Electromechanical brake system for a motor vehicle with yaw motor limitation

Abstract

The invention relates to a method for controlling electromechanical wheel brakes (104, 106, 108, 110) of a motor vehicle by means of a local wheel brake control unit (118, 120, 122, 124) assigned to the wheel brakes, the wheel brake control unit (118, 120, 122, 124) being connected to a central brake control unit (102) of the motor vehicle via a data link (154). The central brake control unit (102) is configured to determine a brake request as a function of actuation information of the brake actuation unit (112) and to transmit a wheel-individual control signal corresponding to the brake request to a local brake control unit (118, 120, 122, 124) of the wheel brakes (104, 106, 108, 110), the local brake control unit (118, 120, 122, 124) of the wheel brakes (104, 106, 108, 110) at least for one wheel (142, 144, 146, 148). The respective control signal can be converted into a modified control signal of the individual wheel.

Description

Field of the Invention

[0001] The present invention generally relates to an electromechanical braking system with yaw moment limitation for a motor vehicle, in particular a service braking system. The present invention also relates to a method for operating such an electromechanical braking system of a motor vehicle. Background Art

[0002] In an electromechanical wheel brake, generally, the brake pedal is decoupled from the braking system, and the wheel brake is designed as an electromechanically actuated wheel brake. The brake pedal is designed to detect the driver's deceleration request.

[0003] When the mechanical connection between the brake pedal and the wheel brake is disconnected, an external energy supply is required, which generates a braking torque or a force for actuating the wheel brake independently of the driver force. In addition, it is necessary to adjust the braking torque or the force of each wheel brake according to the driver's request. For this purpose, it is also necessary to detect the driver's manipulation of the brake pedal by sensors. This can occur in a known manner, for example, by redundant measurement of the brake pedal travel or the driver's foot force, where the driver braking request for the electromechanical braking system can be generated based on this information.

[0004] Due to the risk of failures in technical systems, which may lead to a reduction in braking capacity and thus to a dangerous situation in adverse cases, it is ensured by a suitable system architecture that even in case of a failure, the driver braking request can be determined and the available brake actuators can be used to implement this braking request.

[0005] In the applicant's document DE 10 2020 213 130 A1, a braking system for a motor vehicle is described, which has a component for determining a setpoint value of a deceleration request based on the driver's manipulation. For this purpose, a method is described, which can still form a deceleration request for the remaining wheel brakes that are still functioning, for example, in case of a failure of a wheel brake or a local brake control unit, so that the vehicle remains controllable when the brakes are manipulated.

[0006] For this purpose, the components of the braking system are designed redundantly, so that, for example, in case of a failure of the central brake control unit, the braking system can still transfer the manipulation information detected by the brake actuating device to the wheel brakes at a backup level. If redundancy is achieved to the greatest extent independently of the relevant components, this results in a large number of components or data links. Therefore, a third data link can be provided in a ring structure, for example, which networks the local brake control units at a backup level with each other.

[0007] Regardless of the redundancy of the specific components of the braking system, it is to be considered that, especially in the case of a front wheel brake failure, a force is built up on the remaining intact wheel brakes such that any possible yaw moment, which can occur when the vehicle rotates about the vertical axis, remains controllable for the driver.

[0008] For this purpose, a method is described in document DE 10 2020 213 130 A1, in which, in the case of a failure of the local brake control unit, the driving stability of the vehicle can generally be increased by limiting the increase in the target deceleration of the vehicle to a specific gradient.

[0009] Its disadvantage may be that, as a result, there can be an overly strong limitation of the increased request for vehicle deceleration, and thus an overly strong limitation of the braking torque to be applied, such that the braking distance is too long.

[0010] Accordingly, a braking system for a vehicle is desired which reduces or, ideally, eliminates these disadvantages, especially with respect to possible yaw moments during braking.

[0011] In particular, only a minimal limitation of the braking torque to be applied should be implemented here in order to provide the highest possible level of safety during the braking operation. The driving stability is maintained.

[0012] The inventors have worked on solving this technical problem. Summary of the Invention

[0013] This object is achieved in a surprisingly simple manner by a braking system for a motor vehicle and a method for operating such a braking system as described in one of the independent claims. Preferred embodiments and refinements of the invention can be inferred from the corresponding dependent claims.

[0014] In a first aspect, the invention accordingly relates to a braking system for a motor vehicle, the braking system comprising:

[0015] electromechanical wheel brakes,

[0016] a brake actuation unit, and

[0017] at least one central brake control unit,

[0018] each of the wheel brakes has a local brake control unit,

[0019] the central brake control unit is directly connected via at least one data link to the brake actuation unit and the local brake control units of the wheel brakes,

[0020] The central brake control unit is designed to determine at least one braking request based on the actuation information of the brake actuation unit in the normal operating mode of the braking system, and transmit the control signal of the individual wheel corresponding to the braking request to the local brake control unit of the wheel brake.

[0021] During operation, for at least one electromechanical wheel brake, the corresponding control signal can be converted into a modified control signal of the individual wheel, and the determination of the modified control signal of the individual wheel is based on the scaling factor (λ[Id]) of the individual wheel or includes the scaling factor (λ[Id]) of the individual wheel.

[0022] According to the present invention, a motor vehicle means a vehicle having axles, wherein at least one of these axles includes steerable wheels, and in addition, the drive of the wheels on at least one axle can be adapted in a wheel-specific manner.

[0023] The braking system may include electromechanical wheel brakes, also referred to as EMBs ("EMB" = electromechanical brake), wherein preferably all wheel brakes of the motor vehicle can be designed as electromechanical or electronically controllable wheel brakes.

[0024] The braking system can preferably be designed as a service brake. However, the braking system according to the present invention can also be used in combination with a parking brake.

[0025] The electromechanical wheel brake can be implemented as an electromechanical disc brake, wherein the acting force or clamping force can be generated by means of an electric motor, a front transmission device and / or a rotary translation mechanism. In this context, the acting force means the force with which the brake lining presses against the brake disc. During operation, the corresponding braking torque is generated at the wheel under consideration in this way. According to the embodiment and the control concept, the control mode can be selected to set a predefined acting force or a predefined braking torque according to the requested deceleration requirement.

