METHOD FOR DEFINING AT LEAST ONE CHARACTERISTIC CURVE OF A PRESSURE-MEDIUM-ACTUATED BRAKE SYSTEM OF A VEHICLE

Abstract

A method for defining at least one characteristic curve of a pressure-medium-actuated brake system of a vehicle, the curve representing a relationship between a brake pressure and a brake demand, and for operating a pressure-actuated brake system of a vehicle, in which at least one brake cylinder can be supplied with a pressurized medium under a braking pressure, and in which the braking pressure is formed based on at least one such characteristic curve, and to a pressure-actuated brake system of a vehicle in which at least one brake cylinder can be supplied with a pressurized medium under a braking pressure.

Claims

1. A method for defining at least one characteristic curve which, in a pressure-actuated brake system of a vehicle, represents a relationship between a brake pressure and a brake demand, the method comprising: a) specifying a brake demand value range for the brake demand, which includes a minimum brake demand, a maximum brake demand, and intermediate values between the minimum brake demand and the maximum brake demand, b) specifying a brake pressure value range for the brake pressure, which includes a minimum brake pressure, a maximum brake pressure and intermediate values between the minimum brake pressure and the maximum brake pressure, c) defining at least two characteristic curve sections of the characteristic curve, by: c1) defining a first support point of the characteristic curve, at which a first brake demand limit value and a first brake pressure are assigned to one another, the first brake demand limit value lying within the brake demand value range and the first brake pressure lying within the brake pressure value range, and the first brake demand limit value representing a minimum brake demand and the first brake pressure representing a minimum brake pressure, c2) defining a second support point of the characteristic curve, at which a second brake demand limit value and a second brake pressure are associated with each other, wherein the second brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the minimum brake demand but smaller than the amount of the maximum brake demand, and wherein the second brake pressure is within the brake pressure value range and is greater than the minimum brake pressure but less than the maximum brake pressure, c2) defining a first characteristic curve section of the characteristic curve which extends between the first support point and the second support point and which, in a first brake demand range, represents the relationship between the brake pressure and the brake demand, c3) defining a third support point of the characteristic curve, at which a third brake demand limit value and a third brake pressure are associated with each other, wherein the third brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the second brake demand limit value but less than or equal to the amount of the maximum brake demand, and wherein the third brake pressure lies within the brake pressure value range and is equal to the maximum brake pressure, c4) defining a second characteristic curve section of the characteristic curve which extends between the second support point and the third support point and which, in a second brake demand range, represents the relationship between the brake pressure and a brake demand.

2. The method of claim 1, wherein the third brake demand limit is smaller in amount than the amount of the maximum brake demand.

3. The method of claim 1, wherein the first characteristic curve section and/or the second characteristic curve section has a linear course.

4. The method of claim 1, wherein the second characteristic curve section directly adjoins the first characteristic curve section.

5. The method of claim 1, wherein the minimum brake demand and the minimum brake pressure are each equal to zero.

6. The method of claim 1, wherein a third characteristic curve section of the characteristic curve is defined, which extends between the third support point and a fourth support point and automatically assigns the maximum brake pressure to each brake demand in a third brake demand area, the fourth support point assigning the maximum brake pressure and the maximum brake demand to each other.

7. The method of claim 6, wherein the first characteristic curve section and/or the second characteristic curve section and/or the third characteristic curve section are formed or specified as a function of a vehicle load of the vehicle, the vehicle load being determined or estimated.

