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摘要: 基于图像的视觉伺服可用于对机械臂的运动进行有效的控制。然而,正如许多研究者指出的,当初始位置和期望位置相距较远时,此种控制策略将因其局部特性而存在收敛性、稳定性问题。通过在图像平面内定义充分的图像特征轨迹,并对这些轨迹进行跟踪,我们可以充分利用基于图像的视觉伺服所固有的局部收敛性及稳定性特性这一优势,从而避免初始位置与期望位置相距较远时所面临的问题。因此,近年来,图像空间路径规划已成为机器人领域的一个热点研究问题。但是,目前几乎所有的有关结果均是针对手眼视觉系统提出的。本文将针对场景摄像机视觉系统提出一种未标定视觉路径规划算法。此算法在射影空间中直接计算图像特征的轨迹,这样可保证它们与刚体运动一致。通过将旋转及平移运动的射影表示分解为规范化形式,我们可以很容易地对其射影空间内的路径进行插值。在此之后,图像平面中的图像特征轨迹可通过射影路径产生。通过这种方式,此算法并不需要特征点结构和摄像机内部参数的有关知识。为了验证所提算法的可行性及系统性能,本文最后给出了基于PUMA560机械臂的仿真研究结果。Abstract: Image-based visual servoing can be used to efficiently control the motion of robot manipulators. When the initial and the desired configurations are distant, however, as pointed out by many researchers, such a control approach can suffer from the convergence and stability problems due to its local properties. By specifying adequate image feature trajectories to be followed in the image, we can take advantage of the local convergence and stability of image-based visual servoing to avoid these problems. Hence, path planning in the image space has been an active research topic in robotics in recent years. However, almost all of the related results are established for the case of camera-in-hand configuration. In this paper, we propose an uncalibrated visual path planning algorithm for the case of fixed-camera configuration. This algorithm computes the trajectories of image features directly in the projective space such that they are compatible with rigid body motion. By decomposing the projective representations of the rotation and the translation into their respective canonical forms, we can easily interpolate their paths in the projective space. Then, the trajectories of image features in the image plane can be generated via projective paths. In this way, the knowledge of feature point structures and camera intrinsic parameters are not required. To validate the feasibility and performance of the proposed algorithm, simulation results based on the puma560 robot manipulator are given in this paper.
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Key words:
- Visual servoing /
- path planning /
- uncalibrated camera /
- projective space /
- fixed-camera configuration
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