DE102006033632B4 - Method for controlling or controlling at least one driving state variable of a vehicle - Google Patents

Abstract

Method for controlling or controlling at least one driving state variable of a vehicle, in which a setpoint value is determined, from which a setpoint value for at least one actuator in the vehicle for changing the current setting is determined, wherein the setpoint value is composed of a stationary setpoint component and a dynamic setpoint component, wherein the stationary setpoint component in a stationary mathematical vehicle model and the dynamic setpoint component in a dynamic mathematical vehicle model is determined, characterized in that in the dynamic vehicle model a feedback of the dynamic setpoint component is performed by comparing the dynamic with the stationary setpoint component and the deviation Input variable for the dynamic vehicle model is determined.

Description

State of the art

The invention relates to a method for controlling or controlling at least one driving state variable of a vehicle according to the preamble of claim 1.

In "ATZ Automobiltechnische Zeitschrift 96", 1994, pages 674-689 describes a driving dynamics control method for motor vehicles, which takes into account both the vehicle longitudinal dynamics and the lateral dynamics, in order to ensure the driving stability in border areas. To influence the lateral dynamics, a yaw rate control is carried out, in which, based on the driver's request, in particular the steering angle, a desired yaw rate is determined, which is compared with the measured yaw rate and based on the regulation. The yaw rate controller hereby provides the yaw moment required for the vehicle transverse guidance, which is implemented by means of the actuators in the vehicle, in particular by targeted braking interventions on individual wheels in the vehicle.

The current driving state also flows into the calculation of the setpoint values by using current vehicle motion variables, for example the lateral acceleration, for the setpoint formation. As a result, the setpoint generation forms an additional closed control loop, which is no longer separated from the actual control. This approach leads to an increased application effort because the number of setting parameters is very high and a variety of complex interactions occur in the components of the regulator.

The generic DE 198 59 966 A1 relates to a device for stabilizing a vehicle. For this purpose, the device contains first determination means with which at least two vehicle movement variables which describe the vehicle movement, in particular in the vehicle transverse direction, are determined. Furthermore, the device contains second determination means with which a characteristic variable is determined for each of the vehicle movement variables. In this case, the second determination means contain adaptation means with which the time profiles of the characteristic variables are adapted to the vehicle behavior. In addition, the device contains control means with which, at least as a function of the vehicle movement variables and the characteristic variables, intervention variables are determined which supply the actuator means for carrying out at least brake interventions and / or engine interventions with which the vehicle is stabilized.

Disclosure of the invention

The invention has for its object to calculate the setpoints for the control or control of a driving state variable in a vehicle in a simple manner and with little effort.

In the method according to the invention for controlling or controlling at least one driving state variable of a vehicle, a setpoint value is determined, which is composed of a stationary setpoint component and a dynamic setpoint component. The steady-state setpoint component is determined in a stationary mathematical vehicle model and the dynamic setpoint component in a dynamic mathematical vehicle model. In this way, the setpoint specification can be performed separately from the control or the control, whereby the application cost for the implementation of the setpoint determination is significantly reduced. Interactions with the actual control or control are avoided, as well as the number of parameters to be set is reduced.

In the mathematical replacement or vehicle model, which is based on the setpoint formation, stationary or dynamic components of the setpoint are determined, wherein in the dynamic vehicle model also a return of the dynamic setpoint share is performed by comparing the dynamic with the stationary setpoint share and off the deviation of an input variable for the dynamic vehicle model is determined. This feedback has additional advantages, since influencing the agility and the damping can already be taken in the setpoint formation via only a few parameters.

With the method according to the invention, setpoint values for all motion-relevant system variables can be determined. Here, a dynamic consistency of the setpoints is guaranteed, and indeed for all driving maneuvers and all driving situations. Compared to prior art embodiments, the application effort is reduced, since due to the separate setpoint specification no mixing with the control or control takes place. The setpoint calculation takes place independently of the control or control to be subsequently performed.

As a desired driver size, which is used as the basis for determining the desired value, for example, the steering angle, the brake pedal position, the accelerator pedal position and / or the vehicle longitudinal speed comes into consideration. Based on these preselected by the driver sizes that are supplied to both the stationary and the dynamic vehicle model, corresponding setpoint components are formed, which in another Process step to dynamic and stationary setpoint components are processed, which are assembled to the final setpoint size. Taking into account the dynamic setpoint share, this is done in such a way that the driver's desired size is initially supplied to both the stationary and the dynamic vehicle model, where in each case a corresponding setpoint value is determined. The dynamic setpoint component is compared in a feedback with the previously determined stationary setpoint component, wherein the deviation is supplied as a control deviation to a controller in which a control output is calculated, which in turn is supplied to the dynamic vehicle model. In this way, the stability of the vehicle is already considered in the calculation of the setpoint.

