Design and control of an aerial manipulator for measuring the depth of concrete cracks

Purpose This paper aims to present an aerial manipulator that can measure the crack depth of concrete structures. Currently, the detection of crack depth in concrete structures depends mainly on manual operations with nondestructive testing (NDT) instruments. There still lacks automatic equipment to release the workers at height from the highly dangerous and time-consuming NDT detection tasks. Design/methodology/approach The proposed aerial manipulator consists of a hexacopter, a two degrees of freedom (DOF) manipulator and a custom-designed ultrasonic crack detector based on the ultrasonic flat-measured principles. A four-phase control strategy is proposed for the aerial manipulator to complete the concrete crack depth measuring task. Findings The experimental results show that the proposed control strategy is effective and the prototype of the aerial manipulator succeeds in contact detection of the cracks in the concrete specimens. The field test results further verify that the proposed aerial manipulator is capable of contact inspection of bridge piers and other similar concrete structures. Originality/value The proposed aerial manipulator provides an unmanned aerial vehicle (UAV) based solution for NDT detection of concrete crack depth. It serves as a novel tool for the inspection personnel working at height to get the interior damage conditions of concrete structures safely and quickly.