【作者】 唐伟；

【导师】 宋笔锋；

【作者基本信息】 西北工业大学 ， 飞行器设计， 2019， 博士

【摘要】 尾坐式小型飞行器(Small Unmanned Air Vehicles,简称SUAV)可同时兼顾旋翼垂直起降能力和固定翼快速巡航能力,使其能在狭小空间起降,具有广阔的应用前景而备受关注。而该类飞行器自身所具有的较强设计离散性、双设计点的动力系统要求、螺旋桨滑流影响下的机体低雷诺数气动特性以及多变量耦合的倾转走廊特性等特殊性,使得该类飞行器具有较多关键设计问题尚待研究,制约了该类飞行器的发展与应用。针对于以上问题,提出了一种仅采用一套动力系统、可同时兼顾垂直起降能力和快速巡航能力的尾坐式X型飞翼布局电动小型飞行器,并基于该飞行器平台研究了具有双设计点的螺旋桨电机动力系统匹配设计优化选择方法、X型机体近距耦合的低雷诺数气动特性、以及考虑螺旋桨滑流的过渡模式倾转走廊及其性能计算分析方法这三方面的关键设计问题,提出了一种基于关键问题特点的尾坐式小型飞行器多学科、多属性设计方法,进而通过X-NMRL(X-type SUAV of Northwestern-Polytechnical-Univerisity MicroAir-Vehicle Research Laboratory)飞行器平台原理样机的研制以及关键设计问题相关飞行试验验证了解决方法的有效性,力图为具有倾转过程的尾坐式飞行器的设计方法建立、动力系统优化选择以及倾转过程设计提供有效的指导作用。全文的主要内容包括:(1)由于国内外对该种飞行器的研究尚没有形成系统的总体参数选择方法,因此,基于传统设计方法改进了可用于电动尾坐式小型飞行器的总体参数选择方法,提出并设计了X型机翼飞翼布局的尾坐式飞行器。该参数选择方法引入起降模式、过渡模式以及固定翼模式下翼载荷与功重比的约束关系,利用不同部件的特征参数与其重量的统计模型估算飞行器起飞总重,进而完成了X-NMRL尾坐式小型飞行器的参数初步选择。(2)为降低两套动力系统带来的死重或变距螺旋桨机构的机构可靠性与同步性隐患,采用了定距螺旋桨的动力系统,从而增加了在满足悬停及巡航两个典型设计点动力需求前提下兼顾两种工况耗能的难度,因此,提出了基于各部件数学模型和匹配特性的双设计点动力系统优化方法。该方法建立了螺旋桨模型、无刷电机模型、电调模型以及锂电池模型,基于定距螺旋桨与无刷电机的匹配特性以及锂电池放电能力限制,以飞行剖面要求下的电流消耗为目标优化动力系统,进而研究了锂电池电压、动力系统个数等特征参数对其性能的影响以及设计优选难易程度定性评判标准。(3)通过基于风洞试验验证的数值模拟方法,研究了X型机体布局形式所具有特殊的低雷诺数近距耦合干扰的气动特性以及纵向与横航向操稳特性,分析了机翼夹角、机翼翼型等参数对机体气动特性的影响,为机体几何参数优选设计提供了依据。研究表明,X型机翼提高了有限展长下飞行器的升力特性,改变了上、下翼的流动特性和压力分布,提高了下翼的最大升力系数与失速迎角,进而改善了飞行器整体的失速特性。X型机体在50°夹角左右获得较好的升力、阻力特性以及失速特性,且同时上下翼采用反弯翼型更有利于飞行器的过渡模式安全完成。(4)基于设计的X-NMRL尾坐式垂直起降飞行器,首先建立了涵盖全部可能飞行速度、全攻角内X型机体的气动模型与基于滑流区内外不同动压及面积的螺旋桨滑流影响下的气动估算模型,进而基于飞行器的能源动力系统模型、考虑螺旋桨滑流的气动模型、考虑螺旋桨滑流舵面操纵模型等各分系统模型,提出了以自由来流速度、俯仰角、迎角、动力系统拉力和升降舵偏角为主要控制参数的多变量耦合倾转走廊的建模、求解及性能分析数值方法。基于倾转走廊,分析了飞行器的倾转走廊边界及其性能云图,研究了飞行器倾转走廊各边界的约束条件和设计参数对倾转走廊边界的影响。(5)基于对X翼尾坐式小型飞行器三个关键设计问题的研究,提出了一种基于关键设计问题特点的尾坐式小型飞行器多学科、多属性设计方法,并建立了该设计方法的设计流程。在改进的总体参数初步选择方法基础上,该方法充分考虑X翼尾坐式小型飞行器必须解决的双设计点动力系统、低雷诺数近距耦合气动特性和螺旋桨滑流下的倾转走廊分析三个关键设计问题,以保证飞行器过渡模式的安全转换和设计结果的有效性。(6)针对于飞行器起降模式下X型机翼较大的迎风面积带来的偏航操纵不足问题,研究了增加滑流内的舵面操纵和增加动力系统的安装角两种方式下的改善效果。基于提出的设计方案以及由关键设计问题研究获得的指导性结论,完成了X-NMRL飞行器原理样机的结构设计与样机制作,并实现了全飞行剖面的飞行试验。为验证上述关键问题解决方法的有效性,通过设计动力系统选择飞行验证试验以及倾转走廊特性飞行验证试验,充分说明了提出的双设计点动力系统选择方法与倾转走廊及其性能计算分析方法的可行性与有效性,对该飞行器乃至该类飞行器的设计、倾转策略与路径设计以及飞控设计均具有重要作用。更多还原

