VEHICLE CONTROL SYSTEM

[0001] The present disclosure relates to a vehicle control system; a vehicle; and a method of controlling a vehicle. Aspects of the invention relate to a system, to a method and to a vehicle.

[0002] It is known from GB 2447672 to provide a computing unit to calculate a hitch angle between a trailer and a vehicle. The computing unit uses image data from three video cameras, fitted respectively to the rear of the vehicle and one on each door mirror, to track the position of a trailer-mounted marker to determine the position of the trailer relative to the vehicle. The computing unit can also predict a trailer target route and this is output to the driver on a display as guide lines overlaid onto a camera view.

[0003] At least in certain embodiments, the present invention relates to an improved control system.

[0004] Aspects of the present invention relate to a system; a vehicle; and a method as claimed in the appended claims.

[0005] According to a further aspect of the present invention there is provided a vehicle control system for controlling a vehicle to facilitate parking a trailer coupled to the vehicle, the vehicle control system comprising a processor configured to:

• • [0006] identify a target parking destination for the trailer;
  • [0007] determine a current trailer position; and
  • [0008] model a target route from the current trailer position to the target parking destination;
  • [0009] wherein the processor is configured to output a vehicle control signal for controlling the vehicle to guide the trailer along the target route. The vehicle control system may be operative to guide the trailer from its current position to the target parking destination. The target route may be modelled to enable the trailer to be reversed and/or towed to the target parking destination. The target parking destination could be just for the trailer. However, at least in certain embodiments, the target parking destination is for the trailer and the vehicle in combination.

[0010] The vehicle control system could be employed to perform a reverse parking manoeuvre, for example to reverse the vehicle and trailer into a parking space positioned substantially in line with the vehicle and the trailer. At least in certain embodiments, the vehicle control system is operable to perform a parallel parking manoeuvre. The vehicle control system can thereby facilitate parallel parking of the trailer and the vehicle in combination. The vehicle control system can be employed to facilitate parking the vehicle and the trailer in a dedicated parking space, for example in a parking lot or a car park; or in a parking space in the street, for example between other parked vehicles.

[0011] The vehicle control signal can define the required steering angle inputs for the vehicle to guide the trailer along the target route. These could be output, for example to an audio or visual system, to prompt the user to make appropriate changes to the steering angle. Alternatively, the vehicle control signal can be output to steering control means for controlling the steering angle. The steering control means can, for example, comprise electronic power assisted steering (EPAS).

[0012] The current trailer position can define a current hitch angle (between the vehicle and the trailer) which determines an actual travel direction of the trailer. The current trailer position can be determined based on one or more sensor signals. The current trailer position can be measured by one or more sensors, such as a rotary sensor, provided at the coupling between the vehicle and the trailer for measuring a hitch angle of the trailer. The current trailer position could be determined by measuring the orientation of the trailer in relation to the vehicle, for example employing one or more ultrasonic sensors or one or more image sensors (for example disposed in a camera). The image data generated by said one or more image sensors could be analysed to track the trailer, for example by identifying a feature of the trailer and/or a target provided on the trailer.

[0013] The target parking destination can comprise position (i.e. spatial) data; and/or orientation (i.e. angular) data. The processor can determine the spatial and/or angular relationship between the current trailer position and the target trailer destination.

[0014] In order to identify the target parking destination, the processor can be configured to receive a detection signal from one or more object sensors disposed on the vehicle and/or the trailer. The detection signal can communicate detection data from said one or more object sensors to the processor. The one or more object sensors can comprise one or more of the following: ultrasonic, laser or electromagnetic sensors. The one or more object sensors could, for example, take the form of parking distance sensors. The one or more object sensors can be arranged to detect obstructions positioned to the side (i.e. laterally) of the vehicle and/or the trailer. The one or more object sensors could also be arranged to detect obstructions positioned in front of or behind the vehicle and/or the trailer. The processor can thereby analyse the detection signal from said one or more object sensors to identify the target parking destination.

[0015] Alternatively, or in addition, the processor can be configured to receive image data from one or more cameras disposed on the vehicle and/or on the trailer. The processor can comprise an image processing module for identifying one or more obstructions in video image data obtained from said camera(s). The image processing module can be configured to identify one or more obstructions proximal to the trailer and/or the vehicle. The processor can thereby analyse the image data from said one or more cameras to identify the target parking destination.

[0016] During a parking manoeuvre, the one or more object sensors and/or the one or more cameras can operate continuously to monitor side and rear obstructions. The trailer rear camera can provide information about the available space at the rear of the trailer and the processor can output a stop signal to stop the vehicle when the trailer is a predefined distance away from an obstruction.

[0017] The processor can be configured to assess candidate parking destinations to determine whether they constitute a suitable target parking destination. The object sensor(s) and/or the camera(s) can generate the data when the vehicle and the trailer are positioned alongside or in front of the candidate parking destination; or as the vehicle and the trailer drive past the candidate parking destination. The processor can analyse the data from said object sensor(s) and/or the camera(s) to detect objects (either fixed or moving), such as parked vehicles, walls, kerbs (curbs). The processor can thereby determine whether there is sufficient space available for parking the trailer and the vehicle (for example based on length and/or width). If there is sufficient space, the processor can identify the target parking destination. The user may subsequently be required to confirm the target parking destination.

