Braking control system

Abstract

A braking control system 60 includes: a first braking ECU 70 for operating a first hydraulic braking device 26 and a first electric parking actuator 31; and a redundant ECU 90 for operating a second electric parking actuator 32 without taking a hydraulic braking device 25 to be a controlled object. The first braking ECU 70 and the redundant ECU 90 are capable of receiving a parking brake operation request via an in-vehicle network. In a case in which the first braking ECU 70 is normal, the first braking ECU 70 operates the first electric parking actuator 31 on the basis of the parking brake operation request. In a case in which an abnormality is occurring in the first braking ECU 70, the redundant ECU 90 operates the second electric parking actuator 32 on the basis of the parking brake operation request.

Description

Braking Control System

[0001] The present invention relates to a braking control system mounted on a vehicle.

[0002] Patent Document 1 discloses a vehicle equipped with an automatic transmission and an electric parking device. The electric parking device includes a first electric parking actuator that generates a parking braking force on a first wheel among a plurality of wheels, and a second electric parking actuator that generates a parking braking force on a second wheel among the plurality of wheels. The braking system of the vehicle includes an upstream hydraulic braking device and a downstream hydraulic braking device as braking devices that generate normal braking forces on the plurality of wheels, as well as a first controller that controls the downstream hydraulic braking device and a second controller that controls the upstream hydraulic braking device.

[0003] When the parking brake switch is operated, the first controller operates the first electric parking actuator to generate parking braking force on the first wheel. The first controller also transmits an operation instruction to the second controller via the in-vehicle network. The second controller operates the second electric parking actuator based on the received operation instruction to generate parking braking force on the second wheel.

[0004] European Patent No. 3529118

[0005] In recent years, there has been a demand for redundancy in electric parking devices.

[0006] A brake control system for solving the above problem is applied to a vehicle including a first wheel and a second wheel, a first wheel cylinder provided on the first wheel, a second wheel cylinder provided on the second wheel, a hydraulic brake device configured to adjust the hydraulic pressure of the first wheel cylinder and the second wheel cylinder, a first electric parking actuator configured to generate a parking braking force at the first wheel, and a second electric parking actuator configured to generate a parking braking force at the second wheel. The brake control system includes a brake control device that activates the hydraulic brake device and at least one of the electric parking actuators, and a redundant control device that does not control the hydraulic brake device and activates at least one of the electric parking actuators. Each of the brake control device and the redundant control device is capable of receiving a parking brake operation request, which is a request for parking braking, via an in-vehicle network. When the brake control device is normal, the brake control device activates one of the electric parking actuators that it can operate, based on the parking brake operation request received via the in-vehicle network. If an abnormality occurs in the braking control device, the redundant control device activates the electric parking actuator that it can operate among the multiple electric parking actuators based on the parking brake activation request received via the in-vehicle network.

[0007] The braking control system described above has the effect of making the electric parking device redundant.

[0008] FIG. 1 is a schematic diagram showing a vehicle equipped with a brake control system according to a first embodiment. FIG. 2 is a diagram showing the brake control system of FIG. 1 and an electric parking device controlled by the brake control system. FIG. 3 is a flowchart showing a series of processes executed by a second brake ECU (a) and a redundant ECU (b) when determining that an abnormality has occurred in a first brake ECU included in the brake control system of FIG. 1. FIG. 4 is a flowchart showing a series of processes executed by a second brake ECU (a) and a redundant ECU (b) when determining that an abnormality has occurred in a redundant ECU included in the brake control system of FIG. 1. FIG. 5 is a flowchart showing a series of processes executed by a first brake ECU (a) and a redundant ECU (b) when the brake control system of FIG. 1 is normal. FIG. 6 is a flowchart showing a series of processes executed by a redundant ECU when determining that an abnormality has occurred in the first brake ECU included in the brake control system of FIG. 1. Fig. 7 is a flowchart showing a series of processes executed by the first brake ECU when it is determined that an abnormality has occurred in the redundant ECU provided in the brake control system of Fig. 1. Fig. 8 is a configuration diagram showing an outline of a brake control system of a second embodiment. Fig. 9 is a configuration diagram showing an outline of a brake control system of a third embodiment.

[0009] (First embodiment) A first embodiment of a brake control system will be described with reference to Figs. 1 to 7. <Vehicle configuration> Fig. 1 shows a vehicle 10 to which a brake control system 60 is applied. Fig. 2 shows the brake control system 60. As shown in Figs. 1 and 2, the vehicle 10 further includes a plurality of wheels, friction brakes 20 in the same number as the wheels, a hydraulic braking device 25, and an electric parking device 30. The plurality of wheels include a first wheel 11 and a second wheel 12. An example of the first wheel 11 and the second wheel 12 is the rear wheels.

[0010] Each of the plurality of friction brakes 20 has a rotating body 21 that rotates integrally with the corresponding wheel, a friction material 22, and a wheel cylinder 23. The friction brake 20 is configured to generate a braking force at the corresponding wheel by pressing the friction material 22 against the rotating body 21. The higher the hydraulic pressure in the wheel cylinder 23, the greater the force pressing the friction material 22 against the rotating body 21, and therefore the greater the braking force generated at the wheel.

[0011] Of the multiple wheel cylinders 23, the wheel cylinder 23 provided on the first wheel 11 corresponds to the "first wheel cylinder," and the wheel cylinder 23 provided on the second wheel 12 corresponds to the "second wheel cylinder."

[0012] The hydraulic braking device 25 includes a first hydraulic braking device 26 and a second hydraulic braking device 27. Each of the first hydraulic braking device 26 and the second hydraulic braking device 27 is configured to be able to adjust the hydraulic pressure of the plurality of wheel cylinders 23. The first hydraulic braking device 26 is configured to be able to adjust the hydraulic pressure of the plurality of wheel cylinders 23 individually. The second hydraulic braking device 27 is configured to be able to generate, in the plurality of wheel cylinders 23, hydraulic pressure corresponding to a required braking force, which is a required value of braking force for the vehicle 10. An example of the configuration of the first hydraulic braking device 26 and the second hydraulic braking device 27 is disclosed in Japanese Patent Application Laid-Open No. 2024-76857.

