Distance control for a vehicle with trailer

Abstract

The present invention refers to a method for controlling a distance of a vehicle (10) to a closest preceding vehicle (60), whereby the vehicle (10) has a trailer (12) connected thereto, comprising the steps of determining a velocity of the vehicle (10), detecting a closest preceding vehicle (60), determining a distance (62) to the closest preceding vehicle (60), and determining a safe distance based on the velocity of the vehicle (10) and the distance (62) to the closest preceding vehicle (60), wherein the method further comprises determining an extra safe distance based on at least one characteristic of the trailer (12), and performing a control of the distance (62) to the closest preceding vehicle (60) to stay above the safe distance plus the extra safe distance. The present invention also refers to a driving assistance system (14) for a vehicle (10), which is adapted to perform the above method. The present invention further refers to a vehicle (10) with an above driving assistance system (14).

Claims

1. A method for controlling a distance of a vehicle to a closest preceding vehicle, whereby the vehicle has a trailer connected thereto, the method comprising: determining a velocity of the vehicle; detecting a closest preceding vehicle; determining a distance to the closest preceding vehicle; determining a safe distance based on the velocity of the vehicle and the distance to the closest preceding vehicle; identifying a type of the trailer based on a rear input from a rear camera of the vehicle; determining an extra safe distance based on at least one characteristic of the trailer; and performing a control of the distance to the closest preceding vehicle to stay above the safe distance plus the extra safe distance by: comparing the distance to the closest preceding vehicle to the safe distance plus the extra safe distance, and controlling the vehicle to reduce the distance to the closest preceding vehicle when the distance to the closest preceding vehicle is greater than the safe distance plus the extra safe distance, and controlling the vehicle to increase the distance to the closest preceding vehicle when the distance to the closest preceding vehicle is smaller than the safe distance plus the extra safe distance, and wherein determining the distance to the closest preceding vehicle comprises: determining a road feature when appearing for a first time at a back of the closest preceding vehicle, determining a distance to the road feature with a pre-set period, until the road feature is not visible, determining a change in distance of the road feature for each period based on a front input from a front camera of the vehicle, and summing up the changes in the distance for all periods, wherein determining the extra safe distance based on at least one characteristic of the trailer comprises: determining a trailer motion model that generates a prediction of unstable swaying condition of the trailer based on odometry data of the trailer and an angle of the trailer, and determining, under consideration of the trailer motion model, the extra safe distance based on the prediction of the unstable swaying condition.

2. The method according to claim 1, wherein determining the extra safe distance based on at least one characteristic of the trailer further comprises determining trailer dimensions and determining the extra safe distance under consideration of the trailer dimensions.

3. The method according to claim 1, wherein determining the extra safe distance based on at least one characteristic of the trailer further comprises determining the at least one characteristic of the trailer based on the type of the trailer.

4. A driving assistance system for a vehicle, wherein the driving assistance system is adapted to perform the method according to claim 1 to control the distance of the vehicle to the closest preceding vehicle.

5. The driving assistance system according to claim 4, wherein the driving assistance system is an adaptive cruise control or an autonomous driving system.

6. A vehicle with a driving assistance system according to claim 4.

7. The method according to claim 1, further comprising: receiving a velocity of the trailer, wherein determining the extra safe distance based on at least one characteristic of the trailer further comprises determining the extra safe distance under consideration of the velocity of the trailer.

8. The method according to claim 1, wherein determining the road feature comprises scanning vertically down within road boundaries to identify a big texture change, providing a boundary box around the big texture change, and detecting the road feature within the boundary box.

9. The method according to claim 1, wherein determining the distance to the closest preceding vehicle comprises generating a ground map, and determining the distance to the closest preceding vehicle based on the ground map.

Description

(1) In the drawings:

(2) FIG. 1 shows a schematic view of a driving assistance system of a vehicle according to a first, preferred embodiment,

(3) FIG. 2 contains three detailed pictures of a road for road feature detection, taken by a camera of the driving assistance system of the vehicle according to the first embodiment, in a perspective view at three subsequent points of time,

(4) FIG. 3 contains three schematic representations of the vehicle of the first embodiment behind a preceding car together with a road feature provided on the road, and

(5) FIG. 4 shows a flow chart of a method for controlling a distance of a vehicle to a closest preceding vehicle in accordance with the driving assistance system and the vehicle of the first embodiment.

