Application Of One Cycle Control For Current In EMS System

Low-speed maglev trains,which overcome the inherent limitations of the wheel-rail train's wheel rail constrains,have advantages of environmental protection,low noise,good climbing ability and small turning radius.These advantages make it a new favorite of urban rail transit.The magnetic wheel modular structure is adopted by excitation part of the suspension train to reduce the mechanical coupling among suspension controlled points.Therefore,the study of vehicle suspension can be refined into a single solenoid suspension control research.In this paper,the single electromagnet levitation system is taken as the research object,the digital one-cycle control(D-OCC)algorithm of the chopper is analyzed,and the mathematical model of the system based on D-OCC of the current loop is established.The simulation and experiment prove that the D-OCC algorithm can follow the command signal quickly and accurately,and it satisfies the stability requirements of the system.Firstly,D-OCC algorithm is derived and the identification method of inductance parameters is given.The control effects of the D-OCC and PID are compared in the way of simulation using Matlab/Simulink.The simulation results show that the dynamic performance of PID control is better,while the D-OCC is better in steady state performance.Secondly,the D-OCC algorithm is applied to constant current control link of suspension system's current control model and force feedback control model respectively.The simulation results show that suspension system with current D-OCC can achieve no-load stable suspension.In the moment of increasing or reducing 50% load,air gap fluctuation amplitude of current control model is 2.3mm,and air gap of the force feedback model is almost not affected.Using two methods to follow sine wave and square wave signal which amplitude is 0.5mm and frequency is 5Hz,simulation results show that there is serious distortion of amplitude with current control model.Under the same conditions,force feedback control model can follow command signal accurately.Finally,an EMS system with DSP28335 is built.The D-OCC algorithm is applied to the current control of the system and it can be suspended stably.The control effects of the EMS system's current control model and the force feedback control model are experimented and compared in several typical working conditions.The simulation and experimental results show that coil current can follow the command signal rapidly and accurately by using D-OCC,and EMS system can suspend stably by using DOCC to controlling system current.Compared with the current control model,the force feedback control model can not only reduce the time constant of the system,but also enhance the anti-disturbance performance of the system.