48 research outputs found

    Numerical methods for the inverse dynamics simulation of underactuated mechanical systems

    Get PDF
    The present work deals with the inverse dynamics simulation of underactuated multibody systems. In particular, the study focuses on solving trajectory tracking control problems of differentially flat underactuated systems. The use of servo constraints provides an approach to formulate trajectory tracking control problems of underacutated systems, which are also called underactuated servo constraint problems

    Numerical methods for the inverse dynamics simulation of underactuated mechanical systems

    Get PDF
    In der vorliegenden Dissertation wird die Simulation der inversen Dynamik unteraktuierter Mehrkörpersysteme behandelt. Insbesondere werden Steuerungsprobleme der Bahnverfolgung für differentiell flache unteraktuierte Systeme untersucht. Mit Hilfe von Servobindungen werden die Steuerungsprobleme der Bahnverfolgung für unteraktuierte Systeme formuliert. Die betrachteten Probleme werden unteraktuierte Servobindungsprobleme genannt. Minimalkoordinaten, abhängige oder redundante Koordinaten werden zur Formulierung unteraktuierter Servobindungsprobleme verwendet. Die Formulierung ergibt differential-algebraische Gleichungen mit hohem Index. Die diskrete Nullraum-Methode ermöglicht den Übergang von redundanten Koordinaten zu Minimalkoordinaten. Da die numerische Lösung der differential-algebraischen Gleichungen mit hohem Index anspruchsvoll ist und die flachheitsbasierte analytische Lösung für komplizierte unteraktuierte Systeme nicht praktikabel ist, werden Methoden zur Indexreduktion vor der direkten Zeitdiskretisierung eingesetzt. Eine spezielle Projektionsmethode wird angewendet, um den Index von fünf auf drei zu reduzieren. Die Methode erfordert die Berechnung von Projektionsmatrizen, die in der redundanten Koordinaten Formulierung konstant und in der Minimalkoordinaten Formulierung zeitabhängig sind. Eine neue Methode, Indexreduktion durch minimale Erweiterung genannt, wird in dieser Dissertation entwickelt und für Servobindungsprobleme unteraktuierter Systeme verwendet. Die beiden Methoden werden auf repräsentative numerische Beispiele angewandt. Insbesondere wird schon gezeigt, dass sich die neu entwickelte Indexreduktionsmethode zur Lösung involvierter Probleme eignet, die bislang mit der Projektionsmethode nicht gelöst werden konnten

    Multibody Systems with Flexible Elements

    Get PDF
    Multibody systems with flexible elements represent mechanical systems composed of many elastic (and rigid) interconnected bodies meeting a functional, technical, or biological assembly. The displacement of each or some of the elements of the system is generally large and cannot be neglected in mechanical modeling. The study of these multibody systems covers many industrial fields, but also has applications in medicine, sports, and art. The systematic treatment of the dynamic behavior of interconnected bodies has led to an important number of formalisms for multibody systems within mechanics. At present, this formalism is used in large engineering fields, especially robotics and vehicle dynamics. The formalism of multibody systems offers a means of algorithmic analysis, assisted by computers, and a means of simulating and optimizing an arbitrary movement of a possibly high number of elastic bodies in the connection. The domain where researchers apply these methods are robotics, simulations of the dynamics of vehicles, biomechanics, aerospace engineering (helicopters and the behavior of cars in a gravitational field), internal combustion engines, gearboxes, transmissions, mechanisms, the cellulose industry, simulation of particle behavior (granulated particles and molecules), dynamic simulation, military applications, computer games, medicine, and rehabilitation

    Deployable antenna phase A study

    Get PDF
    Applications for large deployable antennas were re-examined, flight demonstration objectives were defined, the flight article (antenna) was preliminarily designed, and the flight program and ground development program, including the support equipment, were defined for a proposed space transportation system flight experiment to demonstrate a large (50 to 200 meter) deployable antenna system. Tasks described include: (1) performance requirements analysis; (2) system design and definition; (3) orbital operations analysis; and (4) programmatic analysis

