Research on controller design and simulation of electro-hydraulic servo system

Electro-hydraulic servo system has nonlinearity and uncertain dynamics, so its theoretical mathematical model can´t sufficiently represent the practical system. In order to acquire more accuracy system mathematical model, system model identification and verification of electro-hydraulic position servo system were carried out based on hardware-in-the-loop simulation environment of Real-time Workshop (RTW) and system identification toolbox in MATLAB. After the mathematical model of the system being built, a new nonlinear hybrid controller was developed composed of a proportional controller, a fuzzy controller and a classical PID controller, for which the parameters of the PID controller can be adjusted online by using the fuzzy control rule. The zero position of fuzzy domain was regarded as the switching threshold to avoid the undesirable disturbances, and stable switching is implemented between the two control methods. By simulations and experiments on an Electro-hydraulic servo test bench the feasibility of the control strategy was validated. The simulation results show that the steady-state error of system is eliminated; the rapidity is enhanced by the Proportion-Fuzzy-PID controller when the system parameter variation was happened, and has good performances using in real applications.