Sliding Mode Control Of Magnetic Levitation Ball System

Because the magnetic levitation system has the characteristics of no mechanical wear,no pollution,no lubrication,and can adjust the position of the suspended object flexibly by adjusting the coil current or voltage,the magnetic levitation technology is widely used in industrial systems.With the development of science and technology,magnetic levitation systems will have greater application prospects.As a classic platform for studying magnetic levitation control systems,maglev ball systems can make researchers focus more on the research of control algorithms.It is a complex single-degree-of-freedom nonlinear system,which has model parameter uncertainty and coil hysteresis,and is susceptible to external disturbances.All of above have brought great challenges to the high-performance control of the magnetic levitation system.As a control method with strong robustness and disturbance suppression ability,sliding mode control has been widely used in the control field in recent years.Therefore,this dissertation makes a more in-depth study on the control of sliding mode control in maglev ball system.However,when the system is subjected to strong interference,the switching gain required for sliding mode control is large,and the states of the system may show large chatter or fluctuation.Therefore,the disturbance observation technology is introduced in this dissertation to estimate the disturbances and uncertainty as the feedforward compensation of the sliding mode controller,and achieved good control results.This dissertation first introduces the background significance and the current research status of magnetic levitation ball system control of domestic and foreign,and briefly analyzes the main problems in current system control.Then the principle of magnetic levitation ball control system is introduced.Finally,three sliding mode control methods suitable for magnetic levitation ball system are designed and implemented to achieve accurate and fast tracking of the desired position.The main work and research contents are as follows:1)Based on electromagnetic force analysis,dynamics analysis,current-voltage relationship analysis of the excitation coil,and equilibrium point force analysis,a nonlinear mathematical model of the magnetic levitation ball system was established.The non-linearity of the system,the higher-order terms of the electromagnetic force ignored during modeling,and the uncertain terms caused by the change in inductance are the main reasons for the parameter uncertainty.External wind,light intensity,human disturbance and system chatter are the main sources of external disturbances.Both of the above points are considered during modeling;2)Aiming at the problems of parameter uncertainty and susceptibility to external disturbances of magnetic levitation system,a continuous sliding mode control method(CSMC+ESO)based on Extended State Observer(ESO)was designed.Designed a continuous sliding mode controller(CSMC)for a magnetic levitation ball system based on power-reach laws to suppress chattering in traditional sliding mode control,and the ESO is designed to estimate parameter uncertainty and the outside world unknown disturbance,then the estimated value was feed-forward compensated to the CSMC,so that a smaller switching gain can be selected to suppress the fluctuation range of the system position state.Simulation results show that compared with CSMC,the proposed method has better position tracking accuracy and anti-interference performance.Experimental results show that compared with CSMC,the proposed method suppresses the fluctuation of the position state and the influence of the disturbance on the system state,and has better position tracking accuracy and faster state convergence speed;3)Aiming at the problem that the magnetic levitation ball system is susceptible to time-varying disturbances,a continuous sliding mode control method(CSMC+GPIO)based on a generalized proportional integral observer(GPIO)is designed.By designing a full-order continuous sliding mode controller(CSMC)of the magnetic levitation ball system,the error system state converges to the sliding mode surface in a finite time and suppresses chattering.GPIO is used to estimate the uncertainty and time-varying disturbance of the system.Then,the obtained estimated value is compensated to the controller in a feed-forward form to suppresse the fluctuation range of the position state.Simulation results show that the proposed method converges faster than CSMC and has better time-varying disturbance suppression performance than CSMC+ESO under the same switching gain.Experimental results show that compared with CSMC,the proposed method reduces the amplitude of position state fluctuations,and compared with CSMC + ESO,the proposed method effectively suppresses time-varying disturbances;4)Aiming at the problem that the system state cannot converge to the set value in a finite time,an adaptive non-singular terminal sliding mode control method based on Reduced-order generalized proportional integral observer(RGPIO)is designed(ANTSMC+RGPIO).The non-singular terminal sliding mode controller(NTSMC)of the magnetic levitation ball system is designed to make the system state converge to the set value in a finite time and avoid the singular problems that may exist in terminal sliding mode control.RGPIO is used to estimate the system uncertainty and Time-varying disturbance,and then compensate the observer's estimated value in feed-forward form to the controller to suppress the chattering phenomenon of sliding mode control.An adaptive non-singular terminal sliding mode control method is designed to further improve the dynamic performance of the system.Simulation results show that compared with the NTSMC+GPIO method,the proposed method has better dynamic performance,and the use of RGPIO also ensures the system's disturbance suppression performance.The experimental results show that compared with NTSMC,the proposed method can well suppress the chattering phenomenon,has better anti-interference performance,and has better dynamic performance than NTSMC + GPIO method;Finally,the dissertation is summarized,aiming at the shortcomings in the research,looking forward to the future research content and direction.