Optimizing terrestrial locomotion of undulating-fin amphibious robots: Asynchronous control and phase-difference optimization

This paper presents an asynchronous motion-control approach for undulating-fin amphibious robots, with emphasis on optimizing the phase differences of bilateral fin-surface waves to mitigate the pitch-angle instability typically observed in synchronous control. A comprehensive ground dynamics model is used in this study, which facilitates the meticulous analysis of pitch-angle variations. Using simulation software, a virtual prototype is developed to validate the control stability. This approach is further substantiated via experimental tests conducted on a physical prototype in diverse terrestrial environments. Simulation and experimental results indicate that asynchronous motion control methods significantly enhancing postural stability undulating-fin robots during terrestrial locomotion. Experimental findings demonstrate that adopting asynchronous motion control reduces the maximum range of pitch angles by 38.9%–42.3%. This method significantly enhancing postural stability of robot terrestrial locomotion. This study provides new insights for the design of undulating-fin amphibious robots.