Crazy robot idea for this year 2
 

the first idea was not circulated much but it was a 3 ball shooter on segway like chassis that could fit on the bridge with any two other robots and would flop over once power is cut.

how ever the second idea is

if you made a flying ball that had about an 18" diameter with bumpers on it that could do to things; fly to opponents end and sit in oppomnents 3 point basket, fly to bridge and hover while touching an alliance robot for 30 seconds and then fall and roll to the ground at the end of the match. http://www.atomicrobotics.com/2011/10/flying-ball/

would this be legal?
would this be a game changer?

I am looking at rules now. can't find rule that says you aren't allowed to be above the opponents fender or touching rims. they assumed this would not be possible with the 14" arm and 60" height limit.

Plus I haven't seen anything about what is considered a balance if after game play your robot falls off bridge.

‎1 battery (or super capcitor if allowed to replace) 1 CIM, 3 small control motors froma quad copter rig, 1 victor, 1 quad copter control board (unless CRIO has to be used), 1 wirless controller, 1 circuit breaker, 1 light, 1 wireless adpter and walla you have a single rotor helicopter self contained that just has to fly for 1 minute with that weight

If CRIO has to be used does the crio have to be on the robot? can it be on the control board and connect to a secondary wireless RC like control system?

Specifically i would be looking for anyway to offload weight from the required "large FRC" components.

Just a thought. Good night

Re: Crazy robot idea for this year 2
 

Fun ideas...however, they're fraught with peril.

For the first one, if it falls over while on the bridge, doesn't that risk unbalancing it due to the centre of gravity shifting? Check out the 5 second rule, [G37].

For the second, among many other potential issues, you will need to deal with having the battery, the cRIO and other heavy things onboard to be considered a robot. Also, how will you avoid unsafe operation?

Re: Crazy robot idea for this year 2
 

Check out flying ball, no unsafe operation unless their is a control issue, in some ways no different than a ground based bot.

the 5 second rule. Doh.... then it would nee to land. as long as partner has flat spot with whole in it to land on we are good.

Re: Crazy robot idea for this year 2
 

In some ways no different, but different in one crucial respect: it's a lot harder to protect the scorer's table and the front row of spectators. A control issue on a regular robot rarely leads to a departure from the playing field; that's hard to guarantee on a flying robot. And because it's above the field barrier, disablement doesn't mitigate the threat nearly as well. (Plus, as determined by the required parts, it would have to weigh a minimum of around 20 lb—that's a lot of momentum to arrest.)

Re: Crazy robot idea for this year 2
 

This has been discussed. Flying is illegal because it is impossible to keep your bumpers in the bumper zone. Bumpers must be in the zone during normal operation, and if flying is normal, you need them there while flying.

In addition, no part of your robot may extend more than 60" off the ground- wait. Only when in contact with the other alliance's carpet. So you're good on that front.

EDIT: I stand corrected. The bumpers need only be in the Bumpers Zone while the robot is standing on a flat floor. See post below.

Re: Crazy robot idea for this year 2
 

That's not what the rule says...

So it seems that a flying robot is completely legal, as long as it is deemed to be safe... good luck with that!

Re: Crazy robot idea for this year 2
 

I stand corrected. The required battery + crio, combined with the limited set of motors, are more than enough to make this impossible in my view, but if you can do it, I think the "safety" rule is the only thing standing in your way. Which would also be near-impossible to satisfy, but you may try as you like.

Re: Crazy robot idea for this year 2
 

Well, I think that the things that make this illegal to be:

^Even if you were able to get flying, you're still restricted to an air ceiling ~10" above the ground.

Read it as you will.

Re: Crazy robot idea for this year 2
 

A giant Helium balloon would off set the weight. Is that legal?

Re: Crazy robot idea for this year 2
 

No it wouldn't. It would add both weight and buoyancy. The specification restricts robots on the basis of weight only.

The helium itself would be legal, unless in a hazardous state.

Re: Crazy robot idea for this year 2
 

Can you fit it in the maximum size?

