Driver assistance system for motor vehicles

Abstract

A driver assistance system for motor vehicles, including a locating system for locating preceding vehicles and a longitudinal guidance module for controlling the longitudinal movement of the host vehicle as a function of location data of located objects. The longitudinal guidance module includes a driving path module, for defining a driving path ahead of the host vehicle, and an adaptive cruise control function, which adjusts a time gap between the host vehicle and a target object located within the driving path to a setpoint value. The longitudinal guidance module includes a dynamic function which, under certain conditions indicating that the target object will leave the driving path, modifies the longitudinal guidance function within the context of a more rapidly commencing acceleration in response to a command of the driver.

Claims

1. A driver assistance system for a motor vehicle, which is a host vehicle, comprising: a locating system configured to locate preceding vehicles; and a longitudinal guidance module configured to control longitudinal movement of the host vehicle as a function of location data of located objects; wherein the longitudinal guidance module includes a driving path module to define a driving path ahead of the host vehicle, and an adaptive cruise control function to adjust a time gap between the host vehicle and a target object located inside the driving path to a setpoint value, wherein the longitudinal guidance module further includes a dynamic function to, under particular conditions indicating that the target object will leave the driving path, modify the longitudinal guidance function when a driver commands a commencement of an acceleration in response to a command of a driver, wherein the dynamic function modifies the longitudinal guidance function by reducing a width of the driving path, wherein when the width of the driving path is to be reduced, checking whether a lateral offset is positive or negative, when the lateral offset is negative, a right boundary of the driving path is shifted to the left, and wherein when a transverse offset is positive, a left boundary of the driving path is shifted to the right, wherein the dynamic function becomes available when the adaptive cruise control function is active, the brake pedal is not actuated by the driver of the host vehicle, and the driver of the host vehicle does not intend to initiate a lane change so that the turn signal is not activated, wherein the dynamic function is only triggered and the driving path is reduced when the following conditions are satisfied: (a) a velocity of the host vehicle is above a first threshold value; (b) an absolute value of a transverse offset of the vehicle is above a second threshold value, which indicates that the vehicle is leaving or about to leave the driving path, wherein the transverse offset is defined as a lateral deviation of the vehicle from a center of the driving path; (c) a curvature of the driving path is below a third threshold value; and (d) actuation of a gas pedal or a twist grip is above a fourth threshold value.

2. The driver assistance system as recited in claim 1, wherein the dynamic function modifies the longitudinal guidance function by reducing the setpoint value for the time gap.

3. The driver assistance system as recited in claim 1, wherein one of the conditions which has to be met for the modification of the longitudinal guidance function is that an absolute value of a lateral offset of the preceding vehicle is smaller than a certain threshold value.

4. The driver assistance system as recited in claim 1, wherein an input device for inputting the driver command is: (i) a device for detecting a position of a gas pedal of the vehicle, or a device for detecting a position of a hand grip of the vehicle, and (ii) for comparing the detected position to a threshold value.

5. The driver assistance system as recited in claim 4, wherein the dynamic function varies the threshold value for the position of the gas pedal or the position of a hand grip, according to a situation.

6. The driver assistance system as recited in claim 4, wherein the dynamic function modifies the longitudinal guidance function by reducing the setpoint value for the time gap, and wherein when the driver actuates the gas pedal or the hand grip and when the gas pedal or the hand grip exceeds a calculated threshold, there is a command for triggering the dynamic function.

7. The driver assistance system as recited in claim 1, wherein the following are satisfied: (e) the brake pedal is not being actuated by the driver of the host vehicle; (f) the driver of the host vehicle is not initiating a lane change, so that the turn signal is not activated; and (g) a following travel situation is present, so that the setpoint time gap selected by the driver is not smaller than an instantaneous time gap.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a block diagram of a driver assistance system according to an example embodiment of the present invention.

(2) FIG. 2 shows four stages of a traffic situation in which a vehicle initially followed in following travel pulls out into an adjoining lane.

(3) FIG. 3 shows the sequence of the same traffic situation as in FIG. 2 using a driver assistance system according to the present invention.

(4) FIG. 4 shows a representation of the motion sequences according to FIG. 3 in a path/time diagram.

(5) FIG. 5 shows diagrams to illustrate the chronological progression of different parameters and variables in a driver assistance system according to an example embodiment of the present invention.

