Department Publications

Novel single-integral representations for the multivariate probability density functions (PDFs) and cumulative distribution functions (CDFs) of the Gaussian class Weibull distribution are derived. The solutions are expressed in terms of familiar mathematical functions which are available in common mathematical software. The well known equal (constant) correlation model is considered. A special linear transformation of independent Gaussian random variables is used to generate correlated Weibull random variables. The advantage of the new representation is that only a single integral computation is needed to compute a N-dimensional distribution. The new representation of the CDF is used for the performance evaluation of a selection diversity combiner operating in equally correlated Weibull fading channels. The new PDF representation is also used for an analysis of the moments of the output signal-to-noise ratio …

This paper outlines the problem of outdoor autonomous robot localization for agricultural operations. Vision based outdoor localization system is developed entirely of off-the-shelf components that can accurately guide a field robot in small agricultural fields. Visual odometry using downward faced camera is proposed as a high resolution relative localization system. A stereo vision based range measurement system is also developed and field tested as an absolute localization system that can bound the incremental error caused by the visual odometry system. The extended Kalman filter with measurement gating is implemented using both visual odometry and stereo range measurement data. Field tests demonstrated proposed system is capable of localization of two wheel tractor at a very low cost with acceptable accuracy in small agricultural fields.

An analytical framework to evaluate the exact performance of multihop amplify-and-forward relaying in the presence of co-channel interference is presented. The new results are formulated based on the recently introduced generalized transformed characteristic function method. The new framework is used to evaluate the exact performance measures such as average symbol error probability, outage probability and ergodic capacity, when the multihop relaying system is operating in identically distributed fading channels with equal power interferers at the relays and the destination.

Novel representations for the multivariate probability density function (PDF) and cumulative distribution function (CDF) of the equi-correlated non-central chi-square (χ 2 ) distribution are derived. The new representations are given as single integral solutions in terms of well known mathematical functions which are available in common mathematical software packages. The advantage of the new representations is that only a single integral computation is needed to evaluate the PDF and CDF for an arbitrary number of dimensions. The new representations are used to numerically evaluate the outage probability of a single user multiple input multiple output system with receiver antenna selection diversity, operating in correlated Rician fading channels. The well known constant (equal) correlation model, which is considered to be a useful model for a closely placed set of antennas, is used for the analysis in this paper. A …

This paper introduces and solves the sum rate maximization problem at the multiple-input multiple-output (MIMO) downlink as a function optimization problem subject to feedback constraints at the uplink. It is first shown that this optimization problem can be reduced to a finite dimensional non-convex optimization problem. Then, the resulting problem can be solved by investigating Schur-concavity of the aggregate communication rate across multiple traffic flows. Necessary and sufficient conditions for the rate optimality of homogenous threshold feedback policies are established. With some surprise, it is shown that homogenous thresholding is not always rate-wise optimal even if mobile users experience the same channel conditions statistically. Applications of these results are illustrated for Rayleigh fading channels.

The Disaster and Emergency Warning Network (DEWN) is a last-mile disaster early warning system based on a suite of mobile technologies. It alerts citizens of impending disasters through SMS/Cell Broadcast activated remote-alarm devices, cell broadcasting to handsets and multi-lingual SMS.

The paper presents the development and the experimental verification of a technique for the identification of obstructions in the line-of-sight path between two or more radio transceivers in a multipath radio environment. The objective of this technique is to use RSS measurements from a mesh of simple sensor nodes to identify intrusions.

Threshold feedback policies are well known and provably rate-wise optimal selective feedback techniques for communication systems requiring partial channel state information (CSI). However, optimal selection of thresholds at mobile users to maximize information theoretic data rates subject to feedback constraints is an open problem. In this paper, we focus on the optimal threshold selection problem, and provide a solution for this problem for finite feedback systems. Rather surprisingly, we show that using the same threshold values at all mobile users is not always a rate-wise optimal feedback strategy, even for a system with identical users experiencing statistically the same channel conditions. By utilizing the theory of majorization, we identify an underlying Schur-concave structure in the rate function and obtain sufficient conditions for a homogenous threshold feedback policy to be optimal. Our results hold for …

Beamforming techniques utilizing only partial channel state information (CSI) has gained popularity over other communication strategies requiring perfect CSI thanks to their lower feedback requirements. The amount of feedback in beamforming based communication systems can be further reduced through selective feedback techniques in which only the users with channels good enough are allowed to feed back by means of a decentralized feedback policy. In this paper, we prove that thresholding at the receiver is the rate-wise optimal decentralized feedback policy for feedback limited systems with prescribed feedback constraints. This result is highly adaptable due to its distribution independent nature, provides an analytical justification for the use of threshold feedback policies in practical systems, and reinforces previous work analyzing threshold feedback policies as a selective feedback technique without …

