Charging pneumatics system before match
 

After we precharge the pneumatics system at the pit, do we have to wait until the autonomous mode before we can charge the pneumatics system? I searched on CD but most of the posts are about off-board compressor in terms of pre-charging.

The only other way I know how to charge the system is to tether to the cRIO and enable the robot while it is on the robot cart.

Is there an easier way?

Re: Charging pneumatics system before match
 

Ed,
There currently is no ruling on when or if a team can pre-charge their pneumatic system prior to entering the field other than for off board compressors. In my opinion, safety demands that no robot be pre-charged in the pit and left in an energized state while waiting in the queue. Teams that use off board compressors should be given time to charge while on the field during setup but again there is no rule on that. In the past, the event managers decided when, how and if teams could pre-charge their pneumatics.

For all off board compressor users, please be advised that the KOP compressor or equivalent, must be under Crio control when charging the pneumatic system.

Re: Charging pneumatics system before match
 

I forgot to mention that we have an onboard compressor. I probably should not have used the term pre-charge because it made it sound like we have an off-board compressor. I have to charge it somehow before autonomous period start or the kicker is not going to work. When will they allow teams to run the compressor? In disabled state, the compressor does not run. The only way I know is to enable it through tether to cRIO while in queue. Or will they allow teams to do that on the field before autonomous period?

Re: Charging pneumatics system before match
 

Ed,
I don't have an answer for you yet. I would think the safest is on the field but that would add to the field turn around time.

Re: Charging pneumatics system before match
 

How do they do it in past years? This is our second year in FRC and first time using pneumatics so we don't know what to expect.

Re: Charging pneumatics system before match
 

I think the determination was done on an event by event basis.

Re: Charging pneumatics system before match
 

At NJ we arrived on the field pre-charged, with a safety lock-out (a metal bar with a long bright pink flag attached to it) that was the last thing pulled off the robot before the team left the robot on the field.

Checklist: Robot on, thinkamajig set, autonomous set, safety bar pulled.

Re: Charging pneumatics system before match
 

Gotta love the use of universal technical terms, along with whatchamacallit, doodlespiel, whosiwhatsit...

;)

Re: Charging pneumatics system before match
 

Ed,

In 2008 we used pneumatics for our arm and gripper. What we would do is have the controls all set to charge went we got into queue and then with one minute left in the match before ours, charge it up. This way we aren't walking around with a robot that is "locked and loaded", but at the same time we weren't delaying the start of the match by doing it on the field during match setup.

Now, there wasn't as much of a risk with stored energy then like a kicker this year, so I would definitely recommend a safety bar/latch of some sort.

Re: Charging pneumatics system before match
 

Tetra year was the last year we needed to pre-charge, and we did it in the queue also, when the match in front of us was almost over.

This year we can fill the tank(s) in the pit, our system doesn't fill cylinders until autonomous starts.

Re: Charging pneumatics system before match
 

I like this approach very much!

Re: Charging pneumatics system before match
 

Our team is going to start with pre-charged pneumatics because they keep our kicker locked in a safe position. In fact, all of our pneumatics are designed to store in a safe position with the power off, so our robot is arguably safer with the pneumatics completely pressurized.

Re: Charging pneumatics system before match
 

James,
You will have to convince your Lead Robot Inspector at each event you attend. I find this hard to believe without seeing it.

Re: Charging pneumatics system before match
 

In the last three years that we've used pneumatics (2006, 2007, and 2008) we would pressurize the system prior to the beginning of the match. We would wait until there was about 1 to 2 minutes left in the match before us and then tether our robot and let the compressor run. This meant that our robot was only charged for a minute or two at most before the match actually started.

Provided this approach is deemed acceptable this year we will probably do the same. Also, our robot will be set so that the kicker is in the fired position as the starting position. This should help to prevent any accidents that could be caused by the kicker firing by mistake.

Re: Charging pneumatics system before match
 

Dustin,
Just to be sure, your kicker will not be outside of the frame perimeter at the begining of the match?

