Research And Production Of High Performance Vector Control For AC Spindle Drive

Spindle drive system is one of the most important components for CNC machine.The pros and cons of its performance is essential to evaluate the overall level of CNC machine.At present,the spindle drive system is moving towards the direction of high-speeding,precision,intelligence and recombination,and plays an important role in the national economy.Induction motor with low price,simple structure,high reliability,easy maintenance and other obvious advantages has been widely used in the spindle drive system.Now,the vast majority of CNC machines use induction motor equipped with frequency converter of vector control.In this paper,the vector control theory of induction motor and the design of PI regulator are briefly analyzed.Then,from the perspective of practical application,it makes a thorough theoretical analysis and simulation and experimental research in terms of several key technologies,such as rotor flux observer,field-weakening control and speed estimation strategy.In vector control system of induction motor,the key point is to estimate rotor flux accurately.The inaccuracy will lead to incomplete decoupling,instability and degradation of dynamic performance.However,the accuracy of the rotor flux observer affected by parameters is introduced into the traditional voltage model and current model.In order to solve these problems,a hybrid model rotor flux observer is proposed.And the parameters are calculated by using the second-order butterworth high-pass filter.Simulation results show that the rotor flux is less affected by the parameters of the motor,and the stability is optimized.In the traditional field-weakening methods,it can’t achieve maximum torque output.In order to solve this problem,a novel approach for the induction machine control which ensures producing maximum torque over the entire field-weakening region is presented.Considering voltage and current constraints,the optimal current vector locus for maximum torque operation was derived by mathematical method.Then,following the design guidelines,an alternative control algorithm was developed for the implementation.The simulation results show that the proposed method can realize the maximum torque output over a wide speed range and the system has a good dynamic response.For high-performance vector control,the closed-loop control of speed is essential.The key problem of the speed sensorless control is how to estimate the speed.The solution is to estimate the speed by using the voltage and current signal which can be measured easily.In this paper,two methods including back electromotive force method and sliding model observer are used.The simulation results show that two methods can estimate the speed accurately.And the advantages and disadvantages of the two methods are analyzed and compared by simulation.Finally,an experimental platform of high performance vector control for AC spindle drive system is built.On this experimental platform,the theoretical analysis and simulation research of the proposed control strategies are verified.The experimental results show that the control strategies can effectively solve some key problems of high performance vector control for AC spindle drive,and can significantly improve the performance of spindle drive system.