Emergence of undulation gait based on embodied position controller and filter

Undulation is the most common gait generated by legless creatures, which enables their robust and efficient locomotion in various environments. Such advantages inspired the control design of many kinds of locomotion robots. Despite their technical details, most of them realize the undulation gait via tracking a predetermined trajectory called serpenoid wave, which is a group of sinusoidal functions with specified phase differences. This approach, however, sounds quite redundant in terms of sensing and control. Therefore, we come up with two research questions: 1. Whether the undulation gait should be predetermined, or it can naturally emerge? 2. Whether sinusoidal waveform is necessary to be encoded in the control signal to make the whole body an “S-shape”? Accordingly, theoretical analysis is performed via dynamic morphological computation. The results show that undulation emerges based on embodied position controller and filter, where binary actuation signals with clocks are required only. The findings not only discover locomotion mechanisms for significantly reducing the sensing and control requirement of generating artificial undulation gait, but also provide additional understandings for biological systems from the mechanical engineering point of view.