(6) FIGS. 1 and 3 refer to a vehicle 10 with a trailer 12 and a driving assistance system 14 for the vehicle 10 with the trailer 12 according to a first, preferred embodiment. The vehicle 10 is shown in FIG. 3. The driving assistance system 14 is schematically depicted in FIG. 1.

(7) As can be seen in FIG. 1, the driving assistance system 14 comprises a central processing module 16, which will be discussed later in more detail. The driving assistance system 14 further comprises a rear camera 18 as rear input, which is mounted at a rear side of the vehicle 10. The driving assistance system 14 further comprises a front camera 20 as front input, which is mounted at a front side of the vehicle 10. The rear camera 18 and the front camera 20 are embodiments of environment sensors for monitoring the environment surrounding the vehicle 10.

(8) The processing module 16 of the driving assistance system 14 comprises a trailer type detection module 22. The trailer type detection module 22 receives the rear input from the rear camera 18 and automatically determines a type of trailer 12 connected to the vehicle 10. The type of trailer 12 is provided to a trailer data extraction module 24 of the processing module 16.

(9) The trailer data extraction module 24 accesses a memory of the driving assistance system 14, where physical data regarding characteristics of the different types of trailers 12 is stored in a database containing physical data for most common trailers. Hence, characteristics of the trailer 12 are automatically determined based on the type of the trailer 12. The trailer data extraction module 24 reads the physical data regarding characteristics of the trailer 12 connected to the vehicle 10. In this embodiment, the physical data comprises dimensions of the trailer 12, i.e. a length and width as well as height of the trailer 12, a weight of the trailer 12, and braking capabilities of the trailer 12 together with the vehicle 10. The trailer data extraction module 24 provides the physical data to an extra safe distance calculation module 26.

(10) The processing module 16 further comprises a trailer angle detection module 28. The trailer angle detection module 28 receives the rear input from the rear camera 18 and determines an angle of the trailer 12 in respect to the vehicle 10. The determination of the angle of the trailer 12 in respect to the vehicle 10 is based in this embodiment on a tow bar detection and segmentation. The angle of the trailer 12 in respect to the vehicle 10 is provided as first input to a trailer motion model module 30.

(11) The processing module 16 also comprises a vehicle odometry module 32. The vehicle odometry module 32 provides odometry information from the vehicle 10 as a second input to the trailer motion model module 30. The odometry information comprises e.g. a velocity the vehicle 10 as determined based on wheel rotation.

(12) The trailer motion model module 30 determines a trailer motion model based on motion characteristics of the trailer 12. The motion characteristics allows predicting trailer 12 movement, in particular for sway conditions. The trailer motion model module 30 receives as input the odometry information of the trailer 12 and the angle of the trailer 12 in respect to the vehicle 10 to predict a movement of the trailer 12.

(13) Both the trailer motion model module 30 and the vehicle odometry module 32 also provide information to the extra safe distance calculation module 26. As can be seen in FIG. 1, also the angle of the trailer 12 in respect to the vehicle 10 is provided as input to the extra safe distance calculation module 26.

(14) The extra safe distance calculation module 26 calculates an extra safe distance for the vehicle 10 with the trailer 12 based on the provided inputs including the physical data of the trailer 12, as provided from the trailer data extraction module 24, the motion model, as provided from the trailer motion model module 30, the odometry information, as provided from the vehicle odometry module 32, and the angle of the trailer 12 in respect to the vehicle 10, as provided from the trailer angle detection module 28. The extra safe distance is an additional safe distance to be added to a safe distance, based on additional requirements when towing a trailer 12. The safe distance refers to a distance that enables the vehicle to securely performing a stop, e.g. without bumping against a preceding vehicle 60. It can be based on the assumption of the preceding vehicle 60 coming to an immediate stop, e.g. in case of an accident, or the preceding vehicle making an immediate breaking maneuver at maximum retardation, or any other suitable retardation.