[0013] The electric parking device 30 includes a first electric parking actuator 31 and a second electric parking actuator 32. The first electric parking actuator 31 is configured to generate a parking braking force at the first wheel 11. The second electric parking actuator 32 is configured to generate a parking braking force at the second wheel 12. Each of the electric parking actuators 31, 32 has an electric motor. The electric parking actuators 31, 32 can generate a parking braking force at the wheel in accordance with the drive of the electric motor. For example, when the electric motor is driven, the friction material 22 of the friction brake 20 is pressed against the rotating body 21, thereby generating a parking braking force at the wheels 11, 12. An example of the configuration of the electric parking actuators 31, 32 is disclosed in Japanese Patent Application Laid-Open No. 2022-85637.

[0014] <In-Vehicle Network> The in-vehicle network of the vehicle 10 will be described with reference to Figures 1 and 2. The vehicle 10 is equipped with a plurality of electronic control units. Hereinafter, the electronic control units will be referred to as "ECUs." ECU is an abbreviation for "Electronic Control Unit." The vehicle 10 is equipped with an in-vehicle network for communication between the plurality of ECUs. The in-vehicle network has a plurality of global communication lines. An example of a global communication line is the CAN bus. "CAN" is an abbreviation for "Control Area Network."

[0015] The multiple global communication lines include a first global communication line 201 and a second global communication line 202. <ECUs Other than ECUs Constituting the Brake Control System> The vehicle 10 includes an integrated ECU 51 and a shift ECU 52 as ECUs other than ECUs constituting the brake control system 60. The integrated ECU 51 transmits various information, requests, and commands to the other ECUs via the in-vehicle network. For example, when an occupant of the vehicle 10 operates the parking brake operation switch 41, the integrated ECU 51 transmits a parking brake operation request, which is a request related to parking braking, to the first global communication line 201 and the second global communication line 202, as indicated by arrow X1 in FIG. 2. The parking brake operation switch 41 is an operation unit operated by the occupant to activate the electric parking device 30. For example, the parking brake operation switch 41 is installed in the vehicle cabin.

[0016] The parking brake operation request includes an apply request and a release request. The apply request is a request to generate parking braking force. The release request is a request to release the state in which parking braking force is being applied.

[0017] The shift ECU 52 controls a shift device provided in the vehicle 10. The shift ECU 52 transmits, to the second global communication line 202, range information that corresponds to the shift range selected by the shift device.

[0018] 1 and 2, the brake control system 60 includes a plurality of ECUs related to vehicle braking. The plurality of ECUs includes a first brake ECU 70, a second brake ECU 80, and a redundant ECU 90.

[0019] The first brake ECU 70 activates the first hydraulic braking device 26. The first brake ECU 70 activates at least one of the multiple electric parking actuators 31, 32. In this respect, the first brake ECU 70 corresponds to a "first brake control device." In this embodiment, the first brake ECU 70 activates only the first electric parking actuator 31 of the multiple electric parking actuators 31, 32.

[0020] The first brake ECU 70 has a processing circuit 71 and a drive circuit 73. The processing circuit 71 has a CPU and a memory that stores control programs executed by the CPU. The control programs include a control program for operating the first hydraulic braking device 26 and a control program for operating the first electric parking actuator 31. The CPU executes the control programs in the memory, allowing the processing circuit 71 to operate the first hydraulic braking device 26 and the first electric parking actuator 31.

[0021] The drive circuit 73 is a circuit for driving the electric motor of the first electric parking actuator 31. When the drive circuit 73 operates based on a command from the processing circuit 71, the drive circuit 73 outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the first electric parking actuator 31.

[0022] The second brake ECU 80 activates the second hydraulic braking device 27. On the other hand, the second brake ECU 80 does not control the electric parking device 30. In this respect, the second brake ECU 80 corresponds to a "second brake control device." The second brake ECU 80 has a processing circuit 81. The processing circuit 81 has a CPU and a memory. The memory stores a control program for activating the second hydraulic braking device 27. The CPU executes this control program, which allows the processing circuit 81 to activate the second hydraulic braking device 27.

[0023] The redundant ECU 90 does not control the hydraulic braking system 25. However, the redundant ECU 90 operates at least one of the electric parking actuators 31, 32. In this respect, the redundant ECU 90 corresponds to a "redundant control device." In this embodiment, the redundant ECU 90 operates only the second electric parking actuator 32 out of the electric parking actuators 31, 32.

[0024] The redundant ECU 90 has a processing circuit 91 and a drive circuit 93. The processing circuit 91 has a CPU and a memory. The memory stores a control program for operating the second electric parking actuator 32. The CPU executes this control program, which enables the processing circuit 91 to operate the second electric parking actuator 32.

[0025] The drive circuit 93 is a circuit for driving the electric motor of the second electric parking actuator 32. When the drive circuit 93 operates based on a command from the processing circuit 91, the drive circuit 93 outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the second electric parking actuator 32.

[0026] The braking control system 60 has a braking communication line 61 as an in-vehicle network for communication between multiple control devices related to vehicle braking. An example of the braking communication line 61 is a CAN bus. The first braking ECU 70, the second braking ECU 80, and the redundant ECU 90 can communicate via the braking communication line 61. On the other hand, the braking communication line 61 cannot be used for communication with ECUs other than those constituting the braking control system 60.

[0027] <Processing flow when determining that an abnormality has occurred in the first brake ECU> Referring to Figure 3, the processing flow when determining that an abnormality has occurred in the first brake ECU 70 when the second brake ECU 80 and the redundant ECU 90 are normal will be described. Figure 3(a) shows a series of processing executed by the second brake ECU 80. Figure 3(b) shows a series of processing executed by the redundant ECU 90.

[0028] 3A, in step S11, the processing circuit 81 of the second brake ECU 80 transmits a monitoring signal to the first brake ECU 70 via the first global communication line 201. The monitoring signal is a signal for confirming whether the destination ECU is operating normally.

[0029] When the first brake ECU 70 receives the monitoring signal from the first global communication line 201, the processing circuit 71 of the first brake ECU 70 transmits a reply signal, which is a response signal to the monitoring signal, to the second brake ECU 80 via the first global communication line 201.

[0030] In this way, if the second brake ECU 80 can receive the reply signal transmitted from the first brake ECU 70 to the first global communication line 201, the second brake ECU 80 can determine that the first brake ECU 70 is normal. However, if an abnormality occurs in the first brake ECU 70 or if communication between the second brake ECU 80 and the first brake ECU 70 via the first global communication line 201 is not normal, the second brake ECU 80 cannot receive the reply signal from the first brake ECU 70 via the first global communication line 201.

[0031] In the following step S13, the processing circuit 81 of the second brake ECU 80 transmits a monitoring signal to the first brake ECU 70 via the brake communication line 61. If the first brake ECU 70 receives the monitoring signal from the brake communication line 61, the processing circuit 71 of the first brake ECU 70 transmits a reply signal in response to the monitoring signal to the second brake ECU 80 via the brake communication line 61.

