Investigation into the Time Varying Mass Effect on Airship Controller Performance

Abstract

This paper addresses the significance of airship time varying inertia properties due to fuel consumption on the performance of an airship controller which is developed under the assumption that these properties are insignificant. A previously developed set of nonlinear, 6–DOF airship equations of motion which include the effect of time-varying mass and inertia properties associated with fuel consumption, as well as wind effect, are used. A proportional-integral controller is implemented to compute the three longitudinal control variables (main thrust, main thrust deflection, and elevator deflection) to control the altitude, pitch angle, and speed (relative to air or to ground). The simulation results obtained are both with and without the time varying mass terms in the equations of motion, in both steady cruise and prevailing wind conditions, for demonstration of the differences between the capabilities of a controller developed for a mass invariant aircraft when used in a ”real” airship experience fuel burn-off.