Method for operating a brake system, control unit and brake system
By storing and using the efficiency value of the pressure generation device in the motor vehicle braking system, the interruption problem of braking force support in the event of sensor failure is solved, and the continuous operation of the braking system and a better driving experience are achieved.
Patent Information
- Application Number
- CN202411825295.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-20
- Filing Date
- 2024-12-12
- Publication Date
- 2025-06-20
AI Technical Summary
In the event of sensor failure or function errors, the prior art requires immediate switching to the mechanical backup stage, resulting in interruption of braking force support and affecting the driving experience.
By obtaining and storing the efficiency value of the pressure generating device according to the braking requirements and the detected hydraulic pressure during normal operation, the pressure generating device is operated according to the braking requirements and the stored efficiency value when the sensor function is incorrect to ensure the continuous operation of the brake system.
In the event of a sensor failure, by considering the efficiency value, the change in the pressure generation device can be compensated, the braking force can be maintained, the time of switching to the mechanical backup stage can be delayed, and the driving experience can be improved.
Smart Images
Figure CN120171491A_ABST
Abstract
Description
Field of the Invention
[0001] The invention relates to a method for operating a braking system of a motor vehicle, wherein the braking system has at least one wheel brake that can be hydraulically actuated, at least one pressure generating device that can be controlled, and at least one actuating element that can be actuated by a user, the pressure generating device being configured to provide hydraulic pressure in a brake circuit having at least one wheel brake, the actuating element being configured to preset a braking requirement, wherein at least one sensor for detecting the actual hydraulic pressure in the brake circuit is assigned to the brake circuit, and wherein the pressure generating device is controlled based on the braking requirement and the actual pressure detected by the sensor in the brake circuit.
[0002] Furthermore, the invention relates to a control unit that is specifically designed to perform the method described above during normal use.
[0003] Furthermore, the invention relates to a braking system of a motor vehicle as described above, which has the control unit described above. Background Art
[0004] With the electrification of motor vehicles, the number and demand for electrified braking systems are also increasing. These electrified braking systems are particularly configured as so-called brake-by-wire systems, and no mechanical connection is required between the brake pedal and the brake circuit or the wheel brakes. In these systems, a pressure generating device is typically used, which can be operated electrically and is controlled based on the detected braking requirement in order to provide the hydraulic pressure required to achieve the desired braking force in a brake circuit having at least one wheel brake. Typically, such a pressure generating device has a controllable electric motor that is operatively connected to a piston pump, which has a hydraulic piston that is movable in a hydraulic cylinder. By moving the hydraulic piston, the hydraulic volume in the brake circuit is displaced, and thereby the hydraulic pressure in the brake circuit is increased. Here, the volume displacement or pressure increase is related to the effective surface of the hydraulic piston, the movement path of the hydraulic piston, and the force with which the hydraulic piston moves in the cylinder. Here, the pressure generated in the brake circuit is monitored by a sensor in order to adjust the control of the pressure generating device such that the actual pressure generated corresponds as accurately as possible to the desired hydraulic pressure generated based on the braking requirement.
[0005] If the information detected by the sensor is unavailable because the sensor has a functional error, for example, it is known that a mechanical intervention of the actuating element can be implemented in the brake circuit as a fallback level. For this purpose, in the known solutions, the brake pedal is directly hydraulically coupled to the brake circuit so that the user or driver of the motor vehicle can directly generate hydraulic pressure in the brake circuit by actuating the brake pedal. Since in this case the brake force amplifier provided by the pressure generating device is canceled, the failure of the pressure sensor and the switchover to the mechanical fallback level are immediately perceptible to the driver. Summary of the Invention
[0006] The method according to the invention has the advantage that in the event of a sensor failure or functional error, it is not necessary to immediately switch to the mechanical fallback level, but rather the brake force support can still be maintained.
