681 Introduction to Computer Graphics

1
Walking
Kinematic control
Legs and upper body controlled kinematically
Dynamic simulation
Legs affect upper body
Legs react to forces imparted by upper body
Torques control legs in attempt to match
kinematic control
2
Walking
Pelvic rotation over point of contact
Pelvic rotation about vertical axis
Pelvic list
Knee flexion
Toe hinge
3
Walking Phases
RTL
LHD
RHD
LTL
Single support
Double support
Double support
Right stance phase
Left swing phase
One-half cycle
4
Walking kinematics
Specify joint angle functions of time for each
joint Empirical clinic data Designed by the
animation
Specify time-space curves for pelvis and feet Use
inverse kinematics to position leg at each time
step
5
Walking dynamics
Kinematically control some parameters Use
dynamics to fill in rest of parametric values
Dynamic simplifications Ignore some dynamics,
e.g. swing leg on balance Ignore temporal
variations, e.g., upward force of stance
leg Replace complexes by simpler ones, e.g., leg
by telescoping joint Decouple forces and sum
affect, e.g. hor. and vert. components
6
Dynamcis for animation
Aid to the animator, not an obstacle
Can be easily overridden
Kinematics used as hard or soft constraints
7
Walking forward dynamics
Phase changes induce joint torques
Simulates body sensors turning on/off muscles
Can use empirically collected data (gait lab data)