Design And Research Of Hybrid Energy Harvester Under Low Frequency Excitation

Vibration energy is almost everywhere in the environment.Various mechanical vibrations,bridge vibration,and human motion contain abundant vibration energy.It is an effective way to replace the traditional battery by harvesting vibration energy in the environment and converting it into electric energy.In recent years,triboelectric energy harvester has been rapidly developed in harvesting ambient vibration energy owing to its merits of light weight,diverse materials,low cost,and high output voltage.But the sparse pulse output,material abrasion in contact mode and charge dissipation in non-contact mode reduce the mechanical durability and electrical stability of triboelectric energy harvester.To improve the mechanical durability and electrical stability of triboelectric energy harvester,an intermittent-contact triboelectric energy harvester(IC-TEH)based on a slidable ropedriven rotor is proposed in this thesis.Through a whirligig-like dynamics mechanism,the rope-driven rotor can convert low-frequency vibrations into high-speed rotation.By converting vibrations into high-speed rotation,IC-TEH can realize frequency-multiplied and high electric output.Since the intermittent sliding contact between the rotor and stator in the rope-driven rotor can constantly replenish the tribo-charges for the friction layer,the ICTEH exhibits high electrical stability.In the ten-day stability test,the normalized voltage of IC-TEH can stabilize at around 81% after a significant decay in the first four days,while the normalized voltage output of the energy harvester operating in non-contact mode attenuates continuously to 48% within 10 days.In addition,IC-TEH has two resonant frequencies,which can expand the working bandwidth of the energy harvester.IC-TEH provides a new strategy for triboelectric energy harvester to achieve high electrical output and maintain long-term stability,which can efficiently harvest low-frequency vibration energy in the environment.There are various forms of energy in the environment.Although the energy harvester designed with a single energy conversion mechanism can realize the harvesting of ambient energy,it still exists the problem of poor environmental adaptability and low output power.To improve the output power and environmental adaptability of the energy harvester,a triboelectric-electromagnetic hybrid energy harvester based on a vibration-to-rotation mechanism is proposed in this thesis.The hybrid energy harvester can transform lowfrequency vibrations into high-speed rotation through the cantilever-driven rotor structure based on rack and pinion.Using the principle of electromagnetic induction,electrostatic induction and triboelectric effect,the advantages of the electromagnetic unit and the triboelectric unit can be complementary,so that the hybrid energy harvester can effectively harvest low-frequency vibration energy in the environment.Under the external excitation,the triboelectric unit of the energy harvester can realize the transition between non-contact and contact mode through the spring between the rotor and the stator,which can replenish the charges for the friction layer to improve the electrical stability of the energy harvester.Under excitation at the frequency of 3 Hz and the pressed depth of 10 mm,the output power of the electromagnetic unit and the triboelectric unit is 7.68 m W and 18.38 μW,respectively.The increase in output power makes the hybrid energy harvester have a broad prospect for powering low-power electronic devices.The two energy harvesters proposed in this thesis can transform low-frequency vibrations into high-speed rotation and can realize frequency-multiplied and high output.By harvesting low-frequency vibration energy in the environment,the electrical energy generated by the energy harvester can power low-power electronic devices,demonstrating the potential of the two energy harvesters in harvesting ambient energy for self-driven or self-powered devices.