Design of a Lyapunov controller for an electro-hydraulic actuator during contact tasks

In this paper, an algorithm is developed for contact task control of electr o-hydraulic actuators. The goal is to design and experimentally evaluate a robust controller that allows a hydraulic actuator to follow a free space t rajectory and then make and maintain contact with the environment for exert ing a desired force. First, the dynamic model of a hydraulic actuator inter acting with nn environment is described. Then, a Lyapunov-based controller is designed, which regulates the actuator's position and upon contact with the environment switches to a force controller. Extended Lyapunov's second method is used for stability analysis of the developed control system, whic h consists of nonsmooth dynamics. The stability of the system is guaranteed by using a smooth Lyapunov function under the condition of existence and u niqueness of Filippov's solution. The efficacy of the proposed nonlinear co ntroller is verified via experiments. The experiments are pel formed on an industrial hydraulic actuator equipped with a servovalve ann include motion through fi-ee space, contact with the environment and the transition betwe en the two.