[0032] In this way, if the second brake ECU 80 can receive the reply signal transmitted from the first brake ECU 70 to the brake communication line 61, the second brake ECU 80 can determine that the first brake ECU 70 is normal. However, if an abnormality occurs in the first brake ECU 70 or if communication between the second brake ECU 80 and the first brake ECU 70 via the brake communication line 61 is not normal, the second brake ECU 80 cannot receive the reply signal from the first brake ECU 70 via the brake communication line 61.

[0033] The processing circuit 81 of the second brake ECU 80 executes the communication determination process of step S15 when a predetermined determination time has elapsed since the monitoring signal was transmitted to the first brake ECU 70 via the brake communication line 61. In the communication determination process of step S15, the processing circuit 81 determines whether communication with the first brake ECU 70 is normal or not by executing the processes of steps S11 and S13. If both the second brake ECU 80 cannot receive a reply signal from the first global communication line 201 and the second brake ECU 80 cannot receive a reply signal from the brake communication line 61, the processing circuit 81 determines that communication between the second brake ECU 80 and the first brake ECU 70 is not normal. On the other hand, if at least one of the following is true: the second brake ECU 80 is able to receive a reply signal from the first global communication line 201; or the second brake ECU 80 is able to receive a reply signal from the brake communication line 61, the processing circuit 81 determines that communication between the second brake ECU 80 and the first brake ECU 70 is normal.

[0034] Then, in step S17, the processing circuit 81 transmits communication availability information, which is information relating to the result of the communication determination process in step S15, to the redundant ECU 90 via the braking communication line 61. Thereafter, the processing circuit 81 ends the series of processes shown in FIG.

[0035] 3B, when the redundant ECU 90 receives the communication availability information transmitted by the second brake ECU 80 in step S17, the processing circuit 91 of the redundant ECU 90 executes step S21. In step S21, the processing circuit 91 transmits a monitoring signal to the first brake ECU 70 via the brake communication line 61.

[0036] When the first brake ECU 70 receives the monitoring signal from the brake communication line 61 , the processing circuit 71 of the first brake ECU 70 transmits a response signal to the monitoring signal to the redundant ECU 90 via the brake communication line 61 .

[0037] In this way, if the redundant ECU 90 can receive the reply signal transmitted from the first brake ECU 70 to the brake communication line 61, the redundant ECU 90 can determine that the first brake ECU 70 is normal. However, if an abnormality occurs in the first brake ECU 70 or if communication between the redundant ECU 90 and the first brake ECU 70 via the brake communication line 61 is not normal, the redundant ECU 90 cannot receive the reply signal from the brake communication line 61.

[0038] The processing circuit 91 of the redundant ECU 90 executes the communication determination process of step S23 when a predetermined determination time has elapsed since the time the monitoring signal was transmitted to the first brake ECU 70. In the communication determination process of step S23, the processing circuit 91 determines whether an abnormality has occurred in the first brake ECU 70. For example, if both of the following conditions (A1) and (A2) are met, the processing circuit 91 determines that an abnormality has occurred in the first brake ECU 70. On the other hand, if at least one of the conditions (A1) and (A2) is not met, the processing circuit 91 determines that the first brake ECU 70 is normal.

[0039] (A1) The communication availability information received from the second brake ECU 80 is information indicating that communication between the second brake ECU 80 and the first brake ECU 70 is not normal. (A2) The communication between the redundant ECU 90 and the first brake ECU 70 is not normal.

[0040] In step S25, the processing circuit 91 transmits information indicating the result of the communication determination process in step S23 to the second brake ECU 80 via the brake communication line 61. This allows the second brake ECU 80 and the redundant ECU 90 to share information about whether the first brake ECU 70 is normal or abnormal. Thereafter, the processing circuit 91 ends the series of processes shown in FIG. 3B.

[0041] <Processing flow when determining that an abnormality has occurred in the redundant ECU> The processing flow when determining that an abnormality has occurred in the redundant ECU 90 when the first brake ECU 70 and the second brake ECU 80 are normal will be described with reference to Figure 4. Figure 4(a) shows a series of processing executed by the second brake ECU 80. Figure 4(b) shows a series of processing executed by the first brake ECU 70.

[0042] 4A, in step S41, the processing circuit 81 of the second brake ECU 80 transmits a monitoring signal to the redundant ECU 90 via the brake communication line 61. If the redundant ECU 90 receives the monitoring signal from the brake communication line 61, the processing circuit 91 of the redundant ECU 90 transmits a response signal to the monitoring signal to the second brake ECU 80 via the brake communication line 61.

[0043] In this way, if the second brake ECU 80 can receive the reply signal transmitted from the redundant ECU 90 to the brake communication line 61, the second brake ECU 80 can determine that the redundant ECU 90 is normal. However, if an abnormality occurs in the redundant ECU 90 or if communication between the second brake ECU 80 and the redundant ECU 90 via the brake communication line 61 is not normal, the second brake ECU 80 cannot receive the reply signal from the brake communication line 61.

[0044] The processing circuit 81 of the second brake ECU 80 executes a communication determination process in step S43 when a predetermined determination time has elapsed since the time the monitoring signal was transmitted. In the communication determination process in step S43, the processing circuit 81 determines whether communication between the second brake ECU 80 and the redundant ECU 90 is normal. If the second brake ECU 80 is able to receive a reply signal from the redundant ECU 90, the processing circuit 81 determines that communication between the second brake ECU 80 and the redundant ECU 90 is normal. On the other hand, if the second brake ECU 80 is unable to receive a reply signal from the redundant ECU 90, the processing circuit 81 determines that communication between the second brake ECU 80 and the redundant ECU 90 is not normal.

[0045] Then, in step S45, the processing circuit 81 transmits communication availability information, which is information relating to the result of the communication determination process in step S43, to the first brake ECU 70 via the brake communication line 61. Thereafter, the processing circuit 81 ends the series of processes shown in FIG.

[0046] 4B, when the first brake ECU 70 receives the communication availability information transmitted by the second brake ECU 80 in step S45, the processing circuit 71 of the first brake ECU 70 executes step S51. In step S51, the processing circuit 71 transmits a monitoring signal to the redundant ECU 90 via the brake communication line 61.

[0047] If the redundant ECU 90 receives the monitoring signal from the braking communication line 61 , the processing circuit 91 of the redundant ECU 90 transmits a response signal to the monitoring signal to the first braking ECU 70 via the braking communication line 61 .

