Method for determining longitudinal force threshold value of tractor

Abstract

A method for determining a tractor longitudinal force threshold value (I) for a tractor longitudinal deceleration force (II) 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, the tractor (12) comprising a set of tractor wheels (18), the invention relates to a method for controlling a traction vehicle (12), comprising a set of traction vehicle wheels (18) adapted to engage with the ground supporting said traction vehicle (12), each wheel of said set of traction vehicle wheels (18) comprising a tire, said method comprising:-determining a traction vehicle transverse force value (III) indicative of a traction vehicle transverse force being or expected to be exerted on said traction vehicle (12), determining, for each wheel of at least one subset of the set of tractor wheels (18), a tractor tire transverse force limit value (IV) by taking into account at least one characteristic of the tire using a tire model for determining a tire transverse force limit; -determining a reference lateral force value (V) using said tractor lateral force value (III) and said tractor tire lateral force limit value (IV); -determining a horizontal friction value (VI) indicative of a possible total horizontal friction available between the ground supporting the tractor (12) and the set of tractor wheels (18), and determining the tractor longitudinal force threshold value (I) using the reference transverse force value (V) and the horizontal friction value (VI).

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 the tractor and a trailer for decelerating the vehicle combination. Furthermore, the invention relates to a method for braking a vehicle combination comprising the 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 a vehicle combination 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 for braking the vehicle combination 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 of the tractor alone 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 can be inactive and thereby properly cooled, for example.

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

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

[0008] An object according to a first aspect of the present invention is to provide a method which can provide useful information relating to the braking of a vehicle combination.

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

[0010] Thus, 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 may be applied to a tractor of a vehicle combination comprising the tractor and a trailer for decelerating the vehicle combination.

[0011] The trailer has a trailer longitudinal extension in the trailer longitudinal direction, a trailer transverse extension in the trailer transverse direction, and a trailer vertical extension in the trailer vertical direction, wherein the trailer longitudinal direction corresponds to the expected travel direction of the trailer when the vehicle combination travels straight forward, the trailer vertical direction corresponds to the normal direction of the 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 lateral extension in a tractor lateral direction, and a tractor vertical extension in a tractor vertical direction, wherein the tractor longitudinal direction corresponds to the intended direction of travel of the tractor when the vehicle combination is traveling straight ahead, the tractor vertical direction corresponds to the normal direction of a planar surface supporting the tractor, and the tractor lateral direction is perpendicular to each of the tractor longitudinal direction and the tractor vertical direction, wherein the tractor longitudinal retarding force extends in a direction parallel to the tractor longitudinal direction. The tractor includes a set of tractor wheels, the set of tractor wheels being adapted to engage a ground supporting the tractor, each wheel of the set of tractor wheels including a tire.

[0013] The method includes: - determining a tractor lateral force value using a tractor lateral force value determination process, the tractor lateral force value indicating a tractor lateral force being or expected to be applied to the tractor, the tractor lateral force value determination process comprising: - Get the trailer mass value, which indicates the current mass of the trailer; - obtaining a trailer operating value, the trailer operating value indicating a current or predicted operating condition of the trailer; - 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 vehicle, and - using the trailer mass value, the trailer handling value and the articulation angle value to determine the tractor lateral force value; - for each wheel of at least a subset of the set of tractor vehicle wheels, determining a tractor vehicle tire lateral force limit value by taking into account at least one characteristic of the tire using a tire model for determining a tire lateral force limit; - Determine the reference lateral force value using the lateral force value of the tractor and the lateral force limit value of the tractor tire; - determining a horizontal friction value indicative of the total possible horizontal friction available between the ground supporting the tractor and the set of tractor wheels, and - Using the reference lateral force value and the horizontal friction force value, determining the tractor longitudinal force threshold value.

[0014] The above method means that the tractor longitudinal force threshold value can be determined with considerable safety and accuracy, since the reference lateral force value can be determined by considering two entities, namely the tractor lateral force value and the tractor tire lateral force limit value.

[0015] Optionally, each wheel of the set of tractor vehicle wheels has a wheel longitudinal direction parallel to the tractor vehicle longitudinal direction when the vehicle combination is traveling straight ahead and a wheel transverse direction parallel to the tractor vehicle transverse direction when the vehicle combination is traveling straight ahead, wherein the characteristics determining the tractor vehicle tire lateral force limit value for each wheel of at least a subset of the set of tractor vehicle wheels include the following: - determining a wheel longitudinal speed value, the wheel longitudinal speed value indicating the speed of the wheel in the wheel longitudinal direction, - determining a wheel lateral speed value, the wheel lateral speed value indicating the speed of the wheel in the wheel lateral direction, - determining a slip threshold value indicating a slip threshold value at which the wheel is expected to slip relative to the ground supporting the tractor, and - using the wheel longitudinal speed value, the wheel lateral speed value and the slip threshold value to determine a wheel-specific tractor tyre lateral force limit value portion forming a portion of the tractor tyre lateral force limit value.

[0016] Optionally, wherein the wheel has a wheel vertical direction perpendicular to each of the wheel longitudinal direction and the wheel lateral direction, and determining the characteristics of the slip threshold comprises using at least: - a contact value proportional to the distance in the longitudinal direction of the wheel along which it is determined that contact has been established between the wheel and the ground supporting the tractor; - a stiffness value indicating the stiffness coefficient of the tire of the wheel; - a vertical force value indicating the force applied to the wheel in the vertical direction of the tractor, and - A friction value indicating the friction between the wheel and the ground supporting the tractor.

[0017] Optionally, the characteristics for determining the lateral force limit value of the tractor tire further include the following items for each wheel in at least a subset of the set of tractor wheels: - determining a longitudinal slip value indicating slip in the longitudinal direction of the wheel using the wheel longitudinal velocity value and a product obtained by multiplying the effective rolling radius of the wheel by an angular velocity value indicating a current angular velocity of the wheel.

[0018] As used herein, the term "effective rolling radius" refers to the ratio of the linear velocity of the center of the wheel in the longitudinal direction of the wheel when no slip occurs to the angular velocity of the wheel. In general, the effective rolling radius is between the height limit of the wheel (i.e., the minimum distance from the ground to the center of the wheel in the vertical direction of the tractor) and the geometric radius of the wheel. The effective rolling radius can be determined in a variety of ways (e.g., by determining the above ratio of the linear velocity of the center of the wheel in the longitudinal direction of the wheel when no slip occurs during different driving conditions to the angular velocity of the wheel). Alternatively, the effective rolling radius can be determined by determining the tire contact angle (i.e., the vertex angle of the triangle connecting the wheel center and each of the rearmost contact point and the frontmost contact point between the tire and the ground supporting the tire) and combining this tire contact angle with the geometric radius of the wheel.

[0019] Optionally, the characteristics for determining the lateral force limit value of the tractor tire further include the following items for each wheel in at least a subset of the set of tractor wheels: - determining a slip angle value using the wheel longitudinal speed value and the wheel lateral speed value, preferably by dividing the wheel lateral speed value by the wheel longitudinal speed value, more preferably by calculating the inverse tangent of an independent variable corresponding to the ratio between the wheel lateral speed value and the wheel longitudinal speed value multiplied by negative one.

[0020] Optionally, the feature of using the tractor lateral force value and the tractor tire lateral force limit value to determine the reference lateral force value includes setting the reference lateral force equal to the one of the tractor lateral force value and the tractor tire lateral force limit value having the largest absolute value.