Re: Charging pneumatics system before match
 

Al,

The kicker cannot leave the frame perimeter due to a mechanical stop (Steel Shaft) so it will be within the frame perimeter at match start. I've found that we can prove this quickly with a level or other straight edge.

Knowing that, would you say that that is an acceptable starting configuration? In terms of legality and safety? I feel that it should be.

Re: Charging pneumatics system before match
 

Dustin,
This is the primary rule and it references other rules...

<G30> ROBOT Volume – During a MATCH, no part of the ROBOT shall extend outside the vertical projection of the FRAME PERIMETER, except as follows:
a. BALL Interaction Volume – Solely for the purposes of interacting with a BALL, MECHANISMS that are below the BUMPER may extend up to the BUMPER PERIMETER, for a period not exceeding two seconds. After returning inside the FRAMER PERIMETER, such MECHANISMS are not permitted to re-extend beyond the FRAME PERIMETER for at least two seconds.

And...

<G10> ROBOT Size – Prior to the MATCH, each ROBOT shall not exceed the NORMAL CONFIGURATION maximum weight or volume specified in Rule <R10>. The Head Referee may call for an inspector's recertification of the ROBOT size and weight prior to the start of any MATCH. Violation (for ROBOTS prior to the match): Prohibition from participating in the MATCH.

Referenced is this...

NORMAL CONFIGURATION – The physical configuration and orientation of the ROBOT when the MATCH is started. This is the state of the ROBOT immediately before being enabled by the Field Management System, before the ROBOT takes any actions, deploys any mechanisms, or moves away from the starting location. This configuration is static, and does not change during a single MATCH (although it may change from MATCH to MATCH).

So as you describe it, I would think it is acceptable.

Re: Charging pneumatics system before match
 

We've got two pistons that retract the kicker, if the latch got bumped loose without the system energized the kicker would snap open. With the system energized the kicker is held firmly in place. Does that make sense?

At least when I was a student pre-charging the pneumatics was never an issue.

Re: Charging pneumatics system before match
 

It is hard to visualize without a picture. Your LRI will make the decision when he/she sees it.

Re: Charging pneumatics system before match
 

Pre-charging the pneumatics by itself is not a huge issue. However, this year, many teams are using that air pressure to deform springs. Weather latched or held by air, the deformed springs can and usually do present a hazard for your team members as they carry a robot on and off the field. In addition to your team members, there are issues with the field personnel and people in the pits.

Your statement that the air pressure holds the system in a safe configuration begs the question of what happens if an air hose lets loose.

Regards,

Mike

Re: Charging pneumatics system before match
 

We've tried that scenario by venting the air pressure, it lets the kicker out nice and slow. I would be worried if a spring came loose though, that would be dangerous.

Re: Charging pneumatics system before match
 

We have added a 3 second delay to our auto to let the compressor run. This delay with the short drive time to the first ball assures that the pneumatic can release the kicker bar.

Re: Charging pneumatics system before match
 

In said hypothetical robot, would detaching the springs until the robot is placed on field, and then re-attaching them be sufficiently safe?

My robot's being inspected at your events, and I'm not 100% sure if a vented piston will hold the kicker back, since I don't have the robot in front of me.

Re: Charging pneumatics system before match
 

Chris,

Like you, I do not have the robot in front of me.

From what I have gathered, teams only have seconds to place their robots on the field and many kicker mechanisms have incredibly strong spring implementations. Detaching and reattaching springs may not be feasible for many...

For stored energy systems, it all comes down to the trigger mechanism.

Let's assume that the trigger is a ratchet latch with a piston actuator. If the piston is the only force holding the ratchet latched, I would likely require a positive fail safe be added so that the rachet can not move if the piston is depressurized.

If the ratchet latch is held by a spring and the piston pulls the latch back to fire the kicker, it sounds like it would be OK dependent upon the ratchet, latch & spring being a good solid design.

It's all subjective so I'll end by asking this...

