As for the difference between a stepper motor and a servo motor, we can use an interesting metaphor to help you understand.
Let's say we have a child who doesn't have a mother to take care of him. He wants to go out and play every day, no matter whether he plays ten circles or fifty circles outside, no one
will care about him. No one knows how long he has been playing outside and how many circles he has played. No one knows if there is any little accident.
This is called open-loop control. Because there's no feedback system in his life that monitors what he's doing in real time.
Just like our numerical control device, it sends some pulse rotation commands to our fixed motor. You might tell it to rotate 100 times according to the command. But does it actually
follow the number of rotations you instructed? No one knows. Because no one monitors or feeds back on it.
Let's talk about servo motors with mom in charge,
At home, there's a child who wants to go out and play. Mom rules that he can only wander around outside for ten laps before coming back in. When the child reaches the third lap,
Mom might call him and ask how it's going. The child has to report back to Mom. As the time nears its end, Mom may also call again to remind the child to come home for dinner.
This mom is well aware of her child's activities outside and can always call them back on time,
This is called closed-loop control. In fact, the role of mother in this servo motor is the existence of an encoder. After this motor has an encoder, it really costs a lot more.
Let's talk about the principle of a closed-loop system. It is still a numerical control device that sends certain pulse commands to the motor, for example, turning 100 times in one minute.
At this point, does it actually turn 100 times, or does it accurately reach 100 turns, or does anything go wrong? The encoder will then perform real-time detection and monitoring. If any
issues arise during the process, the encoder can promptly make adjustments to ensure it reaches its target accurately. In other words, it transforms from a child who doesn't listen to its
mother into a well-behaved baby that listens to its mother
Every mother seems to be born with the ability to manage her children precisely. She can ensure that they arrive at school on time, eat meals on schedule, take baths and go to bed
promptly. And complete their homework on time, with an extremely high level of accuracy. This is the power of our encoder; its value lies in its remarkable precision.
Price
The value difference between a servo motor and a stepper motor is very large. A high servo motor may be several times or even ten times more expensive than a stepper motor, and the
most expensive part of it is the encoder. A single encoder. accounts for about 80% of the total value of a servo motor.
Sum up
In practical cases, stepper motors can also have closed-loop systems, while servo motors differ between semi-closed and fully closed loops. It's like a child who was previously under strict
supervision but suddenly the mother returns. Just like our unpredictable lives, everything is subject to change; anything can happen. The key lies in how you manage your current situation.
