Design of a Cable-Mounted Robot for Near Shore Monitoring

摘要

The coasts are an essential resource. About 600 million people reside along the coasts at an elevation of less than 10 meters above sea level, with this number projected to double by 2060 [1]. In addition to being critical to human society, biodiverse coastal habitats such as estuaries, wetlands, coral reefs, and upwelling areas support and provide breeding grounds for organisms such as fish, marine mammals, sea turtles, and migratory birds. Given the role the coasts play in billions of lives, monitoring this highly dynamic environment is an urgent concern for both safety and conservation efforts. Due to climate change, vulnerable coastal ecosystems are experiencing strains from sea level rise, increased temperatures, changes in storm patterns, and ocean acidification [1], [2]. These changes necessitate reliable observations that will help us achieve a better understanding of the coasts. However, surveying the coastal waters is not an easy task. Coasts are affected by a unique mix of environmental and human influences that vary over time. These influences range from natural erosion and accretion to substantial coastal engineering. Individual coastal sites can be difficult to reach and may have considerably different needs and vulnerabilities [3]–[5]. For instance, during extreme scenarios such as hurricane landfall, capturing transient event data is crucial for the accurate development of local coastal models [3]. The diverse conditions along the coasts create a complicated environment for any observation system to navigate. Within this environment, there is space for new and inexpensive approaches to coastal monitoring. Researchers need an affordable and reliable method of data collection to further understand this critical area. We propose a robotic system that can contribute to widespread, low cost, and consistent coastal monitoring. The robot traverses a fixed, partially underwater cable and autonomously collects data as it moves through the water. By fixing the motion of the robotic system to a single degree of freedom, it can easily overcome the many challenges of navigating a coastal environment. Specifically, it is better able to return to a precise location over time for measurements in long-term studies and minimizes the need for human supervision and maintenance, reducing costs while increasing sampling rates. The system will collect information regardless of weather and with much greater temporal resolution than manual methods. It is also highly modular and can be equipped with different sensor suites depending on the application and deployment location. Following our system proposal, we describe the design and testing of a prototype constructed during summer 2020 and culminating with two days of data collection tests off the coast of Mattapoisett, Massachusetts in the United States. We conducted multiple experiments to test different configurations of our design to compare their performance in each of three focus areas: simplicity, reliability, and versatility. Our prototyping and testing phases lay the groundwork for further development of this system. In this paper, we present the results of our tests and recommendations for future research.