Design and Implementation of Iterative Learning Control for an Electro-Hydraulic Servo System

Abstract

In order to produce an accurate movement of double-acting hydraulic cylinder of the Electro-Hydraulic Servo System (EHSS), an Iterative Learning Controller (ILC) approach is implemented in this work. Nonlinearity and imprecision occurs in the hydraulic systems because of friction. Traditional controllers are incapable of providing effective control performance throughout the entire operating range and insufficient to handle repetitive task. To manage the repetitive task, a memory-based learning control analysis is suitable. This research focuses to construct the ILC for governing the servo spool valve, which is responsible for the hydraulic cylinder displacement. The proposed ILC consists of learning filter, learning gain and robustness filter. Proportional, Integral and Derivative (PID) controller is devised to validate the outcome of ILC. Controllers are constructed based on the system modelling. The effectiveness of the suggested controller is shown through simulation and experimental findings. ILC provides an average of 50% minimal overshoot and settles 7 sec before the PID controller is designed. Due to model uncertainty, PID controller results 0.2 sec better rise time than ILC. In ILC's architecture objective function is designed to achieve minimal overshoot and quick settling of hydraulic cylinder. So, no consideration is given to the error indices. These findings will help hydraulic stamping application, which requires the accurate displacement of piston to avoid damage of work piece. These results show that the proposed controller achieves desired outcome displacement of hydraulic cylinder.