[0018] The processor can be configured to perform a check to ensure that there is sufficient space around the trailer and/or the vehicle to manoeuvre the vehicle and/or the trailer into the target parking destination. Based on predefined trailer parameters (such as the trailer length, width and axle location), the processor can calculate a trailer route corridor required to reverse the trailer. Based on predefined vehicle parameters (such as turning radius), the processor can calculate a vehicle route corridor required to reverse the vehicle. The processor can analyse the detection signal to identify one or more obstacles proximal to the vehicle and/or the trailer and determine if there is sufficient space available to reverse the trailer. The processor can be configured to modify the target route of the trailer to remain within the calculated trailer route corridor and/or vehicle route corridor.

[0019] The processor can be configured to define a longitudinal axis of the target parking destination. At least in certain embodiments, the longitudinal axis can be defined substantially parallel to a detected object, such as a kerb (curb) or a wall. The target route can be modelled at least substantially to blend into the longitudinal axis of the target parking destination. The longitudinal axis can define a centre line of the target parking destination. Thus, once parked, the trailer can be arranged coincident with or substantially parallel to the longitudinal axis of the parking space. The processor can be configured to approximate the target parking destination as a rectangle having a longitudinal axis. The dimensions of the rectangle can be defined to match at least the maximum external dimensions of the vehicle and the trailer. The target route typically has an S-shape.

[0020] The target route can comprise one or more curves; and/or one or more linear sections. The target route can comprise only one reversing movement; or can comprise a sequence of forward/reverse movements. The target route could, for example, comprise a single reversing movement to position the trailer with the target parking destination followed by a forward movement to align the vehicle with the target parking destination. The user could specify whether a single reversing movement or multiple reversing movements are to be performed. The processor could be configured to output braking signals and/or acceleration signals for controlling the braking and acceleration respectively of the vehicle. Alternatively, the driver of the vehicle can control one or both of vehicle acceleration and braking. The processor can be configured to output driver prompts, for example to perform one or more of the following functions: accelerate, decelerate, change gear (such as select Drive or Reverse), engage a parking brake and so on. The processor could be configured to inhibit the maximum speed of the vehicle, for example to 10 km/h.

[0021] The vehicle control signal can map a rotational centre of the trailer to the target route. The vehicle control signal can be generated to maintain the rotational centre of the trailer substantially coincident with the target route.

[0022] The target route can define a target trailer travel direction at each point along its length. The processor can be configured to control the vehicle to match the actual trailer travel direction to the target trailer travel direction as it travels along the target route. The vehicle control signal can control the steering angle of the vehicle to maintain the actual trailer travel direction at least substantially coincident with the target trailer travel direction. The actual trailer travel direction can thereby match the target trailer travel direction.

[0023] The processor can be configured to identify permissible target parking destinations. The permissible target parking destinations could be based on the identification of one or more obstructions. The processor can be configured to identify said permissible target parking destinations based on one or more of the following: a maximum permissible hitch angle; the detected space available for the trailer and/or the vehicle; a detected terrain parameter (such as an incline or gradient). The processor can be configured to inhibit selection of an impermissible target parking destination.

[0024] The processor can be configured to receive image data from one or more video cameras disposed on the vehicle and/or the trailer. The processor can comprise an image processing module for identifying obstruction(s) in video image data obtained from one or more optical cameras. The image processing module can be configured to identify one or more obstructions proximal to the trailer and/or the vehicle; and/or along the modelled target path. Alternatively, or in addition, ultrasonic and/or laser sensor systems could be provided for detecting said obstruction(s). The processor could be configured dynamically to modify the target route if an obstruction is identified.

[0025] The processor could be configured to determine if there is sufficient space available to manoeuvre the trailer to the target parking destination. Based on predefined trailer parameters (such as the trailer length, width and axle location), the processor can calculate a route corridor required to reverse the trailer. The imaging system can then identify obstacles proximal to the vehicle and/or the trailer and determine if there is sufficient space available to reverse the vehicle and the trailer to the target parking destination. The processor can be configured to modify the target route of the trailer to remain within the calculated route corridor.

[0026] The processor can be configured to output the target parking destination and/or the target route to a display. The target parking destination and/or the target route could, for example, be overlaid onto a video image from one or more of said video camera(s).

[0027] The target parking destination can optionally be modified by a user. A human machine interface can be provided for modifying the target parking destination. The human machine interface can, for example, comprise a display device, such as an LCD screen. An input means can be provided for the human machine interface. The input means can, for example, comprise one or more of the following: a touchscreen, a capacitive sensor, a joystick, a rotary wheel, a trackball, voice recognition, gesture recognition, and eye tracking. A graphical image can be displayed on the display device to represent the target parking destination. The position and/or the orientation of the graphical image can be controlled using the input means. The position and/or the orientation of the graphical image can be converted to data to identify said target trailer destination and output to the processor.

[0028] A scaling function can be applied to the graphical image as it is moved around the screen. The scaling function has particular application when the graphical image is displayed in a perspective view, for example as an overlay onto a video image from a camera disposed on the vehicle or the trailer.

[0029] The graphical image can represent a footprint of the trailer, for example representing an outline of the trailer on the ground. The graphical image could, for example, comprise a rectangle. Alternatively, the graphical image could provide a 3-dimensional representation of the trailer, for example a vector image or a rendering of the trailer. The graphical image can provide a scale representation of the trailer.

