possible solution to the static problem
 

As seen in last weekend's regional competitions the electro-static discharge caused by the rover wheels and the floor can fry speed controllers, driver stations, and even knock the field systems out of whack.

It could be possible that anti-static spray could be used on your drive wheels and control board to prevent any catastrophic discharge. Plus the spray is pretty cheap and can be picked up at almost any office supply store for around $3-4, you can also buy industrial-strength spray from McMaster-Carr for $11.57 for a 11.5oz can (part # 6038T11)

Any thoughts?

Re: possible solution to the static problem
 

Thought #1: If that spray affects traction, don't even think about it.
Thought #2: Might be worth it for a team with a practice robot and field to try it out.
Thought #3: Why not just put a wire hanging from your frame almost to the ground? You've got plenty of wire, I'm assuming. Can't be that hard to attach it to the frame...

Re: possible solution to the static problem
 

The FRP is non conducting, so there is no path from the robot to the ground while it is driving around. If you are driving full speed into a wall or airlock, there may not be enough contact with the carpet to discharge the build up into the ground before it contacts the field frame.

Re: possible solution to the static problem
 

Ah. That complicates matters.

How about grounding the airlocks? Teams can't do that, but if FIRST figures out how to do it, then the issue won't exist anymore. At least, not as much.

Re: possible solution to the static problem
 

Your first though scares me that you are more worried about a team getting traction then a team frying their driver station. :confused:

Re: possible solution to the static problem
 

Eric might have been thinking about the rules....

Re: possible solution to the static problem
 

There are spares (or were) at the event.

Quite honestly, I don't really like the control system this year. There have been reports on top of reports of things breaking, frying at the slightest provocation, releasing magic smoke, etc. You'd think that with over a year to design for that, they'd be better. On the flip side, customer service has been excellent for the teams that do break system elements. I'm sure that there will be improvements for next year.

Re: possible solution to the static problem
 

My first thoughts are about the teams. What fun is it going to be if a team blows their driver station or power blocks and cant run.

Re: possible solution to the static problem
 

What fun is it going to be if the team finds that they can't run because they're in violation of a rule? Remember, violation of the robot rules not only keeps you from competing, but if it happens on the field, it's grounds for a disable and a card.

Re: possible solution to the static problem
 

Just out of curiosity, have you actually used the control system at all this year? Are your comments based on actual experience and personal practical knowledge? Or just second-hand information provided by others that you have not personally verified or validated?

I am just trying to understand how to calibrate credibility levels of the comments.



.

Re: possible solution to the static problem
 

I didn't see anything at the mini-regional I was at, but if this is a problem with the field, FIRST needs to be contacted.

Re: possible solution to the static problem
 

Just on what I've seen on CD. This may be a small portion of teams that each fry multiple components, or not. I am not involved with a team this year due to location (no team within about 100-200 miles, and no car). However, my old team reports that if you set up the control system as spec'd, you should be fine (other than the risk of frying that has been reported).

Re: possible solution to the static problem
 

I don't know how much it would affect traction, or if it would at all as the spray's viscosity is almost the same as water and it dries without leaving any sort of residue or film on the rover wheel plastic.

As I said in my first post you could also spray it on the more sensitive parts of your electronics and control board to reduce the likelihood of releasing the magic smoke.

The issue is is that the regolith sheets are over carpet and when you drive a robot over it the floor works like a capacitor, storing the charge until it builds up to the point of catastrophic discharge. At the Manchester Regional the field crew's solution was to spray water on the field to dampen the static, but I think that having water and electronics that close is asking for trouble plus it makes the field dangerous for people to walk on.

Re: possible solution to the static problem
 

FIRST is well aware of the problem. Dean and Woodie were both at BAE and there is even a video around here somewhere of Dean spraying parts of the field down with water.

Re: possible solution to the static problem
 

Hey Dave,
Just admit it, the GDC made a plastic wheel on plastic surface game so they could do accellerated ESD testing on the new control components. ;)

Re: possible solution to the static problem
 

Eric--do you think we hear about problems more than we hear about things working well?

We haven't had any hardware trouble with the system, aside from some "no comm" during testing/practice, which might be due to the WGA location on the robot. And we used it almost continously from late December till ship.

Re: possible solution to the static problem
 

I think we all have seen the 100+ reply thread about failing Jaguars, but outside of that my experience with the new system has been largely positive (though I still maintain that it is 5x bigger and heavier than it needs to be).

Re: possible solution to the static problem
 

Can the moderators merge this thread with this one: Field Static Solutions?

Re: possible solution to the static problem
 

Just out of curiosity, are you still questioning the fact that teams have had problems with the control system?

Re: possible solution to the static problem
 

I'm aware of many Driver Station issues, ESD sensitivity among them, and I hope appropriate corrective measures can be determined before too many weeks of competition go on.

Where have you seen reports of ESD frying speed controllers?

The data logs from the field electronics don't seem to show anything specifically ESD-related, with the understandable exception of a missing ground connection causing issues until reconnected.

Grounding them wouldn't seem to be as useful as insulating them. Simply taping over the airlock metal to attenuate the spark when a robot bumps into it ought to be a good solution.

If it leaves no residue, it can't really affect anything, including static electricity. Obviously it must be leaving something behind.

