Trailer brake control

Abstract

A method for controlling a trailer brake (42) includes determining an inclination (83) of a ground (87) on which a trailer (20) is located, determining a first set value (SP1) in dependence of the inclination (83), determining a current trailer brake demand provided for applying the trailer brake (42), determining a second set value (SP2) in dependence of the current trailer brake demand, determining a maximum set value (SPmax) out of the first set value and the second set value, and controlling a trailer brake (42) of the trailer (20) for generating a brake force.

Description

TRAILER BRAKE CONTROLFIELD

[0001] The present disclosure relates generally to a trailer brake system configured for controlling a trailer brake of a trailer of a vehicle combination.BACKGROUND

[0002] Avehicle combination including a vehicle and a trailer may be used forthe transportation of goods and materials. Each, the vehicle and the trailer of the vehicle combination may be equipped with a separate brake system for individual braking of the vehicle and the trailer. A trailer brake of the trailer may be activated to achieve better brake performance of the vehicle combination and to reduce a pushing force of the trailer (negative coupling force between the vehicle and the trailer). When the pushing force applied by the trailer to the towing vehicle, also referred to as coupling force, exceeds a certain level, overrunning or jack-knifing of the trailer may occur. The coupling force is mainly generated by the trailer weight and the inertia during breaking. An excessive coupling force may effect that the towing vehicle is excessively pushed and the vehicle's track guiding forces are overcome. This results in a yaw moment and hence movement about the vertical vehicle axis of the towing vehicle which cannot be overcome by the wheel-ground contact. The towing vehicle then starts to skid.

[0003] Patent application US 2023 / 0009316 A1 , entitled “Trailer Brake Control System”, published on January 12, 2023, discloses a vehicle combination with a vehicle and a trailer. The vehicle combination is equipped with a service brake system to reduce the speed of the vehicle and a trailer brake system to reduce the speed of the trailer. The operator of the vehicle combination may manually activate the service brake system, for example by depressing a brake pedal. The manual operation may also activate the trailer brake system. Moreover, the trailer brake system may be actuated automatically by a control unit independent of the direct operator activation, for example when a pushing force of the trailer has been detected. This automated braking control is also termed as electronic trailer braking or trailer brake assist (TBA) functionality.BRIEF SUMMARY

[0004] It would be beneficial to provide a trailer brake control for a vehicle combination to improve the performance of trailer braking. Thus, there is provided a method for controlling a trailer brake according to a first aspect of the invention as claimed by claims 1 to 16, a control unit according to a second aspect of the invention as claimed by claim 17 and a vehicle combination according to a third aspect of the invention as claimed by claim 18.

[0005] The vehicle combination may comprise a towing vehicle, a trailer coupled to the towing vehicle, and a control unit, wherein the trailer comprises a trailer brake system with at least one trailer brake.

[0006] The towing vehicle may be of any type, as for example an agricultural vehicle such as a tractor, a harvester, a combine or a sprayer. The vehicle may comprise separate vehicle brakes and may be a part of the vehicle combination. The vehicle brakes may be applied when a service brake actuation device is operated by an operator.

[0007] The trailer may be used to transport any agricultural material, such as crop for example. The trailer may also be part of the vehicle combination when coupled to a coupling system of the vehicle, for instance by means of a drawbar. The coupling system may comprise a hitch for raising or lowering the coupling system. When the trailer is towed by the towing vehicle, wheels of the trailer are set in rotational movement. The at least one trailer brake may be attached to the trailer and may apply a brake force to reduce a rotational speed of the wheels of the trailer. The wheels of the trailer may be braked by separate trailer brakes. Each trailer brake may comprise an (electro-)hydraulic brake actuator, an (electro-)pneumatic brake actuator or an electromechanical brake actuator. The trailer brake system may adjust the actuation pressure for generating the brake force in accordance with a trailer brake demand. The trailer brake demand may be generated automatically by the control unit or by a (manual) operation of a trailer brake actuation device. For example, the trailer brake actuation device may be a foot operable brake pedal or a hand operable input element such as a deflectable joystick. The foot operable brake pedal may also be used asservice brake actuation device to simultaneously apply the vehicle brakes and the trailer brakes. The hand operable input element may be an input element for an independent manual operation of the trailer brake system as disclosed in patent application GB 2405473.6, entitled “Manual brake controlling of a trailer brake”, filed on April 18, 2024. Depending on a grade of deflection of the brake pedal or the hand operable input element, the control unit may adjust the trailer brake demand to be sent to the trailer brake system so that the brake force of the trailer brakes can be variably adjusted by an operator according to his (manual) operation of the trailer brake actuation device.

[0008] The control unit is configured to carry out at least one method for controlling the trailer brake. While the at least one method is executed by the control unit, the control unit may receive different signal inputs, process the signal inputs and automatically generate the trailer brake signal in response thereof. The control unit may send the trailer brake signal to the trailer brake system to apply the trailer brakes.

[0009] The method for controlling the trailer brake comprises steps for determining an inclination of a ground on which a trailer is located, determining a first set value in dependence of the inclination, determining a current trailer brake demand provided for applying the trailer brake, determining a second set value in dependence of the current trailer brake demand, determining a maximum set value out of the first set value and the second set value, and controlling the trailer brake of the trailer for generating a brake force.