8. A characteristic curve, comprising: a curve, which, in a pressure-fluid-actuated brake system, represents a relationship between a brake pressure and a brake demand; wherein the curve has been defined or determined by performing the following: a) specifying a brake demand value range for the brake demand, which includes a minimum brake demand, a maximum brake demand, and intermediate values between the minimum brake demand and the maximum brake demand, b) specifying a brake pressure value range for the brake pressure, which includes a minimum brake pressure, a maximum brake pressure and intermediate values between the minimum brake pressure and the maximum brake pressure, c) defining at least two characteristic curve sections of the characteristic curve, by: c1) defining a first support point of the characteristic curve, at which a first brake demand limit value and a first brake pressure are assigned to one another, the first brake demand limit value lying within the brake demand value range and the first brake pressure lying within the brake pressure value range, and the first brake demand limit value representing a minimum brake demand and the first brake pressure representing a minimum brake pressure, c2) defining a second support point of the characteristic curve, at which a second brake demand limit value and a second brake pressure are associated with each other, wherein the second brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the minimum brake demand but smaller than the amount of the maximum brake demand, and wherein the second brake pressure is within the brake pressure value range and is greater than the minimum brake pressure but less than the maximum brake pressure, c2) defining a first characteristic curve section of the characteristic curve which extends between the first support point and the second support point and which, in a first brake demand range, represents the relationship between the brake pressure and the brake demand, c3) defining a third support point of the characteristic curve, at which a third brake demand limit value and a third brake pressure are associated with each other, wherein the third brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the second brake demand limit value but less than or equal to the amount of the maximum brake demand, and wherein the third brake pressure lies within the brake pressure value range and is equal to the maximum brake pressure, c4) defining a second characteristic curve section of the characteristic curve which extends between the second support point and the third support point and which, in a second brake demand range, represents the relationship between the brake pressure and a brake demand.

9. A method for operating a pressure-medium-actuated brake system of a vehicle, in which at least one brake cylinder can be acted upon by a pressure medium which is under a braking pressure, and in which the braking pressure represents a relationship between the braking pressure and a braking demand, the method comprising: c) determining the brake pressure based on the first characteristic curve section or the second characteristic curve section depending on the brake demand at least by: a1) checking whether the brake demand is in the first brake demand range or in the second brake demand range, and a2) if the brake demand is in the first brake demand range, then determining the brake pressure according to the first characteristic curve section, and a3) if the brake demand lies in the second brake demand range, then determining the brake pressure according to the second characteristic curve section, and then d) applying the determined brake pressure to the at least one brake cylinder; wherein the characteristic curve, which in a pressure-actuated brake system of a vehicle, represents a relationship between a brake pressure and a brake demand, is determined by the following: e) specifying a brake demand value range for the brake demand, which includes a minimum brake demand, a maximum brake demand, and intermediate values between the minimum brake demand and the maximum brake demand, f) specifying a brake pressure value range for the brake pressure, which includes a minimum brake pressure, a maximum brake pressure and intermediate values between the minimum brake pressure and the maximum brake pressure, g) defining at least two characteristic curve sections of the characteristic curve, by: c1) defining a first support point of the characteristic curve, at which a first brake demand limit value and a first brake pressure are assigned to one another, the first brake demand limit value lying within the brake demand value range and the first brake pressure lying within the brake pressure value range, and the first brake demand limit value representing a minimum brake demand and the first brake pressure representing a minimum brake pressure, c2) defining a second support point of the characteristic curve, at which a second brake demand limit value and a second brake pressure are associated with each other, wherein the second brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the minimum brake demand but smaller than the amount of the maximum brake demand, and wherein the second brake pressure is within the brake pressure value range and is greater than the minimum brake pressure but less than the maximum brake pressure, c2) defining a first characteristic curve section of the characteristic curve which extends between the first support point and the second support point and which, in a first brake demand range, represents the relationship between the brake pressure and the brake demand, c3) defining a third support point of the characteristic curve, at which a third brake demand limit value and a third brake pressure are associated with each other, wherein the third brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the second brake demand limit value but less than or equal to the amount of the maximum brake demand, and wherein the third brake pressure lies within the brake pressure value range and is equal to the maximum brake pressure, c4) defining a second characteristic curve section of the characteristic curve which extends between the second support point and the third support point and which, in a second brake demand range, represents the relationship between the brake pressure and a brake demand.

10. The method of claim 9, wherein the brake demand, based on which the brake pressure is determined using the characteristic curve, is generated by a vehicle longitudinal deceleration control system, a driver assistance system and/or by an autonomous vehicle control system.

