Electro-permanent Magnets For Quadcopters


Imagine a quadcopter hovering above a payload – a can of beans, perhaps. The ‘copter descends onto the payload, activates an electromagnet, and flies away with a hobo’s dinner. Right now, this is a bit of an impossibility. A normal electromagnet that powerful would consume an amazing amount of power, something quads don’t usually have in abundance. With the OpenGrab project, the dream of a remote-controlled skycrane is within reach, thanks to some very clever applications of magnetics.

The tech behind the OpenGrab is an electro-permanent magnet, basically an electromagnet you can turn on and off, but doesn’t require any power to stay on. OpenGrab was heavily influenced by a PhD thesis aimed at using these devices for self-assembling buildings.

This project had a very successful Kickstarter campaign and has seen some great progress in the project. While beer doesn’t come in steel cans anymore, we can imagine a whole lot of really cool applications for this tech from infuriating electronic puzzles to some very cool remote sensing applications.

40 thoughts on “Electro-permanent Magnets For Quadcopters

  1. I read beans as beer. Everything made since except how a magnet could pick up an aluminum can…

    I was also disappointed by the electro-permanent magnet. I was hoping for a rare earth strength magnet that you could turn on/off at will. Wrapping an electromagnet around a permanent magnet then applying an opposite field to cancel/dim or increase the magnet’s force, while very cool and hugely practical in this case, is only an always on rarely off device. I was hoping for a stay on or stay off device. Still very cool!

    1. The hobo could be in Europe and be unlucky enough to have a steel can, then he lost his beer to the diabolical hacker.

      Just got back from a Wiki-frenzy because I thought I remembered some beverage cans being magnetic. Turns out they use to be. I would blame you this Wiki-tangent, but they happen all too often.

      1. More usefully:

        “An electropermanent magnet is a solid-state device which allows an external magnetic field to be modulated by an electrical pulse. No electrical power is required to maintain the field, only to do mechanical work or to change the device’s state. The electropermanent magnets described in this thesis contain two magnetic materials, one magnetically hard (e.g. Nd-Fe-B) and one semi-hard (e.g. Alnico), capped at both ends with a magnetically soft material (e.g. Iron) and wrapped with a coil. A current pulse of one polarity magnetizes the materials together, increasing the external flow of magnetic flux. A current pulse of the opposite polarity reverses the magnetization of the semi-hard material, while leaving the hard material unchanged. This diverts some or all of the flux to circulate inside the device, reducing the external magnetic flux.”

        IN other words, current is not needed to keep it off either. Only to change states.

    2. Actually, the electro-permanent magnet has both a “hard” (permanent) and a “semi-hard” (i.e., magnetizeable) core. The magnetization of the semi-hard core can be switched using the coil, and will keep its magnetization after current has been applied.

      The upshot is that you literally get a programmable magnet where the external magnetic field can be scaled between zero (semi-hard core magnetized opposite to the permanent magnet, so all the field lines loop around inside the device), to roughly twice that of the permanent magnet. You don’t need any energy to keep the device in the OFF state, and you don’t need any energy to keep in the ON state – just to switch between the two.

      Here’s a nice explanation:


    1. hmm let’s see:
      solid state electronics vs. a mechanical solution.

      Whatever force the magnet holds up with (say it’s 10kg like this one) you’re going to need your mechanical solution to just as much force (even with a wedge, you’re just making the instantaneous power lower, but making it last longer). That’s gonna take a bit of power.
      I would suspect that would use much more power than the electronic solution.

      lastly, reliability: in the short term a mechanical solution might not always remove the object. The electrical solution has a much lower rate of failure. (or if they’re similar, the electrical solution would cost a lot less.) In the long term, a mechanical solution will certainly wear out faster than an all electrical one.

      So while it may seem simpler (and the concept of how it works definitely is), there are many many reasons why the electronic solution is much better.

  2. The most efficient way to have a powerful magnet on a quadcopter without the use of much power is through magnetic shielding. This is accomplished by having N52 Neodymium magnets attached to the the bottom of the ‘copter. next there must be magnetic shielding panels attached to servos to maneuver them in front of the magnets(to stop magnetism) and also to the side of the magnets (to enable magnetism). below the magnets and shields there should be placed a steel plate for objects to be forced onto. the steel plate is influenced by magnetic field of the neodymium magnets, protects the magnets, and provides the gaps for the shields to slide. the gapping should be very tight (less than 1/16″) between the magnets, the shields, and the plate.

    the plate will eventually become magnetized just from being in such close contact with powerful magnets for and extended period of time. so even when the magnets are shielded, it will still cause some things to stick to them. however, one would assume that this would not affect the performance with heavier objects.

      1. Oh, well that just sparked a brilliant idea. I’ll just have to call it something, let me see… what about… the self perpetuating system inducing continuous and constant kinetic energy! It is just so brilliant I’m sure no one would have ever tried it before.

    1. there are no fail secure electromagnets. fail secure locks are latched, the electromagnet releases the latch when there is power.
      maglocks (the ones that magnetically hold the door) are always fail-safe (meaning the magnet is not holding the door if it loses power).

  3. Whoa whoa whoa…..

    Who says you need lots of power? I’ll let Mr. Wizard show you a 2 pound magnet holding up a 100 pound boy…..with a single AA battery. Scale the magnet down, and bingo….

    Skip to 2:10

    1. If you read the Hizook.com article (linked elsewhere), you’ll notice that the electropermanent magnets originated from 1960s era Bell telephone equipment. No one is making claims about “inventing” anything… just re-purposing..

  4. 2 permanent magnets + with C shaped piece of magnetic perminable material to “turn” the flux around so it flows out of one. + a keeper bar. Remove/replace the keeper bar and you’ve got your “switchable” magnet. Force is produced in same way as that of a solenoid. Put a wedge on one side of the magnet if you want to force a stuck object off the magnet.

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