How to distinguish servo motors, servo motors, and stepper motors?

How to distinguish servo motors, servo motors, and stepper motors? There are many types of motors, and each motor has its own advantages and disadvantages, so its purpose is also different. Here is a brief introduction to the differences between servo motors, servos, and stepper motors, in order to make them as familiar and understandable as possible.

In fact, servo motors are a type of motor mainly used for precise position, speed, or torque output. To be precise, a servo motor is not a motor, but a system. So just one motor cannot be considered a servo motor because they do not have the function of a servo motor.

A servo motor is a motor system that includes a motor, sensors, and controller. DC brushless motors can be a part of servo motors, and AC motors can also be, but they are not servo motors. As a system, it can have reduction gears or not.

So what is a servo? The servo is a common term used by people who play with models of airplanes and ships. Because this type of motor is commonly used for rudder control.

The servo motor is actually a low-end servo motor system, and it is also the most common servo motor system, so it is called Servo in English, which is the abbreviation of Servomotor.

It compares the PWM signal with the voltage of the sliding resistor and achieves fixed control gain position control through hardware circuits. That is to say, it includes a motor, sensors, and controller, and is a complete servo motor (system). The price is low, the structure is compact, but the accuracy is very low, and the position stabilization ability is poor, which can meet many low-end needs.

The English name for stepper motor is stepper/step/stepping motor. Mainly relying on the sequence of stator coils being energized, a magnetic field is formed sequentially at different angles, and the stator rotates by pushing and pulling.

The advantage of a stepper motor is that you can eliminate the sensor used to measure the motor's rotation angle. Therefore, it has certain advantages in structure and price. And its position and speed control are relatively simple.

Its disadvantage is that, firstly, compared to motors of the same power, the load is relatively small and cannot output large torque without an angle sensor. Secondly, the power consumption is relatively high, either fully open or fully closed. So either it's close to full power consumption, or it can't output power. (The specific reasons and structure can be found in relevant materials, which are everywhere online and not difficult to understand. I won't elaborate on them here.).

Therefore, stepper motors are generally only used in situations where the load is small and very certain, the position accuracy requirement is not very high, and they are sensitive to volume or want to achieve high reliability at lower prices. The most common ones are optical drives, scanners, copiers, and so on. Of course, like servo motors, it is also favored by amateur enthusiasts who do not have the ability to build servo motor systems themselves, and is used to replace complete servo motor systems in some amateur projects.

So give a simple example. A common action of scanners (including those used in modern business printers) is to quickly move from one end of the slide to the other before truly scanning. Actually, that's the system looking for position zero. There is a stepper motor used inside, which drives the scanner to move.

But when starting the scanning task, the system does not know the exact position of the scanner (because there is no position sensor), so it can only drive the scanner towards the other side of the slide first. At the end of the slide, there is a touch switch that generates an electrical signal once the scanner touches it.

This way, the system knows that the scanner has reached its end, and at this point, the position of the scanner is determined, and scanning can begin. This stepper motor will shut down after completing the task (due to its high power consumption), so once there is vibration or something, the scanner can easily shift. So the next time the stepper motor is powered on, it is necessary to perform the action mentioned earlier again to determine the position of the scanner.