1,720,979 research outputs found
Direct model reference adaptive control of coupled tank liquid level control system
Full text linkIndustries such as petro-chemical industries, paper making industries, waste management and others are the vital industries where liquid level and flow control are essential. Liquids will be processed by chemical or mixing treatment in the tanks, but always the level fluid in the tanks must be controlled, and the flow between tanks must be regulated in the presence of nonlinearity and inexact model description of the plant. This project investigates the usage of Direct Model Reference Adaptive Control (DMRAC) in controlling the liquid level in the second tank of Coupled-Tank plant through variable manipulation of water pump in the first tank. It is to show that DMRAC could produce appropriate control signal to the coupled-tank system in response to the given desired water level with plant nonlinearity and measurement noise present simultaneously. The ability to use only input-output measurement of the plant in adaptation mechanism is the DMRAC’s special characteristics that does not require the explicit identification of the model description nor the solution to linear(or nonlinear) equations of the respective plant dynamics. A dynamic model of the plant is initially developed. Simulation studies are then conducted based on the developed model using Matlab and Simulink. A series of tracking performance tests, disturbance rejection and plant parameter changes are conducted to evaluate the controller performance in comparison to PID controller. The outcome of the project reveals that DMRAC is more robust than PID controller when there is a change in system parameters despite of its sensitivity to measurement noise. The framework of this project is generic enough to have an overview of the possible outcome before implementing the DMRAC controller in real-time system in the future
An enhanced time synchronization protocol in automated surface vehicles
Full text link1056-1069Mobility of an autonomous surface vehicle (ASV) has caused the wireless sensor and actuator networks (WSANs) onboard to be mobile as well. However, the time synchronization of a WSAN on ASV is more challenging due to the environmental harshness and node mobility. In this paper, an enhanced control-theoretic distributed time synchronization protocol called Time Synchronization using Distributed Observer algorithm with Sliding mode control element (TSDOS) is presented to solve the time synchronization issue in ASV. This TSDOS protocol feeds a sliding mode control element on the relative comparative error to estimate the skew rate and relative skew rate. Through the theoretical analysis and simulations, TSDOS has showed the advantages of totally distributed, robust to node failure and time-varying clock frequencies, which are the situations usually faced by an ASV. In addition, TSDOS also has better or comparable performance over existing protocols in terms of rate of convergence, consensus error spike, and steady-state error
Distributed cooperative formation control of a generic non-holonomic multi-agent system.
Full text link2502-2509This paper presents a study of distributed cooperative formation control of a generic multiple agent robots which is applicable for underwater system application such as multiple-autonomous surface vehicles (ASV). The control objective of the group of ASV agent is to maintain a certain formation in a predefined geometric pattern, notably a symmetric formation shape. In addition, the centroid of this to-be-sustained formation is to follow a designated leader agent whose dynamics resembles that of its followers. The contribution made in this paper is the introduction of an adaptive law capable of adjusting the strength of the state consensus control. Despite of partial information available to subset of agents, the formation control objective can still be achieved. The control scheme features a robustification term owed by a signum function which forces the state consensus error to zero. The control scheme is verified through numerical simulation which shows convergence of state consensus error to zero
Classes Of Control Architectures For AUV: A Brief Survey.
Full text linkThis paper provides a brief survey on the control architectures used in the underwater system and robotics research for AUV application
Distributed adaptive cooperative control with fault compensation mechanism for heterogeneous multi-robot system
Full text linkIn this paper, a distributed adaptive consensus law with fault compensation for a heterogeneous multi-robot system (MRS) is proposed. The design paradigm adopted in this work involves a leader-following cooperative algorithm featuring two distinct adaptive coupling gains to compensate for multiple additive time-varying faults. Exacerbating the situation, the follower robots commissioned in the leader-following mission are non-identical due to their dynamic characteristic as normally exist in a physical setup. The capability of the proposed scheme is investigated and compared with the other two recent works in two facets; one is to gauge how the algorithm is able to mitigate faults of varying nature in the presence of heterogeneous robot(s) while maintaining the platoon formation during the leader-following task; two is the ability to cope with subsequent topology reconfiguration. The stability and the robustness of the proposed scheme against bounded time-varying faults are proven using rigorous Lyapunov analysis. The proposed control strategy exempts the use of an observer or estimator, thereby simplifies the synthesis and implementation on mobile robots. The simulation results of the proposed adaptive consensus law demonstrate the best performance as compared to the other two recent works in the presence of multiple faulty robots
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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