DE102005037479B4 - Vehicle dynamics control system for a two-lane motor vehicle - Google Patents

Abstract

Vehicle dynamics control system for a two-lane motor vehicle, the dynamic behavior with respect to a specification of the driver in at least two degrees of freedom by a number of degrees of freedom corresponding number of model-based controlled actuators, which determine the behavior of the vehicle with respect to these degrees of freedom, characterized in that in the activation of the actuators for the variably adjustable degrees of freedom, the transfer functions of a model-based precontrol are set independently of one another to different values, wherein the transfer functions include a factor describing the stationary behavior of the vehicle and a factor describing the dynamic transient behavior.

Description

The invention relates to a vehicle dynamics control system according to the preamble of claim 1. The prior art is, for example, on the DE 691 08 480 T2 referenced, in which a certain way is described to control the longitudinal dynamics and the lateral dynamics of a motor vehicle in dependence on each other. In particular, however, describes the DE 35 32 222 C2 a closest vehicle dynamics control system.

A variety of vehicle dynamics control systems are known, with which a targeted change in the driving dynamics of a two-lane motor vehicle, and in particular its transverse dynamics and yaw dynamics is possible. These control systems use different actuators or different intervention principles. Thus, a stabilizing yaw moment can be applied to the steered front wheels by providing an additional steering angle or the overall steering angle. But this is also possible by providing a steering angle to possibly slightly steerable wheels of the rear axle. It is possible to apply a stabilizing yawing moment but also by targeted distribution of the drive torque or the so-called. Drag torque of the vehicle drive unit between the left and right Fzg.-side both on the front and on the rear axle of the vehicle by means of suitable Kupplungsansteuerungen. Also by individual wheel modulation of the brake pressure at the individual wheels, a stabilizing yaw moment can be generated, as well as by modulation of the roll stiffness distribution between the front and rear axles, also by redistribution of transmitted over the wheels longitudinal forces of the vehicle drive unit between the front and rear axles.

In the known prior art, at least in terms of the lateral dynamics and yaw dynamics of the vehicle usually a control, ie, a target-actual comparison, wherein it is ensured that a predetermined by the driver steering request is implemented in a suitable manner. In the German Offenlegungsschrift DE 102 36 734 A1 Furthermore, a method is described for guiding a multi-lane vehicle on a curved path, which in the form of a pre-control of two input variables, namely the driver-specified steering angle and the current vehicle speed, actuates two actuators, namely one of the steerable (front) wheels of the vehicle steering actuator and any suitable actuator, with which the longitudinal force distribution between the Fzg. wheels of the two Fzg.seiten is designed differently.

In the DE 35 32 222 C2 a steering control system is described, which can read records of two or more (so-called) target vehicles, so that the driver can choose between different target vehicles as desired. This determines, taking into account the driver's steering input and the driving speed, a target value for the yaw dynamics and the lateral dynamics. For this purpose, a set of equations of motion for a vehicle model is solved using vehicle parameters (such as inertia yaw moment, wheel spacings, steering stiffness) that correspond to the setpoint values determined by the vehicle model, as predetermined by the target vehicle. The setpoint values of the vehicle parameters may be equal to the actual values of the vehicle parameters of the controlled vehicle; alternatively, the target vehicle may be different from the controlled vehicle type.

The present invention is a further improvement in terms of a feedforward control of the vehicle behavior to be shown (= task), although in the detailed embodiments analogous to the just mentioned prior art of a steering specification of the Fzg driver is assumed and therefore in particular the lateral dynamics and yaw dynamics of the vehicle is relevant, but the present invention is simply transferable to the other degrees of freedom of a two-lane motor vehicle, namely both on its longitudinal dynamics, as well as on the hub dynamics and / or the pitch dynamics and / or the rolling dynamics of Fzg. structure.

The solution to this problem arises with the features of claim 1; advantageous developments are content of the dependent claims.

According to the invention can (again based on the example of steering by the driver, ie based on a steering angle specification and the affected transverse dynamics and yaw dynamics of the vehicle) via at least two independent actuators (or control capabilities) at least in the linear range of dynamic vehicle behavior, the two Degrees of freedom of the lateral dynamics and the yaw dynamics of the motor vehicle via a (coordinated) pilot control can be set independently. Thus, if all the wheels of the vehicle are steerable, for example, be set in extreme cases that the vehicle on a steering input of the driver out no yaw, but at a slip angle of 0 ° only a transverse movement (of course, in addition to the longitudinal movement) performs. Of course, however, such extreme conditions are not shown; However, it should be possible to be able to represent different proportions of yawing and transverse movement within reasonable limits in the example, and independently. Should be doing the vehicle with the illustrated yaw and transverse motion no longer be movable along the desired curved path, the driver can adjust his steering specification accordingly.