[0007] To this end, according to the present invention, it is provided that, during the still existing full functionality or error-free operation of, in particular, a pressure sensor, an efficiency value of the pressure generating device is determined and stored based on the braking requirement and the detected actual hydraulic pressure, and in the case of a functional error of the sensor, the pressure generating device is controlled at least based on the braking requirement and the stored efficiency value. As long as the sensor does not have an error function, the efficiency value can thus be determined during the continuous operation of the braking system, which efficiency value is in particular generated from the relationship between the corresponding braking requirement and the resulting hydraulic pressure detected by the sensor respectively. Herein, the efficiency value takes into account in particular changes in the pressure generating device, which may occur over time, for example due to wear. Thus, the efficiency of the pressure generating device decreases over time, for example because the sealing of the piston pump decreases, or because the mechanical structure of the transmission arranged between the electric motor and the piston pump becomes slack or has an increased clearance due to wear. Therefore, what is taken into account by the efficiency value is that the behavior of the pressure generating device may change especially with increasing age. Thus, by taking the efficiency value into account in the control of the pressure generating device, this change can be compensated, and thus the hydraulic pressure in the brake circuit can be adjusted sufficiently precisely even without the value of the pressure sensor. Therefore, in the case of a functional error of the sensor, by taking the efficiency value into account, at least as much as possible the pressure regulation that can usually be achieved by the sensor is compensated. Thereby, the continued operation of the braking system can be achieved without knowing the actual pressure, so that the brake booster is additionally available to the driver. Thereby, in particular, a slow or sliding switch to the mechanical standby level can be made, which enables the driver to still use the brake booster at least for a certain period of time. In addition, other boundary conditions that are important for the efficiency of the pressure generating device are taken into account hereby, such as the temperature of the hydraulic medium in the pressure generating device or the brake circuit, the age of the components of the braking system, or the transmission lag of the transmission connecting the electric motor and the piston pump. Therefore, preferably, the efficiency value is determined based on the current temperature, the age of the braking system (in particular the pressure generating device), the transmission lag, and / or the detected actual pressure of the sensor. Thereby, in particular, one or more characteristic curves and / or characteristic graphs that are advantageously used in the failure of the sensor or in the error function of the sensor are generated, in order to select, for example, an efficiency value suitable for the current operating situation based on the current temperature.
[0008] Preferably, the efficiency value is detected and stored regularly, in particular at preset time intervals or with each braking requirement. This ensures that a relatively current efficiency value that can be used for the continuous operation of the braking system is available when the sensor fails.
[0009] Preferably, the pressure generating device has a controllable electric motor and a hydraulic piston drivable by the electric motor for generating hydraulic pressure, wherein the electric motor is coupled to the hydraulic piston via a transmission, and wherein the efficiency value of the transmission is determined as the efficiency value. In this regard, the pressure generating device is in particular an electric piston pump. Since the transmission in particular has different efficiencies at different temperatures, which can arise for example from the temperature-dependent dimensions of the transmission components, the efficiency of the transmission is very important for the hydraulic pressure in the brake circuit. Thus, in the same control of the electric motor, the generated hydraulic pressure can increase or decrease with temperature changes. Although this effect is usually recognized by sensors and regulated by controlling the pressure generating device, in the case of sensor failure, now by means of the present method, this effect is at least partially compensated by knowledge of the efficiency value.
[0010] Furthermore, it is preferably provided that the current pressure value of the hydraulic medium in the brake circuit is estimated based on the actual torque of the electric motor, the piston pump, in particular the hydraulic acting surface of the hydraulic piston of the piston pump, and the efficiency value. By means of the estimated pressure value, it is furthermore possible to achieve the above-described advantageous regulation of the pressure generating device, which results in the customary behavior of the brake system for the driver. From knowledge of the actual torque and the hydraulic acting surface of the hydraulic piston, the theoretical contribution of the pressure generating device to the hydraulic pressure in the brake circuit can be determined. By taking into account the efficiency value, this contribution is advantageously corrected in order to optimize the control of the pressure generating device in order to compensate for temperature influences, aging phenomena, etc.
[0011] Preferably, the pressure value is estimated based on the transmission ratio of the transmission of the pressure generating device and the direction of movement of the electric motor. If the transmission has a transmission ratio, then this is advantageously taken into account. By taking into account the direction of movement, it is achieved that the efficiency of the transmission is optimally taken into account, since this efficiency can be different depending on the direction of movement or action of the electric motor.
[0012] According to a preferred refinement of the invention, the pressure generating device is controlled based on the braking requirement and the estimated pressure value in order to maintain the optimal operation of the brake system in the event of a sensor failure. Preferably, the brake system is only switched to the mechanical standby level (if possible) after the elapse of a preset time in order to avoid the last stored efficiency value being too small such that it can no longer ensure the optimal continued operation of the brake system, for example because the ambient temperature or the brake circuit temperature has changed by more than a preset limit value since the last detected efficiency value. Particularly preferably, in the event of a fault or when an incorrect function of the sensor is recognized, a warning message is furthermore sent to the driver, so that the driver can promptly seek a workshop in order to be able to repair the brake system.
