DE102019200537A1 - Method for operating a motor vehicle and motor vehicle - Google Patents

Abstract

In a method for operating a motor vehicle (1), a variable that is characteristic of a current driving situation is used to determine whether there is a stable driving situation by checking whether the size meets a criterion. If a stable driving situation is recognized, values of a number of vehicle model sizes (L, Vc) are determined by means of an estimate, a stored vehicle model which contains the vehicle model sizes is updated by the current values of the vehicle model sizes (L, Vc) and the updated vehicle model for trajectory control of a driver assistance system (8). The following are selected as sizes:
a steering angle of a front axle and / or a rear axle, a steering speed of the front axle and / or rear axle, a yaw rate (ψ̇), a driving speed (V) of the motor vehicle (1), a yaw acceleration, a derivative of the lateral acceleration, a derivative of a vertical acceleration, one Absolute deviation between the lateral acceleration and the product of the yaw rate (ψ̇) and driving speed (V), a longitudinal acceleration, which each exceed and / or fall below a threshold value, as well as the steering angle of the front axle, the lateral acceleration and the yaw rate (ψ̇) have the same signs , a state of stability control systems is inactive and / or a signal which is characteristic of the presence of precipitation has a value which is characteristic of the absence of precipitation.

Description

The invention relates to a method for operating a motor vehicle. Furthermore, the invention relates to a motor vehicle which is in particular set up to carry out the method according to the invention.

Modern motor vehicles regularly have driver assistance systems which are intended to support a driver of the motor vehicle, for example by relieving the driver or carrying out interventions which an average driver can hardly or not at all. The latter category includes, for example, anti-lock braking systems, vehicle dynamics controls and the like. The aforementioned categories also include the aforementioned systems, lane keeping assistants, etc., possibly in combination with an (at least partially autonomous) automatic driving system. Such driver assistance systems regularly calculate the steering or other interventions for the desired trajectory (i.e. the desired travel route) on the basis of a virtual (mathematical) vehicle model which contains chassis parameters such as wheel base or yaw gain of the motor vehicle as the vehicle model sizes. This applies to both manual and automated driving. The chassis parameters reflect the state of construction of the vehicle with the intended tire model and without (or at least with a standardized) load.

As is known, the chassis parameters differ from model to model, so that each vehicle model has its own vehicle model, i. H. an assigned data record must be created. Standardized test drives are usually carried out for this purpose. However, any actual change to the motor vehicle (e.g. higher payload, different tires, aging and the like) usually also leads to a change in the values of the vehicle model, so that calculations based on the factory values can become inaccurate.

The invention is based on the object of enabling more precise parameterization for driver assistance systems.

This object is achieved according to the invention by a method for operating the motor vehicle with the features of claim 1. In addition, this object is achieved according to the invention by a motor vehicle with the features of claim 10. Further advantageous and partly inventive embodiments and developments of the invention are in the Subclaims and the description below.

The method according to the invention is used for the preferably automated (in particular autonomous) operation of a motor vehicle. The motor vehicle (according to the invention) has a chassis with at least one front wheel and with at least one rear wheel.

• ◦ einen insbesondere absoluten (d. h. insbesondere mittels eines spezifisch zugeordneten Sensors erfassten) Lenkwinkel einer Vorderachse und/oder einer Hinterachse, der geringer und/oder größer ist als ein Schwellwert,
• ◦ eine vorzugsweise absolute Lenkgeschwindigkeit der Vorderachse und/oder der Hinterachse, die geringer als ein Schwellwert ist,
• ◦ eine vorzugsweise absolute Gierrate (auch als „Giergeschwindigkeit“ bezeichnet), die geringer als ein Schwellwert ist,
• ◦ eine Fahrgeschwindigkeit des Kraftfahrzeugs, die geringer und/oder größer als ein Schwellwert und/oder konstant ist,
• ◦ eine insbesondere absolute Gierbeschleunigung, die geringer als ein Schwellwert ist,
• ◦ eine Ableitung der insbesondere absoluten Querbeschleunigung, die geringer als ein Schwellwert ist,
• ◦ eine Ableitung einer insbesondere absoluten Vertikalbeschleunigung, die geringer als ein Schwellwert ist,
• ◦ eine absolute Abweichung zwischen der Querbeschleunigung und dem Produkt aus Gierrate und Fahrgeschwindigkeit, die nicht größer als ein Schwellwert ist,
• ◦ der Lenkwinkel der Vorderachse, die Querbeschleunigung und die Gierrate weisen gleiche Vorzeichen auf,
• ◦ ein Zustand von vorzugsweise allen vorhandenen Stabilitätsregelungssystemen ist inaktiv,
• ◦ ein Signal, das für Vorliegen von Niederschlag charakteristisch ist, weist einen für fehlenden Niederschlag charakteristischen Wert auf, und
• ◦ eine vorzugsweise absolute Längsbeschleunigung, die geringer als ein Schwellwert ist.