[0030] The vehicle control signal can comprise a steering control signal for controlling a steering angle of the vehicle. The steering control signal can be output to an electronic power assisted steering (EPAS).

[0031] According to a still further aspect of the present invention there is provided a vehicle control system for controlling a vehicle to facilitate reversing a trailer coupled to the vehicle, the vehicle control system comprising a processor configured to:

• • [0032] generate a target route from the current trailer position to the target parking destination;
  • [0033] wherein the processor is configured to generate the target route by modifying a pre-defined path based on a determined angular offset and/or positional offset between the current trailer position and the target parking destination.

[0034] The pre-defined path can comprise first and second curves. The first and second curves can be arranged in an S-shape. The processor can be configured to increase or decrease an included angle of one or both of said first and second curves in dependence on said angular offset. The processor can be configured to define a minimum radius of curvature in the target route based on a jack-knife angle of the trailer.

[0035] According to a further aspect of the present invention there is provided a vehicle comprising a vehicle control system of the type described herein.

[0036] According to a yet further aspect of the present invention there is provided a method of controlling a vehicle to facilitate parking a trailer coupled to the vehicle, the method comprising:

• • [0037] identifying a target parking destination for the trailer;
  • [0038] determining a current trailer position;
  • [0039] modelling a target route from the current trailer position to the target parking destination; and
  • [0040] outputting a vehicle control signal for controlling the vehicle to guide the trailer along the target route.

[0041] According to a yet further aspect of the present invention there is provided a method of generating a target route for reversing a trailer from a current position to a target parking destination; the method comprising:

• • [0042] modifying a pre-defined path based on a determined angular offset and/or positional offset between the current position and the target parking destination to generate the target route. The pre-defined path can be stored in memory. The pre-defined path can, for example, comprise first and second curves, for example arranged in an S-shape. The method can comprise applying a minimum radius of curvature to the target route, the minimum radius of curvature being based on the jack-knife angle of the trailer. The method can comprise identifying the target parking destination, for example based on data received from one or more sensors disposed on the vehicle.

[0043] The methods described herein can each be computer-implemented, for example on a computational apparatus comprising one or more microprocessors. According to a yet further aspect of the present invention there is provided a computer program product comprising a computer readable storage medium including computer readable program code, where the computer readable program code when executed on a computer causes the computer to perform the method(s) described herein.

[0044] The term processor used herein is to be understood as covering both single processors and multiple processors. For example, the processing steps described herein could be performed by a single processor; or could be performed by separate processors.

[0045] Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

[0055] A vehicle control system 1 for assisting with the reversing of a vehicle 3 and a trailer 5 in accordance with an aspect of the present invention will now be described with reference to FIGS. 1 to 8.

[0056] The vehicle control system is operable to facilitate parking 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 vehicle control system 1 is configured to control the steering of the vehicle 3 such that the vehicle 3 and the trailer 5 perform a parallel parking manoeuvre and reverse into a target parking destination P_TAR. In the present embodiment, the operation of the throttle and brakes of the vehicle 3 are controlled by the user, but these control functions could be automated.

[0057] A plan view of the vehicle 3 and the trailer 5 is shown in FIG. 1. The vehicle 3 has two front wheels W1, W2 and two rear wheels W3, 4. As illustrated in FIG. 2, the front wheels W1, W2 of the vehicle 3 are steerable in conventional manner to define a steering angle θ. The trailer 5 has two wheels TW1, TW2 which are not steerable.

[0058] As shown in FIGS. 1 and 2, the vehicle 3 is provided with a vehicle imaging system comprising a centrally mounted rear vehicle camera 9; and left and right side vehicle cameras 10, 11 mounted in respective wing mirrors 13, 15. The vehicle 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. The vehicle 3 optionally also comprises an obstruction detection system, for example side radar sensors 7A, 7B for detecting the presence of an obstruction in the rear three quarters position of the vehicle 3.

[0059] 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 19 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.

[0060] The trailer 5 is provided with a trailer imaging system comprising a centrally mounted rear trailer camera 29; and left and right side trailer cameras 30, 31 mounted on respective sides of the trailer 5. The trailer cameras 29, 30, 31 are optical cameras arranged to provide video images of the area around the trailer 5 which may otherwise be obscured from view. The fields of view TV1, TV2, TV3 of the trailer cameras 29, 30, 31 are illustrated by dashed triangles in FIGS. 3 and 4. The trailer 5 optionally also comprises an obstruction detection system, for example parking sensors 32A, 32B, for detecting the presence of obstructions at the rear of the trailer 5. The image data from the trailer cameras 29, 30, 31 and/or obstruction data from the obstruction detection system is transmitted to the vehicle 3 over either a wired connection or a wireless communication channel.

[0061] The vehicle control system 1 comprises an electronic control unit (ECU) having an electronic processor 33, as shown schematically in FIG. 2. The processor 33 comprises image processing means in the form of an image processing module 33A for analysing the image data. The vehicle cameras 9, 10, 11 and the trailer cameras 29, 30, 31 each output image data to the image processing module 33A for analysis. In use, the image processing module 33A analyses the image data from the vehicle cameras 9, 10, 11 to identify the target 25 to determine the position and orientation of the trailer 5 in relation to the vehicle 3. Moreover, the image processing module 33A analyses the image data from the vehicle cameras 9, 10, 11 and the trailer cameras 29, 30, 31 to identify obstructions proximal to the vehicle 3 and the trailer 5.

