Dynamics Modeling And Simulation Of Tethered Stratospheric Aircraft

The super-pressurized balloon platform and its trajectory control method exploiting the differences of wind velocity between different altitudes is presented. The dynamics of the tethered stratospheric aircraft including the super-pressurized balloon, the tether and the tethered trajectory control system is analyzed and modeled. A feasible method of equilibrium point estimation is proposed according to the characteristics of the entire flight system. A dynamic simulation of the modeled system using Matlab/Simulink is provided in this thesis, and a feasible linearization method is proposed. The main contents of this thesis are as follows:The development and actuality of stratospheric platform are introduced, and the necessities and importance of conducting a research on super-pressurized balloon platform and its trajectory control are depicted subsequently Then the tethered stratospheric aircraft consisting of the super-pressurized balloon, the tether, and the tethered trajectory system is summarized, and a terse analysis of the modeling difficulties existing are provided. The dynamics modeling method of Lagrange's Equation, which is usually used in multi-link system, and its infeasibility in the application of modeling herein, is indicated. Then a feasible modeling method is proposed. The modeling of the tethered stratospheric aircraft adopts a thought as the following: analyzing the characteristics of the flight system from an overall perspective using a model of lump-mass-and-spring, considering the super-pressurized balloon and the tethered trajectory system as the tether nodes, and creating mathematical model for each part of the flight system respectively according to its characteristics while integrating all parts through 'interface'. The equilibrium point of the flight system is defined, and the difficulty of equilibrium point estimation is analyzed, and a feasible method of equilibrium point estimation through trend line, which does not depend on the number of the segments of tether, is proposed. The interfaces linking each part of the flight system is analyzed, and each part of the system is encapsulated rationally. The Matlab/Simulink simulation model is constructed according to the mathematical model, and the dynamic simulation result is provided. This simulation model does not depend on the segments of the tether either. Finally, the atmosphere density model and the wind velocity model is simplified aptly, and then a feasible linearization method serving as a preparation of the future study of control strategy, is proposed.