Radar Identification of Naval Vessels

A scheme is presented for the identification of naval vessels via active multiple-frequency radar interrogation. A major virtue of the described method is the use of a response waveform synthesized using amplitude data only. A prediction correlation using natural resonances associated with substructures on the vessels is applied to synthetically generated matched-filter response waveforms. The identification scheme is tested using measured model data for 8 vessels on a simulated sea surface. A correct identification probability of roughly 77 percent is obtained.     

舰载飞机的滑跳起飞过程及其数学描述

简要地阐述了舰载飞机滑跳起飞的过程，给出了描述滑跳起飞跑道斜坡段形状的实用工程计算公式，并逐一建立了舰载飞机滑跳起飞在每个起飞阶段的运动方程，特别是在斜坡两轮滑跑段的运动方程（数学模型）。这些数学模型有助于分析舰载飞机滑跳起飞的动态特性。     

A Sampled Data Delay-Lock Loop Implemented as a Kalman Predictor

Performance data is presented for a sampled data delay-lock-loop incorporating a Kalman predictor. The jitter response due to noise and the deterministic response to aircraft maneuvers are investigated as a function of the Kalman model parameters. The predictor's transient response to step, ramp, and parabolic inputs and the number of iterations required for convergence for typical initialization errors are determined. It is shown how values for the model parameters may be chosen to obtain satisfactory noise, maneuver, and lock-up performance.     

战斗机地面斜板起飞初探

应用数字仿真方法，计算了歼击7型飞机的地面斜板起飞性能，并分析了计算结果，初步探索了采用地面斜板起飞缩短飞机起飞距离问题，对斜板形状对飞机起飞性能的影响及斜板起飞中飞机姿态的控制进行了分析讨论，为进一步研究斜板起飞技术打下了基础。     

Effect of a Few Dominant Specular Reflectors Target Model Upon Target Detection

Some data indicate that aircraft targets viewed from certain aspects are well modeled as consisting of a few specular reflectors. The effect of a simplified form of this target model upon radar detection performance for two different waveforms has been analyzed. The signal-to-noise ratio (SNR) required for detection as a function of waveform bandwidth for a conventional-single-channel waveform and for a four-channel frequency diversity waveform is evaluated. It is shown that for either waveform there is an optimum bandwidth to minimize the SNR required for detection. In addition, the single-channel minimum is less than the four-channel minimum. The best performance occurs for the single-channel waveform when the waveform bandwidth just resolves the individual reflectors. For typical targets, this bandwidth is of the order of 35 to 75 MHz. It is also shown that only a 0.8-dB loss relative to this minimum is incurred when using a four-channel narrow bandwidth waveform.     

飞机襟翼声疲劳应力的仿真与模式识别

利用回归分析方法，建立声激励下飞机襟翼振动总加速度和总应力对总声压的仿真模型，及总应力对振动总加速度的仿真模型。通过模式识别，得到结构应力响应、结构加速度响应与总声压线性和非线性关系的界限，以及结构应力响应与加速度线性和非线性关系的界限。     

Identification of ground targets from sequential high-range-resolution radar signatures

An approach to identifying targets from sequential high-range-resolution (HRR) radar signatures is presented. In particular, a hidden Markov model (HMM) is employed to characterize the sequential information contained in multiaspect HRR target signatures. Features from each of the HRR waveforms are extracted via the RELAX algorithm. The statistical models used for the HMM states are formulated for application to RELAX features, and the expectation-maximization (EM) training algorithm is augmented appropriately. Example classification results are presented for the ten-target MSTAR data set.     

滑跃起飞过程舰体周围流场的数值模拟

采用数值计算的方法,研究了舰体周围的气流分布情况.给出了不同条件下气流分布的差异以及舰载机滑跃起飞过程对舰面气流分布的影响.计算结果表明,舰体周围的气流分布是相当复杂的,尤其在舰体不同位置会产生不同强度的漩涡.它对于舰载机滑跃起飞气动特性的影响是不可忽略的.侧向风会大大增加舰面气流的湍流程度.本文计算为进一步研究和改善舰面气流分布以提高舰载机滑跃过程的气动特性具有参考价值.     

