Zhejiang Sankai Mechanical and Electrical Co., Ltd

Servo Motor

What is Servo Motor



A servo motor is a self-contained electrical device, that rotate parts of a machine with high efficiency and with great precision. The output shaft of this motor can be moved to a particular angle, position and velocity that a regular motor does not have. The Servo Motor utilizes a regular motor and couples it with a sensor for positional feedback. The controller is the most important part of the Servo Motor designed and used specifically for this purpose.


Advantages of Servo Motor

Higher Output Power

A servo motor produces a high output power. If you are into intense mathematical problems, you can calculate the output independently, but you can also let a servo drive do the job for you.



Efficient & Accurate

Ensuring accuracy is something everyone strives for, which is a specialty for the servo motor. It attains its precision by a rotating motor that relays a signal back to its position and speed drive. Encoder accuracy guarantees that everything comes out smoothly.

Accelerated Torque

Looking at the differences between a servo and a stepping motor, you will find that a servo motor can speed up loads due to its high torque ratio. It gets the increased torque from using gearboxes along with the engines to provide a reliable speed.

Short Period Management

An excellent detail about a servo motor is that it uses as much power as necessary, meaning it won't exert any extra energy, allowing for efficient power and torque usage for shorter periods.


Why Choose US



Our Factory
Zhejiang Sankai Machine and Electric Co.,Ltd is an integrative and professional manufacturer of power transmission device, which specialize in scientific research, production and marketing.


Adopting advanced detecting equipment and means, company establishes a quality control system that is in accordance with 1S0900 I: 2015. Products are sold all over the country, exporting to Southeast Asia, Europe, America and other regions. Sankai will continue, as we always do, to strive to become a leader of power transmission industry.


Our Products
Our company specialize in High Precision Planetary Gearbox, NMRV series Worm Gearbox, UDL series Stepless Speed Variator, SRC series Helical Gearbox, SKM series Helical-Hypoid Gearbox, Precision Gearbox for Robot Arm and PC Helical Gear Unit.


Quality services
Sincerely Sankai determine to provide service of better quality, in-time and fast reply to our clients. And Sankai is looking forward to cooperating with domestic and foreign friends and grow together with our hard work and professionalism.

Servo Motor Gear Box


Types of Servo Motor

AC Servo Motor - The most commonly used type of servo motor. These are typically synchronous motors meaning the motor speed is determined by the frequency of the supply voltage and the number of poles. These motors are usually fitted with an encoder which is used for giving closed-loop control feedback. They are also typically brushless motors, meaning no physical connection between the rotating shaft and the outside world. This makes AC brushless servo motors very efficient and reliable. They are used for high repeatability and high accuracy applications and can be controlled precisely. Common applications are robotics and industrial automation.


DC Servo Motor - These are simpler motors and are often mechanically commutated using brushes. The speed of the motor is directly proportional to the supplied voltage. The most common types of DC motors used in servo (closed-loop) applications are permanent magnet motors. DC motors offer a simpler, lower-cost design but are less efficient than an AC servo motor. DC servo motors are used in light-duty, low-cost applications.


Linear Servo Motors - A linear servo motor is similar to a rotary AC motor other than it is peeled open and laid flat. The permanent magnets are now the motor's stationary part, and the stator is now the moving part. Linear motors can produce high linear forces and can achieve very high accelerations. They are used for such applications as simulators and high-frequency testing.


Working Principle of Servo Motor

The servo system is an automatic control system that enables the output controlled quantities such as the position, orientation, and state of an object to follow any change in the input target (or given value). The servo mainly relies on pulses for positioning. Basically, it can be understood that when the servo motor receives a pulse, it will rotate the angle corresponding to the pulse to achieve displacement. Because the servo motor itself has the function of sending pulses, so the servo motor When rotating an angle, a corresponding number of pulses will be sent out. In this way, it will echo with the pulses received by the servo motor, or a closed loop. In this way, the system will know how many pulses are sent to the servo motor, and how many pulses are received back at the same time. , In this way, the rotation of the motor can be precisely controlled, so as to achieve precise positioning, which can reach 0.001mm. DC servo motors are divided into brushed and brushless motors. Brushed motors are low in cost, simple in structure, large in starting torque, wide in speed regulation range, easy to control, and require maintenance, but inconvenient maintenance (replacement of carbon brushes), electromagnetic interference, and environmental requirements. So it can be used in common industrial and civil occasions that are sensitive to cost.

