数字单周期电流控制在电磁悬浮系统中的应用

在串级控制的电磁悬浮系统中，电流环的响应速度和精度对整个悬浮控制起着至关重要的作用. 为了加快悬浮系统电流环的响应速度以及减小跟随误差，基于TMS320F28335设计了EMS （electromagnetic suspension system）的数字单周期控制（digital one-cycle control，D-OCC）电流控制器. 以悬浮斩波器为研究对象，建立起D-OCC的数学模型，对额定悬浮工作点处斩波器电流的D-OCC算法进行了详细推导；通过Simulink平台对算法进行仿真验证，并将D-OCC的电流环投入到实际悬浮系统中进行悬浮实验. 实验结果表明:对频率为5 Hz，幅值为3 A的方波信号进行跟随时，传统PID控制在方波上升沿和下降沿均存在一定的超调，且稳定后存在不小于20 mA的跟随误差，D-OCC在调节过程中不存在超调，且稳定后没有跟随误差，说明D-OCC算法能够实现对指令电流快速、准确跟随；采用电流环D-OCC的悬浮系统起浮过程需要约0.4 s的调整时间，并且悬浮稳定后可以克服50%荷载扰动和1.5 mm气隙扰动，说明该方法可以实现系统稳定悬浮，且具有较强的鲁棒性能. 

Application of Digital One-Cycle Control for Current in Electromagnetic Suspension System

In an electromagnetic suspension system （EMS） with cascade control, the response speed and accuracy of the current loop play a vital role in the overall suspension control. A current controller was designed for digital one-cycle control （D-OCC） based on TMS320F28335 for the suspension system, in order to improve the response speed of the current loop and reduce the following error. Taking a chopper circuit as the research object, the D-OCC’s mathematical model was established and the control algorithm of rated suspension point was derived in detail. The algorithm was validated through Simulink, and the current loop controlled by D-OCC was incorporated into the actual EMS. Experimental results show that the conventional PID control has a certain overshoot at the wave’s rising and falling edges when a square wave signal with frequency of 5 Hz and amplitude of 3 A is followed. Moreover, there is a following error of not less than 20 mA after the stabilization. However, there is no overshoot in the adjustment process and no following error after stabilization, when following the same wave with the method of D-OCC. This means that the D-OCC algorithm can follow the instruction current quickly and accurately. The floating process of the suspension system using the D-OCC current loop requires an adjustment time of about 0.4 s, and the system can overcome the 50% load disturbance and the 1.5 mm air gap disturbance; this shows that the method can achieve the system stable levitation and has strong robust performance.