Method for determining longitudinal force threshold value of longitudinal deceleration force of tractor

Abstract

The invention relates to a method for determining a tractor longitudinal force threshold value (formula) for a tractor longitudinal deceleration force (formula) that can be applied on a tractor (12) of a vehicle combination (10) comprising the tractor (12) and a trailer (14) for decelerating the vehicle combination (10). The trailer (14) has a trailer longitudinal extension in a trailer longitudinal direction (LTL), a trailer transverse extension in a trailer transverse direction (TTL), and a trailer vertical extension in a trailer vertical direction (VTL), the trailer longitudinal direction (LTL) corresponding to an expected direction of travel of the trailer (14) when the vehicle combination (10) is driven in a straight forward direction, and the trailer longitudinal direction (LTL) corresponds to the expected direction of travel of the trailer (14) when the vehicle combination (10) is driven in a straight forward direction. The trailer vertical direction (VTL) corresponds to a normal direction of a planar surface supporting the trailer (14), and the trailer transverse direction (TTL) is perpendicular to each of the trailer longitudinal direction (LTL) and the trailer vertical direction (VTL). The tractor has a tractor longitudinal extension in a tractor longitudinal direction (LTR), a tractor transverse extension in a tractor transverse direction (TTR), and a tractor vertical extension in a tractor vertical direction (VTR), the tractor longitudinal direction (LTR) corresponding to an expected direction of travel of the tractor (12) when the vehicle combination (10) is driven in a straight forward direction, and the tractor longitudinal direction (LTR) corresponds to an expected direction of travel of the tractor (12) when the vehicle combination (10) is driven in a straight forward direction. The towing vehicle vertical direction (VTR) corresponds to a normal direction of a planar surface supporting the towing vehicle (12), and the towing vehicle transverse direction (TTR) is perpendicular to each of the towing vehicle longitudinal direction (LTR) and the towing vehicle vertical direction (VTR), where the towing vehicle longitudinal deceleration force (formula) extends in a direction parallel to the towing vehicle longitudinal direction (TTR).

Description

Technical Field

[0001] The invention relates to a method for determining a tractor longitudinal force threshold value of a tractor longitudinal deceleration force which can be applied to a tractor of a vehicle combination comprising a tractor and a trailer for decelerating the vehicle combination. Furthermore, the invention relates to a method for braking a vehicle combination comprising a tractor and a trailer. Furthermore, the invention relates to each of a computer program, a computer readable medium, a control unit and a vehicle combination.

[0002] The present invention is applicable to heavy vehicles, such as trucks, buses and construction equipment. Although the present invention will be described with respect to a vehicle combination including a truck, the present invention is not limited to this particular vehicle combination, but may also be used for vehicle combinations including other vehicles, such as work machinery, buses, etc. Background Art

[0003] A vehicle combination typically includes a tractor and a trailer. The tractor may include a tractor brake assembly and the trailer may include a trailer brake assembly to ensure that the vehicle combination can be properly braked.

[0004] It may be desirable to brake the vehicle combination by operating the tractor brake assembly rather than the trailer brake assembly. For example, the tractor may include a tractor brake assembly for regenerative braking of the tractor, and it may be desirable to employ regenerative braking solely on the tractor in order to ensure that a relatively large amount of energy is regenerated when deceleration of the vehicle combination is requested.

[0005] As another non-limiting example, it may be desirable to use only the service brakes of the tractor brake assembly when braking the vehicle combination in order to ensure that the trailer brake assembly may be inactive and thereby properly cooled, for example.

[0006] However, braking the vehicle combination by operating only the tractor vehicle brake assembly may present certain challenges, such as increasing the risk of jackknife or swing-out of the trailer.

[0007] From the foregoing it can be appreciated that it is desirable to obtain information indicating under what conditions a vehicle combination may be braked solely by the towing vehicle. Summary of the invention

[0008] It is an object of the present invention to provide a method which can provide useful information regarding the braking of a vehicle combination.

[0009] This object is achieved by a method according to claim 1 .

[0010] Therefore, a first aspect of the invention relates to a method for determining a tractor longitudinal force threshold value of a tractor longitudinal deceleration force which can be applied to a tractor of a vehicle combination comprising a tractor and a trailer for decelerating the vehicle combination.

[0011] The trailer has a trailer longitudinal extension along a trailer longitudinal direction, a trailer transverse extension along a trailer transverse direction, and a trailer vertical extension along a trailer vertical direction. The trailer longitudinal direction corresponds to the intended travel direction of the trailer when the vehicle combination travels straight ahead, the trailer vertical direction corresponds to the normal direction of a planar surface supporting the trailer, and the trailer transverse direction is perpendicular to each of the trailer longitudinal direction and the trailer vertical direction.

[0012] The tractor has a tractor longitudinal extension in a tractor longitudinal direction, a tractor transverse extension in a tractor transverse direction, and a tractor vertical extension in a tractor vertical direction. The tractor longitudinal direction corresponds to the intended travel direction of the tractor when the vehicle combination travels straight ahead, the tractor vertical direction corresponds to the normal direction of a planar surface supporting the tractor, and the tractor transverse direction is perpendicular to each of the tractor longitudinal direction and the tractor vertical direction, wherein the tractor longitudinal deceleration force extends in a direction parallel to the tractor longitudinal direction.

[0013] The method comprises: − determining a trailer lateral force value indicative of a trailer lateral force being or predicted to be exerted on said tractor in a lateral direction of said tractor using a trailer lateral force value determination procedure, said trailer lateral force value determination procedure comprising: − obtaining a trailer mass value indicating the current mass of the trailer; − obtaining a longitudinal trailer inclination angle value indicating an inclination angle of the ground supporting the trailer along the longitudinal direction of the trailer; − determining a longitudinal weight force value indicative of a longitudinal weight force exerted on the trailer in a longitudinal direction of the trailer based at least on the trailer mass value and the longitudinal trailer inclination angle value; − determining an articulation angle value indicating a current articulation angle between the longitudinal direction of the tractor vehicle and the longitudinal direction of the trailer; − Determine the trailer lateral force value using the longitudinal gravity value and the articulation angle value; − determine a horizontal friction value indicative of the total possible horizontal friction available between the ground supporting the tractor and the ground engaging members of said tractor, and − Determine the tractor longitudinal force threshold using the trailer lateral force value and the horizontal friction force value.

[0014] The method according to the first aspect of the invention takes into account the above longitudinal gravity value when determining the tractor longitudinal force threshold. This means that the tractor longitudinal force threshold can be determined with a relatively high level of accuracy, which in turn means that the vehicle combination is properly controlled.

[0015] Optionally, the trailer lateral force value determination procedure further includes: − obtaining a longitudinal trailer deceleration value indicative of a longitudinal trailer deceleration being or predicted to be imposed on the trailer; − determining a longitudinal inertial trailer force value indicative of a longitudinal inertial force exerted on the trailer in a transverse direction of the trailer based at least on the trailer mass value and the longitudinal trailer deceleration value, and − The longitudinal inertia trailer force value is also used to determine the tractor longitudinal force threshold value.

