Underwater robot designs inspired by the behavior, physiology, and anatomy of fishes can provide enhanced maneuverability, stealth, and energy efficiency. Over the last two decades, robotics researchers have developed and reported a large variety of fish-inspired robot designs. The purpose of this review is to report different types of fish-inspired robot designs based upon their intended locomotion patterns. We present a detailed comparison of various design features like sensing, actuation, autonomy, waterproofing, and morphological structure of fish-inspired robots reported in the past decade. We believe that by studying the existing robots, future designers will be able to create new designs by adopting features from the successful robots. The review also summarizes the open research issues that need to be taken up for the further advancement of the field and also for the deployment of fish-inspired robots in practice.

https://iopscience.iop.org/article/10.1088/1748-3190/11/3/031001/pdf

Fish-inspired robots: design, sensing, actuation, and autonomy--a review of research.

Biomechanics of Locomotion in Sharks, Rays, and Chimeras

To investigate the undulating median fin propulsion and its potential for implementation in man-made underwater vehicles, a "fin actuator" has been developed. The device consists of eight parallel bellows actuators or PBAs (fin rays) arranged in a series and interconnected via a flexible material (fin membrane). The PBAs are pneumatically driven and allow for bending movements in any orientation plane. Position data are provided by flexible electrogoniometers. The forces generated from the fin actuator undulations are measured by a pair of tri-axial force sensors. Initial testing has concentrated on 2D fin ray motions, whereby each PBA moves laterally, with the deflection angle performing a sinusoidal variation. Preliminary measurements, for a range of the propulsive waveform parameters, demonstrate reversible thrust generation and good agreement with the theoretical predictions of a momentum-based model.

Development and evaluation of an experimental undulating-fin device using the parallel bellows actuator

This paper aims to design a novel bionic fish propelled by oscillating paired pectoral fins. Flapping motion deformation of the nature sample, the cow-nosed ray, is realized with simple mechanical structure through optimization. Locomotion analysis of the nature sample under linear cruise swimming conditions is carried out. Simplified mathematical models of the pectoral fin are obtained to be the design foundation of the bionic fin rays and the bionic fish. The number of fin rays is decided according to the passing kinematic wave shape and number. Distance and structure parameters are optimized, and determined by the minimum area error method. A novel two-stage slide–rocker mechanism is designed to fulfill the driving requirements with only one servo motor. System design of a new bionic fish robot is presented, including the mechanical design and the control method. Main bionic characteristics extracted from the cow-nosed ray are fulfilled by the prototype and verified by experiments.

Design Optimization of a Bionic Fish with Multi-Joint Fin Rays

The range of physiological adaptations possessed by marine animals allowing them to successfully operate in the marine environment is a plentiful source of inspiration for the designers of Autonomous Underwater Vehicles. This chapter compares the total energetic cost of straight line swimming for both marine animals and AUVs, using cost of transport (COT) as a comparative metric. COT is a normalised measure of the energetic cost of transporting the animal’s or vehicle’s mass over a unit distance. It includes non propulsion power requirements as well as considering the energy lost by actuators and mechanical couplings and energy lost in the wake. Comparisons presented in this chapter show that marine animals typically have higher optimum COT than engineered systems of equivalent size. However parallels may be drawn, for example, to increase range both marine animals and AUVs appear to favour reducing non-propulsion power costs and travelling slowly to ensure operating at the minimum COT.

/pdf/nature-in-engineering-for-monitoring-the-oceans-comparison-4vv0avusht.pdf

Nature in engineering for monitoring the oceans: comparison of the energetic costs of marine animals and AUVs

This paper described our work in probing into fish robot with pectoral fin propulsion. The aim of this project is to develop a robot fish mimicking cownose ray that swims with flexible pectoral fins in oscillation motion. According to the analysis of cownose ray'motion, a novel robot fish prototype propelled by pectoral fins was designed, The effect of flapping parameters (frequency and amplitude) and flexibility of fins on the propulsive performance was studied through a series of experiments underwater. Experiments showed that the velocity was almost in linear relationship with flapping frequency and amplitude below 2.0Hz, and the propulsive efficiency without chord-wise or span-wise ribs is higher than that with ribs. The conclusion is deduced that if the flexibility was selected properly, the pectoral fins with flapping mode would be an efficient propulsion mode for underwater vehicles.

Ji Li

Papers

Design and experiments of robot fish propelled by pectoral fins