A speed detection method and system for an AC servo motor

Abstract

The invention discloses a speed detection method for an alternating current servo motor. The method includes the following steps that S1, the alternating current servo motor is started, and the initial position of an absolute type encoder installed on the alternating current servo motor is read and saved; S2, every other preset interval time t, current positions of the absolute type encoder are read and saved, and k detection positions are obtained; S3, values of (k-1) positions of alternating current servo motor rotation corresponding to the k detection positions are acquired; S4, the detection frequency k of the speed of the alternating current servo motor is compared with a preset sliding parameter x, and the comparison result is obtained; S5, according to the comparison result, the interval time t, the detection frequency of the speed of the alternating current servo motor, the values of the (k-1) positions of alternating current servo motor rotation and the sliding parameter x, the speed of the alternating current servo motor is calculated. The speed detection method has the advantages that when the motor runs at low speed, detection precision of a system is improved, and ideal speed characteristics and servo performance are achieved.

Description

technical field [0001] The invention relates to the technical field of AC servo motors, in particular to a speed detection method and system for AC servo motors. Background technique [0002] When the AC permanent magnet synchronous motor is running at low speed, it will appear low-speed instability. The so-called low-speed instability refers to the phenomenon that when the motor running speed is lower than a certain critical value, its running speed is pulsating. This phenomenon is also called low-speed jitter or low-speed crawling. In addition to the performance of the motor itself, in terms of detection, when the absolute encoder has a fixed number of digits (resolution), when the motor is running at a low speed, the accuracy and dynamic performance of speed detection are greatly limited. Therefore, the motor is often in a state of irregular rotation and stop, and the speed is difficult to control, which in turn affects the low-speed performance index of the entire servo...

AI Technical Summary

Problems solved by technology

[0006] When the motor is running at low speed, the difference between the output data of the absolute encoder decreases within the same time period. In order to ensure the detection accuracy, that is, each time there is a detection data that is not equal to the previous value, it is necessary to extend the sampling interval of the K method. , which increases the detection cycle of the motor speed, making the dynamic characteristics of the motor speed and the ability to suppress the disturbance torque worse, thereby affecting the stability of the entire servo system, and even causing the system to fail to operate stably in serious cases

Therefore, the traditional motor speed detection method is difficult to make the system obtain ideal speed characteristics and servo performance at low speeds

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