A Low-Cost Robotic System for the Efficient Visual Inspection of Tunnels

Abstract

We introduce a low-cost robotic system designed to enable the safe, objective and efficient visual inspection of tunnels. The system captures high resolution images and processes them to produce maps of tunnel linings that are suitable for detailed inspection.It is unique in that the total cost of hardware is an order of magnitude less than most existing systems while producing an equivalent or higher quality of output. The device makes use of consumer-grade digital cameras and high-power LEDs in a rotating rig, carried by a lightweight aluminium frame which is designed to reduce vibrations during data capture. It is portable and installable by hand and has a modular design, making it possible to adapt to different types of carriage units, tunnels and sensors.Within the paper, we share insight into features of the device's design, including lessons learned from trials of earlier prototypes and comparisons with alternative systems. Using field data gathered from a 2km utility tunnel, we demonstrate the use of our system as a means of visualising tunnel conditions through image mosaicing, cataloguing tunnel segments using barcode detection and improving the objectivity of visual condition surveys over time by the detection of sub-mm crack growth.We believe that our device is the first to provide comprehensive survey-quality data at such a low cost, making it very attractive as a tool for the improved visual monitoring of tunnels.

Developments in 3D Visualisation of the Rail Tunnel Subsurface for Inspection and Monitoring

“…These include: Pushcarts/Rail-Trolley (RT), Road-Rail Vehicle (RRV) and Robotic Traction Unit (RTU). Merging resultant overlapping orthophotos via mosaicing [14,15] allows tunnels to be 'unwrapped'-permitting analysis in 2D-although we more frequently find studies adopt 3D CRP topography model reconstruction via 'Structure from Motion' (SfM) algorithms [16][17][18][19].…”

“…In (i), we group: Borehole/Drill Core Sampling [190,191], Electrical Resistivity Tomography (ERT) [192][193][194][195], Endoscopic Probing [196,197] and Schmidt Hammer Strength Testing [53,198]. In group (ii), we gather: Radiography/Muon Tomography [199,200] and multiple additional prototype robotic RTSSI systems [14,166,[201][202][203][204]. Group (iii) accounts for Time Domain Reflectometry schemes [205,206] and other Embedded Sensors [207].…”

A Multi-camera Mobile System for Tunnel Inspection

“…A challenge of tunnel inspection is to detect damages with mm to sub-mm accuracy. To this end, Stent et al (2015) proposed a low-cost system to inspect 0.3 mm cracks using two consumer-grade digital cameras installed on a robotic rotating arm. One of the advanced mapping systems in GNSSdenied areas, proposed by Chapman et al (2016), includes an array of 16 cameras and light sources to monitor the roadway tunnels.…”

A novel robotic framework for safe inspection and telemanipulation in hazardous and unstructured environments

“…An image mosaicing algorithm was used to splice adjacent images while the gradient of the luminance along line edges was utilized for the detection of cracks. A low cost robotic system was designed in [294] to capture images, process them and then produce maps of tunnel linings for manual detailed inspection afterwards. Crack detection and measurement were achieved in [295] using a mobile robot system consisting of optical, mechanical and data storage devices.…”

“…A similar system was presented in [303] using a rig of DSLR cameras, however the capture process is manual. The system in [294] also uses multiple DSLR cameras in combination with a polarised LED array for lighting. Another project is that of Tunnelings [304].…”