Method for controlling a braking system

Abstract

The invention relates to a method for controlling a braking system (2) of a motor vehicle (80), comprising a regenerative braking unit (4) and a hydraulic braking unit (6), comprising the steps of determining (200) an emergency braking maneuver to be performed by a driver of the motor vehicle (80) by means of a first control unit (SG1) of the regenerative braking unit (4), determining (300) a gradient for building up a regenerative braking torque (RM) by means of the first control unit (SG1), building up (400) the regenerative braking torque (RM) according to the determined gradient by means of the first control unit (SG1), and building up (500) an additional hydraulic braking torque (HM) by means of a second control unit (SG2) of the hydraulic braking unit (6).

Description

[0001] The invention relates to a method for controlling a braking system of a motor vehicle, a braking system for use in a motor vehicle and a motor vehicle with such a braking system.

[0002] Today's electrically powered motor vehicles, such as electric or hybrid vehicles, typically feature a regenerative braking system in addition to a hydraulic braking system, which allows energy to be recovered and fed into the batteries of the electric or hybrid vehicle. The regenerative braking system uses an electric motor that switches to generator mode when the brake pedal of the electric or hybrid vehicle is activated, converting the vehicle's kinetic energy into electrical energy during deceleration.

[0003] However, since the regenerative braking system does not guarantee sufficient braking force during heavy braking maneuvers, cooperation with the hydraulic braking system is essential for safety reasons. As soon as the braking demand exceeds the maximum regeneration capacity, the hydraulic brakes are used to bring the vehicle to a safe stop. To control the interaction between the regenerative and hydraulic braking systems, methods and systems for controlling the interaction between the regenerative and hydraulic braking systems are known from the prior art, for example, from DE 10 2015 210 104 A1, AT 522117 A1, and DE 10 2021 204 984 A1.

[0004] Disadvantageously, the determination of a current regenerative braking torque and the determination of a current hydraulic braking torque in known systems are carried out via different control units. Although there is usually a communication link between the control units, communication is inherently subject to a delay. Furthermore, a regenerative braking torque builds up much more quickly than a hydraulic braking torque. This inevitable delay between the activation of the regenerative and hydraulic braking torque ultimately leads to slippage on the axles of the vehicle in question or on the tires of the vehicle during more severe braking maneuvers, which leads to a significantly longer braking distance and thus endangers the safety of the vehicle occupants.

[0005] It is therefore an object of the present invention to at least partially remedy the above-mentioned disadvantages known from the prior art. In particular, it is an object of the present invention to provide a method for controlling a braking system and a braking system for use in a motor vehicle that guarantees effective minimization of a braking distance and thus increased driving safety in a simple and cost-effective manner. Furthermore, the method for controlling a braking system and the braking system for use in a motor vehicle should preferably simultaneously ensure the most effective and environmentally friendly operation of a motor vehicle.

[0006] The above object is achieved by a method having the features of claim 1, a braking system according to claim 10, and a motor vehicle having the features of claim 11. Further features and details of the invention emerge from the respective subclaims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the braking system according to the invention or the motor vehicle according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0007] According to the invention, a method for controlling a braking system of a motor vehicle with a regenerative braking unit and a hydraulic braking unit is provided.

[0008] The method according to the invention comprises the steps of determining an emergency braking action to be carried out by a driver of the motor vehicle by means of a first control unit of the regenerative braking unit, determining a gradient for building up a regenerative braking torque by means of the first control unit, building up the regenerative braking torque according to the determined gradient by means of the first control unit, and building up an additional hydraulic braking torque by means of a second control unit of the hydraulic braking unit.

[0009] According to the invention, the method in question, in particular through the inventive steps of detecting or determining a planned emergency braking, building up a regenerative braking torque according to a predetermined gradient for building up the regenerative braking torque, and building up an additional hydraulic braking torque, is designed to guarantee, in a simple and cost-effective manner, an effective minimization of a braking distance and thus increased driving safety. The method according to the invention also enables the most effective and environmentally friendly operation of a motor vehicle.

[0010] By building up a regenerative braking torque according to a predetermined gradient, as provided for by the invention, it is possible, in particular, to contribute to braking early on and thereby minimize, and in particular optimize, slip on the wheels or axles of a motor vehicle. By minimizing or optimizing slip, a hydraulic braking torque that builds up with a delay for physical reasons can also be used as effectively as possible. In addition to contributing to braking, electrical energy can be generated by the targeted buildup of the regenerative torque while minimizing or optimizing slip.

