Experimental Physics and
Industrial Control System

Kevin Peterson via Tech-talk <tech-talk at aps.anl.gov> · Thu, 3 Aug 2023 11:55:51 -0500

The DVAL is the position field that is usually autosaved. The readback

fields (RBV, DRBV, and RRBV) are not writable and cannot be restored by

autosave.

The setPosition method of a model-3 motor driver is called when an

autosaved position is restored. The position argument should be the

DVAL to be restored divided by the MRES, which should have units of steps.

What happens when the setPosition method sends the command to the

controller to redefine the position is obviously controller-dependent.

The RMP and REP fields are usually updated by queries of the theoretical

(motor) and feedback (encoder) positions in the controller or axis poll

methods.

Whether or not the motor record accepts the restored position depends on

the RSTM field. The "normal" motor record behavior is discard the

restored position if the controllers position is sufficiently non-zero

(>RDBD). This results in setPosition not being called.

I don't know why the RMP/REP fields would change when setting using SET

to redefine the VAL field, but not when VAL was restored by autosave.

I do have some questions, however:

1. What is the value of the FOFF field? Does OFF remain constant when

restarting the IOC?

2. Does the problem persist if the DVAL field is autosaved instead of

the VAL field?

3. What is the output of the following command after the IOC is done

booting:

  epics> dbpr "xxx:m1", 9

Kevin

On 7/13/23 08:41, 岳宗仰 via Tech-talk wrote:

Hi, tech-talk,

I have a motion controller, and write driver support for it by model 3.

After power off, the pulse information and encoder counts of motor has

been lost, and we want to save this informations.

The setPosition(double position) has been rewrote.（I think this method

is used for autosave）

Through it, I can reset the pulse counts at any position.

$caput xxx.m1.SET 1

$caput xxx:m1.VAL 0

So I use autosave module, and save the .RBV and .VAL PV.

After IOC and controller restart, the .RBV and .VAL PV has been changed,

But .RMP, .REP PV not changed and the register of pulse counts of

controller also not change.

Have you met this case?

I would appreciated some suggestions.

Zongyang yue

Thanks