Braking method and control device for a vehicle combination

Abstract

The present invention relates to a braking method for a vehicle assembly (1) and a control device (37) for performing the braking method, wherein the braking method comprises the following steps: - obtaining a braking request (11), - controlling the output of an initial braking pressure (p0) to the trailer braking system (9), - obtaining the actual longitudinal acceleration aLong and the actual lateral acceleration aLat of the vehicle assembly (1), - determining a minimum coefficient of friction (MFC) taking into account the obtained actual longitudinal acceleration aLong and the actual lateral acceleration aLat, - determining a subsequent braking pressure (pn) for the trailer braking system (9) based on the minimum coefficient of friction (MFC), - controlling the output of the subsequent braking pressure (pn) to the trailer braking system (9) in coordination with the braking request (11).

Description

Technical Field

[0001] The present invention relates to a braking method for a vehicle combination and a control device configured to perform the braking method according to the invention, and to a vehicle combination having the control device according to the invention. Background Technology

[0002] The vehicle combination consists of a tractor and at least one trailer, with trucks and semi-trailers falling under this concept in particular.

[0003] Especially during braking, when, for example, a tractor and a trailer are braked at different intensities, a dangerous driving situation may occur.

[0004] This can lead to situations such as trailer swaying, vehicle assembly skidding, or bending, each constituting an uncontrollable and therefore dangerous driving condition for the vehicle assembly. The ultimate goal is to avoid such dangerous driving conditions.

[0005] To enhance the driving safety of vehicle combinations, modern vehicle combinations can incorporate a large number of sensors and assistance systems, such as yaw sensors, anti-lock braking systems (ABS) for tractors and trailers, anti-slip regulation (ASR), and electronic tractor and trailer stability program (ESP).

[0006] A braking method for a vehicle combination is known from EP3727965B1, wherein the stability of the vehicle combination, in particular the angle between the tractor and the trailer, is monitored during the braking process.

[0007] A braking method for a vehicle combination is known from EP1427619B1, wherein the driving state of the vehicle combination is monitored, particularly the presence of an unstable driving state, so as to reduce the braking torque of the trailer when the unstable driving state is detected.

[0008] A braking method for a vehicle combination is known from DE102021121833A1, wherein braking force is distributed between the tractor and the trailer based on acquired driving state information, wherein the trailer ABS is preferably present.

[0009] All of these documents utilize a large number of systems and sensors, which increases complexity, probability of failure, and not only that, cost.

[0010] In the event of a malfunction, such as a trailer ABS failure, one strategy might be to brake the trailer with only a significantly reduced braking force to prevent unstable driving conditions. However, this reduces the total braking force of the vehicle combination, resulting in a longer braking distance, which could potentially lead to a dangerous driving situation. Summary of the Invention

[0011] Therefore, the object of the present invention is to provide a safe and efficient braking method for vehicle combinations, particularly for situations where trailer ABS is absent or not in operation.

[0012] According to the present invention, this task is solved by a braking method for a vehicle combination, wherein the vehicle combination consists of a tractor having a tractor braking system and at least one trailer having a trailer braking system, wherein the trailer braking system does not have a functioning trailer ABS, and the braking method includes the following steps: - Obtain braking request, - Control the output of initial braking pressure (p0) to the trailer braking system. - Obtain the actual longitudinal acceleration (aLong) and actual lateral acceleration (aLat) of the vehicle combination. - Determine the minimum coefficient of friction (MFC) by taking into account the actual longitudinal acceleration (aLong) and the actual lateral acceleration (aLat) obtained. - Determine the subsequent braking pressure (pn) for the trailer braking system based on the minimum coefficient of friction (MFC). - In coordination with the braking request, the subsequent braking pressure (pn) is output to the trailer braking system control.

[0013] Braking requests can be obtained, for example, based on the driver's intention via the brake pedal in the towing vehicle. Braking requests can also be obtained from assistance systems, such as emergency braking systems (AEB) or cruise control (ACC), as well as from autonomous systems.

[0014] The tractor braking system and the trailer braking system are preferably connected to each other in a pressure-transmitting and / or signal-transmitting manner, so that a braking request obtained in the tractor can be forwarded to the trailer.

[0015] The coefficient of friction is a measure of the maximum energy that can be transmitted between the wheels of a vehicle and the road.

[0016] The initial braking pressure (p0) is output to the trailer braking system to cause the operation of the trailer brakes and the braking of the trailer's braked wheels. The initial braking pressure (p0) is preferably selected such that it is high enough to cause (negative) actual longitudinal acceleration (aLong), but at the same time low enough to prevent the trailer's braked wheels from locking up, even on surfaces with low coefficients of friction, such as snow, ice, or rain.

[0017] The actual longitudinal acceleration (aLong) and actual lateral acceleration (aLat) are preferably obtained by an acceleration sensor or by sensors from which the actual longitudinal acceleration (aLong) and actual lateral acceleration (aLat) can be derived. The sensors are preferably components of the tractor unit.

[0018] When discussing increases in actual longitudinal acceleration (aLong) or actual lateral acceleration (aLat) below, only their absolute values ​​will be considered. The enhanced braking of the vehicle combination therefore corresponds specifically to an increase in (negative) actual longitudinal acceleration.