[0048] In this way, if the first brake ECU 70 can receive the reply signal transmitted from the redundant ECU 90 to the brake communication line 61, the first brake ECU 70 can determine that the redundant ECU 90 is normal. However, if an abnormality occurs in the redundant ECU 90 or if communication between the redundant ECU 90 and the first brake ECU 70 via the brake communication line 61 is not normal, the first brake ECU 70 cannot receive the reply signal from the brake communication line 61.

[0049] The processing circuit 71 of the first brake ECU 70 executes a communication determination process in step S53 when a predetermined determination time has elapsed since the time the monitoring signal was transmitted to the redundant ECU 90. In the communication determination process in step S53, the processing circuit 71 determines whether an abnormality has occurred in the redundant ECU 90. For example, if both of the following conditions (A3) and (A4) are met, the processing circuit 71 determines that an abnormality has occurred in the redundant ECU 90. On the other hand, if at least one of the conditions (A3) and (A4) is not met, the processing circuit 71 determines that the redundant ECU 90 is normal. However, if either one of the conditions (A3) and (A4) is met, it can be assumed that communication using the brake communication line 61 is abnormal.

[0050] (A3) Communication between the second brake ECU 80 and the redundant ECU 90 via the brake communication line 61 is not normal. (A4) Communication between the first brake ECU 70 and the redundant ECU 90 via the brake communication line 61 is not normal.

[0051] In step S55, the processing circuit 71 transmits information indicating the result of the communication determination process in step S53 to the second brake ECU 80 via the brake communication line 61. This allows the first brake ECU 70 and the second brake ECU 80 to share information about whether the redundant ECU 90 is normal or abnormal. Thereafter, the processing circuit 71 ends the series of processes shown in FIG. 4B.

[0052] <Processing flow for parking braking when the brake control system is normal> The processing flow when the electric parking device 30 is operated when the brake control system 60 is normal will be described with reference to Figure 5. Figure 5(a) shows a series of processes executed by the first brake ECU 70. Figure 5(b) shows a series of processes executed by the redundant ECU 90. Here, "the brake control system 60 is normal" means that all of the following conditions (B1) to (B4) are met.

[0053] (B1) All ECUs 70, 80, 90 are normal. (B2) The first brake ECU 70 can receive the parking brake operation request via the first global communication line 201.

[0054] (B3) The redundant ECU 90 can receive the parking brake operation request via the second global communication line 202. (B4) Communication between the plurality of ECUs 70, 80, 90 via the brake communication line 61 is normal.

[0055] The processing circuit 71 of the first brake ECU 70 repeatedly executes the series of processes shown in Fig. 5A. In step S211, the processing circuit 71 of the first brake ECU 70 determines whether the first brake ECU 70 has received a parking brake operation request via the first global communication line 201. If the first brake ECU 70 has received a parking brake operation request (S211: YES), the processing circuit 71 proceeds to step S213. On the other hand, if the first brake ECU 70 has not received a parking brake operation request (S211: NO), the processing circuit 71 temporarily terminates the series of processes shown in Fig. 5A.

[0056] In step S213, the processing circuit 71 activates the first electric parking actuator 31 based on the parking brake operation request received via the first global communication line 201. If the parking brake operation request is an apply request, the processing circuit 71 activates the first electric parking actuator 31 to generate a parking braking force on the first wheel 11. If the parking brake operation request is a release request, the processing circuit 71 activates the first electric parking actuator 31 to release the state in which the parking braking force is being generated on the first wheel 11.

[0057] In the following step S215, the processing circuit 71 transmits an operation instruction to the redundant ECU 90 via the brake communication line 61. The operation instruction is an instruction corresponding to the parking brake operation request received by the first brake ECU 70 via the first global communication line 201. Thereafter, the processing circuit 71 temporarily ends the series of processes shown in FIG.

[0058] The processing circuit 91 of the redundant ECU 90 repeatedly executes the series of processes shown in FIG. 5B. In step S221, the processing circuit 91 determines whether the redundant ECU 90 has received the activation command transmitted by the first brake ECU 70 to the brake communication line 61. If the redundant ECU 90 has not received the activation command (S221: NO), the processing circuit 91 temporarily terminates the series of processes shown in FIG. 5B. On the other hand, if the redundant ECU 90 has received the activation command (S221: YES), the processing circuit 91 proceeds to step S223.

[0059] In step S223, the processing circuit 91 activates the second electric parking actuator 32 based on the activation command received from the first brake ECU 70. If the activation command is a command corresponding to an apply request, the processing circuit 91 activates the second electric parking actuator 32 to generate a parking braking force on the second wheel 12. If the activation command is a command corresponding to a release request, the processing circuit 91 activates the second electric parking actuator 32 to release the state in which the parking braking force is being generated on the second wheel 12. Thereafter, the processing circuit 91 temporarily ends the series of processes shown in FIG. 5B.

[0060] <Processing flow related to parking braking when it is determined that an abnormality has occurred in the first brake ECU> The processing flow when an abnormality has occurred in the first brake ECU 70 while the redundant ECU 90 is operating normally will be described with reference to Figure 6. Figure 6 shows a series of processes executed by the redundant ECU 90. The processing circuit 91 of the redundant ECU 90 repeatedly executes this series of processes.

[0061] In step S311, the processing circuit 91 determines whether the redundant ECU 90 has received a parking brake activation request via the second global communication line 202. If the redundant ECU 90 has received a parking brake activation request (YES in step S311), the processing circuit 91 proceeds to step S313. On the other hand, if the redundant ECU 90 has not received a parking brake activation request (NO in step S311), the processing circuit 91 temporarily terminates the series of processes shown in FIG.

[0062] In step S313, the processing circuit 91 activates the second electric parking actuator 32 based on the parking brake operation request received via the second global communication line 202. If the parking brake operation request is an apply request, the processing circuit 91 activates the second electric parking actuator 32 to generate a parking braking force on the second wheel 12. If the parking brake operation request is a release request, the processing circuit 91 activates the second electric parking actuator 32 to release the state in which the parking braking force is being generated on the second wheel 12. Thereafter, the processing circuit 91 temporarily ends the series of processes shown in FIG.

[0063] <Processing flow related to parking braking when it is determined that an abnormality has occurred in the redundant ECU> The processing flow when an abnormality has occurred in the redundant ECU 90 while the first brake ECU 70 is operating normally will be described with reference to Figure 7. Figure 7 shows a series of processing steps executed by the first brake ECU 70. The processing circuit 71 of the first brake ECU 70 repeatedly executes this series of processing steps.

