567 research outputs found
Shape recognition and classification in electro-sensing
This paper aims at advancing the field of electro-sensing. It exhibits the
physical mechanism underlying shape perception for weakly electric fish. These
fish orient themselves at night in complete darkness by employing their active
electrolocation system. They generate a stable, high-frequency, weak electric
field and perceive the transdermal potential modulations caused by a nearby
target with different admittivity than the surrounding water. In this paper, we
explain how weakly electric fish might identify and classify a target, knowing
by advance that the latter belongs to a certain collection of shapes. Our model
of the weakly electric fish relies on differential imaging, i.e., by forming an
image from the perturbations of the field due to targets, and physics-based
classification. The electric fish would first locate the target using a
specific location search algorithm. Then it could extract, from the
perturbations of the electric field, generalized (or high-order) polarization
tensors of the target. Computing, from the extracted features, invariants under
rigid motions and scaling yields shape descriptors. The weakly electric fish
might classify a target by comparing its invariants with those of a set of
learned shapes. On the other hand, when measurements are taken at multiple
frequencies, the fish might exploit the shifts and use the spectral content of
the generalized polarization tensors to dramatically improve the stability with
respect to measurement noise of the classification procedure in
electro-sensing. Surprisingly, it turns out that the first-order polarization
tensor at multiple frequencies could be enough for the purpose of
classification. A procedure to eliminate the background field in the case where
the permittivity of the surrounding medium can be neglected, and hence improve
further the stability of the classification process, is also discussed.Comment: 10 pages, 15 figure
Electrocommunication for weakly electric fish
This paper addresses the problem of the electro-communication for weakly
electric fish. In particular we aim at sheding light on how the fish circumvent
the jamming issue for both electro-communication and active electro-sensing. A
real-time tracking algorithm is presented
Modeling active electrolocation in weakly electric fish
In this paper, we provide a mathematical model for the electrolocation in
weakly electric fishes. We first investigate the forward complex conductivity
problem and derive the approximate boundary conditions on the skin of the fish.
Then we provide a dipole approximation for small targets away from the fish.
Based on this approximation, we obtain a non-iterative location search
algorithm using multi-frequency measurements. We present numerical experiments
to illustrate the performance and the stability of the proposed multi-frequency
location search algorithm. Finally, in the case of disk- and ellipse-shaped
targets, we provide a method to reconstruct separately the conductivity, the
permittivity, and the size of the targets from multi-frequency measurements.Comment: 37 pages, 11 figure
First results on a sensor bio-inspired by electric fish
This article presents the first results of a work which aims at designing an active sensor inspired by the electric fish. Its interest is its potential for robotics underwater navigation and exploration tasks in conditions where vision and sonar would meet difficulty. It could also be used as a complementary omnidirectional, short range sense to vision and sonar. Combined with a well defined engine geometry, this sensor can be modeled analytically. In this article, we focus on a particular measurement mode where one electrode of the sensor acts as a current emitter and the others as current receivers. In spite of the high sensitivity required by electric sense, the first results show that we can obtain a detection range of the order of the sensor length, which suggests that this sensor principle could be used in future for robotics obstacle avoidance
Underwater robot navigation around a sphere using electrolocation sense and Kalman filter
International audienceThe aim of this paper is to perform the navigation of an underwater robot equipped with a sensor using the electric sense. The robot navigates in an unbounded environment in presence of spheres. This sensor is inspired of some species of electric fish. A model of this sensor composed of n spherical electrodes is established. The variations of the current due to the presence of the sphere is related to the model of Rasnow [3]. Unscented Kalman Filter is used to localize the robot with respect to the sphere and to estimate the size of the sphere. We show that bio-inspired motions improve the detection of the spheres. We illustrate the efficiency of the method in two cases: a two electrodes sensor and a four electrodes sensor
Fish Geometry and Electric Organ Discharge Determine Functional Organization of the Electrosensory Epithelium
Active electroreception in Gymnotus omarorum is a sensory modality that perceives the changes that nearby objects cause in a self generated electric field. The field is emitted as repetitive stereotyped pulses that stimulate skin electroreceptors. Differently from mormyriformes electric fish, gymnotiformes have an electric organ distributed along a large portion of the body, which fires sequentially. As a consequence shape and amplitude of both, the electric field generated and the image of objects, change during the electric pulse. To study how G. omarorum constructs a perceptual representation, we developed a computational model that allows the determination of the self-generated field and the electric image. We verify and use the model as a tool to explore image formation in diverse experimental circumstances. We show how the electric images of objects change in shape as a function of time and position, relative to the fish's body. We propose a theoretical framework about the organization of the different perceptive tasks made by electroreception: 1) At the head region, where the electrosensory mosaic presents an electric fovea, the field polarizing nearby objects is coherent and collimated. This favors the high resolution sampling of images of small objects and perception of electric color. Besides, the high sensitivity of the fovea allows the detection and tracking of large faraway objects in rostral regions. 2) In the trunk and tail region a multiplicity of sources illuminate different regions of the object, allowing the characterization of the shape and position of a large object. In this region, electroreceptors are of a unique type and capacitive detection should be based in the pattern of the afferents response. 3) Far from the fish, active electroreception is not possible but the collimated field is suitable to be used for electrocommunication and detection of large objects at the sides and caudally
- …