[0026] The electromechanical wheel brake can also be designed as an electromechanical drum brake, wherein the motor / transmission unit actuates the expansion module, and the expansion module presses the brake lining against the brake drum with an expansion force determined based on the required requested deceleration, thereby generating the corresponding braking torque. According to the embodiment and the control concept, the actuation can be implemented such that a defined expansion force or a defined braking torque is set according to the deceleration request.

[0027] The braking control unit is preferably an electronic brake pedal. Such an electronic brake pedal (also referred to as an ePedal) typically has a braking control unit for actuation by the vehicle driver, on which a return device acts. The degree of actuation of the braking control unit is detected here by a sensor, for example in the form of an actuation travel, actuation angle and / or applied actuation force, where an actuation signal is generated based on the detected sensor quantity. The braking system can then be actuated based on the actuation information of the braking control unit.

[0028] The actuation information can include the degree of actuation of the braking control unit, in particular the actuation angle, actuation travel, or actuation force, or the braking request itself. For example, since the mechanical data of the brake pedal is not necessary here but can provide information about the deceleration to be applied by a driving function, the braking request can be transmitted directly as actuation information for an autonomous driving function. Accordingly, what is referred to as "actuation information" does not only refer to the actuation of the brake pedal, but to the actuation of the brake itself.

[0029] For this purpose, the braking control unit can be directly connected to the central brake control unit via at least one data link.

[0030] In the normal operating mode of the braking system, the central brake control unit can be designed to determine at least one braking request based on the actuation information of the braking control unit obtained via the data link and to transmit a control signal corresponding to the braking request to the local brake control unit of the wheel brake.

[0031] The central brake control unit can be set here as the central node of a star link, such that the central brake control unit is directly (i.e., straight) connected on the one hand to the braking control unit and on the other hand to the local brake control unit and can be connected to other elements of the braking system. Each link of this star link can then form a data link. In the context of the present invention, a "data link" can correspondingly also include a plurality of individual links that together establish a data link between a plurality of elements of the braking system.

[0032] According to an embodiment of the present invention, it is provided that the central brake control unit is also connected to the vehicle's data bus via a data line.

[0033] According to a preferred embodiment of the present invention, the electromechanical wheel brakes can each have an electromechanical actuator. The local brake control unit is correspondingly designed to control the respective electromechanical actuator based on the received control signal to generate a braking torque, such that a braking torque can be achieved at the wheel during operation of the braking system.

[0034] According to a preferred embodiment of the invention, the local brake control units of the wheel brakes are each connected to a wheel speed sensor of the wheel associated with the wheel brake to transmit information. In this way, for example, functions related to anti-lock brake control can be implemented for the wheel brakes, however, these functions will not be described in more detail here. The braking system forming the subject matter of the invention can be combined with such anti-lock brake control as described, for example, in document DE 10 2020 213 130 A1, or can also be combined with other controls (such as anti-slip control). Document DE 102020 213 130A1 is hereby fully incorporated into the scope of this disclosure and forms the subject matter of this application.

[0035] According to a preferred embodiment of the invention, the local brake control unit can include an adjustment module, which is designed to determine a control signal based on the actuation information.

[0036] The actuation information can detect, for example, the actuation stroke x of the brake pedal 踏板 , and can be supplied to a functional block for driver request detection. Other information can also be considered here, such as the pedal actuation speed v 踏板 , for example, it can provide information on whether the braking request belongs to an emergency braking operation. Additionally, according to an improvement of the invention, the central brake control unit can also include such an adjustment module, for example, for redundancy.

[0037] A braking request in the form of a vehicle deceleration request Z Request can be generated therefrom in another functional block. The vehicle deceleration request Z Request describes the theoretical deceleration of the vehicle to be achieved by the wheel brakes. Then, the vehicle deceleration request Z Request can be provided to another functional block for determining the braking force distribution, wherein vehicle data such as the weight of the vehicle, the wheelbase, or the position of the vehicle's center of gravity can also be considered.

[0038] From the values thus determined, a corresponding wheel individual control signal can be determined during operation for at least one wheel. Here, the value of the braking force required to implement the vehicle deceleration request Z Request in the functional block can determine the force F Sp,Request [Id] that the wheel brakes apply in a wheel individual manner, where Id = VL, VR, HL, HR (VL = left front, VR = right front, HL = left rear, HR = right rear), and transmit this force as a control signal to the local brake control unit of the wheel brake.

[0039] According to the provisions of the present invention, the control signal of an individual wheel is converted into a modified control signal of the individual wheel for at least one wheel. This should be understood to mean that the control signal of the individual wheel can be modified again. If the control signal of the individual wheel includes the force F Sp,Request [Id] of the individual wheel, then according to the present invention, the modified force F Sp,Final_Request [Id] of the individual wheel can be determined as the modified control signal of the individual wheel.

[0040] The advantage of this additional modification is that the generation of yaw moment can be suppressed to the greatest extent. In this way, the undesired rotation or swaying of the vehicle about the vertical axis (i.e., about the vertical axis of the vehicle-fixed coordinate system) can be reduced. The modification of the individual wheel can very advantageously take into account additional factors, so that compared with the method described in DE 10 2020 213 130 A1, the minimum reduction of the braking force of the individual wheel is achieved.

[0041] Here, the determination of the modified control signal of the individual wheel can advantageously be based on the scaling factor λ[Id] of the individual wheel (where Id = VL, VR, HL, HR), or include the scaling factor λ[Id] of the individual wheel. The scaling factor λ[Id] of the individual wheel can in particular be or include a state-dependent scaling factor λ[Id] of the individual wheel. "State-dependent" should be understood to mean that when determining the modified control signal of the individual wheel, the states of the remaining wheel brakes can be detected and taken into account. Therefore, other state-dependent signals or influencing factors can also be considered when controlling each wheel brake.

