Research And Implementation Of Sliding Mode Tracking Control Algorithm Of Electro-Hydraulic Servo System

Electro-hydraulic servo systems exhibit strong nonlinearity,and hydraulic parameter uncertainties caused by changes in hydraulic oil volume parameters,unknown load stiffness,viscous damping,compressible volume modulus,valve nonlinearity,and oil temperature variations can be considered as structural matching disturbances,which are usually unknown constants.External load disturbances caused by driving forces or torques used for motion control in mechanical devices are generally considered as nonmatching uncertainties.Both of these may result in a certain reduction in the dynamic performance,steady-state performance and system stability margin of the electrohydraulic servo control system.In order to ensure that the hydraulic servo system can achieve precise and rapid tracking of the control target in complex situations,and has strong robustness and antiinterference ability,this paper proposes a disturbance observation compensation control method based on sliding mode variable structure ideas,as well as model linearization based on Lie derivative to achieve high-precision tracking control of the hydraulic servo system under uncertainty and external disturbance.Firstly,the working principle of the hydraulic servo system is analyzed,and a thirdorder nonlinear state-space equation is established considering the parameter uncertainty and disturbance terms of the system.For the external load disturbance and non-matching uncertainty of the system,a sliding mode control strategy is studied.A sliding mode variable structure controller is designed to improve the robustness of the system.Sliding mode observers are designed for second and third-order disturbances,and their convergence is analyzed to achieve high-precision error tracking of the system.For the control complexity and various uncertainties caused by the nonlinear characteristics of the system,the Lie derivative homomorphism transformation is used to perform feedback linearization of the system state space model,establish a linear state model of the system,and reduce the complexity of the system parameters.To address the switching jitter problem caused by the nature of sliding mode control,a method to eliminate the jitter is studied.The designed sliding mode observer is combined with the sliding mode controller,and the observation data of the observer is introduced and compensated in the observer.Based on the feedback linearization model,terminal sliding mode disturbance observers and sliding mode controllers are designed.Simulation results show that the designed sliding mode control based on linearized models can achieve better tracking performance and smaller jitter phenomenon.On the comprehensive experimental platform for hydraulic servo actuators control,the nonlinear sliding mode control algorithm,observation-based sliding mode control algorithm,and sliding mode control algorithm under linearization conditions designed in this paper are experimentally verified.The experimental results verify the rationality and effectiveness of the sliding mode algorithm designed in this paper.