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A Comprehensive Guide To DC Servo Motor

As the globe is progressing rapidly towards advancement, DC servo motors play a significant role in various fields. This advanced piece of equipment is planned to provide fast acceleration, precise positioning, as well as smooth operation throughout numerous range of applications.

Whether you are a starter or an experienced electrical engineer, this useful guide will equip you with a thorough understanding of DC servo motors. In this article, we will discuss everything related to DC servo motors. We will cover definitions, qualities, working principles, benefits, where they are used, etc. Without any further delay, let’s begin with our topic:

1. What is a DC servo motor?

Before introducing a DC servo motor, it is necessary to know what a basic DC motor is. An efficient machine that converts electrical energy into mechanical energy is known as a direct current motor or simply a DC motor. They are only utilized to produce rotation (continuous) and are not considered a great option for accurate movements.

On the other hand, a servo motor is special. It provides precise control of the movement of its drive shaft. If you require equipment that can take precise movements for your project a servo motor might be the best alternative. DC servo motor can perform position control, torque control and speed control, and you can also easily communicate with line of sight RS485, RS232, CAN bus, etc.

2. Working principle of DC servo motor

Feedback control systems, electromagnetism, and error correction play an important role in the working of DC servo motors. The motor starts its operation upon receiving a command signal. In this way, a positive feedback signal is generated. The magnetic field is generated when the current provided to the motor flows through the stator. The generated field interacts with an electromagnet or permanent magnets that are located within the rotor. Thus, resulting in the generation of torque that is helpful for the beginning of the rotation.

However, if any difference is detected between the command and feedback signal, then it results in the generation of an error connection signal that is amplified by an advanced amplifier known as an error-sensing amplifier. Error sensing amplifier helps in adjusting the speed, position as well as acceleration to match the command input. Several important parts including a control circuit, DC motor, and potentiometer play an important role in the efficient working of a DC servo motor.

3. Analysis of the internal structure of the DC servo motor

We can study the DC servo motor in two parts portion:

1.Electronic section
2.Mechanical gear section

Electronic section

It is an integral portion of the DC servo motor. It refers to important parts of the motor that are responsible for controlling the position of the motor. Besides position, the electronic section also regulates the speed and torque of the motor.

Several important parts including feedback sensors, motor drive circuitry, power amplifiers, control electronics, protection circuitry, digital signal processing (DSP), or microcontrollers are installed on the electronic section of the motor.

DC servo gear motor

In a DC servo motor, we can also add the gearbox on the top of the motor, the section’s role is to generate a low-speed high torque yield. The torque of the servo motor is the amount of rotating force a servo motor can apply. The working of the gear section is based upon the principle of gear ratio. Let’s understand the gear ratio.

Imagine two gears, an input gear having 12 teeth, and an output gear having 36 teeth. Now we can put both gears together to form a simple gear arrangement. This simple arrangement has a gear ratio of 3 ratio 1. It means for every three complete rotations of the input gear, the output gear will take only one complete rotation.

Due to this, the angular velocity of the larger gear has become one-third of the smaller gear. Also, the torque for the larger gear becomes three times compared to the smaller gear. And that’s how a low speed high torque output is achieved using simple gear arrangement. Industrial servo motors work on the same concept.

A DC motor is used for driving the gear section of a DC servo motor. In the gear section, the output gear in the motor section is connected with a compound gear train. For this specific servo motor, the equivalent gear ratio between the motor and output gear is 260 ratio 1. It means whenever the motor rotates 260 times, the output gear rotates only one time. Because of this, the output gear has a very low speed as compared to the motor but a very large torque.

4. Characteristics and advantages of DC servo motors

1.Constant torque speed regulation, during the process of servo motor speed regulation from rated speed to low speed, the torque is constant and will not decay. This ensures the torque of the wheeled electric vehicle during low-speed hillside operation and prevents the vehicle from rolling away.An ordinary brushless DC motor, according to the characteristics of the motor, has basically no torque between 0-300r/min and cannot drive the load normally.
2.The density and efficiency of DC servo motors are very high. Compared with the 4-pole-pair DC square wave brushless motors, DC servo motors are more high-density motors with 5-pole pairs and 10-pole pairs, which can save a lot space for mechanical structural engineers.
3.The DC servo motor has the function of locking torque, which is an essential function for our lifting equipment.
4.Because the DC servo motor has an encoder inside, it can achieve high-precision control, such as speed control, position control and torque control, etc. Thus, the synchronization of several wheels can be achieved very well.
5.Equipped with easy control techniques, they are easy to operate
6.DC servo motor drivers usually support CAN bus, RS232 and RS485 communication control
7.Due to the fact that they offer great reliability and low maintenance, they also provide stable performance and a long lifecycle.

