"Ignoramus28206" wrote in message
...
On 2011-02-28, Ned Simmons wrote:
On Mon, 28 Feb 2011 09:09:48 -0600, Ignoramus28206
wrote:

This is about putting a gear motor on the axis.

I am very puzzled.

I have this servo gear motor mounted on the knee. It is a 65V motor,
4.4 amp continuous and 26 amp maximum. 15:1 gear reducer.

http://igor.chudov.com/projects/Brid...ntrol-to-Knee/

It works fine and if I apply power to it from a large battery charger,
it goes up and down very well.

The next thing I did is I connected it to a A-M-C 30A8 drive, the same
kind as what I have on all other axes.

http://igor.chudov.com/manuals/A-M-C/30A8-Datasheet.pdf

This servo drive gets 72V DC power from the same DC power supply as
all other drives.

I have NOT connected this drive to EMC2 at all, and I send it a analog
signal from just a little DC power supply.

I tried torque mode and velocity mode.

It behaves VERY weirdly. If I tell it to move the knee down, it moves
it a little (think 0.5 inch), and then stops and the knee actually
comes back up (like by 0.1 inch)!

It does not move it up by more than 0.1 inch and does not come back,
as in the opposite example.

I am struggling to find an explanation.

The only one that I can come up with about this going down behavior,
is that perhaps the pneumatics of the pneumatic knee support is
messing me up.

Or, perhaps, this is a bad servo drive.

I am at a big loss, any ideas would be most welcomed.

i

Is the current limit set to an appropriate value?

Have you measured the actual output current via the current monitor
pin?


Ned, I will try to measure the current, indeed. I am not sure what
exactly is wrong, but it is a great idea. I have another 30A8 and I
can easily swap it.


Suggest use an automotive battery charger that has an ammeter on
it....connect directly to motor leads and note current draw going up and
also when going down--adjust your counterweight so as to obtain an appx
equal reading in both directions.

After that, your tuning should be a fairly textbook example unless you've
locked the knee or weighted the table down with an engine block or other
heavy item...

Suggest if you have a dc ammeter off of an old welder you can then place it
in series with the amp motor leads for adjusting your offset and curr
pots--after that you finally want to adjust gain for a critical or slight
underdamp.

AMC has a much better .pdf someplace in their tech litereature--explains
servo setup / tuning theory from a generic viewpoint sorry I don't have time
to look for it at the moment maybe later.

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