Servo Motor

 

A servo motor is a type of motor that is highly accurate and fully obedient to the control signals. It is able to convert the input voltage signal into torque and speed, thereby driving and controlling the object, ensuring that its speed and position achieve the desired accuracy. Therefore, servo motors are very commonly used in position and speed scenarios requiring precise control, such as widely used in automation equipment, robots and CNC machine tools.

 

The servo motor is usually closely coupled with the servo drive to form a "servo system". The system includes accessories such as servo controller and encoder, which monitors the position and speed of the rotor through the feedback signal of the encoder, and makes real-time adjustment according to the control demand to ensure the high precision and stability of the system.

 

The structure of the servo motor is usually composed of a stator and a rotor. There is usually only one field winding on the stator, which is used to generate a fixed magnetic field; The rotor, however, may contain permanent magnets or induction windings. By changing the current in the stator windings, the rotor is driven and rotates accordingly, allowing for precise speed and position control. This structural design enables the servo motor to respond quickly to the control signal and provide excellent performance in a variety of application scenarios.

 

 

Servo motor plays a key role in many industrial applications, especially where there are strict control requirements for speed and position.

 

1. Precise control of speed and position

Servo motor can accurately control the motion position and speed, positioning accuracy of 0.001 mm, to ensure that the mechanical equipment runs smoothly and accurately. Whether it is processing equipment, robots, or precision instruments, servo motors can provide high-precision control to meet the needs of complex precision operations.

 

2. Closed-loop control

Servo motor adopts closed-loop control system, which can monitor the difference between the actual output and the preset target in real time. The speed, position and direction are adjusted through the feedback system to ensure that the mechanical parts operate according to the set trajectory or expected state. This closed-loop design effectively improves the stability of equipment operation and the reliability of control.

 

3. Fast response

The dynamic response time of the servo motor is usually within tens of milliseconds, which can quickly respond to changes in the control signal. The fast response characteristic is particularly important in applications with high dynamic performance requirements, such as robots, automated production lines and other scenarios, helping to achieve efficient and fast action execution and switching.

 

4. High performance

Servo motor still maintains high power output and efficiency under high-speed operation, which is very suitable for operation under high-speed or heavy load conditions. Even in harsh industrial environments, the servo motor can achieve stable high-performance output with low energy consumption and improve the overall efficiency of the equipment.

 

 

The working principle of servo motor can be simply understood as a process of "input signal drives output motion".

 

1. Input control signal

The system first receives the input control signal. This signal usually contains a set point about position, speed, or torque, specifying the action the servo motor needs to perform or the state it needs to reach.

 

2. Servo controller

After the control signal enters the servo controller, the controller will adjust the parameters such as current, voltage and frequency according to the signal instruction to meet the target requirements. The servo controller processes the feedback information in real time and adjusts the output of the servo motor to ensure that it is consistent with the set target.

 

3. Servo motor

After receiving instructions from the controller, the servo motor starts to work. The motor provides the corresponding torque and speed according to the control signal, and drives the mechanical parts to move precisely. The encoder inside the servo motor also continuously monitors the actual output value and feeds the information back to the controller.

 

4. Output motion

The servo motor precisely outputs the motion according to the requirements of the input signal, thus completing the expected action of the system. This precision control process makes servo motors widely used in applications such as industrial automation, numerical control equipment and robotics.

 

Through this process, the servo motor realizes the motion control of high precision, high response and high efficiency, which provides guarantee for the accurate operation of the equipment.

 

 

Accuracy: The servo motor realizes the closed-loop control of position, speed and torque, with higher accuracy. The servo system detects the position and speed of the motor through the feedback device (such as the encoder), which can effectively overcome the out-of-step problem that may be caused by the stepper motor. The control mode of the stepper motor is usually open loop, and the out-of-step phenomenon may occur when the load changes greatly or at high speed.

 

Speed: The high-speed performance of the servo motor is better than that of the stepper motor, and the rated speed is usually between 2000 and 3000 RPM, and has better constant speed. The speed of the stepper motor is generally low, and the high-speed performance is not as good as the servo motor, so it is more suitable for medium and low speed applications.

 

Adaptability: servo motor anti-overload ability is strong, usually can withstand three times the rated torque of instantaneous overload, suitable for load fluctuations, as well as the need for rapid start and stop conditions. The stepper motor does not have strong anti-overload ability, and it is easy to lose step in the case of large load.

 

Stability: The servo motor runs smoothly at low speed, and will not produce obvious "stepping" phenomenon like the stepper motor, so it is better in the occasions that require high-speed response and smooth low-speed operation.

 

Response time: The dynamic response time of the servo motor is short, usually in tens of milliseconds to complete the acceleration and deceleration, suitable for applications with high response speed requirements. The response time of the stepper motor is relatively slow, especially when the load changes greatly, which may cause lag.