[0010] The first set value, the second set value and / or the maximum set value may be a pressure set value or a force set value for controlling the brake force of the trailer brakes accordingly. The control unit may receive the inclination of the ground on which the trailer is located from an inclination sensor. The inclination sensor may be integrated in the vehicle combination, for example in the vehicle or in the trailer. Moreover, the control unit may receive the inclination from an inertial navigation system (INS) of the vehicle. The inclination may be determined in respect of a horizontal plane. The inclination may also consider the driving direction of the vehicle combination. The inclination may be a positive value if the vehicle combination drives uphill and a negative value if the vehicle combination drives downhill. The more negative the inclination is, the stiffer is the ground the vehicle combination is moving on downhilland the greater may be the brake force of the trailer brakes required to avoid overrunning or pushing of the trailer. Thus, the first set value is increased by the control unit with a more negative inclination to provide a sufficient brake force for braking the downhill moving trailer. The current trailer brake demand may depend on an automatic brake demand generated by the control unit or a manual brake demand generated by the operator (e. g. by operation of the trailer brake actuation device) whichever brake demand is the greater. In case of an automatically generated trailer brake demand, the current trailer brake demand may correspond with a pushing force of the trailer. The current trailer brake demand may be increased more by the control unit, the more the trailer pushes the towing vehicle. But the operator may nevertheless demand a trailer brake demand being greater than the automatically generated trailer brake demand. Hence, the second set value may correspond with the automatically generated trailer brake demand if the automatically generated trailer brake demand is greaterthan the operator demanded trailer brake demand and vice versa to provide a sufficient trailer brake force according to the higher trailer brake demand. The control unit may compare the first set value with the second set value to determine the greater set value as maximum set value (e. g. maximum set pressure). Then, the control unit may control the trailer brake system to apply the trailer brakes with a brake force in accordance with the maximum set value.

[0011] The method may comprise determining the current trailer brake demand as an average of trailer brake demand.

[0012] The control unit may calculate the average current trailer brake demand based on recorded trailer brake demands determined within a predefined time period. The recoded trailer brake demands may have been stored in a memory of the control unit. The average current trailer brake demand may be less volatile than the recorded trailer brake demands. Hence, the determination of the second set values based on average trailer brake demands may provide more stable values. In addition, a smoother application of the trailer brakes may be achieved.

[0013] The method may comprise determining the current trailer brake demand by a sensor.

[0014] The current trailer brake demand may be determined based on an appropriate sensor, such as a voltage sensorfor measuring an electrical signal or a pressure sensorfor measuring a fluidic signal, such as a hydraulic or pneumatic signal. For example, the sensor may be integrated in a fluidic signal line between the vehicle and the trailer or in a fluidic interface for connectingthe fluidic signal line. The fluidic interface may be part of the vehicle or part of the trailer. The fluidic signal line may transfer a (hydraulic or pneumatic) fluid with a pressure value in accordance with the current trailer brake demand. The control unit may receive the sensor signals from the sensor. Hence, the control unit may also process fluidic brake signals in addition to electric brake signals, for example to determine the average current trailer brake demand or the maximum set value.

[0015] The method may comprise determining a pushing force of the trailer based on a calculation of a coupling force Fcbetween the vehicle and the trailer.

[0016] The pushing force of the trailer may correspond with the coupling force Fc. The coupling force Fcmay be calculated based on a tractive force of the vehicle FTRV and / or a tractive force of the vehicle combination (including the towing vehicle and the trailer) FTRC as disclosed in patent application WO 2022 / 157571 A1 , entitled “Trailer Brake Control System”, published on July 28, 2022, which is hereby incorporated by reference in its entirety. Hence, the pushing force of the trailer may be considered by the control unit for determining or adjusting the current trailer brake demand.

[0017] The method may comprise determining whether a trailer braking assist (TBA) functionality is activated.

[0018] The trailer braking assist (TBA) functionality may be stored in a memory of the control unit. When activated, the control unit may automatically detect excessive pushing of the trailer (e. g. when driving downhill) causing an overrunning or jack-knifing condition and may automatically apply the trailer brakes in response thereof to reduce pushing of the trailer in order to avoid overrunning or jack-knifing of the trailer. The trailer braking assist (TBA) functionality may also adjust the brake force of the trailer brakes when the trailer brakes are applied by an (insufficient) manually generated trailer brake demand, e. g. by operation of the trailer brake actuation device. The trailer braking assist (TBA) functionality is disclosed in applicant's patent application US 2023 / 0009316 A1 , entitled “Trailer Brake Control System”, published on January 12, 2023, which is hereby incorporated by reference in its entirety. Hence, the control unit may improve the braking performance of the trailer braking assist (TBA) functionality.

[0019] The method may comprise providing a first brake signal and / or a second brake signal in dependence of the maximum set value.

[0020] The first and the second brake signal may correspond with the maximum set value so that the trailer brakes may apply a brake force in accordance with the maximum set value. The first brake signal may be provided by the control unit in dependence of a specific operation of the human machine interface (HMI) of the vehicle combination, as for example the trailer brake actuation device. The second brake signal may be provided by the control unit in dependence of a specific driving condition. For example, the second brake signal may be provided if the vehicle combination moves along a curve. Hence, the first brake signal may be provided if a first condition is fulfilled and the second brake signal may be provided if a second condition is fulfilled.

[0021] The first brake signal and / orthe second brake signal may be provided if the service brake actuation device has been released.

[0022] As mentioned above, the service brake actuation device may be a brake pedal that may be used to apply the vehicle brakes and the trailer brakes simultaneously. The service brake actuation device may be released when the operator removes his foot from the brake pedal. The release of the service brake actuation device may be a requirement of the first condition to provide the first brake signal. The second brake signal may be provided if both the release of the service brake actuation device and the second condition are fulfilled. When the service brake actuation device has been released, the trailer brakes may be released later than the vehicle brakes due to the first brake signal. Hence, a smoother transition of the brakes of the vehicle combination may be realized to provide an improved driving comfort of the vehicle combination.

[0023] The first brake signal and / or the second brake signal may be provided if the inclination of the ground is below an inclination threshold value.

[0024] The inclination of the ground may be determined as mentioned above. The inclination threshold value may be equal or less than -4° for example. The detection of an inclination belowthe inclination threshold may be an additional requirement of the first condition to provide the first brake signal as well as of the second condition to provide the second brake signal. The stiffer the inclination of the ground is, the grater may be the coupling force or the pushing force of the trailer. Thus, an inclinationdependent activation of the trailer brakes based on the first orthe second brake signal may reduce the pushing force of the trailer.

[0025] The inclination threshold value may be negative.

[0026] Hence, the first or the second brake signal may be used when the vehicle combination, or more specifically the trailer, is moving downhill only. But the trailer brakes may not be applied when the vehicle combination is moving uphill to avoid that applied trailer brakes reduce the tractive force of the vehicle to tow the trailer.

[0027] The first brake signal may be provided as long as a timer may be active.

