Braking system and method for signal transmission in a braking system

Abstract

The present invention relates to a braking system (101) comprising a brake pedal (102), at least two wheel brakes (103, 104, 105, 106), and at least two brake control units (107, 108). The brake pedal (102) outputs one or more of the actuation signals from a set of actuation signals to both brake control units (107, 108). The brake control units (107, 108) can each individually calculate a user's braking request from the set of actuation signals and control the wheel brakes (103, 104, 105, 106) according to the calculated braking request. In the case of a brake pedal with limited signal output, a braking request with high integrity should be determined even if one brake control unit (107, 108) fails. According to the invention, a signal forwarder (109, 114) is arranged in the signal path between the brake pedal (102) and at least one of the brake control units (107, 108), which signal forwarder is designed to forward the actuation signals directed to the failed brake control unit (107, 108) to the functioning brake control unit (107, 108), at least in the event of a failure of the brake control unit (107, 108) downstream of the signal forwarder (109, 114), so that the functioning brake control unit (107, 108) receives the complete set of actuation signals.

Description

[0001] The present invention relates to a braking system comprising a brake pedal, at least two wheel brakes, and at least two brake control units, wherein the brake pedal is configured to determine a set of at least two actuation signals indicative of a user's braking request expressed by actuation of the brake pedal, wherein the brake pedal is configured to output one or more of the actuation signals to both brake control units, wherein the brake control units are configured to each individually calculate a user's braking request from the set of actuation signals and to actuate the wheel brakes in accordance with the calculated braking request. The invention further relates to a method for signal forwarding in such a braking system.

[0002] In modern vehicle braking systems, especially those without a hydraulic connection to the brake pedal, two redundant brake control units are increasingly being used to provide a fallback level even if one of the brake control units fails and to prevent a complete failure of the braking system if one of the brake control units fails. Currently, the brake pedal in such a braking system delivers a set of actuation signals to at least two brake control units. These actuation signals are then processed in each brake control unit and subsequently exchanged between brake control units via a communication line, e.g., the vehicle bus. Only after the signals have been exchanged and the plausibility check has been completed can a final driver braking request with the highest integrity (ASIL D) be generated.For example, depending on the operating mode of the braking system, either the first brake control unit or the second brake control unit is responsible for executing the braking request via the wheel brakes. Furthermore, the brake control units can also operate in a cooperative mode, i.e., permanently or in specific operating modes, they can each take over various steps until the final driver braking request is generated.

[0003] If one of the brake control units fails, depending on the design of the brake pedal and the signal processing of the remaining brake control unit, a complete set of actuation signals may no longer be available. In this case, it is no longer possible to determine the user's braking request with integrity according to ASIL D, but only according to ASIL B or ASIL QM, for example.

[0004] In principle, to overcome this problem, the brake pedal could be designed more complexly so that it can transmit a complete set of actuation signals to all brake control units. However, as a wear part, it is desirable to keep the brake pedal as simple as possible to minimize initial installation and maintenance effort and costs.

[0005] A braking system mentioned above is known, for example, from DE 10 2011 084 534 A1, in which a multiplexer is arranged downstream of two processing units. If a first processing unit serving two parking brake actuators fails, a second processing unit takes over the control of at least one electric parking brake actuator. For this purpose, the first processing unit has means for error detection, which, in the event of a fault, sends a signal to a switch or multiplexer, which connects the control circuit of at least one actuator to the second processing unit.

[0006] DE 10 2011 016 125 A1 discloses a braking system with a processing device comprising a multiplexer coupled to output sides of a first evaluation unit and a second evaluation unit. The multiplexer can be controlled by a monitoring unit depending on the functionality of at least the first evaluation unit in order to selectively output the actuation signal generated on the basis of a first sensor signal or the actuation signal generated on the basis of the second sensor signal.

[0007] US 5,615,930 A discloses that in a braking system, a multiplexer is connected to the output ports of two control systems. The multiplexer samples the data appearing at each output port of the control system and generates a combined data stream. The combined data stream is transmitted via the data link to a microprocessor. The microprocessor separates the data stream into the original data. This reduces the wiring effort.