舰—机适配条件对舰载机滑跃起飞性能的影响

针对不同舰-机适配条件下舰载机起飞安全性的问题,建立了飞机滑跃起飞动力学分析模型,用数值方法分析了飞机起飞质量、甲板参数、舰船航行速度等因素对飞机滑跃起飞性能的影响。仿真结果表明：舰载机起飞质量增大会减小其离舰爬升率;平直甲板越长或斜甲板出口倾角越大,离舰爬升率越大;但是出口倾角太大时,会使飞机离舰迎角超出限制;增大舰船的行驶速度,可以缩短舰载机起飞所需甲板的长度。     

舰载机滑跃起飞斜板形状的优化研究

根据动力学原理，建立了考虑起落架变形运动影响的飞机在甲板上的运动方程，提出了舰载飞机滑跃起飞斜板形状的最优化数学模型性能指标，约束条件和目标函数。其中，引进了罚函烽，把有约束的极值问题化为无约速的极值问题，并采用Ｐｏｗｅｌｌ法以及用商代替导数的ＤＦＰ方法进行了优化计算。计算结果表明，对斜板形状进行优化后，可以在很大程度上提高舰载机的斜板滑跃起飞性能。     

舰载机前起落架突伸动力学分析及试验方法

 为了了解舰载机前起落架突伸试验与实际突伸过程的当量关系,本文以某舰载机为研究对象,建立了全机弹射起飞动力学模型,进行了全机弹射起飞动力学分析,得到了前起落架突伸过程中的动态响应。提出了基于当量质量的前起落架突伸动力学试验方法,设计了试验方案,建立了前起落架突伸动力学试验分析模型,进行了突伸动力学分析。进而依据全机突伸动力学分析结果,对基于当量质量的前起落架突伸动力学试验中相关参数的选取进行了探讨研究,结果表明:当突伸当量质量系数取0.8时,突伸动力学响应特性与全机弹射起飞突伸过程的动态响应结果比较吻合。     

舰载机斜板滑跃起飞情况地面载荷

设置舰艏斜板以减少舰载机起飞滑跑距离、降低甲板风要求,从而实现无弹射系统情况下的短距起飞作业,这已在一些“蓝水”海军强国的航空母舰上得到了多年应用。给定航母起飞甲板长度和斜板曲线构型,飞机能否成功滑跃起飞取决于它的气动特性、最大起飞质量、发动机推力、出口速度和起落架强度。 本文提出了一种舰载机斜板滑跃起飞情况地面载荷的计算方法,也建立了完整的斜板曲线方程（曲线已经过飞机适配性优化）。文中还应用本方法计算了某双座多用途舰载教练机的滑跃起飞地面载荷。     

Effectiveness of Airborne Integral Relay Operations

"Integral relay" is a relay concept in which all the aircraft in a control sector that are under the control of an Army flight operations center (FOC) are electronically capable of functioning as relays for communication with aircraft out of direct contact with the FOC. This paper deals with the effectiveness of integral relay operations based on the assumption of random spatial distribution of aircraft. It describes the development of a control sector line-of-sight (LOS) model and of a methodology for effectiveness analysis, and the application of the methodology to one numerical example. It is shown that the LOS conditions in the control sector may be represented by two LOS characteristics which are functions of both aircraft clearance and the terrain and FOC characteristics. Probabilities of direct and indirect (via relay) LOS between the FOC and randomly located aircraft are derived for operations without and with integral relay. The effectiveness, expressed as an increase in LOS probability, is a function of aircraft density and the above two LOS characteristics and is representative of the control sector as a whole. Numerical results are obtained by probability analysis and statistical sampling.     

鸭式旋翼/机翼飞机悬停状态飞行动力学特性

针对鸭式旋翼/机翼(Canard Rotor/Wing,CRW)飞机独特的气动布局,常规的分析方法及经验公式很难准确地对CRW飞机进行飞行动力学研究,通过飞行辨识对CRW飞机悬停状态特性进行了研究。首先,设计了飞行试验并获得了高质量的飞行数据,基于频率响应对CRW飞机的状态空间模型进行了简化。然后,在频域内对飞机的动力学参数进行了拟合优化,获得了CRW飞机悬停状态的动力学模型,并用飞行数据对所建模型进行了验证。最后,用辨识所得参数与常规直升机悬停状态时的参数进行了对比。结果显示悬停时CRW飞机的操纵导数和阻尼导数均比常规直升机小,经分析,操纵导数的减小主要是CRW飞机独特的旋翼设计所致,阻尼导数减小的原因主要是旋翼气动影响以及鸭翼、平尾、垂尾的结构影响。动力学特性分析结果为CRW飞机旋翼模式总体设计的进一步优化提供了指引和参考,所建立的模型可用于控制系统设计。     

