Research On Velocity Estimation And Control About Pmsm Servo System

The permanent magnet synchronous motor (PMSM) AC servo system has employed many perfect control strategies, such as vector control, direct torque control, sensorless control, and even many novel control strategies including intelligent control, sliding mode control,etc., have been applied into the system. However, because of its widely use in aerospace, machine tools, robotics, industrial automation, electrical industry and so on, it needs more and more high performance,and many scientists are still diligently studying some key aspects and detail technologies about the servo system. In this paper,some research about velociy control based on the vector control system such as identification of the moment of inertia, the design of speed controller,etc., which affect the servo sytem's performance, have been done through other new methods.Firstly, the angular velocity and acceleration through first-order and second-order differential calculation of the position pulses from photoelectric encoder have serious errors. Single-dimension Kalman filter with adaptive system noise variance is proposed to estimate velocity, since the noise variance is associated with velocity and its variations. Combining with virtual error model method presented by Jazwinski, a polynomial expression multiplied by exponential is established to describe the adaptive noise variance approximately. Regarding the velocity out of Kalman filter as the reference input, the software PLL-type regulator is utilized to estimate acceleration, whose integral is another estimated velocity. Regulating the optimal proportional gain and integral gain, the acceleration can be estimated without differential computation when the PLL's estimated velocity can strictly follow the Kalman filter's estimated velocity. The step velocity and sinusoidal velocity signals are used to verify the above algorithm. The results demonstrate that the simplified single-dimension Kalman algorithm becomes succinct, and the filtered speed becomes smooth without jump and obvious ripple phenomenon, and the acceleration has fewer spikes than that of the differential method.Secondly, the ant colony vector moving algorithm is proposed to identify the load torque and moment of inertia for load-running PMSM servo system while run-time loading, in order to adjust the PI parameters and compensate the torque. Vector moving is decomposed into horizontal and vertical directions, one for moment of inertia, the other for load torque, and every ant position means one possible solution. With the sampled sequences of d-axis current and speed data, based on the minimum variance principle, the pheromone expression model is established, making the closer distance between the ant position and actual load and inertia, the more pheromone. The expecting distribution for ant colony is calculated after the total pheromone statistics. The ant colony is inspired to move towards the optimal direction with the convergence point for the identified results. The normalized distribution for ant colony is selected to improve convergence performance when the dynamic ant colony distribution is converted to the normalized range. Additonally, after analyzing the motor model, the output quantities error function which contains the parameters to be estimated, is established. The single-layer neural network using gradient method to dynamically update the weights is proposed to achieve estimation. Learning rate affects estimation accuracy and convergence rate.Then, the deadbeat ripple-free method is proposed for the design of PMSM servo system's digital speed controller. The continuous domain transfer function of PMSM drive model is converted into the form of discrete Z-domain transfer function. According to the speed command input in the Z-transform form, the error transfer function is pre-determined, making the speed can be output stable within a limited sample periods. Then on the basis of deadbeat ripple-free zero-pole configuration principle, the Z-form digital speed controller is derived to keep the current command from the controller become stable in several periods.Finally, to resolve the velocity resonace in the spring connection, the notch filter is designed by FIR and IIR method.The proposed ideas and methods have been verified by simulations and experiments, and the results shows that they are effective.In the follow-up study, these methods required to be constantly further improved so that they can be applied to the practical products.