In this letter, we propose a single-actuator gripper that can lift thin objects lying on a flat surface, in addition to the ability as a standard parallel gripper. The key is a crawler on the fingertip, which is underactuated together with other finger joints and switched with a passive and spring-loaded mechanism. While the idea of crawling finger is not a new one, this letter contributes to realize the crawling without additional motor. The gripper can passively change the mode from the parallel approach mode to the pull-in mode, then finally to the power grasp mode, according to the grasping state. To optimize the highly underactuated system, we take a combination of black-box optimization and physics simulation of the whole grasp process. We show that this simulation-based approach can effectively consider the pre-contact motion, in-hand manipulation, power grasp stability, and even failure mode, which is difficult for the static-equilibrium-analysis-based approaches. In the last part of the letter, we demonstrate that a prototype gripper with the proposed structure and design parameters optimized under the proposed process successfully power-grasped a thin sheet, a softcover book, and a cylinder lying on a flat surface.

中文翻译：

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一种具有被动可切换欠驱动表面的肌腱驱动机器人夹持器及其基于物理仿真的参数优化

在这封信中，我们提出了一种单驱动器抓手，除了作为标准平行抓手的能力之外，它还可以举起躺在平坦表面上的薄物体。关键是指尖上的一个履带，它与其他手指关节一起欠驱动，并通过被动和弹簧加载机制进行切换。虽然爬行手指的想法并不新鲜，但这封信有助于实现无需额外电机的爬行。夹持器可以根据抓取状态被动地从平行接近模式转变为牵引模式，最后转变为动力抓取模式。为了优化高度欠驱动的系统，我们结合了整个抓取过程的黑盒优化和物理模拟。我们表明这种基于模拟的方法可以有效地考虑接触前的运动，手操纵、动力抓取稳定性，甚至失效模式，这对于基于静态平衡分析的方法来说是困难的。在这封信的最后一部分，我们证明了在所提出的过程中优化了所提出的结构和设计参数的原型夹持器成功地抓住了薄片、平装书和位于平坦表面上的圆柱体。