Josep Font Llagunes - McGill Universityfont/downloads/CIM_biomechanics.pdfJosep M. Font Llagunes...

Josep M. Font LlagunesDepartment of Mechanical Engineering Biomedical Engineering Research Centre Technical University of Catalonia (UPC)[email protected]

Simulation and design of an active orthosis for an incomplete spinal cord injured subject

Applied Mechanics GroupBARCELONATECHMontreal, 13 June 2011

CIM Seminar in Robotic Mechanical SystemsMcGill University

Applied Mechanics GroupBARCELONATECH

Location

Barcelona


The region: Catalonia


The city: Barcelona


UPC Campus in Barcelona

Applied Mechanics Group

Ana BarjauProfessor

Josep Maria FontProfessor

Rosa PàmiesAssistant Professor

Gil SerrancolíPhD Student

Joaquim AgullóFull Professor

Teaching• Industrial Engineering (UPC) Mechanics and Advanced Mechanics

•Master Biomedical Engineering (UPC‐UB)Biomechanics

Research funding• Technical University of CataloniaResearch in Biomechanics

•Ministry of Science and InnovationAnalysis and design of active orthoses



Research of the Group


• “Application of multibody dynamics techniques to active orthosis design for gait assistance”Research Project (2010‐2012)

Muscle, EMG, Control

Muscle, EMG, Control

Mechanical Design, Contact Model

Mechanical Design, Contact Model

Multibody ModelSimulation

Multibody ModelSimulation

Patient Selection, Gait Criteria, TrialsPatient Selection, Gait Criteria, Trials

Biomechanics Lab


Laboratori de Biomecànica

Motion capture system (12 cameras)


Laboratori de Biomecànica

Foot-ground contact force measurement (2 force plates)


Electromyography


Biomechanics Lab

1. Introduction

2. Musculoskeletal modeling

‐ Biomechanical model‐Muscle modeling: functional and denervated muscles

3. Simultaneous human‐orthosis actuation

4. Mechanical design of an A‐SCKAFO

5. Conclusions


Outline

Applied Mechanics GroupBARCELONATECH1. Introduction

Spinal Cord Injury (SCI)C1

C7

Head, neck, upper limb joints

Cervical vertebrae

T1

T12

Thoracic vertebrae Trunk muscles, abdominal muscles

L1

L5 Hip, knee, ankle, toes

Lumbar vertebrae

S1

S5Sacral vertebrae

L1

T10

ASIA Impairment Scale: Level A: Complete SCI.Level E: Normal motor and sensory function.Levels C‐D: Motor function partially preserved in lower limbs.


Spinal Cord Injury (SCI)

Incomplete spinal cord injured subject at the SCI Unit at Hospital Juan Canalejo (La Coruña, Spain)


Objectives of the work

• Quantify the simultaneous contribution of the musculoskeletal system and an active orthosis to the net joint moments during normal gait.

Fundamental hypothesis: Combined human‐orthosis actuation produces net joint torque patterns similar to those of normal unassisted walking.(Kao et al., J. Biomech, 43, 2010) (Lewis and Ferris, J. Biomech, 44, 2011)

• Present a new design of an active stance‐control knee‐ankle‐foot‐orthosis (A‐SCKAFO) to assist incomplete SCI subjects that preserve motor function at the hip.


MethodologyInverse Dynamic Analysis + Passive torques (muscle atrophy in SCI)

Muscle‐orthosis load sharing optimization problem

net joint torque

muscle‐orthosis torque

1. Introduction





5. Conclusions


Outline

Applied Mechanics GroupBARCELONATECH2. Musculoskeletal modeling

Biomechanical multibody model• Planar biomechanical model in the sagittal plane: 12 rigid bodies, 14 DoF.• Human‐orthosis actuation: 8 muscle groups + 3 external torques

1 – Iliopsoas, 2 − Rectus Femoris, 3 – Glutei, 4 – Hamstrings, 5 – Vasti, 6 – Gastrocnemius, 7 − Tibialis Anterior, 8 – Soleus.

Muscle groups:

0 0.2 0.4 0.6 0.8 1

0

50

100

ankl

e to

rque

(N

m)

0 0.2 0.4 0.6 0.8 1

-50

0

50

knee

torq

ue (

Nm

)0 0.2 0.4 0.6 0.8 1

-50

0

50

hip

torq

ue (

Nm

)TOr HSr TOr

(+) plantar flexion

(+) extension

(+) flexion

0 0.2 0.4 0.6 0.8 1

0

50

100

ankl

e to

rque

(N

m)

normal pathological

0 0.2 0.4 0.6 0.8 1

-50

0

50

knee

torq

ue (

Nm

)0 0.2 0.4 0.6 0.8 1

-50

0

50

hip

torq

ue (

Nm

)TOr HSr TOr

(+) plantar flexion

(+) extension

(+) flexion


Inverse Dynamic Analysis

(McDonald et al., J. Biomech, 28, 2005) (Lebiedowska and Fisk, Clinical Biomech, 14, 1999)

• 2D walking kinematic benchmark from (Winter, 1991)• Non‐pathological gait, female m=57.75 kg, fs=70 Hz

• Denervation atrophy in partially functional muscles• Modelled by means of stiff and dissipative elements

• K and C estimated from experimental data of SCI

Passive torque in incomplete SCI

Normal gait inverse dynamics


Muscle modeling: Innervated and denervated muscles

• Spinal cord injuries result in complete or partial paralysis of muscles innervated by spinal segments at or below the trauma.

