Messages

51

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

« on: July 17, 2018, 12:58:00 PM »

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

52

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

« on: July 17, 2018, 06:03:46 AM »

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

53

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

« on: July 16, 2018, 06:39:06 PM »

Sounds as if the tacho gain may need adjustment, but will have to leave this to Craig as it is getting late for my brain. There is mention in the manual of adjusting the tacho to match it to the command voltage, but I'm not sure what this actually does and there is no circuit diagram. In any case, Craig is most likely to have experience in this area.

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

Allan

Allan

54

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

« on: July 16, 2018, 05:34:39 PM »

Mick

I wholly understand your wish to use what you have if at all possible. I would be the same. The thing that makes us suspect a fault is simply that you have stated that the motors would not run at full speed when you applied 9V to the command imput and adjusted the gain pot. But nothing quite makes sense at this stage so we need to try to narrow things down.

At least we are now confident of your wiring and of the power supply to the bus.

I may not be around much over the next 3 days as we have visitors and other committments.

Allan

55

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

« on: July 16, 2018, 04:58:37 PM »

Mick

The CSMIO output is not simply proportional to speed, it is a function of position error.  You have such a high integral gain that this is likely to rapidly force the output to 10V unless the motor is stationary. I would suggest that for now you manually set all but the proportional gain to zero in the CSMIO manual tuning. Increase the Kp until the motor just starts to oscillate, then back  a little. Aim for the maximum Kp without oscillation.  If the motor starts to run away rather than oscillate reverse the sense of the encoder (tick box in the plugin).

I was just thinking that we are currently tending to suspect the drive as being potentially faulty, but could it be that it is the motor itself that is bad. Maybe loss of field magnetisation, for example. I am just thinking aloud that the motor would be a lot easier to test than the drive, as potentially you would only need to supply armature valtage at sufficient current. See what Craig thinks about this as a possibility.

Allan
 

56

Mach4 General Discussion / Re: Problem running XY Offset Calibration Probe

« on: July 16, 2018, 04:01:39 PM »

Pleased  you got it sorted.

Allan

57

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

« on: July 16, 2018, 03:56:03 PM »

Hi All

The wiring checks out correctly as we have previously established. I think you are better off using STP to pins 1 and 14 of the CSMIO rather than grounding locally as I think Craig was implying. The quasi-differential connection I recommend could reduce ground noise slightly, at least at low frequencies. The encoder

Your encoders are correctly wired including 0V and 5V. The 5V is indeed supplied by CSMIO to power the encoders. In any case you said that the encoders were working correctly when set for 10000 counts per revolution.

Your motor needs 33V per 1000 rpm, so you should be good for something approaching 3000 rpm maximum speed.

I wouldn't adjust the current limit at this point as it should already be set correctly. It would perhaps be worth applying 10V as Craig suggests and adjusting RV2 (command gain) to see if you can achieve anywhere near the desired speed.  As Craig says, initially do this with no load on the motor. I don't hold out much hope, as I believe you said you had applied over 9V using a battery and that you had adjusted the gain pot.

If you still have negative results, I again suggest the easiest way to confirm if the drive is dead would be to swap it out with another.


I tend to go along with Craig in that if the drive is defective, it would be better to ditch it and replace with ac servo motors and matched drives, but of course that will cost you a significant amount, as well as having to potentially modify the mechanical arrangements and wiring - altogether quite a bit of work.

Allan

58

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

« on: July 16, 2018, 09:19:43 AM »

Mick

There are a few variants of the motor, with a voltage coefficient ranging from approximately 20V to 50V per 1000rpm. So your bus voltage sounds crudely OK but it might be worth a quick check under load.

You said you connected CSMIO pins 1 and 14 to the command + and command -. That is correct. The input circuit can certainly withstand +/-10V


Do you have a spare card that you could quickly swap in as a quick and easy check on the drive? You may need to keep to the existing personality module.

I'm off to work on a sick bandsaw now so will sign out for a while.

Craig

CSMIO has signal and ground outputs for each channel, so it sounds to me as if they are single ended but can conveniently be wired to the differential opamp using STP.


Allan

59

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

« on: July 16, 2018, 06:38:15 AM »

Mick

Thanks for the manuals. I see now what type of kit you have.

The motor speed is proportional to the (effective) armature voltage applied to it. As you have applied both 1.5v and 9.5V and these resulted in similar speeds, something is clearly wrong and I would start by checking the bus voltage, as this is the maximum that can possibly be provided by the bridge output circuit of the drive. I'm not sure which motor you have but the specs give the voltage factors per radian per second so this should enable you to estimate the required voltage for the maximum speed you need to operate at.

The drives appear to be designed for a voltage input, so we are OK in that respect. They either implement a simple (switched mode) amplifier or a velocity loop if you have the tacho installed. Either way, they convert input command voltage to motor speed, which is what we need.

Sorry if this seems tedious, but we need to proceed logically one step at a time to try to identify the issue. If the bus voltage seems OK then something within the drive must be limiting its performance.

As Craig says, advise us if you have the tacho installed.

Allan

60

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

« on: July 15, 2018, 06:16:45 PM »

Craig

Could it further be that even if the servo is voltage input, it is set for position or torque control rather than velocity control?

Allan