Design and investigation of a compliant-pneumatic quasi-zero stiffness device for energy harvesting

Vibration energy harvesting is a feasible method for providing energy to low-power devices. However, most vibration energy harvesting devices are incompetent in facing low-frequency issues. Moreover, the existing low-frequency vibration energy harvesters are mainly based on rigid parts like cam, rod and springs, results in complex and bulky structures, which further limit their application scenarios. In this paper, a compact quasi-zero stiffness with adjustable positive stiffness is realized by a parallel combination of flexible bistable beam and pneumatic cylinder. The feasibility of the design is validated through both simulation and experimental studies. Experiment results show that the maximum voltage of the series connection piezoelectric energy harvester is 16.2 V with an external resistance of 8 MΩ and the maximum power is 191.5 μW with an external resistance of 0.3 MΩ at the condition of 22 Hz excitation frequency, a 20 g tip mass and 1.5 mm amplitude. The flashing experiment of the LED light shows that the flashing time interval of the LED light is as short as 2 s under the excitation level of 22 Hz, whether it is in series, in parallel or a single beam. The results show that the device responds well to low-frequency energy harvesting within the designed QZS region.