[0064] In step S411, the processing circuit 71 determines whether the first brake ECU 70 has received a parking brake operation request via the first global communication line 201. If the first brake ECU 70 has received a parking brake operation request (YES in step S411), the processing circuit 71 proceeds to step S413. On the other hand, if the first brake ECU 70 has not received a parking brake operation request (NO in step S411), the processing circuit 71 temporarily terminates the series of processes shown in FIG.

[0065] In step S413, the processing circuit 71 activates the first electric parking actuator 31 based on the parking brake operation request received via the first global communication line 201. If the parking brake operation request is an apply request, the processing circuit 71 activates the first electric parking actuator 31 to generate a parking braking force on the first wheel 11. If the parking brake operation request is a release request, the processing circuit 71 activates the first electric parking actuator 31 to release the state in which the parking braking force is being generated on the first wheel 11. Thereafter, the processing circuit 71 temporarily ends the series of processes shown in FIG. 7 .

[0066] <Functions and Effects of the Present Embodiment> (1-1) In the brake control system 60, the first brake ECU 70 controls the first hydraulic brake device 26 of the hydraulic brake device 25, and also controls the first electric parking actuator 31 of the multiple electric parking actuators 31, 32. The redundant ECU 90 does not control the hydraulic brake device 25, and controls the second electric parking actuator 32 of the multiple electric parking actuators 31, 32. The first brake ECU 70 and the redundant ECU 90 can receive a parking brake operation request sent by the integrated ECU 51.

[0067] When the first brake ECU 70 is functioning normally, the processing circuit 71 of the first brake ECU 70 activates one of the multiple electric parking actuators 31, 32 that it can operate, based on the parking brake operation request received via the first global communication line 201. When an abnormality occurs in the first brake ECU 70, the processing circuit 91 of the redundant ECU 90 activates one of the multiple electric parking actuators 31, 32 that it can operate, based on the parking brake operation request received via the second global communication line 202. In other words, the brake control system 60 can generate parking braking force for the vehicle 10 even if an abnormality occurs in the first brake ECU 70. Therefore, the brake control system 60 can make the electric parking device 30 redundant.

[0068] (1-2) Although the first brake ECU 70 is normal, an abnormality may occur in the redundant ECU 90. In this case, the processing circuit 71 of the first brake ECU 70 activates an electric parking actuator that it can activate among the multiple electric parking actuators 31, 32, based on the parking brake operation request received via the first global communication line 201. In other words, the brake control system 60 can generate a parking braking force on the vehicle 10 even if an abnormality occurs in the redundant ECU 90.

[0069] (1-3) When the brake control system 60 is functioning normally, if the first brake ECU 70 receives a parking brake operation request via the first global communication line 201, the processing circuit 71 of the first brake ECU 70 activates the first electric parking actuator 31. Furthermore, the processing circuit 71 transmits an operation command corresponding to the parking brake operation request to the redundant ECU 90 via the brake communication line 61, as indicated by arrow X2 in FIG. 2 . When the redundant ECU 90 receives the operation command, the processing circuit 91 of the redundant ECU 90 activates the second electric parking actuator 32. As a result, when the brake control system 60 is functioning normally, if the parking brake operation request is an apply request, the brake control system 60 can generate parking braking force on both the first wheel 11 and the second wheel 12. Furthermore, if the parking brake operation request is a release request, the brake control system 60 can eliminate the state in which parking braking force is being generated on both the first wheel 11 and the second wheel 12.

[0070] (1-4) The brake control system 60 further includes a second brake ECU 80. The second brake ECU 80 determines whether communication with the first brake ECU 70 via the first global communication line 201 is normal. The second brake ECU 80 also determines whether communication with the first brake ECU 70 via the brake communication line 61 is normal. Meanwhile, the redundant ECU 90 determines whether communication with the first brake ECU 70 via the brake communication line 61 is normal. If communication between the second brake ECU 80 and the first brake ECU 70 is not normal and communication between the redundant ECU 90 and the first brake ECU 70 is not normal, there is a possibility that an abnormality has occurred in the first brake ECU 70.

[0071] Therefore, the second brake ECU 80 transmits communication availability information, which is information regarding whether communication between the second brake ECU 80 and the first brake ECU 70 is normal, to the redundant ECU 90 via the brake communication line 61. If both of the following are true: the communication availability information received from the second brake ECU 80 indicates that communication between the second brake ECU 80 and the first brake ECU 70 is not normal; and the communication between the redundant ECU 90 and the first brake ECU 70 is not normal, the redundant ECU 90 determines that an abnormality has occurred in the first brake ECU 70. In other words, the redundant ECU 90 can determine whether an abnormality has occurred in the first brake ECU 70 without making the brake communication line 61 redundant in the brake control system 60.

[0072] (1-5) The brake control system 60 includes a redundant ECU 90 in addition to the first brake ECU 70 and second brake ECU 80 that operate the hydraulic brake device 25. The first brake ECU 70 and the redundant ECU 90 can operate the electric parking device 30. Therefore, the brake control system 60 can make the electric parking device 30 redundant without making design changes to the configuration of the second brake ECU 80 that operates the second hydraulic brake device 27.

[0073] Second Embodiment A second embodiment of the brake control system will be described with reference to Fig. 8. Note that the second embodiment differs from the first embodiment in part of the circuit configuration of the first brake ECU and the redundant ECU. In the following description, differences from the first embodiment will be mainly described, and the same components as those in the first embodiment will be designated by the same reference numerals, and redundant description will be omitted.

[0074] As shown in FIG. 8 , the braking control system 60A includes a plurality of ECUs configured to be able to communicate with each other via a braking communication line 61. The plurality of ECUs includes a first braking ECU 70A, a second braking ECU 80, and a redundant ECU 90A. In this embodiment, the first braking ECU 70A corresponds to the "first braking control device," and the redundant ECU 90A corresponds to the "redundant control device." Each of the first braking ECU 70A and the second braking ECU 80 is capable of communicating with other on-board ECUs, such as the integrated ECU 51, via a first global communication line 201. The redundant ECU 90A is capable of communicating with other on-board ECUs, such as the integrated ECU 51, via a second global communication line 202.

