in humans." Journal of Applied Physiology (2006): 18-25.Simple Machine Elements. 23 October 2011. .The Hygenic Corporation. (2006). Resistance Band & Tubing Instruction Manual. Akron, OH, USA.Torsion Springs. 23 October 2011. .

20Flex2PlayAn ankle strengthening device with virtualreality interface for children with cerebral palsy

October 26, 2011BME 401 Senior DesignMentor: Jack Engsberg, PhDAmanda Meppelink(Presenter), Kelly Hill, Liz Phillips21