Automated and non-contact inspection using airborne ultrasonic transducer arrays

该研究计划的主要目标是开发利用空气耦合超声换能器对复杂结构进行非接触表征和检测的新策略。利用单元件换能器在空气中产生和测量超声波，可用于距离检测和无损检测(NDT)。然而，由于复杂的对准过程，应用仍然局限于对简单结构(如板或壳)的非接触检测。为了克服这一局限性，本研究将研究多元件换能器策略。*在过去的十年中，多元件微电子机械系统(MEMS)被提出用于分布式或聚焦式超声波的产生和测量。然而，减少换能器占地面积是为了便于携带，因此功率要求、频率范围和换能器布置目前不适用于实际结构的无损检测或医学成像。因此，要实现该领域对空气耦合检测方法的认可，必须在以下几个方面取得重大突破：检测性能、对复杂几何的一致性和过程自动化。*为了解决这些问题，必须开发一种用于非接触表面测绘和内部结构检测的综合方法。这就是为什么拟议的研究计划沿着三个不同的研究方向组织：设计稀疏的空气耦合换能器阵列，提出自动检测周围物体的方法，以及开发用于内部结构表征的先进成像算法。其创新之处在于将稀疏换能器阵列与先进的阵列处理方法相结合，以检索周围物体及其内部结构的指示。*目标应用包括自动车辆(无人机、自动驾驶汽车)的复杂环境特征，用于结构预测性维护的被动声检测(轴承或接触监测、泄漏检测、疲劳测试)，但更具体地说，是对民用或航空航天结构(复合材料组件、混凝土板)的自动化和非接触式检测。*拟议的研究计划将首次解决使用空气耦合检测方法对复杂结构进行检测的挑战：表面不平、介质不均匀、局部曲率。这种方法的展示将为工业(航空航天、土木工程)甚至生物医学(自动干预的非接触成像)领域的自动化检查开辟新的途径，这可能会减少无损检测和医疗程序中的诊断时间，同时限制可能损害预后的人工干预。

The main objective of this research program is to develop new strategies for non-contact characterization and inspection of complex structures using air-coupled ultrasound transducers. Generation and measurement of ultrasound waves in air using single element transducers is well mastered for range detection and Non-Destructive Testing (NDT). However, due to the complex alignment process, applications are still limited to non-contact inspection of simple configurations such as plates or shells. To overcome this limitation, multi-elements transducer strategies will be investigated in this research.***In the past decade, multi-element Micro-ElectroMechanical Systems (MEMS) have been proposed for distributed or focalized generation and measurement of ultrasound waves. However, the reduction of transducer footprint was prioritized for portability, such that power requirements, frequency range, and transducer arrangements are currently not adapted for NDT or medical imaging of realistic structures. ***For this reason, in order to achieve acceptance of the air-coupled inspection method in this field, a major breakthrough has to be made on the following requirements: detection performance, conformation to complex geometries, and process automatization. ***To address these issues, an integrated approach for non-contact surface mapping and inner structure inspection has to be developed. This is why the proposed research program is organized along three distinct research thrusts: design sparse array of air-coupled transducers, propose automated methods for surrounding object detection, and develop advanced imaging algorithms for inner structure characterization. The novelty resides in the use of sparse transducer arrays in combination with advanced array processing methods in order to retrieve indications on the surrounding objects and their inner structure.***Targeted applications include complex environment characterization for automated vehicles (drones, autonomous cars), passive acoustic detection for predictive maintenance of structures (bearing or contact monitoring, leak detection, fatigue testing), but more specifically automated and non-contact inspection of civil or aerospace structures (composite assemblies, concrete slabs).***The proposed research program will address for the first time the challenges associated with the use of air-coupled inspection methods for complex structures: surface irregularities, inhomogeneous medium, local curvature. The demonstration of such method will open new avenues for automated inspection in both industrial (aerospace, civil engineering) or even biomedical (non-contact imaging for automated interventions) domains, that might decrease diagnostics time in both NDT and medical procedures, while limiting the human intervention that may impair the prognostics.