ÿþ<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta name="Author" content="Alexander Schulz"> <meta name="GENERATOR" content="Editpad"> <title>PhD-Theses</title> </head> <body> <table BORDER=0 CELLSPACING=0 CELLPADDING=0 COLS=3 WIDTH="100%" > <tr> <td width="250"><center><font size=-1> PhD-Theses&nbsp; <a href="#phd1">1</a>&nbsp; <a href="#phd2">2</a>&nbsp; <a href="#phd3">3</a>&nbsp; <a href="#phd4">4</a>&nbsp; <a href="#phd5">5</a>&nbsp; </font></center></td> <td width="250"><center><font size=-1><a href="#award1">Positions and Awards</a>&nbsp;</font></center></td> <td width="250"><center><font size=-1> Books&nbsp; <a href="#book1">1</a>&nbsp; <a href="#book2">2</a>&nbsp; <a href="#book2">3</a>&nbsp; </font></center></td> </tr> </table> <!-- -------------------------- Navigation ----------------------------------- --> <center> <h1> PhD-Theses completed in 2003</h1></center> <hr SIZE=1 WIDTH="100%"> <h3>From Editor</h3> <font size=-1>Through the listing of PhD theses and habilitations world-wide completed, books published as well as prizes awarded, the International Journal of Fluid Power strives to keep its readers informed of new literature and scientific works. Names of authors, title, number of pages, publisher, ISBN, date, abstract and in case of PhD theses, name of university and institute are desired. The abstract should not exceed 200 words. The Journal solicits your help in keeping the listing current by asking you to transmit conference and meeting information formally or informally by post, fax or email to <br>Prof. Dr.-Ing. Monika Ivantysynova, Technical University of Hamburg-Harburg, Institute for Aircraft Systems Engineering, Nesspriel 5, 21129 Hamburg, Germany, Phone: +49 40 428788 - 203, Fax: +49 40 428788 - 270, Email: <a href="mailto:M.Ivantysynova@tu-harburg.de">M.Ivantysynova@tu-harburg.de</a></font> <hr SIZE=1 WIDTH="100%"> <!-- -------------------------- Beginn PHD THESES----------------------------------- --> <h3> <a name="phd1">Leon Dahlén</a></h3> <b> Numerical and Experimental Study of Performance of a Hydraulic Motor </b> <br> Department of Applied Physics and Mechanical Engineering, Luleå University of Technology, Sweden <br> ISSN 1402-1544 <p><font size=-1> The aim of this study was to develop an understanding of the fluid properties that influence the efficiency of hydraulic systems in a steady-state, especially components in hydrostatic transmission systems under different running conditions. The aim has also been to investigate and model the sources of losses in hydraulic machines, in order to estimate the losses, taking fluid properties into ac-count. Finally, the technique of optimization has been introduced in order to improve the efficiency of a distributor valve in a radial piston hydraulic motor, Marathon M200. <br> From an experimental field-test, which was performed on a belt conveyer using a hydrostatic transmission system, the overall ef-ficiency of the hydrostatic transmission was compared when using a mineral oil, Shell Tellus TX 68, a synthetic fluid, Mobil SHC 526, and a vegetable fluid, Binol Hydrap II. The experimental field-test showed that vegetable and synthetic fluids improve the effi-ciency compared to mineral oil. The three fluids have the same viscosity but experimental tests showed that the temperature (&beta)- and pressure(&alpha) -viscosity coefficient differs between them. It was also found that the pressure-viscosity coefficient (&alpha) of mineral oil was higher compared to vegetable and synthetic fluids. The proposed steady-state model gives greater accuracy regarding overall efficiency than the Wilson model, when examining fluid properties that differ in other aspects than their viscosity. <br> The study has focused on losses in lubricated sliding contacts within a radial piston hydraulic motor, Marathon M200, and an analysis of the losses has been made using the finite element method (FEM). A FEM software package, Solvia, which takes into account fluid properties, such as temperature- and pressure- viscosity coefficient, heat conduction and specific heat, has been used to simulate the behaviour and to estimate the losses in tribological contact. This approach of simulation has been applied to two different tribological contact within the hydraulic motor: to a journal bearing contact and to a hydrostatic annular multi-recess plane thrust bearing. <br> The theoretical studies have been compared to experimental results performed in a test stand. The theoretical studies have shown that the piston cam-roller contact in the motor might enter a lubrication regime other than full film lubrication, which can result in an increase in the torque loss. Results from the experimental tests have also shown that the total torque losses of the motor increase at high load and low speed. <br> By using an FEM software package linked to an optimization algorithm, the losses in the tribological contact in a distributor valve were reduced significantly. The study shows that the optimized geometry of the distributor valve in the motor can successfully be improved, with regard to losses, by small changes in the geometry. Combining an FEM software package with the optimization routine offers an effective tool for designers to simulate and improve the efficiency of a hydraulic unit. </font> <p><font size=-1> <a href="#top">Back to