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
i uploaded the model to the Sketchup Library if anyone wants to play with it.... just search for "Quadcopter Mass"
timmy
or you could power up the "anti-gravity" module.....
timmy
Gerard,
best idea so far imo, would be interesting to think about the mechanics of such an arrangement, I will be thinking about this :) Perhaps, even a mechanical mount concept which detects a failure of motor torque and lift at the same time to activate it to swing the arm up (or down) and over placing the motor as close to the opposite side as possible?
"collapse" sounds too tame. blow it off with a pyro - that would be a lot quicker and more fun.
timmy
yours is basically the same mass movement concept but you would have to make sure it worked in both x and y directions. depending on which engine fails you you have 4 possible directions you have to move the CG not just 2.
timmy
Well, another approach would be to collapse an arm of a failing motor. The CG in this case would drop down and move horizontally to a center closer to what those props can lift automatically without a lot of complicated science of machinery.
bad picture 2 - hope these are not displayed full size that would be unfortunate for everyone -_-
The best way to do this is to actually incorporate a moving mass concept into the design of the vehicle itself as opposed to an add on. if you had most of the support "stuff" on a moving plate you wouldn't have to move it so far and all the wiring would move with it. basically, make this the frame of the vehicle. it has bothered me for some time that there hasn't been a solution for single engine quad failure when the physics are so easy?
timmy
Very interesting. Moving the center of mass to allow some control effect is a great idea.
Another way might be to have batts supported laterally on a boom, with the mounts attached with cable attached to a brushless motor so in this situation the controller could simply slide a batt accross using the cable and even rotate the battery mount boom to position the center of mass efficiently. The rotating battery mount could even be used as the basis of a pan gimbal under normal operation - Ill try draw up an example of what I mean.
It seems the counter weight would have to be quite heavy to counteract the loss of the motor.
I assume this only works in a very stable flight mode correct? If you're flying around or doing anything remotely acrobatic, you'll get forces that might resemble a bad motor unless somehow you are able to detect if a motor went out.
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