[0013] Preferably, the estimated pressure value is compared with the pressure value detected by the pressure sensor. Thus, functional errors of the pressure sensor can be recognized, for example. Particularly preferably, during normal operation, i.e., when the pressure sensor is working error - free, the efficiency value is determined or corrected based on the above - mentioned comparison, so that the efficiency value is obtained based on the estimated pressure. In the case of a malfunction of the pressure sensor, it is preferably switched from the measured pressure value to the estimated pressure value. Since the efficiency value has already been obtained based on the estimated pressure value, a simple switch between the measured pressure value and the estimated pressure value can be made. In addition, the following advantage results, namely that a pressure regulator originally present in the system can be included.
[0014] According to a preferred refinement of the invention, a target torque is preset for the electric motor based on the braking requirement and the efficiency value, taking into account the braking amplification, so that for the driver, the malfunction of the sensor is at least not immediately noticeable.
[0015] The control unit according to the invention is characterized in that it is specifically designed to carry out the method according to the invention during normal use. The above - mentioned advantages result therefrom.
[0016] The braking system according to the invention is characterized by the control unit according to the invention. The above - mentioned advantages result therefrom. Description of the Drawings
[0017] The invention will be explained in more detail below with the aid of the drawings. For this purpose,
[0018] Figure 1 a favorable braking system for a motor vehicle is shown in a simplified illustration,
[0019] Figure 2 a flow chart for explaining a favorable method for operating the braking system is shown, and
[0020] Figure 3 a schematic overview of the favorable method is shown. Detailed Description of the Invention
[0021] Figure 1 A favorable braking system 1 for a motor vehicle, which is not shown in detail here, is shown in a simplified illustration. The braking system 1 has a master brake cylinder 2, which is currently configured as a tandem cylinder and is hydraulically connected to two brake circuits 3, 4 of the braking system 1. Each brake circuit 3, 4 has at least one, currently two hydraulically actuable wheel brakes 5. The wheel brakes 5 are configured as friction brakes.
[0022] The master brake cylinder 2 is assigned an actuating element 6, which is currently in the form of a brake pedal and can be actuated by the driver of the motor vehicle. The brake pedal is mechanically coupled to a piston, in particular a tandem piston 2 of the master brake cylinder 2. A sensor 7 is assigned to the brake pedal 6, which sensor monitors the actuation of the actuating element 6, in particular the actuation path, the actuation speed and / or the actuation force. The master brake cylinder 2 is also connected to a pedal feel simulator 8, into which the hydraulic volume displaced from the master brake cylinder 2 by actuating the brake pedal can be introduced, so that the driver also obtains a reproducible and comfortable brake pedal feel despite the hydraulic / mechanical decoupling of the wheel brakes 5 from the brake pedal 6. For this purpose, a controllable disconnect valve 9 is provided between the master brake cylinder 2 and the wheel brakes in the respective brake circuits 3, 4, which disconnect valve is arranged between the pedal feel simulator 8 and the wheel brakes 5. If the disconnect valve 9 is opened, the hydraulic volume from the master brake cylinder 2 is directly guided into the pedal feel simulator 8.
[0023] Furthermore, the brake system 1 has a pressure generating device 10, which has an electric motor 11, which is connected to a hydraulic pump, in particular via a transmission 17, and the hydraulic pump is currently configured as a piston pump 12. The transmission 17 has a transmission ratio that is particularly advantageous for the operation of the piston pump. The pressure generating device 10 is connected to the respective disconnect valve 9 and the wheel brakes 5 and the respective brake circuits 3, 4. If the electric motor 10 is actuated, the electric motor drives the hydraulic pump, whereby the hydraulic volume is displaced in the respective brake circuits 3, 4 and a corresponding hydraulic pressure is generated there, which hydraulic pressure can be used to actuate the wheel brakes 5. By means of inlet valves and outlet valves assigned to the wheel brakes 5 (schematically shown by the box 13 in Figure 1 ), the available actual hydraulic pressure is specifically distributed to the individual wheel brakes 5 in order on the one hand to meet the braking requirements and in order on the other hand to implement, for example, driving safety functions, such as the ABS or ESP function of the brake system.
[0024] The brake system 1 also has sensors 14, in particular pressure sensors, for detecting or monitoring the hydraulic pressure p provided by the pressure generating device 10 ist . Furthermore, a current sensor 15 is assigned to the electric motor 11, by means of which current sensor the operating current of the electric motor 11 can be monitored.
