Servo drives (servo drives), also known as “servo controllers” and “servo amplifiers”, are a kind of controller used to control servo motors. Its function is similar to that of frequency converters on ordinary AC motors. It is mainly used in high-precision positioning systems. Generally, the servo motor is controlled by three methods of position, speed and torque to achieve high-precision positioning of the transmission system. It is currently a high-end product of transmission technology.

Servo drives are an important part of modern motion control and are widely used in automation equipment such as industrial robots and CNC machining centers. Especially the servo drive used to control the AC permanent magnet synchronous motor has become a research hotspot at home and abroad. Current, speed, and position 3 closed-loop control algorithms based on vector control are generally used in the design of AC servo drives. Whether the speed closed-loop design in this algorithm is reasonable or not plays a key role in the performance of the entire servo control system, especially the speed control performance.

In the speed closed loop of the servo drive, the real-time speed measurement accuracy of the motor rotor is very important to improve the dynamic and static characteristics of the speed control of the speed loop. In order to seek a balance between measurement accuracy and system cost, an incremental photoelectric encoder is generally used as a speed sensor, and the corresponding common speed measurement method is the M/T speed measurement method. Although the M/T speed measurement method has a certain measurement accuracy and a wide measurement range, this method has its inherent defects, mainly including: 1) At least one complete code wheel pulse must be detected in the speed measurement cycle, which limits the minimum Measurable speed; 2) The two control system timer switches used for speed measurement are difficult to strictly keep in sync, and the speed measurement accuracy cannot be guaranteed in the measurement occasions with large speed changes. Therefore, it is difficult to improve the speed following and control performance of the servo drive by using the traditional speed loop design scheme of the speed measurement method.