Messages

41

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

« on: July 28, 2018, 12:21:24 PM »

Hi Mick

No, I don't think this is at all likely. The tacho and the command input are isolated from each other as both feed via resistors  into a summing junction of an op amp if I remember correctly. This summing junction is a low impedance input. The command input is further isolated by the input differential amplifier.

Allan

42

General Mach Discussion / Re: Spindle Encoder Wiring.

« on: July 22, 2018, 06:25:25 PM »

Hi Mick

It would be perverse if the spindle encoder were wired differently from the other 2, as they all share the exact colours and are presumeably the same brand.

I can't think of how you could verify which are 0V and 5V (the only critical lines) unless you are prepared to open the case and look at the circuit board. If the encoder were mine, I'd just conneft as per the other two.

Maybe someone who uses a Denford could chip in, or perhaps Denford's tech support could help if you are nervous.

Allan

43

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

« on: July 19, 2018, 06:06:04 PM »

All in all I think you are to be congratulated on the result you have achieved given your unfamiliarity of feedback
control systems.

Absolutely agreed.

Allan

44

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

« on: July 19, 2018, 04:28:12 PM »

Hi All

Mick, I did think you still had Kp set at 550. I cannot fault the way you have attempted to optimise tuning of the CSMIO, and if you feel that the axis is performing as well as it originally did, and/or are satisfied with it, so be it.

Out of interest, did you get the CSMIO scope to work, or did you just use the figure for following error? The scope would allow  you to see how fast the axis reacts to a step change, and how well damped the resulting transients are.

Like Craig, however, I feel that the velocity loop is weak and this may well be what is preventing the auto-tune completing sensibly as well as rendering your overall manual tune sub-optimal. If you feel inclined to push for better performance, this is the area that I feel needs your attention. You will need a scope, or as I have suggested you could probably use the CSMIO scope if you don't possess one. But if you proceed, do take care not to invoke the position loop as well. You would tune that, repeating the process you've already carried out, after you had optimised the velocity loop. Either use a signal generator to feed the command inputs, or if that is not available, try using Vff (only) with CSMIO as I suggested earlier.

Best of luck if you proceed with it. It might be wise to mark the original position of RV4 just in case you have to revert to the status quo.

Allan

45

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

« on: July 19, 2018, 12:01:11 PM »

Hi all

Good news that the system is now operating, at least at some level.

I  am a bit concerned that we are still unsure that the amp and motor are working to specification. The forward gain does seem rather low suggesting the amp or motor may be at fault in some way. The motor can possibly be verified by substitution. We can try adjusting RV4 but ideally need a signal generator and scope to do so. But I think it could be done via the CSMIO scope and I think we could generate the velocity steps via Mach or CSMIO if we use Vff and set all other PID coefficients to zero to eliminate any feedback within the position loop, as this would detract from optimising the amp's velocity loop. Does anyone out there agree with this or have any alternative ideas; or does the system seem  responsive enough as it is?

If the velocity loop is too limited in bandwidh, or is Poorly damped, we may have difficulty tuning the position loop, or the overall dynamics may be rather limited. The Kv Mick has achieved seems low to me - when I was using v2.910, admittedly  with Mach4, Kv was typically over 100000.

Mick

Thanks for the more detailed explanation of how you have reconnected the encoder and analogue output. I was struggling to see how it could work with the encoder on one axis and the analogue output on another. Haven't personally had any hardware faults but I suppose it is possible. Which axis is the motor on?

Craig

Sure, technology continues to advance, but it will be some time before these changes become common practice in the home shop. Heck, many users still cling to Mach3 despite the superiority of Mach4. They have a system that does what they ask, and that is all they need or desire. Anyway, we need to get back on topic.

Allan

46

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

« on: July 18, 2018, 06:25:49 PM »

Mike

Is the analogue drive to the motor you are using mapped to the same  channel as the encoder inputs? It sounds like your motor is hooked up to the output of channel 1 but you are taking encoder feedback to channel 0 on the CSMIO. This doesn't matter per se, but it would make things more logical if the two used the same CSMIO channel. Have a look at the plugin settings to see if they are correct.

Allan

47

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

« on: July 18, 2018, 04:59:50 PM »

Hi Mick

Sounds like things are making some sort of sense at last. I think the reversal you have seen could be due to a slight offset error. Although this could be ajusted using the pot on the main PCB, I wouldn't bother as the CSMIO can set the overall offset for you at the press of a button.

