Braking method, electronic braking system, and vehicle

Abstract

The invention relates to a braking method and an electronic braking system (20) which are designed to perform slip control for a first wheel (13) and for a second wheel (14) of a vehicle (10), the first wheel (13) and the second wheel (14) being arranged on different sides of an axle (30) of the vehicle (10). For at least one operating condition of the vehicle (10), in order to decelerate the vehicle, an asynchronous slip-demand generation process (32; 36) is carried out in order to generate first slip demands (27) for the first wheel (13) and second slip demands (28) for the second wheel (14), which have differing time-dependent profiles.

Description

[0001] Braking procedure, electronic braking system and vehicle

[0002] The invention relates to a braking method and an electronic braking system. The invention particularly relates to such a braking method and such an electronic braking system in which slip requirements are generated for the wheels of the vehicle in order to improve stability.

[0003] An electronic braking system (EBS) is a braking system that uses electronic sensors and control units to distribute braking force to individual wheels and improve vehicle stability in critical situations. An EBS offers several advantages, such as improved braking performance. By electronically controlling the braking force, the braking power can be adjusted to achieve a shorter braking distance with improved vehicle control. The EBS thus contributes to increased safety.

[0004] Vehicle dynamics control, also known in technical terms as electronic stability control (ESC), can be part of a modern EBS (Electronic Braking System). Vehicle dynamics control is a safety system designed to improve vehicle stability in critical driving situations. It continuously monitors vehicle movements and detects when the vehicle is about to skid or lose control. If the vehicle dynamics control system detects a skidding motion, it intervenes automatically by braking one or more wheels and / or reducing engine torque to mitigate the risk of the vehicle skidding. Vehicle dynamics control thus makes a significant contribution to increasing road safety and preventing accidents.

[0005] US 2014 / 081546 A1 describes a method for determining the braking force for different wheels of a vehicle using control units. In one embodiment, a target slip can be determined for exactly one wheel in order to brake that wheel. WO 2013 / 072100 A1 discloses a braking system designed such that only wheels on one axle are assigned brakes that can be automatically actuated by a control unit.

[0006] However, conventional systems do not yet adequately address driving situations such as performing emergency braking while traveling straight on a road surface with a relatively low coefficient of friction. In such situations, the vehicle's stability can be compromised. In particular, undesirable yaw rates can be induced. This impairs the vehicle's stability during the braking process.

[0007] Therefore, there remains a need for methods and devices that offer improvements in terms of a vehicle's behavior during deceleration.

[0008] The object of the invention is to provide an improved braking method and an improved electronic braking system that offer advantages with regard to braking distance and vehicle stability. In particular, the object of the invention is to provide an improved braking method and an improved electronic braking system that, at least during emergency braking on a road surface with a low coefficient of friction, provides improvements with regard to vehicle stability.

[0009] The problem is solved by a braking method, an electronic braking system, and a vehicle as specified in the independent claims. The dependent claims define advantageous embodiments.

[0010] According to one aspect of the invention, a braking method is provided which includes the implementation of a slip control for a first wheel and for a second wheel of a vehicle, wherein the first wheel and the second wheel are arranged on opposite sides of an axle of the vehicle. The slip control comprises: providing first slip requirements for the first wheel and second slip requirements for the second wheel, wherein, for at least one operating state of the vehicle, an asynchronous slip requirement generation is carried out to achieve vehicle deceleration, in which the first slip requirements and the second slip requirements are generated with different time-dependent profiles.

[0011] The braking method achieves various technical advantages and effects. Asynchronous slip demand generation improves vehicle stability during braking, particularly emergency braking, on a road surface, at least under certain operating conditions. Specifically, asynchronous slip demand generation can improve vehicle stability when braking on a road surface with a relatively low coefficient of friction, for example, less than 0.5. Furthermore, asynchronous slip demand generation can shorten the braking distance, at least under certain operating conditions.In particular, it has been shown that improvements in vehicle stability can be achieved by using a slip control system in which the first and second wheels, located on opposite sides of the same axle (for example, a rear axle), are not controlled in a parallel sequence. This reduces the driver's need for counter-steering, which in turn improves vehicle safety.

[0012] Advantageously, asynchronous slip request generation can feature the generation of the first slip requests and the second slip requests with a phase shift.

[0013] This results in further improvements in vehicle stability during emergency braking. The driver needs to make less counter-steering adjustments during the braking process. The risk of instability during emergency braking while driving straight ahead on a slippery road surface is reduced.

[0014] Advantageously, asynchronous slip requirement generation can involve generating the first slip requirements and the second slip requirements such that the first slip requirements exhibit first periodic variations and the second slip requirements exhibit second periodic variations, with the second periodic variations exhibiting the phase offset to the first periodic variations.

[0015] This results in further improvements in vehicle stability during emergency braking. The driver needs to make less counter-steering adjustments during the braking process. The risk of instability during emergency braking while driving straight ahead on a slippery road surface is reduced.

[0016] Advantageously, the first periodic variations can have a first period and the second periodic variations can have a second period that is equal to the first period.

[0017] This results in further improvements in vehicle stability during emergency braking. The driver needs to make less counter-steering adjustments during the braking process. The risk of instability during emergency braking while driving straight ahead on a slippery road surface is reduced.

[0018] Advantageously, asynchronous slack request generation can involve generating the first slack requests with a first rate of change as a function of time and the second slack requests with a second rate of change as a function of time, where the second rate of change is different from the first rate of change.

