Resonant Frequency Adaptive Tracking Ultrasonic Wireless Power Supply Technology

In order to supply power to the internal sensors of a container with a closed metal shell,such as a shell,a fuel tank,or a pressure vessel,a means of wireless power supply across the metal is needed.However,due to the electromagnetic shielding effect of metal,the traditional wireless transmission technology cannot realize the energy transmission across the metal.In this environment,the piezoelectric ultrasonic wireless power supply technology can realize the wireless transmission of electric energy without compromising the integrity of the metal.The piezoelectric transducer at the transmitting end is used to generate ultrasonic waves,which penetrate the metal medium and are accepted by the transducer at the receiving end.And converted into electrical energy.The performance of this ultrasonic wireless power supply technology depends on whether the transducer and the metal medium are in a common resonance state.When the two enter the resonance state,the metal wall produces the maximum amplitude of mechanical deformation at the output end,so that the maximum amplitude voltage can be output.However,this resonance state will be destroyed under certain circumstances.For example,when the thickness of the metal wall,the temperature of the metal medium,the material of the metal inner wall,etc.change,the resonance frequency may change,thereby affecting the power and efficiency of the ultrasonic wireless power supply.In response to the above problems,this thesis analyzes the equivalent circuit model of the common resonance system of the piezoelectric transducer and the metal medium to explain its electrical characteristics;through theoretical analysis and experimental verification,the factors affecting the resonance frequency of the piezoelectric metal composite structure and its The law of change: A resonant frequency adaptive tracking scheme for ultrasonic wireless power supply is proposed,which makes the application of this technology universal.The main content of this article is as follows:(1)Based on the working principle of the piezoelectric transducer,the composition and related issues of the cross-metal piezoelectric ultrasonic wireless power supply system are analyzed and researched,including the basic composition of the ultrasonic wireless power supply system and the propagation of mechanical vibration in elastic media.,The basic characteristics of piezoelectric ceramics,and the derivation of the electromechanical equivalent circuit of the piezoelectric transducer module.(2)Establish an equivalent circuit model of the piezoelectric metal common resonance composite structure.The electromechanical equivalent method is used to obtain the equivalent electrical model of the composite structure.Through the simulation analysis of the equivalent model and the experimental test of the composite structure,the change rule of the resonant frequency of the composite common resonance system is clarified.(3)Propose an oscillating circuit that can realize adaptive tracking of resonant frequency.According to the characteristics of the state when the piezoelectric metal composite structure is in resonance,the oscillating circuit is designed with positive feedback so that the oscillating frequency of the oscillating circuit is equal to the resonant frequency of the composite structure.Finally,an experimental platform was built to verify the resonant frequency self-adaptability,load characteristics and temperature characteristics of the overall circuit.On the one hand,this thesis explains the changing law of the resonant frequency of the composite structure,and conducts experimental tests;on the other hand,it uses self-excited oscillation to track the resonant frequency of the composite structure,and abandons the complex loop in the traditional scheme.This technology can be applied to occasions where electromagnetic wireless energy transmission cannot work normally in military,industrial,medical and other fields.