11. The method of claim 10, wherein the vehicle longitudinal deceleration control controls an estimated or determined actual vehicle longitudinal deceleration to a target vehicle longitudinal deceleration, wherein the brake demand, based on which the brake pressure is determined using the characteristic curve, being formed as a function of the target vehicle longitudinal deceleration.

12. The method of claim 9, wherein the brake pressure is determined based on the third characteristic curve section if the brake demand lies in the third brake demand range, and then the at least one brake cylinder is acted upon with the maximum brake pressure.

12. The method of claim 9, wherein the brake system comprises at least two independent electronic brake control units, a first electronic brake control unit and a second electronic brake control unit, and at least one solenoid valve device controlled independently by the first electronic brake control unit and the second electronic brake control unit, wherein the characteristic curve is implemented in the first electronic brake control unit and in the second electronic brake control unit, and wherein the braking demand is input into the first electronic brake control unit and into the second electronic brake control unit, and wherein the first electronic brake control unit and the second electronic brake control unit electrically actuate the at least one solenoid valve device independently of one another as a function of the brake demand, to generate the brake pressure.

14. The method of claim 12, wherein: a) if the brake demand is in the first brake demand area or in the second brake demand area, it is checked whether an electronic brake control unit of the first electronic brake control unit or the second electronic brake control unit has a defect, and if this is the case, then the at least one solenoid valve device is controlled by the remaining functional electronic brake control unit which has no defect to generate the brake pressure, but b) if the brake demand is in the third brake demand area, no check is made whether an electronic brake control device of the first electronic brake control device and/or the second electronic brake control device is defective, and the at least one solenoid valve device is actuated by the first electronic brake control device and/or by the second electronic brake control device to generate the brake pressure.

15. The method of claim 14, wherein the check as to whether an electronic brake control unit of the first electronic brake control unit and/or the second electronic brake control unit has a defect is carried out by self-monitoring of the first electronic brake control unit and the second electronic brake control unit, or by external monitoring, the first and second electronic brake control units monitoring each other.

16. The method of claim 8, wherein the braking system includes: a) an electro-pneumatic service brake system, wherein the at least one brake cylinder is an active brake cylinder which is applied by increasing the brake pressure in the application direction and by decreasing the brake pressure in the release direction, and/or b) an electro-pneumatic parking brake system, wherein the at least one brake cylinder is a passive spring brake cylinder which is applied by increasing the brake pressure in the release direction and by decreasing the brake pressure in the application direction.

17. A pressure medium-actuated brake system of a vehicle, comprising: at least one brake cylinder, which can be acted upon by a pressure medium which is under a brake pressure; wherein the at least one brake cylinder is controlled by performing the following: c) determining the brake pressure based on the first characteristic curve section or the second characteristic curve section depending on the brake demand at least by: a1) checking whether the brake demand is in the first brake demand range or in the second brake demand range, and a2) if the brake demand is in the first brake demand range, then determining the brake pressure according to the first characteristic curve section, and a3) if the brake demand lies in the second brake demand range, then determining the brake pressure according to the second characteristic curve section, and then d) applying the determined brake pressure to the at least one brake cylinder; wherein the characteristic curve, which in a pressure-actuated brake system of a vehicle, represents a relationship between a brake pressure and a brake demand, is determined by the following: e) specifying a brake demand value range for the brake demand, which includes a minimum brake demand, a maximum brake demand, and intermediate values between the minimum brake demand and the maximum brake demand, f) specifying a brake pressure value range for the brake pressure, which includes a minimum brake pressure, a maximum brake pressure and intermediate values between the minimum brake pressure and the maximum brake pressure, g) defining at least two characteristic curve sections of the characteristic curve, by: c1) defining a first support point of the characteristic curve, at which a first brake demand limit value and a first brake pressure are assigned to one another, the first brake demand limit value lying within the brake demand value range and the first brake pressure lying within the brake pressure value range, and the first brake demand limit value representing a minimum brake demand and the first brake pressure representing a minimum brake pressure, c2) defining a second support point of the characteristic curve, at which a second brake demand limit value and a second brake pressure are associated with each other, wherein the second brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the minimum brake demand but smaller than the amount of the maximum brake demand, and wherein the second brake pressure is within the brake pressure value range and is greater than the minimum brake pressure but less than the maximum brake pressure, c2) defining a first characteristic curve section of the characteristic curve which extends between the first support point and the second support point and which, in a first brake demand range, represents the relationship between the brake pressure and the brake demand, c3) defining a third support point of the characteristic curve, at which a third brake demand limit value and a third brake pressure are associated with each other, wherein the third brake demand limit value lies within the brake demand value range and is greater in amount than the amount of the second brake demand limit value but less than or equal to the amount of the maximum brake demand, and wherein the third brake pressure lies within the brake pressure value range and is equal to the maximum brake pressure, c4) defining a second characteristic curve section of the characteristic curve which extends between the second support point and the third support point and which, in a second brake demand range, represents the relationship between the brake pressure and a brake demand.

