Modeling and simulation of an electro-hydraulic actuation system through subsystem characterization

An electro-hydraulic actuation system with flow and pressure transmitters and LVDT integrated to a data-acquisition system has been investigated here for identifying an appropriate model necessary for dynamic performance prediction through MATLAB/SIMULINK simulation. The actuation test system consists of an electrically driven hydraulic power pack feeding a linear actuator with a proportional valve controlling the flow to and from the actuator, while the power pack includes a reservoir, fixed-discharge axial piston pump, a pressure relief valve and a non-return valve. A non-linear state-space model for the system has been obtained with the command electrical signal to the proportional valve as the input and the actuator displacement as the output. Experimental characterization of actuator friction, the relief valve, the non-return valve and the transmission line along with a neural-network model for the proportional valve has been carried out and integrated to the model of the actuation dynamics. The model has then been used for performance prediction to assess the importance of each subsystem model through a comparison against experimental results. It has been found that the contributions of the valve modeling and actuator friction are significant. A need to characterize the end-cushioning effect has been identified.