That's not how it works. You can't just apply a magic static-insensitivity solution to electronic components. What the spray does is reduce the ability of exposed surfaces to accumulate electrons and charge the system up to voltage levels where ESD is a problem. It doesn't work in many situations, though.[/quote]

Re: possible solution to the static problem
 

My thoughts as well. People were not reporting getting shocks when the robots were touched at the ends of the rounds. So any electrostatic charge that had built up was still there until grounded. The people on the FRP weren't grounded either.

Re: possible solution to the static problem
 

I have to jump in here-

during build season our team had horrible issues with static frying the ethernet ports on our driver stations. We had hooked up the cRIO on an old drive base and used it for programming while the competition robot was in the shop. We have ALWAYS had static charge accumulation on our chassis from our large rubber wheels running on carpet to the point where we would drag a grounding strip below most of our machines (with a sign that says "if you can read this we are screwed")
What we found was that even if we grounded the driver station to the nth degree if we tethered the robot to the station to dump code it would wipe out the ethernet port. We did this twice in the build season and Andymark graciously did a quick resupply of components for us.

Our solution to programming once we determined the problem was to dump our code remotely and we simply had no more problems with the driver station.

That is until NJ....

Obviously you cannot program remotely in the pits at the event. Therefore we were required to tether the robot. Almost immediately driver station issues began and we solved them by adding a switch in the line between the driver station and the robot. Doing that prevents the driver station destruction but we already have blasted one of the ports in the 5 port switch.

During calibration of the camera on the field we also had a driver station power supply blow out for no apparent reason and only a trip to Radio Shack and $30 was able to fix it. (there aren't resupplies in the pit area or on the Andymark page!)

Those at NJ may have noticed that our pit is fanatical about static charge now. We wear Static Guard like cologne. Nobody touches the robot or controls without a ground discharge procedure. But there are times when connection between the robot and the driver station is necessary and at those times we keep our fingers crossed and a new driver station ready.


But perhaps what is the most frustrating of all is the response we keep getting from FIRST - " OH we haven't heard of any problems" . I'm sorry but I hear a roar of problems when I talk to teams and I am not making this all up.

All we want is a control system with the reliability we have had in the past. I like the cRIO unit well enough. It is the peripheral parts that seem to be "less than satisfactory". And it would have been nice to have as greater degree of testing and ready support for this system before were received it in the AS WAS state it went out in.

WC :cool:

Re: possible solution to the static problem
 

Hey folks,

Not sure if all your static issues are wheels and airlocks; our (1391) experience at Jersey was something else altogether. Almost all of us are spinning some sort of insulator (rubber, plastic, urethane, etc.) around - quite often - another insulator (PVC or ABS rollers) and when they aren't enough alike .... whoops. We have created VanderGraf generators that send spike charges from the rollers into someplace or another that finds its way to where we don't want it to be.

During practice rounds, we watched our robot run for 25 seconds, then stop as the CRIO rebooted, then run another 10 seconds, reboot, etc. This was early on and no one else had run into this, so we began from ground (no pun intended) up back in the pits. Curiously, static wasn't considered early - we looked at current draws, 24V supply, voltage differentials, code, etc - anything that we thought might stop he processor cold. Eventually, at 7:45 in the evening, I disconnected everything, including motors, ancillary code, and hand manipulated our belt collector - bam! same behavior as all day. We could shut off the CRIO with me as the motive force.

By next morning we had: 1. rubberized our PVC rollers with DipIt spray paint (to make the roller more similar to our belt); 2. put a 3/8" aluminum rod across the frame that touched the roller (to dissipate charge rather than having it build up and spike), and 3. begun to spray our belt prior to each round with Static-Guard (yep, the grocery store solution.)

No more problems. Ends up the static spikes were traveling through PWM cable connections - can't expect any processor to handle that, other than to reboot. We built the static generator, after all. All the ideas mentioned previously won't deal with the delivery of an internal spike to the processor, so think through your observations carefully. I really don;t think frame charge is the issue - you did insulate your processor board after all, right? The processor was just doing what it was designed to do to avoid damage. The clue we finally had that it was PWM was that even when the camera was turned off, and we had disconnected the wires to the Victors (but not the PWMs), the camera's servos were 'twitching' the camera for a couple spikes before the CRIO cut out.

Hope this helps.

Re: possible solution to the static problem
 

At Manchester people were having issues with driver's stations frying themselves when running in tethered mode on the practice field. At the end of the first day they had teams searching for spares. It just seems to me that while the new system is fancier and more advanced it's not as durable as the old IFI system.

Re: possible solution to the static problem
 

There are some of us in FIRST who do understand the importance of ESD control.

If you work on or near sensitive electronics hardware ESD controls are generally the rule. In my experience involving spacecraft hardware at NASA/JPL, there are very tight restrictions and mandatory training to avoid ESD issues. Dave's "other cars on Mars" (Spirit and Opportunity) were built with great care to avoid ESD.

We have requirements for use of grounded equipment, wrist straps, conductive garments and work surfaces (including floors), ESD-safe chairs with chains that drag on the floor, minimum relative humidity (>30%), air ionizers, avoidance of static-producing materials (i.e. no paper, styrofoam, teflon, adhesive tape or other non-conducting items) within one-meter of critical hardware. We use bleed resistors (10-100 MOhm) between electronics chassis and power/return line to avoid static charge build-up.

One of the tricky issues with ESD is that it can cause "latent" damage. A piece of equipment might continue to work after a "zap", but in reality some internal damage may have occurred. The next zap - even a tiny one, can cause a permanent failure.

