ARTIFICIAL LATERAL LINE AND ... - Semantic Scholar
ARTIFICIAL LATERAL LINE AND HYDRODYNAMIC OBJECT TRACKING J.Chen1, J. Engel1, N. Chen1, S. Pandya1, S. Coombs2, C. Liu1 1
Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign 2 Bowling Green State University
ABSTRACT We report the development of biologically inspired artificial lateral line sensor for underwater flow field imaging. The artificial lateral line is based on an array of integrated, elevated hotwire elements. The static and dynamic behavior of the array, packaged as superficial sensors or canal embedded ones, are discussed. We have developed a complete system and demonstrated mimicking the functions of “soft touch” of real biological lateral line. The sensor array can track the distance and location of an oscillating dipole source.
(a)
superficial
(b)
1. INTRODUCTION The lateral line is a sensory system ubiquitous in fish and amphibian species, yet it is often overlooked because it is not visually apparent, and because it is not part of the basic five senses of biology (vision, hearing, touch, taste, and smell). The lateral line is part of the octavalateralis system, commonly found in fishes and amphibians. It is a primitive mechanosensory system that runs along the length of the fish. It’s sense has been described as “touch at a distance” [1] because it can provide visualization of hydrodynamic flow in the near field. The lateral line system is composed of a large array of distinct neuromast that serve as individual sense organs. The neuromast themselves are the actual mechanosensory organs that respond to the fluid displacement[2]. The number of neuromast found in a lateral line system can vary from species to species, from tens to thousands. These organs can be classifieds into two categories, depending on how they are packaged[3, 4]. The neuromast found exposed on the surface of the fish are called superficial neuromast, which responds to fluid velocity. They are typically found in several distinct locations on the head and the trunk of a fish, as represented by the dots in Figure 1a. A second type of neuromast, called canal neuromast, is packaged in fluidfilled canals beneath the surface of the skin. The canal serves to protect the neuromast as well as to filter out low frequency dc flow that can saturate the sensor system. These are represented by shaded stripes. The neuromast itself is a complex structure that contains tens to hundreds of hair cells, which carry the transduction mechanism that converts mechanical displacement to electrochemical signals through the nerve fibers. The hair cells are packaged inside a gelatinous sack called the cupula.
Figure 1 (a) Schematic of a lateral line system on a fish, as represented by the shaded gray regions. The black dots are the individual neuromast. (b) schematic of the lateral line canal system. The neuromast, each may contain tens to hundreds of discrete hair cells, reside in the canal and is trigged with fluid motion.
Fish use the lateral line to detect and track prey and predator, orient to current, and match speed to neighboring fish in a school [5]. The lateral line is also used by fish to form a hydrodynamic image of its surrounding in order to navigate around obstacles without the use of vision [6]. It has been shown that without the lateral line, fish’s prey capture capability is severely inhibited [7]. With such variety of functional features in mind, we will examine the basic design and operation of the lateral line to see if we can learn from it, and perhaps obtain some inspiration for using arrayed micromachined sensor to perform functions similar to those performed by the lateral line. The motivation of our work is to develop an artificial lateral line with array of sensors that mimic the functionalities of superficial and canal neuromast, and provide alternative sensory ability to underwater vehicle, for surveillance, navigation, and maneuvering capabilities. We will describe and characterize the artificial sensors and demonstrate the ability of the sensor array to perform the source localization similar to that of the lateral line.
2. SENSOR DESIGN AND SELECTION To develop an artificial lateral line system, we need a sensor that can respond to fluid displacement and velocity whose size should be in the range of a neuromast (tens to hundreds of micron) and can be easily arranged and fabricated in array. Some other important characteristics are:
Flat frequency response to 300 Hz Large dynamic range Noninvasive transducer element Directional sensitivity
The frequency response to small signal heating is characterized under water, and the response to small ac signal at an overheat of 0.05 is plotted in Figure 3. This is sufficient for measuring the hydrodynamic flow in the frequency range interested by the biological systems.
Direct optical measurement of water motion such as LaserDoppler velocimetry or surface reflection is a possible solution to image water motion, but it’s difficult to implement, bulky to setup, and has a relatively larger time constant. There have been efforts to fabricate a micromachined hair cell to measure fluid flow and displacement using a piezoresistive element[8, 9], a strain gauge[10], or capacitive plates[11], but non of them can satisfy all the requirements and have sufficient sensitivity.
