Electric motors have applications in many fields, including the well-known stepper motors and servo motors. However, many users are unaware of the main differences between these two types of motors and don't know how to choose between them. So, what are the differences between stepper motors and servo motors?
The differences between them are briefly described below in five aspects:
1. Working principle
These two types of motors differ significantly in their operating principles. A stepper motor is an open-loop control element that converts electrical pulse signals into angular or linear displacement.
Servo systems primarily rely on pulse positioning. The servo motor itself has a pulse function, so when the servo motor rotates, it will emit a corresponding number of pulses, allowing the servo motor to receive pulse responses or form a closed loop. This enables the system to clearly understand how many pulses are collected and accurately control the motor's rotation, thus achieving accurate positioning.
2. Control precision
The precision of stepper motors is generally achieved through precise control of the step angle, which can be achieved using various microstepping gears. The control precision of servo motors is ensured by a rotary encoder at the rear of the motor shaft; generally, servo motors offer higher control precision than stepper motors.
3. Speed and overload capacity
Stepper motors are prone to low-frequency vibrations when operating at low speeds. Therefore, damping techniques are typically used to overcome this vibration when stepper motors are running 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, with servo motors generally having a higher rated speed than stepper motors. The output torque of a stepper motor decreases as speed increases, while a servo motor provides constant torque output. Therefore, stepper motors generally lack overload capacity, while AC servo motors have stronger overload capabilities.
4. Operating performance
Stepper motors are generally controlled in an open-loop manner. When the starting frequency is too high or the load is too heavy, malfunctions or blockages may occur. Therefore, it is necessary to address the speed issue or add encoder closed-loop control to check what constitutes a closed-loop stepper motor. Servo motors, on the other hand, use closed-loop control, which is easier to control and less prone to failure.
5. Cost
Stepper motors offer an advantage in terms of 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 inevitably lead to their higher price.
In summary, stepper motors and servo motors differ significantly in their working principles, control precision, overload capacity, operational performance, and cost. However, both have their own advantages. Users need to consider their specific needs and application scenarios when making a choice.
