DE102004058676A1 - Lane keeping system for motor vehicles with trajectory determination - Google Patents

Abstract

The invention relates to a device for holding a vehicle in its lane, comprising a steering actuator (3), with which a steering torque (M¶A¶) can be exerted on the steering (1) of the vehicle (11), and a lane recognition system (12 ), with which the relative position of the vehicle (11) with respect to its lane (10) and a lane curvature can be determined. A particularly robust LKS control system comprises a device (14) for trajectory determination, which determines a trajectory (kappa) from the geometric data determined by the lane recognition system (12), which should follow the vehicle (11), and a trajectory slave controller (15). to which information (kappa) is supplied via the trajectory (13) as a reference variable and which controls the vehicle movement in such a way that the vehicle (11) follows the trajectory (13).

Description

The The invention relates to a device for holding a vehicle in his lane according to the generic term of claim 1, and a corresponding method according to the preamble of claim 8.

Out The prior art, a variety of systems are known that the Assisting drivers of a motor vehicle to keep the vehicle in its lane. These systems will be also referred to as LKS systems (LKS: Lane Keeping Support). Known LKS systems essentially comprise a lane detection system, such as. a video system that shows the relative position of the vehicle in the lane (the so-called shelf), the orientation of the vehicle and the course of the lane can be determined. If the steering angle selected by the driver from the predetermined by the lane course target steering angle strongly deviates, are with the help of a steering actuator, such. one Servomotor, artificial Steering forces on the steering of the vehicle exercised. These steering forces are so strong that they can be haptically captured by the driver and tell the driver how he would have to operate the steering to to keep the vehicle in its lane.

The Lane detection system may e.g. be realized as a video system, whose video signals are processed by a signal processing software Be the ones you want geometric data (storage, orientation, road curvature) supplies. Other lane detection systems include e.g. B. a magnetic sensor, the vehicle position in conjunction with integrated in the roadway Magnets detected or optionally also radar sensors.

Out the geometric position data and the road curvature then by means of a mathematical reference model (mathematical Algorithm) calculates a reference steering angle, which is at the steering would have to be taken to keep the vehicle optimally in its lane. At a Deviation of the driver steering angle from the reference steering angle then becomes with the help of a steering actuator a support torque on the steering applied. This support moment is calculated on the basis of a given characteristic curve, which is a functional relationship between the assist torque and the steering angle difference represents.

For this is also on the pamphlets Naab, Reichhart: "Driver Assistance Systems for Lateral and Longitudinal Vehicle Guidance Heading Control and Active Cruise Support "AVEC 94, and Shimakage, Kawazoe, Sadano, Murakami: "Design of Lane-Keeping Control with Steering Torque input for Lane-Keeping Support System ", SAE Technical Papers 2001-01-0480.

Known LKS systems have so far not been able to drive the vehicle automatically keep in his lane, but only have the job the driver in a deviation of his steering activity of the by the lane course predetermined target steering movement by directed, artificial steering wheel forces to support. The driver must therefore continue to steer actively.

It It is therefore the object of the present invention to provide an LCS system, which is capable of automatically driving the vehicle in a predetermined lane to hold without the driver must actively operate the steering for this purpose.

Is solved this task according to the invention by the specified in claim 1 and in claim 8 Characteristics. Further embodiments of the invention are the subject of dependent claims.

One essential idea of the invention is that of the lane detection system supplied data and current driving state variables, such as the yaw rate, to determine a trajectory (i.e., trajectory) of the vehicle should follow, and the vehicle traverse movement with the help of a trajectory follower and a steering actuator to regulate such that the vehicle of the trajectory follows. The trajectory follower is this information about the Trajectory (such as a path-dependent curvature) supplied as a reference variable.

One Inventive LKS system thus comprises a device for trajectory determination and a downstream trajectory follower, as well as a steering actuator as an actuator of the scheme. Such a combination of trajectory determination and downstream trajectory follower has the essential Advantage that the vehicle automatically in the specified lane can be held without the driver being active in the steering must intervene.

The Device for trajectory determination and trajectory slave controller are preferably deposited as software in a vehicle control unit.

When Controlled variables become preferably the float angle and / or the yaw rate of the vehicle used. According to one preferred embodiment The invention regulates the trajectory slave controller next to the slip angle and / or the yaw rate of the vehicle preferably also a wheel angle or a size proportional thereto. The additional regulation of the wheel angle has the advantage of having delay times in the actuator (steering actuator) and the controlled system (steering) of the trajectory slave controller be taken into account can.

Of the Trajectory slave controller calculated as a function of the control deviation (s) the controlled variable (s) preferably a steering wheel angle (or an equivalent Size) the to be adjusted by the steering actuator.

