In this study, an ASV was developed to work in seaweed beds. In coastal areas, the distance from obstacles is close, and seaweed and marine debris drift by, requiring a high-precision self-positioning system and actuators that can cope with seaweed beds. We created an ASV that solves these problems. Aiming for social implementation, we created a control system focusing on ease of use and robustness. We verified the validity of the system by performing automatic control in a real sea area using the created ASV.
In recent years, there has been an increasing need for projects aimed at monitoring coastal areas, such as inspections of offshore wind turbines and cultivation of seaweed beds as part of blue carbon projects. On the other hand, as the population decreases due to the declining birthrate and aging population, these operations are required to be performed unmanned using robots and other equipment. In Japan, there is a small vessel license system, and the hurdle to owning a small vessel to perform such work is high and uncommon. In response to this problem, our laboratory is developing an ASV (Autonomous Surface Vehicle) system, named ‘μ-ASV’, which does not require a licence and can be operated by a small number of people (Kawamura, Y, Tahara, J, et al. 2019; Kawamura, Y, Tahara, J, et al. 2020). The μ-ASV is a completely original vehicle developed by our laboratory, including the control system, hull, electric circuit, and software. It is being developed for applications in fisheries, port surveillance and infrastructure inspection. As examples of our previous research, we have produced sea urchin density maps using sea urchin recognition from underwater camera images (Fig. 1), and seafloor maps (Fig. 2) using sonar data and μ-ASV wake data (Morito, M, Tahara, J, et al. 2023).
However, in actual operation, there were several problems as shown below.
- Algae and marine debris would get caught in the thrusters, rendering them inoperable.
- The accuracy of GPS and magnetic sensors is low, and there are cases where WayPoint control fails.
- Stable communication bandwidth is required for the control software to operate, and if communication deteriorates, ASV control becomes impossible.