Servo Motor Gear Box

Servo Motors Parts



A servo motor consists of three main components:
A motor: This can be either a DC motor or an AC motor depending on the power source and the application requirements. The motor provides the mechanical power to rotate or move the output shaft.
A sensor: This can be either a potentiometer, an encoder, a resolver, or another device that measures the position, speed, or torque of the output shaft and sends feedback signals to the controller.
A controller: This can be either an analog or a digital circuit that compares the feedback signals from the sensor with the desired setpoint signals from an external source (such as a computer or a joystick) and generates control signals to adjust the motor's voltage or current accordingly.


Dozens of parts make up a servo motor with each and every single part playing a vital role in the device's functionality. Here are its most important parts and the significant roles they play in the functionality of the servos.
Stator - A stator creates a rotating magnetic field to efficiently generate torque.
Winding - Current flows in the winding produces a rotating magnetic field.
Shaft - The shaft transmits the motor output power. This load is driven through the transfer mechanism.
Rotor - A rotor is a permanent magnet that is positioned externally to the shaft.
Encoder - An optical encoder always observes and calculates the number of rotations being completed and watches the position of the shaft.
Each part of the servo motor serves a huge purpose in making the servos properly function or work.


How to Control a Servo Motor
Servo Motor Gear Box
Servo Motor Gear Box
Servo Motor Gear Box
Servo Motor Gear Box

The control of a servo motor depends on the type of motor, the feedback mechanism, and the application requirements.
Generally, there are two types of control signals that can be used to control a servo motor: analog and digital.
Analog control signals are continuous voltage or current signals that vary proportionally to the desired setpoint. They are typically used for simple or low-cost servo systems that do not require high accuracy or resolution. For example, a potentiometer can be used to generate an analog control signal for a hobby servo motor.
Digital control signals are discrete pulses or bits that represent the desired setpoint in a coded form. They are typically used for complex or high-performance servo systems that require high accuracy, resolution, or communication. For example, a pulse-width modulation (PWM) signal can be used to generate a digital control signal for a brushless DC servo motor.
The controller of a servo motor can be either an external device or an integrated circuit within the motor. The controller receives the control signals from an external source (such as a computer or a joystick), and the feedback signals from the sensor and generates the appropriate control signals for driving the motor.
The controller can also implement various control algorithms to optimize the performance of the servo motor. Some of the common control algorithms are:
Proportional-integral-derivative (PID) control: This is a feedback-based control algorithm that adjusts the control signal based on the proportional, integral, and derivative terms of the error signal. It is widely used for servo systems that require a fast and accurate response.
Fuzzy logic control: This is a rule-based control algorithm that adjusts the control signal based on fuzzy sets and linguistic variables. It is useful for servo systems that deal with uncertainty or nonlinearities.
Adaptive control: This is a self-tuning control algorithm that adjusts the control parameters based on the changing conditions of the servo system. It is beneficial for servo systems that face disturbances or variations.

Servo Motor Gear Box


Applications of Servo Motors

Servo motors have a wide range of applications in various fields and industries. Some of the common applications are:
Robotics: Servo motors are used to provide precise motion and force for robotic arms, legs, joints, grippers, etc. They enable robots to perform tasks such as picking, placing, welding, assembling, etc.
CNC machinery: Servo motors are used to drive the axes of CNC machines such as lathes, mills, routers, etc. They enable CNC machines to perform accurate and complex machining operations such as cutting, drilling, engraving, etc.
Automated manufacturing: Servo motors are used to control the movement and position of various components and devices in automated manufacturing systems, such as conveyors, feeders, loaders, unloaders, etc. They enable automated manufacturing systems to achieve high productivity and quality.
Medical equipment: Servo motors are used to operate various medical devices and instruments such as surgical robots, scanners, pumps, ventilators, etc. They enable medical equipment to perform precise and safe operations and treatments.


Servo Motors Versus Other Motor Technologies

Servo versus stepper
Rather than relying on feedback loops, stepper motors move through a fixed number of steps per rotation, which can be controlled by discrete pulses from the stepper drive. This can have advantages and disadvantages, depending on the application. Learn more.


Servo versus induction
Induction motors have historically been used for single-speed applications, such as conveyors. Although modern induction motors and drives can incorporate feedback, they are not usually the best choice for highly dynamic applications requiring the most precise positioning.


Servo motor advantages
Servo systems provide the greatest possible positional accuracy, speed control and dynamic response. They are also highly torque-dense, delivering exceptional torque across the entire speed range.