5. The difference between a DC servo motor and a DC brushless motor

DC brushless servo motors are different from DC servo motors. Read on to know about the difference:
1.Different structures

The brushless DC motor is composed of a motor body and a driver and is a typical electromechanical integration product.Brushless motor refers to a motor without brushes and commutator (or collector ring), also known as commutator-less motor

2.Method of controlling:

Digital and analog controls are used in DC servo motors

Electronic commutation is used to regulate the algorithms of machines. Hall Effect sensors play an important role in DC brushless motors.


DC servo motors are used in different fields and sectors because they give efficient performance.

On the other hand, DC brushless motors entertain with high-speed operation along with quick responses.


Maintenance is often required for the smooth operation of the DC servo motor

DC brushless motors come with a maintenance-free design


DC servo motors are used in applications and equipment that have high requirements for precision control and low speed.

Brushless DC motors have natural advantages for fixed-speed operation, such as water pumps and oil pumps.

6. The difference between a DC servo motor and a stepper motors


A stepper motor operates on a signal typically sent as a step and direction command to the motor’s drive. These dictate the distance moved and velocity. However, some stepper motors also operate in closed and open-loop systems.

In a DC servo motor, the controller sends the command to the motor’s drive via pulse and direction or an analog or digital command. Which is related to position, speed, or torque. Once the drive sends the appropriate current to each phase of the motor. Built-in encoders record real-time positional data which is fed back to the controller.


A DC servo motor may entertain machines with great torque and more rapid speed. But there are still many cases where a stepper motor might be a better fit. For instance, in some applications, using a stepper motor can help your bottom line as it requires less routine and emergency maintenance.

7. The difference between a DC servo motor and an AC servo motor

There is a great difference between a DC servo motor and an AC servo motor. A detailed difference is listed hereunder:

1.Power supply:

As suggested by the name, direct current is used in DC servo motors for efficient operation. For example, batteries.

On the contrary, alternating current is used in AC servo motors..


DC servo motors have low voltage, high power, and high current, and are prone to overheating. They are not suitable for equipment that operates continuously for a long time.However, if you can add air-cooling assistance accessories such as cooling fans, you can also run it for a long time.
AC servo motors have high voltage and low current, which are suitable for equipment requiring long-term continuous operation.

3.Control method:

Digital or analog control methods are often employed in DC servo motors in order to control torque, speed, and rotations. The direction of the flow of current can be altered by commutators.

An AC servo motor is usually equipped with wound coils or permanent magnets along with a stator. Precise control is managed by electronic commutation.

4.Performance characteristics:

At low speeds, DC servo motors offer high torques. Similarly, you can get a dynamic response, uninterrupted duty cycles, and high-speed operation via an AC servo motor.


DC servo motors find application in numerous industries that require accurate monitoring including the printing sector, industrial automation, CNC machining, etc.

AC servo motors are the best option in high-speed packaging, automated manufacturing, etc.

8. Application of DC servo motor

Any industry that requires precise motion control, accurate positioning, high level of torque at minimum speed should get a DC servo motor. A high-speed servo motor finds its place in numerous fields. They are considered the top priority in the following sectors:

1.Robotics,AGV, RGV
2.CNC machining including lathes, milling machines, etc.
3.Plotters and printers
4.Industrial machines including pick-and-place machines, packaging machinery, conveyor systems, etc
5.Camera stabilization systems, such as Steadicams and gimbals
6.Medical equipment
7.Aerospace and defense
8.Automotive systems including throttle control mechanisms, seat adjustment, etc.

9. DC servo motor market distribution

Several important parameters including manufacturers, suppliers, and distributors play a key role in DC servo motor market distribution.


The DC servo motor market is populated by numerous professional manufacturers. Such developers develop motors in a wide range of sizes, configurations, and specifications according to the needs of industries and machines.


Based on the demand, the suppliers contact the manufacturer and get their order ready. They play an important role in DC servo motor market distribution. Distributors mostly contact wholesale suppliers to get a quote on DC servo motors.


They play an important role as an intermediate agent between supplier and end-user. They stock various configurations of DC servo motors according to the client’s requirements from the supplier and provide them to end-users.

According to an estimate, the market size of servo motors will reach $22.5 billion soon (by 2030). As the trend of DC servo motors is increasing rapidly, they have become the top option over other motors because they find their place in numerous applications. This distribution is affected by different market trends including competitive landscape, economic status, industry course, etc.

10. DC servo motor prospect and opportunity analysis.

 Doubtlessly, a DC-integrated servo motor plays an important role in providing accurate control of motion across various industries. Their demand is increasing rapidly because of the great adoption of robotics and advanced machines in various industries.

Industries prefer reliable and highly efficient solutions to increase their productivity and outcomes. In order to fulfill the current situation, a DC servo motor is a perfect fit. DC servo motors offer numerous opportunities. They have become an important component in various machines including robotics, and wind turbines. CNC machining, etc.

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