Effects of yaw-roll coupling ratio on the lateral-directional departure prediction and restraint

The experimental data obtained from yaw-roll coupled wind tunnel tests are used for lateral-directional departure prediction, by linearizing the_b model to extract nominal dynamic derivatives at each coupling ratio.The prediction results are compared with those of the existing engineering methods which are based on the conventional aerodynamic derivatives.The comparison shows that the yaw-roll coupling ratio has a great influence on the departure susceptibility.The departure resistance will loss in partial region of the coupling ratio when the angle of attack is higher than a critical value.According to the stable and unstable regions of coupling ratio, a two-segment stability augmentation system with two different feedback gain matrices is obtained by pole-placement method.The two-segment stability augmentation system is used in the simulations of straight and level flight, steady turn, spin recovery and Herbst maneuver.The simulation results are also compared with the applications of a fixed-gain stability augmentation system designed by the conventional aerodynamic derivatives.When the yaw-roll coupling effects are fully considered, the two-segment stability augmentation system is more effective for departure restraint and can provide a better flying quality with less control energy.     

临近空间太阳能飞行器横航向稳定性

临近空间太阳能飞行器的横航向气动导数和质量特性与常规飞行器存在显著差异,其横航向模态具有不同于常规飞行器的特点。理论分析表明,临近空间太阳能飞行器滚转交感动导数较大,偏航阻尼动导数较小,导致螺旋模态发散;航向气动阻尼力矩和惯性力矩之比较大,因而荷兰滚模态阻尼比较大。为解决常规线性化动力学模型无法体现风场影响的问题,以地速在机体坐标系中的投影作为状态变量,建立了考虑风场影响、适用于地速为0 m/s状态的线性化横航向动力学模型。利用此模型分析了临近空间太阳能飞行器在水平风和垂直风中的横航向稳定性。分析结果表明,稳定风场对横航向模态特征根无影响,但会导致横航向模态特征矢量发生改变。建立的动力学模型可用于此类飞行器的动力学分析和仿真。     

空气动力迟滞引起飞机横航向极限环振荡的一种近似解法

 本文给出近似解析公式,确定空气动力迟滞引起的飞机横航向极限环振荡特性。计算表明,它与文献[1、2]中提出的数值迭代法求得的结果相当一致,并消除了该文中求出的滚转迟滞引起的滚转速率极限环振荡振幅不是最大幅值的缺陷。     

飞机平尾偏转对大迎角动态气动特性的影响

给出了 BJ-1背景机有不同平尾偏角时静态和大振幅俯仰振荡情况下的气动特性。根据风洞实验结果,采用基于三角剖分数据库建模的方法,计算了任意平尾偏角和任意振动频率时的背景机动态气动特性,与实验结果比较表明,提出的有平尾偏角的建模方法能提供任意舵偏时的全机气动特性。在非定常建模的基础上,采用动导数仿真,分析了不同平尾偏角时的动导数,结果表明,水平尾翼偏角主要对零动态阻尼所对应迎角有较大影响,随着舵偏角的增大,该迎角减小。     

Time delay compensation in lateral-directional flight control systems at high angles of attack

The previous studies of time delay compensation in flight control systems are all based on the conventional aerodynamic derivative model and conducted in longitudinal motions at low angles of attack. In this investigation, the effects of time delay on the lateral-directional stability augmentation system in high-α regime are discussed based on the $\dot{\beta }$ model, which is proposed in our previous work and proved as a more accurate aerodynamic model to reveal the lateral-directional unsteady aerodynamic characteristics at high angles of attack. Both the $\dot{\beta }$ model and the quasi-steady model are used for simulating the effects of time delay on the flying qualities in high-α maneuvers. The comparison between the simulation results shows that the flying qualities are much more sensitive to the mismatch of feedback gains than the state errors caused by time delay. Then a typical adaptive controller based on the conventional dynamic derivative model and a gain-prediction compensator based on $\dot{\beta }$ model are designed to address the time delay in different maneuvers. The simulation results show that the gain-prediction compensator is much simpler and more efficient at high angles of attack. Finally, the gain-prediction compensator is combined with a linearized $\dot{\beta }$ model reference adaptive controller to compensate the adverse effects of very large time delay, which exhibits excellent performance when addressing the extreme conditions at high angles of attack.     

