Tuning the Dynamics of Bistable Mechanisms by Introducing Travel Limits

Abstract

Vibrations are a promising source for powering wireless sensors, for example in low-frequency environments like human motion. These environments suffer from unpredictable vibration spectra and their low-frequency and large amplitude characteristics offer great possibilities for mechanisms with double well potential energy characteristics. The dynamical output performance of a bistable mechanism depends on the oscillation in the large amplitude trajectory between the two potential wells. However, requires enough force to overcome potential energy barrier. This work aims to improve the occurrence of interwell oscillation by lowering the potential energy barrier between the two potential wells by the influence of hard mechanical travel limits. A bistable mechanism is numerically modelled and experimentally tested to investigate the influence of the mechanical travel limits for low-frequency excitations. An axial loaded buckling beam was used to introduce bistability and combined with a parallel guidance mechanism to compensate for the strong negative stiffness. A single-degree of freedom model is used to model the bistable characteristics and is expanded with a coefficient of restitution model to represent the mechanical characterization of the travel limits. This combination resulted in a decrease in required force for the oscillation in the desired large amplitude trajectory by constraining the oscillator motion with travel limits. Furthermore, the results from the numerical bistable model in combination with mechanical characteristics of the travel limits at impact, proves to be in good agreement with the experimentally obtained results.