Abstract:
This paper presents a concept of a multi-copter that can be reconfigured between a quadcopter, hexacopter, octocopter and decacopter. The maximum useful weights of the octocopter, hexacopter and quadcopter, were 77%, 55% and 32% that of the decacopter. The controls for each of the configurations are identified and for the configurations with control redundancy, the power optimal controls are presented. A dynamic simulation model is implemented and used to compare the various configurations. Over a range of aircraft useful weights, it was observed that the decacopter required minimum power when the useful weight was greater than around 30% of its maximum, due to lower induced and profile power requirements of the lighter loaded slower spinning rotors. At lower useful weights, the hexacopter required less power due to its significantly lower empty weight. The octocopter and quadcopter did not emerge as low-power configurations of choice. Increasing the number of rotors increased the maximum hover endurance. At a useful weight corresponding to 53% of the decacopter's maximum useful weight, the decacopter's hover endurance time was 9% higher than that of the hexacopter. At low useful weights, the maximum pitch and yaw accelerations generated by the hexacopter were around 80-95% higher than the decacopter, but at higher useful weights the decacopter's accelerations were around 60% higher. All multi-copter configurations displayed a longitudinal and lateral phugoid mode in hover. Compared to the hexacopter, the phugoid modes for the decacopter had significantly higher components of surge rate compared to pitch rate, or sway rate compared to roll rate, while the modal damping ratios were 20-40% lower.