Use of compliant actuators in prosthetic foot designs

Compliant actuation, as opposed to conventional, stiff actuators
like electrical drives, is currently growing in importance
and has applications in a variety of robotic technologies
where accurate trajectory tracking is not prevalent: bipedal
walking robots, assistive technology, rehabilitation training.
Instead of introducing compliance on the control level
through application-specific software, this approach is based
on inherent adaptable compliance on a purely mechanical
level. In this way intrinsic compliance is assured at all time,
enhancing system safety.
The equivalent torsion spring stiffness of an actuated joint
and the equilibrium position of its end effectors, i.e. the
joint's configuration in which the actuator torque is zero,
leaves us with two adaptable mechanical parameters to be
set for each joint, which evidently increases the complexity
of control. This is easily countered with the range of potential
benefits, adding value to existing applications and also
creating new applications in robotics. Some examples of
prosthetic foot designs are discussed in which these compliant
actuators are incorporated. What we can learn from this
in view of designing humanoid robots is briefly discussed.