[0028] The timer may be activated when a requirement of the first condition for providing the first brake force is fulfilled, for example if the service brake actuation device has been released. The timer may be implemented as a countdown to detect the elapse time of one second for example. Alternatively, the elapse time may be of any other value. As long as the elapse time has not been elapsed, the timer may be active. If the elapse time has been elapsed, the timer may stop and get inactive. Then, the first brake signal may be set from the maximum set value to zero (cancelled) in order to open the trailer brakes. Thus, in response to the release of the service brake actuation device, the trailer brakes may be opened shortly after the release of the vehicle brakes due to the time delay of the timer.

[0029] The method may comprise determining a steering angle of the towing vehicle, wherein the second brake signal may be provided if the steering angle is greater than a first steering threshold value.

[0030] If the steering angle is greater than the first steering threshold value, a requirement of the second condition to provide the second brake signal may be fulfilled. The first brake signal may be provided if both the steering angle is greater than the first steering threshold value and the first condition are fulfilled. The first steering angle threshold may be any value within a range between 50° and 70°, as for example 60°. Since a movement of the vehicle combination along a curve may increase the risk of overrunning or jackknifing of the trailer, the risk may be mitigated when the trailer brakes may be applied accordingto the second brake signal.

[0031] The method may comprise determining a calculated summation of the current trailer brake demands, settingthe second brake signal to zero if the calculatedsummation of the current trailer brake demands is below a current trailer brake demand threshold.

[0032] Hence, excessive braking of the trailer brakes due to an activation based on the second brake signal may be avoided.

[0033] The method may comprise determining a distance driven by the towing vehicle, and setting the second brake signal to zero if the distance is greater than the length of the towing vehicle.

[0034] Again, excessive braking of the trailer brakes due to an activation based on the second brake signal may be avoided.

[0035] The method may comprise setting the second brake signal to zero if the steering angle may be smaller than a second steering threshold value being smaller than the first steering threshold value.

[0036] The second steering angle threshold may be any value within a range between 30° and 50°, as for example 40°. As long as the steering angle is greater than the second steering threshold value, the second brake signal may be provided by the control unit to ensure activation of the trailer brakes according to the maximum set value to avoid overrunning or jackknifing of the trailer. When the steering angle is smaller than the second steering threshold value, the risk of overrunning or jackknifing of the trailer may be small enough to release the trailer brakes again.

[0037] The method may comprise determining a maximum brake signal out of the first brake signal and the second brake signal, and controlling the trailer brake of the trailer in accordance with the maximum brake signal.

[0038] As mentioned above, both the first and the second brake signal may correspond to a maximum set value determined accordingto the same algorithm. But the first brake signal and the second brake signal may be determined at different time points depending on when the requirements of the first condition or the second condition have been fulfilled. So, the maximum set value determined at a time point when the first condition has been fulfilled may be different to the maximum set value determined at a time point when the second condition has been fulfilled. Hence, the control unit may determine the maximum brake signal out of the first brake signal and the second brake signal to ensure that the trailer brakes provide a sufficient brake force accordingto the maximum brake signal.

[0039] The method may comprise providing a basic brake signal based on an application of the service brake actuation device, an application of the trailer brake actuation device and / or in response to a push condition of the trailer, determining a maximum brake signal out of the basic brake signal, the first brake signal and / or the second brake signal, and controlling the trailer brake of the trailer in accordance with the maximum brake signal.

[0040] The push condition of the trailer may be detected by the trailer braking assist (TBA) functionality of the control unit as mentioned above. The trailer braking assist (TBA) functionality may automatically provide the basic brake signal without any application of the service brake actuation device or the trailer brake actuation device, or adjust a basic brake signal provided by an application of the service brake actuation device or the trailer brake actuation device to ensure a sufficient basic brake signal for avoiding pushing of the trailer. The control unit may compare the basic brake signal, the first brake signal and the second brake signal with each other to determine the maximum brake signal out of these three brake signals. I. e, the basic brake signal may be compared with the first and / or second brake signal, and the first brake signal may be compared with the second brake signal. Hence, the control unit may determine the maximum brake signal irrespectively whether an application of the trailer brakes is demanded by the operator or automatically by the control unit. Hence, it is ensured that the trailer brakes provide a sufficient brake force according to the maximum brake signal.

[0041] As disclosed above, the control unit is configured to execute different actions. Each action may be implemented as one or more method steps of the method executable by the control unit. Hence, each action for which the control unit is configured to execute may be defined as a method step.

[0042] Within the scope of this application, it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Several aspects of the invention will now be described, byway of example only, with reference to the accompanying drawings, in which:

[0044] FIG. 1 illustrates a vehicle combination with a vehicle and a trailer each equipped with a brake.

[0045] FIG. 2 illustrates a simplified view of a control unit.

[0046] FIG. 3 illustrates a flow diagram for a first method M1 .

[0047] FIG. 4 illustrates a flow diagram for a second method M2.

[0048] FIG. 5 illustrates a flow diagram for a third method M3.

[0049] FIG. 6 illustrates an aspect of the subject matter in accordance with one embodiment.DETAILED DESCRIPTION

[0050] FIG. 1 shows a vehicle combination 1 with a vehicle 10 and a trailer 20. Such a vehicle combination is disclosed in patent application US 2023 / 0009316 A1 , entitled “Trailer Brake Control System”, published on January 12, 2023, which is hereby incorporated by reference in its entirety. The vehicle 10 may be an agricultural vehicle such as a tractor, a harvester, a combine, a sprayer or of any other type such as a truck. The trailer 20 may be detachably connected to a coupling system 11 of the vehicle 10 via a drawbar 21 and may be used for an agricultural operation such as storing crop. A prime mover of the vehicle 10, such as an internal combustion engine, may generate a tractive force to drive the vehicle 10 in a forward driving direction 85 as indicated by an arrow and to tow the trailer 20. The vehicle combination 1 moves downwards on an inclined ground 87 with a negative inclination 83 in respect of a horizontal plane. The inclination 83 may be determined by an inclination sensor 89 of the vehicle 10 and / or an inertial navigation system 4 (INS) of the vehicle 10. The inclination signal is sent to a control unit 80 exemplarily integrated in the vehicle 10.

