EP4724312A1

EP4724312A1 - Assisted recovery mode

Info

Publication number: EP4724312A1
Application number: EP24731544.3A
Authority: EP
Inventors: Aaron Ward; Rowena FURBY; James Coleman; Benjamin Gibbs
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2023-06-12
Filing date: 2024-06-05
Publication date: 2026-04-15
Also published as: WO2024256233A1; AU2024304530A1; CN121311397A

Abstract

Aspects of the present invention relate to a control system (100) for controlling a recovery mode of a vehicle (200) for recovery of an object connected to a hitch point (210A-B) of the vehicle (200), the control system (100) comprising one or more processors (120) collectively configured to: receive a tractive effort signal (160) indicative of a threshold of tractive effort required by one or more wheels (280A-D) of the vehicle (200) to move the object; receive torque data (162) from a torque delivery system (225) of the vehicle (200), wherein the torque data (162) is indicative of a torque applied to the one or more wheels (280A-D) of the vehicle (200); determine, in dependence on the torque data (162), a tractive effort of the one or more wheels (280A-D) of the vehicle (200); and output a control signal (170) to a braking system of the vehicle (200) to control a braking of the one or more wheels (280A-D) as the determined tractive effort approaches the threshold of tractive effort. Aspects of the invention are also related to a system incorporating a control system (100) and a braking system (220) of a vehicle (200), a vehicle (200) incorporating a system or a control system (100), and a method (300) of controlling a recovery mode of a vehicle (200).

Description

ASSISTED RECOVERY MODE

TECHNICAL FIELD

The present disclosure relates to a vehicle control system and control method for controlling an assisted recovery mode of a vehicle. Aspects of the invention relate to a control system, a system, a vehicle and a method.

BACKGROUND

It is known to use a vehicle to provide recovery assistance to an object such as another vehicle that has broken down or is stuck in a stationary position, for example, due to a slippery surface such as mud or sand, or due to an obstruction on the ground preventing the object from moving. To provide recovery assistance, the vehicle will usually be connected to the recovery vehicle via a hitch point and a tow rope. The vehicle will then put into drive to pull the object to another location, either to get further assistance or to a position where it is able to move. However, factors such as the characteristics of the terrain that the vehicle is on and the weight of the object can make it difficult for the vehicle to maintain traction throughout the recovery process, which can hamper the success of the recovery.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a control system, a system, a vehicle, a method, and computer readable instructions as claimed in the appended claims.

This disclosure provides a technique for improving the assisted recovery of a vehicle. The technique determines the tractive effort of the wheels of the vehicle as torque is applied, and controls a braking applied to the wheels as the determined tractive effort approaches a threshold of tractive effort.

According to an aspect of the present invention there is provided a control system for controlling a recovery mode of a vehicle for recovery of an object connected to a hitch point of the vehicle. The control system comprises one or more processors collectively configured to receive a tractive effort signal indicative of a threshold of tractive effort required by one or more wheels of the vehicle to move the object. The one or more processors are also configured to receive torque data from a torque delivery system of the vehicle, wherein the torque data is indicative of a torque applied to the one or more wheels of the vehicle, and determine, in dependence on the torque data, a tractive effort of the one or more wheels of the vehicle. The one or more processors are then configured to output a control signal to a braking system of the vehicle to control a braking of the one or more wheels as the determined tractive effort approaches the threshold of tractive effort.

In this way, a vehicle may be recovered more efficiently because the vehicle performing the recovery is less likely to suffer loss of traction during the recovery process. The threshold of tractive effort corresponds to the amount of tractive effort required by each of the wheels of the first vehicle to move the object. As torque is applied to the drivetrain and the tractive effort approaches the threshold of tractive effort, the braking can be controlled to provide more traction between the wheels of the vehicle and the surface on which it is located. In this respect, it will be appreciated that the threshold of tractive effort required by the wheels proximate to the hitch point may be higher than those remote from the hitch point due to the additional load from the object at the hitch point. As such, a different amount of braking may be required at the wheels proximate to the hitch point compared to that required at the wheels remote from the hitch point. As such, each wheel may have the same or a different threshold of tractive effort, and similarly, each wheel may have the same or a different braking applied thereto.

The control system comprises one or more controllers collectively comprising at least one electronic processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute the instructions thereon so as to: receive a tractive effort signal indicative of a threshold of tractive effort required by one or more wheels of the vehicle to move the object; receive torque data from a torque delivery system of the vehicle, wherein the torque data is indicative of a torque applied to the one or more wheels of the vehicle; determine, in dependence on the torque data, a tractive effort of the one or more wheels of the vehicle; and output a control signal to a braking system of the vehicle to control a braking of the one or more wheels as the determined tractive effort approaches the threshold of tractive effort.

Optionally, the one or more processors may be collectively configured to output the control signal to the braking system of the vehicle so as to apply a braking to the one or more wheels as the determined tractive effort approaches the threshold of tractive effort, and to start to reduce the braking at a predetermined rate when the determined tractive effort is equal to or greater than the threshold of tractive effort.

In this way, the brakes of the vehicle are pre-loaded until the tractive effort reaches the threshold to provide more traction between the vehicle and the ground, and then the braking is gradually reduced once the actual tractive effort reaches the threshold to allow the vehicle to slowly start to move away without any significant wheel slip.

