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为了分析和预测飞机的尾旋特性,一般通过旋转天平风洞试验测定飞机模型在不同姿态角时绕风轴以不同旋转速率作等速旋转状态下的气动特性。针对上述情况,研制FD09低速风洞旋转天平试验系统,介绍该旋转天平试验系统的设计特点、性能指标,并进行SDM标模和战斗机模型对比验证。结果表明:本试验系统工作稳定可靠,试验结果与参考曲线有较好的重复性,并且本试验系统试验曲线的光滑性要更好一些,同时本试验系统给出的试验数据精度较高,可以用于开展型号试验及相关空气动力学研究。 相似文献
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为了验证现代试验设计(MDOE)方法在高速风洞试验中应用的可行性,进一步提高风洞试验效率,采用区组化的回归组合设计进行了某运输类飞机亚声速基本纵向常规测力风洞试验,通过少量关键控制点数据建立了气动力参数随马赫数和迎角变化的二阶响应面模型,并进行了方差分析及显著性检验。同时,通过额外增加的试验点检验响应面模型的精准度。试验及分析结果表明:通过回归组合设计少量试验点建立的纵向气动力系数响应面模型预测误差满足高速风洞飞机模型测力试验精度指标要求,方差分析(ANOVA)及显著性检验结果正确反映了迎角、马赫数对飞行器基本气动特性的影响规律,突显出MDOE方法应用于风洞试验方案设计及数据分析的显著优势。 相似文献
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针对航空发动机试验工厂的业务特点进行了CAPP系统的设计开发,设计了结构化工艺和非结构化工艺两种基本模式的工艺管理方法,并实现了CAPP系统与ERP系统的集成。 相似文献
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非线性气动弹性模型参考自适应控制 总被引:1,自引:0,他引:1
首先将含有前/后缘双控制面二元机翼的动态方程以状态空间形式描述,然后考虑俯仰方向的迟滞非线性模型存在参数不确定性的情况下,利用Lyapunov稳定性理论进行了结构化模型参考自适应控制律设计。仿真结果显示:所设计的控制律能够使开环不稳定的气动弹性系统快速地达到稳定状态。由于最大控制面偏转的存在,来流速度较高时闭环系统仍会发生颤振;根据控制面最大偏转的不同取值,文中给出了闭环临界颤振速度的变化曲线。 相似文献
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考虑进口非均匀的喷管设计及冷流条件下的性能研究 总被引:1,自引:0,他引:1
超燃冲压发动机尾喷管与燃烧室直接相连,由于没有几何喉道和收缩段的整流作用,实际工作过程中尾喷管的进口气流是非均匀的,因而有必要研究非均匀进口条件下的尾喷管设计方法。以超燃冲压发动机尾喷管非均匀进口马赫数分布为条件,采用有旋特征线设计了超燃冲压发动机非对称尾喷管的等熵膨胀型线。利用数值模拟和试验相结合的方法研究了冷流条件下喷管的气动性能。结果表明,在相同的进口条件下,相对于假定进口马赫数均匀分布设计得到的喷管,考虑进口马赫数非均匀分布设计的喷管推力增加0.6%~2.0%,负升力降低可达82.0%,俯仰力矩增加8.6%~13.0%,这说明在喷管的设计过程中考虑进口参数分布的非均匀性是有必要的。 相似文献
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对未知着降区平坦度测量是无人机在复杂地形下安全着陆的关键问题。首先,根据小孔成像原理推导出基于单目序列图像的未知区域深度计算方程;其次,针对稀疏匹配存在深度信息重构误差大而稠密匹配在平滑区域误匹配率高的问题,提出一种基于Delaunay三角剖分的稠密点特征生成算法;然后,分别对序列图像中的2帧图像提取亚像素级Harris角点和尺度不变特征变换(SIFT)特征点,并分别进行特征点匹配;再以2种特征点间的欧氏距离作为约束条件将2种特征点进行融合,生成准稠密特征点;最后,将准稠密特征点进行Delaunay三角剖分,并根据每个剖分三角形上3个顶点像素偏差的方差值制定稠密特征点的生成策略,并结合所提出的深度计算方程计算整个未知区域各点的深度信息。通过Vega Prime(VP)搭建仿真演示验证系统,实验结果表明在机载相机距地面400m处计算高度分别为90m和55m的物体深度信息时,其深度测量相对误差不超过0.89%,具有较高的精度。 相似文献
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A hierarchical updating method for finite element model of airbag buffer system under landing impact
《中国航空学报》2015,(6)
In this paper, we propose an impact finite element(FE) model for an airbag landing buffer system. First, an impact FE model has been formulated for a typical airbag landing buffer system. We use the independence of the structure FE model from the full impact FE model to develop a hierarchical updating scheme for the recovery module FE model and the airbag system FE model.Second, we define impact responses at key points to compare the computational and experimental results to resolve the inconsistency between the experimental data sampling frequency and experimental triggering. To determine the typical characteristics of the impact dynamics response of the airbag landing buffer system, we present the impact response confidence factors(IRCFs) to evaluate how consistent the computational and experiment results are. An error function is defined between the experimental and computational results at key points of the impact response(KPIR)to serve as a modified objective function. A radial basis function(RBF) is introduced to construct updating variables for a surrogate model for updating the objective function, thereby converting the FE model updating problem to a soluble optimization problem. Finally, the developed method has been validated using an experimental and computational study on the impact dynamics of a classic airbag landing buffer system. 相似文献