-10
output/input (dB)
-
-15
slope= -20dB/dec
-20 -25 -30 -35 -40 10
100
1000
10000
100000
frequency (Hz)
Figure 3 Frequency response testing of a micro fabricated HWA in water.
3. EXPERIMENTAL SETUP To understand the behavior of the lateral line to hydrodynamic flow, a well-defined stimulus is used instead. The stimulus often used is a dipole source, or vibrating sphere. In addition, the fields created by aquatic animals tend to be predominantly dipolar [15]. The experimental setup is shown in Figure 4.
(a) 12V 12V
0.1nF
R1
12V
100Ω
10kΩ 0.1µF
-
LM358a
INA2126a
+
Ranm
Dipole source
+
100Ω
-12V
0.1µF
Figure 2 (a) SEM of the HWA array, and (b) schematic of the circuit used during the testing.
We have developed a surface-micromachined, out-of-plane hot-wire anemometer that can be made into large arrays [12]. There have been studies on hydrodynamic imaging in relation to lateral line by Coombs and colleagues using hotfilm anemometry (HFA) [13], and the data suggested that HFA can detect particle displacement down to the hundreds of nanometer range, adequate compared to biological neuromast in similar flow [14].
h
z
(b)
y
x
Sensor position 16
Sensor position 1
Figure 4 Schematic of the experimental setup. The sensor array runs along the x-axis, and the dipole field is created by a sphere oscillating in the x-axis. The amplitude of the oscillation is measured by an accelerometer attached to the rod connecting the sphere to the shaker. The distance between the dipole and the sensor is designated h.
The solution of the dipole source is An array of hot-wire anemometer used during testing is shown in Figure 2(a), and the constant temperature circuitry with an offset trimmer and gain stage is shown in Figure 2(b). For individual sensor testing, a commercial Grass Telefactor P55 amplifier is used in conjunction with a highpass filter instead of the gain stage.
u=−
((
)
)
a 3U 0 ( kr ) 2 + j 2kr − 2 cos θiˆr + ( jkr − 1)sin θiˆθ e − j (ωt −kr ) 2r 3
(1)
The solution of the wave equation for pressure has two terms. The first term drops off at 1/r and is proportional to k2. This term is dominant when kr >> 1, and usually referred to as the propagating sound (pressure) wave in the
far field. The second term drops off at 1/r2, and is dominant when kr
Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign 2 Bowling Green State University
ABSTRACT We report the development of biologically inspired artificial lateral line sensor for underwater flow field imaging. The artificial lateral line is based on an array of integrated, elevated hotwire elements. The static and dynamic behavior of the array, packaged as superficial sensors or canal embedded ones, are discussed. We have developed a complete system and demonstrated mimicking the functions of “soft touch” of real biological lateral line. The sensor array can track the distance and location of an oscillating dipole source.
(a)
superficial
(b)
1. INTRODUCTION The lateral line is a sensory system ubiquitous in fish and amphibian species, yet it is often overlooked because it is not visually apparent, and because it is not part of the basic five senses of biology (vision, hearing, touch, taste, and smell). The lateral line is part of the octavalateralis system, commonly found in fishes and amphibians. It is a primitive mechanosensory system that runs along the length of the fish. It’s sense has been described as “touch at a distance” [1] because it can provide visualization of hydrodynamic flow in the near field. The lateral line system is composed of a large array of distinct neuromast that serve as individual sense organs. The neuromast themselves are the actual mechanosensory organs that respond to the fluid displacement[2]. The number of neuromast found in a lateral line system can vary from species to species, from tens to thousands. These organs can be classifieds into two categories, depending on how they are packaged[3, 4]. The neuromast found exposed on the surface of the fish are called superficial neuromast, which responds to fluid velocity. They are typically found in several distinct locations on the head and the trunk of a fish, as represented by the dots in Figure 1a. A second type of neuromast, called canal neuromast, is packaged in fluidfilled canals beneath the surface of the skin. The canal serves to protect the neuromast as well as to filter out low frequency dc flow that can saturate the sensor system. These are represented by shaded stripes. The neuromast itself is a complex structure that contains tens to hundreds of hair cells, which carry the transduction mechanism that converts mechanical displacement to electrochemical signals through the nerve fibers. The hair cells are packaged inside a gelatinous sack called the cupula.