According to the method, it is determined on the basis of at least one variable that is characteristic of a current driving situation whether the current driving situation is a stable, ie in particular stationary, driving situation. For this purpose, it is checked whether the respective size fulfills a predefined criterion assigned to the respective size. If a stable driving situation is recognized, current (actual) values of a number of vehicle model sizes are then determined using an estimate. A preset, preferably factory-specified vehicle model, which contains the vehicle model sizes, is then updated by the current values of the vehicle model size or the possibly several vehicle model sizes. This updated vehicle model is used (in particular during further driving) for trajectory control of a driver assistance system. The at least one size and the respective assigned criterion (for recognizing the current driving situation) are selected from a group comprising:

• Insbesondere a steering angle of a front axle and / or a rear axle which is in particular absolute (ie in particular detected by means of a specifically assigned sensor) and which is less and / or greater than a threshold value,
• Vorzugsweise a preferably absolute steering speed of the front axle and / or the rear axle, which is less than a threshold value,
• Vorzugsweise a preferably absolute yaw rate (also referred to as “yaw rate”), which is lower than a threshold value,
• A driving speed of the motor vehicle which is lower and / or higher than a threshold value and / or constant,
• Insbesondere a particular absolute yaw acceleration that is less than a threshold value,
• ◦ a derivation of the particular absolute lateral acceleration, which is less than a threshold value,
• ◦ a derivation of an in particular absolute vertical acceleration that is less than a threshold value,
• ◦ an absolute deviation between the lateral acceleration and the product of yaw rate and driving speed, which is not greater than a threshold value,
• Lenk the steering angle of the front axle, the lateral acceleration and the yaw rate have the same signs,
• Zustand a state of preferably all existing stability control systems is inactive,
• ◦ a signal which is characteristic of the presence of precipitation has a value which is characteristic of the absence of precipitation, and
• ◦ a preferably absolute longitudinal acceleration, which is less than a threshold value.

For the most reliable detection of the stable driving situation, several of the above-mentioned variables are expediently monitored for compliance with the respectively assigned criterion. It is also preferably monitored whether the lateral acceleration is less than an assigned threshold value.

In other words, while the motor vehicle is in operation in suitable driving situations (namely the stable driving situations identified on the basis of the above criteria), the vehicle model currently stored, specifically its vehicle model sizes - at least relevant model sizes therefrom - are updated (“updated”). This can change from ride to ride. or model sizes that change over the service life of the motor vehicle are kept up to date and thus the most precise possible trajectory control and / or other steering and / or braking interventions are carried out as precisely as possible. A wheelbase that has changed due to the load, properties of the chassis that have changed due to aging (e.g. damper behavior and the like) or similar influences can be continuously taken into account. The use of stable driving situations is advantageous because changes in driving behavior (sudden steering movements, brake interventions and the like), which can influence the current geometry of the chassis, can only be expected with a comparatively low probability.

An output signal from a rain sensor and / or a camera is used, for example, as a signal that indicates the presence of precipitation. Additionally or alternatively, it is also considered whether at least the windshield wiper is active (over a longer period than is required to clean the windshield).

The driving speed is determined, for example, on the basis of satellite-based location information and / or wheel speeds or the like.

To determine the yaw rate, the various accelerations and the steering angle, preferably assigned sensors (for example, rotation sensors, acceleration sensors, angle sensors and the like) are used.

Optionally, the variables described above for the detection of the stable driving situation are filtered in order, for example, to ignore signal noise in the detection.

In an expedient method variant, an additional criterion for the stable driving situation is that the size or the respective size continuously fulfills the respectively assigned criterion over a predetermined period of time (for example 2 to 5 seconds). This simplifies a comparatively reliable detection of the stability of the current driving situation.

In a preferred variant of the method, stationary cornering is used in particular as a stable driving situation. This is advantageous in that many vehicle models contain the yaw rate, steering angle or at least related parameters. As can be seen, these can be measured comparatively easily when cornering. As an alternative or in addition, stationary driving straight ahead is used as a stable driving situation.

