Simplified Three-Vector-Based Model Predictive Thrust Force Control Of Double-Side Linear Vernier Permanent Magnet Motors

With the advantages of high efficiency and high thrust density,linear vernier permanent magnet(LVPM)motors have broad application prospects in the field of long-distance rail transit.However,due to the inherent structural problems,the thrust force ripples of LVPM motors are large,which puts forwards higher requirements for control algorithms.Model predictive control has the characteristic of simple control principle,and has the ability to deal with multi-constraint problems.It has practical significance to introduce this method into the drive control of linear motors.In order to improve the limited modulation area of conventional model predictive thrust force control(MPTFC)strategy,a simplified three-vector-based MPTFC method with cascaded optimization process is proposed.Three different voltage vectors in each control period are selected through a novel cascaded optimization process,and the corresponding action time is allocated reasonably.Hence,a full range and continuous modulation(point-line-plane)can be realized,and the steady-state performance of thrust force and flux linkage of the double-side LVPM motor can be improved.In order to reduce the computational burden caused by the traversal optimization in conventional MPTFC,simplified candidate control sets of active vectors and improved optimization pricinple are proposed.Two active vectors are selected by a simplified cost function which only contains flux term,so the balance of weighting factor between thrust force and flux linkage is eliminated.The feasibility and effectiveness of the proposed method are validated from aspects of theory,simulation and experiment.The main contents of this paper are as follows:1.The mechanical characteristics and magnetic field modulation principle of the double-side LVPM motor are briefly described,and the relevant electromagnetic properties are analyzed by finite element simulation software.According to the principle of coordinate transformation,the mathematical models of the double-side LVPM motor under common coordinate systems are built by referring to the modeling method of rotary motors.2.The specific implementation steps and limitations of conventional MPTFC are described in detail.On this basis,the modulation range and duty cycle calculation principle of two-vector-based MPTFC are studied.Simulation models are built to verify the performance of the two control methods.3.Considering the large thrust force and flux ripples caused by the limited modulation area of conventional MPTFC,a simplified three-vector-based MPTFC with cascaded optimization process is proposed.The optimized calculation effiency and expanded modulation area of voltage vectors can be realized,and the improved steady-state performance can be achieved.Simulation models are established to validate the practicability of the proposed method.4.The motor drive platform based on d SPACE DS1103 is established,and the realization of some parts of software and hardware is briefly introduced.Taking the double-side LVPM motor as the control object,the dynamic and steady-state performances of research algotithms and the proposed method in this paper are verified by comparative experiments.