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Multibody systems simulation software 79 SPH REV 04 03 02 M Z G 07 04 03 SPH 02 X G REV 01 GRF Y G 05 SPH 06 05 UNI 01 GROUND Fig. 3.2 Double wishbone suspension system schematic items such as the parts, joints, imparted motions and applied forces. The model may well include other elements that include, for example, springs, dampers and beams. The drawing of a schematic is an important first step as it will help the user not only to plan the data that will need to be collated but more importantly to estimate the degrees of freedom in the system and develop an understanding of how the mechanism will work. The use of a modern GUI should not discourage this process. Figure 3.2 provides an example of a system schematic for a double wishbone suspension system. Users may develop their own style when drawing a schematic but the symbols shown in Figure 3.3 are provided as a suggested starting point for the sketching of the various elements of a model. 3.2.2 Reference frames The three-dimensional description of a multibody system requires the use of reference frames, not only to set up the configuration and physical properties of the model, but also to describe the calculated outputs such as the displacements, velocities and accelerations. There are three types of righthanded Cartesian co-ordinate systems that will be used in this text: (i) The Ground Reference Frame (GRF). This is by definition the single inertial reference frame that is considered to be fixed or at ‘absolute’ rest. Any point defined to belong to this reference frame has zero velocity and acceleration. The ground reference frame is taken to be fixed on a body or part known as the ground part, the physical significance of which may vary from model to model. For a single suspension model the ground part may be taken to encompass the points on the vehicle body or subframe to which the suspension linkages attach. For a full vehicle model the ground part would relate to the surface of the road used to formulate the contact forces and moments in the tyre model. In addition to providing the single inertial reference frame the ground reference frame can be considered to be the origin of
80 Mutibody Systems Approach to Vehicle Dynamics 01 GROUND Ground part 02 Part identification number Z G X G GRF Y G Ground reference frame 02 Point identification number SPH Spherical joint M Motion input REV Revolute joint F Applied force CYL Cylindrical joint Spring TRA Translational joint Damper UNI Universal joint PLA Planar joint Fig. 3.3 Suggested symbols for elements of system schematic the entire model. As such the absolute co-ordinates and orientations of all other reference frames and points in the model are measured relative to the ground reference frame. Throughout this text the ground part is taken to be the first part in the model and the ground reference frame to be the first frame O 1 . Practitioners may also describe this frame as a ‘global’ system. The exact terminology may vary with different multibody system programs but the notion is identical between them. (ii) The Local Part Reference Frame (LPRF). Each body or part in the system can be considered to have a local part reference frame that moves and changes orientation with the part. This is referred to in MSC.ADAMS as a body co-ordinate system (BCS). The position and orientation of the local part reference frame is defined relative to the ground reference frame. The use of a local axis system on the part may be desirable to facilitate the definition of points on the body by perhaps exploiting the symmetry of the body where the axes of symmetry, at the model definition stage, are not parallel to the axes of the ground reference frame. The use of a local part reference frame is optional and if omitted the local part reference frame can be considered to be coincident with and parallel to the ground reference frame at the model definition stage. (iii) Markers. Markers, in MSC.ADAMS terminology, are the points located throughout the model to define, for example, mass centres, the positions of joints, the ends of springs and the graphical representation of the bodies used for subsequent animations. Markers may belong to the ground part or any moving part in the system, in which case the marker will move and rotate with the part. In some cases a marker is only required to define the
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Multibody Systems Approach to Vehic
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Multibody Systems Approach to Vehic
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Contents Preface Acknowledgements N
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Contents vii 4.10.1 Problem definit
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Contents ix 8.2.1 Active suspension
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Preface This book is intended to br
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Preface xiii vehicle design process
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Acknowledgements Mike Blundell In d
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Nomenclature xvii {z I } 1 Unit vec
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Nomenclature xix O n Frame for part
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Nomenclature xxi p Magnitude of re
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1 Introduction The most cost-effect
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Introduction 3 subsequent ‘classi
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Introduction 5 Fig. 1.4 Linearity:
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Introduction 7 While apparently a s
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Introduction 9 3. The body yaws (ro
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Introduction 11 Aspiration Definiti
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Introduction 13 Decomposition: Synt
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Introduction 15 The best multibody
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Introduction 17 shows good correlat
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Introduction 19 generated in numeri
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Introduction 21 1.9 Benchmarking ex
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2 Kinematics and dynamics of rigid
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Kinematics and dynamics of rigid bo
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Kinematics and dynamics of rigid bo
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Multibody systems simulation softwa
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4 Modelling and analysis of suspens
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Modelling and analysis of suspensio
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Tyre characteristics and modelling
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Modelling and assembly of the full
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7 Simulation output and interpretat
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Simulation output and interpretatio
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8 Active systems 8.1 Introduction M
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Active systems 443 mechanical actua
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Active systems 445 Table 8.1 MSC.AD
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Active systems 447 Body acceleratio
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Active systems 449 impressions of t
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Active systems 451 For this reason,
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Appendix A: Vehicle model system sc
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Appendix B: Fortran tyre model subr
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Appendix C: Glossary of terms Agili
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Appendix C: Glossary of terms 489 a
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Appendix C: Glossary of terms 491 t
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Appendix C: Glossary of terms 493 e
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Appendix C: Glossary of terms 495 m
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Appendix C: Glossary of terms 497 h
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Appendix C: Glossary of terms 499 t
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Appendix C: Glossary of terms 501 s
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References 503 Blundell, M.V. The m
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References 505 Hudi, J. AMIGO - A m
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References 507 Palmer, D. Course no
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References 509 European ADAMS News
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Index Abuse loads, 148 3 g bump, 14
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Index 513 Elk Test, 1 El-Nasher, 29
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Index 515 generalised translational
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Index 517 steer axis inclination, 1
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