METHOD FOR OPERATING A VEHICLE, COMPUTER PROGRAM, CONTROL SYSTEM AND VEHICLE

Abstract

A method for operating a vehicle (1), comprising: receiving (S1) sensor data (S) of a sensor system (3) of the vehicle (1), the sensor data (S) including a current steering-angle (?) and steering-angle velocity (W) of the vehicle (1) driving on a road (14) with a curve (13), determining (S2) a radius ahead R.sub.A of the curve (13) at a position ahead (P2) that the vehicle (1) will reach in a predetermined time span T based on an odometry-based radius ahead R.sub.O by the equation:

[00001]$R_O=R_C-T\left[\left(L.Math.W\right)/({\sin }^2\left(?\right)\right],$ wherein L is a distance between front and rear wheels (17, 18) of the vehicle (1) and R.sub.C is a radius of the road (14) at the current position (P1) of the vehicle (1), and performing (S6) a curvature control function based on the determined radius ahead R.sub.A.

Claims

1. A method for operating a vehicle, comprising: receiving sensor data of a sensor system of the vehicle, the sensor data including a current steering-angle ? and steering-angle velocity W of the vehicle driving on a road with a curve; determining a radius ahead R.sub.A of the curve at a position ahead that the vehicle will reach in a predetermined time span T based on an odometry-based radius ahead R.sub.O given by the equation:
R.sub.O=R.sub.C?T[(L.Math.W)/(sin.sup.2(?)], wherein ? is the steering-angle, W is the steering-angle velocity, L is a distance between front and rear wheels of the vehicle and R.sub.C is a radius of the road at the current position of the vehicle; and performing a curvature control function based on the determined radius ahead R.sub.A.

2. The method according to claim 1, wherein a nominal velocity V.sub.A of the vehicle at the position ahead is determined based on the determined radius ahead R.sub.A and a predetermined maximum lateral acceleration A.sub.MAX by the equation: $V_A={\left(A_{MAX}.Math.R_A\right)}^{1/2},$ the curvature control function is performed based on the determined nominal velocity V.sub.A.

3. The method according to claim 1, wherein an expected acceleration of the vehicle at the position ahead is determined based on a current velocity V.sub.C of the vehicle and a nominal velocity V.sub.A of the vehicle at the position ahead, a presence of lane markings of the road is detected and a track quality of the detected lane markings is determined based on the sensor data, a lane-based radius ahead R.sub.L of the curve at the position ahead is determined based on the detected lane markings, and the curvature control function is performed based on the odometry-based radius ahead R.sub.O and the lane-based radius ahead R.sub.L such that the radius ahead R.sub.A is set equal to the minimum of the lane-based radius ahead R.sub.L and the odometry-based radius ahead R.sub.O when the determined track quality is above a predetermined track quality threshold and the determined expected acceleration corresponds to a braking of the vehicle, the radius ahead R.sub.A is set equal to the maximum of the lane-based radius ahead R.sub.L and the odometry-based radius ahead R.sub.O when the determined track quality is above the predetermined track quality threshold and the determined expected acceleration corresponds to a positive acceleration of the vehicle, and the radius ahead R.sub.A is set equal to the odometry-based radius ahead R.sub.O when the determined track quality is at or below the predetermined track quality threshold.

4. The method according to claim 3, wherein the lane-based radius ahead R.sub.L is determined by the equation: $R_L=1/\left[\left(6.Math.a.Math.T\right)+\left(2.Math.b\right)\right],$ wherein a and b are the first two coefficients of a third-degree polynomial and T is the predetermined time span.

5. The method according to claim 1, wherein performing the curvature control function includes controlling an acceleration and/or a jerk of the vehicle based on a current velocity V.sub.C of the vehicle at a current position and a nominal velocity V.sub.A of the vehicle at the position ahead.

6. The method according to claim 5, wherein controlling the acceleration and/or the jerk of the vehicle includes a proportional and/or derivative controlling of the acceleration and/or the jerk, and the nominal velocity V.sub.A of the vehicle at the position ahead is a setpoint in the proportional and/or derivative controlling and the current velocity V.sub.C of the vehicle is a process variable of the proportional and/or derivative controlling.