[0075] The first brake ECU 70A can operate any of the multiple electric parking actuators 31, 32. For example, the first brake ECU 70A includes a processing circuit 71, a first drive circuit 73A, and a second drive circuit 74A. The first drive circuit 73A drives the electric motor of the first electric parking actuator 31. When the first drive circuit 73A operates based on a command from the processing circuit 71, the first drive circuit 73A outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the first electric parking actuator 31. The second drive circuit 74A drives the electric motor of the second electric parking actuator 32. When the second drive circuit 74A operates based on a command from the processing circuit 71, the second drive circuit 74A outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the second electric parking actuator 32.

[0076] The redundant ECU 90A can operate only the second electric parking actuator 32 out of the multiple electric parking actuators 31, 32. For example, the redundant ECU 90A includes a processing circuit 91, a third drive circuit 93A, and a switch circuit 96A. The third drive circuit 93A is a circuit that drives the electric motor of the second electric parking actuator 32. When the third drive circuit 93A operates based on a command from the processing circuit 91, the third drive circuit 93A outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the second electric parking actuator 32.

[0077] The switch circuit 96A is configured to be able to select either the drive signal output by the second drive circuit 74A or the drive signal output by the third drive circuit 93A and output it to the second electric parking actuator 32. In this embodiment, the switch circuit 96A selects either the drive signal output by the second drive circuit 74A or the drive signal output by the third drive circuit 93A based on an instruction from the processing circuit 91.

[0078] <Processing flow for parking braking when the brake control system is normal> The following describes the processing flow when the brake control system 60A is normal and the electric parking device 30 is operated. Here, "the brake control system 60A is normal" means that all of the above conditions (B1) to (B4) are met.

[0079] In this case, the processing circuit 91 of the redundant ECU 90A operates the switch circuit 96A so that the switch circuit 96A can select the drive signal output by the second drive circuit 74A. When the processing circuit 71 of the first brake ECU 70A receives a parking brake operation request via the first global communication line 201, it operates the first drive circuit 73A and the second drive circuit 74A based on the parking brake operation request. The drive signal output by the first drive circuit 73A is then output to the first electric parking actuator 31. This allows the processing circuit 71 to operate the first electric parking actuator 31 based on the parking brake operation request.

[0080] The drive signal output by the second drive circuit 74A is input to the switch circuit 96A of the redundant ECU 90A. The switch circuit 96A then outputs the drive signal of the second drive circuit 74A to the second electric parking actuator 32. This allows the processing circuit 71 to operate the second electric parking actuator 32 based on the parking brake operation request.

[0081] In other words, when the first brake ECU 70A is normal, the first brake ECU 70A can operate the first electric parking actuator 31 and the second electric parking actuator 32 that it can operate, among the multiple electric parking actuators 31, 32, based on the parking brake operation request. In this case, the processing circuit 71 does not need to send an operation instruction in response to the parking brake operation request to the redundant ECU 90A via the brake communication line 61.

[0082] <Processing Flow for Parking Braking When It is Determined that an Abnormality Has Occurred in the First Brake ECU> The processing flow when an abnormality has occurred in the first brake ECU 70A while the redundant ECU 90A is normal will be described.

[0083] In this case, the processing circuit 91 of the redundant ECU 90A operates the switch circuit 96A so that the switch circuit 96A can select the drive signal output by the third drive circuit 93A. When the processing circuit 91 of the redundant ECU 90A receives a parking brake operation request via the second global communication line 202, it operates the third drive circuit 93A based on the parking brake operation request. The drive signal output by the third drive circuit 93A is then output to the switch circuit 96A. The switch circuit 96A outputs the drive signal of the third drive circuit 93A to the second electric parking actuator 32. This allows the processing circuit 91 to operate the second electric parking actuator 32 based on the parking brake operation request.

[0084] In other words, if an abnormality occurs in the first brake ECU 70A, the redundant ECU 90A can activate the second electric parking actuator 32 that it can operate itself out of the multiple electric parking actuators 31, 32 based on a parking brake activation request.

[0085] Therefore, the brake control system 60A can achieve the same effects as those of (1-1), (1-2), (1-4), and (1-5) in the first embodiment. (Third Embodiment) A third embodiment of the brake control system will be described with reference to FIG. 9. Note that the third embodiment differs from the above-described embodiments in part of the circuit configuration of the first brake ECU and the redundant ECU. In the following description, differences from the above-described embodiments will be mainly described, and the same components as those in the above-described embodiments will be designated by the same reference numerals, and redundant description will be omitted.

[0086] As shown in FIG. 9 , the braking control system 60B includes a plurality of ECUs configured to be able to communicate with each other via a braking communication line 61. The plurality of ECUs includes a first braking ECU 70B, a second braking ECU 80, and a redundant ECU 90B. In this embodiment, the first braking ECU 70B corresponds to the "first braking control device," and the redundant ECU 90B corresponds to the "redundant control device." The first braking ECU 70B and the second braking ECU 80 are able to communicate with other on-board ECUs, such as the integrated ECU 51, via a first global communication line 201. The redundant ECU 90B is able to communicate with other on-board ECUs, such as the integrated ECU 51, via a second global communication line 202.

[0087] The first brake ECU 70B can operate any of the multiple electric parking actuators 31, 32. For example, the first brake ECU 70B includes a processing circuit 71, a first drive circuit 73B, and a second drive circuit 74B. The first drive circuit 73B is a circuit that drives the electric motor of the first electric parking actuator 31. When the first drive circuit 73B operates based on a command from the processing circuit 71, the first drive circuit 73B outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the first electric parking actuator 31. The second drive circuit 74B is a circuit that drives the electric motor of the second electric parking actuator 32. When the second drive circuit 74B operates based on a command from the processing circuit 71, the second drive circuit 74B outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the second electric parking actuator 32.

[0088] The redundant ECU 90B can operate any of the multiple electric parking actuators 31, 32. For example, the redundant ECU 90B includes a processing circuit 91, a third drive circuit 93B, a fourth drive circuit 94B, a first switch circuit 96B, and a second switch circuit 97B. The third drive circuit 93B is a circuit that drives the electric motor of the first electric parking actuator 31. When the third drive circuit 93B operates based on a command from the processing circuit 91, the third drive circuit 93B outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the first electric parking actuator 31. The fourth drive circuit 94B is a circuit that drives the electric motor of the second electric parking actuator 32. When the fourth drive circuit 94B operates based on a command from the processing circuit 91, the fourth drive circuit 94B outputs a drive signal. The electric motor is driven based on the drive signal, thereby operating the second electric parking actuator 32.

[0089] The first switch circuit 96B is configured to be able to select either the drive signal output by the first drive circuit 73B or the drive signal output by the third drive circuit 93B, and output it to the first electric parking actuator 31. In this embodiment, the first switch circuit 96B selects either the drive signal output by the first drive circuit 73B or the drive signal output by the third drive circuit 93B, based on an instruction from the processing circuit 91.