    Prestressed cable domes: structural behavior and design

    Get PDF
    The introduction of tension as the predominant means of load transfer offers the potential for using less material to carry more loads. Cable domes are such unconventional structures based on the tensegrity principle. They rely on the assembly of prestressed cables in equilibrium with vertical struts. Members are stressed purely in axial tension or compression and as a consequence, the materials are used efficiently. Not much has been written about the structural design of cable domes. This study was based on an extensive review of technical literature and direct correspondence with the designers of cable domes. The contributions of this study will benefit both structural designers and academic researchers interested in the design of roofs for novel structures such as large arenas and stadia. The primary objective of this dissertation was to provide both an intuitive and mathematical understanding of the structural behavior of radial-type cable domes subject to various loadings, and to determine their limit states. An accompanying objective was to find improved methods for their design and construction. To accomplish these goals, a series of twelve 400 ft. span domes with varying depth-to-span ratios, number of polygon sides and number of polygonal hoops were examined. Three limit states were evaluated, namely 1) buckling of struts, 2) serviceability, and 3) rupture of cables. The main cause of instability was established and a potential design solution in the form of enhanced struts has been recommended. The study was made efficient by the use of a two-dimensional model. For dome designs governed by axisymmetric loads, the planar model was sufficient for member design. The analysis procedure was further streamlined using an influence surface analysis (based on the Müller-Breslau principle) that helped to identify governing load combinations for the design of members. Domes vulnerable to wind uplift were recognized and prestressing force levels were increased accordingly. As such, the findings from the influence surface analysis proved to be a good indicator of the adequacy of prestressing forces assigned to a dome. Further, the results revealed that additional prestressing forces were necessary to meet the serviceability criterion, beyond simply ensuring that cables remained in tension under all loading conditions. The most important geometric parameters for structural design were identified as: the number of sectors, the number of polygonal hoops, hoop radii, rise-to-span ratio, and depth-to-span ratio. They greatly influenced the amount of prestressing forces required for the overall stability of a dome. The results showed that the radial stiffness of a hoop cable is inversely proportional to the hoop radii and the number of sectors. Domes with smaller depth-to-span ratios required higher prestressing forces for stability and to achieve a desired elevation (shape). The critical loads for strut members were determined using the Stiffness-Probe Method. The method gave a physical understanding of the loss of capacity in struts due to applied axial loading. The use of prestressed stays increased a strut’s buckling capacity to more than four times when compared with the critical loads of struts without stays. Consequently, stayed-struts are recommended as an alternative design solution for enhancing the load-carrying capacity of cable domes. The erection procedure for cable domes typically constitutes 40% of the project cost. Noting that the strut forces were relatively small when compared with the diagonal cable forces, prestressing the struts as part of the erection process may prove to be an economical alternative for reducing the overall project cost. This approach has been proposed for future study. For well-designed cable domes, i.e., domes that are adequately prestressed and whose cables remain in tension under all loading conditions, the study revealed that the cause for potential dome demise is usually due to buckling of struts or displacements exceeding the acceptable ranges for serviceability. As these limit states were found to occur well within the elastic range of the members, the findings justify the use of elastic design for cable domes

    Emerging Trends in Mechatronics

    Get PDF
    Mechatronics is a multidisciplinary branch of engineering combining mechanical, electrical and electronics, control and automation, and computer engineering fields. The main research task of mechatronics is design, control, and optimization of advanced devices, products, and hybrid systems utilizing the concepts found in all these fields. The purpose of this special issue is to help better understand how mechatronics will impact on the practice and research of developing advanced techniques to model, control, and optimize complex systems. The special issue presents recent advances in mechatronics and related technologies. The selected topics give an overview of the state of the art and present new research results and prospects for the future development of the interdisciplinary field of mechatronic systems

    The 24th Aerospace Mechanisms Symposium

    Get PDF
    The proceedings of the symposium are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, latches, connectors, and other mechanisms for large space structures

    Propulsion Test Handbook: MSFC and SSC

    Get PDF
    This Handbook was prepared to provide Propulsion Test Personnel a central source of fundamental reference material. The Testing Process, which is a three-part process of pre-test activities, testing, and post-test activities, involves a collaborative effort from the mechanical, electrical, safety, and environmental disciplines in the test environment. Pre-test activities, testing, and post-test activities processes will vary, per test requirements; however, the content of this Handbook should cover basic procedures and standards that are shared across Centers

    Mathematical and Numerical Aspects of Dynamical System Analysis

    Get PDF
    From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”
    corecore