This paper describes the synthesis and evaluation of a "virtual odometer" for a Quadrotor Micro Aerial Vehicle. Availability of a velocity estimate has the potential to enhance the accuracy of mapping, estimation and control algorithms used with quadrotors, increasing the effectiveness of their applications. As a result of the unique dynamic characteristics of the quadrotor, a dual axis accelerometer mounted parallel to the propeller plane provides measurements that are directly proportional to vehicle velocities in that plane. Exploiting this insight, we encapsulate quadrotor dynamic equations which relate acceleration, attitude and the aerodynamic propeller drag in an extended Kalman filter framework for the purpose of state estimation. The result is a drift free estimation of lateral and longitudinal components of translational velocity and roll and pitch components of attitude of the quadrotor. Real world data sets gathered from two different quadrotor platforms, together with ground truth data from a Vicon system, are used to evaluate the effectiveness of the proposed algorithm and demonstrate that drift free estimates for the velocity and attitude can be obtained.

Although many recent stereo vision algorithms have been able to create disparity maps with high accuracy, because of the sequential nature it is difficult to adopt them for real time applications. Biologically motivated algorithms involving Gabor filters demonstrate inherent parallelism and could be effectively implemented in parallel hardware such as Graphics Processing Units (GPUs). We present a real time stereo vision algorithm based on Gabor filters which effectively use the memory hierarchy and the threading resources of the Graphics Processing Unit (GPU). Since the 2D filtering process is a critical activity which takes upto 50% of the total time to create the disparity map, we evaluate the GPU implementation of three filtering methods. Using the optimal filtering method out of them, we were able to achieve a frame rate of 76 fps for a 512x512 image stream on a NVIDIA GTX 480 GPU, and a 170x speed-up compared to the conventional CPU based implementation.

This paper presents a methodology to diagnose some heart diseases which can be identified using heart sounds. As the first stage, audio files in . wav format are acquired using an electronic stethoscope and entered to a database with patient symptoms. Prominent features and statistical parameters needed for disease detection are extracted from the heart sound samples using some algorithm. Patient's heart sound fde and symptoms are given as inputs to the developed software for analysis to find out the diseases

Localization Assistance for Mobile Robot Navigation in Real, Populated Environments - Shibaura Institute of Technology Skip to main navigation Skip to search Skip to main content Shibaura Institute of Technology Home Shibaura Institute of Technology Logo English 日本語 Home Profiles Research units Research output Activities Press/Media Prizes Search by expertise, name or affiliation Localization Assistance for Mobile Robot Navigation in Real, Populated Environments Peshala Jayasekara, Takeshi Sasaki, Hideki Hashimoto Functional Control Systems Research output: Contribution to journal › Article › peer-review Overview Original language English Pages (from-to) 2P1-Q13(1)-2P1-Q13(2) Journal Default journal Publication status Published - 2011 May 28 Cite this APA Standard Harvard Vancouver Author BIBTEX RIS Powered by Pure, Scopus & Elsevier Fingerprint Engine™ All content on this site: …

Developingautonomous mobile robots thatcan coexist with human in populatedenvironments isstill considered a bigchallenge, Tb address thisproblemwe propose, a novel scheme to assist mobile robots by providing localizationinformationexternally Thisscheme eombines the autonomous navigation and target tracking research fieldsto arrive at a structured assistance system for autonomous mobile robots. In the proposed scheme, the environment issensed using a laserrange finder and camera based sensor unit. Using Rao-Blackwellizecl panicle filtertechnique, the robots that need assistance are continuously tracked, tncontrast with conventional laserrange finderbasedtrackingsystems, the placementof sensor ischanged to a levelabove average human heightand the mobile robots are medified by attaching a cylindrical pole. The experiments show the validity of the proposed scheme forsimultaneous localization assistance formultiple mobile robots. IXvomobile robots were simultaneously navigated ingiventrajectoriesusing assistance data, successfully

Autonomous personal vehicle systems face many challenges due to complex and unpredictable environments. Thus, much of such platforms' computational resources are wasted on trying to localize in a given environment, slowing down the navigation phase. To overcome this problem we propose intelligent assistance, a novel scheme to assist autonomous mobile platforms by providing localization information externally. In the proposed scheme, the moving targets are detected using a laser range finder and camera based sensor unit and tracked using particle filter based technique. Calculated localization is fed back to the mobile platform as assistance information. The preliminary experiments show the validity of the proposed scheme for mobile robots.