Servo Motor Gear Box

How to Choose a Servo Drive Vs A VFD



Servo Drives and VFDs are used in machines to drive motors and control motion. They seem to do the same thing, so why choose a servo drive vs. a VFD?
VFDs are used with induction motors in applications that require velocity control. The ability to control velocity by varying the frequency of the voltage delivered to the motor distinguishes VFD systems. Another significant difference is that they do not use feedback on the motor, resulting in open-loop velocity control. This means that if there is a stall or if the load changes, VFDs will not compensate, resulting in less precise velocity control than servos. VFDs can be set to ramp up to a specific speed and then drive at that speed for extended periods.
As with many engineering decisions, there are no hard and fast rules, and there are numerous examples of servo drives and VFDs having capabilities beyond their traditional roles. For example, technological advancements and the constant need to provide more features make it no longer difficult to find servo drives that can power induction motors - both with and without feedback. Similarly, numerous VFDs can power motors with feedback (an induction motor with feedback is commonly referred to as a Closed Loop Vector motor or CLV). As a result, some areas overlap the capabilities of servo drives and VFDs.
When coordinated motion between multiple axes is required, servo drives are unquestionably the best option. Or when quick acceleration and deceleration are required, as with pick-and-place gantries. Or when exact sub-micrometer positioning is required for semiconductor applications or when precise velocity control is required to grow a silicon ingot.
When the velocity of a conveyor belt must be set to a specific speed, VFDs are the obvious choice. Alternatively, hydraulic pumps and air blowers can be used. Or in the case of some electric vehicles, where precise control is not required.

When both can do the job, the middle ground is reached. For example, in velocity mode and position mode applications, the precision would be considered a little loose for a servo but well within the capabilities of a VFD.
Conveyor systems are an excellent example. On the one hand, a simple conveyor application may only need to turn on in the morning and run at the same speed throughout the day. A variable frequency drive (VFD) would be an excellent choice. A servo system would be a better choice for a more demanding conveyor system that needed to start, stop, go forward, backward, match speed with another conveyor, and more.
There is a wide range of conveyor systems with varying requirements, some of which fall within the overlapping capabilities of both servos and VFDs. When there is no clear choice, the analysis boils down to performance, features, and price.


Servo Motor Hardware

Industrial servo motor control systems are composed by a group of devices responsible for actuating the servomotor under the project specifications in order to attend the process needs. The system is often segmented on the following device modules: 

Control System: The control system is responsible for reading the plant status and executing automation algorithms that will provide the necessary instructions for the servo system to execute. PLCs and CU (Control Units) are the brains of the operation; it is where bits and bytes will tell the hardware what to do;


Power System: Since we are dealing with the most diverse power specifications when it comes to industrial motors, Power Systems are responsible for treating the Power into the project specifications in all aspects, from power filtering, power isolations, power AC-DC/DC-DC/DC-AC conversion and finally delivering the final power specification directly to the motor. Reactors, Line Filters and Motor Modules make up the power group;


Motor and Data Exchange: Once the control system has run the control algorithms and the power has been transformed into the necessary specifications, this energy will now be converted in a physical actuation of the motor axis. The motor, in some advanced control systems, does not even need to be, necessarily, servo motors. Many servo controllers also support common induction motors + encoders as the mechanical output of the system. However, of course, the convenient equipment (servo or induction motor) should be specified according to the proper application needs.



How to Maintain Servo Motor

Regular Inspection: Perform visual inspections of the servo motor to check for any signs of damage, loose connections, or abnormal wear. Look for loose screws, damaged cables, or worn-out components. Inspect the motor's cooling system, such as fans or heat sinks, and ensure they are clean and free from debris.


Lubrication: Follow the manufacturer's guidelines for lubrication intervals and use the recommended lubricants. Proper lubrication helps reduce friction, heat, and wear within the motor. Pay attention to the motor's bearings and ensure they are adequately lubricated.


Cable Management: Proper cable management is crucial for the reliable operation of AC servo motors. Ensure that cables are securely fastened and protected from potential sources of damage, such as sharp edges or excessive bending. Check for any signs of cable wear or insulation damage and replace damaged cables promptly.


Environmental Considerations: AC servo motors may be exposed to harsh environmental conditions in certain applications. Take measures to protect the motor from excessive dust, moisture, or temperature extremes. Use appropriate enclosures or covers to shield the motor from environmental elements that could potentially affect its performance and reliability.


Calibration and Tuning: Periodically calibrate and tune the servo motor to maintain accurate control. Follow the manufacturer's guidelines for calibration procedures, which may involve adjusting the motor's feedback devices, controller settings, or gain parameters. Proper calibration ensures precise positioning and speed control.


Monitoring and Diagnostics: Implement a monitoring system to track the motor's performance parameters such as temperature, vibration, and current draw. By monitoring these parameters, you can identify any abnormalities or early signs of motor degradation. Use diagnostic tools or software provided by the manufacturer to analyze and interpret the collected data.



Q: What is a servo motor and its function?

A: A servomotor is a closed-loop servomechanism that uses position feedback (either linear or rotational position) to control its motion and final position. The input to its control is a signal (either analog or digital) representing the desired position of the output shaft.

Q: What is the difference between servo motor and normal motor?

