基于CFD方法的固定翼无人机着陆控制建模

为了实现固定翼无人机低速平稳着陆的目的,以某型无人机为例,阐述以计算流体动力学(CFD)方法求解固定翼无人机气动力系数的过程,即构建飞机几何模型、设定计算域并划分网格、基于非耦合隐式求解器求解在K-E湍流模型下各飞行状态的气动系数.提出以较大迎角低速滑翔降落的着陆控制方法,基于求解的气动特性,计算飞机降落前的理想状态,并基于状态反馈的纵向控制律实现着陆控制.在Simulink环境中,基于AeroSim工具箱构建仿真程序,验证了方法的有效性.     

Design of a Commercial Hybrid VTOL UAV System

For the last four decades Unmanned Air Vehicles (UAVs) have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Even though civilian UAVs currently constitute 3 % of the UAV market, it is estimated that their numbers will reach up to 10 % of the UAV market within the next 5 years. Most of the civilian UAV applications require UAVs that are capable of doing a wide range of different and complementary operations within a composite mission. These operations include taking off and landing from limited runway space, while traversing the operation region in considerable cruise speed for mobile tracking applications. This is in addition to being able traverse in low cruise speeds or being able to hover for stationary measurement and tracking. All of these complementary and but different operational capabilities point to a hybrid unmanned vehicle concept, namely the Vertical Take-Off and Landing (VTOL) UAVs. In addition, the desired UAV system needs to be cost-efficient while providing easy payload conversion for different civilian applications. In this paper, we review the preliminary design process of such a capable civilian UAV system, namely the TURAC VTOL UAV. TURAC UAV is aimed to have both vertical take-off and landing and Conventional Take-off and Landing (CTOL) capability. TURAC interchangeable payload pod and detachable wing (with potential different size variants) provides capability to perform different mission types, including long endurance and high cruise speed operations. In addition, the TURAC concept is to have two different variants. The TURAC A variant is an eco-friendly and low-noise fully electrical platform which includes 2 tilt electric motors in the front, and a fixed electric motor and ducted fan in the rear, where as the TURAC B variant is envisioned to use high energy density fuel cells for extended hovering time. In this paper, we provide the TURAC UAV’s iterative design and trade-off studies which also include detailed aerodynamic and structural configuration analysis. For the aerodynamic analysis, an in-house software including graphical user interface has been developed to calculate the aerodynamic forces and moments by using the Vortex Lattice Method (VLM). Computational Fluid Dynamics (CFD) studies are performed to determine the aerodynamic effects for various configurations For structural analysis, a Finite Element Model (FEM) of the TURAC has been prepared and its modal analysis is carried out. Maximum displacements and maximal principal stresses are calculated and used for streamlining a weight efficient fuselage design. Prototypes have been built to show success of the design at both hover and forward flight regime. In this paper, we also provide the flight management and autopilot architecture of the TURAC. The testing of the controller performance has been initiated with the prototype of TURAC. Current work focuses on the building of the full fight test prototype of the TURAC UAV and aerodynamic modeling of the transition flight.     

无人机六自由度飞行建模与仿真研究

鉴于无人机在军事和民用领域广泛的发展,用数字仿真的手段可以验证无人机在特定条件下是否达到了飞行品质的要求,进而进行半实物仿真,最后进行飞行试验。通过飞行仿真可以缩短无人机的研制周期,降低研制经费和风险。无人机六自由度飞行仿真建模研究对无人机系统的初期研究和后期模拟训练器的研制都起着重要的作用。课题组利用Simulink工具进行了无人机六自由度飞行建模仿真研究,所建立的无人机的六自由度空气动力学模型既可以进行纯数字的仿真试验,也可以为后续研制高逼真的无人机模拟训练器中无人机动力学模型设计打下基础。     

Backstepping - Sliding Mode Controllers Applied to a Fixed-Wing UAV

This paper deals with the design of five controllers, based on Backstepping and Sliding Modes, which are applied to a fixed-wing unmanned aerial vehicle (UAV). We are interested to realize a comparative analysis of such methodologies in order to know what controller has a better performance when they are used to the autonomous flight (altitude, yaw and roll) of a fixed-wing UAV. The designed controllers are: Backstepping, Sliding Mode control (SMC), Backstepping with Sliding Mode control, Backstepping with two Sliding Mode control, and Backstepping with high order Sliding Mode (HOSM) control. Simulation results are obtained in order to analyze the controllers performance. We finally present an experimental result, in open-loop, with the purpose of validate the magnitude of the control signals obtained in the simulations.     

微型固定翼无人机机电性能测试与试验

为解决当前微型无人机机电性能研究较少的问题,研究了微型固定翼无人机静态和动态工作机电特性,建立该平台飞行功率与工作电流、拉力、螺旋桨风场等因素间的数学模型.以后退式无人机机体为基础,研究螺旋桨在旋转中不同平面中不同距离、工作电流等因数下无人机风场变化.最后通过该平台验证该无人机的工作特性和可行性.试验结果表明,无人机电机转速、拉力与工作电流呈对数关系,其拟合系数R2大于0.95,同时拉力与转速两者之间呈直线比例关系.随着无人机载重的不断增加,机翼变形也不断增加.从风场曲面得出距离螺旋桨15 cm处的风速最小,在左右5 cm处的风速最大,螺旋桨中心位置形成了一个低于最大风速的管道.此外,通过分析实验数据得到了平行和垂直于螺旋桨转动平面,及风场变化的三维曲面和等高曲面图等,曲面图直观反映无人机在不同工作电流的风场变化特性,为今后微型固定翼无人机的设计和应用提供必要理论依据.     

