A method and procedure for mobile robots to inspect expansive pipe structures have been showcased through successfully examining various defects on a 3 m long steel pipe, employing guided acoustic wave sensors.
Robot. Image Credit: Dr Jie Zhang
Under the guidance of Professor Bruce Drinkwater and Professor Anthony Croxford, the University of Bristol team formulated an approach utilized in examining a lengthy steel pipe hosting various flaws.
These included circular holes of varying sizes, a crack-like defect, and pits, all assessed along a specifically designed inspection path to achieve complete detection coverage for a defined reference defect.
The study, published today in NDT and E International, demonstrates the successful examination of extensive plate-like structures. Their approach involved a network of individual robots, each equipped with sensors capable of emitting and capturing guided acoustic waves, operating in pulse-echo mode. This strategy proved effective in their examination methodology.
This method has the major benefit of reducing communication between robots without synchronization, thus increasing the possibility of onboard processing to reduce data transfer costs and overall inspection expenses. The inspection was distributed into a defect detection and a defect localization stage.
There are many robotic systems with integrated ultrasound sensors used for automated inspection of pipelines from their inside to allow the pipeline operator to perform required inspections without stopping the flow of product in the pipeline. However, available systems struggle to cope with varying pipe cross-sections or network complexity, inevitably leading to pipeline disruption during inspection. This makes them suitable for specific inspections of high value assets, such as oil and gas pipelines, but not generally applicable.
Dr. Jie Zhang, Lead Author, University of Bristol
Zhang continues, “As the cost of mobile robots has reduced over recent years, it is increasingly possible to deploy multiple robots for a large area inspection. We take the existence of small inspection robots as its starting point, and explore how they can be used for generic monitoring of a structure. This requires inspection strategies, methodologies, and assessment procedures that can be integrated with the mobile robots for accurate defect detection and localization that is low cost and efficient.”
Zhang adds, “We investigate this problem by considering a network of robots, each with a single omnidirectional guided acoustic wave transducer. This configuration is considered as it is arguably the simplest, with good potential for integration in a low cost platform.”
The techniques utilized in this study possess broad applicability to similar scenarios, enabling swift quantification of the influence of detection or localization method choices. These methods hold relevance across various materials, pipe configurations, noise environments, and guided wave modes, facilitating the comprehensive exploration of sensor performance parameters, defect types and sizes, and operational modes.
Additionally, these techniques can evaluate detection and localization performance based on specified inspection parameters, such as predicting the minimum detectable defect under specific probabilities of detection and false alarms.
The group examines partnership opportunities with industries to improve present prototypes for actual pipe inspections. This work is funded by the UK’s Engineering and Physical Sciences Research Council (EPSRC) as a part of the Pipebots project.
Journal Reference:
Zhang, J., et al. (2023). Pipe inspection using guided acoustic wave sensors integrated with mobile robots. Science Direct. doi.org/10.1016/j.ndteint.2023.102929