[0019] The minimum coefficient of friction (MFC) corresponds to the coefficient of friction that can be assumed to be at least between the wheel and the road surface.

[0020] The minimum coefficient of friction (MFC) is determined by taking into account the actual longitudinal acceleration aLong and the actual lateral acceleration aLat. For example, the minimum coefficient of friction (MFC) can be deduced from the existence of a negative actual longitudinal acceleration, i.e., deceleration.

[0021] At the start of the braking process, there is no knowledge of the current coefficient of friction between the wheels of the vehicle assembly and the road. After braking is completed with the initial braking pressure (p0), the minimum coefficient of friction (MFC) can be determined, and this minimum coefficient of friction (MFC) can be assumed for subsequent braking processes with subsequent braking pressures (pn). Because the minimum coefficient of friction (MFC) is known, the subsequent braking pressure pn can therefore be preferably increased without causing the braked wheels of the trailer to lock up and resulting in unstable and / or dangerous driving conditions.

[0022] The configuration of different subsequent braking pressures pn with different minimum coefficients of friction (MFC) can be performed, for example, according to predetermined configuration rules. The basic correlation is that the higher the minimum coefficient of friction (MFC), the higher the subsequent braking pressure (pn) can be selected.

[0023] The control output of subsequent braking pressure (pn) is coordinated with the braking request, meaning that braking is performed only as strongly as requested.

[0024] If, based on the determination of the minimum coefficient of friction (MFC), the possible subsequent braking pressure pn would result in a greater deceleration than specified in the braking request, then braking shall be performed only at the pressure required for the braking request.

[0025] If, based on the determination of the minimum coefficient of friction (MFC), the possible subsequent braking pressure (pn) is insufficient to fulfill the braking request, braking will still be performed only at the possible subsequent braking pressure (pn) to avoid unstable and / or critical driving conditions. The subsequent braking pressure pn thus provides an upper limit to the pressure output to the trailer braking system control.

[0026] Therefore, even in vehicle combinations without trailer ABS or with inactive trailer ABS, dangerous driving conditions caused by braking, such as trailer swaying, vehicle combination skidding, or bending, are avoided.

[0027] At the same time, a high total braking force of the vehicle combination is still achieved because the subsequent braking pressure pn that can be controlled and output to the trailer braking system achieves a significantly higher braking effect compared to the case where the trailer is braked only uniformly with a greatly reduced braking force.

[0028] Furthermore, according to the present invention, this task is accomplished by a control device for a braking system, wherein the control device is configured to execute the method according to the present invention.

[0029] The control device is preferably arranged in the tractor unit, for example, it may be the brake control device of the tractor unit, which is configured to perform the method according to the invention.

[0030] Furthermore, according to the invention, this task is accomplished by a vehicle combination comprising a tractor having a tractor braking system and at least one trailer having a trailer braking system, and a control device according to the invention for performing the method according to the invention.

[0031] The advantages mentioned above can be derived similarly.

[0032] According to a first embodiment of the method, the minimum coefficient of friction (MFC) is determined according to the following formula:

[0033] Where aLat is the actual lateral acceleration, aLong is the actual longitudinal acceleration, and g is the gravitational acceleration.

[0034] The sum of squares of the actual lateral acceleration aLat and the actual longitudinal acceleration aLong, normalized by gravity, has proven to be a good measure of the minimum coefficient of friction (MFC).

[0035] According to another embodiment of the method, the method is performed repeatedly, preferably continuously, wherein each subsequent braking pressure (pn) is regarded as the initial braking pressure (p0) of the next subsequent braking pressure (pn+1).

[0036] This leads to an iterative method. Typically, by controlling the output initial braking pressure (p0), only a small braking force is generated by the trailer braking system, which specifically results in only a small (negative) actual longitudinal acceleration (aLong). The actual longitudinal acceleration (aLong) is the input used to determine the minimum coefficient of friction (MFC). Subsequent braking pressures pn can then be higher than the initial braking pressure (p0) because the minimum coefficient of friction (MFC) is known. Higher subsequent braking pressures (pn) in turn cause a higher braking force generated by the trailer braking system. Higher braking force causes a higher (negative) actual longitudinal acceleration (aLong), which leads to a larger minimum coefficient of friction (MFC) thus determined. The next subsequent braking pressure (pn+1) can now be higher than the subsequent braking pressure (pn), which in turn leads to a further increase in braking force.

[0037] This method is preferably repeated or performed so frequently or continuously that the actual longitudinal acceleration aLong no longer increases further. Therefore, the minimum coefficient of friction (MFC) also no longer increases further, and the resulting subsequent braking pressure remains constant.

[0038] Furthermore, changes in road conditions can be detected through repeated, preferably continuous execution, and the subsequent braking pressure pn of the controlled output can then be adapted accordingly. For example, a smooth road section will cause a sharp drop in the (negative) actual longitudinal acceleration (aLong), which in turn results in a smaller minimum friction coefficient (MFC) and a correspondingly smaller next subsequent braking pressure (pn+1).

[0039] According to another embodiment of the method, the method further includes the step of: - Obtain load state information of the vehicle combination, wherein the load state information is additionally considered when determining the subsequent braking pressure pn and / or when controlling the output initial braking pressure (p0), preferably such that the subsequent braking pressure pn and / or the initial braking pressure (p0) for the trailer braking system increases with the increase of load state.

