Re: encoder readings problem

[Jon Elson <elson-at-pico-systems.com>]

nasir2ahmed-at-yahoo.com wrote:

> we are using the stg model 1 card for emc software to control our 
> lathe machine
>
> we are having trouble to successfully run stg with emc.the problem we 
> are facing is that our position counter starts very fast readings and 
> it continous flow even  we estop the whole system and emc software, it 
> continouslly flow and give the highest
>
> out put voltages at DAC. this problem is only coming in our Y-axis. 
> and because of this problem our machine had three seviour acciedent. 
> this problem can come at any time not continouslly.
>
> and when  we restart our emc software the machine will work correctlly.
>
> is this the problem of pid settings? or this problem is directlly 
> related with any out side distortion.
>
I'm not clear on what is happening.  When this happens, the position 
count is changing
even when in E-stop, and there is nothing moving?  Is that correct?
If so, you have either a defective encoder, encoder cable or STG card.
The PID parameters won't have any effect on this.  To prevent accidents,
you should have the error tolerances set to a small value, so the machine
estops quickly when the encoder error happens.

If you can trigger the problem by moving the machine in some way, 
tapping on things, jiggling
cables, or whatever, try swapping the encoders to a different axis input 
on the STG
card.  Then you should be able to find out whether it is the encoder or 
the STG card.

If you mean that the machine continues to move after estop, then your estop
circuit is not working.  You MUST, for safety, have an all-hardware estop
circuit that removes power from the servo amps.

Jon