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Broida T.J. Chandrashekhar S. Chellappa R. 《IEEE transactions on aerospace and electronic systems》1990,26(4):639-656
Consideration is given to the design and application of a recursive algorithm to a sequence of images of a moving object to estimate both its structure and kinematics. The object is assumed to be rigid, and its motion is assumed to be smooth in the sense that it can be modeled by retaining an arbitrary number of terms in the appropriate Taylor series expansions. Translational motion involves a standard rectilinear model, while rotational motion is described with quaternions. Neglected terms of the Taylor series are modeled as process noise. A state-space model is constructed, incorporating both kinematic and structural states, and recursive techniques are used to estimate the state vector as a function of time. A set of object match points is assumed to be available. The problem is formulated as a parameter estimation and tracking problem which can use an arbitrarily large number of images in a sequence. The recursive estimation is done using an iterated extended Kalman filter (IEKF), initialized with the output of a batch algorithm run on the first few frames. Approximate Cramer-Rao lower bounds on the error covariance of the batch estimate are used as the initial state estimate error covariance of the IEKF. The performance of the recursive estimator is illustrated using both real and synthetic image sequences 相似文献
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A. Benavoli L. Chisci A. Farina L. Ortenzi G. Zappa 《IEEE transactions on aerospace and electronic systems》2006,42(4):1224-1239
The paper aims at contrasting two different ways of incorporating a priori information in parameter estimation, i.e., hard-constrained and soft-constrained estimation. Hard-constrained estimation can be interpreted, in the Bayesian framework, as maximum a posteriori probability (MAP) estimation with uniform prior distribution over the constraining set, and amounts to a constrained least-squares (LS) optimization. Novel analytical results on the statistics of the hard-constrained estimator are presented for a linear regression model subject to lower and upper bounds on a single parameter. This analysis allows to quantify the mean squared error (MSE) reduction implied by constraints and to see how this depends on the size of the constraining set compared with the confidence regions of the unconstrained estimator. Contrastingly, soft-constrained estimation can be regarded as MAP estimation with Gaussian prior distribution and amounts to a less computationally