top</a></font> <h3> <a name="phd2">Marc E. Münzer</a></h3> <b> Resolved motion control of mobile hydraulic cranes </b> <br> Institute of Energy Technology, Aalborg University, Aalborg, Denmark <br> ISBN 87-89179-44-7 <p><font size=-1> This thesis deals with resolved motion control of mobile hydraulic cranes. With a resolved motion control scheme the operator controls the tool centre directly and a computer coordinates the motion of the individual joints. <br> The control structure used in this thesis is distributed joint control. The central controller sends a reference joint velocity to the individual joint controllers mounted at each joint. The individual joint controllers are programmed with the flow characteristic of the valve, the geometry of the joint, and a velocity control algorithm. This control structure supports the current trend in industry of mobile hydraulic proportional valves with embedded micro-controllers. <br> The joint controller presented in this thesis uses a single angular position sensor for feedback control of the joint velocity. A fur-ther sensor is added to add artificial damping to the joint motion. Two sensor strategies are implemented, the first based on a pressure sensor, the second based on a strain gauge. Since the motion of one joint affects the other joints in the system, an analytic stability analysis was performed taking into account the interaction between the joints. <br> The central controller presented in this thesis implements flow sharing, deflection compensation, gain scheduling, and redundancy control. A core part of this thesis is experimental implementation of all the ideas on a real mobile hydraulic crane. </font> <p><font size=-1> <a href="#top">Back to top</a></font> <h3> <a name="phd3">Liu Rong</a></h3> <b> Theoretical and Application Researches on Hydraulic Servo Control with Generalized Pulse Code Modulation </b> <br> State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, China <p><font size=-1> As the computer technology is widely used and developed, the digitization of electro-hydraulic control system and their components is a direction for progress. Electro-hydraulic servo control with on/off valves is a simple and efficient means, and a new development direction in fluid power transmission and control. The generalized pulse code modulation (GPCM) control hydraulic servo control, with the common on/off valves used as control components, is a cheap and practical new type of electro-hydraulic switch control system. It is applicalbe for the hydraulic control system, which has high flow rate, wide speed control range and foul work conditions. Theoretical and experimental studies of GPCM control are carried out in the thesis. <br> The mechanism of pulse code modulation (PCM) control is described and several typical circuits of PCM control are established. The generalization pulse code modulation (GPCM) is proposed for the first time to solve the contradictions between the control pre-cision and range, and between the stability and speed of PCM control system. Through the theoretical analysis, the mathematics model of GPCM hydraulic control is constructed, and it provides the base for study of GPCM control system. By means of the non-linear analysis tools, the GPCM control system is studied profoundly, and the results verify that the GPCM control can realize the stable operation for electro-hydraulic control system. Moreover, the method to determine minimum orifice areas of GPCM is in-ferred, and the coding rule also is studied. All these studies make sure that the GPCM control system can obtain good performance of control precision and large speed regulation range. <br> To take advantage of computational fluid dynamics (CFD), the theoretical analysis for the relation between the pressure distribu-tion and flow rate following the flow direction in the GPCM valve is performed, and the results can be used to design the GPCM valve structure. <br> A position servo control system is set up with a GPCM valve and hydraulic cylinder. The control strategy for the system is pro-posed by theoretical and simulation research. It is a hybrid control strategy, which include Bang-Bang control, PID control and fuzzy control. It does not depend on the system model precision and having the good performance verified by experiments. <br> Finally, the GPCM position servo system is served as a driven unit for a multi-joints manipulator, and the manipulator position-ing and tracking control are studied. The parameters of each controller of the manipulator is tuned to maintain that all joints move in harmony, and the positioning and tracking experimental results satisfy the requirements. </font> <p><font size=-1> <a href="#top">Back to top</a></font> <h3> <a name="phd4">Martin Schmidt</a></h3> <b> Untersuchung und Ansätze zur modellhaften Beschreibung der Alterung auf Estern basierender Zwischenstoffe für den Einsatz in umweltverträglichen Tribosystemen </b> <br> Institute for Fluid Power Drives and Controls (IFAS), University of Aachen (RWTH), Aachen, Germany <br> Language: German <p><font size=-1> Due to poor design of tribological systems or usage for applications the systems are not designed for, a commercial waste of bil-lions of EUR occurs annually. Therefore, tribological systems and lubricants are not only of great technical relevance but also of great economical