[0062] The image processing module 33A is configured to multiplex the images from the trailer cameras 29, 30, 31 to generate a composite image 35 showing a panoramic view to the rear of the trailer 5, as shown in FIG. 7. The resulting composite image 35 can be output to a display screen 37 to be viewed by the user substantially in real-time. The display screen 37 can be provided in an instrument cluster or in an infotainment console. The image data from the vehicle cameras 9, 10, 11 and the trailer cameras 29, 30, 31 could be combined to provide a plan view of the vehicle 3 and the trailer 5 (as if viewed from a position above the vehicle 3 and the trailer 5).

[0063] The processor 33 comprises an identification module 33B configured to identify the target parking destination P_TAR for the vehicle 3 and the trailer 5. The identification module 33B receives detection signals from the first and second radar systems 7A, 7B, 32A, 32B and identifies the presence/absence of obstructions on each side of the vehicle 3 and the trailer 5. In the present embodiment, the detection signals are generated as the vehicle 3 and the trailer 5 pass a candidate parking destination. The identification module 33B can thereby assess a candidate parking destination to determine whether it represents a suitable parking destination for the vehicle 3 and the trailer 5. In particular, the identification module 33B determines whether there is sufficient space available to accommodate the vehicle 3 and the trailer 5 and also to manoeuvre them into position. If there is sufficient space, the identification module 33B outputs a signal to indicate that a suitable parking destination has been identified along with positional data indicating the position of the target parking destination P_TAR. The user is subsequently required to accept the target parking destination P_TAR.

[0064] The identification module 33B defines a third longitudinal axis X3 representing a centre line of the target parking destination P_TAR. The third longitudinal axis X3 can, for example, be defined substantially parallel to an object, such as a kerb (curb) or a wall, detected during analysis of the detection signals from the vehicle and trailer side radar systems 7A, 7B, 32A, 32B.

[0065] The processor 33 further comprises vehicle/trailer guidance means in the form of a guidance module 33C. The guidance module 33C 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 33C is configured to output a control signal for controlling the steering angle θ of the front wheels W1, W2 of the vehicle 3 to guide the trailer 5 along a target route R. The target route R is generated by the guidance module 33C to guide the trailer 5 from its current position to the target parking destination P_TAR. The target route R can be modelled at least substantially to blend into the third longitudinal axis X3 of the target parking destination P_TAR. The target route R is illustrated by a continuous line in FIG. 3.

[0066] The vehicle control system 1 comprises a human machine interface (HMI) module 39. The HMI module 39 is coupled to the display screen 37 and is configured to superimpose a graphical image 41, representing the target parking destination P_TAR of the trailer 5, onto the composite image 35. In the present embodiment the graphical image 41 comprises a rectangle 43 which represents the footprint of the vehicle 3 and the trailer 5 in combination. The graphical image 41 is sized to provide a scale representation of the vehicle 3 and the trailer 5 within the composite image 35. The dimensions of the vehicle 3 are defined in a data file accessible to the HMI module 39. To provide an accurate representation of the trailer 5, the trailer dimensions can be specified by the user and stored in the data file with the vehicle dimensions. In the present embodiment a portion of the graphical image 41 is semi-transparent to reduce obfuscation of objects in the composite image 35. It will be appreciated that the present invention is not limited to the display of a rectangle 43 and other graphical images can be used to represent the vehicle 3 and the trailer 5.

[0067] The HMI module 39 is coupled to input means 45 in the form of a touch screen and a rotary dial. Optionally, the input means 45 can be operated by the user to adjust the position of the graphical image 41 within the composite image 35. The user can thereby adjust the position of the target parking destination P_TAR for the trailer 5. The input means 45 can optionally also enable the user to define the angular orientation of the graphical image 41 to adjust the orientation of the target parking destination P_TAR. The HMI module 39 could optionally also be configured to allow the user to adjust the target route R.

[0068] The HMI module 39 performs a scaling operation on the graphical image 41 to adjust its size based on its position within the composite image 35, for example to increase/decrease its size in dependence on its virtual position in relation to the camera generating the video image. The graphical image 41 can optionally also be modified to alter its perspective, for example to simulate foreshortening, as it is moved within the composite image 35. The graphical image 41 can thereby provide an accurate representation of the size of the trailer 5 within the composite image 35. The processor 33 could be configured to identify areas or regions which are unsuitable for positioning the trailer 5. The HMI module 39 can be configured to represent any such areas as an overlay on the composite image 35. Alternatively, or in addition, the HMI module 39 can be configured to prevent the graphical image 41 being moved to locations identified by the processor 33 as being unsuitable for positioning the trailer 5. For example, the processor 33 could determine that a region displayed in the composite image 35 is unsuitable due to the detection of one or more obstructions by the image processing module 33A or the identification module 33B. Alternatively, or in addition, the processor 33 could assess one or more terrain parameters, such as incline or gradient, to identify unsuitable regions for the trailer 5. The terrain parameters could be assessed from the image data derived from the vehicle cameras 9, 10, 11 and/or the trailer cameras 29, 30, 31. Alternatively, or in addition, one or more of the following types of sensor could be employed to monitor the terrain: ultrasonic sensors/cameras, laser scanners and radar. The resulting terrain data could be used to restrict selection of the target parking destination P_TAR; and/or control vehicle operating parameters, for example to engage four wheel drive or to select a low transfer range; and/or request user confirmation of the selected target parking destination P_TAR.

