The Study Of Moving Magnet Ultra Low Frequency Transducer

As a new type of underwater acoustic transducer which can working in ultra-low frequency band,moving magnet transducer has a wide application prospect,but the analysis method of moving magnet transducer is not perfect.This paper proposes a new structure of moving magnet transducer,which combines the structural characteristics of a cylindrical moving magnet transducer and a flat-plate moving magnet transducer.Under the condition of keeping the volume of the core unchanged,the driving electromagnetic force of the transducer is doubled.At the same time,the analysis method of moving magnet transducer is studied,and the theoretical derivation of moving magnet transducer and the analysis process and optimization design of the finite element method are given.Finally,the experimental prototype test was made.The magnetic field of moving magnet transducer is studied by magnetic circuit analysis method.The expressions of parameters such as flux linkage,electromagnetic force,inductance and back electromotive force are given.The mathematical model of the electromechanical conversion effect of the moving magnet transducer is established.The equivalent circuit of moving magnet transducer is constructed by the principle of machine-acoustic-electrical equivalent,and the electrical and acoustic characteristics of moving magnet transducer are given.Based on the equivalent circuit method,moving magnet transducer is optimized.The magnetic field finite element model and the sound field finite element model of moving magnet transducer were established using finite element software.The structure of the magnetic core is optimized by the finite element model of the magnetic field,and the electromagnetic force is accurately solved and optimized.The correctness of the theoretical electromagnetic force expression is verified.The sound power level of moving magnet transducer is given.The mode of the piston radiator is analyzed to avoid the bending resonance of the piston radiator,and the piston radiator is optimized.At the same time,in order to maintain the safety during the operation of the transducer,the two finite element models are combined to analyze the static adsorption force of the ferromagnetic core to the permanent magnet array and the static restoring force provided by the resonant spring system.Vibration modal analysis of the transducer ensures that the destructive mode of the transducer is outside the operating frequency bandAccording to the optimization result,the prototype of moving magnet ultra-low frequency transducer is made.The maximum diameter of the prototype is 310 mm,the maximum height is 318.6mm,and the mass is 30 kg.The test results in air show that the prototype system stiffness is 350N/mm,the system damping is 111.99N·s/m,and the simulation parameters are corrected according to the test results.The underwater test results show that the resonant frequency is 42 Hz,the maximum sound power level is 166.58 dB,and the sound power level is about 150 dB away from the resonant frequency,and the underwater test results are compared with the modified simulation results.