The Setpoint values of the individual controlled variables (yaw rate, Slip angle and / or wheel angle) are preferably of a control unit considering the trajectory derived from the known single-track model. The Actual values of the controlled variable (s) preferably detected by sensors using appropriate sensors.

Of the Trajectory slave controller is preferably implemented as a state controller and Z. B. deposited as software in a control unit.

One Inventive LKS system accordingly comprises a closed loop with a device for trajectory determination, a downstream trajectory follower and a steering actuator, being the trajectory follower the control element and the steering actuator forms the control element of the control.

The Invention will be exemplified below with reference to the accompanying drawings explained in more detail. Show it:

1 a schematic representation of the steering of a motor vehicle;

2 the trajectory of a vehicle in a lane;

3 a block diagram of a control system for holding the vehicle in its lane; and

4 an embodiment of a trajectory follower for three controlled variables.

1 shows a front wheel steering 1 a car with a steering wheel 2 , a handlebar 5 a steering gear 6 with a gear ratio N and a tie rod 8th , by means of a front wheel 7 is steered. The steering 1 further comprises a steering actuator 3 , such as a servomotor, with the via a belt drive 4 a moment M _A on the handlebar 5 can be exercised. The transmission ratio is denoted by N _A.

The illustrated steering is mechanically identical to most conventional vehicle steering systems and is used here as part of a LKS control system to the vehicle 11 ( 2 ) by exerting an artificial guiding moment M _A in its lane 10 to keep.

2 shows the trajectory of a vehicle 11 in a lane 10 by lane markings 9 is limited. The vehicle 11 includes a lane detection system 12 , such as As an image processing system, the relative position of the vehicle 11 regarding the lane markings 9 (the so-called filing), the orientation of the vehicle 11 , as well as the road course determined. The image processing system includes a video camera and a special image processing software that determines the desired geometric data (storage, orientation and lane course) from the image data.

The geometric data then becomes a device 14 (please refer 3 ) for trajectory determination, which, taking into account current driving state variables, such as the yaw rate or the vehicle speed, a trajectory 13 calculates the vehicle 11 should follow to get in the lane 10 to stay. The trajectory 13 preferably has a course that is possible in the middle of the roadway 10 lies.

3 shows an overview of the entire LKS control system. The LKS control system essentially comprises the lane detection system 12 including image processing software, the facility 14 for trajectory determination and a subsequent control loop 16 , The control loop 16 includes a trajectory follower 15 , as well as a block 3 in which an LKS algorithm and a steering controller, such. B. a servomotor, are summarized. The vehicle 11 forms the controlled system of the regulation.

The trajectory 13 is preferably calculated as a curvature curve κ (x) as a function of the distance traveled (x) and to the trajectory slave controller 15 output. The trajectory information κ can also be a fixed (path-independent) value.

The trajectory follower 15 controls in the present embodiment, three control variables, namely the yaw rate dψ / dt, the slip angle β and the wheel angle δ and calculates it taking into account the trajectory 13 a steering wheel angle δ _L. The one in the block 3 contained LKS algorithm generates from this a manipulated variable (eg a moment) for the steering actuator, which then has a corresponding guide moment M _A on the steering 1 of the vehicle 11 exercises. By this regulation, a natural, similar to the steering behavior of the driver steering behavior can be achieved.

In the 3 illustrated elements 12 . 14 - 16 are preferably deposited as software in a vehicle control unit.

dψ/dtstat = v·κ (3)wobei l der Achsabstand des Fahrzeugs, l_v der Abstand der Vorderachse zum Fahrzeugschwerpunkt, l_h der Abstand der Hinterachse zum Fahrzeugschwerpunkt, m die Fahrzeugmasse, v die Fahrzeuggeschwindigkeit, C_h, C_v die Achssteifigkeit an der Vorder- bzw. der Hinterachse und κ die von der Einrichtung 14 zur Trajektorienbestimmung berechnete Sollkrümmung. 4 shows a detailed view of the trajectory follower 15 for regulating the wheel angle δ, the slip angle β and the yaw rate dψ / dt. The trajectory follower 15 includes three nodes 18 . 19 . 20 , on each of which the control difference of the controlled variables δ, β, dψ / dt is determined. The setpoint values (provided with the index stat) of the individual control variables are derived from the stationary single-track model of the vehicle lateral movement and calculated taking into account the trajectory information x. The stationary setpoint variables δ _stat , β _stat , dψ / dt _stat can, for. B. calculated as follows:

dψ / dt stat = v · κ (3) where l is the center distance of the vehicle, l _{v is} the distance between the front axle and the center of gravity of the vehicle, l _{h is} the distance between the rear axle and the center of gravity of the vehicle, m is the vehicle mass, v is the vehicle _speed , C _h , C _{v is} the axle stiffness at the front or rear axle and κ those of the institution 14 Calculated desired curvature for trajectory determination.

