Research On Electro-spindle System Supported By AC Hybrid Magnetic Bearings

Magnetic bearings have widely potential application prospect in the area of machinery industry, aerospace, energy resource and communication due to the advantages of no abrasion, no lubricated, no pollution, high-precision, long service life, etc. A new-style AC hybrid magnetic bearing is proposed in the dissertation. Compared with the traditional DC magnetic bearing, the AC HMB has many advantages, such as compact configuration, low cost, convenient driving and control, etc. On this basis, a new-style construction of electric spindle supported by five degrees of freedom AC hybrid magnetic bearings (HMBs) is designed, state equation was established, and a dynamic decoupling control approach based on inverse system method is developed for the new-style construction. The digital control system of electric spindle supported by five degrees of freedom AC HMBs is developed. The basic theory and typical tests of electric spindle system’s five degrees of freedom suspension supporting technology are researched. The detail contents are as follows:Firstly, a new-style construction of electric spindle supported by five degrees of freedom AC HMBs is introduced. The configurations and working principle of axial one-degree freedom active magnetic bearing (AMB) and radial two degrees of freedom AC hybrid magnetic bearing (HMB) are introduced in detail respectively, and mathematics models of them are educed. An axial AMB and a radial AC HMB experiment prototypes are designed.Secondly, Nonlinearities of suspension forces of axial AMB and radial AC HMB are analyzed by using simulation software MATLAB. Coupling between two degrees of freedom of radial AC HMB are also analyzed by using MATLAB. The experiment prototype models of axial AMB and radial AC HMB are built by using finite element analysis software ANSOFT, the mechanical structures and magnetic circuit configurations of these two experiment prototype are calculated and analyzed, and the rationality and feasibility of configuration design are proved.Thirdly, a state equation for a kind of five degrees of freedom AC HMBs is set up, the parameters of the electric spindle is also designed. A dynamic decoupling control approach based on inverse system method is developed for the five degrees of freedom rotor system supported by AC HMBs, which is a multivariable, nonlinear, strong coupled system. The analytical inverse system of the HMBs is obtained by analyzing the reversibility of the mathematical model. The inverse system compensates original system to pseudo linear system which has linear transmission relationship. Then linear system theory is applied to this pseudo linear system to synthesize and simulate. The simulation results have shown that inverse system control strategy can realize dynamic decoupling control among five degrees of freedom of the system.Finally, the five degrees of freedom AC HMBs system’s software and hardware circuits based on digital signal processor TMS320F2812 DSP have been designed, the flow charts for main program and interrupt programs have been listed too. Local experiment is done. The detailed experimental and testing procedures have been proposed, which establishes a good foundation for the next parameters debugging and function test.