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Modelling and assembly of the full vehicle 331 V X β V y cm V x Y Fig. 6.6 Body slip angle (iv) (v) (vi) Pitch angle Yaw rate Roll rate Another measure often determined during test or simulation is the body slip angle, . This is the angle of the vehicle velocity vector measured from a longitudinal axis through the vehicle as shown in Figure 6.6. The components of velocity of the vehicle mass centre V x and V y , measured in vehicle body reference frame, can be used to readily determine this. 6.4 Suspension system representation 6.4.1 Overview In Chapter 4 the modelling and analysis of the suspension system was considered in isolation. In this section the representation of the suspension as a component of the full vehicle system model will be considered. As stated the use of powerful multibody systems analysis programs often results in modelling the suspension systems as installed on the actual vehicle. In the following discussion a vehicle modelled with the suspension represented in this manner is referred to as a ‘Linkage model’. Before the advent of computer simulation classical vehicle dynamicists needed to simplify the modelling of the vehicle to a level where the formulation of the equations of motion was manageable and the solution was amenable with the computational tools available at the time. Such an approach encouraged efficiency with the analyst identifying the modelling issues that were important in representing the problem in hand. The use of modern software need not discourage such an approach. The following sections summarize four vehicle models, one of which is based on modelling the suspension linkages with three other models that use alternative simplified implementations. All four models have been used to simulate a double lane change manoeuvre (Blundell, 2000) and are compared in Case study 7 at the end of this chapter. The four models described here
332 Multibody Systems Approach to Vehicle Dynamics involve levels of evolving detail and elaboration and can be summarized as follows: (i) A lumped mass model, where the suspensions are simplified to act as single lumped masses which can only translate in the vertical direction with respect to the vehicle body. (ii) An equivalent roll stiffness model, where the body rotates about a single roll axis that is fixed and aligned through the front and rear roll centres. (iii) A swing arm model, where the suspensions are treated as single swing arms that rotate about a pivot point located at the instant centres for each suspension. (iv) A linkage model, where the suspension linkages and compliant bush connections are modelled in detail in order to recreate as closely as possible the actual assemblies on the vehicle. 6.4.2 Lumped mass model For the lumped mass model the suspension components are considered lumped together to form a single mass. The mass is connected to the vehicle body at the wheel centre by a translational joint that only allows vertical sliding motion with no change in the relative camber angle between the road wheels and the body. The camber angle between the road wheels and the Spring damper Spring damper Rear right sliding mass TRANS TRANS Spring damper Rear left sliding mass TRANS Spring damper TRANS REV Fig. 6.7 REV Front right sliding mass and wheel knuckle Lumped mass model approach Front left sliding mass and wheel knuckle
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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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3 Multibody systems simulation soft
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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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down and even more difficult to asc
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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 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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