Figure 1 (a) Schematic of a lateral line system on a fish, as represented by the shaded gray regions. The black dots are the individual neuromast. (b) schematic of the lateral line canal system. The neuromast, each may contain tens to hundreds of discrete hair cells, reside in the canal and is trigged with fluid motion.
Fish use the lateral line to detect and track prey and predator, orient to current, and match speed to neighboring fish in a school [5]. The lateral line is also used by fish to form a hydrodynamic image of its surrounding in order to navigate around obstacles without the use of vision [6]. It has been shown that without the lateral line, fish’s prey capture capability is severely inhibited [7]. With such variety of functional features in mind, we will examine the basic design and operation of the lateral line to see if we can learn from it, and perhaps obtain some inspiration for using arrayed micromachined sensor to perform functions similar to those performed by the lateral line. The motivation of our work is to develop an artificial lateral line with array of sensors that mimic the functionalities of superficial and canal neuromast, and provide alternative sensory ability to underwater vehicle, for surveillance, navigation, and maneuvering capabilities. We will describe and characterize the artificial sensors and demonstrate the ability of the sensor array to perform the source localization similar to that of the lateral line.
2. SENSOR DESIGN AND SELECTION To develop an artificial lateral line system, we need a sensor that can respond to fluid displacement and velocity whose size should be in the range of a neuromast (tens to hundreds of micron) and can be easily arranged and fabricated in array. Some other important characteristics are:
Flat frequency response to 300 Hz Large dynamic range Noninvasive transducer element Directional sensitivity
The frequency response to small signal heating is characterized under water, and the response to small ac signal at an overheat of 0.05 is plotted in Figure 3. This is sufficient for measuring the hydrodynamic flow in the frequency range interested by the biological systems.
Direct optical measurement of water motion such as LaserDoppler velocimetry or surface reflection is a possible solution to image water motion, but it’s difficult to implement, bulky to setup, and has a relatively larger time constant. There have been efforts to fabricate a micromachined hair cell to measure fluid flow and displacement using a piezoresistive element[8, 9], a strain gauge[10], or capacitive plates[11], but non of them can satisfy all the requirements and have sufficient sensitivity.
-10
output/input (dB)
-
-15
slope= -20dB/dec
-20 -25 -30 -35 -40 10
100
1000
10000
100000
frequency (Hz)
Figure 3 Frequency response testing of a micro fabricated HWA in water.
3. EXPERIMENTAL SETUP To understand the behavior of the lateral line to hydrodynamic flow, a well-defined stimulus is used instead. The stimulus often used is a dipole source, or vibrating sphere. In addition, the fields created by aquatic animals tend to be predominantly dipolar [15]. The experimental setup is shown in Figure 4.
(a) 12V 12V
0.1nF
R1
12V
100Ω
10kΩ 0.1µF
-
LM358a
INA2126a
+
Ranm
Dipole source
+
100Ω
-12V
0.1µF
Figure 2 (a) SEM of the HWA array, and (b) schematic of the circuit used during the testing.
We have developed a surface-micromachined, out-of-plane hot-wire anemometer that can be made into large arrays [12]. There have been studies on hydrodynamic imaging in relation to lateral line by Coombs and colleagues using hotfilm anemometry (HFA) [13], and the data suggested that HFA can detect particle displacement down to the hundreds of nanometer range, adequate compared to biological neuromast in similar flow [14].
h
z
(b)
y
x
Sensor position 16
Sensor position 1
Figure 4 Schematic of the experimental setup. The sensor array runs along the x-axis, and the dipole field is created by a sphere oscillating in the x-axis. The amplitude of the oscillation is measured by an accelerometer attached to the rod connecting the sphere to the shaker. The distance between the dipole and the sensor is designated h.
The solution of the dipole source is An array of hot-wire anemometer used during testing is shown in Figure 2(a), and the constant temperature circuitry with an offset trimmer and gain stage is shown in Figure 2(b). For individual sensor testing, a commercial Grass Telefactor P55 amplifier is used in conjunction with a highpass filter instead of the gain stage.
u=−
((
)
)
a 3U 0 ( kr ) 2 + j 2kr − 2 cos θiˆr + ( jkr − 1)sin θiˆθ e − j (ωt −kr ) 2r 3
(1)
The solution of the wave equation for pressure has two terms. The first term drops off at 1/r and is proportional to k2. This term is dominant when kr >> 1, and usually referred to as the propagating sound (pressure) wave in the
far field. The second term drops off at 1/r2, and is dominant when kr
