I have designed a concept for a new type of quadrotor. It can tilt its rotors in any direction using 6 stepper motors. This ability should lead to a quicker response. Another advantage is that it can carry equipment on its side. This quadrotor should fly with its body tilted backwards, not tilting its body but its rotors as it flies. The quadrotor should be able to fly with all rotors turning in the same direction, compensating rotation around its z-axis with the steppers. It looks heavy, but I have found a propeller motor combination on robbe.de that should work, giving 2,4kg thrust.
On the drawing the batteries are on the sides and the camera or tool should be in front. Turning the rotors left and right, the axis is a carbon fibre tube inside another tube.
Comments
good work
From the mechanical point of view:
Don't incline propelers, incline the whole frame. Get rid of these servos or servomotors. You will gain on the wight and also the SW PID part will be easier to deal with. Just put one vertical wing on the frame and incline the whole frame horizontaly when are willing to fly horizontaly as a fixed wing. Who does mind if you incline propellers or the frame? A camera mount? Mount position can be modified.
Don't forget, that the fly speed will be limitted to the propeler design air flow mass speed. I suppose the upper limit at 70mph.
You will have to fork changes to the APM or other SW. Big deal! Don't abandon, get a team! :-)
I'm wondering if the design has potential as a VTOL plane structure... probably go a long way to keeping a light airframe stable in wind when landing.
I chose stepper motors because servo motors have a slight movement in the gears. I have checked on youtube, I thought stepper motors were faster. Perhaps I have to rethink. The motor propeller combination I have found on robbe.de should give 2.4kg using 7V and 17A with 11x10 APC-E and the 4240/12 motor. I imagine that this quadrotor would have a better position stability, even in windy conditions. Complexity is an obvious drawback. The batteries on the sides are not currently mounted to any plastic, but should be. By moving the batteries further to the back, a heavier weight on the front arm can be balanced.
http://m.youtube.com/watch?v=TnGhEInTXYc
Interesting to see something new.
I wonder about the way payload is fixed on the sides in a very unbalanced way...
Actually this design may add redundancy. I would bet this design could handle a single point failure on any motor/ESC. The 2 good cross diagonal motors take up the load and fly like a Chinook helicopter. The angles could be adjusted to maintain stability in pitch and yaw about the new axis about these 2 motors. And the single remaining off axis good motor could go nearly horizontal and tilt up and down to balance the roll moment about the 2 good motors. Just a thought.
Questions:
1. If you're going to get that complicated with the control system, why not just use a helicopter? It's more efficient and has fewer failure points.
2. Why use stepper motors over servos? It would probably could work, but it sounds like a heavy solution with slow response to me.
The fundamental advantage of a multi-rotor is the ability to use a mechanically simple frame and power system and pair them with sensors and a micro-controller to maintain stability. Adding a lot of actuators starts to negate the keep-it-simple advantage that makes them desirable. Additionally, the added weight from actuators and linkages is that much less payload you could be carrying.
In a traditional quadcopter the power system has 8 fundamental points of failure (4x ESC + 4x Motor/Prop). To these 8 points, this design adds 12 more points of failure (6x Stepper drivers, 6x Stepper motor/linkages). I fear adding more failure points without gaining any sort of redundancy is moving in a dangerous direction.
I think it would certainly be possible to make something like this fly, but I'm personally concerned that this is a solution looking for a problem that doesn't exist.
Interesting design! But why stepper motors instead of servo's? There can be some quite big gyroscopic moments from the props also (coaxial propellers could overcome this ). Finding motors + props with enough thrust won't be so hard but the power consumption might be quite high. That's ok if you can take a lot of batteries but all the weight you spend on the tilting mechanisms will be less weight you can spend on your batteries.
Check the flight time before you build it :)