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special issue modeling analysis and control methods for improving vehicle 1 dynamic behavior modeling analysis and control methods for improving vehicle review dynamic behavior overview toshimichi takahashi abstract so called ...

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            Special Issue Modeling, Analysis and Control Methods for Improving Vehicle                                 1
                           Dynamic Behavior
                               Modeling, Analysis and Control Methods for Improving Vehicle
              Review           Dynamic Behavior (Overview)
                                                                                                 Toshimichi Takahashi
                                                            Abstract
               So-called vehicle dynamics (or controllability         behavior, the vehicle dynamics control and state
             and stability) refer to the "running, cornering and      estimation, and the analysis of driver-vehicle
             stopping" of automobiles, which are the most             system, are briefly summarized.  Also, the
             important and basic performance of automobiles.          purpose and background of these studies are
             Therefore, many studies have been undertaken             mentioned.  Moreover, a brief introduction to the
             from several points of view all over the world.  In      three technical papers included in this special
             this paper, our former studies, which focused on         issue is presented.
             the analysis and modeling of vehicle and tire
               Keywords     Vehicle dynamics, Modeling, Simulation, Control system, State estimation, Tire model,
                            Optimum control, Driver-vehicle system
                                                                                       R&D Review of Toyota CRDL  Vol. 38  No. 4
                          2
                               1.  Introduction                                                                                                                                      Chapter 5.
                               Among the many points of view and stages in                                                                                                               Finally, the purpose and outline of the three
                          research and development in the vehicle dynamics                                                                                                           technical papers included in this special issue are
                          field, we have been studying fundamental subjects                                                                                                          briefly explained.
                          focusing on the following concepts and purposes,                                                                                                                2.  Tire modeling
                          mainly in the three following categories for                                                                                                                   In addition to the analysis and modeling of tire
                          improving vehicle dynamic behavior and safety.                                                                                                                                                                          1, 2)
                          Here, it should be also noted that the "tire" is one of                                                                                                    transient properties,                                                      we have also been
                          the key factors influencing our research activities,                                                                                                       developing a software system to model a tire steady
                                                                                                                                                                                     state characteristics using the so-called Magic
                          either directly or indirectly, because the tire plays an                                                                                                                        3-5)
                          essential role in all aspects of vehicle behavior.  This                                                                                                   Formula                       which has frequently been employed in
                          paper provides a brief summary and background of                                                                                                           vehicle dynamics simulation in recent years.  The
                          our studies.  The layout of this paper is as follows.                                                                                                      goal is to describe the tire force and moment
                               (1) Analysis and modeling of vehicle and tire behavior                                                                                                properties very accurately over wide ranges of input
                               Considering the importance of the tire to vehicle                                                                                                     variables including combined slip cases, this being
                          maneuvering, we have been studying and modeling                                                                                                            very important to the analysis of vehicle dynamic
                          tire characteristics, especially from the viewpoint of                                                                                                     behavior with multi-body dynamics simulation
                          developing accurate tire models for use in vehicle                                                                                                         software like ADAMS or DADS, as well as by in-
                          simulation calculations.  In Chapter 2, we                                                                                                                 house development.
                          summarize the models we have developed to                                                                                                                      To establish the Magic Formula (abbreviated to
                          describe the tire steady state characteristics.                                                                                                            MF) tire model, the optimum values for many MF
                               In the analysis of vehicle dynamic behavior, the                                                                                                      parameters and coefficients have to be decided by
                                                                                                                                                                                     using measured data for each tire.  Figure 1 shows
                          road surface has been assumed to be flat and even in                                                                                                                                                                                                           7)
                          most cases, even though actual roads inevitably have                                                                                                       the structure of our software system,                                                                    which can
                          some undulations and unevenness.  Our trial for                                                                                                            handle the tire side force, the longitudinal force, and
                          analyzing the braking performance of a vehicle on                                                                                                          the self aligning torque.  The software was
                          uneven roads is briefly explained in Chapter 3.                                                                                                            developed in a Matlab/Optimization toolbox
                                                                                                                                                                                     environment to support the use of a wide range of
                               (2) Vehicle dynamics control and state estimation                                                                                                                                                             6, 7)
                               In recent years, various kinds of control systems                                                                                                     tires and test facilities.