[0040] The coefficient of friction, and consequently the maximum transferable force between the wheels and the road in a vehicle assembly, is strongly related to gravity, i.e., to the load applied to the respective wheels. Subsequent braking pressure pn and / or initial braking pressure (p0) can be higher in a loaded vehicle condition than in an unloaded vehicle condition.

[0041] Preferably, for a specific minimum coefficient of friction (MFC) and a specific vehicle load condition, predetermined subsequent braking pressures pn and / or initial braking pressures (p0) are preset, specifically such that the subsequent braking pressures pn and / or initial braking pressures (p0) increase in the same way as the minimum coefficient of friction (MFC) and the load condition increases. The correlation between the load condition and the subsequent braking pressures (pn) and / or initial braking pressures (p0) to be controlled can, for example, extend linearly.

[0042] Load status information can be obtained via load sensors in various known ways, such as by means of suspension or airbag pressure monitoring, tire pressure monitoring, or force sensors.

[0043] According to another embodiment of the method, the method further includes the following steps: - Obtain curve radius information, wherein the curve radius information is additionally considered when determining the subsequent braking pressure (pn) and / or when controlling the output initial braking pressure (p0), preferably such that the subsequent braking pressure (pn) and / or the initial braking pressure (p0) for the trailer braking system decreases as the curve radius decreases.

[0044] The subsequent braking pressure (pn) and / or initial braking pressure (p0) for the trailer braking system decrease as the curve radius decreases. Preferably, this is understood to mean that the corresponding subsequent braking pressure (pn) and / or initial braking pressure (p0) are lower at smaller curve radii than at larger curve radii.

[0045] Based on the curve radius information, in particular, the braking strategy can be selected, specifically when there is a curve radius below the limit value (e.g., a curve radius of 300m or 200m), the curve braking strategy is selected, while the straight driving strategy is selected when the curve radius is above the limit value.

[0046] In cornering braking strategies, the focus can be on the stability of the vehicle combination, and specifically on controlling a lower initial braking pressure (p0). Conversely, in straight-line driving strategies, the focus can be on achieving higher braking force, and specifically on controlling a higher initial braking pressure (p0), which results in a shorter braking distance for the vehicle combination.

[0047] Curving radius information can be obtained in various known ways, such as by using steering angle sensors, yaw rate sensors, wheel speed sensors, especially by comparing the independent wheel speeds on each side, combining lateral acceleration sensors with the combined vehicle speed, or by using a camera system. Furthermore, cornering radius information can be obtained by combining yaw rate sensors with the combined vehicle speed, by comparing the actual yaw rate with a set yaw rate, and / or by comparing longitudinal and lateral acceleration.

[0048] According to an improved embodiment of the aforementioned method, the maximum braking pressure for the tractor braking system is limited based on the curve radius information, preferably such that the maximum braking pressure for the tractor braking system decreases as the curve radius decreases.

[0049] The description of the aforementioned embodiments applies similarly to the relationship between the reduction of the maximum braking pressure used in the tractor braking system and the reduction of the cornering radius.

[0050] This prevents the trailer from pushing too hard against the tractor. Especially on curves, such excessive pushing by the trailer against the tractor can lead to instability, such as buckling.

[0051] According to another embodiment of the method, the initial braking pressure p0 is controlled based on the curve radius information, and in particular, the output is controlled based on the minimum friction coefficient (MFC) related to the actual lateral acceleration aLat, which is preferably calculated according to the following formula:

[0052] Where aLat is the actual lateral acceleration, aLong is the actual longitudinal acceleration, and g is the gravitational acceleration.

[0053] When driving in a curve—which is assumed, for example, to have a curve radius below a threshold value (such as a 300m or 200m curve radius)—a real lateral acceleration (aLat) already exists based on the vehicle combination's speed. This real lateral acceleration (aLat)—which exists solely due to cornering, i.e., specifically without braking intervention—can be used to determine the minimum coefficient of friction (MFC).

[0054] Therefore, the minimum coefficient of friction (MFC) due to cornering can be taken into account when controlling the initial braking pressure (p0), and in particular, the initial braking pressure (p0) can be higher than when no information about the minimum coefficient of friction (MFC) is available. This results in a reduction in the braking distance of the vehicle combination.

[0055] According to another embodiment of the method, the initial braking pressure (p0) is controlled according to the following: - The speed (v) of the vehicle combination and / or - Temperature signal from an external temperature sensor and / or - Wiper signal from wiper sensor / rain sensor and / or - Map / navigation information data and / or - The previous minimum coefficient of friction (MFC) was determined.

[0056] The speed v of the vehicle combination significantly affects its behavior during braking, particularly its stability. Therefore, at higher speeds (v) of the vehicle combination, it may be necessary to control the output with a lower initial braking pressure (p0) than at lower speeds (v) of the vehicle combination.

[0057] External temperature can be an indicator of current road conditions. For example, when the external temperature is significantly above 0°C, the presence of thin ice cannot be directly assumed, which means that the controlled initial braking pressure (p0) can be higher than if there were a thin ice hazard.