[0019] This results in good vehicle stability during emergency braking. The risk of instability during emergency braking while driving straight ahead on a slippery road surface is reduced. Furthermore, with such asynchronous slip demand generation, corrective action is easily implemented upon detection of driver counter-steering and / or excessive lateral acceleration. In particular, at least one of the first slip demands and / or the second slip demands can be adjusted to reduce the detected instabilities while maintaining asynchronous control for the first and second wheels. Advantageously, the asynchronous slip demand generation can include a step of setting at least one of the first slip demands and at least one of the second slip demands based on vehicle parameter values, with this setting step being repeated multiple times.

[0020] This ensures good vehicle stability during emergency braking. The initial and subsequent slip requirements can each be generated taking into account the current conditions and vehicle parameter values.

[0021] Advantageously, at least one operating condition for which asynchronous slip request generation is carried out to achieve vehicle deceleration can depend on the road surface condition of the roadway on which the vehicle is located.

[0022] This allows asynchronous slip request generation to be selectively activated when it offers advantages in terms of stability and / or braking distance for the specific road surface conditions. In particular, asynchronous slip request generation can be selectively activated in operating conditions where a conventional vehicle dynamics control strategy would result in yaw rates that would necessitate undesirably frequent counter-steering.

[0023] Advantageously, at least one operating condition for which asynchronous slip requirement generation is carried out to achieve vehicle deceleration can depend on a coefficient of friction between the vehicle and the road surface.

[0024] This allows asynchronous slip demand generation to be selectively activated when it offers advantages in terms of stability and / or braking distance for the respective coefficient of friction. In particular, asynchronous slip demand generation can be selectively activated at coefficients of friction where conventional vehicle dynamics control strategies would result in yaw rates requiring undesirably frequent counter-steering. Advantageously, asynchronous slip demand generation can be selectively implemented based on a comparison of the coefficient of friction thresholds.

[0025] This allows the asynchronous slip demand generation to be selectively activated at friction values ​​where a conventional control strategy for vehicle dynamics would lead to yaw rates that would require undesirably frequent counter-steering.

[0026] Advantageously, at least one operating state for which asynchronous slip demand generation is performed to achieve vehicle deceleration can depend on the vehicle's longitudinal acceleration. The method can include the detection of the longitudinal acceleration.

[0027] This allows asynchronous slip request generation to be selectively activated when asynchronous slip request generation offers advantages in terms of stability and / or braking distance for the respective longitudinal acceleration.

[0028] The braking method can advantageously include determining the coefficient of friction based on the longitudinal acceleration.

[0029] This makes it easy to determine the coefficient of friction, for example from a longitudinal acceleration detected at the start of a braking process.

[0030] Advantageously, the asynchronous slip requirement generation can be selectively performed depending on a longitudinal acceleration threshold comparison.

[0031] This allows asynchronous slip request generation to be selectively activated when it offers advantages in terms of stability and / or braking distance for the respective longitudinal acceleration. Advantageously, asynchronous slip request generation can be implemented in response to a driver-initiated deceleration request for at least one operating state of the vehicle. The method can thus...

[0032] have slip control in which a first slip of the first wheel is controlled based on the first slip requirements and in which a second slip of the second wheel is controlled based on the second slip requirements.

[0033] This allows asynchronous slip request generation to be selectively activated when it offers advantages over conventional control strategies in terms of the operating state, in order to implement the driver's desired deceleration. This can lead to improvements in stability and / or braking distance.

[0034] Advantageously, asynchronous slip request generation can be performed as a reaction to a driver-initiated deceleration request when the vehicle is traveling straight ahead.

[0035] This allows the asynchronous slip request generation to be selectively activated during braking while driving straight ahead, and optionally also depending on road surface conditions, in order to reduce the risk of unwanted instabilities arising from the vehicle dynamics control.

[0036] Advantageously, the axle on which the first wheel and the second wheel are located can be a rear axle of the vehicle.

[0037] This can advantageously improve stability during braking.

[0038] Advantageously, the braking process can be carried out automatically by an electronic braking system or an electronic control unit.

[0039] This advantageously improves stability during braking. According to a further aspect of the invention, an electronic braking system for a vehicle is provided, which is configured to perform slip control for a first wheel and a second wheel of the vehicle, wherein the first wheel and the second wheel are arranged on opposite sides of an axle of the vehicle. The electronic braking system comprises at least one electronic control unit configured to provide first slip requests for the first wheel and second slip requests for the second wheel. The at least one electronic control unit is configured to perform asynchronous slip request generation for at least one operating state of the vehicle in order to achieve vehicle deceleration, in order to generate the first slip requests and the second slip requests with different time-dependent profiles.

[0040] The electronic braking system offers various technical advantages and benefits. It is designed such that, through asynchronous slip request generation, improved vehicle stability during braking, particularly emergency braking, is achievable on a road surface under certain operating conditions. Specifically, the electronic braking system can provide improved vehicle stability when braking on a slippery road surface through asynchronous slip request generation. Furthermore, a reduction in braking distance can be achieved through asynchronous slip request generation under certain operating conditions.In particular, it has been shown that improvements in vehicle stability can be achieved by using a slip control system in which the first and second wheels, located on opposite sides of the same axle (for example, a rear axle), are not controlled in a parallel sequence. This reduces the driver's need for counter-steering, which in turn improves vehicle safety.

[0041] Optional features of the electronic braking system, which can be implemented according to various embodiments, and their respective technical effects and advantages correspond to the optional features and effects described with reference to the braking method. The electronic braking system may include a longitudinal acceleration sensor for detecting the longitudinal acceleration of the vehicle in which the electronic braking system can be installed. Alternatively or additionally, the electronic braking system may include an interface for receiving an output signal from a longitudinal acceleration sensor for detecting the longitudinal acceleration of the vehicle in which the electronic braking system can be installed or is installed. The electronic braking system may be configured to selectively activate asynchronous slip request generation based on the output signal of the longitudinal acceleration sensor.

