SERVOs & EMC

Hi folks,

You guys are giving me a headache ! I have trouble to follow you.

LM628-9:

I don't care do check the papers now, - and I maybe I have missed
out on something significant. I thought you set the velocity in the
trajectory profile, and also the acc/deceleration . It is years
back, so my memory may fail me.

Following errors: ( Matt Shaver 's note / Jon Elson)

This is new to me, - I thought EMC had something. Bye to the low
cost servo amp ! Now I guess I understand some of Jon's struggle.

Sorry Jon, I got something more for you:

It looks like you may have some qualities I lack ! Patients and a
newer giving up attitude.

I used a transconductance amplifier in one of my designs, - and I
ended up in something not nice at all. As I now understand it, you
also use a current loop, - ergo the same thing. What you get is a
torque controlled servo. Here is where my problems started. ( maybe
I just couldn't tune it right ? ) Anyway, I gave up the design.
It has gone some time, and I can't recall the details, but
something strange happened to the current. The whole thing started
to be to complex, so I started on something a bit different. But
what I would like, would be something simple.

You may have answered this, if not directly. Why care about the
current ?

I may be stupid, but.... if you let the motor draw what ever it
needs, ( sure have some limit ) but the thing is that with a
tacho, you should have it under control. You may need to insert
some filter coefficients into the PWM part ?
Sorry, I am confused here. I had some other designs too, maybe I
think of something from these too. Sorry, my mind is just a mess
right now.

What you indicate is that you will not be able to pick up any lags
quick enough - if you don't use the current ?
But I have seen other designs from well known manufactures that has
done this. You could change a motor to another size, without any
adjustments.
I do admit, they had something hidden in "black boxes" - to do the
PWM control . But as I can remember, they did not have any current
gain adjustments, other than tripping an over current switch.

Do you have any idea ?


Matt Shaver: ( pseudo code )

May I should keep quit - as my mind may fail me. ( you see my
confusion above )

Maybe it could work, I see you left out the encoder front end to
another chip. It would be very nice.
I did something once, - I don't recall much of it. All I remember is
that you have a large range to cover. I had the problem with some
way of tuning it, the response was not fast enough, but then again I
didn't sample it faster than 500kHz (?). If I am not too wrong, I
think I had some trouble to solve the lag this thing is inducing by
itself.

No, you better ask some of the other guys. My mind is flashing
"overload" :-)

I have some design ideas I will try out, and there is some encoder
to tacho chips around, but it seems all of them has limitations.
Soon I just want to bail out !

In closing:

This was just a mess, maybe I should not send it at all ? But on the
other hand, you all know I am stupid now and then :-)

I feel that we ( or I am ) making a mess of it. There is digital,
analog, mechanical, and software components to consider. There is
limits in all of them. We would like to overcome some of them, but
at the same time we mess up something else in the total picture.
What are we doing wrong ?
I would like to KISS ! ( well not all of you, what I meant was Keep
It Stupid Simple )

- and no, I have not been drinking. ( ? send ot not to send ? )

//ARNE