Position control of a ducted fan VTOL UAV in crosswind

This paper describes a control strategy to stabilize the position of a vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV) in crosswind despite unknown aerodynamic effects. The proposed approach overcomes the problem of gyroscopic coupling by taking advantage of both the structure of the thrust mechanism, which is made of two counter rotating propellers, and the control strategy which involves a decoupling of the yaw rate dynamics from the rest of the system dynamics. The controller is designed by means of backstepping techniques that allow the stabilization of the vehicle's position while online estimating the unknown aerodynamic effects.     

Development and Application of Controller for Transition Flight of Tail-Sitter UAV

There is renewed interest in tail-sitter airplanes on account of their vertical takeoff and landing capability as well as their efficient horizontal flight capabilities. The transition from a vertical near-hover mode to a horizontal cruise mode is a critical component of the tail-sitter flight profile. In practice, this transition is often achieved by a stall-and-tumble maneuver, which is somewhat risky and therefore not desirable, so alternative maneuvering strategies along controlled trajectories are sought. Accordingly, this paper presents the synthesis and application of a transition controller to a tail-sitter UAV for the first time. For practical reasons, linear controllers are designed using the PID technique and linked by gain scheduling. The limits of the PID controller are complemented by a so-called $\mathcal{L}_{1}$ adaptive controller that considers the coupling effect, reduces the effort for appropriate gain selection, and improves the tracking performance at different points during operation. Each transition trajectory is controlled by the flight velocity and path angle using dynamic inversion. The transition control law is tested on a tail-sitter UAV, an 18-kg vehicle that has a 2-m wingspan with an aspect ratio of 4.71 and is powered by a 100-cm³ gasoline engine driving an aft-mounted ducted fan. This paper describes not only the synthesis and the onboard implementation of the control law but also the flight testing of the fixed-wing UAV in hover, transition, and cruise modes.     

Two-Step System Identification and Trajectory Tracking Control of a Small Fixed-Wing UAV

An approach for obtaining dynamically feasible reference trajectories and feedback controllers for a small unmanned aerial vehicle (UAV) based on an aerodynamic model derived from flight tests is presented. The modeling method utilizes stepwise multiple regression to determine relevant explanatory terms for the aerodynamic coefficients. A dynamically feasible trajectory is then obtained through the solution of an optimal control problem using pseudospectral optimal control software. Discrete-time feedback controllers are further designed to regulate the vehicle along the desired reference trajectory. Simulations in a realistic operational environment as well as flight testing of the feedback controllers on the aircraft platform demonstrate the capabilities of the approach.     

Pitch Loop Control of a VTOL UAV Using Fractional Order Controller

Pitch loop control is the fundamental tuning step for vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs), and has significant impact on the flight. In this paper, a fractional order strategy is designed to control the pitch loop of a VTOL UAV. First, an auto-regressive with exogenous input (ARX) model is acquired and converted to a first-order plus time delay (FOPTD) model. Next, based on the FOPTD model, a fractional order [proportional integral] (FO[PI]) controller is designed. Then, an integer order PI controller based on the modified Ziegler-Nichols (MZNs) tuning rule and a general integer order proportional integral derivative (PID) controller are also designed for comparison following three design specifications. Simulation results have shown that the proposed fractional order controller outperforms both the MZNs PI controller and the integer order PID controller in terms of robustness and disturbance rejection. At last, ARX model based system identification of AggieAir VTOL platform is achieved with experimental flight data.     

An Approach Toward Visual Autonomous Ship Board Landing of a VTOL UAV

We present the design and implementation of a vision based autonomous landing algorithm using a downward looking camera. To demonstrate the efficacy of our algorithms we emulate the dynamics of the ship-deck, for various sea states and different ships using a six degrees of freedom motion platform. We then present the design and implementation of our robust computer vision system to measure the pose of the shipdeck with respect to the vehicle. A Kalman filter is used in conjunction with our vision system to ensure the robustness of the estimates. We demonstrate the accuracy and robustness of our system to occlusions, variation in intensity, etc. using our testbed.     

无人机飞行仿真系统多智能体建模分析与应用研究

无人机飞行仿真系统包含多个功能模块,采用多智能体(multi-Agent)技术研究无人机飞行仿真系统,分析并建立基于多智能体的飞行仿真系统的层次结构和运行机制,进而利用智能体对无人机仿真模型的各子模块模型运行过程进行建模,最后在JADE环境下建立了多智能体无人机飞行仿真系统的实例模型.这种方法可以通过仿真模型各子系统智能体之间的交互来完成无人机飞行仿真系统中飞行仿真的主要功能,从而满足无人机模拟训练系统的设计需求,在无人机模拟训练系统研究中具有广阔的应用前景.     

