Study On A Rotary Magnet Exciting Piezo-generator Based On Frequency Tuning Of A Overhanging Beam Held By Magnet

To improve the reliability and environmental adaptability of the piezoelectric generators,a rotary magnet exciting piezo-generator based on frequency tuning of a overhanging beam held by magnet was proposed,which was made by using the rotary magnets to excite the overhanging beam held by magnets based on L-shaped piezo-cantilever.The characteristics of power generation were studied theoretically and experimentally.The main contents are summarized as follows:1.The finite element simulation model of overhanging beam held by magnets based on L-shaped piezo-cantilever was established.The influence of the width ratio,thickness ratio and Young's modulus ratio on the stress distribution and deformation were analyzed,and influence of the distance of holding magnets?the initial distance between the holding magnet and held magnet?and span ratio of held beam?the ratio of the distance between fixed end and the center of the holding magnet to its maximum?on the stress distribution,natural frequency and mode were studied.The results show that:?1?The stress decreases with the increasing of Young's modulus ratio/distance of holding magnets/span ratio of held beam,and there are optimal width ratio and thickness ratio to improve the stress distribution of piezo-cantilever;The displacement of overhanging beam decreases with the increasing of the width ratio/thickness ratio/Young's modulus ratio;?2?The first-order natural frequency of overhanging beam held by magnets decreases with the increasing of the distance of holding magnets/additional mass,and increases with the increasing of span ratio of held beam,and the same surface of piezo-cantilever has the same charge polarity,which can improve the power generation.2.The finite element simulation model of the exciting force between the exciting magnet and excited magnet was established.The influence of the distance of exciting magnets/thickness ratio of exciting magnets/diameter ratio of exciting magnets/ratio of the number of exciting magnets?ratio of the number of exciting magnets to the maximum number of exciting magnets?on the exciting force were studied;The dynamics response model of piezo-generator was established and the MAPLE simulation program was designed.The influence of the ratio of the number of exciting magnets/system equivalent stiffness/damping ratio/additional mass on its output performance were studied.The results show that:?1?The amplitude of exciting force decreases with the increasing of the distance of exciting magnets,and increases with the increasing of thickness ratio of exciting magnets.And there are optimal diameter ratio of exciting magnets and ratio of the number of exciting magnets which make the amplitude achieve a maximum;?2?The waveform of exciting force is related to the diameter ratio of exciting magnets/ratio of the number of exciting magnets;It is changed from the half sine wave to the sine wave exciting and then to the forward biased sine wave exciting along with the increasing of the ratio of the number of exciting magnets;?3?There is a ratio of the number of exciting magnet for the amplitude ratio to achieve maximum peak.And the amplitude of peak to achieve maximum decreases with the increasing of the damping ratio,and the number of peaks decrease with the increasing of the ratio of the number of exciting magnets;?4?There are many optimal rotary speeds for the amplitude ratio to achieve peak,and the optimal rotary speeds increase with the increasing of the equivalent stiffness,and decrease with the increasing of additional mass.3.To verify the correctness of the theory and simulation,the prototype was made and tested,the effects of the distance of exciting magnets/additional mass/ratio of the number of exciting magnets/distance of holding magnets/span ratio of held beam on the output voltage were obtained.And the influence of distance of holding magnets/span ratio of held beam/load resistance on output power were studied.The results show that:?1?The amplitude of output voltage to achieve peak decreases with the increasing of the distance of exciting magnets/span ratio of held beam,and increases with the increasing of distance of holding magnets;?2?There is a ratio of the number of exciting magnet for the amplitude of output voltage to achieve maximum peak,and the number of peaks decrease with the decreasing of the ratio of the number of exciting magnet;?3?There are many optimal rotary speeds for the amplitude of output voltage to achieve peak,and the optimal rotary speeds decrease with the increasing of the distance of holding magnets/additional mass,and increase with the increasing of span ratio of held beam;?4?When the rotary speed is 234r·min^-1,the maximum output power is 10mW and the load resistance is 200K?.