[0042] Therefore, the present invention provides a braking system for a vehicle, in which the braking torque applied to each wheel is only very slightly restricted or constrained, preferably as little as possible. In this way, the highest possible safety level can be provided during braking operations. This has a positive impact on driving stability, especially in difficult and dangerous situations. The present invention can thus find an optimal solution between the two partially contradictory demands of minimizing yaw moment and minimizing braking distance.

[0043] Additional influencing factors can include, for example, status information regarding all wheel brakes herein, which can be stored or provided as EMB_Status[Id], where Id = VL, VR, HL, HR. This status information can accordingly include individual wheel signals or additional individual wheel information. In particular, this includes information on which wheel brakes are operative and which wheel brakes are inoperative or in a fault state. The status information EMB_Status[Id] can include individual wheel information regarding the function of all wheel brakes of the vehicle, which can be encoded accordingly. A status-dependent scaling factor λ[Id] can accordingly provide an individual wheel value or gradient based thereon for modifying the braking request of the wheel brake.

[0044] Furthermore, an identifier is proposed which, during the operation of the wheel brake, contains information on which wheel brake the individually modified force F Sp,Final_Request [Id] should currently be determined for.

[0045] After selecting the current target wheel brake, the scaling factor λ[Id] can be applied to the individually determined wheel force F Sp,Request [Id] according to the braking force distribution. According to a preferred embodiment of the invention, the individually determined wheel force F Sp,Request [Id] is multiplied by the individual wheel scaling factor λ[Id] to obtain the corresponding value of the individually modified force F Sp,Final_Request [Id]. The individually modified force F Sp,Final_Request [Id] can accordingly be based on or include the status-dependent scaling factor λ[Id].

[0046] Different from the gradient for reducing the braking force of all wheels mentioned in DE 10 2020 213 130 A1, the gradient or scaling factor λ[Id] proposed herein is formed in more detail, as it allows for a corresponding individual modification of the braking request for each individual wheel.

[0047] According to an equally preferred embodiment of the invention, the individually modified control signal or the individually modified force of the wheel is additionally limited to the maximum allowable force F Sp,Max [Id].

[0048] According to a preferred embodiment of the invention, the maximum allowable force F Sp,Max [Id] can likewise be calculated in a status-dependent manner based on the status information EMB_Status[Id].

[0049] Thus, the individually modified force F Sp,Final_Request[Id] can be obtained according to the following steps: the individual wheel force F Sp,Request [Id] is multiplied by the scaling factor λ[Id] of the individual wheel, and subsequently compared with the maximum allowable force F Sp,Max [Id]. According to the invention, the modified force F Sp,Final_Request [Id] of the individual wheel is determined as the smaller value of the two values thus formed. The modified force F Sp,Final_Request [Id] of the individual wheel can accordingly be determined according to the following rule:

[0050] F Sp,FinalRequest [Id] = Minimum{F Sp,Max [Id], (λ[Id] * F Sp,Request [Id])}.

[0051] For example, if the left front (VL) wheel brake is considered, the result is as follows:

[0052] F Sp,FinalRequest [VL] = Minimum{F Sp,Max [VL], (λ[VL] * F Sp,Request [VL])}.

[0053] If all wheel brakes are in a faultless state, i.e., not in a fault mode, the scaling factor of the individual wheel satisfies λ[Id] = 1.0, and the maximum allowable force F Sp,Max [Id] corresponds to the theoretical value F Sp,Sys,Max [Id] of the maximum predeterminable force of this wheel brake:

[0054] λ[VL, VR, HL, HR] = {1.0, 1.0, 1.0, 1.0}

[0055] F Sp,Max [VL, VR, HL, HR] = {F Sp,Sys,Max,VA, F Sp,Sys,Max,VA, F Sp,Sys,Max,HA, F Sp,Sys,Max,HA,}.

[0056] Here it is assumed that the maximum value of the force for the front axle ("VA") is different from that for the rear axle ("HA"). Thus, for example, the maximum value of the force can be axle-dependent, but can also be adjusted for a specific vehicle.

[0057] The corresponding values can be stored, for example, in a decision matrix, which can include information about the driving behavior of the vehicle or about the speed of the vehicle as well as the corresponding fault rules or fallback rules. The decision matrix can preferably be stored in the memory of the local brake control unit such that the local brake control unit can directly access the decision matrix. In an improved embodiment of the invention, the decision matrix can also be additionally stored in the memory of the central brake control unit.

[0058] However, the corresponding information can also be provided to the central brake control unit via a data link to the vehicle or the vehicle bus. Thus, the decision matrix can be conveniently constructed and adapted customized to the vehicle. The decision matrix can also be stored accordingly in the memory of the vehicle.

[0059] In this way, various fault rules or fallback levels ("RFE" = Rückfallebene) can be defined and stored in a very advantageous manner. These can be adapted to a specific vehicle or can also be adjusted, for example, according to the user behavior or the driving behavior of the vehicle.

[0060] As previously mentioned, the maximum allowable force F Sp,Max [Id] and the scaling factor λ[Id] of the individual wheel can both be based on the status information EMB_Status[Id], which offers several advantages.

[0061] For example, if it is determined based on the status information EMB_Status[Id] that a wheel brake (HR, HL) of a rear wheel fails, the maximum force of the wheel brake of the oppositely located rear wheel can be limited to the value F Sp,RFE,Max,HA defined for this fault, which in turn can depend on the corresponding vehicle or the driving behavior of the vehicle. These values and rules can be stored particularly advantageously in the decision matrix.

[0062] For the purposes of the present invention, the defined values can also be modified according to the vehicle speed. Thus, for example, it is feasible to allow a different yaw moment at a lower vehicle speed than at a higher vehicle speed. The principle is that when driving at a low speed (e.g., at 20 km / h), the establishment of the yaw moment is slower than when driving at a high speed (e.g., at 80 km / h or higher). Taking this into account, at a low speed, for example, the difference in the force of the wheel brake VL and the diagonally opposite wheel brake HR in the case of a fault can be allowed to be greater than at a higher speed. In other words, at a lower vehicle speed, the difference in the forces of the diagonally arranged wheel brakes (VL - HR or VR - HL) does not necessarily generate a large or inadmissible high yaw moment and can therefore be allowed within certain limits.

