| Permanent magnet synchronous motors have the advantages of high efficiency and low speed and high torque,so they are often used in modern direct-drive elevator systems as traction machines.Low-speed running performance is an important index in the application of permanent magnet traction machine.In the traction machine control system,in order to ensure good low-speed operation performance,high-resolution photoelectric encoders are usually required.In order to reduce costs and improve the market competitiveness of traction drive system products,we hope to replace high-resolution photoelectric encoders with low-cost low-resolution incremental encoders.However,it will bring the problem of reduced stability and anti-disturbance ability of the traction machine system.Therefo re,this paper studies the stability and anti-interference of low-speed encoder-based permanent magnet traction system during low-speed operation.First of all,a low-resolution encoder permanent magnet traction system is used to establish a traction machine mathematical model and its vector control scheme.On this basis,the quantitative relationship between encoder resolution and speed measurement error is analyzed to clarify the causes of low-speed operating performance deterioration caused by low-resolution encoders,which lays a theoretical foundation for the study of low-speed speed measurement methods and anti-disturbance control strategies.In view of the deterioration of the stability of low-speed operation,according to the idea of model method and non-model method,continuous speed observer method and least square interpolation method are used to optimize the speed measurement method.A continuous speed observer suitable for the low-speed operation of the system is constructed to estimate the rotor position and speed,which improves its estimation accuracy.It is verified on the simulation platform and experimental platform that the method can improve the stability of low-speed operation.In addition,the speed measurement method based on the least squares interpolation method is studied.By smoothing the stepped position,the speed fluctuation is suppressed.The method does not depend on the inertia parameters of the motor,and the effectiveness of the method is verified by simulat ion.Aiming at the anti-disturbance capability of low-speed operation,the predictive control strategy of the traction machine model adapted to the low-resolution encoder is studied,and the transfer function of the control system is derived.The root locus method was used to analyze its stability,and the theoretical basis of the parameter selection of the speed prediction controller was studied.By comparing with the traditional PI controller,the effectiveness of the researched predictive control strategy in the low-resolution encoder traction system is verified.Based on the above theoretical research,a Matlab/Simulink simulation platform for low resolution encoder traction machine vector control system based on predictive control strategy was built.The effectiveness of the speed measurement method and control strategy studied is verified on the simulation platform. |