For something as heavy as a typical FRC robot, the required helium-carrying device will most likely have a hard time fitting in the field, if not the venue. Trust me on this. For something like a 18" sphere, with bumpers and battery, you could probably fit said helium-carrying device into the field if you didn't max-weight the robot. However, maneuverability would be highly limited due to rules about leaving the field boundary.

Re: Crazy robot idea for this year 2
 

Under normal atmospheric conditions, helium has a lifting ability of 1 gram per liter*. The maximum volume of your robot is 28x38x60. Let's pretend you fill that entire volume with helium (impossible, since you would need to lose some volume for the electronics, battery, bumpers, etc.)

28" x 38" x 60" x 1 gram/liter = 2.3 pounds of lifting capability. Not even enough for the cRIO itself.

* http://science.howstuffworks.com/helium2.htm

Re: Crazy robot idea for this year 2
 

It gets better. You also have to have something to hold the helium. However, you could possibly get better lift by pressurizing the helium, allowing more liters to be added... which opens up its own set of problems, including the fact that helium escapes from containers very easily if there are any holes at all.

Re: Crazy robot idea for this year 2
 

That's where the bumper zone is located, but it only matters with regard to R29 (in fact, it's only ever mentioned in these two rules).

[R29] Bumpers must be located entirely within the Bumper Zone when the Robot is standing normally on a flat floor.

Otherwise no one would be able to wheelie onto the bridge, lift themselves across the barrier, etc.

It seems the GDC also has chosen not to answer the question of whether a circular (or spherical) robot has no exterior vertices or infinite ones, so you might not need bumpers at all! ([R27]: "Robots are required to use Bumpers to protect all exterior vertices of the Frame Perimeter".)



True, all robots are limited to 60" while in contact with the "carpet and/or Key on their Alliance Station end of the Court" [G20].
...However, "Otherwise, Robots are limited to 84 in tall" [also G20].
...However, "The vertical measurement is always in relation to the Robot." [Q&A, G20]. Those tricky GDCers ;)

So as long as your flying robot is not over 84" tall and not over 60" tall when placed on the Court before the match [G01]--with respect to itself--it should pass G20 and G01. (G01 is not clear about cases in which the robot is never actually placed on the Court, i.e. it floats.)


Now the safety thing, that's an issue. Field personnel have enough problems without a flying ball of helium filled with a battery+cRio*+router+/-bumpers flying at their heads. Yikes!


*[R52] Robots must be controlled via one programmable National Instruments cRIO (part # cRIO-FRC or cRIO-FRCII), with image version FRC_2012_v43. Other controllers shall not be used.

Re: Crazy robot idea for this year 2
 

The design also assumes that the life of the battery can handle the required current that it will take to lift ~25lbs off the ground. This includes the electronics, battery, motors, and "bumpers".

There's a reason Quadrotors became more popular among hobbyists after LiPo batteries became mainstream.

Each year I've tried to figure out how to incorporate a quadrotor into the game. Alas, it hasn't been pragmatic enough for 4 years. Maybe next year :rolleyes:.

Re: Crazy robot idea for this year 2
 

Helium balloons float because helium weighs less than air. Shoving more helium molecules into the same volume won't increase lift, it'll actually decrease it! Imagine you have two 1-liter bottles of soda. They each weigh a certain amount. Now I hand you a 1-litter bottle that's been insanely pressurized and actually contains 2 liters of soda - which is heavier? The pressurized bottle weighs the same (discounting the container weight) as the two unpressurized bottles!

Re: Crazy robot idea for this year 2
 

Of course, I didn't specify how much extra you pressurize it. The kind of pressures I'm used to dealing with for air/helium, you can't measure them in PSI unless you really like small decimals.

I'd also note that at least one maker of the size of helium balloons that can possibly lift an FRC robot does specify that they be pressurized, and goes to great lengths to have the balloons maintain that pressure. This is partially because said balloons need to maintain a given shape, granted--but you have to wonder if it doesn't give a tad bit of extra lift.

(Then again, these helium balloons can weigh several hundred pounds empty.)

Re: Crazy robot idea for this year 2
 

A perfect battery can support around 60A draw for the whole match, at around 11.5 volts. Lets be generous and say you only want a few moments of flying and the battery can support 150A at around 10.5V. This is 1575 Watts, which should be able to lift around 16-17lbs.

