Failure of Robot Interface

Technical Technical Discussion
1

Anyone who saw our first round of the finals at the Midwest Regional knows that we didn’t function at all after sustaining an impact from another robot. It was thought at first that it was a battery problem, and that is what you heard from the announcer if you watched the webcast, or were there. Well, the problem was not a battery connection, or any other kind of external connection for that matter. Immediately following the round, we gave all the connections a thorough inspection, and could find nothing wrong with the robot. We were still getting power, but we had no radio communication. Well, one of the engineers gave the console a couple of taps and it came back to life. Something inside of the actual component of the radio equipment must have broken. Whatever it was, it definitely didn’t help us out any.

Has anyone else had problems of this sort?

2

we can’t run the robot in tether mode. it doesn’t supply a constant current to the OI. no idea how/when it happened, but it doesn’t work now. radio on the other hand works fine.

3

ACK!!!

Greg and I got pretty mad in our 2nd qualifying match. We put our robot out, set autonomous, and had the controller set up correctly. We were getting a valid signal and weren’t disabled. Autonomous started and the robot didn’t move but light turned on. During human control period, nothing responded even though the OI said we were getting a signal and not disabled.

We tested the robot after the match and it was fine. Next match, our robot ran perfectly without any changes except changing a constant for amount of turn in autonomous. That weird and it did not seem at all our fault that nothing worked.

4

I heard that 1064 found that if you shake the modem it can cause your controller to reset…seems that there might be some quality problems this year in the control systems.

5

Hey! Hold on there for a second. Let’s not blame the controller or the modem until we know for sure. There was a number of teams we found running radio, not tether in the pits. This has occurred at every event for the last two years that we have attended. Although it is claimed that there is no interference when this would occur, I am not yet convinced that some interference might be possible. It might not be data but it might be RF intermod. We are still looking into this and will pursue it with Innovation First in two weeks.
Baxter took a very hard hit in that match. We have had more than once, a broken pico fuse holder on the controller. It is possible that this might be why it began working after some tapping on the case.
It is common to try and get a long tether to allow you to drive while not using the modem. Cheaper, small diameter serial cables have significant loss of both DC and signal. If you were using anything longer than a 10’ cable suspect that the cable is at fault.

6

Team 1064 did indeed experience problems in St. Louis with our modem. We had lost communication in a couple of matches and could not figure out what had happened. The basic error light came on and it was fixed with the reset button, but it was still a problem. So we looked over everything in the pit and upon instruction from the head Innovation First guy, took it to the back of the arena and powerd up via radio. We found no problems at first, but when an engineer from team 71 that was helping us find the problem shook the model around a bit, we experienced the problem we had on the field.

The strange part about this is that in Chicago, with the same modem (new cable that got replaced in St. Louis), we experienced no problems whatsoever. We took harder shots in Chicago than in St. Louis too. So I’m not really sure what happened there. Maybe we passed our misfortune on to you guys somehow. Hope it is fixed for you before Houston. Good luck there!

7

*Originally posted by Matt McNelley *
**Anyone who saw our first round of the finals at the Midwest Regional knows that we didn’t function at all after sustaining an impact from another robot. It was thought at first that it was a battery problem, and that is what you heard from the announcer if you watched the webcast, or were there. Well, the problem was not a battery connection, or any other kind of external connection for that matter. Immediately following the round, we gave all the connections a thorough inspection, and could find nothing wrong with the robot. We were still getting power, but we had no radio communication. Well, one of the engineers gave the console a couple of taps and it came back to life. Something inside of the actual component of the radio equipment must have broken. Whatever it was, it definitely didn’t help us out any.

Has anyone else had problems of this sort? **

We had some similar and very weird problems last year where we would suddenly loose connection while at our school. Once we changed a fuse near the modem port and the problem went away, so we thought we had solved it.

Then just prior to the Summer Classic last summer, we had the same problem again and changing the fuse did nothing.

We then did a major rewire job with a different circuit breaker panel, and once again all went well.