[0058] Road conditions can be inferred to a limited extent using wiper sensors / rain sensors, especially regarding wet or dry roads. On dry roads, the controlled initial braking pressure (p0) can be higher than if the road is wet.

[0059] Map / navigation information data can include information about road surface type, such as gravel or asphalt. On asphalt, the controlled initial braking pressure (p0) can typically be higher than on gravel.

[0060] The previous braking process / previous minimum coefficient of friction (MFC) can also be used to some extent as an indicator of road conditions. If, for example, the previous braking process has indicated a high minimum coefficient of friction (MFC), then the initial braking pressure (p0) controlled during re-braking can ideally be even higher.

[0061] All or at least some of the sensor data and information described are already present in modern vehicle assemblies. Utilizing this data and information allows for a better adaptation of the controlled output initial braking pressure (p0) to actual road conditions, which in turn shortens the braking distance of the vehicle assembly.

[0062] According to another embodiment of the method, the subsequent braking pressure (pn) for the trailer braking system is determined by means of a predefined configuration rule based on minimum friction coefficient (MFC) and / or curve radius information and / or load state information of the vehicle combination, preferably at discrete intervals.

[0063] Configuration rules can be set, for example, in the form of data stored in the tractor, electronically accessible tables, or control curves. With the help of predefined configuration rules, the acquired and determined correlations can be processed quickly and reliably.

[0064] The choice of discrete intervals can, for example, specify that the determined minimum coefficient of friction (MFC) is categorized into a predetermined number of ranges or intervals. Similar intervals or ranges can also be set for curve radius information and / or load condition information. By setting discrete intervals, complexity can be reduced.

[0065] According to another embodiment of the method, the initial braking pressure (p0) and / or the subsequent braking pressure (pn) are applied to the trailer braking system in a time-limited, preferably pulsed manner.

[0066] In particular, by pulsed initial braking pressure (p0), the negative effects of wheel lock-up on the trailer can be reduced, as the wheels only lock up briefly. This may occur, for example, when the controlled output initial braking pressure (p0) is selected too high for the actual road conditions. Therefore, setting a time-limited, preferably pulsed initial braking pressure (p0) and / or subsequent braking pressure has similar advantages and disadvantages to intermittent braking.

[0067] According to another embodiment of the method, the method further includes the step of: - Obtain the connection force between the trailer and the tractor, wherein, from the point where the connection force exceeds a threshold value, the maximum braking pressure used for the tractor's braking system is limited, preferably to prevent bending.

[0068] By measuring the coupling force between the trailer and the tractor, it is possible to identify strong pushing of the tractor by the trailer. In response to exceeding the (negative) coupling force threshold, the maximum braking pressure used for the tractor's braking system is limited so that the (negative) coupling force, i.e., the pushing, no longer increases further, thereby preventing buckling and maintaining driving stability in particular.

[0069] The connection force can be obtained in a known manner, for example, by means of a force gauge in the tractor connection interface.

[0070] According to another embodiment of the method, the method further includes the step of: - Obtain the yaw rate of the tractor, preferably using a yaw rate sensor, wherein, from the point where the yaw rate exceeds a limit value, the maximum braking pressure used for the tractor braking system is limited, preferably to prevent buckling.

[0071] Exceeding the yaw rate limit indicates that, especially when cornering, the trailer is pushing the tractor so forcefully that there is a risk of the trailer pushing the rear of the tractor away laterally. This lateral push of the tractor's rear end corresponds to unstable driving conditions, particularly bending. This can be avoided by limiting the braking pressure of the tractor's braking system when the yaw rate limit is exceeded, thus maintaining driving stability.

[0072] In particular, the method according to the invention, or an embodiment thereof, can also be used for stabilization in the sense of yaw control, where the deceleration of the vehicle is not the primary objective, but rather maintaining driving stability. Attached Figure Description

[0073] The present invention will be further described below with reference to the accompanying drawings. Wherein: Figure 1 A schematic diagram of a vehicle assembly is shown, which is configured to perform a braking method in one embodiment. Figure 2 This illustrates the pressure distribution in existing braking methods. Figure 3 The pressure direction is shown in one embodiment of the braking method; Figure 4a shows an example of pressure distribution at the trailer braking system for discrete regions of minimum friction coefficient; Figure 4b An example is shown of the pressure trajectory at the trailer braking system for the minimum coefficient of friction region 3 with respect to the mass of the vehicle assembly; Figure 5a An example is shown showing the pressure distribution at the trailer braking system with respect to the curve radius; Figure 5b An example is shown showing the limitation on the pressure direction at the tractor braking system regarding the curve radius; Figure 6 The flowchart illustrates one implementation of the braking method. Detailed Implementation

[0074] Figure 1 A schematic diagram of vehicle assembly 1 is shown, which is configured to perform the braking method in one embodiment. Vehicle assembly 1 consists of a tractor 3 having a tractor braking system 7 and a trailer 5 having a trailer braking system 9. The tractor braking system 7 and the trailer braking system 9 together constitute the braking system 10 of vehicle assembly 1. Trailer 5 may also correspond to a semi-trailer.

[0075] The tractor braking system 7 consists of the brake 41a of the tractor 3 and the control device 37a of the tractor 3. The trailer braking system 9 consists of the brake 41b of the trailer 5 and the control device 37b of the trailer 5.

