Router browns out with multiple CIMS driving WCD
 

We have a 6 CIM West coast drive, and whenever we try to turn the router browns out. We tried dropping to 4 CIMS and it still happened. 2 CIMS worked, and we tried rotating out the motors so that wasn't the problem. If you turn the robot by hand it also turns easily and it doesn't appear to be a problem with the gearboxes. Each motor is pulling approximately 40-45 amps when in max load and we don't believe that would be normal in this type of drivetrain. Has anybody experienced this before?

Re: Router browns out with multiple CIMS driving WCD
 

What kind of wheels?

What's the wheelbase and trackwidth?

How far did you drop the center wheels?

What's your gear ratio?

Put it up on blocks and tell us how much current it draws.

Re: Router browns out with multiple CIMS driving WCD
 

Did you look at the Driver log file to see how low the voltage was pulled?

Re: Router browns out with multiple CIMS driving WCD
 

We're using the AndyMark 8" pneumatic wheels

It's a 6 wheel drive. The wheels are 12.5" apart.

The center wheels are dropped 1/8".

Not sure about the ratio but it's the 2.06 spread for the 3 CIM WCD from West Coast Products. With an 11 pinion input.

It's pulling 10 amps on the blocks, but if you reverse directions it goes over 50

Also, when it drops out the voltage drops under 9.

Re: Router browns out with multiple CIMS driving WCD
 

1/8" may not be enough for pneumatic wheels.

Full throttle?

The numbers are ambiguous and seemingly inconsistent:

10 amps total divided by 6 motors would be only 1.7 amps per CIM, which is less than their free amps.

50 amps per motor times 6 motors would be 300 amps, which would pop your main breaker.

Please elaborate.

Re: Router browns out with multiple CIMS driving WCD
 

The robot radio shouldn't brownout until ~4.5v if it's wired to the VRM.

Re: Router browns out with multiple CIMS driving WCD
 

Yes that was all per motor, but only 4 motors are on right now. It was also full throttle. However the 50 amps were only a spike as we reversed direction so the breaker didn't pop because it was instantaneous.

Also we thought about the 1/8" not being enough but it has worked previously, we are only experiencing this today. Also its pulling these amps on the blocks so the wheel drop shouldn't affect the amps right now...

Re: Router browns out with multiple CIMS driving WCD
 

Can someone please comment:

For a 4 CIM West Coast drive, is 10 amps per CIM par for the course for full throttle up on blocks?

How about 1/8" center drop for 8" pneumatic wheels?

Re: Router browns out with multiple CIMS driving WCD
 

We're running a similar setup. We've got the 8" pneumatic wheels, WCD gear boxes with the same gear ratio (I think), 3 CIMs each side, and a 1/8" drop. The only difference is our C/C of wheels is about 7.9". We're driving and turning without an issue. I'm sure the larger C/C distance isn't helping but I wouldn't think it would cause consistent brown outs though.

Can you compress the C/C distance?

Not sure about the current. Never checked on blocks.

Re: Router browns out with multiple CIMS driving WCD
 

We are using 8 6" pneumatic wheels and 6 CIMs and are using a 3/16" drop this year because of the pneumatic wheels.

You might also take a look at what pressure you are using in your tires.
Higher pressures would probably help with scrubbing.

We are also current limiting in the program to maintain voltage to the RoboRio.

Re: Router browns out with multiple CIMS driving WCD
 

Well we found out through the VRM that it is in fact not the radio but the RoboRIO that is browning out. There isn't a very easy way to change the drop or the C/C without redoing the entire chassis and I don't think that would be necessary since it had already worked earlier in the week.

Re: Router browns out with multiple CIMS driving WCD
 

We've been running 3/16 and a high difference in pressure between the center and outer wheels and we have been pretty good. One of these changes is easy and the other probably is not.

Re: Router browns out with multiple CIMS driving WCD
 

difference in what direction?

Re: Router browns out with multiple CIMS driving WCD
 

I think the trend has been over-inflating the center wheels and under-inflating the front & back wheels, which kind of adds to the drop center effect. But of course I can't answer for 422.

Re: Router browns out with multiple CIMS driving WCD
 

Fix! Well that was interesting. There was a fault in the PD board (orange light) so once we cleared it it seems to work as expected. Thanks to everybody though!

Re: Router browns out with multiple CIMS driving WCD
 

With a non-traction-limited 6CIM drive, I can verify that this can (and does) happen reversing direction without a voltage ramp.

Re: Router browns out with multiple CIMS driving WCD
 

Yeah you got it.

I posted that while eating at the shop today and frankly I'm surprised I completed sentences...

Re: Router browns out with multiple CIMS driving WCD
 

A sticky fault on the PD is there to catch your attention to something that happened some time ago. I do not believe it affects the current usage or roboRIO brownout prevention. I suspect that other things changed as well, such as changing out the battery, and perhaps even some wiring or mechanical changes.

So the problem wasn't fixed by clearing the sticky fault. You may have a weak battery in your midst that will reintroduce the problem another day. You may also have some binding or electrical connection issues that are inconsistent and may reintroduce the issue.

So, please experiment and look for the issue. Also, be sure to open the DS log file viewer. You can click on the gear on the DS and open the viewer. Look at those logs and compare to others. If you don't see the issue, please post the file or a picture of the viewer.

The other day, the robot was pulling a bit while the drivers were testing it out. The programmers opened up the log viewer and clicked to see the motor currents while others started feeling motors and tracing wires. Sure enough, one drive motor was disconnected. Guess which team found the issue first?

My point is that the log file has valuable info and can help identify many issues.
Greg McKaskle

Re: Router browns out with multiple CIMS driving WCD
 

All closely related threads:

Power draw issues


Battery Voltage problem

Voltage Drop issues


Robot loses communication while going over obstacles


Router browns out with multiple CIMS driving WCD