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    ISSN 0280-5316ISRN LUTFD2/TFRT--5781--SE

    Bucket and Vehicle OscillationDamping for a Wheel Loader

    Tommy Ikonen

    Department of Automatic ControlLund UniversityNovember 2006

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    Document name

    MASTER THESIS

    Date of issue

    November 2006

    Department of Automatic Control

    Lund Institute of Technology

    Box 118

    SE-221 00 Lund Sweden Document NumberISRNLUTFD2/TFRT--5781--SE

    Supervisor

    Amos Albert and Dieter Schwarzmann at Bosch inGermany.Karl-Erik rzen at Automatic Control in Lund.

    Author(s)

    Tommy Ikonen

    Sponsoring organization

    Title and subtitle

    Bucket and Vehicle Oscillation Damping for a Wheel Loader (Dmpning av svngningar fr en hjullastare)

    Abstract

    A wheel loader is a tractor-like universal working machine with a bucket in the front which can be used fordigging, loading and transporting different type of material. A driver of such a vehicle needs a lot of trainingand experience before he can handle the vehicle in a safe and efficient way. In order to reduce these demandson the driver, the vehicle should be made more autonomous. As a first step in this direction, inertial bucketstabilization is considered in this thesis. When transporting a load on uneven terrain the bucket with the load

    starts to oscillate together with the whole vehicle. These oscillations could cause load loss, or worse, causefragile load to break. The oscillations of the vehicle are also uncomfortable for the driver. Normally the driverhas to manually avoid these problems by driving slower or choosing another route and thus needs to haveexperience in these situations. In the thesis it is investigated if the oscillations of the bucket and vehicle itselfcan be compensated for by moving the boom where the bucket is mounted. Due to economical reasons thecompensation should be achieved by controlling the already available hydraulic system on the wheel loader.

    Keywords

    Classification system and/or index terms (if any)

    Supplementary bibliographical information

    ISSN and key title

    0280-5316ISBN

    Language

    EnglishNumber of pages

    71

    Security classification

    Recipients notes

    The report may be ordered from the Department of Automatic Control or borrowed through:University Library, Box 3, SE-221 00 Lund, Sweden

    Fax +46 46 222 42 43

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    v

    Acknowledgements

    This masters thesis has been done in 20 weeks during the months June to November 2006 atRobert Bosch GmbH outside Stuttgart. It is part of my studies at the engineering programme

    Computer Science and Engineering at the Lund University in Sweden.It has been a wonderful time for me here in the south of Germany. Apart from that the

    thesis has been a very interesting project, the colleagues at work and the people I have livedwith have been absolutely great.

    First of all I would like to thank Dr. Amos Albert, my supervisor at Bosch, a man whoknows everything. He seems to have an answer to all of my questions. I also would like tothank Dieter Schwarzmann who was my second supervisor at Bosch for the help I have got.Dr. Torsten Lilge at the Department of Automatic Control at the University of Hannoverhas provided me with some information that has simplified a lot of work, which I am verygrateful for. Also thanks to Dr. Seppo Tikkanen and Sebastian Oschmann at Bosch Rexrothwho have guided me in the right direction in my work. And last I would like to thank Prof.Karl-Erik rzn at the Department of Automatic Control at the Lund University for inform-

    ing me about the opportunity to do my masters thesis at Bosch in Germany. Thank you all!

    Schwieberdingen, 3rd November 2006Tommy Ikonen

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    Contents

    Abstract iii

    Acknowledgements v

    Nomenclature viii

    1 Introduction 1

    1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Description of a Wheel Loader . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    1.2.1 Wheel Loader Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.2 Wheel Loader Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    1.3 Aim of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 Outline of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    2 Model of Wheel Loader 5

    2.1 Model of Mechanical System . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    2.1.1 Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.1.2 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    2.2 Model of Hydraulic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.1 Hydraulic Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.2 Hydraulic Cylinder Model . . . . . . . . . . . . . . . . . . . . . . . . . 10

    2.3 Resulting Model of the Wheel Loader . . . . . . . . . . . . . . . . . . . . . . 112.3.1 Transformation of Boom Angle to Piston Position . . . . . . . . . . . 112.3.2 Transformation of Cylinder Force to Torque . . . . . . . . . . . . . . . 132.3.3 Nonlinear Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

    3 Simulation Results with Nonlinear Model 15

    3.1 Validation of Model Against Simmechanics-Model . . . . . . . . . . . . . . . 15

    3.2 Behavior of Nonlinear Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

    4 Definition of Test Scenario 20

    4.1 Boom Angle and Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.2 Road Disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204.3 Performance Measure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

    5 Analysis of Linearized Model 24

    5.1 Input-Output Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.2 Controllability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245.3 Observability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.4 Modal Dominance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

    5.5 Root Locus Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

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    CONTENTS vii

    6 Control of Wheel Loader 30

    6.1 Limitations of the Flow to the Cylinder . . . . . . . . . . . . . . . . . . . . . 306.2 Conventional Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316.3 State-feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

    6.3.1 Design of State-feedback Controller. . . . . . . . . . . . . . . . . . . . 316.3.2 Control with full State Information. . . . . . . . . . . . . . . . . . . . 34

    6.4 State Observer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.4.1 Design of Observer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386.4.2 Performance of Kalman Filter. . . . . . . . . . . . . . . . . . . . . . . 39

    6.5 Unknown Input Observer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436.5.1 Design of Observer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436.5.2 State-feedback Control with Feedforward . . . . . . . . . . . . . . . . 45

    6.6 HControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506.7 Comments on the Different Control Strategies. . . . . . . . . . . . . . . . . . 54

    6.7.1 Comments on Feedforward . . . . . . . . . . . . . . . . . . . . . . . . 546.7.2 Comments on Achieving Both Aims of the Thesis. . . . . . . . . . . . 55

    7 Conclusion 56

    7.1 Summary of Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 567.2 Further Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

    A Model Parameters 58

    B Scaling of a Linear System 59

    C Discretization of Linear System 60

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    Nomenclature

    Abbreviations

    MDI Model Dominance IndexPID Proportional Intergral DerivativeLQR Linear Quadratic RegulatorSI-units International System of Units (from French: Systme international dunits)UIO Unknown Input Observerrpm Revoluti