Wireless Power Transfer For Quadrotors


Quadrotors are great, but what kind of range can you get on them, really? What if you could charge them up just by flying over high voltage power lines, by or temporarily hovering by a charging station? That’s just what [Dr. Carrick Detweiler] wrote a paper about! (Caution: PDF)

The paper discusses the method of wireless power transfer via magnetic resonance, which, depending on the scale, can transfer power at medium distances (~1 meter). This outperforms inductive coupling which requires a much closer proximity (~1-2 centimeters) for power to transfer. It does still require a certain amount of accuracy, but as we all know, quadrotors have no problem with even the most complex aerodynamic feats!

There is an excellent demonstration video of a small scale wireless quadrotor prototype after the break.

Curious about wireless power transfer? We also covered a great article about the theory behind evanescent wave coupling a few years ago!

[Via Hizook]

35 thoughts on “Wireless Power Transfer For Quadrotors

  1. James, please have another cup of coffee and rewatch that video. (Or actually read the paper)

    This research is about using a UAV as an autonomous charging unit to recharge remote sensor stations.

    It has nothing to do with trying to charge a UAV from power lines.

    Stealing power from a power line would use inductive resonance, and would work at a range of several meters.

    The downside is the amount of power obtained is pretty low, so it would be faster to program a UAV to just steal from outdoor outlets instead. (Since you are stealing anyway)

      1. Remember the experiment where you drop a magnet down a copper pipe, and the magnet slows down? The same principles are at work.
        Since you’re causing a load, the power plant has to work harder to push electricity through it.

        The only real difference between stealing from outlets and stealing from power lines is who you’re taking it from.

      2. No. It’s like a transformer. The primary draws little power, until something draws power from the secondary. Or a generator is easy to spin, until you connect a load to it, then it gets much harder. It’s not like light or radio, where the energy just flies through space waiting to be collected, both coils interact.

        The exact details of which, I’m not sure of.

    1. This would be extremely useless if it were to charge the quad. I don’t know what a modern quad draws but my collective pitch can draw over 10 amps at 11 v continuously while hovering which is 20x what this thing can do. Now charging sensors that is cool and actually useful.

    2. I wondered, cos in the diagram why is the load coil on the bottom, and the drive coil on the copter? Seemed kinda massively wrong.

      Still, tiny airborne petrol tanker of the future here we go!

      1. Has any case actually being documented? We’ve all heard of clever farmers keeping a big spool of wire near to power lines and powering his house, but I think it’s an urban legend.

        1. you could get some power running 1000 feet of fencing under a power line and insulating it.. you’re picking up capacitive coupling at 60hz. but you really do need 1000+ feet of fencing to get any significant power from it

    1. Not really. If the devices are in the middle of nowhere, somewhere hard to get to, it’s infinitely easier than sending a person up. Even if the magnetic transfer was inefficient (and I don’t think it is), as a means of getting small amounts of power to awkward locations, can you think of a better solution?

    1. Inductive coupling is like a DC generator, the electromagnetic field is trying to drag the electrons down the wire.

      Magnetic resonance is like an AC alternator or a transformer, the changes in magnetic flux causes a wave of electrons to move through the line.

  2. It would be interesting to see some wireless sensor nodes monitoring the environment for example. Built to monitor and record on very low power and then when the receiver is in range draw enough power to transmit the data back. Effectively like an RFID tag that can program the code it transmits. I can see this having applications at sea and in the air with weather warnings or in space for monitoring with a flyby or perhaps even rovers deploying sensor nets on other planets.
    I would love to see some more information about this. Details on the coupling between the load coil and the RX resonant coil as well as operating frequencies, dimensions, components, extra would be much appreciated. Perhaps an instructible :D

  3. Why does hackaday always warn us away from reading pdfs?
    What is the problem with pdf? Will it break my computer or something?
    Please can we have similar warnings for videos and pictures and complicated words.

    1. PDF is actually a variation of postscript, which is a complete programming language. A lot of viruses have been written to turn a PDF into a nasty delivery system, and many people do not want to open them if they don’t know who wrote it.

      1. there is also a more practical reason like not wanting to waste bandwidth on you smartphone/mobile device if your not gonna be able or wanting to read those pdf while on the move.. (have you seriously ever tried to read a pdf on a smartphone i can tell you its a real pain in the A**)

    1. @kpharck: Acceleration due to gravity is about 9.8 meters per second squared. It’s not a property of the individual pendulum. The relevant properties of any individual ideal simple pendulum in a vacuum are “their mass and pivoting distance,” i.e. moment of inertia.

        1. When considering a compound pendulum mass does factor into the frequency. Given the accuracy of quadcopter aerobatics simple pendulum models probably do not sufficiently describe the motion and won’t work for flight controls

          1. Why don’t you read the paper before making wrong assumptions?
            “Just as the pendulums’ resonant frequency can be determined
            by their mass and pivoting distance, coils can
            be designed to have the same resonant frequency by their
            capacitance and inductance.”

  4. How about simply building a UAV that simply uses very little power to begin with? UAVs based on copter or aircraft designs are going to inherently need alot of energy because must use energy to produce lift to just stay aloft. If you built a uav based on a dirigible or lighter than air aircraft, you’d only need energy for propulsion and could stay aloft much longer before needing a charge. Perhaps such a uav could even all it energy needs from solar energy and stay aloft continuously.

    1. Problems with blimps/dirigibles:

      * Hydrogen is hard to store reliably due to it’s small molecule size making it easy for it to leak out of even steel containers.
      * Manufacturing Hydrogen on-site is a significant safety risk.
      * Helium is a very limited natural resource that is irreplaceable in many important situations such as research and medicine. We are already fast on our way towards depleting the world’s supply of helium and we have no, even remotely, cost effective way to manufacture more.
      * Blimps and dirigibles are extremely slow compared to almost all ‘copter-based UAVs.
      * Even extremely large/massive blimps/dirigibles are well known for being very unstable and uncontrollable in even moderate windy conditions.

      As with anything, this is a case of using the right tool for the right job. Blimps/dirigibles are very promising for situations such as indoor UAVs and extremely high altitude situations (70,000+ feet) where turbulence isn’t much of an issue and high speed isn’t usually needed. The use-case being discussed here isn’t, necessarily, the best fit for them.

  5. Very neat,

    A note of worry though:

    Most modern automatically piloted UAV’s rely on precision magnetometer’s in combination with GPS to maintain position, unless you have image-analysis to back up your position (not as robust) you can end up messing up your Gyro with one of these and crashing :c

    Power lines, magnetic resonance would probably be bad things to fly beside if you have one of these types of UAV’s

  6. Does this mean we are any closer to wireless power transmission inside my house?? :)
    I am okay with accepting the (undocumented?) risks of living inside a powerful electromagnetic field if it means that all of my devices, appliances, etc., “just work” and I don’t have to mess around with power cords or perhaps even batteries. I am jaded, as I read Popular Mechanics and watched sci fi shows growing up……I still don’t have a flying car or robotic personal assistant either, but I will take wireless power for all of my devices….if we are close to that.

    1. Main problem with that, I think, is that power cords just aren’t that bad. Doesn’t bother me plugging things in. Batteries, OTOH, still have some marginal pain. You don’t have to buy as many anymore, now everything’s rechargeable, but auto-charging batteries would be nice. Like Qi, but without having to even bother taking stuff out of your pocket. Your TV remote could charge, or have no batteries at all, as it sat on your couch.

      I’d give that up for a robot chum though.

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