Computational Study of the Flight Dynamics, Stability andControl of an Unmanned Aerial Vehicle in an IntegratedSimulation Framework

摘要

In recent years, modeling and simulation tools have been used extensively for the development and assessment of various flight vehicles. This paper presents an attempt at developing an integrated simulation framework encompassing aerodynamics, flight stability and control analysis for fixed wing Unmanned Aerial Vehicles (UAVs) and its application to the study of flight stability and evaluation of the flight control systems in the design/modification process of the UAV. The objectives of the framework are to understand flight instabilities experienced by the UAV and to propose solutions for the flight stability and control problems via this integrated framework. The core of the framework involves the incorporation and integration of the UAV aerodynamic characteristics, flight stability and control derivatives and digital flight control system into a six degree-of-freedom flight simulation model, the outputs of which are visualized graphically. The framework has options for de-coupled longitudinal and lateral stability analysis based on the small disturbance theory to understand the stability modes of the UAV as well as a coupled longitudinal and lateral stability analysis to study the effects of the aerodynamic coupling caused by the single propulsion system to the stability and control characteristics. The model is created within the programmable software environments of Matlab, Simulink and Aerospace Blockset which are used to construct the six-degree-of-freedom model for the dynamical motion of the UAV. The inputs to the model include the aerodynamic information based on the aerodynamic characteristics, stability and control derivatives, engine characteristics, flight variables and atmospheric disturbances. The outputs sought are the responses of the flight variables depicting lateral, longitudinal and directional stability characteristics of the UAV and are generated within the framework. Virtual Reality based systems such as the FlightGear software are then used as a graphical interface for displaying the UAV flight paths, the orientation of the vehicle and the stability and control characteristics of the UAV computed from the results. With this framework, it is possible to assess the impact of flight control system and its modifications on the stability and control of the UAV during the design phase.