[0016] When determining the tractor longitudinal force threshold, the longitudinal inertia trailer force value is also considered to further improve the accuracy of determining the tractor longitudinal force threshold.

[0017] Optionally, the trailer lateral force value determination procedure further includes: − determining a lateral centrifugal force value indicative of a centrifugal force exerted on the trailer in a lateral direction of the trailer based at least on the trailer mass value, and − The lateral centrifugal force value is also used to determine the trailer lateral force value.

[0018] Considering the lateral centrifugal force value when determining the tractor longitudinal force threshold value can further improve the accuracy of determining the tractor longitudinal force threshold value.

[0019] Optionally, the trailer lateral force value determination procedure further includes: − obtaining a lateral inclination angle value indicating an inclination angle of the ground supporting the trailer in a lateral direction of the trailer; − determining a lateral weight force value indicative of a lateral weight force of the trailer exerted on the trailer in a lateral direction of the trailer based at least on the trailer mass value and the lateral inclination angle value, and − The lateral weight force value is also used to determine the trailer lateral force value.

[0020] If the trailer is supported by sloping ground, this may result in lateral weight forces acting on the trailer, and the above program steps may take into account the lateral weight forces when determining the tractor longitudinal force threshold, which lateral weight forces depend on the tilt angle in the lateral direction of the trailer.

[0021] Optionally, the trailer lateral force value determination procedure further comprises multiplying each force value indicative of a force in the longitudinal direction of the trailer by the sine of the articulation angle value.

[0022] Optionally, the trailer lateral force value determination procedure further comprises multiplying each force value indicative of a force in a lateral direction of the trailer by the cosine of the articulation angle value.

[0023] Optionally, the tractor comprises a tilt sensor adapted to determine a longitudinal tractor tilt angle value indicating a tilt angle of ground supporting the tractor along a longitudinal direction of the tractor. Furthermore, obtaining the longitudinal trailer tilt angle value indicating the tilt angle of ground supporting the trailer along a longitudinal direction of the trailer comprises: − obtaining a speed value indicating a current speed of the tractor vehicle in a longitudinal direction of the tractor vehicle; − obtaining a distance value indicating the distance between the tilt sensor and a reference point of the trailer in the longitudinal direction of the tractor, and − using the speed value and the distance value to determine the time that has passed from a first moment when the tilt sensor is at a certain global position to a second moment when the reference point of the trailer is at the same global position, and − Determining the longitudinal trailer inclination angle value using one or more longitudinal tractor inclination angle values ​​determined by the inclination sensor and the elapsed time.

[0024] The above procedure means that longitudinal trailer tilt angle values ​​can be determined without necessarily requiring the trailer itself to be equipped with a tilt sensor.

[0025] Optionally, the tractor comprises a set of ground engaging member axles, wherein the set of ground engaging member axles comprises at least one axle, and wherein each ground engaging member axle is connected to a respective ground engaging member of the tractor. The method comprises performing the following operations for each ground engaging member axle in the set of ground engaging member axles: − determining a trailer axle lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member axle based on the trailer lateral force value; − determining a horizontal friction force value indicative of a possible total horizontal friction force available between the ground supporting the tractor and said respective ground engaging members of said ground engaging member axles; − determining the axle tractor longitudinal force threshold using said trailer axle lateral force value and said horizontal friction force value, and The axle tractor longitudinal force threshold for each ground engaging member axle in the set of ground engaging member axles is aggregated to obtain the tractor longitudinal force threshold.

[0026] Performing the above steps for each ground engaging member axle may further enhance the accuracy of the method.

[0027] Optionally, the step of determining a trailer axle lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member axle based on the trailer lateral force value comprises using a moment balance equation using the following inputs: − the trailer lateral force value; − the distance from each ground engaging member axle to the centre of gravity of the tractor in the longitudinal direction of the tractor, and − The distance from the connection point to the centre of gravity of the tractor in the longitudinal direction of the tractor.

[0028] Optionally, the method comprises performing the following operations for each ground engaging member of the tractor: − determining a trailer ground engaging member lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member based on the trailer lateral force value; − determining a horizontal friction value indicative of the possible total horizontal friction available between the ground supporting the tractor and said ground engaging members; − determining a ground engaging member tractor longitudinal force threshold using said trailer ground engaging member lateral force value and said horizontal friction force value, and The ground engaging member tractor longitudinal force threshold values ​​of each ground engaging member of the tractor are summed to obtain the tractor longitudinal force threshold value.

[0029] Performing the above steps for each ground engaging member may further enhance the accuracy of the method.

[0030] Optionally, the step of determining a trailer ground engaging member lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member based on the trailer lateral force value comprises using a moment balance equation using the following inputs: − the trailer lateral force value; − the distance from each ground engaging member to the centre of gravity of the tractor in the longitudinal direction of the tractor, and − The distance from the connection point to the centre of gravity of the tractor in the longitudinal direction of the tractor.

[0031] A second aspect of the invention relates to a method for braking a vehicle combination comprising a tractor and a trailer, the tractor comprising a tractor brake assembly for regenerative braking of the tractor, and the trailer comprising a trailer brake assembly for braking the trailer. The method according to the second aspect of the invention comprises: − determining the tractor longitudinal force threshold using the method according to the first aspect of the invention, and − Operate the towing vehicle brake assembly to provide a braking force less than or equal to the towing vehicle longitudinal force threshold.

[0032] The method according to the second aspect of the invention means that the vehicle combination can be braked with a suitably low risk for undesirable operating conditions of the vehicle combination, such as a kink.

[0033] Optionally, the method further comprises: − obtaining a deceleration request value indicating a requested deceleration of the vehicle combination; − determining a requested braking force to be applied to said vehicle combination based on said deceleration request value; − In response to the requested braking force being less than or equal to the tractor longitudinal force threshold, operating the tractor brake assembly but not operating the trailer brake assembly to brake the vehicle combination.

[0034] The above means that the vehicle can be braked by the towing vehicle brake assembly alone, which in turn means that the vehicle combination can be braked by regenerative braking.

[0035] Optionally, determining a requested braking force to be applied to the vehicle combination based on the deceleration request value further comprises obtaining a tractor vehicle mass value indicative of a current mass of the tractor vehicle and a trailer mass value indicative of a current mass of the trailer.

[0036] Optionally, determining a requested braking force to be applied to the vehicle combination based on the deceleration request value further comprises determining a longitudinal trailer inclination angle value indicative of an inclination angle of ground supporting the trailer in a longitudinal direction of the trailer.

[0037] Optionally, determining a requested braking force to be applied to the vehicle combination based on the deceleration request value further comprises determining a longitudinal tractor inclination angle value indicative of an inclination angle of ground supporting the tractor in a longitudinal direction of the tractor.

[0038] A third aspect of the invention relates to a computer program comprising program code means for executing the method of the first or second aspect of the invention when the program is run on a computer.

