Current measurement on AKD Drive + AKM Motor

[Ansari07]

Hello All,

I was wondering if there is any way to measure the phase currents/voltages that are being source to the AKM motor by the AKD drive? If not, can I design an observer in LabView to get an estimate of these values?

Regards,

Ansari

[Blizzard]

Hi Ansari,

Are you and 73X Motion controller? Also, are you using Kollmorgen WorkBench to interface with your AKD Drive and Motor? If you are using Workbench, you can look at page 25 of the document I have linked below to see how you can set the current and voltage parameters of your motor. 

Getting Started with NI 7340/7350 Motion Controllers and AKD Servo Drives: http://www.ni.com/pdf/manuals/375543a.pdf

Best regards,

Anna L

[Ansari07]

Thanks for the reply, Blizzard.

A little bit of background on my requirements may be in order. I am looking to build a complete evaluation system for brushless servo control, for research purposes. I would like to be able to apply the theory of sensored and sensorless control, linear and non-linear control, torque ripple reduction techniques, robust control, etc. on my system. For these reasons, I would like a number of quantities to be measurable from the system. I can get the rotor position and speed information from the encoders. The other critical measrements I require are:

- At least two of the three, phase currents going into the motor

- The phase or line voltages of the motor

At this point I am open to any of the configuration options suggested in this white paper(Building an NI Motion Control System). I went through the document you suggested, and concluded the following (please correct me if I am wrong):

1. The drive configuration using AKD WorkBench allows you only to set the continuous current sourced by the AKD drive to the motor. This setting is based on the motor ratings. The fields under the "Motor" tab are auto-populated if an AKM motor is selected.

2. The analog outputs on pins 7 and 8 from connector X8 give the tachometer voltage and hence, the actual motor speed information.

3. The analog inputs on pins 9 and 10 will take the speed setpoint information, that can be used in speed regulation or speed control in closed loop.

4. The AKD drive does not provide real time measurements of the currents and voltages that are being sourced to the motor it is driving.

Theoretically, I could insert an ammemeter in each of the lines of my AKD-to-AKM cable, and hook a couple of voltmeters between phases a-b and b-c, but I guess that will not be recommended by NI or Kollmorgen, as it would require cutting open the AKD-to-AKM motor cable.

I contacted Kollmorgen too, a few days ago. Still waiting to hear from them. Having said all this, is there anyway to obtain these measurements?

Thanks for taking the time to read.

Regards,

Ansari

[Blizzard]

Hi Ansari,

Thanks for your detailed response. It sounds like you have a pretty exciting application! 

You are correct that you can only set the continuous current sourced by the AKD drive to the motor. Also, you are correct about the analog output and input pins on the AKD.  Unfortunately, you cannot get the real-time currents and voltages sourced to the motor. With this being said, there is no way to obtain your phase voltages and currents without adding ammeters and voltmeters. You are again are correct, though that this is not recommended. 

Best of luck with your project and have a good afternoon.

Regards,

Anna L