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针对一类变体飞行器控制问题, 提出一种平滑切换线性变参数(LPV) 鲁棒控制器设计方法. 建立变体飞行器切换LPV 模型, 设计平滑切换控制器, 其中偶数子系统控制器由相邻两个子系统控制器线性插值得到. 给出保证切换LPV 系统指数稳定且具有一定鲁棒性能的充分条件, 由于考虑了调参变量的渐变特性, 所得切换律没有平均驻留时间的限制. 仿真结果表明, 所提出方法使得飞行器系统既具有良好的稳定性和鲁棒性, 又能实现平滑切换.
相似文献23.
A method for image analysis, representation and re-synthesis is introduced. Unlike other schemes it is not pixel based but rather represents a picture as vector data, from which an altered version of the original image can be rendered. Representing an image as vector data allows performing operations such as zooming, retouching or colourising, avoiding common problems associated with pixel image manipulation. This paper brings together methods from the areas of computer vision, image compositing and image based rendering to prove that this type of image representation is a step towards accurate and efficient image manipulation. 相似文献
24.
A new facial image morphing algorithm based on the Kohonen self-organizing feature map (SOM) algorithm is proposed to generate a smooth 2D transformation that reflects anchor point correspondences. Using only a 2D face image and a small number of anchor points, we show that the proposed morphing algorithm provides a powerful mechanism for processing facial expressions. 相似文献
25.
Visual Speech Synthesis by Morphing Visemes 总被引:6,自引:0,他引:6
We present MikeTalk, a text-to-audiovisual speech synthesizer which converts input text into an audiovisual speech stream. MikeTalk is built using visemes, which are a small set of images spanning a large range of mouth shapes. The visemes are acquired from a recorded visual corpus of a human subject which is specifically designed to elicit one instantiation of each viseme. Using optical flow methods, correspondence from every viseme to every other viseme is computed automatically. By morphing along this correspondence, a smooth transition between viseme images may be generated. A complete visual utterance is constructed by concatenating viseme transitions. Finally, phoneme and timing information extracted from a text-to-speech synthesizer is exploited to determine which viseme transitions to use, and the rate at which the morphing process should occur. In this manner, we are able to synchronize the visual speech stream with the audio speech stream, and hence give the impression of a photorealistic talking face. 相似文献
26.
Rahul Singh Richard M. Voyles David Littau Nikolaos P. Papanikolopoulos 《Autonomous Robots》2001,10(3):317-338
We present an approach for controlling robotic interactions with objects, using synthetic images generated by morphing shapes. In particular, we attempt the problem of positioning an eye-in-hand robotic system with respect to objects in the workspace for grasping and manipulation. In our formulation, the grasp position (and consequently the approach trajectory of the manipulator), varies with each object. The proposed solution to the problem consists of two parts. First, based on a model-based object recognition framework, images of the objects taken at the desired grasp pose are stored in a database. The recognition and identification of the grasp position for an unknown input object (selected from the family of recognizable objects) occurs by morphing its contour to the templates in the database and using the virtual energy spent during the morph as a dissimilarity measure. In the second step, the images synthesized during the morph are used to guide the eye-in-hand system and execute the grasp. The proposed method requires minimal calibration of the system. Furthermore, it conjoins techniques from shape recognition, computer graphics, and vision-based robot control in a unified engineering amework. Potential applications range from recognition and positioning with respect to partially-occluded or deformable objects to planning robotic grasping based on human demonstration. 相似文献
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为研究环翼式桥墩环翼式挡板的最佳延伸长度,进行了不同流速和不同环翼式挡板延伸长度下环翼式桥墩的局部防冲刷试验。试验结果表明:环翼式挡板的延伸长度不同,桥墩的冲刷效果有较大的差别,当环翼式挡板的延伸长度与桥墩的半径相同时,与无挡板的桥墩相比最大冲坑深度可减小57.6%,近底垂向流速最大可减小70.4%,近底紊动强度也明显减小,防冲刷效果显著。 相似文献
29.
By considering the effect of hydraulic pressure filled in wing crack and the connected part of main crack on the stress intensity
factor at wing crack tip, a new wing crack model exerted by hydraulic pressure and far field stresses was proposed. By introducing
the equivalent crack length l
eq of wing crack, two terms make up the stress intensity factor K
I at wing crack tip: one is the component K
I(1) for a single isolated straight wing crack of length 2l subjected to hydraulic pressure in wing crack and far field stresses, and the other is the component K
I(2) due to the effective shear stress induced by the presence of the equivalent main crack. The FEM model of wing crack propagation
subjected to hydraulic pressure and far field stresses was also established according to different side pressure coefficients
and hydraulic pressures in crack. The result shows that a good agreement is found between theoretical model of wing crack
proposed and finite element method (FEM). In theory, an unstable crack propagation is shown if there is high hydraulic pressure
and lateral tension. The wing crack model proposed can provide references for studying on hydraulic fracturing in rock masses. 相似文献
30.
根据大化水电站扩建工程枢纽布置的需要,引水渠右侧、接头土石坝坡脚处设置了一段圆弧型翼墙,因基础地质较差,采取了一系列工程处理措施,经过两年多时间的运行,证明上游翼墙设计合理、工程处理合适。 相似文献