Key Techniques Research Of Cooperative Formation Biomimetic Flight Control For Multi-UAV

With maturing development of the single UAV technology, task requirments of UAV are changed to rigorousness in military and civil fields, and then more and more attention is paid to the flight phenomena made by migration birds (such as Canadian geese, swan) during long distance journey, which suggested followers are able to take advantage of significant amount of power-savings due to drag reduction induced by the vortices generated from the leader's wings. In the wake of this feature of migration birds, more and more study passions are focused on the project of multi-UAV biomimetic CFF in the whole world in order to accomplish the complicated missions safely and effectively in military field. As great benefits are drawn from the applications of multi-UAV CFF, especially the applications, so it is urgent to enhance the research work of this field to shorten the gap to the foreign countries and accumulate knowledge in theory aspect for the development of our UAVs in the future. This thesis analyzes multi-UAV CFF from four major standpoints: aerodynamic coupling, dynamic modeling, control desiging and CFF testbed based on hardware-in-the-loop.This thesis discusses firstly the very important problem of aerodynamic coupling involved in close-proximate flight in-depth after summarizing previous researches on multi-UAV CFF, and introduces three different vortex models, and then a simple and versatile multi-UAV model has been evolved by introducing"Leader- Follower"frame as its reference in the dynamic modeling. Nonlinear 6-DOF, rigid body, equations of motion developed in the LF frame are used to model the UAVs in the group. The nonlinear equations of motion contain the wind effect terms and their time derivatives to represent the aerodynamic coupling involved in CFF. These wind terms are obtained using an averaging technique that computes the effective induced wind components and wind gradients in the UAV's body frame. This way, the equations of motion based on the assumption that the plane is exposed to uniform wind components and gradients can be used. This is because the non-uniform wind field is very complicated to analyze multi-UAV CFF dynamic characteristics so that the averaing technique is used to approximate the non-uniform wind field as uniform wind components and gradients.An algorithm that generates a safe and feasible trajectory for the formation-keeping and formation-reconfiguration of multi-UAV CFF is one of kernel study contents of this thesis. It is a combination of integral controller, including Variable Structure System Sliding Mode Control and Nonlinear Dynamic Inversion Control with Neutral Network. A nonlinear, 6 DOF multi-UAV simulation has been developed in MATLAB 7.1 to test the efficacies of the dynamic models and the nonlinear controller. Simulation results show that the controller is capable of producing both efficient formation-keeping and formation-reconfiguration under the effect of vortex-induced wind.At the end of this thesis, the other kernel study content is the design and building process of hardware-in-the-loop testbed system of multi-UAV CFF which is described in detail. Three subsystems constitute the testbed system: the flight control system based on DSP technique, the flight control system-virtual prototype based on Statemate technique and ground test subsystem. Although, Virtual Prototype (VP) is digitized software model, it is a new technology in correspondence with the idea of System Design Automation (SDA), which realizes all functions of physical prototype. Finally, we implement the proposed control scheme on the testbed, and the flight tests display successfully that the follower can fly along the flight path of the leader UAV and keep formation distance, and to further ensure that the theory and design of multi-UAV CFF controller are effective and correct.