18. The pressure-medium operated brake system of claim 17, wherein the pressure medium-actuated brake system includes at least two independent electronic brake control units, a first electronic brake control unit and a second electronic brake control unit, and at least one solenoid valve device independently controlled by the first electronic brake control unit and the second electronic brake control unit, wherein the characteristic curve is implemented in the first electronic brake control unit and in the second electronic brake control unit, and wherein the brake demand is input into the first electronic brake control unit and into the second electronic brake control unit, and wherein the first electronic brake control unit and the second electronic brake control unit electrically actuate the at least one solenoid valve device independently of one another as a function of the brake demand, to generate the brake pressure.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0061] FIG. 1 shows an example of a characteristic curve showing a relationship between a brake demand and a brake pressure.

[0062] FIG. 2 shows a schematic representation of an autonomous driving system showing a longitudinal deceleration control system and a braking system controlled by the longitudinal deceleration control system, as well as a vehicle that can be braked by the braking system.

[0063] FIG. 3 shows a flow chart of an exemplary embodiment of a method for controlling the braking system.

[0064] FIG. 4 shows a braking system according to an exemplary embodiment.

DETAILED DESCRIPTION

[0065] In FIG. 4, a pressure-fluid-actuated electronically controlled service brake system 100 of, for example, a heavy commercial vehicle is shown in highly schematic form, which is configured, for example, as an electro-pneumatic brake system and, in particular, as an electro-pneumatic brake pressure-controlled brake system (EBS).

[0066] The service brake system 100 here has, for example, at least two independent electronic brake control units, a first electronic brake control unit Brake-ECU 1 and a second electronic brake control unit Brake-ECU 2, which control the brake control/regulation functions and other higher-level functions such as a brake slip control (ABS), a traction slip control (ASR) and/or a vehicle dynamics control and/or also an axle-by-axle or side-by-side brake pressure distribution (BDV). Since the two electronic brake control units Brake-ECU 1 and Brake-ECU 2 are mutually redundant brake control units in the sense that if one of the electronic brake control units Brake-ECU 1 or Brake-ECU 2 fails, the other one, If one of the electronic brake control units Brake-ECU 1 or Brake-ECU 2 fails, the other, still intact electronic brake control unit Brake-ECU 1 or Brake-ECU 2 executes the brake control/brake regulation functions and the other higher functions, all the relevant software functions in particular are implemented in full in both electronic brake control units Brake-ECU 1 or Brake-ECU 2.

[0067] The two electronic brake control units Brake-ECU 1 or Brake-ECU 2 receive here, for example, from a Highly Automated Driving System (HADS) 200 a service brake request or demand signal a.sub.soll representing a target vehicle longitudinal deceleration a.sub.soll requested as a service brake demand and process this in order to control at least one solenoid valve arrangement or device 1 independently of one another depending on the service brake demand signal a.sub.soll. For this purpose, a characteristic curve 2 described in more detail later is implemented in the first electronic brake control unit Brake-ECU 1 and in the second electronic brake control unit Brake-ECU 2.

