RE: [CAD_CAM_EDM_DRO] Re: Relinear encoder source: Now Limbo Rock

Well, if your motor controller literally shuts off the power to the motor
(as the CompuMotor systems do), you'll have no actual feed rate, so the
deviation will be large enough for you to check. If the controller does not
shut off power, you can expect the servo to continually fall behind the
"correct" location. (Eventually, it would catch up if the move reached its
completion point and no other moves were programmed into the system) If you
can measure the current location of the motor, and know its "correct"
location, you should be able to detect the slip. Similarly, if the motor
actually stalls, measuring current location vs "correct" location should
detect this. Be careful, though. The idea of a servo is to supply enough
current to the motor to make it move to the correct location. This means
that, in the case of a stalled motor, the current could rise enough to
damage the windings. That's why controllers typically shut down if the
actual and "correct" locations differ.

In terms of software detection - Is there any reason that you couldn't use
an interrupt to detect the occurrence of the fault, or add a couple of
instructions in your control loop to detect the same? I did this work using
Opto-22 I/O rails running into a Metrabyte 8255 based I/O board in a PC. Of
course, I was building a system to run in one of our manufacturing plants,
rather than a system to be sold many times over for profit, so the economic
considerations were quite a bit different.

-- Carol & Jerry Jankura
Strongsville, Ohio
So many toys, so little time



-----Original Message-----
From: cadcamcenter@... [mailto:cadcamcenter@...]
Sent: Monday, May 21, 2001 10:14 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Relinear encoder source: Now Limbo Rock


<jerry.jankura@s...> wrote:
.. When this occurred, the motor was shut down and allowed to "free

> wheel" until the controller was reset. One line from the controller

back to

> the computer was set to logic zero to alert the computer of the

problem.

> Your software had to detect this line and take appropriate action.

With

> CompuMotor controllers, this was a "wired-or" connection so several

motor

> controller failures could be checked by monitoring one

"but with> the servo motor how is stalling detected?"

Jerry

Thanks for this enlightenment.

It will be tough to depend on software. How about something like this:

In the CAM software will be a record of the feedrate.
With a linear encoder, we can extract the actual feedrate achieved.
Will having a slower feedrate than the one set indicate inadequate
torque?

Programing Einsteins on this list should find it a breeze to come up
with a program to compare the 2? Perhaps even with "set-able"
sensitivitly?

Thanks

Chubby Checker


Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
discussion of shop built systems, for CAD, CAM, EDM, and DRO.

Addresses:
Post message: CAD_CAM_EDM_DRO@yahoogroups.com
Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
Moderator: jmelson@... timg@... [Moderator]
URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
bill,
List Manager

FAQ: http://www.ktmarketing.com/faq.html

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/