Precision Modeling and Optimally-safe Design of Quadcopters for Controlled Crash Landing in Case of Rotor Failure

The seminal work cited in [1],[2] showed, for the first time, that flight stability of quadcopters would be possible in case of one or even multiple rotor failures. However, the quadcopter can remain airborne only by going through a spinning maneuver about an axis, fixed w.r.t the vehicle (i.e., resolved yaw). Furthermore, positional control can be achieved by periodically tilting this axis. This paper builds upon this concept with two major improvements: (1) introducing a precise aerodynamic model of propellers that takes the flapping torque due to unbalanced lifting force in the advancing and retreating blades subjected to freestream, into account, and (2) adding to the stability and flight efficiency of the quadcopter by introducing symmetric fixed tilting angles to the trust vectors. In our previous work [3], it was shown how the flight stability and energy efficiency can be improved by introducing fixed tilting angles in the thrust vectors. For controlled crash landing in case of one rotor failure, where a resolved yaw maneuver would be inevitable, introducing a titling angle in rotors can generate a reasonable resolved-rate-yaw spinning speed to keep the quadcopter airborne at a lower rotational speed of the blades by taking advantage of the freestream generated by spinning. This tilting angle would also lead to passive stability in yaw motion of the quadcopter before the failure. Our hypothesis was successfully tested via simulations.