witricity legality?

Technical Electrical
1

I seriously want my team to do this next year but im sure about how legal it would be based on this and last years rules.
witricity is basically the cordless transmission of power. By using coils that resonate on the same frequency one will pick up the power that the other is broadcasting(no signals are being sent only electromagnetic waves), using this with victors it think would make a very sweet crap drive, but im not sure if it would be legal via this and last years rules.

thanks for the help
cody

1 Like
2

Not to rain on your parade, but FIRST’s rules are the least of your concerns. Physics and the FCC will stomp this many times over.

  1. The drive train uses a lot of energy.
  2. RF transmission is lossy.
  3. The energy that leaks out will affect other systems.

Do you have any examples of this “witricity” as you call it? I’d be interested to see their numbers.

Cool idea though.

3

Regardless of legality this doesnt seem like a great idea. Two things that come to mind would be the interference of magnetic fields and electronics. Also based on the wikipedia article the efficiency is not very good, researchers needed two 24in coils and only tansmitted at 40% efficiency, not great for battery life.

4

witricity which using resonating magnetic coils was proved possible my mit last year by using it to light a 60watt light bulb 2m away. With stuff blocking directing line of sight

also Tessala (can’t spell) using witricity to transmit massive voltages over great distances, one example is that in a eletrical field you can light flourencent lights with out plugging them in.

the laws of physics allow this to work, but im not sure if the metal frame would interfere. Also other eletronics can work in a witricity feild if they don’t opperate on the same frequency they will not conduct the current. Which is why you make sure that the cycles of the field is very high (10megahertz or higher).

MIT tested this device, there was 40% power loss in transmission. If we weren’t going for speed this could be viable i think. You know for a engineering award.

5

You could also just build your own slip rings to transmit the power to the motors in the crab drive. It would most likely be a lot simpler.

6

Rather than planning this as a power transmission method for a FIRST robot drivetrain, where robustness and reliability are paramount, this sounds like a great science fair project.

If you do your research and start building prototypes and testing them now then you will not only have a good science fair project, but… if you can move more than 40 amps through the ether with minimal losses, then you will have something that your team can check against the FRC rules for legality.

Just keep in mind, however, that transmitting current is quite different from transmitting voltage. Also keep in mind that when a CIM is drawing 40amps at 10 volts, that is 400 watts of power. If you have a 40% power loss then you have 160 watts of heat showing up somewhere. Any compact, lightweight system is going to start getting really hot, really fast.

So if you are interested in this system, study it. Research it. Test it. And should you get it to the stage where you can use it in an FRC robot, then worry about what the FRC rules are. Even if it doesn’t work for FRC, it will still be a very cool science fair project.

Jason

7

That would probably be legal, however would be difficult to do as stated in the other posts.
Another way which might be easier but probably illegal is to make a microwave transmitter to beam microwave frequencies to a reciever. The reciever is usually a rectenna, which converts microwave to electricity. It could be relativley efficient also.
However, that could be extremley dangerous and illegal in the competion. Other methods that would be safer are also availiable like laser beaming.
One may actually be able to replicate experiments such as this one

Anyway, I hope that helped.

Amir M.

8

I see no FIRST rule that would prevent the use of Witricity.

That being said, you still have a lot of things to overcome
1> Matching resonators for transmission and reception. Any impedence mismatch will greatly reduce your transmission efficiency.
2> Each device would need a separate frequency to transmit power.
3> You would need to make sure you do not induce any current in any robot frame on the field, to do so would break FIRSTs rules.
4> You would need to make sure you do not interfere with any signals on the field.
5> Power losses would limit your robot and multiple transmitters in series (Battery to dist block, dist block to Victors, Victors to motors, etc) would cut your power even more.

While I think your idea is novel, and would win you an engineering award, I don’t think it would provide a viable robot on the field.

9

<3 the typo (=

as previously said, i dont think your idea is exactly feasable. It could potentially win you an award, but youll probably be impeded by rules, physics, losses, etc.

Something also tells me that transmitting 400W of power with EM radiation is a really bad idea…

10

I too am looking forward to seeing a sweet crap drive! :slight_smile:

Seriously, Take a shot at energizing a sensor or two (a few tenths of a watt) that are on the extremities of your robot.

Then, maybe graduate to energizing a coprocessor out on one of those extremities.

You can graduate to transmiting serious power after successfully getting a few watts to coprocessor. Along the way you can navigate the safety and other rules.

Blake

11

<R01>
Energy used by FIRST Robotics Competition ROBOTS, (i.e., stored at the start of a
MATCH), shall come only from the following sources:
 Electrical energy derived from the onboard 12V and 7.2V batteries
 Compressed air stored in the pneumatic system, stored at a maximum pressure of 120 PSI
in no more than four Clippard Instruments tanks. Extraneous lengths of pneumatic tubing
shall not be used to increase the storage capacity of the air storage system.
 A change in the altitude of the ROBOT center of gravity.
 Storage achieved by deformation of ROBOT parts. Teams must be very careful when
incorporating springs or other items to store energy on their ROBOT by means of part or
material deformation. A ROBOT may be rejected at inspection if, in the judgment of the
inspector, such items are unsafe.

Good science fair project, poor (due to rules) way of powering a FRC robot.

Edit: I misread the original post, and thought they were talking about ‘sending’ additional power to the robot from the pits/stands/etc.

12

From what I can tell, they are not proposing to use this system to generate power, but to transmit power (presumably from the 12v battery). I don’t think there’s anything illegal about it, but… why, exactly, do you (the original poster) need it? Not that that’s ever a good reason not to try something new, but there seem to be some disadvantages to this system…

13

Oh, ok. That makes much more sense, and powering sensors with it would definitely be a useful application. I wonder if you’d have to get FCC clearance to run such a device, since it uses the airwaves.

