A Truly Redundant Aerial Manipulator System with Application to Push-and-Slide Inspection in Industrial Plants

We present the design, control and motion planning of an aerial manipulator for a non-trivial physical interaction task, namely pushing while sliding on curved surfaces. The proposed robotic system is motivated by the increasing interest on autonomous Non-Destructive Tests used for the integrity assessment of industrial plants. The proposed aerial manipulator consists of a multidirectional-thrust aerial vehicle to enhance physical interaction capabilities, endowed with a 2-DoFs lightweight arm to enlarge its workspace. This combination constitutes a truly redundant manipulator that goes beyond standard aerial manipulators with collinear multirotors. The robot controller is based on a PID method with 'displaced' positional part inspired by controllers for manipulators with elastic joints and grounded on several experimental trial-and-error tests. In this work we experimentally show that the proposed aerial manipulator system, equipped with an Eddy Current probe, is able to scan a metallic pipe sliding the sensor over its surface and preserving the contact. From the acquired data, a weld on the pipe is successfully detected and mapped.