[0042] This allows asynchronous slip request generation to be selectively activated when asynchronous slip request generation offers advantages in terms of stability and / or braking distance for the respective longitudinal acceleration.

[0043] Advantageously, the electronic braking system can be configured to carry out the braking procedure according to one aspect or embodiment.

[0044] This allows the effects and advantages explained with reference to the braking procedure to be realized.

[0045] According to a further aspect of the invention, an electronic control unit for an electronic braking system is specified, which is configured to carry out the braking procedure according to one aspect or embodiment.

[0046] This allows the effects and advantages explained with reference to the braking procedure to be realized.

[0047] According to a further aspect of the invention, a vehicle is provided which has the electronic braking system and / or the electronic control unit according to one aspect or embodiment. This provides a vehicle whose electronic braking system offers improved stability with a short braking distance, at least in some situations (for example, for certain road conditions).

[0048] The vehicle can be a commercial vehicle, for example a truck, a tractor unit or a bus.

[0049] This provides an improved braking procedure and an improved electronic braking system specifically for such commercial vehicles, where, due to their size and weight, the electronic braking system typically has a particularly complex design and vehicle stability is especially important in the event of emergency braking.

[0050] According to a further aspect of the invention, a machine-readable command code is specified which, when implemented by at least one programmable circuit of at least one electronic control unit for an electronic braking system, causes the at least one control unit to carry out the braking procedure according to one aspect or embodiment.

[0051] This allows the effects and advantages described in connection with the braking procedure to be realized efficiently using appropriately configured electronic control units.

[0052] According to a further aspect of the invention, a non-volatile storage medium containing a machine-readable instruction code is provided. When implemented by at least one programmable circuit, this code causes at least one electronic control unit for an electronic braking system to execute the braking procedure according to one aspect or embodiment. The storage medium can be a memory (in particular, a non-volatile memory) of the at least one electronic control unit for the electronic braking system. This allows the effects and advantages described in connection with the braking procedure to be realized efficiently using appropriately configured electronic control units.

[0053] According to a further aspect of the invention, the braking method, the electronic braking system, the vehicle, the machine-readable command code or the non-volatile storage medium is used to shorten the braking distance of a vehicle by automatically selecting the operating-state-dependent controller from the ABS controller and the slip controller of the vehicle dynamics control, which is used to convert a driver-side deceleration request into an actuating value for at least one braking force, depending on an operating state of the vehicle.

[0054] The braking method, the electronic braking system and the vehicle according to aspects and embodiments of the invention make it possible in some situations to shorten the braking distance while maintaining good vehicle stability.

[0055] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments. Embodiments of the invention are described below, particularly with reference to the figures. These figures do not necessarily represent the embodiments to scale. Rather, where expedient for clarification, the figures are shown in schematic and / or slightly distorted form. In the figures, elements that correspond with regard to their design and / or function are designated by identical or similar reference numerals.

[0056] Fig. 1 shows a vehicle that has an electronic braking system according to one embodiment;

[0057] Fig. 2 shows first and second slip requirements that can be generated by a vehicle dynamics control system according to an exemplary embodiment; Fig. 3 shows further first and second slip requirements that can be generated by a vehicle dynamics control system according to an exemplary embodiment; Fig. 4 shows yet more first and second slip requirements that can be generated by a vehicle dynamics control system according to an exemplary embodiment;

[0058] Fig. 5 shows the vehicle of Fig. 1 in a side view;

[0059] Fig. 6 shows a flowchart of a braking procedure according to an exemplary embodiment;

[0060] Fig. 7 shows a friction coefficient threshold comparison;

[0061] Fig. 8 shows a longitudinal acceleration threshold comparison;

[0062] Fig. 9 is a flowchart of a braking procedure according to an exemplary embodiment;

[0063] Fig. 10 shows an electronic control unit for an electronic braking system according to one embodiment;

[0064] Fig. 11 shows a vehicle system that has an electronic braking system according to one embodiment;

[0065] Fig. 12 shows speed profiles during a braking process; and Fig. 13 is a flowchart of a braking procedure according to an exemplary embodiment.

[0066] The invention, which is described in detail below with reference to embodiments illustrated in the figures, presents technically advantageous braking methods and electronic braking systems configured to selectively generate asynchronous slip demands for wheels of a vehicle arranged on the same rear axle, such that the control sequence for a first wheel and a second wheel is not parallel. In particular, the slip demands are also not parallel.

[0067] The term "vehicle dynamics control" (also known as electronic stability control (ESC)) refers to a vehicle system and procedure designed to improve vehicle stability and control in critical driving situations. Vehicle dynamics control continuously monitors various driving signals such as speed, steering angle, and lateral acceleration. In response to a detected potential loss of vehicle control, the system can automatically intervene by selectively applying braking force to individual wheels to stabilize the vehicle. This reduces the risk of oversteer or understeer and enhances driving stability in curves or during sudden evasive maneuvers.

[0068] A "slip controller" is a component designed to generate control signals to achieve target slip values. The slip controller can be a component of the vehicle dynamics control system, but is not limited to this. In particular, the slip controller can be a component of the vehicle dynamics control system designed to generate control signals for brake pressures so that individual wheels can be braked based on slip requirements.

[0069] Slip requirements are defined as requirements used for slip control. These slip requirements vary over time. For example, they can define target slip values ​​as a function of time for the first wheel and the second wheel.

[0070] “Asynchronous slip requirements” are understood to be slip requirements that have different time dependencies in a time interval in which both first slip requirements for a first wheel and second slip requirements for a second wheel are generated.

[0071] The term "brake cylinder" includes, in particular, a spring-loaded cylinder. Specifically, the brake cylinders described in the context of embodiments can each be designed as spring-loaded cylinders.