The actual control algorithm 17 is preferably implemented as a state controller, such as LQR state controller. This controller type shows a good stability and a high robustness against parameter fluctuations of the controlled system. Other types of controllers that imprint sturdy stability on the system are also suitable.

When driving, the previously calculated trajectory 13 from the vehicle 11 traced and constantly recalculated, preferably when the Q of the trajectory follower 15 falls below a predetermined value. The control quality Q can be determined, for example, by evaluating the quadratic deviations of the control differences, where: Q = ∫ (dψ / dt stat - dψ / dt) 2 + (β stat - β) 2 + (δ stat - δ) 2 / dt (4)

If the trajectory 13 is calculated as a path-dependent function κ (x), the trajectory slave controller moves 15 this function up to a defined distance x _end . The distance x _end can z. B. be covered in a computing cycle way or z. From the look ahead range of the lane detection system 12 or the speed v of the vehicle 11 and should be the foresight of the lane detection system 12 do not exceed. After traveling the distance x _end , a new trajectory information κ is then determined on the basis of the changed lane course.

at Using a fixed (path-independent) curvature value κ, the Trajectory information κ preferably in shorter predetermined intervals calculated.

1

steering

2

steering wheel

3

steering actuator with LKS algorithm

4

belt

5

handlebars

6

steering ratio

7

front

8th

tie rod

9

lane marker

10

roadway

11

vehicle

12

Lane departure warning system

13

trajectory

14

Facility for trajectory determination

15

Trajectory slave controller

16

loop

17

control algorithm

18 19, 20

subtracting node

κ (x)

trajectory curvature

δ

wheel angle

δ _L

steering wheel angle

β

float angle

dψ / dt

yaw rate

Claims (10)

Device for holding a vehicle ( 11 ) in its lane ( 10 ), comprising - a steering actuator ( 3 ), with which a steering torque (M _A ) on the steering ( 1 ) of the vehicle ( 11 ), and - a lane detection system ( 12 ), which determines the relative position of the vehicle ( 11 ) with regard to its lane ( 10 ) as well as information regarding the lane course can be determined, characterized by a device ( 14 ) for trajectory determination, which is derived from the traffic lane recognition system ( 12 ) obtained a trajectory ( 13 ), which should follow the vehicle, and - a trajectory follower ( 15 ), which receives information (κ) about the trajectory ( 13 ) is supplied as a reference variable and controls the vehicle movement such that the vehicle ( 11 ) of the trajectory ( 13 ) follows. Device according to Claim 1, characterized in that the trajectory slave controller ( 15 ) the slip angle (β) and / or the yaw rate (dψ / dt) of the vehicle ( 11 ) regulates. Device according to Claim 1 or 2, characterized that the trajectory slave controller the wheel angle (δ) or a proportional size regulates. Device according to one of the preceding claims, characterized in that a closed loop ( 18 ), in which the trajectory slave controller ( 15 ) the control member and the steering actuator ( 3 . 16 ) forms the actuator of the control. Device according to one of the preceding claims, characterized in that the trajectory slave controller ( 15 ) is a state controller. Device according to one of the preceding claims, characterized in that the trajectory slave controller ( 15 ) is a curvature (κ (x)) as a function of the path (x). Device according to one of the preceding claims, characterized in that from the trajectory information (κ) a desired yaw rate (d ψ / dt _stat ), a target slip angle (β _stat ) and / or a desired wheel angle (δ _stat ) be calculated. Method for holding a vehicle ( 11 ) in its lane ( 10 ), in which by means of a lane detection system ( 12 ) the relative position of the vehicle ( 11 ) with regard to its lane ( 10 ) and with the help of a steering actuator ( 3 ) a steering torque (M _A ) on the steering ( 1 ) of the vehicle ( 11 ) is applied to the vehicle ( 11 ) in its lane ( 10 ), characterized in that from the lane detection system ( 12 ) obtained a trajectory ( 13 ) determining the vehicle ( 11 ) and a trajectory follower ( 15 ) a trajectory information (κ) is supplied as a reference variable which controls the vehicle movement in such a way that the vehicle ( 11 ) of the trajectory ( 13 ) follows. Method according to claim 8, characterized in that that the yaw rate (d ψ / dt) and / or the slip angle (β) form the controlled variables. Method according to claim 9, characterized in that that the wheel angle (δ) or a proportional size one forms another controlled variable.