Modelling and system identification of uninhabited airship with a slung payload

This paper discusses modelling of a multibody system consisting of airship, gondola, and a slung payload. Lighter-than-air vehicles undergo inertial forces that are often neglected in heavier-than-air vehicles. These inertial forces are modelled using added mass and added inertia. The dynamics of the multibody system were first modelled using the Udwadia–Kalaba method. Three constraints were derived and enforced. The resulting equation of motion was used to identify the added mass, added inertia, and inertia of the airship through system identification procedure. The proposed system identification method utilizes semidefinite programming with equality and inequality constraints to find any unknown parameters in the mass matrix of the multibody system. Three experiments were carried out to perform the system identification and validate the dynamic model. The identified mass matrix was used to reconstruct the trajectories of the experiments. Using the experimentally obtained mass matrix demonstrated 35% lower error when compared with simulated trajectories using approximated mass matrices.