Present Study
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Present Study Patient Specific Motion Modeling and Assistive Devices S Russell, P Sheth, B Bennett, P Allaire, M Abel University of Virginia, Motion Analysis and Motor Performance Laboratory, Charlottesville, VA. Develop patient specific full body gait model Develop patient specific full body gait model Develop applied joint torques from desired Develop applied joint torques from desired Angular Momentum Angular Momentum Implementation of newly developed foot model Implementation of newly developed foot model Application and validation of Optimized Application and validation of Optimized contact model between foot and floor contact model between foot and floor Angular Momentum used to develop stable walking in Angular Momentum used to develop stable walking in bipedal gait models (Goswami, Popovic) bipedal gait models (Goswami, Popovic) Previously used to: Previously used to: Determine energy lost at heel strike/foot contact Determine energy lost at heel strike/foot contact Control strategy for full body model in single support Control strategy for full body model in single support 3-D kinematics collected via Vicon implementing a 3-D kinematics collected via Vicon implementing a 38 marker Helen-Hayes full body set 38 marker Helen-Hayes full body set 3 subjects with no history of lower extremity 3 subjects with no history of lower extremity pathology were used to develop/validate patient pathology were used to develop/validate patient specific models specific models Stable walking patterns are predicted using Stable walking patterns are predicted using the angular momentum about the full body the angular momentum about the full body CoM as the high level control CoM as the high level control Analysis found angular momentum computed Analysis found angular momentum computed from experimentally measured kinematics was from experimentally measured kinematics was invariant with speed ( invariant with speed ( + + 20%) 20%) Consistent with published data (Popovic) Consistent with published data (Popovic) Allows simulation of various speed from same Allows simulation of various speed from same angular momentum control matrix [A] angular momentum control matrix [A] Subject specific models make no assumption Subject specific models make no assumption regarding symmetry and model entire gait regarding symmetry and model entire gait cycle cycle Our research has found that children with Our research has found that children with Cerebral Palsy walk with angular momentum Cerebral Palsy walk with angular momentum patterns similar to typical walkers patterns similar to typical walkers Extension of this work is under way Extension of this work is under way Full 3-D simulations Full 3-D simulations Prediction pathologic gait Prediction pathologic gait Acknowledgements The authors would like to thank the staff at the Gait and Motion The authors would like to thank the staff at the Gait and Motion Analysis Lab, Kluge Children’s Rehabilitation Center at the Analysis Lab, Kluge Children’s Rehabilitation Center at the University of Virginia, where experiments were conducted. This University of Virginia, where experiments were conducted. This work was supported in part by NSF grant 0503256. work was supported in part by NSF grant 0503256. INTRODUCTION RESULTS (cont) DISCUSSION METHODS (cont) RESULTS Angular Momentum Control METHODS Tested Subjects Simulations completed successfully Simulations completed successfully implementing, patient specific model, implementing, patient specific model, foot/floor contact model, and PD control foot/floor contact model, and PD control for both single and double support phase for both single and double support phase Model successfully predicted gait Model successfully predicted gait kinematics and ground reaction force for kinematics and ground reaction force for individual patients individual patients Plots show lower extremity joint kinematics of a single patient. Results shown include experimentally measured joint angles for the ankle, knee, and hip joint. Also shown are the lower extremity joint angles predicted using the patient specific model, revised foot model, improved floor contact