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Servo vs. Stepper

In this corner, we have the servo motor, requiring a controller, amplifier, motor and encoder. In the other corner, we have the stepper , requiring only a controller (microstepping) and a motor. Can I get some input on the drawbacks of using a stepper (with encoder if needed) for a very fast (a few mm in milliseconds) but very precise movement under negligible torque requirements? I am trying to position a 3mmx3mm device for testing. The positioning will be based on feedback from a vision system for alignment. Servos are believed to be the way to go by the mechanical engineers based, I think, on a belief that they are faster and more accurate. I think the stepper will due the job. My understanding is that the servo is desirable for fast moves OVER DISTANCE. Can I get some hallelujahs out there?

Thanks, Frankly Speaking

Reply to
frank murphy
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Hi Frank,

I would suggest a dc servo because you will get much more precision. Two ways to go....you can use a servo with an encoder or linear scale with a tachometer or one that uses the encoder/resolver as a tachometer. Pick a PWM amp, a servo of appropriate size and and encoder with appropriate counts. You did not mention the load you are trying to move so it would be difficult to point you in a direction there. Pacific Scientific has some great stuff... If you are still uncertain you might want to call their tech support....

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make some great brushless products that should be able to get the job done.....By the way, this stuff is not cheap and you did not mention a budget....so you got my 2 cents and hope it helps....Good luck with your project.....Ross :>)

Reply to
Ross Mac

I suspect either can be made to work without too much trouble. Stepper systems tend to be simpler for smaller loads, and less expensive. Stepper systems have a bad rap with "fast" moves because what happens is they are used open loop and the torque requirements exceed the motor's capability and they are not able to keep up. because there is no position feedback, they are now out of position. However, many stepper systems can have feedback so this shoul not be something yIt is possible to add position feedback to a stepper system, although this reduces its simplicity and cost advantages.

There are other issues such as cogging that could come into play as well.

You probably won't go wrong using a servo, but might go wrong if you misapply a stepper.

Reply to
bob peterson

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