[0039] A fourth aspect of the present invention relates to a computer readable medium carrying a computer program, the computer program comprising program code means for executing the method of the first aspect or the second aspect of the present invention when the program product is run on a computer.

[0040] A fifth aspect of the present invention relates to a control unit configured to perform the method according to the first or second aspect of the present invention.

[0041] A sixth aspect of the invention relates to a vehicle combination comprising a tractor, a trailer and a control unit according to the fifth aspect of the invention.

[0042] Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Embodiments of the invention cited as examples will be described in more detail hereinafter with reference to the accompanying drawings.

[0044] In the attached picture:

[0045] Figure 1 is a schematic plan view of a vehicle combination;

[0046] Figure 2 is a schematic plan view of a vehicle combination;

[0047] Figure 3 is a schematic side view of a vehicle combination;

[0048] Figure 4 is a schematic rear elevation view of the vehicle combination; and

[0049] Figure 5 It is a schematic plan view of a vehicle combination. DETAILED DESCRIPTION

[0050] Figure 1 1 is a schematic plan view of a vehicle combination 10 including a tractor 12 and a trailer 14. By way of example only, and as Figure 1 As indicated, the tractor 12 may include a propulsion assembly 16 for propelling the tractor 12 and, therefore, the vehicle combination 10. As a non-limiting example, the propulsion assembly 16 may include an electric motor. Figure 1 In the embodiment of the invention, the propulsion assembly 16 is connected to a set of ground engaging members 18 via a device including a shaft 20. Figure 1 In the embodiment of the present invention, the ground engaging members 18 are implemented as wheels, but it is also contemplated that the ground engaging members 18 may be implemented as tracks (not shown) or the like. In addition, it is also contemplated that the propulsion assembly 16 may include one or more electric motors, each of which is arranged at the hub of a ground engaging member (such as a wheel) of the tractor 12.

[0051] like Figure 1 As indicated, the trailer 14 has a longitudinal direction L TL The longitudinal extension of the trailer and the transverse direction of the trailer T TL The trailer's transverse extension and the trailer's vertical direction V TL The trailer extends vertically. The longitudinal direction of the trailer L TLCorresponding to the expected driving direction of the trailer 14 when the vehicle combination 10 is driving straight forward, the vertical direction V TL corresponds to the normal direction of the plane surface supporting the trailer 14, and the trailer transverse direction T TL Perpendicular to the trailer's longitudinal direction L TL and the trailer vertical direction V TL Each one of them.

[0052] Similarly, and also as Figure 1 As indicated, the tractor 12 has a longitudinal direction L of the tractor. TR The tractor longitudinally extends along the tractor transverse direction T TR The tractor extends transversely and along the vertical direction V of the tractor TR The tractor extends vertically. The longitudinal direction of the tractor L TR Corresponding to the expected driving direction of the tractor 12 when the vehicle combination 10 is driving straight forward, the vertical direction V TR Corresponding to the normal direction of the plane surface supporting the tractor 12, and the tractor transverse direction T TR Perpendicular to the longitudinal direction L of the tractor TR and the tractor vertical direction V TR Each one of them.

[0053] In addition, if Figure 1 As indicated, the tractor 12 may include a tractor brake assembly for regenerative braking of the tractor 12. As a non-limiting example, the propulsion assembly 16 may be used for regenerative braking of the tractor 12 and may therefore form a part of or even constitute a tractor brake assembly for regenerative braking of the tractor 12. Thus, when the propulsion assembly 16 is implemented as, for example, an electric motor, such an electric motor may function as a generator and generate electrical energy for storage in an electrical storage assembly (not shown), such as a battery (not shown). However, it is also contemplated that the tractor brake assembly for regenerative braking of the tractor 12 may include or even be constituted by one or more electric hub motors 22, 24, each of which may operate as a generator and generate electrical energy for storage in an electrical storage assembly (not shown), such as a battery (not shown).

[0054] Additionally, other embodiments of the tractor 12 may include a tractor brake assembly for braking the tractor 12 without necessarily having regenerative capabilities. For example, such embodiments may include one or more service brakes ( Figure 1 not shown).

[0055] Regardless of the embodiment, the tractor brake assembly is adapted to generate a brake in a direction parallel to the longitudinal direction L of the tractor. TR The longitudinal deceleration force of the tractor extending in a parallel direction .

[0056] Additionally, the trailer 14 may include a trailer brake assembly 26 for braking the trailer. The trailer brake assembly 26 may include one or more service brakes for regenerative braking, one or more electric machines, or any combination thereof.

[0057] In addition, if Figure 1 As indicated, the trailer 14 is pivotally connected to the trailer 12 via a connection point 28. Such a connection point 28 can be implemented, for example, as a so-called fifth wheel. Thus, the trailer 14 is connected to the tractor 12 so that it can be pivoted in the tractor longitudinal direction L. TR and the trailer longitudinal direction L TL The articulation angle Ψ is formed between . Furthermore, the above-mentioned articulation angle Ψ can be varied, preferably in a stepless manner, depending on the operating conditions of the vehicle combination 10, for example. Figure 1 The articulation angle Ψ is represented by a negative sign, which means that Figure 1 Under the condition of , the hinge angle Ψ is negative.

[0058] also, Figure 1 The vehicle combination 10 shown may include a control unit 30 configured to carry out the method according to the invention. Figure 1 In the embodiment of FIG. 1 , the control unit 30 is located in the tractor 12 , but other locations of the control unit 30 are also contemplated.

[0059] Figure 2 is with Figure 1 A schematic plan view of a vehicle combination 10 similar to the vehicle combination 10 is shown. Figure 2 In the drawings, the trailer 12 and the tractor 14 are shown at a distance from each other in order to illustrate the forces acting between the tractor 12 and the trailer 14. However, it should be noted that when the trailer 14 is connected to the tractor 12 via the connection point 28, a coupling force is generated between the tractor 12 and the trailer 14.

[0060] from Figure 2 It can be seen that during the driving of the vehicle combination 10, the trailer will move along the trailer longitudinal direction L TL The trailer longitudinal force , and along the transverse direction of the trailer T TL Lateral force from trailer Further details of these forces are presented below.

[0061] The above forces will generate a force between the tractor 12 and the trailer 14 along the longitudinal direction L of the trailer. TL and trailer transverse direction T TL Connection Strength It should be noted that the connection force Not necessarily completely corresponding to the trailer longitudinal force and trailer lateral force This is because the trailer longitudinal force and / or trailer lateral forces At least a portion of the load may be borne by, for example, a ground engaging member of the trailer 14, such as a wheel.

[0062] exist Figure 2 In FIG. 1 , the above-mentioned connection forces associated with the tractor 12 and the trailer 14 are presented. Figure 2 As indicated, the connection force Respectively with the trailer longitudinal direction L TL and trailer transverse direction T TL Therefore, in order to Convert to the longitudinal direction L of the tractor TR and the tractor transverse direction T TR , the current articulation angle Ψ can be taken into account.

