Electro Permanent Magnet for reliable cargo lifting on a quad (kickstarter)

Small light Open Source/HW electro-permanent 10kg (ideal) cargo holding magnet for the DIY multicopter drone and robotics communities

I stumbled upon this idea by reading this great article by Travis Deyle about electro-permanent magnets. These magnets are programmed (on off) with a current pulse. No static energy is required. Changing the magnetic field does require energy and is in the hundreds of mJ for our purposes. These electro-permanent magnets are just as strong as Neodymium magnets.

pdf link to the PHD thesis covering this is on the project page

there been a lot of concern of magnetic interfence with the compass, so here is the spiel

there should be no external field since the field lines are closed through the cargo iron in the on state or through the iron in the device itself.
in the prototype the iron goes beyond its saturation, the thickness should 1mm not 0.5mm same goes for the target. looking at the theoretical performance and the prototypes performance about half the field leaks, eg are not going through the metal. i expect the leakage to go down to below 10%.
a laser cut iron cover covering the magnet itself with some distance in the 5mm range,  less 0.1mm thick will absorb the rest of the leakage. we should have a factor of 100 maybe 1000 that we can reduce the external field before one has to invent crazy things. mu metal might give us a few orders of magnitude more, but since its low saturation and some other factors i need to the math to get a quantitative idea on its performance.

long story short simple easy to implement shielding with proper construction should allow one to mount the compass right on top of the magnet

I hope you like my project and am looking forward to some feedback

http://www.kickstarter.com/projects/412473553/opengrab-open-hardwar...

Views: 2599


Developer
Comment by Rob_Lefebvre on November 27, 2012 at 11:04am

I backed this a few minutes after I saw it.  This will be a great way to do cool things with payloads!

Comment by Todd Hill on November 27, 2012 at 11:39am

That's sweet.  I have been trying to trouble shoot a means for grasping objects as well.  However, I am trying to use the legs of my copter.  You can see the direction I am trying to go with this in the most recent photos I uploaded.  I was afraid of adding additional magnets to my copters, but this look promising.  


Moderator
Comment by Ruwan on November 27, 2012 at 12:12pm

Great project. Backed! 

Comment by Travis on November 27, 2012 at 6:55pm

EP Magnets are AWESOME.  I wrote an extensive article about them over on Hizook a while back that explains the physics.  Go check it out:  http://www.hizook.com/blog/2010/12/07/electropermanent-magnets-prog...

Comment by Eric Lewis on November 27, 2012 at 8:04pm

As stated in the article The issue of the magnetic field interfering with the compass may be a deal breaker. Maybe some good mounting of hardware can overcome the issue.

Goodluck

Comment by Helldesk on November 27, 2012 at 8:21pm

How much does mu-metal cost? Covering all but the business end with such plating might attenuate the magnetic field a little bit. Also, can the current compass library learn two different states of a source of static magnetic interference?


Developer
Comment by Rob_Lefebvre on November 27, 2012 at 8:54pm

We've discussed this elsewhere, but I believe it to be a non-issue.  As long as the magnet is far enough away from the APM.  We'll see, but I'm confident it's either not a problem, or easy to solve with MuMetal.

I have HUGE magnets in the 3800W motor on my heli, and it's not causing a problem.

And the pulse, worst case you'd get a little blip of yaw.

Comment by Jack Crossfire on November 28, 2012 at 1:04am

No fair that my fully assembled $50 twig didn't get funded, but the electromagnet does.

Comment by Andrew Bremer on November 28, 2012 at 2:01am

That design looks awesome dude - I've thrown $45 at it so far! Also, how heavy is the magnet assembly itself going to be out of interest?

Comment by Jean on November 28, 2012 at 4:05am
@Andrew "The complete device will have a mass of about 50 grams capable of holding a mass of 10kg in optimal conditions, in practice it should securely hold 1kg of cargo on a quadrocopter."

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