Strange system problem

[Bill Becker]

We a very strange problem hit us in the elimination rounds at NYC. Our code and systems were working fine during all the qual matches and then in the elims, our robot appeared to continuously reset whenever the drive motors were run. This happened in autonomous and during operator control. The operator interface would report no data radio when the robot reset. It also did the same thing in the pits on the tether after we were eliminated.

After reading many of the posts in this forum, it seems like there are a few possibible problems, but I wanted to ask here because we won't have a lot of time to troubleshoot at nationals and it won't be much fun if we can't resolve it quickly. Our backup battery was pretty low on charge, but I wouldn't think that just driving the motors with the wheels free spinning on tether would cause voltage to go too low. Our programmer swears that he didn't change anything in the code. Could it be a faulty speed controller??? or could our controller been damaged? Any other possible causes?

Thanks!

[vtrehan]

My first guess is a poor or low on charge battery. Same thing happened to us during a practice match in Waterloo, as soon as the battery was changed, everything was back to normal. Make sure the battery is completely charged, you might be using up a completely charged battery every match.

Another possibility is a screwup in the communications between the OI and the RC, for which you will need to confer with the Innovation First.

Our programmer swears that he didn't change anything in the code.

And last and the most important thing is to keep trusting your programmer, we are all good people.

Take it easy,
Vivek.

[sanddrag]

We had a main battery that seemed to take a good charge and get up to about 13.2V but it turned out this was only a "surface charge" and after a few seconds of use the battery voltage dropped very low. We never had reset problems because our backup battery was always fully charged but the main battery did cause slow robot movement. Use your Operator interface to see what the voltage of your main battery drops to when you drive.

[Mike Betts]

Bill,

Insure that both the 12V SLA and 7.2V Ni-CAD have a full charge. Also check the integrity of electrical connections on all 6 AWG terminations (2 on SLA, 2 on 120A CB and 2 on power dist panel).

A combination of a low Ni-CAD and a high external resistance will cause the problems you have observed.

Regards,

Mike

[Kevin Sevcik]

Low backup battery is probably causing the resetting when the main voltage dips low. The main voltage could be sagging for some of the reasons listed above. Another possibility is binding in your drivetrain that you can't see, or possibly an intermittent short somewhere tripping your main or secondary breakers and dragging the voltage low enough in the meantime to reset the robot controller.

[sanddrag]

Originally Posted by Kevin Sevcik

possibly an intermittent short somewhere tripping your main or secondary breakers

if the main breaker trips you are out, it doesn't reset. There could be a high resistance connection somewhere, but drivetrain binding is more likely.

[Andy A.]

I would suspect a mechanical bind and/or poor electrical connections. I'm leaning towerds a bad connection.

Do a resistence test on your frame and battery- Shorting to the frame could easily drop your voltage low enough to reset your controller if the nicad is not charged. That short may be in the wiring between the motors and victors, so it wouldn't show up unless the victors were supplying power. Carefully inspect all the drive motor wiring by hand, looking for abrasions and pinched wires, crimps that may be working loose or any exposed conductors.

I also suggest that you remove breakers to all your drive motors, and plug them back in one at a time till you have tested each motor through the speed range individually. While you do this, use a multimeter with a clamp type ammeter to monitor the current draw of each motor. On blocks, each motor should draw something like 5 amps (thats been a typical number for my team, others may consider that high or low). If a motor is higher then others, or one side of your drive is drawing more then the other, you've narrowed your problem down to a binding or a loose connection. Also check the current draw from the battery while the robot is at rest and when the drive starts to move. Look for a high draw at rest, which would indicate a problem in breakers or associtated wiring (as opposed to the wiring from the victors to the motors).

The electrical problem is easy enough to deal with, since it'll probably just need a little electrical tape or a tighted screw. If it's mechanically related, you'll need to figure out just where all the excess friction is coming from.

Are you using the kit gearboxs?