For the detection of stationary cornering, the parameters and criteria used are in particular that the particular absolute steering angle of the front axle and / or the rear axle is lower and / or greater than a threshold value, and the particular absolute steering speed of the front axle and / or the rear axle is lower than a threshold value which, in particular, absolute lateral acceleration is less than a threshold, which, in particular, absolute yaw rate is less than a threshold, the driving speed is lower and / or greater than a threshold, which, in particular, absolute yaw acceleration is less than a threshold, the derivation of the particular absolute lateral acceleration is less than a threshold value, the derivation of the particular absolute vertical acceleration is less than a threshold value, the absolute deviation between the lateral acceleration and the product of yaw rate and vehicle speed is not greater than a threshold value, the V the steering angle of the front axle, lateral acceleration and yaw rate are the same, no stabilization control systems are engaged and / or no precipitation (i.e. H. especially no rain or snow) is detected.

For the detection of stationary straight-ahead driving, the following are used as parameters and criteria in particular that the driving speed does not change, ie is constant, the absolute driving speed, in particular, is lower and / or greater than a threshold value, the absolute value in particular Steering angle of the front axle and / or rear axle is less and / or greater than a threshold value, the absolute steering speed of the front axle and / or the rear axle is less than a threshold value, the absolute lateral acceleration in particular is less than a threshold value, the absolute longitudinal acceleration in particular is less than is a threshold value and / or the absolute yaw rate in particular is lower than a threshold value.

In a further expedient method variant, an agilizing intervention by chassis control systems is prevented during the estimation of the current values of the vehicle model sizes. In other words, a suspension ban is issued for these chassis control systems. This can advantageously prevent a short-term influencing of the driving situation or the values to be determined which falsifies the determination of the current values. In this case, the estimation is therefore not only performed passively, but actively, requiring a reduction in the interventions of the chassis control systems.

As an estimate of the current values of the vehicle model sizes, in a preferred method variant, a difference between a preset (for example, factory-set or determined from a previous determination) setpoint of the yaw rate and a current, preferably measured, actual value of the yaw rate is minimized. In a simple variant, an equation is derived from a vehicle model, preferably the so-called single-track model, which contains the yaw rate and the vehicle model size to be updated, and then replaces the stored target value of the yaw rate with the current actual value. The updated value of the vehicle model size to be updated can then be read out. Optionally, an actual minimization is carried out in such a way that the target value of the yaw rate is gradually adjusted to the current actual value in order to keep jumps between the stored and the current values of the vehicle model sizes within a predetermined range.

wobei L den Radstand, V die Fahrgeschwindigkeit, δv den Lenkwinkel der Vorderachse, öh den Lenkwinkel der Hinterachse und ψ̇ die Gierrate bezeichnet.In a preferred variant of the method, an actual value of a wheelbase between the front axle and the rear axle is determined based on the (current) yaw rate as the vehicle model size, in particular during a stationary cornering. The following formula, derived from the single-track model, is preferably used: $$L=\frac{V\cdot \left(\delta v-\delta H\right)}{\psi }$$

where L denotes the wheelbase, V the driving speed, δv the steering angle of the front axle, öh the steering angle of the rear axle and ψ̇ the yaw rate.

In an alternative or optionally additional method variant, the actual value of the wheelbase is determined during a stationary straight-ahead drive. In particular, a time interval between a vertical excitation of the wheels of the front axle and the rear axle and the current driving speed are used. E.g. When stationary straight-ahead driving, at which the driving speed is preferably below a predetermined threshold value, driving over a bump, a pothole or the like is used as a vertical excitation. The detection of this vertical excitation is based in particular on the signals (or in particular time derivatives thereof) from travel sensors on the respective wheels or axles, wheel speed sensors and / or vertical acceleration sensors on the axles, on the basis of a pitch rate (or its derivation) of the vehicle, based on a Roll rate (or its derivative) of the vehicle, based on the air pressure in an air spring of the chassis and / or based on a hydraulic pressure in a damper system of the chassis. In particular, a pattern for one axle is detected in the corresponding signal (which is assigned to the front axle or a front wheel, for example) and a check is carried out to determine whether a sufficiently similar pattern (e.g. the same deflection of a vertical acceleration) is also used for the other (in particular the rear one) Axis can be detected. If this is the case, the spatial distance, which is then set equal to the wheelbase, is determined on the basis of the time interval between the corresponding signal patterns (also referred to as “excitation profile”) between the front and rear axles and the current driving speed. This is a comparatively simple procedure for determining the wheelbase that is independent of the single-track model or other vehicle models.