7. The method according to claim 1, wherein performing the curvature control function includes determining a first time phase of negative jerk, a second time phase of zero jerk and a third time phase of positive jerk based on a current velocity V.sub.C of the vehicle at a current position and on a nominal velocity V.sub.A of the vehicle at the position ahead, said first, second and third time phases being continuous with each other.

8. The method according to claim 1, wherein performing the curvature control function includes controlling an acceleration of the vehicle to be below a predetermined acceleration threshold and/or controlling a jerk of the vehicle to be below a predetermined jerk threshold.

9. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to claim 1.

10. A control system for a vehicle which is configured to perform the method according to claim 1.

11. A vehicle comprising a control system according to claim 10.

Description

[0067] In the following, the invention will be described in detail based on preferred embodiments with reference to the following figures.

[0068] FIG. 1 shows a top view of a vehicle according to an embodiment;

[0069] FIG. 2 shows the vehicle of FIG. 1 on a road;

[0070] FIG. 3 illustrates a steering-angle of the vehicle of FIG. 1;

[0071] FIG. 4 shows a view similar as FIG. 2, wherein the road comprises lane markings;

[0072] FIG. 5 shows a data point of a determined lane-based radius of a curve of the road of FIG. 4;

[0073] FIG. 6 shows a timely evolution of an acceleration and a jerk of the vehicle of FIG. 1 when driving through a curve of the road shown in FIG. 2 or 4;

[0074] FIG. 7 shows a control system of the vehicle of FIG. 1; and

[0075] FIG. 8 shows a flowchart illustrating a method for operating the vehicle of FIG. 1.

[0076] In the figures, like reference numerals designate like or functionally equivalent elements, unless otherwise indicated.

[0077] FIG. 1 shows a schematic top view of a vehicle 1. The vehicle 1 is, for example, a passenger vehicle. The vehicle 1 may also be another kind of vehicle such as a van or truck. The vehicle 1 comprises a control system 2 for controlling the vehicle 1.

[0078] As shown in FIG. 1, the vehicle 1 comprises a sensor system 3 including several environmental sensor units 4, 5, 6, 7 arranged at the vehicle 1. The sensor system 3 comprise, in particular, one or more camera devices 4 such as one or more front camera devices. The camera devices 4 are configured for obtaining image data I of a surrounding 8 of the vehicle 1 and for sending the image data or results of an image analysis of the image data to the control system 2. The front camera device 4 is attached to a front windscreen 9 of the vehicle 1.

[0079] The sensor system 3 further comprise, for example, one or more radar devices 5 for obtaining radar data of the surrounding 8 of the vehicle 1. The sensor system 3 may further comprise, for example, one or more lidar devices 6 for obtaining lidar data of the surrounding 8 of the vehicle 1.

[0080] The sensor system 3 further comprises a steering-angle sensor 10 arranged at a steering shaft 11 of the vehicle 1. The steering shaft 11 is connected to a steering wheel 12 of the vehicle 1. The steering-angle sensor 10 is configured to measure a steering-angle ? (FIG. 3) and a steering-angle velocity W of the vehicle 1.

[0081] The sensor system 3 may comprise further sensors such as ultrasonic sensors 7, one or more rain sensors and/or one or more light sensors (not shown).

[0082] In the following, a method for operating the vehicle 1 will be described with reference to FIGS. 2 to 8. The method is, in particular, a method for performing a curvature control of the vehicle 1 to smoothly drive the vehicle 1 into and out of a curve 13 of a road 14 (FIG. 2).

[0083] FIG. 2 shows the vehicle 1 of FIG. 1 on the road 14 comprising the curve 13. The vehicle 1 is shown in FIG. 2 on a first position P1 (current position) before entering the curve 13. The vehicle 1 is driving at the current position P1 with a current velocity V.sub.C. Furthermore, the vehicle 1 is shown in FIG. 2 with dashed lines on a second position P2, where the vehicle 1 has entered the curve 13. The second position P2 is ahead of the first position P1 with respect to a driving direction 15 of the vehicle 1.

[0084] In a first step S1 of the method, the control system 2 of the vehicle 1 receives sensor data S (FIG. 7) of the sensor system 3 (FIG. 1) of the vehicle 1. The sensor data S include odometry data of the steering-angle sensor 10 (FIG. 1), in particular a current steering-angle ? and a current steering-angle velocity W of the vehicle 1. Further, the sensor data S include image data I of the camera device(s) 4 (FIG. 1) of the vehicle 1. The control system 2 comprises, for example, a receiving unit 16 (FIG. 7) for receiving the sensor data S from the sensor system 3.