[0068] As shown in FIG. 2, the Highly Automated Driving System (HADS) 200 includes a longitudinal deceleration controller 300 that adjusts an actual vehicle longitudinal deceleration a.sub.ist measured on the vehicle, for example, using a longitudinal deceleration sensor, to the target vehicle longitudinal deceleration a.sub.soll representing the respective service brake demand.

[0069] The at least one solenoid valve arrangement 1 of FIG. 4 can be formed in particular in a pressure control module 3 known per se, which is electrically controlled here, for example, by the first and second electronic brake control units Brake-ECU 1 and Brake-ECU 2 in order to control a regulated service brake pressure on the basis of a supply pressure originating from a pressure reservoir 4. The electrical control by the two electronic brake control units Brake-ECU 1 and Brake-ECU 2 specifies a target service brake pressure. For example, one such pressure control module 3 can be provided for the front axle and one for the rear axle of the vehicle, in particular a single-channel pressure control module on the front axle and a dual-channel pressure control module on the rear axle.

[0070] In a known manner, such a pressure control module 3 has an integrated local electronic control unit which receives a signal representing the set service brake pressure from the two electronic brake control units Brake-ECU 1 and Brake-ECU 2, furthermore the solenoid valve device 1, in particular as an inlet/outlet valve combination, as well as a relay valve pneumatically controlled by the solenoid valve device 1, via the operating output of which the actual service brake pressure is then output to at least one brake actuator 5, in this case at least one active service brake cylinder, which is measured by an integrated pressure sensor. The measured actual service brake pressure is then reported to the integrated local electronic control unit of the pressure control module 3, which then controls the integrated inlet/outlet valve combination to adjust the actual service brake pressure to the target service brake pressure. This realizes a service brake pressure control.

[0071] The characteristic curve 2 already mentioned above shows a relationship between the service brake pressure p and the service brake demand a.sub.soll. The characteristic curve 2 therefore assigns a specific service brake pressure p to a specific service brake demand a.sub.soll, as can be easily imagined from FIG. 1.

[0072] In order to form or define the characteristic curve 2 before its actual application or implementation, a service brake demand value range is defined or established for the service brake demand, which comprises a minimum service brake demand, a maximum service brake demand and intermediate values between the minimum service brake demand and the maximum service brake demand. The values of this service brake demand value range can be formed, for example, by a requested deceleration a in m/s.sup.2 or also by a certain percentage, which then lies, for example, between 0% for the minimum service brake demand and 100% for the maximum service brake demand, with the limits included. In FIG. 1, this service brake demand value range is plotted on the Y axis.

[0073] Furthermore, a service brake pressure value range is also specified or defined for the service brake pressure p, which comprises a minimum service brake pressure (e.g. p.sub.min=0), a maximum service brake pressure (maximum applicable brake pressure) and intermediate values between the minimum service brake pressure and the maximum service brake pressure (maximum applicable brake pressure). In FIG. 1, this range of service brake pressure values is plotted on the X axis.

[0074] A first interpolation or support point 6, 6′, 6″ is then defined by the characteristic curve 2, at which a first service brake demand limit value 8 and a first brake pressure p.sub.1 are assigned to one another, the first service brake demand limit value 8 lying within the service brake demand value range and the first brake pressure p.sub.1 lying within the brake pressure value range, and the first service brake demand limit value 8 representing a minimum service brake demand and the first service brake pressure representing a minimum service brake pressure. In the example of FIG. 1, the first service brake demand limit value 8 is equal to 0 m/s.sup.2, for example, and the first service brake pressure is equal to 0 bar, for example. The first support point 6 of the characteristic curve 2 therefore may form the origin of the diagram of FIG. 1 here.

