Research On Decoupling Control Of Magnetic-fluid Double Suspension Bearing System

With the magnetic suspension as the main method and hydrostatic bearing as the secondary one,the bearing capacity and stiffness can be improved substantially by the Magnetic-Liquid Double Suspension Bearing(MLDSB).Due to small film thickness,strong damping,positive stiffness and repulsion of hydrostatic bearing system,and large air gap,weak damping,negative stiffness and suction of magnetic suspension system,the operation stability of MLDSB can be reduced sharply by the coupling and the interference between two bearing system.So the MLDSB coupling characteristic of bearing system is analyzed,and the produce mechanism of coupling force is revealed,and then the decoupling controller can be designed in the paper.The main research contents of this paper are as follows:(1)For the problem of mutual coupling of MLDSB is raised.According to the Force model of physical model,Maxwell electromagnetic levitation theory and hydrostatic bearing support theory,the basic coupled mathematical model of MLDSB is established.It can provide the theoretical foundation for studying the design of decoupling controller of MLDSB.(2)The transfer function of a single degree-of-freedom(DOF)magnetic-fluid double suspension support system is established.According to the Bristol matrix its coupling is severely.For this phenomenon,Similar Feed-Forward Decoupling Controller and DiagonalMatrix Decoupling Controller are designed,and the decoupling effect of two controller with Simulink modules can be contrasted and analyzed.(3)For the multiple DOF Spatial coupling of MLDSB is raised.The State Feedback method is selected as the design method of the multiple DOF decoupling controller.For the multiple DOF mathematical model of MLDSB is analyzed.The state-space equation is obtained,and the multiple DOF transfer function G(s)is solved.And the decoupling characteristics of controller can be verified with the Simulink module.(4)For the decoupled system model,a controller is designed.First,the single / multiple overall control scheme is designed,and through the assistance of the root locus method and the empirical method,its controller is finally solved.The results show that the control effect is good and meets the theoretical requirements of design.In conclusion,the complete decoupling control of MLDSB system can be achieved with the various decoupling methods in this article.And its controller can also meet the system control needs.This artical can provide a theoretical reference for the structural design and performance analysis of the MLDSB system.