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] Modern electrically powered vehicles, such as electric or hybrid vehicles, typically feature a regenerative braking system in addition to a hydraulic braking system. This system recovers energy and feeds it back into the vehicle's batteries. The regenerative braking system incorporates an electric motor that, when the brake pedal is pressed, switches to generator mode, converting the vehicle's kinetic energy during deceleration into electrical energy.

[0003] Since the regenerative braking system does not guarantee sufficient braking force during hard braking maneuvers, cooperation with the hydraulic braking system is essential for safety reasons. Thus, as soon as the braking requirement exceeds the maximum regeneration capacity, the hydraulic brakes are engaged to bring the vehicle to a safe stop. 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] A disadvantage of known systems is that the determination of the current regenerative braking torque and the determination of the current hydraulic braking torque are carried out by different control units. While a communication link between the control units usually exists, communication is inherently subject to a delay. Furthermore, regenerative braking torque builds up much faster than hydraulic braking torque. This unavoidable delay between the control of regenerative and hydraulic braking torque ultimately leads to wheel slippage at the axles or tires of the vehicle during hard braking maneuvers, resulting in a significantly longer braking distance and thus endangering the safety of the vehicle occupants.

[0005] It is therefore an object of the present invention to at least partially overcome the aforementioned 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 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 efficient and environmentally friendly operation of the motor vehicle possible.

[0006] The foregoing problem is solved by a method with the features of claim 1, a braking system according to claim 10, and a motor vehicle with the features of claim 11. Further features and details of the invention will become apparent from the respective dependent claims, 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 and the motor vehicle according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

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

[0008] The inventive method comprises the steps of determining an emergency braking maneuver to be performed 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 present method, in particular through the inventive steps of detecting or determining a planned emergency braking maneuver, 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 effective minimization of braking distance and thus increased driving safety in a simple and cost-effective manner. The inventive method also enables the most efficient and environmentally friendly operation of a motor vehicle.

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

[0011] The method according to the invention can preferably be used in a motor vehicle that is at least partially electrically powered. Within the scope of the invention, an emergency braking maneuver to be carried out by the driver of a motor vehicle can be understood, in particular, as an emergency braking maneuver planned by the driver due to an emergency situation. Within the scope of the invention, determining a gradient for building up a regenerative braking torque can be understood, in particular, as determining a rate of change over time for building up a regenerative braking torque. This rate of change over time can be linear or non-linear.

[0012] With a view to accurately and reliably detecting an emergency stop performed by a motor vehicle driver, it can advantageously be provided that the first control unit is used to acquire data for determining whether an emergency stop is to be performed by the driver of the motor vehicle. The acquired data preferably includes the travel distance of the motor vehicle's brake pedal, and in particular the rate of change of the brake pedal's movement. To distinguish, for example, a brief accidental touch of the brake pedal from a deliberate, forceful application of the brake pedal during an emergency stop, it can advantageously be provided that an emergency stop is only classified as a deliberate emergency stop once a threshold for the travel distance of the brake pedal or the rate of change has been exceeded.

[0013] Since communication links are often subject to a delay, the invention further provides, for the purpose of initiating the method in question at an early stage, that an emergency braking maneuver to be performed by the driver of the motor vehicle is determined independently by the first and second control units, preferably being determined first by the first control unit and subsequently by the second. The first control unit can preferably detect an emergency braking maneuver by means of a brake pedal movement. The second control unit can preferably determine a pedal movement indirectly by means of a brake pressure build-up, which builds up in the hydraulic brake unit from the moment a brake pedal is touched, in particular from the point at which a specific brake pressure is exceeded.

[0014] Within the framework of flexibly variable accuracy with regard to slip reduction, the invention advantageously provides for the method to be applied axle-specifically or wheel-specifically. An axle-specific application of the method promises a simpler and more cost-effective implementation, whereas a wheel-specific application focuses more on improved control and stability and further reduction of the braking distance. An axle-specific application of the method can be understood, in particular, as establishing a specific gradient for building up a regenerative braking torque for both wheels of an axle of a motor vehicle, i.e., of the same magnitude.A wheel-specific application of the method in question can be understood 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, i.e., in different sizes.

