System for a towing vehicle

Abstract

The present invention relates to a vehicle control system (1) for controlling a trailer (5) coupled to a vehicle (3) during a reversing operation. The vehicle control system includes a processor (29) configured to determine an actual trailer travel direction (T.sub.ACT) based on one or more sensor signals. The processor (29) receives a demanded trailer travel direction (T.sub.DEM), for example from a user. A maximum permissible hitch angle (.sub.MAX) is calculated by the processor (29) and the demanded trailer travel direction (T.sub.DEM) is limited to an angle less than or equal to the calculated maximum permissible hitch angle (.sub.MAX). The present invention also relates to a vehicle (3) incorporating the vehicle control system (1); and a method of controlling the reversing of the trailer (5).

Claims

1. A system for a vehicle having a trailer coupled thereto, the system comprising a processor configured to: receive a demanded trailer travel direction; calculate a maximum permissible hitch angle; limit the demanded trailer travel direction to an angle less than or equal to the calculated maximum permissible hitch angle; and responsive to calculating the maximum permissible hitch angle, output a steering control signal to control a steering angle of the vehicle to guide the trailer in the demanded trailer travel direction.

2. The system as claimed in claim 1, wherein the processor is further configured to determine an actual trailer travel direction based on one or more sensor signals, and to estimate a distance to be travelled by the vehicle at least substantially to match the actual trailer travel direction with the demanded trailer travel direction.

3. The system as claimed in claim 1, further comprising a display in communication with the processor and operative to display system information for a driver.

4. The system as claimed in claim 3, wherein the display is operative to display one or more of the following: (a) the actual trailer travel direction; (b) the demanded trailer travel direction; (c) a numerical or graphical indication of the estimated distance to be travelled; (d) a location where the actual trailer travel direction will at least substantially match the demanded trailer travel direction; (e) an angular offset between the actual trailer travel direction and the demanded trailer travel direction; (f) the maximum permissible hitch angle; (g) a current steering angle; and (h) one or more trajectory lines representing a predicted path of the vehicle and/or the trailer.

5. The system as claimed in claim 1, wherein the processor is further configured to output the steering control signal to an electronic power assisted steering (EPAS) module.

6. The system as claimed in claim 1, wherein the demanded trailer travel direction is specified by a user.

7. A vehicle comprising the system as claimed in claim 1.

8. A method of operating a vehicle coupled to a trailer during a reversing operation, the method comprising: receiving a demanded trailer travel direction; calculating a maximum permissible hitch angle; limiting the demanded trailer travel direction to an angle less than or equal to the calculated maximum permissible hitch angle; and responsive to the calculating, outputting a steering control signal to control a steering angle of the vehicle to guide the trailer in the demanded trailer travel direction.

9. The method as claimed in claim 8, wherein the steering control signal is output to an electronic power assisted steering (EPAS) module to provide automated control of the steering angle of the vehicle.

10. The method as claimed in claim 8, further comprising determining an actual trailer travel direction based on one or more sensor signals, and estimating a distance to be travelled by the vehicle at least substantially to match the actual trailer travel direction with the demanded trailer travel direction.

11. The method as claimed in claim 8, further comprising displaying system information for a driver.

12. The method as claimed in claim 8, further comprising displaying one or more of the following: (a) the actual trailer travel direction; (b) the demanded trailer travel direction; (c) a numerical or graphical indication of the estimated distance to be travelled; (d) a location where the actual trailer travel direction will at least substantially match the demanded trailer travel direction; (e) an angular offset between the actual trailer travel direction and the demanded trailer travel direction; (f) the maximum permissible hitch angle; (g) a current steering angle; and (h) one or more trajectory lines representing a predicted path of the vehicle and/or the trailer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which:

(2) FIG. 1 shows a plan view of a trailer coupled to a vehicle incorporating a system in accordance with an embodiment of the present invention;

(3) FIG. 2 shows a schematic representation of the vehicle and the system in accordance with an embodiment of the present invention;

(4) FIG. 3 illustrates the vehicle and trailer dimensions and associated nomenclature;

(5) FIG. 4 shows a first display image from a rear camera mounted to the vehicle with information overlaid onto the video image to facilitate reversing the trailer (which is omitted from the image for clarity); and

(6) FIG. 5 shows a second display image from the rear camera with an alternate set of information overlaid onto the video image.

