Kakogawa Atsushi, Kaizu Yuki, Ma Shugen
Department of Robotics, Ritsumeikan University, Shiga, Japan.
Front Robot AI. 2021 Feb 22;8:631242. doi: 10.3389/frobt.2021.631242. eCollection 2021.
This paper proposes an underactuated grippers mechanism that grasps and pulls in different types of objects. These two movements are generated by only a single actuator while two independent actuators are used in conventional grippers. To demonstrate this principle, we have developed two kinds of gripper by different driving systems: one is driven by a DC motor with planetary gear reducers and another is driven by pneumatic actuators with branch tubes as a differential. Each pulling-in mechanism in the former one and the latter one is achieved by a belt-driven finger surface and a linear slider with an air cylinder, respectively. The motor-driven gripper with planetary gear reducers can pull-up the object after grasping. However, the object tends to fall when placing because it opens the finger before pushing out the object during the reversed movement. In addition, the closing speed and the picking-up speed of the fingers are slow due to the high reduction gear. To solve these drawbacks, a new pneumatic gripper by combining three valves, a speed control valve, a relief valve, and non-return valves, is proposed. The proposed pneumatic gripper is superior in the sense that it can perform pulling-up after grasping the object and opening the fingers after pushing-out the object. In the present paper, a design methodology of the different underactuated grippers that can not only grasp but also pull up objects is discussed. Then, to examine the performance of the grippers, experiments were conducted using various objects with different rigidity, shapes, size, and mass, which may be potentially available in real applications.
本文提出了一种欠驱动抓取器机构，该机构能够抓取并拉动不同类型的物体。这两种动作仅由单个致动器产生，而传统抓取器使用两个独立的致动器。为了证明这一原理，我们通过不同的驱动系统开发了两种抓取器：一种由带行星齿轮减速器的直流电机驱动，另一种由带分支管作为差动装置的气动致动器驱动。前一种和后一种的每种拉入机构分别通过带传动的指面和带气缸的线性滑块来实现。带行星齿轮减速器的电动抓取器在抓取物体后可以拉起物体。然而，在反向运动过程中，由于在推出物体之前手指张开，放置物体时物体容易掉落。此外，由于高减速比齿轮，手指的闭合速度和抓取速度较慢。为了解决这些缺点，提出了一种通过组合三个阀（一个调速阀、一个溢流阀和止回阀）的新型气动抓取器。所提出的气动抓取器的优势在于，它能够在抓取物体后进行拉起动作，并在推出物体后张开手指。在本文中，讨论了不同欠驱动抓取器的设计方法，这些抓取器不仅可以抓取物体，还可以拉起物体。然后，为了检验抓取器的性能，使用了各种具有不同刚度、形状、尺寸和质量的物体进行实验，这些物体在实际应用中可能会用到。