Optionally, the one or more processors may be collectively configured to determine the predetermined rate in dependence on the determined tractive effort, wherein the predetermined rate increases as the determined tractive effort decreases with increasing vehicle speed.

In this way, the braking applied is reduced more quickly as the vehicle starts to move forward and the amount of tractive effort decreases with increasing speed.

Optionally, the one or more processors may be collectively configured to determine the predetermined rate based at least in part on one or more environmental conditions of the vehicle.

In this way, the rate at which the braking is reduced is adjusted according to the environmental conditions of the vehicle. For example, if the surface on which the vehicle is located is wet, icy, loose or susceptible to damage, the braking will be reduced at a slower rate. Optionally, the one or more environmental conditions may comprise one or more of a terrain mode, a temperature, and a signal indicative of an activation of one or more windscreen wipers of the vehicle.

Optionally, the predetermined rate may comprise a first predetermined rate for a first set of wheels, and a second predetermined rate for a second set of wheels.

In this way, the braking at each set of wheels (e.g., the front wheels or the rear wheels) will be reduced at a different rate so as to maintain traction at the wheels more susceptible to slippage during a recovery, for example, the axle having less vertical load. For example, the braking at wheels proximate to the hitch point may be reduced at a faster rate, whilst braking at the wheels remote from the hitch point may be reduced at a slower rate to provide more the traction at these wheels for a longer period. It will be appreciated that the first set of wheels may be coupled to a first axle and the second set of wheels may be coupled to a second axle.

Optionally, the one or more processors may be configured to output the control signal to the braking system of the vehicle so as to reduce the braking applied to a first set of wheels to approximately zero, and reduce the braking applied to a second set of wheels to a pre-determined level. For example, the first set of wheels may comprise a pair of wheels proximate to the hitch point, and the second set of wheels may comprise a pair of wheels remote from the hitch point.

In this way, a small amount of braking is applied throughout the assisted recovery to the wheels that are most susceptible to slippage. For example, a small amount of braking may be maintained at the wheels remote from the hitch point where there is less vertical load to thereby provide more traction at these wheels.

Optionally, the tractive effort signal may comprise resistance data indicative of a coefficient of friction between the one or more wheels of the vehicle and a surface on which the vehicle is located, wherein the one or more processors are further configured to determine, in dependence on the resistance data and a weight distribution of the vehicle, the threshold of tractive effort required by the one or more wheels of the vehicle to move the object.

In this way, the threshold of tractive effort at the one or more wheels may be determined based on the coefficient of friction between the wheels and the ground (e.g., as estimated by a tractive resistance system) and the weight distribution of the vehicle. In this respect, it will be appreciated that there may be an uneven weight distribution, for example, due to the gradient of the vehicle and the load exerted on the hitch point by the object, and thus a different threshold of tractive effort may be determined for each wheel. Optionally, the weight distribution may be determined based on changes in the height and/or air pressure of the suspension system at each wheel of the vehicle.

Optionally, the tractive effort signal may comprise a target limit of a torque to be applied by a drivetrain of the vehicle to move the object, wherein the one or more processors are further configured to determine, in dependence on the target limit of a torque to be applied and a radius of the one or more wheels, the threshold of tractive effort required by the one or more wheels of the vehicle to move the object.

The target limit of torque corresponds to the amount of longitudinal force that needs to be applied to the wheels of the first vehicle by the drivetrain to move the object from its stationary position, whilst still maintaining traction, and the threshold of tractive effort corresponds to the amount of tractive effort required by the wheels of the vehicle to move the object. As such, the threshold of tractive effort can be determined by dividing the target limit of torque to be applied by the wheel radius. In such cases, the threshold of tractive effort determined from the target torque limit may be used to refine the coefficient of friction estimation.

Optionally, the one or more processors may be further configured to receive gradient data indicative of a gradient of the vehicle, receive resistance data indicative of a rolling resistance between the vehicle and a surface on which the vehicle is located, receive load data indicative of a load on the hitch point from the object, and determine, in dependence on the gradient data, resistance data and load data, the target limit of a torque to be applied by a drivetrain of the vehicle to move the object.

Optionally, the one or more wheels may comprise a pair of wheels proximate to the hitch point. The one or more wheels may further comprise a pair of wheels remote from the hitch point.

According to another aspect of the invention, there is provided a system comprising the control system as mentioned above and a braking system of the vehicle.

Optionally, the system may further comprise a torque delivery system of the vehicle.

According to yet another aspect of the invention, there is provided a vehicle comprising the system as mentioned above or the control system as mentioned above.

According to a further aspect of the invention, there is provided a method for controlling a recovery mode of a vehicle for recovery of an object connected to a hitch point of the vehicle. The method comprises receiving a tractive effort signal indicative of a threshold of tractive effort required by one or more wheels of the vehicle to move the object. The method also comprises receiving torque data from a torque delivery system of the vehicle, wherein the torque data is indicative of a torque applied to the one or more wheels of the vehicle, and determining, in dependence on the torque data, a tractive effort of the one or more wheels of the vehicle. The method also comprises outputting a control signal to a braking system of the vehicle to control a braking of the one or more wheels as the determined tractive effort approaches the threshold of tractive effort.

According to a still further aspect of the invention, there is provided a computer readable instructions which, when executed by a computer, are arranged to perform the method as mentioned above.