[0008] The systems known in the prior art therefore involve signal redirection after processing the actuation signals and do not offer a solution to the problem described above.

[0009] The invention is therefore based on the object of providing improved signal transmission in a braking system mentioned above without making the brake pedal more complex.

[0010] According to the invention, this object is achieved by a braking system according to claim 1 and a method according to claim 13. Accordingly, a signal forwarder is arranged in the signal path between the brake pedal and at least one of the brake control units. This signal forwarder is configured to forward the actuation signals directed to the failed brake control unit to the functioning brake control unit, at least in the event of a failure of the brake control unit downstream of the signal forwarder. As a result, the functioning brake control unit receives the complete set of actuation signals, and the user's braking request can be determined with integrity according to ASIL D, even if one of the brake control units fails. The solution according to the invention therefore improves the safety and functionality of the braking system in the event of a brake control unit failure, so that, ideally, the failure of a brake control unit does not lead to a deterioration in the performance of the braking system.At the same time, a more complex design of the brake pedal is not necessary.

[0011] The use of a dedicated signal forwarder has the additional advantage that even if the brake control unit downstream of the forwarding unit fails, the brake pedal can continue to send the actuation signals to the same address (the corresponding forwarding unit). Certain simple forwarding protocols require or prefer fixed end addresses for signal transmission, and the use of a forwarding unit therefore allows these protocols to continue to be used unchanged.

[0012] The "complete set of actuation signals" refers to all actuation signals currently output by the brake pedal, as long as each brake control unit still receives at least one actuation signal. For example, if one sensor in a set of two pairs of redundant brake pedal sensors fails, the "complete set of actuation signals" would still be understood as a set of three actuation signals being output.

[0013] The brake pedal is preferably an electromechanical brake pedal. Alternatively, the brake pedal can also act on a hydraulic component of the braking system (e.g., a master cylinder).

[0014] Preferably, the set of actuation signals comprises at least two actuation signals generated by different sensors of the brake pedal. "Different sensor" is understood here only as physically different sensors (i.e., there are at least two sensors in the brake pedal), whereby the sensors may be of the same sensor type or of a different sensor type.

[0015] The brake pedal may include a pedal travel sensor and / or a force sensor and / or an angle sensor and / or an optical sensor to generate the set of at least two actuation signals. The same sensor type may also be used in duplicate.

[0016] When processing the actuation signals, a weighted calculation of the actuation signals is preferably carried out depending on their signal type and the numerical value of the signal (e.g., using a characteristic curve that is specific to the set of sensors used). For example, actuation signals from force sensors can be weighted less heavily than actuation signals from pedal travel sensors or angle sensors when the signal values ​​are low, since the former are more affected by signal noise when the pedal actuation is low. The numerical values ​​of the unprocessed actuation signals can first be converted into standardized (and thus comparable) actuation signals before being calculated (e.g., using a functional relationship or lookup table). This can be necessary, especially when different sensor types (force sensor, travel sensor, etc.) are used.

[0017] Preferred embodiments and further developments of the invention can be found in the respective subclaims.

[0018] According to a preferred embodiment of the invention, the brake pedal comprises at least two sensors of a different sensor type. The brake pedal can thus comprise two different sensors, selected, for example, from a pedal travel sensor, a force sensor, an angle sensor, or an optical sensor, to generate the set of at least two actuation signals.

[0019] Particularly preferably, the brake pedal comprises two pairs of redundant sensors of the same type, for example, two force sensors and two pedal travel sensors or two force sensors and two angle sensors. In this case, two actuation signals from sensors of different types are preferably sent to each brake control unit. This increases the reliability of the braking system, since the failure of one sensor does not result in a deterioration in the determination of the braking command. However, the solution according to the invention also allows the number of sensors in the brake pedal to be limited or even reduced (e.g., from 6 to 4 or 2) without reducing the reliability.

[0020] Particularly preferably, the signal forwarder comprises a multiplexer configured to forward the actuation signals directed to the failed brake control unit to the functioning brake control unit in the event of a failure of the downstream brake control unit. This solution is particularly advantageous because no processing or duplication of the actuation signals directed to the downstream brake control unit takes place; instead, the actuation signals directed to the failed brake control unit are simply forwarded to the functioning brake control unit in the event of a failure of the brake control unit downstream of the multiplexer.