[0025] The sensor values are monitored / detected by a control unit 16, and the pressure generating device 10 and the valves (box 13) are actuated. Here, the control unit 16 is configured to carry out the method described below.
[0026] During normal operation of the braking system 1, a braking requirement is generated by actuating the actuating element 6, which is detected by the control unit 16. Under normal conditions, the separating valve 9 is open, so that actuation of the brake pedal only causes the hydraulic volume to move from the master brake cylinder 2 into the pedal feel simulator 8, but not into the brake circuits 3, 4. Instead, depending on the detected braking requirement, the pressure generating device 10 is controlled by the control unit 16 to generate the hydraulic target pressure p required to achieve the braking requirement in the brake circuits 3, 4 soll , which hydraulic target pressure is subsequently supplied to the selected wheel brakes 5 by controlling the valves (block 13) in order to ensure the desired deceleration. Here, the control unit 16 is configured to implement brake force support or increase (growth), whereby the hydraulic pressure available in the brake circuits 3, 4 is significantly greater than the hydraulic pressure generated by the driver in the master brake cylinder 2
[0027] If the sensor 14 fails or the information or signal provided by the sensor 14 disappears, then the separating valve 9 has hitherto been closed, so that the driver can mechanically generate, by actuating the actuating element 6, the hydraulic pressure generated in the master brake cylinder 2 directly in the corresponding brake circuit and can apply this hydraulic pressure to the wheel brakes 5. However, subsequent loss of brake force support may lead to a corresponding reduction in the power of the braking system 1, where the driver immediately perceives the cancellation of the brake force support
[0028] Instead, what is achieved by the method now advantageously carried out by the control unit 16 is that even in the case of a malfunction of the sensor 14, advantageous brake force support is still ensured
[0029] Figure 2 and Figure 3 For this purpose, the method described subsequently is shown schematically:
[0030] Figure 2 A simplified flow chart is shown here, and Figure 3 a more detailed illustration is shown. Here, a dashed separating line is drawn in Figure 3 , where above the separating line the physical characteristics of the system are shown, and below the separating line an advantageous method is shown in the form of an electrical circuit diagram
[0031] When the driver actuates the actuating element 6, the target pressure p is calculated soll , and the pressure generating device 10 is controlled according to this target pressure. Here, the control unit 16 in particular calculates the volume flow V soll , which volume flow is required in order to achieve the target pressure p in the brake circuits 3, 4 by means of the pressure generating device 10 sollHere, preferably, the pressure regulator 18 is present in the control unit 16, and the pressure regulator consists of an open-loop controller and a closed-loop controller. Through the open-loop controller, the volume flow rate V is preferably controlled according to the PV curve or the pressure-volume curve or one or more stiffness curves of the wheel brake and the equipment itself that forms the basis of the braking system. soll According to the target pressure p generated by the braking force requirement soll , the desired volume flow rate is directly obtained through the PV curve. Then, the motor 11 or its power electronics 21 is controlled by the speed regulator 19 and the torque regulator 20 in order to achieve the target pressure p. soll .
[0032] However, since the braking system 1 may also be subject to the following interference factors, such as leakage, gas inclusions in the brake lines, or temperature-related viscosity changes of the brake fluid, etc., a closed-loop controller is additionally provided. The closed-loop controller, in particular through the regulation loop and the PID regulator, according to the actual pressure p actually present in the braking system ist obtains the deviation from the target pressure p soll and the actual pressure p ist , and based on this pressure difference, corrects or adjusts the control of the pressure generating device 10, so that the actual pressure corresponds to the target pressure as accurately as possible.
[0033] As Figure 3 shown, the hydraulic pressure p detected by the sensor 14 ist is generated according to the volume V moved by the piston pump 12 ist , and this volume is generated according to the piston surface A of the piston and the path x that the piston moves ist . Here, the path x is generated according to the force F acting on the piston ist . The force F ist is generated according to the rotation of the motor 11 and the transmission ratio of the transmission 17.
[0034] If the information about the actual pressure p ist usually provided by the pressure sensor 14 fails, for example due to a malfunction of the sensor 14, then it is no longer possible to perform the corresponding adjustment or correction.
[0035] Currently, it is set to avoid the mechanical standby level, and in addition, maintain the braking force support for at least a preset period of time. Thus, for the driver, a better pedal feel and better braking power of the braking system 1 are retained. For this purpose, through the control unit 16, with the help of the observer 22, alternative information is calculated, and one value or multiple values of the sensor 14 should be replaced by this alternative information, and the target pressure p soll is provided, and then this target pressure is considered instead of the sensor value of the sensor device 14.