demanding unconstrained LS optimization with a cost suitably modified by the mean and covariance of the Gaussian distribution. Results on the design of the prior covariance of the soft-constrained estimator for optimal MSE performance are also given. Finally, a practical case-study concerning a line fitting estimation problem is presented in order to validate the theoretical results derived in the paper as well as to compare the performance of the hard-constrained and soft-constrained approaches under different settings 相似文献
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Selecting the optimal machining parameters for impeller surface is a challenging task in the automatic manufacturing industry, due to its free-form surface and deep-crooked flow channel. Existing experimental methods require lots of machining experiments and off-line tests, which may lead to high machining cost and low efficiency. This paper proposes a novel method of machining parameters optimization for an impeller based on the on-machine measuring technique. The absolute average error and standard deviation of the measured points are used to define the grey relational grade for reconstructing the objective function, and the complex problem of multi-objective optimization is simplified into a problem of single-objective optimization. Then, by comparing the values of the defined grey relational grade in a designed orthogonal experiment, the optimal combination of the machining parameters is obtained. The experiment-solving process of the objective function corresponds to the minimization of the used errors, which is advantageous to reducing the machining error. The proposed method is efficient and low-cost, since it does not require re-clamping the workpiece for off-line tests. Its effectiveness is verified by an on-machine inspection experiment of the impeller blade. 相似文献
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阻尼不相似动力学模型的时域响应修正方法 总被引:1,自引:0,他引:1
动力学相似的缩比模型试验中,阻尼往往难以保证相似,使得缩比模型的动响应测试数据难以直接换算到结构原型上,因此提出一种阻尼不相似动力学模型的时域响应修正方法来解决这一问题。该修正方法假定缩比模型的阻尼可用比例阻尼模型近似表征,并直接从实际缩比模型与理想缩比模型的一般强迫振动响应计算方程出发,利用线性系统的叠加原理和模态叠加法,将动响应修正量的求解转换为理想模型在一个等效附加激励力作用下的时域响应求解。同时,针对实际工程中响应测点数目有限的问题,利用模态缩聚法进行了未测量点的响应反演。该修正方法仅需已知结构原型和实际缩比模型的模态阻尼比,以及准确建立的实际缩比模型的质量矩阵和刚度矩阵,即可实现实际缩比模型在任意激励工况下的测试动响应修正。以某型飞机的翼梁缩比模型为研究对象,对所提出的响应修正方法进行了验证。试验和计算结果对比分析表明,修正后的响应功率谱密度(PSD)和响应的均方根(RMS)值与理想模型基本一致,表明了本文方法的可行性和有效性。 相似文献
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针对一般稳态燃油前馈PID算法在发动机过渡态过程中控制效果差的问题,提出了一种基于动态优化数据的涡轴发动机瞬态控制方法。采用带约束限制的序列二次规划(SQP)优化算法采集包线范围内各点的过渡态参数变化数据作为样本数据,利用稀疏化的最小二乘支持向量机(LSSVM)对样本数据进行训练、测试,将训练得到的LSSVM模型作为前馈与PI构成闭环控制器共同对涡轴发动机进行过渡态控制。通过对民用涡轴发动机部件级模型的包线内某两点不同功率水平进行仿真,结果表明,过渡态过程中动力涡轮转速超调量与下垂量均小于0.4%,稳态误差为0,动力涡轮转速稳定时间小于2s,各参数均未超限,因此,该控制器能有效提高涡轴发动机过渡态控制效果,实现对参数的限制管理。 相似文献
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运用ANSYS CFX 11.0和home-code程序对AI222发动机风扇流路气动参数进行了3维CFD(Computational Fluid Dynamics)计算;通过3维建模,实现了风扇主要积分特性和局部参数计算。通过与风扇进行大量试验结果的对比,验证了计算结果,并找出了产生差别的原因,得到了风扇总特性以及气流径向参数的计算值与试验值的吻合度。结果表明:通过运用3维建模计算方法简化了风扇设计过程,缩短了风扇从设计到试验的时间,降低了航空发动机部件的设计成本。 相似文献