Machining-Based Coverage Path Planning for Automated Structural Inspection

Abstract

The automation of robotically delivered Non Destructive Evaluation (NDE) inspection shares many aims with traditional manufacture machining. This paper presents a new hardware and software system for automated thickness mapping of large-scale areas, with multiple obstacles, by employing CAD/CAM inspired path planning to implement control of a novel mobile robotic thickness mapping inspection vehicle. A custom post-processor provides the necessary translation from CAM Numeric Code through to robotic kinematic control to combine and automate the overall process. The generalised steps to implement this approach for any mobile robotic platform are presented herein and applied, in this instance, to a novel thickness mapping crawler. The inspection capabilities of the system were evaluated on an indoor mock-inspection scenario, within a motion tracking cell, to provide quantitative performance figures for positional accuracy. Multiple thickness defects simulating corrosion features on a steel sample plate were combined with obstacles to be avoided during the inspection. A minimum thickness mapping error of 0.21 mm and mean path error of 4.41 mm were observed for a 2 m 2 carbon steel sample of 10 mm nominal thickness. The potential of this automated approach has benefits in terms of repeatability of area coverage, obstacle avoidance and reduced path overlap, all of which directly lead to increased task efficiency and reduced inspection time of large structural assets. Note to Practitioners-Current industrial robotic inspection approaches largely consist of manual control of robotic platform motion to desired points, with the aim of producing an number of straight scans for larger areas, often spaced meters apart. Structures featuring large surface area and multiple obstacles, are routinely inspected with such manual approaches, which are both labour intensive, error prone and do not guarantee acquisition of full area coverage. The presented system addresses these limitations through a combined hardware and software approach. Core to the operation of the system is a fully wireless, differential drive crawler with integrated active ultrasonic wheel probe, to provide remote thickness mapping. Automation of path generation algorithms is produced using commercial CAD/CAM software algorithms, and this paper sets out an adaptable methodology for producing a custom post-processor to convert the exported G-Codes to suitable kinematic commands for mobile robotic

Coverage trajectory planning for a bush trimming robot arm

“…Robotic bush trimming is a task related to the coverage path planning problem that has been extensively studied in the literature (Galceran & Carreras, ). The task is fundamental to several robotic applications: agricultural fields plowing (Jin & Tang, ), crops harvesting (van Henten et al, ), lawn mowing (Arkin, Fekete, & Mitchell, ), inspection of underwater structures (Englot & Hover, ), environment surveillance with unmanned aerial vehicles (UAVs; Nama, Huanga, Lia, & Xub, ), spray‐painting of automotive parts (Sheng, Xi, Song, Chen, & Macneille, ), spray forming (Sheng, Chen, Xi, Chen, & Motivation, ), computer numerical control (CNC) machining (Macleod, Dobie, Pierce, Summan, & Morozov, ), laser cutting (Ma et al, ), and cleaning (Palacin, Palleja, Valganon, Pernia, & Roca, ). The problem is intimately related to the traveling salesman problem (TSP).…”

Vision guided robotic inspection for parts in manufacturing and remanufacturing industry

“…A dry-coupled wheel transducer [9,25] that houses two piezoelectric ultrasonic elements with a nominal centre frequency of 5 MHz is attached to the robot as shown in Fig. 4.…”

Determining Position and Orientation of a 3-Wheel Robot on a Pipe Using an Accelerometer

“…A test rig was manufactured with 3 points of contact to simulate a 3 wheeled robot. The Vicon MX Giganet system utilising 12 Vicon T160 cameras was used to measure ground truth position and orientation of the test rig, as done in previous studies [26] [7] and was calibrated before use. The Vicon is a photogrammetry 6 DOF motion capture system which utilizes several cameras to track the position and orientation of an arrangement of retroreflective markers.…”

“…Three-wheeled mobile crawler robots are becoming increasingly used in the inspection industry due to their advantages over conventional 4-wheeled robots [6]. These are namely; increased manoeuvrability, more simple kinematics compared to other wheeled robot types and more accurate dead reckoning, which is not feasible for 4-wheel designs due to wheel slippage [7] [8].…”