A Pin-Array Structured Climbing Robot for Stable Locomotion on Steep Rocky Terrain

Abstract

Climbing robots face significant challenges when navigating unstructured environments, where reliable attachment to irregular surfaces is critical. We present a novel mobile climbing robot equipped with compliant pin-array structured grippers that passively conform to surface irregularities, 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 features. 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 degrees) 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.

Figures (9)

• Figure 1: The pin-array unit passively adapts to irregular terrain shapes, enabling stable ground-gripping locomotion (top). The robot demonstrated stable adhesion performance on steeply inclined rocky terrain (bottom left) and was also deployed in a natural rough landscape (bottom right).
• Figure 2: Overview of the pin-array structured gripping technology: (a) hardware structure, (b) gripping mechanism, and (c) mechanical model of contact. A concave shape is exemplified as a terrain surface in (b); however, the same mechanism also works for convex shapes for gripping.
• Figure 3: Pin-array gripper unit design. Sixty-six pins are installed and driven by a single actuator.
• Figure 4: Holding force measurement setup. The pin-array gripper's engaging performance was tested on various convex and concave objects with different ${\it \Phi} = \pm30^{\circ}, \pm60^{\circ}, \pm90^{\circ}$, while the height of the force application point from the terrain was kept constant at $d = 0.14$ m.
• Figure 5: Simulation results validating the mechanical model of the pin-array gripper. The points correspond to the measurements from the holding force evaluation tests and are largely encompassed within the confidence interval.