I think we're learning lessons this year in the importance of ESD control. Basically, we've got six van de Graaff generators running around on a good insulator with equipment that is likely more susceptible to ESD than what was used in the past. The fact that we're seeing DS and robot resets attributed to ESD is frankly frightening to me. The guidelines from FIRST to deal with this threat needs some beefing up.

There's another thread dealing with this matter as well: Field Static Solutions

That thread should be merged with this one. Those out there with real-world experience in ESD control should post recommendations for teams. FIRST needs to take the appropriate measures with the field (some of which are already in place, like the earth ground at the alliance stations).

Re: possible solution to the static problem
 

All,

I'm not saying we don't have a static problem. I'm suggesting that some people are jumping to conclusions here and what we need is some level thinking...

I found Steve's post about his team's roller system most illuminating...

I also agree with Gary and Tom that we are not getting the complaints of static from the robot operators and field reset crews that we did in 2004 ( http://www.chiefdelphi.com/forums/sh...ad.php?t=27912, http://www.chiefdelphi.com/forums/sh...ad.php?t=27914, et cetera).

Also, It would not appear that the floor and wheel material are far enough apart on the triboelectric series to be effective as static generators. Although I'd love to hear the input of a materials engineer on this...

On a slightly deviant note, it is interesting that we are reporting problems when tethered on the practice field. My team also runs untethered at the school... If this is true, I would think that this scenario (running tethered) should be reproducible in any of our classrooms when we are practicing.

I plan to look into this last point tomorrow...

Regards,

Mike

Re: possible solution to the static problem
 

Glad to be illuminating; more often the kids on my team will tell you I generate heat instead. One more thing - we ran for two weekends in our gym untethered (and tethered in our shop) without ever seeing this issue. That's why we were confounded about it rising in the regional. I think it ended up being a difference in atmospheric conditions (underneath the floor in Jersey is a solid-ice hockey rink) that made it far more dry than where we originally designed and ran our machine.

Re: possible solution to the static problem
 

Just as an anecdote to this:

While we didn't have any shutdowns or 'no comm' failures during our regional we did have 2 opponents robots shut down while we were in contact with them.

Our robot, with it's propellers, generates a large static charge. Both robots that shut down had just intruded into our ball pickup section (we were in the act of pinning them ... niether robots were near the airlock). Niether team ever figured out why they shut down ... but I suspect static discharge. Our electronics system is completely isolated from our chassis.

Re: possible solution to the static problem
 

Re: possible solution to the static problem
 

To the best of my knowledge, I have never questioned that. If you can point to a specific statement where I have done so, please let me know and I will correct it. If you cannot, I trust you will correct your statement and your insinuation.

To the contrary, I am particularly concerned about making sure FIRST and the control system designers are able to gather accurate, factual, and correct information about the performance of (and where appropriate, lack thereof) the new control system. We are all intently interested in hearing first-hand, direct experiences from those that have had issues with the system, in as much specific detail as possible. Gathering as much of this sort of information as is available is the only way that the problems can be tracked down, diagnosed, and corrected. Posts like the one above from Steve Compton are full of great information and particularly useful. **

Conversely, unverified third-hand stories about how "I think my friend's uncle's cousin's Little League coach's team might have had a problem with a garstuckle that was ever so slightly out of plumb" are not particularly helpful. Frequently, they are actually detrimental to the process of getting the problem solved, as they cause a lot of energy to be expended chasing down false leads. So, it is important to identify and understand the difference.

-dave

** and toward that end, I would urge everyone with real, first-hand experiences with problems with the control system to please, please, please let the appropriate people know. Simply posting a story here on CD is not good enough. FIRST (in particular, Chris Jennings and Matt Pilotte) and the folks at National Instruments, Luminary Micro and KwikByte, have to know what is going on. They have to get real data on the performance, experiences, and problem reports associated with the control system. Please make sure you get your information and direct observations to them. One of the best ways to do this is to use the 2009 FRC Control Systems Forums.


.

Re: possible solution to the static problem
 

I used to work at iRobot on Roomba, and some of the very early testing models had static issues (we were trying to cause them, we kept a special testing room at 10% humidity or less). As we insulated more and mor, and protected the processor more and more, the static would build up higher and higher until it eventually caused permanent damage when it did zap (it will always zap eventually). The adding static bleeders really helps the situation.

to the earlier comment that you might not be in contact with the carpet long enough before you hit the field wall - Electricity is pretty fast. If you have a good ground tail, it should bleed off the charge almost immediately.

I hope things are better this upcoming week. At least Seattle and Portland don't have issues with low humidity.

When I was working at iRobot to troubleshoot this, we picked up a simple static meter to measure the static on objects. It's very odd waving a box at your target and getting a static reading. The sensor on the front of the box was just a PCB with a giant copper pad that you had to point at your target. It was pretty cool.

Re: possible solution to the static problem
 

Yes the FRP is non-conducting but the use of a few static discharge wicks in light contact with the FRP floor may equalize the potential between the floor and the robot. This is common practice in aircraft design where static discharge wicks attached to control surfaces and trailing edges help prevent buildup by discharging to the air. It is also good practice to bond any metal parts that may be floating from the main chassis, except of course for the camera and cRIO.

In Florida, we usually have such high humidity that static is rarely a problem. But this year, with the unusual cold, many days here remind me more of the static environment of the Northeast or Canada. Our students have been getting zapped left and right, much to their surprise. We haven't had any resulting electrical problems (yet).