Later, we had the same problem again. An additional symptom that appeared and seemed related was that our robot sometimes did strange random things, motors twitched off and on, the light went on and off, and these things occurred repeatedly and together. More than once, we had a cyclical connecting/ disconnecting occurring with the light going off and then on again every second or two, while the motors activated and deactivated. We also had the no data light turning on. It seemed like our robot was betwitched.

We tried a lot of different things to try to handle it. Finally we changed out the radio on the operator interface and since then no problem. This time, the solution seemed to be clear in our case, in that the problem kept occurring and then the second the radio was changed, it was gone and never came back. (We had tried tightening the connections from the radio to the operator interface and changing the radio wire, with no success.)

Hope the data helps in some way.

Good luck guys. I know it is not fun, especially during the finals of a competition.

8

We had that happen the day we shipped the Robot. We came to the conclusion that it was a loose connection. It had all the symptoms you listed. But we have been in some tough battles since (one of our PWMs’ was destroyed) but the interface has been rock steady since.

9

Well, our Robot Controller is pretty much out of the way from all impact, and is VERY PROTECTED.

I don’t think we will have any problems with it, since it’s well mounted deep inside… (My idea, hehe, me a smart person!)

Funny, “I” and the rest of the team thought the PWM Cable was destroyed because of hole drilling…

10

Our operator interface had to be sent back a week before our first competition because the LED display suddenly stopped working. And while I cant remember why it wasnt working, it wasnt our fault, it was some defect or something. The OI was still functional, but most of the LEDs and the team number/voltage display was either really dim or totally off. I think we ended up having some problems when we got the OI back, but I cant really remember.

11

Team 538 had alot of problems with our radio in St. Louis also. We first blamed it on First, They were having alot of problems with there equipment. I looked for anyone running off tether,
but found nothing. We did however find a few people using 2 way radios. We had no more trouble the next day, but I find it strange that we where dead the whole match, no light, no nothing. We replace the O/I with a loner from FIRST, and did not
have any more problems. Just in case.

12

*Originally posted by Ian W. *
**we can’t run the robot in tether mode. it doesn’t supply a constant current to the OI. no idea how/when it happened, but it doesn’t work now. radio on the other hand works fine. **

Team 548 had the exact same problem at Great Lakes, our problems were solved when we tethered our robot and plugged the OI into the wall. I don’t remember exactly but one of our electrical engineer explained the problem, something like there wasn’t enough power to run the robot and the OI so the robot got first priority and the OI went below sufficient running voltage and kept reseting.

Hope this answerer the question if anyone wants a more detailed explanation let me know and I’ll talk to the engineer.

Lindsey

13

Hey there. I feel a little out of place as I generally stay away from the electronics part of our robot and work on the mechanical aspects of it. Keep this in mind as I continue with my guesswork. Basically, Two Minute Warning takes several really, really, really rough hits in final rounds in Chicago (We actually had both of our wings bent. That’s right, 20 mm extruded aluminum bent.) After a few hits like this, we take a really, really hard one at the end of our autonomous mode. When human control starts we have no radio contact. In my head, what has happened is a circuit board or something couldn’t take the hit and shaked or a wire inside bent or something, resulting in it reseting or something to that matter (I told you I tend to stay away from controls stuff). In order to keep this from happening in the future, could I simply either get some foam or rubber gromets to act as shock absorbers between the radio controller and the frame of the robot? If you respond to my question, please explain as much as you can, either what actually happened or what might fix it in the future. Thanks

14

*Originally posted by Lindsey *
**Team 548 had the exact same problem at Great Lakes, our problems were solved when we tethered our robot and plugged the OI into the wall. I don’t remember exactly but one of our electrical engineer explained the problem, something like there wasn’t enough power to run the robot and the OI so the robot got first priority and the OI went below sufficient running voltage and kept reseting.

Hope this answerer the question if anyone wants a more detailed explanation let me know and I’ll talk to the engineer.