[0051] The inertial navigation system 4 provides position and time signals for determining an absolute position of the vehicle combination 1 at a specific point oftime. The inertial navigation system 4 may comprise an inertial measurement unit (IMU) with a gyroscope for determining a vehicle speed, a vehicle acceleration and / or inclination 83 of the vehicle 10. The inertial navigation system 4 may also comprise a global navigation satellite system (GNSS) receiver receiving position and time signals from a GNSS such as GPS or Galileo. The IMU may provide additional orientation information about the orientation and movement of the vehicle combination 1 for improving the accuracy of the position estimation and the reference points of the GNSS receiver. Based on received position and time signals, the vehicle combination 1 can move autonomously along a travel path.

[0052] Due to the negative inclination 83, the trailer 20 is accelerated by gravity and induces a force at the coupling system 11 pushing the vehicle 10 down the inclined ground 87. 1, e., the negative inclination 83 causes an overrunning of the trailer 20. The coupling system 11 comprises a force sensor 81 to determine a force representative for the pushing force at the coupling system 11 pushingthe vehicle 10, i. e., the coupling force between the vehicle 10 and the trailer 20. The force sensor 81 may alternatively implemented as a pressure sensor for measuring a pressure between the vehicle 10 and the trailer 20, for example. Moreover, the control unit 80 provides a trailer brake assist (TBA) functionality as disclosed in US 2023 / 0009316 A1 mentioned above to detect a push condition. The pushing force of the trailer 20 may be calculated by the control unit 80 as a coupling force Fcbased on a tractive force of the vehicle FTRV and a tractive force of the vehicle combination FTRC as disclosed in patent application WO 2022 / 157571 A1 , entitled “Trailer Brake Control System”, published on July 28, 2022, which is hereby incorporated by reference in its entirety, without any sensor values of the force sensor 81 .

[0053] The vehicle 10 comprises front and rear wheels 15, 16. The front wheels 15 can be braked by a vehicle brake 18 that can be used as a service brake and / or as a parking brake. Analogously, the rear wheels 16 can be equipped with brakes for service or parking braking. The vehicle 10 is also equipped with a steering system to steer the front wheels 15. The steering angle of the front wheels 15 is measured by a steering angle sensor 91 providing a corresponding steering angle signal to the control unit 80.

[0054] The trailer 20 comprises wheels 25 that can be braked by trailer brakes 42. To brake the trailer 20, a trailer brake system 30 of the vehicle 10 including a trailer brakevalve 30a and / or further valve arrangements is provided to forward a fluidic brake signal (e. g. a pneumatic or hydraulic brake signal) to the trailer 20 via a standardized trailer control coupling 31 . The further trailer supply coupling 32 is provided for air or oil supply to trailer brakes 42 of the trailer 20. Both trailer couplings 31 , 32 are used to connect at least the trailer brake system 30 to a brake system 40 of the trailer 20. The brake system 40 serves to actuate the trailer brakes 42 of the wheels 25 of the trailer 20. The trailer brake system 30 is connected with the control unit 80 providing an automatic application of the trailer brakes 42.

[0055] The vehicle 10 also comprises a human-machine interface with several input elements as for example a speed foot paddle 71 and / or a drive lever 72 to receive the operators input forvehicle speed orvehicle acceleration, an acceleration rate input 73 to adjust the degree of acceleration / deceleration when moving the drive lever 72, a steering wheel to steer the front wheels 15 of the vehicle 10, a clutch pedal 74 to disconnect a transmission 50 from the prime mover as for example an internal combustion engine, and a HMI terminal 75 to enable the operator to input or display various parameters in connection with the vehicle 10, the trailer 20 and / or the vehicle combination 1 . The trailer brake assist (TBA) functionality can be switched on (active) or off (inactive), for example by means of a switch or key of the human-machine interface. When the trailer brake assist (TBA) functionality is activated, the control unit 80 activates the trailer brake 42 automatically if the pushing force of the trailer 20 (or coupling force Fc) exceeds a threshold value to reduce the pushing force.

[0056] The human-machine interface also comprises a service brake actuation device 76 to generate a service brake demand according to the operators input for actuating the vehicle brake 18 of the vehicle 10 for service braking and a park brake switch or a park brake lever 1~t to receive the operators input to activate the vehicle brake 18 for park braking. The service brake actuation device 76 may be a foot-operated device such as a brake pedal, a hand-operated device such as a joystick or a combination of both. When the operator of the vehicle combination 1 activates the service brake with the service brake actuation device 76, the service brake demand is generated. The service brake demand is transferred to a vehicle brake system 79 to generate an actuation pressure for the vehicle brake 18 according to the grade of actuation of the service brake actuation device 76. In case of a fluidic vehicle brake system 79, the servicebrake demand is directly forwarded by a pressurized fluid such as air or oil to the vehicle brake system 79 to generate the actuation pressure. In case of an electrical vehicle brake system 79, such as an electro-mechanical, an electro-pneumatic or electro-hydraulic vehicle brake system, the service brake demand is transferred to a control unit 80 to adjust the actuation pressure for the vehicle brake 18 provided by the vehicle brake system 79. The service brake demand is also used for a trailer brake demand to be transferred to the trailer brake system 30. The trailer brake valve 30a of the trailer brake system 30 provides and adjusts a fluidic brake signal in accordance with the grade of actuation of the service brake actuation device 76. The brake signal is transferred via the trailer control coupling 31 to the brake system 40 of the trailer 20 to generate an actuation pressure for the trailer brakes 42 according to the brake signal. Thus, the vehicle brake 18 and the trailer brakes 42 are both activated simultaneously during service braking.

[0057] When the control unit 80 receives a service brake demand from the service brake actuation device 76, the control unit 80 may receive signals from or send control signals to various components of the vehicle 10, including the following: A transmission 50 to adjust the vehicle speed or the vehicle acceleration depending on the service brake demand and receive parameters such as an output rotational speed of the transmission 50, a rotation direction of an output shaft of the transmission 50 or a system pressure of a hydraulic branch of the transmission 50 (e. g. in case of a continuous variable transmission (CVT)).

