Accuracy enhancement of a device for automated underbridge inspections

Abstract

The inspection and maintenance of bridge decks is a procedure that requires objectivity and systematic steps; great benefits would derive from the adoption of automated techniques minimizing the human intervention. From this point of view, the laser scanner technology can provide excellent results; in order to reconstruct the geometry of the underbridge, the scanning head can be mounted on a motorized cart travelling on a walkway moved by a truck. The motion of the laser scanning head must be compensated in post-processing in order to obtain a reliable reconstruction of the underbridge geometry; the accuracy of the reconstruction depends on the accuracy of the trajectory itself. This paper describes the actions undertaken to improve a measurement system based on noncontact techniques (laser distance meters and vision systems) aimed to reconstruct the scanning head trajectory with respect to a reference system integral to the bridge deck. The measurement uncertainty of the proposed system was evaluated by numerical simulations and then experimentally verified. At first, the developed mathematical model was validated through a comparison with an ideal system simulated in SimMechanics. Experiments performed in a controlled environment proved the validity of the proposed approach.