Design of a Passive Gravity Compensation Mechanism for Wearable Bilateral Lower Limb Exoskeletons
Tongshu Chen, Ke Shi, Maozeng Zhang, Aiguo Song
AI summary
Problem
Existing passive lower limb exoskeletons rely on bulky, complex multi-spring gravity compensation systems that compromise compactness, reliability, and practical wearability.
Approach
The authors develop a synthetic centroid mapping method to design a unilateral gravity compensation unit, then extend it to a bilateral configuration using a differential mechanism that distributes force from a single constant-force spring to both legs.
Key results
- Novel differential gravity compensation unit (D-GCU) based on synthetic centroid mapping
- Compact bilateral exoskeleton prototype built with a single spring and lightweight materials
- Experimental validation confirms effective leg weight compensation during assisted walking
- Multi-degree-of-freedom gravity balance achieved with significantly reduced mechanical complexity
Why it matters
Provides a practical, reliable pathway for designing wearable passive exoskeletons for rehabilitation and mobility assistance without the bulk of traditional spring arrays.
Abstract
Gravity compensation has been widely employed in lower limb exoskeletons to reduce leg load and alleviate muscle fatigue. Passive compensation approaches offer inherent safety and lightweight advantages; however, existing designs are often constrained by the bulk and complexity of spring-based mecha- nisms, which compromises the compactness and reliability of the exoskeleton. To address these limitations, a gravity compensation mechanism is developed for a wearable passive bilateral lower limb exoskeleton, featuring a compact, simple, and robust design. A unilateral compensation concept based on a synthetic centroid mapping method is first introduced and then extended to a bilateral configuration through a differential structure. Combined with an adaptive constant-force mechanism, the resulting system maintains structural simplicity and spatial efficiency, making it suitable for wearable applications with limited integration space. An exoskele- ton prototype is constructed based on the proposed mechanism, and its performance is evaluated through experiments. The re- sults demonstrate that the proposed system effectively compensates for leg weight during walking while maintaining a lightweight, low-complexity, and structurally robust design.