14

I think it maybe illegal per <R53>

[quote=The Rules;]<R53> Custom circuits shall NOT directly alter the power pathways between the battery, fuse
blocks, speed controllers, relays, motors, or other elements of the robot control system
(including the power pathways to other sensors or circuits). Custom high impedance voltage
monitoring or low impedance current monitoring circuitry connected to the ROBOT’S
electrical system is acceptable, because the effect on the ROBOT outputs should be
inconsequential.[/quote]

This would certainly be a custom circuit and it is directly altering pathways to the speed controller (or sensors or anything else).

15

Induction is cool for short distance low current applications… but I don’t think it would work very well (excluding rules) for running a robot. Tesla devoted a lot of his work to wireless energy transmission, and never really got anything that was very efficient over much of an appreciable distance, plus when he tried to market some of his more long-range methods of transmitting large amounts of energy to the U.S., they were deemed unsafe.

But don’t mistake me about him… nothing against Tesla. He did a TON of work with EMF that we use all the time today, it’s just that long range energy transmission never really worked out for him (or anyone else for that matter).

Also, let’s say the frequency you were using for transmission was somewhere up in the microwave spectrum, and let’s assume your transmission in 100% efficient (it wouldn’t be, it decays at the square of the distance your antenna is from your source, but just for fun). Also, let’s say you want to run four CIM motors at up to 40A. 40A12V= 480W, 480W4motors=1.92kW.

As much fun as a 2kW microwave sounds, I don’t think I want to be anywhere near it (unless lead shielding was provided for the operator stations). :yikes:

Fun idea though…

q

16

From an engineering viewpoint, it’s not a very good idea…wires work so well for carrying electric current. Wireless signal transmission makes sense because the information is what is important, not the power being used by the transmitter. Wireless transmission of power itself is not a very good idea, because it is very inefficient compared to wires (I think the inverse square law has something to do with it?)

It would be fun to experiment with, and as suggested low power applications such as powering custom sensor circuits would be a more suitable application than the drive system, also more likely to be meet the rules.

17

A couple things to note…

You’ll need a way to convert the DC of the battery to AC in the transmitting coil. Not hard to do, but it’ll hurt the efficiency. You also have to match the resonant frequencies of the transmitting and receiving coils, and match the frequency of the DC to AC inverter to those. A little harder to do, but still possible, with patience and a little research.

The power is transmitted much like it is between the two windings of a transformer - the changing magnetic field generated by the transmitting resonator passes through the receiving resonator and generates a voltage there. The difference is that the magnetic field is not in the least bit confined, which is what the ferrite core of a transformer does. What’ll happen is that that changing magnetic field you generate will induce currents in every loop of metal within its range, particularly the robot chassis, manipulator, neighboring robots, metal field elements, belt buckles, tools in the pit, hoop-shaped body piercings, whatever happens to be around. It can really wreak havoc on your electronics. Plus, metals get hot really fast when you induce currents in them. And, the more power you try to transmit, the greater the volume the magnetic field takes up, so more things draw power away from your transmitter.

Then, at the receiving end of the power transmission system, you’ll need to rectify the AC back to DC. If you’re going to run a sensor with it, you’ll need to regulate the supply.

Hang on…if you run a sensor this way, you’ll have to get the data back to the RC…with a wire, since other radios on the robot are prohibited.

In short, assuming this might by some stretch be legal, then trying this on a robot will at best waste power, and at worst cause enough heating in the chassis (large current in a thin piece of metal) to catch something on fire. Hmmmm, maybe that could be your science project - ignite a sheet of paper wirelessly.

BTW, one problem with Tesla’s demonstration with the fluorescent tube is that there was no easy way to confine the volume which the fields operated in - if your neighbor’s transmitter was on, your lights were on. It still needed quite a lot of work to be practical.

It sounds like something really cool to tinker with, and pretty inexpensive, but there’s a lot that’s got to happen before it’s practical and safe for use on a robot. Have fun with it.

  • Steve
18

i don’t believe that the energy that is lost in the 40% transmission lose is lost to the frame i think that the energy is lost just to space

also the energy from the robot will stil come from the battery no an out side place.

i agree with you that this would be a very sweet science experment (to bad im to old for our counties science fair). but i think this would be the spirt of first to try to put one of these things on a robot

19

I decided to look into what this year’s rules have to say. I found one “debatable” against:

The radio modems provided in the 2008 Kit Of Parts are the only permitted method for communicating to and from the ROBOT during the MATCH (except as noted below in Rule and Rule ). Radio modems from previous FIRST competitions must not be
used. The radio modem must be connected directly to the Robot Controller using one of the DB-9 cables provided in the 2008 Kit Of Parts. No other form of wireless communications shall be used to communicate to, from or within the ROBOT (e.g. no Bluetooth devices are permitted on the ROBOT).
I say this is debatable only because the rule is referring to wireless communication, not necessarily energy transfer.

However, it may also be legal:

Additional electronic components for use on the ROBOT must be either COTS items, or assembled from COTS items. Additional electronic components include any object that intentionally conducts electricity, other than Innovation First Inc. relays and speed controllers, wires, connectors, solder, and fabricated printed circuit boards.

I think, if you made adequate provision for isolating the frame and a wired communication to the RC, you might be able to convince the GDC to allow it. However, I also think they would be more likely to not allow it.

20

good point it my be legal and possible but in terms of power use, it looks very impossible in practice.