[0036] To this end, consider at least one other sensor present in the braking system, in particular a plurality of sensors, such as in particular the values of one or more current sensors 15. The current sensors 15 in particular detect the currents iU, iV, iW of the individual phases of the windings of the electric motor 11. Furthermore, preferably, based on the detected current values, the actual torque M of the electric motor 11 is determined or calculated with the aid of a model 23 of the electric motor 11. ist .
[0037] Furthermore, consider the efficiency of the pressure generating device 10, in particular the transmission 17 that connects the electric motor 11 to the piston pump 12. The efficiency of the transmission 17 is very important for converting the torque of the electric motor into the hydraulic pressure that can be provided by the hydraulic piston of the piston pump. By an advantageous method, in order to calculate alternative information, at least the efficiency of one transmission 17 is considered in the event of a failure of the pressure sensor information.
[0038] According to Figure 1 , in step S1, the braking system 1 is put into operation. In the subsequent step S2, the functionality of the braking system 1 and in particular the pressure sensor 14 is monitored. When the pressure sensor 14 is operating properly and there is pressure sensor information, the braking system 1 continues to operate as a by-wire braking system in step S3 as is common. Here, however, the efficiency value of the pressure generating device 10 is continuously determined and monitored with the aid of an observer 22, and in particular this efficiency value is stored in step S4 by the control unit 16 at regular intervals. The efficiency value is in particular determined based on the current braking requirement, the current actual pressure in the braking system 1 and provided by the pressure generating device 10, the current temperature of the pressure generating device 10, at least the age of the pressure generating device, the transmission ratio of the transmission, the transmission hysteresis of the transmission 17 and / or the direction of movement of the piston or the electric motor 11. In particular, the efficiency value is generated based on the deviation of the actual pressure from the target pressure preset by the braking force requirement.
[0039] The torque M of the electric motor 11 determined from the phase currents by means of the sensor 15 ist is proportional to the load acting on the electric motor 11, which load corresponds to the actual pressure in the respective brake circuits 3, 4. Therefore, preferably, based on the actual torque M of the electric motor 11 ist the hydraulic pressure in the brake circuit is estimated as alternative information. If the actual torque M of the electric motor 11 ist is known, then preferably the hydraulic pressure p is estimated as follows based on the effective surface A of the hydraulic piston of the piston pump 12, the determined efficiency value, the transmission ratio of the transmission ist :
[0040]
[0041] Accordingly, the target torque M corresponding to the target hydraulic pressure p can be determined based on the target pressure acting on the pressure piston, the effective surface A of the pressure piston, the transmission ratio of the transmission, and the efficiency value described above. soll The target torque M soll :
[0042]
[0043] The target torque M soll is preferably determined by a calculation unit 24 which also determines the target pressure p for the observer 22. soll .
[0044] The torque deviation ΔM is generated by the target torque M soll and the actual torque M ist , and the volume correction ΔV is generated by the torque deviation and the amplification factor f of the amplifier 25 of the electric motor 11:
[0045] ΔM = target torque - actual torque
[0046] ΔV = ΔM * f
[0047] Preferably, the target speed ω of the electric motor 11 soll is calculated from the volume correction and is taken into account by the speed controller in addition to the actual speed ω ist . The correction of the working speed ω of the electric motor 11 or the pressure piston pump is preferably determined by a PID control loop, so that the braking pressure can be adjusted overall without the pressure sensor 14.
[0048] According to an alternative method, an estimated pressure is determined with the aid of the determined efficiency value and the detected direction of movement of the electric motor 11 and thus of the transmission 17 which, in the event of an error, is used instead of the measured actual pressure p ist for adjusting the target pressure p soll . In this case, the devices 24 and 25 can be dispensed with.
[0049] The accuracy of the calculated pressure depends to a large extent on how closely the actual transmission efficiency approaches the estimated value. Since the transmission efficiency can change depending on the parameters described above, the transmission efficiency is determined and stored during continuous operation as already described above. Since the stored efficiency value can only be used for a short time period due to rapidly changing parameters depending on the operating situation, it is preferably provided that the once-stored efficiency value is used for a maximum of 10 or 15 braking processes after the sensor 14 has failed. The use of the efficiency value may also be restricted by a preset time period. With the end of this time period or the permitted braking processes, the braking system 1 is then preferably switched to the mechanical standby level.
