Abstract:
A method and a device for influencing the handling characteristics of a vehicle, by increasing the vehicle stability and hence increasing the driving comfort for the driver of the vehicle. This is done by activating at least two systems in the vehicle, which improve the handling characteristics and thus the vehicle stability. The activation of a system occurs in a specified sequence as a function of the activation and/or of the effect of the preceding systems on the handling characteristics achieved by the activation. The sequence provided for this purpose is the initial activation of a chassis system, followed by a steering system and finally by a brake system.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method and a device for coordinating the subsystem of a vehicle dynamics network system. The increasing complexity and the rising number of electronic systems in vehicles, which actively affect handling characteristics or vehicle stability, requires a controller network in order to achieve an optimal interaction of the individual electronic systems.  
       BACKGROUND INFORMATION  
       [0002]     European Patent no. 0 507 072 discusses a network system, which relays the instruction to execute the driver command in a hierarchical structure of an overall system from top to bottom. This results in a clear structure having elements independent of one another.  
         [0003]     German patent document no. 44 39 060 discusses a complex vehicle control system, which combines, for example, an antilock braking system (ABS) with a traction control system (TCS) and a yaw moment control (GMR) in a vehicle stability control (FSR). If an error occurs in this control system, then, if possible, only the affected component will be switched off.  
         [0004]     German patent document no. 41 40 270 discusses a method, in which, during braking and/or acceleration maneuvers, the suspension systems are operated in such a way that on every wheel unit the current normal force between tire and road surface, or the wheel load, is influenced in the direction of its highest possible value.  
         [0005]     German patent document no. 39 39 292 discusses a network control system comprising an active chassis control and an antilock braking system (ABS) and/or traction control system components (TCS), which, during the ABS or TCS control phases, always implement the damping force adjustments in such a way that wheel load fluctuations are minimal.  
       SUMMARY OF THE INVENTION  
       [0006]     The exemplary embodiment and/or exemplary method of the present invention is to a method or a device for influencing the handling characteristics of a vehicle. The influence is directed at increasing the vehicle stability while maintaining the driving comfort for the driver of the vehicle. This goal is achieved by activating at least two systems in the vehicle, which improve the handling characteristics and hence the vehicle stability. The activation of a system occurs in a specified sequence as a function of the activation and/or of the effect of the preceding systems on the handling characteristics achieved by the activation.  
         [0007]     The emphasis here is primarily on the stabilization of the handling characteristics. The sequence is established on the basis of the effects of the interventions of the systems on the handling characteristics. A further important aspect in the choice of the sequence of the activated systems is the perceptible driving comfort of the driver. Thus priority is given to the intervention of a system, in which the driver of the vehicle least notices the effect of the intervention on the handling characteristics, i.e. the stabilizing effect. For example, an additional steering intervention for stabilizing the vehicle, which is superimposed on the steering interventions on the part of the driver and produced by the activated steering system, is noticed more distinctly than an intervention of the chassis system (e.g. an adjustment of the hardness of the spring or damper). Furthermore, a driver senses a braking action and hence a change in the longitudinal movement of the vehicle more strongly than is the case in an additional steering intervention. With the activation of a chassis system, followed by a steering system and finally a brake system, this results in a prioritization of the activation, which provides the driver with an increased vehicle stability with a high driving comfort at a minimal loss of speed or an optimized braking deceleration performance. The advantage vis-à-vis available strategies for peaceful coexistence is the increase of the overall utility without giving up the basic idea of autonomous subsystems.  
         [0008]     In the exemplary embodiment and/or exemplary method of the present invention, the operating state of the activated system and/or the achievable effect on the handling characteristics are taken into account in the activation of the systems. This allows for a situation-dependent activation of the individual actuators of the system.  
         [0009]     The exemplary embodiment and/or exemplary method of the present invention ascertains a deviation between specifiable nominal handling characteristics and the current actual handling characteristics. The handling characteristics are influenced subsequently by the activation of the systems as a function of the ascertained deviation.  
         [0010]     In a further embodiment, the deviation between specified nominal handling characteristics, provided in particular as handling characteristics according to the driver command, and the current actual handling characteristics is ascertained by a stabilization variable, which represents the deviation. It is furthermore provided that a nominal yaw moment is assigned to the stabilization variable as a function of the stabilization variable. The activation of the systems can subsequently occur as a function of the ascertained nominal yaw moment.  
         [0011]     An advantage of the exemplary embodiment and/or exemplary method of the present invention lies in the fact that the activation of the systems reduces the ascertained deviation between nominal and actual handling characteristics to a minimum. An increase in vehicle stability can thereby be achieved. The functional activation of the systems in the specified sequence is arranged or configured to reduce the deviation to a minimum by the activation of a preceding system. The reduction of the deviation achieved in preceding systems is then taken into account in the activation of the subsequent systems.  
         [0012]     Checking the necessity of activating subsequent systems, which is performed following the implemented activation of a preceding system, also has an advantageous effect. Thus, if the deviation between the nominal and the actual handling characteristics has been sufficiently reduced by preceding systems, an activation of subsequent systems in the sequence may be omitted.  
