New advances in flight control systems

Abstract

EDITORIALNew advances in flight control systems Flight control systems are obviously very important for vehicles, such as aircrafts, helicopters, satellites, launch vehicles, missiles, hypersonic vehicles, airships, etc. Flight control systems play a crucial role in the stability augmentation of such flight vehicles. In the past, because most flight vehicles were assumed to be a rigid body, the flight control systems were generally transformed into linear systems by linearization. Consequently, traditional control methods proposed for flight control systems were mainly concerned with PID or gain scheduling-based techniques.With the higher requirements placed on aeronautical and space systems, in both transient and steady state phases, the required control performances expected from the flight control system has become more demanding. In this case, the PID-based algorithms are not satisfactory. In fact, with the expanded flight envelope of modern vehicles, the dynamics of such vehicles are inherently nonlinear. These nonlinearities include couplings, uncertainties, unmodeled dynamics, etc. The performance of the flight control systems to some extent is dominated by the aforementioned nonlinearities. If the nonlinearities are not very prominent, PID-based algorithms may be still sufficient. However, when the nonlinearities are prominent, for example, when flight vehicles perform a large aggressive maneuver, the nonlinearities will play a dominant role in the dynamics and, in turn, affects the performance of the flight control system. Under these circumstances, robust nonlinear control algorithms are necessary. The objective of this special issue is to bring attention to the latest advancements in flight control systems. With this goal in mind, we have invited several well-known researchers to present their recent research results in robust and nonlinear controls. The special issue consists of six papers that cover several different flight control systems. Garcia and Keshmiri[1] consider the safe control of the Meridian unmanned aerial system with abnormal conditions. A novel adaptive nonlinear model predictive controller is proposed and conceptually proven to ensure safe control of the Meridian unmanned aerial system in offnominal conditions. Controller performance is improved by updating the physics-based model by using real-time nonlinear estimation of aerodynamic forces. The authors also show that the proposed predictive controller coupled with real-time parameter identification, exhibits robust characteristics and successfully mitigates the impact of nonlinear and unsteady aerodynamics while preventing loss of control. The guidance control problem for a small unmanned aerial vehicle (UAV) is proposed in Liu, McAree, and Chen [2] so that the UAV will perform path-following under wind disturbances. A disturbance observer-based control approach is adopted. The wind information is first estimated by a nonlinear disturbance observer; then, it is incorporated into the nominal path-following controller to formulate ...