<p>Experimental comparison of the effect of the number of redundant rotors on the fault tolerance performance for the proposed multilayer UAV & nbsp;</p>

In this paper, experimental investigation of the flight performance of the proposed universal Unmanned Aerial Vehicle (UAV) in case of rotor failures is presented. In the experimental flight tests, proposed universal UAV that can be converted to many different configurations due to its non-standard multi layer structure was used in two different configurations as a standard octorotor and a multi-layer dodecarotor. Multiple outdoor experiments are conducted to show flight safety and reliability of the proposed UAV in terms of rotor failure tolerance. In order to evaluate flight safety and reliability of the proposed UAV, take-off, hovering and landing flight performance analyzes were performed in cases where one or two motors/propellers were completely lost. As performance criteria, errors in the UAV's roll, pitch and yaw angles, altitude error and vibration in three axes were determined. The flight test results are presented both numerically and graphically. According to the results, multi-layer dodecarotor type has shown a more stable flight performance in terms of angular position errors. In addition, in both types of UAVs, in the case of failure of two rotors rotating in the opposite direction, it has been observed that the error in yaw angle is less than a rotor failure, as expected. Likewise, in the case of failure of two rotors rotating in the same direction, performance loss was observed in the control of yaw angle. (C) 2021 Published by Elsevier B.V