Within the scope of this application it is expressly intended 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. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a block diagram illustrating a control system according to an embodiment of the present invention;

Figure 2A shows a schematic illustration of a vehicle according to an embodiment of the present invention; Figure 2B shows a schematic illustration of a rear-view of the vehicle of Figure 2A;

Figure 3 shows a first flowchart showing operations performed by the control system of Figure 1 according to an embodiment of the present invention;

Figure 4 shows a second flow chart showing operations performed by the control system of Figure 1 according to an embodiment of the present invention;

Figure 5 shows a schematic illustration of the operation of the vehicle of Figure 2A during the operations performed by the control system of Figure 1 ;

Figures 6A-6B show a schematic illustration of the operation of the vehicle of Figure 2A during the operations performed by the control system of Figure 1 .

DETAILED DESCRIPTION

With reference to Figure 1 , there is illustrated a control system 100 for a vehicle. The control system 100 as illustrated in Figure 1 comprises one controller 110, although it will be appreciated that this is merely illustrative. The controller 1 10 comprises processing means 120 and memory means 130. The processing means 120 may be one or more electronic processing device 120 which operably executes computer-readable instructions. The memory means 130 may be one or more memory device 130. The memory means 130 is electrically coupled to the processing means 120. The memory means 130 is configured to store instructions, and the processing means 120 is configured to access the memory means 130 and execute the instructions stored thereon.

The controller 110 comprises an input means 140 and an output means 150. The input means 140 may comprise an electrical input 140 of the controller 110. The output means 150 may comprise an electrical output of the controller 110. The input means 140 is arranged to receive a tractive effort signal 160 indicative of a threshold of tractive effort required by one or more wheels of the vehicle to move an object connected to a hitch point of the vehicle. Optionally, the tractive effort signal 160 may be indicative of a target limit of torque to be applied to a drivetrain of the vehicle during the assisted recovery of an object, from which the threshold of tractive effort may be derived. The tractive effort signal 160 may comprise one or more of a gradient signal, a resistance signal, and a load signal, from which the threshold of tractive effort and/orthe target limit of torque may be derived. The gradient signal is an electrical signal indicative of a gradient of the vehicle. The gradient signal may be received from an inertial measurement device of the vehicle. The resistance signal is an electrical signal indicative of a rolling resistance between the vehicle and the surface on which the vehicle is located and/or a coefficient of friction between the vehicle and the surface on which the vehicle is located. The resistance signal may be received from a tractive resistance system of the vehicle. The load signal is an electrical signal indicative of changes in the load experienced by the vehicle. The load signal may be received from a suspension system of the vehicle, and comprise data indicative of changes in one or more characteristics of the suspension system of the vehicle, such as the height and/or air pressure of the front and/or rear suspension of the vehicle, which in turn is indicative of changes in the load experience by the vehicle.

The input means 140 is also arranged to receive a torque signal 162 from a torque delivery system of the vehicle. The torque signal 162 is an electrical signal which is indicative of the amount of torque being delivered to the drivetrain and/or one or more wheels of the vehicle. The input means 140 may be optionally arranged to receive an environmental conditions signal 164 from one or more sensors of the vehicle indicative of one or more environmental conditions in which the vehicle is operating. For example, the environmental conditions signal 164 may include one or more of a terrain mode signal indicative of a terrain mode of the vehicle, a temperature signal from a temperature sensor indicative of the surrounding temperature, and a signal indicative of the activation of one or more of the windscreen wipers of the vehicle. The input means 140 may also be optionally arranged to receive a recovery mode signal 166 from a user via a human-machine interface (HMI) of the vehicle 200 instructing the controller 110 to start operating the vehicle in a recovery mode which aids an assisted recovery of an object.

The output means 150 is arranged to output a brake control signal 170 to a braking system of the vehicle to control one or more braking characteristics of the vehicle. The output means 150 may be optionally arranged to output a torque control signal 172 to a torque delivery system of the vehicle, the torque control signal 172 being indicative of the target limit of a torque to be applied by a drivetrain of the vehicle during the assisted recovery of an object. The output means 150 may also be optionally arranged to output a driver control signal 174 to a human-machine interface (HMI) of the vehicle requesting the driver of the vehicle to move the vehicle. In cases where the vehicle is an autonomous or semi-autonomous vehicle, it will be appreciated that the driver control signal 174 may be output to an autonomous control system.

Figure 2A illustrates a vehicle 200 according to an embodiment of the present invention. The vehicle 200 comprises a controller 100 as illustrated in Figure 1 . The controller 110 is shown as mounted within the vehicle 200 and is in communication with a braking system 220 of the vehicle 200 such that the brake control signal 170 can be transmitted to the braking system 220. The controller 110 is in further communication with a torque delivery system 225 located within the vehicle 200 such that the torque signal 162 can be received from the torque delivery system 225, and optionally, the torque control signal 172 can be transmitted to the torque delivery system 225. Vehicle 200 may be an EGO vehicle, i.e., a vehicle that is equipped with autonomous or semi-autonomous driving technology and is capable of sensing and navigating its environment without direct input from a human driver.

Vehicle 200 has at least one hitch point for connecting the vehicle 200 to an object in need of recovery, or needing to be moved to another location. For example, vehicle 200 may have a first hitch point 210A located at the front of the vehicle 200, proximate to a front set of wheels 280A, 280B. It will of course be appreciated that this is purely illustrative and the first hitch point 210A may be located at any suitable position on the front of the vehicle 200. Similarly, there may be more than one hitch point located on the front of the vehicle 200.

