Offshore robots are transforming how we maintain wind farms and underwater infrastructure in the North Sea, but they’ve often met their match in powerful waves – until now.

A breakthrough by Edinburgh engineers could help these automated workers brave the roughest seas.

Leading companies like Fugro are already deploying offshore robots – including uncrewed surface vessels (USVs) and remotely operated vehicles (ROVs) – for subsea inspections.

While these robots excel in calm waters, they’ve struggled in the wave-dominated zones where wind farms and tidal turbines typically operate.

Until now.

Engineers at the University of Edinburgh have proposed a way for subsea vehicles to stabilise their performance and respond quicker to disturbances. This could benefit marine renewable asset inspections and potentially reduce green energy costs.

ROVs under control

Precise positioning and control are crucial in high energy zones, especially for submerged structures. Conventional methods like traditional feedback or piloted control do not work so well, according to engineers.

They have proposed a new control system. This incorporates wave predictions from a buoy armed with sensors in the North Sea.

A recent paper in the International Journal of Robotics Research, with Kyle Walker as first author, has set a new way of doing things with an ROV.

Their system combines a Deterministic Sea Wave Predictor (DSWP) with a Nonlinear Model Predictive Controller (NMPC). This builds on the concepts of Model Predictive Control (MPC). This latter technique was traditionally used for motion planning, rather than wave disturbances.

Such waves can be serious and are common around marine renewables. However, ocean waves can be determined through predictions.

The DSWP continually measures the height of waves upstream from the vehicle. It then formulates a forecast as to how the waves will change as they arrive at the location.

Creating accurate short-term forecasts for the controller allows it to assess how best to control the vehicle.

The DSWP helps regulate the ROVs’ responses to the waves. By considering patterns of ocean waves, from the DSWP within the NMPC vehicle controller, the system was able to both predict and compensate for wave disturbances.

Wave forecasts meet robotics

The tests took place in the University of Edinburgh’s FloWave testing tank. This is designed to simulate waves and currents for the testing and development of novel ocean energy technologies.

Using this tank, the team could see whether they could incorporate wave predictions with smart robots to improve performance. The trial used real-time data, captured by a buoy in the North Sea.

Lead author Dr Francesco Giorgio-Serchi has experience in working on predictive control of unmanned underwater vehicles.

“The FloWave is an amazing facility of our very own university and unique in the UK. We have had experience working at the FloWave in the past when we were trying to understand how accurately we can estimate the forces from waves and currents on a stationary underwater vehicle,” he said. “That work spurred the idea for these newly published results.”

Tests at the Edinburgh facility showed good results for the wave predictions and control model.

The scientists reported a mean average improvement of 52%.

Performance improvements reduced uncertainty and time delays in disturbance predictions.

“In terms of accuracy of replicating realistic sea conditions, this is very accurate, meaning we can literally generate a common sea state in the tank that is very representative of the conditions you would encounter at sea,” Giorgio-Serchi continued.

“Because the main novelty of our work lies with the capability to predict what the impending disturbance on the vehicle will be like, we can exploit the technology to enable very accurate control of the vehicle.”

This is the first time where considerations of sea wave activity have been demonstrated within the robot’s control system.

“This technique ensures that the vehicle can stay stationary even under big perturbations, enabling safer and more accurate inspection tasks,” he added.

Versatility in the market

Though innovative, the system is surprisingly versatile. Walker worked on the project as part of his PhD. He mentioned the method can apply to most vehicles currently available on the market, with little need to change a robot’s hardware.

“As our control method uses wave data from external sensors at a separate location from the vehicle (wave buoys that are already deployed), all that is needed is a communication link between the two to transfer the data,” he said. This uses the “base station as a middleman and the pre-existing vehicle tether to transfer data quickly and reliably”.

In this instance, he said, the focus is on smaller-scale underwater ROVs, “due to their susceptibility to disturbances, but this can apply to any vehicle regardless of size”.

Their design allows semi-autonomy for the offshore renewables sector. The operator can still do some inspection or manipulation, without having to keep the vehicle stationary at the same time. The controller takes care of that.

“We’re hopeful this can facilitate greater uptake of robotics with respect to marine renewables,” Walker said. The aim is to tackle areas where “it’s incredibly difficult to operate due to the turbulent conditions”.

Rewards for renewables

This technological step could be transformative to cut the costs of producing clean energy. These “smart robots” could reduce costs by making the inspection and maintenance of offshore turbines cheaper, safer and more efficient.

Removing the need for ships and helicopters – and overall sending people offshore – would have a substantial impact.

“There isn’t a limitation with respect to the sector – any underwater environment where the sensor data mentioned is accessible is a valid use case. Essentially, our method just widens the range of sea conditions ROVs can be deployed in by improving control performance under wave disturbances,” Walker explained.

This research was part of ORCA Hub. This helps drive new, innovative research into autonomous tech and human-machine collaboration. The aim is to be more safe, more economic and more efficient around offshore infrastructure.

There are inevitably questions around potential job losses amid a move to automation. But the rise in technology is also about reducing the exposure of people to harm. Workers will continue to be needed, but there will be more opportunities to remain onshore – with all the benefits that brings to communities and families.

By including wave predictions in smart robotics, operators could enable predictive control and precision of ROV operations even when facing some of the most chaotic conditions of the North Sea.

This innovation shows improved precision and control of ROVs are possible in the face of strong waves.

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