Using Second battery to Charge Tanks

[wilsonmw04]

Greetings,

After reading a "what do you do in between matches" tread, it seems like it is common practice for some teams to charge their air tanks with one battery, then swap out a fresh battery before heading to the field.


I have seen one post on the Q&A on this topic:

Question: Can the air tanks on the robot be pre-charged with air before entering the arena? If so can they be charged with a seperate power source than the battery used in the match?

Reply: Review R69 and Blue Box in the manual.

Here is R69 and the Blue Box:

<R69> Compressed air for the pneumatic system on the ROBOT must be provided by one and only one compressor. This compressor may be either the compressor from the KOP, or an equivalent compressor that does not exceed any of the KOP compressor performance specifications (specifically: nominal 12v, 1.03 cfm flow rate, 120psi maximum working pressure). Compressed air shall not come from any other source. Off-board compressors must be controlled and powered by the ROBOT.

If an alternative compressor is used, the team may be required to provide documentation to show compliance with the performance specifications.
The only difference between an on- and off-board compressor is that the off-board compressor is physically removed from the ROBOT. The intent of this rule is to permit teams to take advantage of the weight savings associated with keeping the compressor off-board. However, using the compressor off-board of the ROBOT does NOT permit non-compliance with any other applicable rules.
The compressor may be mounted on the ROBOT, or it may be left off the ROBOT and used to pre-charge compressed air in the storage tanks prior to bringing the ROBOT onto the FIELD.

So, is it legal?
I read this as one compressor and one battery mounted on your robot. Therefore, it would be illegal to change the battery after the tanks have been charged.

Am I reading the rule correctly?

[jwfoss]

Use battery one to charge the robot up, making sure that it is the robot controlling the compressor, not just hard wired or an external switch.

Turn robot off.

Remove battery and replace with a fresh battery two.

Go to field and compete.

[Travis Hoffman]

As long as the "practice" battery is connected to the robot's electrical system via the red Anderson connector, and the compressor is connected to a Spike relay on the robot, then yes, you can use the practice battery to charge the air tanks and then swap in a fresh "match" battery before heading to the field.

If you powered the compressor DIRECTLY from the practice battery, bypassing the robot's control system entirely, that would not be permitted.


Greetings,

After reading a "what do you do in between matches" tread, it seems like it is common practice for some teams to charge their air tanks with one battery, then swap out a fresh battery before heading to the field.


I have seen one post on the Q&A on this topic:



Here is R69 and the Blue Box:




So, is it legal?
I read this as one compressor and one battery mounted on your robot. Therefore, it would be illegal to change the battery after the tanks have been charged.

Am I reading the rule correctly?

[Racer26]

This is one of those rules I've always thought was silly. As long as teams are using the proper safety mechanisms, why does the ROBOT battery have to power the off-board compressor.

I've always seen nearly every team with an off-board compressor charge their system, THEN change the battery immediately before the MATCH.

1075 built a robotic cart years ago (it hasn't been used this year, due to malfunctions we haven't had time to fix). It runs an IFI control system, just like our 2000-2008 robots did, (its actually running the system from our 2004 or 2006 robot), uses Black Jaguars to control its drive motors (they're 24VDC motors), and has a separate 12V system to power the control system, and various 12V components, including lights, music, horns, etc (yes, we know musical carts in pits is a no-no, so we generally don't use it at official competitions). We also built a compressor onto the cart, with all the proper interlocks (pressure switch shutoff, etc) but in recent years have not been allowed to use it to pressurize the robot. (We've still used it for blowing metal filings away, and blowing up trackballs)

It gives absolutely zero competitive advantage, and I don't understand why we're not allowed to use it, since its equally safe.

[scottydoh]

It gives absolutely zero competitive advantage, and I don't understand why we're not allowed to use it, since its equally safe.

<R69> Compressed air for the pneumatic system on the ROBOT must be provided by one and only one compressor. This compressor may be either the compressor from the KOP, or an equivalent compressor that does not exceed any of the KOP compressor performance specifications (specifically: nominal 12v, 1.03 cfm flow rate, 120psi maximum working pressure). Compressed air shall not come from any other source. Off-board compressors must be controlled and powered by the ROBOT.

