A servo motor is a conventional motor fitted with an additional control sensor acting as a feedback device. A stepper motor is a brushless motor operated in tandem with an on-board driver.

As mentioned above, a servo motor is an ordinary motor equipped with an extra control sensor for feedback purposes. During operation, the controller maintains the motor at a set position. This interconnection principle enables the equipment to achieve speed and precision down to less than 1 micrometer.

To lock motion at a position and prevent reverse movement, the controller must continuously switch the motor current to the opposite direction until the next command is received. This method eliminates step loss, as the encoder constantly monitors shaft deviation and corrects errors by reversing the motor direction each time.

Disadvantages of Servo Motors

• Costly maintenance

• High upfront cost

A stepper motor is a brushless motor operated together with an on-board driver. Typically, stepper motors feature multiple phases (windings), which are energized alternately by the driver. The motor rotates when short pulses are applied to one of the stator windings, causing the magnetic rotor to shift position.

Stepper motors generally deliver low power and are not suitable for high-speed and continuous rotation.

Depending on rotor design, the motor’s physical step angle ranges from 90 degrees to 0.9 degrees. Software algorithms can be utilized to subdivide step angles, reduce driver noise, and improve precision by increasing the number of steps per revolution. Precision can reach 20 micrometers.

Despite the high precision of stepper motors, they have a notable drawback: since there is no feedback sent from the motor to the controller, step loss occurs under higher loads, and the controller cannot track the stepper motor’s operating status without an angular sensor.

Disadvantages of Stepper Motors

• Step loss under high acceleration and heavy loads

• Difficult maintenance

Encoder-equipped stepper motors are identical to conventional stepper motors except for the additional wiring for the angular encoder. This solves the problem of step loss but adds substantial cost. Furthermore, a dedicated controller with step error correction functionality is mandatory.

Notwithstanding these drawbacks, stepper motors are widely adopted in large-scale industrial and consumer applications:

• Heavy-duty, high-precision machinery (metal processing, laser cutting)

• Light-duty CNC equipment (consumer 3D printers, engraving machines)

• Robotics (robots with complex kinematics)

• Toys (model cars, model aircraft)

Frequently Asked Questions

What similarities exist between stepper motors and servo motors?

Stepper motors are used in 3D printers and other equipment requiring precise motion control. Servo motors are deployed in devices that demand smooth motion.

The key similarity between stepper motors and servo motors is that both employ electromagnets to generate motion.

What advantages do servo motors have over stepper motors?

Servo motors can deliver high torque at high speeds. They are also easy to control and can be programmed to execute complex tasks, such as moving robotic arms in three-dimensional space. Servo controllers are less expensive than stepper controllers and have lower power requirements, making them ideal for mobile robots used in automobile manufacturing or warehouse automation.

Why choose a stepper motor instead of a servo motor?

The primary distinction between stepper motors and servo motors is that stepper motors are usually cheaper. Stepper motors also do not require load feedback to determine the amount of power to be applied to the motor shaft.

Which is more powerful: a stepper motor or a servo motor?

Stepper motors are less powerful than servo motors due to limited versatility. Servo motors can rotate continuously in any direction, while stepper motors only rotate in discrete steps.

Stepper motors have a more intricate internal design yet cost less to manufacture and operate. Servo motors carry a higher price tag and require greater operating power, but they offer superior precision and controllability.