Design of a crash-resistant PD-controlled quadcopter using coaxial propeller system

The versatility of the quadcopter as one of the most flexible aerial vehicle has earned its spot as a favourite for drones and hobby projects. Conventional quadcopters are in use today, which consists of four propellers attached to four motors on the quadcopter body. The propellers are paired such that the opposite pairs rotate in the same direction whereas the adjacent pairs rotate in the opposite direction. The different motions of the quadcopter are produced by the variation of angular velocities of at least one of the four motors. Conventional quadcopters, however, have the drawback in case of a motor failure that eventually makes it prone to crashes. This is because in such event the resultant torque cannot be removed and thus, stabilizing a failed motor quadcopter is impossible. We have provided an innovative coaxial-propelled quadcopter system where we have changed the configuration of rotation of the propellers. In our coaxial configuration, we have opted to rotate all upper propellers in one direction, and all lower propellers in the opposite, consequently canceling out any resultant torque during hover. Our study shows that the motor failure phenomenon faced in the conventional quadcopter is tackled in our system by turning off of the active motor opposite to the failed motor. The solution applied in the proposed system thus resulted in the stabilization of the quadcopter even if one of the motor fails. Our system also shows higher efficiency by producing thrusts at lower angular velocities of the motors.