Bionic Body Wave Control for an Eel-Like Robot Based on Segmented Soft Actuator Array

Using body wave to swing forward is the most common propulsion method for underwater creatures, which can achieve flexible swing and multi-directional steering. Related robotics researches in recent years employed rigid structure and hinge connection to build the entire swing body, which were driven by conventional motors. However, soft robotics provides an alternative to make the robot behave like a bionic fish in terms of swing flexibility, actuation and efficiency. In this article, the authors develop the entire eel-like fish with a fully soft flexible body, which is composed of four fiber-reinforced, bidirectionally bending, fluidic elastomer actuators (FEAs) as its tail. This robotic fish tail has multiple segments connected in series with different waveforms to make the overall fish tail exhibit fluctuating forward performances. The FEA uses the typical dual-chamber configuration, and PWM sine wave signals are utilized to effectively control such a hydraulic mechanism. With experiments, the swing of each tail section is tested, and various factors with respect to the swing frequency and amplitude are studied. The results illustrate the feasibility and superiority of the proposed body wave control method.