[0021] Optionally, the tractor lateral force value determination process further includes: - obtaining a longitudinal trailer tilt angle value, the longitudinal trailer tilt angle value indicating an inclination angle of the ground supporting the trailer in the longitudinal direction of the trailer; - determining a longitudinal weight value based at least on the trailer mass value and the longitudinal trailer inclination angle value, the longitudinal weight value being indicative of a longitudinal weight force exerted on the trailer in a longitudinal direction of the trailer, and - Use this longitudinal weight value to determine the lateral force value for the towing vehicle.

[0022] Using the above longitudinal trailer inclination angle value means that the tractor lateral force value can be determined with a relatively high degree of accuracy.

[0023] Optionally, the tractor lateral force value determination process further includes: - obtaining a longitudinal trailer deceleration value, the longitudinal trailer deceleration value indicating a longitudinal trailer deceleration being or expected to be applied to the trailer; - determining a longitudinal inertia force value based at least on the trailer mass value and the longitudinal trailer deceleration value, the longitudinal inertia force value being indicative of a longitudinal inertia force exerted on the trailer in a transverse direction of the trailer, and - Use this longitudinal inertia force value to determine the lateral force value for the towing vehicle.

[0024] Using the above-mentioned longitudinal trailer deceleration value means that the tractor lateral force value can be determined with a relatively high degree of accuracy.

[0025] Optionally, the tractor lateral force value determination process further includes: - determining a transverse centrifugal force value based at least on the trailer mass value, the transverse centrifugal force value being indicative of the centrifugal force exerted on the trailer in a transverse direction of the trailer, and - Use this lateral centrifugal force value to determine the tractor lateral force value.

[0026] Optionally, the tractor lateral force value determination process further includes: - obtaining a lateral inclination angle value, the lateral inclination angle value indicating an inclination angle of the ground supporting the trailer in the lateral direction of the trailer; - determining a lateral gravity value based at least on the trailer mass value and the lateral inclination angle value, the lateral gravity value indicating a lateral gravity force exerted on the trailer in a lateral direction of the trailer, and - Use this lateral weight value to determine the tractor lateral force value.

[0027] Optionally, the tractor lateral force value determination process further includes: - Multiply each force value indicating a force in the longitudinal direction of the trailer by the sine of the articulation angle value.

[0028] Optionally, the tractor lateral force value determination process further includes: - Multiply each force value indicating a force in the transverse direction of the trailer by the cosine of the articulation angle value.

[0029] Optionally, the tractor comprises a set of axles. The set of axles comprises at least one axle, and each axle is connected to a respective wheel in the set of tractor wheels. The method comprises performing the following for each axle in the set of axles: - determining a trailer axle lateral force value based on the trailer lateral force value, the trailer axle lateral force value indicating a trailer lateral force being or expected to be applied to the axle; - for at least one, preferably each, of the one or more wheels connected to the axle, determining a tractor axle lateral force limit value by taking into account at least one characteristic of the tire using a tire model for determining the tire lateral force limit; - using the trailer axle lateral force value and the tractor axle lateral force limit value to determine the reference axle lateral force value; - determining a horizontal axle friction value indicative of a possible total horizontal friction available between the ground supporting the tractor and at least one, preferably each, of the one or more wheels connected to the axle; - using the reference axle lateral force value and the horizontal axle friction force value to determine a towing vehicle axle longitudinal force threshold, and The axle tractor longitudinal force thresholds for each axle in the set of axles are summed to obtain the tractor longitudinal force threshold.

[0030] 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 axle based on the trailer lateral force value comprises using a moment balance equation using the following inputs: - the lateral force of the trailer; - the distance from each wheel 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.

[0031] Optionally, the method comprises performing the following on at least a plurality of wheels, preferably each wheel, of the set of tractor wheels: - determining a trailer wheel lateral force value based on the trailer lateral force value, the trailer wheel lateral force value indicating the trailer lateral force being or expected to be applied to the wheel; - for the wheel, determining a tractor tire lateral force limit value using a tire model for determining a tire lateral force limit by taking into account at least one characteristic of the tire; - using the trailer wheel lateral force value and the tractor wheel lateral force limit value to determine a reference wheel lateral force value; - determining a horizontal wheel friction value indicative of a possible total horizontal friction available between the ground supporting the tractor and at least one, preferably each, of the one or more wheels connected to the wheel; - using the reference wheel lateral force value and the horizontal wheel friction force value to determine a tractor vehicle wheel longitudinal force threshold value, and The wheel tractor longitudinal force threshold values ​​for each wheel in the set of wheels are summed to obtain the tractor wheel longitudinal force threshold value.

[0032] Optionally, the step of determining a trailer wheel lateral force value indicative of a trailer lateral force being or predicted to be exerted on the wheel based on the trailer lateral force value comprises using a moment balance equation using the following inputs: - the lateral force of the trailer; - the distance in the longitudinal direction of the tractor from each of a plurality of wheels of the set of tractor wheels, preferably from each wheel, to the centre of gravity 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.

[0033] 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 comprising: - Determining the tractor longitudinal force threshold using a method according to any of the preceding claims: - operating the tractor vehicle brake assembly to provide a braking force less than or equal to the tractor vehicle longitudinal force threshold.

[0034] 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 the vehicle combination based on the deceleration request value, and - in response to the 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.

[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 indicating 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 tilt angle value indicating an angle of inclination 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 performing the method of any one of the first or second aspects 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 any one 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 of any one of the first and second aspects 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 detailed 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 3a is a schematic plan view of a wheel;

[0048] Figure 3a is a schematic side view of a wheel;

[0049] Figure 4 is a schematic side view of a vehicle combination;

[0050] Figure 5 is a schematic rear view of the vehicle combination, and

[0051] Figure 6 It is a schematic plan view of a vehicle combination. DETAILED DESCRIPTION

[0052] Figure 1 1 is a schematic plan view of a vehicle combination 10 including a tractor 12 and a trailer 14. Figure 1As indicated in FIG. 1 , 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 , the tractor 12 includes a set of tractor wheels 18 adapted to engage the ground supporting the tractor 12. Each wheel in the set of tractor wheels 18 includes a tire. Figure 1 In the embodiment of the vehicle combination 10 of the embodiment of the invention, the tractor 12 comprises a pair of dual rear wheels and a pair of front wheels. However, it is certainly conceivable that other embodiments of the vehicle combination 10 may include a tractor with another implementation of the set of tractor wheels 18.

[0053] In addition, Figure 1 In the embodiment of the present invention, the propulsion assembly 16 is connected to the pair of dual rear wheels via a device including an axle 20. In addition, it is also conceivable that the propulsion assembly 16 may include one or more electric motors, each of which is arranged at the wheel hub of the wheel of the tractor 12.

[0054] like Figure 1 Indicated in the figure, the trailer 14 has a longitudinal direction L TL The longitudinal extension of the trailer on the trailer, in the transverse direction of the trailer T TL The transverse extension of the trailer and the vertical extension of the trailer V TL The vertical extension of the trailer on the longitudinal direction of the trailer L TL Corresponding to the expected direction of the trailer 14 when the vehicle combination 10 is traveling straight ahead, the trailer 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 of them.

[0055] Similarly, and also as Figure 1 Indicated in the figure, the tractor 12 has a longitudinal direction L of the tractor TR The longitudinal extension of the tractor on the tractor, the transverse direction T of the tractor TR The lateral extension of the trailer and the vertical direction V of the tractor TR The tractor longitudinal direction L TR Corresponding to the expected direction of the tractor 12 when the vehicle combination 10 is traveling straight ahead, the tractor vertical direction V TR corresponds to the normal direction of the plane surface supporting the trailer 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 of them.

[0056] In addition, if Figure 1 As indicated in , 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 conceivable that the tractor brake assembly for regenerative braking of the tractor 12 may include or even consist of one or more wheel hub motors 22, 24, each of which may function as a generator and generate electrical energy for storage in an electrical storage assembly (not shown), such as a battery (not shown).

