Experimental Physics and
Industrial Control System

Kay-Uwe Kasemir <[email protected]> · Thu, 07 Aug 2003 08:54:14 -0600

At 08:40 8/7/2003, Juraj Krempasky wrote:
>Dear all, 
>
>I observed something like a 'direction bit flip' when using the OMS motor card in JOG mode. The motor starts moving and then at full speed (!!!) reverts the direction. The limit switch it is now heading to is ignored, probably because it is believing to move in the opposite direction. Let me add, that the motor setup is a simple 0-360 deg rotation with 2 limit switches. One of the switches is used to set the motor counter to a certain value (motor initialization), so the motor counter never runs out of certain values between its limit switches. 
>
>Anybody observed similar behaviour, is the JOG mode somehow deprecated? 

Can you confirm that the OMS board is really changing the direction bit
that's going to your driver/amplifier?

I have seen a motor change direction because e.g.
the JOG mode parameters (acceleration, speed) where configured
such that in JOG mode the pulses came out too fast for the motor
to follow. That can happen because the JOG mode parameters are separate
from the "normal" parameters.
The motor would then skip pulses or stop & restart in the opposite direction.
Not because it was _told_ to go into the opposite direction
but simply because the motor could not keep up with the incoming pulses.
Sort of like a digital scope that's undersampling a high-frequency signal
and then you see all sorts of strange effects.

-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System