Research On One-cycle Digital Control For Switching Power Amplifier In Magnetic Suspension Bearings

One-cycle control has the advantages of simple control,small calculation,high control precision and strong robustness.Applied in full digital control system of the magnetic suspension bearings,whose sample signals are discontinuous,the one-cycle digital control has higher control precision than the conventional control algorithms.So it can improve the suspension performance of magnetic suspension bearings.Futher study of one-cycle digital control for switching power amplifier in magnetic suspension bearings was made in this paper.With the consideration of coil resistance voltage drop,four types of digital one-cycle control,the unipolar one-cycle control with following the average current,the unipolar one-cycle control with following the final current,the bipolar one-cycle control with following the average current and the bipolar one-cycle control with following the final current,were optimized when applied in switching power amplifier for magnetic suspension bearings,improving the control precision.The feasibilities of these four algorithms were verified by MATLAB simulation.The steady and dynamic current ripples were analyzed.Mathematical models of current ripples were derived.Simulations were conducted on by MATLAB to verify the accuracy of the models.Ways of reducing the current ripple were obtained from theoretical analysis.Simulation results show that the unipolar one-cycle control has more applying value compared with the bipolar one,because its current ripple is smaller.The current has time delay under the one-cycle digital control.So the sources of time delay were located according to the digital control principle.Two simple and general time delay compensation methods were proposed to eliminate the time delay.Effectivenesses of the compensation models were verified by MATLAB simulation.And the simulation results show that the model II is better.Hardware and software design of the full digital controller based on DSP+FPGA applied in magnetic suspension bearings were introduced.Experiments of the modified one-cycle control,the current ripple analysis and the time delay compensation were carried out.Experimental results further verified the conclusions concluded by theoretical anlaysis and simulation.