Zero-stiffness in rolling-lobe air springs for passive, load adaptable and low-frequency vibration isolation

Abstract

Low-frequency vibration isolation is crucial for engineering structures and devices susceptible to low-frequency vibrations. Traditional linear isolators fail to provide effective low-frequency isolation without compromising static load capacity. At the same time, quasi-zero-stiffness designs struggle with load adaptability, maintaining zero-stiffness over a large displacement range, or require active components to achieve the former. Combining all of these features, this study investigates rolling-lobe air spring isolators as a passive vibration isolation alternative, aiming to achieve zero-stiffness across a wide displacement range under varying loads. To identify factors affecting vibration isolation performance in rolling-lobe isolators, this research examines various design parameters, including isolator geometry, internal pressure, external volume and membrane behavior. These parameters’ influence on the stiffness and damping characteristics is investigated through a rapid prototyping approach employing 3D-printing to fabricate and test 86 unique isolator configurations. The experimental data informs a predictive model based on a Duffing oscillator, which is then applied in single degree-of-freedom simulations to assess isolation efficiency across different loads and excitation levels. The simulation results demonstrate effective isolation from close to 2 Hz onwards for the most promising configuration. Key findings are that higher internal pressures, controlled membrane deformation, and the addition of external volumes greatly enhance isolation performance. These insights provide valuable guidelines for designing rolling-lobe isolators capable of achieving zero-stiffness under varying loads and excitation levels, making them suitable for applications demanding robust passive vibration isolation over a broad range of operating conditions.