Servo drives, also called “servo controllers” or “servo amplifiers”, are control devices used to control servo motors. They work similarly to frequency converters acting on ordinary AC motors and are an important part of servo systems, mainly used in high-precision positioning systems. Usually, servo motors are controlled in three ways: position, speed, and torque, to achieve high-precision transmission system positioning.
1. Power
(1) Rated power: refers to the power that the servo drive can continuously output under normal working conditions, usually in watts (W) or kilowatts (kW). It determines the power of the motor that the servo drive can drive and is one of the important bases for selecting a servo drive.
(2) Peak power: refers to the maximum power that the servo drive can output in a short period of time. In some applications that require rapid acceleration, deceleration or overcoming large loads, peak power plays a key role and reflects the overload capacity of the servo drive.
2. Voltage
Input voltage: The power supply voltage required by the servo drive. Common types include single-phase 220V, three-phase 380V, and DC power supply. Different application scenarios and motor requirements correspond to different input voltage levels. The input voltage must match the power supply system, otherwise the drive may not work properly or even be damaged.
3. Current
(1) Rated current: The current value that the servo drive can continuously output under rated operating conditions. It matches the rated current of the motor and determines the driving force that the drive can provide to the motor.
(2) Peak current: The maximum current that the drive can output in a short period of time.
4. Control accuracy
(1) Position control accuracy: measures the accuracy that the servo drive can achieve in position control mode, usually expressed in pulse equivalent or minimum position resolution. High-precision position control is essential for applications that require precise positioning, such as robots and CNC machine tools.
(2) Speed control accuracy: refers to the accuracy of the servo drive in controlling the motor speed, generally expressed in speed fluctuation. In some applications that require high speed stability, speed control accuracy directly affects product quality.
(3) Torque control accuracy: refers to the control accuracy of the servo drive on the motor output torque. In some applications that require precise torque control, such as robot force control and electric injection molding machine pressure control, torque control accuracy determines the system control performance and product quality.
5. Response speed
(1) Current loop response speed: The current loop is an important part of the internal control of the servo drive. It is responsible for quickly adjusting the motor current to meet the torque control requirements.
(2) Speed loop response speed: The speed loop is used to control the motor speed. Its response speed is generally slower than the current loop, usually in milliseconds (ms). The speed loop response speed determines the motor’s ability to follow changes in speed.
(3) Position loop response speed: The position loop is the outermost control loop in the servo system. It controls the movement of the motor based on the deviation between the target position and the actual position. The response speed of the position loop is relatively slow, but it also has an important impact on the positioning accuracy and dynamic performance of the system.
6. High-precision control
(1) Good linearity: A highly linear relationship between the output signal and the input signal can be achieved, ensuring that the movement of the servo motor accurately follows the changes in the control signal. In applications that require high-precision positioning and motion control, such as semiconductor manufacturing equipment and precision machine tools, the positioning accuracy can be controlled at the nanometer level.
(2) Low distortion: The control signal has a high degree of restoration and less harmonic distortion, allowing the motor to run according to the expected motion trajectory, which helps to improve processing accuracy and product quality.
7. Fast response
(1) Fast current response: The output current can be adjusted quickly to meet the current demand of the motor during movement. This enables the servo motor to respond quickly to control instructions, achieve rapid position and speed changes, shorten the movement cycle, and improve production efficiency.
(2) Smooth output: Provides smooth voltage and current output to reduce jitter and noise during motor operation. This is crucial for some equipment that requires high running smoothness, such as medical equipment, optical instruments, etc., and helps to improve the reliability and service life of the equipment.
8. Low noise
(1) Adopt linear amplification technology: Linear servo drives usually adopt linear power amplifiers, whose working principle is to linearly amplify the input signal so that the output signal can accurately track the changes of the input signal. This amplification method avoids the high-frequency switching noise common in switching power supplies, thereby reducing the noise level of the drive itself.
(2) Optimized power supply design: Linear servo drives are usually equipped with high-quality power modules with good voltage regulation and filtering performance. These power modules can provide stable and pure DC power to the drive, reducing the impact of power supply noise on the drive and motor.
9. Complete protection functions
(1) Multiple protection mechanisms: Equipped with multiple protection functions such as overcurrent protection, overvoltage protection, overheating protection, and overpower protection. When an abnormal situation occurs, it can quickly detect and take corresponding measures, such as cutting off the power supply or issuing an alarm signal to protect the drive and motor from damage caused by overload, overvoltage, overheating and other faults.
(2) These characteristics of linear servo drives make them widely used in the field of industrial automation with extremely high requirements for accuracy, speed and stability, but the relatively high cost and high power consumption limit their application in some cost- and power-sensitive occasions to a certain extent.
