Dynamic Modeling and Simulation Analysis for Stratospheric Airship

A complete six-degree-of-freedom dynamic model is addressed for a stratospheric airship. Particular characteristics of the stratospheric airship are introduced. Besides, the airship’s equations of motion are constructed by including the factors about buoyancy, aerodynamic force, and added mass. Based on the model, Dynamic stability analysis, control and response simulation of airship are accomplished. The results show that stratospheric airship is stable both in longitudinal and lateral direction within specific bounds of attitude angles. With the control surface and thrust, stratospheric airship is local controllable. The presented model is feasible and it call be used in engineering practice. Introduction With the accumulation of knowledge and statistics data about stratospheric layer, it is proved that stratosphere is the most peaceful layer in atmosphere with a stead wind and has the protection of mesosphere and ionosphere. Therefore, in recent years, the trend of developing stratospheric platform springs up over a lot of countries [1]. Paiva [2] designed a robust PID controller for airship attitude based on the linear simplified model, the controller combines the robust pole placement techniques to ensure the performance of the closed-loop system response. Acosta [3] designed position PD controller and velocity dynamic inversion controller for Titan airship using feedback linearization method. Hygounenc [4] designed longitudinal motion controller for speed and pitch control, and the result of simulation is presented. Trevino [5] conducted a stability controller for a Tri-Turbofan airship using receding horizon control method. This paper introduces a modeling method for stratospheric airship. Based on the model, dynamic stability analysis, response of control and the simulation results are presented. Modeling of Stratospheric Airship The dynamic modeling method for stratospheric airship is similar to traditional aircraft dynamic model which is addressed from momentum theorem and angular momentum theorem [6]. The most particular property being different from the traditional aircraft is that airship is a kind of buoyancy vehicle. Therefore buoyancy, additional inertia forces and other particular properties should be considered in modeling. To develop a meaningful mathematical model of the airship, it is first necessary to make some assumptions which constrain the problem to practical bounds and which help to provide dynamic visibility by reducing the equations of motion to a reasonable simple level. The assumptions are:  The familiar aircraft dynamic modeling methods apply.  Rigid body motion only is considered, aeroelastic effects are omitted.  The airship is symmetric about Oxz plane, both gravity center and centroid lie in that plane.  The mass of the airship remains constant. The layout of the airships is classical. It has four mutually perpendicular rear fin surfaces, each incorporating an aerodynamic flap-type control surface, and it has two independently controlled thrust vectoring propulsion units mounted either side of the aft end of the gondola. The structure International Conference on Advances in Mechanical Engineering and Industrial Informatics (AMEII 2015) © 2015. The authors Published by Atlantis Press 824 diagram of the stratospheric airship is shown in Figure 1. As in typical aircraft practice, it is convenient to define a right-handed orthogonal axis system fixed in the airship and constrained to move with it. Two coordinate systems are defined in this paper. One is the inertial coordinate system Oxgygzg with the origin at arbitrary point on the ground, the Oxg axis coincident with north and the Ozg axis pointing in the center of the Earth. The other is the body coordinate system Oxyz with the origin at the center of volume (CB), the Ox axis coincident with the axis of symmetry of the envelop, and the Oxz plane coincident with the longitudinal plane of symmetry of the airship.