(6) FIG. 6 shows a flowchart to explain a possible mode of operation of the driver assistance system according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(7) The driver assistance system shown in FIG. 1 includes a locating system 10, for example an angle-resolving radar sensor, and a longitudinal guidance module 12, which controls the longitudinal guidance of the vehicle based on the location data received from locating system 10 by outputting commands to a drive system of the vehicle, which is not shown, via an output 14.

(8) Longitudinal guidance module 12 includes a driving path module 16 which, based on data it receives from locating system 10 and/or based on dynamic data which characterize the movement state of the host vehicle, defines a driving path 18 (FIG. 2) ahead of the host vehicle, i.e., a strip-shaped zone on the roadway which extends essentially in the driving direction and which at least has the width of the host vehicle and within which the vehicle will presumably move during the further course of the trip. Specifically, the driving path module 16 establishes a left and a right boundary of driving path 18.

(9) Longitudinal guidance module 12 furthermore includes an adaptive cruise control function 20, which is also shown symbolically here as a block and which is active whenever at least one preceding vehicle is located inside driving path 18. For this purpose, the adaptive cruise control function compares the location data, in particular the lateral positions of the located non-stationary objects, to the boundaries of the driving path supplied by driving path module 16. The object inside the driving path for which the smallest distance is measured forms the target object for the adaptive cruise control. Based on the distance and the relative speed of the target object, a positive or negative setpoint acceleration, which is then output via output 14, is calculated in such a way that the host vehicle follows the target object with a time gap selectable by the driver.

(10) Longitudinal guidance module 12 furthermore includes a dynamic module 22, which receives the location data of the target object as well as the driving path data via the adaptive cruise control function and/or driving path module 18. Dynamic module 22 is connected to an input device 24, which in the shown example is formed by the gas pedal or a twist grip and via which the driver is able to actively input a command. When the location data of the target object indicate that this target object is about to leave the driving path, and when the dynamic module at the same time receives the driver command, dynamic module 22 acts on adaptive cruise control function 20 in such a way that an acceleration of the host vehicle, which would normally only occur when the target object has in fact left the driving path, already commences sooner and/or is more pronounced.

(11) The purpose of dynamic module 24 is to be explained based on FIGS. 2 and 3.

(12) FIG. 2 shows four stages A, B, C, D of a traffic situation in which a vehicle 26 switches from a central lane 28 of a roadway onto a right adjoining lane 30. The future course of vehicle 26 is indicated by a dotted arrow. A following vehicle 32 is equipped with a driver assistance system and is to be referred to hereafter as “the host vehicle.” It is assumed in FIG. 2 that the driver assistance system is a conventional system, which does not include dynamic module 22. Velocity v of host vehicle 32 is indicated by a vector arrow.

(13) In stage A, velocity v of host vehicle 32 is greater than that of preceding vehicle 26 so that the distance between the vehicles decreases. Locating system 10 has detected preceding vehicle 26 and recognized that this vehicle is situated inside driving path 18. Adaptive cruise control function 20 orders a negative acceleration of the host vehicle so that its velocity decreases, and the host vehicle does not pull up too closely to preceding vehicle 26.

(14) In stage B, velocity v of the host vehicle has decreased to the velocity of the preceding vehicle, so that the distance and the time gap between the two vehicles remain constant. The preceding vehicle has moved slightly to the right and is in the process of crossing the boundary between lanes 28 and 30. However, it is still situated inside driving path 18, so that the adaptive cruise control is continued.

(15) In stage C, preceding vehicle 26 has completely left central lane 28 so that host vehicle 32 could actually accelerate again. However, since preceding vehicle 26 has not yet completely left driving path 18, it is not yet released as a target object, and the adaptive cruise control is continued further, so that the host vehicle continues to drive at the slower velocity of preceding vehicle 26, and follows it with a constant time gap.

(16) Only in stage D has preceding vehicle 26 left driving path 18, and host vehicle 32 is accelerated again, so that a passing maneuver is initiated.

(17) FIG. 3 shows the sequence of the same traffic situation as in FIG. 2; however, this time under the assumption that the host vehicle is equipped with a driver assistance system according to the present invention including dynamic module 22. In stage A, the situation is the same as in FIG. 2. In stage B, the locating system has recognized that the lateral position of preceding vehicle 26 has changed. The driver of host vehicle 32 also recognizes that preceding vehicle 26 is about to pull out onto adjoining lane 30, and he or she thereupon actuates input device 24 to trigger the dynamic function. The dynamic function thereupon causes driving path 18 to be narrowed in that the right boundary of the driving path is moved to the left. Preceding vehicle 26, however, has also not yet left the narrowed driving path, so that the adaptive cruise control is continued further in stage B.