[0076] The control unit 37a of the tractor 3 and the control unit 37b of the trailer 5 are interconnected, for example by means of a trailer-CAN, as indicated by the double arrow between the control units 37a and 37b. The control units 37a and 37b can also be considered as the control unit 37 of the vehicle assembly.

[0077] It is also possible that only the control device 37a exists in the tractor unit 3, which is then considered the control device 37. This control device 37 then controls both the tractor braking system 7 and the trailer braking system 9, for example, via pneumatic and / or hydraulic connections.

[0078] Trailer 5 does not have a working trailer ABS. This includes both defective trailer ABS and trailer ABS that is not present.

[0079] For example, when communication between trailer 5 and tractor 3, particularly between control units 37a and 37b, is impossible, trailer 5 will not have a functioning trailer ABS. This may be the case when communication is interfered with, or when trailer 5 is not configured for communication. Another possibility for trailer 5 not having a functioning trailer ABS is that only one-way communication originating from trailer 5 is possible. Yet another possibility is that although bilateral communication between trailer 5 and tractor 3 is possible, for example via a CAN bus, trailer 5, particularly control unit 37b, reports a malfunction in the trailer ABS.

[0080] A braking request 11 is obtained via the brake pedal 21 and transmitted to the control device 37a. The braking request 11 can also be made by a control device not shown, such as an ACC control device. In particular, the braking request 11 does not necessarily have to be initiated by the driver, but can be made autonomously.

[0081] Furthermore, by means of the steering angle sensor 45, the curve radius information 17 related to the curve radius r obtained by the steering angle sensor 45 is transmitted to the control device 37a.

[0082] By means of the towing port 31 with a force gauge, the connecting force 33 between the trailer 5 and the tractor 3 is obtained and transmitted to the control device 37a.

[0083] The actual longitudinal acceleration aLong and the actual lateral acceleration aLat of the vehicle assembly are obtained by the acceleration sensor 39 and transmitted to the control device 37a.

[0084] Data from the external temperature sensor 23, data from the wiper sensor 47 / rain sensor 25, map / navigation information data 27, vehicle combination 1 speed v, yaw rate 35, and information about the previous braking process / previous minimum friction coefficient MFC determination 29 are also transmitted to the control unit 37a.

[0085] The load sensor 43 acquires the load status 15 of the trailer and transmits the load status information 13 to the control device 37b.

[0086] Through the communication connection between control devices 37a and 37b, all information transmitted to the respective control devices 37a and 37b is available in both control devices 37a and 37b. Alternatively, only one control device 37 may be provided, and all the aforementioned data and information may be available to that control device.

[0087] See below for reference Figure 6 To further explain, based on the acquired braking request 11, actual longitudinal acceleration aLong, actual lateral acceleration aLat, load status information 13, curve radius information 17, external temperature sensor 23, wiper sensor 47 / rain sensor 25, map / navigation information data 27, and previous braking process / previous minimum friction coefficient MFC determination 29, the initial braking pressure p0, subsequent braking pressure pn, and next subsequent braking pressure pn+1 are controlled and output to the brake 41b of the trailer 5.

[0088] Here, the subsequent braking pressure pn and the next subsequent braking pressure pn+1 are also related to the minimum friction coefficient MFC, which is determined by taking into account at least the actual longitudinal acceleration aLong and the actual lateral acceleration aLat.

[0089] Furthermore, based on the connecting force 33 and the yaw rate 35, the maximum braking pressure p3 is controlled to be output to the brake 41a of the tractor, thereby preventing bending in particular.

[0090] Figure 6 The flowchart of one embodiment of the braking method claimed is shown.

[0091] In step S1, a braking request 11 is obtained, which may be issued by the driver and / or (partially) the autonomous system.

[0092] In step S2, load state information 13 of vehicle assembly 1 is acquired, for example via a load sensor, by means of suspension or airbag pressure monitoring, tire pressure monitoring, or force sensor. Load state information 13 is considered when determining subsequent braking pressure pn and / or when controlling the initial braking pressure p0, preferably similar to that regarding… Figure 4b Explanation.

[0093] In step S3, corner radius information 17 is acquired, for example by means of a steering angle sensor 45. The corner radius information 17 is considered when determining the subsequent braking pressure pn and / or when controlling the initial braking pressure p0, preferably similar to the information regarding... Figure 5a Explanation.

[0094] In step S4, the initial braking pressure p0 is controlled to be output to the trailer braking system 9. In addition to the load status information 13 and the curve radius information 17, the initial braking pressure p0 is controlled to be output based on the vehicle combination speed v, the data of the external temperature sensor 23 (especially the external temperature), the data of the wiper sensor 47 / rain sensor 25 (especially the data on the presence of wet road surface), the map / navigation information data 27 (especially the information on ground / road surface conditions), and the information on the previous braking process / previous minimum friction coefficient MFC determination 29.

[0095] The more information available in step S4, the more accurately the initial braking pressure p0 can be adapted to the actual road conditions. Specifically, this means that the initial braking pressure p0 can be selected such that a certain braking power is achieved while still preventing unsafe driving conditions, such as those caused by wheel lock-up of trailer 5.

