The basic structure and working principle of servo motor

The main structure of a servo motor consists of four parts. They are the rotor, stator, brake (holding brake), and encoder.

The rotor is the rotating part of the motor, generally consisting of shafts, and permanent magnets (rotor core). The stator is the fixed part of the motor, generally consisting of bearings, motor casing, stator core, windings, and other parts. The brake (holding brake) is an optional part, generally installed at the back of the motor, used to keep the motor rotor position when the motor is powered off, to prevent unnecessary damage caused by the load dragging the motor rotation due to the gravity of the load. Encoder plays the role of feedback motor rotor position, the role is equivalent to the eyes of the servo system.

Working Principle

1.System working principle

Servo system consists of servo motor and servo drive, servo drive receives the control instruction signal from the upper controller, at the same time, the drive compares the motor state of the encoder feedback and the instruction of the controller, when there is a difference between the two, the drive adjusts the current to the motor, controls the motor torque output to make the motor accelerate or decelerate, and ultimately, the state of the motor tends to be the same as the input instruction.

2. Driver working principle

The driver generally has two parts of the circuit, the power supply part and the control part.

Power supply section: The current is created to drive the servo motor, and its duty is to transmit the current to the motor, and it is further described as the rectification of the commercial power supply as shown in the figure below, which is divided into the current converter section that creates the DC power supply, and the inverter section that creates the current by inputting the UVW phase according to the motor slewing angle.

Control section: Depending on the control mode selected by the customer, the driver will turn on and call the relevant control function module. For example, under the current loop control mode, the driver is only responsible for controlling the torque of motor output to follow the command changes, and does not control the speed and position of the motor. Under the position loop control mode, the driver needs to control the motor torque output and motor speed at the same time, so as to achieve the purpose of controlling the motor position.