In-pipe Robot Perception for Challenging Altered Environments
- Publication Type:
- Thesis
- Issue Date:
- 2021
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Robotics can play a crucial role in the condition assessment of critical infrastructure assets such as underground drinking water pipes. Currently, water utilities worldwide spend billions of dollars every year to reliably inspect and rehabilitate corroding and deteriorating pipes. Internal pipe linings are widely used as a renewal method to increase structural strength. Post pipe-lining quality assurance and long-term performance monitoring of the applied liners are essential for maintaining pipe assets. In this regard, this thesis focuses on the development of a multi-sensor approach to liner defect mapping in underground human-altered environments.
A mobile robotic sensing system that can scan, detect, locate, and measure internal pipeline defects is proposed. This is achieved by generating three-dimensional RGB-D maps using stereo camera vision in combination with an infrared laser profiling unit. The system does not involve complex calibration procedures and utilises orientation correction to provide accurate real-time RGB-D maps. Defects are identified and colour mapped for easier visualisation. The robotic sensing system was extensively tested under laboratory conditions, followed by field deployment in buried water pipes in Sydney, Australia. The experimental results showed that the RGB-D maps were generated with millimetre-level accuracy and with demonstrated liner defect quantification.
The accuracy of the map is dependent on the robot localisation. Therefore, a cost-effective UHF-RFID tags were used for robot localisation inside pipelines. The results showed that unlike outdoor RFID localisation, inside the pipeline, the signal behaves uniquely, which makes the localisation task challenging and unique. Signal processing using a Gaussian process combined particle filter was applied to accurately localise the robot. Experiments carried out on field-extracted pipe samples from the Sydney Water pipe network showed that using the RSSI and Phase data together in the measurement model with the particle filter algorithm improves the localisation accuracy up to millimetre-level, through utilisation of a two-antenna sensor model.
Robot localisation assumes an accurate map. In pipes, this is tedious and therefore SLAM is desirable. A novel solution for SLAM using UHF-RFID signal processing for underground pipe environments is proposed. The problem was formulated as a Graph-SLAM combining signal cross-correlation and mapping with respect to the RFID sensor measurements. Experiments in the laboratory showed that the solution can localise the robot with 2.5-centimetres accuracy while building the RFID map. The results showed that the solution allows accurate identification of defect locations in a 50-meter long pipe, and performs vastly better than standard encoder-based localisation methods.
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