wobei Vc die charakteristische Geschwindigkeit bezeichnet.In a further variant of the method, a characteristic speed is determined as a (further) vehicle model size on the basis of the yaw rate (in particular determined by measurement technology) and the actual value of the wheelbase (determined in one of the above ways). The following formula, derived from the single-track model, is preferably used: $$Vc=\raisebox{1ex}{$V$}\!\left/ \!\raisebox{-1ex}{$\sqrt{\frac{V\cdot \left(\delta v-\delta H\right)}{\mathrm{\psi }\cdot L}}$}\right.$$

where Vc denotes the characteristic speed.

wobei GV die stationäre Gierverstärkung bezeichnet. Die maximale Gierverstärkung tritt dabei regelmäßig - zumindest bei einem untersteuernd ausgelegten Kraftfahrzeug - bei der charakteristischen Geschwindigkeit auf. In an optional development of the invention, a (in particular stationary) yaw gain is determined on the basis of the characteristic speed as (again another) vehicle model size. The relationship between the (stationary) yaw rate and the stationary steering wheel angle is described as a (stationary) yaw gain. The following formula, preferably derived from the single-track model, is used in particular to determine the yaw gain: $$GV=\frac{V}{L\cdot \left(1+\frac{V^{\mathrm{2nd}}}{V{c}^{\mathrm{2nd}}}\right)}$$

where GV is the stationary yaw gain. The maximum yaw gain occurs regularly - at least in the case of an understeering motor vehicle - at the characteristic speed.

The motor vehicle according to the invention has the chassis, which has at least one front wheel (preferably two front wheels) and the at least one rear wheel (preferably two rear wheels, so that in particular a two-lane motor vehicle is present), and a vehicle controller. The vehicle controller is set up to carry out the method described above preferably automatically.

In a preferred embodiment, the vehicle controller is at least essentially formed by a microcontroller with a processor and a data memory, in which the functionality for carrying out the method according to the invention is implemented in terms of programming in the form of operating software (firmware), so that the method - possibly in interaction with one Vehicle user - automatically executed when the operating software is executed in the microcontroller. In the context of the invention, the controller can alternatively also be provided by a non-programmable electronic component, e.g. a user-specific, integrated circuit (also briefly: “ASIC”) can be formed, in which the functionality for implementing the method according to the invention is implemented using circuitry means.

The conjunction “and / or” is to be understood here and in the following in particular in such a way that the features and quantities linked by means of this conjunction can be formed or used both together and as alternatives to one another.

• 1 in einer schematischen Seitenansicht ein Kraftfahrzeug mit einem Fahrzeugcontroller, und
• 2 in einem schematischen Ablaufdiagramm ein von dem Fahrzeugcontroller durchgeführtes Verfahren zum Betrieb des Kraftfahrzeugs.

An exemplary embodiment of the invention is explained in more detail below with reference to a drawing. In it show:

• 1 in a schematic side view of a motor vehicle with a vehicle controller, and
• 2nd In a schematic flowchart, a method carried out by the vehicle controller for operating the motor vehicle.

Corresponding parts and sizes are always provided with the same reference symbols in all figures.

In 1 is schematically a motor vehicle 1 shown. The car 1 has a chassis (not shown). The chassis includes two front wheels 2nd and two rear wheels 4th so that there is a two-lane vehicle. Also includes the motor vehicle 1 a vehicle controller 6 . In this is a driver assistance system 8th , which is set up for autonomous driving. The driver assistance system 8th this is based on a mathematical vehicle model that contains several vehicle model sizes. In the vehicle controller 6 is also a module 10th implemented, which is set up to estimate current values (“actual values”) of two vehicle model sizes. The vehicle controller 6 is set up to carry out a method described in more detail below, preferably automatically. In addition, the motor vehicle has 1 a rain sensor 12th , a yaw rate sensor 14 and a speed sensor 16 on. These are signal transmission technology with the module 10th coupled. The driver assistance system 8th is with the front wheels 2nd and the rear wheels 4th , specifically their brakes, as well as with a steering system and a drive motor of the motor vehicle 1 coupled.

The car 1 , specifically its vehicle controller 6 is set up in a first step S1 the operating procedure (shown in 2nd ), on the basis of (measured) variables that are characteristic of a current driving situation, to determine whether the current driving situation is a stable driving situation, specifically a stationary cornering. The module checks 10th of the vehicle controller 6 whether the respective size fulfills a predetermined criterion assigned to the respective size. In the present exemplary embodiment, the module determines 10th whether an absolute - by means of the yaw rate sensor 14 detected - yaw rate ψ̇ is lower than an assigned threshold value. The module also checks 10th by means of the rain sensor 12th whether there is precipitation (rain or snow). The module also checks 10th whether the driving speed V is less than an assigned threshold.

