Research On Bearingless Induction Motors And Sliding Mode Variable Structure Control System

A bearingless induction motor(BIM)integrates rotor rotation and suspended function which has a series of better characteristics than the conventional asynchronous motor,such as no friction,no lubrication,long service life,high speed high precision running,and so on.Therefore,it shows extremely important application value in some special fields,for example,the turbo molecular pump,flywheel battery,aerospace,water craft,sterile workshop,vacuum technology,life science and other fields.Based on the National Natural Science Foundation of China(51475214)and the Natural Science Foundation of Jiangsu Province of China(BK20141301),the mathematic model of the BIM,the air gap magnetic field oriented control,the sliding mode variable structure control based on the novel reaching law,the sliding mode variable structure control based on the load torque observer,digital control system are studied.The specific research contents are as follows:1.The research background and the research status at home and abroad about the bearingless motor are summarized,besides,the research status and development trend of BIM are described.The working mechanism of BIM is analyzed,and the mathematical model of BIM is established.The BIM control system based on air gap magnetic field oriented control is proposed to solve the coupling problem between the electromagnetic torque and the radial force.2.In order to solve the low performance problem of the BIM control system under disturbances(parameter change,load mutation),a BIM sliding mode control method based on an adaptive variable-rated exponential reaching law is proposed.Firstly,in order to suppress the inherent chattering in the sliding mode algorithm,an adaptive variable-rated exponential reaching law is put forward on the basis of adding the1 L norm of state variables to the conventional exponential reaching law,and smoothing the symbol function.Then,the sliding mode controller of BIM speed loop is designed by using the novel reaching law,and the BIM sliding mode control system is constructed.The simulation results show that this method can realize the accurate tracking of the rotational speed error to the given speed,and improve the speed regulation performance of BIM.3.In order to further improve the control performance of BIM control system under disturbance conditions,a load torque sliding mode observer is built to observethe torque based on sliding mode speed control system.Meanwhile,the output of the load torque is as the feed-forward compensation for the control system,which provides the required current for disturbance variation.What's more,the integral identification method is used to implement the on-line identification of rotational inertia,and the rotational inertia can be updated to the load observer in real time.The results show that the proposed method is robust to the uncertain disturbance of the system,and it improves the dynamic and static performance of the BIM control system.4.This paper constructs the sliding mode digital control system experiment platform with DSP TMS320F2812 as the core,and carries out the rotor rotation,rotor suspension and anti-disturbance ability test.According to the experimental results,it can be known that the proposed novel sliding mode control strategy can not only improve the anti-disturbance ability and operation quality of the BIM speed regulation system greatly,but also weaken the inherent chattering of the sliding mode system effectively.