[0057] Additionally, other implementations of the tractor 12 may include a tractor brake assembly for braking the tractor 12 without necessarily having regenerative capabilities. For example, such implementations may include one or more service brakes ( Figure 1 not shown).

[0058] Regardless of the implementation method, the tractor brake assembly is suitable for generating a brake force in the longitudinal direction L of the tractor. TR The longitudinal deceleration force of the tractor extending in a parallel direction .

[0059] 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, one or more electric motors for regenerative braking, or any combination thereof.

[0060] In addition, if Figure 1 , the trailer 14 is pivotally connected to the trailer 12 via a connection point 28. Such a connection point 28 can be realized, 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 With the trailer longitudinal direction L TL The articulation angle Ψ is formed between . Furthermore, the articulation angle Ψ can preferably be varied in a continuous manner, depending on the operating conditions of the vehicle combination 10, for example. Figure 1 The articulation angle Ψ in is indicated by a minus sign, which means that Figure 1 A negative articulation angle Ψ is used under the conditions of .

[0061] in addition, 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 conceivable.

[0062] 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 figure, 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.

[0063] from Figure 2 It can be seen that during driving of the vehicle combination 10, the trailer will move in the trailer longitudinal direction L TL The trailer longitudinal force is applied to And in the transverse direction of the trailer T TL The trailer lateral force is applied to . Further details of these forces are presented below.

[0064] The above forces will respectively cause the tractor 12 and the trailer 14 to move in the longitudinal direction L of the trailer. TL and trailer transverse direction T TL Connecting force 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.

[0065] exist Figure 2 In the above, the above-mentioned connection forces related to the tractor 12 and the trailer 14 are introduced. In addition, as Figure 2 Medium indication, connection force Respectively with the trailer longitudinal direction L TL and trailer transverse direction T TL Therefore, in order to Transform to the longitudinal direction L of the tractor TR and the tractor transverse direction T TR , the current articulation angle Ψ may be taken into account.

[0066] also, Figure 2 The longitudinal deceleration force of the tractor applied to the tractor 12 is shown. .also, Figure 2 Indicates lateral force of tractor , that is, in the transverse direction T of the tractor TR The force exerted on the tractor by the wheels of the tractor 12 is applied to the tractor.

[0067] The total horizontal force exerted on the tractor 12 via the set of tractor wheels 18 (i.e., from contact between the wheels and the ground supporting the tractor 12) is limited by the total horizontal friction force available between the ground supporting the tractor and the tractor wheels 18. restrictions.

[0068] For example only, the total horizontal friction force can be calculated using the weight of the tractor 12 To determine, that is, in the vertical direction V of the tractor TR The sum of the forces exerted on the set of tractor wheels 18 from the ground supporting 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, a friction value μ indicating the friction between the set of tractor wheels 18 and the ground supporting the tractor 12 may be used.

[0069] Such friction force value μ may be determined using any known process, 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 the set of tractor wheels 18 .

[0070] Thus, the total horizontal friction force can be determined from :

[0071] However, it should be noted that the total horizontal friction force can also be determined according to other procedures By way of example only, if we consider the respective friction force values ​​µ indicating the friction force between one wheel of the tractor 12 and the ground supporting the tractor 12 i , then the total horizontal friction force It can be determined according to the following, where M is the number of wheels in the set of tractor wheels 18: in: It is in the vertical direction V of the tractor TR The force exerted on the i-th wheel in the set of tractor wheels 18 from the ground supporting the tractor 12, and is a friction value indicative of the friction between the i-th wheel in the set of tractor wheels 18 and the ground supporting the tractor 12 .

[0072] For example only, information from, for example, a wheel suspension (not shown) of the tractor 12 may be used to determine the vertical position of the tractor in the vertical direction V TR The force exerted on the i-th wheel in the set of tractor wheels 18 from the ground supporting the tractor 12.

[0073] As a further alternative, Equation 3 above may also be applied to each wheel member axle of the tractor 12 .

[0074] How to determine the total horizontal friction , the following conditions should be met to prevent the set of tractor wheels 18 from slipping and / or sliding:

[0075] 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 axles or even the wheels of the tractor 12.

[0076] Thus, although only by way of example, Equation 3 may be expanded to a tractor 12 including a set of axles, wherein the set of axles includes at least one axle, and wherein each axle is connected to a respective wheel of the tractor 12. Assuming the tractor includes N axles, Equation 3 may be expanded according to the following terms: Where index i indicates the i-th axle.

[0077] Similarly, although by way of example, Equation 3 may be extended to the tractor 12 to each wheel in the set of tractor wheels 18. Assuming the set of tractor wheels 18 includes M wheels, Equation 3 may be extended according to the following terms: Where index j indicates the jth wheel.

[0078] For the sake of brevity, the following examples are mainly based on Equation 3 above. However, it should be noted that the following examples can be expanded in a straightforward manner to each of Equation 4 and Equation 5, respectively.

[0079] Thus, using Equation 3 as an example, the longitudinal deceleration force of the tractor is The maximum value of (which will be referred to as the tractor longitudinal force threshold value hereinafter) can be determined according to the following items:

[0080] Likewise, the total horizontal friction It may be determined, for example, according to any of the processes described above.

[0081] Although the longitudinal force threshold of the tractor The above determination correctly represents the kinematics of the vehicle combination 10, but the inventors of the present invention have realized that the tractor longitudinal force threshold value can be determined in an alternative manner. , in order to achieve a tractor longitudinal force threshold value indicative of proper safe operation of the vehicle combination 10 .

[0082] Specifically, the inventors have recognized that the tractor lateral force in, for example, Equation 6 above can be modified to , in order to take into account not only the kinematic conditions of the vehicle combination 10, but also the tire characteristics of each wheel in at least a subset of the set of tractor wheels 18. Thus, equation 6 can be reproduced according to the following terms: in and: is a tractor lateral force value indicating a tractor lateral force being or predicted to be exerted on the tractor 12, and is a tractor tire lateral force limit value determined by taking into account the characteristics of the tire of each wheel in at least a subset of the set of tractor wheels 18 .

[0083] Although the present invention is described above in Equation 8 as a modification of Equation 3, it should be noted that similar modifications may of course be made to each of Equations 4 and 5.

[0084] Thus, the method according to the first aspect of the invention comprises: - Determine the tractor lateral force using the tractor lateral force determination procedure The tractor lateral force value indicates the tractor lateral force being or expected to be applied to the tractor 12. The tractor lateral force value determination process includes: ○ Get the trailer mass value , the trailer mass value indicates the current mass of the trailer 14; ○ obtaining a trailer operating value indicating a current or predicted operating condition of the trailer 14; ○ Determine the articulation angle value Ψ, which indicates the longitudinal direction L of the tractor TR With the trailer longitudinal direction L TL The current articulation angle between ○ Use trailer mass value , trailer operation value and articulation angle value Ψ to determine the lateral force value of the tractor .

[0085] Furthermore, the method according to the first aspect of the invention comprises, for each wheel of at least a subgroup of the set of tractor wheels 18, determining a tractor tire lateral force limit value using a tire model for determining a tire lateral force limit by taking into account at least one characteristic of the tire The implementation of the tire model is described below.

[0086] In addition, the method includes using the lateral force value of the tractor and tractor tire lateral force limit To determine the reference lateral force value (See Equation 8 above).

[0087] Additionally, as described in detail above with reference to each of Equations 1 and 2, the method includes determining a horizontal friction force value , which indicates the total horizontal friction available between the ground supporting the tractor 12 and the set of tractor wheels 18.