                          have been offered in vehicles on the market to                                                                                                                 Examples of established MF models are shown in
                          improve the vehicle dynamic behavior and safety.                                                                                                           Figs. 2 and 3.  These figures show that the models
                          The control algorithms of these systems and the state
                          estimation techniques, which estimate the state
                          variables of vehicle motion and tire characteristics                                                                                                             FFllaa tt B Bee ltlt M M//CC       TTrraaileile rr    VVeehhiiclcle Me Measeasuurrememenentt          .  ..  .  .  .
                          etc., are the key technologies used in the
                          development of all these control systems.  Chapter 4                                                                                                                            InIntteerfarfaccee a anndd  PPrree--PPrroocceessssiinngg
                          discusses some of our former studies in this                                                                                                                                                      < < wwiitthh//wwiitthouthout  CCoonnssttrraaiinened Cd Coondindittiioonnss > >
                          category.                                                                                                                                                      MMeaseasuurreded D Daattaa
                                                                                                                                                                                                                                                                               OnOnee S Stteepp
                               (3) Analysis of driver-vehicle system                                                                                                                                         MMFF Co Coeeffifficciieennttss                               IIddenenttiiffiicatcatiioonn
                               One of the most pressing and important problems                                                                                                             CoCoeeffifficciieennttss                    MMFF Pu Purree S Slliipp Pa Parraammeetteerrss
                          facing automobile manufacturers is the reduction of                                                                                                              IIddenenttiiffiicatcatiioonn
                          the number of traffic accidents while increasing                                                                                                                                                    PaParraammeetteerrss                  MMFF C Coommbbinineedd S Sllipip
                                                                                                                                                                                       < w< wiitthh//wwiitthouthout        IIddeenntitiffiiccaatitioonn                     PaParraammeetteerrss
                          traffic safety.  Given that almost accidents are                                                                                                                  CCoonnssttrraaiinened Cd Condiondittiiononss > >
                          caused by human-related factors, the study of driver-
                          vehicle closed-loop systems is extremely important.
                          Our recent study in this field is introduced in                                                                                                            Fig. 1              Structure of tire model identification system.
                          R&D Review of Toyota CRDL  Vol. 38  No. 4
                                                                                                                                    3
           identified by our system agree with the measured                  vehicle chassis elements on braking performance
           data very well.   Figure 2 shows the so-called                    have rarely been reported.  Then, analytical and
           friction circle or friction ellipse, and Fig. 3 shows             experimental studies were performed, in which the
           the braking force characteristics of a passenger                  braking performance of straight-running vehicles on
           vehicle tire (PV tire) and a commercial vehicle tire              uneven roads and the influence of chassis elements
                                                                                                                      8)
           (CV tire) on ice road.  From Fig. 3, we can see that              on that performance were investigated.
           there are rather large differences between the two                  For the analysis, a model for simulating of vehicle
           kinds of tires, namely, the maximum braking force                 behavior was developed based on the half car model,
           divided by the vertical load of the CV tire is smaller            as shown in Fig. 4.  The tire braking force
           than that of the PV tire, and the decrease in the                 characteristics that depend on the vertical load and
           braking force after the peak of the CV tire is much               the wheel slip ratio were described by the Magic
           larger than that of PV tire.  These differences may be            Formula explained in a former chapter.  In the
           caused by the difference in the inflation pressure,               simulation, vehicle responses such as the
           which relates to the vertical load distribution per unit          deceleration of the vehicle, the stopping distance
           area in the contact patch, and therefore a difference             after braking and the tire vertical load can be
           in the generation of water between the tire and the
           icy road may be induced.  In this case, the pressure
           was set to 220 kPa for the PV tire and 705 kPa for                      1500                   Camber angle 0 deg
           the CV tire.                                                                                   Plots : measurements
              3.  Braking performance on uneven roads                             )          6 kN         Curves : MF model
                                                                                  N1000
                                                                                   (
             Although vehicle behavior during steering and/or                     e
                                                                                  c
                                                                                  r
           braking has been studied very widely for many                          o                   4 kN
                                                                                  ng F
           years, most studies have assumed the road surface to                   i
                                                                                  k
