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根据一种远程自主水下航行器的组成和特点,建立了纵向运动的非线性数学模型,并进行了线性化处理。在此基础上,基于滑模控制理论,分别研究了基于水平舵的纵向低速巡航控制和高速巡航控制及基于前、后垂向推进器的纵向悬停控制。仿真结果初步表明:该控制器可满足水下航行器纵向巡航控制和悬停控制的需要,并对参数不确定性和未建模动态都具有良好的鲁棒性。 相似文献
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针对四旋翼飞行器在飞行过程的水平漂移问题,提出利用改进的金字塔LK光流算法予以改善.首先,通过VisualStudio2013仿真,确知改进的金字塔LK光流算法比传统金字塔LK光流算法对图像的速度信息提取精度更高.然后,再建立四旋翼飞行器的动力学模型,将两种光流算法导入MATLAB的仿真模型中,得出:四旋翼飞行器能有效根据改进的金字塔LK光流算法获得速度信息以降低水平漂移.最后,通过在轴距为430 mm的四旋翼飞行器的平台上进行飞行试验,结果表明:采用改进的金字塔LK光流算法能使四旋翼飞行器的水平漂移程度降低,可实现较为稳定的悬停. 相似文献
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在触控交互中,缺少触觉反馈会造成用户操作水平的降低和用户体验的下降.前人研究对在触控交互中增加触觉反馈这一方法进行了探索.然而,由于现有触摸屏技术仅能在用户点击屏幕后检测用户手指的位置,触觉反馈也只能在用户点击屏幕之后发挥作用.新的传感技术可以在触摸屏上方的悬浮空间(hover space)内提前检测到手指的位置.利用多对象选择任务(multi-target pointing task)比较了在悬浮空间中增加4种反馈方式对用户操作水平和用户体验的影响.实验结果显示,增加的点击振动反馈受到了用户的普遍青睐.然而,增加的触觉反馈对于用户的操作效率和正确率却没有影响.根据这些结果和前人的研究,提出了在悬浮空间中增加触觉反馈的设计建议. 相似文献
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Ila Berman 《Architectural Design》2010,80(3):66-73
Since 2005, when Hurricane Katrina wreaked havoc on the Gulf Coast and New Orleans, our polarised perception of land and water has been irrevocably shifted by the failure of static levee flood-control systems. Ila Berman explains how a more fluid geographical approach to land and water, which places an emphasis on continuous mutable ecologies, is key to a more sustainable future. She describes four experimental projects that are ground-breaking in their treatment of the relationship between the aquatic and terra firma. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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直升机旋翼桨叶绕流的欧拉方程计算 总被引:2,自引:0,他引:2
描述了求解直升机旋翼悬停流场的数值方法。利用悬停流场的准定常特性,采用有限体积空间离散和龙格库塔时间步进格式,在桨叶固连旋转坐标系下直接求解以相对物理参数为变量的三维无粘可压欧拉方程,没有附加任何尾迹模型,其中,应用了多项加快收敛技术。计算了二叶模型旋翼在亚、超音速的流动,并与相应的国外实验数据作了对比,吻合良好。表明应用欧拉方程能够模拟多叶旋翼的悬停流场。 相似文献
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Jan W. Kruyt GertJan F. van Heijst Douglas L. Altshuler David Lentink 《Journal of the Royal Society Interface》2015,12(105)
Airplanes and helicopters use high aspect ratio wings to reduce the power required to fly, but must operate at low angle of attack to prevent flow separation and stall. Animals capable of slow sustained flight, such as hummingbirds, have low aspect ratio wings and flap their wings at high angle of attack without stalling. Instead, they generate an attached vortex along the leading edge of the wing that elevates lift. Previous studies have demonstrated that this vortex and high lift can be reproduced by revolving the animal wing at the same angle of attack. How do flapping and revolving animal wings delay stall and reduce power? It has been hypothesized that stall delay derives from having a short radial distance between the shoulder joint and wing tip, measured in chord lengths. This non-dimensional measure of wing length represents the relative magnitude of inertial forces versus rotational accelerations operating in the boundary layer of revolving and flapping wings. Here we show for a suite of aspect ratios, which represent both animal and aircraft wings, that the attachment of the leading edge vortex on a revolving wing is determined by wing aspect ratio, defined with respect to the centre of revolution. At high angle of attack, the vortex remains attached when the local radius is shorter than four chord lengths and separates outboard on higher aspect ratio wings. This radial stall limit explains why revolving high aspect ratio wings (of helicopters) require less power compared with low aspect ratio wings (of hummingbirds) at low angle of attack and vice versa at high angle of attack. 相似文献
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共轴双旋翼悬停地面效应分析 总被引:2,自引:1,他引:2
共轴双旋翼直升机在近地悬停时存在复杂的旋翼/旋翼/地面干扰效应.为分析近地悬停时共轴双旋翼流场及拉力变化,发展一种共轴双旋翼悬停地面效应计算方法.首先,分别采用升力面法和面元法模拟桨叶和地面对流场的作用,使用三阶精度时间步进格式进行桨叶尾迹计算,并在尾迹迭代过程中引入"等体积"法修正尾迹.然后,运用模型得到共轴双旋翼无地效的诱导速度分布和单旋翼地面效应下的拉力增益并与试验结果对比,验证方法的合理性.最后,基于算例,分析了共轴双旋翼在地面效应悬停状态下的特性,包括尾迹及流场特点、诱导速度与拉力分布、旋翼间干扰和拉力增益.结果表明:悬停地面效应下共轴双旋翼的尾迹发生卷起并径向扩展,其桨盘平面的诱导速度由上旋翼、下旋翼和地面共同引起;分析也表明了悬停地面效应下共轴双旋翼桨盘平面诱导速度及桨叶拉力分布更均匀,在相同功率下,共轴双旋翼的地面效应拉力增益大于同实度单旋翼的拉力增益. 相似文献