The method can be used both in regulations and in controls of driving state variables in vehicles. It can be considered both the vehicle lateral dynamics and the driving dynamics in the method of control or regulation as well as a combination of vehicle longitudinal and vehicle transverse dynamics.

list of figures

• 1 ein Blockschaltbild mit der Darstellung der Sollwertermittlung unter Berücksichtigung von stationären und dynamischen Sollwertanteilen,
• 2 Kurvenverläufe für die Querbeschleunigung, die Gierrate und den Schwimmwinkel, jeweils dargestellt für ein lineares und ein erweitertes stationäres Modell,
• 3 Kurvenverläufe für die Querbeschleunigung, die Gierrate und den Schwimmwinkel als Funktion eines vorgegebenen Lenkwinkelverlaufs (oberes Schaubild), jeweils dargestellt für ein erweitertes stationäres Modell, für ein dynamisches Modell und für ein erweitertes dynamisches Modell,
• 4 Kurvenverläufe für die Querbeschleunigung, die Gierrate und den Schwimmwinkel, jeweils als Reaktion auf einen vorgegebenen Lenkwinkelverlauf (oberes Schaubild), dargestellt für ein erweitertes stationäres Modell, für ein dynamisches lineares Modell und für ein dynamisches Modell mit Rückführung.

Further advantages and embodiments can be found in the further claims, the description of the figures and the drawings. Show it:

• 1 a block diagram with the presentation of the setpoint determination taking into account stationary and dynamic setpoint components,
• 2 Curves for the lateral acceleration, the yaw rate and the slip angle, respectively shown for a linear and an extended stationary model,
• 3 Curves for lateral acceleration, yaw rate and slip angle as a function of a given steering angle progression (upper graph), respectively, shown for an extended stationary model, for a dynamic model and for an extended dynamic model,
• 4 Curves for the lateral acceleration, the yaw rate and the slip angle, respectively in response to a given steering angle curve (upper diagram), shown for an extended stationary model, for a dynamic linear model and for a dynamic model with feedback.

Embodiment (s) of the invention

• Einschlag der vorderen Räder δ_F ,
• Fahrzeugmasse m,
• Fahrzeugträgheitsmoment um die Hochachse J,
• Fahrzeuglängsgeschwindigkeit ν_x ,
• Fahrzeugquergeschwindigkeit ν_y ,
• Schwimmwinkel β,
• Fahrzeugquerbeschleunigung α_y ,
• Fahrzeuggiergeschwindigkeit ψ̇,
• Querkraft an der Vorderachse F_F ,
• Normalkraft an der Vorderachse F_zF ,
• Querkraft an der Hinterachse F_R ,
• Normalkraft an der Vorderachse F_zR ,
• Schräglaufwinkel der vorderen Räder α_F ,
• Schräglaufwinkel der hinteren Räder α_R ,
• Steifigkeit der Vorderachse c_F ,
• Steifigkeit der Hinterachse c_R ,
• Abstand zwischen der Vorderachse und dem Fahrzeugschwerpunkt l_F ,
• Abstand zwischen der Hinterachse und dem Fahrzeugschwerpunkt l_R ,
• Moment um die Hochachse M_z .

The following symbols are used in the following description and in the claims:

• Impact of the front wheels δ _F .
• Vehicle mass m,
• Vehicle moment of inertia about the vertical axis J .
• Vehicle longitudinal speed ν _x .
• Vehicle lateral velocity ν _y .
• float angle β .
• Vehicle lateral acceleration α _y .
• Vehicle yaw rate ψ̇,
• Lateral force on the front axle F _F .
• Normal force at the front axle F _zF .
• Lateral force on the rear axle F _R .
• Normal force at the front axle F _zR .
• Slip angle of the front wheels α _F .
• Slip angle of the rear wheels α _R .
• Stiffness of the front axle c _f .
• Stiffness of the rear axle c _R .
• Distance between the front axle and the center of gravity of the vehicle l _F .
• Distance between the rear axle and the center of gravity of the vehicle l _R .
• Moment around the vertical axis M _z ,

In the following, an embodiment will be described with reference to FIG 1 illustrated block diagram explained.

