Evaluation on Swimming Efficiency of an Eel-inspired Soft Robot with Partially Damaged Body

In this paper, we present an evaluation of swimming efficiency of a previously developed tethered eel-inspired soft robot, when the body suffered from partial damage (i.e., losing control) at its lower region (tail part). Swimming strategy of body damage was constructed based on controlling inputs of four pairs of soft actuators that constitute the eel robot. The tail part will be passive (i.e., without active control). We also varied shifting phase of control inputs in order to seek the best range for creating smooth propagation waves from anterior to posterior part of the robot body, which mimics the movement of an anguilliform swimmer. At two modes (including normal body and passive tail), the robot performed better velocity in the range of shifting phase s from 30 % to 50 %. Interestingly, the robot’s swimming velocity with a passive tail was improved compared to that of the robot with normal state (without damaged parts). We also evaluated cost of transport (COT) in all cases, and the best value of COT is 11.06 created by the robot with passive body. In this mode, the robot also swims with the highest velocity of 14.34 cm/s (0.27 BL/s). The result in this paper can be utilized to optimize the design and efficiency of swimming elongated soft robots.