Reducing stick-slip friction in hydraulic actuators

Stick-slip friction in hydraulic actuators is a problem for accuracy and repeatability. Friction compensation has been approached through various control techniques. This work presents an alternative solution, namely, friction avoidance. By rotating the piston and rod the Stribeck region of the friction-velocity curve is avoided and the axial friction opposing the piston movement is linearized, making control more accurate and robust. Simulation results are presented to validate this approach and identify the operating limits for the rotational velocity.