Ship Happens: A Multipurpose Autonomous Surface Vehicle Testing Platform

Autonomous surface vehicles (ASVs) are robotic self-propelled vehicles that autonomously operate on the surface of the water. They are extremely useful for collecting data and automating tasks in an ocean environment. ASVs offer a more efficient and cost-effective solution to many traditional processes out on the water, with widespread applications in scanning, mapping, sampling, and aquafarming. To this end, we seek to lower the barrier to entry of building ASVs is lowered to further this technology’s applications. This paper outlines outline the process of designing and manufacturing a low-cost ASV platform through a case study of MIT Arcturus’ ASV, Ship Happens. Ship Happens was designed as a base platform that can be modified to perform a variety of tasks near the coast or in inland waters. The major considerations in our design were cost, ease of manufacturing, maneuverability, stability, and adaptability to different missions. This paper presents design principles and priorities in designing a similar surface vehicle so that the reader might adapt our design for their own uses.As a flexible base platform, Ship Happens is a 5 ¾’ catamaran capable of holding up to 300 pounds of equipment. Overall, the entire base platform without sensors and electronics cost less than $500 in materials and can be manufactured and assembled by just one to two people. The design offers a more economical alternative to test on the water long-term.For propulsion, Ship Happens uses two Blue Robotics T200 Thrusters at each hull’s stern. To increase our maneuverability and prevent us from drifting into obstacles, we developed an optional low-cost azimuth thruster pod design which rotates in the yaw direction using servo motors, allowing us to engage our thrusters in any direction. The system is also mounted to a linear sliding mechanism to allow us to lift the thruster into the hull during transit and easily deploy the thrusters in the water.In designing the power electronics of the system, we aimed to cut down on costs without compromising the safety of the ASV. Therefore, we implemented many of the standard safety features one might expect of a mid-size electric development catamaran. However, when it came to implementing overcurrent protection, fuses posed an issue: when the fuses blow and the vessel is out on the water, the vehicle is left adrift and we must retrieve it. To remedy this while still accounting for field shorts and current spikes, we designed an overcurrent protection circuit that will allow the ASV to react to any overcurrent scenario while retaining power to communication systems and to reactivate remotely should the protection circuit be triggered. Our overcurrent protection system prevents spikes in current from damaging sensitive, more expensive components using a combination of optoisolators, fuses, and current sensing. This system was also designed to be relatively inexpensive, costing less than $2K (before the cost of the computer) using off-the-shelf parts.Ultimately, we hope that our design can be adapted for use by those interested in producing their own ASV prototyping platform for near-coast or inland waters. We hope that readers will take elements of our design which are useful to them and adapt to their uses, with the ultimate goal of furthering the application of this burgeoning technology.