[0050] Preferably, efficiency values are determined and stored using each braking process. If it is determined in step S2 that the sensor information is no longer available, then in a subsequent step S5, the efficiency values stored in step S4, in particular the last stored efficiency value, are used, and the hydraulic pressure is estimated as described before in order to perform the control of the pressure generating device 10 based on the estimated hydraulic pressure (as substitute information).
[0051] To ensure that no pressure remains in the system when the driver releases or no longer operates the actuating element 6, it is preferably provided that when the actuating element 6 is released, the hydraulic piston of the piston pump is pulled back such that, for example, the pressure piston can pass over the pressure relief hole in the hydraulic cylinder and thereby the hydraulic medium can escape to reduce the remaining hydraulic pressure. Alternatively or additionally, the outlet valve of the wheel brake 5 or the switching valve or disconnecting valve 9 of the brake system 1 is preferably opened, which enables pressure relief.
Claims
1. A method for operating a braking system (1) of a motor vehicle, wherein: The brake system (1) comprises at least one hydraulically actuatable wheel brake (5), at least one actuatable pressure generating device (10) and at least one driver-actuatable actuating element (6), the pressure generating device being used to provide hydraulic pressure in a brake circuit (3, 4) having the at least one wheel brake (5), the actuating element being used to predetermine a braking request, wherein at least one sensor (14) for detecting an actual hydraulic pressure in the brake circuit (1) is associated with the brake circuit (3, 4), and wherein the pressure generating device (10) is actuated as a function of the braking request and the actual hydraulic pressure in the brake circuit (1) detected by the sensor (14), characterised in that an efficiency value of the pressure generating device is determined and stored as a function of the braking request and the detected actual pressure, and in the event of a malfunction of the sensor (14), the pressure generating device (10) is actuated at least as a function of the braking request and the stored efficiency value.
2. The method according to claim 1, characterized in that The efficiency value is detected and stored regularly, in particular at predefined time intervals or with each braking request.
3. The method according to any one of the preceding claims, characterized in that The pressure generating device (10) has a controllable electric motor (11) and a piston pump (12) drivable by the electric motor (11) for generating the hydraulic pressure, wherein the electric motor (11) is coupled to the piston pump (12) via a transmission (17), and an efficiency value of the transmission (17) is determined as the efficiency value.
4. The method according to any one of the preceding claims, characterized in that The current pressure value in the brake circuit (1) is estimated as a function of the actual torque of the electric motor (11) and the hydraulic effective surface of the piston pump (12) as well as the efficiency value.
5. The method according to claim 4, characterized in that The pressure value is estimated based on the transmission ratio of the transmission (17) of the pressure generating device (10) and the movement direction (ω) of the electric motor (11).
6. The method according to claim 4 or 5, characterized in that: The pressure generating device (10) is controlled according to the estimated pressure value.
7. The method according to any one of claims 4 to 6, characterized in that The estimated pressure value is compared with the pressure value detected by the pressure sensor (14), in particular in order to ascertain the efficiency value.
8. The method according to any one of the preceding claims, characterized in that A target torque is predefined for the electric motor (11) as a function of the braking request, as a function of the efficiency value and in particular as a function of the estimated pressure value.
9. A control unit (16) for operating a brake system (1), wherein: The brake system (1) comprises at least one hydraulically actuatable wheel brake (5), at least one controllable pressure generating device (10) and at least one operating element (6) operable by a user, the pressure generating device being used to provide hydraulic pressure in a brake circuit (3, 4) having the at least one wheel brake (5), the operating element being used to preset a braking requirement, wherein at least one sensor (14) for detecting the actual hydraulic pressure in the brake circuit (3, 4) is associated with the brake circuit (3, 4), and characterized in that the control unit (16) is specially designed for carrying out the method according to any one of claims 1 to 8 in normal use.
10. A braking system (1) for a motor vehicle, wherein: The brake system (1) comprises at least one hydraulically actuatable wheel brake (5), at least one controllable pressure generating device (10) and at least one operating element (6) actuatable by a driver, the pressure generating device being used to provide hydraulic pressure in a brake circuit (3, 4) having the at least one wheel brake (5), the operating element being used to predetermine a braking requirement, wherein the brake circuit (3, 4) is assigned at least one sensor (14) for detecting the actual hydraulic pressure in the brake circuit (3, 4), and is characterized by having a control unit according to claim 9.