Research on magneto-hydraulic proportional control strategy for single degree of freedom supporting system of magnetic–liquid double suspension bearing

Abstract

Compared with the traditional active electromagnetic bearing, the additional hydrostatic supporting concept is imported to form magnetic–liquid double suspension bearing (MLDSB) without affecting the support performance. Therefore, the bearing carrying capacity and stiffness are greatly increased and the operational stability and reliability of MLDSB are also improved. The controlling strategy and the regulating mode have the major impact on the safe and stable operation of MLDSB, which directly determines the performance quality. MLDSB adopts the magnetic–liquid coupling supporting mode with electromagnetic suspension as the main and hydrostatic supporting as the supplement, which greatly increases the complexity and difficulty of MLDSB. Therefore, the proportional control strategy and the magneto-hydraulic coupled nonlinear controller of MLDSB are explored in this paper. First, the regulation mechanism of the single degree of freedom (DOF) supporting system is revealed, and the proportional–integral–differential controller of the electromagnetic and hydrostatic closed-loop is designed. Then, the fuzzy control idea is introduced into the single DOF supporting system to design a magnetic–liquid variable proportional fuzzy controller, and the difference between the proportional/variable proportional control modes is compared. Finally, the rotor displacement following characteristics and anti-interference characteristics in the proportional/variable proportional control mode are compared on a magnetic–liquid double suspension test bench. The results show that compared with the proportional control method, the variable proportional control method combines the advantages of fast regulation speed of the electromagnetic system and the stable and reliable advantages of the hydrostatic system. In the same step signal, the rotor can achieve unbiased following under two control modes of proportional/variable proportion, and the adjustment time of the variable proportional control mode is shorter. In two control modes, the rotor can be restored to the original equilibrium position. The maximum offset under the variable proportional control mode is smaller, and with the continuous increase of the displacement, the performance of the variable proportional control method is more obvious. The stability control of MLDSB is provided on the theoretical basis in this article.