By Ariana Hurtado
Andy Gower, subsea control systems specialist with TotalEnergies Subsea Technologies, detailed the company's new AUV development process, the challenges the team faced as well as the results of the AUV pipeline inspection development project, as he led a subsea robotics technical session Tuesday afternoon at the Offshore Technology Conference (OTC).
“The AUV inspection development project has been a very long-term collaboration between ourselves [Total] and Chevron and our development program partner, Oceaneering,” Gower said. “It’s been in progress for seven or eight years. And initially we started off with a torpedo classic AUV, and we identified there was a need to change the vehicle in that we needed a new hovering-capable vehicle—and that started the development cycle.”
The team wanted to design a new vehicle that was capable of performing end-to-end pipeline inspection.
Identifying challenges and needs
Gower said this new vehicle would provide the team with “lots of opportunity to improve data.”
With a hovering-capable AUV, they could operate in low altitudes and over the pipe, and deploy sensitive sensors to exactly where it was needed to provide the quality data from a pipeline inspection.
“That required us to develop capabilities and behaviors to support those aids,” he said. “Firstly, we wanted to operate the vehicle in a very tight envelope on top of pipe, low altitude, aiming for 2 meters, and so we had to develop some pipeline tracking capability. We wanted feature-based navigation, and we accepted that if we wanted to remove surface localization support, we needed to offset any INS drift through the mission. So the ability to detect features and to give us positional updates was quite key.”
The vehicle also had to be stable to ensure accurate placement of sensors and avoid collisions.
“We wanted to be able to repeatedly apply sensors to exactly where we needed them,” he said “Because we were operating in low altitude, we were in the zone of obstacle collision. So we wanted the ability to have obstacle avoidance and detection behaviors, [while] still maintaining the capability to inspect from pipeline start to end.”
The team also aimed to complete this mission in a single pass.
“We wanted to look at the operational efficiency by being able to take all the information we needed from a single pass,” Gower said. “So that meant if we identified a feature or anomaly, we would want to do some adaptive behaviors to gather as much data as we could in that single mission. The idea being we didn’t want to come back with an ROV later to inspect the gaps in our data.”
Validating the technology
The big question was how the team could validate the vehicle.
“We knew the vehicle’s capability and performance, and we knew it was going to be an evolution,” Gower said.
So the next step was to develop and define a testing program to validate it.
“There’s lots of questions that we have to ask ourselves,” he said. “It’s autonomous. It’s inspecting pipeline. It could be an endurance of 20, 30 kilometers. How do we cover the testing area? How many cameras and sensors do we need to deploy to look for what the vehicle is doing and to make sure the vehicle is performing as per expectations?”
Gower said the team took a slightly different view. Rather than specify what the vehicle should be able to do and look for a pass or fail outcome, they wanted to design experiments.
“We wanted to take a very scientific approach,” he said. “So we asked ourselves what do we want the vehicle to do and how do we show the vehicle is fit for purpose or good enough? And we knew there had to be some playgrounds and controlled testing.”
A playground offered the team the opportunity to fix and specify the test conditions, whereas an operational pilot offshore has no control because the environment would be just as the group found it.
“So we knew there would be a significant challenge to go from this very controlled environment into this very uncertain environment,” he continued. And could we extrapolate the results we saw in a controlled environment? We knew that we had confidence in the performance offshore. We knew there would be constraints with near-shore or playground testing.”
The team was also doing non-commercial work and made the decision very early on to commit to this being a technical program.
“We didn’t want to carry out an offshore pilot to do semi-commercial work, which meant we had a significant constraint on our offshore time,” he said. “We had a small number of days on the vessel, so we were constrained by that.”
Results
“We were very successful at low-altitude tracking of a large pipeline,” Gower said. “Very, very successful.”
Pipe tracking was 99% successful, and he said the team exceeded every one of its expectations.
“What was very important was that we accepted that autonomy is not a binary pass/fail,” continued. “There is a shade of performance in autonomy. We can’t accept pass or fail, specifically in this application. And the principle is we can’t control the operational pipe envelope or environment. We have to accept there is an evidence of unknown and uncertainty.”
Moreover, the team met its goal to carry out testing in one mission.
“We gained confidence that we could carry out an entire pipeline assessment in one pass at low altitude,” he said. “The challenge was, though, we were looking for thousands of tests. We only managed 100 experiments because of all the constraints we had. Some of them totally agnostic. So in essence what we managed to do is define a process that we can use to evaluate a vehicle. It’s agile. We can react to an offshore campaign very successfully.”
05.03.2022
