drive for Fanuc "red cap" brushless motors

[jmelson]

I have just developed a signal converter that allows Fanuc red cap brushless motors to be used with Pico Systems, as well as other brushless drives. The problem was that Fanuc had a proprietary scheme for encoding the commutation information. My converter reads the proprietary position information at startup and converts to standard Hall signals. Once the motor has passed the index position, the converter counts the quadrature pulses to determine the right commutation phase.

I will be demoing a prototype of this at the EMC Fest in Wichita May 21-27, and should have it out as finished product in about a month after that.

Jon

[Al_The_Man]

Will it be small enough to fit in the Red Cap?
Do you have a projected price yet?
Al.

[jmelson]

Originally Posted by Al_The_Man Will it be small enough to fit in the Red Cap? Do you have a projected price yet? Al.

I hadn't thought of trying to fit it inside the cap, but that is definitely possible. I have been looking at red cap motors on eBay, and I see some of them have the external connector wired to the encoder with a flexible printed circuit. So, it would be a major hassle to make such an installation on those motors. The PC board with the electronic components would only be about 5 mm thick, so it seems like it should fit in there, at least in the larger motors. It will probably be less than 2" square. It would require some modification of the internal wiring. I would have to at least leave holes for the screw terminal blocks, as many people would not want to modify the inside of the motors. But, I could sure sell it without the connectors, and you could hand wire it as you desire.

As for price, I'm not too sure at the moment. There is not a lot to it - a crystal oscillator, an CPLD, and a differential receiver chip. I think maybe the no-connector version might be able to go for $50, and the one with connectors might run $65. The CPLD is $12, so that sets the price floor.

Jon

[Al_The_Man]

After looking at the cap and encoder on the ones I have it looks like it would be a squeeze.
I guess it could go in the enclosure, do you intercept all the differential signals?
Have you done any extensive testing?
I am definitely interested as I am ready to use a Fanuc motor for a spindle.
Al.

[Al_The_Man]

Another couple of questions come to mind. Is the interface set up for 8 pole motors, which most Fanuc are as far as I have found.
Also if you count the encoder pulses after the marker, how does different encoder counts/rev affect this?
Does the motor need to be rotated initially to set up the configuration?
Al..

[jmelson]

Originally Posted by Al_The_Man After looking at the cap and encoder on the ones I have it looks like it would be a squeeze. I guess it could go in the enclosure, do you intercept all the differential signals?

The four commutation signals are not differential, but the encoder ABZ are. The prototype doesn't use the differential pair of ABZ, but the final version will do that.

Have you done any extensive testing? I am definitely interested as I am ready to use a Fanuc motor for a spindle. Al.

EXTENSIVE testing? I NEVER do extensive testing, just enough to make sure it works! This is a hand-wired prototype, and I was astounded that it worked at all on the first try, and perfectly on the second. I just made the motor move for the first time less than 24 hours ago!

I will have to do some more testing when I get final boards made, and I'm sure we will do some testing of it at the EMC Fest when I show it off. But, really, if the motor moves smoothly over a range of speeds, there isn't a whole lot more to do.

The brushless DRIVE, itself, has had quite a bit more testing, I've been using them on my own machine as well as having sold a few of them. The big problem with brushless drives is motor/encoder compatibility, and the only way to know for SURE is to test at least a motor from the same series.

Jon

[jmelson]

Originally Posted by Al_The_Man Another couple of questions come to mind. Is the interface set up for 8 pole motors, which most Fanuc are as far as I have found. Also if you count the encoder pulses after the marker, how does different encoder counts/rev affect this? Does the motor need to be rotated initially to set up the configuration? Al..

Yes, the motor I am testing with is 8 pole, and all the ones that are clearly described also seem to be 8 pole.

I think the red cap "pulse coder" is standard at 2500 pulses/rev, which equals 10,000 quadrature counts/rev. If there are any that are different, then the program will have to be changed to adapt.

The commutation is initially controlled by the B1 through B8 signals, and once the index pulse is seen, then position is counted from the quadrature encoder. The motor runs normally in both modes, I can't detect the changeover by feeling the shaft. So, that initial move to get to the index pulse would be during the axis home sequence, and would be under control of the CNC program.

Jon

[Al_The_Man]

The Encoders I have are 2000p/rev.
Fanuc also have 1000, 2500, 3000 and some at 10,000.
Al.

[jmelson]

Originally Posted by Al_The_Man The Encoders I have are 2000p/rev. Fanuc also have 1000, 2500, 3000 and some at 10,000. Al.

Well, that is no problem, I just need to know in advance what resolution you need. I may have enough space in the CPLD to make the resolution jumper selectable, but I can't guarantee it until I try it.

Jon

[Musick7]

Originally Posted by jmelson I have just developed a signal converter that allows Fanuc red cap brushless motors to be used with Pico Systems, as well as other brushless drives. The problem was that Fanuc had a proprietary scheme for encoding the commutation information. My converter reads the proprietary position information at startup and converts to standard Hall signals. Once the motor has passed the index position, the converter counts the quadrature pulses to determine the right commutation phase. I will be demoing a prototype of this at the EMC Fest in Wichita May 21-27, and should have it out as finished product in about a month after that. Jon

If you like I can get you some dimensions for this. I have a Fanuc Robot S5 I sent you a PM with a link. It has 5 servos on it and I think the top 2 are teh same size and the lower 2 are the same and the very bottom is different as well... I just got it Today givin to me from my Work!!!! I was so excited about it. I got the Controller the 2 hand held Wands or computers all the cables! The Robot its self works just fine! The controller is screwed up but the instructor said the drivers and encoder just might be able to be salvaged...

[Musick7]

First time uploading to this site hope i did it right

[Musick7]

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