Robotic system for inspection of test objects with unknown geometry using NDT methods

Abstract

Purpose The purpose of this paper is to develop a portable non‐destructive testing (NDT) robotic arm that can be carried by climbing and walking robots (CLAWAR). The arm is required to maintain, during a scanning trajectory, a desired NDT probe contact force and orientation to evaluate defects in geometrically complex industrial infrastructure and products such as turbine blades. Design/methodology/approach A seven‐axis arm transportable by CLAWAR was developed to deploy NDT probes with suitable dexterity. It was equipped with a force sensor to scan a complex shape by keeping the NDT probe normal to the surface while maintaining a constant contact force with it. Two approaches were used. One used permanent magnet adhesion to obtain secure contact while the other used position‐force‐moment (PFM) feedback to adapt the arm. Findings Tests were performed on turbine blades with eddy‐current inspection techniques to assess the quality of defect data using manual inspection and automated inspection. Significant improvements in the quality of inspection were observed when using robotic scanning as compared to manual inspection. Practical implications The results have practical implications for the remote inspection of very large infrastructures such as petrochemical storage tanks, bridges, pressure vessels, etc. or where the inspection is performed in hazardous environments and the test surface is not known a priori with any accuracy. Originality/value The work is a novel application of the PFM control of a seven‐axis robot arm to scan unknown contoured surfaces to ensure reliable NDT data acquisition at scanning speeds of up to 0.5 mm s −1 .