Papers by Author: Wen Cao

Abstract: Piezoelectric transducer with negative impedance matching circuit is put forward to enhance its performance in broadband frequencies. The typical multi-physics problem is coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations, and it is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-impedance in series. When proper negative synthesized elements are connected, the performance of low frequencies and bandwidth are enhanced obviously.

Abstract: Piezoelectric acoustic sensor with negative impedance matching circuit is put forward to enhance its sensitivity at low frequencies. The multi-physics problem coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-capacitance, resistance in series. Sensitivity is obtained from 1kHz to 5kHz. When used proper electrical elements, the sensitivity of the piezoelectric sensor can even exceed that of no matching circuit over 2 factors in broad band.

Abstract: Piezoelectric material shunted with negative capacitance can be used to insulate sound theoretically. But sound insulation of the system is limited by many factors. The dielectric and mechanical loss of the piezoelectric system deteriorate seriously the ability at some frequencies. According to the ideal electric elements formulas, the capacitance has imaginary part because of the loss. It has important influence on sound insulation ability. If a series resistance is introduced into the shunting circuit to form the imaginary part to compensate the loss, it is dependent on frequency. Sound insulation would be increased only in narrow band, and at some frequencies the system with the shunting circuit even becomes unstable.

Abstract: Piezoelectric system shunted with proper negative capacitance in series has low dynamic stiffness. According to frequency characteristic equations of the piezoelectric system, optimal parameters and characteristics of both shunted series structures were deduced and compared theoretically. One is negative-capacitance and resistance in series, and the other is negative-capacitance, resistance and inductance in seires. It presented that high damping characteristic can be obtained at low frequencies when shunted with series negative-capacitance. If proper inductance is included in shunt circuit, effective bandwidth could be extended and the peak of amplitude of response is decreased, what’ more, the stability of this structure is enhanced. This technology can be used in vibration isolators or sensors and the shunt structure including inductance is recommended.

Abstract: When a proper shunt circuit is connected with a curved piezoelectric membrane, its bended stiffness can be intensified. The system can be used for sound isolation. This mechatronic system， a typically multi-physics problem, was analyzed with FEM in detail. Frequency response characteristics were obtained when shunted with negative-capacitance in parallel. Transmission Loss was presented from 100Hz to 1000Hz. A wonderful sound isolation performance is obtained when shunted with proper values of negative capacitance. Negative capacitance and the loss of piezoelectric material are the main factors of the system. At some frequencies, the sound isolation performance can be increased when a compensated resistance paralleled with negative capacitance. This compensation is dependent on the frequencies. Due to its ordinary electrical parameters, the sound isolation system is realizable in practice. This sound isolation technology can be used in some fields such as windows of room and car.