 

Comfort: The heat and noise of the servo motor are low, and the internal heat and noise of the motor are reduced due to the efficient operation brought by the closed-loop control. And stepper motor because there is no closed-loop control, often produce more vibration and noise.

 

Structure: The servo motor has no brush and commutator, which reduces friction loss, so the work is more reliable and the maintenance cost is low. The stepper motor generally does not have a brush, but its internal structure is different from that of the servo motor, and it will generate greater heat at high speed.

 

Heat dissipation: The heat dissipation of the stator winding of the servo motor is more convenient, and it can keep the temperature stable under long running. The stepper motor because of the structure and control mode, the heat dissipation efficiency is relatively low, easy to appear in the long time high load temperature rise problem.

 

Inertia: The inertia of the servo motor is usually small, the system response is faster, suitable for high-speed and frequent start-stop applications. The inertia of the stepper motor is relatively large, and the inertia is obvious when starting and stopping, which is not as flexible as the servo motor.

 

Application scenario: servo motor suitable for high speed, large torque working state, especially in the speed and precision of high requirements of industrial automation occasions. Stepper motor is more used in low speed, positioning accuracy requirements are relatively low occasions, such as printers, engraving machines and so on.

 

Volume and weight: at the same power, the volume and weight of the servo motor are often smaller than that of the stepper motor, making it more suitable for space-limited applications. Stepper motors are usually larger in volume and are not as superior as servo motors in scenarios where miniaturization needs to be higher.

 

 

Servo motors can be divided into many types according to their driving mode, structure and application scenarios, each type has its own characteristics and is suitable for different industrial needs.

 

Dc servo motor

Dc servo motor using DC power supply, fast response speed, simple control, often used in the need of high precision control occasions. Its structure is relatively simple, but the carbon brush needs to be replaced regularly to maintain normal operation.

 

Ac servo motor

Ac servo motors are powered by AC power and are suitable for operation in high speed or heavy load conditions. It has the advantages of high efficiency and low maintenance cost, so it is widely used in the field of industrial automation.

 

Brush servo motor

Brush servo motors rely on a carbon brush paired with a commutator to change the direction of the current. Although brushed motors are less costly and easier to control, the wear of the carbon brush leads to increased maintenance frequency and is suitable for use in some light-load applications.

 

Brushless servo motors

Brushless servo motor replaces mechanical commutation by electronic commutation, has no carbon brush, low maintenance cost and long service life. The brushless motor has the advantages of high efficiency and low noise, and is suitable for equipment that needs to work stably for a long time.

 

Continuous servo motor

Continuous servo motors are capable of continuous rotation and are suitable for application scenarios that control the direction and speed of motion, such as robots and automated production lines. This type of motor can achieve stable speed and high-precision positioning during movement.

 

Direct drive servo motor

Direct drive servo motor adopts direct drive mode, without intermediate transmission mechanism, the servo motor is directly connected to the load, providing extremely high control accuracy. This type of motor is usually used in equipment requiring high precision and high speed response, such as semiconductor equipment, CNC machine tools, etc.

 

Micro servo motor

Small size and light weight, micro servo motors are suitable for precision instruments, micro-robots and other scenarios that require miniaturization and high-precision control. Its precise control and low energy consumption make it an ideal choice for portable and small equipment.

 

 

Choosing a servo motor is an important step in ensuring efficient and stable operation of the equipment.

 

1. Determine the application

Determine the type of servo motor according to the specific application. For example, for industrial automation and manufacturing equipment, servo motors with high precision and high dynamic response are needed; And in small robots, automatic doors and other applications, you need a small size, moderate power servo motor.

 

2. Determine the motor characteristics

The characteristics of the motor such as output power, speed, torque, control accuracy, dynamic response and load performance are the key to choosing a servo motor. According to the load requirements of the equipment, choose the appropriate torque and power to ensure that the motor can provide enough driving force. At the same time, the stability and efficiency of the motor in high-speed operation should be considered to meet the operation needs of different applications.

 

3. Determine the type of drive

Different servos use different drive types. When choosing a servo motor, verify that the drive it is paired with is compatible and capable of providing sufficient voltage, current, and control functions to ensure optimal motor performance.

 

4. Consider suppliers and services

Choosing a reliable supplier and brand can greatly improve the experience and service life of your servo motor. Excellent suppliers can not only provide suitable motor products, but also provide comprehensive technical support and after-sales service to ensure the normal operation and daily maintenance of the motor.

 

VSD company has rich experience in motor research and development and dozens of technical patents, can provide a variety of servo motor options according to your needs, and support customized services. Whether you need high precision positioning or fast dynamic response, VSD can recommend the right motor solution for you.