面向球果抓取的主动式三指手爪设计与试验

Design and Experiment of Active Gripper for Spherical Fruit Grasping

摘要:

为解决球形果实快速、稳定抓取问题，设计了一种主动式三指手爪。该手爪指部机构末端安装有球状主动滚轮，主动滚轮外附着柔性膜以增加手爪柔顺性与摩擦力。每个指部机构具有2个自由度，可实现手指开合以及主动滚轮旋转。工作时3根手指相互配合，在摩擦力作用下球果向手爪内部运动，可在仅接触球果条件下实现球果快速、稳定抓取，无需精确控制手爪位置和姿态。为阐述抓取过程中主动式手爪与球果的交互关系，推导了主动式手爪-球果交互模型。选取番茄、苹果以及橙子为典型球形抓取对象，开展了3款手爪（主动式手爪、鳍状软爪以及平行刚爪）的抓取试验。抓取试验结果表明，所设计主动式手爪平均首次抓取成功率为96.7%，平均抓取无损率为98.3%，平均任务时间为5.9 s，在抓取成功率、抓取质量以及抓取效率3方面均有较好表现，验证了该主动式手爪的有效性。

Abstract:

In order to solve the problem of fast and stable spherical fruit grasping, a novel active three-finger gripper was proposed. A spherical active roller was installed at the end of the finger mechanism. A flexible-silicone membrane was attached to the active roller to increase the compliance and friction of the gripper. Each finger mechanism had two degrees of freedom, which can realize the opening and closing of the finger and the rotation of the active roller. The three fingers cooperated with each other during work, and the spherical fruit can be translated toward the gripper under the friction. The spherical fruit can be grasped quickly and stably by only touching it, without the need to precisely control the position and posture of the gripper. In order to illustrate the interactive relationship between the designed active gripper and the spherical fruit, an interaction model between them was derived. Finally, in order to verify the effectiveness of the gripper, tomatoes, apples and oranges were selected as typical spherical grasping objects, and a grasping experiment based on three types of grippers (the active gripper, the fin-ray soft gripper and the parallel rigid gripper) was conducted. The experimental results showed that the active gripper had an average first-time grasping success rate of 96.7%, an average grasping intact rate of 98.3%, and an average task time of 5.9 s, achieving relatively good performance in terms of grasping success rate, grasping quality and grasping efficiency.