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Modelling and analysis of suspension systems 149 a conceptual suspension layout. The resulting loading environment for each component may be used by designers to sketch a meaningful first-sight design. This can avoid packaging difficulties induced by ill-informed sketching of components and the subsequent ‘stealing’ of space needed for section modulus in key components. Service loads are altogether more detailed. They are typically well-defined events where road profiles and speeds are well known. Once a reasonably representative geometry and suspension setting data set is available, the description of events may be combined with some form of enveloping tyre model in order to predict load–time histories for each component in the suspension. This in turn may be passed to finite element-based fatigue calculation methods in order to evaluate the number of times a component may be subject to this event before failure. Hypotheses such as the linear damage accumulation hypothesis (Miner’s rule) may be used to sum up the contribution of different events to the life of the component. Interested readers are referred to the SAE Fatigue Design Handbook (Rice, 1997) for more information on component fatigue analysis. With the calculation of service loads, instead of a single set of peak loads as produced from the design loads there is a vast amount of time-domain data. Typical data rates for service load events are around 200 points per second and service load events last of the order of 10 seconds. With a repertoire of up to 20 events describing a typical durability sign-off, it may be seen that the calculation of service loads results in an increase in the quantity of results data of the order of five orders of magnitude. Calculation and subsequent processing times rise too, though not quite by the same amount since linear static FE calculation times are a significant proportion of the overall elapsed time following design load calculations. However, as an overall process time amplification the expectation should be between two and three orders of magnitude for the calculation and use of service loads as compared to design loads. For some simple components, the use of a previously verified and correlated rig test may prove less onerous to the organization. 4.2 Types of suspension system There are various suspension systems used on cars and trucks and as described in Chapter 3 specialized versions of MBS programs such as the ADAMS/Chassis and ADAMS/Car programs provide templates with preprogrammed configurations of suspension systems commonly used by automotive manufacturers. Many established textbooks on vehicle dynamics and some that focus on suspensions provide a detailed treatment of the various types of suspension system and their function. The coverage here will be to briefly mention some of the most common systems and then to direct our attention to the MBS modelling and simulation environment. The double wishbone and McPherson strut systems are very common and will provide the basis for the ensuing discussion. At the time of writing the following configurations, shown graphically in Figure 4.12, are those, for example, provided with the ADAMS/Chassis program to model vehicle front suspension systems. Note that the software follows its roots and uses the Short–Long Arm naming convention used
150 Multibody Systems Approach to Vehicle Dynamics Hotchkiss McPherson Strut SLA (Coil) SLA (Perch) SLA (Torsion Bar) Twin I-Beam Fig. 4.12 Graphical representation of front suspension configurations in ADAMS/Chassis (provided courtesy of MSC.Software) in the USA for a double wishbone suspension system. The systems are also shown as ‘half vehicle’ models, the approach being to model both left and right sides of the system. The systems shown include: (i) Hotchkiss (3 Link or Beam Leaf model) (ii) McPherson Strut (iii) Short–Long Arm (Coil, Perch or Torsion Bar) (iv) Twin I-Beam For the rear suspension the following examples shown in Figure 4.13 are some of the suspensions, in addition to the Hotchkiss suspension already shown in Figure 4.12 for the front, that are provided in ADAMS/Chassis: (i) 4 Link Panhard (ii) 4 Link Watts
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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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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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