(18) In stage C, preceding vehicle 26 has not only left central lane 28 completely, but also driving path 18, so that the adaptive cruise control function releases vehicle 26 as a target object, and already in this stage allows the acceleration of host vehicle 32. The passing maneuver is thus initiated sooner and accordingly is completed sooner, so that vehicle 26 is able to switch sooner again to the central adjoining lane 28 when an even slower vehicle is driving further ahead.

(19) FIG. 4 shows the motion sequence illustrated in FIG. 3 in the form of a path/time diagram. Time t is plotted on the vertical axis, and location x in the longitudinal direction of the roadway is plotted on the horizontal axis. A curve 26a shown with dotted lines indicates the location of preceding vehicle 26 as a function of time t. A curve 32a shown in solid lines indicates the location of host vehicle 32 in the motion sequence according to FIG. 3. By comparison, a curve 32b shows the location of host vehicle 32 in the motion sequence according to FIG. 2. The points in time which correspond to stages A through D in FIGS. 2 and 3 are all plotted as horizontal lines.

(20) Dynamic module 22 causes host vehicle 32 to already be accelerated again in stage C, as is indicated by curve 32a. Vehicle 26 is passed (curve 32a intersects curve 26a) at a point in time E. Without the dynamic module, the acceleration of the host vehicle would only just have begun at this point in time (stage D), and vehicle 26 would not be passed until a considerably later point in time E′.

(21) FIG. 5 illustrates an example in which dynamics module 22 not only causes a reduction of the driving path, but also a reduction of the setpoint time gap with which the target object is followed. Curve 34 in the upper diagram in FIG. 5 indicates the progression of a logic variable FS as a function of time t. When this variable has the value 0, driving path 18 has the regular width. When, in contrast, the variable has the value 1, the width of the driving path is reduced by a certain amount. This amount may be fixed or variable and, in any case, is selected in such a way that the width of the driving path is greater than the width of the host vehicle.

(22) Curve 36 in the second diagram in FIG. 5 indicates the value of a logic variable TS as a function of time t. This variable denotes a reduction in the setpoint time gap with which vehicle 26 is followed. TS=1 means that the adaptive cruise control takes place with the regular time gap selected by the driver. TS=0 means that the time gap is decreased by a certain amount, so that host vehicle 32 is temporarily accelerated. In the shown example, the driving path reduction begins in stage B, and the setpoint time gap is also reduced a little later.

(23) Curve 38 in the third diagram in FIG. 5 indicates the state of a logic variable ZO as a function of time t. Variable ZO indicates whether the target object is detected (ZO=1) or released (ZO=0). In the shown example, the release of the target object takes place at point in time D.

(24) Curve 40 in the fourth diagram in FIG. 5 indicates the value of a logic variable G as a function of time t. Variable G marks the gear change at which the gear level of the vehicle transmission is reduced by one gear to enable a swifter acceleration. This gear change is automatically triggered by the transmission management system of the vehicle, depending on the acceleration requirements output via output 14.

(25) Curve 42 in FIG. 5 indicates rotational speed N of the drive motor as a function of time t, and curve 44 indicates acceleration a of the host vehicle as a function of time t.

(26) In the shown example, the timing of the reduction of the time gap represented by variable TS is selected in such a way that the phase of the temporary acceleration triggered by the reduction of the time gap has not yet been completed at point in time D at which the target object is released. In this way, it is prevented that the vehicle is decelerated again so as to maintain the reduced setpoint distance before the acceleration commences again at point in time D. As is indicated by curve 40, the gear change in this example takes place simultaneously with the reduction of the time gap (curve 36). Rotational speed N increases suddenly in the process, corresponding to the smaller gear level, and then another rotational speed build-up corresponding to the acceleration of the vehicle follows. As a result of the gear change and the corresponding increase in rotational speed at point in time S, the driver receives the feedback that the dynamic function was triggered in response to his/her command.

(27) One example of a possible special embodiment of the dynamic function is represented in FIG. 6 in the form of a flowchart. The routine represented by this flowchart is cyclically repeated in longitudinal guidance model 12 as long as adaptive cruise control function 20 is active.

