| For the demands of high speed and high accuracy, the use of active magnetic bearings (AMBs) plays a key role in various situations such as clean room, compressor, satellite and so on, due to their contactless nature, no lubricated, no pollution, high-precision, long service life, and etc.. A new-style AC active magnetic bearing is proposed in the dissertation. Compared with the traditional DC magnetic bearing, the AC AMB has many advantages, such as compact configuration, low cost, convenient driving and control, and so on. A new-style construction of electric spindle supported by five degrees of freedom AC active magnetic bearings is designed in this paper, state equation was established. Aim for lower temperatures, the optimum design for structural parameters of active magnetic bearing was discussed by using finite element method, and we get complete design parameters. On this basis, we adopted the improved H∞output feedback control method to suppress the radial and axial directions position perturbation of AMB systems effectively. The digital control system of electric spindle supported by five degrees of freedom AC AMBs is developed. The basic theory and proportional integral derivation (PID) robustness stability region tests of electric spindle system’s five degrees of freedom suspension supporting technology are researched. The dissertation research is supported by National Natural Science Foundation of China project (60974053) and Jiangsu Province Natural Science Fund (BK2012707). The main contents of the dissertation and the achievements are as follows:1. A three-phase AC active magnetic bearing was designed which was used in high speed electric spindle’s suspension, respectively. The flux path of this magnetic bearing was calculated by using equivalent magnetic circuit, and the mathematical models of suspension forces were deduced respectively. Then based on the mathematics models, the relatively design parameters were given. The control strategy of three-phase AC active magnetic bearing was also proposed, respectively.2. Radial active magnetic bearing’s thermal field parametric finite element method is proposed. A model of equivalent thermal conductivity of the stator coil winding is set up, by means of which the difficulty in calculating the active magnetic bearing thermal field is reduced to some extent. The air gap heat exchange between the stator and rotor is worked out. By means of setting up the equivalent thermal circuit, the way to heat dissipation of the stator coil winding is given and temperature rise influence on coil winding is legitimately treated. On the basis of the equivalent volume of the stator is calculated, heat generation rate of winding copper loss is precisely calculated. According to the electromagnetic field design parameters, the active magnetic bearing’s temperature field and thermal loss is further analyzed, so, thermal Field numerical calculation of the radial active magnetic bearing is given, which could help optimum design of active magnetic bearing in the future. Based on the orthogonal design method which has three three levels factors, a parameters optimum design method was researched in this thesis. On the premise that the product design could satisfy the demands of maximum static suspension forces and maximum suspension forces, an optimization design method about active magnetic bearing was studied and the best combination of the parameters about temperature are given. The simulation proved the validity of the model and the practicability of the method used in the research.3. We propose the improved H∞output feedback control method for suppressing the radial and axial directions position perturbation of AC AMB systems. In this research, two other control options for high speed machine were designed based on the optimal output feedback and the improved H∞output feedback control methods to improve the radical and axial position regulation of AMB. The output feedback control gain matrix with the minimum performance index is obtained by solving the Riccati equation and fed back to the system in order to achieve the system’s performance. The above designed controllers can efficiently regulate the radial and axial directions position deviation of for AMB systems. Simulations for the two control methods were carried out using Matlab and Simulink for AMB system models. Results show that the improved H∞output feedback controller has a better position deviation control performance over the optimal output feedback under condition of decreasing the disturbance of reaction.4. A method is proposed for finding all PID controllers that satisfy a robust performance constraint for a given transfer function of any order with time-delay by using the frequency response. The H-infinity index of additive weight uncertainty on the basis of robustness stability condition of closed loop system is first get by small gain theorem. Then, Based on the boundary crossing theorem, the parameter boundaries with the expected decay ratio index of PID controller are derived. The system can be stabilized and robustly meet the performance requirements by choosing PID controllers parameter in the stability region. The proposed method avoids the complexity of stability regions of PID parameters, the closed-loop system has strong robustness for any order time-delay system with no accurate model. The simulation results demonstrate the validity of this method. 5. Finally, the five degrees of freedom AC AMBs system’s software and hardware circuits based on digital signal processor TMS320F2812DSP have been designed, the flow charts for main program and interrupt programs have been listed too. Local experiment is done. The verification on the effectiveness of the being proposed algorithm in chapter five was put forward by a living example to realize the AC active magnetic bearing stably suspension. The detailed experimental and testing procedures have been proposed, which establishes a good foundation for the next parameters debugging and function test. |
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