                                                                                  a 500
           be even and flat.  The analysis of vehicle behavior                    r
                                                                                  B              Vertical Load 2 kN
           on uneven roads is thought to be very important,
           however, when considering actual roads.  On the
           other hand, it seems that many studies of brake                                                         Slip Ratio
           systems and their performance have been                                    00      0.2     0.4     0.6     0.8     11
           undertaken, but that analyses of the influence of                           (a) Passenger vehicle tire : 195/65R15
                                                                                     5.0
                  6000                    Vertical Load 5  kN                                            Camber angle 0 deg
                          10 deg          Camber angle 0 deg                         4.0                 Plots : measurements
                                          Plots : measurements                    )          40 kN       Curves : MF model
                                                                                  N
                )                         Curves : MF model                       k
                N 4000       6 deg                                                e (3.0
                                                                                  c
                  (                                                               r
                e                                                                 o
                c             4 deg                                                F
                r                                                                 g
                                                                                  n      26 kN
                 Fo                                                               i  2.0
                e                                                                 ak
                d                                                                 r
                Si2000      Slip Angle 2 deg                                      B
                                                                                     1.0
                                                                                              Vertical Load 14 kN
                         Braking Force (N)              0 deg                                                      Slip Ratio
                                                                                     0.00     0.2     0.4     0.6     0.8     1
                    0
                     0           2000         4000         6000                          (b) Commercial vehicle tire : 11R22.5
           Fig. 2   Combined slip characteristics on dry road                Fig. 3  Pure braking force characteristics on ice road.
                    (Passenger vehicle tire : 195/65R15).
                                                                                                 R&D Review of Toyota CRDL  Vol. 38  No. 4
          4
          calculated, provided the vehicle initial speed, the          (C) Harder suspension bush ( kxf = 330 kN/m, 
          time history of the brake fluid pressure and the                 c = 800 Nsec/m )
                                                                            xf
          longitudinal road profile are given as inputs.               (D) Higher tire inflation pressure + Larger damping 
            Figure 5 shows the calculated and measured                     of shock absorber + harder suspension bush
          values for the influence of the chassis elements'            In Fig. 5, the difference in the stopping distance
          characteristics on the braking performance, in which        between each vehicle and the standard vehicle is
          the parameters of the chassis elements were changed         indicated as a ratio (%) relative to the stopping
          from those of a standard vehicle (see Table 1) as           distance of the standard vehicle both for calculated
          shown below.                                                and measured results.  Positive values indicate a
            (A) Higher tire inflation pressure ( k = 215 kN/m )       shorter stopping distance than the standard.
                                              tf
            (B) Higher tire inflation pressure + Larger damping       Although some differences can be seen in the figure,
                of shock absorber ( c = 1350 Nsec/m )                 overall we can say that the tendency for the chassis
                                    f
                                                                      elements to influence the braking performance as
                                                                      calculated agrees rather well with the experiments.
                                                                       In addition, the influences of the longitudinal
                                                                              8.0
                                                                              6.0         Experiment
                                                                              4.0      Calculation
                                                                              2.0   (A)
                                                                              0.0             (B)      (C)        (D)
                                                                         ference Ratio of  -2.0
                                                                         Dif -4.0
                                                                            Stopping Distance (%)
                                                                             -6.0
              Fig. 4  Vehicle model and symbol notation.                 Fig. 5  Comparison of stopping distance between
                                                                                 calculation and experiments.
                                            Table 1 Parameter values of standard vehicle.
          R&D Review of Toyota CRDL  Vol. 38  No. 4
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...Special issue modeling analysis and control methods for improving vehicle dynamic behavior review overview toshimichi takahashi abstract so called dynamics or controllability the state stability refer to running cornering estimation of driver stopping automobiles which are most system briefly summarized also important basic performance purpose background these studies therefore many have been undertaken mentioned moreover a brief introduction from several points view all over world in three technical papers included this paper our former focused on is presented tire keywords simulation model optimum r d toyota crdl vol no chapter among stages finally outline research development field we studying fundamental subjects explained focusing following concepts purposes mainly categories addition safety here it should be noted that one transient properties key factors influencing activities developing software steady characteristics using magic either directly indirectly because plays an esse...

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