model, and angular momentum based PD control for joint torques 0.6 0.8 1 1.2 1.4 1.6 1.8 -100 0 100 200 300 400 500 600 700 800 900 G round reaction forces (N ew ton) Tim e (s) Sim ulated G RF Force P late data Full body model developed for Full body model developed for each patient via MSC.Adams each patient via MSC.Adams using LifeMod using LifeMod Patient anthropometrics used Patient anthropometrics used with the GeBOD data base to with the GeBOD data base to create patient specific models create patient specific models Model Model 19 body segments 19 body segments 16 joints 16 joints Full 3-D with motion Full 3-D with motion constrained to sagittal plane constrained to sagittal plane Ground Contact Ground Contact Ground placement optimized resulting in GRF Ground placement optimized resulting in GRF equaling Body weight equaling Body weight Coulomb friction applied between floor and foot Coulomb friction applied between floor and foot geometries geometries Contact parameters (stiffness/damping) Contact parameters (stiffness/damping) optimized in both planes to match optimized in both planes to match experimentally measured GRF experimentally measured GRF Similar solution parameters suggest Similar solution parameters suggest optimization process is not mandatory optimization process is not mandatory Model Development Foot Model Foot Model Previous model consisted of Previous model consisted of only heel and toe ellipsoids only heel and toe ellipsoids Resulted in piece wise motion Resulted in piece wise motion of modeled CoP of modeled CoP Non-smooth GRF Non-smooth GRF New model includes contact New model includes contact ellipsoids along metatarsals ellipsoids along metatarsals connecting heel/toe connecting heel/toe ellipsoids ellipsoids Smooth/continuous GRF Smooth/continuous GRF Facilitates smooth CoP motion in Facilitates smooth CoP motion in both sagittal and frontal planes both sagittal and frontal planes Angular momentum of each segment about the body Angular momentum of each segment about the body CoM calculated and averaged for each test subject CoM calculated and averaged for each test subject Data used to populate 19xN matrix [A] where: Data used to populate 19xN matrix [A] where: N = # data points over gait cycle N = # data points over gait cycle PD control used to determine joint torques for PD control used to determine joint torques for each point of gait cycle, 1,2,…N each point of gait cycle, 1,2,…N Simulations run using angular momentum [A] as Simulations run using angular momentum [A] as negative feedback for PD control resulting in negative feedback for PD control resulting in minimized error between desired and simulated minimized error between desired and simulated angular momentum angular momentum Angular Momentum Control 0 10 20 30 40 50 60 70 80 90 100 -20 0 20 A nkle (deg.) JointA ngles Inverse F orw ard 0 10 20 30 40 50 60 70 80 90 100 -50 0 50 100 K nee (deg.) Inverse F orw ard 0 10 20 30 40 50 60 70 80 90 100 -50 0 50 G aitcycle (% ) H ip (deg.) Inverse Forw ard Comparison of actual patient vertical ground reaction force, measured experimentally, and the vertical component of the ground reaction force predicted by the model using Angular momentum control and the new foot and ground contact model. References Goswami, A., Kallen, V. (2004). Goswami, A., Kallen, V. (2004). Proc IEEE ICRA ’04 Proc IEEE ICRA ’04 , 3785-3790. , 3785-3790. Popovic, M., et al. (2004). Popovic, M., et al. (2004). Proc IEEE ICRA ’04, Proc IEEE ICRA ’04, 2405-2411. 2405-2411. Popovic, M., et al. (2004). Popovic, M., et al. (2004). Proc IEEE/RSJ IROS ’04 Proc IEEE/RSJ IROS ’04 , 1685-1691. , 1685-1691.
description
Patient Specific Motion Modeling and Assistive Devices. S Russell, P Sheth, B Bennett, P Allaire, M Abel. University of Virginia, Motion Analysis and Motor Performance Laboratory, Charlottesville, VA. INTRODUCTION. METHODS (cont). RESULTS (cont). Angular Momentum Control. Foot Model - PowerPoint PPT Presentation
Transcript of Present Study
Present Study
Patient Specific Motion Modeling and Assistive Devices S Russell, P Sheth, B Bennett, P Allaire, M Abel
University of Virginia, Motion Analysis and Motor Performance Laboratory, Charlottesville, VA.
