Interview: Building a robot to navigate the high seas

On 19 September 2020, to commemorate the 400th anniversary of the Mayflower’s voyage to the New World, an autonomous trimaran vessel, the Mayflower Autonomous Ship, will trace the route of the original Mayflower in 1620, sailing from Plymouth, UK, to Plymouth, Massachusetts, US.

Although remotely controlled ships are not a new concept, Don Scott, chief technology officer of the Mayflower Autonomous Ship, says the project is at the bleeding edge. “What’s new about the project is the marine autonomy aspect, creating the ship as an edge device that operates on its own, sensing its environment, making intelligent decisions and acting on them without any human intervention,” he says. “That’s what makes this vehicle really innovative.”

The Mayflower is a prototype, a proof of concept, to demonstrate that a solar-powered autonomous ship can navigate the oceans safely and cope with changeable weather, other ships, and encounters with marine creatures and submerged hazards. 

Scott has worked on the oceans for 30 years. For him, one of the biggest challenges in developing an autonomous ship is the unpredictable nature of the sea. “You certainly don’t approach these engineering tasks lightly,” he says. “You very quickly get humbled by the power of the ocean.” 

He says one of the philosophies that underpins the design is that the Mayflower Autonomous Ship needs to operate in an extremely hostile and dynamic environment, which is very unpredictable.

Until very recently, undertaking such an engineering task would have seemed impossible. For Scott, the recent convergence of technologies such as computing power at the edge and the growth of machine learning has meant that today it is possible to have an edge device make decisions in a timeframe that enables a vehicle to operate within the environment it was designed for.

Engineering for unpredictability requires partitioning different tasks, so that there is a strong sense of separation and layering between the software running on the edge devices. The architecture is highly modularised, where each edge device maintains its own situational awareness and communicates upstream and downstream with other modules. 

Sensor inputs include six cameras, an automatic identification system, wind speed and direction sensors and obstacle avoidance sonar. Scott says: “Each of these collects unstructured data, which is then processed and fed into a data server to provide the information needed for the vessel to navigate.”

Weather forecasts are provided via application programming interfaces (APIs) to The Weather Company. “Weather updates will be our highest priority,” says Scott. “We will steer around a storm cell, for sure.”

The Mayflower is designed to run autonomously, but it will have the ability to send and receive data. Given that the ocean offers limited low-bandwidth satellite communications, weather data is given a priority. “It is critical information – we will get what we can get,” says Scott.

IBM PowerAI Vision models are being used to provide object classification and object tracking for the vessel’s computer vision system, he says, adding: “All of this information is fed into a navigation hazard map used by a collision avoidance module.”

The collision avoidance module takes this data to determine a series of potential courses and speeds, which are then fed into a route planner, which Scott says is essentially an autonomous system that determines the course the vessel should take. “Layered on top of the route planner is our safety manager, which deals with more localised information, such as wave direction and the unpredictable aspects of the ocean,” he adds.

Each system on the vessel is redundant, with a backup module running in parallel, which is ready to take over if the primary system fails. One of the hazards of the ocean is short circuits, so the Mayflower Autonomous Ship has been built in a way that enables it to continue if systems are damaged.

“Any system that is exposed to the ocean needs to be isolated to protect against electricity shorts,” says Scott. “We are hedging our bets on the electrical reliability of the system by putting in a backup system.”