In this paper, we aim to study the swimming performance of fish robots by using a statistical approach. A fish robot employing a carangiform swimming mode had been used as an experimental platform for the performance study. The experiments conducted aim to investigate the effect of various design parameters on the thrust capability of the fish robot with a flexible caudal fin. The controllable parameters associated with the fin include frequency, amplitude of oscillation, aspect ratio and the rigidity of the caudal fin. The significance of these parameters was determined in the first set of experiments by using a statistical approach. A more detailed parametric experimental study was then conducted with only those significant parameters. As a result, the parametric study could be completed with a reduced number of experiments and time spent. With the obtained experimental result, we were able to understand the relationship between various parameters and a possible adjustment of parameters to obtain a higher thrust. The proposed statistical method for experimentation provides an objective and thorough analysis of the effects of individual or combinations of parameters on the swimming performance. Such an efficient experimental design helps to optimize the process and determine factors that influence variability.

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In this initial work, we discuss the application of Lighthill's small-amplitude elongated body theory (EBT) in improving the swimming efficiency. The prototype considered in the study is a slender fish model capable of performing various motion patterns. The mechanical design of the prototype, derivation of equations and the results are first discussed. We apply a body motion function with linear envelop to control the swimming of fish robot. We also study the influence of different combinations of amplitudes and frequencies on the swimming performance. The analysis shows that a high frequency with low amplitude mode is better at a given power consumption. Different definitions of swimming efficiency in robotic fishes are also discussed. By virtue of the current off-line based approach, a closed-loop swimming control method and an on-line swimming gait planning scheme are suggested.