         [0013]     For influencing handling characteristics, particularly vehicle stability, the exemplary embodiment and/or exemplary method of the present invention is arranged or configured to influence a force between the vehicle body and at least one wheel unit by activating a chassis system. For example, an advantageous adjustment of the spring and/or damping property of the chassis may be performed on this basis. The handling characteristics may be additionally influenced by activating the position of at least one steerable wheel of a steering system. As in the case of a chassis system and a steering system, an advantageous influence on the handling characteristics may also be exerted via the activation of a brake system. Thus the activation of the braking force of at least one wheel of the motor vehicle can have a favorable effect on the handling characteristics in that critical driving situations are detected and mitigated independently of the situation of the driver. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows the intake of the operating parameters of the systems within the vehicle controller network as well as the activation of the vehicle dynamics systems.  
         [0015]      FIG. 2  shows in a flow chart the processing of the deviation between nominal and actual handling characteristics and the influence of the vehicle dynamics systems on the handling characteristics.  
         [0016]      FIG. 3  shows the control sequence in the vehicle network system.  
         [0017]      FIG. 4  shows the algorithm for calculating the normal force intervention of a chassis system in the vehicle network.  
         [0018]      FIG. 5  shows the determination of the lateral force intervention of a steering system.  
         [0019]      FIG. 6  shows the determination of the longitudinal force intervention of a brake system. 
     
    
     DETAILED DESCRIPTION  
       [0020]      FIG. 1  shows an exemplary embodiment for influencing the handling characteristics of a motor vehicle, with special emphasis being placed on increasing the vehicle stability. In addition to the current actual yaw rate Ψ act  ( 160 ) from a yaw-rate sensor  110 , the performance quantities  170 ,  180 ,  190  of the existing systems, chassis control  120 , steering  130  and vehicle dynamics control  140 , are read in the control block  100 . From the ascertained or determined performance quantities ( 170 ,  180 ,  190 ), the nominal yaw rate In case of a deviation between the actual value  160  and the nominal value  210  of the yaw rate On the basis of these interventions, the roll inclination may be suppressed by stabilizing interventions  175  using a chassis system  120 , as can be implemented, for example, by an electronic active roll stabilizer (EAR) or an active body control (ABC). In addition, with the use of such a chassis component, the roll momentum distribution (e.g. the oversteering and understeering behavior) may be influenced.  
         [0021]     With the help of a steering system  130 , as featured in electronic active steering (EAS) or steer by wire (SbW) systems, in addition to the steering movements of the driver, steering interventions  185 , which result in an increase in the vehicle stability may be superimposed on the steering. In addition, with the activation of a vehicle dynamics control  140 , as is implemented by an electronic stability program (ESP), vehicle-stabilizing brake interventions  195  may be undertaken.  
         [0022]     In a block diagram,  FIG. 2  depicts the mode of operation in the ascertainment of the necessary control interventions for increasing the vehicle stability. By comparing a suitable actual value  200  with nominal value  210 , a system deviation  230  is ascertained in block  220 . System deviation  230 , for example, can be formed by a difference between the actual yaw rate Furthermore, however, a formation of the system deviation by comparing the actual sideslip angles with the nominal sideslip angles is conceivable as well. Based on system deviation  230  thus obtained, a nominal yaw moment M Z  ( 250 ) with regard to the vehicle&#39;s gravitational center is calculated in block  240  for the required stabilization of the handling characteristics. Nominal yaw moment M z  ( 250 ) thus ascertained from system deviation  230  is relayed as an actuating command to vehicle controller network  260 . From this vehicle controller network, chassis system  120 , steering system  130  and brake system  140  are activated in the specified sequence and as a function of their possible influence on the handling characteristics.  
         [0023]     The flow chart in  FIG. 3  shows the implementation of the activation of the control systems in the specified sequence and as a function of nominal yaw moment M z  ( 250 ). Based on the originally ascertained nominal yaw moment M z  ( 250 ), a modification is performed on nominal yaw moment  250  in block  300 , which is necessary due to a residue moment  360  of a preceding control intervention. In block  310 , current nominal yaw moment  302  thus ascertained is used as a function of current performance quantities  170  of the chassis to determine the intervention of chassis system  120  in the moment modification of the vehicle&#39;s gravitational center. In the process, the calculated chassis interventions are converted into actuating commands  175  for the chassis. The moment modification with regard to the vehicle&#39;s gravitational center produced by the intervention in chassis system  120  is subsequently determined in block  315  and is used in block  320  for modifying nominal yaw moment  302 .  
         [0024]     The residue yaw moment  322  thus produced is then used in block  330 , corresponding to the procedure in the activation of the chassis control, as a function of the current performance quantities of steering  180  for determining the intervention of steering system  130  in the moment modification of the vehicle&#39;s center of gravity. In the process, the calculated steering interventions are converted into actuating commands  185  for steering system  130 . The moment modification with regard to the vehicle&#39;s gravitational center produced by the intervention is then determined in block  335  and is used in block  340  for modifying residue yaw moment  322 . Residue yaw moment  342  thus produced is subsequently used in block  350 , corresponding to the procedure in the activation of the preceding vehicle controls, as a function of the current performance quantities ( 190 ) of the brake system for determining the intervention of brake system  140  in the moment modification of the vehicle&#39;s center of gravity. In the process, the calculated brake interventions are converted into actuating commands  185  for the brake system.  
