4569846498

More documents

Recommendations

Info

Modelling and analysis of suspension systems 201 Vertical acceleration 1 Acceleration (g) 0.1 0.01 Perception threshold Comfort threshold Severe discomfort threshold 60 mph average road 120 mph average road 0.001 0.1 1 10 100 Frequency (Hz) Fig. 4.65 A prediction of the harmonic response of a vehicle body in comparison with the acceleration curves laid down in ISO2631-1:1997 1 Vertical acceleration limits Acceleration (g) 0.1 0.01 Perception threshold Comfort threshold Severe discomfort threshold 5% motion sickness threshold 60 mph average road 60 mph 0.2 Hz ride 0.001 0.1 1 10 100 Frequency (Hz) Fig. 4.66 A prediction of the harmonic response of a vehicle body in comparison with the acceleration curves laid down in ISO2631-1:1997 with the inclusion of motion sickness threshold data, comparing a 0.2 Hz vehicle with a 1 Hz vehicle the road and not exacerbated in the vehicle. For the 0.2 Hz car, however, it can be seen that the vehicle resonance on its suspension contributes to a significant exceedance of the threshold motion sickness – the suspension will make people ill. Considering Figure 4.66 in some detail, it would seem that a practical limiting suspension frequency is where the 5% motion sickness line crosses the comfort threshold. This is around 0.65 Hz. For motorsport or military vehicles, it may be acceptable to use the severe discomfort threshold; in this case the practical lower limit for ride frequencies is around 1.25 Hz. It should be noted that the threshold values for accelerations drop off significantly above 2 Hz. For this reason, motor vehicles rarely have primary
202 Multibody Systems Approach to Vehicle Dynamics ride modes much above 2.5 Hz, even quite aggressively suspended ones. There is thus a ‘window’ in which we position the primary ride behaviour of our vehicles to make them compatible with the operators. For autonomous vehicles that never carry humans, these restrictions are relaxed and the suspension primary ride frequency can be chosen on the basis of some other functional aspect. 4.10 Case study 5 – Suspension vector analysis comparison with MBS 4.10.1 Problem definition The following study is intended to demonstrate the application of the vector theory outlined in Chapter 2 to a range of suspension analyses. Before the advent of computer programs to analyse the motion of suspension linkages vehicle designers resorted to graphical methods or simplified calculations often using two-dimensional representations to study the suspension in a fore–aft or transverse plane. These methods are still taught and included in many texts addressing vehicle dynamics. They can develop an understanding of suspension design, and the effect on total vehicle performance, that can be lost using the automated methods in modern computer aided analysis. The aim of this textbook is to bridge the gap between traditional vehicle dynamics theories and the multibody systems approach. The following calculations are typical of the processes carried out using MBS software. While the methods used here do not represent exactly the internal machinations of, for example, the MSC.ADAMS software they do give an indication of the computational process involved. The example chosen here is based on a typical double wishbone suspension system. The answers obtained are compared with those running an MSC.ADAMS model using the same data. The calculations will include a series of analyses including: ● Geometry analysis ● Velocity analysis ● Acceleration analysis ● Static force analysis ● Dynamic force analysis The geometric data required to define this problem is defined in Figure 4.67. Note that in this example the x-axis is orientated towards the front of the vehicle rather than pointing to the rear as used generally throughout this text. This is therefore the front left suspension system on the vehicle. 4.10.2 Velocity analysis The starting point for this analysis is to establish a boundary condition, or road input, at the tyre contact patch P as the vehicle negotiates the road hump shown in Figure 4.68 with a forward speed of 15 m/s. The analysis is
Page 2 and 3:
Multibody Systems Approach to Vehic
Page 4 and 5:
Multibody Systems Approach to Vehic
Page 6 and 7:
Contents Preface Acknowledgements N
Page 8 and 9:
Contents vii 4.10.1 Problem definit
Page 10 and 11:
Contents ix 8.2.1 Active suspension
Page 12 and 13:
Preface This book is intended to br
Page 14 and 15:
Preface xiii vehicle design process
Page 16 and 17:
Acknowledgements Mike Blundell In d
Page 18 and 19:
Nomenclature xvii {z I } 1 Unit vec
Page 20 and 21:
