83,354 research outputs found
Performance Comparison of the Simscape Multibody Solvers for Articulated Mechanical Systems
No full textSIMSCAPE MULTIBODY is considered an efficient simulation tool for the dynamic analysis of articulated mechanical systems due to the ease of modeling complex mechanical systems, the CAD import feature, and allowing for the implementation of advanced control techniques. Therefore, the objective of this study is to evaluate the performances of seven solvers implemented in SIMSCAPE MULTIBODY in terms of the error and the total elapsed simulation time. As the benchmark problem, a physical pendulum under three different load scenarios is considered, namely dynamic torque, no torque, and static torque. Computed angular position and angular velocity values at the final time step are compared with those obtained from the SIMULINK model. In addition to comparing the total elapsed simulation times in the SIMSCAPE MULTIBODY environment, the total elapsed simulation times are also compared with those obtained from SIMULINK simulations. The numerical results found in this study show a good agreement between the effectiveness of the solvers analyzed and appreciable differences in their efficiency
Letter from E. O. Patterson to Secretary of the Interior
No full textLetter from E. O. Patterson to Secretary of the Interior on automobile fees in the park
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
A Comprehensive and Systematic Literature Review on Flying Cars in Contemporary Research
No full textThe integration of flying cars into urban transportation represents a significant advance in scientific and technological de velopments. This paper provides a comprehensive review of flying cars within the context of Urban Aerial Mobility (UAM), addressing the critical need for Vertical Take-Off and Landing (VTOL) vehicles in contemporary urban environments. The study is divided into two main parts: a historical review and a systematic literature review. The historical review, which covers developments up to 2013, traces the evolution of flying cars from their conceptual inception to early practical implementations. From 2013 onwards, the focus shifted to a systematic literature review, which meticulously analyzes research from the past decade to the present day. This bifurcated approach not only highlights the technological and infrastructural advancements but also underscores the social considerations and regulatory frameworks necessary for the successful deployment of flying cars. The paper commences with a categorization of flying vehicles, which serves to establish a contextual understanding. The methodology employed in this study, namely the systematic literature review, is then described. An in-depth bibliometric analysis of the selected references follows this. The findings are presented through a conceptual structure map, which delineates the boundaries of the research field. The paper discusses a number of key issues, including technological innovations, infrastructure requirements, societal impacts, and regula tory challenges. In addition, the paper highlights the practical implications and recommendations for the successful integration andadoption of flying cars. Additionally,the paper compares various flying car concepts with each other in terms of several aspects and presents a preliminary sizing study of the selected flying car concept via a demonstrative example. Finally, the paper identifies promising avenuesforfuture research in the field ofvertical take-off and landing vehicles,with the aim of enhancing the framework for urban air mobility. This comprehensive review synthesizes existing knowledge and provides an integrative view essential for future research and development in flying cars
Comparison of Two Control Strategies for a Quarter Drone System
No full textThe paper aims to present a comparison of the two different control strategies, PD and LQR, using the virtual prototype of an experimental platform called quarter drone by the authors. The model analyzed is composed of the arm of a drone that is free to rotate only around one of its axes. To maintain the prototype in a stable configuration, two types of controllers are compared for the present model, namely PD and LQR controllers. Subsequently, the better performing control system is used for trajectory tracking. The realization of the virtual prototype is performed through the use of SOLIDWORKS software, while the dynamic analysis of the system and the development of the control law are carried out in the SIMULINK environment, using the SIMSCAPE MULTIBODY toolbox. Finally, by using a simple theoretical model, the thrust is modeled, and the number of revolutions is calculated to verify the accuracy of the obtained results
Analysis of the Friction Impact on the Performance of the Linear Quadratic Regulator Controller Applied to the Multibody Model of the Furuta Pendulum
No full textThis paper investigates the influence of dry friction on a linear control system applied to the Furuta pendulum. First, the various types of dry friction laws applicable in a multibody model are presented and categorized into two main groups, that is, static models and dynamic models. By following a detailed description of the dynamic system considered in this study, as well as a general overview of the linear-quadratic control method, the paper examines first the behavior of the multibody system at hand in the absence of friction. Subsequently, through initial theoretical exploration, the paper analyzes and discusses the response of the multibody system in the presence of several types of friction. All simulations are conducted in the MATLAB-SIMULINK environment utilizing the SIMSCAPE MULTIBODY toolbox. The obtained results contribute to a deeper understanding of how dry friction influences the control system of the Furuta pendulum in particular and underactuated nonlinear multibody systems in general
Integrating Gain-Scheduling and Polynomial Interpolation with the Linear-Quadratic Regulation Approach for Enhancing the Nonlinear Performance of a Robotic Arm
No full textIn the realm of nonlinear control, where complex dynamics and trajectory variations pose substantial challenges, this work presents an enhancement to the traditional Linear-Quadratic Regulator (LQR) approach by incorporating polynomial interpolation of the gains. This approach synergizes the robustness of LQR for regulation and stabilization with the adaptability of polynomial gain scheduling, enabling continuous and responsive control across a wide range of trajectories. The integration not only enhances system accuracy but also significantly improves stability under nonlinear conditions. Dynamical simulations performed in Matlab/Simulink with the Simscape Multibody toolbox reveal that the proposed polynomial gain scheduling method considerably reduces control error compared to the classical LQR, particularly in the presence of nonlinear disturbances such as dry friction
A Systematic Literature Review of the Urban Air Mobility Systems that Are Revolutionizing the Urban Transport
No full textUrban Air Mobility (UAM) revolutionises urban transportation by integrating aerial vehicles. It encompasses electric aircraft, drones, and autonomous systems, and addresses traffic challenges. This analysis contextualises the evolution of UAM, drawing on pioneering studies. A systematic literature review, using the Web of Science database, reveals that UAM publications have increased, mainly from the United States. Key areas of focus within this field include vehicle design, energy management, and social impact, whereas the areas of optimisation and simulation exhibit comparatively less development. Results from the multiple correspondence analysis reveal three domains: technology and development, implementation and social acceptance, as well as safety and legal aspects. The broad scope of this analysis aids in understanding the transformative dynamics of urban mobility
A Dynamic Study on the Key Aspects of a Helicopter Main Transmission System
No full textThe following paper aims to present the fundamental aspects of the helicopter main transmission and its further dynamic analysis. The first part of the paper can be seen as a preliminary description of the world of helicopters, with a focus on the main transmission. Thus, the components that characterize it and the different controls to perform flight maneuvers are described. The main transmission described in the paper is a virtual prototype designed in the SOLIDWORKS environment. Having finished this purely descriptive analysis, the focus is placed on the heart of the work, namely, the dynamic analysis. To this end, the transmission modeling is carried out in a multibody environment, more specifically through MATLAB/SIMULINK. The evaluation of the force field exerted to the mechanism is carried out using the aerodynamic coefficients CL and CD, whose values are derived through XFOIL aerodynamic simulation software
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