[0088] Furthermore, the method comprises using a reference lateral force value and horizontal friction value To determine the tractor longitudinal force threshold .

[0089] Reference lateral force value This can be determined in a number of different ways, for example using the lateral force value of the towing vehicle and tractor tire lateral force limit Any combination of , where a and b are predetermined coefficients. However, as a non-limiting example, using the tractor lateral force value and tractor tire lateral force limit To determine the reference lateral force value The characteristics may include the reference lateral force Set equal to the value with the largest absolute value between the lateral force value of the tractor and the lateral force limit value of the tractor tire. Therefore, the force reference lateral force value can be determined according to the following terms :

[0090] The following will refer to Figure 3a and Figure 3b Introduction to the lateral force limit of tractor tires Non-limiting example of determination. Figure 3a is a plan view of a wheel forming part of the set of tractor wheels 18, and Figure 3b It should be noted that the following description applies to each wheel in the set of tractor wheels 18.

[0091] from Figure 3a As can be seen from the figure, each wheel in the set of tractor wheels 18 has a Figure 3a (not shown) when driving straight ahead in the longitudinal direction L of the tractor TR Parallel to the longitudinal direction of the wheel L W Similarly, each wheel in the set of tractor wheels 18 has a Figure 3a (not shown) when traveling straight ahead in a lateral direction L of the tractor TR Parallel to the wheel transverse direction T W . Figure 3a The longitudinal direction L of the wheel is shown W With the tractor longitudinal direction L TR . As an example only, the steering angle δ may be detected by a steering angle sensor (not shown) or by a steering wheel sensor (not shown) that detects the position of a steering wheel (not shown). For non-steering wheels, the steering angle δ is constant and may be zero.

[0092] As a non-limiting example, determining the characteristics of the tractor tire lateral force limit value for each wheel in at least a subset of the set of tractor wheels 18 may include the following process: - Determine the longitudinal wheel velocity value v Lw (refer to Figure 3b ), the wheel longitudinal speed value indicates the wheel longitudinal direction L W Speed ​​on - Determine the wheel lateral velocity value v Tw (refer to Figure 3a ), the wheel lateral speed value indicates the wheel lateral direction L W The speed of - Determine the sliding threshold , the slip threshold value indicating a slip threshold value over which the wheels are expected to slip relative to the ground supporting the tractor 12, and - Use the wheel longitudinal velocity value v Lw , wheel lateral velocity value v Tw and sliding threshold To determine a wheel specific tractor tire lateral force limit value portion which forms part of the tractor tire lateral force limit value.

[0093] The following will introduce an exemplary implementation of the above content. As a non-limiting example, a wheel longitudinal velocity value v Lw and the wheel lateral velocity v Tw Each of the input functions determines the wheel longitudinal direction L according to the following terms w and the wheel transverse direction T wThe slip value on each of :

[0094] According to the above slip value , the slip amplitude can be determined according to the following terms:

[0095] In addition, the above exemplary implementation can be used in the vertical direction V of the wheel. W The force F exerted on the wheel VW (refer to Figure 3b ). Wheel vertical direction V W Perpendicular to the longitudinal direction of the wheel L W and the wheel transverse direction L W As an example only, the wheel vertical direction V W Can be parallel to the vertical direction V of the tractor TR As a non-limiting example, the wheel vertical direction V may be determined using information from, for example, a wheel suspension system (not shown) associated with the wheel. W The force F VW .

[0096] Using the above information, the wheel longitudinal direction L can be determined according to the following items W and the wheel transverse direction T W The maximum force F on LW 、F TW :

[0097] Thereafter, the wheel longitudinal direction L is used W With the tractor longitudinal direction L TR The steering angle δ between them can be W and the wheel transverse direction T W The maximum force F on the above mark LW 、F TW Transform to the longitudinal direction L of the tractor TR and the tractor transverse direction T TR Specifically, the tractor lateral direction T associated with the wheel currently being evaluated TR The lateral force limit value F of the tractor tire on TTR This can be determined based on the following:

[0098] From the above, it can be appreciated that equation 17 indicates the tractor tire lateral force limit value F of one wheel in the set of tractor wheels 18: TTRTherefore, in order to obtain the lateral direction T of the tractor TR Total tractor tire lateral force limit value F TTR,总 , for each wheel in at least one subset of the set of tractor wheels 18, the following equation may be used: Where index j indicates the jth wheel, and M indicates the number of wheels in a subgroup of the set of tractor wheels 18. As a non-limiting example, the subgroup may be the same as the set of tractor wheels 18, such that M indicates the number of wheels in the set of tractor wheels 18.

[0099] In addition, if Figure 3b Indicated in the figure, the wheel has a vertical direction V W , the wheel vertical direction is perpendicular to the wheel longitudinal direction L W and the wheel transverse direction T W In addition, although only as an example, determining the sliding threshold The features may include using at least the following: - With the wheel longitudinal direction L W The distance on the contact value is proportional to l a , along which contact value it is determined that contact has been established between the wheel and the ground supporting the tractor 12. Figure 3b , as a non-limiting example, the contact value l a It may be equal to half of the above distance. However, it is also conceivable that a contact value l may be used. a Other variations of . - Stiffness value c p , the stiffness value indicates the stiffness coefficient of the tire of the wheel. - Force value F VW , the force value indicates the vertical direction V of the wheel W The force exerted on the wheel. - the aforementioned friction value µ, which indicates the friction between the wheels and the ground supporting the tractor 12 .

[0100] As an example only, the above parameters may be used to determine the sliding threshold according to the following items :

[0101] About Slip Value , referring to Equations 10 and 11 above, these slip values For example, the longitudinal speed of the wheel can be calculated by including the value v LW and by converting the effective rolling radius R of the wheel e Multiply by the angular velocity value indicating the current angular velocity of the wheel The product obtained is used to determine the indicated wheel longitudinal direction L W The longitudinal slip value on As an example only, the longitudinal slip value This can be determined based on the following:

[0102] As used herein, the effective rolling radius R e It refers to the linear velocity v of the wheel center in the longitudinal direction of the wheel when no slip occurs. LW The ratio of the angular velocity ω of the wheel. Effective rolling radius R e like Figure 3b Instructions. Figure 3b It can be seen that the effective rolling radius R e Between the wheel height limit R h (i.e., in the vertical direction V of the wheel W The minimum distance from the ground to the center of the wheel) and the geometric radius R of the wheel g between.

[0103] The linear velocity v of the wheel center in the longitudinal direction of the wheel when no slip occurs during different driving conditions can be determined in various ways (e.g., by determining LW The effective rolling radius R is determined by the above ratio of the angular velocity ω of the wheel e Alternatively, refer to Figure 3b The effective rolling radius can be determined by determining the tire contact angle θ (i.e., the vertex angle of the triangle connecting the center of the wheel and each of the rearmost and forwardmost contact points between the tire and the ground supporting the tire) and combining this tire contact angle with the geometric radius of the wheel.

[0104] However, the determination of the lateral force limit value of the tractor tire may also include using the wheel longitudinal speed value v LW and the wheel lateral velocity v TW , preferably by setting the wheel lateral velocity value v TW Divide by the longitudinal speed of the wheel v LW , more preferably by calculating and wheel lateral velocity value v TW and the wheel longitudinal velocity v LW The slip angle is determined by multiplying the ratio by the inverse tangent of the corresponding independent variable. .

[0105] Thus, although only as an example, the slip angle value This can be determined based on the following:

[0106] As a non-limiting example, the longitudinal slip value and slip angle It can be used to determine the wheel longitudinal direction L according to the following terms w and the wheel transverse direction T w The slip value on each of :

[0107] The above introduction involves the lateral force limit value F of the tractor tire. TTR Determination of the lateral force limit of the tractor tire for one wheel or the total tractor tire lateral force limit F TTR,总 .

