Classification and characteristics of servo motors

Classification and characteristics of servo motorsServo motor is a micro motor used as an actuator in an automatic control device. Its function is to convert an electrical signal into the angular displacement or angular velocity of the shaft.

Servo motors are divided into two categories: AC servo and DC servo

The basic structure of an AC servo motor is similar to that of an AC induction motor (asynchronous motor). AC servo motors have the characteristics of stable operation, good controllability, fast response, high sensitivity, and strict non-linearity indicators of mechanical characteristics and adjustment characteristics.

The basic structure of a DC servo motor is similar to that of a general DC motor. The DC servo motor has good linear regulation characteristics and fast time response.

Advantages and disadvantages of DC servo motors

Advantages: precise speed control, hard torque and speed characteristics, simple control principle, convenient use and low price.

Disadvantages: brush commutation, speed limit, additional resistance, wear particles (not suitable for dust-free and explosive environments)

Advantages and disadvantages of AC servo motors

Advantages: good speed control characteristics, smooth control can be achieved in the entire speed zone, almost no oscillation, high efficiency of more than 90%, low heat generation, high-speed control, high-precision position control (depending on the encoder accuracy), rated operating area Inside, it can achieve constant torque, low inertia, low noise, no brush wear, maintenance-free (suitable for dust-free, explosive environment)

Disadvantages: The control is more complicated, the driver parameters need to be adjusted on-site to determine the PID parameters, and more connections are required.

DC servo motors are divided into brush and brushless motors

The brush motor has low cost, simple structure, large starting torque, wide speed range, easy control, and maintenance is required, but it is easy to maintain (change the carbon brush), generate electromagnetic interference, and has requirements for the use environment, and is usually used for cost* *General industrial and civil occasions.

The brushless motor is small in size, light in weight, large in output, fast in response, high in speed, small inertia, stable torque and smooth rotation, complex control, intelligent, flexible electronic commutation mode, square wave or sine wave commutation, maintenance-free motor, high efficiency and energy saving , Small electromagnetic radiation, low temperature rise and long life, suitable for various environments.

AC servo motors are also brushless motors, divided into synchronous servo drive and asynchronous servo motors. At present, synchronous motors are generally used in motion control.

They have a large power range, a large power, large inertia, low speed, and an increase in speed with power. The uniform drop is suitable for low-speed and stable operation.

The rotor inside the servo motor is a permanent magnet. The driver controls U/V/W three-phase electricity to form an electromagnetic field. The rotor rotates under the action of this magnetic field.

At the same time, the motor’s built-in encoder transmits the feedback signal to the driver. The values are compared to adjust the angle of rotor rotation.

The accuracy of the servo motor is determined by the accuracy of the encoder (number of lines).