Abstract: Aiming at the characteristics of electro-hydraulic force servo system, such as parametric uncertainties, uncertain nonlinearities and external disturbances, combining feedback linearization theory with sliding mode control theory, a sliding mode control method based on feedback linearization was proposed to realize the high precision tracking of electrohydraulic force servo system. Firstly, the nonlinear mathematical model of the electro-hydraulic force servo system was established. The differential geometry theory was used to transform the dynamic characteristics of the nonlinear system into linear dynamic characteristics, and the input-state accurate linearization was realized. Then, the sliding mode variable structure control was introduced into the controller, and the feedback linearization sliding mode controller was designed. The stability of the proposed controller based on feedback linearization was proved by Lyapunov stability principle. Finally, the simulation model of electro-hydraulic force servo system and controller was established by using MATLAB/ Simulink software, and the sliding mode controller based on feedback linearization was simulated and verified. The influence of different amplitude signals and random interference on the control effect was studied. The simulate experiment results show that comparing with the PID control algorithm, the force tracking error is reduced by 96.7 % and the adjustment time is reduced by 90 % by using sliding mode control method based on feedback linearization. The result shows that the control algorithm effectively reduces the influence of nonlinear factors on the tracking accuracy, improves the force tracking accuracy of the system, and has better robustness and better control effect.
Key words:  electro-hydraulic servo system; feedback linearization controller; sliding mode control algorithm; force tracking; robustness; MATLAB/Simulink