[0085] In a second step S2 of the method, the control system 2 determines a radius ahead R.sub.O of the curve 13 at the position ahead P2 based on the odometry data (?, w). The position ahead P2 is, in particular, a position that the vehicle 1 will reach in a predetermined time span T (e.g., 1 second or 2 seconds). The control system 2 comprises, for example, a first determining unit 20 (FIG. 7) for determining the odometry-based radius ahead R.sub.O. The odometry-based radius ahead R.sub.O is determined based on the following relations.

[0086] A current radius R.sub.C (FIG. 3) of the vehicle 1 at the position P1 can be expressed by using the trigonometric function for a right-angled triangle as

[00009]$R_C=L/\tan \left(?\right).$

[0087] Herein, L is a distance between front wheels 17 and rear wheels 18 (FIG. 3) of the vehicle 1.

[0088] Further, the first derivative with respect to time of the current radius R.sub.C is then given by

[00010]${\mathrm{dR}}_C/\mathrm{dt}=L.Math.d/\mathrm{dt}\left[1/\tan \left(?\right)\right]$${\mathrm{dR}}_C/\mathrm{dt}=-L.Math.d?/\mathrm{dt}/({\sin }^2\left(?\right)].$

[0089] Hence, the odometry-based radius ahead R.sub.O (FIG. 2) of the curve 13 at the position P2 can be written as

[00011]$R_O=R_C+{\mathrm{dR}}_C/\mathrm{dt}$$R_O=R_C-T\left[\left(L.Math.w\right)/({\sin }^2\left(?\right)\right],$$\mathrm{wherein}$$W=d?/\mathrm{dt}.$

[0090] In a third step S3 of the method, the control system 2 determinesin the case that lane markings 19 (FIG. 4) of the road 14 on which the vehicle 1 is driving are detected in the image data Ia lane-based radius ahead R.sub.L of the curve 13 at the position ahead P2. The control system 2 comprises, for example, a second determining unit 21 (FIG. 7) for determining the lane-based radius ahead R.sub.L.

[0091] Furthermore, a track quality (e.g., a level of a track quality) of the detected lane markings 19 are determined. The track quality (e.g., the track quality level) corresponds, in particular, to an image quality of the image data I received by the camera device(s) 4 and/or a detection quality of the lane markings 19 in the image data I. The track quality (e.g., track quality level) is, for example, determined and/or provided by the camera device(s) 4. Alternatively or in addition, the track quality (e.g., the track quality level) may also be determined by the second determining unit 21 (FIG. 7) of the control system 2.

[0092] In a variant, also an error ?R.sub.L (FIG. 5) of the lane-based radius ahead R.sub.L may be determined based on the detected lane markings 19. The error ?R.sub.L may, in particular, be used as a measure of the track quality (e.g., a measure of the track quality level) of the detected lane markings 19.

[0093] The lane-based radius ahead R.sub.L is determined by the equation

[00012]$R_L=1/\left[\left(6.Math.a.Math.T\right)+\left(2.Math.b\right)\right].$

[0094] Therein, a and b are the first two coefficients of a third-degree polynomial (P(x)=ax.sup.3+bx.sup.2+cx+d) estimated as a fit (e.g., best-fit) to the curve 13. Further, T is the predetermined time span of step S2.

[0095] In a fourth step S4 of the method, the control system 2 determines a radius ahead R.sub.A to be used in a curvature control function. The radius ahead R.sub.A is determined based on the odometry-based radius ahead R.sub.O determined in step S2 and on the lane-based radius ahead R.sub.L determined in step S3.

[0096] In particular, an arbitration (i.e., decision) between the determined odometry-based radius ahead R.sub.O and the determined lane-based radius ahead R.sub.L is performed based on the determined track quality of the detected lane markings 19 (e.g., based on the determined track quality level of the detecting the lane markings 19 and/or based on the determined error ?R.sub.L of the lane-based radius ahead R.sub.L) and based on an expected acceleration A.sub.A (FIG. 4) of the vehicle 1 at the position ahead P2. The control system 2 comprises, for example, an arbitration unit 22 (FIG. 7) for determining the radius ahead R.sub.A based on the odometry-based radius ahead R.sub.O and on the lane-based radius ahead R.sub.L.

