A Pin-Array Structure for Gripping and Shape Recognition of Convex and Concave Terrain Profiles

TL;DR

This work introduces a pin-array gripper that can grasp both convex and concave terrain and simultaneously sense terrain shape via dense per-pin tactile feedback. A mechanistic friction model and a two-holder pin architecture underpin secure engagement and adaptability, while per-pin sensors provide high-resolution 3D terrain information. Prototypes demonstrate holding forces around 5–10 N and the ability to classify terrain shapes, with 3D mapping achieving a mean height error of about 7.67 mm. The approach enables autonomous locomotion on unstructured surfaces by combining adaptive grasping with real-time terrain sensing and mapping, reducing reliance on pre-mapped or pre-observed footholds.

Abstract

This paper presents a gripper capable of grasping and recognizing terrain shapes for mobile robots in extreme environments. Multi-limbed climbing robots with grippers are effective on rough terrains, such as cliffs and cave walls. However, such robots may fall over by misgrasping the surface or getting stuck owing to the loss of graspable points in unknown natural environments. To overcome these issues, we need a gripper capable of adaptive grasping to irregular terrains, not only for grasping but also for measuring the shape of the terrain surface accurately. We developed a gripper that can grasp both convex and concave terrains and simultaneously measure the terrain shape by introducing a pin-array structure. We demonstrated the mechanism of the gripper and evaluated its grasping and terrain recognition performance using a prototype. Moreover, the proposed pin-array design works well for 3D terrain mapping as well as adaptive grasping for irregular terrains.

Figures (12)

• Figure 1: The proposed gripper and conceptual illustration of application to a robot.
• Figure 2: Schematic of the proposed gripping structure. The upper illustration shows the basic structure of the gripper. The lower side view illustrations show the movement of pins and holders when gripping convex/concave shapes.
• Figure 3: Mechanistic model of the proposed gripper when gripping terrain surface.
• Figure 4: Procedure of shape recognition by the gripper. The lower illustration shows a close-up of the sensor section and the relationship between the height of a pin $h_i$ and the sensor resistance value $r_i$.
• Figure 5: Overview of the gripper prototype (top), gripping and lifting convex/concave terrains composed of climbing holds (bottom).