基于激光测距的月球探测重载六足机器人自主避障控制

月面未知环境下具有高承载力的六足移动机器人是月球探测中不可或缺的装备。六足机器人虽然可以借助足地接触信息和姿态信息在不平坦路面行走,在遇到较小障碍物时可以做出适当的反射动作,但当遇到无法逾越的障碍物时,基于视觉信息实现腿式机器人避障运动是非常重要的。针对电驱动六边形对称分布的六足机器人,基于激光测距仪的信息实现了模拟月壤地面的地形建模,提出基于虚拟机体模型的自主避障策略,获得最优可行方向和运动最短距离,规划了实时避障的机体和足端运动轨迹。实验结果表明,六足机器人可以实时、准确地跟踪避障策略得到实时偏航角度,实现了机器人在未知环境下的自主避障运动,为月球探测重载足式机器人研究奠定了基础。     

Performance evaluation and parametric analysis on cantilevered ramp injector in supersonic flows

The cantilevered ramp injector is one of the most promising candidates for the mixing enhancement between the fuel and the supersonic air, and its parametric analysis has drawn an increasing attention of researchers. The flow field characteristics and the drag force of the cantilevered ramp injector in the supersonic flow with the freestream Mach number 2.0 have been investigated numerically, and the predicted injectant mole fraction and static pressure profiles have been compared with the available experimental data in the open literature. At the same time, the grid independency analysis has been performed by using the coarse, the moderate and the refined grid scales, and the influence of the turbulence model on the flow field of the cantilevered ramp injector has been carried on as well. Further, the effects of the swept angle, the ramp angle and the length of the step on the performance of the cantilevered ramp injector have been discussed subsequently. The obtained results show that the grid scale has only a slight impact on the flow field of the cantilevered ramp injector except in the region near the fuel injector, and the predicted results show reasonable agreement with the experimental data. Additionally, the turbulence model makes a slight difference to the numerical results, and the results obtained by the RNG k−ε and SST k−ω turbulence models are almost the same. The swept angle and the ramp angle have the same impact on the performance of the cantilevered ramp injector, and the kidney-shaped plume is formed with shorter distance with the increase of the swept and ramp angles. At the same time, the shape of the injectant mole fraction contour at X/H=6 goes through a transition from a peach-shaped plume to a kidney-shaped plume, and the cantilevered ramp injector with larger swept and ramp angles has the higher mixing efficiency and the larger drag force. The length of the step has only a slight impact on the drag force performance of the cantilevered ramp injector. However, it makes a difference to the flow field in the vicinity of the fuel injector, and the subsonic region becomes narrower with the increase of the length of the step.     

优化方法在电子学支架模型修正中的应用

文章针对电子设备支架的动力学建模中由于简化及人为引入阻尼造成的模型误差问题,开展了基于随机振动试验数据的模型修正工作。采用参数优化方法建立了支架随机振动响应修正的数学模型。用ANSYS参数化设计语言(APDL)对该问题进行了优化求解,修正后的模型能够满足工程应用要求。     

Design exploration for a single expansion ramp nozzle (SERN) using data mining

The single expansion ramp nozzle is an essential component for hypersonic vehicles to improve their internal/external integral level and produce most of the thrust force. The two-dimensional coupled implicit Reynolds Averaged Navier–Stokes (RANS) equations and the two-equation RNG k–ε turbulent model have been employed to numerically simulate the flow field in a single expansion ramp nozzle, and the interactions between the parametric parameters and the objective functions, namely the thrust force and the lift force, have been investigated by using the data mining technique coupled with a design of the experiment. The obtained results show that the physical model has a good two-dimensional structure, and the numerical results show very good agreement with the available experimental data. At the same time, the grid scale has only a slight impact on the pressure distribution. The influences of the horizontal length of the inner nozzle, the external expansion ramp and the internal cowl expansion on the thrust force performance are substantial, as are the effects of the internal cowl expansion and the external expansion ramp on the lift force performance. Further, optimized configurations of the single expansion ramp nozzle are obtained by using single- and multi-objective design optimization methods coupled with the Kriging surrogate model, and the optimized performances show very good agreement with the numerical predictions. The discrepancies between the optimized performances and the numerical predictions are less than 0.05%, and the method proposed in this paper is efficient in designing and optimizing the nozzle configuration.     

非平稳随机振动问题的矩方程求解法

本文将矩方程法推广到宽带激励下线性或非线性系统的非平稳随机振动问题,求得了通用的公式,并将它们应用于几类常见的非平稳随机振动。对于若干例子的计算结果表明,矩方程法能够较有效地处理宽带激励下系统的非平稳随机振动问题。     

行星际互联网中基于Raptor码的分布式存储策略

针对行星际互联网节点存储资源严重受限及存储可靠性问题,提出一种基于Raptor码的分布式存储策略(DSSR)。采用定向随机漫步机制,使得源数据包能够迅速遍历整个网络。在预编码阶段利用基于ID的估计方法进行网络全局信息估计,无需额外的全局信息估计阶段。通过设计合理的数据包选择机制使得最终编码度分布趋于理想度分布。分析和仿真结果表明,与相关文献提出的分布式存储策略相比,该方法大幅度减少了数据包传输时的随机漫步步长,同时提高了译码性能,简单易行。     

Matlab在光纤陀螺随机漂移建模中的应用

光纤陀螺随机漂移是捷联惯导系统的主要误差源,对其建立一个精确的、适用的模型有利于减小光纤陀螺漂移,提高系统精度。本文根据时序建模理论,利用Matlab中的自带函数,建立了光纤陀螺随机漂移模型。Matlab在光纤陀螺漂移建模中的应用,避免了传统编程建模的繁琐,简化了建模的计算过程,大大减小了工作量,提高了建模效率。     

MEMS陀螺仪随机漂移误差研究

降低MEMS陀螺仪的随机漂移误差是提高陀螺仪性能的主要方法之一。基于随机序列时序分析法的基本原理，在对MEMS陀螺仪的初始测量数据采用均值估计法进行预处理后，对去除渐进项后的残差信号进行AR（1）建模，并依据该模型对残差信号进行了Kalman滤波，有效提高测量精度。通过对残差信号进行Allan方差的分析，分离出了陀螺仪随机漂移中的主要随机误差源。通过对具体测量数据的处理结果表明，经过这样的处理，陀螺仪噪声的零偏稳定性和速率随机游走分别提高了4倍和7倍。     

光纤陀螺随机漂移ARMA模型研究

从理论上证明了山多个ARMA过程组成的平稳随机过程，可以南一个等效ARMA模型描述，并推导废模型的数学表达式。提出了一种新的平稳随机过程建模的有效方法，并应用于光纤陀螺随机漂移建模。采用功率谱密度分析光纤陀螺随机漂移组成，从而确定随机漂移的ARMA模型的形式和阶数。通过对实际光纤陀螺数据分析和建模，利用所得随机漂移模型对陀螺输出数据补偿，检验模型的适用件。结果表明废建模方法正确町行，采用该方法建立的光纤随机漂移模型具有很好的适用性，可以有效抑制光纤陀螺随机漂移。