[0069] The guidance module 33C is configured to generate the target route R to guide the trailer 5 from its current location to the identified target parking destination P_TAR. The target route R defines a target trailer travel direction T_TAR for guiding the trailer 5 from its current position to the target parking destination P_TAR. The target route R can comprise rectilinear and/or curved sections. The target route R is arranged coincident with a midpoint of the trailer 5 in its current position. The current position of the trailer 5 is monitored compared to the originally calculated target route R. Small deviations are managed within the vehicle control system 1. Larger deviations can trigger a recalculation of the target route R. If the target parking destination P_TAR becomes unachievable from the current position, the user is alerted and a corrective manoeuvre is suggested (for example travel forward a short distance).

[0070] The user positions the graphical image 41 within the composite image 35 to define the target parking destination P_TAR of the trailer 5. The guidance module 33B determines the target route R between the current trailer position and the target parking destination P_TAR. As illustrated in FIG. 4, the vehicle steering angle θ is controlled such that a centre of rotation 49 of the trailer 5 defines a first path 51 which at least substantially matches the target route R. The trailer hitch 19 defines a second path 53 as the trailer 5 follows the target route R; and a centre of rotation 55 of the vehicle 3 defines a third path 57 as the trailer 5 follows the target route R. In an alternate embodiment, the guidance module 33B could be configured to generate the second or third paths 53, 55 to guide the trailer 5 to the target parking destination P_TAR and to control the vehicle steering angle θ to follow said second or third paths 53, 55. The target route R is a straight line if the target parking destination P_TAR is in line with the trailer 5. Otherwise, the target route R comprises a curve based on the geometry of the vehicle and trailer and location of the target destination.

[0071] With reference to FIGS. 5A-5E, the guidance module 33B implements a geometric algorithm to generate the target route R. The guidance module 33B utilises the angular offset between the current trailer longitudinal axis X2 and the target trailer longitudinal axis X2_TAR; and the lateral offset between the current trailer position and the parking destination PTAR (measured perpendicular to the trailer longitudinal axis X2. As shown in FIG. 5A, the algorithm defines a default S-shaped path 55 (shown in phantom in FIGS. 5B-5E) comprising first and second curves A, B. The first curve A defines a first included angle of +45°; and the second curve B defines a second included angle of −45°. If required, a scaling function (along an X axis and/or a Y axis) is applied to the S-shaped path 55 to link the actual longitudinal axis X2 of the trailer 5 to the target longitudinal axis X2_TAR of the trailer 5 when it is in the target parking destination P_TAR. The guidance module 33B can optionally be configured to define a minimum radius of curvature for the first and second curves A, B to ensure that the hitch angle φ does not equal or exceed the jack-knife angle.

[0072] The S-shaped path 55 is positioned to link the actual longitudinal axis X2 of the trailer 5 to the target longitudinal axis X2_TAR. A scaling function and/or a rotation function can be applied to the S-shaped path 55 depending on the position and/or orientation of the target parking destination P_TAR in relation to the current trailer position. The S-shaped path 55 is then modified by adjusting the included angle of either the first curve A or the second curve B in dependence on the angular offset between the actual longitudinal axis X2 and the target longitudinal axis X2_TAR.

[0073] In the present embodiment, the guidance module 33B identifies which of the first and second curves A, B opens onto the side of the S-shaped path 55 to which the target longitudinal axis X2_TAR is oriented. The guidance module 33B then modifies the included angle of the identified curve A, B corresponding to the angular offset between the actual longitudinal axis X2 and the target longitudinal axis X2_TAR. This technique will now be described with reference to FIGS. 5B-5E.

[0074] In the scenario illustrated in FIG. 5B, the target longitudinal axis X2_TAR is offset by −45° and is directed to the left side of the S-shaped path 55. Accordingly, the included angle of the first curve A (which opens to the left side of the S-shaped path 55) is reduced by 45°. As the pre-defined included angle is +45°, the first curve A is effectively removed from the S-shaped path 55 leaving only the second curve B. The resulting modified curve is defined as the target route R.

[0075] In the scenario illustrated in FIG. 5C, the target longitudinal axis X2_TAR is offset by −90° and is directed to the left side of the S-shaped path 55. Accordingly, the included angle of the first curve A is reduced by 90° to define an included angle of −45°, thereby reversing the curvature direction of the first curve A. The resulting modified curve is defined as the target route R.

[0076] In the scenario illustrated in FIG. 5D, the target longitudinal axis X2_TAR is offset by +45° and is directed to the right side of the S-shaped path 55. Accordingly, the included angle of the second curve B (which opens to the right side of the S-shaped path 55) is increased by 45°. As the pre-defined included angle is —45°, the second curve B is effectively removed from the S-shaped path 55 leaving only the first curve A. The resulting modified curve is defined as the target route R.