Develop patient specific full body gait modelDevelop patient specific full body gait model Develop applied joint torques from desired Develop applied joint torques from desired
Angular MomentumAngular Momentum Implementation of newly developed foot modelImplementation of newly developed foot model Application and validation of Optimized contact Application and validation of Optimized contact
model between foot and floormodel between foot and floor
Angular Momentum used to develop stable Angular Momentum used to develop stable walking in bipedal gait models (Goswami, Popovic)walking in bipedal gait models (Goswami, Popovic)
Previously used to:Previously used to: Determine energy lost at heel strike/foot contactDetermine energy lost at heel strike/foot contact Control strategy for full body model in single supportControl strategy for full body model in single support
3-D kinematics collected via Vicon implementing a 38 3-D kinematics collected via Vicon implementing a 38 marker Helen-Hayes full body setmarker Helen-Hayes full body set
3 subjects with no history of lower extremity pathology 3 subjects with no history of lower extremity pathology were used to develop/validate patient specific modelswere used to develop/validate patient specific models
Stable walking patterns are predicted using the Stable walking patterns are predicted using the angular momentum about the full body CoM as angular momentum about the full body CoM as the high level controlthe high level control
Analysis found angular momentum computed Analysis found angular momentum computed from experimentally measured kinematics was from experimentally measured kinematics was invariant with speed (invariant with speed (++ 20%) 20%) Consistent with published data (Popovic)Consistent with published data (Popovic) Allows simulation of various speed from same angular Allows simulation of various speed from same angular
momentum control matrix [A]momentum control matrix [A] Subject specific models make no assumption Subject specific models make no assumption
regarding symmetry and model entire gait cycleregarding symmetry and model entire gait cycle Our research has found that children with Our research has found that children with
Cerebral Palsy walk with angular momentum Cerebral Palsy walk with angular momentum patterns similar to typical walkerspatterns similar to typical walkers
Extension of this work is under wayExtension of this work is under way Full 3-D simulationsFull 3-D simulations Prediction pathologic gaitPrediction pathologic gait
AcknowledgementsThe authors would like to thank the staff at the Gait and Motion Analysis Lab, Kluge The authors would like to thank the staff at the Gait and Motion Analysis Lab, Kluge
Children’s Rehabilitation Center at the University of Virginia, where experiments Children’s Rehabilitation Center at the University of Virginia, where experiments were conducted. This work was supported in part by NSF grant 0503256.were conducted. This work was supported in part by NSF grant 0503256.
INTRODUCTION RESULTS (cont)
DISCUSSION
METHODS (cont)
RESULTS
Angular Momentum Control
METHODS
Tested Subjects
Simulations completed successfully implementing, Simulations completed successfully implementing, patient specific model, foot/floor contact model, patient specific model, foot/floor contact model, and PD control for both single and double support and PD control for both single and double support phasephase
Model successfully predicted gait kinematics and Model successfully predicted gait kinematics and ground reaction force for individual patientsground reaction force for individual patients
Plots show lower extremity joint kinematics of a single patient. Results shown include experimentally measured joint angles for the ankle, knee, and hip joint. Also shown are the lower extremity joint angles predicted using the patient specific model, revised foot model, improved floor contact model, and angular momentum based PD control for joint torques
0.6 0.8 1 1.2 1.4 1.6 1.8-100
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Simulated GRFForce Plate data
Full body model developed forFull body model developed for each patient via MSC.Adamseach patient via MSC.Adams using LifeModusing LifeMod Patient anthropometrics usedPatient anthropometrics used with the GeBOD data base towith the GeBOD data base to create patient specific modelscreate patient specific models ModelModel
19 body segments19 body segments 16 joints16 joints Full 3-D with motionFull 3-D with motion constrained to sagittal planeconstrained to sagittal plane
Ground ContactGround Contact Ground placement optimized resulting in GRF Ground placement optimized resulting in GRF
equaling Body weightequaling Body weight Coulomb friction applied between floor and foot Coulomb friction applied between floor and foot
geometriesgeometries Contact parameters (stiffness/damping) optimized in Contact parameters (stiffness/damping) optimized in
both planes to match experimentally measured GRFboth planes to match experimentally measured GRF Similar solution parameters suggest optimization Similar solution parameters suggest optimization
process is not mandatoryprocess is not mandatory
Model Development
Foot ModelFoot Model Previous model consisted ofPrevious model consisted of only heel and toe ellipsoidsonly heel and toe ellipsoids
Resulted in piece wise motionResulted in piece wise motion of modeled CoPof modeled CoP Non-smooth GRFNon-smooth GRF
New model includes contactNew model includes contact ellipsoids along metatarsalsellipsoids along metatarsals connecting heel/toe connecting heel/toe
ellipsoidsellipsoids Smooth/continuous GRFSmooth/continuous GRF Facilitates smooth CoP motion inFacilitates smooth CoP motion in both sagittal and frontal planesboth sagittal and frontal planes
Angular momentum of each segment about the body Angular momentum of each segment about the body CoM calculated and averaged for each test subjectCoM calculated and averaged for each test subject
Data used to populate 19xN matrix [A] where:Data used to populate 19xN matrix [A] where: N = # data points over gait cycleN = # data points over gait cycle PD control used to determine joint torques for each PD control used to determine joint torques for each
point of gait cycle, 1,2,…Npoint of gait cycle, 1,2,…N Simulations run using angular momentum [A] as Simulations run using angular momentum [A] as
negative feedback for PD control resulting in negative feedback for PD control resulting in minimized error between desired and simulated minimized error between desired and simulated angular momentumangular momentum
Angular Momentum Control
0 10 20 30 40 50 60 70 80 90 100-20
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Gait cycle (%)
Hip
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InverseForward
Comparison of actual patient vertical ground reaction force, measured experimentally, and the vertical component of the ground reaction force predicted by the model using Angular momentum control and the new foot and ground contact model.