【Abstract】 The tail-sitter vertical take-off and landing(VTOL)small unmanned air vehicles(SUAVs)are a kind of vehicles with VTOL ability of helicopter and high-speed cruising ability of fixedwing at the same time.With these abilities,they can take off in narrow space easily so that they attract a lot of attention and have a very wide application prospect.But there are many key technologies restricting their development,such as the obvious design discreteness,the requirement of two design points for propulsion,the low Reynolds number aerodynamics in slipstream and the conversion corridor with coupled variables.In view of the above problems,this thesis proposes a X-type flying-wing tail-sitter VTOL SUAV with one group of propulsions,and it also can vertically take off and land like helicopters and cruise like fixed-wings.On basis of this vehicle,the optimization method for propellermotor propulsion with two design points,the low Reynolds number aerodynamics of X-wing with semi-wings interaction,and the analysis method of conversion corridor and its performance contour in transition mode,are all studied in detail.And the design method based on key problems is built.Then the principled prototype of X-NMRL is produced,and the related flight tests are carried out to prove the effectiveness and feasibility of above solving methods.Then the guidance for design,propulsion selection and conversion design are given.The main issues and achievements in this thesis are as follow:(1)Without systematic design method for the tail-sitter VTOL SUAVs,the improved parameter selection method based on traditional method is proposed,and the design of X-wing VTOL SUAV is finished.The relationship,between wing-load and power-weight ratio in takeoff and landing mode,transition mode and fixed-wing mode,is drawn into the improved design method.And the total weight is obtained by the statistics model between characteristic parameters and component weight.Finally,the parameter selection of the X-NMRL is finished.(2)To reduce the hidden trouble caused by weight redundancy of two groups of propulsions and the mechanism reliability of variable pitch propellers,the fixed pitch propellers are always used for SUAV,but the difficulty is increased to achieve better efficiency under the condition of thrust requirements at two design points.The propeller calculation model,brushless electric motor model,the electronic speed control model and Li-po battery model are constructed,and the optimization for better current consumption is carried out under the condition of matching property and battery discharge ability.Then the effects of battery voltage and propulsion group number on performance are studied,and the criterion are obtained to show the difficulty for design or selection.(3)Using the numerical method verified by wind tunnel tests,the low Reynolds number aerodynamics of X-wing with semi-wings interaction and the longitudinal and lateral stability are studied.The influence of wing-angle and wing airfoil on aerodynamics are analyzed to make foundation for parameters optimal selection.The research shows that X-wing can improve the lift performance in finite span,and change the flow characteristics and pressure distribution on upper and lower wing.The maximum lift coefficient and stall angle of attack are improved for lower wing.The airframe with 50 deg wing-angle will achieve better aerodynamic performance and stall property,and reflexed airfoil will benefit the transition mode to keep control enough.(4)Based on X-NMRL vehicle,the aerodynamic model at every possible angle of attack and velocity is obtained,and the estimation model for wings in slipstream is established according to the different kinetic pressure and immersed area.Combined with the subsystem models,the conversion corridor model construction method is introduced with main parameters of velocity,pitching angle,angle of attack,thrust and elevator deflection.Using this method,the conversion corridor and its performance contour can be obtained.With the analysis on the conversion corridor boundaries and their dominated parameters,the conclusions are drawn to guide the vehicle design and the transition trajectory selection.(5)Based on the study on three key problems of X-NMRL VTOL SUAV,a multidisciplinary and multi-attribute design method is proposed with the consideration of key problems.This method fully considers the characteristics of the propulsion with two design points,aerodynamics in low Reynolds number and conversion corridor analysis.It will ensure the safe transition and the design effectiveness.(6)In rotor mode,the windward area of X-wing is so big that the yaw control will be not enough to control against disturbance.Then two methods to increase yaw control ability,adding the control surfaces in slipstream or adding the propulsion installation angle,are introduced.According to the conclusions drawn from key technology studies,the principle prototype is produced and the flight tests are carried out.To verify the effectiveness and feasibility of above methods for key technologies,the flight tests for propulsion selection and conversion corridor property are designed and finished.The flight tests show the methods proposed for propulsion selection with two design points and conversion corridor analysis are effective and acceptable.And they are meaningful for the preliminary design,transitional strategy and trajectory design,especially for the design of this kind of tail-sitter VTOL SUAVs.更多还原