A Pin-Array Structured Climbing Robot for Stable Locomotion on Steep Rocky Terrain
Keita Nagaoka, Kentaro Uno, Kazuya Yoshida
AI summary
Problem
Climbing robots struggle to reliably attach to unstructured, irregular surfaces without complex sensing or control. Existing grippers often lack true grasping capability or are limited to convex geometries, restricting adaptability to natural rocky terrain.
Approach
The authors developed a hexapod climbing robot equipped with six pin-array gripper units that use split pins with elastic springs and metal spines. A single actuator passively drives the pins to conform to surface irregularities and mechanically interlock, generating holding forces without prior terrain sensing.
Key results
- Designed a hexapod robot with six pin-array gripper units featuring 132 compliant pins for passive terrain conformity
- Developed and validated a probabilistic Monte Carlo model predicting grasping force variability based on pin contact probability and force distribution
- Demonstrated static stability up to a 65° incline and successful locomotion on 10°–30° indoor slopes and outdoor natural rock
- Identified individual pin force variability and contact number as primary sources of grasping uncertainty
Why it matters
Provides a practical, low-complexity gripping solution for exploration and disaster-response robots operating on unstructured natural terrain.
Abstract
Climbing robots face significant challenges when navigating unstructured environments, where reliable attach- ment to irregular surfaces is critical. We present a novel mobile climbing robot equipped with compliant pin-array structured grippers that passively conform to surface irreg- ularities, ensuring stable ground gripping without the need for complicated sensing or control. Each pin features a vertically split design, combining an elastic element with a metal spine to enable mechanical interlocking with microscale surface fea- tures. Statistical modeling and experimental validation indicate that variability in individual pin forces and contact numbers are the primary sources of grasping uncertainty. The robot demonstrated robust and stable locomotion in indoor tests on inclined walls (10◦–30◦) and in outdoor tests on natural rocky terrain. This work highlights that a design emphasizing passive compliance and mechanical redundancy provides a practical and robust solution for real-world climbing robots while minimizing control complexity.