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Hand Wheel Encoder


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I have on several occasions used a hand wheel encoder (manual pulse generator) as part of a setup scheme for multiple axis machines. The encoders typically have a resolution of 400 counts per revolution (post quad).

When using the hand wheel encoder I simply use it as the master and engage master following for that axis or group of axes. However my problem begins when I scale the encoder so that 1 revolution of this encoder give 1 inch of travel on the specified axis. As you might guess I can easily get a quantization problem when doing this since the resolution between the encoder and the axis being moved becomes so different.

This is where I begin to wonder what I am doing wrong because this is apparently a 'standard' resolution for a hand wheel encoder (in fact it is hard to find higher resolution had wheel encoders) but when i look at CNC machines this type of jogging is commonly done and do not seem to suffer from this problem.

Is there some type of filtering, dampening, or averaging of this signal so that this is minimized more? Are there other approaches to this problem i should be using instead of the master following I am currently using?


Thanks in advance for you suggestions.

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It sounds like what you mean by quantization error is that the slide motion is rough. You are saying that you scale it such that each click of your hand wheel is .0025". If you use the master handwheel function in PMAC you are essentially creating instaneous step inputs to the position command, with no commanded accel/decel/velocity, which, if the move is far enough for given machine might seem rough. Delta Tau mentions using an exponential filter (see User's Manual) as a possibility to smooth this, although I believe that most people implement a handwheel by writing a PLC to read the input from the handwheel and then "jog" the axis based on this input. That way the jog acceleration and jog velocity can be adjusted to make the operation more smooth. The handle.plc in the NC package is an example. This is from the delta tau web site:




This should help

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Is the PDF file you linked an example of the Handle.plc in the NC package?

If not can you please link this as well, I cant seem to find it.




You should ask Delta Tau for this...not to be difficult, but I am not sure if I have a current revision version, and I am not sure if it is public domain code or not.


Now that I look at it, the thing that I posted uses the master handwheel function, and not the jog to position function that I refer to. Ask Delta Tau for Handle.plc for an example of the other.

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