Low cost three phase brushless amplifier

[Troubleshooter]

I am using cRIO for a specialty three phase brushless motor control application.  NI has a NI-9505 module for control of brushed motors.  I have not found one for brushless motors.  There are lots of third party integrated brushless motor controllers on the market.  They will not work for me.  I need to directly control the output transistors from cRIO.

I guess I am looking for a low cost three phase bridge amplifier.  The low cost is necessary since this will become part of an OEM product.  The motor is rated for 40 volts and 10 amps. 

Does anyone have any suggestions?

[Jochen]

Our R&D team is evaluating options to develop a cRIO drive module for BLDC motors, but due to the significant temperature dissipation of power drives, it's very unlikely, that it's possible to develop a cRIO module, that meets the current rating of your motor, so an external solution is required.

The easiest way to drive a BLDC motor is using a digital I/O module in combination with an external FET bridge. Here is an example how to do that. Please follow also the links there to more advanced types of control.

If you are also looking for a cost efficient solution for deploying your code to an OEM type of system, you may consider using NI single board RIO.

Kind regards,

Jochen

[Troubleshooter]

My goal is to do something like the example you provided in the link.  I just need a source for a ready made amplifier board or amplifier module.

[Jochen]

I'm sorry, but I don't know a vendor, that provides 3-phase MOSFET bridge modules, but using this phrase for a quick Google search returns some promising results, so this might be helpful.

Jochen

[Troubleshooter]

The products that come up from a "3-phase MOSFET bridge" Google search are generally chip level devices.  I need a ready made board or a module that I can wire to my cRIO, motor, and power supply and begin to use immediately.  Making custom boards is not feasible for this project.

[Jochen]

Well, that's apparently exactly the problem. Typically you either can find complete drives in the market, that provide a higher level command interface (e. g. +/- 10 V or fieldbus interfaces like EtherCat, CANOpen and so on) or you can purchase low-level devices for developing motion controllers/drives. Here are the links to analog or EtherCat drives offered by NI. These devices provide direct connectivity to cRIO (Second ethernet port for the EtherCAT version or drive interface modules for the analog version)

What you are looking for is kind of something inbetween the high-level and the low-level device classes but I guess there is not really a market for semi-finished BLDC motion drives. So you probably will have to decide if you want to solder something by your own or if you want to buy a ready to use drive.

Jochen

[Troubleshooter]

A ready to use drive will not work.  The purpose of the project was to replace an existing customized COTS motion controller with single board RIO.  The single board RIO would allow the addition of some new features and allow the product to be programmed with LabVIEW.

It sounds like my choices are: use single board RIO and make my own board level amplifier or do not use LabVIEW or NI products at all.

[Jochen]

Hi,

I'm sorry for the delayede response, but for some reason the answer that I have posted yesterday didn't make it to the forum. Fortunately there was an autosaved version of my post. So here it is:

As already said, I'm really not sure, if there are ready to use MOSFET bridges available on a board level.

I have just talked to Ben_B, who is the systems engineer who has developed the example, that I have posted above. Apparently Ben has experienced the same problem as you do, so he has developed the bridge board by himself.

Ben has offered to provide the schematics for the board if you would like to get them. Just let me know and I will arrange for that.

If you are planning to deploy a higher volume of these systems, I would recommend, that you contact your local NI sales representative who should be able to find a solution for the external MOSFET bridge. One idea could be to involve one of the NI Alliance Members who has experience and ressources to design and manufacture boards like that.

I hope that helps,

Jochen

[Troubleshooter]

I am glad to hear that I am not the only one with this problem.  I was just trying to follow NI's recommendation on how to control brushless motors with cRIO.

I would like to get a copy of Ben_B's schematic.

[Ben_B · Accepted solution]

Here are the gerber files and original source files for the board that I built.  It was designed in EagleCAD, and the final design is drive1.brd.  I don't think that there were any errors with that revision of the board, so it should be good to go if you built it that way.

Other than a couple of bridge-on-a-chip solutions that I found, there weren't any options for low-power dumb motor drives (drives without control logic built in).  Since I wanted to do my own control algorithm development, that meant I either needed to crack open a commercial drive or build my own.  I obviously went the second route.

Good luck.