[0077] In the scenario illustrated in FIG. 5E, the target longitudinal axis X2_TAR is offset by +90° and is directed to the right side of the S-shaped path 55. Accordingly, the included angle of the second curve B is increased. However, to compensate for the lateral offset of the trailer 5, the second curve B is increased by 45° to 0°, thereby removing the second curve B. The first curve A is also increased by 45° to 90° (again to compensate for the lateral offset of the target parking destination P_TAR). The resulting modified curve is defined as the target route R.

[0078] In a second process step, the vehicle control system 1 attempts to identify the presence of any obstructions (denoted generally by the reference numeral 46 in FIGS. 6A and 6B). Typical obstructions include kerbs, walls, vehicles, etc. The vehicle control system 1 can optionally also determine terrain parameters, for example to detect a metalled surface indicating a road; and/or terrain features, for example gradient changes. As described herein, the obstructions 46 can be identified by the image processing module 33A and/or other detection systems. The guidance module 33B modifies the target route R generated in the first process step. By way of example, the guidance module 33B will give a higher priority to a route which guides the trailer 5 to the target parking destination P_TAR whilst remaining on a road than a route which provides the shortest achievable path.

[0079] With reference to FIGS. 6A and 6B, in order to guide the trailer 5 the guidance module 33B calculates the required vehicle steering angle θ to achieve the appropriate trailer angle δ at intervals x, 2x, 3x . . . nx along the route R, where x equals half the combined length of the vehicle 3 and the trailer 5. The interval distance x is configurable and can be reduced, for example to ¼ the combined length of the vehicle 3 and the trailer 5 to provide improved accuracy, albeit at the expense of increased processing load on the processor 33 The trailer angle δ is the angle between an expected angular position of the trailer 5 at a particular interval and the position of the trailer 5 before the manoeuvre starts. Once the guidance module 33B has calculated the required trailer angle δ at the calculating points (defined by the n intervals along the target route R), the trailer angles δ_n, δ_n+1 at adjacent calculation points are compared to determine the difference between the trailer hitch angles φ_n, φ_n+1 at adjacent interval points.

[0080] If the hitch angle φ can be achieved between the two calculation points, the guidance module 33B stores the values in memory and, during the manoeuvre, accesses the stored values after each interval to set the next interval value as the desired hitch angle φ. If the guidance module 33B detects a large deviation between the present hitch angle φ and the expected hitch angle φ it restarts the calculation to avoid failure.

[0081] If the hitch angle φ between the two calculation points cannot be achieved (for example based on the maximum steering angle θ of the vehicle and the trailer geometry), the guidance module 33B compares the required hitch angle φ_n, φ_n+1 between first and second intervals x to establish if this hitch angle φ can be achieved while considering surrounding conditions. If the comparison of the hitch angle φ_n, φ_n+1 between the first and second intervals x is possible, the guidance module 33B stores the values in memory and, during the manoeuvre, accesses the stored values after each interval to set the next interval value as the desired hitch angle φ. If the guidance module 33B fails to achieve the required hitch angle φ for four (4) consecutive interval points (i.e. x to 4x), an alternative target route R is calculated while considering space requirement and the surrounding obstructions 46. If the guidance module 33B is unable to establish a viable alternative target route R, the guidance module 33B calculates an alternate position between failure points identified by means of driving forward in the available space to complete the manoeuvre. During the route calculation the guidance module 33B determines whether the hitch angle φ change between two intervals can be achieved. If the hitch angle φ cannot be achieved then the calculation needs to check if the hitch angle φ change calculated in alternative routes in two previous and two subsequent intervals can be achieved. If this fails then the calculation starts again or requests an initial drive forwards to reduce the rate of change of hitch angle. A forward shuffle could also be requested mid-manoeuvre.

[0082] The angular change Ω in the trailer angle θ at intervals along the target route R is illustrated in FIG. 6B. The angular change Ω is illustrated with reference to a first time t and a second time t+1, but the calculation of the required angle change is based on distance rather than time.

[0083] As described herein, the steering angle θ of the vehicle 3 is controlled to maintain the actual travel direction T_ACT of the trailer 5 substantially coincident with the target trailer travel direction T_TAR during the reversing manoeuvre along said target route R. The guidance module 33C can control the steering angle θ of the front wheels W1, W2 to guide the trailer 5 along the target travel direction T_TAR. Once the target parking destination P_TAR has been identified, the target route R could be fixed or could be revised dynamically, for example as the manoeuvre is performed.

[0084] The control algorithm for generating a control signal to guide the vehicle 3 along the target route R will now be described with reference to FIG. 8. 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 φ. During reversing, the trailer 5 travels in a direction T_ACT corresponding to the hitch angle φ (unless the hitch angle φ exceeds a jack-knife angle for the trailer 5, as described herein).

[0085] The image processing module 33A calculates the hitch angle φ with reference to the target 25 and outputs a hitch angle signal to the guidance module 33C. When reversing, the guidance module 33C calculates the required steering angle θ based on the following equation:

θ_t+1=θ_t+min(max(k(φ_req−φ_cur),−α),α)

[0086] Where: θ_t+1 and θ_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);

• • [0087] φ_req and φ_cur are the requested and current hitch angles;
  • [0088] α is the maximum steering offset value; and
  • [0089] k is a constant multiplier.