With a proposed vehicle dynamics control system, therefore, virtually any behavior of the vehicle can be represented, in particular by the fact that for at least two (the possible) degrees of freedom independently different responses to a specification of the driver can be set, via different transmission functions of a model-based Pilot control, which will be discussed in more detail later. In the prior art, however, no methods for the control engineering design of a vehicle dynamics control are known, which describe a systematic design of a control system for implementing, for example, a desired lateral dynamics and a desired yaw dynamics of a vehicle by means of a precontrol. For the rest, it is not the aim of the control systems on the market (eg in the case of ESP or so-called active steering of the applicant) to set the lateral dynamics and yaw dynamics independently of each other. Due to existing in the prior art restrictions this is due to the present controller structures and the objectives pursued practically not possible.

Deviating from the already cited several examples of a different adjustment of the lateral dynamics and the yaw dynamics of a motor vehicle is in a generalization, the operation of a corresponding vehicle dynamics control system in the presence of suitable actuators basically transferable to all possible degrees of freedom of Fzg. Chassis. Thus, in addition to or alternatively to the lateral dynamics or yaw dynamics, the longitudinal dynamics of the vehicle as well as the stroke dynamics and / or the pitch dynamics and / or the roll dynamics of the vehicle body can be controlled accordingly. In principle, therefore, any combination of the six possible degrees of freedom of a motor vehicle can be controlled accordingly, by specifying a corresponding number of desired transmission functions (for these degrees of freedom).

These transfer functions (or desired transfer functions) as well as the fact that it is a model-based feedforward control, characterizing features of claim 1. In this case, the model-based feedforward can basically build on any models; Preferably, however, a so-called linear single-track model (known to the person skilled in the art) is used which, incidentally, may also be suitably extended, for example with regard to longitudinal dynamic influences or with regard to the dynamic lateral force structure and / or rolling dynamics of the vehicle. Moreover, the dynamic driving behavior of the vehicle (in particular with regard to lateral dynamics and yaw dynamics) not only in the linear range, but also limited in the so-called. Transition region for so-called tire saturation (the latter is the area in which despite increasing the wheel slip angle no further increase in Radseitenkraft can be achieved) by a linear Einspurmodell describe. However, it is primarily intended to be possible to set different values of the transfer functions for the linear range of the dynamic vehicle behavior.

A transfer function in the sense of the present explanation now describes the relationship between a variable predefined by the driver and the corresponding vehicle response thereto. So much simplified is the context Y = G _Y · X, where X is the default of the driver, ie, for example, a default steering angle, Y the behavior of the vehicle thereon, so for example, the yaw rate and / or the slip angle and / or Transverse acceleration, and G _Y the associated transfer function or transfer matrix or vector, according to the invention for at least two degrees of freedom, the transfer functions are adjustable to different values. (The sign "·" stands for a multiplication). In this case, the individual transmission functions preferably include a proportion or factor describing the stationary behavior of the vehicle and a proportion or factor describing the (dynamic) instationary behavior of the vehicle. The latter can be described by a system of equations in the manner of a vibration equation (or in other words by a vibration equation in a broader sense), as the characteristic quantities, at least in analogy to a vibration equation, inter alia, the vibration bandwidth or natural frequency, a damping factor and the Zero contains or may contain.

