Self-Cleaning ExScan and Underground Reflectors

This project addresses the issue of reflector obscuration in longwall mines, which hinders the performance of optical and infrared sensing systems and compromises safety and automation. The objective was to develop a low cost, robust, and reliable self-cleaning reflector for underground coal mines, specifically targeting the ExScan 3D Underground Mapping system.

The approach involved researching and testing commercially available transparent hydrophobic coatings, hydrophilic films, anti-graffiti films, and hydrophobic films. These coatings were applied to half of each side of reflectors, which were then installed underground for evaluation. The performance of coated and uncoated sections was compared to assess the effectiveness of the coatings in preventing dust build up.

Additionally, variations in reflector geometry were investigated to determine whether changes in profile affected dust accumulation. The possibility of using flexible reflectors that move with underground ventilation to mitigate dust build up was also explored. The project also included preliminary design work on an improved water spray mechanism for the ExScan system.

Vibrating mechanisms were also evaluated, and a vibrating reflector was designed, built, and tested in the laboratory. This vibrating reflector aimed to shake off artificially applied coal dust coatings and maintain optimal reflector cleanliness.

The following was undertaken:

• Market survey performed to discover commercially available coatings and films of various types;
• Suitable coatings were investigated and evaluated in situ;
• Active water-based and brush-based cleaning systems were investigated;
• Several reflector vibrating mechanisms were evaluated;

• A viable reflector vibrating mechanism was designed, built and lab-tested.

Only a small number of commercially available coatings were found suitable for this application with only one being found to have any positive effect on the mitigation of dust build up on reflectors. Even with the mitigation techniques investigated and evaluated by this project, it is not clear whether the dust mitigation problem is solvable to the reliability required for tracking every roof support using a laser scanner.