Stability Augmentation for Crosswind Landings Using Dynamic Cell Structures

Abstract

This paper presents a Dynamic Cell Structure (DCS) based flight control system capable of enhancing lateral stability of aircrafts during severe crosswind landings. Two hybrid control systems are proposed. The first control system involves a Proportional Integral Derivative (PID) component and a modified DCS while the second control system involves a Non-linear Dynamic Inversion (NDI) component and a modified DCS. Three important changes have been made to the original DCS learning algorithm to increase the speed and accuracy of offline learning on the DCS. The classic gain controller within the NDI block is replaced with a PID component. Readings from the localizer of an aircraft are used to form a 2-dimensional input space and supplied to the control system in order to generate appropriate control surface deflections. The aim of the control system is to generate accurate control surface deflections such that precisely sufficient roll is produced to keep the aircraft along runway centerline (as required by the maneuver of crab landing). Simulations are carried out using a Piper PA-46 Malibu on the X-Plane simulator with the proposed control systems, and compared against the performance of the lateral stability component of a baseline PID system, dual-PID control system as well as that of a PID-NDI control system. Both the DCS-based hybrid control systems have shown tremendous improvement over the baseline PID system. Of all the systems compared, the DCS-NDI hybrid provides the best performance in terms of convergence time and average deflection from runway centerline. However, the computational complexity involved in the NDI block calls for a high performance system that can perform these complex computations in realtime. Considering the systems without an NDI component, the DCS-PID hybrid provides the best performance. The DCS-PID hybrid involves lesser computation as compared to the DCS-NDI hybrid, and performs better than the dual-PID control system. At high, yet realistic crosswind speeds of 50kts, both the proposed hybrid control systems are capable of converging to and maintaining runway centerline whereas the baseline PID system fails.