I do not believe that it is possible to lift all of the required hardware (battery (13lbs), cRIO (1.4-2lbs), cRIO modules, power board (1.6lbs), digital sidecar (0.25lbs), main breaker, bumpers, motors, radio (0.5lbs) etc) with the battery's available power. This is even without accounting for losses such as resistance in wiring and motor inefficiencies. In fact, that 1575W of theoretically available electrical power is probably around 1200W if you use RS775-18s at peak efficiency (78%). Voltage at the motors will be lower than 10.5V, so ding some more power...

I think it's safe to say that the battery cannot output enough power to lift the absolute minimum FRC legal robot.

Re: Crazy robot idea for this year 2
 

This is still not how buoyancy works. The idea is to get the least weight to take up the most volume. The volume determines how much lift is produced. The lifting element is there to maintain volume with as little weight as possible. Because pressure of a gas is not related to the molecular weight of that gas, elements with very low molecular weights are used to match the outside atmospheric pressure, so the volume of the balloon is maintained. Your manufacturers suggest inflating beyond that pressure to give additional rigidity and in case of leaks, but once the balloon volume is full, all you're doing is putting more weight into the balloon.

Re: Crazy robot idea for this year 2
 

A leaping robot that jumps forward over the fender and then clambers up the baskets -- blocking all four of them with a shape change -- is both technically feasible and within the rules.

We thought of it day one, then said, 'naah.'

Re: Crazy robot idea for this year 2
 

You could have always put a fan, on the robot, went over the bump/bridge. Sat in your alley, and aim at the top 3 hoops. I think that is a smart plan for defense.

But once again, I would love a flying robot.:o

Re: Crazy robot idea for this year 2
 

Don't encourage him Max :rolleyes:

Re: Crazy robot idea for this year 2
 

???
This years set of motors has one of the highest power densities I have seen in FIRST. If you ran all of the 550s (all 8) into a single gearbox (low reduction, high speed), and put a large prop on it, you could get some substantial lift.

Motor power breakdown:
-AndyMark motors (AM- 0912)> 180.83W * 2 = 361.66W (current is below limit)
-Banebots RS-550-120-------> 253.52W * 4 = 1014.08W **(slightly less due to current limits, at this power level, they draw 43.2 amps each)
-Fisher Price 00801-0673-----> 291.59W * 2 = 583.18W **(prob. not quite this high, this would require 54.76 amps per motor)
----> this comes out to 1958.92 Watts, theoretically. So, How much would that be able to lift? (more specifically, how much would that be able to lift using a propeller?)

Re: Crazy robot idea for this year 2
 

It depends on the prop, and the air density. Quite possibly even the specific prop. The one overarching question which won't be answered by motor power is prop thrust--motor power is good for getting that thrust, but can't be precisely correlated without some testing. A 27x13 is quite a hefty prop, even for a hefty motor like an FP.

And I've seen a case where the same prop tested at two different thrust levels in two different locations. Not fun trying to figure out why...I suspect it had something to do with either the air density or a mounting change, or both.

Re: Crazy robot idea for this year 2
 

Well, air density at FIRST venues, which are often climate controlled and at fixed altitudes, shouldn't be too hard to calculate, plus the mounting won't change as long as it is on the robot. Additionally, the same website also sells 26, 24, 22, 21, 20.5, and 20 inch props in varying pitches.

Does anyone have performance data from 2009 for similarly sized propellers?

Re: Crazy robot idea for this year 2
 

Don't get caught up in the details with props and their inefficiencies, sizes, etc. Do the broadest, most basic calculation possible to check and see if it is within the realm of feasibility.

If we take a minimum robot mass (25lbs) and use the entire cross sectional area of the robot envelop, 28inX38in we find that we will need to generate approximately 0.0235psi (162Pa) of dynamic pressure just to 'hover' in free air, ignoring ground effects.

