| Enclosed metal containers are used in harsh conditions to protect internal targets out of external environment.Realizing electrical-contactless power transfer(CPT)through metal wall is a challenging research project,because it's difficult to pass the metal wall for the electromagnetic energy due to electromagnetic shielding effect of metal.However,ultrasonic wave transfers effectively in objects of high density.Therefore,this thesis studies some principles and technologies of contactless power transfer technology using ultrasonic wave as indirect energy(short for ultrasonic contactless power transfer,UCPT)which takes metal as transmission medium.In this paper,a high-fidelity model in which losses were considered for electric-ultrasonic-electric channel(short for EUE channel)was proposed to adopt circuit theories to study UCPT system.In proposed model,the components in UCPT system were equal to two-port network,and the losses of the piezoelectric components and non-piezoelectric components were represented by attenuation coefficients and loss coefficients,respectively.The cascade structure was analyzed and the circuit model of EUE channel was derived based on two-port circuit theory.Transmission parameters of two-port circuit theory were used to analyze the input and the output characteristics of the EUE channel.The calculation results,COMSOL FEM simulation results and experimental results showed that the proposed model was more accurate compare to the existing model,although the calculation time was slightly increased.The error of the output power under different working frequencies and the average error of the proposed model were much smaller than those of existing model,in which the average error of the output power decreases about 6.4 times in the proposed model compared to the existing model.The calculation results of the proposed model were still matched to the experiment results when the parameters in EUE channel changed.In addition,40W output power was realized in experiment.It's necessary for UCPT system to transfer data when transferring energy.Using one pair of transducer to to transfer power and data simultaneously is required when the installation space is limited,where the data transmission affects the power transmission less is also necessary.In this paper,two kinds of technology to transmission power and data simultaneously were studied:(1)The power and data were transferred simultaneously but in different directions where the data was transferred from the receiving side to transmitting side.One pair of transducer was used,and the power and data were transferred in the same working frequency.The voltage on the transmitting transducer was different for different loads in the receiving side based on the proposed model derivation.Therefore,2 amplitude shift keying(2ASK)technology was used to to transfer data.In receiving side,the modulation circuit and the voltage stabilizing circuit were designed.In transmitting side,the demodulation circuit was designed.The experiment result showed that the output voltage was kept 5V.In terms of data backward transmission,the data transfer speed was up to 1.6kbps in ideal condition and the speed was up to 1.43kbps when transferring image.(2)The power and data were transferred simultaneously and codirectionally.Langevin-type transducer and aluminum plates were used to compose UCPT system,and two working frequencies were derived.According to the proposed model,the model of Langevin-type transducer and the model of UCPT system composed of Langevin-type transducer were derived.The calculation results and the experiment results showed that there were two output peaks in certain frequency range.Accordingly.2 frequency shift keying technology(2FSK)was adopted to design modulation and demodulation circuit in transmitting side and receiving side,respectively.The experiment result showed the output powers were up to 25W in the two frequencies when the load was a bulb.The output voltage was kept 18V when the load was 100?.In terms of data transmission,the data transfer speed was up to 300bps in ideal condition and the speed was up to 240bps when transferring image.Two methods to improve power transfer quality were proposed:(1)Compensation method was proposed based on the special electrical characteristic of the transducer.Based on the simpliest equivalent circuit model of Langevin-type transducer,the compensation circuit was designed both in transmitting side and receiving side.Changing the impedance characteristic and realizing power control were realized based on transmitting compensation.Stable output voltage was realized based on receiving compensation.An electric-ultrasonicelectric type isolated power supply was proposed based on the compensated UCPT system.and the ability of anti-electromagnetic interference of UCPT and ICPT technology was compared.The experiment showed that,the compensation method changed the impedance characteristics,controlled the power and made the output power stable,and the anti-electromagnetic ability was better of UCPT technology,and the proposed power supply based on the proposed compensation method supplied for the gate driver efficiently.(2)To make the output power more constant,two pairs of transducer were used to compose the closed-loop system of UCPT technology.One pair of transducer was used to transfer energy from the transmitting side to the receiving side,and another pair was used to transfer the voltage signal of the load from receiving side to transmitting side.The duty of BOOST circuit was controlled to realize the constant output voltage.The transfer function was derived and the analysis of the function showed the stability of the proposed closed-loop system.The experimental result showed that the proposed method made the output voltage constant when the load varied suddenly,and the dynamic performance and the stable performance of the proposed system was excellent.The exploratory research of this thesis is helpful for improving the research level,enriching the research content of ultrasonic contactless power transfer technology,and is beneficial to the related engineering applications. |
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