This is why. The inspection checklist also specifically says the off board compressor MUST be powered by the ROBOT control system.

Are there other safe way to pressurize the system? Yes. But having everything controlled by the robot control system makes things go much smoother for both team and inspectors.

[Alan Anderson]

This is one of those rules I've always thought was silly. As long as teams are using the proper safety mechanisms, why does the ROBOT battery have to power the off-board compressor.

It's sort of a second-level requirement. The system providing the pneumatic pressure must be inspected to verify that the pneumatic system of the robot complies with the rules. To make that inspection practical, the compressor must be controlled and powered by the robot. It would not be reasonable to ask inspectors to vet any random pressurization system that a team might choose to use.

[Racer26]

...The ROBOTs are required to have the regulators, and the relief valve regardless of whether the compressor is on or off-board. They're also required to have a High-side gauge. I'm failing to see how the method of getting the pressure there matters. Have the team pressurize the system during inspection using their method of choice, see that the system they're using shuts off when the robot reaches ~120psi (as they already do now) and voila.

Realistically, theres only 3 compressors on the market (at least, widely known to the FRC community), that are legal anyway. Its easy enough to check if the compressor being used is one of those 3 (The old Thomas KOP unit, The Viair 92C (new KOP) and Viair 90C.

Frankly, if the compressor is not physically on the robot, I don't see why it matters what compressor you use. A higher flow rate compressor means it fills faster, but if you're not generating the compressed air during the MATCH, who cares, its not giving you any advantage because you have a finite amount of air storage on the ROBOT.

[scottydoh]

...The ROBOTs are required to have the regulators, and the relief valve regardless of whether the compressor is on or off-board. They're also required to have a High-side gauge. I'm failing to see how the method of getting the pressure there matters. Have the team pressurize the system during inspection using their method of choice, see that the system they're using shuts off when the robot reaches ~120psi (as they already do now) and voila.

Realistically, theres only 3 compressors on the market (at least, widely known to the FRC community), that are legal anyway. Its easy enough to check if the compressor being used is one of those 3 (The old Thomas KOP unit, The Viair 92C (new KOP) and Viair 90C.

Frankly, if the compressor is not physically on the robot, I don't see why it matters what compressor you use. A higher flow rate compressor means it fills faster, but if you're not generating the compressed air during the MATCH, who cares, its not giving you any advantage because you have a finite amount of air storage on the ROBOT.


You seem to be missing the point here.

Its makes the inspection process 10x easier. If every team has to provide spec sheets proving that their non KoP compressor meets the required specs, you can be certain that there will be many more problems/headaches for teams. FIRST says this is a rule, so just accept that fact. I had to help at least 2 teams reconfigure their pneumatic system simply because they didn't read the rules this past Thursday.

[wilsonmw04]

Use battery one to charge the robot up, making sure that it is the robot controlling the compressor, not just hard wired or an external switch.

Turn robot off.

Remove battery and replace with a fresh battery two.

Go to field and compete.

I understand that's how it's done, but is it legal?

A robot is one compressor and 1 battery. By using two batteries you are effectively using more "electrical energy" than is available in one battery. This is what I am questioning.
When I was asking about off board compression, I was told we had to use the same battery as we would use in the match. Why is keeping the compressor on the robot given an exemption to that rule?

[Mark McLeod]

When I was asking about off board compression, I was told we had to use the same battery as we would use in the match. Why is keeping the compressor on the robot given an exemption to that rule?
I assume you asked the GDC in a Q&A not some random volunteer.
Remember, even answers from the Lead Robot Inspector may change as the season progresses and they all come to a common rules interpretation.
I don't recall any such Q&A though.

I think your issue here is how the question is framed and (presumably answered by the GDC).

The answer you received appears to simply be addressing the issue that the compressor must be powered through the robot by the robot battery whenever it is operated, not that batteries cannot be changed.

The robot can only be powered by a single battery while in a match.
A match doesn't begin in the pit or on the queue or in a previous on-field appearance where pressure wasn't releaved afterwards.
A match begins when the field sounds.

[wilsonmw04]

I assume you asked the GDC in a Q&A not some random volunteer.
I don't recall any such Q&A though.

I think your issue here is how the question is framed and (presumably answered by the GDC).

