Method for controlling an electric braking system of a motor vehicle and control unit

Abstract

A method for controlling an electric braking system of a motor vehicle, which further comprises a hydraulic braking system with a brake pedal and an actuation sensor for detecting an actuation of the brake pedal, comprises the steps: a. Determine whether the current hydraulic level of the hydraulic brake system is sufficient for the use of the hydraulic brake system, b. If it has been determined that the current hydraulic fill level of the hydraulic braking system is insufficient for the use of the hydraulic braking system, actuation of the electric braking system using measurement data from the brake pedal actuation sensor or using control data from a control unit of an autonomous or semi-autonomous driving function of the motor vehicle. The process makes it possible to move a motor vehicle under its own power at an early stage of production.

Description

The invention relates to a method for controlling an electric brake system of a motor vehicle, which further comprises a hydraulic brake system having a brake pedal and an actuation sensor for detecting an actuation of the brake pedal, and a control device for an electric brake system of a motor vehicle, a computer program product and a motor vehicle.Motor vehicles are generally manufactured in manufacturing processes, which often include automated and / or partially automated processes. Typically, the motor vehicles are manufactured on production lines which automatically transport the workpieces at a certain speed along the production line and thus bring them from one production station to the next production station. Occasionally, it may happen that a lack of one of the motor vehicles that is only partially completed is detected, so that the workpiece has to be removed from the production line and optionally remachined.If the motor vehicle is not capable of moving itself, it must be removed from the production line in a complicated manner, for example with the aid of a lift truck. For this purpose, the production line, in other words the conveyor belt, generally has to be stopped, which leads to a delay for the further motor vehicles located in the production process. As a result, any interruption of the production process, in other words any stopping of the production line or of the conveyor belt, is associated with financial losses.There are a large number of possible causes for a motor vehicle not to be able to leave the production line from its own power. Trivial reasons for this would be, for example, if not all four wheels have yet been mounted or if the drive or parts of the drive have not yet been installed. A relatively frequently occurring reason is, however, the case of motor vehicles which are otherwise already designed ready for driving, when the drive and the wheels are already ready for use, but the brake system is not yet usable. Safe movement of the motor vehicle under its own force is then not possible.It is therefore the object of the present invention to specify a possibility for removing an as yet unfinished motor vehicle from the production line with reduced outlay, such that reworking can then be carried out on the motor vehicle.The object is achieved by a method of the type mentioned at the beginning, having the steps: a. determining whether a current hydraulic fill level of the hydraulic brake system is sufficient for use of the hydraulic brake system, b. If it has been determined that the current hydraulic fill level of the hydraulic brake system is not sufficient for use of the hydraulic brake system, actuating the electric brake system using measurement data of the actuation sensor of the brake pedal or using control data of a control unit of an autonomous or semi-autonomous driving function of the motor vehicle.The object is furthermore achieved by a control device for an electric brake system of a motor vehicle, wherein the control device is configured to execute a method according to the invention, by a computer program product which comprises instructions which, when the program is executed by a control device, cause the latter to execute a method according to the invention, and by a motor vehicle having a control device according to the invention and / or having a control device in which a computer program product according to the invention is stored.The solution according to the invention is based on the finding that the filling of the hydraulic circuit of the hydraulic brake system often takes place only late in the production process, and that up to this point in time the motor vehicles cannot be moved autonomously, for example when reworking is required. It has likewise been recognized that an electrical brake or an electrical brake system which is generally likewise present is often ready for use even before the hydraulic brake system. For the contemplated movements within the scope of the production process, it is sufficient if a relatively small deceleration power is provided. Such a small deceleration power can generally also be provided by the existing electric brake system, for example an electric parking brake.Many motor vehicles today are also already equipped with an actuation sensor for the brake pedal. The method according to the invention can therefore often be carried out without having to provide structural changes. It is achieved in this way that the removal of partially finished motor vehicles from the production line is simplified in many cases. It can thus furthermore often be prevented that the production line or the conveyor line must be stopped, so that production delays and a reduction in production capacity can be avoided.It is possible within the scope of the method according to the invention that the motor vehicle is conventionally controlled by a driver, wherein the driver can express a deceleration request by actuating the brake pedal. The actuation of the brake pedal and the deceleration response that follows can then be registered by a control unit which, in turn, can actuate the electric brake system in order to realize the requested deceleration.It is likewise possible for the motor vehicle to have a system for autonomous or semi-autonomous driving. If this system is already operational, the motor vehicle can move autonomously. In this case, the braking request can be transmitted from the system for autonomous or semi-autonomous driving to the control device, which can then in turn actuate the electric brake system.It is possible that, in order to determine whether a current hydraulic fill level of the hydraulic brake system is sufficient for the use of the hydraulic brake system, a check is made as to whether a parameter for deactivating the hydraulic brake or the hydraulic brake system is set in a control unit of the motor vehicle. This parameter may be set in various ways. For example, in a basic setting of the motor vehicle, the corresponding parameter can be set, so that the electric brake system