| With the rapid development of power electronic technology, micro-processor technology, rare-earth permanent magnet material technology and control theory, permanent magnet AC (PMAC) servo system, as an important drive part of the advanced automatic devices such as industrial robots and numerical control machines, has been developed to a high level of technology. The performance of the servo system is the pacing factor of the equipment running ability. Its application spreads in many fields of industrial application. Nowadays, most of the PMAC servo systems used in our country are imported from other countries. This situation restricts the development of our country's robot, numerical control and factory automatic equipment. Digital PMAC servo system is the development mainstream of AC servo system. Sponsored by the National High Technology Research and Development Program of China (863 Program) and Delta Power Electronics Environmental & Educational Foundation, PMAC servo system are detailed in two aspects of control strategies and system design. The investigated contents are shown as follows.The development on full digital PMAC servo system is carried out. A set of PMAC servo system with full digits based on DSP structure has been developed. The corresponding control mode, I/O interfaces and network communication function have been designed and developed according to the basic requirements of commercial servo pack. The menu interface of operational panel and its corresponding monitor software of host pc have been also designed. The new servo pack is helpful to the further research on PMAC servo system and supply a new blueprint for the future industrialization.The study on a novel improved feedforward decoupling method of current control is investigated. In order to improve the robustness and decoupling characteristic of current control methods with the variation of inductance and resistance, a unified structure of current controller is established based on two-degree of freedom in the synchronous reference frame. Four different kinds of values for feedback gain are investigated. The robust performance of current controller is analyzed deeply using singular value theory for the variation of inductance and resistance. Theory analysis and experimental results show that the improved current decoupling control strategy can enhance the decoupling ability and improve the robustness.Compensation method on the voltage distortion based on the online adaptive parameter identification is proposed. Dead-time effects in PWM voltage source inverter is analyzed in detail. A new method via the intermediate parameter based on online adaptive identification of motor parameters is proposed to compensate for the time-varying voltage distortion. Experimental results demonstrate the validity of the proposed method.The optimal design of speed controller parameter via PSO (Particle Swarm Optimization) is developed. The basic principle of PSO and its improved methods are introduced. The convergence analysis of two-dimension problem and parameter choice of PSO are discussed. A comprehensive satisfactory degree function is proposed as the performance evaluation function. Based on above works, a new optimal method is proposed to optimize the parameters of speed controller of PMAC servo system. Simulation and experimental results show that the proposed method has simple algorithm, easy implementation, faster convergence and higher quality solution.In order to resolve the stability problem at low speed using low-resolution encoder which digital filters and conventional instantaneous speed estimator cannot maintain the stability, a new speed observer based on multirate sampling observer is proposed to estimate the instantaneous low speed, a novel pole placement and observer gain method are also proposed. Simulation and experimental results demonstrate that the proposed observer can maintain the observer stability, especially in low speed range and improve the low speed estimation performance.
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