Servodrives (SERVodrives) also known as "servo controller", "servo amplifier", is used to control a servo motor controller, its role is similar to the inverter on the ordinary AC motor, part of the servo system, mainly used in high-precision positioning system. Generally, the servo motor is controlled by position, speed and torque in three ways to achieve high-precision positioning of the transmission system. It is a high-end product of transmission technology at present. 

Servo drivers are used in industrial robots and CNC machining centers and other automation equipment. 

In the speed loop of servo drive, the real-time speed measurement accuracy of motor rotor is very important to improve the dynamic and static characteristics of speed control. In order to find the balance between measurement accuracy and system cost, incremental photoelectric encoder is generally used as the speed sensor, and the corresponding speed measurement method is M/T speed measurement method. 

Although M/T velocimetry has certain measuring accuracy and wide measuring range, this method has its inherent defects, including: at least one complete code disc pulse must be detected during the velocimetry period, which limits the minimum measurable speed; 

The timer switches of the two control systems used for speed measurement are difficult to keep in strict synchronization, and the accuracy of speed measurement cannot be guaranteed in the measurement occasions where the speed changes greatly. Therefore, it is difficult to improve the speed following and control performance of servo driver by using the traditional speed loop design. 

Operating Principle

At present, the mainstream servo driver uses digital signal processor (DSP) as the control core, which can realize more complex control algorithm and realize digitalization, networking and intelligence. Power devices generally use intelligent power module (IPM) as the core design of the drive circuit,IPM internal integration of the drive circuit, at the same time with over voltage, over current, overheat, undervoltage and other fault detection and protection circuit, in the main circuit also added soft start circuit, in order to reduce the impact of the start process on the driver. The power drive unit first rectifying the input three-phase or mains power through the three-phase full-bridge rectifier circuit to obtain the corresponding DIRECT current. Three-phase permanent magnet synchronous AC servo motor is driven by three-phase sinusoidal PWM voltage inverter. The whole process of power drive unit can be simply said to be the process of AC-DC-AC.