RE: Epics servo motor controller support

[Mark Rivers <RIVERS@BNLX26.NSLS.BNL.GOV>]

Nick writes:

>Subject: Epics servo motor controller support
>A common problem we astronomers seem to be addressing is how to add
>record, device and driver support for a range of DC servo motor
>controllers. The accelerator community really appears to have used
>stepper motors exclusively.
>Questions:
>1. Has anyone added support for a DC motor controller?

I am currently controlling DC servo motors using EPICS, with the OMS stepper
motor controller and a DC servo driver which accepts pulse/direction inputs.
This is thus one quick and dirty solution to the problem.

>   Has anyone thought about integrating a servo control record
>   with the existing stepper motor record and so creating a generic
>   `motor control record'? I feel this may be the most elegant way
>   to achieve the ends but it would require some modification to the
>   released version of the stepper motor record.

You should be aware that Tim Mooney at the APS has created a new (1.5 years
old?) motor record. This record has many nice features, like backlash
correction, dial and user coordinates etc.  It has a few problems, like
some dependencies on the Oregon Microsystems board. The device support is
presently only for an OMS stepper board, but there is an almost immediate
need to expand this to other stepper and DC controllers.

You might also be interested to know that Oregon Microsystems is a few months
away from releasing a VME motor controller which can control steppers and DC
servos (with direct DC servo output) from the same board.  My guess is the two
types of motors will be programmed very similarly, so the device support may 
need very little work.

>I would like to come up with a definition for a generic motor control
>record, and would be willing to accept suggestions on how this may be
>done. Although this has been done to death a bit, I feel we may have to
>accept the provision for a filename that specifies a device dependant
>initial configuration. Otherwise it will be impossible to cope with the
>large number of controllers out there.

Motors in general (stepper and DC servo) are the most important devices on
the CAT beamlines, so we would be very interested in working with you on this.

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