[0072] The term "braking force," as used here, also includes braking pressure and / or braking torque. Therefore, building up a braking force can involve building up braking pressure and / or braking torque. A control value for a braking force can also represent a control value for braking pressure and / or braking torque.

[0073] Longitudinal acceleration refers to acceleration along the longitudinal direction of the vehicle frame. Lateral acceleration refers to acceleration perpendicular (especially perpendicular) to the longitudinal direction of the vehicle frame.

[0074] Fig. 1 shows a vehicle 10. The vehicle 10 can be a commercial vehicle, for example, a truck, a tractor, or a bus. The vehicle 10 has front wheels 11, 12 and corresponding front wheel brake cylinders 15, 16. The vehicle 10 is shown schematically in Fig. 1 with a two-axle configuration. However, the braking methods and electronic braking systems disclosed in this application are not limited to this configuration but can also be applied to a vehicle with more than two axles. The operating principle is analogous to that described with reference to the vehicle 10. The vehicle 10 has a first rear wheel 13 and a second rear wheel 14. The first rear wheel 13 and the second rear wheel 14 are arranged on opposite sides 30.1, 30.2 of a rear axle 30 of the vehicle, and rear wheel brake cylinders 17, 18 are located on each side.Vehicle 10 has a first rear wheel brake cylinder 17, which is assigned to the first rear wheel 13. Vehicle 10 has a second rear wheel brake cylinder 18, which is assigned to the second rear wheel 14. Vehicle 10 has an electronic braking system (EBS) 20. The EBS 20 can be an EBS for installation in a truck, tractor, or bus. The EBS 20 has a vehicle dynamics control system 21. The vehicle dynamics control system 21 has a slip control unit 22. The slip regulator 22 is configured to provide control values ​​19.1 for building up a first rear wheel braking force P" through the first rear wheel brake cylinder 17. The slip regulator 22 is configured to provide further control values ​​19.2 for building up a second rear wheel braking force P"' through the second rear wheel brake cylinder 18.The slip controller 22 is configured to generate the actuating values ​​19.1 and the further actuating values ​​19.2 according to slip requirements in order to achieve a first target slip of the first rear wheel 13 and a second target slip of the second rear wheel 14.

[0075] The vehicle dynamics control system 21 is configured to generate and utilize asynchronous slip requests in order to improve stability during emergency braking by executing the slip control of the first rear wheel 13 and the slip control of the second rear wheel 14 asynchronously (i.e., not in parallel). Slip requests are provided for both the first rear wheel 13 and the second rear wheel 14, but these have different time dependencies. For this purpose, the vehicle dynamics control system 21 can include a generation device 23 configured to perform asynchronous slip request generation, capable of generating both the first slip requests 27 and the second slip requests 28. The first slip requests 27 can be used to control the slip of the rear wheel 13, and the second slip requests 28 can be used to control the slip of the second rear wheel 14.The EBS 20 is configured such that, during asynchronous slip request generation, the first slip requests 27 and the second slip requests 28 are generated with different time profiles within a time interval in which both the first slip requests 27 and the second slip requests 28 are generated. The EBS 20 is configured to determine, depending on the operating state (i.e., depending on an operating state of the vehicle 10), whether the asynchronous slip request generation should be executed.

[0076] The EBS 20 can be configured so that the asynchronous slip request generation is used only for slip control for wheels 13, 14 of exactly one axle 30 (for example, for the rear wheels 13, 14 on the different sides of the rear axle 30), while other techniques can be used to build up a braking force P, P' for wheels 13, 14.

[0077] The EBS 20 can be configured such that asynchronous slip request generation is performed depending on one or more operating parameters (for example, the road surface condition of the lane on which the vehicle 10 is located, and / or a yaw rate and / or a steering angle). For example, the EBS 20 can be configured to determine whether asynchronous slip request generation should be performed based on an output signal from a longitudinal acceleration sensor 29. The longitudinal acceleration sensor 29 can communicate directly or indirectly with the EBS 20 or be integrated into the EBS 20.

[0078] The slip controller 22 of the vehicle dynamics control system 21 can use various input signals, such as wheel speeds, to generate corresponding actuating values ​​19.1, 19.2 for building up the first rear wheel braking force P" and the second rear wheel braking force P"'. Such control strategies are familiar to those skilled in the art. The EBS 20 can, in particular, be configured to determine, in response to a driver-initiated deceleration request 26, whether the asynchronous slip request generation should be executed in order to improve stability during emergency braking, for example, during emergency braking where the longitudinal acceleration meets a condition, depending on the operating condition, and optionally to shorten the braking distance.

[0079] The EBS 20 can receive the driver's deceleration request 26 from a brake force sensor 24. The brake force sensor 24 can have a brake pedal 25 or be coupled to the brake pedal 25. The brake force sensor 24 can be configured to provide the driver's deceleration request 26 for implementation by the slip controller 22 of the vehicle dynamics control 21 of the EBS 20.

[0080] Figures 2, 3, and 4 show examples of asynchronous slack request generation. In each case, the slack requests are generated along a

[0081] Slip axis 34 is plotted as a function of time along a time axis 33. Figures 2 and 3 show, by way of example, a time-dependent progression of the first slip requirements 31, 38 and a time-dependent progression of the second slip requirements 32, 39, which are each oscillating over time. The first slip requirements 31, 38 and the second slip requirements 32, 39 are generated in such a way that the slip control for the first rear wheel 13 and the second rear wheel 14 does not take place in an identical control sequence. The first slip requirements 31, 38 and the second slip requirements 32, 39 exhibit a phase shift 37, 40. The first slip requirements 31, 38 and the second slip requirements 32, 39 can each have the same period.For example, the first slip requirements 31 can have a first period 35 of a time-dependent variation of the first slip requirements 31, and the second slip requirements 32 can have a second period 36 of a time-dependent variation of the second slip requirements 32, where the second period 36 is equal to the first period 35.

