Design of a Low-Frequency Vibration Isolator With Large-Stroke and Variable-Payload Capabilities Using Gear-Spring Units

Low-frequency vibration isolation is essential in precision engineering, robotics, and biomedical applications, where even minor disturbances can degrade the system's performance. This article proposes a low-frequency vibration isolator with large-stroke and variable-payload capabilities. The vibration isolator is constructed with a parallel mechanism consisting of six identical RRR legs. Vibration isolation is realized from zero-stiffness conditions by integrating a gear-spring unit (GSU) into each leg of the mechanism. Each GSU comprises a pair of gears and a position-adjustable linear spring controlled via a lock slider. The significance of this design approach is that it can provide the vibration isolator with a large isolation stroke and the capability to cope with variable payloads. In this work, the conceptual design of the vibration isolator, vibration isolation analysis, performance evaluation, and simulation verification are presented. The simulation results show that the response of the vibration isolator is significantly smaller than its excitation, achieving an acceleration reduction exceeding 97%. Vibration isolation is effective across a broad frequency range - including near-zero frequencies - and adaptability to varying equilibrium positions and payloads. The results also reveal improved isolation with higher loads and reduced friction.