The Effects of Maglev Chopper's Control Cycle on Suspension Performance in EMS System

The cascade control strategy of current inner loop and airgap outer loop is usually adopted in electromagnetic suspension (EMS) system. The current loop and airgap loop adopt different control cycles in controller design, and the current loop control cycle is required to be shorter than the airgap loop control cycle. In theory, the shorter the control cycle of the inner loop, the better the following effect of the chopper current, and the more beneficial to the suspension system. However, it also needs the higher controller performance and control algorithm efficiency. With the suspension control performance permitted, reducing the current loop control frequency can effectively reduce the requirements of the controller performance and expand the selection range of the controller. In order to determine the appropriate control period of the current loop in the digital suspension system, the mathematical model of the suspension system and the maglev chopper is established, then the quantitative relationship between the current loop control period and the coil current ripple is deduced. Based on Simulink, the coupling simulation model of the maglev chopper and the suspension system is established, where the influence of the chopper control period on the performance of the suspension system is simulated and analyzed.