and ecological importance. Lubricants are increasingly attracting public awareness due to the fact that every year millions of tons of used lubricants in Europe end up polluting the environment and are not recycled in the system. <br> This is the reason why this research work deals with the development of environmentally friendly tribological systems of high aging stability. On the one hand, new environmentally friendly fluids based on native resources are being investigated and developed. On the other hand, laboratory and endurance tests are performed to investigate the aging behaviour of environmentally friendly fluids which are commonly used in machine tools, e.g. hydraulic and gear fluids as well as cutting fluids. A point of interest is to analyse the impact of the specific structure of the tribological system the lubricant is applied to on the lubricant s aging behaviour. Exem-plary, the tribological systems of a gearing, a hydraulic pump and the cutting process are investigated. <br> Further, the research work focuses on the development of new ways of evaluating datasets using modern database methods. One of the ways in which the results are evaluated uses an evaluation matrix. This provides information regarding the aging behaviour of the various fluid/material combinations which were analyzed. It therefore offers a means of assessing suitability as a tribological system from the point of view of fluid aging. Another approach involves the set up of a neural network to simulate the aging of na-tive ester fluids. This model is an important tool for chemists and engineers dealing with the development or application of lubri-cants. It allows the assessment of the aging stability of fluids in dependency on the fatty acid composition and temperature without the need for testing. Additionally, this new established method shows a trend for future research work which comprises the simula-tion of aging of lubricants in complex hydraulic systems. </font> <p><font size=-1> <a href="#top">Back to top</a></font> <h3> <a name="phd5">Kong Xiaowu</a></h3> <b> Study of load sensing system with long pipes </b> <br> State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou, China <p><font size=-1> In large construction machinery, some actuators are far away from centralized hydraulic power source. There inevitably exist long pipes between pump and actuators. Practices show that these long pipes make an unfavorable influence to electro-hydraulic control system, especially to load-sensing system. In this dissertation, load-sensing system with long pipes is considered as the main subject investigated. Flow characteristics of fluid in long pipes is studied firstly, a simple and practice mathematic model of fluid pipe is put forward. Based on it, the pipe effects on load sensing system are studied by theoretical analysis and experiments. Finally, two kinds of schemes are put forward to improve the performance of load sensing system with long pipes. One is to adopt the opti-mum design method for pipes in load sensing system, another is to apply electro-hydraulic load sensing system, which is based on both electrical feedback for long distance actuators and fluid pipe feedback for short distance actuators. </font> <p><font size=-1> <a href="#top">Back to top</a></font> <!-- -------------------------- Beginn AWARDS etc. ----------------------------------- --> <br>&nbsp; <center><h1><a name="award1">Awards in 2003</a></h1></center> <hr SIZE=1 WIDTH="100%"> <br><b>Best Paper Award at the Bath Workshop on Power Transmission & Motion Control, PTMC 2003</b> <br> <br><b>A New Approach to Predict the Load Carrying Ability of the Gap between Valve Plate and Cylinder Block</b> <br>Huang Changchun (Technical University of Hamburg-Harburg, Germany) <br>Proc. of Power Transmission and Motion Control PTMC'2003 <br><p> <p><font size=-1> <a href="#top">Back to top</a></font> <br>&nbsp; <br>&nbsp; <br> <!-- -------------------------- Beginn BOOKS ----------------------------------- --> <center> <h1>Books & Proceedings Published in 2003</h1></center> <hr SIZE=1 WIDTH="100%"> <h3> <a name="book1">Proceedings of the 18th International Symposium on Hydraulics and Pneumatics </a></h3> <p><b>Edited by P. Noskievic, R. Farana and P. Konarik</b> <p> Publisher: Czech Mechanical Engineering Society in cooperation with VSB - Technical University of Ostrava <br>ISBN: 80-02-01567-3 <br>&nbsp; <p><font size=-1> <a href="#top">Back to top</a></font> <h3> <a name="book2">Power Transmission and Motion Control PTMC'2003 </a></h3> <p><b>Edited by C. R. Burrows and K. A. Edge</b> <p>Publisher: Professional Engineering Publishing Ltd. <br>ISBN: 1-86058-414-4 <br>&nbsp; <p><font size=-1> <a href="#top">Back to top</a></font> <h3> <a name="book3">Traktorhydraulik <br>Komponenten und Systeme von landwirtschaftlichen Traktoren </a></h3> <p><b>Edited by H. Hesse</b> <p>Publisher: Expert-Verlag GmbH <br>ISBN: 3-8169-2299-6 <br>&nbsp; <p><font size=-1> <a href="#top">Back to top</a></font> <br>&nbsp;<br> <center> <p><b><font color="#000000"><font size=+1><a href="issue11.html">BACK</a></font></font></b></center> <hr WIDTH="100%"> <font face="Arial,Helvetica">&copy;2003 <a href="mailto:info@fluid.power.net">Fluid Power Net</a> All rights reserved. <a href="http://fluid.power.net/fpn/docs/disclaimer.html">Disclaimer</a></font> </body> </html>