1. Definition：

The servo motor is an automatic control system that allows for precise control of the object's position, orientation, state and other output controlled quantities by controlling the input quantity (given value). The etymology of Servo comes from Latin language “Servus”, which means to faithfully execute the master's orders.

Servo system generally consists of Servo Drive and Servo Motor. The Servo Drive provides Servo Motor the voltage and current to operate, and also control the output torque, output speed and stop position of the motor by adjusting the voltage (current) supplied to the motor. Types of Servo Motors are classified into different types based on their construction, such as the AC servo motor, and DC servo motor.

2. characteristic：

1. High precision

The servo motor is a closed-loop mechanism. Servo drive adjusts and controls the operation of motor according to the positional feedback of encoder. And because of the encoder, missed steps which is a common defect in step motor, would not appear in servo motor. Besides, encoder can adjust the output torque, speed, rotation angle and so on based on the status of load, which achieve compliance with instructions. The encoder with great precision can achieve very precise control and position. For example, the optical encoder commonly used in the industry has a single-turn resolution of 23bit, and the unit positioning accuracy is 1/8388608 after conversion, which divides a 360 degree circle of the motor into 8388608 parts.

2. Various control mode

Most servo motors support 6 control modes: position control, speed control, torque control, position-speed control switch, position-torque control switch and speed-torque control switch. According to the requirements of the equipment, different control methods can be selected flexibly to achieve different control effects.

3. widely used

The application of servo motor covers a wide rang. Common servo motors on the market from a few watts to dozens of kilowatts are available for related products.

4. High efficiency and long life

Due to the special closed loop control system, Servo Motor is able to control the motor output according to the status of load. With small heat, its efficiency is obviously higher than the ordinary motor, and the general conversion efficiency can reach more than 90%. It always has been the useful tool to be energy-efficient for the company. At the same time, because the servo motor (AC) belongs to brushless motor, the motor drive current commutation which is carried out in the driver with electronic components. Compared with the traditional brush of brushed motor, which is easy to wear, the servo motor is maintenance-free, with a life span of more than 10 years, and even has been used for decades and can operate normally.

3. Application

Servo motors have been around for a long time and are utilized in many applications which is used in machinery, metallurgy, electric power, petrochemical, shipbuilding, aerospace, construction, transportation, agriculture, scientific research and testing, etc. According to the classification of equipment, it can also be divided into machine tools, printing equipment, medical equipment, semi-conductive manufacturing equipment, 3C product manufacturing equipment, injection molding equipment, food processing equipment, security equipment, packaging equipment, textile equipment, laser processing equipment, robots, automatic production lines, etc. 

4. Basic construction

Servo motor is comprised of several parts namely a rotor, stator, holding brake, and encoder

The rotor is the rotating part of the motor, which is composed of a shaft and a permanent magnet (rotor core). The stator is the fixed part of the motor, which is generally composed of bearing, motor housing, stator core and winding. Brake (holding brake) is an optional accessory, which is generally installed at the back of the motor. It is used to keep the rotor position of the motor when the motor is power off, so as to prevent unnecessary damage caused by the load dragging the motor to rotate due to the gravity effect of the load. The encoder plays the role of provide the positional feedback of motor rotor, which is equivalent to the servo motor eye.

5. Working principle 

1.How the system works
Servo system is composed of servo driver and servo motor. Servo driver receives the control commands from the controller. At the same time servo drive will compare the control commands with the feedback about motor status from encoder. When there is a difference between these two parameters, servo driver will adjust the current supplied to the motor, control the motor output torque to make the motor speed up or slow down. Finally the motor state will be consistent with input instruction.
2.Working principle of servo driver

The driver consists of two circuits: the power supply part and the controlling part
Power supply part: This part supply current and drive the motor, whose duty is to pass the electricity to the motor. Further explain that the commercial power supply is rectified as shown in the figure below. There are two parts; converter part and inverter part. Converter part is used to producing DC power and inverter part is used to input UVW phase power according to the motor turning angle

Controlling part: Depending on the control mode selected by the customer, the driver will open and choose the relevant control function modules. For example, in the current loop control mode, the driver is only responsible for controlling the motor's output torque following the command changes, and does not control the motor's speed and position. Under the position loop control mode, the driver needs to control the output torque and motor speed of the motor at the same time. So as to achieve the purpose of controlling the position of the motor.

3.naming rule

Servo motor naming rules