ReferencesGoswami, A., Kallen, V. (2004). Goswami, A., Kallen, V. (2004). Proc IEEE ICRA ’04Proc IEEE ICRA ’04, 3785-3790., 3785-3790.Popovic, M., et al. (2004). Popovic, M., et al. (2004). Proc IEEE ICRA ’04,Proc IEEE ICRA ’04, 2405-2411. 2405-2411.Popovic, M., et al. (2004). Popovic, M., et al. (2004). Proc IEEE/RSJ IROS ’04Proc IEEE/RSJ IROS ’04, 1685-1691., 1685-1691.
Present Studies
Patient Specific Motion Modeling and Assistive Devices S Russell, P Sheth, B Bennett, P Allaire, M Abel
University of Virginia, Motion Analysis and Motor Performance Laboratory, Charlottesville, VA.
Develop plantar flexion assist ankle foot orthosis (AFO) to promote heel strike while Develop plantar flexion assist ankle foot orthosis (AFO) to promote heel strike while facilitating 3 rockers of stancefacilitating 3 rockers of stance
Develop passive brace to store energy lost at heel strike and return it during pre swingDevelop passive brace to store energy lost at heel strike and return it during pre swing Develop motorized walker to predict gait events and assist subjects in walking and turningDevelop motorized walker to predict gait events and assist subjects in walking and turning
Develop an AFO which limits plantar flexion during Develop an AFO which limits plantar flexion during swing due to conditions such as equinus or drop footswing due to conditions such as equinus or drop foot
Allow patient kinematics to exploit all three rockers Allow patient kinematics to exploit all three rockers during stance (Figure 1)during stance (Figure 1)
Development of “real time” prediction of Gait events Development of “real time” prediction of Gait events from forces applied to walker handles during walkingfrom forces applied to walker handles during walking
Development of shared control algorithm to control Development of shared control algorithm to control electric motors for desired walker motionelectric motors for desired walker motion Hold walker position fixed in cases of impending fall Hold walker position fixed in cases of impending fall
(instability)(instability) Interject energy during strategic gait events (push off)Interject energy during strategic gait events (push off) Facilitate directional control of walkerFacilitate directional control of walker Negate additional work of dragging a walker during gaitNegate additional work of dragging a walker during gait
INTRODUCTION
Smart WalkerEnergy Return AFOPlantar Flexion Assist AFOObjectives
Energy stored at heel strikeEnergy stored at heel strike Body weight compresses springsBody weight compresses springs Springs held in compression by multi-tooth ratchet systemSprings held in compression by multi-tooth ratchet system Tension in cables released to facilitate full range of motionTension in cables released to facilitate full range of motion
Energy returned during push offEnergy returned during push off Body rotates forward over foot (2Body rotates forward over foot (2ndnd rocker) rocker) Foot is dorsi-flexed taking slack out of cableFoot is dorsi-flexed taking slack out of cable Weight in on ball of foot activating mechanism to release Weight in on ball of foot activating mechanism to release
springssprings Springs create plantar flexion moment about ankle joint via Springs create plantar flexion moment about ankle joint via
cablescables
Energy added from ankle plantar flexion at push off for Energy added from ankle plantar flexion at push off for CP gait typically 15-20% less than normal gaitCP gait typically 15-20% less than normal gait
Develop an AFO to store the energy lost during heel Develop an AFO to store the energy lost during heel strike and return the energy later in gait cycle (i.e. strike and return the energy later in gait cycle (i.e. push off)push off)
Return .4 J/kg of energy to gait at push off (15% total Return .4 J/kg of energy to gait at push off (15% total normal energy added at push off)normal energy added at push off)
Allow patient kinematics to exploit all three rockers Allow patient kinematics to exploit all three rockers during stance (Figure 1)during stance (Figure 1)
