Valve characterization to implement feed-forward control of hydraulically actuated joints

Abstract

This thesis characterizes the flow behavior of a Hydraforce SP08-47CL valve given a specific pulse-width modulation (pwm) duty cycle. With a description of valve behavior, a feed-forward term can be implemented in the positional control loop of a hydraulically actuated robotic prototype. In order to isolate valve behavior, a test bed apparatus consisting of three separate hydraulic cylinders was constructed to decouple joint movement, and multiple tests were conducted, recording cylinder velocities given a constant pwm signal at a system pressure of 3.45MPa. After theoretically justifying the empirical results, a quadratic and bi-linear curve fit to the data provided a practical solution to an otherwise computationally expensive problem.