Theoretical And Experimental Research On Wireless Energy Transmission Based On Ultrasonic Lamb Waves

At present,most of the ultrasonic wireless energy transmission technologies through metal walls are based on ultrasonic bulk waves as the energy carrier.Due to the propagation characteristics of the ultrasonic bulk wave,it is required that the ultrasonic transducer must be strictly centered on the inner and outer sides of the metal wall in order to detect the structure point by point.Therefore,the wireless energy transmission technology based on ultrasonic bulk wave have the shortcomings of low detection efficiency and high cost,and it is also lack of applicability in some closed occasions with strict space constraints.Moreover,the bulk wave method can only achieve one-to-one energy transmission,which means that it dissatisfies the the power supply demand of a large number of distributed sensors.Based on the above two problems,the application of ultrasonic bulk waves in the field of wireless energy transmitting is limited.At the same time,compared with the bulk waves,guided waves have outstanding characteristics: it is far greater than the propagation distance of the bulk wave,but its attenuation is smaller than that of the bulk wave,which can realize flexible and rapid nondestructive testing for large structural components of any shape.Because of its simple system composition,it can be applied as an important technical means to realize online dynamic monitoring of structural health.However,compared with ultrasonic bulk wave,the propagation process of guided wave is more complicated,which is mainly reflected in two characteristics: multimodal characteristics,that is,there are multiple guided wave modes at the same frequency;frequency scattering characteristics,that is,the propagation velocity of the same guided wave mode at different frequencies is different.Therefore,in the process of exciting high signal-to-noise ratio guided wave signals,there is a problem of poor flexibility of modal signals under specific frequencies.This will not only increase the difficulty of waveform recognition,but also lead to energy loss at other frequencies during continuous wave energy transmission.In response to the above problems,this paper proposes a wireless energy transmission system based on ultrasonic Lamb waves,and analyzes and studies its energy transmission principles and different transmission efficiency enhancement methods.The main work is as follows:Based on the pin-force model under the ideal paste solution,the system energy transfer function of the whole process of Lamb wave excitation-propagation-reception is derived,and its energy transmission principle is explained;a Lamb wave excitation-propagation-reception experimental platform based on piezoelectric wafer active sensor(PWAS)is developed.The effectiveness of the Lamb wave electromechanical coupling model is verified by numerical simulation and experimental results.Furthermore,according to the Lamb wave modal modulation theory,the single-mode Lamb wave is selectively excited.According to the impedance conjugate matching condition,the impedance matching circuit was designed using Smith impedance circle diagram,and the experimental platform of the ultrasonic Lamb wave wireless energy transmission system was built.The feasibility of applying the impedance matching method proposed in this paper to enhance the transmission efficiency was experimentally verified.For the one-dimensional linear uniform PWAS array,the beamforming optimization method is studied using the far-field beamforming theory,and the optimization parameter design is carried out,and the relevant experimental platform is built to verify the feasibility of the PWAS array to enhance the energy transmission efficiency.