大迎角耦合运动非定常空气动力特性

采用某飞机大迎角大振幅运动风洞实验结果，分析了大迎角非定常空气动力的一些特性。结果表明，飞机机动飞行时多自由度运动的气动特性比单自由度运动复杂，耦合运动时的气动特性和两个单自由度运动的气动特性的叠加结果相比有一定差别。此外，旋转天平实验结果同本实验的结果相比差别较大。     

Investigation of Vortex Interaction in Canard-FSW Configurations Based on the Numerical Wind Tunnel Method

The vortex interference mechanism on low Reynolds number between the canard and main wing of the canard-forward sweep wing (Canard-FSW) configurations is simulated numerically by employing the numerical wind tunnel method. The variations of aerodynamic characteristics of Canard-FSW configurations with different positions of the canard are investigated, finding that the aerodynamic interference and mutual coupling effect between the canard and main wing have made great contributions to the lift and stability characteristics of the whole aircraft. Canard can radically improve the surface flow pattern of the main wing. And its own vortex can have a favorable interference on the main wing and can effectively control the airflow boundary layer separation. At small angles of attack, the aerodynamic characteristics are sensitive to the positions of the canard and the main wing, but at high angles of attack, the aerodynamic performances of the configuration are not only related to the shape of the canard (forward or backward), but also with the size of control force as well as the features of the vortices generated above the main wing and the canard. The different configurations and vortices are illustrated using the velocity vector, streamlines and pressure contours.     

倾转旋翼机流动机理及气动干扰特性试验

采用试验方法测量了悬停和过渡状态倾转旋翼机旋翼/机翼气动干扰特性,部分揭示了干扰流动的机理。基于3D-PIV(particle image velocimetry)技术的流场测量结果,发现大总距状态相对于小总距时倾转旋翼下洗流收缩更为剧烈,并有更强烈的卷起涡;揭示了“喷泉效应”的产生机理,受旋翼诱导作用的影响,“喷泉”中心的位置会随着总距和间距的改变而发生显著变化。测量了不同构型及状态参数对倾转旋翼/机翼之间气动干扰影响,发现减小垂直或水平距离均可使倾转旋翼升力有所增大,但将会增加机翼受到的旋翼下洗载荷。进行了该构型过渡状态气动干扰特性试验,获得旋翼、机翼综合气动特性与机翼攻角之间的影响关系,在较大机翼攻角时,将会加强对旋翼下洗流的阻碍作用,对旋翼起到类似“地面效应”的增升效果,但该现象随着机翼的偏转不断削弱;机翼升力随机翼段攻角增加呈现出先增大后减小的趋势。      

某典型飞行器模型俯仰/滚转两自由度耦合动态气动特性

先进飞行器在大迎角高机动飞行过程中,气动力复杂演化与运动姿态剧烈变化的相互作用,容易诱发俯仰拉起的滚转或侧偏等耦合运动,呈现出十分强烈的多自由度动态气动力特性。为此,选取某典型四代机修型设计模型,利用FL-26风洞专用的俯仰/滚转两自由度动态试验装置,开展了单自由度和俯仰/滚转两自由度耦合运动的动态气动力特性研究。结果表明,研究模型在迎角30°左右会出现滚转单自由度的侧偏和小振幅摇滚运动现象;俯仰单自由度振动条件下,模型法向力和俯仰力矩会出现明显的气动迟滞特性;在强迫俯仰/自由滚转（或强迫滚转）两自由度耦合运动情况下,模型的侧偏运动幅值得到了一定的抑制,但纵横向气动力都出现了迟滞现象,甚至是多个气动迟滞环结构,容易引发耦合失稳发散。     

Three-axis coupled flight control law design for flying wing aircraft using eigenstructure assignment method

