A Rotary-Cage Valve (RCV) for Variable Damper in Prosthetic Knee.

The hydraulic microprocessor-controlled prosthetic knee is a widely used replacement for the human knee. As a typical damper component, the rotary-cage valve (RCV) can effectively decouple the pressure difference and the actuation force, thereby increasing the energy efficiency. We design and analyze a RCV for prosthetic knee and demonstrate how it fulfill the gait features. We also build its pressure-flow-angle model (PFA) to describe its force-velocity characteristics with different inner cage angles. Through experiments, the numerical model of PFA is specified and the PFA-based control strategy is constructed for pressure control. We built a passive actuation platform to test the RCV and compare it with a BLDC motor. The trajectory tracking and impact experiments were conducted, and the results show that RCV can be controlled to profile specific trajectories with high energy efficiency. Meanwhile, RCV provides considerable compliance and backdrivability for the joint.