Practical Part-Specific Trajectory Optimization for Robot-Guided Inspection via Computed Tomography

Abstract

Robot-guided computed tomography enables the inspection of parts that are too large for conventional systems and allows, for instance, the non-destructive and volumetric evaluation of mechanical joining components within already assembled cars in the automotive industry. However, the typical scan time required by such setups is still significant and represents a major barrier for its industrial large-scale application. As an approach to mitigate the necessary time demand, we propose a part-specific adjustment of the acquisition trajectory. Common circular standard trajectories are inherently inefficient, since they are applied independently of the considered inspection task, while the use of acquisition orbits tailored particularly to the investigated object effectively allows a reduction of the required number of projections, which in turn has the potential to directly decrease the scan time significantly. In contrast to former simulation-guided approaches, this work is considered to be the first successful task-specific trajectory optimization being performed on a robot-based industrial CT platform and aims towards providing a first proof of concept that such methods can be practically applied in a shop floor environment. Based on representative results, a reduction of the number of required projections by approx. 55 % or an image quality improvement according to the root-mean squared error by approx. 40 % compared to the conventionally applied planar acquisition trajectory was achieved.

Fully automatic online geometric calibration for non‐circular cone‐beam CT orbits using fiducials with unknown placement

“…Robotic arms-based industrial CBCT using arbitrary orbits may also benefit from the proposed method for non-destructive testing. 8,34,[68][69][70][71] Future work on the calibration algorithm includes tuning the initialization process and incorporating machine learning techniques for better localization, improving the fiducial labeling process to allow for more arbitrary scanning orbits, such as non-continuous orbits, evaluating system sensitivity to misalignment in different geometric parameters, and optimization of code implementation to further improve speed and performance. Future physical experiments include more realistic setups using cadavers or patients.…”

“…For this application, the proposed method can be added to the arsenal of existing methods, 42,48–50,52,53 especially for systems with unpredictable characteristics. Robotic arms‐based industrial CBCT using arbitrary orbits may also benefit from the proposed method for non‐destructive testing 8,34,68–71 …”

Enabling 3D CT-scanning of cultural heritage objects using only in-house 2D X-ray equipment in museums

“…Calibration is also important for non-standard trajectories, which are for example encountered in robotic CT 42 . Highly flexible robotic arms have been designed that can allow for adapting the acquisition trajectory to the object.…”

IntelliScan: Improving the quality of x-ray computed tomography surface data through intelligent selection of projection angles

“…The concept of using a priori object information to improve the quality of XCT reconstructions is not new. A review of the literature shows that a number of methods for optimizing the XCT scan strategy based on a priori object information have been proposed [5][6][7][8][9][10][11][12][13]. These approaches generally aim to select an optimal object scan orientation, or source-detector scan trajectory; this is achieved by simulating projections for all possible object orientations, and then selecting the object orientation or source-detector trajectory that maximizes some quality metric.…”

“…Herl et al [9] developed a method to select projection angles to reconstruct a region of interest of an object using a dual robot XCT system; the completeness of Radon sampling and material penetration lengths were used to select projections from a set of candidate projections. Herl et al further developed their method in [10] by investigating the use of an alternative quality metric based on the modulation transfer function and noise power spectrum of the reconstruction, which has also been utilised in recent work by Bauer et al [12].…”