The answer you received appears to simply be addressing the issue that the compressor must be powered through the robot by the robot battery whenever it is operated.

And that is the question I think is core to my problem. When does the robot become the robot?
From my POV once you use the battery to compress air in your tanks, that battery becomes part of the robot for that match. If you removed the battery after the compression, you are using two batteries for a match.

Mark,
The question regarding swapping batteries was asked in the Q & A and they directed the petitioner to R69. I'm just not sure how that answers the question.

[Mark McLeod]

From my POV once you use the battery to compress air in your tanks, that battery becomes part of the robot for that match. If you removed the battery after the compression, you are using two batteries for a match.


Then I posit that you cannot change your battery after you have used the energy to download any code that will be used in said match. :)

[wilsonmw04]

Then I posit that you cannot change your battery after you have used the energy to download any code that will be used in said match. :)

I would disagree because changing code does not store anything that could do work for the robot. :]
Thanks for being lighthearted about this. This is not a hypothetical for my team. With such a large set of tanks this year, it take over one minute to charge our system. If we could do that with another battery it could be a substantial advantage for the team. I just don't see how it jives with the rules. I know others do it; the GDC is rather vague on the issue. I just don't like gray areas. It get's folk in trouble and feelings hurt.

[BigJ]

Then I posit that you cannot change your battery after you have used the energy to download any code that will be used in said match. :)

Probably should just use the same battery you used to image the cRIO last. :p

[Mark McLeod]

I don't believe any rule supports your self-imposed position.
I don't beleve the GDC supports your position, otherwise, they would say so.

I believe only one battery can be used during a match.
A match begins with the field sound and ends with the refs all clear flag.
(it doesn't end with a field sound this season).

I don't accept the stored energy argument (even without the evidence of a rule), otherwise, springs, elastic tubing and other potential energy storage is also suspect. Thereby excluding human muscle power from the robot, as well, if the battery is the sole source of energy.

My beliefs don't constrain the GDC, but are what I will advise any team that asks.

I'm rooting for your students.:)

[wilsonmw04]

I'm rooting for your students.:)


As am I. They are a great group of kids.

Dude, just saw you'll be at VCU in a week. I'll look you up. It will be nice to match a face to a CD tag.

[Mark McLeod]

As am I. They are a great group of kids.

Dude, just saw you'll be at VCU in a week. I'll look you up. It will be nice to match a face to a CD tag.

Your honorable stance teaches them all they need to know to have a successful and fulfilling life.

I'm a mentor with team 2402 from Fredericksburg. I'm older than my photo appears (my hair is graying now) -that was taken more than 10 years ago.
I get around...

Go Rams!

[Mr. Van]

So... has anyone come to a conclusion on this issue?

It is very clear that the robot must be controlling the compressor when it is filling the tanks - on board or not.

There is a very interesting question regarding switching the battery after the compression is complete. For many robots this is not a real "game changer", but at least one example that's been mentioned on these forums is a robot that requires 7 minutes to compress its tanks!

This is roughly about 40% of the total energy output from the battery in the duration of a match.

Yes, it is legal to store this much energy in springs on the robot, but there is no rule saying that "springs must be stretched/compressed under the control of the ROBOT".

It seems to me that the answer to this question could indeed be a "game changer" in certain circumstances.

When does a robot become the ROBOT?

-Mr. Van
Coach, Robodox

[Mark McLeod]

To have the force of a rule there must be a clear interpretation from the GDC and uniform "enforcement" across all events. That's the rule "rule."

I don't mean "enforcement" in the sense that an authority such as the Lead Inspector must stand over us. It's on the honor system. We all want to do the right thing.
I just mean that the event authority (and in this case it would be the Lead Robot Inspector's responsibility) makes it clear that's how the rule will be read.

Since, teams have done this for year's under essentially the same rule set, I think it's a stretch to say this is a rule, much less a uniform interpretation.
From their Q&A response and actions, or lack thereof, I don't believe that the GDC agrees with this particular interpretation.
The Q&A response seemed to be that there was obviously no such rule limiting when the battery can be changed.

I think we are all leaving with the same interpretation that we came in with...
There is no way to prove an anti-rule.

[Joe Ross]

Do teams with onboard compressors vent their pneumatic system every time they change batteries?

