A Review of Passive Linear Gravity Compensation Mechanisms

This study presents a review of passive linear gravity compensation (GC) mechanisms. Linear GC is defined as the realization of a displacement-independent constant upward force along a vertical axis to balance the gravitational load over the entire stroke. This paper focuses on passive systems that counteract gravity solely through mechanical or magnetic energy storage elements, without relying on external power sources. The main energy sources in passive systems—springs, permanent magnets, counterweights, and fluid pressure—are surveyed with emphasis on their ability to generate a constant force. Representative spring-based constant-force mechanisms, cam–spring linkages, and quasi-zero-stiffness magnetic gravity compensators are summarized, together with their applications in vibration isolation systems. Finally, reported performance data are compiled to outline the practical operating envelope of passive linear GC in terms of force level, stroke, and equivalent stiffness. This review reveals that permanent-magnet-based approaches are advantageous for short-stroke, high-precision applications, whereas spring-based mechanisms offer superior suitability for long-stroke requirements due to their greater design flexibility. Consequently, this review provides a strategic selection guideline based on the inherent trade-offs of energy-storage elements to meet specific application requirements.