WO2009037025A1

WO2009037025A1 - Method for controlling a driver assistance system

Info

Publication number: WO2009037025A1
Application number: PCT/EP2008/059555
Authority: WO
Inventors: Lutz Buerkle; Tobias Rentschler; Thomas App
Original assignee: Robert Bosch Gmbh
Priority date: 2007-09-14
Filing date: 2008-07-22
Publication date: 2009-03-26
Also published as: DE102007043913A1; DE102007043913B4

Abstract

The invention relates to a method for controlling a driver assistance system (1) of a vehicle (100), comprising at least one assistance function, such as particularly the LKS (Lane Keeping Support) function. According to said method, a guiding torque is applied to the steering system of the vehicle (100) when the LKS function is activated to keep the vehicle in the lane (21). The method according to the invention is characterized by detecting whether the vehicle (100) is cornering. During cornering of the vehicle (100), the driver assistance system (1) is controlled in such a manner that the LKS function assumes a symmetric guidance behavior.

Description

title

Method for controlling a driver assistance system

State of the art

The invention relates to a method for controlling a driver assistance system according to the preamble of claim 1. Driver assistance systems are known which assist the driver in maintaining a selected lane. The driver assistance system includes assistance functions such as LDW (Lane Departure Warning) and / or LKS (Lane Keeping Support). The assistance function LDW warns the driver against leaving the lane by generating optical and / or acoustic and / or haptic signals. The assistance function LKS actively intervenes in onboard systems of the vehicle, such as the steering system, and / or the braking system or an ESP system to keep a lane deviating vehicle in the lane. For this purpose, the driver assistance system comprises a sensor system, in particular comprising at least one video sensor, for detecting lane markings or the like.

DE 101 37 292 A1 discloses a method for operating a driver assistance system of a vehicle, in particular a motor vehicle, with a power-assisted steering. This method is characterized by the following steps:

Acquiring or estimating environmental data of a preferably current traffic situation, Detecting or estimating, preferably momentary, movement data of the vehicle,

Comparing the detected or estimated environmental data with the movement data of the vehicle,

- Change of support of a steering handle according to the comparison.

From DE 10 2005 048 014.4 a driver assistance system with a lane keeping function is known, which comprises a device for the detection of lanes on the road and a control device for engaging in the steering system of the vehicle in the sense of tracking. Furthermore, the driver assistance system comprises means for detecting the position of the vehicle with respect to the edges of the lane, as well as means for detecting cornering of the vehicle. The controller performs its control function in response to the position of the vehicle on the lane and in response to turning the vehicle.

If the LKS function is now active and supports the driver in maintaining the lane, the driver perceives the guiding intervention of the LKS function as unbalanced and therefore disturbing when cornering.

Disclosure of the invention

System acceptance by the driver is increased, thereby improving the ride comfort subjectively perceived by the driver. Advantageous effects

The invention enables a further improvement of the driving comfort in a vehicle equipped with a driver assistance system and thereby an increased acceptance of such a system in the driver. Due to the fact that a guiding engagement of the LKS function is perceived by the driver as a symmetrical engagement even when the vehicle is cornering, regardless of the direction in which its steering wheel deflection deviates from the reference trajectory, such an intervention is no longer perceived as disturbing. The symmetry during cornering is advantageously achieved by applying a torque to the steering system of the vehicle, which results as the difference between the torque applied by the LKS function and the weighting factor-weighted restoring torque of the steering. The weighting factor is advantageously represented as a function of the angular difference between a reference angle and the steering angle. Further advantages emerge from the subclaims, the description and the drawing.

Brief description of the drawings

Embodiments of the invention are explained below with reference to the drawing. Showing:

Figure 1 is a block diagram of a driver assistance system with LKS function;

Figure 2 is a plan view of a traffic area with a vehicle;

Figure 3 is a diagram showing a guide characteristic of the LKS function; Figure 4 is a diagram showing a weighting factor.

Embodiments of the invention

Embodiments of the invention are explained in more detail below with reference to the drawing. The invention is based on the recognition that the acceptance of a driver assistance system and the assistance functions provided by it can be substantially improved if the guidance interventions provided in the driver assistance system are based more strongly on the driver's subjective sense of safety and comfort. Thus, especially when cornering a symmetrical guidance intervention in the driver find a greater appeal than a single-ended engagement.