[0096] In step S5, the actual longitudinal acceleration aLong and the actual lateral acceleration aLat of vehicle assembly 1 are obtained, for example by means of acceleration sensor 39.

[0097] Subsequently, in step S6, the minimum friction coefficient MFC is determined based on the obtained actual longitudinal acceleration aLong and actual lateral acceleration aLat, preferably according to the following formula:

[0098] Where g is the acceleration due to gravity.

[0099] For the case where the curve radius information 17 indicates that the vehicle is traveling on a curve, the minimum friction coefficient MFC can be determined based on the actual lateral acceleration aLat generated by the curve travel. This minimum friction coefficient can also be taken into account when controlling the output of the initial braking pressure p0 to the trailer braking system 9.

[0100] In step S7, the subsequent braking pressure pn for the trailer braking system 9 is determined based on the minimum coefficient of friction (MFC). The configuration of different subsequent braking pressures pn for different minimum coefficients of friction (MFC) can be performed, for example, according to a predetermined configuration rule A within discrete intervals, as shown in Figure 4a. The basic correlation is that the higher the minimum coefficient of friction (MFC), the higher the subsequent braking pressure pn can be selected.

[0101] In step S8, the subsequent braking pressure pn is controlled and output to the trailer braking system 9 in coordination with the braking request 11, which means braking is performed only as strongly as requested.

[0102] Then, the process can jump back to step S5, so that steps S5 to S8 of the braking method are repeatedly or continuously executed, wherein each subsequent braking pressure pn is regarded as the initial braking pressure p0 of the next subsequent braking pressure pn+1.

[0103] This leads to an iterative method that approximates the maximum possible next subsequent braking pressure pn+1. The maximum possible next subsequent braking pressure pn+1 is reached when the actual longitudinal acceleration aLong, generated by the subsequent braking pressure pn (which is considered the initial braking pressure p0), no longer increases further. Therefore, the minimum coefficient of friction MFC also no longer increases further, and the resulting next subsequent braking pressure pn+1 remains constant at the maximum height.

[0104] Steps S9 and S10 may be performed in parallel or additionally during the repeated or continuous execution of steps S5 to S8.

[0105] In step S9, the connection force 33 between the trailer 5 and the tractor 3 is obtained, for example by means of a traction port 31 with a force gauge, wherein, from the point where the connection force limit value 34 is exceeded, the maximum braking pressure p3 for the tractor braking system 7 is limited, preferably to prevent bending.

[0106] Step S10 is performed in parallel or in coordination with step S9, as indicated by the double arrows between S9 and S10. In step S10, the yaw rate 35 of the tractor 3 is obtained, for example by means of a yaw rate sensor in the tractor, wherein, from the point where the yaw rate exceeds the limit value 36, the maximum braking pressure p3 for the tractor braking system 7 is limited, preferably to prevent buckling.

[0107] Figure 6 The advantages of the method shown are described in the reference section. Figure 2 and 3 Further explanation.

[0108] Figure 2 The diagram illustrates the pressure trajectory of a prior art braking method for a vehicle combination without a functioning trailer ABS, where the curves shown represent the pressure trajectory at the trailer braking system. The pressure trajectory p is shown on the y-axis, and the time trajectory t is shown on the x-axis.

[0109] To avoid compromising the driving safety and stability of the vehicle combination, the trailer is braked only with significantly reduced pressure at a height where the initial braking pressure p0 is currently present, in an intermittent braking manner. This ensures that the trailer wheels will not lock up at any time. However, this significantly reduces the total braking force of the vehicle combination, resulting in a longer braking distance. Furthermore, in the method according to the prior art, the initial braking pressure p0 cannot be selected based on additional information (e.g., cornering radius information 17, external temperature sensor 23, wiper sensor / rain sensor 25, map / navigation information data 27 and / or previous braking process / previous minimum friction coefficient MFC determination 29), causing it to generally behave lower.

[0110] Figure 3 This diagram illustrates the pressure distribution at point 9 of the trailer braking system, representing an embodiment of the braking method claimed in this invention. (Coordinate axis markings are shown.) Figure 2 The coordinate axis markings correspond accordingly. After the first pulse with an initial braking pressure p0, the pressure controlled and output to the trailer braking system 9 increases to a subsequent pressure pn. This subsequent pressure is higher because the minimum coefficient of friction (MFC) is determined by means of the method according to the invention, which ensures that the trailer wheels do not lock up under the higher controlled output subsequent braking pressure pn. This achieves higher braking power, which shortens the braking distance of the vehicle assembly 1 while ensuring driving stability.

[0111] exist Figure 3 In the example shown, the control output of the subsequent pressure pn is performed in a pulse manner, but this can also be performed continuously.

[0112] Figure 4a shows an example of the pressure distribution to the trailer braking system control output for discrete minimum friction coefficient (MFC) regions Z1 to Z4. Here, a pressure range is assigned to each specific MFC region Z1 to Z4.

[0113] For example, if a small minimum friction coefficient MFC is determined based on the obtained actual longitudinal acceleration aLong and actual lateral acceleration aLat, then a discrete minimum friction coefficient MFC region Z1 is assigned to the minimum friction coefficient, which has only one fixed pressure value.