[0063] also, Figure 2 The longitudinal deceleration force of the tractor applied to the tractor 12 is shown in FIG. .also, Figure 2 The lateral traction force is shown in , that is, via the ground engaging member of the tractor 12 in the lateral direction T of the tractor TR The force exerted on the tractor.

[0064] The total horizontal force that can be applied to the tractor 12 via its ground engaging members (i.e., from contact between the ground engaging members and the ground supporting the tractor 12) is limited by the total horizontal friction force available between the ground supporting the tractor and the ground engaging members of the tractor 12. restrictions.

[0065] For example only, the total horizontal friction force can be calculated using the weight of the tractor 12 to determine, that is, from the ground supporting the tractor in the vertical direction V of the tractor TR The sum of the forces exerted on the ground engaging members of the tractor. The total mass of the tractor can be It is determined by multiplying by the acceleration value g corresponding to the acceleration due to gravity. Furthermore, to determine the total horizontal friction force, a friction value μ indicating the friction between the set of ground engaging members of the tractor 12 and the ground supporting the tractor 12 may be used.

[0066] Such friction value μ may be determined using any known procedure, such as using sensors (such as cameras) to monitor the condition of the ground on which the tractor 12 is traveling and / or by using a brush model or using slip values ​​associated with ground engaging members of the tractor 12 (such as wheels).

[0067] Therefore, the total horizontal friction force can be determined from the following equation :

[0068] However, it should be noted that the total horizontal friction Other determinations may also be made. By way of example only, if a single friction value µ indicating the friction between one ground engaging member of the tractor 12 and the ground supporting the tractor 12 is considered, i , then the total horizontal friction force It can be determined according to the following equation: in: The vertical direction V of the tractor is from the ground supporting the tractor 12. TR The force applied to the i-th ground engaging member of the tractor 12, and is a friction value indicative of the friction between the i-th ground engaging member of the tractor 12 and the ground supporting the tractor 12 .

[0069] By way of example only, information from, for example, a ground engaging suspension device (not shown) of the tractor 12 may be used to determine the vertical direction V of the tractor from the ground supporting the tractor 12. TR The force applied to the i-th ground engaging member of the tractor 12 .

[0070] As a further alternative, Equation 3 above may also be applied to each ground engaging member axle of the tractor 12 .

[0071] How to determine the total horizontal friction , the following conditions should be met in order to avoid slipping and / or sliding of the ground engaging members of the tractor 12:

[0072] For simplicity, Equation 3 above relates to the total force of the tractor 12. However, it should be noted that Equation 3 can be extended to the ground engaging member axles or even each ground engaging member of the tractor 12.

[0073] Thus, although by way of example only, Equation 3 may be expanded to a tractor 12 that includes a set of ground engaging member axles, wherein the set of ground engaging member axles includes at least one axle, and wherein each ground engaging member axle is connected to a respective ground engaging member (such as a wheel) of the tractor 12. Assuming the tractor includes N axles, Equation 3 may be expanded as follows: Where index i represents the i-th ground engaging member axle.

[0074] Similarly, although by way of example only, Equation 3 may be extended to the tractor 12, to each ground engaging member (such as a wheel) of the tractor 12. Assuming the tractor includes M ground engaging members, Equation 3 may be extended as follows: Where index j represents the jth ground engaging component.

[0075] For the sake of brevity, the following examples are primarily based on Equation 3 above. However, it should be noted that the following examples can be extended to each of Equation 4 and Equation 5 in a straightforward manner.

[0076] Therefore, using Equation 3 as an example, the maximum longitudinal deceleration force of the tractor is (hereinafter referred to as the tractor longitudinal force threshold) can be determined according to the following equation:

[0077] Likewise, the total horizontal friction For example, it can be determined according to any of the procedures mentioned above.

[0078] Lateral traction It is along the transverse direction of the tractor TR The force applied to the tractor 12 and the connection force between the tractor 12 and the trailer 14 For example, A is the sum of the forces applied to the tractor 12. This may itself be a centrifugal force, as will be explained further below.

[0079] Similarly, along the transverse direction T of the trailer TL Connection Strength It may be related to the centrifugal force exerted on the trailer 14. On the other hand, along the longitudinal direction L of the trailer TL Connection Strength Can be with the quality of trailer 14 And the longitudinal acceleration of the trailer 14. This will also be further explained in detail below.

[0080] As already implied above, in order to Switch to tractor transverse direction T TR , the information indicating the current articulation angle Ψ can be used as follows:

[0081] From studying Equations 6 and 7 above, it can be seen that the connection force between the tractor 12 and the trailer 14 is indicated by The information is used to determine the longitudinal deceleration force of the tractor The longitudinal force threshold of the tractor This may be useful information when the tractor longitudinal deceleration force may be applied to the tractor 12 of the vehicle combination 10 including the tractor 12 and the trailer 14 to decelerate the vehicle combination 10.

[0082] Along the longitudinal direction L of the trailer TL and trailer transverse direction T TL Connection Strength According to the following equation, it can be converted into an indication of the direction of the tractor moving or predicted in the lateral direction T TR The trailer lateral force applied to the tractor is the trailer lateral force :

[0083] In particular, the inventors of the present invention have realised that the longitudinal direction L of the trailer can be determined with a suitable level of accuracy. TL Connection Strength , which in turn can increase the above-mentioned tractor longitudinal force threshold Determine accuracy.

[0084] For this purpose, refer to Figure 3 , showing that at an inclination angle of The vehicle combination 10 is driven on a slope. Figure 3 It can be seen that the tilt angle This will result in the trailer being TL The gravity is applied to the trailer 14 and will thus form the connection force Along the trailer longitudinal direction L TL part of.

[0085] To this end, a first aspect of the present invention relates to a method for determining the longitudinal deceleration force of a tractor The longitudinal force threshold of the tractor The method of claim 1, wherein the tractor longitudinal deceleration force may be applied to the tractor 12 of the vehicle combination 10 including the tractor 12 and the trailer 14 to decelerate the vehicle combination 10.

[0086] refer to Figure 3 The method comprises determining an indication that a current is being or is predicted to be moving in a lateral direction T of the tractor TR The trailer lateral force applied to the tractor is the trailer lateral force , see Equation 8 above. Trailer lateral force is determined using a trailer lateral force value determination procedure including the features presented below.

[0087] The procedure includes obtaining a trailer mass value mass indicating the current mass of the trailer 14 For example only, the trailer mass value mass may be determined using information such as from a ground engaging member suspension system (not shown) of the trailer 14 . As an alternative or in addition to using information from the ground engaging member suspension system, information indicative of the trailer's own weight and the current weight of the cargo being carried by the trailer 14 may be used.

[0088] Furthermore, the procedure includes obtaining an indication of the ground surface supporting the trailer 14 along the trailer longitudinal direction L TL The longitudinal trailer tilt angle value of the tilt angle . Tilt angle value For example, the tilt sensor 32 of the trailer 14 may be used to determine the tilt angle value. Alternatively, information from a map system or the like may be used to determine the tilt angle value. Thus, using information about the topography of the ground, for example using a mapping system, and the current position of the trailer 14, which may be determined, for example, using a global positioning system (not shown), a tilt angle value may be determined. .