As regards the actuators, with which the behavior of the vehicle can be adjusted as desired, these may be all actuators or actuators, which will be described in connection with the explanation of the plurality of known vehicle dynamics control systems, the influence on the lateral dynamics and the yaw dynamics have already been mentioned. For influencing the roll dynamics, stroke dynamics and pitch dynamics, further actuators basically known to the person skilled in the art may be provided. In this case, the actuators are preferably also selected such that these actuators are approximately equally distributed over the two axles of the vehicle for influencing two or more degrees of freedom. Is it in the degrees of freedom to be influenced (again, as always exemplified) to the lateral dynamics and the yaw dynamics of Vehicle, it is advantageous to assume a first possibility of intervention on the front axle and a second possibility of engagement on the rear axle, in each case either via the steering and / or the drive and / or brakes in any combination. In principle, although two Verstelling opportunities on a (common) axis can be used, but this is unfavorable from a practical point of view, since at tire saturation on this axis the actuating efficiency of both actuators would be lost, while in the case of distribution on two axes in the case of saturation of an axis at least the Actuating the actuator remains on the other axis. Furthermore, as a rule, the actuators of one axle influence one another. While in the linear region of the vehicle behavior preferably steering and / or Rad longitudinal forces applying actuators are used, in the (already mentioned above) transition area due to a realization of a longitudinal force distribution between the front and rear axle and / or an influence of the Vertical dynamics of the vehicle and ultimately on intervention in the power output or torque output of Fzg. Drive unit possible.

The hereby proposed different transfer functions for at least two degrees of freedom can be specified automatically in the control system as a function of boundary conditions, in particular as a function of the driving speed and / or the steering angle predetermined by the driver. Alternatively or additionally, however, it is also possible for different transfer functions, which have an effect on at least two degrees of freedom, to be predeterminable by the driver, wherein the possibility of specifying any desired values does not seem favorable, but the possibility should exist of selecting among discrete values to meet.

Returning again to the preferred example case, namely that a desired yaw rate and / or a desired slip angle and / or a desired lateral acceleration or desired transmission functions (or desired transmission behavior) for the yaw rate (dynamic and / or stationary ) and should be specifiable for the slip angle (dynamic and / or stationary), theoretically, a variety of parameters can be freely specified. If, for example, as already stated above, the transfer functions include a portion describing the stationary behavior of the vehicle and a portion describing the (dynamic) instationary behavior of the vehicle, the latter being able to be described by an oscillation equation in the broadest sense, which can be described as quantities u. a. contains the vibration bandwidth and the natural frequency, a damping factor and the zeros, you get already for these two degrees of freedom using two independent actuators (namely, for example, for a front-wheel steering and for a rear-wheel steering) 16 parameters. In each case for the front axle actuator and for the rear axle actuator then fall in each case for both the yaw rate and for the float angle 4 parameters, namely in each case the so-called. Stationary part and the three mentioned instationary shares.

It is quite possible that a target driving behavior of the vehicle by means of physically interpretable controller with respect to bandwidth, damping, stationary behavior and zeros of the transfer functions between a steering angle specification of the driver and the slip angle and / or yaw rate of the vehicle can be adjusted, especially in the context the interpretation of a specific vehicle dynamics control system of a particular vehicle or vehicle type. For example, an applicator may well be provided with 16 knobs or the like for the 16 parameters mentioned in the previous paragraph, under the said physical interpretation.

However, it may well be that a free selectability for all parameters in reality is not feasible at all, because, for example, the respective actuator can not follow a corresponding specification, for example because its dynamics are insufficient (in terms of bandwidth or because of rate limitation) and / or because the required body energy is too high. Therefore, it is proposed to make the specification of the mentioned parameters relative to the passive driving behavior. This results in a simple intuitive parameterization, for example, if a specification in a percentage change to the behavior of a conventional, uncontrollable driving behavior of the vehicle can be made. If the requirement is moderate (eg 10% change), the respective actuator will not be overwhelmed.

In the context of this, therefore, the conventional driving behavior in the linear range and transition range can first be identified. In this case, either the data for the linear single-track model can be determined once by means of identification and from this the equivalent parameters or characteristic maps can be calculated which are required for the definition of the transfer functions. However, it is also possible to directly identify courses of these parameters over the driving speed (and / or over the predetermined steering angle and / or over the steering angle speed or the like) in driving tests. Subsequently, a desired dynamics can be set relative to these variables, wherein once again the possibility exists of making an adjustment, for example, to travel speed and / or steering angle specification and / or steering angle velocity (or as a function of these and / or other variables). The 16 parameters already mentioned above by way of example can then be interpreted as physical "rotary buttons" with which the desired behavior of the vehicle can be determined, preferably in relation (for example by% data) to the conventional vehicle (whose transmission functions are not are changeable). For a reduction in complexity, it may be useful to group together those parameters that describe the dynamic portion of the transfer functions, each in a "rotary knob", ie. H. Coming back to the already mentioned oscillation equations analogy only provide one knob for the bandwidth or for the damping or for the zeros.

