10 research outputs found
Implementation of an Intelligent Target Classifier with Bicoherence Feature Set
ABSTRACT: This paper examines the feasibility of bispectral analysing of acoustic signals emanated from underwater targets, for the purpose of classification. Higher order analysis, especially bispectral analysis has been widely used to analyse signals when non-Gaussianity and non-linearity are involved. Bicoherence, which is a normalized form of bispectrum, has been used to extract source specific features, which is finally fed to a neural network classifier. Vector quantization has been used to reduce the dimensionality of the feature set, thereby reducing computational costs. Simulations were carried out with linear, tan and log-sigmoid transfer functions and also with different code book sizes. It is found that the bicoherence feature set can provide acceptable levels of classification accuracy with a properly trained neural network classifier
Investigations on Ultrasonic Transducer Array Systems for NDE of Underwater Pipelines
The main objective of carrying out this investigation is to develop suitable transducer array systems so that underwater pipeline inspection could be carried out in a much better way, a focused beam and electronic steering can reduce inspection time as well. Better results are obtained by optimizing the array parameters. The spacing between the elements is assumed to be half the wavelength so that the interelement interaction is minimum. For NDT applications these arrays are operated at MHz range. The wavelengths become very small in these frequency ranges. Then the size of the array elements becomes very small, requiring hybrid construction techniques for their fabrication. Transducer elements have been fabricated using PVDF as the active, mild steel as the backing and conducting silver preparation as the bonding materials. The transducer is operated in the (3,3) mode. The construction of a high frequency array is comparatively complicated. The interelement spacing between the transducer elements becomes considerably small when high frequencies are considered. It becomes very difficult to construct the transducer manually. The electrode connections to the elements can produce significant loading effect. The array has to be fabricated using hybrid construction techniques. The active materials has to be deposited on a proper substrate and etching techniques are required to fabricate the array. The annular ring, annular cylindrical or other similar structural forms of arrays may also find applications in the near future in treatments were curved contours of the human body are affected
A Realization Of An Fpga Sub System For Reducing Odometric Localization Errors In Wheeled Mobile Robots
This paper introduces a simple and efficient method
and its implementation in an FPGA for reducing the odometric
localization errors caused by over count readings of an
optical encoder based odometric system in a mobile robot
due to wheel-slippage and terrain irregularities. The detection
and correction is based on redundant encoder measurements.
The method suggested relies on the fact that the
wheel slippage or terrain irregularities cause more count
readings from the encoder than what corresponds to the
actual distance travelled by the vehicle. The standard quadrature
technique is used to obtain four counts in each encoder
period. In this work a three-wheeled mobile robot
vehicle with one driving-steering wheel and two-fixed rear
wheels in-axis, fitted with incremental optical encoders is
considered. The CORDIC algorithm has been used for the
computation of sine and cosine terms in the update equations.
The results presented demonstrate the effectiveness
of the techniqueCochin University Of Science And TechnologyJournal of Automation, Mobile Robotics & Intelligent Systems VOLUME 3, No 3 200
An Encoded Infrared Sheet Of Light Navigational Beacon System For Precise Localization Of Indoor Mobile Robot Vehicles
A new localization approach to increase the navigational
capabilities and object manipulation of autonomous
mobile robots, based on an encoded infrared sheet of light
beacon system, which provides position errors smaller than
0.02m is presented in this paper. To achieve this minimal
position error, a resolution enhancement technique has
been developed by utilising an inbuilt odometric/optical
flow sensor information. This system respects strong low
cost constraints by using an innovative assembly for the
digitally encoded infrared transmitter. For better guidance
of mobile robot vehicles, an online traffic signalling capability
is also incorporated. Other added features are its less
computational complexity and online localization capability
all these without any estimation uncertainty. The
constructional details, experimental results and computational
methodologies of the system are also describedCUSATJournal of Automation, Mobile Robotics & Intelligent Systems VOLUME 3, N° 2 200
Implementation of a Neural Network Classifier for Noise Sources in the Ocean
The paper investigates the feasibility of implementing an intelligent
classifier for noise sources in the ocean, with the help of artificial neural networks,
using higher order spectral features. Non-linear interactions between the component
frequencies of the noise data can give rise to certain phase relations called Quadratic
Phase Coupling (QPC), which cannot be characterized by power spectral analysis.
However, bispectral analysis, which is a higher order estimation technique, can
reveal the presence of such phase couplings and provide a measure to quantify such
couplings. A feed forward neural network has been trained and validated with higher
order spectral featuresCochin University of Science and TechnologyPROCEEDINGS OF SYMPOL 200
RMAC-M: Extending the R-MAC Protocol for an Energy Efficient, Delay Tolerant Underwater Acoustic Sensor Network application with a mobile data mule node
One of the major applications of underwater acoustic sensor networks (UWASN) is ocean environment
monitoring. Employing data mules is an energy efficient way of data collection from the underwater sensor
nodes in such a network. A data mule node such as an autonomous underwater vehicle (AUV) periodically
visits the stationary nodes to download data. By conserving the power required for data transmission over
long distances to a remote data sink, this approach extends the network life time. In this paper we propose a
new MAC protocol to support a single mobile data mule node to collect the data sensed by the sensor nodes in
periodic runs through the network. In this approach, the nodes need to perform only short distance, single hop
transmission to the data mule. The protocol design discussed in this paper is motivated to support such an
application.
The proposed protocol is a hybrid protocol, which employs a combination of schedule based access
among the stationary nodes along with handshake based access to support mobile data mules. The new
protocol, RMAC-M is developed as an extension to the energy efficient MAC protocol R-MAC by extending
the slot time of R-MAC to include a contention part for a hand shake based data transfer. The mobile node
makes use of a beacon to signal its presence to all the nearby nodes, which can then hand-shake with the
mobile node for data transfer. Simulation results show that the new protocol provides efficient support for a
mobile data mule node while preserving the advantages of R-MAC such as energy efficiency and fairness.Cochin University of Science and TechnologyPROCEEDINGS OF SYMPOL-201
Towards Improving the Geolocation Estimates Using Light Tags
Gathering the positional information of highly migratory marine species like tuna, shark and certain classes of whales in the open ocean using light intensity measurements is a promising technique. Light intensity measurements are carried out using an archival light tag, comprising of a digital high resolution light sensor and a microcontroller. The accurate estimation of the times of sunrise and sunset events are very important for the precise estimation of the geolocation. The proposed tag can measure the light intensity more accurately up to 0.015 lux. The day light intensity variation furnished by the light tag in conjunction with astronomical equations can provide positional information of the species. The accuracy of the geolocation estimates is improved by judiciously selecting the appropriate thresholds for the dawn and dusk, depending on the overall percentage of light intensity variations