Differences Between Servo Motors and Stepper Motors

A servo motor is a conventional motor equipped with an additional control sensor that acts as a feedback device. A stepper motor is a brushless motor that operates in conjunction with an onboard driver.

Servo Motors

As mentioned, a servo motor is a standard motor fitted with a control sensor that serves as a feedback mechanism. During operation, the controller maintains the motor at the set position. This interconnected principle enables the device to achieve speeds and precision down to 1 micron or less.

To lock movement in a position without allowing reverse motion, the controller must continuously switch the motor current in the opposite direction until the next command is received. This method eliminates step skipping because the encoder constantly monitors shaft deviation and corrects errors by reversing the motor's direction each time.

Disadvantages of Servo Motors:

• Expensive repairs

• Higher cost

Stepper Motors

A stepper motor is a brushless motor that works with an onboard driver pair. Typically, stepper motors have multiple phases (windings) that are alternately activated by the driver. The motor rotates by applying short pulses to one of the stator windings, causing the magnetic rotor to move.

Stepper motors are generally lower in power and not suitable for high-speed or continuous rotation.

Depending on the rotor design, the motor's physical pitch can range from 90 degrees to 0.9 degrees. Software techniques can further refine the angle, reducing driver noise and improving precision by increasing steps per revolution. Accuracy can reach 20 microns.

Despite their high precision, stepper motors have a significant drawback: since there is no feedback from the controller, they skip steps under higher loads, and the controller cannot track the motor's operation without an angle sensor.

Disadvantages of Stepper Motors:

• Step skipping under high acceleration and heavy loads

• Difficult to repair

An encoder-equipped stepper motor differs from a traditional one only in its additional angle encoder wiring. This solves the step-skipping issue but significantly increases cost. Moreover, a special controller with step-error correction is required.

Despite these drawbacks, stepper motors are widely used in large-scale industrial and domestic applications, such as:

• Heavy-duty and high-precision machinery (metalworking, laser cutting)

• Light CNC machines (home 3D printers, engravers)

• Robotics (robots with complex kinematics)

• Toys (cars, airplanes)

Frequently Asked Questions

What are the similarities between stepper and servo motors?
Stepper motors are used in 3D printers and other devices requiring precise motion control, while servo motors are used where smooth movement is needed. Both use electromagnets to generate motion.

What advantages do servo motors have over stepper motors?
Servo motors can deliver high torque at high speeds. They are easier to control and can be programmed for complex tasks, such as moving a robotic arm in 3D space. Servo controllers are also cheaper than stepper controllers and have lower power requirements, making them ideal for mobile robotics in automotive manufacturing or warehouse automation.

Why use a stepper motor instead of a servo motor?
The main difference is that stepper motors are generally cheaper than servo motors. They also do not require load feedback to determine the power needed for the motor shaft.

Which is more powerful: stepper or servo?
Stepper motors are less powerful than servo motors due to their lack of versatility. Servo motors can rotate continuously in any direction, while stepper motors only move in discrete steps.

Stepper motors have a more complex design but are cheaper to manufacture and operate. Servo motors are more expensive and require higher power, but they offer better precision and control.