[0108] However, as shown above, for example in Equation 8, the method according to the present invention also uses the tractor lateral force value , the tractor lateral force value indicates the tractor lateral force being or expected to be applied to the tractor 12. The following will describe in detail the method for determining the tractor lateral force value. The implementation method of the features.

[0109] Thus, the method of the first aspect of the present invention comprises determining the tractor lateral force value using a tractor lateral force value determination process The tractor lateral force value indicates the tractor lateral force being or expected to be applied to the tractor 12, and the tractor lateral force value determination process includes: - Get the trailer mass value , the trailer mass value indicates the current mass of the trailer 14; - obtaining a trailer operating value indicating a current or predicted operating condition of the trailer 14; - Determine the articulation angle value Ψ, which indicates the longitudinal direction L of the tractor TR With the trailer longitudinal direction L TL The current articulation angle between - Use trailer mass value , trailer operation value and articulation angle value Ψ to determine the lateral force value of the tractor .

[0110] The above process includes obtaining the trailer mass value quality , the trailer mass value mass indicates 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.

[0111] In addition, the above-mentioned tractor lateral force value determination process includes determining an articulation angle value Ψ, which indicates the longitudinal direction L of the tractor TR With the trailer longitudinal direction L TL . 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, for example, to Equation 38 below.

[0112] Furthermore, various parameters and combinations of these parameters may be used for the trailer operating values. This will be described in further detail below.

[0113] from Figure 2 It can be seen that the lateral force of the tractor In the transverse direction of the tractor T TR The force exerted on the tractor 12 Thus, the connection force between the tractor 12 and the trailer 14 As an example only, the force applied to the tractor 12 is This may thus be a centrifugal force, as will be explained further below.

[0114] Similarly, the trailer transverse direction T TL The connection force on This may be related to the centrifugal force exerted on the trailer 14. On the other hand, the longitudinal direction L of the trailer TL The connection force on Possibly with the quality of the trailer 14 And the longitudinal acceleration of the trailer 14. This will also be described in further detail below.

[0115] As shown above, in order to Transform to the tractor's transverse direction T TR , the information indicating the current articulation angle Ψ may be used according to:

[0116] In the longitudinal direction of the trailer L TL and trailer transverse direction T TL The connection force on It can be converted into trailer lateral force value according to the following terms The trailer lateral force value indicates the lateral direction of the tractor T TR The lateral forces of the trailer that are being or are expected to be exerted on the tractor:

[0117] A first example of a trailer handling value may be a longitudinal trailer tilt angle value indicating the relative position of the ground supporting the trailer 14 in the trailer longitudinal direction L T To this end, refer to Figure 4 , which shows the vehicle combination 10 at a tilt angle Drive on a slope. Figure 4 It can be seen that the tilt angle Will generate in the trailer longitudinal direction L TL The gravity exerted on the trailer 14 will form a longitudinal direction L of the trailer. TL The connection force on part of.

[0118] Therefore, the first implementation of the above-mentioned tractor lateral force value determination process includes obtaining the longitudinal trailer tilt angle value The longitudinal trailer inclination angle value indicates that the ground supporting the trailer 14 is in the longitudinal direction L of the trailer. TL The tilt angle on the 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 terrain, for example using a mapping system, and the current position of the trailer 14 (which may be determined using a global positioning system (not shown) for example), a tilt angle value may be determined. .

[0119] However, the method includes at least one method based on the trailer mass value. and longitudinal trailer tilt angle value To determine the longitudinal gravity value , the longitudinal gravity value indicates the longitudinal direction L of the trailer. TL The longitudinal gravity force exerted on the trailer 14. As a non-limiting example, the longitudinal gravity value This can be determined based on the following: .

[0120] In addition, the first implementation of the above-mentioned tractor lateral force value determination process includes using the longitudinal gravity value To determine the lateral force of the tractor By way of example only, the above may be determined based on the following items: .

[0121] As an example only, the trailer lateral force value determination process may also include obtaining the longitudinal trailer deceleration value , which indicates the longitudinal trailer deceleration being or expected to be imposed on the trailer 14. Thus, a second example of a trailer handling value may be the longitudinal trailer deceleration value described above. .

[0122] Generally speaking, the longitudinal trailer deceleration value can be negative, thus indicating a requested deceleration, i.e., in the longitudinal direction L of the trailer TL By way of example only, a longitudinal trailer deceleration value may be determined using a sensor (not shown) associated with the trailer 14, such as an accelerometer (not shown). However, it is also contemplated that the longitudinal trailer deceleration value may be determined by other means (eg, using a deceleration request signal indicating a requested deceleration of the trailer 14). .

[0123] Furthermore, the trailer lateral force value determination process may include at least one step based on the trailer mass value. and longitudinal trailer deceleration value To determine the longitudinal inertia trailer force , the longitudinal inertia trailer force value indicates the value of the trailer in the transverse direction L TL The longitudinal inertia force exerted on the trailer 14. For example only, the longitudinal inertia trailer force value is This can be determined based on the following: .

[0124] Thus, although only as an example, the longitudinal inertia trailer force value and longitudinal gravity The following terms (eg, see Equation 25 above) may be combined to form the trailer longitudinal direction L TL The connection force on is part of or even constitutes the connecting force: .

[0125] In addition, although only as an example, the trailer lateral force value determination process may also include: - At least based on the trailer mass value To determine the lateral centrifugal force The lateral centrifugal force value indicates the lateral direction T of the trailer. TL The centrifugal force exerted on the trailer 14, and - Use lateral centrifugal force value To determine the trailer lateral force .

[0126] As an example only, the lateral centrifugal force value The trailer 14 may be positioned in the trailer longitudinal direction L based on the indication TLThe longitudinal velocity value of the speed on 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 (reference Figure 6 ). As a non-limiting example, the lateral centrifugal force value This can be determined based on the following:

[0127] Compared with the above lateral centrifugal force value Similarly, in the lateral direction T of the tractor TR The force exerted on the tractor 12 It may include a lateral direction T of the tractor TR The lateral centrifugal force value of the centrifugal force applied to the tractor 12 The relevant addend, the value of the lateral centrifugal force is based at least on the value of the mass of the tractor , indicating that the tractor 12 is in the longitudinal direction L of the tractor TR The longitudinal velocity value of the speed on and the tractor curvature radius , which indicates the radius of curvature of the path currently followed by the center of gravity of the tractor 12. Therefore, similar to equation 26 above, the lateral centrifugal force value of the tractor 12 is This can be determined based on the following:

[0128] In an embodiment of the present invention, a speed sensor (not shown) of the tractor 12 may be used to determine the longitudinal velocity value The longitudinal speed value indicates that the tractor 12 is moving in the longitudinal direction L of the tractor. TR In addition, although it is only for example, in the embodiment of the present invention, it is indicated that the trailer 14 is in the longitudinal direction L of the trailer. TL The longitudinal velocity value of the speed on Can be set equal to the longitudinal velocity value The longitudinal speed value indicates that the tractor 12 is moving in the longitudinal direction L of the tractor. TR On speed.

[0129] Returning to the lateral centrifugal force value of the trailer 14, although it is only for example, the lateral centrifugal force value of the trailer 14 The trailer transverse direction T may be formed according to the following term (see, for example, Equation 25 above): TL The connection force on is part of or even constitutes the connecting force:

[0130] It should be noted that the lateral centrifugal force value Only a portion of the trailer lateral force value can be added Thus, the factor C in equation 28 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 only by way of example, 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 in the longitudinal direction L of the trailer. TL The distance between the ground engaging member of the trailer 14 and the center of gravity of the trailer and the distance in the longitudinal direction L of the trailer TL The distance between the connection point 28 and the center of gravity of the trailer 14. In this regard, please refer to Equation 46 below, which describes an example of how the above distance can be taken into account.

