Experimental Physics and
Industrial Control System

Ron Sluiter <[email protected]> · Tue, 28 May 2013 10:48:20 -0500

Hello Emma,

On 5/27/2013 5:57 PM, Emma Shepherd wrote:

The .RDBD field of the motor record limits the smallest allowed move

I would describe this slightly differently...
The motor resolution field (MRES) defines the smallest allowed move.

The motor record limits the retry deadband (RDBD) to be >= motor

resolution (MRES).

This prevents the record from attempting to do retry moves that are

smaller than MRES.

  - quite often we want to set this very low so that we can do small step moves.

By "this", I presume you are referring to the retry deadband (RDBD) and

that you want to set RDBD less than the motor resolution.

How does the Delta Tau handle a relative move that is less than MRES?

The only motor controller I have investigated for this scenario (i.e.,

relative moves < MRES) is the OMS VME58.

Rather than accumulating "too small" relative moves, the OMS VME58

ignores them.

For example, if I set MRES=0.1, Max retry count (RTRY) = 100 and the

position error at the end of a move is 0.09, the OMS VME58

will be command to do 100 retries, but nothing moves (I am referring

here to a hypothetical motor record where RDBD is not

limited by MRES).

It would be better if we could somehow decouple the use of .RDBD in the retry sense from the smallest allowed move.

On the other hand, all of the above may be off base and what you are

asking for (as Tim alluded to) is to

have RDBD ignored on the initial move (on a change in VAL/DVAL/RVAL). In

other words, RDBD only applies

to retries.

Which is it?

Ron

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System