[0082] Figure 4 shows an example of asynchronous slip requirement generation where a rate of change (for example, the magnitude of a step change 41', 42' of the slip requirements) differs for a time-dependent progression of the first slip requirement 41 and for a time-dependent progression of the second slip requirement 42. The first slip requirement 41 and the second slip requirement 42 can have the same target slip step 43. The different rates at which the first slip requirement 41 and the second slip requirement 42 change as a function of time provide asynchronous slip requirement generation.Asynchronous slip requirement generation can be implemented such that, driven by an event, for example, in response to the detection of a driver intervention (such as a steering movement) and / or a lateral acceleration that fulfills an adaptation function, at least one of the first slip requirements 41 or the second slip requirements 42 is adjusted. This adjustment 44 can be carried out in such a way that the first slip requirements 41 and the second slip requirements 42 continue to be generated asynchronously. This can improve stability, for example, during emergency braking while driving straight ahead on a slippery road surface.

[0083] Fig. 5 schematically shows the vehicle 10 on a roadway 47. The roadway 47 has a surface condition 42, which may depend, for example, on the material, the presence or absence of moisture, or other parameters. As already explained, the EBS 20 can be configured to take a coefficient of friction into account during the asynchronous generation of the desired braking demand. This coefficient of friction, in conjunction with the normal force exerted by the vehicle 10 on the roadway 47, determines a frictional force 48 between the wheels 11, 13 and the roadway 47. To determine the coefficient of friction, the EBS 20 can, at the beginning of a braking process or before the start of a braking process initiated in response to the driver's deceleration request 26, determine a longitudinal acceleration A and thus the coefficient of friction based on an output signal from the longitudinal acceleration sensor 29.The EBS 20 can be configured to translate the driver's deceleration request 26 into brake pressures depending on the longitudinal acceleration A detected in this way and / or the friction coefficient derived from it. The vehicle's speed V 10 can also be used by the EBS 20 to build up the brake pressures.

[0084] Fig. 6 is a flowchart of a braking procedure 50. The braking procedure 50 is a method for converting the driver's deceleration request to build up the first rear wheel braking force P" and the second rear wheel braking force P"'. The braking procedure 50 can be executed automatically with or by the EBS 20. The braking procedure 50 can be executed automatically with or by one or more electronic control units of the EBS 20.

[0085] Braking procedure 50 includes a step 51 for determining an operating state of the vehicle 10. Determining the operating state may involve determining a quantity dependent on road surface properties (for example, determining a coefficient of friction between the vehicle 10 and the road surface and / or determining a longitudinal acceleration of the vehicle 10). Determining the operating state may involve using one or more sensors, which may be integrated into the EBS 20. Alternatively or additionally, determining the operating state may involve direct or indirect communication between the EBS 20 and one or more sensors to determine the operating state. This communication may take place via a vehicle data bus and / or dedicated signal lines.

[0086] The braking method 50 includes a step 52 of asynchronous slip requirement generation. The first slip requirements 28, 31, 38, 41 for the first rear wheel 13 and the second slip requirements 29, 32, 39, 42 for the second rear wheel 14 are generated on the same axle 30 in such a way that a different, non-parallel control sequence results for controlling the slip for the first rear wheel 13 and the second rear wheel 14, even during braking while driving straight ahead.

[0087] The braking procedure 50 has a step 53 of generating first actuating values ​​19.1 and second actuating values ​​19.2 in order to build up the first rear wheel braking force P" and the second rear wheel braking force P"' when deceleration is desired during straight-line driving, optionally depending on further parameters (for example, depending on a longitudinal acceleration A and / or vehicle speed V), whereby the slip of the first rear wheel 13 and the slip of the second rear wheel 14 are controlled with different, non-time-synchronous control sequences.

[0088] The braking procedure 50 can be a repetition of the explained

[0089] Procedural steps 51, 52, 53 are shown.

[0090] The asynchronous slip request generation can be selectively executed depending on an operating state of the vehicle 10, in any case during emergency braking while driving straight ahead, if a coefficient of friction between the road surface 47 and the vehicle 10 is less than a coefficient of friction threshold value and / or if the longitudinal acceleration A of the vehicle 10 is less than a longitudinal acceleration threshold value.

[0091] Fig. 7 schematically shows coefficients of friction plotted along a coefficient of friction axis 61. The coefficient of friction determined by the EBS 20 can be compared by the EBS 20 with at least one coefficient of friction threshold value 62. The EBS 20 can determine whether the coefficient of friction is a first coefficient of friction 63, which is greater than the coefficient of friction threshold value 62, or a second coefficient of friction 64, which is less than the coefficient of friction threshold value 62. Depending on the threshold comparison of the coefficient of friction, the EBS 20 can execute the asynchronous slip demand generation. The EBS 20 can execute the asynchronous slip demand generation if the coefficient of friction is less than the coefficient of friction threshold value 62. Fig. 8 schematically shows longitudinal accelerations plotted along a longitudinal acceleration axis 65.The longitudinal acceleration retrieved by the EBS 20 from the longitudinal acceleration sensor 29 can be compared by the EBS 20 with at least one longitudinal acceleration threshold 66. The EBS 20 can determine whether the longitudinal acceleration is a first longitudinal acceleration 67, which is greater than the longitudinal acceleration threshold 66, or a second longitudinal acceleration 68, which is less than the longitudinal acceleration threshold 66. Depending on the threshold comparison of the longitudinal acceleration, the EBS 20 can execute the asynchronous slip request generation. The EBS 20 can execute the asynchronous slip request generation if the longitudinal acceleration is less than the longitudinal acceleration threshold 66, depending on the threshold comparison of the longitudinal acceleration.