[0011] The method according to the invention can preferably be used in an at least partially electrically powered motor vehicle. An emergency braking maneuver to be performed by a driver of a motor vehicle can be understood, within the scope of the invention, in particular, as an emergency braking maneuver planned by the driver due to an emergency situation. Determining a gradient for building up a regenerative braking torque can be understood, within the scope of the invention, in particular as determining a temporal rate of change for the buildup of a regenerative braking torque. The temporal rate of change can be linear or non-linear.

[0012] With regard to precise and reliable detection of an emergency braking maneuver to be performed by a driver of a motor vehicle, it can advantageously be provided that data for determining an emergency braking maneuver to be performed by a driver of the motor vehicle is detected by means of the first control unit, wherein the detected data preferably comprise a travel distance of a brake pedal of the motor vehicle, in particular a rate of change of a movement of the brake pedal. In order to be able to distinguish a brief, accidental touch of a brake pedal, for example, from a deliberate, forceful actuation of a brake pedal to be performed during an emergency braking maneuver, it can advantageously be provided that an emergency braking maneuver is only classified as a deliberate emergency braking maneuver once a threshold value of a brake pedal travel distance or a rate of change is exceeded.

[0013] Since a communication connection is often subject to a delay, the invention further provides, for the purpose of initiating the present method at an early stage, that an emergency braking maneuver to be performed by a driver of the motor vehicle is determined independently by the first and second control units, wherein the emergency braking maneuver is preferably determined first by the first control unit and subsequently by the second control unit. An emergency braking maneuver to be performed can be detected by the first control unit, preferably based on a brake pedal movement. A pedal movement can be determined by the second control unit, preferably indirectly, based on a built-up brake pressure that builds up in the hydraulic brake unit when a brake pedal is touched, in particular when a specific brake pressure is exceeded.

[0014] Within the scope of flexibly variable accuracy with regard to reducing slip, the invention can advantageously provide for the method to be applied in an axle-specific or wheel-specific manner. An axle-specific application of the present method promises simpler and more cost-effective implementation, whereas a wheel-specific application focuses more on improved control and stability and a further reduction in braking distance. An axle-specific application of the present method can be understood, in particular, to mean that a specific gradient for building up a regenerative braking torque is established equally, i.e., of the same magnitude, for both wheels of an axle of a motor vehicle.A wheel-specific application of the present method can be understood accordingly to mean that a specific gradient for building up a regenerative braking torque for individual wheels of an axle of a motor vehicle can also be built up differently, ie in different sizes.

[0015] Within the scope of a simple and at the same time effective optimization of a slip of the wheels of a motor vehicle during a braking process and correspondingly a minimization of a braking distance of the motor vehicle, it can also be advantageous if the determination of a gradient for building up a regenerative braking torque takes place in the form of a targeted limitation of the gradient for building up a regenerative braking torque, wherein the build-up of the regenerative braking torque is preferably limited for a parameterizable time.

[0016] With regard to a particularly precise and targeted limitation of a gradient for building up a regenerative braking torque, it is further conceivable that the targeted limitation of a gradient for building up a regenerative braking torque only occurs after an emergency braking maneuver to be performed by a driver of the motor vehicle has also been determined by the second control unit. In addition to a targeted limitation of a gradient for building up a regenerative braking torque, a targeted shaping of a hydraulic braking torque preferably takes place. In this way, on the one hand, as much regenerative energy as possible can be harvested without, on the other hand, increasing the braking distance. Furthermore, this can contribute to deceleration at an early stage.

[0017] Furthermore, within the scope of a particularly precise and targeted limitation of a gradient for building up a regenerative braking torque, it can be provided that the determination of a gradient for building up a regenerative braking torque takes place on the basis of a past time after a determination of an emergency braking to be carried out by a driver of the motor vehicle.

[0018] Likewise, within the scope of a particularly precise and targeted limitation of a gradient for building up a regenerative braking torque, it can be provided that the determination of a gradient for building up a regenerative braking torque is carried out on the basis of a regenerative target braking torque that is present when determining an emergency braking maneuver to be carried out by a driver of the motor vehicle.

[0019] In order to further increase the safety of a vehicle during an emergency braking procedure, it can also be advantageous if the determination of a gradient for building up a regenerative braking torque takes into account one of the following variables: - the current road condition, - current visibility conditions, - the current status of the hydraulic brake unit, - a current state of the regenerative braking unit, - a current temperature, - current traffic conditions.

[0020] The variables mentioned can in particular contribute to achieving a more precise assessment of a possible hazard potential in the event of an emergency braking maneuver of a motor vehicle. It is also understood in the present case that individual, several or all of the mandatory and / or optional steps of the method according to the invention can be carried out in the proposed order, but also deviating from the proposed order. In this case, individual, several or all of the mandatory and / or optional steps of the method according to the invention can in particular be carried out repeatedly, for example cyclically. It is further understood that individual, several or all of the mandatory and optional steps of the method according to the invention can also be carried out at least partially automatically orcan be carried out in an automated and / or self-learning manner, in particular can be implemented by a computer, preferably via computer-implemented simulation methods.

