1,720,961 research outputs found
Optimized fuzzy logic sliding mode control with proportional-integral-derivative for an electrohydraulic actuator system
Get PDFThe electrohydraulic actuator (EHA) system generates a trajectory by transferring high force densities in the form of pressurized fluid flows to a hydraulic actuator. Moreover, the sliding mode control (SMC) approach has been discovered as a potential method for the EHA trajectory tracking control system. However, high-frequency proportional valve activity has occurred during the practical application of the conventional SMC approach, resulting in tracking performance degradation. Furthermore, a preferable SMC sliding surface design is necessary to improve the precision of trajectory tracking performance, and the SMC designs involve complicated procedure and mathematical formulations. Therefore, this thesis proposes an optimized fuzzy logic (FL) SMC with a proportional-integral-derivative (PID) structure for trajectory tracking control in an EHA system. The proposed control strategy was designed with the switching function modification based on an FL approach in the conventional SMC algorithm called FLSMC. A particle swarm optimization (PSO) algorithm was implemented as the FLSMC design involves a complicated procedure and mathematical formulations to obtain the optimal value of the designed control variables. By adopting the same design concept, the conventional SMC approach was developed for performance comparisons. Furthermore, in an attempt to achieve the objectives of precise trajectory tracking control, a hybrid control structure of FLSMC and PID feedback control (FLSMCPID) is proposed and implemented. Due to the difficulty of concurrent hybrid design, the PSO algorithm was employed to determine the optimal control variables value. For performance comparisons with the proposed hybrid control strategy, a hybrid conventional SMC and PID feedback control (SMCPID) was established by using the same design concept. Simulations utilizing a linear EHA system model obtained using the grey-box identification approach and experimentation on an EHA system workbench for various trajectories and under the consequences of variation in supply pressure were conducted to evaluate the performance of the proposed control strategies. A linear type actuation of the EHA system using a single-ended cylinder controlled by a proportional valve was considered in the experimental design. The simulation and experimental results demonstrate that higher effectiveness, precision, and robustness were achieved by the EHA system with the FLSMC and FLSMCPID as compared to the established conventional SMC and SMCPID approaches, respectively. Moreover, the experimental results verified that the EHA system with the FLSMCPID achieved 82.1%, 78.9%, 94.8%, and 88.8% improvement in the precision tracking control for 0.25 Hz sinusoidal, multi-sinusoidal, point-to-point, and chaotic trajectories, respectively, and enhanced the robustness by 33.3% compared to the FLSMC control strategy. It is envisaged that the proposed FLSMC and FLSMCPID control strategies can be utilized for effective, precise, and robust tracking control of various EHA systems
Stability analysis of a small scale remotely operated underwater glider
Get PDFThe conventional process of maintaining underwater depth level for Unmanned Underwater Vehicles (UUVs) requires an operator to have a high skill and experience. Therefore, it is an important assessment to develop an automatic control scheme for underwater depth level control system and fabricate an underwater vehicle’s prototype body as a test-bed to implement and study the performance of control scheme. Hence, the purposes of this research are to design, model and fabricate a prototype body of a Remotely Operated underwater Glider (ROG) and analyze stability equilibrium of the new glider design. This research also attempts to develop a programmable ON/OFF control scheme for the underwater depth level control system and study the performance of the control scheme by experimental verification and trials. The ROG is modelled based on the SLOCUM glider and Seaglider designs using SolidWork and MAXSURF HYDROMAX is employed to calculate the stability equilibrium. The collected real time data are analyzed using the MATLAB System Identification ToolboxTM to verify the ROG’s net weight-depth system. As a conclusion, the ROG has a cylindrical body shape and the stability calculation shows that the ROG is at stable equilibrium state when heeling from 0
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Depth level control system using peripheral interface controller for underwater vehicle
Get PDFThis research explained on a design and development of an Automatic Depth Control System for underwater vehicle. Definition of underwater vehicle is a robotic sub-sea that is a part of the emerging field of autonomous and unmanned vehicles. This project shows the implementation’s development of an Automatic Depth Control System on a test prototyping vehicle especially involved small-scale and low cost sub-sea robots. The Automatic Depth Control System assembled with mechanical system and module of electronic system for development of a controller
Depth Level Control System using Peripheral Interface Controller for Underwater Vehicle
Get PDFThis research explained on a design and development of an Automatic Depth Control System for underwater vehicle. Definition of underwater vehicle is a robotic sub-sea that is a part of the emerging field of autonomous and unmanned vehicles. This project shows the implementation’s development of an Automatic Depth Control System on a test prototyping vehicle especially involved small-scale and low cost sub-sea robots. The Automatic Depth Control System assembled with mechanical system and module of electronic system for development of a controller
Design of a body with depth control system for an underwater glider
No full textThis paper describes a design development of an underwater glider which includes the body design, controller design and the sensor integration. The underwater glider is used for deep water to observe large areas with minimal use of energy and move through the water by changing the body weight. The glider contained a cylindrical body attached with two wings and a fix tail. The controller has been designed to use a comparator circuit integrate with a pressure sensor to control the depth level. The pressure sensor mounted on the glider used to sense the underwater pressure. For the beginning, this underwater glider is limited to a depth of 0-10 meters
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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