340vdc brushless motor with CompactRIO?

[paubine]

I want to do motion control with a Parker BE-34 340VDC brushless motor with the CompactRIO....

I saw that the NI 9505 is 8 to 30V ... what can I do to control the motor? amplifier?

Can the NI 9505 give +- 10v ? and just use a servo drive from parker?

I'm really confused!
Thanks,
Patrick

[paubine]

PWM... I begin to understand...keep reading....

[Jochen]

The NI 9505 is an H-bridge power drive for brushed DC motors, so it's not a fit for brushless motors. As you have suggested, you should use an external drive that does the commutation. Typically these drives accept a +/-10 V command input signal which could be provided by an analog output module like the NI 9263.

Regards,

Jochen Klier
National Instruments

[paubine]

I still don't know a lot about motion control... still learning and learning... but.. I feel like controlling a dc brushed motor is well done with the CompactRIO, the closed-loop is in the LabVIEW programmation,  everything is in the PAC. (43 minutes webcast about the DC brushed control)

But if I control a DC brushless motor, Can i do something similar? I need an external servo drive or not servo drive and why?,  I feel like I don't use the power of the PAC to do calculation? I would like to use the encoder A B etc... directly in the digital input module of the CompactRIO (like a dc brushed), do the calculation/pid in LabVIEW and then send the +-10v analog or +-10 pwm to a device that will transform the signal to the high voltage dc brushless motor...

Do I misunderstand something?

Thanks again for your help!

Patrick

[Jochen]

I feel like controlling a dc brushed motor is well done with the CompactRIO, the closed-loop is in the LabVIEW programmation,  everything is in the PAC. (43 minutes webcast about the DC brushed control).
But if I control a DC brushless motor, Can i do something similar?
Yes, you can do this, but as NI currently doesn't provide a power drive for cRIO that does electronic commutation which is required by brushless motors, you need an external drive.

I need an external servo drive or not servo drive and why?
See above. The NI-9505 is a simple H-bridge module for brushed motors, so you can't use it, but using external power drives is a very typical usecase for cRIO based motion control systems.

 I feel like I don't use the power of the PAC to do calculation? I would like to use the encoder A B etc... directly in the digital input module of the CompactRIO (like a dc brushed), do the calculation/pid in LabVIEW and then send the +-10v analog or +-10 pwm to a device that will transform the signal to the high voltage dc brushless motor...
That's a wrong impression. You should configure your drive for torque/current mode. In this mode it will output current that is proportional to the control signal (+/- 10 V) of your cRIO system. In many cases no encoders are used with brushless motors but hall sensors that are used by the drive for the electronic commutation. Most of these drives export an emulated encoder signal that you can use with your cRIO system to close the position loop. So all the position control is done within the cRIO.

Regards,

Jochen

[paubine]

Thanks again Jochen, I understand better!

So I will use a Parker Aries Drive +-10v to control the BE34 motor and send the the voltage with the NI-9263.

Aries : http://www.parkermotion.com/literature/pdf/aries.pdf

1. The NI-9263 is 16bit resolution and the input of the Aries is 14bits resolution, is it a problem?

For the 2 encoders (emulated from the 2 Aries drive = A1, B1, C1 and A2, B2, C2) and the encoder from the master shaft (not emulated) (A3,B3,C3)  --> TO the CompactRIO...

2. Which Digital Input module should I use? in the webcast they use a NI-9411 6 channel, so I should use 2 NI -9411 or I can use a 32 digital input?

Thanks,

Patrick

[paubine]

I think it's good to say that the encoder of the master shaft is slow = about 1 rps, so about 2000 pulse/sec.

The 2 slave driven axes are really fast = ball screw table.

thanks,

Patrick

[chris.b]

1. The NI-9263 is 16bit resolution and the input of the Aries is 14bits resolution, is it a problem?

Not at all.  You will just lose the extra 2 bits of resolution you will have with the NI-9263 and operate at 14-bits of effective resolution.

2. Which Digital Input module should I use? in the webcast they use a NI-9411 6 channel, so I should use 2 NI -9411 or I can use a 32 digital input?

If you need more than the 6 channels on the NI-9411, you can use one of the 8- or 32-channel C-Series DIO modules.

[paubine]

The NI 9425 is SE and the NI 9411 is DIFF/SE... I don't see any 32 digital input modul with DIFF.

I can use SE even with fast encoders?

Patrick

[chris.b]

In reference to your question about SE or Differential DIO modules, this will depend on your encoders.  If they are differential, you will need a Differential cRIO module.

It looks like the Aries drive you are planning on using utilizes non-standard encoder inputs: "Encoder Out: RS-422 compatible differential driver."

I found some information on the RS-422 standard at this website: http://www.interfacebus.com/Design_Connector_RS422.html#c
Because the RS-422 standard is not the same as the standard TTL, you could not be able to write the RS-422 encoder outputs directly to a differential DIO cRIO module.  It may be possible to use a RS-422 to TTL converter.  Would it possible to use standard TTL encoders for your application?