Design and nonlinear dynamics of tri-stable piezoelectric vibration energy harvester with a bio-inspired RRS structure

A novel tri-stable piezoelectric vibration energy harvester (PVEH) with a raceway-roller-spring (RRS) structure inspired by soybean pod is proposed for efficient vibration energy harvesting. Its main advantage is that the RRS structure eliminates any use of magnets and can be flexibly designed into various morphologies to achieve the expected nonlinear tri-stability by self-defining the raceway's coordinates. Firstly, the detailed design steps and nonlinear tri-stability induction mechanism of RRS structure were studied, and then the nonlinear dynamic model of PVEH with RRS structure was derived to explore the system dynamics and harmonic response under sweep frequency and harmonic excitation. Finally, a prototype is manufactured and used for experimental investigation and validation. The results indicate that the PVEH with asymmetrical RRS structure can generate a peak voltage and power of 30.4 V and 241 μW, respectively, achieving the normal power density (NPD) of 4.82 μW mm⁻³.g⁻².Hz⁻¹ over an effective bandwidth of 3.6 Hz (2.4–6 Hz), which is higher than that of the comparisons, meeting the self-powering demands of low-power electronic devices.