What are the main differences between stepper motors and servo motors?

1. Stepper Motor

Moreover, it can perform open-loop position control, and a specified position increment is obtained by inputting a pulse signal. Compared with the traditional DC control system, the cost of such a so-called incremental position control system is significantly reduced, and there is almost no need for system adjustment. The angular displacement of the stepper motor is strictly proportional to the number of input pulses, and is synchronized with the pulses in time. Therefore, as long as the number of pulses, frequency and phase sequence of the motor windings are controlled, the required angle, speed and direction can be obtained.

my country's stepper motors started to develop in the early 1970s. From the mid-1970s to the mid-1980s, it was the finished product development stage, and new varieties and high-performance motors were continuously developed. At present, with the development of science and technology, especially the development of permanent magnet materials, semiconductor technology, and computer technology, stepper motors have been widely used in many fields.

2. Servo Motor

Servo motors can control speed and position with high accuracy. They can convert voltage signals into torque and speed to drive the controlled object. The rotor speed of the servo motor is controlled by the input signal and can respond quickly. In the automatic control system, it is used as an actuator and has the characteristics of small electromechanical time constant and high linearity. It can convert the received electrical signal into angular displacement or angular velocity output on the motor shaft. It is divided into two categories: DC and AC servo motors. Its main characteristics are that there is no self-rotation when the signal voltage is zero, and the speed decreases uniformly with the increase of torque.

DC servo motors can be used in spark machines, manipulators, precision machines, etc. They can be equipped with 2500P/R high-resolution standard encoders and tachometers, and can be equipped with reduction gears to bring reliable accuracy and high torque to mechanical equipment. They have good speed regulation and the highest output power per unit weight and volume, which is greater than that of AC motors and far exceeds that of stepper motors. The multi-stage structure has small torque fluctuations.

3. The main differences between stepper motors and servo motors

1. Differences in working principles

Stepper motors rotate by activating each electromagnetic coil in turn. When current passes through each coil, the electromagnetic force causes the rotor to rotate against the gear or transmission system. Each time the electromagnetic coil is activated, the rotor moves one step at a fixed angle. Therefore, the movement of the stepper motor is discrete, and the position of each step can be precisely controlled.

In contrast, servo motors achieve precise control and positioning through feedback control systems. The system structure of a servo motor includes a motor, an encoder, and a feedback controller. The encoder monitors the position of the motor rotor in real time and feeds the data back to the controller. The controller adjusts the motor's speed and torque output based on the difference between the desired position and the actual position to ensure precise motion control.

2. Differences in control methods

Stepper motors are usually controlled using an open-loop system. In this system, the controller sends instructions to the motor, and the motor performs the corresponding actions according to the instructions. Since each step of the stepper motor is discrete and there is a fixed angle between any two steps, under normal conditions, position feedback is not required. This makes the stepper motor system relatively simple and the control method is also relatively simple.

Servo motors generally use closed-loop control systems. Closed-loop control systems control the rotation of the motor through real-time position feedback. The encoder monitors the actual position of the motor rotor and feeds this information back to the controller. The controller compares it with the input position command and adjusts the motor based on the difference. This closed-loop control system can provide higher control accuracy and stability and is suitable for applications that require high-precision positioning.

3. Differences in output torque characteristics

Stepper motors generally have high torque output, especially at low speeds, and their output torque performance is better than servo motors. This makes stepper motors excellent in applications that need to carry large loads or have high static torque requirements. However, during high-speed operation or acceleration/deceleration, the output torque of stepper motors will drop significantly, resulting in poor dynamic response performance of the control system.

The servo motor has a relatively smooth and stable torque output characteristic. Through a closed-loop control system, the servo motor can provide stable torque output over the entire speed range. This makes the servo motor suitable for applications that require high-speed operation, high acceleration/deceleration performance, and precise positioning.

4. Differences in control system complexity

Since the stepper motor uses open-loop control, its control system is relatively simple, and only the appropriate pulse signal is required to achieve basic rotation. This makes the stepper motor easier to integrate into various control systems, and the cost is relatively low.

The control system of the servo motor is relatively complex, requiring components such as encoders and feedback controllers to achieve closed-loop control. This makes the integration requirements of the servo motor higher and the cost relatively high. But its high precision and stability are essential in some applications.