A Single-Input State-Switching Building Block Harnessing Internal Instabilities

TL;DR

This paper introduces a novel single-input, contactless bistable mechanism that uses internal instabilities and information-based decision-making to enable efficient state switching with only one cyclic input.

Contribution

It presents a new elastic design strategy leveraging internal instabilities for single-input state transitions in bistable mechanisms, validated through modeling and experiments.

Findings

Nonlinear spring with quadratic stiffness is key for state regulation.

The mechanism achieves contactless, energy-efficient switching.

Experimental results confirm the design's effectiveness.

Abstract

Bistable mechanisms are prevalent across a broad spectrum of applications due to their ability to maintain two distinct stable states. Their energy consumption is predominantly confined to the process of state transitions, thereby enhancing their efficiency. However, the transition often requires two distinct inputs, implicating the requirement of multiple actuators. Here, we propose an elastic and contactless design strategy for inducing state transitions in bistable mechanisms, requiring only a single cyclic input. The strategy leverages internal information, interpreted as system state, as an extra input to make a weighted decision for transitioning to the subsequent state. We characterize the behavior using a spring-based rigid-body model, consisting of a column near bifurcation, combined with a non-linear spring connected to a bistable element that represents the information state. The results show that a nonlinear spring with a quadratic stiffness function, i.e., representing internal instability, is crucial for regulating state-switching behavior. We then demonstrate this design strategy by developing a monolithic and compliant design embodiment and experimentally evaluate its behavior.