CN105752079B

CN105752079B - Method for operating a motor vehicle

Info

Publication number: CN105752079B
Application number: CN201511018676.4A
Authority: CN
Inventors: G.庞格拉茨; D.科瓦克
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2015-01-02
Filing date: 2015-12-31
Publication date: 2020-12-18
Anticipated expiration: 2035-12-31
Also published as: CN105752079A; DE102015200002A1

Abstract

The invention relates to a method for operating a motor vehicle, wherein a drive and/or a brake and/or a steering of the motor vehicle are controlled and/or regulated as a function of an operating state of the motor vehicle. According to the invention, the longitudinal acceleration and the lateral acceleration of the motor vehicle are determined, wherein a combined acceleration variable of the motor vehicle is determined using the determined longitudinal acceleration and the determined lateral acceleration, and wherein the combined acceleration variable is compared to a predeterminable threshold value. If the predeterminable threshold value is exceeded, the drive and/or the brake and/or the steering of the motor vehicle can be controlled in such a way that the vehicle speed can be reduced at least temporarily.

Description

Method for operating a motor vehicle

Technical Field

The invention relates to a method for operating a motor vehicle and to a control device and/or a regulating device.

Background

Motor vehicles are known from the market, in which the operation of a drive can be influenced by means of a control device. In this way, certain critical driving situations can be reliably controlled if necessary without intervention by the driver and accidents are thereby avoided.

Disclosure of Invention

The problem on which the invention is based is solved by the method according to the invention and by the control device and/or the regulating device according to the invention. Advantageous refinements include: acquiring the combined acceleration variable when the float angle or the steering angle of the motor vehicle is used; determining the float angle of the motor vehicle from the steering angle using a constant factor; the constant factor is approximately 0.5; acquiring the combined acceleration variable when the rotational acceleration of the motor vehicle is used; predetermining the threshold value as a function of the position of at least one operating element of the motor vehicle; presetting the threshold value according to the maximum allowable lateral acceleration; the method is only performed when the steering angle is not equal to zero; the threshold value is predefined as a function of the position of the accelerator pedal and/or the brake pedal. The features which are essential for the invention are also described in the following description and the drawings, where the features can be essential for the invention not only in their individual form but also in various combinations, without this having to be specified again in detail.

The invention relates to a method for operating a motor vehicle, wherein a drive and/or a brake and/or a steering of the motor vehicle are controlled and/or regulated as a function of an operating state of the motor vehicle. According to the invention, the longitudinal acceleration and the lateral acceleration of the motor vehicle are determined, wherein the combined acceleration variable of the motor vehicle is determined using the determined longitudinal acceleration and the determined lateral acceleration. Furthermore, the combined acceleration variable is compared with a predefinable threshold value. If the predeterminable threshold value is exceeded, the drive and/or the brake and/or the steering of the motor vehicle are controlled in such a way that the vehicle speed can be reduced at least temporarily.

As already described above, the method according to the invention additionally also takes into account the lateral acceleration for determining the driving situation of the motor vehicle. This makes it possible in particular to improve the sensitivity of the fault detection during a steady curve drive. The "tolerance" can likewise be increased in this way if the driving situation is unstable. The method according to the invention furthermore has the advantage that it is less or not at all associated with a so-called "moment of inertia", which characterizes the rotating mass of the motor vehicle. In particular, this relates to the rotating element of the drive and the wheel of the motor vehicle. Furthermore, the method according to the invention has the advantage that: undesired interventions can be substantially avoided when the motor vehicle is traveling straight, i.e. when the steering angle (or steering wheel angle) has at least approximately the value zero.

For example, the combined acceleration variable can be characterized in a simplified manner by "absolute acceleration" according to the following equation (1):

a _ abs = a _ l ä ngs cos (beta) + a _ quer sin (beta) (1), wherein,

a _ abs = absolute acceleration of the vehicle;

a _ l ä ngs = longitudinal acceleration of the vehicle;

a _ quer = lateral acceleration of the vehicle; and is

Beta = floating angle of the motor vehicle, as it is explained in further detail below.