[0131] However, it should also be noted that, although only as an example, the trailer lateral force value determination process may also include obtaining a lateral tilt angle value The lateral inclination angle value indicates that the ground supporting the trailer 14 is in the lateral direction T of the trailer. TL To this end, refer to Figure 5 , which shows the implementation of a trailer 14 located on a transversely inclined slope.

[0132] Thus, although only as an example, the trailer lateral force value determination process may include at least based on the trailer mass value and lateral tilt angle values To determine the lateral gravity , the lateral gravity value indicates the lateral direction T of the trailer. TL The lateral gravity applied to the trailer 14. In addition, the process may also include using the lateral gravity value To determine the trailer lateral force value. Thus, although only as an example, the above equation 28 can be expanded according to the following terms:

[0133] Likewise, the factor C in Equation 29 may be in the range of 0 to 1 and may be related to the longitudinal direction L of the trailer. TL The distance between the ground engaging member of the trailer 14, the center of gravity of the trailer 14 and the connection point 28 is related to the distance between the ground engaging member of the trailer 14, the center of gravity of the trailer 14 and the connection point 28. As indicated above with reference to equation 24, the trailer lateral force value determination process can also include indicating the longitudinal direction L of the trailer TL Each force value of the force on is multiplied by the sine of the articulation angle value Ψ. Similarly, referring again to Equation 24, for example, the trailer lateral force value determination process may also include the following steps: TL Each force value on is multiplied by the cosine of the articulation angle value Ψ.

[0134] As shown above, the longitudinal trailer tilt 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. As will be described in detail below. Thus, the tractor 12 may include a tilt sensor 34 adapted to determine a longitudinal tractor tilt angle value The longitudinal tractor inclination angle value indicates that the ground supporting the tractor 12 is in the longitudinal direction L of the tractor. TR In addition, refer to Figure 4 , obtain the indication that the ground supporting the trailer 14 is in the longitudinal direction L of the trailer TL The longitudinal trailer tilt angle value of the tilt angle on This can include: - Get speed value , which indicates that the tractor 12 is moving in the longitudinal direction L of the tractor TR The current speed on the - Obtain a distance value 36, which indicates the distance in the longitudinal direction L of the tractor TR The distance between the tilt sensor 34 and the reference point of the trailer 14 is shown in FIG. Figure 4 As indicated in FIG. 1 , the reference point may be the center of gravity of the trailer 14 . - Use speed value and distance value 36 to determine the first instant in time at which the tilt sensor 34 is located at a global position The second instant in time when the trailer's reference point 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 time that has passed To determine the longitudinal trailer tilt angle value .

[0135] As indicated above, the above examples are generally based on Equation 3, such that the methods are performed at the tractor level. However, as indicated 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 includes a set of axles, wherein the set of axles includes at least one axle and wherein each axle is connected to a respective wheel of the set of tractor wheels, the method according to the first aspect of the invention may include performing the following for each axle in the set of axles: - Based on trailer lateral force values , determine the trailer axle lateral force value , the trailer axle lateral force value indicates the trailer lateral force being or expected to be applied to the axle; - for at least one, preferably each, of the one or more wheels connected to the axle, determining a tractor axle lateral force limit value by taking into account at least one characteristic of the tire using a tire model for determining the tire lateral force limit; - using the trailer axle lateral force value and the tractor axle lateral force limit value to determine the reference axle lateral force value; - determining a horizontal axle friction value indicative of a possible total horizontal friction available between the ground supporting the tractor 12 and at least one, preferably each, of the one or more wheels connected to the axle, and - using the reference axle lateral force value and the horizontal axle friction force value to determine a towing vehicle axle longitudinal force threshold, and Axle tractor longitudinal force threshold for each axle in the set of axles Sum to obtain the tractor longitudinal force threshold .

[0136] In addition, although it is only an example, based on the trailer lateral force value to determine a trailer axle lateral force value indicative of the trailer lateral force being or expected to be applied to the axle The steps may include using the moment balance equation using the following inputs: - Trailer lateral force ; - In the longitudinal direction L of the tractor TR The distance l from each axle to the center of gravity of the tractor 12 f , l r ,as well as - In 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 .

[0137] Similarly, although by way of example only, embodiments may also be performed at the wheel level. Thus, embodiments of the present invention may include performing the following items on at least a plurality of wheels, preferably each wheel, in the set of tractor wheels 18: - Based on the trailer lateral force value , determine the lateral force value of the trailer wheel , the trailer wheel lateral force value indicates the trailer lateral force being or expected to be applied to the wheel; - for the wheel, determining a tractor tire lateral force limit value using a tire model for determining a tire lateral force limit by taking into account at least one characteristic of the tire; - using the trailer wheel lateral force value and the tractor wheel lateral force limit value to determine a reference wheel lateral force value; - determining a horizontal wheel friction value indicative of a possible total horizontal friction available between the ground supporting the tractor and at least one, preferably each, of the one or more wheels connected to the wheel, and - using the reference wheel lateral force value and the horizontal wheel friction force value to determine a tractor vehicle wheel longitudinal force threshold value, and The wheel traction vehicle longitudinal force threshold for each wheel in the set of wheels The sum is performed to obtain the longitudinal force threshold of the tractor wheel .

[0138] In addition, although it is only an example, based on the trailer lateral force value to determine a trailer wheel lateral force value indicative of the trailer lateral force being or expected to be applied to that wheel The steps may include using the moment balance equation using the following inputs: - Trailer lateral force ; - In the longitudinal direction L of the tractor TR The distance l from each of the plurality of wheels in the set of tractor wheels 18, preferably from each wheel, to the center of gravity of the tractor 12 is f , l r ,as well as - In 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 .

[0139] It is also contemplated that embodiments of the present invention may use a combination of the axle level methods and wheel level methods indicated above. By way of example only, it is contemplated that embodiments of the present invention may use an axle level method for certain axles of the tractor and a wheel level method for the remaining wheels in the set of tractor wheels 18.

[0140] Regardless of how the tractor longitudinal force threshold is determined , which are preferably used in 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.

[0141] The method includes: - Determining the tractor longitudinal force threshold using the method according to the first aspect of the invention (eg according to any of the embodiments described above) ,as well as - Operate the tractor vehicle brake assembly to provide a force less than or equal to the tractor vehicle longitudinal force threshold braking force.

[0142] As a non-limiting example, the method for braking the vehicle combination 10 may also include: - Get the deceleration request value , the deceleration request value indicating a requested deceleration of the vehicle combination 10 ; - Based on the deceleration request value To determine the requested braking force to be applied to the vehicle combination 10 ,as well as - Braking force in response to request Less than or equal to the longitudinal force threshold of the tractor , the vehicle combination 10 is braked by operating the tractor brake assembly but not the trailer brake assembly.

[0143] 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 To determine the 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 .

[0144] As an example only, the requested braking force It can be expressed as the longitudinal direction of the tractor L TR The force on the .

[0145] Strength It may be related to the resistance (eg, drag) exerted on the vehicle combination 10 .

[0146] In addition, based on the deceleration request value To determine the requested braking force to be applied to the vehicle combination 10 It may also include determining a longitudinal trailer tilt angle value indicating an angle of inclination of the ground supporting the trailer in a longitudinal direction of the trailer.

[0147] Optionally, determining a requested braking force to be applied to the vehicle combination based on the deceleration request value may further include determining a longitudinal tractor tilt angle value indicating an angle of inclination of ground supporting the tractor in a longitudinal direction of the tractor.