[0063] If a wheel brake (VR, VL) of a front wheel fails, for example due to driving stability reasons, the theoretical value of the force of the diagonally arranged wheel brakes (HL, HR) of the rear wheels can be multiplied by a scaling factor λ[Id], where λ[Id] < 1.0, for example 0.7, so that the theoretical value is thus reduced. If λ[Id] approaches or is equal to zero, the component of this rear wheel brake is significantly reduced and braking is performed almost only by other wheel brakes (for example, another diagonally arranged wheel brake). The larger the scaling factor λ[Id], the stronger the braking intervention of the wheel brake to which the scaling factor λ[Id] is applied during braking in such a failure case.

[0064] The scaling factor λ[Id] can be a constant value within the full vehicle speed range. However, according to a preferred embodiment of the present invention, the scaling factor λ[Id] can also particularly depend on the vehicle speed V Kfz . Thus, it is possible to advantageously better control the (intervention) ratio of the wheel brake diagonally arranged with the faulty wheel brake during braking.

[0065] Furthermore, for example, during braking at low speeds, a higher value of λ[Id] can cause the diagonally arranged rear wheel brakes to assume a greater braking ratio and a stronger braking effect, while at medium and higher vehicle speeds, a smaller λ[Id] may be required from the perspective of driving stability.

[0066] According to a preferred embodiment of the present invention, an adjustment module or a control module that causes the local brake control unit to execute the method steps described above can be stored in the local brake control unit. The adjustment module can specify which queries or control steps should be executed within the current control loop (Loop) to control the braking torque generated by the force actuator. Accordingly, the control signal determined within the scope of this method can be, in particular, the theoretical force as described above, but in the case of drum brakes, it can be the theoretical expansion force, or it can also be the theoretical braking torque. The above functional blocks can be components of the adjustment module.

[0067] Performing the method according to the present invention by or through the adjustment module can not only prevent the wheels connected to the local brake control unit from locking, but also particularly limit the yaw moment. In a preferred embodiment of the present invention, the adjustment module can also process signals generated or formed by the local brake control unit. Therefore, the local wheel speed, the local actual force of the electromechanical wheel brake, and the deceleration request can be used to calculate the local theoretical force.

[0068] According to a preferred embodiment of the present invention, additional signals or information are provided to the adjustment module and are used to determine the scaling factor λ[Id] and / or the maximum allowable force F Sp,Max[Id]. In addition to the local wheel position and the deceleration request, these may also include at least one of the following signals or information:

[0069] - The wheel speed of at least one of the other three wheels,

[0070] - The status of at least one of the other three local brake control units or wheels,

[0071] - The force exerted by at least one of the other three local brake control units or wheels.

[0072] However, preferably, instead of using only the signal of one of the other three local brake control units or one of the other three wheels, the signals of all local brake control units or wheels are used.

[0073] According to another equally preferred embodiment of the present invention, the adjustment module also uses other signals. These other signals may include the signals or information of a sensor group or an inertial sensor system, and thus include, for example, yaw angular velocity, longitudinal acceleration, lateral acceleration, and / or steering wheel angle.

[0074] Based on these additional signals or information, the scaling factor λ[Id] can be even more precisely adapted to the specific situation. The resulting advantage is that the braking system according to the present invention has higher fault tolerance. For example, if the force exerted by the other wheel brakes in the backup stage is absent or insufficient, the yaw angular velocity and lateral acceleration can be used as an alternative.

[0075] In addition to the rule-based system described herein, it is also conceivable to alternatively or additionally use a self-learning system or a system with artificial intelligence to determine the scaling factor λ[Id] and / or the maximum force F Sp,Max [Id]. For example, such a system can also consider the specific driving behavior in relation to the driver.

[0076] The present invention very advantageously enables, for example, the storage of special parameterizations, which can depend on the considered fault situations and vehicle behavior. Therefore, the braking system according to the present invention can also be designed in an application-specific manner.

[0077] Correspondingly, the present invention also includes a method for controlling the wheel brakes of a motor vehicle, in particular electro-mechanical wheel brakes, wherein the braking system as defined above is used.

[0078] The method provides at least one local wheel brake control unit assigned to the wheel brakes,

[0079] wherein the wheel brake at least has a force actuator, which is driven by an electric motor to generate a braking torque acting on the wheel associated with the wheel brake,

[0080] Wherein, the wheel brake control unit is connected to the central brake control unit of the motor vehicle via a data link,

[0081] Wherein, the wheel brake control unit is connected to the brake operation unit via a data link,

[0082] Wherein, the brake operation unit is designed to detect a deceleration request.

[0083] Other details of the present invention can be learned from the description of the illustrated embodiments and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] In the drawings:

[0085] Figure 1 A schematic diagram of an exemplary brake system is shown,

[0086] Figure 2 An exemplary adjustment module for determining individual wheel control signals by the central brake control unit according to the operation information in the normal operation mode is shown,

[0087] Figure 3 An exemplary adjustment module for determining the modified force of the individual wheel is shown,

[0088] Figure 4 An exemplary embodiment with a scaling factor λ[Id] related to the vehicle speed V Kfz is shown,

[0089] Figure 5 An exemplary embodiment is shown, in which an overview of the available signals for determining the modified force of the individual wheel is shown,

[0090] Figure 6 Another exemplary embodiment with a sensor group for determining the modified force of the individual wheel is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0091] In the following detailed description of the preferred embodiments, for clarity, the same reference numerals denote substantially the same parts in these embodiments or these embodiments. However, for better elucidating the present invention, the preferred embodiments shown in the drawings are not always drawn to scale.

