High-Load-Density Electro-Permanent Magnetic Foot with Controllable Adhesion for Quadruped Wall-Climbing Robots

2026-05-29

AI Summary

This study addresses the challenge of poor controllability in magnetic adhesion for quadruped robots performing high-payload climbing on ferromagnetic surfaces. The authors propose a magnetic foot system based on a circular Halbach meshed electro-permanent magnet (CHN-EPM). By engineering a three-dimensional magnetic circuit with distributed parallel flux paths, the design significantly enhances magnetic flux utilization and robustness against air gap variations and partial contact. Precise adhesion control and real-time state monitoring are achieved through a two-stage pulsed current strategy, a dedicated magnetization drive circuit, and flexible pressure-sensing feedback. The resulting single-foot adhesion force exceeds 1000 N, yielding a payload-to-weight ratio greater than 200:1. Stable, high-load adhesion and robust locomotion are successfully demonstrated on complex ferromagnetic surfaces, including ceilings, vertical walls, and substrates with paint coatings, holes, or curvature.

Abstract

To enable reliable climbing locomotion of quadruped robots on ferromagnetic surfaces, this paper presents a high-load-density electro-permanent magnetic foot with controllable adhesion, featuring force-feedback circular Halbach-net electro-permanent magnet (CHN-EPM) adhesion units and a magnetization control system. Due to its three-dimensional magnetic circuit structure and flux-concentration effect, the CHN-EPM enables a distributed parallel magnetic flux path with enhanced flux utilization, resulting in reduced sensitivity to air-gap variations and allowing effective adhesion to be maintained even under partial contact conditions. The proposed CHN-EPM generates a maximum adhesion force exceeding 1000 N with a load-to-weight ratio over 200:1. A magnetization driver and a two-stage pulse current control strategy are developed to regulate the excitation current amplitude and duration, enabling accurate and reliable magnetization. By incorporating a flexible pressure sensor for contact force feedback, the system can effectively monitor attachment and detachment states, ensuring robust adhesion switching under uncertain contact conditions. The proposed system is integrated into a commercial quadruped robot (Unitree GO2), demonstrating high-load adhesion on ceiling and vertical-wall surfaces and stable locomotion on painted, perforated, and curved ferromagnetic surfaces.

Problem

• wall-climbing robots
• controllable adhesion
• electro-permanent magnet
• high load density
• ferromagnetic surfaces

Innovation

• electro-permanent magnet
• Halbach array
• controllable adhesion
• wall-climbing robot
• magnetic flux concentration