(15) The processing module 16 still further comprises a road edge detection module 34. The road edge detection module 34 receives the front input from the front camera 20 and determines edges or boundaries of a road 50, which can be seen in FIG. 2. Hence, the road edge detection module 34 receives frames as provided from the front camera 20. The information is provided for further processing to a road feature detection and tracking module 36.

(16) The road feature detection and tracking module 36 performs a scanning vertically down in the frames provided from the front camera 20 within the road boundaries to identify a big texture change. It provides a boundary box 58 around the big texture change. Then, the road feature detection and tracking module 36 determines road features 52, 54, 56, which are in this embodiment a dashed lane segment 52 and a road hole 54, as can be seen e.g. with respect to FIG. 2, or an object 56, as can be seen with respect to FIG. 3. The road features 52, 54, 56 are detected and tracked within the respective boundary boxes 58 through frames provided by the front camera 20. Tracking of road features 52, 54, 56 can be seen in FIG. 2, where road features 52, 54, 56 are tracked through different frames. The road features 52, 54, 56 are tracked within their boundary boxes 58 when travelling from their first appearance behind the closest preceding vehicle 60, as can be seen in part a. of FIG. 2, until they reach the vehicle 10, as can be seen in part b. of FIG. 2.

(17) The processing module 16 still further comprises a distance determination module 38. The distance determination module 38 operates based on a ground map, which is a two-dimensional representation of a surrounding of the vehicle 10 in the kind of a top view. Hence, the distance 62 to the closest preceding vehicle 60 based on the ground map. The ground map is generated by the road feature detection and tracking module 36 or the distance determination module 38.

(18) Determination of the distance 62 between the vehicle 10 and the closest preceding vehicle 60 comprises determining each road feature 52, 54, 56, when appearing for a first time at a back of the closest preceding vehicle 60, until the road features 52, 54, 56 is not visible anymore. Hence, the distance 62 to the closest preceding vehicle 60 can be determined by the time, the road feature 52, 54, 56 requires for traveling along arrow 64 through the frames from the closest preceding vehicle 60 to the vehicle 10, as can be seen in FIG. 3. In this embodiment, the road features 52, 54, 56 are detected and tracked with a pre-set period, which corresponds to the period the frames as generated by the front camera 20. The distance determination module 38 then provides the determined distance 62 to a feedback module 40.

(19) In particular, the distance determination module 38 works as follows. A first difference vector 66 is calculated based on a current position of a ground plane point, i.e. the respective road feature 52, 54, 56, and a reference ground plane point position. The reference ground plane point position is the position of the respective road feature 52, 54, 56, when appearing for a first time at the back of the closest preceding vehicle 60. The first difference vector 66 corresponds to a first change in distance, which is the length of the first difference vector 66 in meters. Subsequent difference vectors 68 are calculated in the same way based on a respective current position of ground plane point, i.e. the road feature 52, 54, 56, and a previous ground plane point position. The subsequent difference vector 68 corresponds to a subsequent change in distance, which is the length of the subsequent difference vector 68 in meters. Further subsequent difference vectors 68 can be calculated, until the road feature 52, 54, 56 is not visible anymore. The distance 62 between the closest preceding vehicle 60 and the vehicle 10 is calculated by adding the lengths of all difference vectors 66, 68 for the respective road feature 52, 54, 56 while traveling along arrow 64.

(20) In an alternative embodiment, a change in distance of the road feature 52, 54, 56 is determined for each frame, and the changes in the distance are summed up for all periods.