Figure 2B illustrates a rear-view of the vehicle 200 of Figure 2A. The vehicle 200 may also have a second hitch point 210B located at the rear of the vehicle 200, proximate to a rear set of wheels 280C, 280D, for connecting the vehicle 200 to an object in need of recovery. It will again be appreciated that this is purely illustrative and the second hitch point 210B may be located at any suitable position on the rear of the vehicle 200. Similarly, there may be multiple hitch points on the rear of the vehicle 200. It will also be appreciated that the vehicle 200 may have one or both of the first and second hitch points 210A, 210B. The hitch points 210A, 210B provide a connection point, to which a rope or some other connection means may be attached to the vehicle 200, to thereby connect the vehicle 200 to an object in need of recovery.

The torque delivery system 225 may be configured to provide torque to at least one wheel 280A-D. Similarly, the braking system 220 may be configured to provide a braking torque to at least one wheel 280A-D. In this respect, it will be appreciated that the wheels 280A-D may be controlled individually, with torque and braking torque being applied directly thereto. Optionally, the front set of wheels 280A, 280B may be coupled to a first axle, and the rear set of wheels 280C, 280D may be coupled to a second axle. The torque delivery system 225 may thus be configured to provide torque to one or both of the first and second axles to thereby provide torque to at least one wheel 280A-D. Similarly, the braking system 220 may be configured to provide a braking torque to one or both of the first and second axles to thereby provide braking to at least one wheel 280A-D.

It will of course be appreciated that the vehicle 200 may be operated to assist in the recovery of any suitable object, including but not limited to, a second vehicle, a trailer, a boat, a boulder, wood logs, or any object having weight that does not exceed the power capabilities of the vehicle 200.

Figure 3 is a flowchart 300 according to an embodiment of the present invention. The flowchart 300 illustrates steps performed by the control system 100 in controlling a recovery mode of a vehicle 200, such as the vehicle 200 illustrated in Figures 2A and 2B. In particular, the memory 130 may comprise computer-readable instructions which, when executed by the processor 120, perform the method 300 according to an embodiment of the invention.

At step 310, the control system is configured to receive a tractive effort signal 160 indicative of a threshold of tractive effort required by one or more wheels 280A-D of the vehicle 200 to move an object connected to a hitch point of the vehicle 200. The one or more wheels 280A-D may comprise the pair of wheels proximate to the hitch point 21 OA, 21 OB. Optionally, the one or more wheels 280A-D may further comprise the pair of wheels remote from the hitch point 21 OA, 21 OB.

Optionally, the tractive effort signal 160 is produced by the controller 110 based on receiving data as input signal 160 relating to the co-efficient of friction between the vehicle 200 and the surface on which the vehicle 200 is located (e.g., as estimated by the tractive resistance system of the vehicle 200).

Alternatively, or additionally, the tractive effort signal 160 is produced by the controller 110 based on receiving data as input signal 160 relating to a target limit of torque to be applied to a drivetrain of the vehicle 200 during the assisted recovery of the object. Optionally, this target limit of torque is also produced by the controller 110 based on receiving data as input signal 160 relating to the gradient of the vehicle 200, the rolling resistance of the vehicle 200, and the load exerted on the hitch point 210A, 210B by the object, as will be described in more detail below with reference to Figure 4.

In general, tractive effort can be determined by one or more of the amount of torque being applied at the wheels of the vehicle 200, the radius of the wheels 280A-D, the gradient of the vehicle 200, the coefficient of friction between the wheels 280A-D and the below surface 270 (e.g., as estimated by the tractive resistance system of the vehicle 200), and the weight at each set of wheels 280A-D. The weight at each set of wheels 280A-D may be based on the weight of the vehicle 200 at zero gradient, and it will be appreciated that the weight of the vehicle 200 may be stored as data in the memory means 130. Alternatively, or additionally, the weight at each set of wheels 280A-D may be estimated using changes to data received from the suspension system of the vehicle 200, such as but not limited to changes in the suspension height and/or air pressure, which may be indicative of a change in weight distribution.

