Design And Control Of A Passively Morphing Quadcopter

This paper presents a novel quadcopter design that uses passive rotary joints to enable rapid aerial morphing without the use of additional actuators. The normally rigid connections between the arms of the quadcopter and the central body are replaced by sprung hinges that allow for the arms of the quadcopter to fold downward when low thrusts are produced by the propellers, resulting in a reduction of the largest dimension of the vehicle by approximately 50%. The ability of the vehicle to reduce its size during flight allows, e.g., for the traversal of gaps through which a non-morphing quadcopter could not pass. The vehicle is designed such that existing quadcopter controllers and trajectory generation algorithms can be used, provided that some additional constraints on the control inputs are met. The nonlinear dynamics of the system are presented, and design rules are given that minimize transition time between configurations and maximize the available range of control inputs. A method for performing gap traversal maneuvers is proposed and validated experimentally.