FIG. 1 shows a block diagram of a driver assistance system 1 with LKS function, which is arranged in a vehicle 100. Via appropriate sensors, preferably a video-based sensor system 3, the course of the lane, in particular the curvature of the lane and its change, as well as the relative position of the vehicle with respect to the traffic lane, in particular its lateral storage and the differential angle over the paths 4, 4.1 a Function module of the driver assistance system 1 supplied, which includes a reference model 6 for the lateral guidance of the vehicle 100. With the aid of the reference model 6, a reference angle δ _Ref , which is required in the current driving situation in order to guide the vehicle in the lane, is determined from the aforementioned input variables. This reference angle is compared with the steering angle δ predetermined by the driver on the steering wheel (summing node 7). Depending on the deviation Δδ = δ _Ref -δ between the actual and the determined by the reference model, for the tracking of the vehicle 100 ideal steering angle, an additional guide moment M _{E is then} determined and the steering system of the vehicle 100 impressed by means of a steering actuator 9 via a LKS function associated guide characteristic. As a reaction of the driver assistance system, the driver on the steering wheel is thus provided with a guiding torque which assists him in guiding the vehicle 100 in the traffic lane 21. By own steering activity, the driver can always influence the lateral guidance of the vehicle and also override the driver assistance system 1. By a corresponding design of the guide characteristic 8 of the LKS function, a desired degree of support can be realized. The path 9.1 in FIG. 1 represents the steering intervention of the LCS system. At the same time, the driver 5 perceives the vehicle position in the lane (path 4.2) and controls the vehicle 100 on the steering wheel (driver steering intervention 5.1). Driver request and system intervention act together on the summation node 10 on the steering system 11 (path 10.1) and control over the paths 12, 12.2 and influencing the steering angle, the transverse movement of the vehicle 100. Via the path 12.1 there is a feedback to the summation node 7. About the Paths 12.1, 12.3, an influence of the functional module 13, the output side (path 13.2) is connected to an input of the summing node 14, which is arranged between the guide curve 8 and the steering splitter 9. The output of the summation node 7 is connected to the function module 13 via the path 13.1. The function module 13 is responsible for the inventive compensation of the imbalance, wherein the restoring torque is linked to a weighting factor. Disturbances affect the vehicle 100 via the schematically indicated path 2.

When steering the vehicle 100, the driver experiences on the steering wheel a dependent on the impact of the steering wheel Restoring moment. This restoring torque results from the impact of the front wheels, the Vorderachsgeometrie and the assist torque of the power steering. The restoring torque is usually designed so that the steering wheel tends to return to a stable zero position.

The invention will be further explained below with reference to Figure 2, Figure 3 and Figure 4.

FIG. 2 shows a plan view of a traffic space 20 with a vehicle 100. The vehicle 100 moves on a lane 21 that is delimited by lane boundaries 21.1 and 21.2. The center of the lane 21 is designated 21.3. By two arrows, the angles δ and δ _{Ref are} indicated.

In a driver assistance system with LKS function, the guide torque is determined via a guide characteristic. The diagram shown in FIG. 3 shows such a guiding characteristic 30. The abscissa of the rectangular coordinate system shown in FIG. 3 plots the angular deviation Δδ between the steering angle δ predetermined by the driver and the reference angle δ _Ref determined by the reference model. On the ordinate of the coordinate system, the applied by the LKS function guide torque M _{E is} plotted. The guide characteristic 30 is designed point-symmetrically with respect to the zero point of the coordinate system. This means that in terms of amount the same steering deviations with different signs have the same magnitude but oppositely directed leadership moments result. The guide torque M _E determined in this way is then superimposed on the existing steering characteristic of the steering system of the vehicle 100. In sum, this results in an asymmetrical steering feel for the driver when cornering. Dodges its steering angle when driving through a curve Turning inside of the curve from the target trajectory, the guiding moment of the LKS function is reinforced by the restoring moment of the steering system. On the other hand, in the case of a steering deviation of the driver to the outside of the curve, the restoring moment of the steering system counteracts the guiding moment and thus leads to a weakening of the system intervention by the LKS function.

It is now, depending on the impact of the steering wheel, the restoring torque of the steering system compensated such that the driver feels the system response of the LKS function when driving through curves as symmetrical, regardless of the direction in which its steering wheel deviation deviates from the reference trajectory.