DETAILED DESCRIPTION OF AN EMBODIMENT

(7) A system 1 for assisting with the reversing of a vehicle 3 and a trailer 5 in accordance with an embodiment of the present invention will now be described with reference to FIGS. 1 to 4.

(8) The system is operable to facilitate reversing of the trailer 5 when it is coupled to the vehicle 3 (the combination of the vehicle 3 and the trailer 5 can be referred to as a rig). More specifically, the system 1 is configured to control the steering of the vehicle 3 such that the trailer 5 is reversed in a direction specified by the user. In the present embodiment, the operation of the throttle and brakes of the vehicle 3 are controlled by the user.

(9) A plan view of the vehicle 3 and the trailer 5 are shown in FIG. 1. The vehicle 3 has four wheels W1-4 and the front wheels W1, W2 of the vehicle 3 are steerable in conventional manner. The trailer 5 has two wheels TW1, TW2 having a fixed orientation.

(10) As shown in FIG. 2, the vehicle 3 is provided with an imaging system comprising a centrally mounted rear camera 9; and left and right side cameras 10, 11 mounted in respective wing mirrors 13, 15. The cameras 9, 10, 11 are optical cameras arranged to face to the rear of the vehicle 3 and their fields of view V1, V2, V3 are illustrated by dashed triangles in FIG. 1. The vehicle 3 optionally also comprises an obstruction detection system, for example side radar systems for detecting the presence of obstructions in the rear three quarters position of the vehicle 3.

(11) A tow hitch 17 is mounted to the vehicle 3 for coupling to a trailer coupling 19 mounted to the trailer 5. The tow hitch 17 is an upwardly projecting tow ball in the present embodiment. The trailer coupling 19 is mounted to a hitch frame 21 disposed at the front of the trailer 5. In the present embodiment, the hitch frame 21 is an A-frame having a front apex 23 to which the trailer coupling 7 is mounted. A target 25 is mounted to a front face 27 of the trailer 5 to enable the position of the trailer 5 relative to the vehicle 3 to be determined, as described herein. The target 25 is a visible image comprising three circles arranged in a triangular formation. It will be appreciated that the present invention can be implemented with other targets 25, for example comprising different symbols/images or non-visible targets.

(12) The system 1 comprises an electronic control unit (ECU) having an electronic processor 29. The processor 29 comprises image processing means in the form of an image processing module 29A for analysing the image data. The cameras 9, 10, 11 each output image data to the image processing module 29A for analysis. In use, the image processing module 29A analyses the image data to identify feature sets corresponding to predefined features. In the present embodiment, the target 25 defines a first feature set 31 and the hitch frame 21 defines a second feature set 33. The image processing module 29A identifies the first feature set 31 and/or the second feature set 33 within the image data to determine the position and orientation of the trailer 5 in relation to the vehicle 3.

(13) The first feature set 31 can be defined in a target geometry file; and the second feature set 33 can be defined in a trailer geometry file. The geometry files can both be stored on a storage medium accessible to the processor 29. The target geometry file can be predefined, for example to define a specific target design supplied by the vehicle manufacturer. The trailer geometry file can comprise data defining the geometry of the hitch frame 21 and optionally also the length and/or wheelbase of the trailer 5. A plurality of trailer geometry files can be stored, for example to represent different sizes/configurations of trailers 5. The system 1 can allow a user to select a predefined trailer model or to define a custom trailer model.

