In order to eliminate the frictional resistance of CNC machine feed platform and improve the machining accuracy and surface roughness, the hidden-pole magnetic suspension linear synchronous motor used to drive the CNC machine tool feed platform was studied. According to the special structure and operation mechanism of the hidden-pole magnetic suspension linear motor, the mathematical model of the electromagnetic force of the motor was established firstly. Then the finite element calculation for the air gap magnetic density, back electromotive force and electromagnetic force of two different structures of the motor of the salient pole and hidden pole was carried out by Finite element software, and the harmonic analysis for air gap magnetic density was done. By comparing the electromagnetic forces of the two motors, it is found that the hidden pole has less fluctuation of the electromagnetic force, so it is more suitable for feed platform as a driving component. Finally, Particle swarm optimization is used to optimize the electromagnetic force of the hidden-pole controlled-magnet linear magnetic suspension synchronous motor, which further reduces the fluctuation of the electromagnetic force, and also improves the efficiency of the motor. The results of the experimental prove the effectiveness of the control method. INDEX TERMS Shidden pole linear synchronous motor, magnetic suspension platform, optimization, particle swarm algorithm.
This paper presents a sliding mode observer (SMO) with new reaching law (NRL) for observing the real-time linear speed of a controllable excitation linear synchronous motor (CELSM). For the purpose of balancing the dilemma between the rapidity requirement of dynamic performance and the chattering reduction on sliding mode surface, the proposed SMO with NRL optimizes the reaching way of the conventional constant rate reaching law (CRRL) to the sliding mode surface by connecting the reaching process with system states and the sliding mode surface. The NRL is based on sigmoid function and power function, with proper options of exponential term and power term, the NRL is capable of eliminating the effect of chattering on accuracy of the angular position estimation and speed estimation. Compared with conventional CRRL, the SMO with NRL achieves suppressing the chattering phenomenon and tracking the transient process rapidly and accurately. The stability analysis is given to prove the convergence of the SMO through the Lyapunov stability theory. Simulation and experimental results show the effectiveness of the proposed NRL method.
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