can be actuated via the brake pedal. As soon as the hydraulic brake system has been filled with hydraulic fluid, the corresponding information can be stored in the control unit or in another computer system and overwrite or deactivate the previously set parameter. Accordingly, it can be provided that, if the information that the hydraulic brake system has been filled with hydraulic fluid, the electric brake system is separated from the brake pedal by control technology.It is possible for a switch or a software switch to be present, with which a user can specifically activate the method according to the invention. Alternatively, it is also possible for the method according to the invention to be activated when a parameter set, which can comprise further parameters in addition to the activation parameter for the method according to the invention, is activated. Such a parameter set can correspond, for example, to a production mode or a workshop mode of the motor vehicle. It is likewise possible for the motor vehicle to automatically activate and deactivate the method according to the invention. The motor vehicle can continuously monitor the readiness for use or the hydraulic fill level of the motor vehicle.It is likewise possible that, in order to determine whether a current hydraulic fill level of the hydraulic brake system is sufficient for use of the hydraulic brake system, it is determined whether a production mode of the motor vehicle is activated. In this case, the brake pedal remains connected to the electric brake system until the production mode is ended. In this way, a very simple control can be achieved, since it does not have to be monitored whether or not hydraulic fluid is actually present in the hydraulic brake system.A combination of the two alternatives described above is likewise possible, so that, for example, it can be provided that the method according to the invention is fundamentally carried out in a production mode, but step b is carried out only when the parameter indicating correct filling of the hydraulic system of the hydraulic brake system has not yet been set.In an alternative embodiment, it is likewise possible that, in order to determine whether a current hydraulic fill level of the hydraulic brake system is sufficient for use of the hydraulic brake system, the hydraulic fill level and / or a hydraulic pressure of the hydraulic brake system is determined. The system is then independent of external inputs or the setting of parameters and connects the brake pedal in terms of control technology to the electric brake system or to a control device of an autonomous or semi-autonomous driving function as soon as it is detected that the hydraulic brake system is not ready for use, since no hydraulic fluid or too little hydraulic fluid is present in the hydraulic brake system. A suitable sensor system can be used to determine the hydraulic fill level and / or the hydraulic pressure.A further development of the method according to the invention is characterized by the following additional method steps:c. continuously checking whether a current hydraulic fill level of the hydraulic brake system is sufficient for use of the hydraulic brake system, andd. when it has been determined that the current hydraulic fill level of the hydraulic brake system is sufficient for use of the hydraulic brake system, ending the activation of the electric brake system using measurement data of the actuation sensor of the brake pedal or using control data of a control unit of an autonomous or semi-autonomous driving function of the motor vehicleIn other words, the method according to the invention can be ended and the standard function, in which the hydraulic brake system is actuated by the brake pedal, can be restored as soon as it is detected that the hydraulic brake system is correctly filled with hydraulic fluid.The electric brake system may be an electric parking brake. Such an electric parking brake is already present in many motor vehicles and can also be referred to as a parking brake. Thus, no physical changes or extensions are necessary on the motor vehicle, but it is sufficient to use the likewise already present control of the parking brake in order to control the electric brake system or the parking brake on the basis of data supplied by the actuation sensor of the brake pedal.The actuation sensor can preferably determine a position of the brake pedal, a rotational angle of the brake pedal and / or an actuation stroke of the brake pedal. A corresponding sensor and a corresponding evaluation unit are already installed as standard in many motor vehicles, so that an implementation of the method according to the invention does not cause any additional costs and no additional production costs here.If a setpoint deceleration determined from data of the actuation sensor is used for activating the electric brake, a dosed activation of the electric brake can take place. In other words, the deceleration effect generated by the electric brake system can then be dependent on a detected pedal position of the brake pedal. Advantageously, the parking brake can thus assume here not only the two states "open" and "closed", but can provide deceleration effects of different severity depending on the braking intention of a driver or another deceleration requirement.It is possible for the method to be executed by a control unit of the motor vehicle for driving dynamics control or using such a control unit. Such a driving dynamics control can also be referred to as "electronic stability control" or ESC. In the ESC system, the information is then stored and kept ready, in particular during the production of the motor vehicle, as to whether or not the hydraulic brake system is sufficiently filled with hydraulic fluid. Updating of this information can take place directly after the hydraulic brake system has been filled. This information can then be used directly to switch between the hydraulic brake system and the electric brake system.Alternatively or additionally, it is also possible for the method to be carried out by a control unit of a brake booster of the hydraulic brake system or using such a control unit. The control device of the brake booster is generally already connected to the actuation sensor of the brake pedal, so that here too the method according to the invention can be implemented with little effort.Exemplary embodiments of the invention are explained in more detail on the basis of the drawings and the following description. The following are shown: FIG. 1 : a first exemplary embodiment of a brake system for carrying out the method according to the invention, FIG. 2 : shows a flow diagram of a first exemplary embodiment of a method according to the invention, FIG. 3 shows a flow diagram of a second exemplary embodiment of a method according to the invention, and FIG. 4 shows a flow diagram of a third exemplary embodiment of a method according to the invention.FIG. 1 shows a schematic overview of an exemplary embodiment