We propose a gripper displacement-magnification mechanism and an extendable finger mechanism, both of which can be attached to a commercially available parallel gripper. We then verify the operation of the mechanism in order to expand applications of the parallel gripper. The displacement-magnification mechanism has a stacked rack-and-pinion system that doubles displacement. The extendable finger mechanism has two nails that extend and contract, reducing impact force and detecting changes in product height from expansion and contraction amounts. The parallel gripper has a width of 95 mm, a depth of 110 mm, and a height of 214 mm and weighs 1.36 kg. It has an open/close stroke of 60 mm, a gripping force of 7.4 N, and an opening/closing speed of 100 mm/s or more. Further, it was confirmed that the ends and inclinations of products can be reliably detected using the extending/contracting nail. The mechanism verification confirmed that our parallel gripper achieved the desired performance and is therefore useful.

Suction is an effective method for picking various objects because it makes trajectory planning and control easy. However, suction has not been used due to misalignment and leakage of suction air when handling a variety of shapes. We therefore develop a hand to handle these characteristics. First, we model the vacuum pump and pad characteristics to allow evaluation of momentum and suction force in the case of leakage. Utilizing this, we select a configuration suitable for the items in the Amazon Robotics Challenge 2017. In addition, we design a mechanism for switching from suction to pinching for grasping items that cannot be sucked. Moreover, robust pinching is made possible by equipping the fingertips with a passive linear motion mechanism. In the Amazon Robotics Challenge 2017, it was shown possible to stably grasp items with irregularities and items with large moments. Furthermore, items that cannot be grasped by suction can also be grasped robustly by switching to the pinching mechanism.