What motors are driving?

Are all your motors moving in the right direction?

Do you have a compressor on board?

-Andy A.

[Not2B]

Along the electrical issues line of trouble shooting...

Check the screws in the lugs for the battery cable. Ours came loose at least twice during the season. We had to check them every few matches.

Although I don't think this sounds like your issue, it's still a good thing to check and eliminate during the trouble shooting.

Good luck finding the "ghost in the machine".

[kjohnson]

I would say a problem with a battery - either main or backup. Try and make sure you have one of each charged and ready to test the problem if it ever happens again. You may also want to try buying new batteries as recharging them too much can drop their output voltage.

[Bill Moore]

Just an idea, but in 2003 at Houston, we had a dificult Saturday morning. Everything ran fine on our robot Friday evening, and the next morning the robot only ran autonomous. When the 15 seconds were over, the robot would not respond to any operator controls. The best we were able to figure is somehow the code got corrupted (static?). Anyway, we went through two matches before we found the problem. Yes, look at all the battery problems mentioned, but also re-download your code to make sure it didn't get corrupted somehow.

[Joe Ross]

The IFI representative on the field can give you a lot of information about what happened, for example, low battery, low backup battery, code errors, or loss of radio.

For anyone, if your robot acts strangely, you should ask the IFI representative immediately if they saw anything. It may save you a lot of time later on.

[Josh Hambright]

Originally Posted by Joe Ross

The IFI representative on the field can give you a lot of information about what happened, for example, low battery, low backup battery, code errors, or loss of radio.

For anyone, if your robot acts strangely, you should ask the IFI representative immediately if they saw anything. It may save you a lot of time later on.

I agree with Joe, the IFI guys are all really great to work with and are always very willing to help troubleshoot your problems. And sometimes its faulty equipment, but more often then not its simple problems like bad cables, disconnected cables, poor connections, bad batteries, bad charge, disconnected battery, inefficent mechanics, shorts, or other problems on our end of the stuff.

I'd say check all the stuff listed above with the batteries, and the shorts, and all that. And if your still having problems, track down one of the IFI guys and see what they cant do to help you.

I know from talking with the IFI reps at Boilermaker and MWR and observing their software in action, they can tell alot about the control system from their handy dandy laptop, everything from disconnected modems to a dead backup is easy to diagnois for them

[Bill Becker]

Thanks! this is great info/advice. I feel much better about our prospects of resolving it quickly now. We will need to borrow a clamp ammeter from someone though.

In Reply to Andy's questions:

Originally Posted by Andy A.

I would suspect a mechanical bind and/or poor electrical connections. I'm leaning towerds a bad connection.


Are you using the kit gearboxs? We are using a two speed pneumatically shifted gearbox. It is possible that the pressure to the pistons got increased somehow and is causing binding.

What motors are driving?Each gearbox is powered by 1 CIM

Are all your motors moving in the right direction? Yes, they worked fine in all of our qual matches.

Do you have a compressor on board? Yes

-Andy A.

[Bill Moore]

Originally Posted by Bill Becker

Thanks! this is great info/advice. I feel much better about our prospects of resolving it quickly now. We will need to borrow a clamp ammeter from someone though.

In Reply to Andy's questions:

Look!! Up in the sky!! It's a bird! It's a plane! NO, IT'S A BIG GREEN TOWER!! !!! !!!! !!

Bill, and all teams, if you need any help or resources in the pits, check with our pit crew. We'll do our best to help get your robot back to tiptop running condition. I'll check with The Lucas tonight to see if we've packed the type ammeter you need to borrow.

Good Luck at Championships!!! (Where are those Divisions? It's already 9:45 AM!! Impatient? Who, ME?)

[Bill Moore]

Originally Posted by Bill Moore

I'll check with The Lucas tonight to see if we've packed the type ammeter you need to borrow.

Bill, we will have the ammeter you need. Just stop by the pits and ask. Good Luck!