What is an AC Servo System?

2020-09-01

AC servo systems include AC servo systems based on asynchronous motors and AC servo systems based on synchronous motors. In addition to the characteristics of good stability, good speed, and high precision, it has a series of advantages. Servo comes from the English word Servo, which means that the system follows external instructions to perform the desired movement. The movement elements include position, speed and torque. The development of the servo system has gone through the process from hydraulics, pneumatics to electrical, and the electrical servo system includes servo motors, feedback devices and controllers.

In the 1960s, the DC motor was first used as the main executive component.

After the 1970s, the cost-effectiveness of the AC servo motor continued to increase, gradually replacing the DC motor as the dominant executive motor of the servo system. The function of the controller is to complete the closed-loop control of the servo system, including torque, speed and position. We usually say that the servo drive already includes the basic functions of the controller and the power amplification part.

Although the open-loop servo system directly driven by a power stepper motor was once widely used in the so-called economical CNC field in the 1990s, it was quickly replaced by AC servo.

In the 21st century, the AC servo system has become more and more mature, the market is showing rapid and diversified development, and many domestic and foreign brands have entered the market to compete. AC servo technology has become one of the supporting technologies of industrial automation.

In the AC servo system, the types of motors include permanent magnet synchronous AC servo motors (PMSM) and induction asynchronous AC servo motors (IM). Among them, the permanent magnet synchronous motor has very good low-speed performance and can achieve high-speed control of field weakening. It has a wide speed range, dynamic characteristics and high efficiency. It has become the mainstream choice for servo systems. Although the asynchronous servo motor has a solid structure, simple manufacture and low price, there is a gap in characteristics and efficiency, and it is only paid attention to in high-power situations.