Nomenclature xix O n Frame for part
Page 22 and 23:
Nomenclature xxi p Magnitude of re
Page 24 and 25:
1 Introduction The most cost-effect
Page 26 and 27:
Introduction 3 subsequent ‘classi
Page 28 and 29:
Introduction 5 Fig. 1.4 Linearity:
Page 30 and 31:
Introduction 7 While apparently a s
Page 32 and 33:
Introduction 9 3. The body yaws (ro
Page 34 and 35:
Introduction 11 Aspiration Definiti
Page 36 and 37:
Introduction 13 Decomposition: Synt
Page 38 and 39:
Introduction 15 The best multibody
Page 40 and 41:
Introduction 17 shows good correlat
Page 42 and 43:
Introduction 19 generated in numeri
Page 44 and 45:
Introduction 21 1.9 Benchmarking ex
Page 46 and 47:
2 Kinematics and dynamics of rigid
Page 48 and 49:
Kinematics and dynamics of rigid bo
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
3 Multibody systems simulation soft
Page 100 and 101:
Multibody systems simulation softwa
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
4 Modelling and analysis of suspens
Page 156 and 157:
Modelling and analysis of suspensio
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175: Modelling and analysis of suspensio
Page 272 and 273: Tyre characteristics and modelling
Page 274 and 275:
Tyre characteristics and modelling
Page 276 and 277:
Page 278 and 279:
Page 280 and 281:
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
Page 288 and 289:
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304 and 305:
Page 306 and 307:
Page 308 and 309:
Page 310 and 311:
Page 312 and 313:
Page 314 and 315:
Page 316 and 317:
Page 318 and 319:
Page 320 and 321:
Page 322 and 323:
Page 324 and 325:
Page 326 and 327:
Page 328 and 329:
Page 330 and 331:
Page 332 and 333:
Page 334 and 335:
Page 336 and 337:
Page 338 and 339:
Page 340 and 341:
Page 342 and 343:
Page 344 and 345:
Page 346 and 347:
Page 348 and 349:
Page 350 and 351:
Modelling and assembly of the full
Page 352 and 353:
Page 354 and 355:
Page 356 and 357:
Page 358 and 359:
Page 360 and 361:
Page 362 and 363:
Page 364 and 365:
Page 366 and 367:
Page 368 and 369:
Page 370 and 371:
Page 372 and 373:
Page 374 and 375:
Page 376 and 377:
Page 378 and 379:
Page 380 and 381:
Page 382 and 383:
Page 384 and 385:
Page 386 and 387:
Page 388 and 389:
Page 390 and 391:
Page 392 and 393:
Page 394 and 395:
Page 396 and 397:
Page 398 and 399:
Page 400 and 401:
Page 402 and 403:
Page 404 and 405:
Page 406 and 407:
Page 408 and 409:
Page 410 and 411:
Page 412 and 413:
Page 414 and 415:
Page 416 and 417:
Page 418 and 419:
7 Simulation output and interpretat
Page 420 and 421:
Simulation output and interpretatio
Page 422 and 423:
Page 424 and 425:
down and even more difficult to asc
Page 426 and 427:
Page 428 and 429:
Page 430 and 431:
Page 432 and 433:
Page 434 and 435:
Page 436 and 437:
Page 438 and 439:
Page 440 and 441:
Page 442 and 443:
Page 444 and 445:
Page 446 and 447:
Page 448 and 449:
Page 450 and 451:
Page 452 and 453:
Page 454 and 455:
Page 456 and 457:
Page 458 and 459:
Page 460 and 461:
Page 462 and 463:
Page 464 and 465:
8 Active systems 8.1 Introduction M
Page 466 and 467:
Active systems 443 mechanical actua
Page 468 and 469:
Active systems 445 Table 8.1 MSC.AD
Page 470 and 471:
Active systems 447 Body acceleratio
Page 472 and 473:
Active systems 449 impressions of t
Page 474 and 475:
Active systems 451 For this reason,
Page 476 and 477:
Appendix A: Vehicle model system sc
Page 478 and 479:
Page 480 and 481:
Page 482 and 483:
Page 484 and 485:
Page 486 and 487:
Page 488 and 489:
Page 490 and 491:
Page 492 and 493:
Page 494 and 495:
Page 496 and 497:
Appendix B: Fortran tyre model subr
Page 498 and 499:
Page 500 and 501:
Page 502 and 503:
Page 504 and 505:
Page 506 and 507:
Page 508 and 509:
Page 510 and 511:
Appendix C: Glossary of terms Agili
Page 512 and 513:
Appendix C: Glossary of terms 489 a
Page 514 and 515:
Appendix C: Glossary of terms 491 t
Page 516 and 517:
Appendix C: Glossary of terms 493 e
Page 518 and 519:
Appendix C: Glossary of terms 495 m
Page 520 and 521:
Appendix C: Glossary of terms 497 h
Page 522 and 523:
Appendix C: Glossary of terms 499 t
Page 524 and 525:
Appendix C: Glossary of terms 501 s
Page 526 and 527:
References 503 Blundell, M.V. The m
Page 528 and 529:
References 505 Hudi, J. AMIGO - A m
Page 530 and 531:
References 507 Palmer, D. Course no
Page 532 and 533:
References 509 European ADAMS News
Page 534 and 535:
Index Abuse loads, 148 3 g bump, 14
Page 536 and 537:
Index 513 Elk Test, 1 El-Nasher, 29
Page 538 and 539:
Index 515 generalised translational
Page 540 and 541:
Index 517 steer axis inclination, 1
show all

4569846498

Create successful ePaper yourself

Delete template?

Save as template?