SATNAB - Voruntersuchung fuer ein satellitennavigationsgestuetztes Bodenexperiment Technischer Bericht

Within the phase 1 of the project SATNAB the theoretical basis for a satellite navigation based ground experiment was developed and analysed. The procedure of measurement offers the possibility to determine the exact position of a mobile, trackborne user by means of a single Navigation satellite of a future European navigation Satellite System (ENSS/ GNSS 2). In this study the requirements of the experiment for different satellite orbits were investigated. Two scenarios for the experiment have to be distinguished. The first scenario is the verification of the accuracy of positioning of the future satellite navigation system, named reference measuring system. The second one implies the application of positioning in track bound traffic, named the location scenario. As the reference measuring system is a standard of comparison for the quality of the satellite navigation, an error budget was built in. Based on that estimation the concept for the scenarios was defined. A realisation concept for the test configuration was also developed. The predictable errors in the control segment and in the space segment were estimated. This investigation focused on the alignment of the antenna and the clock synchronisation between the oscillator of the space segment and the one placed in the moving vehicle. The procedure of the experiment was summarised in an schedule for the next phases. (orig.)SIGLEAvailable from TIB Hannover: F99B692 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Bonn (Germany)DEGerman

Numerical methods in vehicle system dynamics: state of the art and current developments

Robust and efficient numerical methods are an essential prerequisite for the computer based dynamical analysis of engineering systems. In vehicle system dynamics, the methods and software tools from multibody system dynamics provide the integration platform for the analysis, simulation and optimization of the complex dynamical behaviour of vehicles and vehicle components and their interaction with hydraulic components, electronical devices and control structures. Based on the principles of classical mechanics, the modelling of vehicles and their components results in nonlinear systems of ordinary differential equations (ODEs) or differential-algebraic equations (DAEs) of moderate dimension that describe the dynamical behaviour in the frequency range required and with a level of detail being characteristic of vehicle system dynamics. Most practical problems in this field may be transformed to generic problems of numerical mathematics like systems of nonlinear equations in the (quasi-)static analysis and explicit ODEs or DAEs with a typical semi-explicit structure in the dynamical analysis. This transformation to mathematical standard problems allows to use sophisticated, freely available numerical software that is based on well approved numerical methods like the Newton-Raphson iteration for nonlinear equations or Runge-Kutta and linear multistep methods for ODE/DAE time integration. Substantial speed-ups of these numerical standard methods may be achieved exploiting some specific structure of the mathematical models in vehicle system dynamics. In the present paper, we follow this framework and start with some modelling aspects being relevant from the numerical viewpoint. The focus of the paper is on numerical methods for static and dynamic problems including software issues and a discussion which method fits best for which class of problems. Adaptive components in state-of-the-art numerical software like stepsize and order control in time integration are introduced and illustrated by a well known benchmark problem from rail vehicle simulation. Over the last few decades, the complexity of high-end applications in vehicle system dynamics has frequently given a fresh impetus for substantial improvements of numerical methods and for the development of novel methods for new problem classes. In the present paper, we address three of these challenging problems of current interest that are today still beyond the mainstream of numerical mathematics: (i) Modelling and simulation of contact problems in multibody dynamics, (ii) Real-time capable numerical simulation techniques in vehicle system dynamics and iii) Modelling and time integration of multidisciplinary problems in system dynamics including co-simulation techniques