Pdynamic = ( fluid density * fluid velocity^2)/2

fluid density = 1.18kg/m^2 (~STP)
Pdynamic = 162Pa

Fluid Velocity => 16.9m/s

Total air flow rate is 28in*38in*16.9m/s = 11.6m^3/s

In a basic sense we need enough power to accelerate 11.6m^3 of air to 16.9m/s in 1s. This can be simplified to a basic energy problem:

Air mass = 11.6m^3*1.18kg/m^3 = 13.7kg

air velocity = 16.9m/s

Air's kinetic energy = 1/2*mass*velocity^2 = 1950Joules

Time available to apply this energy = 1s

Total power required by this method = 1950J/1s = 1950W to maintain hover, including no inefficiencies.

This is about what PAR_WIG1350 figured that eight motors, drawing well over 280A, could produce.

It is technically unfeasible with our legal battery. It is technically unfeasible with our required main breaker. Even if these barriers were removed, the motors would not last long at peak power.

Re: Crazy robot idea for this year 2
 

With the exception of the battery, the limits are all purely thermal, Through strategic placement of the breakers and motors the propwash might keep them cool enough to avoid anything failing mid-match.

Also, I find it strange that you bring up ground effects while referencing a post made by someone with a ground effect related username.

Re: Crazy robot idea for this year 2
 

Hah, I did not know that PAR WIG was a reference to ground effect aircraft until I looked it up just now.

The 25lbs I figured for the minimum required hardware did not include eight motors, controllers, and wiring. Add another 6-8lbs for those motors, and it's too heavy to take off again. One would probably need 10-14 motors of similar power to get airborn.

The RS550, FP, and AM motors are not especially efficient, especially at max power. They are also quite heavy for their power output. For example, this brushless motor (just something I found on a google search) brags a higher peak power rating than any FRC motor, save the CIM, at 2.8oz of weight, almost a 1/3 the weight of an RS550. FRC equipment is just a bad way to go about trying to make a flying robot.

Re: Crazy robot idea for this year 2
 

what if during auto mode a robot placed a ball on the opposing alliances bridge then had a manipulator push on that ball to lower the bridge. This action alone would actually be quite helpful and if another robot on you alliance got the balls of the coopertion bridge there could be 6 balls on their side and 12 on yours. The balls stolen from their bridge could even be collected and scored which would be quite awesome!

Re: Crazy robot idea for this year 2
 

You guys need to read up on flight theory, and EricH needs to read up about buoyancy.

In order to make a craft fly you don't necessarily need to generate more thrust than weight. Furthermore, a helicopter isn't exactly a giant propeller on top of a body. It is a rotating wing. A quadrotor relies on conservation of momentum to stay aloft - push air under it to force it upwards. A wing however relies on bernoulli's principle where fast moving air over the top of a wing results in a lower pressure which "sucks" the craft upwards.

The maximum takeoff weight of a 747 is ~980000lbs however its engines only generate ~67000lbs times 4 = 268000lbs How does it fly? :D

By this ratio, a robot weighing 120lbs.. if shaped like a 747, would only need 33lbs of thrust to fly which is quite possible!

Even though it is possible, to achieve it within the confines of FIRST rules makes it extremely difficult.

Re: Crazy robot idea for this year 2
 

This would depend on the ref's interpretation of 'translative' contact with the bridge. The example given in the rule is that contact is translative through the robot, but another example would be translative through the balls.

Re: Crazy robot idea for this year 2
 

For rotary wing aircraft, you require much more power due to losses and inefficiencies.

Check this link out to see the differences in propellers and rotors:
http://www.heli-chair.com/aerodynamics_101.html

Theoretical thrust developed by common airplane engine - propeller combinations:
300 hp, 78" propeller develops 1,300 pounds of thrust
80 hp, 50" propeller develops 400 pounds of thrust
1.5 hp, 12" propeller develops 10.5 pounds of thrust

Theoretical lift developed by common helicopters:
300 hp, 30' rotor develops 3,400 pounds of lift
25 hp, 12' rotor develops 347 pounds of lift
2 hp, 6' rotor develops 39 pounds of lift

Re: Crazy robot idea for this year 2
 

I don't know about you, fox, but I ain't flyin' no fixed-wing aircraft controlled by the FRC control system in no FRC arena! No way, no how--there isn't enough room for anything that big without a ton of power--also known as a great way to drain batteries. It'd probably hit the wall before it got up to speed anyway. And if it did get up to speed, take off, and not hit the wall, I doubt it could turn fast enough to stay in the arena. That puts the crowd at risk. A helicopter has a much, much smaller takeoff area, and can be slower flying around.

