主动式声学超表面研究及其控制系统设计

Study of active acoustic metasurface and design of its control system

为克服目前声学超表面存在可重构性差、功能单一以及稳定性较差等不足,基于声学理论并结合可编程逻辑控制器设计了一种可精密调节的多模式共振腔型声学超表面.首先建立了超表面狭缝宽度与相位变化的理论模型,并利用此模型分别计算出实现连续可调的声聚焦及声折射功能所需的狭缝宽度,且基于执行系统中的电机最大速度对其进行修正;其次设计包含单主多从模式硬件平台和电机运动软件算法的控制系统;最后利用自主研发的声场测试试验台对该超表面进行声波波阵面调制试验,并基于有限元方法分别对超表面调节入射平面波的声场进行数值模拟.试验和数值仿真结果表明,设计的控制系统可精确同步调控超表面狭缝宽度实现多种功能,设计的算法误差在0~1.1%,系统运行平顺性和鲁棒性得到提高,提出的主动式声学超表面解决了传统声学超表面可重构性差和因流体波动性导致共振腔室体积时变问题,增强了超表面的实际应用性,对声学超表面在主动声波操控方面提供了一定的指导.

In order to overcome the deficiencies of poor reconfigurability, single functionality and insufficient stability of current acoustic metasurfaces, a precision-tuneable multi-mode resonator-type acoustic metasurface is presented based on acoustics which contains a programmable logic controller. Firstly, the theoretical model of the slit width and phase variation of the metasurface is proposed. The slit width distributions required to achieve continuously tuneable acoustic focusing and acoustic refraction are calculated, respectively. Then they are modified based on the maximum speed of the motor in the actuation system. Secondly, the control system including a hardware system with single-master multi-slaver mode and an algorithm for regulating the motor rotation output is designed. Finally, several tests to modulate acoustic wave fronts are carried out on the proposed metasurface by using a self-developed test apparatus. How the metasurface manipulates the acoustic field of an incident plane wave is numerically simulated based on the finite element method. The experimental and numerical results show that the designed control system can accurately and synchronously tune the slit width of each unit of the metasurface and achieve multi functions. The error of the designed algorithm is between 0 and 1.1%. Moreover, the initial design of the control system is improved to achieve smoothness and robustness in its operation. The problems of the poor reconfigurability of the conventional acoustic metasurfaces as well as the time-varying volume of the resonator chamber caused by the fluctuation of the fluidic system are overcome by the proposed active acoustic metasurface, which can enhance the practical applicability of the metasurface. Thus, this research provides a certain guidance for acoustic metasurfaces in active acoustic wave manipulation.