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

Hi All

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.

So my inclination would be to first check the tacho and then to try setting RV2 to 10V at the maximum motor speed, as the manual suggests. (At its most basic, the tacho is simply compared with the command to create the error signal at the feedback summing  point.) Then adjust RV1 if need be so that the maximum required speed is obtained with a command voltage of 10V.

If the tacho measures OK (which I suspect it will) and the amp still fails after the above procedure, I would assume that the amp is in some way defective.

I wouldn't mess with the other pots as these should be OK. The possible exception is loop stability, but I would leave that alone for now as it would ideally need a signal generator and scope to correctly set it, though the CSMIO could probably be used if need be.

Allan

Hi Both

Thanks, Craig for the information. It's a little over my head but only had chance to read it once. Will go through it again and absorb. I always like to understand how something works as it makes it so much easier to fix when it goes wrong.

Thanks for the info Allan. The manual says to adjust RV1 first until the motor stops moving at 0v. Then apply max speed 10v and adjust the command gain RV2  until the desired speed is reached. The way I am reading it is RV2 controls the max speed you want not RV1. Please correct me if I am wrong or is the way you're saying a better option?

Cheers
Mick

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

Hi,
I would still at least in the first instance follow the procedure in the manual. If the tacho proves good, and as Allan suggests I too think it likely that it is
good, then adjust the taco gain, that is Kt in my pic, so that Vf is nearly equal Vin. That assures a small error, e in my pic, which is the ideal.

I rather suspect that there is a fault with the amplifier part, G in my pic, it should have a very high gain which the feedback loop tames.  OPs experiment
of disconnecting the tacho results in sufficient gain where if it were operating normally the forward gain would be excessive.

Craig

Mick

You are absolutely right, I was working from memory and mixed up RV1 and RV2. It's great that you check over everything as opposed to blindly accepting it.

Craig

Are you sure that it is the Ki rather than the Kd in the CSMIO that provides the equivalent of the tacho feedback? Surely it is Kd that provides the velocity term. (I may be confused as I am writing this after a good lunch with plenty of champagne and red wine.)

Allan

Hi Allan,
the symbols I've used relate to the pics they are used in, they have no relation to the terminology used by CSMIO.

My intention was to show, in the simplest of terms, the similarities of the two. A proper mathematical description of each
would hopelessly obscure what is was trying to do.

Craig

Hi All

Just thinking aloud again. I'm a bit concerned that if we have to run the drive open loop (i.e. without the tacho), its gain might be so high that in order to avoid frequent saturation of the circuits we may have such a small output from the CSMIO that noise becomes an issue. Presumably if the drive were equipped with the torque mode personality module, gain would be tempered by internal passive feedback.

Allan

Hi Allan,
yes exactly, if indeed the drive has a velocity mode module fitted the I would have expected the amplifier to saturate almost immediately
the moment Mike opened the tacho feedback loop. From his description he had good control over speed of the servo. This leads me to believe
that the drive is faulty OR, and more likely, wildly mistuned in such a manner that it bears little resemblance to the manufacturers intention.

Craig

Hi Both

Thanks for all your input.

One step forward ten steps back. Had 3 hours trying to get somewhere with this.

Checked the voltage from the Tach at full rpm and it puts out around 32v. So went through the process of adjusting RV1. Then RV2 to get my desired RPM. Adjusted the tach to 10v as the controller is putting out. Then totally lost control of the motor. Limit switches, emergency stop and even disconnecting the wires from the command hi Lo would not stop the motor. Had to shut the machine down to stop the motor. 

Re-booted mach3 and the controller and the motor fires up again with no command from mach3. Check the voltage on pins 1 and 14 and we have 10v??. Disconnected the wires from pins 1 and 14 and the motor still continues to run. Shutting the machine down is the only way of stopping it.

By this point, I am losing my head a little so decided to try plugging the tacho back in and go through the same procedure with tuning. Now it allows me to gain a higher rpm with RV2 although not as high as without the tach. Same problem though the motors spin flat out on power up except this time the limits and emergency stops work. 

Anyway besides this there are lots of strange things going on.

Sometimes Mach 3 screen jumps to the end of the program as soon as you press start as in a split second.
It sometimes ignores the stop command.
Sometimes If you press the emergency stop the axis on the screen continues going.
icon.DLL defective plugin error pops up when I boot.
INTI.DLL defective plugin error when I boot.
Then sometimes it works perfectly but still get the errors.


I have tried that many things today my head is blown.

Think i'm going to send one of the drives away to get check out. At least then I can rule out the drive. I'll swap the motor over from the Z-axis as well. 

You guys have been great. I can't thank you enough for the time you spent with your advise.

Cheers Mick