Preferably, the variables a _ abs, a _ l ä ngs and a _ quer each correspond to the value of the vector on which these variables are based.

In particular, the safety of the motor vehicle can be improved by means of the invention when the motor vehicle is driving in a curve and at the same time a comparatively high lateral acceleration is present, which corresponds, for example, to two thirds of the lateral acceleration possible on the respective circular lane.

Even when the motor vehicle is subjected to an undesired acceleration, for example as a result of a device failure ("hardware failure") in the control and/or regulating device of the motor vehicle or as a result of a program failure ("software failure") of a computer program running in the control and/or regulating device, the method according to the invention can detect the resulting driving situation and intervene if necessary, and in this case in particular suddenly and strongly throttle or even shut down the drive.

Particularly critical driving situations may be obtained on a driving lane with a comparatively low friction factor, for example with approximately μ_RCoefficient of friction of = 0.3. According to the invention, even at relatively high lateral accelerations, the prevention of one or more driven wheels slipping (Durchdrehen) can be achieved and the vehicle can thus also remain on the driving lane without driver intervention. This improves the safety of the motor vehicle.

In particular, according to the invention, it can be provided that the combined acceleration variable is determined using the float angle or steering angle of the motor vehicle. The steering angle () is the angle between the longitudinal axis of the motor vehicle and the axis which characterizes the steering deflection (Lenkausschlag) of the steerable wheels, in particular the front wheels. By means of the steering angle, a particularly simple and nevertheless relatively accurate knowledge of the combined acceleration variable is possible.

In one embodiment of the method, the float angle of the motor vehicle is determined from the steering angle using a constant factor. The floating angle (beta) is the angle between the direction of motion of the motor vehicle at the center of gravity and the longitudinal axis of the motor vehicle. For example, the constant coefficient is 0.5 and the following equation (2) is used accordingly:

ß = 0.5 * (2)。

by means of this equation, the float angle can be determined from the steering angle in an approximate manner that can be used for the invention. This saves effort and costs.

In addition, it can be provided that the combined acceleration variable is determined when the rotational acceleration of the motor vehicle is used. Preferably, the combined acceleration variable is formed as a sum which is composed of the absolute acceleration and the rotational acceleration which are characterized by equation (1). It is also preferred that in this said sum the rotational acceleration is characterized by its value (betrg). The accuracy of the method according to the invention can be further improved by the supplementary application of the rotational acceleration.

In a further embodiment of the method, the threshold value is predefined as a function of the position of at least one operating element of the motor vehicle, in particular as a function of the position of the accelerator pedal and/or the brake pedal (to which the combined acceleration variable is compared). This makes it possible to adapt the method to the respective driving situation particularly precisely and thus to improve the driving stability of the motor vehicle. Alternatively or additionally, the threshold value is predefined as a function of the maximum permissible lateral acceleration. The accuracy of the method according to the invention can thereby be further improved.

In a further embodiment of the method, the method is only carried out if the steering angle is not equal to zero. This effectively prevents the method according to the invention from possibly performing undesired interventions on the operation of the drive when the motor vehicle is moving straight, as a result of which the safety can be further improved.

The invention further relates to a control and/or regulating device for a motor vehicle, wherein the control and/or regulating device is designed to carry out a method for operating the motor vehicle as described above with the aid of various embodiments.

Drawings

Exemplary embodiments of the present invention are explained below with reference to the drawings. In the drawings:

fig. 1 shows a simplified representation for a motor vehicle in a first driving situation in which driving is performed in a constant curve;

fig. 2 shows a view for a motor vehicle according to the one-way lane model in a second driving situation; and

fig. 3 shows a flow chart for a method for operating a motor vehicle.

In all the figures, the same reference numerals are used for functionally equivalent elements and variables, even in the case of different embodiments.