[0021] In one embodiment, a signal forwarder is arranged in each of the two signal paths between the brake pedal and one of the brake control units, which is configured to forward the actuation signals directed to the failed brake control unit to the functioning brake control unit in the event of a failure of the downstream brake control unit. This solution is particularly advantageous because it offers greater reliability regardless of which brake control unit fails and how the signal forwarders are designed. Particularly preferably, a multiplexer is arranged in each of the two signal paths between the brake pedal and one of the brake control units, which is configured to forward the actuation signals directed to the failed brake control unit to the functioning brake control unit in the event of a failure of the downstream brake control unit.

[0022] Preferably, the signal forwarder is arranged on the same circuit board as the downstream brake control unit, wherein the signal forwarder preferably has a power supply independent of the rest of the brake control unit. This simplifies the design of the braking system, as no additional circuit board or electronics unit needs to be installed to accommodate the signal forwarder. Preferably, the power supply of the signal forwarder is configured at least in parallel with the rest of the brake control unit, so that the signal forwarder is not powered via the brake control unit. This improves reliability, as the probability of a joint failure of the signal forwarder and the downstream brake control unit is reduced.

[0023] Preferably, the brake pedal does not include a signal processing unit and outputs unprocessed actuation signals. The solution according to the invention is particularly advantageous for such a simply designed brake pedal.

[0024] In a preferred embodiment, the braking system is configured such that no processing of the actuation signals takes place from the brake pedal via the signal forwarder to the input in a signal processing unit of the processing brake control unit. This ensures that both brake control units are supplied with unprocessed actuation signals and, in the event of a brake control unit failure, the functioning brake control unit has a complete set of unprocessed actuation signals. This configuration allows a user's braking request to be determined with high integrity (preferably ASIL D) in a particularly large number of situations, even in the event of a brake control unit failure.

[0025] Preferably, the brake pedal is configured such that it can output each actuation signal in the set of actuation signals only once. The solution according to the invention makes it possible to circumvent the limitations of such a brake pedal without having to modify the brake pedal itself or accepting limited braking command detection in the event of a malfunction.

[0026] Preferably, each wheel brake is assigned a wheel brake control unit, with each wheel brake control unit being connected to both brake control units. This embodiment ensures that, in the event of a failure of the other brake control unit, each of the brake control units can not only continue to determine the user's braking request with high integrity (preferably ASIL D), but can also independently control each of the wheel brake control units to implement the braking request.

[0027] Preferably, the actuation signals output by the brake pedal to the two brake control units differ when the brake pedal is actuated. This refers to the type of actuation signals, not necessarily their signal value.

[0028] Preferably, the signal forwarder forwards the actuation signals via a forwarding line independent of a vehicle system bus. This further improves the reliability of the braking system. Furthermore, the braking system's response time is improved because the forwarding line does not have to be shared with other system components.

[0029] A further aspect of the invention provides a method for signal conduction in a braking system according to one of the preceding embodiments, comprising the following steps: - Determining a set of actuation signals by the brake pedal which is indicative of a braking request of a user expressed by an actuation of the brake pedal, - Output of one or more actuation signals by the brake pedal to both brake control units, - Determine whether the brake control unit downstream of the signal forwarder has failed, and if so, - Forwarding the actuation signals directed to the failed brake control unit to the functioning brake control unit.

[0030] Features disclosed with respect to the braking system can also be used in a method according to the invention and vice versa.

[0031] In a further embodiment, the method comprises the step: - Determining a braking request of a user by at least one brake control unit that has received a complete set of actuation signals.

[0032] This step is preferably performed after the step of forwarding the actuation signals directed to the failed brake control unit to the functioning brake control unit. The method may additionally comprise the step: - Determining a braking request of a user by at least one brake control unit that has received an incomplete set of actuation signals.

[0033] This procedural step is to be understood as meaning that, in the event that no functioning brake control unit has received a complete set of actuation signals, a user's braking request is still determined. However, this braking request is then usually determined with lower quality and integrity (e.g., if only an actuation signal from a force sensor is present). This step can be relevant, for example, in the event of the failure of one or more sensors in the brake pedal or the failure of a brake control unit and the upstream signal forwarder.

