a four rotor quad copter needs all four engines/props to be functioning to fly - if either a prop or motor fails the air vehicle rolls in the direction of that engine due to the change in the center of lift and it tumbles out of the sky like a rock. one potential solution to this condition would be to cycle the opposite prop to control the roll but with stop/reverse time it takes to go from lift to negative lift makes that a non-starter. another solution would be to kill the rotor opposite the failed motor, lose yaw control, spin like a top, and descend at whatever rate that your weight would cause at about 1/2 the lift the vehicle might need to maintain altitude; this solution is better than crashing upside down but probably would still result in a high rate descent and a very hard landing. this proposed device shifts the CG toward the new center of lift from the three functioning engines and gives these engines some control over pitch, yaw, AND ROLL.
so, how does it work? if an engine failure on a quad occurs, the flight control computer (a human couldn't do this quickly enough) would issue a command to cut the rubber bands at the red radio controlled solenoids of all but the one that would pull the battery away from the dead engine. because of the planform of the battery the design rotates it as it moves if it needs to move in the direction that aligns with it's long side. the resultant CG shift would hopefully be enough to allow the three remaining engines to maintain a level orientation and perhaps limp back to a graceful emergency landing; worst case would be to descend at whatever rate that 3/4 of your lift would allow depending on the air vehicle weight. the drawings currently are for an 11.5"x11.5"x0.5" frame which would move the battery CG approximately 5"; a smaller frame would also work but not move the CG as much. The battery movement results in a significant CG shift in the direction of the new center of lift.
The color codes on the pictures are -
orange - plate and track for movement in one direction
blue - plate and track for movement in a direction 90 deg from the first plate
yellow - components of the rubber band assembly (red actuators)
green - traveling center post and tray with gearing to turn battery if necessary
pink - wire paths to be used as necessary
if you see a basic flaw in this or have any suggestions i really would appreciate your input.
timmy
Comments
@Chris Anderson.. Have you guys tried what @Thomas mentions above? Just to have an answer?
APM disarms automatically @ 10 seconds without throttle. With Naza it's a bit trickier. There are different modes having different behavior. In general, it should stay in the air if you have the throttle under 10% for a second. That should only disarm when 3 seconds on the ground and throttle <10%. So it's not that bad probably, but I wouldn't recommend testing it out in the air.
There's a TED talk featuring the guy from that robotics lab that does all the crazy quadcopter stuff like juggling and cooperatively building things. In the TED talk, he snips off half of two props, and the machine flies while spinning rapidly.
It looked like he had full control, flying the thing about with no visible issues.
Most multirotor controllers disarm when throttle goes under 10-20%. So it's probably not a good idea to execute this test. If you do, make sure to record a video of the event so we can all enjoy the crash.
Here's a video showing how far a quad can travel horizontally in poor or zero control conditions. I think it's better to just let it drop, take the loss and move on.
https://www.youtube.com/watch?v=zzzSJzCBrm4
and the answer to my question is.....
timmy
one of my questions (i have lots more) is this......
if the quad does a full roll and then finds itself flyable again (engine or esc healed) can it stop rolling and then return to controlled flight? for sake of my question just assume it was a bad solder joint that momentarily caused the esc to not funtion....
timmy
That Bicopter idea seems to be something that could be done. I had an esc failing on a quad and it will flip that quick, that you could take the first flip in an stabilized mode as a detector for the faulty motor diagonal.
its like turning a quad into a bi copter in an instant.
i have a simple solution, give the copter a cg that is lower than the motors, when a motor fails, the opposite cuts and the two remaining go to full power, no need for custom frame
it would simply spin to earth, only modification would be a code that tells it to detect uncontrollable rotation or a code that allows a manual switch off of the motor that is on the plain of rotation
My frame that i custom designed, the motors are 10CM above the central platform and effectively act as a parachute in decent, if i had the ability i would be able to activate two opposing motors and slow decent.
i have a simple solution, give the copter a cg that is lower than the motors, when a motor fails, the opposite cuts and the two remaining go to full power, no need for custom frame
it would simply spin to earth, only modification would be a code that tells it to detect uncontrollable rotation or a code that allows a manual switch off of the motor that is on the plain of rotation
My frame that i custom designed, the motors are 10CM above the central platform and effectively act as a parachute in decent, if i had the ability i would be able to activate two opposing motors and slow decent.
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