Are you able to get a high enough motor speed with 9V input now, and is the motor running smoothly? If speed is still limited I would be inclined (maybe with Craig's approval) to try a small adjustment of RV4 which affects loop gain. Maybe a little iteration of the settings of the 3 pots RV1, RV2, and RV4 would give you the result you require.

I have always presumed the red is positive pin 1 on the CSMIO and the blue is negative pin 14 on the CSMIO.

Yes this is the correct connection. Remember to start with Kd = Ki =Kvff = 0, and gradually increase Kv. Start with Kv = 10 and increase in steps of 10x to maybe 100000. If the motor suddenly runs away, reverse the sense of the encoder feedback and try again. If the motor begins to oscillate, reduce Kv.

It's always safest to have your eStop act directly on the drive enable as well as going independently to the CSMIO so that Mach knows what's going on. At its simplest, you could just add another contact block to your eStop switch and wire this in series with the connection to the drive enable. Some folks use a Piltz (may be incorrectly spelt!)  safety relay, but  this isn't necessary.

Craig

I doubt if we'll ever agree, but here is my final take on things. The greatest advantage of the matched servo and drive is that the drive has knowledge of all motor parameters. This is especially important in the drive's current loop, less so in the velocity loop, and less again in the position loop. Providing the drive takes care of the current and velocity loops, all that's needed to implement the position loop is encoder feedback and the calculation of a few Z transforms. I'm sure that the fast processor within the CSMIO is perfectly capable of doing that. I use Chinese Kinco drives and servos as you know, and like the DMM these are packed with features and flexibility. I am not aware that any significant features are lost by setting analogue mode and using the IP-A for the position loop. The CSMIO offers all the tuning features you need, including the scope, in its plugin. Don't just take my word for it - you only have to look at posts from folks like Hood to see that the IP-A is capable of excellent results.

Allan

48

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

« on: July 18, 2018, 06:57:29 AM »

Mike

Once you have disconnected the 2 command wired to attach your battery and pot, the CMIO cannot affect your measurements, but. The problem you could face is that if the CSMIO has to be enabled in order to enable your drive, the encoder inputs would make it throw a following error as the motor position would no longer correspond to what Mach had commanded. This would disable Mach and your drive. To eliminate this possibility enable your drive directly by connecting 24V to the enable line instead of using CSMIO. (You cannot just disable the motor in Mach as it would no longer activate your enable output.)

Craig

Fully agree. The amp simply balances the scaled tacho output against the scaled command to provide the error signal, and the actual scaling is not critical. As you say, if Mike cannot achieve full speed with 10V at the test point, the only solution, if we are to assume that the amp is otherwise working properly, is to reign back the tacho gain until full speed can be achieved. With any luck it will still be possible to adjust the command gain so that 10V, or something close, is needed at the input  to give full speed. It sounds as if the forward gain of the amp is fairly low, which could be by design or because of some component failure. We are confident that the PSU and the tacho are working correctly, but are we sure the motor itself is OK as that could conceivably be a possible cause as it contributes to the loop gain? Mike has said he could swap motors to check this.

Does the DMM support analogue input, or would its use mean replacing the CSMIO as well? I don't see much difference in having the position loop within CSMIO as opposed to within the drive. Either way it needs some adjustment to suit the machine.

Allan

49

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

« on: July 17, 2018, 06:09:16 PM »

Mick

Are you using Mach3 3.043.062, which is generally said to be the most stable release, with the CSMIO plugin version 2.910?

Have you removed that huge integral term Ki from the CSMIO tuning setup?

Does the motor turn or run away when both command inputs are connected to 0V? If so, it would suggest that the tacho is connected backwards (unlikely). If not, I would connect something like a pot to 10V and see if the drive and motor increase speed and run stably as to adjust the voltage from 0 to 10V. Then reverse polarity and repeat. The point here is to completely exclude the CSMIO until we are sure the drive and motor are working properly.

As a general point of principle, you might consider wiring the drive enable line directly into your emergency stop circuit, so that you are not dependent on any software device to turn off the drive in an emergency.

You have so many issues just now, it's hard to know where to start, but if it were me I'd stick to one device at a time and get it working before connecting everything in a feedback circuit, as this inter-dependence makes it harder to establish where a problem might lie.. If you feel you must use the CSMIO as a signal source, set all coefficients except Kvff to zero, as this will remove any feedback within the CSMIO and allow you to generate independent voltages as if you were using a signal generator.

Allan

50

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

« on: July 17, 2018, 02:23:19 PM »

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