of a brake system 2 for carrying out the method according to the invention. The brake system 2 belongs to a motor vehicle, not shown in detail. The brake system comprises a brake booster 4 and a driving dynamics control (ESC) 6 and the four wheel brakes 10.1, 10.2, 10.3 and 10.4. Brake booster 4 is connected to driving dynamics controller 6 and wheel brakes 10.1-10.4 via hydraulic lines 14 and 16.1-16.4. In the illustrated state, these hydraulic lines 14 and 16.1-16.4 are not ready for operation, which is indicated by the symbolically illustrated lightning.The brake booster 4 is capable of determining an actuation of a brake pedal, not shown. For this purpose, a sensor, likewise not shown, is connected to the brake booster 4. The sensor can be, for example, a rotational angle sensor or another sensor suitable for determining the pedal travel of the brake pedal. The brake booster 4 thus receives a signal from the sensor as an input variable, which signal can be interpreted by the brake booster 4 as a braking request 12 of a driver of the motor vehicle.In the event that it has been detected that the hydraulic lines 14 and 16.1-16.4 are not filled in such a way that the hydraulic brake system 24 is ready for use, the detected driver braking request is transmitted to the control unit of the driving dynamics controller 6 via the signal path 18. As already described, the wheel brakes 10 cannot be actuated hydraulically in the situation shown. In the exemplary embodiment shown, the wheel brake 10.1 corresponds to the left front wheel brake, the wheel brake 10.2 corresponds to the right front wheel brake, the wheel brake 10.3 corresponds to the left rear wheel brake and the wheel brake 10.4 corresponds to the right rear wheel brake. The two rear wheel brakes 10.3 and 10.4 are not only part of the hydraulic brake system 24, but also part of the electric brake system 26, which, in addition to the wheel brakes 10.3 and 10.4, also comprises the battery 8. The battery 8 can be a 12 V battery, for example the battery belonging to the 12 V on-board power supply system. The battery 8 is connected to the right rear wheel brake 10.3 and the left rear wheel brake 10.4 via the power supply paths 22.3 and 22.4, respectively.The driving dynamics control 6 is connected via the signal paths 20.3 and 20.4 to the left rear wheel brake 10.3 and the right rear wheel brake 10.4, respectively. The driving dynamics controller 6 thus controls the two rear wheel brakes 10.3 and 10.4 according to the braking request 12 of the driver or the corresponding deceleration request of the autonomous or semi-autonomous driving system of the motor vehicle, so that the desired deceleration effect results.FIG. 2 shows a flow diagram of a first exemplary embodiment of a method according to the invention. In step S 10, it is determined whether a current hydraulic fill level of the hydraulic brake system is sufficient for use of the hydraulic brake system. For this purpose, the actual hydraulic fill level of the hydraulic brake system can be determined by means of a suitable sensor arrangement, or a parameter set or stored in a control unit can be queried. In other words, the hydraulic fill level is then determined and compared with a reference value, or alternatively it is checked whether a status associated with an inoperative hydraulic brake system is present. This can be the case, for example, when a corresponding production mode or workshop mode is activated.If it has been detected in step S 10 that the hydraulic brake system is not ready for use, it is determined in step S 20 whether a brake request is present. For this purpose, on the one hand, an actuation of a brake pedal by means of a sensor can be monitored as described above. Alternatively or in parallel, such a braking request can also be received by a control device of an autonomous driving function of the motor vehicle. If an actuation of the brake pedal is detected, a desired setpoint deceleration can be determined from this actuation.In step S 30, the electric brake system is then actuated on the basis of the present brake request. In this case, a control mechanism can be present which determines a respectively current actual deceleration and matches it with the desired deceleration and controls the system in such a way that the desired deceleration matches the actual deceleration.FIG. 3 shows a flow chart of a second exemplary embodiment of a method according to the invention. In a step S 110, the fill level of the hydraulic system is determined as already described above. Step S 110 therefore corresponds to step S 10 from the method described in connection with FIG. 2. If it is detected that the hydraulic brake system is ready for use, the hydraulic brake system is used in step S 120 to implement a possible brake request and the method is ended.If it is detected that the hydraulic brake system is not ready for use, an operative connection is established between the brake pedal and the electric brake system in step S 130. In other words, the system is thus placed in a stand-by state in which an incoming brake request can be immediately forwarded to the electric brake system and converted there. For this purpose, the brake pedal can be connected to the electric brake system by control technology.In step S 140, it is checked whether the motor vehicle is in an autonomous driving mode. If the motor vehicle is in an autonomous driving mode, the electric brake system is correspondingly connected to the control device of the autonomous driving mode in step S 150. If the control device then outputs a braking request, this is implemented using the electric brake system and the method is then ended. Here, too, as described above, there may be a setpoint deceleration which is matched to an actual deceleration by means of the control unit and the electric brake system.If it has been detected in step S 140 that no autonomous driving mode is activated, the brake pedal is monitored in step S 160. If an actuation of the brake pedal is detected, the electric brake is actuated on the basis of the brake request thus arriving. The method is then ended. The same applies here as already described above for the regulation of the braking power.FIG. 4 shows a flow chart of a third exemplary embodiment of a method according to the invention. The method illustrated corresponds in principle to the exemplary embodiment described in FIG. 3. However, the method is not ended after steps S 120, S 150 and S 160, but rather the method is returned to step S 110. Accordingly, the method is able to react flexibly to changes in the state of the hydraulic brake system, since it is continuously checked whether it is ready for use.List of reference characters2 Brake system 4 Brake booster 6 Driving dynamics control 8 Battery 10 Wheel brake 12 Signal recognition of driver brake request 14 Hydraulic force transmission 16 Hydraulic force transmission 18 Signal path 20 Signal path 22 Power supply 24 Hydraulic brake system 26 Electric brake system