[0092] Figure 1 A simplified schematic diagram of an exemplary brake system 100 is shown. The brake system 100 includes electro-mechanical wheel brakes 104, 106, 108, 110,

[0093] a brake operation unit 112,

[0094] At least one central brake control unit 102, wherein,

[0095] Each of the wheel brakes 104, 106, 108, 110 has a local brake control unit 118, 120, 122, 124,

[0096] The central brake control unit 102 is directly connected via at least one data link 154 to the brake actuation unit 112 and the local brake control units 118, 120, 122, 124 of the wheel brakes 104, 106, 108, 110,

[0097] Wherein, the central brake control unit 102 is designed in the normal operating mode of the brake system 100 to determine at least one braking request based on the actuation information of the brake actuation unit 112 and to transmit the wheel individual control signals corresponding to the braking request to the local brake control units 118, 120, 122, 124 of the wheel brakes 104, 106, 108, 110,

[0098] Wherein, during operation, for at least one electromechanical wheel brake 104, 106, 108, 110, the corresponding control signal can be converted into a wheel individual modified control signal,

[0099] Wherein, the determination of the wheel individual modified control signal is based on the wheel individual scaling factor λ[Id] or includes the scaling factor of the wheel individual.

[0100] In this case, the brake system 100 has a central brake control unit 102, four electromechanical wheel brakes 104, 106, 108 and 110, a brake actuation unit 112, a vehicle bus 114 and a parking brake actuation device 116. Each wheel brake has a local brake control unit 118, 120, 122, 124, an actuator 126, 128, 130, 132 and a wheel speed sensor 134, 136, 138, 140, and corresponds one-to-one with the wheels 142, 144, 146, 148.

[0101] The brake actuation unit 112 is designed herein as a brake pedal (ePedal) with a fully mechanical pedal feel simulator. The brake actuation unit 112 has two independent signal output terminals 150, 152, wherein, when the vehicle driver actuates the brake actuation unit 112, the first actuation information and the second actuation information are provided via the signal output terminals 150, 152 respectively. The first actuation information is determined by the first sensor assembly, and the second actuation information is determined by the second sensor assembly. The first sensor assembly and the second sensor assembly are preferably independent of each other and preferably determine the actuation information based on different physical quantities, so as to provide redundancy.

[0102] Two separate signal outputs 150, 152 are not mandatory for the present invention. Thus, a braking system 100 having only one signal output 150 is also particularly conceivable and feasible.

[0103] In the present exemplary embodiment, the first signal output 150 is connected to the central brake control unit 102 via a data link 154. Furthermore, the central brake control unit 102 is directly connected to the local brake control units 118, 120, 122, 124 of the wheel brakes 104, 106, 108, 110, the vehicle bus 114, and the parking brake actuator 116 via the data link 154. Thereby, when the vehicle is in an autonomous or semi-autonomous driving mode, a braking request can be transmitted via the vehicle bus 114, for example. The data link 154 accordingly forms a star-shaped link, with the central brake control unit 102 arranged at the central node of this star-shaped link.

[0104] The central brake control unit 102 is configured to generate control signals for the brake control units 118, 120, 122, 124 of the wheel brakes 104, 106, 108, 110 based on the first actuation information received from the brake actuation unit 112 and / or based on a braking request received from the vehicle bus 114, and to transmit these control signals to the brake control units 118, 120, 122, 124 via the data link. The brake control units 118, 120, 122, 124 are configured to control the actuators 126, 128, 130, 132 in accordance with the received control signals, so as to generate braking torques at the wheels 142, 144, 146, 148 during operation. The wheel speeds of the wheels 142, 144, 146, 148 are respectively monitored by wheel speed sensors 134, 136, 138, 140 here, and the corresponding wheel speed information is transmitted to the central brake control unit 102 via the first data link 154. Based on the wheel speed information and, optionally, taking into account additional information, the central brake control unit 102 can implement a brake control function, such as anti-lock control.

[0105] In the present exemplary embodiment, the second signal output 152 of the brake actuation unit 112 is directly connected to the local brake control unit 118 of the wheel brake 104 via a second data link 156. Thus, in the fallback operation mode of the braking system 100, for example in the event of a fault of the central brake control unit 102, the actuation information can be directly transmitted from the brake actuation unit 112 to the local brake control unit 118 of the wheel brake 104. The design of the second signal output 152 is not mandatory for the present invention and is shown here only as an example.

[0106] In the present exemplary embodiment, the electromechanical wheel brakes 104, 106, 108, 110 are implemented as electromechanical disc brakes; however, the electromechanical wheel brakes can also be designed as electromechanical drum brakes.

[0107] The brake actuation unit 112 is an electronic brake pedal. The actuation information may include the degree of actuation of the brake actuation unit 112, in particular the actuation angle, actuation stroke, or actuation force, or the braking request itself. The brake actuation unit is directly connected to the central brake control unit 102 via at least one data link 154.

[0108] The local brake control units 118, 120, 122, 124 and / or the central brake control unit 102 include an adjustment module, which is designed to determine a control signal based on the actuation information.

[0109] As Figure 2 shown in the exemplary embodiment of, when determining the braking force distribution, additional vehicle data 214, such as the weight of the vehicle, the wheelbase, or the position of the center of gravity of the vehicle, is considered in the functional block 212. In the case shown in the exemplary embodiment, the fixedly predetermined braking force distribution between the front axle and the rear axle of the vehicle is used as a basis. Alternatively, the distribution of the braking force to be applied between the front axle and the rear axle of the vehicle can also be determined according to the intensity of the vehicle deceleration request Z Request . Then, according to the braking force distribution of the braking force F Request required to implement the vehicle deceleration request Z B determined in this way, the acting force F Sp,Request [Id] to be applied by the wheel brakes 104, 106, 108, and 110 is determined in the functional block 216.

[0110] According to the present invention, at least for one wheel, preferably for all wheels, the individual wheel control signal or the individual wheel acting force F Sp,Request [Id] to be applied is converted into an individual wheel-modified control signal or an individual wheel-modified acting force F Sp,Final_Request [Id].