[0034] It is preferred if, after determining that the brake control unit downstream of the signal forwarder has failed, the functioning brake control unit is designated as the brake control unit solely responsible for determining the braking request. Depending on the design and operating mode, the functioning brake control unit may already be the brake control unit solely responsible for determining the braking request if the other brake control unit fails. In other cases, however, for complete braking request determination with high integrity, the functioning brake control unit must first take over the tasks of the failed brake control unit.

[0035] The braking system may comprise failure detection means configured to detect the failure of one of the brake control units and to communicate this to the functioning brake control unit (and optionally also to other control units of the vehicle).

[0036] Further details of the invention emerge from the description of the illustrated embodiments and the appended claims. The drawings show: Fig. 1 A schematic representation of the signal paths in a prior art brake control unit, Fig. 2 a schematic representation of the signal paths in a first embodiment of the invention, Fig. 3 a schematic representation of the signal paths in a second embodiment of the invention, and Fig. 4 a flowchart of a method according to the invention.

[0037] In the following detailed description of preferred embodiments, like reference numerals designate substantially the same or identical parts in or on these embodiments. However, to better illustrate the invention, the preferred embodiments illustrated in the figures are not always drawn to scale.

[0038] Fig. Figure 1 shows a schematic representation of the signal paths in a prior art brake control unit 1. The braking system 1 comprises a brake pedal 2, at least two wheel brakes 3, 4, 5, 6, and at least two brake control units 7, 8. The brake pedal 2 is configured to determine a set of at least two actuation signals indicative of a user's braking request expressed by actuating the brake pedal 2. The brake pedal 2 is configured to output one or more of the actuation signals to both brake control units 7, 8. The actuation signals can be generated by at least two brake pedal sensors.

[0039] The brake control units 7, 8 are each configured to individually calculate a user's braking request from the set of actuation signals and to actuate the wheel brakes 3, 4, 5, 6 according to the calculated braking request. For this purpose, each of the brake control units 7, 8 comprises a signal processing unit 9, a braking request determination unit 10, and a braking execution unit 11. Actuation signals processed by the signal processing unit 9 can be exchanged via a system bus 12. After a plausibility check, the brake control unit 7, 8, which is responsible for the operating state, determines a braking request via the braking request determination unit 10 and then executes it via the corresponding braking execution unit 11 in the form of braking control commands to the wheel brakes 3, 4, 5, 6.

[0040] If one of the brake control units 7, 8 or the data connection via the system bus 12 fails, data exchange and plausibility checks can no longer take place and the braking request can now be determined by the remaining or responsible braking request determination unit 10 on an incomplete data basis and thus with reduced integrity.

[0041] Fig. 2 and Fig. 3 show a first and a second embodiment of a braking system 101 according to the invention. The braking system 101 comprises a brake pedal 102, four wheel brakes 103, 104, 105, 106, and two brake control units 107, 108. The brake pedal 102 is configured to determine a set of at least two actuation signals indicative of a user's braking request expressed by an actuation of the brake pedal 102. The brake pedal 102 is configured to output one or more of the actuation signals to both brake control units 107, 108, wherein the actuation signals output to the two actuation signals differ (at least partially) and together form the complete set of actuation signals.

[0042] The brake control units 107, 108 are each configured to individually calculate a braking request of the user from the set of actuation signals and to control the wheel brakes 103, 104, 105, 106 in accordance with the calculated braking request.

[0043] According to the invention, Fig. 2, a signal forwarder 109 is arranged in the signal path between the brake pedal 102 and one of the brake control units 107. This signal forwarder is configured to forward the actuation signals directed to the failed brake control unit 107 to the functioning brake control unit 108 via a forwarding line 110, at least in the event of a failure of the brake control unit 107 downstream of the signal forwarder 109, so that the functioning brake control unit 108 receives the complete set of actuation signals. The signal forwarder 109 preferably comprises a multiplexer. This embodiment is useful, for example, in braking systems 101 in which the brake control unit 108 is fundamentally the prioritized brake control unit and, during normal operation, always assumes the braking request calculation and control of the wheel brakes 103, 104, 105, 106.The brake control unit 107 then serves only as a fallback level / support and, in the event of failure of the brake control unit 108, can only perform a braking request calculation and control with reduced integrity, since not all actuation signals are present.

