Do you know how to choose between stepper motors and servo motors?

When it comes to precision motion control, two popular types of motors are servo motors and stepper motors. Both have their unique strengths and weaknesses, and the choice between the two depends on the specific application requirements.As an open-loop control system, the stepper motor has an essential connection with modern digital control technology. In the current domestic digital control system, stepper motors are widely used. With the emergence of all-digital AC servo systems, servo motors are increasingly used in digital control systems. In order to adapt to the development trend of digital control, most of the motion control systems use stepper motors or all-digital AC servo motors as executive motors. Although the two are similar in control methods (pulse and direction signals), there are big differences in performance and applications. Now compare the performance of stepper motors and servo motors one by one.

Servo motors are known for their high precision and accuracy, making them ideal for applications where high performance is critical. They use closed-loop control, which means they continuously receive feedback from sensors and adjust their position and velocity accordingly. This makes them highly responsive to changes in load, speed, and torque, and allows them to maintain a consistent speed and position.

Stepper motors, on the other hand, are simpler and more cost-effective, making them ideal for applications that require basic motion control. They operate in open-loop control, which means they do not receive feedback and therefore do not adjust their position or velocity. Instead, they move in precise increments or steps, making them suitable for applications that require precise positioning, such as 3D printing or CNC machines.

Another key difference between the two is their torque characteristics. Servo motors have a much higher torque output than stepper motors, making them suitable for applications that require high torque at low speeds. Stepper motors, on the other hand, have a lower torque output but can maintain a constant torque across a wide range of speeds.

The low-frequency characteristics of stepper motors and servo motors are different (anti-resonance)

One shortcoming of the stepping system is that there is an inherent resonance point. The SR series stepping driver automatically calculates the resonance point and adjusts the control algorithm to achieve the purpose of suppressing resonance and greatly improves the stability of the intermediate frequency. It has greater torque output at high speed and more excellent high-speed performance.

The servo motor runs very smoothly and does not vibrate even at low speeds. The AC servo system has a resonance suppression function, which can make up for the lack of mechanical rigidity, and the system has a frequency analysis function (FFT) inside the system, which can detect the mechanical resonance point and facilitate system adjustment.

Working principle

These two motors are very different in principle. The stepper motor is an open-loop control element stepper motor that converts the electrical pulse signal into angular displacement or linear displacement. Check the working principle of the stepper motor.

The servo mainly relies on pulses for positioning. The servo motor itself has the function of sending pulses, so every time the servo motor rotates an angle, it will send out a corresponding number of pulses. In this way, it forms an echo with the pulses received by the servo motor, or it is called a closed loop. It will be clear how many pulses are sent and how many pulses are received back, so that the rotation of the motor can be precisely controlled to achieve precise positioning.

Cost

Stepper motors have an advantage in cost performance. To achieve the same function, the price of servo motors is higher than that of stepper motors with the same power; the advantages of high response, high speed and high precision of servo motors determine the high price of products. , which is unavoidable.

Running performance

Stepper motors are generally open-loop controlled, and when the starting frequency is too high or the load is too large, there will be a step-out or stalling phenomenon, so it is necessary to deal with the speed problem or increase the encoder closed-loop control when using it. Check what is a closed-loop step Into the motor; while the servo motor adopts closed-loop control, which is easier to control and does not have out-of-step phenomenon.

Speed and overload capacity

Stepper motors are prone to low-frequency vibrations when they are running at low speeds, so when stepper motors are working at low speeds, damping techniques are usually required to overcome low-frequency vibrations, such as adding a damper to the motor or using subdivision technology on the driver, etc. ; But the servo motors do not have this phenomenon, and its closed-loop control characteristics determine its excellent performance when running at high speed. The torque-frequency characteristics of the two are different, and the rated speed of the general servo motor is greater than that of the stepper motor. The output torque of the stepper motor will decrease with the increase of the speed, while the output torque of the servo motor is constant, so the stepper motor generally has no overload capacity, while the AC servo motor has a strong overload capacity.

To sum up, stepper motors and servo motors are quite different in terms of working principle, overload capacity, operating performance and cost. But both have their own advantages. If users want to make a choice, they need to combine their actual needs and application scenarios.

In terms of complexity, servo motors are typically more complex and require more setup and tuning than stepper motors. They also tend to be more expensive. Stepper motors, on the other hand, are simpler and more straightforward to use, and can be a cost-effective solution for basic motion control.

In summary, servo motors are ideal for high-performance applications that require high precision, responsiveness, and torque. Stepper motors, on the other hand, are more suitable for applications that require basic motion control and precise positioning. Ultimately, the choice between the two depends on the specific requirements of the application, and careful consideration should be given to factors such as precision, torque, complexity, and cost.