setting zero on an encoder

[chuck53]

I am planning on installing a rotary resolver (encoder) on a stamping press and was curious as to whether or not I'm going to have problems setting zero, running to a PLS.
If there are any suggestions or imformation I would appreciate the input
C.J.Hall

 

[gcaudill]

chuck53,

If the rotor/resolver was aligned from the factory you should not have to re-align the resolver at motor installation. Only if the motor has been disassembled should it be necessary to re-align the resolver.

I would assume that you are using a brushless DC (a.k.a. permanent magnet rotor) motor since the motor has a resolver. It is important that the resolver is correctly aligned to provide for proper commutation of the motor. Proper commutation is necessary for precise speed and position control.

With that said, I wonder why you are using a resolver on a motor that is used on a stamping press. Is speed control critical in your application?

 

[MechEng13]

gcaudill,

We have resolvers on our presses, they are part of the Rockford Control Package. Can't say that I have learned enough about them to know what they do.



Alan M. Etzkorn
Hoffco/Comet Industries Inc.

http://www.hoffcocomet.com

 

[gcaudill]

MechEng13,

Sounds like what you and chuck53 are saying is that the resolver is on the press and not the motor. This could provide very accurate position repororting to something, but I'm not sure why.

 

[MechEng13]

That sounds about right from my end. Our control systems have Sensor capabilities, and my guess is that the resolver reports to the control for when to turn the sensors on and off, as well as muting the light curtains on the upstroke.



Alan M. Etzkorn
Hoffco/Comet Industries Inc.

http://www.hoffcocomet.com

 

[Paulcet]

I think MechEng is right about reasons for the encoder/resolver.

Chuck53: I don't think you will have any problems setting zero. Most PLS systems have a zero input, and many encoders also have a zero output. If you haven't already, check out Electrocam (

http://www.electrocam.com).

Very versatile products.

 

[wildwood]

Some of these systems have a reference cycle to orient the press timing. Single stroke and continuous do. However the inch mode will allow for TDC calibration. Simply getting TDC close will allow the encoder to resolve calibration.

 

[avigodner]

A remark about encoder vs resolver comparison in the context of brushless motor sinusoidal commutation.

Relatively expensive absolute encoder is an absolute position sensor just as resolver.

Absolute position is not available from relatively cheap incremental encoder. Therefore, Hall sensors or special commutation encoder with emulated Hall signals are used for initial coarse commutation unless absolute zero position is found.

For such an application, Hall sensors (commutation encoder) may be eliminated by using a kind of phase search procedure (see Smart Initialization article overview at

http://www.drbrushless.com

for more info).