自适应调频声衬及其控制系统设计

为克服现有声衬结构固定、敏感频率无法调节的弊端,提出了一种逆压电效应的调频式声衬结构。该声衬由颈部、共振腔以及压电膜片组成亥姆霍兹共振器。采用有限元法对声衬结构的固有频率、声场分布进行了计算,研究了压电膜片变形与共振频率偏移的关系。在阻抗管内对压电声衬致动前后系统的传递损失进行了对比,系统传递损失峰值频率与驱动电压呈线性关系,灵敏度为0.1Hz/V。在建立控制电压-驱动电压-噪声频率的对应关系的基础上,提出了一种基于光敏电阻的直流升压电路,采用LabVIEW软件编制了压电声衬的自适应控制程序,当噪声频率从746变化至788Hz时,驱动电压由110V自动升高至420V,声衬始终工作于共振状态,实现了宽频噪声的自适应控制。

Design of Piezoelectric Tunable Liner and Control System

A tunable liner (TL) based on the inverse piezoelectric effect is developed to tackle the shortage of traditional liners, such as unchangeable structure and uncontrollable sensitive frequency. It consists of a neck, resonant chamber and piezoelectric patch which forms a Helmholtz resonator. The finite element modeling (FEM) is used to calculate the resonant frequency and sound pressure distribution of the acoustic system. The transmission loss measurement is carried out in an impedance tube to demonstrate the broadband noise control effect of the linear system. The result indicates that the TL peak frequency remains linear to the drive voltage and the sensitivity is measured to be 0.1 Hz/V. A DC amplifier circuit using photoresistor is designed to construct the function of control voltage, driving voltage, and noise frequency. The control algorithm is developed by LabVIEW software. When the noise frequency drifts from 746 Hz to 788 Hz, the driving voltage can be modulated automatically from 110 to 420 V, and the liner keeps resonating. The adaptive noise control is realized to reduce broadband noise.