Mechanical Improvements to TCERA, a Tunable Compliant Energy Return Actuator

Abstract

TCERA (Tunable Compliance Energy Return Actuator) is a robotic emulation of a human femur-tibia system in a walking or running gait. TCERA features two parallel air springs to compliantly transmit or absorb torque about the knee. The radial positions of the springs as well as their relative lengths are adjustable, which effectively alter the torsional stiffness and equilibrium angle of the knee system, respectively. These functions are operable independently, and thus decouple the kinematic relationship and control of the torsional stiffness and femur-tibia angle. The actuator derives its inspiration from an analysis of the human gait, in which it can be seen that the torsional compliance about the knee is varied to specific stiffness values throughout the cycle. Special mechanical considerations have been taken into account to achieve swift changes in position without compromising the static integrity of the actuator.