Design And Optimization Of Direct-driven Permanent Magnet Synchronous Machine For Electric Spindle

CNC machine tools is an important manifestation of the national basic manufacturing. High end CNC machine tools is the representative of the national sophisticated processing technology, the proof of the national manufacturing strength and the core competitiveness of the national equipment manufacturing. As a core component of high-end CNC machine tools, electric spindle determines the level of technology and processing capacity of high-end CNC machine tools. High-speed electric machine and its control technology are the key technologies of electric spindle, so the quality of drive machine is of vital importance to electric spindle. Nowadays, asynchronous machine is still widely used in electric spindle, however, the disadvantages of low efficiency, low power factor and the heat produced by the rotor, obstruct the development of electric spindle. Therefore, it is necessary to develop direct-driven permanent magnet synchronous machine(PMSM) for electric spindle and to explore the relevant law. The objective of this paper is to explore some valuable conclusions of direct-driven PMSM for electric spindle, while the parameters of controller are under consideration, and to design a direct-driven PMSM which meets the requirements of electric spindle.First of all, the development and research status of electric spindle and direct-driven PMSM at home and abroad are talked about in this paper. And the key technologies of electric spindle are showed in this paper as well. Then the characteristics of electric spindle and direct-driven PMSM are also described.Secondly, this paper summarizes the mathematical model of interior permanent magnet synchronous machine(IPMSM) and obtains the voltage equation and torque equation in the d-q coordinate system. Moreover, this paper discusses the operating modes and control strategies of direct-driven PMSM for electric spindle. Considering the capacity of the controller, this paper discusses how the current limit and voltage limit affect the machine's operation, and why the flux-weakening effect of d-axis component of armature reaction is necessary while the machine operates at high speed. The design method of direct-driven PMSM for electric spindle is also briefly discussed in the paper.In addition, this paper points out the technical requirements of direct-driven PMSM for electric spindle and preliminarily designs the machine. The research direction of this paper is to design a machine which meets the technical requirements, and study the techniques to improve torque density, while considering how to reduce the torque ripple and cogging torque, in order to improve the torque characteristics of the machine. Parametric method and Taguchi method are used to analyze how the slot opening width, the embedding depth of permanent magnets, shape of flux-barrier, auxiliary slots, slot skewing and rotor skewing affect the torque characteristics of the machine, and some valuable conclusions are drawn.The final design of the machine is checked in some areas, such as the demagnetization of permanent magnets in short circuit condition, mechanical strength and temperature distribution. The analysis results show that the design meets the requirements of demagnetization of permanent magnets, mechanical strength and temperature. And some margin is left.Finally, this paper constructs a vector control system model(MTPA), using the Matlab/Simulink software, to verify the feasibility and rationality of the final design.