Effects of Canopy-Payload Relative Motion on Control of Autonomous Parafoils

An eight-degree-of-freedom model is developed that accurately models relative pitching and yawing motion of a payload with respect to a parafoil. Constraint forces and moments are found analytically rather than using artificial constraint stabilization. A turn rate controller common in precision placement algorithms is used to demonstrate that relative yawing motion of the payload can result in persistent oscillations of the system. A model neglecting relative payload yawing failed to predict the same oscillations. It is shown that persistent oscillations can be eliminated by reduction of feedback gains; however, resulting tracking performance is poor. A reduced-order linear model is shown to be able to adequately predict relative payload dynamics for the proposed turn rate controller on the full eight-degree-of-freedom system.