(21) Apart from the distance 62 provided from the distance determination module 38, the feedback module 40 receives the extra safe distance as provided from the extra safe distance calculation module 26. The safe distance is specified as a time of two seconds in this embodiment. The extra safe distance provided from the extra safe distance calculation module 26 is provided in terms of time and added to the safe distance to obtain a desired distance between the closest preceding vehicle 60 and the vehicle 10. Based on the distance 62 provided from the distance determination module 38, the feedback module 40 performs a control of the distance 62 between the vehicle 10 and the closest preceding vehicle 60 and provides a control output to an output module 42, which applies the control output to the vehicle 10 by breaking or accelerating the vehicle 10. Hence, the feedback module 40 controls the vehicle 10 to reduce its distance 62 to the closest preceding vehicle 60, if the distance 62 to the closest preceding vehicle 60 is bigger than the safe distance plus the extra safe distance, or to increase its distance 62 to the closest preceding vehicle 60, if the distance 62 to the closest preceding vehicle 60 is smaller than the safe distance plus the extra safe distance. Accordingly, the distance 62 is reliably maintained.

(22) The control by the feedback module 40 is performed under additional consideration of further control parameters including speed limits, pre-set preferred traveling velocity, and traffic conditions. In general, the control is performed so that the distance 62 does not go below the desired distance to the preceding vehicle 60, whereas an increase of the distance 62 to the preceding vehicle 60 compared to the desired distance is tolerated, as long as it is based on additional control input.

(23) The feedback module 40 continuously checks the distance 62 with respect to determine an updated extra safe distance.

(24) Subsequently, a method for controlling the distance 62 of the vehicle 10 to the closest preceding vehicle 60 is discussed with respect to the flow chart of FIG. 4. The driving assistance system 14 is adapted to perform the method to control a distance 62 of the vehicle 10 to a closest preceding vehicle 60. The driving assistance system 14 is an adaptive cruise control or an autonomous driving system in according to the first embodiment. The different method steps can be performed in different sequences. Although described in a given order, this does not constitute a limitation that the method steps have to be performed in the described order.

(25) The method starts with step S100, which refers to determining a velocity of the vehicle 10. The vehicle information is obtained from the vehicle odometry module 32 as discussed above.

(26) In step S110, the closest preceding vehicle 60 is detected. The closest preceding vehicle 60 refers to a vehicle directly ahead of the own vehicle 10. Vehicles approaching on lanes belonging to opposite driving directions are not considered. Furthermore, in situations with multiple lanes for the same direction, the closest preceding vehicle 60 refers to the closest preceding vehicle 60 on the same lane. The closest preceding vehicle 60 is determined and tracked as a basis for the determination and tracking of road features 52, 54, 56 in the road feature detection and tracking module 36.

(27) In step S120, a distance 62 to the closest preceding vehicle 60 is determined. The distance 62 is determined as described above with respect to the distance determination module 38.

(28) In step S130, the safe distance is determined based on the velocity of the vehicle 10 and the distance 62 to the closest preceding vehicle 60. In this embodiment, the distance is defined in terms of time, so that by specifying a time of e.g. two seconds as equivalent to the safe distance considers both the velocity of the vehicle 10 and the distance 62 to the closest preceding vehicle 60.

(29) In step S140, the extra safe distance is determined, as discussed above with respect to the extra safe distance calculation module 26.

(30) In step S150, a control of the distance 62 to the closest preceding vehicle 60 is performed to stay above the safe distance plus the extra safe distance. The control is performed as discussed above with respect to the feedback module 40. Hence, the control of the distance 62 to the closest preceding vehicle 60 is performed by determining a distance 62 to the closest preceding vehicle 60, comparing the distance 62 to the closest preceding vehicle 60 to the safe distance plus the extra safe distance, and controlling the vehicle 10 to accelerate or decelerate via output module 42.

REFERENCE SIGNS LIST

(31) vehicle 10 trailer 12 driving assistance system 14 processing module 16 rear input, rear camera 18 front input, front camera 20 trailer type detection module 22 trailer data extraction module 24 extra safe distance calculation module 26 trailer angle detection module 28 trailer motion model module 30 vehicle odometry module 32 road edge detection module 34 road feature detection and tracking module 36 distance determination module 38 feedback module 40 output module, control output 42 road 50 road feature, dashed line segment 52 road feature, road hole 54 road feature, object 56 boundary box 58 preceding vehicle 60 distance 62 arrow 64 first difference vector, first change in distance 66 subsequent difference vector, subsequent change in distance 68