Biologically inspired behaviour design for autonomous robotic fish

SUMMARYA mechanistic understanding of how fishes swim in unsteady flows is challenging despite its prevalence in nature. Previous kinematic studies of fish Kármán gaiting in a vortex street behind a cylinder only report time-averaged measurements, precluding our ability to formally describe motions on a cycle-by-cycle basis. Here we present the first analytical model that describes the swimming kinematics of Kármán gaiting trout with 70-90% accuracy. We found that body bending kinematics can be modelled with a travelling wave equation, which has also been shown to accurately model free-stream swimming kinematics. However, freestream swimming and Kármán gaiting are separated in the parameter space; the amplitude, wavelength and frequency values of the traveling wave equation are substantially different for each behavior. During Kármán gaiting, the wave is initiated at the body center, which is 0.2L (where L is total body length) further down the body compared with the initiation point in free-stream swimming. The wave travels with a constant speed, which is higher than the nominal flow speed just as in free-stream swimming. In addition to undulation, we observed that Kármán gaiting fish also exhibit substantial lateral translations and body rotations, which can constitute up to 75% of the behavior. These motions are periodic and their frequencies also match the vortex shedding frequency. There is an inverse correlation between head angle and body angle: when the body rotates in one direction, the head of the fish turns into the opposite direction. Our kinematic model mathematically describes how fish swim in vortical flows in real time and provides a platform to better understand the effects of flow variations as well as the contribution of muscle activity during corrective motions.

mentioning

confidence: 70%

A kinematic model of Kármán gaiting in rainbow trout

Akanyeti

Liao

2013

“…Fig.2) would create differential bending maxima along the lengths of parallel fin rays, thereby transmitting information about the shape and size of the obstacle around which the fish is trying to navigate. Researchers interested in the bioinspired design of autonomous underwater vehicles have already focused on programming the obstacle avoidance behavior of robotic fish (Bandyopadhyay et al, 1997;Liu and Hu, 2006;Shao et al, 2005;Shin et al, 2008;Yu et al, 2004), but have not yet looked to the biological mechanisms by which live fish accomplish this task. Robotic fish are programmed to avoid obstacles.…”

Section: Pectoral Fins As Mechanosensorsmentioning

confidence: 99%

“…While the issue of obstacle avoidance has been a subject of interest for control algorithms for robotic fish (Bandyopadhyay et al, 1997;Liu and Hu, 2006;Shao et al, 2005;Shin et al, 2008;Yu et al, 2004), we are not aware of any research that has investigated how live fish are able to successfully navigate obstacles in a complex environment if visual or lateral line sensory input is impeded. It has been observed that blind cavefish will make contact with walls using their pectoral fins during wall-following behavior (Sharma et al, 2009;Windsor et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Pectoral fins aid in navigation of a complex environment by bluegill sunfish under sensory deprivation conditions

Flammang

Lauder

2013

SUMMARYComplex structured environments offer fish advantages as places of refuge and areas of greater potential prey densities, but maneuvering through these environments is a navigational challenge. To successfully navigate complex habitats, fish must have sensory input relaying information about the proximity and size of obstacles. We investigated the role of the pectoral fins as mechanosensors in bluegill sunfish swimming through obstacle courses under different sensory deprivation and flow speed conditions. Sensory deprivation was accomplished by filming in the dark to remove visual input and/or temporarily blocking lateral line input via immersion in cobalt chloride. Fish used their pectoral fins to touch obstacles as they swam slowly past them under all conditions. Loss of visual and/or lateral line sensory input resulted in an increased number of fin taps and shorter tap durations while traversing the course. Propulsive pectoral fin strokes were made in open areas between obstacle posts and fish did not use the pectoral fins to push off or change heading. Bending of the flexible pectoral fin rays may initiate an afferent sensory input, which could be an important part of the proprioceptive feedback system needed to navigate complex environments. This behavioral evidence suggests that it is possible for unspecialized pectoral fins to act in both a sensory and a propulsive capacity. Supplementary material available online at

“…More complex robotic models of undulatory locomotion have the advantage of being more biomimetic (Barrett et al, 1999;Liu and Hu, 2006;Long et al, 2006a;Long et al, 2006b;Long et al, 2011;Tangorra et al, 2010), but are more difficult to alter quickly and change individual parameters such as flexural stiffness.…”

Section: Introductionmentioning

confidence: 99%

Undulatory locomotion of flexible foils as biomimetic models for understanding fish propulsion

Shelton

Thornycroft

Lauder

2014

104

An undulatory pattern of body bending in which waves pass along the body from head to tail is a major mechanism of creating thrust in many fish species during steady locomotion. Analyses of live fish swimming have provided the foundation of our current understanding of undulatory locomotion, but our inability to experimentally manipulate key variables such as body length, flexural stiffness and tailbeat frequency in freely swimming fish has limited our ability to investigate a number of important features of undulatory propulsion. In this paper we use a mechanical flapping apparatus to create an undulatory wave in swimming flexible foils driven with a heave motion at their leading edge, and compare this motion with body bending patterns of bluegill sunfish (Lepomis macrochirus) and clown knifefish (Notopterus chitala). We found similar swimming speeds, Reynolds and Strouhal numbers, and patterns of curvature and shape between these fish and foils, suggesting that flexible foils provide a useful model for understanding fish undulatory locomotion. We swam foils with different lengths, stiffnesses and heave frequencies while measuring forces, torques and hydrodynamics. From measured forces and torques we calculated thrust and power coefficients, work and cost of transport for each foil. We found that increasing frequency and stiffness produced faster swimming speeds and more thrust. Increasing length had minimal impact on swimming speed, but had a large impact on Strouhal number, thrust coefficient and cost of transport. Foils that were both stiff and long had the lowest cost of transport (in mJ m −1 g −1 ) at low cycle frequencies, and the ability to reach the highest speed at high cycle frequencies.