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Modelling and assembly of the full vehicle 377 Table 6.5 MSC.ADAMS command file sample for ‘front axle control’ driver model data_element create variable & variable_name ground_plane_velocity & function “( (“, & “VX(m_body_CG,base)**2 ”, & “VY(m_body_CG,base)**2”, & ”)**0.5 ) / 1000” data_element create variable & variable_name demanded_yaw_rate & function “varval(ground_plane_velocity) *”, & “AKISPL(varval(path_length),0,path_curvature_spline)” data_element create variable & variable_name beta & function“ASIN(VY(m_body_CG,base,m_body_CG)/”, & “(varval(ground_plane_velocity) 0.00001))” data_element create variable & variable_name centacc & function “(VARVAL(latacc)* COS(VARVAL(beta))) ”, & “(VARVAL(longacc)* SIN(VARVAL(beta)))” data_element create variable & variable_name front_axle_no_slip_yaw & function “(“, & “VARVAL(centacc) ”, & “ WDTZ(m_body_CG,base,m_body_CG)”, & “* DX(m_body_CG,mfr_upright_wheel_centre,m_body_CG)”, & “ )”, & “ /”, & “ ( varval(ground_plane_velocity) 0.00001 )” data_element create variable & variable_name yaw_rate_error & function “ varval(demanded_yaw_rate) varval(front_axle_no_slip_yaw)” For a variety of events, this formulation produces good driver/vehicle behaviour, representative of real vehicle and driver behaviour (Figure 6.45). The simulated driver and vehicle behaviour for a post-limit turn-in event is compared here to a real vehicle. Note the freewheeling analytical model (of a significantly different vehicle) displays greater body slip angle, while the real vehicle displays greater oversteer. 6.13.3 Body slip angle control Skilled drivers, particularly rally drivers, frequently operate at large body slip angles. Colloquially, there is much talk of body slip angles being in excess of 45 degrees but recorded data suggests this is not the case despite appearances. Large body slip angles generally slow progress; although some of the yaw transients are rapid, in general the actual body slip angles are comparatively small (Figure 6.46). In general, drivers greatly overestimate body slip angle subjectively.
378 Multibody Systems Approach to Vehicle Dynamics Fig. 6.45 Driver and vehicle behaviour for a post-limit turn-in event (photograph courtesy of Don Palmer, www.donpalmer.co.uk) The steering system on a vehicle has only 20–25 degrees (less on the rally car) of lock and so realistically, control beyond these body slip angles is unlikely without very large amounts of space indeed. Most drivers are acutely sensitive to the rate of change of body slip angle, albeit they do not always respond correctly to it. Instead a ‘threshold’ behaviour appears common, with drivers neglecting body slip angle until either the angle becomes large or its rate of change becomes large. For road cars, our goals are to have a road car manage its own body slip angle so as not to put pressure on drivers in an area where in general skill is lacking. For driver modelling purposes, a separate body slip angle control loop is desirable to catch spins but need not be terribly sophisticated since if it is
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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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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 495 m
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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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