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931.
932.
迎风格式在二维非结构网格中的应用 总被引:2,自引:0,他引:2
将原来在结构网格中提出的AUSM+ (AdvectionUpstreamSplittingMethod)格式 ,推广应用于二维非结构网格中 .利用格林 高斯公式对控制体内的变量进行线性重构 ,获得空间二阶精度 ,并采用Barth型限制器以抑制数值解的振荡 .为提高计算效率 ,采用了自适应多重网格法 .最后给出了NACA0 0 1 2翼型和平板激波反射的几个Euler方程的算例 ,并进行了分析比较 . 相似文献
933.
934.
在模式识别领域中,如何实现更高精度的分类一直是个核心问题。本文提出了将自适应RBF神经网络与小生境遗传算法相结合的方法,其中自适应RBF神经网络通过对样本判断,自动实现对RBF网络添加新的隐层节点或者将样本归于已存在的隐层节点所属的类;小生境遗传算法用于寻找最优的网络宽度值。两者相结合最后确定一个隐层节点数与类别数相同的俭省的网络。用歼击机故障数据进行仿真,比较结果表明此方法能实现更高精度的故障认定。 相似文献
935.
Cheng Pan Zengke Li Jingxiang Gao Fangchao Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(6):1859-1869
In the application of precise point positioning (PPP), especially in the dynamic mode, the classical Kalman filter (KF) usually produces a large number of estimation errors or diverges when there are gross errors in the observation data or unexpected turbulences occur in target motion state or both of them. For such problem, a variational Bayesian (VB)-based robust adaptive Kalman filtering (VB-RAKF) is proposed in this paper. This filter introduces a classification robust equivalent weight function to resist observation gross error and the inverse Wishart prior to model inaccurate process noise covariance matrix (PNCM). To improve the instantaneous accuracy of state estimation, the VB approach is used to obtain better estimations of inaccurate PNCM. Several sets of observation data collected by IGS reference stations and vehicles are employed to check the robustness and positioning accuracy of the VB-RAKF model. The results show that the VB-RAKF algorithm is more robust than the KF, and can effectively resist the gross error in observation data and control state disturbance. In the IGS reference station tests, when compared to the KF, the static positioning accuracies of the VB-RAKF in the north, east and up directions are improved by 13%, 8% and 22%, respectively, and the simulated dynamic positioning accuracies of the VB-RAKF in the north, east and up directions are improved by 19%, 9% and 21%, respectively. The in-vehicle dynamic test verifies that the VB-RAKF outperforms the KF, and shows that the VB-RAKF has better performance than the KF when dealing with observation data which has obvious gross errors, and similar performance as the KF when gross errors are small. 相似文献
936.
随着设计空间的增大和优化问题非线性程度的提高,基于代理模型的优化(SBO)过程收敛越来越慢,并且在局部勘测上呈现不足。本文发展了一种高效自适应全局优化方法,在整个样本细化迭代过程中采用变设计空间取样:即在每一步样本细化迭代过程中,利用当前设计空间中的样本建立代理模型,并且根据样本的内部特征,利用模糊聚类算法将该设计空间分割成几个子空间,然后在每个子空间内通过最大化目标函数的期望提高函数和最小化模型预测目标来增加新的样本,之后对子空间进行融合更新设计空间。6个解析测试算例的结果表明,所发展的方法相比于一般的代理模型优化方法,具有更好的鲁棒性以及全局探索和局部勘测能力,更适用于具有强非线性和多极值的优化问题。RAE2822气动优化实例表明,所发展的方法在处理工程实际问题时,仍然能够保持很好的效率、鲁棒性和自适应性。 相似文献
937.
张世俊 《空间控制技术与应用》2018,44(1):56-61
摘要: 针对四足机器人腿部关节控制和转弯步态规划问题,建立四足机器人单腿动力学模型,分析其多输入多输出、时变、耦合和非线性等特性,建立并推导一种具有输入解耦形式的多输入输出特征模型;在此基础上设计由多变量黄金分割自适应控制律和微分控制律组成的控制器;其次提出一种对角转弯步态,通过修正左右腿的迈步步长实现机器人的转弯,进一步分析步长修正量与转弯半径的关系;最后通过虚拟样机技术,分别进行机器人零负载和50 kg负载情况下的直行和转弯步态仿真,仿真结果验证所提方法的有效性. 相似文献
938.
This paper addresses the fixed-time adaptive model reference sliding mode control for an air-to-ground missile associated with large speed ranges, mismatched disturbances and un-modeled dynamics. Firstly, a sliding mode surface is developed by the tracking error of the state equation and the model reference state equation with respect to the air-to-ground missile. More specifically,a novel fixed-time adaptive reaching law is presented. Subsequently, the mismatched disturbances and the un-modeled dynamics are treated as the model errors of the state equation. These model errors are estimated by means of a fixed-time disturbance observer, and they are also utilized to compensate the proposed controller. Therefore, the fixed-time controller is obtained by an adaptive reaching law and a fixed-time disturbance observer. Closed-loop stability of the proposed controller is established. Finally, simulation results including Monte Carlo simulations, nonlinear six-DegreeOf-Freedom(6-DOF) simulations and different ranges are presented to demonstrate the efficacy of the proposed control scheme. 相似文献
939.
Jian Huang Weidong Hu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
With the intense increase in space objects, especially space debris, it is necessary to efficiently track and catalog the extensive dense clusters of space objects. As the main instrument for low earth orbit (LEO) space surveillance, ground-based radar system is usually limited by its resolution while tracking small space debris with high density. Thus, the obtained measurement information could have been seriously missed, which makes the traditional tracking method inefficient. To address this issue, we conceived the concept of group tracking. For group tracking, the overall tendency of the group objects is expected to be revealed, and the trajectories of individual objects are simultaneously reconstructed explicitly. According to model the interaction between the group center and individual trajectories using the Markov random field (MRF) within Bayesian framework, the objects’ number and individual trajectory can be estimated more accurately in the condition of high miss alarm probability. The Markov chain Monte Carlo (MCMC)-Particle algorithm was utilized for solving the Bayesian integral problem. Furthermore, we introduced the mechanism for describing the behaviors of groups merging and splitting, which can expand the single group tracking algorithm to track variable multiple groups. Finally, simulation of the group tracking of space objects was carried out to validate the efficiency of the proposed method. 相似文献
940.
为解决雷达图像仿真中海量地面材质数据的存储和加载问题,采用基于自适应最大行程长度编码和修正 偶对的压缩算法进行材质数据的压缩,从而有效地减少了数据的存储量,消除数据传输的瓶颈,提高了数据传输的 吞吐能力。压缩算法面向 GPU快速处理,得到压缩数据适用于 GPU进行快速解压。 相似文献