[0114] In the case of a slightly higher minimum coefficient of friction (MFC), the value is assigned to region Z2, where different pressure values ​​can exist, for example, based on load condition information 13 (see...). Figure 4b ) and / or curve radius information 17 (see Figure 5a Different pressure values ​​exist for each.

[0115] The minimum friction coefficient MFC regions Z3 and Z4 also have a range of possible pressure values. In this example, only pulsed pressure values ​​are controlled within the minimum friction coefficient MFC regions Z1 to Z3. Within the minimum friction coefficient MFC region Z4, continuous pressure values ​​are controlled at a corresponding height.

[0116] Within the minimum friction coefficient (MFC) region Z4, the minimum friction coefficient (MFC), determined by the actual longitudinal acceleration aLong and the actual lateral acceleration aLat, is so high that wheel lock-up of trailer 5 can be reliably eliminated, thereby controlling the output of continuous high braking pressure.

[0117] Figure 4b An example is shown of the direction of pressure output to trailer braking system 9 with respect to the mass m of the vehicle combination within the boundary of the minimum friction coefficient region 3.

[0118] The coefficient of friction, and thus the maximum transmittable force between the wheels and the road in vehicle assembly 1, is strongly related to gravity, i.e., to the load applied to the respective wheels. Under loaded vehicle conditions, subsequent braking pressure pn can be higher than under unloaded vehicle conditions. The same applies to the initial braking pressure p0.

[0119] In this example, the determined minimum coefficient of friction is assigned to the minimum coefficient of friction region 3, where there is a medium mass such that the subsequent braking pressure ultimately controlled to the trailer braking system 9 is at a height of pn.

[0120] Figure 5a An example is shown showing the direction of pressure output to the trailer braking system 9 regarding the curve radius information 17, specifically the curve radius r. In this example, curve radii r greater than 300m are considered as straight-line travel.

[0121] When driving on curves, vehicle assembly 1 is more prone to unstable driving conditions, such as trailer swaying, vehicle assembly sideslip, or bending. Therefore, the subsequent braking pressure pn is controlled and output based on the curve radius information 17.

[0122] For example, the basic mechanism is similar to Figure 4b As stated above. Within the region of minimum friction coefficient, it can be based on... Figure 5a Determine the subsequent braking pressure pn to be controlled and output to the trailer braking system 9. For example, when the curve radius r is 225m, control the output of the subsequent braking pressure pn within the relevant minimum friction coefficient region. The same applies to the initial braking pressure p0.

[0123] Figure 5b An example is shown of the percentage limit of the pressure direction of the control output of the opposing tractor braking system 7 with respect to the curve radius r.

[0124] Because the subsequent braking pressure pn output to the trailer braking system 9, based on the determined minimum coefficient of friction (MFC), typically results in a lower braking power for the trailer braking system 9 compared to the tractor braking system 7, the trailer 5 pushes against the tractor 7. The smaller the curve radius r, the greater the risk of buckling if the trailer 5 pushes against the tractor 7.

[0125] To prevent excessive pushing and especially the danger of bending in curves, the maximum braking pressure p3 of the tractor braking system 7 is limited according to the curve radius r.

[0126] The smaller the curve radius r, the higher the percentage limit of the maximum braking pressure p3 of the tractor braking system 7. In this example, the curve radius is 225m, which makes the maximum braking pressure p3 of the tractor braking system 7 according to... Figure 5b The curve shown is restricted.

[0127] The corresponding curves regarding the correlation between the pressure reduction of the tractor braking system 9 and the yaw rate or coupling force can have similar or related trends.

[0128] This provides a safe and efficient braking method for vehicle combination 1, particularly for situations where trailer ABS is absent or not in operation.

[0129] Reference numerals (part of the specification)

[0130] 1. Vehicle Combination

[0131] 3 tractor units

[0132] 5 trailers

[0133] 7. Tractor Braking System

[0134] 9. Trailer braking system

[0135] 10. Braking system of vehicle assembly

[0136] 11 Braking Request

[0137] 13 Load Status Information

[0138] 15 Load Condition

[0139] 17. Curve radius information

[0140] 21 Brake Pedal

[0141] 23 External temperature sensor

[0142] 25. Wiper sensor / Rain sensor

[0143] 27 Map / Navigation Information Data

[0144] 29. Previous braking process / Previous minimum coefficient of friction (MFC)

[0145] 31 Traction port with force gauge

[0146] 33 Connecting Force

[0147] 34. Connection Force Limit Value

[0148] 35 yaw rate

[0149] 36. Yaw angular velocity limit value

[0150] 37 Control device

[0151] 37a Tractor control device

[0152] 37b Trailer control device

[0153] 39 Accelerometer

[0154] 41a Tractor brake

[0155] 41b Trailer brake

[0156] 43 Load Sensor

[0157] 45 Steering angle sensor

[0158] 47 Wiper Sensor

[0159] p0 Initial braking pressure

[0160] pn subsequent braking pressure

[0161] pn+1 Next subsequent braking pressure

[0162] p3 Maximum braking pressure of the tractor braking system

[0163] MFC Minimum Coefficient of Friction

[0164] aLong Actual longitudinal acceleration

[0165] aLat actual lateral acceleration

[0166] v The speed of the vehicle combination

[0167] r Curve radius

[0168] A Configuration Rules

[0169] Z1 MFC Region 1

[0170] Z2 MFC Region 2

[0171] Z3 MFC Region 3

[0172] Z4 MFC Region 4

[0173] Δt is the duration of the pressure pulse.

