Symmetric and Asymmetric Actuation Mechanisms of an Elastic Beam Actuated Bionic Fish

To enhance the propulsion capacity and maneuverability of bionic fish in complex aquatic environments, this study presents the design of a prototype, EBA-bot II, actuated by an elastic beam actuation mechanism. A mechanical structure capable of both symmetric and asymmetric actuation was developed, and a dynamic model of the elastic beam actuation system was established. Based on this model, the motion responses of the bionic fish under different actuation modes were systematically analyzed. Comparative simulations and experimental trials were conducted to validate the model's accuracy in predicting propulsion speed and simulating turning behaviors. The results demonstrate that symmetric actuation enables stable linear swimming, whereas asymmetric actuation provides effective turning capabilities and achieves circular trajectories, indicating excellent maneuverability and controllability. This work offers both theoretical and experimental foundations for the development of highly maneuverable bionic underwater robots.