[0090] The second switch circuit 97B is configured to be able to select either the drive signal output by the second drive circuit 74B or the drive signal output by the fourth drive circuit 94B and output it to the second electric parking actuator 32. In this embodiment, the second switch circuit 97B selects either the drive signal output by the second drive circuit 74B or the drive signal output by the fourth drive circuit 94B based on an instruction from the processing circuit 91.

[0091] <Processing flow for parking braking when the brake control system is normal> The following describes the processing flow when the brake control system 60B is normal and the electric parking device 30 is operated. Here, "the brake control system 60B is normal" means that all of the above conditions (B1) to (B4) are met.

[0092] In this case, the processing circuit 91 of the redundant ECU 90B operates the first switch circuit 96B so that the first switch circuit 96B can select the drive signal output by the first drive circuit 73B, and the processing circuit 91 operates the second switch circuit 97B so that the second switch circuit 97B can select the drive signal output by the second drive circuit 74B.

[0093] When the processing circuit 71 of the first brake ECU 70A receives a parking brake operation request via the first global communication line 201, it operates the first drive circuit 73B and the second drive circuit 74B based on the parking brake operation request. The drive signal output from the first drive circuit 73B is then output to the first switch circuit 96B of the redundant ECU 90B. The first switch circuit 96B outputs the drive signal of the first drive circuit 73B to the first electric parking actuator 31. This allows the processing circuit 71 to operate the first electric parking actuator 31 based on the parking brake operation request.

[0094] Furthermore, the drive signal output by the second drive circuit 74B is output to the second switch circuit 97B of the redundant ECU 90B. The second switch circuit 97B outputs the drive signal of the second drive circuit 74B to the second electric parking actuator 32. This allows the processing circuit 71 to operate the second electric parking actuator 32 based on the parking brake operation request.

[0095] In other words, when the first brake ECU 70B is normal, the first brake ECU 70B can activate the first electric parking actuator 31 and the second electric parking actuator 32 that it can activate itself out of the multiple electric parking actuators 31, 32 based on a parking brake activation request.

[0096] <Processing Flow for Parking Braking When It is Determined that an Abnormality Has Occurred in the First Brake ECU> A processing flow when an abnormality has occurred in the first brake ECU 70B while the redundant ECU 90B is normal will be described.

[0097] In this case, the processing circuit 91 of the redundant ECU 90B operates the first switch circuit 96B so that the first switch circuit 96B can select the drive signal output by the third drive circuit 93B, and the processing circuit 91 operates the second switch circuit 97B so that the second switch circuit 97B can select the drive signal output by the fourth drive circuit 94B.

[0098] When the processing circuit 91 of the redundant ECU 90B receives a parking brake operation request via the second global communication line 202, it operates the third drive circuit 93B and the fourth drive circuit 94B based on the parking brake operation request. The drive signal output from the third drive circuit 93B is then output to the first switch circuit 96B. The first switch circuit 96B outputs the drive signal of the third drive circuit 93B to the first electric parking actuator 31. This allows the processing circuit 91 to operate the first electric parking actuator 31 based on the parking brake operation request.

[0099] The drive signal output by the fourth drive circuit 94B is output to the second switch circuit 97B. The second switch circuit 97B outputs the drive signal of the fourth drive circuit 94B to the second electric parking actuator 32. This allows the processing circuit 91 to operate the second electric parking actuator 32 based on the parking brake operation request.

[0100] In other words, when an abnormality occurs in the first brake ECU 70A, the redundant ECU 90B can operate the first electric parking actuator 31 and the second electric parking actuator 32 that it can operate, among the multiple electric parking actuators 31, 32, based on a parking brake operation request. As a result, even when an abnormality occurs in the first brake ECU 70, the redundant ECU 90B can generate a parking braking force on the vehicle 10 that is equivalent to that when the first brake ECU 70 is normal.

[0101] Therefore, the braking control system 60B can obtain the same effects as those of (1-1), (1-2), (1-4), and (1-5) in the first embodiment. (Modifications) The above-described embodiments can be modified as follows. The above-described embodiments and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0102] In the first embodiment, when the first brake ECU 70 is normal, the processing circuit 71 of the first brake ECU 70 does not need to send an operation command corresponding to the parking brake operation request to the redundant ECU 90. Even in this case, the first electric parking actuator 31 of the multiple electric parking actuators 31, 32 is operated, and therefore the parking braking force is generated in the vehicle 10.

[0103] If the second brake ECU 80 cannot communicate with the first brake ECU 70 via the first global communication line 201, the first brake ECU 70 may not receive the parking brake operation request via the first global communication line 201. Therefore, if the second brake ECU 80 cannot communicate with the first brake ECU 70 via the first global communication line 201, the second brake ECU 80 may transmit communication availability information indicating that communication between the second brake ECU 80 and the first brake ECU 70 is not normal to the redundant ECU 90 via the brake communication line 61, regardless of whether communication with the first brake ECU 70 via the brake communication line 61 is normal.

[0104] -If only one of the multiple electric parking actuators 31, 32 can generate a parking braking force, the parking braking force generated by activating that one actuator may be greater than the parking braking force generated when both of the multiple electric parking actuators 31, 32 are activated.

[0105] Although the first brake ECUs 70, 70A, 70B and the redundant ECUs 90, 90A, 90B are operating normally, an abnormality may occur in the second brake ECU 80. Even in this case, the first brake ECUs 70, 70A, 70B can receive the parking brake operation request via the first global communication line 201. Furthermore, the first brake ECUs 70, 70A, 70B can transmit an operation instruction corresponding to the parking brake operation request to the redundant ECUs 90, 90A, 90B via the brake communication line 61. Therefore, it is preferable that the brake control systems 60, 60A, 60B proceed with the process shown in FIG. 5.

