Design, modelling and control of collaborative samara autorotating wings (SAW)

Abstract

Current methods of airdropping payloads accurately use the autonomously guided parafoil systems. Such approaches have limited trajectory options, hence limited accuracy, and could deliver only one payload with one airdrop. The Samara Autorotating Wings (SAW) is disposable type of aerial deployment system proposed in this paper to drop light-weight electronic payloads to remote locations accurately. Using autorotation as its main technique of lift creation, the concept borrows the natural dispersion method from maple seeds and takes advantage of the gyroscopic stability of a spinning mass. It does not require any propulsion system on-board and is equipped with an actuator to change the angle of attack of the wing for directional control. The concept also features a collaborative autorotation mode whereby multiple wings are attached together to form a larger rotor hub that benefits from increased angular momentum and control authority which is especially important at higher altitudes where the air is less dense. Although there have been other works on using autorotation to deliver payloads, this is the first documented effort in using a collaborative form of autorotation. The chordwise geometrical wing shape of SAW is optimized to achieve the maximum lift force during its autorotating descent. A nonlinear control method is conceived to regulate the descent direction and speed of SAW. This proposed control scheme enables an omni-directional guide slope, allowing SAW to be more maneuverable than parafoils or fixed-wing type of aerial deployments. SAW with different numbers of wings are tested against each other for drop characteristics and control performance, in simulated models and in physical experiments that involve a vertical wind tunnel with and integrated motion-captured system and free-fall drop tests.