A practical filter error method for aerodynamic parameter estimation of aircraft in turbulence

It is common for aircraft to encounter atmospheric turbulence in flight tests. Turbulence is usually modeled as stochastic process noise in the flight dynamics equations. In this paper, parameter estimation of nonlinear dynamic system with both process and measurement noise was studied, and a practical filter error method was proposed. The linearized Kalman filter of first-order approximation was used for state estimation, in which the filter gain, along with the system parameters and the initial states, constituted the parameter vector to be estimated. The unknown parameters and measurement noise covariance were estimated alternately by a relaxation iteration method, and the sensitivities of observations to unknown parameters were calculated by finite difference approximation. Some practical aspects of the method application were discussed. The proposed filter error method was validated by the flight simulation data of a research aircraft. Then, the method was applied to the flight tests of a subscale aircraft, and the aerodynamic stability and control derivatives were estimated. All the estimation results were compared with the results of the output error method to demonstrate the effectiveness of the approach. It is shown that the filter error method is superior to the output error method for flight tests in atmospheric turbulence.     

PPK信号自同步磁带记录

介绍一种新的PPK信号磁带记录技术,其新颖点在于实现了PPK信号和同步解调时钟在同一磁道上记录,彻底消除磁带扭斜对PPK信号磁带计测精度的影响,并且在磁带抖动影响下获得4‰的精度     

舵模型风洞颤振试验中亚临界技术的应用研究

为降低模型和风洞设备的损坏率，用随机激励和频响函数分析法，测定进入颤振临界点之前舵面颤振试验模型在不同风洞气流动压下的模态频率和阻尼比，由阻尼外推法或稳定参数法确定颤振临界动压。数次进入颤振状态的试验结果证明，所获得的颤振临界参数有较高的精度。     

柔性飘带气动特性初探

气动中心首次进行了柔性飘带弹的气动特性试验，对柔性飘带提供安定作用的机理进行了分析。常规刚性尾翼（舵）是基于自身升力产生安定力矩，而柔性飘带的安定性是由它产生的总阻力提供的。文中还对影响飘带气动特性诸因素进行了探讨。     

超临界自然层流翼型NPU-L72513的风洞试验研究

超临界自然层流翼型具有很好的应用前景。西北工业大学翼型研究中心设计的我国第一个超临界自然层流翼型 NPU-L72513在 CARDC 高速所的跨声速风洞进行了试验,证明超临界自然层流翼型 NPU-L72513具有优良气动特性,其设计是成功的。同时说明我国已初步具有自行设计超临界自然层流翼型和进行相应风洞试验的能力。     

基于路径的数字系统功能测试

本文介绍基于路径的数字系统功能测试方法。路径表示系统在输入信号作用下状态的转换。文章提出并实现了遍历路径的测试矢量生成算法;讨论了利用数字系统硬件描述语言及其模拟器生成被测系统在测试矢量序列激励下的无故障响应序列的方法;并介绍运用无故障响应序列与实际响应序列进行比较测试的故障定位法。应用上述方法,笔者在研制的NAT-403Ⅰ型数字设备自动测试仪上对三种板级数字系统进行了测试,获得预期的效果。     

利用试验数据的结构动力学数学模型修正统一方法

近20年来提出了一系列利用试验数据的结构动力学数学模型修正方法，用统一的观点来考查和比较各种不同的模型修正方法显得十分重要。本文提出一种统一方法，将数学模型修正表述为推广的最小二乘或贝叶斯系统识别问题，可通过优化方法求解。其中残差定义为由数学模型计算的动态参量和相应测试量、或其组合量之差。选择不同的残差量，如特征值、特征向量、特征方程、正交性条件、系统输入（力）、输出（响应）、频率响应等，可导出各种设计参数型数学模型修正方法。最后对由统一方法导出的各种数学模型修正算法进行了分析、比较和讨论。用统一方法推导的各种方法不仅涵盖了现有的主要设计参数型模型修正方法，而且还演绎出一些新的算法。     

某舰飞行甲板区域流场特性的水洞试验

为了满足舰载直升机的需要，南航直升机技术研究所对某舰飞行甲板区域流场进行了水洞试验。本文详述了水洞试验的方法和技术，通过对舰模在各种水速、各种航行偏角状态下的试验，得到了大量照片，并据此对该舰机库后部、飞行甲板上部周围流场进行了分析，得出了在飞行甲板机库门外有一趋于收缩的稳态区，随着流速Ｖ的增大，这一区域变短。稳态区之后很快变为乱流区。从侧面上看，稳态区高度有从降低再向上扩散的趋向。在向右偏航时，     

谱载下基于模糊Miner法则的疲劳寿命估算

在载荷谱中,当疲劳应力稍低于疲劳极限时,对构件是否造成损伤呈现出某种"模糊"过渡状态.运用模糊数学的隶属函数,建立了考虑"模糊"损伤状态的Miner法则.按照常规Miner法则和模糊Miner法则,分别给出了程序块谱作用下疲劳寿命的估算公式.实例估算与试验结果的对比表明:采用模糊Miner法则,可使疲劳寿命的估算误差减少18.33%.     

Flutter analysis of hybrid metal-composite low aspect ratio trapezoidal wings in supersonic flow

An effective 3D supersonic Mach box approach in combination with non-classical hybrid metal-composite plate theory has been used to investigate flutter boundaries of trapezoidal low aspect ratio wings. The wing structure is composed of two main components including alu-minum material (in-board section) and laminated composite material (out-board section). A global Ritz method is used with simple polynomials being employed as the trial functions. The most important objective of the present research is to study the effect of composite to metal proportion of hybrid wing structure on flutter boundaries in low supersonic regime. In addition, the effect of some important geometrical parameters such as sweep angle, taper ratio and aspect ratio on flutter boundaries were studied. The results obtained by present approach for special cases like pure metal-lic wings and results for high supersonic regime based on piston theory show a good agreement with those obtained by other investigators.