Optimization Design And Test Research On Electro-spindle System Supported By AC Hybrid Magnetic Bearings

Magnetic bearings have huge potential application foreground in the high-speed machine tool spindle system due to the advantages of no friction,in-gage,high-speed,high-precision,long service life,and so on.Magnetic bearings have changed the traditional supporting forms fundamentally,and created favorable conditions for improving the technological capability of high-speed machine tool spindle system.Because of the research of magnetic bearing at home and abroad is give first place to DC active magnetic bearings(AMBs) much at present,and the cost of DC power amplifiers is much higher than AC power converters.Be based on the principle of bearingless motor,our team have researched a new kind of AC two degrees of freedom hybrid magnetic bearing(HMB) and an innovated AC-DC three degrees of freedom hybrid magnetic bearing,which combine radial and axial hybrid magnetic bearings in a unit.This two kinds of magnetic bearings both use AC power converters to provide radial control current.This paper works is joint supported by National Natural Science Foundation of China project "Research on high-speed machine tool spindle system supported by AC hybrid magnetic bearing"(50575099) and National High Technology Research and Development Program of China (863 Program) project "Research on the application of bearingless permanent magnet synchronous motor in the robot-driven system"(2007AA04Z213).Based on the research of monolithic construction of high-speed electric spindle supported by five degrees of freedom AC hybrid magnetic bearings,the mechanical structure and magnetic circuit configuration of AC two degrees of freedom hybrid magnetic bearing and AC-DC three degrees of freedom hybrid magnetic bearing are designed and optimized.The digital control system of high-speed electric spindle supported by five degrees of freedom AC hybrid magnetic bearing is developed.The basic theory and typical tests of high-speed machine tool spindle system’s five degrees of freedom suspension supporting technology are researched.The detail contents are as follows:1.The working principle of AC hybrid magnetic bearing is introduced.Based on the configuration and working principle of several kinds of typical magnetic bearings are analyzed, the method of parameters design and design steps are presented.Two kinds of mechanical structure of high-speed electric spindle supported by five degrees of freedom AC hybrid magnetic bearings are designed.2.The configurations of AC two degrees of freedom hybrid magnetic bearing and AC-DC 3 degrees of freedom hybrid magnetic bearing are designed and optimized,respectively.The flux path of this two kinds of magnetic bearings are calculated by using equivalent magnetic circuit, the formulas and mathematics models of the axial and radial magnetic suspension forces are deduced respectively.Then based on the mathematics models,the control strategy of AC two degrees of freedom hybrid magnetic bearing and AC-DC three degrees of freedom hybrid magnetic bearing are proposed,respectively.The relatively design parameters are also given. Nonlinearities of suspension forces and cross coupling between different degrees of freedom are analyzed by using simulation software MATLAB.The mechanical structures and magnetic circuit configurations of this two kinds AC hybrid magnetic bearings are calculated and analyzed by using finite element analysis software ANSOFT,and the rationality and feasibility of configuration design are proved.3.To use the chip TMS320F2812 DSP of TI company as the digital controller of five degrees of freedom AC hybrid magnetic bearings system.The digital control system of five degrees of freedom AC hybrid magnetic bearings is designed.The hardware circuits are developed,such as displacement interface circuit,DSP development board,power driver circuit,and so on.The related software is designed,and related program flow charts are given.4.This paper takes the AC two degrees of freedom hybrid magnetic bearing as the object of study,the typical tests of high-speed electric spindle system supported by five degrees of freedom AC hybrid magnetic bearings are researched.The debugging methods and steps of tests are given. The VB debugging interface boundary based on visualization window is developed and designed. The floating test,static suspension test and disturbance test are carried out,and the correlatively displacement waveforms and current waveforms are given.The test results are analyzed,and the test conclusions are given.The validity of theory research is verified by the test results and conclusions.The results of theory research and test have shown that the configurations design are reasonable,parameters design are accurate,and control performance of digital control system is excellent for high-speed machine tool electric spindle supported by five degrees of freedom AC hybrid magnetic bearings.