Brian

You can monitor the position, but it will have to be through another hardware channel, if available. The same IC hardware is used for real encoder or open loop stepper. You can continuously monitor position in a PLC and kill a move if there is excess error, or you can do a pull-in move at the end of the move, or both.

It was only one axis, and the loop was closed in the UMAC. I sent the torque command over Profibus and read position from the encoder. This was on an ABB drive with an induction motor.

The Clipper has can work in direct PWM mode, but your amplifier has to be compatible. It sounds like your amplifier is traditional analog. The Clipper doesn't have true DACs, but produces a PWM signal that looks like an analog signal to most amps. Be sure to set your frequencies correctly(in the manual), or your motor will jitter and overheat.

That is correct. If you use the motor in a coordinate system, then you can scale counts to real world units, but as far a PMAC is concerned, it only looks at counts.

No. That is the way it has always worked, and it works very well. Direct PWM is better, but analog still works well.

PMAC doesn't know and doesn't care about the relationship of volts to speed(or torque). It will adjust the analog signal to match the commanded position. All scaling of what the analog signal means is done in the drive. PMAC is blind to the scaling, and whether the drive is in torque or velocity mode.

If you mean to use fieldbus instead of analog command and encoder feedback, then yes I have done this using Profibus. Loop update rate was 2ms, so it is not for demanding applications.

The drive signal to your amplifier is directly proportional to load, if you have a torque-mode amplifier.

Sina- It appears that unless you have an oddball potentiometer, then you are seeing the same issues I am seeing. I've only ever seen 2 types of rotary pots. Ones with linear tapers, and ones with audio tapers. What your graph shows is neither, so I am inclined to believe that the internal circuitry of the ACC-28E is affecting the reading. Do you know of any fixes for this, other than a signal conditioner? Regards, Brian

Sina- Please confirm that your voltages are linear. My DMM readings match the ACC-28E values, but they are not linear. The string pot by itself has linear resistance, but when connected to the ACC-28E, the voltage output is non-linear. That tells me that the ACC-28E input impedance is rather low, and affecting the readings, but I couldn't find the specs for it. Your DMM is probably about 10G Ohms. I don't remember if I checked voltages without the ACC-28 connected. I am not using bipolar, but unipolar 0-10VDC. I have it wired for differential input, so it is really looking at a 0-10VDC range. Also, the readings occasionally jump to a large value, but still within the normal range of the register. I doubt that it is noise. Is it possible that something else is writing to the that address? All my cards are addressed differently. Regards, Brian

I am using the -5VDC and +5VDC from the ACC28E. Analog- is connected to -5VDC and one end of the pot. +5VDC is connected to the other end of the pot. Analog+ is connected to the wiper. I originally tried this using +15VDC through a resistor to give 10VDC at the pot, but I had the same results. The channel jumpers are set up for unipolar, and the resistor packs are in the default positions.

I am trying to read a 10k string pot that is connected to an analog input on an ACC-28E. The problem is that the input is not linear. The resistance change of the pot is linear, but apparantly due to the input impedance, the voltage input is not linear. How do I get around this? This must be a common application.

Here is a basic example. There are other ways to do the same things, but this example will show you how to do what is needed in 95% of applications.Pcommserver Example.zip

I can't say for sure, but I don't see any reason why it wouldn't. Unless you have an existing project that you are upgrading, I would stay away from the PMAC Panel product. It uses dll calls, and the new Pcommserver is the best way to go. I have done quite a bit with Labview and ActiveX calls to Pcommserver. It is much more stable, and you can have both your Labview application and PEWIN32PRO2 open and communicating at the same time. I can send you some basic VIs that show how it is done.

The problem I have with the suggestions is that the problem appears to be random. I cannot duplicate it. The machine is in production 24/7, and this problem happens 3-4 times a day. I could gather on each move, then upload only if the move gets aborted. The ballscrew has been lubricated, but that did not help. I am using IMS steppers and drives, if that helps.

I have a 4-axis Clipper system. 2 axes are closed-loop stepper, and 2 axes are servo. I am having what appears to be a resonance issue with one of the stepper axes. It is a ballscrew axis, and most of the time it works great. It is tuned well, but occasionally, it will start a move and make a horrible sound, then fault on following error. The sound is like it is resonating badly, but the stepper is not stalling. The unusual part is that the move parameters never change and the load never changes. Any ideas as to what might be causing this?

Are there any examples of real projects available? I'm not looking for any thing complex, but just the basics.