[Racer26]

You seem to be missing the point here.

Its makes the inspection process 10x easier. If every team has to provide spec sheets proving that their non KoP compressor meets the required specs, you can be certain that there will be many more problems/headaches for teams. FIRST says this is a rule, so just accept that fact. I had to help at least 2 teams reconfigure their pneumatic system simply because they didn't read the rules this past Thursday.

I'm not missing any point. FIRST has said right in the rule book this year, that any compressor meeting those requirements is legal. That means that any team using a non-KOP compressor has to prove this anyway.

Consider: Hypothetical robot RedABot has an offboard compressor, powered and controlled by the ROBOT battery per the current rules. RedABot has some onboard air tanks for storage. RedABot fills its tanks to ~120psi, the compressor shuts off via sensors and is disconnected, the battery is switched, and then RedABot is placed on the field.

Hypothetical robot BlueABot is identical to RedABot in every way. BlueABot also has an offboard compressor, non-KOP, much higher flow-rate, powered and controlled by some external system. BlueABot fills its tanks to ~120psi, the compressor shuts off via sensors and is disconnected, battery switched, and BlueABot is placed on the field.

At the start of the MATCH (after the MC counts down), how are RedABot and BlueABot different? Does BlueABot have a competitive advantage? Why? Was BlueABot any LESS safe in its method of reaching this point?

Telling teams that their off-board compressor must still be powered by the ROBOT battery and controlled by the ROBOT's CONTROL SYSTEM doesn't simplify inspections, it makes them more complex. The simplest inspection of the control of the compressor, is does it turn on, and pressurize the system to 120psi, then shut off. If yes, all is well. Also, it means that instead of a simple air hose connection on the end of the dump valve, teams need to also create some method of attaching power and signal wires to their off-board compressor from the PDB and sidecar. It makes the whole system needlessly complicated.

EDIT: Also, I STRONGLY disagree with your statement of "FIRST says its a rule, so just accept that fact." This program is all about nurturing young minds to solve problems, and become the best they can be. The program is FAR from perfect, and there are lots of ways for it to improve. Also, asking WHY is ALWAYS an EXCELLENT way to learn things. Asking WHY something is done a particular way always leads to learning. Often, there's something more than meets the eye. There could be consequences of not doing things a certain way that you don't think of. Alternatively, the people you're asking may not have thought of your solution, and they'll learn from you. I never accept "because I said so" as an answer. There is ALWAYS an underlying reason, even if its not immediately obvious.

[scottydoh]

I don't understand why we're still arguing this. If everyone really had this much of a problem with the rule, then someone should contact FIRST.

[wilsonmw04]

I don't understand why we're still arguing this. If everyone really had this much of a problem with the rule, then someone should contact FIRST.

Someone has (please see OP). GDC is still ambiguous since R69 does not specify or pertain to robot battery changes.

Q & A will be asked again soon, but i'm not sure that the answer will be any different than was already stated.

[Alan Anderson]

Telling teams that their off-board compressor must still be powered by the ROBOT battery and controlled by the ROBOT's CONTROL SYSTEM doesn't simplify inspections, it makes them more complex.

Under the existing rules, every robot's pneumatic system works the same. The robot powers and controls the compressor. That's a specific level of complexity that the inspectors must deal with. The only difference with an off-board compressor is simply that the compressor itself is not mounted on the robot.

Under your preferred relaxation of the rules, teams could have different methods for pressurizing their system. That would make inspections more complex. I won't detail all the things I can think of, but there would have to be some major changes to the pneumatic system rules in order to accommodate less restricted off-board sources of compressed air without adding significant burden to the inspection process.

[Matt Krass]

Your honorable stance teaches them all they need to know to have a successful and fulfilling life.

I'm a mentor with team 2402 from Fredericksburg. I'm older than my photo appears (my hair is graying now) -that was taken more than 10 years ago.
I get around...

Go Rams!

He's lying, his hair isn't graying, its gray :)

I believe the intention of the ruling is to make sure the pneumatics are charged and controlled under the same rules and conditions (and safety systems) any other robot with the compressor on-board would have. This makes sense, and while cumbersome, I can understand it.

