Swimming and Crawling with an Amphibious Snake Robot

We present AmphiBot I, an amphibious snake robot capable of crawling and swimming. Experiments have been carried out to characterize how the speed of locomotion depends on the frequencies, amplitudes, and phase lags of undulatory gaits, both in water and on ground. Using this characterization, we can identify the fastest gaits for a given medium. Results show that the fastest gaits are different from one medium to the other, with larger optimal regions in parameter space for the crawling gaits. Swimming gaits are faster than crawling gaits for the same frequencies. For both media, the fastest locomotion is obtained with total phase lags that are smaller than one. These results are compared with data from fishes and from amphibian snakes.