The restoring moment of the steering system on the steering wheel can be described by the following relationship:

In this mean:

l _v distance between the center of gravity of the vehicle and the front axle; l _h distance between the center of gravity of the vehicle and the rear axle; 1 axial distance; n _r constructive caster; m mass of the vehicle; v speed of the vehicle; N gear ratio of the steering gear; k _s power steering assist ratio; δ steering angle. The restoring moment accordingly increases linearly with the steering angle. The quantity k _s describes the steering assistance by the power steering and can assume values between 0 and 1 depending on the degree of assistance. The value k _s = 0 stands for full servo assistance. The value k _s = l stands for steering without assistance from the power steering.

So that the driver feels the system reaction of the LKS function when driving through a curve as symmetrical, the restoring moment of the steering system is compensated according to the invention that a weighting factor g _{R is} formed, that the restoring torque M _{R is} weighted with this weighting factor, and that the weighted restoring torque is subtracted from the guide moment M _E derived from the guide characteristics of the LKS function. This is illustrated by the following relationship:

(2) M _LKS = M _E -g _R -M _R.

The resulting torque M _LK s is then impressed on the steering system of the vehicle 100 with a steering actuator.

According to the invention, the weighting factor g _R is derived as a function of the deviation Δδ between the reference angle and the steering angle applied by the driver from a further characteristic curve 40, which is shown in the diagram shown in FIG. This characteristic curve 40 is limited symmetrically with respect to the y-axis of the coordinate system shown in FIG. 4 and to a maximum value g _R , _m a _x . In addition, g _R always assumes the value zero, although this also does the guiding characteristic. For the description of the characteristic curve shown in FIG. 4, in an advantageous embodiment of the invention, a similar functional relationship can be selected as for the guiding characteristic curve 30 of the LCS function, wherein, however, care must be taken that the consequent result Characteristic curve should be axisymmetric and limited to the maximum value g _R , _max . This can advantageously be achieved by using the amount of the functional relationship for the guide characteristic as a characteristic curve for the weighting factor and multiplying it by a scaling factor.

Claims

claims

A method for controlling a driver assistance system (1) of a vehicle (100) having at least one

Assistance function, in particular the function (LKS = Lane Keeping Support), in which, when the function is activated, a guiding torque is applied to the steering system of the vehicle (100) in order to keep it in the traffic lane (21), characterized in that it checks that whether the vehicle (100) makes a turn, and that, when cornering the vehicle (100), the driver assistance system (1) is controlled in such a way that a symmetrical guiding behavior of the function results.

2. A method for controlling a driver assistance system (1) according to claim 1, characterized in that on the

Steering system of the vehicle (100) a resulting moment (M _LKS ) is applied, which measures according to the following relationship:

^M Lκs = ^M E-§R- ^M R ' ^with

M _LKS resulting moment,

M _E leadership moment,

M _R restoring moment, g _R weighting factor.

3. The method according to any one of the preceding claims, characterized in that the restoring moment (M _R ) of the steering system is set according to the following relationship:

M _R return torque; l _v distance between the center of gravity of the vehicle and the front axle; l _h distance between the center of gravity of the vehicle and the rear axle; 1 axial distance; n _r constructive caster; m mass of the vehicle; v speed of the vehicle; N gear ratio of the steering gear; k _s power steering assist ratio; δ steering angle.

4. Method for controlling a driver assistance system according to one of the preceding claims, characterized in that the weighting factor (g _R ) is a function of the angular difference (Δδ) between the reference angle (δ _Ref ) and the steering angle (δ).

5. The method according to any one of the preceding claims, characterized in that the reference angle (δ _Ref ) is derived from an axisymmetric characteristic (40).

6. The method according to any one of the preceding claims, characterized in that the weighting factor (g _R ) is limited to a maximum value (g _R , _max ).

7. The method according to any one of the preceding claims, characterized in that the weighting factor (g _R ) is always assigned the value zero, when the guide moment (M _E ) assumes the value zero, so if no leadership intervention by the driver assistance system.

8. Device for controlling a driver assistance system (1) of a vehicle (100) with at least one assistance function, in which, when the function is activated, a guiding torque is applied to the steering system of the vehicle (100) in order to keep it in the lane (21), characterized by means for verifying that the vehicle (100) is making a turn and when cornering control the driver assistance system to provide symmetrical leadership of the function.