[0111] Figure 3 For this purpose, an exemplary adjustment module according to the present invention is shown, which is used to determine the individual wheel-modified acting force F Sp,Request [Id] based on the determined acting force F Sp,Final_Request [Id] to be applied. According to the present invention, the occurrence of yaw moment can be reduced by this additional modification while minimizing the simultaneously applied braking torque limit as much as possible. In this way, the undesired rotation or swaying of the vehicle about the vertical axis (i.e., about the vertical axis of the vehicle-fixed coordinate system) can be further reduced.

[0112] As can be seen in Figure 3 , for the modification of the individual wheels, additional influencing factors are considered. These additional influencing factors (e.g., status information EMB_Status[VL, VR, HL, HR] regarding all wheel brakes) are provided to the functional block 312. The status information includes individual wheel information regarding the functionality of the individual wheel brakes 104, 106, 108, and 110. Based on this, the scaling factor λ[VL, VR, HL, HR] and the maximum value F Sp,Max [VL, VR, HL, HR] are determined and provided to another functional block 314.

[0113] For this purpose, information regarding the driving behavior of the vehicle or regarding the vehicle speed, as well as corresponding fault rules or fallback rules, can also be considered.

[0114] Subsequently, based on the identifier, the individual wheel scaling factor λ[Id] and the individual wheel maximum value F Sp,Max [Id] are determined in the functional block 314, where the identifier indicates for which of the wheel brakes 104, 106, 108, and 110 to be actuated the modified force F Sp,Final_Request [Id] of the individual wheel to be determined is to be determined.

[0115] Then, in another functional block 316, for the selected wheel brake, the individual wheel force F Sp,Request [Id] is multiplied by the individual wheel scaling factor λ[Id]. For the sake of clarity only, the value thus obtained is also designated as the intermediate value F Figure 3 of the modified force of the individual wheel in the Sp,Intermediate_Request [Id].

[0116] Finally, in yet another functional block 318, based on the intermediate value F Sp,Intermediate_Request [Id] of the modified force of the individual wheel and the individual wheel maximum value F Sp,Max [Id], the result value F Sp,Final_Request [Id] is determined, where according to the invention, the modified force F Sp,Final_Request [Id] of the individual wheel represents the smaller of the two values.

[0117] The modified force F Sp,Final_Request [Id] of the individual wheel is determined accordingly according to the following rule:

[0118] F Sp,FinalRequest [Id] = Minimum{F Sp,Max [Id], (λ[Id] * F Sp,Request [Id])}.

[0119] Therefore, Figure 3 the modified force F of the wheel individual shown in Sp,Final_Request [Id] represents the force to be set at the correspondingly selected wheel brakes 104, 106, 108, and 110 according to the present invention.

[0120] The functional state of each of the individual wheel brakes 104, 106, 108, and 110 is defined in the signal or status information EMB_Status[Id]. In the simplest case, classifications such as "functioning properly" or "fault / shut down" can be used here. Intermediate classifications such as "only half of the force available" or "reduced dynamics" can also be used here. Based on this status information, in order to avoid or reduce the yaw moment from the perspective of vehicle dynamics, the scaling factor λ[Id] and the limit value F Sp,Max [Id] are determined for all wheel brakes, especially the still functioning wheel brakes.

[0121] For example, if the wheel brake VL is no longer functioning, the predetermined force of the diagonal wheel brake HR (which is assumed to still be functioning properly in this example) is scaled to a smaller value by means of the scaling factor λ[Id]. This can also occur depending on the vehicle speed, as shown in more detail in the exemplary embodiment below in Figure 4 .

[0122] However, in the simplest case, the functioning wheel brake HR can also be deactivated during the braking operation by means of λ[HR]=0.0.

[0123] Therefore, both the maximum allowable force F Sp,Max [Id] and the scaling factor λ[Id] of the wheel individual are based on the status information EMB_Status[Id].

[0124] For example, if it is determined based on the status information EMB_Status[Id] that the wheel brakes (HR, HL) of the rear wheels are faulty, the maximum force of the opposite rear wheel brakes can be limited to the value F Sp,RFE,Max,HA defined for this fault, which in turn can be related to the corresponding vehicle or the driving behavior of the vehicle.

[0125] For example, the stored value F Sp,RFE,Max,HA ("FBL" = backup level, "HA" = rear axle) can also be modified according to the vehicle speed. Therefore, it can be stipulated that, for example, different yaw moments are allowed at slower vehicle speeds than at higher vehicle speeds.

[0126] If the wheel brakes (VR, VL) of the front wheels fail, for reasons of driving stability, the theoretical value of the force of the diagonally arranged wheel brakes of the rear wheels can be multiplied by a scaling factor λ[Id], where λ[Id] < 1.0, for example 0.7, such that the theoretical value is thus reduced. If λ[Id] approaches or is equal to the zero value, the component of the rear wheel brakes is significantly reduced and braking is effected almost exclusively by the other diagonally arranged wheel brakes. The larger the scaling factor λ[Id], the stronger the corresponding braking intervention of the wheel brakes to which this scaling factor λ[Id] is applied in such a failure situation.

[0127] The function blocks 312, 314, 316 and / or 318 can include corresponding regulating modules or can be part of a regulating module. The decision matrix can be stored in a memory associated with the regulating module. The decision matrix is preferably stored in the memories of the local brake control units 118, 120, 122, 124, but can also be implemented additionally in the central brake control unit 102.

[0128] The scaling factor λ[Id] can be a constant value over the entire vehicle speed range. In the case where the wheel brakes 104, 106, 108 and 110 are fully available, the scaling factor λ[Id] can be formed accordingly as follows:

[0129] λ[VL,VR,HL,HR] = {1.0, 1.0, 1.0, 1.0}

[0130] However, according to a preferred embodiment of the invention, the scaling factor λ[Id] can also be specifically related to the vehicle speed V Kfz such that, advantageously, better control of the component of the wheel brakes diagonally arranged to the failed wheel brakes can be effected during a braking operation.

