Local gravity control method for solving load-mismatch issue in isolators

Abstract

Quasi-zero stiffness (QZS) shows significant advantages in low frequency vibration isolation. However, the isolation performance is heavily dependent on the rated load and prone to load-mismatch. Here, a general local gravity control method (LGCM) is proposed to eliminate these limitations by introducing an expected constant force to adjust the equivalent gravity of the mismatched load. As a result, the isolators can be maintained at an ideal static equilibrium point with low dynamic stiffness. The load-mismatch was investigated and emphasized combined with the spring-link mechanism (SLM). The analysis indicated that the load-mismatch results in stiffness hardening, natural frequency increasing, and vibration isolation band shortening. The principle of the LGCM was fully revealed in the respect of conceptual design, electromechanical coupling analysis, control system and operation mechanism. The harmonic balance method (HBM) was used to model the response of the periodic and sweep excitation. The electromechanical coupling simulation was implemented to theoretically verify adjustment ability of LGCM. A prototype based on SLM and Arduino UNO was fabricated and tested with proportional-integral-derivative (PID) to validate the effectiveness of the LGCM. The results illustrates that the vibration transmissibility in mismatched isolator at resonance frequency is decreased by 50 % with LGCM, which means that the resonance frequency can be decreased efficiently, and the isolation band is significantly broadened. The LGCM can be easily attached to any QZS systems, which can be regarded as a general patch for the bug of load-mismatch and is conducive to broaden the load-variable applications of QZS isolators.