Servo System
Servo is a closed-loop feedback control drive system that receives signals and executes quickly and accurately commands from the PLC. The servo set includes a servo controller (servo drive), a servo motor and an encoder to feedback signals from the motor to the controller. Servos are used for precise position control, torque adjustment to suit different applications, and extremely fast speed changes (response in ms).
What is a servo motor? Structure and working principle of servo motor?
1. Structure and classification:
The servo motor is a component in the servo system. The servo motor receives the signal from the controller and provides the necessary movement force to the mechanical devices when operating with extremely high speed and accuracy.
Servo motors are divided into 2 types: AC servo motor, DC servo motor. AC servos can handle higher currents and tend to be used in industrial machinery. DC servos are not designed for high currents and are generally more suitable for smaller applications.
The structure of AC servo motor consists of 3 parts: stator, rotor (usually permanent magnet type) and encoder:
- The stator consists of a coil wound around the core, which is powered to provide the force needed to rotate the rotor.
- The rotor is made of a permanent magnet with a strong magnetic field.
- The encoder is mounted on the rear of the motor to accurately feedback the speed and position of the motor to the controller.
The controller (Servo drive) is responsible for receiving the control command signal (pulse/analog) from the PLC and transmitting the command to the servo motor to control the servo motor to operate according to the command, and at the same time receive feedback signal continuously. about current position and speed of servo motor from encoder.
2. Working principle:
In principle, the servo motor is an independent device. However, servo motor has practical significance only when operating in servo system.
The servo operating mode is formed by closed-loop feedback systems. The servo motor receives an electrical pulse signal (PWM) from the controller to operate and is controlled by an encoder.
When the motor is running, the speed and position will be fed back to this control circuit through the encoder. When any reason prevents movement and distorts the desired speed and position, the feedback mechanism will feed back the signal to the controller. From the feedback signal, the servo controller will compare with the command signal and make appropriate adjustments, ensuring the servo motor works properly as required to achieve the most accurate speed and position.
Benefits of using AC servo
+ Extremely precise speed, position and torque control.
+ Fast response and response speed, low inertia (almost no inertia).
+ Operation efficiency is as high as 90%, low heat generation and almost no fluctuation.
+ High speed and fast, continuous changing working frequency.
+ Quiet, light, energy-saving operation.
AC servo system is suitable for most industrial applications such as machine tools, packaging machines, printers, cutters, roll collection applications, applications that need to be stopped at the right position, wire assembly lines, CNC machines, robotic arms…