[0131] Figure 4 For this purpose, an exemplary embodiment with a scaling factor λ[Id] = f(V Kfz related to the vehicle speed V is shown, in which exemplary embodiment, for purposes of illustration only, the vehicle speed V Kfz ) is used. Kfzis divided into four different speed ranges I, II, III, and IV with corresponding different scaling factors λ[Id]. In the first speed range I, the scaling factor λ[Id] remains constant here. This is followed by a second speed range II with a linearly decreasing scaling factor λ[Id]. In the next two speed ranges III and IV, the scaling factor λ[Id] also decreases linearly, but with a correspondingly smaller slope. The result of this design of the scaling factor λ[Id] is that the faster the vehicle travels, the stronger the limitation of the implemented intervention or braking torque. In other words, the lower the speed, the smaller the limitation; the higher the speed, the greater the limitation. It is obvious to those skilled in the art that this process of the scaling factor λ[Id] changing in this way only represents an exemplary embodiment, and of course, the scaling factor λ[Id] and the vehicle speed V Kfz between other relationships and rules can also be stored and applied.

[0132] In addition, for example, during braking, a higher λ[Id] value at low speeds can make the diagonal rear-wheel brakes assume a greater braking proportion and higher braking efficiency, while at medium and high vehicle speeds, a small λ[Id] is required in terms of driving stability. The design of the proportionality factor λ[Id] can also additionally depend on whether the corresponding wheel is associated with the front axle or the rear axle.

[0133] In this exemplary embodiment, for this purpose, an adjustment module is stored in the central brake control unit 102, and the adjustment module executes the method steps described above. The adjustment module specifies which queries or control steps are to be executed within the current control loop to control the braking torque generated by the force actuator. In the above exemplary embodiment, the control signal determined within the scope of this method relates to the theoretical acting force. Of course, it can also relate to the theoretical expansion force or the theoretical braking torque.

[0134] By utilizing or having the adjustment module execute the method according to the present invention, the occurrence of yaw moment can be suppressed to the greatest extent or ideally completely avoided. According to the first embodiment, the adjustment module mainly uses the signals formed on or in the local brake control units 118, 120, 122, 124 here. The local wheel speed, the local actual acting force of the electromechanical wheel brakes 104, 106, 108, 110, and the deceleration request are used to calculate the local theoretical acting force.

[0135] In the exemplary embodiment, the adjustment module can use additional signals and information to determine the scaling factor λ[Id] and / or the maximum allowable acting force F Sp,Max [Id]. Figure 5For this purpose, exemplary embodiments are shown, in which an overview of further available signals or information for determining the modified forces of the individual wheels is shown. In addition to the local wheel position and the deceleration request, these signals also include:

[0136] - the wheel speed of at least one of the further three wheels 142, 144, 146, 148,

[0137] - the state of at least one of the further three local brake control units 118, 120, 122, 124 or the wheels 142, 144, 146, 148, and / or

[0138] - the force of at least one of the further three local brake control units 118, 120, 122, 124 or the wheels 142, 144, 146, 148.

[0139] For the brake system 100 according to the invention, it is provided that not only the signals of one of the further three local brake control units 118, 120, 122, 124 or the wheels 142, 144, 146, 148 are used, but also the signals of all local brake control units 118, 120, 122, 124 or the wheels 142, 144, 146, 148.

[0140] According to another, particularly preferred embodiment of the invention, as Figure 6 shown, the adjustment module also uses other signals. These signals can include signals or information of the sensor group and / or the steering wheel angle.

[0141] Based on these additional signals or information, the scaling factor λ[Id] can be adapted even more precisely to the specific situation. The resulting advantage is that the brake system according to the invention has a higher fault tolerance. For example, if the forces of the other wheel brakes are absent or insufficient in the fallback level, the yaw angular velocity and / or the lateral acceleration can be used as an alternative.

[0142] For example, for the data processing within the adjustment module, the reference speed of the vehicle can be derived from the sum of the wheel speeds of the individual wheels 142, 144, 146, 148. In particular, the state of the local brake control units 118, 120, 122, 124 can be additionally queried here, where only those wheel speeds transmitted from the brake control units 118, 120, 122, 124, or those wheel speeds whose state indicates that the wheel brakes are in good working order, are considered when determining the reference speed.

[0143] The specific determination of the reference speed (i.e., the specific calculation rule) can also depend on the position of the wheel brakes on the vehicle here.

[0144] According to another embodiment, it can also be provided that when determining the vehicle reference speed and / or the vehicle deceleration and / or the change in the rotational behavior of the wheels, the vehicle reference speed and / or the vehicle deceleration and / or the change in the rotational behavior of the wheels determined at an earlier time are taken into account. In this way, short-term fluctuations in the determined values can be filtered out, thus enabling a coordinated control behavior.

[0145] Furthermore, according to another embodiment of the present invention, the reliability of the method can be improved by using the maximum individual wheel speed of the wheels as the vehicle reference speed when the vehicle reference speed is determined by the wheel brake control unit assigned to the rear wheels.

[0146] Similarly, according to yet another embodiment of the present invention, determining the rotational behavior of the wheels associated with the wheel brakes includes determining the change in the wheel speed of the wheels, wherein a classification of the deceleration behavior is derived based on the determined change in the wheel speed, and the classification of the deceleration behavior is taken into account when determining the control mode.

[0147] For example, if the right rear wheel HR is considered, according to the present invention, the force of the left rear wheel can be incorporated into the calculation of the force specification of the right rear wheel. Thus, for example, in order to achieve the highest possible stability of the vehicle, the force specification can be reduced to the level of the left rear wheel, plus an offset value that is selected based on the level of the allowable yaw moment. This can occur if there is a large difference between the forces of the right rear wheel and the left rear wheel.

[0148] The present invention very advantageously enables the storage of special parameterizations, which can depend, for example, on the observed fault situations and the vehicle behavior. Thus, the braking system according to the present invention can also be designed in an application-specific manner.

[0149] The present invention also provides a method for controlling the wheel brakes 104, 106, 108, 110 of a motor vehicle, in particular electromechanical wheel brakes, wherein the braking system 100 described above is used.

