A Study on Motion Control System Design for an Unmanned Aerial Vehicle with Single Ducted-Fan

Abstract

In the modern technology era, the development of automatic flight control and technologies directly applied to the military and civilian fields have gradually evolved. Since the early 1950s, several types of technology of unmanned aerial vehicles (VTOL UAVs) have been researched such as helicopters, quadrotors, missiles, etc. Among them, the single ducted-fan unmanned aerial vehicle (DUAV) technology has grown based on its characteristics. Moreover, the single DUAV system has successfully demonstrated departures from unprepared sites, ship deck spaces, moving trucks, and so forth, because of its high maneuverability and efficiency in flight trajectory. However, the ducted-fan vehicle has been normally subjected to turbulent environments and gusty winds. The single DUAV system is mainly required to accurately follow a predefined trajectory, especially, the landing process should as well be considered as one of the most important aspects in the development of control systems. Obviously, the landing operation is defined consist of lowering the altitude and performing the yaw motion. However, the aerodynamic forces and moments which acted on the single DUAV including several elements as air conditions of the environment often appear uneven aerodynamic forces. And, other parts are constants such as body force, buoyancy, and so forth. They result in high nonlinearities, parametric uncertainties, and unknown disturbance and make the motion control difficult. Particularly, the high nonlinearities—unpredictable factors, for instance— can lead to the single DUAV’s instability. To cope with these issues, this dissertation aims to present a new studying control strategies for the altitude and the yaw angle motions in the landing process of the single DUAV by proposing mathematical modeling and designing control methods with several approaches. In this dissertation, instead of modeling the directly entire dynamics motion of the whole single DUAV system, the proposed modeling strategy based on the decentralized and motion controls is designed. These targets are completely carried in this dissertation out as follows Firstly, the description and mathematical model of the single DUAV system are greatly illustrated. The configuration of the single DUAV system consists of mechanical and electrical designs, and a prototype is developed for experiment tests. Accordingly, the decentralized model of the altitude and the yaw motion of the single DUAV system is identified by using experimental datasets and MATLAB Identification System Toolbox. Secondly, the altitude motion control of the single DUAV is essentially considered. In this correspondence, an extension of pole-placement control by combining the pole placement and feedback linearization control with fuzzy law (F-PPFC) is approached. The tracking issues as well as reducing the chattering phenomenon and arbitrarily exploiting the numeric control gains by the fuzzy law are covered by the proposed control. Additionally, this method has been the separation from the physical parameters of the system by using feedback linearization theory. The stability of the F-PPFC control is guaranteed by the Lyapunov theory. To consolidate the satisfactory performance of the proposed F-PPFC control, simulation and experiment tests are implemented by a comparison of the performance of a PID method with the Ziegler-Nichols tuning and a conventional sliding mode control. Thirdly, the yaw motion control of the single DUAV has been intended to design as the next step of the landing process. To cope with the uncertainties and unknown disturbance, the novel combination of a robust adaptation law and the pole-placement control (RAPPC) is accomplished. Here, pole-placement control is a strong solution for controlling linear systems with nominal physical parameters. Additionally, the adaptation with the sigma modification law has been designed to compensate for the uncertainties and bound unknown disturbance of the single DUAV system. Besides, the characteristic polynomial of the proposed RAPPC scheme is guaranteed to be uniformly ultimately bounded using the Lyapunov stability theory. To assert the practical feasibility of the RAPPC control, simulation tests with RAPPC without sigma-modification law and PID controls are conducted. Next, experiments are implemented between the RAPPC and PID controllers. Finally, the parametric uncertainties and unknown disturbance have been considered to handle with as the above-mentioned solution; nevertheless, the single DUAV system also exists the other high nonlinearities. In particular, one of the high nonlinearities is undesirable factors, for instance, which can lead to the single DUAV’s instability. For clearly, the power systems may lose one or two of their steering actuators of rudders during their mission, which will reduce the control performances of the whole single DUAV system. This is an undesirable situation that requires the designed control scheme with unchanged control gains to increase the power capacity of the remaining actuators of rudders. For this purpose, an adaptive super-twisting sliding mode with a time-delay estimation technique (ASTSMCTDE) is proposed. The global stability of the proposed control is guaranteed by the Lyapunov theory. Besides, a comparison between the ASTSMC-TDE and a PID controller was implemented. The performance of the comparison is investigated through two different operation modes, namely the normal and abnormal modes. Moreover, to validate the practical feasibility of the proposed control, simulations and experimental tests were conducted.