Research On Sensorless Position Control Technology Of Surface Magnet Synchronous Motor In Full Speed Range

Permant magnet synchronous motor has the advantages of high power density,high efficiency and simple control.However,the presence of its position sensor limits the application scenario of PMSM.Based on this,position sensorless control technology has emerged and is widely used in many applications.However,the more mature position-free algorithms have certain limitations,and a single algorithm can not achieve stable control in the full speed range.Therefore,in this paper,different algorithms are used for different speed ranges,and several types of algorithms are combined to form a composite position-freelgorithm to realize PMSM position-free control in the full speed range.For the medium and high speed ranges,a sliding mode observer based on the extended counter-electromotive force is studied to estimate the rotor position.For the sliding mode jitter inherent to the sliding mode observer,the effects of switching function and sliding mode gain on the sliding mode jitter are studied and analyzed.For the switching function,hyperbolic tangent function and saturation function are used to suppress the sliding mode jitter respectively.For the sliding mode gain,fuzzy control is used to regulate the sliding mode gain.Subsequently,the second-order super-spiral sliding mode observer is improved by combining the advantages of switching function and fuzzy control of sliding mode gain to suppress sliding mode jitter.The improved second-order superhelix slip mode observer can automatically adjust the slip mode gain of both slip mode surfaces when the system approaches the slip mode surface,and the slip mode jitter is not included in the estimated inverse electric potential of the slip mode observer,which eliminates the use of low-pass filter and effectively improves the accuracy of the rotor position estimated by the slip mode observer.For the low-speed range,the high-frequency injection method applicable to the SPMSM is being investigated.The high-frequencye-pulse-injection method is compared with the high-frequency square-wave injection method.The high-frequency pulsation injection method limits the system bandwidth due to the use of band-pass and low-pass filters,which leads to a decrease in the system response speed.The square wave injection method,however,eliminates the use of bandpass filters and increases the cutoff frequency of low-pass filters,effectively reducing the bandwidth limitation of bandpass and low-pass filters.The simulation results demonstrated that the square wave injection method can effectively improve the response speed of the system while accurately estimating the rotor position.For the zero-speed range,the initial position determination is performed by the prepositioning method,and the reliability of the initial position determination is improved by the secondary positioning method considering that the prepositioning method may lead to positioning failure due to the positioning blind area.A weighted coefficient method is used to transition the position angle in order to make a smooth and stable transition of the position-free algorithm for different speed ranges,and the position angle after the transition is used to re-estimate the speed.This includes the construction of a full-speed range composite positionless sensor control algorithm by combining the square wave injection method in the low-speed range with the improved second-order superhelical sliding mode observer method in the medium-and high-speed ranges using the weighted coefficient transition method.An experimental platform of SPMSM is built to debug the hardware and software system,and the experimental results show the feasibility and effectiveness of the composite positionless control algorithm.