Automated and non-contact inspection using airborne ultrasonic transducer arrays

本研究计划的主要目标是开发使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，很好地掌握了距离检测和无损检测（NDT）。然而，由于复杂的对准过程，应用仍然局限于非接触检查的简单配置，如板或壳。为了克服这一限制，本研究将探讨多元件换能器策略。***在过去的十年中，多元件微机电系统（MEMS）被提出用于分布式或集中产生和测量超声波。然而，减少换能器占用空间的优先考虑是便携性，因此功率要求、频率范围和换能器布置目前不适合无损检测或现实结构的医学成像。因此，为了使空气耦合检测方法在该领域得到认可，必须在以下要求上取得重大突破：检测性能、符合复杂几何形状、过程自动化。***为了解决这些问题，必须开发一种非接触式表面测绘和内部结构检查的综合方法。这就是为什么拟议的研究计划沿着三个不同的研究重点组织：设计空气耦合换能器的稀疏阵列，提出周围物体检测的自动化方法，以及开发用于内部结构表征的先进成像算法。其新颖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。***目标应用包括自动化车辆（无人机，自动驾驶汽车）的复杂环境表征，结构预测性维护的被动声学检测（轴承或接触监测，泄漏检测，疲劳测试），但更具体地说，民用或航空航天结构（复合材料组件，混凝土板）的自动化和非接触检测。***拟议的研究计划将首次解决与复杂结构使用空气耦合检测方法相关的挑战：表面不规则，不均匀介质，局部曲率。这种方法的演示将为工业（航空航天、土木工程）甚至生物医学（用于自动干预的非接触式成像）领域的自动检测开辟新的途径，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为干预。

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.