A proposed vehicle dynamics control system is quite combinable or compatible with existing methods for longitudinal dynamics compensation, d. H. a compensation of the longitudinal dynamics influences on the lateral dynamics and the yaw dynamics is simultaneously possible when controlling at least two actuators. Furthermore, a combination with conventional driving stabilization regulations or yaw rate regulations is simply possible. Advantageously, an interpretation of the proposed feedforward control with different controller structures is possible, so for example. Via inverse model feedforward or 2DOF structure (= two degrees of freedom) or P / PID controller or a controlled pilot model, each stationary and / or dynamic. It is also possible to use compensation for the actuator dynamics via inverse models (linear, nonlinear) or other structures (controlled feedforward control, 2DOF structure, PID controller), if the actuator dynamics (for example with regard to bandwidth and setting rate) are not sufficiently fast, It should also be noted that quite a variety of details may deviate from the above explanations, without departing from the content of the claims.

Basically (based on the repeatedly mentioned preferred application) allows a proposed control system free design of the lateral dynamics and yaw dynamics of a vehicle in the linear range of driving behavior and limited in the transition region. The desired driving behavior can be adjusted by means of physically interpretable "buttons", for example, for bandwidth, attenuation, stationary behavior and zeros with respect to transmission behavior between steering specification by the driver and slip angle, yaw rate and / or lateral acceleration of the vehicle. In principle, any transverse dynamics and yaw dynamics (as a function of the actuator dynamics and setting rate limitations) can be impressed on the vehicle. A vehicle equipped with a system according to the invention can thus be impressed with the driving behavior of a (any) other (also virtual) vehicle (at least if there is sufficient actuator dynamics). By means of this function, a differentiation of the driving behavior can be carried out by using different parameterizations, in the simplest case in the form of a so-called driving dynamics switch. A free specification of the lateral dynamics and the yaw dynamics thereby causes a freely definable lateral and yaw behavior in the linear region and in the transition region of the tires, a forward-looking stabilization by precontrol, the avoidance of driver-induced vibrations, easier controllability of the vehicle by increasing the linear range and an increased stability reserve.

Claims (9)

Driving dynamics control system for a two-track vehicle whose dynamic behavior corresponding number of model-based controlled actuators which determine the behavior of the vehicle with respect to these degrees of freedom can be changed with respect to a specification of the driver in at least two degrees of freedom by the number of degrees of freedom, characterized, in that in the activation of the actuators for the variably adjustable degrees of freedom, the transfer functions of a model-based precontrol are set independently of one another to different values, wherein the transfer functions include a factor describing the stationary behavior of the vehicle and a factor describing the dynamic transient behavior. Vehicle dynamics control system according to claim 1, wherein different transfer functions for at least two degrees of freedom as a function of the driving speed and / or predetermined by the driver steering angle and / or the predetermined steering angle speed are specified. Vehicle dynamics control system according to claim 1 or 2, wherein the different transfer functions, which have an effect on at least two degrees of freedom, are specifiable by stating the ratio to the conventional, uncontrollable driving behavior of the vehicle. Vehicle dynamics control system according to one of the preceding claims, wherein the different representable vehicle reactions to a specification of the driver relate to the lateral dynamics and / or yaw dynamics and / or longitudinal dynamics of the vehicle. Vehicle dynamics control system according to one of the preceding claims, wherein the different representable vehicle responses to a specification of the driver affect the stroke dynamics and / or the pitch dynamics and / or the roll dynamics of the vehicle body. Vehicle dynamics control system according to one of the preceding claims, wherein the dynamic transient behavior describing factor of the transfer functions is described by a system of equations in the manner of a vibration equation, the or as sizes u. a. contains the bandwidth, a damping factor and the zero point. Vehicle dynamics control system according to claim 6, wherein a target driving behavior of the vehicle by means of physically interpretable controller with respect to bandwidth, damping, stationary behavior and zeros of the transfer function between a steering angle specification of the driver and the slip angle and / or the yaw rate and / or the lateral acceleration of the vehicle is adjustable , Vehicle dynamics control system according to one of the preceding claims, wherein one of the actuators on the front axle of the vehicle and another on the rear axle of the vehicle is effective. Vehicle dynamics control system according to one of the preceding claims, wherein actuators for adjusting wheel steering angles on the front axle and / or rear axle are provided and / or actuators for applying different longitudinal wheel forces on the two sides of an axle or the vehicle.