Summary There are numerous applications in the field of structural dynamics that require the accurate measurement of evolving deformation fields. Although there are several sensors for direct displacement measurements at a specific point in a uniaxial direction or multicomponent deformations, there are only very limited, and relatively quite expensive, methodologies for obtaining the 3‐dimensional components of a displacement of a dynamically evolving (i.e., not pseudostatically) deformation field. This paper reports the results of a comprehensive experimental study to assess the accuracy and performance of a class of inexpensive vision‐based sensors (i.e., RGB‐D sensors) to acquire dynamic measurements of the displacement field of a test structure. The sensor was subjected to a broad variety of different dynamic motions of varying amplitude and spectral characteristics and with varying configurations of the position and orientation of the sensor with respect to the target structure. Particular attention was devoted to quantifying the influence of various test conditions, such as amplitude, frequency, sampling rate, spatial distortion, and relationships between the RGB pixel‐based measurements and the depth measurements. It is shown that the class of sensors under discussion, when operated under the performance envelope discussed in this paper, can provide, with acceptable accuracy, a very convenient and simple means of quantifying 3‐dimensional displacement fields that are dynamically changing at relatively low‐frequency rates typically encountered in the structural dynamics field.

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The advent of inexpensive digital cameras with depth sensing capabilities (RGB-D cameras) has opened the door to numerous useful applications that need quantitative measures of dynamic fields whose simultaneous time history quantification (at many points as dictated by the resolution of the camera) provides capabilities that were previously accessible only through expensive sensors (e.g., laser scanners). This paper presents a comprehensive experimental and computational study to evaluate the performance envelope of a representative RGB-D sensor (the first generation of Kinect sensor) with the aim of assessing its suitability for the class of problems encountered in the structural dynamics field, where reasonably accurate information of evolving displacement fields (as opposed to few discrete locations) that have simultaneous dynamic planar translational motion with significant rotational (torsional) components. This study investigated the influence of key system parameters of concern in selecting an appropriate sensor for such structural dynamic applications, such as amplitude range, spectral content of the dynamic displacements, location and orientation of sensors relative to target structure, fusing of measurements from multiple sensors, sensor noise effects, rolling-shutter effects, etc. The calibration results show that if the observed displacement field generates discrete (pixel) sensor measurements with sufficient resolution (observed displacements more than 10 mm) beyond the sensor noise floor, then the subject sensors can typically provide reasonable accuracy for transnational motion (about 5%) when the frequency range of the evolving field is within about 10 Hz. However, the expected error for torsional measurements is around 6% for static motion and 10% for dynamic rotation for measurements greater than 5°.

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