Control of the Swimming System of a Multimodal Marine Robot : An Experimental Study of Bio-Inspired Approaches and Control Strategies for Coordinated Swimming in Underwater Robotics

Sammanfattning

Underwater robots offer a promising solution for exploring areas deep beneath the ocean surface, both for collecting data to study the marine environment and for conducting rescue operations in locations inaccessible to humans due to extreme underwater conditions. Bioinspired underwater robots have gained significant attention for their ability to mimic the locomotion of marine animals. One of the main reasons for adopting fish-like movement is that traditional commercial underwater robots, which typically rely on propellers, can potentially harm marine life through their mechanical movement and the noise they generate. The RoboIguana is a bioinspired robot modeled after the Galápagos marine iguana, the world’s only marine lizard. This unique animal uses its tail for swimming and its limbs for locomotion along the seafloor, demonstrating both streamlined propulsion and agile underwater movement. The aim of this thesis is to identify the control parameters required for the RoboIguana’s tail to generate optimized forward propulsion. These parameters are tested on the tail using a custom-built, rigid, and stable experimental setup designed to hold the tail underwater, while supporting the necessary sensors outside the water to analyze the tail’s movement. The forward propulsion force generated by the tail is influenced by four control parameters: yaw amplitude, sway amplitude, frequency, and the phase shift applied to the sway motion. Experimental results indicate that the propulsion force increases with higher movement frequencies and larger amplitude values. However, these increases also result in greater electrical current consumption by the tail.