Design and preliminary testing of the RIC hybrid knee prosthesis.

We present a novel hybrid knee prosthesis that uses a motor, transmission and control system only for active dynamics tasks, while relying on a spring/damper system for passive dynamics activities. Active dynamics tasks require higher torque, lower speed, and occur less frequently than passive dynamic activities. By designing the actuation system around active tasks alone, we achieved a lightweight design (1.7 Kg w/o battery) without sacrificing peak torque (85Nm repetitive). Preliminary tests performed by an able-bodied person using a bypass orthosis show that the hybrid knee can support reciprocal stairs ambulation with low electrical energy consumption.