[0015] Within the framework of a simple yet effective optimization of wheel slip of a motor vehicle during a braking process and corresponding minimization of the vehicle's braking distance, it can also be advantageous if the determination of a gradient for building up a regenerative braking torque is carried out 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 a view to particularly precise and targeted limitation of a gradient for building up regenerative braking torque, it is also conceivable that the targeted limitation of a gradient for building up regenerative braking torque only occurs after an emergency braking maneuver initiated by the driver of the vehicle is also determined by the second control unit. In addition to the targeted limitation of a gradient for building up regenerative braking torque, a targeted shaping of a hydraulic braking torque preferably takes place. In this way, as much regenerative energy as possible can be recovered without increasing the braking distance. Furthermore, deceleration can be initiated at an early stage.

[0017] Furthermore, in the context of a particularly precise and targeted limitation of a gradient for building up a regenerative braking torque, it may be provided that the determination of a gradient for building up a regenerative braking torque is based on a time elapsed after a determination of an emergency braking maneuver to be carried out by a driver of the motor vehicle.

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

[0019] To further increase the safety of a vehicle during an emergency braking maneuver, it can also be advantageous to determine a gradient for building up a regenerative braking torque taking into account one of the following parameters: - of the current road surface condition, - current visibility conditions, - of the current state of the hydraulic brake unit, - of the current state of the regenerative braking unit, - a current temperature, - current traffic conditions.

[0020] The aforementioned parameters can, in particular, contribute to a more precise assessment of the potential danger during an emergency braking maneuver of a motor vehicle. It is also understood that individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out in the proposed sequence, but also in a different sequence. In this context, individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, e.g., 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.can be executed automatically and / or self-learning, in particular can be implemented by a computer, preferably via computer-implemented simulation methods.

[0021] The invention also 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 whether an emergency braking maneuver is to be performed by the driver of the motor vehicle, for determining a gradient for building up a regenerative braking torque, and for building up the regenerative braking torque according to the determined gradient, as well as a hydraulic braking unit with a second control unit for building up an additional hydraulic braking torque. Thus, the braking system according to the invention 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 each other, preferably via a BUS system.

[0022] The invention also 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, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each 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 representation of the inventive method 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. Figure 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. As can be seen from Figure 1, the method according to the invention comprises the steps of acquiring 100 data for determining 200 an emergency braking maneuver to be performed by the driver of the motor vehicle 80 using a first control unit SG1, determining 200 an emergency braking maneuver to be performed by the driver of the motor vehicle 80 using a first control unit SG1 of the regenerative braking unit 4, and determining 300 a gradient for building up a regenerative braking torque RM using the first control unit SG1. Furthermore, according to the method according to the invention, building up 400 the regenerative braking torque RM according to the determined gradient using the first control unit SG1 and building up 500 an additional hydraulic braking torque HM using a second control unit SG2 of the hydraulic braking unit 6 are provided.

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

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

[0030] The method in question can also be applied in an axle-specific or wheel-specific manner.

[0031] Furthermore, determining a gradient for building up a regenerative braking torque RM can advantageously be carried out 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.

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

[0033] Determining a gradient 300 for building up a regenerative braking torque RM can also advantageously be done on the basis of a past time after a determination 200 of an emergency braking maneuver 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 when a determination 200 of an emergency braking maneuver to be carried out by a driver of the motor vehicle 80 is carried out.

[0034] Fig. Figure 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. As can be seen in Figure 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 maneuver 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, as well as a hydraulic braking unit 6 with a second control unit SG2 for building up 500 an additional hydraulic braking torque HM.

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

[0037] According to Fig.Figure 3 plots the magnitude of a moment M (hydraulic moment HM and regenerative moment RM) against time t. A driver braking request 8 is recognized as an emergency braking maneuver by the first control unit SG1 at time 1 ZP1. Subsequently, a gradient is determined to build up a regenerative braking torque RM. From the moment a driver braking request 8 is recognized by control unit 2, a hydraulic braking torque HM is continuously built up. The second control unit SG2 only recognizes the initiation of an emergency braking process after a pressure threshold is exceeded at time ZP2. The time difference Δt describes the time difference between the determination of an emergency braking maneuver to be performed by the driver of the 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 gained during a braking process through regenerative braking. From time point ZP3 onwards, there is no longer an emergency braking situation, for example, because the coefficient of friction can then transfer the entire deceleration torque. From time point ZP3 onwards, the gradients are then "free" again. Reference symbol list 2. Braking system 4 regenerative braking units 6 hydraulic brake unit 8 Driver brake request 80 motor vehicles 100 Collecting data to determine emergency braking 200 Determining an emergency stop 300 Determining a gradient to build up a regenerative braking torque 400 Building up the 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 torque 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 which is present when determining (200) an emergency braking to be carried out by a driver of the motor vehicle (80). [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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