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<== Date ==> <== Thread ==>

Subject: Re: Proper initialisation of Motor Record .RMP value
From: Ron Sluiter <sluiter@aps.anl.gov>
To: <tech-talk@aps.anl.gov>
Date: Tue, 22 Oct 2013 09:49:45 -0500
Hello Peter,

The EPICS motor record has no allowance for rolling over the DBF_LONG (epicsInt32) RMP field.

If the application and the motion control system support it, then one way to avoid the whole problem would be to reduce the motor resolution field (MRES).  For example, if this was a ACS SPD-32M mini-stepping motor driver module configured for 8 mini-steps per full step, you could reduce that to 6 mini-steps per full step and adjust the MRES according. Again, only if the application can support the reduced resolution.

Ron


On 10/21/2013 9:55 PM, Peter Linardakis wrote:

We're pretty new at controlling motors using EPICS and we've run into a few small issues.  After a crate reboot, some of a bank of 28 motors end up with a motor.RMP value that is quite close to the signed 32-bit integer limit (both at max and min ends).  If we then try move the motor more than the difference, the motor just stops.  We're not running a complicated setup, we just home the motors using limit switches.  We do not use encoders at this time.

My question is,
how do we properly initialise the .RMP value to some known value, probably zero?  At this stage of the game, we're not looking to use an autosave module or similar.

Regards
Peter

Dr Peter Linardakis

Accelerator Research and Development Engineer

Nuclear Physics | Research School of Physics and Engineering

Australian National University

e: peter.linardakis@anu.edu.au

p: (02) 6125 2862 f: (02) 6215 0748



References:
Proper initialisation of Motor Record .RMP value Peter Linardakis

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