[0058] The control unit 80 may automatically generate a service and / or trailer brake demand to apply the vehicle brakes 18 and / or the trailer brakes 42 for stability control or dynamics control of the vehicle 10 or the vehicle combination 1 . Hence, the control unit 80 may provide the functionality of an anti-lock braking system (ABS) or an electronic stability control (ESC) in addition to the trailer brake assist (TBA) functionality.

[0059] Moreover, the human-machine interface of the vehicle 10 comprises a trailer brake actuation device 78 to generate a trailer brake demand accordingto the operators input for actuating the trailer brakes 42. The trailer brake actuation device 78 is a separate actuation device in addition to the service brake actuation device 76 as shown in FIG. 1 for operating the trailer brake 42 independently from the service brakeactuation device 76. The trailer brake actuation device 78 may be a hand-operated device communicatively connected with the control unit 80 as disclosed in patent application GB 2405473.6, entitled “Manual brake controlling of a trailer brake”, filed on April 18, 2024, which is hereby incorporated by reference in its entirety. When the operator operates the trailer brake actuation device 78, a trailer brake demand in accordance with the grade of actuation of the trailer brake actuation device 78 is generated and transferred to the control unit 80. The control unit 80 controls the trailer brake system 30 to generate a corresponding fluidic brake signal for braking the trailer 20. Then, the brake signal is transferred via the trailer control coupling 31 to the brake system 40 of the trailer 20 to generate an actuation pressure for the trailer brakes 42 according to the brake signal. A fluidic brake signal may also be generated in response of an operation of the service brake actuation device 76. The service brake actuation device 76 may be in fluid communication with the trailer brake system 30 for providing the brake signal without interaction of the control unit 80.

[0060] FIG. 2 shows the control unit 80 comprising an I / O interface 5, a controller 6 and a memory 7. The I / O interface 5, the controller 6 and the memory 7 may be attached to a printed circuit board (PCB). The control unit 80 may receive and send signals or data via the I / O interface 5. The I / O interface 5 may be a wireless interface or a connector. The I / O interface 5 may be connected with at least one of the inertial navigation system 4, the speed foot paddle 71 , the drive lever 72, the acceleration rate input 73, the clutch pedal 74, the HMI terminal 75, the service brake actuation device 76, the park brake lever 77, the inclination sensor 89, the steering angle sensor 91 , the vehicle brake system 79, the trailer brake actuation device 78, the transmission 50 and the trailer brake system 30 for transferring signals. The controller 6 may optionally represent a combination of two or more networked controllers. The controller 6 may store the data or signals received by the control unit 80 in the memory 7. Any threshold value used for any method disclosed herein may be stored in the memory 7. The memory 7 may contain additional data or executable computer program products, for example in terms of a computer-implemented method, that may be retrieved, processed or executed by the controller 6. Data or signals resulting from the processing of data or signals or from the execution of a computer program product may be stored to the memory 7 or sent to the I / O interface 5 by the controller 6.

[0061] FIG. 3 shows a flow chart of a first method M1 , FIG. 4 a flow chart of a second method M2 and FIG. 5 a flow chart of a third method M3. Each method M1 , M2 and M3 may be at least partly a computer-implemented method stored as a computer program product in the memory 7 of the control unit 80. The control unit 80 is configured to carry out each of the methods. Computer-implemented parts of each method may be executed by the controller 6 of the control unit 80. Non-computer-implemented parts of each method may be executed manually or by other components of the system. Each method is described byway of example of several steps without any restriction in respect of these steps. I. e. the number or the order of steps may be adapted, for example single steps may be excluded and / or added and executed earlier or later than described. The methods M1 , M2 and M3 may be executed in parallel. When a method proceeds from one step to a next step, the previous step may still be active so that both the one and the next step may be executed in parallel. Accordingly, the control unit 80 may execute two or more method steps in parallel irrespectively whether the method steps are part one the same method or of different methods.

[0062] The method M1 starts with step S100 and proceeds to step S102. At step S120, the control unit 80 checks whether the trailer brake assist (TBA) functionality is switched on (active) or off (inactive). The activation status of the trailer brake assist (TBA) functionality can be changed by the operator of the vehicle combination 1 by means of the human-machine interface. As mentioned above, the trailer brake assist (TBA) functionality is disclosed in patent application US 2023 / 0009316 A1 . If the trailer brake assist (TBA) functionality is switched off (inactive), the method proceeds to step S126. Otherwise, the method proceeds to step S104 and S106 sequentially or simultaneously.

[0063] At step S104, the control unit 80 determines a basic brake signal BSFDC based on an operation of the service brake actuation device 76 or based on an operation of the trailer brake actuation device 78 or based on an automatically generated trailer brake signal in response to a push condition of the trailer 20 as disclosed in patent application US 2023 / 0009316 A1 mentioned above. The basic brake signal BSFDC may be temporarily stored in the memory 7 of the control unit 80 and is provided for step S122 of method M1 .

[0064] At step S106, the control unit 80 performs an error check of the vehicle brake system 79 and / or the trailer brake system 30 including the brake system 40. For example, the control unit 80 may check whether the values of the trailer brake system 30 are working correctly, the trailer brakes 42 are working correctly, the CAN bus is working correctly, or perform any other diagnosis that may be relevant for an accurate operation of the trailer brakes 42. If the error check has not been passed, the method proceeds to step S126. If no error has been detected, the error check has been passed and the method proceeds to step S108.

[0065] At step S108, the control unit 80 determines the inclination 83 of the ground 87 the vehicle combination 1 is located on. The inclination 83 is measured by the inclination sensor 89 of the vehicle 10. The control unit 80 receives a corresponding signal from the inclination sensor 89. As can be seen in FIG. 1 , the vehicle combination 1 moves on the inclined ground 87 downwards in driving direction 85. Hence, the inclination sensor 89 provides a negative sensor signal indicating the downward movement of the vehicle combination 1 . In case of an uphill movement, the sign of the sensor signal is positive. I. e., the steeper the inclination 83 is, the grater is the strength of the sensor signal whereas the sign of the sensor signal represents uphill or downhill movement of the vehicle combination 1 . Moreover, the inertial navigation system 4 may provide a sensor signal to the control unit 80 representative for the negative inclination 83.