[0044] Both in Fig. 2 as well as in Fig. 3, each of the brake control units 107, 108 comprises a signal processing unit 111, a braking request determination unit 112, and a braking execution unit 113. It should be noted that the units 111, 112, 113 do not have to be physically different units, but that the corresponding functions can be performed in one unit (e.g., as an ASIC or via software in the brake control unit 107, 108). The brake control unit 107, 108, which is responsible depending on the operating state, determines a braking request via the braking request determination unit 112, which is then executed via the corresponding brake execution unit 113 in the form of brake control commands to the wheel brakes 103, 104, 105, 106.

[0045] In contrast to the design of the Fig. 2 includes the braking system 101 in Fig. 3 in the signal path between the brake pedal 102 and each of the brake control units 107, 108, a signal forwarder 109, 114 is provided, each of which is configured to forward the actuation signals directed to the failed brake control unit 107, 108 to the functioning brake control unit 108, 107 via an associated forwarding line 110, at least in the event of a failure of the brake control unit 107, 108 downstream of the signal forwarder 109, 114, so that the functioning brake control unit 108, 107 receives the complete set of actuation signals. This embodiment is useful, for example, in those brake systems 101 in which the brake control units 107, 108, during normal operation, take over the braking request calculation and wheel brake control, e.g., depending on the operating mode or alternately.Each of the brake control units 107, 108 can then, in principle, carry out a complete brake request calculation and control with the highest integrity (ASIL D) in the event of failure of the other brake control unit 108, 107.

[0046] Fig. 4 shows a flowchart of a method according to the invention. First, in step 200, a set of actuation signals from the brake pedal 102 is determined, which is indicative of a user's braking request expressed by an actuation of the brake pedal 102. This set of actuation signals is divided in step 210 and output to the two brake control units 107, 108, with each brake control unit 107, 108 receiving at least one actuation signal.

[0047] In step 220, it is determined (e.g., by means of failure detection) whether the brake control unit 107, 108 downstream of the signal forwarder 109, 114 has failed. If not, in step 230, a braking request calculation and control of the wheel brakes 103, 104, 105, 106 is performed by the currently responsible brake control unit 107, 108 or by both brake control units 107, 108 jointly (depending on the control concept).

[0048] If it is determined in step 220 that the brake control unit 107, 108 downstream of the signal forwarder 109, 114 has failed, then in step 240 the functioning brake control unit 108, 107 is designated as the brake control unit 108, 107 solely responsible for determining the braking request. In the following step 250, the actuation signals directed to the failed brake control unit 107, 108 are forwarded to the functioning brake control unit 108, 107. In step 260, the functioning brake control unit 108, 107 performs the braking request calculation and actuation of the wheel brakes 103, 104, 105, 106 using the complete set of actuation signals. List of reference symbols 1 braking system 2 brake pedal 3 wheel brake 4 wheel brake 5 wheel brake 6 wheel brake 7 Brake control unit 8 Brake control unit 9 Signal processing unit 10 Brake request determination unit 11 Brake execution unit 12 System bus 101 Braking system 102 Brake pedal 103 Wheel brake 104 Wheel brake 105 Wheel brake 106 Wheel brake 107 Brake control unit 108 Brake control unit 109 signal forwarders 110 forwarding line 111 Signal processing unit 112 Brake request determination unit 113 Brake execution unit 114 signal forwarders 200 steps 210 steps 220 steps 230 steps 240 steps 250 steps 260 steps QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2011 084 534 A1

[0005] DE 10 2011 016 125 A1

[0006] US 5,615,930 A

[0007]

