Horizontal Stiffness Characteristics of Three-Wire Pendulum in Air Spring Vibration Isolator: Modelling and Simulation

Air spring vibration isolator is a major approach to attenuate ground/base vibration for precision equipment. Three-wire pendulum can be used as the horizontal isolation mechanism in air spring vibration isolator. Horizontal stiffness variation due to change of equilibrium position, referred to as the horizontal stiffness characteristics, are essential for analysing interaction between different mechanisms in vibration isolator. Analytical model for calculating horizontal stiffness characteristics of three-wire pendulum within a certain range around its initial position is established. Then the three-wire pendulum in an air spring vibration isolator prototype and related variants are analysed using the proposed model. Static and dynamic rigid multibody simulations are also carried out to verify the analytical model and reveal effects of model parameters on the stiffness characteristics. Results show that the difference between simulated and analytical stiffness characteristics is acceptable, and stability can be predicted using the analytical model. Besides, primary parameter affecting the stiffness and stability is identified. The proposed model offers an analytical method to quickly examine the property of three-wire pendulum before further investigation.