[0097] When the determined level of the track quality is equal to or below a predetermined track quality threshold, the radius ahead R.sub.A is set equal to the odometry-based radius ahead R.sub.O.

[0098] When the determined level of the track quality is above the predetermined track quality threshold and the determined expected acceleration corresponds to a braking of the vehicle 1, the radius ahead R.sub.A is set equal to the minimum of the lane-based radius ahead R.sub.L and the odometry-based radius ahead R.sub.O.

[0099] When the determined level of the track quality is above the predetermined track quality threshold and the determined expected acceleration corresponds to a positive acceleration, the radius ahead R.sub.A is set equal to the maximum of the lane-based radius ahead R.sub.L and the odometry-based radius ahead R.sub.O.

[0100] In the variant, the track quality may also be estimated based on determining an error ?R.sub.L of the lane-based radius ahead R.sub.L, as illustrated in FIG. 5. FIG. 5 shows a data point 23 of the determined lane-based radius ahead R.sub.L in a radius-position diagram together with an error bar 24 corresponding to the determined error ?R.sub.L. Also shown in FIG. 5 is a predetermined threshold Rth for the error ?R.sub.L of the lane-based radius ahead R.sub.L. In the example shown in FIG. 5, the determined error ?R.sub.L is smaller than the predetermined threshold Rth. However, when the lane markings 19 (FIG. 4) are poorly visible and/or the image quality of the image data I is low, the error ?R.sub.L can also be larger than the predetermined threshold Rth.

[0101] In the example of FIG. 5, when the determined error ?R.sub.L is equal to or above the predetermined threshold R.sub.th, the radius ahead R.sub.A is set equal to the odometry-based radius ahead R.sub.O.

[0102] Further, in the example of FIG. 5, when the determined error ?R.sub.L is below the predetermined threshold R.sub.th and the determined expected acceleration corresponds to a braking of the vehicle 1, the radius ahead R.sub.A is set equal to the minimum of the lane-based radius ahead R.sub.L and the odometry-based radius ahead R.sub.O.

[0103] Furthermore, when the determined error ?R.sub.L is below the predetermined threshold R.sub.th and the determined expected acceleration corresponds to a positive acceleration, the radius ahead R.sub.A is set equal to the maximum of the lane-based radius ahead R.sub.L and the odometry-based radius ahead R.sub.O.

[0104] In a fifth step S5 of the method, the control system 2 determines a nominal velocity V.sub.A (FIG. 2) at the position ahead P2 based on the determined radius ahead R.sub.A and a predetermined maximum lateral acceleration A.sub.MAX by the equation:

[00013]$V_A={\left(A_{MAX}.Math.R_A\right)}^{1/2}.$

[0105] The control system 2 comprises, for example, a third determining unit 25 (FIG. 7) for determining the nominal velocity V.sub.A.

[0106] In a sixth step S6 of the method, the control system 2 performs a curvature control function based on the determined nominal velocity V.sub.A corresponding to the determined radius ahead R.sub.A of the curve 13, 13 at the position ahead P2.

[0107] The control system 2 comprises, for example, a curvature control unit 26 (FIG. 7) for performing the curvature control function. In particular, an acceleration A(t) and a jerk J(t) (FIG. 6) of the vehicle 1 are controlled such that the current velocity V.sub.C (FIG. 2) of the vehicle 1 is changed towards the nominal velocity V.sub.A of the vehicle 1 in a suitable manner.

[0108] The curvature control unit 26 comprises a proportional derivative control unit 27 (PD-control unit 27). The nominal velocity V.sub.A of the vehicle 1 at the position ahead P2 is a setpoint 28 of the PD-control unit 27. Further, the current velocity V.sub.C of the vehicle 1 is a process variable 29 of the PD-control unit 27. The PD-control unit 27 performs, in particular, a control based on a difference of the current velocity V.sub.C and the nominal velocity V.sub.A.

[0109] The curvature control unit 26 further comprises a fourth determining unit 28 for determining time phases T1 T2, T3, T4, T5 of acceleration A(t) and jerk J(t) (FIG. 6). The fourth determining unit 28 includes, for example, a state machine or another logic unit for determining the time phases T1, T2, T3, T4, T5.

