Research On Friction And Clearance Model Identification And Compensation Method Of Valve-Controlled Cylinder System

As research and development in domestic servo technology continues to improve,electro-hydraulic position servo systems have emerged as one of the most important control and execution mechanisms in industrial automation.Combined with mechanical demand analysis,the existence of friction and clearance links can easily lead to response lag,limit cycle oscillation,and other detrimental effects,resulting in large challenges to system stability and control precision.Analysis of its performance is urgently needed,and on this basis,a suitable controller is developed to improve the entire control process and achieve accurate control in practical applications.Therefore,this thesis considers an electro-hydraulic servo system as the experimental object,aiming at the nonlinear mechanical clearance of the electro-hydraulic servo system transmission and the friction in the power mechanism,the mathematical modeling and compensation control research are carried out to improve the performance index of the electro-hydraulic position servo system.First,according to the actual mechanical structure of the semi-physical simulation test stand and the working principle of the valve-controlled actuator system,this thesis proposes a nonlinear mathematical model,in which the internal friction of the hydraulic cylinder and clearance of the transmission mechanism are mainly considered.Considering the friction dynamic characteristics and clearance discontinuity characteristics of the actual electro-hydraulic servo test bench,an improved Lu Gre model and quasilinear clearance hysteresis model that adapts to the electro-hydraulic servo system,and the parameters to be identified for each model are given that provide a theoretical basis for subsequent nonlinear factor analysis,affecting servo system performance and control strategy design.Second,aiming at the problem that the parameters of nonlinear models are difficult to accurately identify,a parameter identification method based on the improved sparrow search algorithm is designed accordingly.Through 12 benchmark test functions,the proposed improved sparrow search algorithm is simulated and analyzed on the aspects of iteration speed,calculation accuracy and motion trajectory,and the effectiveness of the improved algorithm is verified.Based on the above identification methods and experimental data from the test bench,a more accurate actual system model is established,which provides feasibility for the subsequent design of accurate compensation methods for nonlinear disturbances.Then,aiming at nonlinear and uncertain factors,an active disturbance rejection controller based on switching control is designed to improve the overall robustness of the servo system.A nonlinear friction observer is designed to observe the internal friction of the servo system,and the parameter adaptive link is designed to correct and estimate the friction parameters and other uncertainties of the system.The clearance discontinuity is corrected by the adaptive control of the dynamic inverse model based on the fastest descending clearance.The effectiveness of the above control strategy in the aspect of position accuracy is verified by the preliminary simulation.Final,an experimental research scheme of the valve-controlled cylinder electro-hydraulic servo system is designed.An electro-hydraulic servo test bed is set up,and a real-time control system is constructed using MATLAB.Based on anti-interference experiment,friction compensation experiment and clearance compensation experiment,the effectiveness and correctness of the designed control strategy and system modeling scheme are verified comprehensively.