Modeling of 9 Degrees of Parafoil Freedom Through Transverse Displacement of Cargo Weight

Parafoil-cargo system, as a complex system, is used widely today and has various usages. this system is a polynomial complex whose components, have dynamic interactions and relative movements. the present study deals with the multibody modeling and simulation of nine degrees of freedom flight dynamics of a parafoil-payload system, whichincludes the three degrees of transfer freedom and the three degrees of the rotational freedom of the parafoil set (the part with the parachute and the ropes attached to it), and the three degrees of relative rotational freedom of the cargo. by kinematic and dynamic analysis of the system components, a nonlinear model with 18 state variables is obtained. this model has three controlling entrances. in addition to symmetric and asymmetric aerodynamic brakes, the shifting of the weight of the cargo with respect to the parafoil is considered, which leads to the rotation and change of the transverse installation angle of the parachute with respect to the parafoil set. the apparent mass and inertia moment of the parafoil parachute, restraining forces, relative movements between objects, longitudinal and transverse installation angles and also the effect of wind are examined. in order to evaluate how the flight dynamics of the system work and the study of the factors affecting it, the nonlinear differential equations of the model are developed. after examining its stability using lyapanov method, the model undergoes a numerical integration as well as simulation for several flight conditions and under different inputs by the code and program developed in matlab software. the simulation results show the flight stability that is achieved after launching from a high altitude and by which the flight dynamic modeling of the system is validated.