Provides the module 10th the module estimates that the driving situation is stable, ie stationary cornering 10th in a second step S2 the actual value of a wheelbase L between the front wheels 2nd and the rear wheels 4th . The formula for determining the wheelbase L is derived from the so-called single-track model. Since the yaw rate ψ̇ is contained in the single-track model, a currently stored target value is adjusted to the measured actual value of the yaw rate ψ̇.

Based on the yaw rate ψ̇ and the wheelbase L will be in a subsequent step S3 a (current) characteristic speed Vc (also based on the single-track model). The vehicle model is then updated with the newly determined actual values.

In a further step S4 the updated vehicle model, specifically the updated values, is sent to the driver assistance system 8th to hand over. The driver assistance system 8th uses the updated vehicle model for trajectory control, which is used, for example, during overtaking and / or evasive maneuvers during assisted or autonomous driving, in order to be able to control the motor vehicle on a plausible and risk-free route.

The object of the invention is not limited to the embodiment described above. Rather, other embodiments of the invention can be derived by the person skilled in the art from the above description.

Reference list

1

Motor vehicle

2nd

Front wheel

4th

Rear wheel

6

Vehicle controller

8th

Driver assistance system

10th

module

12th

rain sensor

14

Yaw rate sensor

16

Speed sensor

S1

step

S2

step

S3

step

S4

step

ψ̇

Yaw rate

L

wheelbase

V

Driving speed

Vc

characteristic speed

Claims (10)

Method for operating a motor vehicle (1) which has a chassis with at least one front wheel (2) and at least one rear wheel (4), the method according to the method on the basis of at least one variable which is characteristic of a current driving situation, it is determined whether the current driving situation is a stable driving situation by checking whether the respective variable fulfills a predetermined, assigned criterion, - If a stable driving situation is recognized, current values of a number of vehicle model sizes (L, Vc, GV) are determined using an estimate, a preset vehicle model, which contains the vehicle model sizes, is updated by the current values of the one or more vehicle model sizes (L, Vc, GV), - The updated vehicle model for a trajectory control of a driver assistance system (8) is used, and - The at least one size and the respective assigned criterion are selected from: Lenk a steering angle of a front axle and / or a rear axle is smaller and / or larger than a threshold value, ◦ a steering speed of the front axle and / or rear axle is less than a threshold value, ◦ a yaw rate (ψ̇) is less than a threshold, Fahr a driving speed (V) of the motor vehicle (1) is lower and / or higher than a threshold value, ◦ yaw acceleration is less than a threshold, ◦ a derivative of the lateral acceleration is less than a threshold value, ◦ a derivative of a vertical acceleration is less than a threshold value, ◦ an absolute deviation between the lateral acceleration and the product of the yaw rate (ψ̇) and driving speed (V) is not greater than a threshold value, ◦ the steering angle of the front axle, the lateral acceleration and the yaw rate (ψ̇) have the same signs, Zustand a state of stability control systems is inactive, ◦ a signal which is characteristic of the presence of precipitation has a value which is characteristic of the absence of precipitation, and ◦ longitudinal acceleration is less than a threshold. Procedure according to Claim 1 , wherein an additional criterion for the stable driving situation is that the size or the respective size continuously fulfills the respectively assigned criterion over a predetermined period of time. Procedure according to Claim 1 or 2nd , where a steady cornering or a steady straight driving is used as a stable driving situation. Procedure according to one of the Claims 1 to 3rd , whereby an intervention by chassis control systems is prevented during the estimation of the current values of the vehicle model sizes. Procedure according to one of the Claims 1 to 4th , wherein a difference between a preset target value of the yaw rate (ψ̇) and a current actual value of the yaw rate (ψ̇) is minimized in the estimation. Procedure according to Claim 5 , an actual value of a wheelbase (L) being determined on the basis of the yaw rate (ψ̇) as the vehicle model size. Procedure according to one of the Claims 1 to 4th , the actual value of the wheelbase (L) being determined during a steady straight-ahead drive on the basis of a time interval of a vertical excitation of the wheels of the front axle and the rear axle and on the basis of the current driving speed (V). Procedure according to Claim 5 and 6 or 7 , a characteristic speed (Vc) being determined on the basis of the yaw rate (ψ̇) and the actual value of the wheelbase (L) as the vehicle model size. Procedure according to Claim 8 , a yaw gain (GV) being determined on the basis of the characteristic speed (Vc) as the vehicle model size. Motor vehicle (1) with a chassis that has at least one front wheel (2) and at least one rear wheel (4), and with a vehicle controller (6) that is set up to implement the method according to one of the Claims 1 to 9 perform.

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