Loss of control during competition

For the last few competitions, we have been dealing with some issues that are extremely detrimental to our robot performance. It has been very difficult to diagnose as it only happen sporadically at competitions and we never experience the issues at home. What happens, usually about mid-match is that our lift will no longer work. When this happens the Robot light on the controller turns red at the same time. I don’t believe that the light is blinking, but given happens in a match, that hasn’t been something we have able to observe closely as the team is anxiously trying to continue competing. One other note that may or may not be related is that our robot seems to loose connection periodically at competitions at a higher frequency than our others competing. Frequently we get connection back, but it also affects our performance.

Details about our robot:

Our lift is powered by 6 motors at a 5:1 ratio. This is common configuration and the symptoms are not motors that are overheated. After resting they don’t come back.
The lift has one IME set as the master, with the other 5 (non-IME) motors set as slaves to that master.
Our lift is split between the two cortex breakers. These are not tripping as the other motors on that breaker continue to work.


We have had the issue with more than one cortex in competition.
Between our last two competition we replaced all motors, sensors, and wiring to insure that there wasn’t some sort of electrical short or grounding issue.

The troubleshooting trees suggest that the possible intermittent loss of power for the whole robot may be vexnet related and that isolation of the key may help. We plan to make that change, but I don’t think that a partial loss of functionality could be attributed to the vexnet key. The programming code is always suspect, but as stated the robot works most of the time without issues. Is there a programming code explanation that would explain our lift working well and then stopping mid-match?

Any thoughts on what might be the issue? How to diagnose? Other?

After chatting with you guys yesterday, and the info in this post, i think it’s an IME static issue. We tried IMEs for the first time on our drive on both 491 and 491A this year, when they were giving us reset issues on 491 we replaced them with quad encoders. We then moved them to 491A’s drive, one IME for each drive side just like on 491. No problems on our field, but they had some minor issues the couple of tournaments before State. State was terrible with resets. Since they luckily got picked for eliminations, I had them unplug both IMEs and quickly helped hack their autonomous to be time based. While we were doing that, I got a nasty zap from their USB extension for their Vex net key. It had an exposed shield around where the key plugged in, and that is what shocked me. I haven’t tested yet, but I wondered about tying the Cortex ground to the chassis of the robot to see if that would help with the seeming static buildup on the Cortex power system. Of course yesterday they started getting shocked by 491’s chassis on that field we were at, I wonder if they sprayed static guard on it?

Based on other posts on the forum this year and our team’s experience, I would agree that the combination of IMEs and static appears to be a likely culprit. Our team does not have IMEs on this year’s robot (the team went with a potentiometer on the lift, encoder on the drive) and we have not experienced connection issues at any of our events (including many of the same events as 323Y). The few problems we have experienced were traced to tripping the PTCs in individual motors.

Hi, I’m the IME-broken-record. I’ve gathered pretty much all of the relevant IME-related material from the VEX forum into one (encyclopedic) place on my blog, and it addresses the many things that can cause what you are seeing. My team also had intermittent, infuriating problems that also seemed to happen much more at competition than in the lab. Could be a million reasons why, as you can read here: http://renegaderobotics.org/why-ill-never-use-imes-againwas-imes-part-2/

@biglesliep - Thanks for the information. I will definitely checkout the information you have provided.