The in 1 with dashed line framed part of the blocks 2 . 3 and 4 includes, represents the actual setpoint calculation taking into account a steady state and a dynamic share, wherein the determined setpoint variables of the vehicle movement of a subsequent control or regulation are supplied to the desired setting of the vehicle. In this embodiment, the setpoint formation is independent and clearly separated from the control or regulation.

The reference value is model-based by a driver's request, such as the steering angle, the pedal travel of the brake and / or accelerator pedal, the currently engaged gear or other variables to be influenced by the driver are supplied to the setpoint block as input variables, both the block 2 with the stationary, mathematical vehicle model as well as the block 3 with the dynamic, mathematical vehicle model. Both in the block 2 as well as in the block 3 appropriate stationary or dynamic setpoint components are determined, wherein the dynamic portion of the setpoint is subtracted from the stationary portion. The result obtained control deviation is a controller 4 supplied, which is exemplified as a PID controller, wherein the calculated controlled variable as input again the dynamic vehicle model 3 is supplied. In this way, the dynamic reference value is determined in a closed loop and stabilized using the stationary model. The final setpoint includes both steady state and dynamic components and is fed to the subsequent controller. By selecting the controller parameters, setpoint generation can be set specifically.

According to the prior art, a quasi-static, linear reference model is used for the setpoint generation of the vehicle stability controller. The starting point is, for example, a linear single-track model: $$\left[\begin{array}{c}{\dot{\nu }}_y\\ \ddot{\psi }\end{array}\right]=\left[\begin{array}{cc}-\frac{c_F+c_R}{m{\nu }_x}& \frac{c_R{l}_R-c_F{l}_F}{m{\nu }_x}-{\nu }_x\\ \frac{c_R{l}_R-c_F{l}_F}{J{\nu }_x}& -\frac{c_R{l}_R^2-c_F{l}_F^2}{J{\nu }_x}\end{array}\right]\left[\begin{array}{c}{\nu }_y\\ \dot{\psi }\end{array}\right]+\left[\begin{array}{c}\frac{c_F}{m}\\ \frac{c_F{l}_F}{J}\end{array}\right]{\delta }_F,$$

$${\nu }_y{}_0=-\frac{m{\nu }_x^3{c}_F{l}_F-{\nu }_x{c}_F{c}_R\left(l_R^2+l_F{l}_R\right)}{m{\nu }_x^2\left(c_R{l}_R-c_F{l}_F\right)+c_F{c}_R{\left(l_F+l_R\right)}^2}{\delta }_F.$$

The differential equation system ( 1 ) dissolved after the rest positions and leads to $${\dot{\psi }}_0=\frac{{\nu }_x{c}_F{c}_R\left(l_F+l_R\right)}{m{\nu }_x^2\left(c_R{l}_R-c_F{l}_F\right)+c_F{c}_R{\left(l_F+l_R\right)}^2}{\delta }_F.$$

$${\nu }_y{}_0=-\frac{m{\nu }_x^3{c}_F{l}_F-{\nu }_x{c}_F{c}_R\left(l_R^2+l_F{l}_R\right)}{m{\nu }_x^2\left(c_R{l}_R-c_F{l}_F\right)+c_F{c}_R{\left(l_F+l_R\right)}^2}{\delta }_F,$$

Equation (2) corresponds to the Ackermann equation and is used for the setpoint calculation.

definiert.If one considers that the derivative of the lateral velocity ν̇ _{y is} equal to zero in stationary cornering, then the lateral acceleration is α _y by $${\alpha }_y={\nu }_x{\dot{\psi }}_0.$$

Are defined.

The setpoint values for the motion quantities ψ̇, ν _y . α _y can thus directly from the steering request of the driver δ _F and the vehicle's longitudinal speed ν _x be calculated using equations (2) to (4). Usually, the desired value for the lateral acceleration to the maximum physically possible size α _y ≤μg is limited. This results in the equation (4) also a limitation for the yaw rate: $$\dot{\psi }\le \frac{\mu G}{{\nu }_x},$$

Exemplary curves of the setpoints ψ̇, ν _y . α _y for a constant steering angle δ _F and increasing longitudinal speed ν _x are in 2 shown by solid lines.

