Research On A Bearingless Induction Motor Control System Based On Nonsingular Terminal Sliding Mode And Disturbance Observer

A bearingless induction motor(BIM)possesses the excellent qualities of magnetic bearing and asynchronous motor simultaneously,which has an irreplaceable position in a great deal of fields.It integrates the characteristics of uniform air gap,sound and simple structure,low cogging torque,wear friction free,lubrication free and long service life.Moreover,the BIM can realize the “magnetic levitation”operation in special environment such as vacuum,corrosion and so on.Based on the National Natural Science Foundation of China(51475214)and the Natural Science Foundation of Jiangsu Province of China(BK20141301),the research on the BIM operation mechanism,the establishment of mathematical model,the nonsingular fast terminal sliding mode variable control,the adaptive exponential sliding mode control based on the disturbance observer and the digital control system are studied.The main contents are as follows:Firstly,the research background,research status,development trend and application area of the BIM are elaborated.The mathematical model of the BIM can be built on the basis of its operating principle;the control system is built based on the air gap magnetic field orientation control method.Not only the rotation and suspension of the BIM can be realized,but also the correctness of mathematical model and suspension mechanism can be verified.Secondly,in order to solve the problem of slow response and system chattering for the BIM speed and radial displacement control,a nonsingular fast terminal sliding mode control(NFTSMC)strategy is proposed.Using this method,the BIM speed controller and the radial displacement controller are designed.By combining the approaching speed with the state variables of the system,the shortcomings of the linear sliding mode poor convergence performance and the terminal sliding mode singularity are compensated.The theoretical simulation results indicate that the presented strategy can not only quickly track the given value of speed and radial displacement simultaneously,but also can weaken the inherent buffeting of the sliding mode system.Thirdly,in the interest of solving the unsatisfactory control performance of the BIM,an adaptive exponential sliding mode control(AESMC)and a disturbance observer for on-line identification of system disturbance variables are designed.The approach speed can change with the sliding surface and the system state.Besides,theoutput of the disturbance sliding mode observer uses as the feed forward compensation for the system speed.The feedback speed can adjust operation condition adaptively with the speed error and reduce the influence of the disturbance.The simulation fruits indicate that the system has strong robustness to uncertainties and achieves the accurate identification of uncertain disturbance,the anti-disturbance ability for BIM control system can be improved simultaneously.Finally,the BIM vector control system is established on the basis of space voltage vector pulse width modulation(SVPWM),and a digital control experiment platform is constructed with control chip TMS320F2812 DSP.The experimental results show that the designed digital control system can realize the stable suspension of the BIM,as well as the static and dynamic performance is excellent.