[0092] Fig. 9 is a flowchart of a braking procedure 54. The braking procedure 54 is a method for converting the driver's deceleration request 26 into a braking force P", P"'. The braking procedure 54 can be executed automatically with or by the EBS 20. The braking procedure 54 can be executed automatically with or by one or more electronic control units of the EBS 20.

[0093] The braking method 54 includes step 51 of automatically determining an operating state, which can be carried out as explained with reference to Fig. 6. Determining the operating state can, in particular, involve determining a longitudinal acceleration A and / or a coefficient of friction.

[0094] Braking procedure 54 includes a step 55 in which at least one value of an operating parameter (e.g., vehicle speed) determined when establishing the operating state is compared with a threshold value assigned to this operating parameter. In particular, step 55 may include a threshold comparison of the coefficient of friction and / or the longitudinal acceleration. The coefficient of friction threshold may, for example, be a maximum of 0.9, 0.8, 0.7, or 0.6. The longitudinal acceleration threshold may be a minimum of 1.0 m / s² and a maximum of 3.0 m / s². 2 , at least 1.5 m / s 2 and a maximum of 2.5 m / s 2 at least 1.6 m / s 2 and a maximum of 2.2 m / s 2such a threshold comparison can efficiently determine whether a braking maneuver is to be carried out on a slippery road surface, where there is a particular risk of instability and asynchronous slip demand generation is therefore particularly advantageous.

[0095] The braking procedure 54 includes a step 56 of asynchronous slip request generation. Step 56 is selectively executed if the comparison in step 55 yields a first comparison result. For example, step 56 can be selectively executed only if the comparison in step 55 has shown that the longitudinal acceleration is less than the longitudinal acceleration threshold. After step 56, the braking procedure 54 continues at step 53.

[0096] The braking procedure 54 includes a step 57 in which a control strategy different from asynchronous slip request generation is selected for controlling the slip of the first rear wheel 13 and the second rear wheel 14. Step 57 is selectively performed if the comparison in step 55 yields a second comparison result that differs from the first comparison result. For example, step 57 can be selectively performed only if the comparison in step 55 has shown that the longitudinal acceleration is at least equal to the longitudinal acceleration threshold. After step 57, the braking procedure continues at step 53.

[0097] The braking method 54 includes a step 53 of generating first actuating values ​​19.1 and second actuating values ​​19.2 in order to build up the first rear wheel braking force P" and the second rear wheel braking force P"' at least when deceleration is desired while driving straight ahead on a smooth road surface, whereby the slip of the first rear wheel 13 and the slip of the second rear wheel 14 are controlled with different, non-time-synchronous control sequences.

[0098] The braking procedure 54 can be a repetition of the explained

[0099] Procedural steps 51, 55, 56, 57, and 53 may be shown. In particular, the

[0100] Procedure steps 51, 55, 56, 57, 53 are repeated continuously (for example, periodically or depending on an event detection) during an ongoing braking process.

[0101] Fig. 10 shows the EBS 20, which includes one or more electronic control units (ECUs) 70 for the vehicle dynamics control system 21. The electronic control unit(s) 70 may include the slip controller 22 of the vehicle dynamics control system 21 and integrated sensors, in particular a lateral acceleration sensor 71 and / or a yaw sensor 72. The control unit(s) 70 may be configured to receive the driver's deceleration request 26 from the brake force sensor 24. The control unit(s) 70 may be configured to receive sensor signals from multiple sensors, for example, from the longitudinal acceleration sensor 29, a steering angle sensor 73, wheel speed sensors 74 for the front and rear wheels, and optional additional sensors.The generating device 23 for generating asynchronous slip requests is configured to generate the first slip requests for the first rear wheel 13 and the second slip requests for the second rear wheel 14, depending on the operating state, such that the first and second slip requests do not occur simultaneously. The asynchronous slip request generation can be operating state dependent, for example, at least when the driver requests deceleration while driving straight ahead, provided that the longitudinal acceleration and / or the coefficient of friction meets a threshold comparison.

[0102] Fig. 11 shows a schematic representation of a vehicle system 80. The vehicle system 80 can be configured for installation in a commercial vehicle or already installed in a commercial vehicle. The vehicle system 80 comprises a vehicle data bus 81 and an EBS. The EBS includes EBS electronics 83 coupled to one or more control units 70. As explained with reference to Fig. 10, the one or more control units 70 can include at least one electronic control unit 70 of the vehicle dynamics control 21. The at least one control unit 70 includes a lateral acceleration sensor and a yaw sensor, which are shown schematically in Fig. 11 as components of the at least one electronic control unit 70. The vehicle system 80 includes front wheel sensors 84, an axle modulator 85, and rear wheel sensors 86.The front wheel sensors 84 and the rear wheel sensors 86 each have at least speed sensors. The EBS electronics are connected to at least the axle modulator 85 via an EBS data bus 82. The vehicle system 80 may include an optical output device 87, for example a display device, a motor 88, and a retarder 89, which may also be connected to the vehicle data bus 81.

[0103] Fig. 12 shows a braking process 90, where a vehicle speed, plotted along a velocity axis 92, is shown as a function of a distance traveled by the vehicle 10 since the start of the braking process 90, plotted along a distance axis 91. A deceleration curve 93 is shown, illustrating the braking process 90 using the braking method and the EBS according to an exemplary embodiment. In addition, a comparative deceleration curve 94 is shown, resulting from a conventional braking method in which no asynchronous slip request generation is used during braking while driving straight ahead.To determine the deceleration curve 93, which is achieved by the braking method and the EBS 20 according to an exemplary embodiment, an implementation of asynchronous slip demand generation was used in which the first rate of change of the first slip demands differs from the rate of change of the second slip demands. The slip demands were capped at 19%.