If you took this robot to your local elementary school for a demo, set it up as you will when going onto & off the field or traveling through the pits or going into the size box for inspection, could you walk out of the room secure in the knowledge that none of the inquiring kids will accidentally trip your mechanism and get hurt?

If your honest answer is yes, you will pass my inspection. If you are feeling a bit of a knot in your gut, think seriously about adding a fail safe device...

Regards,

Mike

Re: Charging pneumatics system before match
 

We have the same need to enter the field with full pressure, and it has never been a problem for us to turn on and charge the system while waiting in queue for the match. The field director at your event could have his own rules, but I think this will be a common need this year.

However there is a pitfall that you need to be aware of. Running your DS just before your match can cause communication problems. If you start up before your team number has come up in the field system, your DS will may not link up properly. We had problems with our DS not communicating and other teams had problems caused by turning on too early. If you turn on in queue to charge your pneumatics, make sure you turn off your robot and log out of the DS before you go on. Wait 15 seconds or so after your team number comes up on the field banner before logging back in and starting your DS. Wait until the DS is ready and confirms the link before turning on your robot on the field. We don't want to see anyone have the same problem that struck us a couple of times in week 1.

Re: Charging pneumatics system before match
 

As long as the robot is disabled there is both a latch and the pistons keeping the kicker stored, I would consider the pistons to be the "fail safe" feature.

I don't think I would leave any unsupervised robot energized and/or turned on with inexperienced users, that just seems like a bad idea in the first place!

Energized pneumatics system could cause hearing damage if discharged improperly, almost any piston has enough force to hurt someone pretty badly in the wrong circumstance, and there are numerable things that could go wrong with the electrical system. Hands can get caught in chains, overheating motors can burn... I could go on...

My point being that these robots aren't little-kid-proof, and they never will be, there will always be some risk involved with working with a FIRST robot. I think we've done the best reasonable job we can do of minimizing that risk.

Re: Charging pneumatics system before match
 

An unsuspecting student programmer in front of you in the Queue or a volunteer field resetter on their first day (or a robot inspector) is for all intents and purposes a "little kid" and safety should be measured in light of that fact. I am stressing that the programmer who backs into your robot, the field resetter who bumps your robot cart while moving around in the dark off field or the inspector who is reaching in to check wiring or breakers doesn't get hurt.

Re: Charging pneumatics system before match
 

Mr. James,

Please don't put words in my mouth because I cause myself enough trouble already... :eek:

I never said the robot would be on. I said in the condition that you will enter and leave the field or travel though the pits or enter the sizing box for inspection...

Many teams will want their robots to do these tasks with springs loaded and/or pneumatics charged and I have absolutely no philosophical problem with that. As long as it is done safely...

My primary concern is for your students as they carry the robot on and off the field. But my elementary school analogy is not really that far off base. Realize that, while "children under 12 must be accompanied in the Pit by an adult at all times" and I am sure you would never leave your robot unsupervised, the Pit is a chaotic and very crowded environment. Little fingers will reach out to explore and it only takes a second...

As you describe your system, it sounds like it would take a double failure to cause an accidental deployment. If so, and I can not say for sure until I see it, you will have no problem with me.

Having said that, I know that I will see many mechanisms which I will find lacking. I have been doing this for 16 years now. I have been injured by my own creations and by the creations of others. As an example, a few tears ago, the top of my head was cut by a robot arm while I was inspecting the operation of gears within the drive train. I had them file the sharp edge smooth but spent the rest of the day with blood matted in my hair...

I would be most interested if you can find any team who has found me to be unfair in my past inspections. Regardless, both you and I have a responsibility to insure the safety of those around us. Just as your team has done "the best reasonable job we can do of minimizing that risk", I will do the best reasonable job I can do to insure that you have.

I look forward to talking to you in Hartford.

Regards,

Mike

Re: Charging pneumatics system before match
 

I did not mean to put words in your mouth! I'm sorry if it came across that way. You strike me as very reasonable. I think we're on the same page here and I hope we don't give you TOO hard a time in CT ;)