Depending on the exact mechanism involved in the static related resets, it could be that a static drain resistor of 100K - 1Meg between chassis ground and electrical ground might afford some protection. This would at least prevent very high static voltages from building up between the chassis ground and the electrical system without interfering with the safety aspects of the electrical isolation. In fact, it would be pretty easy to have a jumper with a resistor that could be installed (or not) to see if it makes a difference. Testing in a low humidity environment is certainly needed and perhaps this could be done in practice matches next week.

We had ESD problem a few decades ago with a communication device that output to line printers. The issue only cropped up in a few locations in the winter and IIRC we solved it with a drain wire on the paper basket and a couple of discharge wicks in the paper path. Although the technology was older (Z80's), the problems were similar - mysterious unexplained resets.

I think FIRST need a "Tiger Team" on this to get control of the issue by next week. Just my $0.02

Re: possible solution to the static problem
 

Perhaps, but as writchie notes, a grounding tail will allow static to discharge readily. We used some finely-stranded #10 wire, about 3 inches long, one end into a ring terminal and the other end fanned out into a good imitation of a paintbrush.

This was purely precautionary, as we have not experienced any issues where we might suspect ESD or static.
Ah, that explains that :D

Folks should also note that just the spark of an ESD event is not the only chance for damage - the spark creates an electromagnetic field which can cause damaging voltages to be induced into near-by conductors. So it's not enough to control when & where it sparks; you need to control the sparks themselves. Team 25, with their anti-static wrist straps and mats, are on the right track, This isn't rocket science people.
Such latently damaged items are also called "walking wounded" and are especially problematic - the wound may also cause unintended operations, but it will be so intermittent it becomes difficult to find. And, in a high-reliability application (such as a spacecraft) it is a disaster.

I will ask our coach to ask Q&A to 'approve' a 1 MOhm resistor between components (frame, power, and cRio) for ESD bleed.

Don

Re: possible solution to the static problem
 

Team-79 Antistatic solution
This should be tied to a bare-metal location on the robot. Allow about 2 inches of chain to drag on the floor.
As electrostatic charges are accumulated during motion, they are simultaneously drained from the robot. Thus dangerous levels never occur.

CHAIN BEADED 12" BRASS
SKU: 34733

77012 WESTINGHOUSE
$1.15

<http://www.acehardwareoutlet.com/(wo...e=chain+beaded>

Re: possible solution to the static problem
 

Unfortunately, this solution would not appear to be permitted at present.

See the Q&A

http://forums.usfirst.org/showthread.php?t=12228

Hopefully there will be an officially sanctioned solution soon.

Re: possible solution to the static problem
 

This problem has now directly affected us and our regional.

Both the ethernet ports on our DS were fried. The first occurred the first day of the regional. We began using the second port at that time.

The second occurred AS the drive team was connecting to the field controls for our first elimination match. We had just tested the robot tethered in the pits. The control panel went directly to the driver station - and they couldn't get connection.

We were forced to remove the DS from our board and remove (12) PWM cables, fasten the new DS and reattach all 12 PWM cables in the time it took the robots to reboot. As a result, autonomous did not work. Two of the PWM cables did not make good connections. This allowed their human player to have their way with us. We lost by two points.

In the second match, the only thing that worked was the drivetrain joysticks. The turret joystick did not work, and none of the analog or digital inputs were sending signals. As a result we went the entire match without being able to score.

We will be grounding the robot from now forward AT ALL TIME if we are going to tether. Period. I strongly suggest other teams do the same.

We were told by field personnel that they had seen another (or more?) DS that had dead ethernet ports. Their guess was that the static discharge is being transferred down the ethernet cable from the robot while tethered.

Be careful and do everything you can to prevent it from happening to you.

Re: possible solution to the static problem
 

actually this is a mechanical solution.
The rule that allows the chain is R05

<R05> Exterior or exposed surfaces on the ROBOT shall not present undue hazards to the team members, event staff or GAME PIECES.

We are not affecting traction as required by R06

<R06> ROBOTs must use ROVER WHEELS (as supplied in the 2009 Kit Of Parts and/or their equivalent as provided by the supplying vendor) to provide traction between the ROBOT and the ARENA....
No other forms of traction devices (wheels, tracks, legs, or other devices intended to provide traction) are permitted.

The chain is a mechanical device fastened to the robot frame and does not violate R41

<R41> All wiring and electrical devices, including all control system components, shall be electrically isolated from the ROBOT frame. The ROBOT frame must not be used to carry electrical current.

By adding a brass chain to the robot frame we have eliminated the buildup of electrical charges. This is a safe and legal method for protecting humans from electrical shock. It also protects the electrical components on the robot.

Re: possible solution to the static problem
 

We experimented with a makeshift grounding cord made out of a shoelace that was attached to the frame of our bot. It dragged along the floor under the robot, to try to eliminate some of the static. It worked well... seeing in how we never fried our driver station.

Re: possible solution to the static problem
 

It depends on where you are. Our CRIO as well as two other team's were cooked over the course of the regional. FTA/ Field Coordination authorized all teams at the regional to use ground wires dragging on the field under the robot.

After everyone started putting these wires on, not a single CRIO failed.

Re: possible solution to the static problem
 

The rules govern. The Q&A "interpretations" of the rules are official. The "lead inspector" is the final authority at each competition. That is how I understand it.

Re: <R05> this rule is prohibitive - not permissive. It doesn't permit you to install something that would not otherwise be permitted.

Re: <R06> The lack of friction in the discharge "wire" was irrelevant to the Q&A answer. The question presumed the traction was immaterial.

