This paper investigates a modified acoustic metamaterial system with local resonators coupled through linear springs. The proposed acoustic metamaterial system can provide three band gaps for broadband vibration suppression. First, the band structure of the modified acoustic metamaterial is calculated by using Bloch’s theorem under the assumption of infinite lattice. The existence of three band gaps is confirmed in the band structure. Effects of mass and spring parameters on the band gap behaviour of the modified metamaterial are investigated through a dimensionless parametric study. Based on the parametric study, optimal dimensionless parameters are proposed to achieve maximal total band gap width in the low frequency range. Subsequently, a more realistic finite lattice model is established. The transmittances of the conventional and modified metamaterial systems are compared. The three band gaps predicted from transmittances and broadband vibration suppression behaviour are consistent with the predictions from infinite lattice model using Bloch’s theorem. Finally, the time-domain responses are simulated and the superiority of the modified acoustic metamaterial over the conventional one is demonstrated.

At present, frequency up-converted piezoelectric energy harvesters are disadvantaged by their narrow range of operating frequencies and low efficiency at ultralow-frequency excitation. To address these shortcomings, we propose herein an impact-driven frequency up-converted piezoelectric energy harvester composed of two driving beams and a generating beam. We find experimentally that the proposed device offers efficient energy output over an ultrawide-frequency-range and performs very well in the ultralow-frequency excitation. A maximum peak power of 29.3 mW is achieved under 0.5g acceleration at the excitation frequency of 12.7 Hz. The performance of the energy harvester can be adjusted and optimized by adjusting the spacing between the driving and generating beams. The results show that the proposed harvester has the potential to power miniaturized portable devices and wireless sensor nodes.

At present, piezoelectric energy harvesters are disadvantaged by their low efficiency and high operating frequencies. To address these shortcomings, we propose herein a hybrid piezoelectric-electromagnetic energy harvester (HPEH) for the low-frequency vibration environment, which is composed of a piezoelectric part featured with a double-clamped trapezoidal beam and an electromagnetic part featured with a magnet sleeve and plane coils. The modeling and experiment of the HPEH were carried out to optimize the structure and performance. We find experimentally that the proposed device not only increases the piezoelectric output but also highly improves the electromagnetic output. At the excitation acceleration 2 m/s², the average output power of the piezoelectric part and the electromagnetic part is increased by 30.5% and 20 times, respectively. The total output power of the HPEH is increased by 52.4%, reaching 0.637 mW. The results show that the proposed HPEH can efficiently use vibration energy to improve its output performance, which has the potential to power wireless intelligent sensor network and wearable electronic devices.

In this paper, a new micromachined tuning fork gyroscope (TFG) with an anchored diamond coupling mechanism is proposed while the mode ordering and the vibration sensitivity are also investigated. The sense-mode of the proposed TFG was optimized through use of an anchored diamond coupling spring, which enables the in-phase mode frequency to be 108.3% higher than the anti-phase one. The frequencies of the in- and anti-phase modes in the sense direction are 9799.6 Hz and 4705.3 Hz, respectively. The analytical solutions illustrate that the stiffness difference ratio of the in- and anti-phase modes is inversely proportional to the output induced by the vibration from the sense direction. Additionally, FEM simulations demonstrate that the stiffness difference ratio of the anchored diamond coupling TFG is 16.08 times larger than the direct coupling one while the vibration output is reduced by 94.1%. Consequently, the proposed new anchored diamond coupling TFG can structurally increase the stiffness difference ratio to improve the mode ordering and considerably reduce the vibration sensitivity without sacrificing the scale factor.

This paper presents the design and analysis of a new micro-electro-mechanical system (MEMS) tuning fork gyroscope (TFG), which can effectively improve the mechanical sensitivity of the gyroscope sense-mode by the designed leverage mechanism. A micromachined TFG with an anchored leverage mechanism is designed. The dynamics and mechanical sensitivity of the design are theoretically analyzed. The improvement rate of mechanical sensitivity (IRMS) is introduced to represent the optimization effect of the new structure compared with the conventional one. The analytical solutions illustrate that the IRMS monotonically increases with increased stiffness ratio of the power arm (SRPA) but decreases with increased stiffness ratio of the resistance arm (SRRA). Therefore, three types of gyro structures with different stiffness ratios are designed. The mechanical sensitivities increased by 79.10%, 81.33% and 68.06% by theoretical calculation. Additionally, FEM simulation demonstrates that the mechanical sensitivity of the design is in accord with theoretical results. The linearity of design is analyzed, too. Consequently, the proposed new anchored leverage mechanism TFG offers a higher displacement output of sense mode to improve the mechanical sensitivity.