(14) The processor 29 further comprises vehicle/trailer guidance means in the form of a guidance module 29B. The guidance module 29B is provided to assist with guiding the trailer 5 when the vehicle 3 and the trailer 5 are being reversed together. In particular, the guidance module 29B is configured to control a steering angle of the front wheels W1, W2 of the vehicle 3 to guide the trailer 5 in a demanded trailer travel direction T.sub.DEM. As described herein, the demanded travel direction T.sub.DEM is defined by the user and represents a target direction of travel for the trailer 5.

(15) The vehicle 3 has a first longitudinal axis X1 and the trailer 5 has a second longitudinal axis X2. The angular offset between the first and second longitudinal axes X1, X2 is referred to as the hitch angle . During reversing, the trailer 5 travels in a direction T.sub.ACT corresponding to the hitch angle (unless the hitch angle exceeds a jack-knife angle for the trailer 5, as described herein).

(16) The image processing module 29A calculates the hitch angle , with reference to said first feature set 31 and/or said second feature set 33, and outputs a hitch angle signal to the guidance module 29B. When reversing, the guidance module 29B calculates the required steering angle 9 based on the following equation:
.sub.t+1=.sub.t+min(max(k(.sub.req.sub.cur),),) Where: .sub.t+1 and .sub.t are the steering angles of the vehicle 3 at frame t+1 and t (auto steering command from the algorithm and current steering from the CAN respectively); .sub.req and .sub.cur are the requested and current hitch angles; is the maximum steering offset value; and k is a constant multiplier.

(17) The value of the gain k can be calculated based on the relationship between and , as shown in FIG. 3. When the trailer hitch length L plus the towbar offset of the vehicle h is equal to the vehicle wheelbase d, then the relationship between and is one (1) for small angles and so the gain k can be set to a value of one (1). The gain k can therefore be calculated based on the following equation:

(18) $k=\frac{L+h}{d}$ Where: L is the hitch length of the trailer 5; h is the tow bar offset of the vehicle 3; d is the wheelbase of the vehicle 3;

(19) The gain k thereby compensates for the fact that longer trailers take longer to reach the requested hitch angle .

(20) The guidance module 29B is configured to calculate a maximum permissible hitch angle .sub.MAX. If the hitch angle exceeds the maximum permissible hitch angle .sub.MAX (which in the present embodiment is the jack-knife angle of the trailer 5), it is no longer possible to reduce the hitch angle by continuing to reverse (i.e. the trailer 5 has jack-knifed). With reference to FIG. 3, the guidance module 29B calculates the maximum permissible hitch angle .sub.MAX by applying the following set of equations:

(21) $R=\frac{d}{\tan \left(\right)}$$={\cos }^{-1}\left(\frac{-\mathrm{Lh}+R\sqrt{R^2+h^2-L^2}}{R^2+h^2}\right)\mathrm{for}\mathrm{positive}$$=-{\cos }^{-1}\left(\frac{-\mathrm{Lh}-R\sqrt{R^2+h^2-L^2}}{R^2+h^2}\right)\mathrm{for}\mathrm{negative}$ Where: R is the turning radius; is the steering angle of the vehicle 3; d is the wheelbase of the vehicle 3; h is the tow bar offset of the vehicle 3; L is the hitch length of the trailer 5;

(22) The wheelbase d, the tow bar offset h and the maximum steering angle .sub.MAX of the vehicle 3 are defined for the vehicle 3. The hitch length L of the trailer 5 is entered during trailer setup by the user (or can be determined during a calibration exercise). The guidance module 29B outputs a maximum hitch angle signal to indicate the maximum permissible hitch angle .sub.MAX for the current steering angle . The guidance module 29B is configured to inhibit the selection of a demanded trailer travel direction T.sub.DEM which is greater than the maximum permissible hitch angle .sub.MAX.