Claims

Method for controlling an electric brake system (26) of a motor vehicle, which further has a hydraulic brake system (24) with a brake pedal and an actuation sensor for detecting an actuation of the brake pedal, having the steps: a. determining whether a current hydraulic fill level of the hydraulic brake system (24) is sufficient for an application of the hydraulic brake system (24), b. If it has been determined that the current hydraulic fill level of the hydraulic brake system (24) is not sufficient for an application of the hydraulic brake system (24), controlling the electric brake system (26) using measurement data of the actuation sensor of the brake pedal or using control data of a control unit of an autonomous or partially autonomous driving function of the motor vehicle.Method according to Claim 1, characterized in that, in order to determine whether a current hydraulic fill level of the hydraulic brake system (24) is sufficient for use of the hydraulic brake system (24), it is checked whether a parameter for deactivating the hydraulic brake (10) is set in a control unit of the motor vehicle.Method according to one of the preceding claims, characterized in that, in order to determine whether a current hydraulic fill level of the hydraulic brake system (24) is sufficient for use of the hydraulic brake system (24), it is determined whether a production mode of the motor vehicle is activated.Method according to one of the preceding claims, characterized in that, in order to determine whether a current hydraulic fill level of the hydraulic brake system (24) is sufficient for use of the hydraulic brake system (24), the hydraulic fill level and / or a hydraulic pressure of the hydraulic brake system (24) is determined.Method according to one of the preceding claims, characterized bythe additional method steps: c. continuously checking whether a current hydraulic fill level of the hydraulic brake system (24) is sufficient for use of the hydraulic brake system (24), and d. if it has been determined that the current hydraulic fill level of the hydraulic brake system (24) is sufficient for use of the hydraulic brake system (24), ending the activation of the electric brake system (26) using measurement data of the actuation sensor of the brake pedal or using control data of a control unit of an autonomous or semi-autonomous driving function of the motor vehicle.Method according to one of the preceding claims, characterized in that the method is carried out using a control unit of the motor vehicle for driving dynamics control (6).Method according to one of the preceding claims, characterized in that the method is carried out using a control unit of a brake booster (4) of the hydraulic brake system (24).Control device for controlling an electric brake system (26) of a motor vehicle, characterized in that the control device is configured to execute a method according to one of the preceding claims.A computer program product, characterized in that the computer program product comprises instructions which, when the program is executed by a control device, cause the control device to execute a method according to one of claims 1 to 8.Motor vehicle having a control device according to Claim 8 and / or having a control device in which a computer program product according to Claim 9 is stored.

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