Field Static Solutions

FIRST General Forum
#21

Our robot has never built up any appreciable static, despite doing burnouts on regolith regularly during build season.

One of our patented good ideas this year was installing brushes on the frame that contact each drive wheel at the top of its rotation. Our intent was to keep the rover wheels clear of FRP dust and other debris to preserve maximum traction (and the brushes do that job very well - there is no dust on our wheels even after a half hour of skidding around on regolith).

Question: Could an unintended side effect of these brushes be that static charge is somehow dissipated and/or counteracted? My software-oriented brain defers to someone with a better knowledge of ESD…

#22

I’m not an EE by any stretch, but would dragging a wire from your frame have the ability to turn the robot into a capacitor? And if so, then would metal to metal contact with another robot during a competition create the possibility of interfering with the link to the field?:confused:

#23

Mark,
The robot already is a capacitor and dragging a chain doesn’t change that since the field is an insulator. Without knowing for sure, the drag chain and staticide that has been applied to the carpet and the software changes for the FMS have minimized if not eliminated the problem. I am personally going with a static buildup as robots depress the regolith over carpet while driving as the cause of a charge buildup that uses the robot as a discharge path when it crosses the boundary. The staticide fixes that, and the drag chain if it crosses, adds to the solution. Don’t fight success.

#24

Thanks! Like I said, I’m not an EE however your plain english explanation was a help.:slight_smile:

#25

Staticide was used on the FLR field, but not on the regolith…I put it on the carpet.

#26

The drag chains are doing the most. Most of the issue were bots with high speed conveyor and other type devices for ball control that were basically big Van Der Graph generators. They were very well insulated by the hard plastic wheels being used this year. Certain environmental field conditions make this much worse (like fields on top of ice rinks). The chains provide a ground path to discharge the large voltages that were building on the bots to the regolith and carpet discharging before they have a chance too short at the field boundaries. Not saying its entirely fixed, but things seem much better now…

#27

Hey pitzoid - is FIRST now putting drag chains on all the trailers? I haven’t seen anything in the update about it, and you’re the first person I’ve heard mention them.

#28

yes

#29

Tom,
They have been on the trailers for the last two weeks as well as the staticide application to the carpet borders. They don’t interfere with the game or the trailer movement and the trailer tongue is conductive to your robot unless you have chosen to insulate the hitch in some fashion. Your inspectors will be able to tell. There was no need to include this in a TU so nothing was contained in the last one.

#30

We had the drag chains on the trailers at the NASA/VCU regional, but did not use the static guard on the carpet at any point during the competition. I never heard any of the teams complain about static issues, and this was the first year I NEVER got shocked by someone’s robot.

#31

Kyle,
The FTA was handling the spray. Is it possible it was done without your knowledge?

#32

Don’t forget that the weather is changing too. Our team has had major static issues with robots in the past (2003 was the worst), but they always cleared up in the first couple weeks of regionals as the weather got warmer and humidity increased.

#33

I am 100% sure that our Static Guard spray never left crate #8.

Also, our field was over a basketball court, not an ice rink.

#34

Here at the CT Regional, we have gone through 2 DS…but only when tethered. We feel we are discharging through the ethernet cable because there is no common ground. Once was when we were on the practice field…we were running our ball collector for a while, then went to move on the Regolith. At that point, comms dropped. A replacement DS was able to work. The second time was in our pit. We were running the ball-collector on the cart for a considerable period of time when comms failed again. Again, a replacement DS worked. We are trying grounding connectors between the DS and the robot. Our cRio itself is mounted on our wood chassis.

Any other thoughts out there?

#35

At SBPLI today we had only one apparent ESD incident where a cRIO rebooted itself. Staticide has been applied since to the robot and there hasn’t been a recurrence.
No DS’s have failed on the field during a match due to ESD.

Spare Parts here has been busy with a lot of DS failures though (maybe ten), some due to physical ethernet port damage, but several I’d attribute to damage from ESD. Some may be repairable with a software reload, but I haven’t had time to look at them.
Several DS’s were dead when the team arrived and hooked up to the field for their next match. We swapped them out before the match started and haven’t had a single robot forced to sit out a match.

We have not been wetting the carpet here, however, this is Long Island and it’s normally humid. The weather, although cold in the mornings, has been warming during the day.

#36

In the LV regional they told us to ground ourselves onto the aluminum before touching the DS or the cables. I have not heard of any DS’s dieing here, although we may have gotten lucky.

#37

The FTA for the Los Angeles applied Staticide to the entire field (regolith included). There was no perceptible change in the traction for the robots (as compared to what I witnessed in San Diego and OKC).

Al Skierkiewicz’ comment above about regolith being a good insulator is true. When treated with Staticide , the trace amount of ammonium salt left on regolith surface provides a leakage path for the charge. The charge can now bleed from the robot, into the trailer, down the chain, onto the regolith surface where it is dissipated across the floor to the carpet, field boundary and finally, earth ground.

#38

Solid grounding in multiple points might create other problems due to ground loops. You can get large currents flowing through low impedance paths that can create undesirable results. I think that bleed resistors (1-10 MOhm) within the robot will help avoid differential charging between the electronics and the chassis. FIRST is not recommending this practice until a better understanding of the problem and mitigation is reached.

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#39

I was FTAA in Connecticut this weekend. Well, there were some issues in Connecticut, but not with the FRP on the field. The chains seem to have done the trick. What was noticed is that driver stations, particularly made with FRP, or lexan were causing the most problems, We were spraying the carpet @ the drivers stations. Theory has it the while walking up to the station, the DR platforms were rubbing against the team member in charge of hooking it up. This created static in the FRP or lexan. When the power or ethernet cable were installed without prior grounding of the the human, the static was discharged from the FRP into the cable. We went through a few DS units.

Please ground yourselves to the driver station framework prior to touching either the cables, or the DS unit.

#40