The Effects of Mass Variation on Closed-loop EHA System under High Leakage Flow Condition

The electrohydraulic actuator (EHA) system is widely used in the current industry applications mainly due to its advantages on high power to weight ratio, precise positioning with fast motion and capability in generating great torque. However, the EHA system is difficult to control especially on position tracking as it has a highly nonlinear system due to many uncertainties parameters such as leakage, friction, pressure, and temperature of fluid. In this paper, the effects of mass variation on position tracking performance of closed loop EHA system with the presence of high servo valve leakage flow condition at short-range displacement of the spool is presented. Firstly, the EHA system is modelled by using MATLAB/SIMULINK. Then, the simulations for position tracking performance on the closed loop EHA system with the variation of servo valve leakage flow are conducted. Furthermore, a proportional integral derivative (PID) controller is proposed and the effects of mass variation on the closed loop EHA system under the presence of high servo valve leakage flow is investigated. A square wave input is used as a reference input for the simulation and graphical form results are obtained. The results show that the closed loop EHA system has high steady state error (SSE) with the increasing of servo valve leakage flow and the high leakage flow presence on closed loop EHA system with high mass has faster response and low SSE. In conclusion, the performance of closed loop EHA system to reach the desired tracking point is undoubtedly decreased when the leakage flow is increased and the closed loop EHA system with higher mass has faster response and highest performance to reach the desired tracking point.