[0066] The method proceeds to step S110 and the control unit 80 checks whether the inclination 83 is below an inclination threshold value. The inclination threshold value may be approximately -4°, for example. If the inclination 83 is greater than the inclination threshold value, the method proceeds to step S126. If the inclination 83 is belowthe (negative) inclination threshold (i. e. steeper inclination), the method proceeds to step S112 and S116 sequentially or simultaneously.

[0067] At step S112, the control unit 80 checks whether the service brake actuation device 76 is released. When the service brake actuation device 76 is not operated by the operator of the vehicle combination 1 , the control unit 80 receives from the service brake actuation device 76 a service brake demand being different to when the service brake actuation device 76 is applied. If the service brake actuation device 76 isoperated, the method proceeds to step S126. If the service brake actuation device 76 is released, the method proceeds to step S114.

[0068] At step S114, the control unit 80 starts the second method M2 as exemplarily shown in FIG. 4 to determine a first (advanced) brake signal BS1 . Hence, the first brake signal BS1 is provided by the control unit 80 if the inclination 83 of the ground 87 is belowthe inclination threshold value. In addition, the first brake signal BS1 is provided by the control unit 80 if the service brake actuation device 76 has been released. The second method M2 is executed in parallel to the other steps of method M1 .

[0069] At step S116, the control unit 80 determines the steering angle of the front wheels 15 of the vehicle 10. The steering angle of the front wheels 15 is measured by the steering angle sensor 91 of the vehicle 10. The control unit 80 receives a corresponding signal from the steering angle sensor 91 . The steering angle may be changed when the operator of the vehicle combination 1 operates the steering wheel.

[0070] The method proceeds to step S118 and the control unit 80 checks whether the steering angle exceeds a first steering angle threshold. The first steering angle threshold may be approximately 60°. If the steering angle of the front wheels 15 is below the first steering angle threshold, the method proceeds to step S126. If the steering angle of the front wheels 15 is greater than the steering angle threshold, the method proceeds to step S120.

[0071] At step S120, the control unit 80 starts the third method M3 as exemplarily shown in FIG. 5 to determine a second (advanced) brake signal BS2. Hence, the second brake signal BS2 is provided by the control unit 80 if the steering angle is greater than the first steering angle threshold. In addition, the second brake signal BS2 is provided if the inclination 83 of the ground 87 is belowthe inclination threshold value. The third method M3 is executed in parallel to the other steps of method M1 and / or M2.

[0072] After steps S104, S114 and S120, the method proceeds with step S122. The control unit 80 compares the basic brake signal BSFDC determined at step S104, the first brake signal BS1 determined at step S114 and the second brake signal BS2 determined at step S120 with each other to determine the maximum brake signal BSmaxout of these three brake signals having the highest signal value. The control unit 80 may read the basic brake signal BSFDC, the first brake signal BS1 and the second brake signal BS2 out of the memory 7 of the control unit 80. Hence, the control unit 80 ensures that thehighest required brake force to reduce the pushing force of the trailer 20 is provided for the trailer brakes 42. If the basic brake signal BSFDC is zero or is not available, the control unit 80 compares the first brake signal BS1 and the second brake signal BS2 only to determine the maximum brake signal BSmax.

[0073] The method proceeds to step S124 and the control unit 80 controls the trailer brake system 30 and the brake system 40 to generate an actuation pressure for the trailer brakes 42 in accordance with the maximum brake signal BSmax.

[0074] When all method steps which may be executed in parallel have been completed, the method may proceed to step S126. At step S126, the method ends. The method may be restarted again by the control unit 80 starting with step S100.

[0075] Method M2 is initiated by method step S114 of method M1 and starts with step S200 to proceed to step S202 and S204 sequentially or simultaneously.

[0076] At step S202, the control unit 80 determines a first set value SP1 in dependence of the inclination 83. The first set value SP1 corresponds with a pressure value or a force value for applying the trailer brakes 42. The first set value SP1 increases with increasing steepness of the inclination 83, for example accordingto a proportional relationship.

[0077] At step S204, the control unit 80 determines the current trailer brake demand representing a set value for the trailer brake force. The current trailer brake demand corresponds with a pressure signal of a fluid provided by the trailer control coupling 31 . A sensor integrated in the trailer control coupling 31 measures the pressure of the fluid as current trailer brake demand. The control unit 80 receives the sensor signal from the sensor. The pressure signal of the fluid may depend on an automatic brake demand generated by the control unit. Moreover, the pressure signal of the fluid may depend on a manual brake demand generated by the operator, e. g. by operation of the trailer brake actuation device 78 or the service brake actuation device 76. If more than one brake demand is generated, the pressure signal of the fluid and consequently the current trailer brake demand corresponds with the highest brake demand. In case of an automatically generated trailer brake demand, the current trailer brake demand may depend on a pushing force acting on the towing vehicle 10 caused by the trailer , e. g. when the trailer 20 moves downhill. The current trailer brake demand may be increased by the control unit the more, the more the trailer pushes the towing vehicle. But theoperator may nevertheless demand a trailer brake demand being greaterthan the automatically generated trailer brake demand. Hence, the second set value may correspond with the automatically generated trailer brake demand if the automatically generated trailer brake demand is greaterthan the operator demanded trailer brake demand and vice versa to provide a sufficient trailer brake force according to the higher trailer brake demand.

[0078] The control unit 80 may calculate the pushing force caused by the trailer 20 in terms of a coupling force Fcbased on a tractive force of the vehicle FTRV and / or a tractive force of the vehicle combination FTRC as disclosed in patent application WO2022 / 157571 A1 mentioned above and further explained with reference to FIG. 6.