Re: <R41> The Q&A questions was specifically in this context.

IMHO attempts to classify a brass chain, or wire, or metalized string, or whatever as "mechanical" and not "electrical" in order to escape an "electrical" rule are likely to carry zero weight. The actual use of the part makes it electrical, mechanical, pneumatic, or in this case electrostatic.

The referenced Q&A answer prohibits a bleed resistor between electrical ground and the mechanical frame and it prohibits a static wick between mechanical frame and the floor. The meaning of "no , and no" is pretty clear, even in a world where the meaning of "is" may be disputed. The GDC could have answered, yes and yes, no and yes, or yes and no, or even "maybe". Instead they said "At this time, no and no, as these would be violations of Rule <R41>." Since a "static discharge wick" is presently prohibited, IMHO the same would apply to drag chain.

I fully agree with you that a chain (or two) would prevent the electrical buildup. So would a static wick, a wire tail, a foil tail, and perhaps other methods. In fact, your chain idea MAY be the best. I've certainly seen it used successfully in the past. Perhap FIRST installing a drag chain on each trailer (which it controls and could easily supply) and allowing teams to install Static wicks made from off the shelf stranded wire will be the solution.

The GDC has determined that for the time being it wants to maintain floating electrical, mechanical, and surface grounds without electrical connection, although it left this open to later revision. While I am surprised by this ruling (especially regarding wicks), I am sympathetic as are most who have been in similar situations with mysterious ESD issues and a large number of units already in the field. At this stage, I think the GDC is trying to minimize the variables in order to reach the quickest possible solution. We should let them do their job. Perhaps, a couple of fried DS and cRIO's are worth it if it quickly leads to a permanent solution. Maybe with week 2 now completed, they will promulgate a fix and/or rule change that is proven not to cause more harm than good.

Personally, I think there may be multiple problems. One results in a dead Ethernet port on the DS. The other results in a cRIO reset, and sometimes a fried cRIO. Since both are proprietary components, we don't know what protection they have internally - we can only speculate. But since the DS doesn't even have a pull up on the digital inputs, it is likely quite vulnerable. I doubt it has Ferrite Beads and TVS diodes on the Ethernet ports and it is possible that the actual damage comes from induced surges.

IMHO, the best course of action for teams is to have only ESD trained team members handle the Ethernet ports and insure that everything is discharged before plugging things in. I would also recommend that teams be prepared to install static wicks (or chains) if these are ruled as permitted. When operating tethered, I would recommend always using a hub or switch with known ESD protection and only connecting/unconnecting the DS cable in the pits.

As for good news, the forcast for the Florida Regional is 81F/61F with humidity of 40% - 50%. With the return of warm nights, the conditions for static should must less than they have recently been, although Murphy makes sure that ESD can get you anywhere. ;)

Re: possible solution to the static problem
 

Our team experienced this, though not at a regional. While I was away for other things, our driver and a few members were driving the robot on gymnastics mats. They quickly found me to inform me that there had been a huge static spark, and one of the jags had been fried.

Totally our fault.

In any case, to those talking about the old system being better- I am no expert, but I see no reason why ESD would not affect the old system (mostly victors). The actual controller would be safe, yes, but everything else would be just as at risk.

Re: possible solution to the static problem
 

Although we did not have any problems at the portland regional i did notice while watching the matches most of the "field problems" happened to the same teams. whenever they had to do a rematch of a rematch, which happened quite a few times, it was the same teams that had problems in the original matches and the rematches.
someone mentioned that portland was lucky, although we may not have been in the worst shape, we weren't lucky. the high humidity in the valley may have helped in the pits but the field was built on an ice rink and in ice rinks they keep the air dry to reduce condensation. cold and dry, the perfect breeding ground for static. another mistake they made was to turn off the house lights during lunch on Saturday, cooling down the field even more, so it took more than an hour an a half to finish the first four quarterfinal matches.

Re: possible solution to the static problem
 

Do you mean the gray chasis with modules on the robot, or do you mean the blue driver station? I'm asking because to my knowledge I hadn't heard of static being an issue with failed Jags or cRIOs. It can cause a reboot, and we have seen some internal fuses blow, but thus far not associated with static, that we know of. Please clarify.

Greg McKaskle

Re: possible solution to the static problem
 

We had a case in NYC of a robot rebooting itself when it ran it's ball conveyor. It could be reproduced in the pits and the problem went away when the conveyor was sprayed with anti-static solution.

Mark Black can give you a report.

Re: possible solution to the static problem
 

The reboot of the cRIO due to static buildup is not ideal, but not unexpected given that the chassis is forced to be floating. Cooking the cRIO is not expected, and that is my real question. Were cRIOs cooked at the event? Mark Black is not back from travel yet.

Re: possible solution to the static problem
 

No. No cooked cRIO's at NYC.
They heldup quite well.

Some teams had issues with loss of comms during matches, a couple of wireless bridge failures, etc.

Humidity wasn't a problem at the Javits Center, because the Hudson river was 100 yards away through a wide open loading dock door, and the weather was unseasonably warm and moist.

Re: possible solution to the static problem
 

Apparently a beaded brass drag chain is not prohibited:

http://forums.usfirst.org/showthread.php?t=12284

But a static discharge wick on the other hand is expressly prohibited:

http://forums.usfirst.org/showthread.php?t=12228

Go figure. I can't wait to see the engineering explanation for this (or has marketing taken over ;) )

We will be installing a drag chain based on this ruling. It appears to be the only pro-active static mitigation method permitted on the field (other than dealing with van de graff generators on the Robots).

