It is most definitely illegal to make a custom circuit to convert the DC power provided by the battery into AC power require for inductance. While in theory DC induction could work the coils quickly become magnetically saturated and therefore not useable. Because you can not provide a source of AC power on the robot (or a custom inverter to convert the battery power) you can not use such a method to power your robot.
Now let’s talk about eddy currents. The M.I.T. experiments you cite did not involve numerous large metal objects such as robots. The large magnetic fields involved in transmitting electricity wirelessly will create millions of small whirling currents in an AL frame causing it to heat and sapping energy from the motors. It’s an amazing and innovative idea, but it will be several years before it reaches fruition.
Please provide the rule which would disallow a custom circuit (inverter) that would change DC to a very specific AC frequency. I do not believe you will find one.
There is plenty of energy lost to free space, because the magnetic coupling between the two coils is inefficient. That’ll put an upper limit of about 60% on your efficiency considering only the coils.
In addition to that, the stray magnetic fields (of which there will be plenty) will pass through parts of the frame, and those fields will generate currents in anything that’s made from a decent electrical conductor, like aluminum or steel. This is not speculation on my part, it’s solidly grounded in electromagnetic theory. In fact, it’s the same effect that makes your desired power transfer work - the changing magnetic field inducing a current in the metallic wire of the second coil - but it’s the stray magnetic field acting somewhere you don’t want it to.
Please provide the rule which would disallow a custom circuit (inverter) that would change DC to a very specific AC frequency. I do not believe you will find one.
I don’t think there’s anything in FIRST rules prohibiting converting DC to AC, but transmitting it to another point through the air violates the FIRST-only radio rules.
Just to verify from real life experience, we use AC in one process on our robot this year and have never had any trouble with it in any of our inspections.
As you probably know, we have a data display on the back of our robot. At midwest, the display would go out a lot because the battery voltage often went low when loads were put on it (i.e. traction motors) causing the display to go dim/out. Since the second half of the boilermaker regional, you may have noticed the display now very rarely blanks or dims now.
We put a circuit in line with the power supply to the rear display that takes in the DC voltage from the battery, and runs that into a switching transistor that flips on and off at about 15KHz, generating AC. This high frequency AC goes into one side of a transformer, and comes our the other side at a high voltage. This high voltage is then rectified using diodes, and regulated back down to a (very very clean and stable) 12 volts, while the input can vary anywhere from about 6.0vdc to 18vdc.
If you have any further questions, just come over to our pit in atlanta and ask for Q.
one debate that is poping up every page that i would like to settle is that witricity is not
radio waves
anykind of standard electromagnetic wave (radio, micro, infared, light, UV, Xray, gamma)
it will not be used to control robot
it will not interfere with body
it will not heat up body
the power for the coils will be from the battery not external.
Q,
I didn’t know about the display, but I follow exactly what you’ve done and it sounds like you’ve got a really slick solution to your problem. Nicely done…nice high frequency means small caps at the rectifier output and not a lot of ripple. Probably a lot cheaper and surely more educational than buying a switching power supply. I’ll try to stop by when I get a chance.
That violates <R53> as I read it. You might successfully argue that it’s a non-functional decoration and thus not part of the “robot control system”, but it looks to me like it’s still covered by the “other sensors or circuits” phrase.
I would venture that “altering the power pathways” essentially means that nothing is supposed to go in between the breaker panels and the Victors/Spikes/RC, or between the Victors/Spikes and the motors. What Qbranch describes doesn’t sound like it’s altering the path to some circuit… the supply/display combo IS the circuit. I can’t understand how <R53> could be read to outlaw this… there are plenty of custom circuits teams have used that derive power from the 12VDC system, but end up using something other than 12VDC at the end.
From this post I will assume that witricity is magic not electromagnetic induction.
Everything I know about electromagnetic induction indicates that using two inducting coils would both interfere with and heat the body of the frame. Take any high school physics book and look up eddy currents. The principle is essentially that any piece of metal contains hundreds of conducting loops which will all form currents when in the presence of a changing magnetic field. Such loops will generate heat and suck power from the desired application. You will notice that there was no nearby metal in the M.I.T. test and that the only barrier used was a WOODEN BOARD.
There are various rules that may come into play on this one. Solenoid actuators and transmitting devices other than the radio modems and a specific signaling device for the hybrid mode are specifically prohibited under current rules. And as Alan has pointed out, R53 most certainly applies. As to some of the previous posts, Tesla coils included, all are fairly lossy devices and/or require rather large electromagnetic fields to operate. Although cool and an interesting way of supplying power to rotating mechanisms, they are likely just too inefficient for use on a robot. Please check into the 60 watt light bulb and look closely at the power input required to light the bulb.
BTW, the circuit used to keep the display from blanking for the Kilobytes is considered a custom circuit and does follow the robot rules in that is specifically does not control any motors or actuators on the robot and thus follows R53. In a similar fashion, the power supply that some teams use to power decorations like the CCFL tubes also modifies the power supply but does not connect to any control on the robot.
Ok, I have had a chance to do a little research on the experiment and this is what I found. The stated efficiency is about 40% and the team claims that they will be able to develop a commercial system that will meet FCC safety standards. The demonstrated system ran at 10 MHz.
A few things came to mind while I was reading some of the articles. 10 Mhz is already used for a variety of very important wireless governmental services such as WWV time standards and GPS synchronization signals. Just above this frequency is an amateur radio band that shares the spectrum with other services. So there is more to consider than just safety issues.
As far as use on a robot, this system is being developed for delivery of power and has no provision for tranmsission of control signals, although there are other devices that do that very well. In the future this might be a pretty cool thing to have on the robot if certain other problems are addressed. Keep thinking, we might see this someday.
y’know i think it would be great to use but it is decades ahead of time. I will try to build a prototype of it over the summer if it works then you will hear the post.