[0079] FIG. 6 schematically depicts the forces exerting on the vehicle combination 1 , in more detail on vehicle 10, for a driving condition in which the vehicle combination 1 is driving downhill on the ground 87 and in which the danger of jackknifing is especially high. The equilibrium of forces applied on the vehicle 10 results in the following equation E1 :

[0080] Fc = FTRC - (FIN + FH+ FAR + FR,RA + FR,FA) (equation E1 ), whereinFcis the coupling force which represents the force applied by the trailer 20 to the vehicle 10. In case of deceleration, the coupling force Fcis of negative sign;FTRC is the tractive force which is supplied to wheels 15, 16 of the vehicle 10 by a prime mover and the transmission 50 to move the complete vehicle combination 1 ;FIN is the inertia force which applies due to the inertia when the vehicle 10 is accelerated or decelerated;FA= mv• a;FHis the downhill-slope force which applies due to the inertia when the vehicle 10 is driving downhill (or uphill) that may be calculated based on the inclination 83:FH= mv• g • sinf'inclination 83");FAR is the air resistance force applied by air resistance and depends on various factors such as the geometry of the vehicle 10;FR,RA and FR,FA are the roll resistance forces applied by rolling resistance between the wheels 15, 16 and ground 87 depending on various parameters such as wheel load and ground / wheel contact parameters.

[0081] The mass mvof the vehicle 10 may be determined by consideringthe empty weight of the vehicle 10 plus additional ballast attached thereto. These values may be stored in the memory 7 of the control unit 80. Alternatively, mass values could be taken from vehicle acceleration or wheel load detection as described in applicant's published patent application EP 2766239 A1 . The same applies to the determination of the vehicle acceleration a, inclination 83 and speed v of the vehicle 10 which may be determined by appropriate sensors. The force must be inserted with negative or positive signs according the effective direction shown in FIG. 6. Similar forces may occur resulting from mass of the trailer 20 and resistances applied on the trailer 20 itself. But the method may only consider the resulting forces applied by the trailer 20 to the vehicle 10, which is the coupling force Fc. Considering parameters applied to the vehicle 10 only has the advantage that the trailer 20 does not need to be equipped with sensors configured to measure a coupling force.

[0082] The method proceeds to step S206 and the control unit 80 determines a second set value SP2 based on an average of several trailer brake demands determined at different time points. I. e., the average of trailer brake demands is determined based on previously determined current trailer brake demands according to step S204.

[0083] The previously determined current trailer brake demands and the corresponding time points are stored in the memory 7 of the control unit 80. For example, the second set value SP2 is calculated by the control unit 80 according to equation E2 (equation E2)with n beingthe number of determined current trailer brake demands and akbeingthe value of the k-th determined current trailer brake demand (determined according to step S204). The parameter k may represent the order of the time point of the determination of a corresponding current trailer brake demand, as for example first time point, second time point, third time point and so on. Analogously to the first setvalue, the second set value SP2 corresponds with a pressure value or a force value for applying the trailer brakes 42.

[0084] After step S202 and step S206, the method proceeds to step S208 to determine the maximum set value SPmaxout of the first and second set value SP1 and SP2 having the highest value.

[0085] The method proceeds to step S210 and the control unit 80 determines the maximum set value SPmaxdetermined at step S208 as the first (advanced) brake signal BS1 . The first brake signal BS1 may be temporarily stored in the memory 7 of the control unit 80 and is provided for step S122 of method M1.

[0086] The method proceeds to step S212 and the control unit 80 checks whether a timer has been elapsed. The timer has been started with step S200 and may be set to approximately one second. As long as the timer has not been elapsed, the control unit 80 repeats the steps S210 and S212. Hence, the control unit 80 provides the first brake signal BS1 for step S122 of method M1 as long as the timer is active. When the timer has been elapsed, the timer is inactive and the method proceeds to step S214.

[0087] At step S214, the control unit 80 resets the first brake signal BS1 to zero. The first brake signal BS1 may be temporarily stored in the memory 7 of the control unit 80 and is provided for step S122 of method M1 .

[0088] Then, the method M2 proceeds to step S216 and ends. The method M2 may be restarted again by the control unit 80 for multiple times while method M1 is executed.

[0089] Method M3 is initiated by method step S120 of method M1 and starts with step S300 to proceed to step S302 and S304 sequentially or simultaneously.

[0090] At step S302, the control unit 80 determines a first set value SP1 in dependence of the inclination 83. The first set value SP1 corresponds with a pressure value or a force value for applying the trailer brakes 42. The first set value SP1 increases with increasing steepness of the inclination 83, for example accordingto a proportional relationship.

[0091] At step S304, the control unit 80 determines the current trailer brake demand analogously to step S204. So, the current trailer brake demand may represent a set value for the trailer brake force and may also be measured by the sensor integrated in the trailer control coupling 31 .

[0092] The method proceeds to step S306 and the control unit 80 determines a second set value SP2 based on an average of previously determined current trailer brake demands analogously to step S206. For example, the second set value SP2 is calculated by the control unit 80 according to equation E2 mentioned above. Analogously to the first set value, the second set value SP2 corresponds with a pressure value or a force value for applying the trailer brakes 42.

[0093] After step S302 and step S306, the method proceeds to step S308 to determine the maximum set value SPmaxout of the first and second set value SP1 and SP2 having the highest value. Steps S302 to S308 may be implemented similarly to steps S202 to S208 of method M2. But method M3 may be startet at a time point different to method M2 so that the values determined at steps S302 to S308 may differ from the values determined at steps S202 to S208.

[0094] The method proceeds to step S310 and the control unit 80 determines the maximum set value SPmaxdetermined at step S308 as the second (advanced) brake signal BS2. The second brake signal BS2 may be temporarily stored in the memory 7 of the control unit 80 and is provided for step S122 of method M1 .

[0095] The method proceeds to step S312 and the control unit 80 checks whether a calculated summation of a predefined number of current trailer brake demands is below a current trailer brake demand threshold. The summation of the predefined number of current trailer brake demands is calculated by the control unit 80 and the current trailer brake demand threshold is received from the memory 7. If the calculated summation of the current trailer brake demands is below the current trailer brake demand threshold, the method proceeds to step S322. Otherwise, the method proceeds to step S314.

