Centimeter-Scale Submarine Robot for Monitoring Coral Reef Ecosystem

Monitoring coral reef ecosystem is of great importance for assessing their health and promoting conservation efforts to protect these valuable and vulnerable ecosystems. Underwater robots provide a feasible approach for long-term monitoring due to their compact size for navigating through narrow passages. However, existing underwater robots face limitations due to their large size, preventing them from entering narrow coral reef caves to gather information. To address this challenge, this paper proposes a highly integrated propeller- driven centimeter-scale submarine robot with a length of 4.4 cm for monitoring coral reef ecosystem. There are two propellers on two sides of the robot, facilitating lift motion, while an additional two propellers are mounted at the tail to enable forward propulsion and turning maneuvers. This robot can realize three degrees of freedom movement, such as circular motion at specific heights or cruising in a spiral paths under the control of external infrared signals. A kinematic and dynamic model is formulated to develop the control strategy. For object monitoring by the proposed submarine robot, distance and displacement measurement algorithms are developed based on a monocular camera. These algorithms have been experimentally evaluated, demonstrating a calculation error of less than 5%.