Chain has the advantage of guaranteed contact with the floor and the disadvantage that a corroded link could cause a high resistance in the discharge path. Movement should mitigate that and the charge can be passed along bead to bead, not to mention that the chains will be new.

The static wick has the advantage of guaranteed continuity but the possibility of becoming no longer in constant contact with the floor.

All in all, I think 79's chain solution is probably the best.

Unfortunately, protecting your own Robot in this manner may not protect you on the field when you contact another robot. If a large charge is allowed to build up on one robot, the discharge transient could possibly end up resetting either cRIO.

Also, it may be a good idea to insure that all power and signal leads have as great a distance from bare chassis metal (and charge generating materials) as possible. Normally, we only need to worry about short circuits. In the high ESD environment, we also have to worry about jumping the spark gap. A 10K charge can cross a 3MM gap.

BTW, it doesn't matter to 75% of the teams what solution is in place after week 6.

IMHO a quick fix that should be explored is to modify the trailers. There are only 6 trailers on the field and 6 drag chains are relatively easy to install. This is an easy fix to install, easy to test, and doesn't involve teams having to scramble to do something. It can be done during practice matches. Split the regionals, put chains on half and not on the other half and then correlate resets, chains, and humidity. If it makes things worse, it will do that for only half of the practice rounds. If it makes things better, it will do that for half of the practice rounds. (I'm ignoring the DS issues - they are a different matter).

The good news is that it looks like the cRIO is proving to be solid and the worst case result is a reset. There is probably no way to do better than that with everything floating. I'm extremely impressed by the cRIO. Great Job NI! and thank you for supporting FIRST.

Re: possible solution to the static problem
 

Couldn't we put a ground plane underneath the regolith and plate the space in between the regolith with something conductive? Wouldn't the trailers then discharge regularly as they run around the field?

Re: possible solution to the static problem
 

The problem appears to be that large charges build up on the robot frame. They have no path outside the robot. The Delrin wheels are a great insulator, so the charges can be thousands of volts different from the floor.

The electrical system floats near ground potential (from the last time it was grounded). It has no connection at all to the robot frame.

The charge on the robot accumulates until it finds a discharge path. This could be to ground, another reservoir like the Electrical system,or another robot. The spark ionizes the air, and the charges then equalize. After the spark ends, you may have two systems charged to high voltage.

I don't think that the exact mechanisms that are causing the problem(s) have been identified. But keeping the robot frame and floor close to the same potential would at least prevent the robot frame from building up a high voltage charge.

Re: possible solution to the static problem
 

our team found out that our robot was a very efficient vann-de-graff generator ( we have super-fuzzy paint rollers spinning against PVC!!!, oh and di i mention, there are two, one at the top, and one at the bottom, with surgical tubin in between...)

i've been shocked many times, and at the PDX regional, several robots would drive across the field, hit the wall, discharge the static and die...

this led to some teams mot doing at all as well as they could have...

also, the feild was set up on top of big rubber mats, on top of an ice rink... (i don't know why they didn't just use the ice!!!

I hope this whole fiasco is figured out before championships!!!!!

-Z

Re: possible solution to the static problem
 

I would get a piece of braided copper ground wire, about 1 in, and drag that. We had a problem with static in our shop when we were testing crab drive ad that is what we did to fix the problem. With our new drive system we have not had any problems with static, knock on wood.

Re: possible solution to the static problem
 

If you read a little more into it, you will notice the chain group was just using chain attached to frame. While the static discharge wick also asked about the use of bleed resistors to ground the frame. We know electrical connections to the frame are prohibited, but I think static wicks attached in a manner similar to the drag chain would be acceptable by the GDC.

Re: possible solution to the static problem
 

Thats how I read it.

Chain attached to frame only = good.
Static wicks attached to control electronics AND frame = bad.

Still better to ask the specific question of "Wicks attached to frame only = good?"

Re: possible solution to the static problem
 

Teenager: Dad, May I use the car?

Teenager: And may I have the $20 bill on the kitchen counter?

Dad: No and No.

Where I come from this means NO, you cannot use the car and NO, you cannot have the 20 bucks. It does not mean the $20 is yours but you can't use the car. ;)

I am not arguing the GDC's intent. I certainlyl have no way of knowing their intent other than by the words they write. I am just pointing out that words have meaning. There is no reasonable engineering basis I can think of why a beaded chain would be allowed and a static wick prohibited just like there is no way under the rules of English to read No and No to mean No and Yes. ;)

It's far less effort to just buy the brass chain. Anyway, the GDC seems to have determined that there are no actual static problem that a spray bottle won't solve.

Re: possible solution to the static problem
 

This is an interesting discussion.
FIRST wants feedback on how our system are performing. The Northern-Climates are expected to have a harder time due to the drop in humidity in the Winter months.

I have dabbled in ESD measurements and the verticle ESD wave occurring across the conductive (ground) playing surface(ice rink) can be pretty large too. This wave requires intense engineering to solve for electronic devices.

Please provide feedback to them, good or bad. Describe how your components are mounted in detail. Wood or Lexan. How do you isolate it from the chassis.
if they are looking for the best way to mount a CRio in space, maybe your design will be selected.