         [0025]     The moment modification with regard to the vehicle&#39;s gravitational center produced by the intervention is then determined in block  355  and is used in block  360  for modifying residue yaw moment  342 . If it is established in the process that following the brake intervention there is still a remaining residue moment  362 , then this can be used via a model correction  365  to perform an additive correction of the moment balance in block  300 . Using nominal yaw moment  302  thus updated, the activation of the control systems can be run through anew.  
         [0026]     The calculation and the verification of the chassis interventions is represented in the flow chart of  FIG. 4 . These interventions can be used to produce modifications of the normal forces that act from the wheels perpendicularly to the ground below. In the present exemplary embodiment, the modification of the normal forces at the wheels of the vehicle is used to bring about a modification of the nominal yaw moment M z  ( 302 ) with regard to the gravitational center. For calculating the required normal force interventions, a controller algorithm is used in block  400 . For activating the individual actuators of chassis system  120 , the actuating reserves  430  of the normal forces at the actuators as well as the current operating state of the actuators of the chassis are taken into account. In this manner, for example, the situation can be prevented that an actuator is activated which has no road adhesion and which hence cannot effect a modification of the normal force. Furthermore, the failure of an actuator can be taken into account in the activation. Via an inverse vehicle model in block  400 , the required nominal actuating variables  405  are ascertained from the intervention selection made and are transferred to the control unit of chassis system  120 .  
         [0027]     As feedback of the chassis system, the actual actuating variables  415  of the actuators are queried in block  420 . Together with the general operating state variables of the components and a chassis model, these actual actuating variables  415  are converted into a normal force distribution. This distribution is used to determine the actuating reserves of normal forces  430 . Finally, in block  440 , the moment modification with regard to the vehicle&#39;s gravitational center through the chassis interventions is estimated with the help of the vehicle geometry. The reduction of the yaw moment thereby ascertained is subtracted from nominal yaw moment  302  and yields residue yaw moment  322 .  
         [0028]     Following the procedure in ascertaining the interventions of the chassis control for modifying the yaw moment in  FIG. 4 , the flow chart of  FIG. 5  shows the calculation and the verification of the steering interventions of steering system  130 . In the present exemplary embodiment, the modification of residue yaw moment  322  with regard to the gravitational center is brought about by a modification of the lateral forces on the steerable wheels. For calculating the required lateral force interventions, a controller algorithm is used in block  500 . For activating steering system  130 , actuating reserves  530  of the lateral forces on the wheels are taken into account as well as the current operating state of the wheels.  
         [0029]     In this manner, for example, the situation can be prevented that a wheel is activated which has no road adhesion and which hence cannot effect a modification of the lateral force. Via an inverse vehicle model, the required nominal steering angles  505  of the wheels are calculated and transferred to steering system  130 . As feedback of the steering system, the actual steering angles  515  of the wheels are queried in block  520 . Together with a tire model, actuating reserves  530  for modifying the lateral forces are ascertained from these actual steering angles  515 . Finally, in block  540 , the moment modification with regard to the vehicle&#39;s gravitational center through the steering interventions is estimated with the help of the vehicle geometry. The reduction of the yaw moment thus ascertained is subtracted from residual yaw moment  322 , thereby yielding the new, updated residual yaw moment  342 .  
         [0030]     As already shown in the chassis interventions in  FIG. 4  and the steering interventions in  FIG. 5 ,  FIG. 6  shows a flow chart describing the calculation, control and verification of the brake interventions. In the present exemplary embodiment, the modification of residue yaw moment  342  with regard to the gravitational center is brought about by a modification of the longitudinal force on the vehicle. For calculating the required longitudinal force interventions, a controller algorithm is used in block  600 . For activating the individual actuators of brake system  140 , actuating reserves  630  of the longitudinal forces on the wheel brakes of the vehicle as well as the current operating state of the brake system are taken into account. In this manner, for example, the situation can be prevented that a brake activation by the vehicle controller network counteracts another brake activation.  
         [0031]     The ascertained brake interventions are transferred to the control unit of brake system  140  via an inverse vehicle model as required nominal variables  605  on the wheels. As feedback of brake system  140 , actual slip variables  615  are queried in block  620 . Together with the general operating state variables of the brake system and a chassis model, these actual slip variables  615  are converted into a longitudinal force distribution. This distribution can be used to determine actuating reserves  630  of the longitudinal forces. Finally, in block  640 , the moment modification with regard to the vehicle&#39;s gravitational center through the brake interventions is estimated with the help of the vehicle geometry. The thus ascertained reduction of the yaw moment is subtracted from residue yaw moment  342  and yields a possibly remaining residual moment  362 .