[0104] Both the deceleration curve 93 and the comparative deceleration curve 94 schematically show the speed profile in response to a driver-initiated deceleration request. According to one embodiment, the braking procedure and the EBS 20 reduce the braking distance from a comparative braking distance 96 to a braking distance 95. A reduction in braking distance 97 divided by the comparative braking distance 96 is significant. For example, in a field test with a truck with a front wheel load of 9740 kg, a rear wheel load of 6197 kg, tires with a tread depth of more than 10 mm each, and twin tires on the rear axle, a braking distance reduction 97 of approximately 5% relative to the comparative braking distance 96 was achieved for a braking maneuver on wet blue basalt (coefficient of friction 0.3) from an initial speed of 25 km / h to a final speed of 15 km / h.During a braking maneuver from an initial speed of 25 km / h to a final speed of 0 km / h, a braking distance reduction of approximately 6% relative to the reference braking distance was achieved. Improvements were also observed in field tests at numerous other friction coefficients, initial speeds, and final speeds. Furthermore, the tests demonstrated a significant improvement in stability during braking. The risk of instabilities developing due to the control processes was reduced.

[0105] In the braking method and the EBS 20, the build-up of braking force is carried out, according to exemplary embodiments, at least for some operating conditions (for example, braking while driving straight ahead on a road surface for which the coefficient of friction is less than a coefficient of friction threshold value, and / or with a longitudinal acceleration that is less than a longitudinal acceleration threshold value) using asynchronous slip request generation.

[0106] Fig. 13 is a flowchart of a method 100. The method 100 can be executed automatically by or with the EBS 20 according to one embodiment. The method 100 is a method for improving vehicle stability during emergency braking while driving straight ahead.

[0107] Procedure 100 includes a step 101 in which the driver's deceleration request 26 is received. Receiving the driver's deceleration request 26 may involve receiving an output signal from the brake force sensor 24.

[0108] Method 100 includes a step 102 in which the driver's deceleration request 26 is implemented by the slip controller 22 of the vehicle dynamics control system to build up a first rear wheel braking force P" and a second rear wheel braking force P"', whereby asynchronous slip request generation is also used at least during a braking operation while driving straight ahead. Method 100 utilizes the braking procedure and / or the EBS 20 and / or the vehicle 10 to improve vehicle stability during emergency braking while driving straight ahead.

[0109] Various modifications can be implemented in other embodiments. For example, while the slip controller can be part of the vehicle dynamics control system and implemented by a control unit of the vehicle dynamics control system, the slip controller can also be designed and implemented differently.

[0110] The methods, the electronic braking system, and the vehicle according to the exemplary embodiments offer improvements with regard to road safety. In particular, the methods, the electronic braking system, and the vehicle according to the exemplary embodiments make it possible, at least in some operating situations, to improve the stability of the vehicle during a braking maneuver.

[0111] Reference symbol list (part of the description)

[0112] 10 vehicles

[0113] 11, 12 front wheel

[0114] 13 first rear wheel

[0115] 14 second rear wheel

[0116] 15, 16 brake cylinders

[0117] 17 first rear wheel brake cylinder

[0118] 18 second rear wheel brake cylinder

[0119] 19 control values

[0120] 20 electronic braking system

[0121] 21 Vehicle dynamics control

[0122] 22 Slip regulators

[0123] 23 Generation plant

[0124] 24 brake force sensors

[0125] 25 Brake pedal

[0126] 26. Driver's request for delay

[0127] 27 initial hatching requirements

[0128] 28 second hatching requirements

[0129] 29 Longitudinal acceleration sensor

[0130] 30 Rear axle

[0131] 30.1 first page

[0132] 30.2 second page

[0133] 31 Time-dependent progression of the first hatching requirements

[0134] 32 Time-dependent course of the second hatching requirements

[0135] 33 Timeline

[0136] 34 target slip pockets

[0137] 35 first period

[0138] 36 second period

[0139] 37 Phase shift

[0140] 38 Time-dependent progression of the first hatching requirements

[0141] 39 Time-dependent course of the second hatching requirements Phase shift Time-dependent course of the first hatching requirements Time-dependent course of the second hatching requirements

[0142] Target slippage

[0143] Adjustment

[0144] roadway

[0145] Road surface conditions

[0146] Frictional force

[0147] Procedure, 52, 53 Procedure step

[0148] Procedure, 56, 57 Procedure step

[0149] coefficient of friction axis

[0150] Friction threshold value, first friction value, second friction value

[0151] Longitudinal acceleration axis

[0152] Longitudinal acceleration threshold, first longitudinal acceleration, second longitudinal acceleration, electronic control unit(s)

