cs.ROMar 17, 2026

LIMBERO: A Limbed Climbing Exploration Robot Toward Traveling on Rocky Cliffs

Authors: Kentaro Uno, Masazumi Imai, Kazuki Takada, Teruhiro Kataonami, Yudai Matsuura, Antonin Ringeval-Meusnier, Keita Nagaoka, Mikio Eguchi, 

Organizations: The authors are with the Space Robotics Lab. (SRL) in Department of Aerospace Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. · The author is with the National Institute of Applied Sciences of Toulouse, 31400 Toulouse, France.

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Abstract

In lunar and planetary exploration, legged robots have attracted significant attention as an alternative to conventional wheeled robots, which struggle to traverse rough and uneven terrain. To enable locomotion over highly irregular and steeply inclined surfaces, limbed climbing robots equipped with grippers on their feet have emerged as a promising solution. In this paper, we present LIMBERO, a 10 kg-class quadrupedal climbing robot that employs spine-type grippers for stable locomotion and climbing on rugged and steep terrain. We first introduce a novel gripper design featuring coupled finger-closing and spine-hooking motions, tightly actuated by a single motor, which achieves exceptional grasping performance (>150 N) despite its lightweight design (525 g). Furthermore, we develop an efficient algorithm to visualize a geometry-based graspability index on continuous rough terrain. Finally, we integrate these components into LIMBERO and demonstrate its ability to ascend steep rocky surfaces under a 1 G gravity condition, a performance not previously achieved yet for limbed climbing robots of this scale.

Figures & tables

Fig. 1: LIMBERO: A Limbed Climbing Exploration Robot. LIMBERO’s spine gripper can hold 15 kg load in Earth gravity (bottom left). Developed algorithm can visualize graspability score in the irregular terrain map (bottom right).
RobotMassNum. ofActive DOFGripperGrasping ForceTerrainGravity
Limbsper LimbActuationGripping Principle   ‡1\;{}^{{\ddagger}1}per Gripper
LEMUR 3 [ 12 ]35 kg47ActiveRadial hooking150 NRocky terrain3/8 G
ReachBot [ 4 ]18 kg83ActiveRadial biting and hooking22 N ‡2Rocky terrain3/8 G
LIMBERO9.7 kg44ActiveRadial biting and hooking150 NRocky terrain1 G
SCALER [ 18 ]9.6 kg46ActiveTwo-fingered biting>> 30 N ‡2Artificial holds1 G
MARCBot [ 27 ]4.8 kg45ActiveRadial biting and hooking49.0 NRocky terrain1 G
TABLE I: Comparative summary of the state-of-the-art limbed climbing robots (ordered by weight).
Fig. 2: Grasping performance by the developed gripper.
Fig. 3: Gripper design: a servo motor drives a worm and two worm wheels, which linearly move the stage (yellow) to tighten or loosen the metal wires, thereby opening and closing the gripper.
Fig. 4: Limb design: three actuators are concentrated at the shoulder via a parallel-linked mechanism, reducing limb inertia while preserving a large workspace. Three pitch joints requiring high torque capacity are equipped with a 3.5:1 planetary gear reduction.
Fig. 5: Base design: an axisymmetric structure accomodates electronics, sensors, and batteries.
Fig. 6: Software architecture implemented for LIMBERO.
Fig. 7: Case study of the gripper mask matching method over various terrain. The terrain array and the gripper mask are illustrated in simplified cross-sectional view.
Fig. 8: The output of the graspability is an interpolated point cloud, with colors representing the graspability score of each point. Higher-resolution settings for voxelization require longer computation time, but achieve more accurate scoring (right).
Fig. 9: Cliff holding test by LIMBERO. The robot demonstrated 1.4 kg payload capacity under Earth gravity.
Fig. 10: Rock climbing with LIMBERO under full Earth gravity. The right foothold history indicates the initial grasping points (black dots) and the step order (numbers) on the graspability-assessed terrain map. The 7th step represents a regrasping action around the same foothold. Regions with very low graspability are omitted from the visualization.
Fig. 11: Power consumption of all actuators of LIMBERO during climbing. Several peaks correspond to periods when the robot pushes the base upward.
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