Detailed Description

Fig. 1 shows a simplified illustration of a motor vehicle 10 which is constantly in a round curve (always to the left or counterclockwise). For this purpose, a circular lane 12 is illustrated in fig. 1. The center of gravity 14 of the motor vehicle 10 is shown in the vehicle center of the motor vehicle 10. The motor vehicle 10 comprises a control and/or regulating device 15 ("control unit"), which is symbolically shown in fig. 1 by a rectangle. The control and/or regulating device 15 can in particular control and/or regulate the drive device 17 and/or the brake device 19 and/or the steering device 21 as a function of the operating state of the motor vehicle 10, which devices are likewise symbolically illustrated by means of a rectangle in fig. 1.

In addition, three acceleration vectors are shown in fig. 1. The vector for the longitudinal acceleration of the motor vehicle 10 (formula symbol "a _ l ä ngs") is shown by arrow 16. The vector for the lateral acceleration of the motor vehicle 10 (formula symbol "a _ quer") is shown by arrow 18. The longitudinal acceleration is defined in the direction of a longitudinal axis 23 of the motor vehicle 10 and the lateral acceleration is defined in the direction of a lateral axis (no reference numeral) of the motor vehicle 10 orthogonal to the longitudinal axis. Accordingly, the longitudinal acceleration and the lateral acceleration have a right angle to each other.

The longitudinal acceleration and the transverse acceleration are detected during operation of the motor vehicle 10, preferably continuously. The vector for the absolute acceleration ("a _ abs") of the motor vehicle 10, which is known when longitudinal and lateral accelerations are applied, is indicated by the arrow 20. Preferably, the longitudinal acceleration, the lateral acceleration and the absolute acceleration are known with respect to the center of gravity 14.

Furthermore, there is an angle between the vector for longitudinal acceleration and the vector for absolute acceleration, which angle is referred to below as the floating angle beta. The floating angle beta is the angle between the direction of motion of the motor vehicle 10 at the center of gravity 14, defined by the direction of the vector 20 for the absolute acceleration, and the longitudinal axis 23 of the motor vehicle 10. In the case of high lateral accelerations, the float angle β is also taken as a measure for the controllability of the motor vehicle 10.

It is noted that some of these parameters are shown exaggerated in fig. 1 (for greater clarity and understanding). In particular, the floating angle beta is generally significantly smaller than that shown in fig. 1.

The relationship between the longitudinal acceleration a _ l ä ngs, the lateral acceleration a _ quer and the absolute acceleration a _ abs of the motor vehicle 10 can be explained with the use of the floating angle beta β as follows, using equation (1):

a_abs = a_längs * cos(ß) + a_quer * sin(ß) (1)。

the parameter "a _ abs" of equation (1) corresponds to the value of the absolute acceleration a _ abs. In the ideal case-and according to equation (1) -the absolute acceleration a _ abs corresponds to the diagonal of a rectangle spanned by the longitudinal acceleration and the lateral acceleration. This rectangle is illustrated in fig. 1 by a dashed edge (no reference numeral).

The absolute acceleration described by equation (1) corresponds to a simplified "combined acceleration variable" which is currently known, i.e., using the known longitudinal acceleration and the known transverse acceleration. The combined acceleration variable may additionally comprise a rotational acceleration, as will be explained in more detail further below with the aid of equation (4).

Fig. 2 shows a so-called "one-way lane model" of a motor vehicle 10 which is currently in a situation deviating from the driving situation of fig. 1. In particular, fig. 2 characterizes a so-called "understeer" of the motor vehicle 10. In this case, the motor vehicle 10 is also driven substantially on a circular curve (all the way to the left or counterclockwise).

The one-way lane model of fig. 2 includes a steerable front wheel 22, a non-steerable rear wheel 24, and a center of gravity 26 existing between the front wheel 22 and the rear wheel 24. The wheel contact point (aufstanddspunkt) of the front wheel 22, which essentially characterizes the contact surface between the wheel and the driving lane, the wheel contact point and the center of gravity 26 of the rear wheel 24 are located on the longitudinal axis 28 of the current one-way lane model.

