Stepper Motor vs Servo Motor: Difference and Comparison

Key Takeaways

1. Control Mechanism: Stepper motors are controlled by sending digital pulses, causing them to rotate at a fixed angle per step. In contrast, servo motors use a closed-loop control system with feedback to adjust their position based on desired and actual positions continuously.
2. Motion Accuracy: Stepper motors offer precise positioning accuracy in discrete increments due to their fixed step angles, while servo motors provide higher overall accuracy and stability through their closed-loop control system.
3. Torque and Speed: Stepper motors provide high holding torque but may not generate high torque at higher speeds. In contrast, servo motors offer high torque even at high speeds, making them suitable for applications requiring rapid changes in direction or speed.

What is a Stepper Motor?

A stepper motor is an electric motor. Its function is to convert electrical pulses into precise mechanical motion. It moves with precise steps, leading to its name, stepper. It comes with good low-speed torque. It has a compact size, and it is budget-friendly as well.

It offers less high-speed torque, and that can pose a shortcoming. It operates in an open loop and has a limited duty cycle. However, its main advantage is its capacity to retain accurate position control without external feedback.

It is made with multiple coils organized in a specific pattern. These coils are energized with electrical pulses to generate magnetic fields. The electrical pulses are delivered within a particular sequence, so the motor moves in a fixed direction.

However, a “missed step” can also occur if the load exceeds the determined capability or the input pulses are too fast. These motors are used in 3D printers, robotics, CNC machines, and automation systems.

What is a Servo Motor?

It is quite the opposite of a stepper motor. While stepper motors move with determined steps, servo motors can rotate constantly and precisely control the angular position.

It is made with a rotor, coils, and a control system for a position feedback device. It always comes with a feedback mechanism, which is rather costly. It is packed with several functions and has high-speed torque.

However, it also retains a few shortcomings, such as requiring tuning and only working with feedback, and it is not budget-friendly as the cost is higher. These motors come in different sizes and are used in CNC machines, aerospace systems, and robotics.

As a closed-loop system, these motors can maintain accurate position even under disturbances or exceeding in load. It also reacts quickly to changes in the control signal.

Difference Between Stepper Motor and Servo Motor

1. Stepper motors are regulated through open-loop control, while servo motors have closed-loop control.
2. Servo motors are faster than stepper motors. Servo motors are capable of accelerating speed and rate and offer precise movements that are quick as well.
3. When it comes to expense, stepper motors cost less than servo motors. The reason behind it is stepper motors do not need a feedback mechanism, but servo motors can not function without one.
4. The control circuitry is less complex for stepper motors; however, servo motors are more complex.
5. Stepper motors deliver more torque at low speeds, but in the case of servo motors, one gets more torque at high speeds.
6. Stepper motors move in small, accurate increments, and as a result, these are more precise than servo motors.

Comparison Between Stepper Motor and Servo Motor

Parameter of Comparison	Stepper Motor	Servo Motor
Control type	It has open-looped control.	It has closed-looped control.
Mode of movement	It moves in discrete steps.	It operated with continuous rotation.
Speed,	Its range of speed is limited and can not go beyond it.	It comes with a wide range of speeds.
Type of application	It is meant to be used in static applications.	It is intended to be used in dynamic applications.
Power efficiency	It is less power efficient.	It is more power efficient.
Maintenance	It does not require a lot of maintenance.	Its gears need regular maintenance for proper functionality.
Expense	It costs less.	It is costlier when compared.

References

1. https://www.sciencedirect.com/science/article/pii/S1474667015362133
2. https://books.google.com/books?hl=en&lr=&id=0m8NTozFZL8C&oi=fnd&pg=PA1&dq=Difference+Between+Stepper+Motor+and+Servo+Motor&ots=MFfZQisIG4&sig=-Rhql1pXi9Bvs4y-BMUz9jLR7-U