(23) The guidance module 29B is configured to calculate the distance to be travelled by the vehicle 3 before the actual trailer travel direction matches the demanded trailer travel direction T.sub.DEM. The distance is calculated based on a predictive path algorithm which models the path to be followed by the vehicle 3. The guidance module 29B calculates the initial required steering angle to achieve the desired hitch angle , then iteratively calculates the required steering angle and hitch angle . The distances to be travelled by the vehicle 3 between each of the iterations are then summed to provide the total distance to be travelled. The guidance module 29B outputs a distance signal to indicate the distance to be travelled by the vehicle 3.

(24) In use, the guidance module 29B is configured to output a steering control signal operative to control the steering angle of the front wheels W1, W2 to adjust the hitch angle , thereby modifying the actual trailer travel direction. Specifically, the guidance module 29B adjusts the steering angle (which can be positive or negative in relation to a reference point) to increase or decrease the hitch angle . The actual trailer travel direction T.sub.ACT can thereby be matched to the demanded trailer travel direction T.sub.DEM specified by the user. The hitch angle signal is updated at least substantially in real time and the guidance module 29B makes corresponding real time adjustments to the steering control signal. The guidance module 29B controls the hitch angle so that the difference between T.sub.ACT and T.sub.DEM is at least substantially zero. A tolerance of +/0.5 between T.sub.ACT and T.sub.DEM provides a good result.

(25) The guidance module 29B can generate a control sequence to reduce or minimise the distance travelled by the vehicle 3 and the trailer 5 to achieve the demanded trailer travel direction T.sub.DEM.

(26) The steering angle control signal is output to an electronic power assisted steering (EPAS) module 35 to control the angle of a steering wheel 37 to provide a required steering angle for the front wheels W1, W2. The EPAS module 35 automatically adjusts the angular orientation of the steering wheel 37 to provide the appropriate steering angle at the front wheels W1, W2 to control the vehicle 3 to match the actual trailer travel direction T.sub.ACT with the demanded trailer travel direction T.sub.DEM.

(27) The system 1 comprises a human machine interface (HMI) module 39. The HMI module 39 is coupled to a display screen 41 which displays a video image 43 from the rear camera 9 (or a composite image derived from the image data for each of the cameras 9, 10, 11). As shown in FIG. 4, the HMI module 39 is configured to overlay graphical symbols over the video image 43. In the present embodiment, the HMI module 39 displays a first arrow A to indicate the actual trailer travel direction T.sub.ACT; and a second arrow B to indicate the demanded trailer travel direction T.sub.DEM. The user can adjust the demanded trailer travel direction T.sub.DEM by varying the orientation of the second arrow B using an input device in communication with the HMI module 39. In the present embodiment, the input device is a rotary knob forming part of the vehicle infotainment system.

(28) In addition to displaying the first and second arrows A, B, the HMI module 39 receives the maximum hitch angle signal from the guidance module 29B. The HMI module 39 displays the maximum permissible hitch angle .sub.MAX on the display screen 41 as an overlay of the video image 43 from the rear camera 9. As illustrated in FIG. 4, the maximum permissible hitch angle .sub.MAX in clockwise (+ve) and counter-clockwise (ve) directions are displayed as first and second dashed lines 45a, 45b. The guidance module 29B inhibits selection of a demanded trailer travel direction T.sub.DEM which is greater than the maximum permissible hitch angle .sub.MAX. This restriction on the demanded trailer travel direction T.sub.DEM is applied by the HMI module 39 which prevents the second arrow B being oriented at an angle greater than the maximum permissible hitch angle .sub.MAX.

(29) The guidance module 29B outputs the steering angle control signal to the HMI module 39 and the current steering angle is represented by a steering wheel symbol 47 which representing the steering wheel 37. The angular orientation of the steering wheel symbol 47 provides an approximate representation of the angular orientation of the steering wheel 37. A numerical indication of the steering angle could be displayed instead of, or in addition to, the steering wheel symbol 47.

(30) The HMI module 39 is configured to overlay a predicted vehicle trajectory onto the video image 43. As shown in FIG. 5, the HMI module 39 displays a first pair of parallel lines 49 representing the predicted trajectory of the vehicle 3; and a second pair or parallel lines 51 representing the predicted trajectory of the trailer 5.