• Muscle dynamics:

Hill‐type muscle‐tendon model

• Partially denervated muscle dynamics:

p – weakness factor (limits activation)

tendon

tendon

muscle fibers

pennation angle

1. Introduction





5. Conclusions


Outline

Applied Mechanics GroupBARCELONATECH3. Simultaneous human‐orthosis actuation

Physiological static optimization approachStep 1: Calculate the maximum muscle force histories compatible with the

contraction dynamics (assumption a = p):

Step 2: Determine the muscle activations and orthosis actuation solving the following static optimization approach at each time step:

R – Matrix of equivalent moment armsA – Combined muscle‐orthosis activation matrixF* – Vector of maximum actuation forces

AIS D Subject: At least half of key muscles below the neurological level have a muscle grade of 3 or more.


Simulation resultsAIS C Subject: More than half of key muscles below the neurological level have a muscle grade less than 3.

0 0.2 0.4 0.6 0.8 1

0

50

100

ankl

e to

rque

(N

m)

AIS C subject

orthosismusclestotal

0 0.2 0.4 0.6 0.8 1

-50

0

50

knee

torq

ue (

Nm

)

(+) plantar flexion

(+) extension

TOr HSr TOr

0 0.2 0.4 0.6 0.8 1

0

50

100

ankl

e to

rque

(N

m)

AIS D subject

orthosismusclestotal

0 0.2 0.4 0.6 0.8 1

-50

0

50

knee

torq

ue (

Nm

)

(+) plantar flexion

(+) extension

TOr HSr TOr


Simulation results: Joint torquesAIS D Subject: At least half of key muscles below the neurological level have a muscle grade of 3 or more.

AIS C Subject: More than half of key muscles below the neurological level have a muscle grade less than 3.


Simulation results: Muscle forces

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)1-Iliopsoas

AIS C subject AIS D subject

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

2-Rectus Femoris

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

3-Glutei

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

4-Hamstrings

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

5-Vasti

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

6-Gastrocnemius

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

7-Tibialis Anterior

0 0.2 0.4 0.6 0.8 10

500

1000

forc

e (N

)

8-Soleus

TOr HSr TOr TOr HSr TOr

1. Introduction





5. Conclusions


Outline

Applied Mechanics GroupBARCELONATECH4. Mechanical design of an A‐SCKAFO

Biomechanical and design specifications

• Knee joint specification: ─ Stance phase: Lock the knee flexion at any angle.─ Swing phase: Control of the flexion‐extension motion.

• Ankle joint specification:─ Passive dorsiflexion torque during early stance and swing.


Biomechanical and design specifications

• Sensors for autonomous control:─ Plantar sensors.─ Angular encoders (knee and ankle joints).

• Total weight: less than 2.5 kg.

• Knee joint specification: ─ Stance phase: Lock the knee flexion at any angle.─ Swing phase: Control of the flexion‐extension motion.

• Ankle joint specification:─ Passive dorsiflexion torque during early stance and swing.


Actuation and sensors

Actuators/joints Sensors

Electrical rotary motor(swing phase)

Mechanical locking system(stance phase)

Passive klenzak joint


Actuation and sensors

Actuators/joints Sensors

Electrical rotary motor(swing phase)

Mechanical locking system(stance phase)

Passive klenzak joint

Knee and ankle encoders(joint angles)

Plantar sensors(foot‐ground contact)

1. Introduction





5. Conclusions


Outline

Applied Mechanics GroupBARCELONATECH5. Conclusions

Conclusions

• We have presented a simple and efficient approach to estimate muscle forces and orthosis actuation in powered assisted walking of incomplete SCI subjects.

─ Physiologically consistent results.

─ Considers the weakness and atrophy of partially denervated muscles in SCI.

─ Provides useful results to assist the selection of actuators in the design of active orthoses.

─ Good correlation with experimental measurements reported in literature.

• We have presented the mechanical design of an active stance‐control knee‐ankle‐foot‐orthosis (A‐SCKAFO) aimed at assisting incomplete SCI subjects.

─ Independent knee actuation and locking systems.

─ Equipped with the required sensors for its autonomous operation.

─ Advantages: Light weight, modularity, energy efficiency.

Josep M. Font LlagunesDepartment of Mechanical Engineering Biomedical Engineering Research Centre Technical University of Catalonia (UPC)[email protected]

Simulation and design of an active orthosis for an incomplete spinal cord injured subject

Applied Mechanics GroupBARCELONATECHMontreal, 13 June 2011

CIM Seminar in Robotic Mechanical SystemsMcGill University

Josep Font Llagunes - McGill Universityfont/downloads/CIM_biomechanics.pdfJosep M. Font Llagunes...

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