Figures 6A-B provide an example for illustrating how tractive effort may be determined. Figure 6A shows the vehicle 200 prior to any load being applied to a hitch point 210A, 210B. The maximum tractive effort required to move a vehicle 200 is typically defined as the coefficient of friction, p, multiplied by the weight (mass multiplied by gravity), mg, (as generally denoted by C) at each set of wheels 280A-B, 280C-D of the vehicle 200. At a zero gradient, assuming the front wheels 280A-B and rear wheels 280C-D are approximately equal distance from the vehicle’s central point (i.e., the centre of mass), the weight (shown generally at A and B) at each set of wheels 280A-B, 280C-D will be approximately % mg, and the suspension heights and/or air pressure (as generally denoted by D and E) will be approximately equal. As illustrated in Figure 6B, when an object (not shown) is connected to the rear hitch point 210B (e.g., via a tow rope 260), this causes a transfer of load from the front wheels 280A to the rear wheels 280C, thus causing a shift in the position of the centre of mass (denoted by C) towards the rear wheels 280C-D, and a change in the weight experienced at each set of wheels 280A-B, 280C-D. As a result, the suspension data may indicate changes to the suspension height and/or air pressure at each end of the vehicle 200, which in turn indicates a new distribution of weight. For example, the suspension height at the front of the vehicle 200 (denoted by D) may increase, whilst the suspension height at the rear of the vehicle 200 (denoted by E) may decrease as a result of the additional load on the rear hitch point 210B. Consequently, due to a change in the position of the centre of mass (denoted by C), the weight (denoted by A) at the front wheels 280A-B may reduce to 3/8mg (i.e., 3/8 of the total weight), whilst the weight (denoted by B) experienced at the rear wheels 280C-D may increase to 5/8mg (i.e., 5/8 of the total weight). Whilst the present example shows a scenario in which the gradient is zero, it will of course be appreciated that the weight distribution may be further affected by a non-zero gradient. For example, if the vehicle 200 was facing in an up-hill direction, the load transfer towards the rear wheels 280C-D may be further increased as a result. Similarly, if the vehicle 200 was facing in a down-hill direction, the amount of load transferred towards the rear wheels 280C-D may be less than that on a zero gradient, and depending on the amount of incline, load may instead be transferred to the front wheels 280A-B as a result (i.e., the amount of load at the rear wheels 280C-D would be reduced).

As such, at step 310, the processing means 120 may, upon executing instructions stored in the memory means 130, determine the threshold of tractive effort based on the coefficient of friction between the wheels 280A-D and the below surface 270 (e.g., as estimated by the tractive resistance system of the vehicle 200), and the weight at each set of wheels 280A-D. As such, it will be appreciated that threshold of tractive effort may be higher at the wheels 280A-D experiencing the most vertical load (i.e., weight). For example, using the above example, the threshold of tractive effort will be higher at the rear wheels 280C-D, compared to that at front wheels 28-A-B where less vertical load is experienced.

The torque at each wheel 280A-D can also be defined as the tractive effort, pmg, multiplied by the radius of the wheels 280A-D. As such, the processing means 120 may be, additionally or alternatively, configured to determine the threshold of tractive effort based on the target limit of torque to be applied, which may be received as input signal 160, or produced by the controller 110 as described with reference to Figure 4 below. Given the target limit of torque to be applied, the threshold of tractive effort may thus be calculated by dividing the target limit of torque by the wheel radius to provide the threshold of tractive effort at each wheel 280A -D. Optionally, the threshold of tractive effort at each wheel 280A-D may then be further adjusted by the weight distribution at each set of wheels 280A-D, such that the limit of tractive effort will again be higher at the wheels experiencing the most vertical load.

As such, at step 310, the processing means 120 may, upon executing instructions stored in the memory means 130, determine the threshold of tractive effort based on the target limit of torque, and the radius of the wheels 280A-D of the vehicle 200, which may be stored as data in the memory means 130.

Optionally, the processing means 120 may be configured to adjust the coefficient of friction estimated by the tractive resistance system 200 based on the threshold of tractive effort determined from the target limit of torque. In this respect, if the threshold of tractive effort determined from the target torque limit is higher than the threshold of tractive effort determined from the estimated coefficient of friction, the estimation of the coefficient of friction can be refined, for example, by increasing the coefficient of friction, so that the resulting threshold of tractive effort matches that determined from the target torque limit. Similarly, the processing means 120 may be configured to adjust or validate the target limit of torque based on the threshold of tractive effort determined from the coefficient of friction estimated by the tractive resistance system 200. At step 320, as torque is applied to the drivetrain to move the vehicle 200, the control system 100 is configured to receive torque data of the vehicle 200. The torque data is received as an input signal 162 at the input means 140 of the controller 110 and comprises data indicative of the torque being applied to the one or more wheels of the vehicle 200. From the torque data, at step 330, the processing means 120 is configured to determine the tractive effort of the wheels 280A-D of the vehicle 200 as torque is being applied, again based on the amount of torque being applied to the one or more wheels 280A-D of the vehicle 200, and the radius of said wheels 280A-D.

As the processing means 120 determines the tractive effort of one or more wheels 280A-D of the vehicle 200, the controller 1 10 outputs, at step 340, a control signal 170 to cause a braking system 220 of the vehicle 200 to control the braking applied to the one or more wheels 280A-D of the vehicle 200 as the measured tractive effort approaches the threshold of tractive effort received or determined at step 310. For example, the control signal 170 may cause the braking system 220 to pre-load the braking applied to the wheels 280A-D of the vehicle 200 as the measured tractive effort approaches the threshold of tractive effort in order to provide more traction between the wheels of the vehicle 200 and the ground 270, and then gradually reduce the braking applied at a predetermined rate once the measured tractive effort is equal to or greater than the threshold of tractive effort, so as to allow the vehicle 200 to slowly start to move away without any significant wheel slip. In this respect, it will be appreciated that the measured tractive effort may reach a level greater than the threshold of tractive effort where the threshold is based on estimated parameters such as an estimated coefficient of friction and/or a target torque limit. Once the measured tractive effort reaches the threshold of tractive effort and the vehicle 200 begins to move away, the tractive effort of the vehicle 200 will reduce proportionally to an increase in speed, and thus the braking applied can be gradually reduced to allow the torque being delivered by the torque delivery system 225 to increase in a controlled manner.