[0110] FIG. 6 shows in an upper panel a timely evolution of an acceleration A(t) of the vehicle 1 driving through the curve 13 (FIG. 2). Further, in a lower panel of FIG. 6, a timely evolution of a jerk J(t) of the vehicle 1 is shown. The jerk J(t) is the first derivative with respect to time of the acceleration A(t). That means, the jerk indicates a timely variation of the acceleration A(t).

[0111] As shown in FIG. 6, a first time phase T1 of negative acceleration (braking) and negative jerk (increasing braking) is determined, the first time phase T1 corresponding, for example, to a state in which and/or before the vehicle 1 enters the curve 13 (FIG. 2). Further, a second time phase T2 of constant negative acceleration (constant braking) and zero jerk is determined, the second time phase T2 corresponding, for example, to a state in which the vehicle 1 is driving within the curve 13. Furthermore, a third time phase T3 of negative acceleration (still braking) but positive jerk (decreasing braking) is determined, third time phase T3 being, for example, a time phase of (preparing) driving, when inside the curve 13, the current velocity V.sub.C is getting close to the nominal velocity V.sub.A. In addition, a fourth time phase T4 of zero jerk and zero acceleration (i.e. constant velocity) is determined. The third and fourth time phases T3, T4 may be called release and constant speed phases. Further, a fifth time phase T5 of positive jerk and positive acceleration is determined. The time phases T1, T2, T3, T4 and T5 are continuous with each other, as shown in FIG. 5.

[0112] The curvature control unit 26 further comprises a limitation unit 29 (FIG. 7) for limiting the acceleration A and/or the jerk J (FIG. 6) of the vehicle 1. In particular, the curvature control function is performed such that the acceleration A (i.e. an absolute value of the acceleration A) of the vehicle 1 is below a predetermined acceleration threshold ?.sub.th. Further, the curvature control function is performed such that the jerk J (i.e. an absolute value of the jerk) of the vehicle 1 is below a predetermined jerk threshold J.sub.th.

[0113] Thus, the radius ahead R.sub.A of the curvature of the curve 13 of the road 14 on which the vehicle 1 is driving (FIG. 2) is anticipated based on odometry data (?, w, FIG. 3) andif lane markings 19 are detectedbased on a curvature of the lane markings 19 (FIG. 4). Based on the radius ahead R.sub.A a nominal velocity V.sub.A as a desired velocity at the position ahead P2 is calculated. Further, a curvature control (FIG. 7) is performed such that in the process of realizing the nominal velocity V.sub.A, braking and positive acceleration as well as the jerk are limited (FIG. 6) to values that ensure the safety and comfort of the driver and other passengers of the vehicle 1.

[0114] Although the present invention has been described in accordance with preferred embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments.

LIST OF REFERENCE SIGNS

[0115] 1 vehicle [0116] 2 control system [0117] 3 sensor system [0118] 4 sensor unit [0119] 5 sensor unit [0120] 6 sensor unit [0121] 7 sensor unit [0122] 8 surrounding [0123] 9 windscreen [0124] 10 steering-angle sensor [0125] 11 steering shaft [0126] 12 steering wheel [0127] 13,13 curve [0128] 14,14 road [0129] 15 driving direction [0130] 16 receiving unit [0131] 17 wheel [0132] 18 wheel [0133] 19 lane markings [0134] 20 determining unit [0135] 21 determining unit [0136] 22 arbitration unit [0137] 23 data point [0138] 24 error bar [0139] 25 determining unit [0140] 26 curvature control unit [0141] 27 PD-control unit [0142] 28 setpoint [0143] 29 process variable [0144] ? steering-angle [0145] ?R.sub.L error [0146] A acceleration [0147] A.sub.A acceleration [0148] A.sub.th acceleration threshold [0149] J jerk [0150] J.sub.th jerk threshold [0151] L distance [0152] P1 current position [0153] P2 position ahead [0154] R.sub.A radius [0155] R.sub.C radius [0156] R.sub.L radius [0157] R.sub.O radius [0158] R.sub.th radius threshold [0159] S1-S6 method steps [0160] T1 time phase [0161] T2 time phase [0162] T3 time phase [0163] T4 time phase [0164] T5 time phase [0165] V.sub.A velocity [0166] V.sub.C velocity [0167] W steering-angle velocity