[0021] The invention also further relates to a braking system for use in a motor vehicle, preferably for carrying out a method described above. The braking system according to the invention comprises a regenerative braking unit with a first control unit for determining an emergency braking action to be carried out by a driver of the motor vehicle, for determining a gradient for building up a regenerative braking torque, and for building up the regenerative braking torque in accordance with the determined gradient, as well as a hydraulic braking unit with a second control unit for building up an additional hydraulic braking torque. The braking system according to the invention thus has the same advantages as those already described in detail with regard to the method according to the invention. Advantageously, the first and second control units can communicate with one another, preferably via a bus system.

[0022] The invention also further relates to a motor vehicle comprising a braking system according to the invention, in particular an electric or hybrid vehicle with a braking system according to the invention.

[0023] Further advantages, features, and details of the invention will become apparent from the following description, which describes exemplary embodiments of the invention in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination.

[0024] They show schematically: Fig. 1: the individual steps of a method according to the invention for controlling a braking system of a motor vehicle, Fig. 2: a braking system according to the invention for use in a motor vehicle according to a first embodiment, Fig. 3: an exemplary graphical progression of the method according to the invention for controlling a braking system of a motor vehicle according to a first embodiment.

[0025] In the following description of some embodiments of the invention, the same reference numerals are used for the same technical features even in different embodiments.

[0026] Fig. 1 shows the individual steps of a method according to the invention for controlling a braking system 2 of a motor vehicle 80.

[0027] As in Fig. 1, the method according to the invention comprises the steps of acquiring 100 data for determining 200 an emergency braking action to be carried out by a driver of the motor vehicle 80 by means of a first control unit SG1, determining 200 an emergency braking action to be carried out by the driver of the motor vehicle 80 by means of a first control unit SG1 of the regenerative braking unit 4, and determining 300 a gradient for building up a regenerative braking torque RM by means of the first control unit SG1. Furthermore, according to the method according to the invention, a build-up 400 of the regenerative braking torque RM according to the determined gradient by means of the first control unit SG1 and a build-up 500 of an additional hydraulic braking torque HM by means of a second control unit SG2 of the hydraulic braking unit 6 are provided.

[0028] The recorded data may include, for example, a movement distance of a brake pedal of the motor vehicle 80, in particular a rate of change of a movement of the brake pedal.

[0029] The emergency braking to be carried out by a driver of the motor vehicle 80 can also be determined by the first and second control units SG1, SG2, preferably each independently.

[0030] The procedure in question can also be applied axle-specifically or wheel-specifically.

[0031] Furthermore, the determination of a gradient for building up a regenerative braking torque RM can advantageously take the form of a targeted limitation of the gradient for building up a regenerative braking torque RM, wherein the build-up of the regenerative braking torque RM is preferably limited for a parameterizable time.

[0032] A targeted limitation of a gradient for building up a regenerative braking torque RM can preferably only take place after an emergency braking to be carried out by a driver of the motor vehicle 80 has also been determined by the second control unit SG2.

[0033] The determination 300 of a gradient for building up a regenerative braking torque RM can further advantageously be carried out on the basis of a time elapsed after a determination 200 of an emergency braking to be carried out by a driver of the motor vehicle 80 or on the basis of a regenerative target braking torque that is present during a determination 200 of an emergency braking to be carried out by a driver of the motor vehicle 80.

[0034] Fig. 2 shows a braking system 2 according to the invention for use in a motor vehicle 80 according to a first embodiment.

[0035] As in Fig. 2, the braking system 2 arranged within the motor vehicle 80 comprises a regenerative braking unit 4 with a first control unit SG1 for determining 200 an emergency braking to be carried out by a driver of the motor vehicle 80, for determining 300 a gradient for building up a regenerative braking torque RM and for building up 400 the regenerative braking torque RM in accordance with the determined gradient, and a hydraulic braking unit 6 with a second control unit SG2 for building up 500 an additional hydraulic braking torque HM.

[0036] Fig. 3 shows an exemplary graphical progression of the method according to the invention for controlling a braking system 2 of a motor vehicle 80 according to a first exemplary embodiment.