(28) In step St1, it is checked whether the adaptive cruise control function is active. When this is not the case (N), the entire routine for the dynamic function is skipped. Otherwise (Y), the data of locating system 10 are queried in step St2. Based on these data, a gas pedal threshold or twist grip threshold is then calculated in step St3. The gas pedal or the twist grip of the vehicle forms input device 24 in this exemplary embodiment. When the driver actuates the gas pedal or the twist grip, and the gas pedal or the twist grip exceeds the threshold calculated in step St3, this is interpreted as a command for triggering the dynamic function. For example, the stronger the lateral position (the position perpendicular to the driving direction) of preceding vehicle 26 deviates from the center of lane 28, or from the center of driving path 18, and the faster the transverse movement of the preceding vehicle takes place, the more strongly the gas pedal threshold or the twist grip threshold is lowered.

(29) In step St4, a series of criteria is then checked, which all have to be met for the dynamic function to be triggered. A first criterion is that velocity v of the host vehicle must be above a certain threshold value S1. In a low velocity range, for example in city traffic, the dynamic function is not useful. Rather, this function is primarily intended for expressway traffic.

(30) A further criterion is that the absolute value |d| of the transverse offset of vehicle 26 must be above a certain threshold value S2.

(31) This criterion is an indication of vehicle 26 being about to leave the driving path. Transverse offset d is defined in the process as the lateral deviation of vehicle 26 from the center of driving path 18.

(32) A further criterion is that curvature k of the driving path is below a certain threshold value S3. The curvature of the driving path is determined by the presumable course of the host vehicle and is, as usual, calculated based on dynamic data of the host vehicle as well as, if necessary, also based on location data denoting the progression of the roadway, for example guard rails, guard rail posts or, when a video system is present, also roadway markings. The limitation to small driving path curvatures is to prevent faulty activations of the dynamic function from occurring in the case of a very curvy roadway due to lateral deviations being erroneously interpreted as an indication of a lane change.

(33) Further criteria relate to the brake pedal not being actuated by the driver of the host vehicle, and the driver of the host vehicle also not being about to initiate a lane change. It is therefore required that the turn signal is not activated, and also a possibly present passing assistance function is not active.

(34) A decisive criterion is furthermore that the extent FP of the actuation of the gas pedal or of the twist grip is above a threshold value S4, which was calculated in step St3.

(35) Finally, the condition must be met that a following travel situation is actually present, i.e., that setpoint time gap Tsetpoint selected by the driver is not smaller than instantaneous time gap Td (instantaneous distance of vehicle 26 divided by velocity v).

(36) When all these conditions are met (Y), a driving path reduction is ultimately carried out in step St7. Otherwise (N) the routine is ended.

(37) In the case of a positive result in step St4, it is checked in step St5 whether all criteria for a reduction of the time gap are met. One of these criteria is that the absolute value |d| of the transverse offset of vehicle 26 not only exceeds threshold value S2, but also a higher threshold value S5. This criterion is an even stronger indication of vehicle 26 being about to leave its own driving lane.

(38) A further criterion is that also extent FP of the actuation of the gas pedal or of the twist grip exceeds a higher threshold value S6. This means that the reduction of the time gap only takes place when the driver emphatically demands the dynamic function, and for this purposes depresses the gas pedal more strongly or twists the driving twist grip further.

(39) Finally, the criterion that the instantaneous time gap Td is not greater than a certain threshold value S7 is also checked. In this way, the reduction of the time gap, and the acceleration of the vehicle associated therewith, are prevented from being initiated too soon.

(40) When all these criteria are met (Y), the width of the time gap is reduced in step St6. Otherwise (N), step St6 is skipped, and the reduction of the driving path follows directly in step St7. However, in step St7 it is only decided that the width of the driving path is to be reduced, and it is not yet established whether this is to take place by shifting the left boundary or the right boundary of the driving path. For this decision, it is checked in step St8 whether the lateral offset d is positive or negative. When it is negative (d<0), this means that vehicle 26 is pulling out to the right, and the right boundary of driving path 18 is shifted (to the left) in step St9. When the transverse offset is positive, the left boundary of the driving path is shifted (to the right) in step St10.

(41) The routine is ended with step St9 or step St10, and a return to step St1 takes place.

(42) Threshold values S1 to S7, which are checked in steps St4 and St5, may be constant or varied according to the situation, depending on the specific embodiment.