Re: Crazy robot idea for this year 2
 

You completely missed the point of my post which was that you don't need to balance weight with thrust to get a vehicle to fly. A Helicopter relies on the same principles as an aircraft however the wings move above the craft rather than the craft moving through the air to generate lift.

And spinning blades are any better? Let me tell you a story now that we're on the safety train--

One time, bout 5 years ago at the RC flying field I am a member of, there was a gentleman tuning a new helicopter he had just built. This was a 0.30 cubic inch engine size heli, nothing big, bout 5lbs weight, with a rotor diameter of about 3 feet. While checking the rotor balance, he lost radio communication and the throttle was stuck wide open. Luckly the collective was in the neutral position so it just sat there on the ground at full power. Well this guy decides that the best thing to do is to reach under the blade and pull the fuel line off the engine. While he was pulling on the line to get it off the radio cut back in and the machine twitched. The sound was sickening- his arm was clipped by the rotor and broke it in three places. We rushed him to the nearby hospital and the resulting damage was so bad it requied 68 stitches, multiple reconstructive surgeries and he nearly lost the arm. This was after they cut off the leather coat he was wearing to get to the wound.

I would far prefer seeing fixed wing aircraft than rotary wing aircraft.

Re: Crazy robot idea for this year 2
 

I got the point of your post. I was pointing out that fixed-wing aircraft are entirely impractical for anything FRC-sized, forcing a helicopter to be the default choice.

Fixed-wing planes have spinning blades too. I've been at a field where in 2 years, 2 people lost or just about lost fingers to an airplane's prop. And that's while I was there--I don't know about any incidents that happened at other times.

If a chopper has a problem, it can reasonably be expected to go in one direction: straight down, as far as it can go. It's relatively easy to figure out that safety: don't get under it. If a fixed-wing bird has a problem, you have a glide slope--and that slope can change based on what happens while it's on that slope. Makes it much harder to dodge, especially with an arena-type setup.

However, neither of the two is as unsafe as both of them in a single package...

Re: Crazy robot idea for this year 2
 

That story sounds like a failure to include emergency shut-down hardware, a failure of patience to let the helicopter simply run out of fuel, and a failure of common sense to not realize how dangerous it was to reach near a spinning rotor.

I can see a similar thing happening with the prop of a fixed-wing RC airplane.

Re: Crazy robot idea for this year 2
 

Correct, but the danger zone with an aircraft is much smaller than with a heli.

If anything was permitted to fly it would have to take place in a similar fashion as the SAE aero competitions if FIRST expected to keep the same kind of hardware. If they were to take place in a FIRST-style venue, the field would have to be enclosed with netting or chainlink fencing (depending on the design limitations of the machines) and the hardware would have to changed sufficiently to make it practical to build aerovehicles which could fly in such a space. Perhaps a minibot style competition where the robot deploys a flying vehicle powered by a similar minibot or LiPo battery and controlled with an RC aircraft control system. You could even tether the vehicle to the robot and send it power/control from the victors mounted on the robot chassis. I think it would be awesome to have the craft fitted with an auto-stabilization system and have the CRIO track the craft using the camera and send it commands autonomously based on that positional feedback and the intended goal of the craft. A fixed wing vehicle could be launched quite easily with a mechanism. Indoor RC flight is a very common and prevalent hobby in Canada since nobody wants to stand in a field trying to fly a model with frozen fingers in the winter. There are piles of small helicopters and aircraft on the market designed for indoor flight.

This all said, the Mabuchi style motors are very common motors for RC aircraft and helicopters and are more than capable pieces of hardware.

Re: Crazy robot idea for this year 2
 

The SAE competition is where I heard about the guys losing fingers. (I didn't actually see the incident--I was most likely fixing my team's plane.)

Indoor RC flight tends to be with very lightweight electrics, often foam, in fairly large venues like large-size gyms. Something the weight of an FRC control system would need a ton more power than one of those flyweights, just to get off the ground. (And that's assuming that you were allowed to power with lipos. Hauling the SLA around, that's slightly insane.)