[0037] According to Fig.3, the magnitude of a torque M (hydraulic torque HM and regenerative torque RM) is plotted against time t. Here, a driver braking request 8 is detected as an emergency braking operation by the first control unit SG1 at time 1 ZP1. A gradient for building up a regenerative braking torque RM is then determined. From the moment a driver braking request 8 is detected by the control unit 2, a hydraulic braking torque HM is also continuously built up, with the second control unit SG2 only detecting the initiation of an emergency braking operation after a pressure threshold has been exceeded at a time ZP2. The time difference Δt describes the time difference between the determination 300 of an emergency braking operation to be performed by a driver of the motor vehicle 80 by the first control unit SG1 and by the second control unit SG2.The time difference between t = 0 and the first time point ZP1 corresponds to the time advantage resulting from regenerative braking with regard to a braking process. From time point ZP3 onward, an emergency braking situation no longer exists, e.g., because the friction coefficient can then transfer the entire deceleration torque. From time point ZP3 onward, the gradients are then "free" again. List of reference symbols 2 braking system 4 regenerative braking unit 6 hydraulic brake unit 8 Driver braking request 80 motor vehicles 100 Collecting data to determine emergency braking 200 Determining an emergency braking 300 Determining a gradient to build up a regenerative braking torque 400 Build-up of regenerative braking torque 500 Building up an additional hydraulic braking torque SG1 Control Unit 1 SG2 Control Unit 2 M Moment ZP1 Time 1 ZP2 Time 2 ZP3 Time 3 HM hydraulic moment RM regenerative moment t time Δt time difference

Claims

[1] Method for controlling a braking system (2) of a motor vehicle (80), having a regenerative braking unit (4) and a hydraulic braking unit (6), comprising the steps: - determining (200) an emergency braking action to be carried out by a driver of the motor vehicle (80) by means of a first control unit (SG1) of the regenerative braking unit (4), - determining (300) a gradient for building up a regenerative braking torque (RM) by means of the first control unit (SG1), - building up (400) the regenerative braking torque (RM) according to the determined gradient by means of the first control unit (SG1), - building up (500) an additional hydraulic braking torque (HM) by means of a second control unit (SG2) of the hydraulic braking unit (6), characterized by that an emergency braking to be carried out by a driver of the motor vehicle (80) is determined independently by the first and second control units (SG1, SG2). [2] Method according to claim 1, characterized by that a recording (100) of data for determining (200) an emergency braking to be carried out by a driver of the motor vehicle (80) is provided by means of the first control unit (SG1), wherein the recorded data preferably comprise a movement distance of a brake pedal of the motor vehicle (80), in particular a rate of change of a movement of the brake pedal. [3] Method according to claim 1 or 2, characterized by that the emergency braking is first determined by the first control unit (SG1) and then by the second control unit (SG2). [4] Method according to one of the preceding claims, characterized by that the procedure is applied axle-specifically or wheel-specifically. [5] Method according to one of the preceding claims, characterized bythat the determination (300) of a gradient for building up a regenerative braking torque (RM) takes place in the form of a targeted limitation of the gradient for building up a regenerative braking torque (RM), wherein the build-up of the regenerative braking torque (RM) is preferably limited for a parameterizable time. [6] Method according to claim 5, characterized by that the targeted limitation of a gradient for building up a regenerative braking torque (RM) only takes place after an emergency braking to be carried out by a driver of the motor vehicle (80) has also been determined by the second control unit (SG2), wherein in addition to a targeted limitation of a gradient for building up a regenerative braking torque (RM), a targeted shaping of a hydraulic braking torque (HM) preferably takes place. [7] Method according to one of the preceding claims, characterized bythat the determination (300) of a gradient for building up a regenerative braking torque (RM) on the basis of a lapsed time takes place after a determination (200) of an emergency braking to be carried out by a driver of the motor vehicle (80). [8] Method according to one of the preceding claims, characterized by that the determination (300) of a gradient for building up a regenerative braking torque (RM) is carried out on the basis of a regenerative target braking torque that is present when determining (200) an emergency braking to be carried out by a driver of the motor vehicle (80). a EEE [9] Method according to one of the preceding claims, characterized by that the determination (300) of a gradient for building up a regenerative braking torque (RM) takes into account one of the following variables: - the current road condition, - current visibility conditions, - a current state of the hydraulic brake unit (6), - a current state of the regenerative braking unit (6), - a current temperature, - current traffic conditions. [10] Braking system (2) for use in a motor vehicle (80), for carrying out a method according to one of the preceding claims, comprising: - a regenerative braking unit (4) with a first control unit (SG1) for determining (200) an emergency braking action to be carried out by a driver of the motor vehicle (80), for determining (300) a gradient for building up a regenerative braking torque (RM) and for building up (400) the regenerative braking torque (RM) according to the determined gradient, - a hydraulic brake unit (6) with a second control unit (SG2) for building up (500) an additional hydraulic braking torque (HM). [11] Motor vehicle (80) comprising a system according to claim 10.

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