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Description
This paper presents a novel method for direct wire offset measurements using photogrammetry, with a focus on integrating a link to gravity. This development is motivated by the High Luminosity Large Hadron Collider (HL-LHC) project, where increased radiation in the Long Straight Section (LSS) necessitates automating the wire measurement process with a Full Remote Alignment System (FRAS). To integrate this system with the rest of the machine, a new process had to be developed.
A prototype has been developed based on a support frame on which four high-resolution cameras and four inclinometers are mounted. Although the prototype currently operates manually, it was designed with future automation in mind, particularly for integration into CERN’s Monorail Inspection Train (TIM).
The methodology begins with an acquisition interface that defines trigger parameters for synchronized data capture, enhancing accuracy and reliability. The key to the process is the identification and measurement of targets and the stretched wire using advanced machine vision techniques. The relative orientation of each camera is calculated using specialized software tools, such as Hexagon DPA-studio and MicMac. Additionally, a custom calibration process of the inclinometer's block is performed, to link the photogrammetry measurements to gravity. The acquired data is processed to calculate the horizontal and vertical offsets.
The comprehensive integration of these components results in a robust and precise method for wire offset measurements, with accuracy expected to meet the stringent requirements of particle accelerator applications. Initial results are extremely promising, showing that the prototype reaches the demanded precision of less than 50µm, making it an excellent solution for the HL-LHC's challenging environment."