Lindsey **

We had our tether port toward the front of the robot, and while driving the 'bot on tether, a person stepped on the tether which yanked the tether port back and damaged it. After a few days, the tether port didn’t work.

We had to send the robot controller back for repairs. In the meantime, Innovation FIRST upgraded our last year’s robot controller to this year’s specs for about $40, and we used it.

15

We had the controller in near the front of our robot and the radio cable plug stuck out about 1/2 inch past the chassis. Well, on our first run we ran it into a pole in our room and it just so happened that it hit right where the plug was and pushed it up breaking a few of the pins. It still worked fine but we did not want to take the risk so we opened it up, took out the port and replaced it with a new one. This voided the warranty but the warranty only covered factory defects anyway so there was nothing to lose. Today, you would never know that we broke it. And the best part is that my brother (electronics/electrical expert) had it all fixed before the engineers got back.:smiley:

16

*Originally posted by Kojib *
** In order to keep this from happening in the future, could I simply either get some foam or rubber gromets to act as shock absorbers between the radio controller and the frame of the robot? If you respond to my question, please explain as much as you can, either what actually happened or what might fix it in the future. Thanks **

Placing rubber grommets, foam or even balsa wood between the radio controller and the frame will certainly help reduce mechanical shock transmitted from an impact to the internal components of the radio controller. Severe mechanical shocks can break fuses, wires, capacitors, resistors or crack solder joints.:ahh: The latter case (cracked solder joints) is often intermittent in nature - which can be really difficult to diagnose. Sometimes tapping on the controller may re-establish the contact, but it doesn’t fix the problem. Tapping on it more may cause it to fail again.

If you observe this intermittent behavior, get a replacement controller and don’t hard mount it to the frame. A thin piece of balsa wood or foam between the controller or frame can help reduce the mechanical shock experienced by the unit considerably.

Good luck, and see you in Houston!

17

our robot controller is strong enough to take some good drops in the build season. It lasted through the shorting of the ower wires to the GYRO. And as for the radio on the robot…it met the midfield barrier and lives to this day.

Kevin Antaki
Team 481

IM Me: xpalendocious

18

There are a lot of questions above me here so let me try a few…
In St. Louis (I was just visiting) there was one player station that had a lot of failures. I think it was the right side Red. From Friday PM to Sat AM I think at least 5 or more teams went dead at that station. So I don’t think anyone had hardware failures at that point.
When tethered there is a strict limit of 25 ft with known good serial cable, if you have that really thin stuff and/or have lights on your button box, the current draw through the cable is high enough to cause a brownout at the OI and it won’t operate. (That is why local power brought it back in the one case above.)
Generally, the Innovation First stuff is pretty well put together and should survive any shocks we can give it. The RC has a few failure points, one being the connectors can’t take side loads. If you don’t tie down all cables entering the RC you are asking for trouble. Another is the Pico fuses are not tied down. Many teams put a piece of tape across the top to hold them in, but there usually isn’t much of a problem. I have seen a few teams this year who mount the RC upside down, which gets gravity working to drop the fuses out.
Beyond that you should check for crimped or severely bent cables. (look for someone who get very aggressive with a tie wrap as the cable goes around a corner.) Sharp bends and crimps on the radio cable especially, spell disaster.

19

if you cant use the tether cable, check the pins on the OI and the cable - you might have bent a pin - very easy to do.

20

We tested the robot after the match and it was fine. Next match, our robot ran perfectly without any changes except changing a constant for amount of turn in autonomous. That weird and it did not seem at all our fault that nothing worked.

I’d hate to tell you but it probably was your programming that was at fault. I know our team had a problem when they downloaded the program into the robot it just stopped working flat out.

Although it is claimed that there is no interference when this would occur, I am not yet convinced that some interference might be possible. It might not be data but it might be RF intermod. We are still looking into this and will pursue it with Innovation First in two weeks

Innovation First would know if there was interference during a match. I saw the device they use to check for it at one regional.