Research On Sliding Mode Control Of Maglev System

With the vigorous industrial development in China,the application of hightech technologies has become particularly significant.The electromagnetic levitation system is one of the major difficulties to be overcome,especially maglev controller.As China has the largest high-speed rail mileages in the world,it is necessary to solve the friction problem of high-speed trains first if China wants to break through the current bottleneck of the high-speed rail speed development.Therefore,the use of the electromagnetic levitation technology is the future development trend of high-speed rail.For the electromagnetic levitation system,the nonlinearity and uncertainty are difficult to be solved by traditional control methods.As a strong robust control strategy,the sliding mode control has been widely used in nonlinear systems.Therefore,this paper used the sliding mode control theory to study the control of the single-degree-of-freedom maglev train system.With the single electromagnetic levitation model as the research object,the paper first introduced the working principle of the levitation model and established a mathematical model of the system based on the kinematics and related physical meanings.Based on the analysis,the paper pointed out that the system was unstable in the open-loop state.Then the approximate linearization method and the feedback linearization method were used to perform the system control separately.The simulation indicated that the global stability of the feedback linearization was relatively good,but the interference immunity of the system was weak due to the inability to accurately compensate the nonlinear part.Secondly,the paper applied the traditional sliding mode control to the electromagnetic levitation system.To solve the problems of slow approach speed and high-frequency buffeting,the combination of exponential approach law and power approach law was used.Moreover,the integral element was also added into the sliding mode surface.The comparison of the simulation results before and after the improvement of the sliding mode control showed that the response speed of the improved sliding mode control system was fast.The amount of overshoot was significantly lower and the buffeting was reduced greatly,but the immunity was still not strong.Finally,considering that the input of the electromagnetic levitation system and the interference are not in the same channel,which cannot meet the invariant matching conditions of the sliding mode control,and the interference immunity is weak,the paper introduced the interference observer into the design to improve the sliding mode control and realize the real-time compensation of the input through the online estimation of interference.The interference observer was used for the gain compensation to design the system control law.During the simulation,sinusoidal interference and slope interference were applied to the electromagnetic levitation system.The results showed that the changes in the suspension gap,electromagnet speed,and coil current of the system were weak.The amplitude was low but the recovery to the desired level was faster.The degree of interference was reduced and the interference immunity of the system was enhanced.