Flying a very small RC off of a robot could be done with comparative safety. However, it would be very difficult to also have it tethered to the robot.

Re: Crazy robot idea for this year 2
 

Rather than making the entire robot fit in the hoop, why not mount a large fan/turbine on the robot. Aiming this at the backboard of the opponents hoops with enough air velocity could make it impossible to score (the upward air speed would have to be greater than the terminal speed of the ball to ensure this) A leaf blower powered by a pair of 500 series motors could probably accomplish this.

Re: Crazy robot idea for this year 2
 

It's not just the velocity. Better to think of it in terms of energy, momentum or force.

Re: Crazy robot idea for this year 2
 

Actually, the applied force and transferred energy, in this case, are velocity dependent according to the drag equation. The fluid density, ball area, and drag coefficient are fixed (unless you are using a very narrow stream of air, which would would change the area parameter). As a result, velocity really is the only relevant property of the airflow.

Re: Crazy robot idea for this year 2
 

The shape and direction of the air stream was exactly what I was getting at. If you have a narrow air stream, drag alone isn't a great model of the situation. If you point the air stream off to the side of the ball, you have to deal with other effects—like the air stream inducing rotation (an off-centre force, or energy used to accelerate the ball angularly), and the tendency of the ball to fall out of the air stream.

Re: Crazy robot idea for this year 2
 

The issue is that the ball is rarely moving through the airstream long enough for it to have any appreciable effect on it. One of my teams did some extensive testing on this concept and deemed it ineffective. We used a ducted fan housing for a radio controlled jet powered by an 0673 FisherPrice motor to no avail.

Re: Crazy robot idea for this year 2
 

That isn't a large enough airstream. The ideal blower would be a large fan, nearly 28 inches, housed in a duct with minimum blade tip clearances and powered by something like a "V-6" (118 style) with 2 cims, 2 0673s, and 2 RS550s. For extra velocity a nozzle with a hoop sized opening could be added. If less turbulence is desired, a grid of drinking straws covering the opening would give you more laminar flow (more directional and uniform). It could me mounted on gimbals and aimed at shooters or (more likely) fixed and angled such that one could park against the fender and defend the 3-point basket. Conveniently, backspin on the balls would create a lift force away from the hoop as a result of the Magnus effect.

Re: Crazy robot idea for this year 2
 

I actually thought about this a bit more after posting, I think the best soulution would be a 37 inch diameter fan pointed up and toward the key. With all the power in the KOP motors you could achieve about 3-4 times as much power as a large gym fan. This would almost certainly deflect any shots enough to miss.

Re: Crazy robot idea for this year 2
 

The air wall was tried in 2006. Early testing indicated that it was useless against any robot shots--range, 60" shooting air at a target about 8' up. (More like 6.5' up if on the ramp.) For a dropping shot this year, you'd need to add some height to that. Hover the ball that year, yep. Add velocity, though, and in the goal every time.

Think about it this way: You need to generate enough drag force on the ball that gravity can take over, or that it will move in a different direction. There are a couple of possible estimates for the drag coefficient of a sphere, namely 0.5 (laminar flow) and 0.2 (turbulent flow). You have an area (pi*D^2)/4, a known air density (1.204 kg/m^3 for 20C), and you can estimate the drag force needed to deflect the ball.

Now, you plug into the equation Fd=Cd*A*density*(V^2)/2, and solve for the velocity needed. Now that you know how fast the air needs to move, you can figure out how big of a fan you'll need, or how much you need to apply a nozzle to get the air moving that fast, using one of several possible methods.

Power in the motors in the KOP has to translate to a fan, and thus to the air. That is where you run into trouble (in addition to keeping most of the air column generated together instead of going off into eddies in the surrounding air--you're probably best off using the turbulent flow analysis for that part of the equation).

Re: Crazy robot idea for this year 2
 

Maybe a hovercraft might work and be legal.

Re: Crazy robot idea for this year 2
 

they were legal in 2009, nobody used one, but the legality was confirmed in Q&A.

New offseason project, convert Jake, our 2009 'bot, into a hovercraft.