Unmanned Systems Technology 004 | Delair-Tech DT18 | Autopilots | Rotron RT600 | Unmanned surface vehicles | AMRC | Motion control | Batteries

56 Smaller craft ASV in Portsmouth, UK, is developing technology for a range of smaller autonomous craft that are used in a wide range of applications. For example, its C-Enduro (examined in detail in UST issue 1) is designed to go to sea for up to three months at a time using wind and solar power, and the company is currently proving the endurance of the craft. Another of its ASV craft, the C-Worker, uses dual 13 kW diesel generators and 10 kW electric motors, and can last for 30 days running at a survey speed of 4 knots. As sonar systems improve, so survey speeds can be increased, so larger and faster vehicles are being developed to carry new sonar systems. Although the quality of the sonar data depends on the price of the sensor, there are advantages to using a USV designed specifically for surveying. Rather than having the sonar placed at a convenient location in a manned ship, the GPS and inertial navigation sensors can be placed at specified points on the boat to make the data more accurate. The design of the C-Worker’s engines is also intended to help improve the quality of the survey data. The dual electric motors were specifically designed to minimise acoustic noise as the craft can run on lithium-ion batteries during a survey and then have them recharged by the diesel generators. The design is deliberately based around using standard components for the generators, pumps, motors and batteries so that if there is problem when operating on the other side of the world, and a spare part is needed, it can be obtained easily. This is a key design criterion. For example, the C-Worker is being used in Japan as a small fixed buoy, using an acoustic modem linked to sensors on the sea bed to look at the movement of the tectonic plates to warn of tsunamis. In China, meanwhile, it is being used to monitor water quality in lakes. The oil and gas industry is also looking to vessels such as the C-Worker, to reduce costs and improve health and safety by taking people out of danger zones. A large survey ship in the Gulf of Mexico can cost $80,000-100,000 a day, but the same functions can be carried out with a USV for a tenth of that. ASV’s experience is showing the limits of the technology though. For example, challenges remain in tracking other craft in a big swell, when they can disappear for a time and reappear in an unexpected position. Radar is also not 100% reliable, especially for detecting wooden vessels such as trawlers, so other detection systems are needed. For long endurance, the lower the power the better, so ASV is looking at techniques such as motion detection to reduce the power consumed by cameras so that they only operate when they detect a movement. Real-time control of the C-Enduro and C-Worker is handled by programmable logic controllers, which are used widely in industry and so are easy to replace if necessary and easy to program reliably. The overall system control and monitoring of the different components in the craft is handled by an embedded PC running a Linux operating system, and ASV is moving to a standard design for the controllers across all the platforms. ASV is also working with safety-critical software developer D-Risq and Cranfield University on a two-year project called USMOOTH which will look at ‘over the horizon’ (OTH) comms technologies such as 4G cellular links. However, ASV sees its main challenge as having enough vehicles to service the market. Its long-term goal is to send vehicles out from Portsmouth harbour, past all the other marine traffic and accounting for sand banks and tides, then out into open water. Once on the open water though the craft can make its own way to its destination, whether it be a survey site or oil rig, with one person monitoring up to six vehicles around the world and dealing with any problems as they arise. The C-Enduro is also being used to test how large fleets of autonomous systems can be managed from the shore, as part of the Autonomous Ocean Sampling Networks project. In this project, the company is working with the UK’s Marine Biological Association and software provider SeeByte to design ways for autonomous craft to handle five scenarios – oil spill, passive acoustic monitoring (PAM), seabed mapping, fish tracking and tidal mixing. In the project, sensor data from Autumn 2015 | Unmanned Systems Technology The Saildrone 1 autonomous sailing boat holds the world endurance record for a wind-powered vessel (Courtesy of Saildrone)