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How to Understand the Difference Between Servo & Stepper Systems
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- Опубликовано: 1 дек 2014
- Hi, Adam Ring here, and I’d like to talk a little bit about the differences between stepper motors and servo motors. Now basically there is a difference in the way they are structured and controlled. Stepper is typically 50 - 100 pull brushless motor where a servo is basically a 4 - 12 pull brushless motor. The stepper as you can see here typically doesn’t have any kind of encoder for feedback, sometimes you can add it later on as an option where a servo is always built with some sort of feedback device whether it be an encoder or a resolver in order to tell its drive the position of its motor shaft.
Now if we take a look at the speed torque curve for each of these motors they’re very different. A stepper motor has a lot of torque at slower speeds, in fact quite a bit of holding torque because of so many pulls it can have a lot of holding torque at low speed, and then the faster that you run, that torque actually starts to drop off. But you look at the speed torque curve of a servo motor its actually very, very flat, and you get a constant torque regardless of what speed you’re traveling up until its maximum speed.
Now we look at the amount of current that a particular motor draws, a stepper motor typically is gonna draw full current whether it’s standing still or running. In some cases drives that you use with them may have a feature where you can reduce the current if they sit still for a long enough time but other than that they are basically just drawing full current all of the time which also produces extra heating as you can imagine. Servo motor on the other hand, It only uses the amount of current that’s required in order to get the motor to hold or move as demanded by the application. So typically they are going to run a lot cooler and they also have a neat little feature that enables them to produce on occasion 2 - 3 times their rated torque for short periods of time as a peak rating.
And we look at the cost of installing a stepper or a servo motor. As you can imagine a stepper motor is typically going to cost less. The motor construction is simpler, you don’t typically have the feedback, and the electronics to control the motor are typically simpler and less expensive. With a servo motor obviously they are going to have some type of feedback device built into the motor and then the drives that we use to control them typically are a little more involved when it comes to how they are designed and built and typically costs a little bit more.
Little bit about the application these might be used in. the stepper motor is used in applications requiring about 2000 rpm or less where you need a lot of torque at the low end, where as a servo motor is typically used for your higher speed applications that are more dynamic and require more acceleration and deceleration typically 2000 rpm and higher.
So depending on whether you’re doing indexing moves with a light load or really dynamic moves with higher loads you can choose whether to use the stepper or the servo motor. Whether you’re in the market to purchase a stepper motor or a servo motor or not really sure which one is the best choice, visit innovativeidm.com we have an excellent knowledge center where you can come and research differences, catalogs, white papers, videos and learn more. After all, we are Innovative-IDM, Home of the Legendary Customer Experience.
Very impressed with the person how ironed your shirt!! Not a single wrinkle!!
wrinkle free cloth?
Check your contrast settings
Very good tutorial, I learned a lot.
typically
So the "comparison" is between an open-loop stepper and a closed-loop servo. Apples and oranges comparison.
What about the comparison between a "closed-loop" stepper and a "closed-loop" servo? Apple to apple comparison?
It has been suggested that steppers can "lose" or "gain" steps. With "open-loop" this issue cannot be determined. With "closed-loop", if this issue is occurring, it should be able to be remedied.
Thoughts?
Do you know what would be better for a nfl skycam with a heavy load?
And here I thought a stepper was just a type of servo with a lot more poles :P
The link to the knowledge center does not work (I'm abroad from USA).
Anyway, thanks for the video.
well... knowledge is not for everyone hahahaha. I can't enter the site either
Howdy. Cannot access your site from UK :( It says "Important note for site admins: If you are the administrator of this website note that your access has been limited because you broke one of the Wordfence firewall rules. The reason your access was limited is: "Access from your area has been temporarily limited for security reasons""
How is this the poster's fault that you use a weird firewall called "Wordfence"? This has nothing to do with you being from the UK.
@@DougBirdacks Nope... I have da same problem and it is the SITE that used the WORDPRESS firewall. Please read it more carefully and I think you are a little offensive...
Servo motors are also heavily used in slow speed applications.
But it's not justified costwise
I was under the impression that applications for one or the other was more than just torque and RPMs? Arn't steppers "angle" based and servo's are velocity based? Meaning you'd not use a servo for moving a printer head that needs very precise control, but you'd use it for rolling up blinds or something?
+John Michael Stock Thank you for your question. Both steppers and servo's can operate in position control mode to move to a very specific position. During the move itself, they also travel at a commanded velocity so they can ramp up from zero speed at a given acceleration rate then decelerate back to zero speed and stop at the desired position. A servo would typically be overkill for an application such as rolling up blinds.
Sir, can you answer a question for me about Stepper Motors? Question: If a Stepper Motor is rated at 4 amps does that mean that it can output 4 amps if used as a generator?
If I want a *STRONG* motor to move as *FAST* and *SILENTLY* as possible, with abillity to remember it's current *POSITION* , even after cutting off the power and turning it back on again, which one do I need? It's for an human-sized animatronic-robot that can move as fast as a human and pick-up objects. Without sounding like an 1980's printer with every moved inch... 😂
Thank you :)
That million dollar smile.
hellloooo !
The camera is on your right, dude !
david cross?
Let me guess, you are an engineer who works at Amazon automation 😂😂😂
Is that Marco Rubio?
great
here is a tip turn off the awful music
He gets just a little too excited at 1:06
I came to the comments to see if anyone else noticed. I'm trying to figure out what was so funny. Is it because he said 'poles'?
What's wrong with this url link
I thought Servo Motors only turn 180 degrees? what's going on here
Uncharted I believe certain ones can continuously spin
Continuous rotation servos can rotate continuously. And most standard servos can be trivially hacked to become continuous rotation servos. (Just how trivial that hack is depends on which model of servos you're hacking.)
I think you mean servomotor used, for example, for radiocontrol. Those, normally small, servos, use a position sensor based on a potentiometer (variable resistance). That is a simple and cheap position sensor. But so they can't rotate continuosly due to that. They are limited to less tan 360º or less.
Some others using, for example, light encoders can rotate more times. Quite probably the encoder shown in this video is of that type
Some cheap servos are nothing but a brushless motor with a limit switch. I struggle to call them servos at all.
Not that RC servo.
I can't get past the guy not looking into the camera
They must have added Captions instead of giving the script in the discription
This guy looks like he could be related to Marco Rubio
He's not. :-)
Typically!