Actual Difference between Servo Motor and Stepper Motor

In electrical and electronics engineering, for robotics design, automation systems, controlling, servo motor, and stepper motor have very important roles. There are many confusions between the servo motor and the stepper motor. So, in this article, we are going to know the actual difference between Servo Motor and Stepper Motor. Although they do almost the same work, but their constructional structure and working procedure are different. So, let's go to know the difference between the stepper motor and servo motor, their applications, advantages, etc.

difference between stepper motor and servo motor

Constructional Difference between Servo Motor and Stepper Motor

1. A servo motor consists of four things in its construction - DC Motor, Gear mechanism, position sensor, and a control circuit.

A stepper motor consisting of continuous rotation DC motor, multitooth stator. It does not have any position sensor or control circuit.

2. Servo motor has less number of poles(generally 4 to 8)

Whereas the stepper motor has 50 to 100 number of poles. 

3. A servo motor has three terminals - Power, Ground, and Control

Whereas a bipolar stepper motor has four or eight terminals and a unipolar stepper motor has 5,6, or 8 terminals.

4. Stepper Motor is more compact than servo motor as it does not have any gear mechanism and designed to operated with low weight loads.

On the other hand, servi motor generally bigger in size than the stepper motor as it has inbuilt gear mechanism and Control circuits.

Operational Difference between Stepper Motor and Servo Motor

Stepper Motor Operation

The operation and controlling of the stepper motor are complex. An external controller(microprocessor) and the motor driver must be required to operate the stepper because it has more than four terminals up to eight terminals and required to individually energize the each electromagnet according to the required position of the rotation of the shaft. Stepper can rotate up to 360 degrees.

Stepper motor Block Diagram
Stepper motor Block Diagram

Servo Motor Operation

The operation of the servo motor more simpler than the stepper motor. The Servo motor cannot rotate in 360 degrees, it only rotates up to 180 degrees. There is no external controller circuit or microprocessor circuit required to control the servo motor. Only PWM(Pulse width modulation) signal is enough for its operation.

As we know servo motor has three terminals, power, ground, and control. Power to the servo motor continuously applied through the power and ground terminals, and the PWM signal applied to the 'control terminal' to control the position of rotation of the motor shaft. By adjusting the pulse signal we can get the accurate position of the shaft.

Servo motor Block Diagram
Servo motor Block Diagram

Difference between features and advantages of Servo and Stepper Motor

1. Torque: Servo motor can provide high torque and also time-dependent peak torque than a stepper motor. Another advantage of servo motor is, we can control the torque as per our requirement.

On the other hand, the Stepper motor also can provide high torque when it is running at a very low speed, when its speed increased torque decreased. Whenever a stepper is running, it only runs in high torque, we cannot control the torque of the stepper motor.

2. Speed: Servo motor is specially designed for high-speed applications. It can rotate in 180 degrees, and provide a much higher speed than a stepper motor. A Servo motor also provides higher acceleration than a stepper motor.

Stepper motor mainly designed to get multiple stepping and accurate positioning, it cannot provide high speed.

3. Stepping: Stepper motors are most suitable for multiple stepping, micro-stepping, and accurate positioning with low inertia. As the stepper motor has a huge no of poles so it can provide all those features regarding stepping.

On the other hand, a servo motor cannot provide multiple stepping, micro-stepping like a stepper motor.

4. Loop Feature: Servo motor works in a closed-loop system. This feature of the servo motor makes it easy to control. We just required a PWM signal to control or operate the servo as per our requirement. In fact, the term 'Servo' indicates the Closed Loop System.

On the other hand, a stepper motor works in an open-loop system, that is why its operation and control is hard. We must need a motor driver and microcontroller to operate a stepper motor.

5. Application: Servo motors are used for high torque, holding, and polling applications. For example, machine tools, actuators, control systems are used servo motors.

On the other hand, stepper motors are used for smooth control operation, accurate positioning, micro-stepping applications. Example - Robotics application, surveillance products, camera, etc.

Other key differences between stepper and servo motor are given below.

Stepper Motor VS Servo Motor

Servo Motor

Stepper Motor

It works in a closed-loop system

It works in an open-loop system

It can rotate up to 180 degrees

It can run up to 360 degrees

Best for high-speed applications

Best for low-speed applications

We can control its torque

We can’t control its torque

Hunting problem, and high inertia at the stopping position

No hunting problem and low inertia at stopping position

It has poles four to eight numbers

It has poles 50 to 100 numbers

Not best for accurate positioning and micro-stepping

Best for accurate positioning and micro-stepping

Best for vertical load, high torque and speed applications

Best for smooth operation, accurate positioning applications

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Actual Difference between Servo Motor and Stepper Motor Actual Difference between Servo Motor and Stepper Motor Reviewed by Author on December 23, 2020 Rating: 5
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