Based upon what I saw on today’s webcast, it appears as if the Edison division replayed about 10% of all qualification matches for reasons of unknown provenance.
My FTC team was asked to replay a match due to “excessive blocking,” in the original match. This is completely absurd on its face in my mind. I’m curious what justification there might’ve been for replaying so many matches today and how they jive with what I typically expect from FRC – that only a field fault warrants replaying a match.
The replays were almost always due to field faults. I heard there were WAY too many powerful wifi sources in the area and it really messed up the communications to the Samantha modules.
I started to wonder if it wasn’t some of the robots and not just the field control, because we had no problems, even when the other 3 robots shut off in one of our matches we just kept going and it worked perfect so it might not be “just” the field control, also if you push the “mode” button on the controller it will disable the joysticks, making teams think that the robot is unresponsive, but you can still move the servo’s. I hope that helped
We also had no real problems except in two matches. The first was when all four robots lost communication for about 3 seconds, and the second was after they reset all the USB controllers and our arms person had the joystick pressed back so it thought zero was in the wrong place.
I definitely believe that most of the individual problems were robot related – specifically the comms from NXT to motor/servo controller. Dick Swan (RobotC author) talked to us at our booth and we proved to him the RobotC bug relating to those communications and PID. I expect that there’s another bug in there as well that’s related to a similar firmware design problem. The connectors on the NXT are not really designed for this environment and that’s an issue that has to be solved as well.
However, I do also believe that there were problems with the wifi network, and the combination of all of the above made it miserable for lots of teams.
I agree, there are so many factors involved it almost can’t be one problem, it might be some robots wired different, programing (we use labview), field control,Samantha, ect. So many things could have caused they shutting down of the robots. Like we had metal shavings in a sensor and that shut down our robot for about a week and it took a long time to find out why it kept reading 0 volts, so there is small things that can really mess up the robots, but if we share what broke/messed up our robot at practice and how to fix it then that can help other teams with the same problem and save a lot of time
I also think that it’s interesting that some robots don’t seem to have any field reset problems, wheras others seem to be fraught with them.
We caugt a problem during Software inspections that was caused directly be loose pins in the power switch connector. Looked like a coms failure, but it was reproducable by wiggling the wires… Squeezed the pins… problem gone.
I suspect the fasults are just compounding in some robots. For example, when I looked at the replay list (Cool mentor Max did a schedule for the replays), a couple of robots were in two replay matches… seems to indicate that the faults followed them. Coincidental that they were heavy defensive robots… that liked to hand out beatings to others?? Not conclusive… but it made me go Hmmmmm.
No matches were replayed which were not determined to be a field fault.
Yes, there were a few isolated instances of network issues, but the majority of the matches which were replayed were caused by USB issues (affecting the joysticks) on the FCS laptop on Edison field #2 Thursday morning.
As others have noted in this thread, the most common issues were robot related (NXT locked-up, Samantha connectivity to the NXT, or Samantha power issues). FIRST is aggressively looking into ways of better mitigating all of these issues (both field & robot related) in the future and the feedback the volunteers got from teams at the championship was extremely helpful.
Thanks for all the GP shown by teams and hopefully FIRST will be able to deliver a number of improvements for next season.
We also did not have any major field issues. Our issues dealt with RobotC. It seems to have a bug in communications with the motor and servo controllers. When this occurs, the NXT constantly tries to reset the motor and servo controllers. A symptom of the problem is that the external battery will register as off and you will no longer have control of the DC motors and servos. This can be a major problem if a motor is being driven at the time. This problem hit us a couple times in autonomous (we had built in a workaround in software for Teleop - we would cycle DC power on the bot via a LEGO motor) and cost us a match. Our battery was unplugged for the match after smoking a motor (and fused motor lead) at the end of autonomous.
This comes from the words of John Tobes and Micheal Coleman.
There is a very consistent problem with NXT lock-ups which are always caused by static arcing.
Micheal was explaining to me FIRST was running some tests on a NXT lockup issue they have where the NXT completely freezes where there was no drop in voltage or Samantha module disconnect.
This happens when a 8000v~ or higher discharge occurs on the Tetrix Motor Controllers.
There was a discharge/ground cable that was given to us at championship and because it wasn’t enforced both sides either using it or not experienced problems.
The people who did use it were at a high state of ground than the people who were not therefore when robots collided with the field or other robots that were charged all the energy was then discharged onto the grounded robot.
The ground cable was nothing more than a wire ( 18 gauge maybe? ) that grounded the chassis to ground ( bare wire on chassis and stripped/bare wire dragging on mat ).
I know from our robot we would get shocked during practice - i believe the theory was to help save samantha.
The “Ground the frame” theory is OK, but that assumes that it’s the robot that is charged up, and not the person. Since the electronics are isolated from the frame, I guess I don’t see how grounding the frame helps. My experience is that any sparks were usually between the frame and the person. Not sure how the ground wire protects the Samantha module.
On our robot, most (if not all) of the wiring is shrouded by metal or Poly. It’s almost impossible to touch the electronics without first touching the frame. I think this offers more protection than just grounding the frame. It
I also noticed that a LOT of the robots that HAD attached the grounding strap had passed over obstacles, so the strap was no longer touching the ground. I guess that’s why they use chains on busses.
Phil, I’m sure you’re aware that the real purpose of the chains hanging from buses and pickups is to attach the Faraday cage to the earth via the Tesla Effect, which prevents the Psi Wave Detectors in the black helicopters from reading your thoughts.
