The Design and Construction of a Novel High Endurance Compound Multicopter

摘要

A multicopter is a type of helicopter that has more than two rotors/propellers that lift and control the platform. They are inherently agile, compact and robust, making them ideally suited for both indoor and outdoor applications. The main disadvantage is the limited endurance due to the heavy Lithium Polymer batteries and the high disk loading through the use of many small propellers. Disk loading is defined as the thrust divided by the disk area. Large propellers have lower disk loading than smaller ones, resulting in higher efficiencies and lower power consumption, while smaller propellers have faster reaction times in spooling up and down. This short reaction time is crucial for outdoor conditions where wind and gusts are present. The solution lies in the combined use of both large lift propellers and small control propellers resulting in a compound multicopter. We conceived an asymmetrical compound hexacopter configuration that combines two large lift propellers with constant rotational velocity, that lift most of the total hexacopter mass, with four small control propellers configured as a quadcopter. This specific design was developed for flight through narrow corridors for the application of inspecting fruit orchards while flying through and not above them, using sideward looking cameras. Compared to a standard quadcopter, the compound hexacopter has up to 60% more endurance with the same width, payload and battery capacity. A concept validator prototype, named the Demonstrator, has been designed, constructed and successfully flight tested. In addition, other compound configurations are possible. The lift propellers with constant rotational velocity open the door for non-battery driven propulsion: fossil fuel or even fuel cell driven motors, as fast reaction time and large variations in power consumption are no longer an issue. This hybrid version dramatically increases the endurance of (compound) multicopters and vastly expands their capabilities.