Design and Control of a Midair-Reconfigurable Quadcopter Using Unactuated Hinges

In this article, a novel quadcopter capable of changing shape midflight is presented, allowing for operation in four configurations with the capability of sustained hover in three. This is accomplished without requiring actuators beyond the four motors typical of a quadcopter. Morphing is achieved through freely rotating hinges that allow the vehicle arms to fold downwards by either reducing or reversing thrust forces. Constraints placed on the control inputs of the vehicle prevent the arms from folding or unfolding unexpectedly. This allows for the use of existing quadcopter controllers and trajectory generation algorithms with only minimal added complexity. For our experimental vehicle at hover, we find that these constraints result in a 36% reduction of the maximum yaw torque the vehicle can produce, but do not result in a reduction of the maximum thrust or roll and pitch torques. Experimental results show that, for a typical maneuver, the added limits have a negligible effect on the trajectory tracking performance. Finally, the ability to change configurations is shown to enable the vehicle to traverse small passages, perch on hanging wires, and perform limited grasping tasks.

Automated summary

This article presents a novel quadcopter that can change shape during flight, allowing for four different configurations without the need for additional actuators. The morphing is achieved through rotating hinges, and control constraints prevent unexpected folding or unfolding, allowing the use of existing controllers and trajectory algorithms with minimal added complexity. Experimental results show that the limitations have negligible effect on trajectory tracking performance and the ability to change configurations enables the vehicle to perform various tasks.