Due to elimination of horizontal and vertical tails, flying wing aircraft has poor longitudinal and directional dynamic characteristics. In addition, flying wing aircraft uses drag rudders for yaw control, which tends to generate strong three-axis control coupling. To overcome these problems, a flight control law design method that couples the longitudinal axis with the lateral-directional axes is proposed. First, the three-axis coupled control augmentation structure is specified. In the structure, a “soft/hard” cross-connection method is developed for three-axis dynamic decoupling and longitudinal control response decoupling from the drag rudders; maneuvering turn angular rate estimation and subtraction are used in the yaw axis to improve the directional damping. Besides, feedforward control is adopted to improve the maneuverability and control decoupling performance. Then, detailed design methods for feedback and feedforward control parameters are established using eigenstructure assignment and model following technique. Finally, the proposed design method is evaluated and compared with conventional method by numeric simulations. The influences of control derivatives variation of drag rudders on the method are also analyzed. It is demonstrated that the method can effectively improve the dynamic characteristics of flying wing aircraft, especially the directional damping characteristics, and decouple the longitudinal responses from the drag rudders.     

反流区对复合高速直升机旋翼气动特性的影响

针对复合式直升机高前进比旋翼反流区严重的特点,建立了适合于高前进比旋翼气动特性的分析方法,以H-34旋翼为例计算了该旋翼在高前进比状态下的气动性能,并与已有的风洞试验数据进行对比验证.在此基础上,进一步分析了反流区对高前进比旋翼气动性能以及对桨叶剖面迎角、升力系数和阻力系数的影响.结果表明:反流区越大,对旋翼的气动性能...     

独柱式变截面倾斜桥塔气动特性风洞试验研究

独柱式桥塔易发生风致振动,当塔柱倾斜且采用变截面形式时,风的作用下常表现出复杂的三维流动效应。为考察独柱式变截面斜塔静动力气动性能,通过桥塔刚性模型测力风洞试验测试了不同风向角下桥塔气动力系数,对比分析了桥塔三维绕流的影响。通过桥塔气弹模型测振风洞试验,测试了涡激振动起振风速及振幅,对比了来流风向及阻尼比对桥塔涡激振动的影响。研究结果表明,桥塔整体气动力系数及断面等效气动力系数沿塔高的变化规律受来流风向角的影响显著,顺桥向风作用下倾斜桥塔易发生横桥向涡激振动,提高结构阻尼比,可有效抑制涡振。     

战斗机大迎角/过失速机动下的进气道气动特性

为掌握战斗机在大迎角和过失速机动飞行时进气道的稳、动态气动特性,采用基于动态嵌套网格的非定常雷诺平均Navier-Stokes （URANS）方程和大迎角风洞试验方法对某战斗机进行了研究,并通过大迎角和过失速机动飞行试验进行了验证。结果表明：大迎角稳态下进气道气动性能随迎角增大逐渐降低,天地相关性吻合良好,而计算仿真和飞行试验均捕捉了眼镜蛇机动下进气道的非定常迟滞效应。通过研究获得了战斗机在大迎角和过失速机动下的进气道气动特性,建立了过失速机动下进气道非定常非线性特性问题的研究方法。     

飞机大迎角机动非线性气动力模型的辨识

给出一种基于最大似然辨识的方法,用以分析飞机模型的大迎角大幅强迫简谐振动获得的气动力和力矩数据,在泛函分析和非定常气动力线性理论的基础上,通过合理的简化建立了能够包括气动力动态失速和涡流破裂及显著气动迟滞效应的大线性气动力模型表达式,并应用飞机模型的试验数据验证了该方法的计算结果,实际计算结果表明该非线性气动力模型能够较为精确地计算飞机模型大幅度迎角简谐振动产生的气动力响应。     

推力矢量对飞机大迎角动态气动特性的影响

推力矢量是提高战斗机大迎角动态气动特性,提升其过失速机动能力和飞行品质的重要手段。新一代战斗机的高机动性要求也使气动和推力矢量的融合控制研究日益重要。针对中国空气动力研究与发展中心∅3.2 m开口低速风洞,研制了喷流模拟器和通气动态试验装置,建立了带推力矢量的大迎角动态试验技术。开展了不同减缩频率、不同落压比、不同喷管偏角时的大迎角俯仰振荡运动特性试验研究。结果表明：与无喷流试验相比,带喷流时模型的动态特性均随着落压比和喷管偏角的变化呈现规律性的变化;力和力矩系数形成的迟滞曲线面积随着落压比和偏角的增加而增加;减缩频率的变化对模型的动态特性影响小于无喷流时的影响。总的来说,推力矢量的影响未改变模型大迎角动态特性的基本规律,但是随着推力矢量角度和大小的变化,有规律地改变了模型动态气动力和力矩的变化幅度。     