Optionally, the processing means 120 may be configured to determine the predetermined rate at which the braking is reduced in dependence on the tractive effort determined at 330, wherein the predetermined rate is reduced as the measured tractive effort decreases with speed. In this respect, it will be appreciated that the tractive effort may be continuously determined as torque is applied to the one or more wheels 280A-D of the vehicle 200. As such, the braking applied to the one or more wheels may be reduced more quickly as the amount of tractive effort decrease and the speed of the vehicle 200 increases. Optionally, once the measured tractive effort has reached the threshold of tractive effort, the predetermined rate at which the braking is reduced may be related to the reduction in tractive effort with increasing speed, as a proportion of the threshold of tractive effort. For example, the braking made be reduced each time the measured tractive effort decreases by an amount equal to 10% of the threshold, and may be reduced by a corresponding proportion (e.g., 10%).

Additionally, or alternatively, the processing means 120 may be configured to determine a first predetermined rate for a first set of wheels, and a second predetermined rate for a second set of wheels. For example, the first set of wheels may comprise the pair of wheels proximate to the hitch point (e.g., wheels 280C, 280D if the rear hitch point 210B is in use) and the second set of wheels may comprise the pair of wheels remote from the hitch point (e.g., wheels 280A, 280B if the rear hitch point 210B is in use). In this way, the braking at each axle will be reduced at a different rate so as to maintain traction at the wheels 280A-D more susceptible to slippage during a recovery (e.g., the pair of wheels on the axle having less vertical load). For example, the braking at the wheels proximate to the hitch point may be reduced at a faster rate, whilst braking at the wheels remote from the hitch point may be reduced at a slower rate to provide more the traction at these wheels for a longer period.

Additionally, or alternatively, the processing means 120 may be configured to determine the predetermined rate at which the braking is reduced in dependence on one or more environmental conditions of the vehicle 200. In this respect, the control system 100 may be configured to receive the one or more environmental conditions as an input signal 164 at the input means 140 of the controller 110, the input signal 164 comprising one or more of a terrain mode signal indicative of a terrain mode of the vehicle, a temperature signal from a temperature sensor indicative of the surrounding temperature, and a signal indicative of the activation of one or more of the windscreen wipers of the vehicle 200. The processing means 120 may then be configured to determine the predetermined rate in dependence on the received environmental conditions. For example, if the terrain mode of the signal is indicative of a terrain where tractive resistance may be reduced (e.g., snow terrain mode, sand terrain mode or mud terrain mode), the braking applied to the one or more wheels may be reduced at a relatively slower rate compared to that used for normal on-road driving mode. As another example, if the temperature signal is indicative of a surrounding temperature equal to or below 0°C, thereby indicating that the surface on which vehicle 200 is operating may be icy and thus tractive resistance may be reduced, the braking applied to the one or more wheels may be reduced at a relatively slower rate compared to that used for temperatures above 0°C. As a further example, if a signal indicating that one or more of the windscreen wipers have been activated is received, thereby indicating that the surface on which vehicle 200 is operating may be wet and thus tractive resistance may be reduced, the braking applied to the one or more wheels may be reduced at a relatively slower rate compared to that used for dry conditions.

Additionally, or alternatively, the control signal 170 may be configured to cause the braking system 220 to reduce the braking applied to the first set of wheels (e.g., the pair of wheels proximate to the hitch point) to approximately zero, and reduce the braking applied to the second set of wheels (e.g., the pair of wheels remote from the hitch point) to a pre-determined level. In this respect, it will be appreciated that the pre-determined level may be a calibratable value, depending on factors such as terrain mode, gradient and other environmental conditions. As such, the pre-determined level may be determined from a look-up table of values associated with different operating variables. In this way, a small amount of braking is applied throughout the assisted recovery to the wheels that are most susceptible to slippage. For example, a small amount of braking may be maintained at the wheels remote from the hitch point (e.g., the front wheels 280A-B if the rear hitch point 210B is in use) where there is less vertical load to thereby provide more traction at these wheels.

Figure 4 is a flowchart 400 according to an embodiment of the present invention. The flowchart 400 illustrates further steps performed by the control system 100 in controlling a recovery mode of a vehicle 200, such as the vehicle 200 illustrated in Figures 2A and 2B and with further reference to Figure 5, which may be used in conjunction with the method described 300 with reference to Figure 3. In particular, the memory 130 may comprise computer-readable instructions which, when executed by the processor 120, perform the method 400 according to an embodiment of the invention. In the example shown in Figure 5, the vehicle 200 is providing assisted recovery to a recovery vehicle 250, a front hitch point 255A of the recovery vehicle 250 being attached to the rear hitch point 21 OB of the vehicle 200 by a connecting means such as a tow rope 260. It will of course appreciate that this is merely illustrative, and that the recovery vehicle 250 may be replaced with any object in need of being recovered or moved to another location.

Optionally, at step 410, the control system is configured to receive user input data from a human-machine interface of the vehicle 200. The user input data is received as an input signal 166 at the input means 140 of the controller 100 and comprises data indicating a request to begin operating in the recovery mode of the vehicle 200.

At step 420, the control system 100 is configured to receive gradient data of the vehicle 200. The gradient data may be received as an input signal 160 at the input means 140 of the controller 110 and comprises data indicative of a gradient of the vehicle 200 as measured by an inertial measurement unit (IMU) of the vehicle 200. It will be appreciated that the gradient of the vehicle 200 is in turn indicative of the incline of a surface 270 on which the vehicle 200 is positioned. In the example shown in Figure 5, the surface 270 is shown as being substantially horizontal, but it will be appreciated that the surface 270 may be inclined, for example, when the vehicle 200 is on a hill.

