RHex: A Simple and Highly Mobile Hexapod Robot

TLDR

The paper presents the design and control of RHex, a power‑autonomous, untethered, compliant‑legged hexapod robot. RHex uses only six hip‑mounted motors, giving it mechanical simplicity that enhances reliability and robustness in real‑world tasks. Experiments show that RHex achieves stable, highly maneuverable locomotion with a simple clock‑driven open‑loop tripod gait, full‑circle leg rotation that avoids toe stubbing, and intrinsic mobility across rugged terrain without sensing, reaching speeds up to one body length per second and traversing height variations beyond its body clearance.

Abstract

In this paper, the authors describe the design and control of RHex, a power autonomous, untethered, compliant-legged hexapod robot. RHex has only six actuators—one motor located at each hip— achieving mechanical simplicity that promotes reliable and robust operation in real-world tasks. Empirically stable and highly maneuverable locomotion arises from a very simple clock-driven, open-loop tripod gait. The legs rotate full circle, thereby preventing the common problem of toe stubbing in the protraction (swing) phase. An extensive suite of experimental results documents the robot’s significant “intrinsic mobility”—the traversal of rugged, broken, and obstacle-ridden ground without any terrain sensing or actively controlled adaptation. RHex achieves fast and robust forward locomotion traveling at speeds up to one body length per second and traversing height variations well exceeding its body clearance.