| Wireless power transfer technology has been widely concerned because of the flexibilityof its power supply.At present,the more mature inductively coupled power transfer technology and magnetically-coupled resonant wireless power transfer technology use electromagnetic field as the transmission medium.When metal obstacles are encountered,energy transmission will be weakened or even blocked.The above problems can be avoided by using ultrasonic coupled wireless power transfer(UCWPT)for power supply in a closed metal container.At present,the focus of attention is on the improvement of energy transmission power and efficiency,but there is insufficient attention to the power consumption of the load.Therefore,the way of simultaneous transmission of energy and signals can transfer the energy received by the device from the inside of the airtight container by signal,thereby increasing the flexibility of power supply and improving the power quality.This will also be a hotspot for future research on wireless power transmission technology.The research background and present situation of UCWPT technology are expounded.The UCWPT system of metal medium is theoretically analyzed.Following this,the equivalent circuit model of the power type piezoelectric transducer is established by the principle of the electromechanical analogy.The equivalent circuit model and transfer function of the UCWPT system is analyzed when the receiving and transmitting side transducers are in the resonant and the non-resonant states respectively.A method of reverse synchronous transmission of energy and signal by ultrasonic wave is proposed.The PWM wave is obtained by comparing the load voltage signal with the triangular wave signal.The change of the load voltage is reflected in the change of the duty ratio of the PWM wave.The PWM wave is used to drive the transducer to realize the signal transmission.The voltage RMS value received is linearly related to the load voltage amplitude.On this basis,Fourier decomposition of PWM wave is carried out,and the transmission of signals is briefly analyzed from the perspective of wave composition.In order to realize the synchronous transmission of energy and signals,according to system requirements such as transducer parameters and load receiving capability,a circuit for ultrasonically transmitting energy and signals synchronously is designed,mainly including a driving power supply,a high-speed comparison circuit,a driving circuit,and signal detection circuit.The main factors that affect the energy transmission capacity are tested.It is found that the amplitude of the DC-side voltage of the power supply,the output frequency of the power supply and the thickness of the metal plate all have an impact on the transmission capacity of the system.The power type piezoelectric transducer has a narrow frequency band.When the output frequency is the optimal operating frequency of the transducer,the transmission capacity of the system is the best,and the relationship between the transmission power and efficiency with the amplitude of the DC side of the power supply is obtained.In addition,the influence of the thickness of the metal plate on the transmission capacity of the system is briefly analyzed from the perspective of wavelength.Experiments on synchronous transmission of energy and signal are carried out,and the transmission of energy and signal in the same direction and opposite direction is completed.When the direction of signal transmission is the same as the direction of energy transmission,the intensity of the signal is reflected by the light and dark changes of the LED load.When the signal transmission direction is opposite to the energy transmission direction,the RMS value of the voltage received by the receiving side of the signal is linear with the load voltage signal,and the signal is transmitted from the inside of the closed metal container to the outside. |
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