ABSTRACT
In the past few years, the unmanned air vehicle (UAV) has found diverse
applications for both civil and military missions. To achieve the stated mission, the
vehicle needs to have a flight control system. For designing the control system, the
flight control engineers must first develop a dynamic aircraft model and verify its
accuracy. Dynamic characteristics of an aircraft are normally described in terms of its
stability and control derivative values. These values are determined either
experimentally; using flight tests or wind tunnel, or mathematically using
computational fluid dynamics (CFD). The experimental approach is generally very
accurate, but time consuming and expensive. The CFD method takes lots of CPU
time and provides less precision than the wind tunnel testing. In this paper, USAF
Digital DATCOM computer program is used to provide estimation of aerodynamic
stability and control characteristics. Even though DATCOM provides less precision
than CFD and wind tunnel tests, it works much more efficiently by reducing
considerable computing time and design cost. Stability and control coefficients and
derivatives obtained from DATCOM can be used to calculate the coefficients of
state-space matrices. The resulting linear model can then be used for control design
tasks. This paper discusses the step by step procedure for obtaining mathematical
models for small UAVs. This procedure is then applied for modeling a remote
controlled UAV called "Sky Raider Mach 1".