A: Servo motors have the ability to be programmed to move in precise increments, so they can control the speed of an object or the direction of movement very precisely. DC motors, on the other hand, are only capable of moving objects in one direction at a time.

Q: Why is it called a servo motor?

A: The term "servo" refers to the control mechanism. In terms of technology, the mechanism that performs control is called the "master" and the mechanism being controlled is called the "slave." Both terms, "servo" and "slave" derive from "servus", the Latin word for slave.

Q: Is a servo motor AC or DC?

A: There are two types of servo motors, AC servos and DC servos. The main difference between the two motors is their source of power. AC servo motors rely on an electric outlet, rather than batteries like DC servo motors.

Q: How does a servo motor work simple?

A: Inside there is a pretty simple set-up: a small DC motor, potentiometer, and a control circuit. Gears attach the motor to the control wheel. As the motor rotates, the potentiometer's resistance changes, so the control circuit can precisely regulate how much movement there is and in which direction.

Q: Is a servo motor a DC motor?

A: But the servo motor is also a kind of DC motor which is specifically designed to work based on the PWM signal. And also the servo motor has high torque as compared to the DC motor. This makes the servo motor more suitable for the application where you want to use any driver for the precise angular rotation.

Q: Why do we need a servo motor?

A: Servos are mainly used on angular or linear position and for specific velocity, and acceleration. Companies heavily use servo motors because of how compact and potent it is. Despite its size, it generates quite the amount of power and is known to be incredibly energy-efficient.

Q: Do servo motors need lubrication?

A: Lubrication: Proper lubrication is crucial for the smooth operation of servo motors. Lubricating the motor bearings and gears helps reduce friction, heat generation, and wear.

Q: When would you use a servo motor?

A: Servo Motor uses include; Robotics – Servo motors are lightweight and small which makes them ideal for use in this upcoming industry. Simulation Applications – another modern industry which involves the use of Servo motors. Their desired features for simulation applications include speed, torque and smoothness.

Q: What is the two main types of servo motor?

A: Generally, there are two main types of this motor based on the supply used for its function. They are AC servo motors & DC servo motors.

Q: Why servo motors are used in industry?

A: Servo motors excel in precision, making them ideal for applications in industrial automation. Their high accuracy allows for easy adjustments to suit specific tasks while ensuring precise results. They also have strong motor output power to provide quick and precise movements while easily adjusting to changing needs.

Q: What is another name for a servo motor?

A: Another name of the servo motor is controlled motor, because these are employed in feedback control systems like output actuators & doesn't utilize for continuous energy alteration.

Q: Can we use DC motor instead of servo motor?

A: In fact, although many servo applications use synchronous AC motors, DC motors can also be used in servo systems. Synchronous AC motors are typically brushless (the exception being universal motors, which are mechanically commutated with brushes and can run on either AC or DC power supply).

Q: Are all servo motors brushless?

A: Both brushed and brushless DC motors can be used in servo systems, although brushed motors are less common in servo applications due to the wear and associated maintenance of the brushes and commutator.

Q: What is the most common servo motor?

A: One of the most prevalent servo motors, the positional rotation variety, is used in many applications. It has a shaft output that rotates at a maximum of approximately 180 degrees and includes several physical stops within its gear mechanism.

Q: What is the difference between a servo and a servo motor?

A: The servomotor includes the motor that drives the load and a position detection component, such as an encoder. The servo system vary the controlled amount, such as position, speed, or torque, according to the set target value (command value) to precisely control the machine operation.

Q: What is the basic servo motor?

A: Servo motors have three wires: power, ground, and signal. The power wire is typically red, and should be connected to positive pole (+) of your power source. The ground wire is typically black or brown and should be connected to the negative pole (-) of your power source.

Q: Is a servo motor AC or DC?

A: AC servo motors are suitable for low power applications. DC servo motors are suitable for high power applications. The AC servo motors are used in applications like robotics, machine tools, semiconductor devices, aircrafts, etc.

Q: What is 3 phase servo motor?

A: A typical 3-phase AC servo motor has a magnetic rotor and a field consisting of three phase windings. An AC servo amplifier, or linear power amplifier, feeds the control winding. Three-phase servo motors can be used at high-speed to drive the load, but are usually used as indexers for part placement.

Q: Which servo motor is best?

A: AC servo motors are highly accurate and easy to control. By only using electricity when in use, they produce less heat, are quieter, and provide more torque per weight. They are also smoother and more stable during operation and require less maintenance.

As one of the most professional servo motor manufacturers and suppliers in China, we're featured by quality products and competitive price. Please rest assured to buy servo motor for sale here from our factory. Contact us for quotation and free sample.

Inline Planetary Reducer, Harmonic Reducer, Motor