非对称喷管流动分离的预测

非对称喷管是超燃冲压发动机和涡轮基组合循环(TBCC)发动机中特有的关键部件,在跨大马赫数范围工作时,往往在非设计点下会出现严重的流动分离。针对非对称喷管在过膨胀状态下的流动分离现象,通过试验验证二维数值计算(计算采用计算流体力学(CFD)方法)的正确性,利用数值计算样本点拟合得到了非对称喷管在过膨胀状态下的分离准则表达式,并进一步通过不同构型的非对称喷管分离的试验数据来验证该准则的准确性和普适性。研究结果表明,通过特定非对称喷管计算分离数据获得的分离准则与试验结果吻合得较好,在所进行的试验模型和条件下,两者之间的均方根误差为3.68%,更好地说明了该分离准则对非对称喷管内的分离预测具有较好的准确性,同时也跨出了其普适性证明的第1步。     

Far-field sonic boom prediction considering atmospheric turbulence effects: An improved approach

Accurate prediction of sonic boom is one of key challenges for the design of a low-boom supersonic aircraft. For most of available far-field prediction methods, the effect of atmospheric turbulence appearing in the planetary boundary layer cannot be considered, which results in remarkable inaccuracy of predicting ground-level sonic boom waveform. Although some efforts have been made to overcome the shortcoming, the turbulence effects are not yet well described so far. This article proposes an improved method by extending the two-dimensional Heterogeneous One-Way Approximation for the Resolution of Diffraction (HOWARD) equation to account for the axial and transverse convections of wind fluctuation as well as the effect of temperature fluctuation. The proposed method is validated by comparing the predictions with the flight-test data of JAXA D-SEND#1 LBM, which shows that the result of the proposed method is in better agreement with the flight-test data than that of the method without considering atmospheric turbulence effects. Then, distortion mechanism of sonic boom waveforms caused by atmospheric turbulence is analyzed by using the proposed method. It is indicated that the effect of turbulent convection makes uniform sonic-boom wavefronts irregular, which creates the condition of diffraction effect to perturb waveforms. Finally, the proposed method is applied to investigate the behavior of two types of waveforms given by the sonic boom minimization theory. Results show that a far-field waveform with a weaker initial shock is more beneficial for low-boom design of a supersonic aircraft.     

On the Ambiguity Function of Random Binary-Phase-Coded Waveforms

The ambiguity function of truly random binary-phase-coded waveforms, as an approximation to those waveforms commonly employed in binary-modulated pseudonoise systems/encoded radar systems, is investigated. In a statistical sense, the ambiguity function is analytically derived in which the normally used deterministic cross-correlation process is replaced by its ensemble average. Various Doppler filter responses are presented and discussed. The results are compared with those obtained by transmitting an aperiodic maximum length pseudorandom sequence. It is shown that the ambiguity function of the latter case is closely represented by the ensemble-average response of the truly random binary signal.     

舰载机斜板／弹射综合起飞的性能收益与关键问题

弹射起飞技术难度大、能量消耗大,弹射系统质量体积大,而滑跃起飞又无法使推重比小的舰载机起飞,难以形成强大战斗力,针对这一问题,提出将弹射起飞和滑跃甲板结合起来的斜板／弹射综合起飞方式。针对这种起飞方式的特点进行了分析,并通过数值仿真,说明了这种起飞方式预期的性能收益以及存在的关键问题。     

分布式非线性气动力模型弹性飞机动力学研究

建立了线性与非线性两种分布式气动力模型,在弹性飞机模型上添加所建立的气动力模型,验证了整个系统的有效性。对所建立的模型进行着陆及突风扰动动力学仿真,对比线性及非线性气动力模型的飞机动力学响应的差异,结果表明非线性气动力模型能够更合理地计算飞机大迎角状态下的气动载荷及动力学响应。     

某预警飞机机头ESM天线罩模型的建立与响应分析

建立了某型预警飞机机头ESM天线罩有限元数值模型,对机头ESM天线罩结构进行了静态应力分析,得到了机头ESM天线罩受力情况,同时进行了机载天线罩模态分析以及响应计算。算例表明,罩体与机身对接约束附近区域应力最大,变形较大的区域集中在两肩附近,受撞击时有明显的局部振动,减小两肩附近的蜂窝尺寸可以改善天线罩的稳定性。