Research On The Current Prediction Control Of Permanent Magnet Linear Synchronous Motor With Segment Windings

Compared with other sophisticated systems, Permanent magnet linear synchronous motor (PMLSM) shows obvious advantage because of high thrust ability, low loss, fast response and ease maintenance. The PMLSM is expected to have a wide range of applications in the Computerized Numerical Control (CNC) machine tools, high-speed transport, electromagnetic catapults and elevating systems. The segment winding PMLSM (SW-PMLSM), whose primary winding is divided into sections with only one unit iron core, can improve the efficiency of the system with reasonable power supply and effective control strategy. Therefore, it is of great meaning to implement effective control of the SW-PMLSM.It's of significance to the high-performance servo systems that the electromagnetic parameters used in the algorithm are precisely evaluated. Taking into account the effect to the SW-PMLSM electromagnetic parameters caused by the rotor position change, the machine model is classified into two kinds: one is the area with the mover; the other is the area without the mover, according to the mover position. The electromagnetic fields of both areas are analyzed based on the electromagnetic theory, and the flux density expression is obtained with the mover in different positions. The self inductance, mutual inductance of one single section and mutual inductance between the two sections are all derived, and the relationships between them and the motor position are acquired. Based on Field Oriented Control (FOC) theory, the relationships between the d-axis, q-axis inductance and the motor position are deduced also. Meanwhile, it's proposed that the flux linkages of the two sections can be acquired through the back EMFs of these section windings, based on the production mechanism of EMF. In addition, the harmonic components of the detent force are gained by its simulation in one periodic. And the curve fitting method is used to reconstruct the detent force, which sets a foundation for the detent force compensation.In the view of the SW-PMLSM dynamic performance, the predictive control strategy is selected to control the current after the comparison among various current control strategies. Based on vector control theory, continuous and discrete system model of the SW-PMLSM are deduced when the mover isn't above the shared area and when it is respectively. Also, the motion equations are derived, which improves the overall control model for the SW-PMLSM, and lays a theoretical foundation for the current predictive control. Having constructed the inverter model and the SW-PMLSM model, this thesis proposes a current predictive control method which is based on the current error vector (named "CEVPC"). The shortcoming of CEVPC control is that it can not realize zero current error. To overcome this disadvantage, another current predictive method is proposed based on SVPWM (named "SVPWM-DBPC") control. The working principle of SVPWM-DBPC is described with the diagram to the product between a matrix and a vector and the voltage vector diagram in the dq coordinate.Since the two current predictive control methods are based on machine model, the control effectiveness relates to the accuracy of the model parameters directly. The relationships between the winding resistance, d-axis and q-axis inductances, flux linkage and the two current predictive control methods are analyzed; the influence of DC-link voltage and inverter current to the system performance are investigated; the adjustment method of the reference voltage vector are studied when the reference voltage vector magnitude exceeds the limit voltage. To the system delay problem, this thesis gains an insight to its mechanism. And the delay phenomena of the predictive quantities are studied, so are the corresponding compensation methods.The whole control system is modeled based on the Flux and Simulink co-simulation platform. The simulations such as: inter-section constant thrust control and inter-section constant velocity control are carried out in the two co-simulation models for CEVPC and SVPWM-DBPC control system respectively. The hardward platform of the system is constructed and full consideration is paid to the critical unit circuits and critical parameters which guarantees stable and safe operation of the SW-PMLSM. The inter-section constant thrust control and inter-section constant speed control for SW-PMLSM based on CEVPC and SVPWM-DBPC are carried out experimentally and respectively, whereby verifies the proposed methods. Experiment test are carried out on the condition that the related primary section is not enable correctly when the mover is on the shared area.Theoretical analysis, simulation and experimental results show that: the proposed control system of the SW-PMLSM based on CEVPC or SVPWM-DBPC realizes whole-range constant thrust control with inter-section constant thrust control method, which is adapt to constant thrust applications; the control system realizes whole-range constant velocity control with inter-section constant velocity control method, which is adapt to constant velocity applications. The completion of both motion control reserves essential techniques for precise position control of SW-PMLSM, and make it to be used in CNC machine tools possible.