The circular arrow 30 shown in the plane of the drawing of fig. 2 around the center of gravity 26 characterizes the yaw rate of the motor vehicle 10

. A steering angle exists between the longitudinal axis 28 and an axis 32 that is indicative of steering misalignment of the front wheels 22. Double arrow 34 represents the spacing (defined in the direction of longitudinal axis 28) between center of gravity 26 and the wheel contact point of front wheel 22. Double arrow 36 represents the spacing (also defined in the direction of longitudinal axis 28) between center of gravity 26 and the wheel contact point of rear wheel 24.

Furthermore, a vector characterizing the direction of movement of the motor vehicle 10 is shown on the center of gravity 26 by means of an arrow 38. A floating angle beta is present between this vector and the longitudinal axis 28 of the motor vehicle 10. Since fig. 1 and 2 each represent different driving situations, the components of the float angle beta in fig. 1 are directed radially inward and radially outward in fig. 2 for the circular lane 12.

On the left in fig. 2, a virtual center point 40 of the circular travel of the motor vehicle 10 is shown. Starting from the center point 40, a connecting

line

42, 44 or 46 is shown to the wheel contact point of the front wheel 22 or to the wheel contact point of the rear wheel 24 or to the center of gravity 26.

In order to follow the equations required for the method according to the invention (in particular in the case of the lateral acceleration a _ quer) in a simple manner and to be able to achieve an effective relationship between steering angle and float angle beta known in the motor vehicle 10 by means of sensors, a simplified solution described by means of the following equation (2) is implemented:

ß = 0.5 * (2)。

the combined acceleration variable mentioned above can thus be determined using the floating angle beta or using the steering angle. For this purpose, the steering angle is preferably used, since the steering angle is particularly simple to know. As also shown in equation (2), the float angle β is determined from the steering angle using a constant factor (which is preferably approximately 0.5).

Although equation (2) is only a relatively rough approximation with respect to the driving dynamics, equation (2) enables relatively accurate results for acceleration-based monitoring of the circular curve of the motor vehicle 10. The accuracy of the model characterized by said equations (1) and (2) can be further improved by supplementing parameters and/or variables, if necessary. For example, the deflection speeds described above can be used in addition

(also referred to as "yaw rate") is used for the model and/or parameters characterizing the chassis of the motor vehicle 10 to which the one-way lane model according to fig. 2 can be additionally applied.

The absolute acceleration a _ abs of the motor vehicle 10 can be described by the equation (3) by combining the equations (1) and (2) as follows:

a_abs = a_längs * cos(/2) + a_quer * sin(/2) (3)。

since, as already explained above, equation (2) is only an approximation and since the steering angle is known in principle independently of the longitudinal acceleration a _ l ä ngs and the transverse acceleration a _ quer, it is entirely possible in the actual operation of the motor vehicle 10 that the absolute acceleration a _ abs or the arrow 20 (see fig. 1) known in this way does not correspond exactly to the diagonal of the rectangle shown in fig. 1. However, the function of the method according to the invention is not impaired thereby.

The "acceleration-based monitoring" already mentioned further above can be realized in particular by: during a curve run, an undesired acceleration of the motor vehicle 10 is detected, so that appropriate countermeasures can then be implemented. Such an undesired acceleration can occur, for example, as a result of a malfunction of a device ("hardware malfunction") in the control device and/or the regulating device 15 or as a result of a malfunction of a program ("software malfunction") of a computer program running in the control device and/or the regulating device 15.

Preferably, the absolute acceleration a _ abs known by means of equation (3) is corrected in dependence on the rotational acceleration a _ rot. The rotational acceleration a _ rot is preferably known about the center of

gravity

14 or 26. A sum is currently formed which is composed of the value of the absolute acceleration and the value of the rotational acceleration. The absolute acceleration a _ abs corrected in this way corresponds to the combined acceleration variable described above, which is then compared with a predefinable threshold value. The predeterminable threshold value corresponds to the maximum permissible acceleration a _ zul _ max. The comparison is characterized by the following equation (4):

a_zul_max < a_abs + a_rot (4)。

the parameters "a _ abs" and "a _ rot" of equation (4) are the numerical values of the vector as the basis, respectively. The variable "a _ zul _ max" corresponds to the predeterminable threshold value and is a scalar.

