Position Sensorless Control Strategy And Initial Position Estimation Of Permanent Magnet Linear Synchronous Motor Feeding System

The traditional feeding system can not satisfy the need of high speed and precision machining increasingly. On the contrary, the feeding system of permanent magnet linear synchronous motor (PMLSM) has the advantages in high speed, high precision, fast response and long journey, so it is widely applied in high speed and precision machining equipments. However, PMLSM feeding systems with mechanical position sensor in existence have many disadvantages such as high cost, low system dependability, and inconvenience of installation and maintenance. As a result, researching for the position sensorless control system with excellent performance has been a research hotspot recently. This dissertation has project background of the National Natural Science Foundation which is titled "Research on high speed and high precision direct drive system without position sensor (No. 50475101)". And the research theme is resolving the key problems of position sensorless control of PMLSM feeding system. A position sensorless control system of PMLSM feeding system is established, the estimation algorithm, optimization and control as well as some key technologies of the permanent magnet linear synchronous motor system are studied systematically by combining theoretical analysis, computer simulation with experiment.In chapter 1, the background and the significance of the research are stated. The development trend and the current research situations of sensorless control of the PMLSM feeding system are introduced in detail. The keystone of the vector control of PMLSM and the essential sensorless control are pointed out. And the main content of this dissertation is proposed.In chapter 2, based on analyzing the space vector transfer laws of the PMLSM, the d-q axis mathematics model and theα-βmathematics model of PMLSM are built. The sensorless position control project of PMLSM is constituted. Simultaneously, the basic simulating modules of PMLSM sensorless control are established using the software Matlab/Simulink.In chapter 3, the significance of estimating the feeding system initial position for PMLSM sensorless position control and the necessity for starting smoothly are analyzed. A method of detecting initial position using saturation effect of the winding inductance is put forward, which is verified through electromagnetic field two-dimension finite element method, and a relationship between winding inductance (current response) and mover position. Then, the process of estimating initial position by injecting voltage impulse vector is expounded. Experimental results show that the precision of the method can arrive 7 electrical degrees, which can satisfy requirements of PMLSM starting smoothly.In chapter 4, an estimated method is put forward, which is using back-EMF to estimate the speed and position at middle-high speed, and using augmented Extended Kalman Filter at low speed, and obtaining a compound checking method using weighted method to merge the forward ways. Simulations demonstrate that the compound method has high performance at dynamic and static state. And the method can estimate the mover speed and position accurately.In chapter 5, based on analyzing merits and demerits of control strategies for PMLSM vector control, a sliding mode speed controller and a sliding mode position controller are designed, considering that the feedback signal is obtained by estimation not by mechanical sensors. Then the stabilization and anti-disturb ability of the designed sliding mode controller are analyzed theoretically. Simulating results show that the performances of strong robustness to external disturbance.In chapter 6, the hardware and software for PMLSM sensorless position control system are built. The composition and pricnciple of the measurement devices of currents and voltages, the fundamentals of the digital signal processor (DSP) and its peripheral circuits, the ways of sensorless estimation software using DSP are represented. Experiments of speed and position estimation without position sensor are made. Experimental results show that the position sensorless control has good performance, and the speed and position of the feeding system can be estimated.In chapter 7, the study contents and conclusions of the dissertation have been summarized. Then, the further research works have been forecast.