[0096] At step S314, the control unit 80 checks whether the steering angle exceeds a second steering angle threshold. The second steering angle threshold is smallerthan the first steering angle threshold and may be approximately 40°. If the steering angle of the front wheels 15 is below the second steering angle threshold, the method proceeds to step S318. Otherwise, the method steps back to S310.

[0097] At step S318, the control unit 80 determines a distance driven by the vehicle 10. For example, the control unit 80 may determine the distance based on at least two position signals (e. g. starting position and current position of the vehicle 10) receivedfrom the inertial navigation system 4. Moreover, the control unit 80 may determine the driven distance of the vehicle 10 based on the vehicle speed and the time of movement. In this case, the method may optionally proceed to step S316 before executing step S318 to determine the vehicle speed.

[0098] At step S316, the control unit 80 determines the vehicle speed. For example, the vehicle speed is received by the control unit 80 from the inertial navigation system 4. Alternatively, the vehicle speed may be provided by a speed sensor of the vehicle 10.

[0099] The method proceeds to step S320 and the control unit 80 checks whether the distance driven by the vehicle 10 is shorter than the length of the vehicle 10. The length of the vehicle 10 may be a predefined parameter stored in the memory 7 of the control unit 80. If the distance driven by the vehicle 10 is shorter than the length of the vehicle 10, the method steps back to step S310. Otherwise, the method proceeds to step S322.

[0100] At step S322, the control unit 80 resets the second brake signal BS2 to zero.The second brake signal BS2 may be temporarily stored in the memory 7 of the control unit 80 and is provided for step S122 of method M1.

[0101] Then, the method M3 proceeds to step S324 and ends. The method M3 may be restarted again by the control unit 80 for multiple times while method M1 and / or M2 is / are executed.

[0102] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.LISTING OF DRAWING ELEMENTS1 vehicle combination 11 coupling system4 inertial navigation system 15 front wheel5 I / O interface 16 rear wheel6 controller 18 vehicle brake7 memory 20 trailer10 vehicle 21 drawbarwheel 91 steering angle sensor trailer brake system a trailer brake valve trailer control coupling trailer supply coupling brake system trailer brake transmission speed foot paddle drive lever acceleration rate input clutch pedal HMI terminal service brake actuation device park brake lever trailer brake actuation device vehicle brake system control unit force sensor inclination inclination sensor driving direction ground

Claims

Docket No. MOD2444CLAIMSWhat is claimed is:1 . A method for controlling a trailer brake (42), comprising:Determining an inclination (83) of a ground (87) on which a trailer (20) is located; determining a first set value (SP1 ) in dependence of the inclination (83); determining a current trailer brake demand provided for applyingthe trailer brake (42); determining a second setvalue (SP2) in dependence of the current trailer brake demand; determining a maximum set value (SPmax) out of the first set value and the second set value; and controlling the trailer brake (42) of the trailer (20) for generating a brake force.

2. The method of claim 1 , comprising: determiningthe current trailer brake demand as an average of trailer brake demands.

3. The method of claim 1 or 2, comprising: determiningthe current trailer brake demand by a sensor.

4. The method of any preceding claim, comprising: determining whether a trailer braking assist (TBA) functionality is activated.

5. The method of any preceding claim, comprising: providing a first brake signal (BS1) and / or a second brake signal (BS2) in dependence of the maximum set value.

6. The method of claim 5, wherein the first brake signal (BS1) and / orthe second brake signal (BS2) is provided if a service brake actuation device (76) has been released.

7. The method of claim 5 or 6, wherein the first brake signal (BS1) and / orthe second brake signal (BS2) is provided if the inclination (83) of the ground (87) is below an inclination threshold value.Docket No. MOD24448. The method of claim 7, wherein the inclination threshold value is negative.

9. The method of any one of claims 4 to 8, wherein the first brake signal (BS1) is provided as long as a timer is active.

10. The method of any one of claims 4 to 9, comprising: Determining a steering angle of the towing vehicle (10); wherein the second brake signal (BS2) is provided if the steering angle is greater than a first steering threshold value.11 . The method of any one of claims 4 to 10, comprising: Determining a calculated summation of the current trailer brake demands; setting the second brake signal (BS2) to zero if the calculated summation of the current trailer brake demands is below a current trailer brake demand threshold.

12. The method of any one of claims 4 to 11 , comprising: determining a distance driven by the towing vehicle (10); and setting the second brake signal (BS2) to zero if the distance is greater than the length of the towing vehicle (10).

13. The method of claim 12, when referred back to claim 10, comprising: setting the second brake signal (BS2) to zero if the steering angle is smaller than a second steering threshold value being smaller than the first steering threshold value.

14. The method of any one of claims 4 to 13, comprising: determining a maximum brake signal (BSmax) out of the first brake signal (BS1 ) and the second brake signal (BS2); and controlling the trailer brake (42) of the trailer (20) in accordance with the maximum brake signal (BSmax).

15. The method of any one of claims 4 to 13, comprising:Docket No. MOD2444 providing a basic brake signal (BSFDC) based on an application of a service brake actuation device (76), an application of the trailer brake actuation device (78) and / or in response to a push condition of the trailer (20); determining a maximum brake signal (BSmax) out of the basic brake signal (BSFDC), the first brake signal (BS1 ) and / or the second brake signal (BS2); and controlling the trailer brake (42) of the trailer (20) in accordance with the maximum brake signal (BSmax).

16. The method of any one of claims 4 to 13, comprising: providing a basic brake signal (BSFDC) based on an application of a service brake actuation device (76), an application of the trailer brake actuation device (78) and / or in response to a push condition of the trailer (20); determining a maximum brake signal (BSmax) out of the basic brake signal (BSFDC), the first brake signal (BS1 ) and the second brake signal (BS2); and controlling a trailer brake (42) of the trailer (20) for generating a brake force in accordance with the maximum brake signal (BSmax).

17. A control unit (80) configured to carry out the method of any preceding claim.

18. Avehicle combination (1 ) comprising: a towing vehicle (10); a trailer (20) coupled to the towing vehicle (10); and a control unit (80) of claim 17; wherein the trailer (20) comprises a trailer brake system (30) with a trailer brake (42).

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