The described acceleration-based monitoring of the motor vehicle 10 can be carried out by applying equation (4), as will be explained in more detail below with reference to fig. 3. As long as the condition characterized by equation (4) is satisfied, an undesired acceleration of the motor vehicle 10 and thus a malfunction, in particular a possible device malfunction or a possible program malfunction in the control device and/or the regulating device 15, can be inferred therefrom. A corresponding measure can be implemented in that the drive device 17 and/or the brake device 19 are preferably controlled in such a way that the vehicle speed of the motor vehicle 10 is at least temporarily reduced. The steering device 21 can also be controlled in order to improve the vehicle stability if necessary.

In the simplest case, the drive 17 (i.e., for example, an internal combustion engine not shown in any more detail in the figures) can be throttled (gedrosselt) in the shortest possible time or even switched off if necessary. The wheels of the motor vehicle 10 may additionally be braked individually or in their entirety.

For example, the driving situation of the motor vehicle 10 as described below can be successfully controlled in this way:

assuming a driving lane with a so-called "low friction factor", for example with a substantially mu_RCoefficient of friction of = 0.3.

First, the motor vehicle 10 is driven with two thirds of the maximum possible lateral acceleration on the respective circular lane 12. The maximum possible lateral acceleration is characterized in that the motor vehicle 10 is just still in the lane. The speed v _ fzg and the steering angle of the motor vehicle 10 are constant. The lateral acceleration a _ quer is constant and the longitudinal acceleration a _ l ä ngs is substantially zero.

A fault (optionally generated manually for testing purposes) then occurs in the drive 17 or in the accelerator pedal sensor or in the control device and/or the regulating device 15, as a result of which a very large or even the maximum possible drive torque is generated in the drive 17.

As a result, undesired slipping of the drive wheels of the motor vehicle 10 occurs and thus, without countermeasures, leaving the selected driving lane on the circular lane 12 occurs. If the rear wheels 24 are driven, an oversteer of the vehicle 10 occurs as an additional result (Ü bersuern).

As soon as a fault is detected according to equation (4) above, the drive device 17 can be throttled strongly or even switched off in the shortest possible time by means of the control device and/or the regulating device 15, with the aim of maintaining the motor vehicle 10 substantially on the selected driving lane on the circular lane 12 without measures being pushed by the driver, in particular without steering the steering wheel.

Fig. 3 shows a representation of a method for operating the motor vehicle 10, in particular a representation of an acceleration-based monitoring of the motor vehicle 10, with the aid of a block diagram.

The combined acceleration variable of absolute acceleration and rotational acceleration is determined in block 50 from equation (4) above. Currently, this is done by means of a sum that is made up of the value of the absolute acceleration a _ abs and the value of the rotational acceleration a _ rot. A comparison between the combined acceleration variable determined in this way and the maximum permissible acceleration a _ zul _ max is then also carried out using equation (4). The maximum permissible acceleration a _ zul _ max corresponds to the predeterminable threshold value.

The block shown to the left or below block 50 in fig. 3 knows the input variables for the comparison described in block 50. In block 52, the driver expectation may be known, for example, from the position of the accelerator pedal and/or the position of the brake pedal. In particular, in block 52, the predeterminable threshold value or the maximum permissible acceleration a _ zul _ max is predetermined as a function of the position of at least one operating element of the motor vehicle 10, in particular as a function of the position of the accelerator pedal and/or the brake pedal.

Alternatively, the threshold value or the maximum permissible acceleration a _ zul _ max can be predefined independently of the position of the accelerator pedal or the position of the brake pedal. The maximum permissible acceleration a _ zul _ max can be predefined, for example, as a function of the maximum permissible lateral acceleration. The parameters known in this way in block 52 are passed to block 50.

