The measurement of ultrasonic surface velocity in concrete and the ultrasonic Time Of Flight method for estimating the depth of surface opening cracks in concrete are important techniques for maintenance of constructions, which are currently performed manually. This paper demonstrates the possibility to automate these measurements by means of an Unmanned Aerial Vehicle (UAV) equipped with a robotic arm, avoiding the risks and costs related to the manual methods. The automated measurements are performed by a special end effector with closed-loop force control that maintains the flying UAV stable while the robotic arm contacts the concrete surface with two piezoelectric transducers for the ultrasonic tests. The system is successfully validated by performing ultrasound measurements from the flying UAV on a test specimen with artificial cracks and on the T9 Metsovo bridge in Greece during an on-field trial, demonstrating an error margin lower than 1 % on crack depth.

中文翻译：

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半自主空中机器人，用于对混凝土结构的裂缝深度和表面速度进行超声评估

测量混凝土中的超声表面速度以及用于估计混凝土表面开口裂缝深度的超声飞行时间法是维护结构的重要技术，目前这些技术都是手动进行的。本文展示了通过配备机械臂的无人机 （UAV） 实现这些测量自动化的可能性，从而避免了与手动方法相关的风险和成本。自动测量由具有闭环力控制的特殊末端执行器执行，该执行器保持飞行无人机的稳定，同时机械臂与两个压电传感器接触混凝土表面进行超声波检测。在现场试验期间，通过飞行无人机对带有人工裂纹的试样和希腊的 T9 Metsovo 大桥进行超声波测量，该系统成功验证了该系统，证明裂纹深度的误差范围低于 1%。