Stepper Motor vs Servo Motor

[AlliedAuto]

Hi all,

What's the main differences between stepper and servo motors and what applications might they be used?

God bless,

Phil.

 

[BobM3]

Stepper motors tend to be used without feedback i.e., send the motor 100 steps and assume it moves that 100 steps worth. Servos use feedback. Send them a command and look at the feedback and make corrections. Both are used in machine tool applications as sell as other systems that need to move objects.

 

[IRstuff]

Mechanically, the biggest difference is that a stepper is designed on purpose to cog, while an ideal servo has no cogging whatsoever.

That's a consequence of the control approaches described above. A closed-loop control system wants linear, or quasilinear behavior, which obviates a coggable motor.

A stepper motor uses the cogging as a means of provide repeatable responses to stepping commands and to stay in the commanded position.

TTFN

FAQ731-376

 

[tygerdawg]

Many modern steppers use "micro-stepping" technologies which provide much more smoother motion than they used to. If the stepper torque is geared through a ballscrew or whatever, you may never notice it.

Servos generally can provide higher speeds, torques, and accelerations than steppers.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[eromlignod]

A few thousand bucks.

My advice is to only use steppers for very low-torque, rotational applications, like rotating a small part or free machine member. Yes, I know that they make big stepper brutes, but I have had lots of problems with such applications in my 22 years' experience. Anything that requires torque or acceleration of even moderate loads usually will need a servo. The cost savings of the stepper will not be worth the headaches you will have with it.

Don
Kansas City

 

[AlliedAuto]

what exactly do you mean by cogging? thanks for all you replies.

 

[IRstuff]

see:

http://www.infolytica.com/en/coolstuff/ex0088/

Some high performance servo motors have no iron in the active portion of the motor, resulting in zero cogging.

TTFN

FAQ731-376