Research on Lateral-Directional Dynamic Characteristics and Control for Large Envelope Flight of Modular Aircraft

The linear parameter varying (LPV) system model of the lateral-directional dynamics for large envelope flight of modular aircraft including various configurations was built. The validity of the aircraft LPV model was verified by the comparison of dynamic simulation between the LPV model and the nonlinear model. The lateral-directional dynamic characteristics under different configurations of modular aircraft in large flight envelope were studied. The stability augmentation system (SAS) for the inner loop and the self-scheduled parameter adjusting H∞ robust controller for the outer loop of the control system were designed based on the lateral-directional dynamic LPV model of modular aircraft to guarantee the control effect for aircraft lateral-directional motion. The closed loop system was simulated and the simulation results indicate the integrated control system could achieve precision tracking of modular aircraft lateral-directional command signals under different configurations in large flight envelope. Introduction Modular aircraft is considered to be the multi-role unmanned aerial vehicle (UAV) that could satisfy future demands. It consists of several demountable structural modules and employs compatible modules to accomplish different military missions, which improves operational efficiency of the aircraft conveniently and swiftly. Due to different aircraft configurations caused by different wing modules, the dynamic characteristics of the aircraft will change substantially, and there will also be a substantial change in aircraft stability and manoeuvrability. In addition, the flight envelope of modular aircraft is larger than the single configuration aircraft. The aircraft stability and manoeuvrability will change greatly as the flight velocity and altitude change. As a result, it is of significance and necessity to analyze the dynamic characteristics of modular aircraft under its different configurations in the large flight envelope. The lateral-directional dynamic characteristics of modular aircraft vary substantially under different configurations, and the flight envelope gets larger. The classic control method designs particular controllers at multiple working points and then employs gain-scheduled methods in the flight envelope according to the flight parameter to obtain the final controller. But when it comes to modular aircraft, the controller should change according to not merely the flight parameter, but the configuration as well. In this situation, using the classic control method would result in very tedious work when we design modular aircraft lateral-directional controller, nor would it guarantee robustness of the system. So the classic control method could not satisfy the control demand for modular aircraft. As a result, it becomes an urgent problem to design the flight control system for modular aircraft in large flight envelope to realize the flight control objectives. One practicable way is to describe the dynamic equations of the modular aircraft by a LPV model, and then employ self-scheduled parameter adjusting control methods based on LPV model to implement the control [1-4]. The merit of this method is it treats the gain-scheduled controller as an integral. Because the parameter-dependent controller would make self-scheduled adjustment, the 1 Advances in Engineering Research (AER), volume 105 3rd Annual International Conference on Mechanics and Mechanical Engineering (MME 2016) Copyright © 2017, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). design of tedious planning and scheduling could be eliminated [5]. In this paper, the research object is the lateral-directional motion of modular aircraft. The lateraldirectional dynamic LPV model of modular aircraft is built. And the modular aircraft lateraldirectional dynamic characteristics under different configurations in large flight envelope are mainly studied. According to the features of modular aircraft, the self-scheduled parameter adjusting control method is designed for the aircraft lateral-directional control system based on the LPV model of it. Simulation is implemented to verify the controller’s ability to realize precision tracking of modular aircraft lateral-directional command signals in large flight envelope. Features of Modular Aircraft Modular aircraft has demountable wings. The high-aspect-ratio straight wing is used under longendurance configuration for surveillance missions, while the low-aspect-ratio swept wing is used under high-speed configuration for strike missions. The stability and manoeuvrability of modular aircraft will change substantially due to the change of the configuration, because the wing area, sweep angle, area and position of control surface and other factors will be different under different configurations, affecting aircraft dynamic characteristics. Modular aircraft has a wider range of flight envelope compared to fixed configuration aircraft because of its multiple configurations. Because aircraft aerodynamic derivatives vary according to the change of flight velocity and altitude, there will be a bigger change in the stability and manoeuvrability of modular aircraft in its flight envelope. The schematic diagram of the two configurations of modular aircraft is shown in Fig. 1 and the flight envelope is shown in Fig. 2. Fig. 1. Schematic diagram of different configurations of modular aircraft. High-speed configuration Long-endurance configuration