[0148] Figure 6FIG. 1 is a schematic plan view of a vehicle combination 10 including a tractor 12 and a trailer 14. Figure 6 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 wheel set 40 is not necessarily steerable.

[0149] Figure 6 The illustrated implementation 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 6 Indicate the following distances: l f In the longitudinal direction of the tractor L TR The distance from the front wheel set 38 to the center of gravity of the tractor 12; l r In the longitudinal direction of the tractor L TR The distance from the rear wheel set 40 to the center of gravity of the tractor 12; l c In the longitudinal direction of the tractor L TR The distance from the connection point 28 to the center of gravity of the tractor 12; l f,t In 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 In the longitudinal direction of the trailer L TL The distance from the connection point 28 to the set of wheels 42 of the tractor 14; is the turning radius of the front wheel set 38; is the turning radius of the rear wheel set 40; R f,t is the turning radius of connection point 28, and R r,t is the turning radius of the set of wheels 42 of the trailer 14 .

[0150] For example only, the distances may be known (e.g., provided by the supplier of the tractor 12 and trailer 14), and the steering angle A steering angle sensor (not shown) can be used to determine the distance l f , l r , l c , l f,t and l r,t And indicate the steering angle The turning radius and the aforementioned articulation angle Ψ can be determined according to the following equations:

[0151] When the tractor 12 is in the longitudinal direction L of the tractor TR Has a certain speed , the trailer 14 is in the longitudinal direction L of the trailer TL Has a certain speed , the aforementioned longitudinal trailer deceleration value indicating the longitudinal trailer deceleration being or expected to be imposed on the trailer 14 has been obtained And the trailer 14 is at an inclined angle When driving on a slope, follow the following Figure 6 implementation plan to determine the Figure 6 The lateral force value of the tractor introduced by each axle of the tractor :

[0152] In the above equations, the superscript “front” indicates forces associated with the front set of wheels 38 of the tractor 12 , the superscript “rear” indicates forces associated with the rear set of wheels 40 of the tractor, and the superscript “cp” indicates forces associated with the connection point 28 .

[0153] The above equation and Figure 6 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 30 to 51 can certainly be extended to any number of wheel sets for each of the tractor 12 and trailer 14.

[0154] 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, the control unit being configured to execute the method of the first aspect or the second aspect of the present invention; - A vehicle combination comprising a tractor 12, a trailer 14 and a control unit 30 according to the above.

[0155] It should be understood that the present invention is not limited to the embodiments described above and shown in the drawings; on the contrary, 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 a tractor vehicle ( ) 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, The trailer (14) has a longitudinal direction (L TL ) on the longitudinal extension of the trailer, in the transverse direction of the trailer (T TL ) and in the trailer's vertical direction (V TL ) on the vertical extension of the trailer, wherein the longitudinal direction of the trailer (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 ) in the longitudinal direction of the tractor, in the transverse direction of the tractor (T TR ) on the tractor lateral extension and on the tractor vertical direction (V TR ) on the tractor vertical extension, wherein the tractor 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 ( ) in the longitudinal direction (L TR ), the tractor (12) comprising a set of tractor wheels (18) adapted to engage the ground supporting the tractor (12), each wheel in the set of tractor wheels (18) comprising a tire, The method comprises: - Use the tractor lateral force determination procedure to determine the tractor lateral force value ( ), the tractor lateral force value indicates the tractor lateral force being or expected to be applied to the tractor (12), and the tractor lateral force value determination process includes: - Get the trailer mass value ( ), the trailer mass value indicating the current mass of the trailer (14); - obtaining a trailer operating value, the trailer operating value indicating a current or predicted operating condition of the trailer (14); - Determine the value of the articulation angle ( ), the articulation angle value indicates the longitudinal direction of the tractor (L TR ) and the longitudinal direction of the trailer (L TL ), and - Use the trailer mass value ( ), the trailer operation value and the articulation angle value ( ) to determine the lateral force value of the tractor ( ); - for each wheel of at least one subgroup of the set of tractor wheels (18), determining a tractor tire lateral force limit value by taking into account at least one characteristic of the tire using a tire model for determining a tire lateral force limit ( ); - Use the stated tractor lateral force values ​​( ) and the tractor tire lateral force limit value ( ) to determine the reference lateral force value ( ); - Determine the horizontal friction value ( ), the horizontal friction value indicating a possible total horizontal friction available between the ground supporting the tractor (12) and the set of tractor wheels (18), and - Using the reference lateral force value ( ) and the horizontal friction value ( ) to determine the tractor longitudinal force threshold ( ).

2. The method according to claim 1, wherein each wheel of the set of tractor vehicle wheels (18) has a longitudinal direction (L) of the tractor vehicle when the vehicle combination (10) is traveling straight ahead. TR ) parallel to the longitudinal direction of the wheel (L W ) and when the vehicle combination (10) is moving forward in a straight line, the vehicle combination (10) is in a lateral direction (T TR ) parallel to the wheel transverse direction (T W ), wherein the tractor tire lateral force limit value is determined ( ) comprises, for each wheel of at least a subset of the set of tractor vehicle wheels: - Determine the longitudinal speed of the wheel (v Lw ), the wheel longitudinal speed value indicates the wheel longitudinal direction (L W ) on the speed, - Determine the wheel lateral velocity value (v Tw ), the wheel lateral velocity value indicates the wheel lateral direction (T W ) on the speed, - Determine the sliding threshold ( ), the slip threshold value indicating a slip threshold value at which the wheel is expected to slip relative to the ground supporting the tractor (12), and - Use the wheel longitudinal velocity value (v Lw ), the wheel lateral velocity value (v Tw ) and the sliding threshold ( ) to determine the lateral force limit value of the tractor tire ( ) is a part of the wheel specific tractor tire lateral force limit value section.

3. The method according to claim 2, wherein the wheel has a longitudinal direction (L W ) and the wheel transverse direction (T W ) is perpendicular to the wheel vertical direction (V W ), wherein determining the characteristics of the sliding threshold comprises using at least the following: - a contact value proportional to the distance in the longitudinal direction of the wheel (l a ), along the contact value, determining that contact has been established between the wheel and the ground supporting the tractor (12); - Stiffness value (c p ), wherein the stiffness value indicates a stiffness coefficient of the tire of the wheel; - Vertical force value (F VW ), the force value indicates the vertical direction of the wheel (V W ) exerted on the wheel, and - a friction value (µ), the friction value indicating the friction between the wheels and the ground supporting the tractor (12).

4. The method according to claim 2 or 3, wherein the characteristics for determining the tractor tire lateral force limit value further comprise, for each wheel of at least a subset of the set of tractor wheels: - Use the wheel longitudinal velocity value (v Lw ) and by dividing the effective rolling radius of the wheel (R e ) multiplied by the angular velocity value indicating the current angular velocity of the wheel ( ) is obtained by multiplying the longitudinal direction of the wheel (L w ) on the longitudinal slip value ( ).

5. The method according to any one of claims 2 to 4, wherein the characteristics for determining the tractor tire lateral force limit value further comprise, for each wheel of at least a subset of the set of tractor wheels: - Use the wheel longitudinal velocity value (v LW ) and the wheel lateral velocity value (v TW ), preferably by adding the wheel lateral velocity value (v TW ) divided by the longitudinal velocity of the wheel (v LW ), more preferably by calculating and the wheel lateral velocity value (v TW ) and the wheel longitudinal velocity value (v LW ) multiplied by the inverse tangent of the corresponding independent variable to determine the slip angle value ( ).