However I fail to see any way in which using a separate 'practice' robot battery bypasses any of those particular intended restrictions, or otherwise gives you an advantage or presents a danger, and thus I would have interpreted the ruling to allow you to swap your battery between charging the pneumatics and competing on the field.

That said, I'm only me, and my name isn't nearly popular enough to sway inspectors or refs ;) ask the GDC for this exact situation. I believe they will rule in your favor, but having it confirmed can help everyone rest easier.

Matt

[Travis Hoffman]

I believe they will rule in your favor...

Famous last words? :eek:

[1708xMr.Roboto]

Team 1708 did this in Washington DC this year,

after our First regional we ended up dumping the compressor and the Clippard tanks, for some of the lighter PVC tanks so we could include a mini bot launcher on our robot. The way our system worked was like this, we had a onboard Spike and when the tanks needed charged (Between Matches) we plugged in the compressor to the spike, and ran the compressor off the robot's battery. You are allowed to do so, as long as you can prove that your compressor and code shut off at 120psi. after that was all said and done, we switched the robot's battery and were ready to rock and roll. This made being in the Finals interesting considering it took about 4 and a half minutes to fill the tanks; and we only had 6 minutes between matches :)

-1708

[MikeE]

Let's try a different tack.

Here is the FRC prime directive:

<R01> Energy used by FRC ROBOTS, (i.e., stored at the start of a MATCH), shall come only from the following sources:
A. Electrical energy derived from the onboard 12V battery (see Rule <R34> for specifications and further details).
B. Compressed air stored in the pneumatic system, stored at a maximum pressure of 120 PSI.
C. A change in the altitude of the ROBOT center of gravity.
D. Storage achieved by deformation of ROBOT parts.

Note that <R01> doesn't say energy can only come from one of these sources, but "from the following sources", so it's clear that they can be used in combination.
Some energy for running the cRIO, motors, etc during the match comes from the onboard 12V battery per <R01>.A
Other energy may come from stored compressed air per <R01>.B
Rule <R69> further restricts the earlier source of this energy to a 12V battery, but doesn't expressly state that it must be the same as that of <R01>.A

[Al Skierkiewicz]

MikeE,
Your response is the defining start of the compressor rules. Those rules that pertain to off board compressors are not meant to give you an advantage over other teams on the field that do not have an off board compressor. To meet R01 while allowing off board compressors, there needed to be some massaging of the rules. The give and take for off board is reduction in robot weight for a limited air capacity. That is all. Those teams with the compressor on the robot must control it from the Crio and so too should off board compressors. On board uses the robot battery and so should off board. There can be no advantage given in either case. While the current rules do not bring robot battery into the equation, teams with on board compressors can pre-charge their pneumatics and then change batteries prior to taking the field. That being said, the same can hold true for off board. Personally, I would like to see a rule allowing only one battery per match. There are many teams that are on the edge of efficient design that are depleting a battery in a single match. If we are trying to inspire, this is one area we have fallen down on the job.
However, with the variety of pneumatic designs we see, I am always fearful of teams in the queue with pre-charged pneumatics.

Mark,
It's time for a new picture.

[wilsonmw04]

MikeE,

However, with the variety of pneumatic designs we see, I am always fearful of teams in the queue with pre-charged pneumatics.

Mark,
It's time for a new picture.

I completely agree with this statement. When you consider the unlimited air supply one can have this year, re-charging is even more advantageous. Maybe we could have a staging area before the match where teams can prep/charge or whatever they need to do to be ready to play. It could be the queuing boxes that you stand in while waiting for the match in front of you to play out. 5 minutes should be more than enough time to prep a robot for play. Could you imagine a kicker from last year extending in the tightly packed group that is a queuing line?

[Richard Wallace]

...

Mark,
It's time for a new picture.Al, I think all grey-haired robot inspectors should follow your lead, by including team shirts, wives, and iconic landscape background in their CD pictures. I'll be working on a new one soon... maybe with the Arch. :]

Also, I completely support your stance that robot inspectors must base our decisions on the robot rules, and interpretations thereof, provided by the Game Design Committee, via the Manual, Team Updates, and official Q&A responses.

[Mark McLeod]

Well, it's not very good, but it's up-to-date now.
The background is the only thing that recommends it.
I don't show up in very many photos.