Distant touch hydrodynamic imaging with an artificial lateral line

Abstract

Nearly all underwater vehicles and surface ships today use sonar and vision for imaging and navigation. However, sonar and vision systems face various limitations, e.g., sonar blind zones, dark or murky environments, etc. Evolved over millions of years, fish use the lateral line, a distributed linear array of flow sensing organs, for underwater hydrodynamic imaging and information extraction. We demonstrate here a proof-of-concept artificial lateral line system. It enables a distant touch hydrodynamic imaging capability to critically augment sonar and vision systems. We show that the artificial lateral line can successfully perform dipole source localization and hydrodynamic wake detection. The development of the artificial lateral line is aimed at fundamentally enhancing human ability to detect, navigate, and survive in the underwater environment.dipole localization ͉ hot wire anemometer ͉ micromachining ͉ wake detection ͉ neuromast A lateral line is a spatially distributed system of flow sensors found on the body surface of fish (1) and aquatic amphibians (2). It is comprised of arrays of neuromasts, which can be classified into two types: superficial neuromasts and canal neuromasts (Fig. 1). A superficial neuromast is situated on the surface of the fish and responds in proportion to fluid velocity (3, 4). In contrast, a canal neuromast is packaged in fluid-filled canals located beneath the surface of the skin and are commonly described as a detector of outside water acceleration that is proportional to the pressure gradient (1, 3-6). As an integrated flow sensing system, such lateral lines form spatial-temporal images of nearby sources based on their hydrodynamic signatures (1, 3, 5) and provide mechanosensory guidance for many different behaviors, including synchronized swimming in schools, predator and obstacle avoidance, prey detection and tracking, rheotaxis, and holding station behind immersed obstacles in streams (4,7,8). This ''distant touch'' sense complements other sensory modalities, including vision and hearing, to increase survivability in unstructured environments. To date, there has never been an engineering equivalent of the fish lateral line system for underwater vehicles and platforms. The goal of the present research is to build an artificial lateral line that mimics the functional organization and imaging capabilities of the biological one. The artificial lateral line can facilitate fundamental studies of biological systems and provide unprecedented sensing and control functions to underwater vehicles and platforms. Specifically, we envision that the distant touch hydrodynamic imaging capability of the artificial lateral line can provide a new sense in addition to sonar and vision. In this article, we demonstrate the functions of an artificial lateral line under two biologically relevant scenarios: (i) localizing a moving target with flapping part (7, 9, 10) and (ii) imaging a hydrodynamic trail for prey capture (11,12). Development of the Artificial Lateral LineThe artificial lateral line ...

Hydrodynamic object recognition using pressure sensing

“…Modelling the pressure sensing after natural or artificial devices (Fan et al 2002;Coombs & Braun 2003;Yang et al 2006), we assume a finite noise-tosignal ratio g in that measurement. This noise level primarily accounts for two sources of ubiquitous noise: the noise induced by the limited capabilities of the mechanotransducers forming the sensing device as well as the signal postprocessing; and the background noise of the fluid flow in which the sensor is placed.…”

“…From the robotic standpoint, Fan et al (2002) reported the first design and fabrication of an artificial lateral line flow sensor. Later, Yang et al (2006) reported the first experimentations where such an artificial LLS is used to detect both a dipole and a wake, hence allowing it to mimic the pressure-sensing capabilities of those encountered in nature. Recently, McConney et al (2009) reported yet another biologically inspired design of sensors showcasing more similarities with neuromasts than any other artificial devices before, and enhancing the detection of flow field perturbations.…”

“…Very recently, the foundations of hydrodynamic mapping using velocity sensing were laid by Sichert et al (2009), in which vectorial velocity sensing was used to locate a moving disturbance and determine certain shape-scaling parameters. Fishes using canal neuromasts of LLS or an artificial sensing device, however, depend primarily on pressure sensing for fixed obstacle detection and identification (Coombs & Braun 2003;Yang et al 2006). In addition, for any hydrodynamic mapping procedure to be general and viable, two key features are required.…”

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