Harvesting weak vibration energy by amplified inertial force and super-harmonic vibration

To harvest vibration energy from a low-frequency and weak excitation, a rigid-elastic bi-stable harvester is proposed. This harvester is composed of an inertial mass, two linkages and two PZT beams. Under external excitation, the inertial force generated by the rigid mass can be amplified through the linkages and applied to the PZT beam, making it take a large deflection and even jump between the potential wells. To tailor the potential energy to an optimal one, the moving and fixed magnets are introduced. The repulsive force between them could elevate the bottom of potential wells and thus decrease the potential barrier, then the harvester could execute snap-through motion more easily. Furthermore, the harvester possesses a superharmonic characteristic. Under a low-frequency base excitation, the PZT beam can execute a super-harmonic vibration, this will increase the change times of stress of PZT material, thereby increasing the output power. The experiment results prove that the harvester could execute super-harmonic vibrations and snap-through motions under weak stochastic excitations. The large output could keep under weak excitations. At PSD = 0.01 g2/Hz, the average output power can reach 0.016 mW. •A rigid-elastic harvester is designed to harvest low-frequency weak vibration energy.•Amplified inertial forces act on piezoelectric beams to produce a large deflection.•Magnets are introduced to tailor potential wells to lower the potential barrier.•Under low-frequency excitation, the PZT beam can execute a super-harmonic vibration.•Experiment proves the harvester generates a large power for weak random excitation.