矢量拉力垂直起降无人机姿态纵向控制研究

针对使用矢量拉力控制纵向飞行姿态转换的坐式垂直起降固定翼无人机,分析其在垂直和水平飞行两种状态转换过程中存在的一些控制问题;建立了其动力模型,并对模型参数进行了整定。针对其在非线性条件下动态性能欠佳的问题,把容易实现、鲁棒性好的PID控制法与智能模糊控制算法结合,设计出自适应模糊PID控制器。并且模糊PID的超调小、动态响应快等特点在仿真和飞行实验中得到验证,使系统的抗干扰性得到提高。     

无人机飞控软件系统建模与测试用例生成研究

软件规模与复杂度的迅速增长已成为设计与检验现代高质量无人机飞行控制软件(FCS)系统的重要挑战。采用模型驱动工程(MDE)的框架,使用嵌入式实时系统建模语言(MARTE)建立起某型无人机飞控软件系统的模型,给出了基于时间自动机的系统动态行为的形式化模型实例;结合无人机FCS系统的应用背景,建立了基于时间自动机模型的测试用例生成方法,包括建立测试用例生成框架、测试用例生成规则以及用例生成策略等;对某型无人机飞控软件系统中的主控模块进行了建模与测试用例生成的实例分析研究。     

Flight control of a rotary wing UAV using backstepping

This paper presents a novel application of backstepping controller for autonomous landing of a rotary wing UAV (RUAV). This application, which holds good for the full flight envelope control, is an extension of a backstepping algorithm for general rigid body velocity control. The nonlinear RUAV model used in this paper includes the flapping and servo dynamics. The backstepping‐based controller takes advantage of the ‘decoupling’ of the translation and rotation dynamics of the rigid body, resulting in a two‐step procedure to obtain the RUAV control inputs. The first step is to compute desired thrusts and flapping angles to achieve the commanded position and the second step is to compute control inputs, which achieve the desired thrusts and flapping angles. This paper presents a detailed analysis of the inclusion of a flapping angle correction term in control. The performance of the proposed algorithm is tested using a high‐fidelity RUAV simulation model. The RUAV simulation model is based on miniature rotorcraft parameters. The closed‐loop response of the rotorcraft indicates that the desired position is achieved after a short transient. The Eagle RUAV control inputs, obtained using high‐fidelity simulation results, clearly demonstrate that this algorithm can be implemented on practical RUAVs. Copyright © 2009 John Wiley & Sons, Ltd.     

一种用于无人机的分布式飞行控制系统设计①

分布式结构已广泛应用于高可靠航空电子设备的设计中。设计了一种基于控制局域网（CAN）的分布式飞行控制计算机,用于在执行飞行任务过程中无人机的飞行控制律解算和系统管理。根据无人机控制的实时性和可靠性需求,提出了一种CAN通信、双端口随机访问存储器（DPRAM）通信和控制任务相互配合的内部通信机制。实验表明根据该通信机制设计的通信方案完全满足无人机控制的实时性和可靠性要求,同时解决了分布式结构引入的数据延时问题。     

飞翼布局无人机控制律设计

以某飞翼布局无人机为设计对象,进行内、外回路的控制律设计.在Matlab/Simulink仿真环境下,建立飞翼布局无人机线性小扰动模型,分析纵向、横航向模态特性,根据本体特性缺陷针对性地设计控制律内回路反馈支路及增益,经反馈补偿后的飞行品质满足GJB 185-1986相关要求.在内回路控制律的基础上设计外回路PI控制器...     

某小型无人机飞控系统的中断控制器设计

为了提高无人机飞行控制系统对外部事件快速响应及实时处理的能力,中断是一种非常有效的实现手段;文章针对以TI公司DSP芯片TMS320LF2407A为核心的某小型无人机机载计算机系统,提出并实现了基于复杂可编程逻辑单元(CPLD),对无人机飞控系统外部中断端口进行扩展和管理的设计方案,详细给出了中断控制系统的硬件接口设计、程序设计及仿真结果;该设计已成功应用于某小型无人机飞控系统中,提高了无人机飞控系统对外部中断事件的管理和实时处理能力。     

无人机模糊飞行控制器设计

近年来,无人机凭借其各种优势,受到了各国越来越多的关注;飞行控制系统是现代无人机的核心,其控制律设计结果对无人机飞行特性的影响至关重要,决定无人机是否能够满足自主飞行要求;为了获得更好的控制效果,保证无人机能更好地适应复杂环境和任务,在常规模糊控制方法的基础上引入修正因子和积分抑制策略,设计出了一种模糊飞行控制器;仿真结果表明,该控制器具有较好的控制效果和较强的鲁棒性,较一般的模糊控制系统具有控制速度快、精度高、鲁棒性强等特点,更能适应无人机的特殊要求.     

小型无人机飞行控制器的硬件设计

以80C196KC单片机和可编程微控制器外围器件PSD813F1为核心设计了小型民用无人机飞行控制器的硬件，对设计中的关键技术进行了研究，系统具有设计精炼，可靠性高，开发性等特点。