[0090] The value of the gain k can be calculated based on the relationship between θ and φ, as shown in FIG. 8. When the trailer hitch length L plus the tow bar offset of the vehicle h is equal to the vehicle wheelbase d, then the relationship between θ and φ 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:

$k=\frac{L+h}{d}$

[0091] Where: L is the hitch length of the trailer 5;

• • [0092] h is the tow bar offset of the vehicle 3;
  • [0093] d is the wheelbase of the vehicle 3;

[0094] The gain k thereby compensates for the fact that longer trailers take longer to reach the requested hitch angle φ.

[0095] The guidance module 33C is configured to calculate a maximum permissible hitch angle φ_MAX. If the hitch angle φ exceeds the maximum permissible hitch angle φ_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 φ by continuing to reverse (i.e. the trailer 5 has jack-knifed). If the detected hitch angle φ is equal to or exceeds the calculated jack-knife angle, the vehicle control system 1 will advise the user to drive forward until it determines that the trailer angle δ at the next interval is achievable while considering space and obstructions. With reference to FIG. 8, the guidance module 33C calculates the maximum permissible hitch angle φ_MAX by applying the following set of equations:

$\begin{array}{c}R=\frac{d}{\tan \left(\theta \right)}\\ \phi ={\cos }^{-1}\left(\frac{-\mathrm{Lh}+R\sqrt{R^2+h^2-L^2}}{R^2+h^2}\right)\mathrm{for}\mathrm{positive}\theta \\ \phi =-{\cos }^{-1}\left(\frac{-\mathrm{Lh}-R\sqrt{R^2+h^2-L^2}}{R^2+h^2}\right)\mathrm{for}\mathrm{negative}\theta \end{array}$

[0096] Where: R is the turning radius;

• • [0097] θ is the steering angle of the vehicle 3;
  • [0098] d is the wheelbase of the vehicle 3;
  • [0099] h is the tow bar offset of the vehicle 3;
  • [0100] L is the hitch length of the trailer 5;

[0101] The wheelbase d, the tow bar offset h and the maximum steering angle θ_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 33C outputs a maximum hitch angle signal to indicate the maximum permissible hitch angle φ_MAX for the current steering angle θ. The guidance module 33C is configured to inhibit the trailer travel direction T_ACT to values which are less than the maximum permissible hitch angle φ_MAX. A minimum radius of curvature of the target route R can be defined to ensure that the trailer travel direction T_ACT is less than or equal to the maximum permissible hitch angle φ_MAX.

[0102] The guidance module 33C calculates the initial required steering angle θ to achieve the desired hitch angle φ, then iteratively calculates the required steering angle θ and hitch angle φ. In use, the guidance module 33C is configured to output a steering control signal operative to control the steering angle θ of the front wheels W1, W2 to adjust the hitch angle φ, thereby modifying the actual trailer travel direction T_ACT. Specifically, the guidance module 33C adjusts the steering angle θ (which can be positive or negative in relation to a reference point) to increase or decrease the hitch angle φ. The actual trailer travel direction T_ACT can thereby be matched to the target trailer travel direction T_TAR required to follow the target route R. The hitch angle signal is updated at least substantially in real time and the guidance module 33C makes corresponding real time adjustments to the steering control signal. The guidance module 33C controls the hitch angle φ so that the difference between the actual trailer travel direction T_ACT and the target trailer travel direction T_TAR is at least substantially zero. A tolerance of +/−0.5° between the actual trailer travel direction T_ACT and the target trailer travel direction T_TAR provides a good result.

[0103] The steering angle control signal is output to an electronic power assisted steering (EPAS) module 45 to control the angle of a steering wheel 47 to provide a required steering angle θ for the front wheels W1, W2. The EPAS module 45 automatically adjusts the angular orientation of the steering wheel 47 to provide the appropriate steering angle θ at the front wheels W1, W2 to control the vehicle 3 to match the actual trailer travel direction T_ACT with the target trailer travel direction T_TAR.

[0104] In use, the vehicle 3 and the trailer 5 are driven past a candidate parking destination. The vehicle and trailer radar systems 7A, 7B, 32A, 32B output detection signals to the identification module 33B as the vehicle 3 and the trailer 5 pass the candidate parking destination. The identification module 33B analyses the detection signals to identify a target parking destination P_TAR. When a suitable target parking destination P_TAR is identified, the user is prompted to confirm that they wish to park the vehicle 3 and the trailer 5. The user can, if necessary, operate the HMI module 39 to adjust the position and/or orientation of the target parking destination P_TAR. The user then confirms the target parking destination P_TAR for the vehicle 3 and the trailer 5.

[0105] The image processing module 33A analyses the image data from the vehicle cameras 9, 10, 11 to identify the target 25 on the trailer 5 and to determine the current position of the trailer 5 in relation to the vehicle 3. The guidance module 33C then models a target route R for the trailer 5 from its current position to the target parking destination P_TAR. A vehicle control signal is output by the guidance module 33C to the EPAS module 45 to adjust the steering angle θ to control the vehicle 3 to match the actual travel direction T_ACT of the trailer 5 with the target travel direction T_TAR. The HMI module 39 can optionally output instructions to prompt the user to select the appropriate drive gear and to operate the vehicle brakes and throttle. The EPAS module 45, in dependence on the vehicle control signal output from the guidance module 33C, then steers the vehicle 3 to guide the trailer 5 along the target route R. A notification can be output by the HMI module 39 to notify the user when the vehicle 3 and the trailer 5 are in the target parking destination P_TAR. The vehicle control system 1 can thereby facilitate reversing the vehicle 3 and the trailer 5 to the target parking destination P_TAR.