Objectives
Cerebral Palsy 764,000 people in the United States have symptoms of Cerebral Palsy (CP)764,000 people in the United States have symptoms of Cerebral Palsy (CP) Metabolic costs of walking 2-3 times higher in individuals with CPMetabolic costs of walking 2-3 times higher in individuals with CP 50% of people with CP are prescribed Ankle Foot Orthotics (AFO)50% of people with CP are prescribed Ankle Foot Orthotics (AFO) Previous research equivocal on effectiveness of AFO’sPrevious research equivocal on effectiveness of AFO’s
Preform real-time prediction of gait events (i.e. heel Preform real-time prediction of gait events (i.e. heel strike, toe off) via forces applied to walker handlesstrike, toe off) via forces applied to walker handles
Create shared control of a motorized posterior walker Create shared control of a motorized posterior walker to facilitate better walking in children with CPto facilitate better walking in children with CP
Objectives
Figure 1. 1st Rocker represents rotation about the heel at initial heel contact allowing the foot to lay flat, 2nd Rocker allows the body to progress forward rotating about the ankle with the foot flat in stance, and the 3rd rocker allows the subject to rotate onto the ball of there foot to facilitate push off during pre swing.
Solid ankle AFO’s and posterior leaf spring Solid ankle AFO’s and posterior leaf spring (PLS) restrict or inhibit one or more kinematic (PLS) restrict or inhibit one or more kinematic rockersrockers
Hinged AFO’s facilitate rockers but cannot Hinged AFO’s facilitate rockers but cannot inhibit foot drop or equinusinhibit foot drop or equinus
Current AFO’s
Based on a double upright AFO with dual action Based on a double upright AFO with dual action jointsjoints Patient specific conical compression springs located Patient specific conical compression springs located
between foot bed and sole of shoebetween foot bed and sole of shoe Ankle plantar flexion compresses the springs via the Ankle plantar flexion compresses the springs via the
cable, moment arm, and pulleyscable, moment arm, and pulleys Spring tension is adjusted to apply patient Spring tension is adjusted to apply patient
specific plantar flexion assist during swing phasespecific plantar flexion assist during swing phase In stance springs are compressed as weight is In stance springs are compressed as weight is
transferred forward releasing tension on moment transferred forward releasing tension on moment arm facilitating full range of motion and all 3 arm facilitating full range of motion and all 3 rockersrockers
Current Solution Design
SpringsPulleys
Moment ArmAssist Adjustors
Upright
Shoe
HingeCable
Sole
An additional An additional benefit of the benefit of the design is the design is the energy return energy return applied during applied during pre swing to pre swing to aid push off as aid push off as the springs the springs decompress decompress as body as body weight is weight is removedremoved
Solid ankle AFO’s are Solid ankle AFO’s are unable to return energy unable to return energy to gait cycle while PLS, to gait cycle while PLS, ground reaction, and ground reaction, and carbon toe off AFO’s carbon toe off AFO’s store and return energy store and return energy at push off but do so by at push off but do so by inhibiting the 2inhibiting the 2ndnd rocker rocker
Current AFO’s
Current Solution Design
Post-processing Post-processing prediction of gait prediction of gait events from handle events from handle forces validated forces validated using VICON using VICON motion analysismotion analysis
Implementation of Implementation of shared control on shared control on steering angle to steering angle to control anterior control anterior walker trajectorieswalker trajectories
Previous Solutions
Current Solution Design
Ratchet Mechanism
Upright
Hinge
Moment ArmTension Adjustor
Springs
ReleaseMechanism
Cable
ReleaseMechanism
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