At step 430, the control system 100 is configured to receive tractive resistance data of the vehicle 200. The tractive resistance data may be received as another input signal 160 at the input means 140 of the controller 110 and comprises data indicative of a rolling resistance between the vehicle 200 and the surface 270 on which the vehicle 200 is located, and more specifically, between the wheels of the vehicle 200 and the below surface 270. The rolling resistance will depend on the vertical load exerted on the wheels (shown for example purposes by arrow A in Figure 5) and the rolling resistance factor between the wheels and the surface 270, the rolling resistance factor being the measure of drag force generated by the wheels as it moves on and through a deformable surface such as mud. For example, the rolling resistance factor for a set of tyres moving along a smooth paved road will have a lower rolling resistance factor than that for a set of tyres moving along a muddy or sandy surface. The tractive resistance data may be measured by a tractive resistance system of the vehicle 200. In this respect, it will be appreciated that the rolling resistance factor may be estimated by a variety of different systems within the vehicle 200, for example, using torque sensors or torque measurements from the powertrain in relation to the gradient and speed of the vehicle 200.

At step 440, the control system 100 is configured to receive a load signal comprising suspension system data of the vehicle 200. The suspension system data may be received as a further input signal 160 at the input means 140 of the controller 110 and comprises data indicative of a change in the height (shown for example purposes by arrow B in Figure 5) of the suspension of the vehicle 200 proximate to at least one of the hitch points 210A, 210B, that is, a change in the height B of the suspension at the front and/or rear end of the vehicle 200. The suspension system data may comprise data indicative of a displacement of the suspension system, which may be measured as one example by one or more position sensors, or in cases where the suspension system is a self-levelling air suspension system, the suspension system data may comprise data indicative of a change in air pressure supplied to the suspension system to change or to maintain the ride height of the vehicle 200. As discussed above, changes in the height B of the suspension system, or changes to the air pressure in the suspension system, is indicative of any changes in the load exerted on the hitch point 21 OB, since this increase in load will cause a corresponding increase in the vertical load A and cause the suspension to compress. A self-levelling air suspension system will operate to counter the compressive force. The suspension system data of the vehicle 200 can thus be used by the processor 120 to determine the load on the hitch point 210B. For example, when a recovery vehicle 250 is attached to the vehicle 200 via the rear hitch point 210B, as shown in Figure 5, and the tow rope 260 is brought under tension, the vehicle 200 will experience an increase of load at the hitch point 210B, which will in turn cause a proportional increase in the vertical load B, and thus a displacement in the rear suspension or a change in air pressure supplied to the rear suspension. In this respect, it will be appreciated that the amount of load on the hitch point 210B will be dependent on the weight of the recovery vehicle 250, the gradient of the surface 270 on which the recovery vehicle 250 is located and the direction in which the vehicle 200 is pulling the object along that gradient (i.e., uphill or downhill).

It will of course be appreciated that the steps 420, 430 and 440 may be performed in parallel or in sequence, and that the data may be received as input signals 160 at the same time or in any order.

At step 450, the control system 100 is configured to determine a target limit of torque to be applied by the drivetrain of the vehicle 200 based on the gradient data, the tractive resistance data and the load determined from the suspension system data. In this respect, the processing means 120 receives the input signal 160 from the input means 140 and, upon executing the instructions stored in the memory means 130, determines the target limit of torque to be applied by the drivetrain. The target limit of torque corresponds to the amount of longitudinal force that needs to be applied to the wheels of vehicle 200 by the drivetrain to move the recovery vehicle 250 from its stationary position, whilst at the same time maintaining enough traction between the wheels of the vehicle 200 and the ground 270 to avoid any wheel slip.

Once the processing means 120 has determined the target limit of torque to be applied by the drivetrain of the vehicle 200, the target limit of torque may then be used by the processing means 120 to determine the threshold of tractive effort required, as described at step 310 above.

Optionally, once the target limit of torque has been determined, the controller 110 may output, at step 460, a control signal 172 to cause the torque delivery system 220 of the vehicle 200 to control the drivetrain as power is applied thereto. In this respect, the torque delivery system 220 may be configured to control the drivetrain such that, as power is applied to the drivetrain, the amount of torque applied by the drivetrain does not exceed the determined target limit.

Optionally, once an initial target limit of torque has been output to the torque delivery system 220, the controller 110 may be configured to output, at step 470, a signal 174 to a human-machine interface of the vehicle 200 instructing the driver of the vehicle 200 to begin moving the vehicle 200 forward so as to move the object (e.g., recovery vehicle 250), if not already doing so. Once an initial target limit of torque has been determined and output to the torque delivery system 220, steps 420-450 can be repeated so as to adjust the target limit of torque throughout the assisted recovery. In this respect, the control system 100 is configured to repeatedly receive input signal 160, the determined target limit of torque changing if and when one or more of the gradient signal, resistance signal and load signal changes.