[0089] Furthermore, the method comprises at least one step based on the trailer mass value. and longitudinal trailer tilt angle value Determine the indication along the longitudinal direction L of the trailer TL The longitudinal gravity value of the longitudinal gravity applied to the trailer 14 As a non-limiting example, the longitudinal gravity value It can be determined according to the following equation: .

[0090] In addition, the procedure includes determining an indication of the longitudinal direction L of the tractor TR and the trailer longitudinal direction L TLThe articulation angle value Ψ of the current articulation angle between . By way of example only, the articulation angle value Ψ may be determined using an articulation angle sensor (not shown) of the vehicle combination 10. By way of example only, such a sensor may be carried by the tractor 12. However, it is also conceivable that the articulation angle value Ψ may be determined without the need for an articulation angle sensor. To this end, reference is made to, for example, Equation 21 below.

[0091] Furthermore, the method comprises using the longitudinal gravity value and the articulation angle Ψ to determine the trailer lateral force As shown in Equation 8 above, the longitudinal gravity value Can constitute the trailer lateral force value part of the longitudinal gravity value The tractor 12 and the trailer 14 are connected along the longitudinal direction L of the trailer. TL Connection Strength part of.

[0092] Additionally, referring to, for example, Equation 1 or Equation 2 above, the method also includes determining a horizontal friction force value indicative of a possible total horizontal friction force available between the ground supporting the tractor 12 and the ground engaging members of the tractor 12 .

[0093] In addition, referring to, for example, Equation 6 above, the method also includes using the trailer lateral force value and horizontal friction value Determining the tractor longitudinal force threshold .

[0094] By way of example only, the trailer lateral force value determination routine may also include obtaining a longitudinal trailer deceleration value indicative of a longitudinal trailer deceleration being or predicted to be exerted on the trailer 14. . Usually, the longitudinal trailer deceleration value Can be negative, indicating a requested deceleration, i.e., a deceleration in the longitudinal direction L of the trailer. TL By way of example only, a sensor (not shown) such as an accelerometer (not shown) associated with the trailer 14 may be used to determine the longitudinal trailer deceleration value. However, it is also conceivable that the longitudinal trailer deceleration value may be determined in other ways. , for example, using a deceleration request signal indicating a requested deceleration of the trailer vehicle 14 .

[0095] Furthermore, the trailer lateral force value determination procedure may include at least one and longitudinal trailer deceleration value Determine the direction along the trailer's transverse direction L TL The longitudinal inertia trailer force value of the longitudinal inertia force applied to the trailer 14 For example, the longitudinal inertia trailer force value It can be determined according to the following equation: .

[0096] In addition, the trailer lateral force value determination procedure may include also using the longitudinal inertia trailer force value Determining the tractor longitudinal force threshold .

[0097] Therefore, although only by way of example, the longitudinal inertia trailer force value and longitudinal gravity can be combined according to the following equations (see, for example, Equation 8 above) to form the longitudinal direction L of the trailer: TL Connection Strength part of or even constitute the connecting force: .

[0098] In addition, by way of example only, the trailer lateral force value determination procedure may also include: − At least based on the trailer mass Determine the direction along the trailer's transverse direction T TL Transverse centrifugal force value of the centrifugal force applied to the trailer 14 ,as well as − Transverse centrifugal force values ​​are also used Determining trailer lateral force values .

[0099] For example only, the lateral centrifugal force value Based on the indication that the trailer 14 is along the trailer longitudinal direction L TL The longitudinal velocity value of the speed and trailer curvature radius The trailer curvature radius indicates the curvature radius of the path currently followed by the center of gravity of the trailer 14 (see Figure 5 ). As a non-limiting example, the lateral centrifugal force value It can be determined according to the following equation:

[0100] Compared with the lateral centrifugal force values ​​mentioned above Similarly, along the tractor transverse direction T TR The force applied to the tractor 12 It may include a direction indicating the lateral direction T of the tractor TR Transverse centrifugal force value of the centrifugal force applied to the tractor 12 The relevant addend, the centrifugal force is based at least on the mass value of the tractor , instructing the tractor 12 to move in the longitudinal direction L of the tractor TR The longitudinal velocity value of the speed and the tractor curvature radius , the tractor curvature radius indicates the curvature radius of the path currently followed by the center of gravity of the tractor 12. Therefore, similar to Equation 9 above, the lateral centrifugal force value of the tractor 12 is It can be determined according to the following equation:

[0101] In an embodiment of the present invention, a speed sensor (not shown) of the tractor 12 may be used to determine a speed indicating that the tractor 12 is moving in the longitudinal direction L of the tractor. TR The longitudinal velocity value of the speed In addition, although it is only by way of example, in an embodiment of the present invention, it is indicated that the trailer 14 is in the trailer longitudinal direction L TL The longitudinal velocity value of the speed It can be set to be equal to the indication that the tractor 12 is along the longitudinal direction L of the tractor TR The longitudinal velocity value of the speed .

[0102] Returning to the lateral centrifugal force value of the trailer 14, although for example only, the lateral centrifugal force value of the trailer 14 The following equation (see, for example, equation 8 above) can be used to form the transverse direction T of the trailer: TL Connection Strength part of or even constitute the connecting force:

[0103] It should be noted that the lateral centrifugal force value Only a portion of the lateral force can be added to the trailer . Thus, the coefficient C in equation 11 above may be in the range of 0 to 1. Here, it should be noted that the ground engaging members of the trailer 14 may bear a portion of the lateral centrifugal force applied to the trailer 14. Thus, although by way of example only, the portion of the lateral centrifugal force that will be applied to the connection point 28 may be determined by a moment balance equation that takes into account the moment balance equation along the trailer longitudinal direction L TL The distance between the ground engaging member of the trailer 14 and the center of gravity of the trailer and the distance along the longitudinal direction L of the trailer TL The distance between the connection point 28 and the center of gravity of the trailer 14. To this end, reference is made to equation 29 below, which presents an example of how the above distance may be taken into account.

[0104] However, it should also be noted that, although by way of example only, the trailer lateral force value determination procedure may also include obtaining an indication of the ground surface supporting the trailer 14 along the trailer lateral direction TTL The lateral tilt angle value of the tilt angle To this end, refer to Figure 4 , which shows an embodiment of a trailer 14 located on a transversely inclined ramp.

[0105] Thus, although by way of example only, the trailer lateral force value determination routine may include a method based at least on the trailer mass value. and the lateral tilt angle Determine the direction along the trailer's transverse direction T TL The lateral gravity value of the lateral gravity applied to the trailer 14 In addition, the procedure may also include using the lateral gravity value Determine the trailer lateral force value. Therefore, although only by way of example, the above equation 11 can be expanded according to the following equation:

[0106] Likewise, the coefficient C in equation 12 may be in the range of 0 to 1 and may be related to the longitudinal direction L of the trailer. TL The trailer lateral force value determination procedure may also include the following steps: TL Each force value of the force is multiplied by the sine of the articulation angle value Ψ. Similarly, referring again to, for example, Equation 7, the trailer lateral force value determination procedure may also include the following steps: TL Each force value of the force is multiplied by the cosine of the articulation angle value Ψ.

