Research On Control Strategies Of 5-DOF Magnetic Suspension System Composed By Conical Bearingless Switched Reluctance Motors

Switched Reluctance Motor(SRM)has the characteristics of simple structure,flexible control and high fault tolerance.It is suitable for harsh environments and high-speed field.Bearingless Switched Reluctance Motor(BSRM)combined with the magnetic suspension technology is expected to further enhance its high-speed operation capability.And special bearing lubrication and heat dissipation design can be eliminated to further improve the power density due to the avoid of high-speed running friction between mechanical bearing and shaft.Conical Bearingless Switched Reluctance Motor(CBSRM)not only maintains the functions of high-speed rotation and radial suspension,but also has the ability to suspend axially.Therefore,the five-degree-of-freedom(5-DOF)magnetic levitation system based on dual structure of 6/4 CBSRM can reduce axial length and enhance system integration.However,enhanced integration brings some difficulties to motor control.For this special 5-DOF magnetic suspension system,twelve currents are needed to be controlled independently to track four radial forces,an axial force and a torque.Moreover,the mathematical model is complicated,and the coupling between levitation forces and torque is strong.So that the decoupling is difficult,and the control algorithm will be complicated.In order to solve the above problems,this paper takes single and double CBSRMs as research objects,and studies operating mechanism,mathematical model and control strategies.Firstly,for CBSRMs,the mathematical model under the two-phase conduction mode is derived based on the rotating coordinate system.Because the mathematical model is complicated,it can be simplified after using the method of current equivalence.On this basis,the compensation control strategy of single CBSRM is studied.The simulation model is built in Matlab/Simulink,and the rotation and suspension experiments are carried out based on motor and hardware platform to verify the control strategy.Secondly,for the 5-DOF magnetic levitation system composed of two CBSRMs,three control strategies are studied,namely compensation control of axial force,current decomposition control and its optimal control.Simulation models are built in Matlab/Simulink to verify these methods.And these control strategies are compared and analyzed.Finally,the experimental platform of the 5-DOF magnetic levitation system is introduced,including the motor prototype and the hardware platform based on DSP28335 and CPLD.The prototype parameters are tested and the preliminary experiments are completed.