Claims

[1] Braking system (101) comprising a brake pedal (102), at least two wheel brakes (103, 104, 105, 106) and at least two brake control units (107, 108), wherein the brake pedal (102) is configured to determine a set of at least two actuation signals which is indicative of a user's braking request expressed by an actuation of the brake pedal (102), wherein the brake pedal (102) is configured to output one or more of the actuation signals to both brake control units (107, 108), wherein the brake control units (107, 108) are each configured to individually calculate a braking request of the user from the set of actuation signals and to control the wheel brakes (103, 104, 105, 106) in accordance with the calculated braking request, characterized byin that a signal forwarder (109, 114) is arranged in the signal path between the brake pedal (102) and at least one of the brake control units (107, 108), which signal forwarder is designed to forward the actuation signals directed to the failed brake control unit (107, 108) to the functioning brake control unit (107, 108), at least in the event of a failure of the brake control unit (107, 108) downstream of the signal forwarder (109, 114), so that the functioning brake control unit (107, 108) receives the complete set of actuation signals. [2] Braking system (101) according to claim 1, characterized by that the brake pedal (102) is an electromechanical brake pedal (102). [3] Braking system (101) according to claim 1 or 2, characterized by that the brake pedal comprises at least two sensors of a different sensor type. [4] Braking system (101) according to one of the preceding claims, characterized bythat the signal forwarder (109, 114) comprises a multiplexer which is designed to forward the actuation signals directed to the failed brake control unit (107, 108) to the functioning brake control unit (107, 108) in the event of failure of the brake control unit (107, 108) downstream of it. [5] Braking system (101) according to one of the preceding claims, characterized by that in both signal paths between the brake pedal (102) and one of the brake control units (107, 108) there is arranged a signal forwarder (109, 114) which is designed to forward the actuation signals directed to the failed brake control unit (107, 108) to the functioning brake control unit (107, 108) in the event of failure of the brake control unit (107, 108) arranged downstream of it. [6] Braking system (101) according to one of the preceding claims, characterized bythat the signal forwarder (109, 114) is arranged on the same circuit board as the downstream brake control unit (107, 108), wherein the signal forwarder (109, 114) preferably has a power supply that is independent of the remaining brake control unit (107, 108). [7] Braking system (101) according to one of the preceding claims, characterized by that the brake pedal (102) does not comprise a signal processing unit and outputs unprocessed actuation signals. [8] Braking system (101) according to claim 7, characterized by that the braking system (101) is arranged in such a way that no processing of the actuation signals takes place from the brake pedal (102) via the signal forwarder (109, 114) to the input in a signal processing unit (111) of the processing brake control unit (107, 108). [9] Braking system (101) according to one of the preceding claims, characterized bythat the brake pedal (102) is arranged so that it can only output each actuation signal in the set of actuation signals exactly once. [10] Braking system (101) according to one of the preceding claims, characterized by that each wheel brake (103, 104, 105, 106) is assigned a wheel brake control unit, wherein each wheel brake control unit is connected to both brake control units (107, 108). [11] Braking system (101) according to one of the preceding claims, characterized by that the actuation signals output by the brake pedal (102) to the two brake control units (107, 108) differ when the brake pedal (102) is actuated. [12] Braking system (101) according to one of the preceding claims, characterized by that the signal forwarder (109, 114) forwards the actuation signals via a forwarding line (110) which is independent of a vehicle system bus. [13] Method for signal conduction in a braking system (101) according to one of the preceding claims, comprising the following steps: - determining (200) a set of actuation signals by the brake pedal (102) which is indicative of a user's braking request expressed by an actuation of the brake pedal (102), - Outputting (210) one or more actuation signals by the brake pedal (102) to both brake control units (107, 108), - determining (220) whether the brake control unit (107, 108) downstream of the signal forwarder (109, 114) has failed, and if so, - forwarding (250) the actuation signals directed to the failed brake control unit (107, 108) to the functioning brake control unit (107, 108). [14] A method according to claim 13, comprising the step: - determining (260) a braking request of a user by at least one brake control unit (107, 108) that has received a complete set of actuation signals. [15] Method according to claim 14, wherein after determining (220) that the brake control unit (107, 108) downstream of the signal forwarder (109, 114) has failed, the functioning brake control unit (107, 108) is designated (240) as the brake control unit (107, 108) solely responsible for determining the braking request.

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