[0107] As already implied above, the longitudinal trailer inclination angle value For example, the tilt sensor 32 of the trailer 14 can be used to determine. However, alternatively, the tilt sensor 34 carried by the tractor 12 can be used to determine the longitudinal trailer tilt angle value. Therefore, the tractor 12 may include a tilt sensor 34, which is adapted to determine an indication that the ground supporting the tractor 12 is in the longitudinal direction L of the tractor. TR The longitudinal tilt angle of the tractor In addition, reference Figure 3 , obtain the indication that the ground supporting the trailer 14 is along the longitudinal direction L of the trailer TL The longitudinal trailer tilt angle value of the tilt angle This can include: − Obtain the instruction for the tractor 12 to move along the longitudinal direction L of the tractor TR The speed value of the current speed ; − Get the indication along the longitudinal direction L of the tractor TR The distance value 36 is the distance between the tilt sensor 34 and the reference point of the trailer 14. For example only, and as Figure 3 As indicated, the reference point may be the center of gravity of the trailer 14 . − Use speed value and the distance value 36 to determine the first moment at which the tilt sensor 34 is located at a certain global position to the second moment when the reference point of the trailer is at the same global position Elapsed time . − Using one or more longitudinal tractor inclination angle values ​​determined by the inclination sensor 34 and the elapsed time To determine the longitudinal trailer tilt angle value .

[0108] As already implied above, the above examples are generally based on equation 3, so that the method is performed at the tractor level. However, as already implied above, for example with reference to equation 4, embodiments may also be performed at the ground engaging member axle level. Thus, when the tractor 12 comprises a set of ground engaging member axles, wherein the set of ground engaging member axles comprises at least one axle, and wherein each ground engaging member axle is connected to a respective ground engaging member of the tractor 12, the method according to the invention may comprise, for each ground engaging member axle of the set of ground engaging member axles, performing the following: − Based on the trailer lateral force , determining a trailer axle lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member axle ; − Determine a horizontal friction force value indicative of the total possible horizontal friction force available between the ground supporting the tractor 12 and the various ground engaging members of the ground engaging member axles ,as well as − Use trailer axle lateral force values and horizontal friction value Determine the longitudinal force threshold of the axle tractor .

[0109] Additionally, the method may further include aggregating the axle tractor longitudinal force thresholds for each ground engaging member axle in the set of ground engaging member axles. , in order to obtain the tractor longitudinal force threshold .

[0110] In addition, although only by way of example, based on the trailer lateral force value Determining a trailer axle lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member axle The steps may include using the moment balance equation using the following inputs: − Trailer lateral force ; − Along the longitudinal direction L of the tractor TR The distance l from each ground engaging member axle to the center of gravity of the tractor 12 is f , l r (See Figure 5 ),as well as − Along the longitudinal direction L of the tractor TR The distance l from the connection point 28 to the center of gravity of the tractor 12 c (See Figure 5 ).

[0111] Equations 31 and 32 below present examples of the use of the moment balance equations according to the above. These equations apply to a tractor vehicle containing two axles, but similar equations can be derived for any number of axles.

[0112] Similarly, although by way of example only, embodiments may also be performed at the ground engaging member level. Thus, embodiments of the present invention may include performing the following operations for each ground engaging member of the tractor 12: − Based on the trailer lateral force , determining a trailer ground engaging member lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member ; − Determine a horizontal friction value indicative of the total possible horizontal friction available between the ground supporting the tractor 12 and the ground engaging members ,as well as − Use the trailer ground engaging member lateral force value and horizontal friction value Determining the Ground Engaging Component Tractor Longitudinal Force Threshold .

[0113] For the above example of determining the lateral force value of the trailer axle, based on the lateral force value of the trailer Determining a trailer ground engaging member lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member The steps may include using the moment balance equation using the following inputs: − Trailer lateral force ; − Along the longitudinal direction L of the tractor TR The distance l from each ground engaging member to the center of gravity of the tractor 12 is f, l r ,as well as − Along the longitudinal direction L of the tractor TR The distance l from the connection point 28 to the center of gravity of the tractor 12 c .

[0114] Equations 31 and 32 below present examples of the use of moment balance equations in accordance with the above. While these exemplary equations are for ground engaging member axles, these equations can be extended to each ground engaging member of the tractor 12 in a straightforward manner.

[0115] Additionally, the method may include summing the ground engaging member tractor longitudinal force thresholds for each ground engaging member of the tractor 12 , in order to obtain the tractor longitudinal force threshold .

[0116] It is also contemplated that embodiments of the present invention may use a combination of the ground engaging member axle level method and the ground engaging member level method noted above. By way of example only, it is contemplated that embodiments of the present invention may use the ground engaging member axle level method for certain axles of the tractor and use the ground engaging member level method for the remaining ground engaging members of the tractor 12.

[0117] How to determine the tractor longitudinal force threshold , which is preferably used for a method of braking a vehicle combination 10 including a tractor 12 and a trailer 14. The tractor includes a tractor brake assembly for regenerative braking of the tractor, and the trailer includes a trailer brake assembly for braking the trailer.

[0118] The method comprises: − Determining the tractor longitudinal force threshold using the method according to the first aspect of the invention (for example according to any of the embodiments presented above) ,and − Operate the tractor vehicle brake assembly to provide a force less than or equal to the tractor vehicle longitudinal force threshold braking force.

[0119] As a non-limiting example, the method of braking the vehicle combination 10 may also include: − Obtaining a deceleration request value indicating a requested deceleration of the vehicle combination 10 . − Based on the deceleration request value Determining a requested braking force to be applied to the vehicle combination 10 . − Braking force in response to request Less than or equal to the longitudinal force threshold of the tractor When the tractor brake assembly is operated but the trailer brake assembly is not operated, the vehicle combination 10 is braked.

[0120] Requested braking force This can be determined in a number of different ways. However, as a non-limiting example, based on the deceleration request value Determining a requested braking force to be applied to the vehicle combination 10 This may include obtaining a tractor mass value indicating the current mass of the tractor and a trailer mass value indicating the current mass of the trailer .

[0121] For example, the requested braking force It can be expressed as the longitudinal direction L of the tractor TR The force can be determined from the following equation: .

[0122] Strength The drag may be related to drag from, for example, drag loads imposed on the vehicle combination 10 .

[0123] In addition, based on the deceleration request value Determining a requested braking force to be applied to the vehicle combination 10 It may also include determining a longitudinal trailer tilt angle value indicative of an angle of inclination of the ground supporting the trailer in a longitudinal direction of the trailer.

