Camera-based noncontact metrology for static/dynamic testing of flexible multibody systems

Abstract

Presented here is a camera-based noncontact measurement theory for static/dynamic testing of flexible multibody systems that undergo large rigid, elastic and/or plastic deformations. The procedure and equations for accurate estimation of system parameters (i.e. the location and focal length of each camera and the transformation matrix relating its image and object coordinate systems) using an L-frame with four retroreflective markers are described in detail. Moreover, a method for refinement of estimated system parameters and establishment of a lens distortion model for correcting optical distortions using a T-wand with three markers is described. Dynamically deformed geometries of a multibody system are assumed to be obtained by tracing the three-dimensional instantaneous coordinates of markers adhered to the system's outside surfaces, and cameras and triangulation techniques are used for capturing marker images and identifying markers' coordinates. Furthermore, an EAGLE-500 motion analysis system is used to demonstrate measurements of static/dynamic deformations of six different flexible multibody systems. All numerical simulations and experimental results show that the use of camera-based motion analysis systems is feasible and accurate enough for static/dynamic experiments on flexible multibody systems, especially those that cannot be measured using conventional contact sensors.

Lens-less PSD measurement of flexible link deflection

“…where S F 3 is the laser spot on the PSD at the fixed end, in {F}. It follows from ( 6) and (11) that…”

“…It is demonstrated that deflection of a flexible body can be measured by capturing and tracing the instantaneous coordinates of markers by multiple cameras and triangulation techniques [11]. This camera-based non-contact metrology for testing of flexible multibody systems, also requires a lens distortion model that accounts for optical distortions.…”

Concentric-circle-based camera calibration

“…Essentially, this task is to find the mapping from 3D light rays to 2D image pixels, or equivalently find a best model that fits those data. It is a classical problem and often a critical step towards many practical robotic vision applications including 3D modelling and measurement [1], robot navigation and camera-based motion analysis systems [2].…”

Space–wavenumber and time–frequency analysis for damage inspection of thin-walled structures

“…[13][14][15][16] Scanning laser vibrometers and camera-based motion analysis systems are two recent prominent systems for full-field measurements. The measured data from such a system contain detailed dynamic characteristics of the measured structure, but the amount of data is often huge.…”

“…Recent developments in full-field noncontact dynamic measurement technologies stimulate further advancement of dynamics-based damage inspection of large structures because fast and accurate measurements of time-varying operational deflection shapes (ODSs) are ready for engineering applications. [13][14][15][16] Scanning laser vibrometers and camera-based motion analysis systems are two recent prominent systems for full-field measurements. The measured data from such a system contain detailed dynamic characteristics of the measured structure, but the amount of data is often huge.…”