Research On Coordination And Control Strategy Of Multi-motor Servo System Considering Intrinsic Nonlinearit

With the rapid development of computer,power electronics,motor technology,network communication and modern control theory,as well as the continuous upgrading of motor core parts,the performance of all kinds of servo systems can also be continuously improved.However,with the continuous advancement of industry 4.0,the manufacturing industry facing personalized customization puts forward new requirements for servo system.Therefore,this paper aims to study the control method of multi motor cooperative drive servo system,from the commonly used dual-motor structure to the four motor synchronous structure with higher requirements for coordination.While taking advantage of the advantages of multi motor servo system,taking into account the complex essential nonlinear factors existing in multi motor system,this paper solves the coordination problem between multi motors,avoids "servo fight" and improves the servo control performance.This paper takes the dual motor and four motor synchronous drive servo system as the research object to study the problem of high-precision and high synchronization servo control.In order to meet the needs of engineering application,several treatment methods of friction and backlash commonly existing in the actual system are proposed in the process of controller design.Based on the backstepping method,combined with the theoretical knowledge of command filtering technology,observer,adaptive control theory and Lyapunov stability theory,this paper designs the servo system controller to solve the corresponding control problems and achieve high tracking accuracy and good multi motor synchronization effect.The main work of this paper is summarized as follows:Firstly,For the dual motor drive servo system with Lu Gre friction,based on the backstepping method and combined with the command filtering technology,a nonlinear double observer is designed to estimate the low-speed nonlinear friction characteristics of the load side,and the self-adaptive friction compensation law is derived for friction compensation.The command filtering technology is used to solve the computational explosion problem of backstepping method,establish the error compensation equation,and improve the tracking accuracy.The synchronous control signal is designed to make the two motors operate synchronously to drive the load together,and the load position can track the expected signal stably.The simulation results show the effectiveness of the design.Secondly,The dual motor structure is extended to the symmetrical servo architecture of four motor synchronous drive,and the four motor synchronous control strategy is given.For the four motor drive servo system with nonlinear backlash,Lu Gre friction and disturbance,an adaptive friction compensation control method based on command filter backstepping method is proposed.Based on the backstepping design based on command filtering in the previous chapter,the robust control term is designed to suppress the influence of backlash nonlinearity,and the adaptive control method is used to compensate the torque disturbance and unmodeled dynamics.Using double observers to observe the parameters in the friction model,an adaptive friction compensation law for friction parameter updating is derived.Finally,the stability of the closed-loop system is proved by Lyapunov theory,and the simulation results verify the effectiveness of the controller.Thirdly,For the four motor synchronous drive servo system with nonlinear backlash and Lu Gre friction,based on the backstepping method,combined with the dynamic surface technology and finite time control technology,an observer based finite time dynamic surface control strategy is designed.The application of dynamic surface technology to deal with the virtual control signal can avoid the repeated derivation of the virtual control signal in the traditional backstepping control,and simplify the structure of the controller.At the same time,a filtering compensation system is established to reduce the filtering error.The robust term is added to the virtual control signal to counteract the influence of backlash nonlinearity.The finite time control technology is adopted to speed up the response speed of the system and further reduce the tracking error.The designed control method can ensure the system to achieve better tracking accuracy and synchronization effect.The simulation results show the effectiveness of the design.