Messages

4001

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 17, 2018, 10:34:59 AM »

Hi,

I'm not too sure how the CSMIO will fit in with torque mode. Certainly the normal assumption is that the CSMIO is followed by a velocity loop, which implies the use of a functioning tacho.

The CSMIO will successfully close a loop with a torque mode amp. When all said and done a velocity loop is just a torque loop with one additional integrator.
The CSMIO already has an integrator and can supply the required gain. With a velocity amp the integral component of the overall loop gain is distributed between
the CSMIO AND the velocity amp whereas the CSMIO supplies all the integral loop gain with a torque mode amp.

Provided there is sufficient stability ( phase margin) that the overall integral gain can be applied the two solutions are dynamically equivalent.

Craig

4002

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 17, 2018, 05:04:33 AM »

Hi,
I don't know if this will help...a bare bones explanation as to how your drives work...or at least supposed to work.

The first pic is a straight openloop transconductance amplifier. Note that there is no means of adjusting the gain. Also the amplifier gain will vary with
temperature, load and DC link voltage, in short the gain is not particularly stable.

The second pic uses feedback to produce a much more stable gain. When the forward path gain ( G.Ki ) is large then the output current is a faithful
amplification of Vin divided by a constant. In practice this constant is gain setting resistors or a pot. Now the gain is easily adjustable and
stable, a marked improvement over the openloop amplifier. This sort of servo amplifier is used for torque mode control and is very common...well used to be,
they are getting to be a dying breed now!

The last pic shows the same transconductance amp as above but the servo has been added with an attached tacho. Note that the output of the amplifier is
still the current, Iout.  The current produces a proportional torque and therefore angular acceleration in the servo resulting in a shaft rotational speed
of W. The tacho produces a voltage proportional to W for the feedback circuit. The speed W is a scaled 'integral' of the current.....you may have thought
you could get away WITHOUT calculus....but no such luck! I have tried to keep the maths to a minimum but the upshot is that with a high forward loop
gain ( G.Kt) servo speed is a faithful amplification of Vin divided by a constant. In practice the constant is set by gain resitors or a pot. Note also that to a large
degree the mechanical load on the servo does not affect the speed......the load is counteracted by the feedback. This is an extremely valuable use of feedback.
Using the same basic amplifier the addition of tacho feedback has turned the amplifier into a load independent velocity control unit.

Either of the two amplifier configurations could be used, remember the CSMIO has its own feedback loops enclosing the amp. With sufficient  forward loop gain
both work well. Your drive has a personality module in it (it has the gain resistors Kt) and so the manufacturer intended that it be used as in the last pic.
You've found though that if you disconnect the tacho it performs more like the second pic despite having the wrong personality module.

My suggestion is try to digest these pics and what they mean and then we'll try to tune the tacho etc to get it to work as in the last pic. If that's not successful
we may have to revert to the simpler current loop model.

Craig

4003

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 17, 2018, 02:29:08 AM »

Hi,
yes it could be but usually what happens if the direction of rotation is inconsistent the axis will run away too one end not
just go slow.

Craig

4004

General Mach Discussion / Re: Knocking X axes, whats going on ??

« on: July 16, 2018, 07:07:03 PM »

Hi,

But Mach 4 works fine

Are we talking Mach4 and the Darwin parallel port or Mach3 an the parallel
port?

Craig

4005

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 16, 2018, 07:02:42 PM »

Hi,

It would also be worth measuring the tacho output to see if it is within the expected limits.

Good idea, get the servo spinning as fast as you can, preferably with some means to measure the speed and
then measure the output of the tacho and compare to the spec.

When I get home tonight I will look a bit more closely, but what it amounts to, at the moment, with you having disconnected
the tacho, is that amp is now a 'voltage driven current output amplifier' also called a transconductance amplifier.

By disconnecting the tacho you have broken the feedback loop which turns the transconductance amp to
a  'voltage driven voltage output amplifier'. Note this feedback loop is within the drive and has nothing to do
with the PID dynamics of the CSMIO.

Much of my University experience with these devices was with a plain transconductance amp, ie torque mode.
Unless someone can tell me what advantage having the extra feedback loop, especially as it doesn't seem to work,
is I would not bother with it. That is a very preliminary assertion on my part and thorough investigation is required
before you adopt the idea.

It may be for instance by removing the tacho feedback you have effectively increased the command gain to where it should be.
Thus with the tacho loop reinstated AND the command gain increased to where it should be then the setup would
now work as the manufacturer intended.

Craig

4006

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 16, 2018, 01:48:52 PM »

Hi,
sorry hit <post> prematurely.....

Command Lo connects to CSMIO 0V
Command Hi connects to CSMIO analogue output
0V (pin4 TB3) connects to CSMIO 0V

Confirm the wiring.

Craig

4007

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 16, 2018, 01:41:03 PM »

Hi,

There are only two wires coming from the command Hi-Low. This is the original wiring. I am not sure what you mean by single end wiring and configuration for this?

The two wires are differential inputs whereas the CSMIO is single ended. Command Lo needs to connect to 0V on the CSMIO.

4008

General Mach Discussion / Re: Mach3 set up for clearpath motors and c62 BOB with Ethernet SmoothStepper

« on: July 16, 2018, 12:58:44 PM »

Hi,
I doubt there is anything 'wrong' with the C62, its just not easy to follow exactly what the manufacturer intended.

The C10's will both be easier AND harder....easier in that you can choose how to arrange the inputs and outputs and harder for the
same reason!

Craig

4009

General Mach Discussion / Re: Knocking X axes, whats going on ??

« on: July 16, 2018, 12:49:15 PM »

Hi,
I suspect that there is a momentary hesitation in Machs pulse stream,

Try slowing Mach from 33kHz to 25kHz and try again. Note that you'll have to restart Mach for the change to take effect..

Craig

4010

General Mach Discussion / Re: CS Labs CSMIO/P-A

« on: July 16, 2018, 09:37:29 AM »

Hi,
got to say these servos and drives are OLD SCHOOL!. To OP: if they even look like crapping out don't waste your time and money fixing them,
get yourself some decent AC servos....modern ones......no bull********* having a controller to close the loop either....proper matching closed loop drives.

I have an Allen Bradley servo for a spindle motor....just brill! I bought second hand reasonably cheaply, they are way too expensive for me new
but Delta and DMM do some very very good stuff which will eat these servos...

Craig