In this respect, it will be appreciated that the input signal 160may be received at any appropriate time, including but not limited to, prior to any torque being applied by the torque delivery system 220, upon torque being applied by the torque delivery system 220, and repeatedly regardless of whether or not torque is being applied by the torque delivery system 220. As such, the input signal 160 may be received at a first point in time before the assisted recovery has commenced, or at a time when the vehicle 200 has been connected to an object (e.g., the recovery vehicle 250) and moved forward enough that the tow rope 260 has been brought under tension to thereby transfer an initial load from the object to the hitch point 210A, 210B of the vehicle 200. In doing so, coarse measurements of the tractive resistance data and the suspension system data can be received and input as input signal 160, to thereby determine an initial target limit of torque. As such, the target limit of torque may be first determined at step 450 when an initial load is sensed via a change to the input signal 160 following activation of the recovery mode at step 310. The data associated with input signal 160is then repeatedly received as the assisted recovery is carried out and torque is applied by the torque delivery system 220, the target limit of torque being continuously adjusted and refined as further data is received. In this regard, if upon determining the target limit of torque, torque is applied by the drivetrain up to that target limit and no movement of the vehicle 200 is detected, the target limit of torque may be gradually increased until the vehicle 200 begins to move. Similarly, the target limit of torque may be gradually reduced as the vehicle 200 moves, for example, if the suspension data indicates that the vertical load at the hitch point 210A, 210B has decreased due to the vehicle 200 travelling down a gradient.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1 . A control system for controlling a recovery mode of a vehicle for recovery of an object connected to a hitch point of the vehicle, the control system comprising one or more processors collectively configured to: receive a tractive effort signal indicative of a threshold of tractive effort required by one or more wheels of the vehicle to move the object; receive torque data from a torque delivery system of the vehicle, wherein the torque data is indicative of a torque applied to the one or more wheels of the vehicle; determine, in dependence on the torque data, a tractive effort of the one or more wheels of the vehicle; and output a control signal to a braking system of the vehicle to control a braking of the one or more wheels as the determined tractive effort approaches the threshold of tractive effort.

2. A control system according to claim 1 , wherein the one or more processors are collectively configured to output the control signal to the braking system of the vehicle so as to apply a braking to the one or more wheels as the determined tractive effort approaches the threshold of tractive effort, and to start to reduce the braking at a predetermined rate when the determined tractive effort is equal to or greater than the threshold of tractive effort.

3. A control system according to claim 2, wherein the one or more processors are collectively configured to determine the predetermined rate in dependence on the determined tractive effort, wherein the predetermined rate increases as the determined tractive effort decreases with increasing vehicle speed.

4. A control system according to claims 2 or 3, wherein the one or more processors are collectively configured to determine the predetermined rate based at least in part on one or more environmental conditions of the vehicle.

5. A control system according to claim 4, wherein the one or more environmental conditions comprises one or more of a terrain mode, a temperature, and a signal indicative of an activation of one or more windscreen wipers of the vehicle.

6. A control system according to any of claims 2 to 5, wherein the predetermined rate comprises a first predetermined rate for a first set of wheels, and a second predetermined rate for a second set of wheels.

7. A control system according to any of claims 2 to 6, wherein the one or more processors are configured to output the control signal to the braking system of the vehicle so as to reduce the braking applied to a first set of wheels to approximately zero, and reduce the braking applied to a second set of wheels to a pre-determined level.

8. A control system according to claims 6 or 7, wherein the first set of wheels comprises a pair of wheels proximate to the hitch point, and the second set of wheels comprises a pair of wheels remote from the hitch point.

9. A control system according to any preceding claim, wherein the tractive effort signal comprises resistance data indicative of a coefficient of friction between the one or more wheels of the vehicle and a surface on which the vehicle is located, and wherein the one or more processors are further configured to determine, in dependence on the resistance data and a weight distribution of the vehicle, the threshold of tractive effort required by the one or more wheels of the vehicle to move the object.

10. A control system according to any of claims 1 to 9, wherein the tractive effort signal comprises a target limit of a torque to be applied by a drivetrain of the vehicle to move the object, and wherein the one or more processors are further configured to determine, in dependence on the target limit of a torque to be applied and a radius of the one or more wheels, the threshold of tractive effort required by the one or more wheels of the vehicle to move the object.

11 . A control system according to claim 10, wherein the one or more processors are further configured to: receive gradient data indicative of a gradient of the vehicle; receive resistance data indicative of a rolling resistance between the vehicle and a surface on which the vehicle is located; receive load data indicative of a load on the hitch point from the object; and determine, in dependence on the gradient data, resistance data and load data, the target limit of a torque to be applied by a drivetrain of the vehicle to move the object.

12. A system comprising the control system of any preceding claim and a braking system of the vehicle.

13. A system according to claim 12, further comprising a torque delivery system of the vehicle.

14. A vehicle comprising the system of claims 12 to 13 or the control system of claims 1 to 1 1 .

15. A method for controlling a recovery mode of a vehicle for recovery of an object connected to a hitch point of the vehicle, the method comprising: receiving a tractive effort signal indicative of a threshold of tractive effort required by one or more wheels of the vehicle to move the object; receiving torque data from a torque delivery system of the vehicle, wherein the torque data is indicative of a torque applied to the one or more wheels of the vehicle; determining, in dependence on the torque data, a tractive effort of the one or more wheels of the vehicle; and outputting a control signal to a braking system of the vehicle to control a braking of the one or more wheels as the determined tractive effort approaches the threshold of tractive effort.