[0106] 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.

[0107] The control techniques described herein are a development of those described in the Applicant's earlier UK patent applications GB1307524.7 (filed on 26 Apr. 2013) and GB1307525.4 (filed on 26 Apr. 2013), the contents of which are incorporated herein in their entirety by reference. Furthermore, the contents of the Applicant's related application entitled “VEHICLE CONTROL SYSTEM” filed on the same day as the present application at the UK Intellectual Property Office are hereby incorporated in their entirety into the present application by reference.

[0108] It will be appreciated that various changes and modifications can be made to the vehicle control system 1 described herein without departing from the present invention. Rather than specify the target parking destination P_TAR by positioning the graphical image 41 on a video image, the graphical image 41 could be positioned on a static image such as a grid or mesh representing a predefined region around the vehicle 3.

[0109] Furthermore, although the vehicle control system 1 has been described with reference to a set of vehicle cameras 9, 10, 11 and a set of trailer cameras 29, 30, 31, it will be appreciated that a single camera could be provided on the vehicle 3 and/or the trailer 5. In a further alternative, the vehicle cameras 9, 10, 11 or the trailer cameras 29, 30, 31 could be used exclusively. A set of parking sensors provided on the trailer 5 could, for example, provide notification to the driver of any obstructions. The hitch angle φ could be measured directly, for example by a rotary encoder.

[0110] Further aspects of the present invention are set out in the following numbered paragraphs:

[0111] 1. A system for controlling a vehicle to facilitate parking a trailer coupled to the vehicle, the system comprising a processor configured to:

• • [0112] identify a target parking destination for the trailer;
  • [0113] determine a current trailer position;
  • [0114] model a target route from the current trailer position to the target parking destination; and
  • [0115] output a vehicle control signal for controlling the vehicle to guide the trailer along the target route.

[0116] 2. A system as described in paragraph 1, wherein the processor is configured to assess candidate parking destinations to determine whether they constitute a suitable target parking destination.

[0117] 3. A system as described in paragraph 1 or paragraph 2, wherein the processor is configured to identify said target parking destination based on a detection signal received from one or more object sensors disposed on the vehicle and/or the trailer.

[0118] 4. A system as described in paragraph 3, wherein the detection signal from said one or more object sensors is operatively generated as the vehicle and the trailer drive past a candidate parking destination.

[0119] 5. A system as described in paragraph 4, wherein the processor is configured to identify said target parking destination based on one or more of the following: a length of the candidate parking destination; a minimum width of the candidate parking destination; an available space to manoeuvre the vehicle and the trailer into the candidate parking destination.

[0120] 6. A system as described in any one of paragraphs 1 to 5, wherein the target route comprises one or more curves joining the current trailer position to the target parking destination.

[0121] 7. A system as described in any one of the preceding paragraphs, wherein the target route is modelled at least substantially to align with a longitudinal axis of the target parking destination.

[0122] 8. A system as described in any one of the preceding paragraphs, wherein the vehicle control signal maps a rotational centre of the trailer to the target route.

[0123] 9. A system as described in any one of the preceding paragraphs, wherein the processor is configured to receive image data from one or more video cameras disposed on the vehicle and/or the trailer.

[0124] 10. A system as described in paragraph 9, wherein the processor is configured to identify one or more obstructions proximal to the trailer and/or the vehicle; and/or along the modelled target route.

[0125] 11. A system as described in paragraph 9 or paragraph 10, wherein the processor is configured to overlay the target parking destination and/or a target route for the trailer on a video image from one or more of said video camera(s).

[0126] 12. A system as described in any one of the preceding paragraphs, wherein the target route can be modified by a user.

[0127] 13. A system as described in any one of the preceding paragraphs, wherein the vehicle control signal comprises a steering control signal for controlling a steering angle of the vehicle.

[0128] 14. A vehicle comprising a system as described in any one of the preceding paragraphs.

[0129] 15. A system for controlling a vehicle to facilitate reversing a trailer coupled to the vehicle, the system comprising a processor configured to:

• • [0130] generate a target route from the current trailer position to the target parking destination by modifying a pre-defined path based on a determined angular offset and/or positional offset between the current trailer position and the target parking destination.

[0131] 16. A system as described in paragraph 15, wherein the pre-defined path comprises first and second curves arranged in an S-shape.

[0132] 17. A system as described in paragraph 16, wherein the processor is configured to increase or decrease an included angle of one or both of said first and second curves in dependence on said angular offset.

[0133] 18. A system as described in any one of paragraphs 15, 16 or 17, wherein the processor is configured to define a minimum radius of curvature in the target route based on a jack-knife angle of the trailer.

[0134] 19. A method of controlling a vehicle to facilitate parking a trailer coupled to the vehicle, the method comprising:

• • [0135] identifying a target parking destination for the trailer;
  • [0136] determining a current trailer position;
  • [0137] modelling a target route from the current trailer position to the target parking destination; and
  • [0138] outputting a vehicle control signal for controlling the vehicle to guide the trailer along the target route.

[0139] 20. A method of generating a target route for reversing a trailer from a current position to a target parking destination; the method comprising:

• • [0140] modifying a pre-defined path based on a determined angular offset and/or positional offset between the current position and the target destination to generate the target route.