Research On Model And Compensation For Open Servo System

Static and dynamic performance was greatly influenced by nonlinear friction in servo motion control system. With the continuous development of technology, higher performance of servo system was required, but friction was seriously restricting the development of servo system. Therefore, friction compensation has become the key technology of high-performance servo control system, which has important theoretical significance and wide application prospect. Aiming at friction of servo motion control system, the further research was made on identification and modification of LuGre model, and design of control strategy, through the methods of integrating theoretical modeling, simulation analysis and experimental research.Firstly, mathematical models were established according to components of open servo system, thus a servo simulation platform was set up. The dynamic characteristics of LuGre model was studied based on the simulation platform, and the distinctions and relations between Stribeck model and LuGre model were analyzed. In addition, the feasibility and validity of the methods was verified, which included the friction parameter identification method and the friction compensation method.Secondly, the parameter identification and modification of LuGre model were achieved. In order to eliminate the negative impact of torque ripple on the friction parameters identification, torque ripple compensation was carried out; Based on the method of steady-state error reverseing friction torque, the static friction parameters of LuGre model were identified accurately by the corresponding relation between speed and friction torque from multi-groups uniform motion experiments; an precise identification method of inertia was proposed base on simplified friction model, thus it provided conditions to the dynamic friction parameters identification of LuGre model;then dynamic parameters of the model were identified accurately using the genetic algorithm; Considering the problem of viscous friction coefficient in the practical application, a modified friction model based on the LuGre model was presented, furthermore, the modified friction model could completely and accurately reflect the friction characteristics of servo system, which had a higher practical value.Finally, the control strategies for friction compensation were investigated. According to the friction parameters identification results of the modified LuGre model, a control method, including torque ripple compensation, speed and acceleration feedforward compensation, and friction feedforward compensation based on modified LuGre model was proposed, and it improved tracking performance of servo system. Considering the parameters of friction model could be changed with the variability of external environment, a method of adaptive friction compensation based on Backstepping design was presented in this paper, which could ensure the asymptotic stability of the close-loop system, overcome the influence of nonlinear friction, and enhance the tracking accuracy of servo control system.