动力失效下变桨距多旋翼无人机的自转着陆分析与控制策略研究

Engine failure is one of the most common flight trouble and significantly destructive for the rotorcraft UAVs (Unmanned Aerial Vehicle). However, the rotors on nowadays multi-rotor UAVs are all set up with fixed-pitch propellers, of which the pitch angle cannot be adjust. Such fixed-pitch propellers make the UAV mechanically simple, but disable the ability of saving the aircraft under engine failure. Moreover, the control quality and energy efficiency is also lowered. This project is going to introduce variable-pitch propellers into multi-rotor UAVs. The best relationship between the motor speed and pitch angle will be analyzed for this research. Considering the aerodynamics factor and nonlinear disturbance, robust control schemes for the multi-rotor UAV is going to be developed, and strictly proved to be stable under stability theory. Research on autonomous autorotation will be focused on two conditions which are vertical landing from hovering state and landing with horizontal velocity. The autorotation landing schemes will be especially designed for the multi-rotor UAVs. The flight control system will be verified gradually by numerical simulation, hardware-in-loop-simulation and full degree of freedom (DOF) experiment. The main tasks of this project are the basics and the key technologies in the field of rotorcraft UAVs. The core results can not only improve the system stability and the control effect, but also actively promote the development of the multirotor and other constructs UAV systems.

空中动力失效是旋翼式无人机较为常见且破坏力较大的飞行故障，而目前广泛应用的多旋翼无人机均采用的是螺距角不可变的固定桨距旋翼，此种旋翼结构虽降低了机身复杂度，却牺牲了动力失效下挽救坠机的能力，且限制了动力机构的控制品质和能量效率。本项目将变桨距结构引入多旋翼无人机，重点研究指定推力输出下转速与桨距的匹配关系，并分析得出能耗的最佳执行区间，充分考虑空气动力学因素和外界非结构化扰动因素，提出具有较强鲁棒性的飞行控制策略，并进行严格的稳定性分析，并在自转着陆问题上针对初始悬停铅直下降和带有水平速度飞行两种情况分别展开研究，设计并优化适用于多旋翼无人机的自转着陆控制策略。项目拟采用“数值仿真-硬件在环仿真-全自由度实验”三个步骤对飞行控制系统进行验证。本项目的研究内容为旋翼式无人机研究领域中的基础和关键技术，对促进多旋翼无人机及其他构型的无人机自主飞行控制研究有较好的推动作用。

本项目围绕可变桨距的多旋翼无人机飞行器的自转飞行问题展了研究，并结合变桨距的动力学特性和旋翼式无人机的飞行特点，对其在动力失效下的自转飞行及着陆过程进行了分析、控制策略设计及实验研究。本项目的主要研究内容和结果有：1）针对变桨距执行机构运转状态及特性进行了建模、分析和优化研究，所提出的分配控制策略能够有效发挥桨距的控制作用，优化了动力效率及执行机构的动态性能，易于在嵌入式系统中实现；2）针对变桨距多旋翼无人机的位置与姿态控制进行了算法研究，在建模不确定性和外界非结构化扰动存在的情况下，设计了可有效搞干扰的非线性鲁棒控制控制器，可实现跟踪误差的指数收敛，保证飞行控制的安全性和可靠性；3）根据变桨距多旋翼无人机的动力学特性，提出其自转飞行状态下的最优控制问题的代价函数，同时整合研究内容二所设计的鲁棒控制方法，设计了变桨距多旋翼无人机的自转飞行控制策略；4）搭建了基于双核心嵌入式微处理器的飞行控制系统，并分别针对两个控制芯片进行了软件及系统开发；5）研制搭建了面向多旋翼无人机的硬件在环实时仿真系统，并开展了项目的实验研究。上述工作能够给未来旋翼式飞行器的发展提供思路，有助于提升我国旋翼式无人机的应用水平。