[0124] Optionally, determining a requested braking force to be applied to the vehicle combination based on the deceleration request value may further comprise determining a longitudinal tractor inclination angle value indicative of an inclination angle of the ground supporting the tractor in a longitudinal direction of the tractor.

[0125] Figure 5 FIG. 1 is a schematic plan view of a vehicle combination 10 including a tractor 12 and a trailer 14. Figure 5 In the particular embodiment of the vehicle combination shown, the tractor 12 includes two sets of wheels, namely a front set of wheels 38 and a rear set of wheels 40. By way of example only, the front set of wheels 38 may be steerable and thus may have a variable steering angle. , but the rear set of wheels 40 are not necessarily steerable.

[0126] Figure 5 The illustrated embodiment of the trailer 14 includes a set of wheels 42, and the trailer 14 is pivotally connected to the tractor 12 via a connection point 28. In addition, Figure 5 The following distances are indicated: l f Along the longitudinal direction of the tractor TR The distance from the front set of wheels 38 to the center of gravity of the tractor 12; l r Along the longitudinal direction of the tractor TR The distance from the rear set of wheels 40 to the center of gravity of the tractor 12; l c Along the longitudinal direction of the tractor TR The distance from the connection point 28 to the center of gravity of the tractor 12; l f,t Along the longitudinal direction of the trailer L TL The distance from the connection point 28 to the center of gravity of the trailer 14; l r,t Along the longitudinal direction of the trailer L TL the distance from the connection point 28 to the set of wheels 42 of the trailer 14; is the turning radius of the front set of wheels 38; is the turning radius of the rear set of wheels 40; is the turning radius of the connection point 28, and is the turning radius of the set of wheels 42 of the trailer 14 .

[0127] For example only, the distances may be known (eg, provided by the supplier of the tractor 12 and trailer 14), and the steering angle may be determined using a steering angle sensor (not shown). Using the above distance l f , l r , l c , l f,t and l r,t And indicate the steering angle The value of the turning radius and the aforementioned articulation angle Ψ can be determined according to the following set of equations:

[0128] When the tractor 12 is moved in the longitudinal direction L of the tractor TR Have a certain speed The trailer 14 is along the longitudinal direction L of the trailer. TL Have a certain speed , having obtained the aforementioned longitudinal trailer deceleration value indicative of the longitudinal trailer deceleration being or predicted to be imposed on the trailer 14 , and the trailer 14 is at an inclination angle of When driving on a slope, you can Figure 5 The following implementation scheme determines the tractor longitudinal force threshold :

[0129] In the above equations, the superscript “front” indicates forces associated with the front set of wheels 38 , the superscript “rear” indicates forces associated with the rear set of wheels 40 of the towing vehicle 12 , and the superscript “cp” indicates forces associated with the connection point 28 .

[0130] It should be noted that Equation 35 above may alternatively be reformulated as the sum of the thresholds for the front and rear groups of wheels as follows:

[0131] The above equation and Figure 5 In connection with the vehicle combination 10, the vehicle combination includes a tractor 12 having two sets of wheels 38, 40 and a trailer 14 having one set of wheels 42. However, the above equations 13 to 35 can of course be extended to any number of sets of wheels for each of the tractor 12 and the trailer 14.

[0132] Although the present invention has been described with respect to methods, it should be noted that the above disclosure is equally applicable to each of the following: − a computer program comprising program code means for executing the method of the first or second aspect of the invention when the program is run on a computer; − a computer-readable medium carrying a computer program, the computer program comprising program code means for executing the method of the first aspect or the second aspect of the present invention when the program product is run on a computer; − a control unit 30, which is configured to execute the method according to the first or second aspect of the invention; − A vehicle combination comprising a tractor 12, a trailer 14 and a control unit 30 according to the above.

[0133] It should be understood that the present invention is not limited to the embodiments described above and shown in the drawings; rather, those skilled in the art will recognize that many changes and modifications are possible within the scope of the appended claims.

Claims

1. A method for determining the longitudinal deceleration force of the tractor ( ) of the tractor longitudinal force threshold ( ), wherein the tractor longitudinal deceleration force can be applied to the tractor (12) of a vehicle combination (10) comprising a tractor (12) and a trailer (14) to decelerate the vehicle combination (10), The trailer (14) has a longitudinal direction (L TL ) of the trailer longitudinally, along the transverse direction of the trailer (T TL ) of the trailer in the transverse direction and in the vertical direction of the trailer (V TL ) of the trailer extends vertically, wherein the longitudinal direction (L TL ) corresponds to the expected driving direction of the trailer (14) when the vehicle combination (10) is driving straight forward, and the vertical direction (V TL ) corresponds to the normal direction of the plane surface supporting the trailer (14), and the trailer transverse direction (T TL ) is perpendicular to the longitudinal direction of the trailer (L TL ) and the trailer vertical direction (V TL ), The tractor (12) has a longitudinal direction (L TR ) of the tractor longitudinally and in the transverse direction of the tractor (T TR ) of the tractor and the vertical direction of the tractor (V TR ) of the tractor extends vertically, wherein the longitudinal direction (L TR ) corresponds to the expected driving direction of the tractor (12) when the vehicle combination (10) is driving straight forward, and the vertical direction (V TR ) corresponds to the normal direction of the plane surface supporting the tractor (12), and the tractor transverse direction (T TR ) is perpendicular to the longitudinal direction of the tractor (L TR ) and the vertical direction of the tractor (V TR ) in each of which the tractor longitudinal deceleration force ( ) along the longitudinal direction of the tractor (T TR ) extends in a direction parallel to The method comprises: − determining, using a trailer lateral force determination procedure, a trailer lateral force value (indicative of a trailer lateral force being or predicted to be exerted on the tractor (12) in a lateral direction of the tractor) ), the trailer lateral force value determination procedure comprises: − Obtain a trailer mass value ( ); − Obtaining a longitudinal trailer inclination angle value indicating an inclination angle of the ground supporting the trailer (14) along the longitudinal direction of the trailer ( ); − At least based on the stated trailer mass value ( ) and the longitudinal trailer inclination angle value ( ) determines the indication along the longitudinal direction (L TL ) the longitudinal gravity value of the longitudinal gravity applied to the trailer (14) ( ); − Determine the longitudinal direction of the tractor (L TR ) and the longitudinal direction of the trailer (L TL ) between the current articulation angle ( ); − Using the longitudinal gravity value ( ) and the articulation angle value ( ) determines the trailer lateral force value ( ); − determining a horizontal friction force value indicative of a possible total horizontal friction force achievable between the ground supporting the tractor (12) and a ground engaging member of the tractor (12) ( ),as well as − Using the stated trailer lateral force values ​​( ) and the horizontal friction value ( ) determines the tractor longitudinal force threshold value ( ).

2. The method according to claim 1, wherein the trailer lateral force value determination procedure further comprises: − obtaining a longitudinal trailer deceleration value indicative of a longitudinal trailer deceleration being or predicted to be imposed on the trailer; − determining a longitudinal inertial trailer force value indicative of a longitudinal inertial force exerted on the trailer in a transverse direction of the trailer based at least on the trailer mass value and the longitudinal trailer deceleration value, and − The longitudinal inertia trailer force value is also used to determine the tractor longitudinal force threshold value ( ).