[0174] D1 Temperature Signal

[0175] D2 Wiper Signal

[0176] D3 Rain Sensor Signal

Claims

1. A braking method for a vehicle assembly (1), wherein, The vehicle assembly (1) consists of a tractor (3) and at least one trailer (5), the tractor having a tractor braking system (7) and the trailer having a trailer braking system (9), wherein the trailer braking system (9) does not have a working trailer ABS, and the braking method includes the following steps: - Obtain braking request (11) (S1). - Control the output of initial braking pressure (p0) to the trailer braking system (9) (S4). - Obtain the actual longitudinal acceleration (aLong) and actual lateral acceleration (aLat) of the vehicle combination (1) (S5). - Determine the minimum coefficient of friction (MFC) (S6) by taking into account the actual longitudinal acceleration (aLong) and the actual lateral acceleration (aLat) obtained. - Determine the subsequent braking pressure (pn) for the trailer braking system (9) based on the minimum coefficient of friction (MFC) (S7). - The subsequent braking pressure (pn) is controlled and output to the trailer braking system (9) in coordination with the braking request (11) (S8).

2. The braking method according to claim 1, characterized in that, The method is performed repeatedly, preferably continuously, wherein each subsequent braking pressure (pn) is regarded as the initial braking pressure (p0) of the next subsequent braking pressure (pn+1).

3. The braking method according to any one of the preceding claims, characterized in that, The minimum coefficient of friction (MFC) is determined according to the following formula: Where aLat is the actual lateral acceleration, aLong is the actual longitudinal acceleration, and g is the gravitational acceleration.

4. The braking method according to claim 2 further includes the following steps: - Obtain the load status information of the vehicle combination (13) (S2). in, When determining the subsequent braking pressure (pn) and / or when controlling the output of the initial braking pressure (p0), the load state information (13) is additionally considered, preferably such that the subsequent braking pressure (pn) and / or the initial braking pressure (p0) for the trailer braking system (9) increase with the increase of the load state (15).

5. The braking method according to any one of the preceding claims further includes the following steps: - Obtain curve radius information (17) (S3). in, When determining the subsequent braking pressure (pn) and / or when controlling the output of the initial braking pressure (p0), the cornering radius information (17) is additionally considered, preferably such that the subsequent braking pressure (pn) and / or the initial braking pressure (p0) for the trailer braking system (9) decrease as the cornering radius (r) decreases.

6. The braking method according to claim 5, characterized in that, The maximum braking pressure (p3) for the tractor braking system (7) is limited according to the curve radius information (17), preferably such that the maximum braking pressure (p3) for the tractor braking system (7) decreases as the curve radius (r) decreases.

7. The braking method according to any one of the preceding claims, characterized in that, The output of the initial braking pressure (p0) is controlled based on the curve radius information (17), and in particular based on the minimum coefficient of friction (MFC) related to the actual lateral acceleration (aLat).

8. The braking method according to any one of the preceding claims, characterized in that, The step (S4) of controlling the output of the initial braking pressure (p0) is based on - The speed (v) of the vehicle combination (1) and / or - Temperature signal (D1) from external temperature sensor (23) and / or - Wiper signal (D2) from wiper sensor (47) and / or - Rain sensor signal (D3) from rain sensor (25) and / or - Map / navigation information data (27) and / or - The previous minimum coefficient of friction (MFC) was determined (29) To control the output.

9. The braking method according to any one of the preceding claims, characterized in that, The determination of the subsequent braking pressure (pn) for the trailer braking system (9) is carried out by means of a predefined configuration rule (A) based on the minimum friction coefficient (MFC) and / or the cornering radius information (17) and / or the load state information (13) of the vehicle combination (1), preferably at discrete intervals.

10. The braking method according to any one of the preceding claims, characterized in that, The initial braking pressure (p0) and / or the subsequent braking pressure (pn) are applied to the trailer braking system (9) in a time-limited (Δt) manner, preferably in a pulse manner.

11. The braking method according to any one of the preceding claims further includes the step of: - Obtain the connection force (33) between the trailer (5) and the tractor (3) (S9). in, From the point where the connection force limit value (34) is exceeded, the maximum braking pressure (p3) for the tractor braking system (7) is limited, preferably to prevent bending.

12. The braking method according to any one of the preceding claims further comprises the following steps: - Obtain the yaw rate (35) of the tractor (3) (S10). in, From the point where the yaw rate exceeds the limit value (36), the maximum braking pressure (p3) for the tractor braking system (7) is limited, preferably to prevent bending.

13. A control device (37) for a braking system (10) of a vehicle assembly (1), wherein, The control device (37) is configured to perform the method according to any one of claims 1 to 12.

14. A vehicle assembly (1) comprising a tractor (3) having a tractor braking system (7) and at least one trailer (5) having a trailer braking system (9), and a control device (37) according to claim 13 for performing the method according to any one of claims 1 to 12.

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