Various types of motors are needed in many fields, including well-known stepper motors and servo motors. However, many users are unaware of the main differences between these two types of motors, and therefore are unsure how to choose. So, what are the main differences between stepper motors and servo motors?
Basic structure
Stepper motor structure diagram
Servo motor structure diagram
The differences between them are briefly described below:
1. Working Principle: These two types of motors differ greatly in their working principles. A stepper motor is an open-loop control element that converts electrical pulse signals into angular or linear displacement. Let's examine the working principle of a stepper motor.
Servo systems primarily rely on pulses for positioning. The servo motor itself has the function of emitting pulses, so for every angle the servo motor rotates, it will emit a corresponding number of pulses. This forms a response, or closed loop, with the pulses received by the servo motor. In this way, the system can clearly know how many pulses were sent and how many pulses were received, thereby enabling precise control of the motor's rotation and achieving accurate positioning.
2. Control Precision: The precision of a stepper motor is generally achieved through precise control of the step angle, which has various subdivisions to achieve accurate control. In contrast, the control precision of a servo motor is ensured by a rotary encoder at the rear of the motor shaft. Generally, the control precision of a servo motor is higher than that of a stepper motor.
3. Speed and overload capacity
Stepper motors are prone to low-frequency vibrations at low speeds. Therefore, damping techniques are typically used to overcome this vibration when stepper motors operate at low speeds, such as adding dampers to the motor or using microstepping technology in the driver. Servo motors, on the other hand, do not exhibit this problem. Their closed-loop control characteristics ensure excellent performance even at high speeds. The torque-frequency characteristics of the two differ; generally, the rated speed of a servo motor is greater than that of a stepper motor. The output torque of a stepper motor decreases as the speed increases, while a servo motor provides constant torque output. Therefore, stepper motors generally lack overload capacity, while AC servo motors have a stronger overload capability.
4. Operating performance
Stepper motors are generally controlled in an open-loop manner. Under conditions of excessively high starting frequency or heavy load, they may experience step loss or stalling. Therefore, it's necessary to address speed issues or add an encoder for closed-loop control. (For more information, see what a closed-loop stepper motor is.) Servo motors, on the other hand, use closed-loop control, making them easier to control and eliminating step loss.
5. Cost: Stepper motors have an advantage in cost-effectiveness. To achieve the same function, servo motors are more expensive than stepper motors of the same power. The high response, high speed and high precision of servo motors determine that the product is more expensive, which is unavoidable.
In summary, stepper motors and servo motors differ significantly in terms of working principle, control precision, overload capacity, operating performance, and cost. However, each has its advantages, and users should consider their specific needs and application scenarios when making a choice.
