Development of an artificial sensor for hydrodynamic detection inspired by a seal’s whisker array

Abstract

Nature has shaped effective biological sensory systems to receive complex stimuli generated by organisms moving through water. Similar abilities have not yet been fully developed in artificial systems for underwater detection and monitoring, but such technology would enable valuable applications for military, commercial, and scientific use. We set out to design a fluid motion sensor array inspired by the searching performance of seals, which use their whiskers to find and follow underwater wakes. This sensor prototype, called the Wake Information Detection and Tracking System (WIDTS), features multiple whisker-like elements that respond to hydrodynamic disturbances encountered while moving through water. To develop and test this system, we trained a captive harbor seal (Phoca vitulina) to wear a blindfold while tracking a remote-controlled, propeller-driven submarine. After mastering the tracking task, the seal learned to carry the WIDTS adjacent to its own vibrissal array during active pursuit of the target. Data from the WIDTS sensors describe changes in the deflection angles of the whisker elements as they pass through the hydrodynamic trail left by the submarine. Video performance data show that these detections coincide temporally with WIDTS-wake intersections. Deployment of the sensors on an actively searching seal allowed for the direct comparison of our instrument to the ability of the biological sensory system in a proof-of-concept demonstration. The creation of the WIDTS provides a foundation for instrument development in the field of biomimetic fluid sensor technology.

Does Vibrissal Innervation Patterns and Investment Predict Hydrodynamic Trail Following Behavior of Harbor Seals (Phoca vitulina)?

“…Although axons/F‐SC is a useful measure to characterize patterns of innervation among phocids, axon density allows comparison among regions of F‐SCs thought to have specific functions from behavioral studies. Hydrodynamic trail following by harbor seals is accomplished using the most ventrolateral vibrissae (Eberhardt et al, ). Harbor seals have increased density of axons in the ventrolateral vibrissae compared to harp seal ( Pagophilus groenlandicus ) vibrissae from the same region.…”

“…Hair shaft movement is thought to stimulate mechanoreceptors at the glassy membrane and in the densely innervated inner‐conical body and ringwulst, which are located around the fluid‐filled ring sinus (RS) about halfway through the F‐SC. How pinniped vibrissae detect mechanosensory signals is poorly understood, since to date functional studies have either focused on microstructure, and innervation patterns (Hyvärinen, ; Marshall et al, , Marshall et al, ; McGovern et al, ; Mattson and Marshall, ; Jones, ; Sprowls, ), hair shaft morphology and mechanics (Hanke et al, ; Wieskotten et al, , ; Murphy et al, ; Summarell et al, ), behavioral performance studies and psychophysical testing (Dehnhardt, ; Dehnhardt and Kaminski, ; Dehnhardt et al, ; Gläser et al, ; Murphy et al, ; Eberhardt et al, ), experimental behavioral studies (Marshall et al, ; Marshall et al, ), or studies on individual whisker use in live harbor seals (Grant et al, ; Murphy et al, ). However, few studies have attempted to integrate morphological, neurobiological, and behavioral data to provide a holistic function hypothesis.…”

“…These presumptive microvibrissae, or the whiskers clustered medially around the nose (as described in Mattson and Marshall, ), appear to be more important in active touch reception. Harbor seals have been observed to use the most medial vibrissae for fine‐scale tactile discrimination tasks (Dehnhardt and Kaminski, ; Grant et al, ; Eberhardt et al, ). Structural and functional differences have been more extensively studied in terrestrial mammals that investigate objects by sweeping their microvibrissae across an object of interest (Brecht et al, ).…”

A Deep-Learning Model for Underwater Position Sensing of a Wake’s Source Using Artificial Seal Whiskers

“…Kottapalli et al developed a MEMS pressure sensor for AUVs that mimics the fish lateral-line [ 23 ]. Motivated by Dehnhardt’s experiments of Harbor seals, Eberhardt et al presented a system of artificial whiskers that produced vibration signals that were related to the hydrodynamic trail of a pilot submarine [ 24 ]. We believe that further development of biomimetic sensory systems would help marine robots to expand their perception of the surrounding fluid motion.…”

Identifying vessel branching from fluid stresses on microscopic robots

“…These fluid stresses provide information about the environment within about a body length of the object in the fluid [42], although extracting this information requires significant computation [6]. Another example of sensing fluid motion is the use of artificial whiskers, modeled on the geometry of seal whiskers, to estimate the direction, size and speed of moving objects from their wakes [12].…”