rotary positioning without Encoder....

hsroomi · Apr 17, 2010

Hi all

Is it possible that a shaft positioning can be done without encoder or a shaft positioning cam???

Thanks

Gil47 · Apr 17, 2010

How fast is the shaft turning in Revs Per Minute or Mins Per Rev.

Does it have a home position

If it is slow turning and has a home position I guess you could use time to get to the position required

Brodin · Apr 17, 2010

Have you looked into a RVDT (Rotary Variable Differential Transformer)?

hsroomi · Apr 17, 2010

shaft is fast turning, it is around 150-180 rev./mins. I don't think so that i can get it with time. Yes shaft has its home position.

hsroomi · Apr 17, 2010

@brodin
i don't want to use any type of transducer, this is my clients requirement.

Homer_BL · Apr 17, 2010

Take a lot of money when You finish Your job. Positioning without ANY position detector is worth a Nobel Price

bernie_carlton · Apr 17, 2010

What type of 'positioning' do you have to do? Number of turns? Position within a turn? Exactly how do they want to position the shaft?

mer · Apr 17, 2010

Encoder

If your using a plc you could use a proxy...switch and read a pick up on the shaft or motor and use a count rung if intersted in this style of position reading these guys on this site can explain it far better than i could ..i know it works well at low rpms we use this style on a polisher where i work to read the polishing stone position/height ..mer

Peter Nachtwey · Apr 17, 2010

hsroomi said:
Hi all
Is it possible that a shaft positioning can be done without encoder or a shaft positioning cam???

Do a search for sensorless motor control or sensorless position control. There, the question is answered.

milldrone · Apr 17, 2010

hsroomi said:
Hi all

Is it possible that a shaft positioning can be done without encoder or a shaft positioning cam???

Thanks

Many years ago in the sawmill industry this type of thing was done on the log carriage.

Here is how it worked. The "sawywer" would signal the "setter" (human riding the carriage with the log) with hand signals. The environment was too noisy for any other form of communication. The "setter" would rotate a shaft with however many clicks of his ratchet handle the communication request indicated. The shaft rotation would advance the log for a thicker or thinner board to be sawed from the log.

DickDV · Apr 17, 2010

It strikes me as ridiculous to ask for positioning without any position sensors. Kind of like asking for an output with no input. But then, I'm not exactly an expert in that field either.

milldrone · Apr 17, 2010

Here is a pic of what I described. I'll leave it to the OP to determine if such a system is feasible for his customer.

Hint: There are several reasons this is not done any more.

Here is the site I captured the pic from.
http://www.garymkatz.com/OnTheRoad/hull_oaks.html

Peter Nachtwey · Apr 17, 2010

Strange, I never knew that place existed.

I had to look that up on Google Earth.

I worked for Applied Theory, now USNR, in Corvallis OR for 3 years but then we only went to new saw/veneer mills or mills with high tech automation.

hsroomi · Apr 18, 2010

I have done this many times, positioning of shaft without any sensor but only for slow speed normally 50rpm can be done easily . but the problem in this case is that the machine is high speed and I am unable to control it. I want positioning with the turn of shaft.
Thankx milldrone
but the problem still exist coz of speed.

rotary positioning without Encoder....

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