In block 54 (preferably in the case of a longitudinal acceleration sensor), the longitudinal acceleration a _ l ä ngs is detected. In block 56 (preferably in the case of a lateral acceleration sensor) the lateral acceleration a _ quer is known. The longitudinal acceleration a _ l ä ngs and the lateral acceleration a _ quer are both then passed to block 58. The absolute acceleration a _ abs is known in block 58 from equation (3) above. For this purpose, the steering angle is known in block 60 and is likewise passed to block 58. In block 58, the float angle beta of the motor vehicle 10 is determined from the steering angle using equation (2).

The absolute acceleration a _ abs known in block 58 is then passed to block 50, which has already been described. In addition, in block 62, the rotational acceleration a _ rot or the rotational acceleration component a _ rot is determined. The results of the learning in block 62 are also communicated to block 50. In block 50, all input variables for carrying out the comparison characterized by equation (4) are thus present.

In block 50, the combined acceleration variable is compared with the predeterminable threshold value, for which purpose the above-mentioned equation (4) is referred to. Based on the results learned in block 50, a fault response is made in the following block 64, if necessary. In particular, if the predeterminable threshold value a _ zul _ max is exceeded, the drive 17 and/or the brake 19 and/or the steering 21 of the motor vehicle 10 can be controlled in such a way that the vehicle speed of the motor vehicle 10 can be reduced at least temporarily.

In particular, a strong throttling or even a shutdown of the drive 17, i.e. for example of the internal combustion engine, can be carried out as a fault response. In this way, a stable holding of the motor vehicle 10 in the circular lane 12 on its driving lane can be achieved.

Preferably, the method described by fig. 3 is carried out in the control device and/or the regulating device 15. In one embodiment of the method, the method is only carried out if the steering angle is not equal to zero. This makes it possible to avoid possible undesired responses of the method when the motor vehicle 10 is traveling straight.

Claims

1. Method for operating a motor vehicle (10), wherein a drive (17) and/or a brake (19) and/or a steering (21) of the motor vehicle (10) are controlled and/or regulated as a function of an operating state of the motor vehicle (10), characterized in that a longitudinal acceleration (a _ l ä ngs) and a transverse acceleration (a _ quer) of the motor vehicle (10) are determined, and a combined acceleration variable of the motor vehicle (10) is determined using the determined longitudinal acceleration (a _ l ä ngs) and the determined transverse acceleration (a _ quer), and the combined acceleration variable is compared with a predeterminable threshold value (a _ zul _ max), and the drive (17) and/or the brake (19) and/or the steering (21) of the motor vehicle (10) are controlled when the predeterminable threshold value (a _ zul _ max) is exceeded in the following manner 21) I.e. to reduce the vehicle speed at least temporarily.

2. Method according to claim 1, characterized in that the combined acceleration parameter is known using the floating angle (β) of the motor vehicle (10).

3. Method according to claim 1, characterized in that the combined acceleration variable is determined using a steering angle () of the motor vehicle (10).

4. A method according to claim 3, characterized in that the float angle (β) of the motor vehicle (10) is known from the steering angle () with a constant coefficient applied.

5. The method of claim 4, wherein the constant factor is 0.5.

6. Method according to any one of the preceding claims 1 to 3, characterized in that the combined acceleration variable is determined using a rotational acceleration (a _ rot) of the motor vehicle (10).

7. Method according to any one of the preceding claims 1 to 3, characterized in that the threshold value (a _ zul _ max) is predefined as a function of the position of at least one operating element of the motor vehicle (10).

8. Method according to any of the preceding claims 1 to 3, characterized in that the threshold value (a _ zul _ max) is predefined as a function of the maximum permissible lateral acceleration (a _ quer).

9. A method according to claim 3, characterized in that the method is only performed when the steering angle () is not equal to zero.

10. Method according to claim 7, characterized in that the threshold value (a _ zul _ max) is predefined as a function of the position of the accelerator pedal and/or the brake pedal.

11. Control and/or regulating device (15) for a motor vehicle (10), characterized in that the control and/or regulating device (15) is configured for carrying out the method according to one of the preceding claims.