| With the rapid development of production scale and technology level in some precision engineering, the demand and requirement for precision positioning platforms with multi-degree of freedom continue to increase, and some performance indexes including position precision,response speed and degree of freedom are also increasing. Traditional planar positioning platforms are based on mechanical superposition method, which make them have some inherent disadvantages including backlash, deformation, friction, complex structure, and big moving mass, and which also makes it difficult to achieve satisfying performances in positioning precision and response speed.The magnetically levitated permanent magnet planar motor (MLPMPM) can drive mover to achieve six-degree-of-freedom movement without being supported by mechanical guides,which makes it have some natural advantages including simple structure, free of mechanical friction, high positioning precision, and rapid response speed. With those merits, the MLPMPM has great potential applications in the area of high-level equipment manufactures.Supported by the National Natural Science Foundation of China under grant 51175296,this dissertation studies some fundamental theories of a typical coreless moving-coil MLPMPM including its operation mechanism, configuration design, electromagnetic analysis, parameter optimization, decoupling control and digital control system. On this basis, the experiment platform of MLPMPM control system is designed and the corresponding experiments are developed. The corresponding experiment results show the correctness of the presented method.The main achievements are outlined as follows:(1) In order to reduce the harmonic content of the magnetic field, a new-type magnet array is presented. The air-gap magnetic field distribution of the typical Halbach two-dimensional magnet array is studied, based on which the two-dimensional magnet array is reconstructed, a new-type magnet array is designed, and the analytical harmonic model for this magnetic array is built. The main parameters of the new-type magnet array are designed with the objective of maximizing the fundamental harmonic magnitude while minimizing the magnetic distortion.The finite-element-method based simulation model is built and the corresponding numerical computation result verifies that the magnetic field produced by this new-type two-dimensional magnet array has some remarkable advantages including higher magnetic flux density of fundamental component, less magnetic distortion, and more consistent magnitude of magnetic flux density.(2) In order to reduce the thrust fluctuation and the coupling thrust/torque, the coil array structure with four-coil characteristic is proposed. Based on the fundamental harmonic model of magnetic field produced by the Halbach permanent magnet array, the thrust model for a single coil is built by using the Lorentz force principle, and then the thrust characteristic of electrified coil is analyzed. The topology structure of coil array is designed based on this thrust model for a single coil, and then the four-coil coil array is presented. This structure can effectively eliminate the thrust fluctuation produced by the even harmonic magnetic field and inhibit the coupling thrust/torque produced by short sides of coils, and further improves the control performance of MLPMPM. The thrust/torque models for the MLPMPM are also built,and then the coil parameters are optimized with the objective of maximizing the ratio between thrust force and power consumption.(3) Aiming at the characteristics of multi-input-multi-output, strong coupling, and multiple degrees of freedom, the decoupling control strategy for MLPMPM is presented, and the corresponding positioning system with six degrees of freedom is designed. Based on the presented thrust/torque models and the id-iq decoupling current allocation, the decoupling current allocation strategy for MLPMPM is given, which physically realizes the decoupling among six-degree-of-freedom movements of MLPMPM. The parameterized finite element model is then built, and the corresponding simulation is developed, which verifies the correctness of the presented decoupling strategy. The dynamic model for the decoupled system of MLPMPM is built, based on which the control strategy and the corresponding control system for the six-degree-of-freedom movement of MLPMPM are designed. Based on the above analysis, the simulation platform is built, and the corresponding simulation result verifies the correctness and effectiveness of the designed control system.(4) Aiming at the model's failure when the mover yawing, the thrust model with small-angled yaw is built for MLPMPM, and the corresponding modified positioning control strategy with six degrees of freedom is presented. The thrust of the mover with small-angled yaw is analyzed, based on which the simplified thrust model and equivalent thrust model for MLPMPM with small-angled yaw are constructed respectively. On this basis, the current compensation strategy and phase correction strategy are presented for MLPMPM with small-angled yaw, and the finite-element-method simulation verifies the correctness and effectiveness of the presented modified strategy. Based on the current compensation strategy and phase correction strategy, the modified positioning strategy with six degrees of freedom for MLPMPMs is presented.(5) The comprehensive experiment platform for MLPMPM is constructed, based on which some experiments are developed. The static experiment platform for MLPMPM is first designed, and then the corresponding static experiment is developed, which verifies the correctness of the presented decoupling current allocation strategy. The software and hardware systems of digital control platform are built based on DSP TMS320 F28335, and then the dynamic experiments for MLPMPM based on the position and speed double closed-loop PID control and active disturbance rejection control are developed. The dynamic performance of the designed closed-loop control systems is analyzed, and the effectiveness of active disturbance rejection control method for MLPMPM with small-angled yaw is verified. |
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