[0075] Furthermore, a second support point 7, 7′, 7″ of the characteristic curve 2 is defined or determined, at which a second service brake demand limit value 9 and a second brake pressure p.sup.2 are assigned to one another, the second service brake demand limit value 9 lying within the service brake demand value range and being greater in amount than the amount of the minimum service brake demand but smaller than the amount of the maximum service brake demand. Furthermore, the second service brake pressure p.sub.2 is within the service brake pressure value range and is greater than the minimum service brake pressure but less than the maximum service brake pressure (maximum applicable brake pressure). In this case, the second service brake demand limit value 9 represents, for example, the largest deceleration in terms of magnitude during partial braking.

[0076] Furthermore, a first characteristic curve section 2a, 2a′, 2a″ of the characteristic curve 2 is defined or determined, which extends between the first support point 6 and the second support point 8, and which, in a first brake demand range I, represents the relationship between the brake pressure p and the service brake demand a.sub.soll. The first characteristic curve section 2a, 2a′, 2a″ therefore assigns a specific service brake pressure p here, for example, to a service brake demand a.sub.soll of a partial braking.

[0077] Furthermore, a third support point 10 of the characteristic curve is also defined, at which a third service brake demand limit value 11 and a third brake pressure p.sub.3 are assigned to each other, wherein the third brake demand limit value 11 lies within the brake demand value range and is greater in amount than the amount of the second brake demand limit value 9 but less than or equal to the magnitude or amount of the maximum demand, and wherein the third brake pressure p.sub.3 lies within the brake pressure value range and is equal to the maximum applicable brake pressure.

[0078] Furthermore, a second characteristic curve section 2b, 2b′, 2b″ of the characteristic curve 2 is also defined, which extends between the second support point 7 and the third support point 10, and which, in a second brake demand range II, represents the relationship between the brake pressure p and a brake demand a.sub.soll.

[0079] Particularly, a third characteristic curve section 2c of the characteristic curve 2 may also be defined, which extends between the third support point 10 and a fourth support point 12 and automatically assigns the maximum brake pressure (maximum applicable brake pressure) to each brake demand a.sub.soll within a third brake demand range III, the fourth support point 12 assigning the maximum brake pressure (maximum applicable brake pressure) and the maximum brake demand to each other. In this third characteristic curve section 2c, the maximum applicable brake pressure is automatically assigned to each brake demand a.sub.soll within the third brake demand area III, so that the third characteristic curve section represents a vertical line, as shown in FIG. 1.

[0080] As further shown in FIG. 1, the courses of the first, second and third characteristic curve sections 2a, 2a′, 2a″, 2b, 2b′, 2b″ and 2c may be linear, whereby the slopes of the first and second characteristic curve sections 2a, 2a′, 2a″, 2b, 2b′, 2b″ may differ. This also applies, for example, with inclusion of the third characteristic curve section 2c.

[0081] Also, for example, different characteristic curves are defined for different load conditions of the commercial vehicle, whereby in FIG. 1, the large dashed line symbolizes the first, second and third characteristic curve sections 2a′, 2b′, 2c of a lightly loaded commercial vehicle, the small dashed line symbolizes the first, second and third characteristic curve sections 2a, 2b, 2c of a medium loaded commercial vehicle and the dash-dotted lines symbolize the first, second and third characteristic curve sections 2a″, 2b″, 2c of a fully loaded commercial vehicle. Depending on the load, the slope of the linear first and second characteristic curve sections 2a, 2b therefore varies, while the third characteristic curve section 2c is the same for all load conditions, because the maximum brake pressure (maximum applicable brake pressure) may be always requested there.

[0082] As already indicated above, the characteristic curve 2 or the load-dependent characteristic curves 2a, 2b, 2c are respectively stored in a memory area of the first and second electronic brake control unit Brake-ECU 1, Brake-ECU 2.

