Synchronous current suppression of active magnetic bearing system based on a nonlinear variable step-size least mean square (LMS) algorithm

Aiming at the problem of synchronous current suppression of active magnetic bearing (AMB) system, a novel nonlinear variable step-size least mean square (NVSLMS) algorithm is improved by using the exponential function and Marr function, and then the step size factor could be adaptively adjusted within the whole speed range. In order to effectively suppress the synchronous current generated by the rotor unbalance, the coil current is viewed as the controlled variable, and a compound controller is designed by combining the proposed NVSLMS algorithm with the original controller of the AMB system. According to the root locus analysis, the strategy of switching step size factor is adopted to ensure the stability of the closed-loop system within the whole speed range. Finally, the magnetically suspended flywheel (MSFW) is used as the experimental object, and the performance of the proposed method is validated by simulation and experiment. The results illustrate that the proposed NVSLMS has good tracking speed and that the performance of the current attenuation is superior to those of the traditional variable step size least mean square methods.