Research on Uniform Cycle Control Ac Servo System

Research on Uniform Cycle Control Ac Servo System
　　CNC equipment is a sort of typical electro-mechanical system, which is the core of equipment manufacturing industry. To realize the performance of high-speed and high-precision, the whole optimal design based on the mechanotronics is necessary, and it requires the cycle of NC instruction to be the same with the cycles of machine and current in the servo system. The thesis purposes on the uniform cycle control of machine-loop and current-loop to get the better performance for the AC servo system, and provides a uniform cycle servo system platform to achieve the integrate uniform cycle control in the CNC equipment.In order to validate the superiority of uniform cycle control, the math model of permanent magnet synchronous motor (PMSM) in the d-q coordinates is built. Compared the control effects of the uniform cycle control structure with the ones of the different cycle control structure, the fluctuation of the uniform cycle control is extremely unconspicuous, and the curves of output Neodymium magnets are more ideal. The transfer functions of uniform cycle control system and different cycle control system are derived respectively in this thesis. The transfer function of uniform cycle control system is provided with the lowest relative degree and the best stability.
　　According to the models of the control system, the simulation platform is designed. Based on the simulation platrom, the velocity control is simulated with the uniform cycle control and the different cycle control. For the problems of current sampling noise, low velocity resolution and burdensome calculation based on the uniform cycle control, the effective solutions are proposed, which include the control algorithm with the integrate int calculation and the integrate int observer of current-loop and machine-loop.For the sake of realizing the uniform cycle control, a mass of calculation is needed to be carried out. In this thesis, the regulation based on the integrate int computing is proposed. To obtain the high-speed and high-precision vector transformation algorithm and simplify the vector transformation formulation, the algorithm of table looking-up which can get high-precision sine and cosine amount rapidly is designed. For the problem that the busbar voltage cannot be utilized sufficiently in 3-phrases PWM control, the algorithm of voltage vector center point translation is put forward, and the validity and precision are verified. Basd on the transfer function of current-loop model and mechanical-loop http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php model in the uniform cycle system, the flow chart of main program for servo control and uniform cycle control are designed. And the control software of system is develped. The hardwares which include control board, power board and power supply board are also designed and developed.To solve the problem of current sampling noise in uniform cycle control system, the recurrence formulas of the low-pass filter and the observer in current-loop are achieved, and the regulation of pole’s selecting is discussed. Also, the adjustor in current-loop is designed and the method of control parameters’selceting is discussed. The simulation models of current-loop and observer are established, and the observer poles’selection and control parameter’s range are acquired from the current control simulation, and the superiority of the observer is validitied. And then, the program models for current low-pass filter and current observer are built. Taking the current control experiment on the experimental platform, the results show that the observer can press the current sampling noise effectively and gain the higher current response frequency.In the uniform cycle servo system, the high machine-loop frequency brings the problem of low velocity resolution.
　　The recurrence of low-pass digital velocity filter is derived, the convergence condition is proposed, and the pole’s selection is dicussed. Based on the current-loop simulation model, the machine-loop simulation model is built, and the simulations of machine-loop and observer are carried out. The simulation results show the validity of the mechanical observer. Also, the velocity filter and machine-loop observer program modules are built, and the velocity control experiment is achieved based on the experimental platform. The experimental results indicate that the system adopting observer in current-loop and machine-loop is of higher response and stability.For the high frequency current control in the high-speed motor, the thesis achieves the conclusion that the frequency of PWM is requied to be 6 times lower than the current frequency. The present position detecting device cannot achieve nice effect in the high-speed condition, and the requirement for the position device in high-speed motor control is proposed. The characteristics of the single pole magnet encoder in the thesis meet the demand of high-speed motor control. For the problem that the angle errors exist in voltage vector transformation, the advancing compensation principle is put foward. Also, the method of angle uploading in encoder induces the delay http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php of angle feedback, and the delay calculation formula of angle feedback is derived. Then, the 4-poles PMSM (20,000 rpm) was designed, and the motor has achieved the highest speed of 22,000 rpm based on the uniform cycle servo control equipment.The successful application in the high-speed motor control indicates that the uniform cycle servo system in this thesis can achieve the high frequency current control and servo control in the condition of that the frequencies of PWM and current get their ultimate proportion. It bears out that the servo system is of the excellent control performance.