An Impact-based Piezoelectric Converter Wrapped With Copper Coils

Thanks to the development of wireless sensor networks,smart wearable devices are reaching people's lives.However,the frequent number of charges,longer charging time,not only affect the user experience,but also become the difficulty of further popularization of wearable devices.This research develops and adapts the energy acquisition technology,makes the wearable device completely passive,fundamentally ends its life problem.At present,the more mature energy acquisition technology mainly collects the four most common energy sources in nature: solar energy,thermal energy,radio frequency(RF)radiant Energy and vibration energy.Considering the application scenario of wearable devices,the vibration energy is selected as the power source.The traditional vibration collector can only work effectively in the resonant frequency band if the size of the transducer is reduced to the desired degree,it will inevitably lead to the resonant frequency higher than the frequency of environmental vibration,so that the two can not match.For this reason,a collision type piezoelectric electromagnetic composite energy collector is proposed in this study.In this study,the energy collector of piezoelectric electromagnetic composite mechanism is analyzed theoretically,and a simplified model of energy acquisition process in a period of magnetic motion is given.According to the model,the Energy acquisition of piezoelectric unit and electromagnetic unit is analyzed theoretically and simulated respectively,and the energy conversion efficiency under the single action of the two mechanisms is obtained,and the reasons that may cause the error are analyzed.The change of energy conversion efficiency under the combination of two mechanisms is summarized,and a standard for evaluating the coupling strength of the system is given.An experimental study on the energy collector of piezoelectric-electromagnetic composite mechanism is carried out.An experimental test platform is set up to calibrate the amplification amplitude of the input signal.The output characteristics of piezoelectric units and electromagnetic units under different amplitude and frequency conditions and magnetic height are studied respectively,and their output capacity is evaluated.Under the excitation of 2G,10 hz,the piezoelectric unit outputs 11 Vpp under the test system with a magnet thickness of 10 mm,and the electromagnetic unit output is 1Vpp.Considering the actual application scenario,the human wearing experiment is carried out on the collector,and the piezoelectric unit and the electromagnetic unit obtain the maximum output when the energy collector is fixed on the wrist and ankle respectively,which is 12.16 m W and 2.36 m W.The influence of induction coil on the output of piezoelectric unit is discussed.Finally,the corresponding power management scheme is given.The energy collector of collision piezoelectric-electromagnetic composite mechanism is optimized.For piezoelectric units,the larger the film size,the higher the output efficiency of the piezoelectric unit,but the design should also consider the actual needs.For the electromagnetic unit,the influence of the structure parameters of the magnet,the height of the cavity and the height of the coil winding on the output of the induction coil is analyzed respectively.