Octo X8 Coaxial - testing motor redundancy

Testing the octo without 1 of the top motors and then 1 of them bottom motors to check what's happens if a prop/motor/esc gets bad during flight.

Previously I've done the same test with a flat hexacopter and an Y6 but they didn't performed very well.

With a flat octocopter, if it looses 1 motor/esc/prop it's barely affected. I was flying my octo and it lost a blade of a prop but I just noticed after I landed.

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Comment by eduardo on August 7, 2013 at 12:49pm

Here are a test with my own rotorcraft controller using ADAPTIVE STABILIZATION.

http://vimeo.com/14367712

As you can see it fly perfect without one arm.

Try this with arducopter and you see that it not work good because ACM not use adaptive stabilization.

Comment by Boris Rabusic on August 7, 2013 at 1:32pm

eduardo, 

it's not actual test since you removed one arm and motor, plus you put one battery to be counter weight on opposite motor.

Real test is to do it:

-in midflight (using remote switch for pwm signal)

-with full load

That is real world test.

I've done it on Naza with hexa and flat octa.

When fully loaded (5 kg), hexa will land, but not so much controllable. Octa is ok.

Comment by eduardo on August 7, 2013 at 2:03pm

Boris, i do more tests with camera and gimbal and 10amp battery on the same frame and it fly very good.

Some time i am fly 500m away and when i land i see that the hexa is flying without one prop.

As you can see this is an very old video. I do this video when i testing my adaptive code. Its only to test the code.

I do the same test with other motor OFF.

BTW, i not removed the ARM ... it broken

Comment by Bernardo M. A. on August 7, 2013 at 3:12pm

Very nice eduardo ;)

I've already done that with MegaPirateNG using a flat hexa and I couldn't take off although it had been hovering with half throttle stick. (I didn't modify the hexa, just disconnected the ESC cable)

When I tried the Y6, it worked partly. I could take off only when specific motors were disconnected.

Comment by Boris Rabusic on August 8, 2013 at 12:29am

eduardo, great, if your adaptive stabilization is better then one in arducopter please share it with arducopter developers

Comment by Vince Hogg on August 9, 2013 at 7:01am

Bernardo.

Thanks for experiment, its interesting to see. Not many people are testing with a motor failed.

I have been designing a new copter and nearly went for x8 but was concerned a lower failed prop might windmill and cause drag. Im glad I went for flat octa.

 

I think it would be possible to write much more motor failure tolerant code (perhaps not on APM). I think it may even be possible gently descend a quad with a failed motor if it was yawed very rapidly to stop it from flipping.

Comment by eduardo on August 9, 2013 at 2:12pm

On quad its impossible to fly without one motor.

Only using some kind of variable pitch or reversing motor this redundancy will be possible.

I tried this type of redundancy 2 year ago without success.

Comment by Bernardo M. A. on August 9, 2013 at 2:42pm

Somebody has told me that there's a code that allows a emergency descent with the quad if 1 motor gets bad but i don't know if it's true.

If you could spin it in yaw very fast it would create a gryoscopic effect that would mantain it leveled although you wqould be running just 3 or 2 motors but i don't know if it's pratical

Comment by Juan Carlos Hdez on August 9, 2013 at 3:45pm

I think I've seen that, spin very fast.

Comment by Vince Hogg on August 9, 2013 at 4:00pm

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