[0083] FIG. 3 shows a flow chart of an exemplary embodiment of a method for operating the pressure fluid-actuated service brake system 100. In a step 101, a brake demand signal according to a brake demand a.sub.soll of the Highly Automated Driving System (HADS) 200 is input to the first and second electronic brake control units Brake-ECU 1 and Brake-ECU 2. This brake demand signal is verified in an optional step 102. In a subsequent step 103, it is verified whether the brake demand a.sub.soll represented by the brake demand signal is in the first brake demand range I or in the second brake demand range II (see FIG. 1). If this is the case, i.e. the brake demand a.sub.soll is either in the first brake demand range I or in the second brake demand range II, it is checked whether the first electronic brake control unit Brake-ECU 1 has a defect. If this is not the case, it is checked in a subsequent step 105 whether the brake demand a.sub.soll, which is represented by the brake demand signal, lies in the first brake demand range I or alternatively in the second brake demand range II.

[0084] If the brake demand lies in the first brake demand range I, then the service brake pressure p is determined in a step 106 according to the first characteristic curve section 2a, 2a′, 2a″. If, however, the service brake demand a.sub.soll lies in the second brake demand range II, then in a step 107 the service brake pressure p is determined according to the second characteristic curve section 2b, 2b′, 2b″. The optionally additionally executed common step 108 then comprises a wheel-individual control or regulation of the service brake pressure p. The service brake pressure p determined on the basis of characteristic curve 2 is then applied to the at least one brake actuator 5.

[0085] This service brake pressure p then provides an actual longitudinal deceleration a.sub.ist of the commercial vehicle in the at least one service brake actuator 5, which is then adapted by the longitudinal deceleration controller 300 of FIG. 2 to the target longitudinal deceleration a.sub.soll corresponding to the braking requirement.

[0086] If it is determined in step 104 that the first electronic brake control unit Brake-ECU 1 has a defect, the at least one solenoid valve device 1 or the at least one pressure control module 3 cannot be actuated by the first electronic brake control unit Brake-ECU 1 in accordance with step 109 in order to generate the service brake pressure p by controlling the at least one pressure control module 3 or the at least one solenoid valve device 1. In this case, the intact second electronic brake control unit Brake-ECU 2, which is redundant with respect to the first electronic brake control unit Brake-ECU 1, then ensures implementation of the service brake demand in accordance with steps 105, 106 or 107 and 108, as described above.

[0087] If it is determined in step 103 that the brake demand or the target vehicle longitudinal deceleration a.sub.soll is neither in the first brake demand range I nor in the second brake demand range II but in the third brake demand range III, no check of the first electronic brake control unit Brake-ECU 1 and/or the second electronic brake control unit Brake-ECU 2 or further components of the service brake system 100 takes place. Rather, as shown in FIG. 1, the maximum brake pressure (maximum applicable pressure) is then assigned to each brake demand a.sub.soll in the third brake demand area III, which is then generated by the at least one pressure control module 3 or the at least one solenoid valve device 1 based on the reservoir pressure of the pressure reservoir 4 and is fed into the at least one brake actuator 5.

[0088] The invention is not limited to an application to a service brake system 100, it can readily be applied to a park brake system to control/regulate parking brake pressure. Because of the passive brake spring cylinders as normally used in such a parking brake system, the maximum pressure becomes the minimum pressure and vice versa.

[0089] The List of References is as follows: [0090] 1 solenoid valve device [0091] 2 characteristic curve (map) [0092] 2a, 2a′, 2a″ first characteristic curve section [0093] 2b, 2b′, 2b″ second characteristic curve section [0094] 2c third characteristic curve section [0095] 3 pressure regulator [0096] 4 pressure reservoir [0097] 5 brake actuator [0098] 6 first support point [0099] 7 second support point [0100] 8 first brake demand limit value [0101] 9 second brake demand limit value [0102] 10 third support point [0103] 11 third brake demand limit value [0104] 12 fourth support point [0105] 100 service brake system [0106] 200 highly automated driving system [0107] 300 longitudinal deceleration controller [0108] Brake-ECU1 first brake control unit [0109] Brake-ECU2 second brake control unit [0110] a.sub.ist actual vehicle longitudinal deceleration [0111] a.sub.soll target vehicle longitudinal deceleration (brake demand) [0112] I first brake demand range [0113] II second brake demand range [0114] III third brake demand range