Elbow Detection in Pipes for Autonomous Navigation of Inspection Robots

Abstract

Nuclear decommissioning is a global challenge with high costs associated with it due to the hazardous environments created by radioactive materials. Most nuclear decommissioning sites contain significant amounts of pipework, the majority of which is uncharacterised with regards radioactive contamination. If there is any uncertainty as to the contamination status of a pipe, it must be treated as contaminated waste, which can lead to very high disposal costs. To overcome this challenge, an in-pipe autonomous robot for characterisation is being developed. One of the most significant mechatronic challenges with the development of such a robot is the detection of elbows in the unknown pipe networks to allow the robotic system to autonomously navigate around them. This paper presents a novel method of predicting the direction and radius of the corner using whisker-like sensors. Experiments have shown that the proposed system has a mean error of 4.69 • in the direction estimation.

Autonomous Elbow Controller for Differential Drive In-Pipe Robots

“…A Tracked, Differential-Drive, Wall-Pressing robot was developed for this task. It is the next prototype in the FURO line [3]. Figure 5 shows an annotated image of the prototype.…”

“…The feelers consist of an encoder to measure the angle, a passive wheel to reduce the contact friction and a spring to pull the feeler onto the pipe wall. The feeler sensors were developed in [3] which describes them in further detail.…”

“…where P R , P G and P B are the three feeler coordinates, which are derived from their kinematic model [3] and shown in Figure 7 as P RGB . The combination of the end positions of the feelers is shown in Figure 10 where P C is the centre of the robot in the y-z axis and P f m is the sum of the feeler end points (1).…”

“…As φ r is unknown, the proposed control method of sensing for exit conditions allows the AEC to work without it and navigate an elbow with any corner angle, this will be explained in greater detail in Section 3.3. The feeler sensors are used to estimate the corner direction (θ d ) and can be used to determine major radius (R) as presented in [3]. Note that θ is the actual corner direction whereas θ d is the estimated direction.…”

“…Currently, there is no way of inspecting this pipework without human intervention, which can be dangerous due to the unknown radiological contaminants inside them. An autonomous pipe inspection robot, FURO I, was proposed in [3], which could be used for such inspections, thus reducing the safety risks to human operators. This paper is an extension of that work, presenting the testing and development of a controller to allow the FURO robot to safely turn through an elbow.…”