In this paper design and implementation of a wide input range Cascaded Buck and Boost (CBB) converter is presented with a robust power controller. Four new control strategies are proposed and tested for this converter based on input voltage and duty cycle of the control signals. Robust feature of the proposed control system ensures constant output DC current required to charge the Lead-Acid batteries in bulk charge mode. The robust feedback controller of the power converter is developed using a microcontroller which is acting as smart controller of the CBB converter. DC-DC converters which are used for battery charging applications with variable power sources should be able to both step-up and step-down the input voltage and provide high efficiency in the whole range of operation. The CBB converter with power switches and diodes is used to achieve above objective. CBB converter is constructed by cascading a Buck and a Boost Converter and eliminating the output capacitor of the buck converter.

As the problem of urban traffic congestion spreads, there is a pressing need for the introduction of advanced technology and equipment to improve the state of the art of traffic control. In this context, the techniques used for sensing traffic flow information plays a vital role, ensuring accurate real time controllability. Closed Circuit Television (CCTV) has gained popularity because of its ability to provide diverse information on relatively large regions leading to opportunities for performing substantially more complex tasks than conventional detection schemes. By processing these video images, traffic parameters such as speed, traffic composition, queue length etc. can be extracted. In addition CCTV images can be further processed for other useful information such as detection of vehicle shapes, vehicle types, occurrence of traffic violations and vehicle identification numbers etc. To introduce CCTV based vehicle …

The rapid growth of mobile broadband penetration across the world indicates that these markets will approach maturity more quickly than previously thought. However in Asian market like Sri Lanka, the mobile broadband market is in its early stages. The operators do not have a clear approach in promoting mobile broadband to consumers; in the other hand consumers do not have previous experience in this method of internet access. Hence there is a definite requirement to identify the key factors & formulate a strategy to increase the adoption of mobile broadband, which in terms increase the penetration & competition in the market. The aim of this study is to examine the penetration; competition & what are the key factors affecting the penetration of mobile broadband in Sri Lankan market. Thus this study includes examining the various attitudinal, normative and control factors affecting the adoption of mobile …

This paper proposes the use of an intrusion detection system (IDS) tailored to counter the threats to an IEC61850-automated substation based upon simulated attacks on intelligent electronic devices (IEDs). Intrusion detection (ID) is the process of detecting a malicious attacker. It is an effective and mature security mechanism. However, it is not harnessed when securing IEC61850-automated substations. The IDS of this paper is developed by using data collected by launching simulated attacks on IEDs and launching packet sniffing attacks using forged address resolution protocol (ARP) packets. The detection capability of the system is then tested by simulating attacks and through genuine user activity. A new method for evaluating the temporal risk of an intrusion for an electric substation based upon the statistical analysis of known attacks is also proposed.

This paper proposes a scheme for auditing the security of an IEC61850-based network based upon a novel security metric for intelligent electronic devices (IEDs). A detailed security analysis on an IEC61850 automated substation is peformed initially with a focus on the possible goals of the attacker. This is followed by the development of a scheme to audit the security of such a network. Security metrics are considered since they provide a tangible means of quantifying the security of a network. The proposed auditing scheme is tested by using it to audit the security of an IEC61850 network. The results are then compared with two other metric schemes-the mean time to compromise (MTTC) metric and the VEA-bility metric, which are used for auditing conventional computer networks. The input data for both metrics are obtained by using a network security tool to scan the IEDs of the network. The impact of using high …

In this paper, a new algorithm for indoor localization using WLAN signal strengths is proposed. The objective of the work was to design a simple and efficient indoor positioning algorithm with good accuracy. The proposed algorithm uses the fingerprinting technique as a pre-processing step. The second step is the application of trilateration within the nearest neighbours found during the first step. The paper describes the algorithm, the environment used to test the algorithm and results obtained. The results show that the proposed algorithm has 44% better accuracy compared to basic fingerprinting technique and the accuracy is 73% better compared to basic trilateration technique. The algorithm has been demonstrated to be independent of the propagation environment and works with no knowledge of the positions and the transmit powers of the WLAN access points in the vicinity. Thus, it is a simple and effective …

One of the most challenging problems of field robots is self-localization, which involves incremental update of position while in motion. Though wheel based odometry is cheaper to implement its accuracy degrades when wheels slip. In this paper performance of low-cost visual odometry approach is experimented as a feasibility test for field robot localization. We have used a downward-facing camera and tested localization error in view of various parameters such as frame size, frame rate, etc. A FFT-based image registration techniques was utilized to determine the precise translation distances and heading between consecutive frames captured from ground surface. Basic navigation experiments, including a loop-closing test and error propagation were conducted and interesting numerical results have been reported.