W型无尾飞机的操纵机理与稳定特性研究

 W型无尾飞机基于前掠翼及翼身融合的一体化设计，取消了平尾和垂尾，可大幅降低雷达反射截面积，减轻结构重量；同时具有亚声速气动效率高、横航向操纵面效率高的优势。根据该构型的特点，配置设计了新型的多操纵面，并研究了其新的操纵机理。在此基础上，计算分析了这一新布局飞机特殊的三轴稳定特性，研究表明，W型无尾飞机的纵向阻尼不足，纵向短周期和长周期模态分别仅满足III级和II级飞行品质；横航向都是静不稳定的，动稳定性表征为滚转模态的发散和荷兰滚模态稳定，并分析了其可能的物理成因。最后研究了横航向静稳定性导数对W型无尾飞机横航向稳定边界的影响。研究方法和结果对于新布局飞机初步设计具有重要参考价值。     

飞机大迎角气动数据的组成与应用

包含非定常气动力在内的由各种方式获得飞机大迎角气动数据,必需经过合理的组合才能形成完整可信的飞机大迎角数据。通过对过失速区飞机运动特点的分析,提出了组成总气 新方法。     

一种前后缘连续变弯度翼型气动特性分析

提出了一种基于厚度不变的翼型前后缘连续偏转变形规律,并以NACA0015翼型为例,实现了翼型变弯度的参数化。以柔性伸缩蒙皮支撑结构和机械结构实现了可连续光滑偏转后缘的变弯度翼型,验证了变形规律。以前后缘偏转角度为参数,计算并分析了各个变形状态下翼型扰流流场和气动特性,讨论了变形参数对气动特性的影响,研究了气动特性的产生机理。研究结果表明:在大迎角下,前缘偏转角对翼型失速有一定的抑制作用;在中小迎角范围内,翼型升阻比随着后缘偏转角的增大而增大,且不论迎角如何变化,总可以通过前后缘偏转来获得较高的升阻比。     

2.4 m跨声速风洞虚拟飞行试验技术研究

风洞虚拟飞行试验(WTBVFT)技术是在风洞环境中对飞行器机动运动最逼真模拟的物理过程,它不仅可以更加有效模拟飞行器的机动运动过程、获取气动/运动耦合特性和揭示气动/运动耦合机理,而且能够实现气动/飞行力学集成的相容性研究。鉴于此,简要介绍了2.4 m跨声速WTBVFT技术,包括:相似准则和模拟方法、试验模型支撑技术、气动/运动参数测试技术和操纵控制技术等,并开展了典型导弹模型开环控制、姿态角闭环控制、加速度闭环控制、俯仰/滚转耦合与解耦控制以及靶试弹道验证等WTBVFT。研究结果表明:WTBVFT系统运动灵活,气动参数和运动参数测量结果准确可靠,能够有效模拟导弹实际飞行过程,具备闭环控制与耦合运动解耦控制的试验模拟能力,初步形成了气动/飞行力学一体化试验研究能力。同时,该研究也为开展控制方法优化与验证、数据修正与应用以及发展复杂构型的WTBVFT奠定了技术基础。     

Investigation of lateral-directional aerodynamic parameters identification method for fly-by-wire passenger airliners

A new identification method is proposed to solve the problem of the influence on the loaded excitation signals brought by high feedback gain augmentation in lateral-directional aerodynamic parameters identification of fly-by-wire（FBW） passenger airliners. Taking for example an FBW passenger airliner model with directional relaxed-static-stability, through analysis of its signal energy distribution and airframe frequency response, a new method is proposed for signal type selection, signal parameters design, and the appropriate frequency relationship between the aileron and rudder excitation signals. A simulation validation is presented of the FBW passenger airliner＇s lateral-directional aerodynamic parameters identification. The validation result demonstrates that the designed signal can excite the lateral-directional motion mode of the FBW passenger airliner adequately and persistently. Meanwhile, the relative errors of aerodynamic parameters are less than 5%.