6. A method according to any one of the preceding claims, wherein the tractor lateral force value ( ) and the tractor tire lateral force limit value ( ) to determine the reference lateral force value ( ) includes setting the reference lateral force equal to a value having a maximum absolute value between the tractor lateral force value and the tractor tire lateral force limit value.

7. The method according to any one of the preceding claims, wherein the tractor lateral force value determination process further comprises: - Get the longitudinal trailer tilt angle value ( ), the longitudinal trailer inclination angle value indicates the inclination angle of the ground supporting the trailer (14) in the longitudinal direction of the trailer; - determining a longitudinal gravity value based at least on the trailer mass value and the longitudinal trailer inclination angle value ( ), the longitudinal gravity value indicates the longitudinal gravity applied to the trailer in the longitudinal direction of the trailer, and - Use the longitudinal gravity value ( ) to determine the lateral force value of the tractor ( ).

8. The method according to any one of the preceding claims, wherein the tractor lateral force value determination process further comprises: - Get the longitudinal trailer deceleration value ( ), the longitudinal trailer deceleration value indicating a longitudinal trailer deceleration being or expected to be imposed on the trailer (14); - at least based on the trailer mass value ( ) and the longitudinal trailer deceleration value ( ) to determine the longitudinal inertia force value ( ), the longitudinal inertia force value indicates the longitudinal inertia force applied to the trailer in the lateral direction of the trailer, and - Using the longitudinal inertia force value ( ) to determine the lateral force value of the tractor ( ).

9. The method according to any one of the preceding claims, wherein the tractor lateral force value determination process further comprises: - at least based on the trailer mass value ( ) to determine the lateral centrifugal force value ( ), the lateral centrifugal force value indicates the value of the lateral centrifugal force in the lateral direction of the trailer (T TL ) exerts a centrifugal force on the trailer, and - Use the lateral centrifugal force value ( ) to determine the lateral force value of the tractor ( ).

10. The method according to any one of the preceding claims, wherein the tractor lateral force value determination process further comprises: - Get the horizontal tilt angle value ( ), wherein the lateral inclination angle value indicates the inclination angle of the ground supporting the trailer (14) in the lateral direction of the trailer; - at least based on the trailer mass value ( ) and the lateral tilt angle value ( ) to determine the lateral gravity value ( ), the lateral gravity value indicates the lateral gravity applied to the trailer in the lateral direction of the trailer, and - Use the lateral gravity value ( ) to determine the lateral force value of the tractor ( ).

11. The method according to any one of the preceding claims, wherein the tractor lateral force value determination process further comprises: - multiplying each force value indicating a force in the longitudinal direction of the trailer by the articulation angle value ( ) is the sine of .

12. The method according to any one of the preceding claims, wherein the tractor lateral force value determination process further comprises: - multiply each force value indicating a force in the transverse direction of the trailer by the articulation angle value ( ) is the cosine of .

13. The method according to any one of the preceding claims, wherein the tractor (12) comprises a set of axles, wherein the set of axles comprises at least one axle and wherein each axle is connected to a respective wheel of the set of tractor wheels, wherein the method comprises performing the following for each axle of the set of axles: - Based on the trailer lateral force value ( ), determine the trailer axle lateral force value ( ), the trailer axle lateral force value indicates the trailer lateral force being or expected to be applied to the axle; - for at least one, preferably each, of the one or more wheels connected to the axle, determining a tractor axle lateral force limit value by taking into account at least one characteristic of the tire using a tire model for determining the tire lateral force limit; - using the trailer axle lateral force value and the tractor axle lateral force limit value to determine a reference axle lateral force value; - determining a horizontal axle friction value indicative of a possible total horizontal friction available between the ground supporting the tractor (12) and at least one, preferably each, of one or more wheels connected to the axle; - determining a tractor axle longitudinal force threshold using said reference axle lateral force value and said horizontal axle friction force value, and The axle tractor longitudinal force threshold for each axle in the set of axles ( ) are summed to obtain the tractor longitudinal force threshold value ( ).

14. The method according to claim 13, wherein based on the trailer lateral force value ( ) to determine the trailer axle lateral force value (indicative of a trailer lateral force being or expected to be applied to the axle) ) step includes using the moment balance equation with the following inputs: - The trailer lateral force value ( ); - in the longitudinal direction of the tractor (L TR ) from each axle to the center of gravity of the tractor (12) f , l r ),as well as - in the longitudinal direction of the tractor (L TR ) from the connection point (28) to the center of gravity of the tractor (12) c ).

15. A method according to any one of the preceding claims, wherein the method comprises performing the following on at least a plurality of wheels, preferably each wheel, of the set of tractor wheels: - Based on the trailer lateral force values ), determine the trailer wheel lateral force value ( ), the trailer wheel lateral force value indicates the trailer lateral force being or expected to be applied to the wheel; - for said wheel, determining a tractor tire lateral force limit value using a tire model for determining a tire lateral force limit by taking into account at least one characteristic of said tire; - using the trailer wheel lateral force value and the tractor wheel lateral force limit value to determine a reference wheel lateral force value; - determining a horizontal wheel friction value indicative of a possible total horizontal friction available between the ground supporting the tractor and at least one, preferably each, of one or more wheels connected to the wheel; - determining a tractor vehicle wheel longitudinal force threshold using said reference wheel lateral force value and said horizontal wheel friction force value, and The wheel traction vehicle longitudinal force threshold value for each wheel in the set of wheels ( ) are summed to obtain the tractor wheel longitudinal force threshold value ( ).

16. The method according to claim 15, wherein based on the trailer lateral force value ( ) to determine a trailer wheel lateral force value indicative of said trailer lateral force being or expected to be applied to said wheel ( ) step includes using the moment balance equation with the following inputs: - The trailer lateral force value ( ); - in the longitudinal direction of the tractor (L TR ) from each of a plurality of wheels in the set of tractor wheels, preferably from each wheel, to the center of gravity of the tractor (12); f , l r ),as well as - in the longitudinal direction of the tractor (L TR ) from the connection point (28) to the center of gravity of the tractor (12) c ).

17. A method for braking a vehicle combination (10), the vehicle combination 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: - using a method according to any of the preceding claims to determine a deceleration force tractor longitudinal force threshold value ( ): - operating the tractor brake assembly (16, 22, 24) to provide a force less than or equal to the tractor longitudinal force threshold ( ) braking force.

18. The method according to claim 17, wherein the method further comprises: - Get the deceleration request value ( ), the deceleration request value indicating a requested deceleration of the vehicle combination (10); - Based on the deceleration request value ( ) to determine the requested braking force to be applied to the vehicle combination ; - In response to the braking force Less than or equal to the force 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.

19. The method of claim 18, wherein determining the 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 the current mass of the tractor vehicle (12). ) and a trailer mass value ( ).

20. The method according to claim 18 or 19, wherein based on the deceleration request value ( ) to determine the requested braking force to be applied to the vehicle combination further comprises determining a longitudinal trailer inclination angle value ( ), the longitudinal trailer inclination angle value indicates the inclination angle of the ground supporting the trailer in the longitudinal direction of the trailer.

21. The method according to any one of claims 17 to 20, wherein based on the deceleration request value ( ) to determine a requested braking force to be applied to the vehicle combination (10) further comprises determining a longitudinal tractor tilt angle value, the longitudinal tractor tilt angle value indicating the tilt angle of the ground supporting the tractor in the longitudinal direction of the tractor.

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

23. A computer readable medium carrying a computer program, the computer program comprising program code means for executing the method according to any one of claims 1 to 21 when the program product is run on a computer.

24. A control unit (30) configured to perform the method according to any one of claims 1 to 21.

25. A vehicle combination (10) comprising a tractor (12), a trailer (14) and a control unit (30) according to claim 24.

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