Research on active magnetic field compensation for high-efficiency Terfenol-D magnetic circuit in magnetostrictive transducers

A high-efficiency Terfenol-D magnetic circuit with large-section permanent magnets is proposed to improve the electroacoustic efficiency of magnetostrictive transducers. This design adopts long Terfenol-D rods with an integral drive instead of the conventional multiple short Terfenol-D rods with segmented drive, eliminating the influence of the high magnetic resistance of permanent magnets in the magnetic circuit. The static magnetic field distribution of the long Terfenol-D rod is reconstructed through an increase in the cross-sectional area of the permanent magnet using active magnetic field compensation technology, effectively compensating for the weak magnetic field in the middle of the long Terfenol-D rod. The electroacoustic efficiency of the transducer improves by increasing the output sound power without reducing the input electrical power. Then, a high-efficiency Terfenol-D magnetic circuit with large-section permanent magnets and a transducer driven by it are designed and fabricated and compared to a segmented driving magnetic circuit. The test results show that the response and electroacoustic efficiency of the transducer driven by the high-efficiency magnetic circuit at 950 Hz are 187.6 dB and 38.6%, respectively, which are approximately 2 dB and 4% higher than those of the conventional segmented magnetic circuit.