Re: possible solution to the static problem
 

The regolith is also nonconductive. I would put it's voltage standoff rating in the tens of Kv range or better. Maybe I am missing something here, but I don't see how a drag chain could have any additional effect. When you use a drag chain over concrete, the material is conductive to some extent and likewise for carpet depending on the humidity and moisture content of the materials. The regolith is adverse to moisture absoption so it's electrical properties should not change over a weekend.

Re: possible solution to the static problem
 

Al -

I had the exact same thoughts 24 hours ago. However, some time with the ESD gun made me revise my thinking.

Think of the regolith as an array of isolated capacitors. As you drive across the surface, you steal charge from these capacitors. Dragging the chain gives it back. If your only static source is the rover wheel / regolith interaction, this should do a good bit to improve things, especially if your chain sweeps the same area your wheels do.

If your charge imbalance comes from your ball manipulation, you won't be able to directly return the charge by this method. However, you will be able to spread the effect over the area you sweep.

Additionally, the capacitors are actually connected with very high value resistors. These will allow the charge imbalance to slowly spread over the surface.

Re: possible solution to the static problem
 

Erik,
Since the gun is the source, what did tests did you perform that led you to this conclusion? If the floor can be modeled as a series of capacitors, what is the other plate of the capacitor and why would a 28x38 robot frame not also be part of the capacitive equivalent circuit? I can agree with the series resistor part, but at the insulation level of fiberglass and gel coating and the material's inability to absorb moisture, the series resistance must be pretty high. i.e.>100Mohm. I have done a cursory check on electrical characteristics of this material and so far I have not found any. However, looking at the gel coating and polymer base material as likely being similar electrical properties, I am guessing the surface resistivity to be in the 10^12 ohms/cm or higher. In putting all the reports together (and in the absence of better testing) I am guessing that the static is a condition of the carpet to FRP transition rather than the robot to FRP. If this is the case, then a drag chain will not be effective until the chain contacts the carpet at the field borders. Should this be the case, then chains should be effective if applied to multiple points on the exterior dimensions of the robot, to insure charge drains off prior to a robot to field border interaction.

Re: possible solution to the static problem
 

Al/Eric

While the chain idea may seem counter intuitive, I've have got PMs from multiple teams saying it worked. Like Eric eludes, the FRP is like a series of capacitors connected by high value resistors. I know some of these bots are building incredible potential by being isolated, running high speed ball manipulation devices like tornado and belt drives and then being completely insulated by at least 3" due to the 6" plastic wheel. So remember that spark gap is all attributable to voltage potential and distance, even if the FRP isn't "real" conductive, a huge potential on a bot could be bleed off. Either a bot is going to build enough potential to have the spark jump from their frame to the FRP floor (which is a scary voltage thought) or they are going to have enough potential to jump from when they get near the grounded arena boundary. I wouldn't be surprised if some of the spark gaps we're getting at the arena boundaries exceed 1-2", big EMPs. You know air isn't really conductive, but I've seen alot of lightening in my time :D It all comes down to the triboelectric series, anything we can do to encourage the static voltage potential to transfer will help the ESD/EMP effects.

Re: possible solution to the static problem
 

Bob,
I understand that if the problem is regolith to carpet and a team has a chain that contacts the carpet before they hit a field border, then it may work as the discharge path is carpet to robot. In looking at Bill's Blog and the suggestion that carpets be made wet at the field borders, there seems to be mounting evidence that the floor materials are the prime fault. When we walk out and set the robot on the playing field, it then becomes the same charge as the Regolith. As robots move about, the charge builds up constantly on all robots as the interface between the FRP and carpet gets exercised. I would like to see if an experiment consisting of wire under the FRP and across the carpet to the field border might work better than water on the carpet. 3M makes a nice product that is a copper foil with a conductive adhesive that could easily be added to the field and would not likely produce any serious change in game play. The tape is available in various widths and can be purchased from Digikey.

Re: possible solution to the static problem
 

As I've previously mentioned in a related thread, an anti-static spray coating like ACL Staticide leaves a slightly conductive film on the surface of the regolith. It's available from McMaster-Carr (7090T37) in a 1-qt spray bottle, enough to treat an entire field. This product is designed to dissipate static charge on slick, non-porous, hard surfaces. If conductive copper tape were attached between the regolith and field boundary at a few locations around the field, the charge will have a path to bleed from the robots, down a chain, across the regolith, through the field structure, and finally to earth ground.

Perhaps someone can measure the change in coefficient of friction for regolith treated with Staticide. I suspect the change in friction would be quite small. The benefits of minimizing loss of comms, DS resets, replayed matches and even damage to electronics should offset a slight change in the playing surface.

Re: possible solution to the static problem
 

Wow! Our robot is very similar in terms of generating static. Our ball collecting mechanism is many brushes made out of pneumatic tubing spinning really fast (like the front brush of many household vacuums) and we are generating a lot of static..

Die, meaning communications being dropped? Driver stations fried? cRio fried?

Hehe, I hope it is figured out before Week six events

But good luck to everyone!

keehun
Team 2502

Re: possible solution to the static problem
 

Dave,
I was up in Milwaukee last night and they reported using the static spray and had no problems that they could pinpoint as a static issue during practice. Milwaukee is on concrete and it was pretty cold up there so the heat is on.

Re: possible solution to the static problem
 

Sorry if this is a repeat I didn't have alot of time to post. We have begun using dryer sheets to wipe both the wheels and any lexan and/or plastic on the robot after every match. Thus far it has worked quite well to reduce the amount of static being carried by the robot. We have added it to our list of procedures after the match and only takes a couple of students a minute or two to do.

