Abstract:  In order to solving the problem of system parameter uncertainty and system dead-zone in the position control process of an electro-hydraulic servo closed pump control system, a series control strategy combining adaptive backstep sliding mode control and the dead-zone inverse compensation control was proposed. Firstly, the mathematical model and simulation model of the electro-hydraulic servo closed pump control system were set up. Secondly, an adaptive backstep sliding mode controller was designed in consequence of the advantages of the adaptive backstep control and the sliding mode control to eliminate mismatched uncertainties and avoid parameter nesting in the electro-hydraulic servo closed pump control system. Subsequently, a dead-zone inverse compensation controller was designed by using the smooth continuous index function to construct the smooth dead-zone inverse function, and the series controller was composed of the two controllers mentioned above. Finally, MATLAB/Simulink software was applied to build the electro-hydraulic servo closed pump control system simulation model for analysis. The research results suggest that the displacement tracking accuracy of the electro-hydraulic servo closed pump control system using the series controller can reach ± 0.6 μm, the steady state accuracy can reach ± 0.3 μm, and the time required to reach the steady state is about 0.6 s. At the same time, the parameter adaptive law adjusts the uncertain parameters of the system in real time during the position control process of the system to improve the steady state control accuracy of the system. The simulation results verify that the proposed series control strategy is of great efficiency.
Key words: electro-hydraulic servo system; closed volume servo drive unit; system parameter uncertainty; position control; adaptive backstep sliding mode control; deadzone inverse compensation; series controller