Muscle-Reflex Model That Encodes Principlesof Legged Mechanics Produces Human Walk-

ingDynamics and Muscle Activities

서울대학교이경호2012. 4. 06

Introduction• Central Pattern Generator(CPG)– complex network of neurons that con-

trols legged locomotion of animals and humans.

– in spinal cord

Introduction• Principle of legged mechanics– it can largely simplify locomotion control– self-stability, compliant leg behavior

• How these principles integrated into human motor control?– spinal reflexes– they can link sensory information into ac-

tivation of the leg muscles

Human Model

SOL : soleus

VAS : vasti

GAS : gastrocnemius

TA : tibialis anterior

GLU : gluteal muscles

HFL : hip flexor muscles

HAM : hamstring

Muscle-tendon model

Muscle Control• positive force feedback (F+)

S : stimulationS0 : prestimulationG : GainF : force△t : time delay

Muscle-tendon model

A : muscle activationfl : force-length relationshipfv : force-velocity relation-ship

Human Model

SOL : soleus

VAS : vasti

GAS : gastrocnemius

TA : tibialis anterior

GLU : gluteal muscles

HFL : hip flexor muscles

HAM : hamstring

Muscle Control• positive length feedback (L+)

Human Model

SOL : soleus

VAS : vasti

GAS : gastrocnemius

TA : tibialis anterior

GLU : gluteal muscles

HFL : hip flexor muscles

HAM : hamstring

Muscle Control• PD control

kp, kd : gain : reference lean an-gle

Double Support

Actual Leg Swing Phase

During actual swing, we mainly rely on a leg’s ballistic motion. The dis-tal leg muscles SOL, GAS, and VAS are silent in that phase. Only TA’s L+, remains active to provide foot clearance with the ground

Pattern Generation

Result• Walking Gait

- Matlab SimMechan-ics

GRF : ground reaction force

Result• Predict Motor Output

Result• Adaptation to Slopes

Discussion• Principles of legged mechanics ex-

plains the basic dynamics of human locomotion– encode several principles of legged me-

chanics with actuators and control, which turned into muscles and reflexes

• Is it sufficient?–more principles of legged mechanics do

certainly exist– level of detail

Discussion• CPG vs Reflex– Actual ratio of central and reflex inputs

is remain uncelar