Just my $.02

Pat

Re: possible solution to the static problem
 

Is also makes your robot "Springtime Fresh"! :D

Re: possible solution to the static problem
 

Let's not forget surface charges. As a material collects charge of a certain polarity, that charge spreads over the surface of the material. The chain brings the opposite charge down to the surface. This allows a restoration over time. Since the buildup occurs over time as well, we have an equalizing effect. The difference in charges will never become large.

Now that the trailers are using a drag chain, I would expect to see no large buildup on the playing field. However, the practice field remains a problem. The trailers on the practice field had no chain. Also, robots on this field have a tether cable attached. If charges are allowed to build, the driver station is subject to potential damage. an arc to the tether from robot frame is likely. the driver station has only minimal esd protection.

I have not heard credible evidence about cRIO damage. So far, there is evidence of only driver stations that have failed. I have seen and heard of only damage to driver stations and analog breakout modules. Other comments, here and elsewhere, have lumped the system failure as a cRIO failure. Please understand, i think WPI did a very good job of making a cRIO based system. it is simply not as rugged as the NI equipment.

(Also, spraying the wheels may work, but is against the rules. This lubricant changes the traction of the wheel.)

jerry

Re: possible solution to the static problem
 

Neither static wicks nor drag chains were permitted by the inspectors at the Florida regional. I suggested to them, (and probably others made similar suggestions), that they consider drag chains on the trailers since that could remain completely under their control. Our drivers saw the chains on the trailers on Saturday.

I know that Team 2383 was having reset issues on Friday that disappeared on Saturday. They would reset every time they contacted a wall. This, however, could have been electrical rather than electrostatic.

I don't know if the "Trailer Drag Chains" have been tried at other regionals but it does appear that at least they do not make matters worse on the actual playing field, at least as far as Robot resets are concerned.

Re: possible solution to the static problem
 

I thought the drag chains worked really well for static at Florida. And reset isn't difficult if you have a list and each person does a specific job. For us coach and one drivers set up robot and trailer, the other driver set up the the control board and tethered BEFORE giving the other 2 the signal to turn on the robot and set autonomous. All the while our human player was taking his moon rocks to fill our robot's hopper. it was really smooth. Another thing to check is the radio ethernet cable. The programmers have to unplug it and sometimes forget to replug it.

Re: possible solution to the static problem
 

This was tested at FIRST last week and deployed to all week three regionals, the real test will be this coming weekend when there's another "ice rink" regional. There's weren't any week 3 ice rink regionals.

Re: possible solution to the static problem
 

I could be mistaken, but I'm pretty sure they had drag-chains on the trailers at the Wisconsin Regional also. (Al correct me if I'm wrong) :)

The Thursday practice day was pretty cold outside, so the heaters were on (which meant we were all walking ESD guns). I don't remember hearing any issues from other teams about loosing coms/reseting except on the practice field where the trailers didn't have any drag chains and the driver station was connected through the Ethernet port to the robot. We lost comms any time we activated a large sheet of fabric in our hopper.

Not sure if the presence of drag chains and no ESD issues was a coinicidence, but it seemed like things actually ran pretty smoothly once we got out on the competition field!

Re: possible solution to the static problem
 

Drag chains were used at the boilermaker regional. No static problems that I saw or heard of. One team about caught their motor on fire, but has nothing to do with static.

Re: possible solution to the static problem
 

TEAM 122 Has been to DC and VCU. We have not seen or had any problems in practice or during matches. The robot has preformed as expected and has not need anything. After attending two events and not missing any practice or matches we are very happy with things.:]
Rick

Re: possible solution to the static problem
 

have we determined that static is the main cause for strange cRio resets while on the field?

I was just wondering because we ran into a strange phenomena while at the lansing district quarter finals. It left our alliance dead in the water, then soon after they had full field problems.

I would describe what happened as a huge hit between our robot and the side of the field, followed by what the field tech said was a cRio reset(they check the packets...)

this caused our robot to be disabled for about 20 seconds while it regained connection to the field. By that time we had all ready been "dumped" on, and plus our other alliance member was having some serious field related issues as well.

Anyways just curious if static was determined to be the main issue with this years game?

Re: possible solution to the static problem
 

The only problem I saw with our robot at SVR was our gaming adapter reset randomly after we hit a wall. Not sure if it was static though.

Re: possible solution to the static problem
 

It was certainly in style to blame static weeks 1 and 2 for everything, and it was probably the cause for a majority of the problems. The drag chains seem to have fixed that. I was in Philly this weekend, and all of the robot troubles I saw on the field could be traced back to a non-static problem.

For example, one team had a piece of debris in their cRIO's ethernet port and another had broken off the retaining clip on the cable.

Re: possible solution to the static problem
 

Several things to respond to here.
Drag chains were added and in place in Milwaukee but so was the ample use of staticide spray at all exposed carpet boundaries on the field. As were all regionals that week and beyond. No static issues were reported to me at Boilermaker.
A CRIO showing loss of packets and then a 20 second loss of control is more indicative of a loss of power to the Crio and subsequent reboot than a static issue. As Bob has pointed out, the static issue has been related to the DS which lacks any static protection particularly on the ethernet ports. A power loss during a hard hit with the field or another robot is not uncommon as well as disconnected 37 pin connectors. Although the main breaker is robust, it may not remain connected during a severe shock depending on it's orientation and mounting. The contacts have a relatively low mass but a multi G shock may inject noise or momentary open circuit under this condition.