Freqmod test result & Q

[Chris Wagner <clwagner-at-eecs.wsu.edu>]

Greetings,

I'm running a test setup (o'scope on the port pins) on a SuSE8.0 base
system with rtai-24.1.9 and freqmod.  I'm working to get an open-loop
(no encoders for now) stepper configuration running. (If I get a good
setup I'll do a fresh install and post the proceedure)

I see two primary types of "jitter" on the step clocks. 1) The time
quantization for the [task] section "period" variable.  This is an
expected effect in a digital timing generator.  2) Some jitter about
the task_period, presumably due to interrupt latency variation.  I have
not run motors yet, so I'm just commenting about what I see on the
scope.  Both of these effects should also be present to some degree in a
steppermod configuration.

Since I have no encoders, I want the control-loops to run like the
pantograph example in the handbook. I sort-of expected to get this
behavior in freqmod by setting P=I=D=Zero, Position-FF gain=1, other
FF's zero. As others have reported to the list, emc does not seem to
like P=0.

My question, ideally should P=I=D=0, PosFF=1,VelFF=AccFF=0
provide the pantograph-like behavior?

-- 
Recreational Calculus - Just For Fun!

Chris Wagner
clwagner-at-eecs.wsu.edu