3. The method according to any one of the preceding claims, wherein the trailer lateral force value determination procedure further comprises: − determining a lateral centrifugal force value indicative of a centrifugal force exerted on the trailer in a lateral direction of the trailer based at least on the trailer mass value, and − The lateral centrifugal force value is also used to determine the trailer lateral force value.

4. The method according to any one of the preceding claims, wherein the trailer lateral force value determination procedure further comprises: − obtaining a lateral inclination angle value indicating an inclination angle of the ground supporting the trailer in a lateral direction of the trailer; − determining a lateral weight force value indicative of a lateral weight force of the trailer exerted on the trailer in a lateral direction of the trailer based at least on the trailer mass value and the lateral inclination angle value, and − The lateral weight force value is also used to determine the trailer lateral force value.

5. The method according to any one of the preceding claims, wherein the trailer lateral force value determination procedure further comprises: − Multiply each force value indicating a force in the longitudinal direction of the trailer by the sine of the articulation angle value.

6. The method according to any one of claims 3 to 5, wherein the trailer lateral force value determination procedure further comprises: − Multiply each force value indicating a force in the transverse direction of the trailer by the cosine of the articulation angle value.

7. A method according to any one of the preceding claims, wherein the tractor comprises a tilt sensor adapted to determine a longitudinal tractor tilt angle value indicative of an angle of inclination of the ground supporting the tractor in a longitudinal direction of the tractor; Wherein obtaining the longitudinal trailer inclination angle value indicating the inclination angle of the ground supporting the trailer along the longitudinal direction of the trailer comprises: − obtaining a speed value indicating a current speed of the tractor vehicle in a longitudinal direction of the tractor vehicle; − obtaining a distance value indicating the distance between the tilt sensor and a reference point of the trailer in the longitudinal direction of the tractor; − using the speed value and the distance value to determine the time that has passed from a first moment when the tilt sensor is at a certain global position to a second moment when the reference point of the trailer is at the same global position, and − Determining the longitudinal trailer inclination angle value using one or more longitudinal tractor inclination angle values ​​determined by the inclination sensor and the elapsed time.

8. The method according to any one of the preceding claims, wherein the tractor (12) comprises a set of ground engaging member axles, wherein the set of ground engaging member axles comprises at least one axle, and wherein each ground engaging member axle is connected to a respective ground engaging member of the tractor (12), wherein the method comprises for each ground engaging member axle of the set of ground engaging member axles: − Based on the trailer lateral force value ( ), determining a trailer axle lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member axle ( ); − determining a horizontal friction force value indicative of a possible total horizontal friction force achievable between the ground supporting the tractor (12) and the respective ground engaging members of the ground engaging member axles ( ),as well as − Using the stated trailer axle lateral force values ​​( ) and the horizontal friction value ( ) Determine the axle tractor longitudinal force threshold ( ),as well as Summarizing the axle tractor longitudinal force threshold for each ground engaging member axle in the set of ground engaging member axles ( ) in order to obtain the tractor longitudinal force threshold ( ).

9. The method according to claim 8, wherein based on the trailer lateral force value ( ) determining a trailer axle lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member axle ( ) step includes using the moment balance equation with the following inputs: − The trailer lateral force value ( ); − Along the longitudinal direction of the tractor (L TR ) is the distance (l) from each ground engaging member axle to the center of gravity of the tractor (12) f , l r ),as well as − Along the longitudinal direction of the tractor (L TR ) the distance (l) from the connection point (28) to the center of gravity of the tractor (12) c ).

10. The method according to any one of the preceding claims, wherein the method comprises performing the following operations for each ground engaging member of the tractor (12): − Based on the trailer lateral force value ( ), determining a trailer ground engaging member lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member ( ); − determining a horizontal friction force value (indicative of a possible total horizontal friction force achievable between the ground supporting the tractor (12) and the ground engaging member ),as well as − Using the trailer ground engaging member lateral force values ​​( ) and the horizontal friction value ( ) Determine the ground engaging member tractor longitudinal force threshold ( ),as well as Summarize the ground engaging member tractor longitudinal force threshold ( ) in order to obtain the tractor longitudinal force threshold ( ).

11. The method according to claim 10, wherein based on the trailer lateral force value ( ) determining a trailer ground engaging member lateral force value indicative of a trailer lateral force being or predicted to be exerted on the ground engaging member ( ) step includes using the moment balance equation with the following inputs: − The trailer lateral force value ( ); − Along the longitudinal direction of the tractor (L TR ) is the distance (l) from each ground engaging member to the center of gravity of the tractor (12) f , l r ),as well as − Along the longitudinal direction of the tractor (L TR ) the distance (l) from the connection point (28) to the center of gravity of the tractor (12) c ).

12. A method for braking a vehicle combination (10) comprising a tractor (12) and a trailer (14), the tractor (12) comprising a tractor brake assembly (16, 22, 24) for regenerative braking of the tractor (12), and the trailer (14) comprising a trailer brake assembly (26) for braking the trailer (14), the method comprising: − Determine the tractor longitudinal force threshold using a method according to any of the preceding claims ( ): − operating the tractor vehicle brake assembly (16, 22, 24) to provide a braking force less than or equal to the tractor vehicle longitudinal force threshold.

13. The method according to claim 12, wherein the method further comprises: − obtain a deceleration request value ( ); − Based on the deceleration request value ( ) determines a requested braking force to be applied to the vehicle combination ( ); − Braking force in response to the request ( ) is less than or equal to the tractor longitudinal force threshold ( ), operating the tractor brake assembly (16, 22, 24) but not operating the trailer brake assembly (26) to brake the vehicle combination.

14. The method of claim 13, wherein determining the requested braking force to be applied to the vehicle combination (10) based on the deceleration request value further comprises obtaining a tractor vehicle mass value ( ) indicative of a current mass of the tractor vehicle (12). ) and a trailer mass value ( ).

15. The method according to claim 13 or 14, wherein based on the deceleration request value ( ) determining a requested braking force to be applied to the vehicle combination (10) further comprises determining a longitudinal trailer inclination angle value ( ).

16. The method according to any one of claims 12 to 15, wherein based on the deceleration request value ( ) determining a requested braking force to be applied to the vehicle combination (10) further comprises determining a longitudinal tractor inclination angle value indicative of the inclination angle of the ground supporting the tractor in a longitudinal direction of the tractor.

17. A computer program comprising program code means for performing the method according to any one of the preceding claims when said program is run on a computer.

18. A computer readable medium carrying a computer program, the computer program comprising program code means for performing the method according to any one of claims 1 to 16 when the program is run on a computer.

19. A control unit (30) configured to perform the method according to any one of claims 1 to 16.

20. A vehicle combination (10) comprising a tractor (12), a trailer (14) and a control unit (30) according to claim 19.

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