Calculating the target values for the vehicle movement alone stationary, has several disadvantages. The vehicle dynamics, ie the differences in the phase position of the individual variables in a dynamic driving maneuver, can not be taken into account. The limitation of the lateral acceleration α _y can be transferred to the yaw rate ψ̇, but remains the default of the cross-speed ν _y or the slip angle β untouched. This leads to the increased set values for the transverse movement.

$$\frac{d\dot{\psi }}{dt}=\frac{1}{J}\left(F_F\left({\alpha }_F\right)l_F-F_R\left({\alpha }_R\right)l_R\right),$$

$${\alpha }_R=\frac{\dot{\psi }{l}_R-{\nu }_y}{{\nu }_x},$$

$${\alpha }_F=\frac{\dot{\psi }{l}_F+{\nu }_y}{{\nu }_x}+{\delta }_F.$$

In order to be consistent with physical constraints, an extended model is proposed. It is also based on the single-track model: $$\frac{d{\nu }_y}{dt}=\frac{1}{m}\left(F_F\left({\alpha }_F\right)+F_R\left({\alpha }_R\right)\right)-{\nu }_x\dot{\psi }.$$

$$\frac{d\dot{\psi }}{dt}=\frac{1}{J}\left(F_F\left({\alpha }_F\right)l_F-F_R\left({\alpha }_R\right)l_R\right).$$

$${\alpha }_R=\frac{\dot{\psi }{l}_R-{\nu }_y}{{\nu }_x}.$$

$${\alpha }_F=\frac{\dot{\psi }{l}_F+{\nu }_y}{{\nu }_x}+{\delta }_F,$$

In this case, a linear tire behavior on the rear axle is assumed: $$F_R\left({\alpha }_R\right)=c_R{\alpha }_R,$$

As a result, a behavior of the reference model which is stable in the vehicle technical sense is ensured.

wobei F_zF die Aufstandskraft der Vorderachse und µ der aktuellen Reibwert bedeutet.In order to realize the limitations of the relevant kinematic variables, it is proposed to extend the linear behavior of the front axle by a force saturation: $$F_F\left({\alpha }_F\right)=\{\begin{array}{cc}{c}_F{\alpha }_F.& \mu F_{zF}>c_F{\alpha }_F\\ \mu F_{zF}.& \mu F_{zF}\le c_F{\alpha }_F\end{array}.$$

in which F _zF the Aufstandskraft the front axle and μ the current coefficient of friction means.

The procedure is not limited to the two featured forms of functions F _F ( α _F ) F _R ( α _R ). Other functions are also conceivable and more detailed models can be used, but this increases the computational effort.

$${\nu }_y{}_0=-\frac{m{\nu }_x^3{c}_F{l}_F-{\nu }_x{c}_F{c}_R\left(l_R^2+l_F{l}_R\right)}{m{\nu }_x^2\left(c_R{l}_R-c_F{l}_F\right)+c_F{c}_R{\left(l_F+l_R\right)}^2}{\delta }_F.$$

und für den gesättigten Bereich $${\dot{\psi }}_0=\mu F_{zF}\frac{l_F+l_R}{m{\nu }_x{l}_R},$$

$${\nu }_y{}_0=\mu F_{zF}\left(\frac{l_F+l_R}{m{\nu }_x}-\frac{{\nu }_x{l}_F}{c_R{l}_R}\right).$$

Solving equations (6) through (10) for the rest positions provides for the linear workspace $${\dot{\psi }}_0=\frac{{\nu }_x{c}_F{c}_R\left(l_F+l_R\right)}{m{\nu }_x^2\left(c_R{l}_R-c_F{l}_F\right)+c_F{c}_R{\left(l_F+l_R\right)}^2}{\delta }_F.$$

$${\nu }_y{}_0=-\frac{m{\nu }_x^3{c}_F{l}_F-{\nu }_x{c}_F{c}_R\left(l_R^2+l_F{l}_R\right)}{m{\nu }_x^2\left(c_R{l}_R-c_F{l}_F\right)+c_F{c}_R{\left(l_F+l_R\right)}^2}{\delta }_F,$$

and for the saturated area $${\dot{\psi }}_0=\mu F_{zF}\frac{l_F+l_R}{m{\nu }_x{l}_R}.$$

$${\nu }_y{}_0=\mu F_{zF}\left(\frac{l_F+l_R}{m{\nu }_x}-\frac{{\nu }_x{l}_F}{c_R{l}_R}\right),$$

Exemplary curves of the setpoints for a constant steering angle and increasing longitudinal speed ν _x are in 2 represented by dashed lines. It stands to reason that the extended model gives the same results for the lateral acceleration α _y as well as for the yaw rate ψ̇ delivers like the limited linear model. The advantage of the extension, however, is that now the slip angle β is consistent with the other sizes α _y , ψ̇ is restricted.