(31) The present invention is applicable to a range of different types of trailer 5. For example, the trailer 5 can be a caravan, a goods trailer, a flatbed trailer, a van trailer, a livestock trailer and so on. Similarly, the present invention is applicable to a range of different types of vehicles 3. For example, the vehicle 3 can be a motor vehicle, such as an off-road or sports utility vehicle; or a towing engine or tractor for a semi-trailer truck.

(32) It will be appreciated that various changes and modifications can be made to the system 1 described herein without departing from the present invention. Further aspects of the present invention are set out in the following numbered paragraphs:

(33) 1. A vehicle control system for reversing a trailer coupled to a vehicle, the vehicle control system comprising a processor configured to:

(34) determine an actual trailer travel direction based on one or more sensor signals; receive a demanded trailer travel direction; and calculate a maximum permissible hitch angle; wherein the processor is configured to limit the demanded trailer travel direction to an angle less than or equal to the calculated maximum permissible hitch angle.
2. A vehicle control system as described in paragraph 1, wherein the processor is configured to estimate a distance to be travelled by the vehicle at least substantially to match the actual trailer travel direction with the demanded trailer travel direction.
3. A vehicle control system for reversing a trailer coupled to a vehicle, the vehicle control system comprising a processor configured to: determine an actual trailer travel direction based on one or more sensor signals; receive a demanded trailer travel direction; and estimate a distance to be travelled by the vehicle at least substantially to match the actual trailer travel direction with the demanded trailer travel direction.
4. A vehicle control system as described in paragraph 3, wherein the processor is configured to calculate a maximum permissible hitch angle; and, optionally, also to limit the demanded trailer travel direction to an angle less than or equal to said maximum permissible hitch angle.
5. A vehicle control system as described in paragraph 1 further comprising a display in communication with said processor and operative to display system information for a driver.
6. A vehicle control system as described in paragraph 5, wherein the display is operative to display one or more of the following: (a) the actual trailer travel direction; (b) the demanded trailer travel direction; (c) a numerical or graphical indication of the estimated distance to be travelled; (d) a location where the actual trailer travel direction will at least substantially match the demanded trailer travel direction. (e) an angular offset between said actual trailer travel direction and said demanded trailer travel direction; (f) the maximum permissible hitch angle; (g) a current steering angle; (h) one or more trajectory lines representing a predicted path of the vehicle and/or the trailer.
7. A vehicle control system as described in paragraph 1, wherein the processor is configured to output a steering control signal to control a steering angle of the vehicle.
8. A vehicle control system as described in paragraph 7, wherein the processor is configured to output the steering control signal to an electronic power assisted steering (EPAS) module.
9. A vehicle control system as described in paragraph 1, wherein the demanded trailer travel direction is specified by a user.
10. A vehicle comprising a vehicle control system as described in paragraph 1.
11. A method of controlling a trailer coupled to a vehicle during a reversing operation, the method comprising: determining an actual trailer travel direction based on one or more sensor signals; receiving a demanded trailer travel direction; and calculating a maximum permissible hitch angle; wherein the method comprises limiting the demanded trailer travel direction to an angle less than or equal to the calculated maximum permissible hitch angle.
12. A method as described in paragraph 11 comprising outputting a steering control signal to control a steering angle of the vehicle.
13. A method as described in paragraph 12, wherein the steering control signal is output to an electronic power assisted steering (EPAS) module to provide automated control of the steering angle of the vehicle.
14. A method of controlling a trailer coupled to a vehicle during a reversing operation, the method comprising: determining an actual trailer travel direction based on one or more sensor signals; receiving a demanded trailer travel direction; and estimating a distance to be travelled by the vehicle at least substantially to match the actual trailer travel direction with the demanded trailer travel direction.
15. A method as described in paragraph 14 comprising displaying a numerical or graphical indication of the estimated distance to be travelled by the vehicle.