[0150] List of reference signs:

[0151] 100 Braking system

[0152] 102 Central braking control unit

[0153] 104 Wheel brake

[0154] 106 Wheel brake

[0155] 108 Wheel brake

[0156] 110 Wheel brake

[0157] 112 Braking operation unit

[0158] 114 Vehicle bus

[0159] 116 Parking brake operating device

[0160] 118 Local brake control unit

[0161] 120 Local brake control unit

[0162] 122 Local brake control unit

[0163] 124 Local brake control unit

[0164] 126 Actuator

[0165] 128 Actuator

[0166] 130 Actuator

[0167] 132 Actuator

[0168] 134 Wheel speed sensor

[0169] 136 Wheel speed sensor

[0170] 138 Wheel speed sensor

[0171] 140 Wheel speed sensor

[0172] 142 Wheel

[0173] 144 Wheel

[0174] 146 Wheel

[0175] 148 Wheel

[0176] 150 Signal output terminal

[0177] 152 Signal output terminal

[0178] 154 Data link

[0179] 156 Data link

[0180] 158 Data link

[0181] 212 Functional block

[0182] 214 Functional block

[0183] 216 Functional block

[0184] 312 Functional block

[0185] 314 Functional block

[0186] 316 Functional block

[0187] 318 Function Block

Claims

1. A braking system (100) for a motor vehicle, the braking system comprising: Electromechanical wheel brakes (104, 106, 108, 110), A brake operating unit (112), At least one central brake control unit (102), Each of the wheel brakes (104, 106, 108, 110) has a local brake control unit (118, 120, 122, 124), The central brake control unit (102) is directly connected via at least one data link (154) to the brake operating unit (112) and the local brake control units (118, 120, 122, 124) of the wheel brakes (104, 106, 108, 110), The central brake control unit (102) is designed in the normal operating mode of the braking system (100) to determine at least one braking request based on the operating information of the brake operating unit (112) and to transmit a control signal for the individual wheel corresponding to the braking request to the local brake control units (118, 120, 122, 124) of the wheel brakes (104, 106, 108, 110). During operation, for at least one electromechanical wheel brake (104, 106, 108, 110), the corresponding control signal can be converted into a modified control signal for the individual wheel, and the determination of the modified control signal for the individual wheel is based on the scaling factor (λ[Id]) of the individual wheel or includes the scaling factor of the individual wheel.

2. The braking system (100) according to the previous claim, characterized in that, The electromechanical wheel brakes (104, 106, 108, 110) are implemented as electromechanical disc brakes or electromechanical drum brakes.

3. The braking system (100) according to any one of the preceding claims, characterized in that, The brake operating unit (112) includes an electronic brake pedal.

4. The braking system (100) according to any one of the preceding claims, characterized in that, The control signal of the individual wheel includes the force (F Sp,Request [Id], where Id = VL, VR, HL, HR) of the individual wheel, and the modified control signal of the individual wheel includes the modified force (F Sp,Final_Request [Id]).

5. The braking system (100) according to any one of the preceding claims, characterized in that, The determination of the scaling factor (λ[Id]) for the individual wheel takes into account the function of at least one further, preferably each further wheel brake (104, 106, 108, 110) of the motor vehicle.

6. The braking system (100) according to any one of the preceding claims, characterized in that, The scaling factor (λ[Id]) of the wheel individual depends on the vehicle speed (V Kfz ).

7. The braking system (100) according to any one of the preceding claims, characterized in that, The scaling factor (λ[Id]) of the individual wheel is constant over the entire vehicle speed.

8. The braking system (100) according to any one of the preceding claims, characterized in that, The modified force (F Sp,Final_Request [Id]) of the wheel individual can be limited to the maximum allowable force (F Sp,Max [Id]) of the wheel brakes (104, 106, 108, 110).

9. The braking system (100) according to any one of the preceding claims, characterized in that, Determine the modified force (F Sp,Final_Request [Id]) of the wheel individual according to the following rules: F Sp,FinalRequest [Id] = Minimum{F Sp,Max [Id], (λ[Id] * F Sp,Request [Id])}.

10. The braking system (100) according to any one of the preceding claims, characterized in that, When calculating the maximum allowable force (F Sp,Max [Id]), information about the driving behavior of the vehicle or information about the vehicle speed and corresponding failure rules or fallback rules are taken into account.

11. The braking system (100) according to any one of the preceding claims, characterized in that, The local brake control units (118, 120, 122, 124) and / or the central brake control unit (102) comprise an adjustment module for calculating a scaling factor (λ[Id]) and / or a maximum allowable force (F Sp,Max [Id]), which preferably takes into account the local wheel position and the deceleration request.

12. The braking system (100) according to any one of the preceding claims, characterized in that, The local brake control units (118, 120, 122, 124) and / or the central brake control unit (102) include a decision matrix for determining the individual scaling factor (λ[Id]) and / or the maximum allowable force (F Sp,Max [Id]) of the wheels, and this decision matrix is stored in the memory.

13. The braking system (100) according to any one of the preceding claims, characterized in that, As an alternative or supplement to the decision matrix, a self-learning system or a system with artificial intelligence is used to determine the scaling factor (λ[Id]) and / or the maximum allowable force (F Sp,Max [Id]) of the individual wheel.

14. The braking system (100) according to the previous claim, characterized in that, Additionally, at least one of the following signals or information is used to calculate a scaling factor (λ[Id]) and / or a maximum allowable force (F Sp,Max [Id]): - The wheel speed of at least one of the other three local wheels (142, 144, 146, 148), - The state of at least one of the other three local brake control units (118, 120, 122, 124) or wheels (142, 144, 146, 148), - The force exerted by at least one of the other three local brake control units (118, 120, 122, 124) or wheels (142, 144, 146, 148), - A sensor set, - The steering wheel angle.

15. A method for controlling wheel brakes (104, 106, 108, 110) of a motor vehicle, in particular electromechanical wheel brakes (104, 106, 108, 110), wherein, The braking system (100) as claimed in any one of the preceding claims is used.

Images