[0153] Lateral acceleration sensor

[0154] Yaw sensor

[0155] Steering angle sensor

[0156] Speed ​​sensors, optional additional sensors

[0157] Vehicle system

[0158] Vehicle data bus

[0159] EBS data bus

[0160] EBS Electronics

[0161] Front wheel sensors 85 Axle modulator

[0162] 86 rear wheel sensors

[0163] 87 optical output device

[0164] 88 engine

[0165] 89 Retarder

[0166] 90 Braking process

[0167] 91 route axis

[0168] 92 Speed ​​axis

[0169] 93 Deceleration curve

[0170] 94 Comparison lag curve

[0171] 95 Comparison braking distance

[0172] 96 braking distance

[0173] 97 Braking distance reduction

[0174] 100 procedures

[0175] 101, 102 Procedure step

[0176] A Longitudinal acceleration

[0177] P, P' Braking force for front wheel

[0178] P“ first rear wheel braking force

[0179] P“' second rear wheel braking force

[0180] V Vehicle speed

Claims

Claims 1. Braking method, comprising: Execution of a slip control (32, 33; 33, 35-37) for a first wheel (13) and for a second wheel (14) of a vehicle (10), wherein the first wheel (13) and the second wheel (14) are arranged on opposite sides (30.1, 30.2) of an axle (30) of the vehicle (10), wherein the slip control (32, 33; 33, 35-37) comprises: providing first slip requests (27) for the first wheel (13) and second slip requests (28) for the second wheel (14), wherein for at least one operating state (V, A; 63, 64; 67, 68) of the vehicle (10) to achieve a vehicle deceleration (93) an asynchronous slip request generation (32; 36) is carried out, in which the first slip requests (27) and the second slip requests (28) are generated with different time-dependent trajectories (31 , 32; 38, 39; 41 , 42).

2. Braking method according to claim 1, wherein the asynchronous slip request generation (32; 36) comprises generating the first slip requests (27) and the second slip requests (28) with a phase shift (37; 40).

3. Braking method according to claim 2, wherein the asynchronous slip request generation (32; 36) comprises generating the first slip requests (27) and the second slip requests (28) such that the first slip requests (27) have first periodic variations (31; 38) and that the second slip requests (28) have second periodic variations (32; 39), wherein the second periodic variations (32; 39) have the phase offset (37; 40) to the first periodic variations (31; 38).

4. Braking method according to claim 3, wherein the first periodic variations (31 ; 38) have a first period duration (35) and the second periodic variations (32; 39) have a second period duration (36) which is equal to the first period duration (35).

5. Braking method according to one of the preceding claims, wherein the asynchronous slip request generation (32; 36) comprises generating the first slip requests (27) with a first rate of change (41 ') as a function of time and the second slip requests (28) with a second rate of change (42') as a function of time, wherein the second rate of change (42') is different from the first rate of change (41 ').

6. Braking method according to one of the preceding claims, wherein the asynchronous slip request generation (32; 36) comprises a step of setting (32) at least one of the first slip requests (27) and at least one of the second slip requests (28) depending on vehicle parameter values ​​(V, A; 63, 64; 67, 68), wherein the setting step (32) is repeated multiple times.

7. Braking method according to one of the preceding claims, wherein the at least one operating state (V, A; 63, 64; 67, 68), for which the asynchronous slip request generation (32; 36) is carried out to achieve the vehicle deceleration (93), depends on a road surface condition (48) of a roadway (47) on which the vehicle (10) is located.

8. Braking method according to claim 7, wherein the at least one operating state (V, A; 63, 64; 67, 68), for which the asynchronous slip request generation (32; 36) is carried out to achieve the vehicle deceleration (93), depends on a coefficient of friction (63, 64) between the vehicle (10) and the road surface (47).

9. Braking method according to claim 8, wherein the asynchronous slip request generation (32; 36) is carried out selectively depending on a friction coefficient threshold comparison (35) of the friction coefficient (63, 64).

10. Braking method according to one of the preceding claims, wherein the at least one operating state (V, A; 63, 64; 67, 68) for which the asynchronous slip request is used to achieve the vehicle deceleration (93) generation (32; 36) is carried out, depends on a longitudinal acceleration (A; 67, 68) of the vehicle (10), and wherein the method includes a detection (31) of the longitudinal acceleration (A; 67, 68).

11. Braking method according to claim 10 depending on claim 8 or claim 9, further comprising a determination of the coefficient of friction (63, 64) based on the longitudinal acceleration (A; 67, 68).

12. Braking method according to claim 10 or claim 11, wherein the asynchronous slip request generation (32; 36) is performed selectively depending on a longitudinal acceleration threshold comparison (35) of the longitudinal acceleration (A; 67, 68).

13. Braking method according to one of the preceding claims, wherein the asynchronous slip request generation (32; 36) is carried out in response to a driver-side deceleration request (26) for the at least one operating state (V, A; 63, 64; 67, 68) of the vehicle (10).

14. Braking method according to one of the preceding claims, wherein the axle (30) on which the first wheel (13) and the second wheel (14) are arranged is a rear axle (30) of the vehicle (10).

15. Braking method according to one of the preceding claims, wherein the braking method (30; 34) is performed automatically by an electronic braking system (20) or an electronic control unit (70).

16. Electronic braking system (20) for a vehicle (10), wherein the electronic braking system is configured to perform a slip control (32, 33; 33, 35-37) for a first wheel (13) and for a second wheel (14) of a vehicle (10), wherein the first wheel (13) and the second wheel (14) are arranged on opposite sides (30.1, 30.2) of an axle (30) of the vehicle (10), wherein the electronic braking system (20) comprises at least one electronic control unit (70) configured to provide first Slip requirements (27) for the first wheel (13) and second Slip requirements (28) for the second wheel (14), wherein the at least one electronic control unit (70) is configured to provide an asynchronous slip requirement for at least one operating state (V, A; 63, 64; 67, 68) of the vehicle (10) to achieve a vehicle deceleration (93). to perform generation (32; 36) to generate the first slip requests (27) and the second slip requests (28) with different time-dependent progressions (31 , 32; 38, 39; 41 , 42).

17. Electronic braking system (20) according to claim 16, wherein the electronic braking system (20) is configured to perform the method (30; 34) according to any one of claims 1 to 15.

18. Vehicle (10) comprising the electronic braking system (20) according to claim 16 or claim 17, wherein the vehicle has a rear axle (30) wherein the first wheel (13) and the second wheel (14) are arranged on different sides (30.1 , 30.2) of the rear axle (30).

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