In order to include the momentum of the vehicle in the setpoint generation, the dynamic model (equations (6) to (11)) is used. In 3 The setpoints for a dynamic driving maneuver formed according to different concepts are shown. In this driving maneuver, the vehicle's longitudinal speed ν _x constant, the steering is similar to the Fishhook maneuver.

The dash-dotted lines correspond to calculations according to the extended stationary model (equations (14), (15)), the dashed lines represent the setpoint specifications by hand dynamic model (equation (1)), and the solid lines show the results of the extended dynamic model (Equations (6) to (11)). It can be seen that the extended dynamic model is capable of determining the physical phase shifts of the kinematic quantities ψ̇, ν _y . α _y as well as the corresponding limitations. However, it has insufficiently damped behavior in critical driving areas.

$$\frac{d\dot{\psi }}{dt}=\frac{1}{J}\left(F_F\left({\alpha }_F\right)l_F-F_R\left({\alpha }_R\right)l_R+M_z\right).$$

Therefore, it is proposed to set both a static and a stationary model as well as a dynamic model for the setpoint formation. In 1 the block diagram of the reference model is shown. To the damping of the dynamic model 3 In critical driving situations, a return is used. Thereby the behavior becomes with the stationary model 2 adjusted and through the regulator 4 fed back. By way of example, this can be done by extending the dynamic model (equations (6) to (11)) with an additional input. This can, for example, the yaw moment around the vehicle's vertical axis M _z his. The differential equations (6), (7) lead in this case $$\frac{d{\nu }_y}{dt}=\frac{1}{m}\left(F_F\left({\alpha }_F\right)+F_R\left({\alpha }_R\right)\right)-{\nu }_x\dot{\psi }.$$

$$\frac{d\dot{\psi }}{dt}=\frac{1}{J}\left(F_F\left({\alpha }_F\right)l_F-F_R\left({\alpha }_R\right)l_R+M_z\right),$$

As a feedback variable, the yaw rate ψ̇ is conceivable since it has the highest vibrations. As a controller, for example, a simple P-controller can be used.

By changing the controller parameters, the setpoint generation can be set specifically. For example, by increasing the controller parameters, more agility and more muted drivability can be achieved.

The driver's request for a deceleration or acceleration can be derived, for example, from the brake or accelerator pedal position and the engaged gear ratio. Based on this information, the model parameters F _zR . F _zR . c _f . c _R be adjusted accordingly.

Exemplary curves of the setpoints ψ̇, ν _y . α _y are in 4 shown. The dotted lines correspond to the extended stationary model calculations (equations (14), (15)), dashed lines represent the dynamic linear model set point specification (equation (1)), and solid lines show the results of the proposed method according to the block diagram after 1 , It is the well-damped behavior, the phasing consistency and the smooth transitions in the borderline clearly visible.

The model-based method is suitable for the realization of any driving dynamics for motor vehicles, e.g. ESP, Active Front Steering, Active Rear Steering, Active Suspension.

Claims (8)

Method for controlling or controlling at least one driving state variable of a vehicle, in which a setpoint value is determined, from which a setpoint value for at least one actuator in the vehicle for changing the current setting is determined, wherein the setpoint value is composed of a stationary setpoint component and a dynamic setpoint component, wherein the stationary setpoint component in a stationary mathematical vehicle model and the dynamic setpoint component in a dynamic mathematical vehicle model is determined, characterized in that in the dynamic vehicle model a feedback of the dynamic setpoint component is performed by comparing the dynamic with the stationary setpoint component and the deviation Input variable for the dynamic vehicle model is determined. Method according to Claim 1 , characterized in that the setpoint specification is performed separately from the control or control. Method according to Claim 1 , characterized in that the deviation of a control, in particular a PID control is subjected. Method according to one of Claims 1 to 3 , characterized in that the determination of the desired value is based on a driver's desired size, which is supplied to both the stationary and the dynamic vehicle model. Method according to Claim 4 , characterized in that the driver's desired size of the steering angle, the brake pedal position, the accelerator pedal position and / or the vehicle longitudinal speed. Method according to one of Claims 1 to 5 , characterized in that setpoint values for the yaw rate, the vehicle lateral velocity and / or the lateral acceleration are determined. Method according to one of Claims 1 to 6 , characterized in that trajectories for the target values are twice continuously differentiable. Control or regulating device for carrying out the method according to one of Claims 1 to 7 ,

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