[0106] The redundant ECUs 90, 90A, 90B may be configured to receive a parking brake operation request via the first global communication line 201. If an abnormality occurs in the integrated ECU 51, the integrated ECU 51 does not transmit a parking brake operation request to either the first global communication line 201 or the second global communication line 202. Even in this case, the redundant ECUs 90, 90A, 90B can receive information transmitted by the shift ECU 52 to the second global communication line 202. Therefore, if the redundant ECUs 90, 90A, 90B analyze the information received from the shift ECU 52 and determine that a parking brake force should be generated, they may transmit a parking brake operation request to the first brake ECUs 70, 70A, 70B via the brake communication line 61. In this case, the processing circuits 71 of the first brake ECUs 70, 70A, 70B operate the electric parking actuators that they can operate, based on the received parking brake operation request. Furthermore, the processing circuit 71 of the first brake ECU 70, 70A, 70B may transmit an operation command corresponding to the parking brake operation request to the redundant ECU 90, 90A, 90B via the brake communication line 61. The processing circuit 91 of the redundant ECU 90, 90A, 90B operates the electric parking actuator that it can operate based on the received operation command. This allows the brake control system 60, 60A, 60B to operate the electric parking device 30 even if an abnormality occurs in the integrated ECU 51.

[0107] The processing circuits 71, 81, and 91 are not limited to those including a CPU and ROM and executing software processing. That is, the processing circuits 71, 81, and 91 may have any of the following configurations (a), (b), and (c):

[0108] (a) The processing circuits 71, 81, and 91 each include one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. Memory, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or special-purpose computer.

[0109] (b) The processing circuits 71, 81, and 91 each include one or more dedicated hardware circuits that perform various processes. Examples of dedicated hardware circuits include application-specific integrated circuits (ASICs) and FPGAs. ASIC stands for "Application Specific Integrated Circuit." FPGA stands for "Field Programmable Gate Array."

[0110] (c) The processing circuits 71, 81, and 91 each include one or more processors that execute some of the various processes in accordance with a computer program, and one or more dedicated hardware circuits that execute the remaining processes of the various processes.

[0111] (Other Technical Ideas) The technical ideas that can be understood from the above-described embodiments and modifications will be described below. [Supplementary Note 1] It is preferable that the brake control device, i.e., the first brake control device, activates the hydraulic brake device and also activates at least the first electric parking actuator among the plurality of electric parking actuators.

[0112] [Supplementary Note 2] It is preferable that the redundant control device does not control the hydraulic braking device, and that it activates at least the second electric parking actuator among the plurality of electric parking actuators.

[0113] [Supplementary Note 3] The in-vehicle network includes a first global communication line for transmitting information to the first brake control device and the second brake control device, and a second global communication line for transmitting information to the redundant control device, and further includes a brake communication line for communication between a plurality of control devices related to vehicle braking including the first brake control device, the second brake control device, and the redundant control device, wherein the first brake control device receives the parking brake operation request via the first global communication line, and the redundant control device receives the parking brake operation request via the second global communication line, and the second brake control device transmits information regarding whether or not communication between the second brake control device and the first brake control device via the first global communication line is normal to the redundant control device via the brake communication line as the communication availability information, and the redundant control device It is preferable to determine that an abnormality has occurred in the first brake control device when both the communication availability information received from the second brake control device indicates that communication between the second brake control device and the first brake control device via the first global communication line is not normal, and communication between the redundant control device and the first brake control device via the brake communication line is not normal.

[0114] It should be noted that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more.

Claims

1. Applied to a vehicle having a first wheel and a second wheel, a first wheel cylinder provided on the first wheel, a second wheel cylinder provided on the second wheel, a hydraulic braking device configured to adjust the hydraulic pressure of the first wheel cylinder and the second wheel cylinder, a first electric parking actuator configured to generate a parking braking force at the first wheel, and a second electric parking actuator configured to generate a parking braking force at the second wheel, the vehicle comprising: a brake control device that operates the hydraulic braking device and also operates at least one of the plurality of electric parking actuators; and a redundant control device that does not control the hydraulic braking device and operates at least one of the plurality of electric parking actuators, each of the brake control device and the redundant control device being capable of receiving a parking brake operation request, which is a request related to parking braking, via an in-vehicle network, and when the brake control device is normal, the brake control device operates the electric parking actuator that it can operate of the plurality of electric parking actuators, based on the parking brake operation request received via the in-vehicle network, A braking control system in which, when an abnormality occurs in the braking control device, the redundant control device activates an electric parking actuator that it can operate itself among the plurality of electric parking actuators based on the parking brake operation request received via the in-vehicle network.

2. A brake control system as described in claim 1, wherein the hydraulic braking device includes a first hydraulic braking device and a second hydraulic braking device, the brake control device is a first brake control device that controls the first hydraulic braking device, and is equipped with a second brake control device that controls the second hydraulic braking device, the second brake control device is capable of communicating with the first brake control device and is configured to transmit communication availability information to the redundant control device, which is information regarding whether communication with the first brake control device is normal or not, and the redundant control device determines that an abnormality has occurred in the first brake control device when both the communication availability information received from the second brake control device indicates that communication between the second brake control device and the first brake control device is not normal and the communication between the redundant control device and the first brake control device is not normal.

3. The brake control system according to claim 1, wherein the brake control device has a first drive circuit that drives the first electric parking actuator and a second drive circuit that drives the second electric parking actuator; the redundant control device has a third drive circuit that drives the second electric parking actuator and a switch circuit that selects either the drive signal output by the second drive circuit or the drive signal output by the third drive circuit and outputs the selected signal to the second electric parking actuator; the redundant control device, when the brake control device is normal, operates the switch circuit so that the switch circuit can select the drive signal output from the second drive circuit; when an abnormality has occurred in the brake control device, causes the third drive circuit to output a drive signal and causes the switch circuit to select the drive signal output from the third drive circuit, thereby operating the second electric parking actuator; and the brake control device, when normal, causes the first drive circuit and the second drive circuit to output drive signals to operate the multiple electric parking actuators.

4. The brake control device has a first drive circuit that is a circuit for driving the first electric parking actuator, and a second drive circuit that is a circuit for driving the second electric parking actuator; the redundant control device has a third drive circuit that is a circuit for driving the first electric parking actuator, a fourth drive circuit that is a circuit for driving the second electric parking actuator, a first switch circuit that selects either a drive signal output by the first drive circuit or a drive signal output by the third drive circuit and outputs the selected signal to the first electric parking actuator, and a second switch circuit that selects either a drive signal output by the second drive circuit or a drive signal output by the fourth drive circuit and outputs the selected signal to the second electric parking actuator; and the redundant control device, when the brake control device is normal, operates the first switch circuit so that the first switch circuit can select the drive signal output from the first drive circuit, and operates the second switch circuit so that the second switch circuit can select the drive signal output from the second drive circuit; and when an abnormality occurs in the brake control device, 2. The brake control system according to claim 1, wherein the first electric parking actuator is operated by outputting a drive signal from the third drive circuit and having the first switch circuit select the drive signal output from the third drive circuit, and the second electric parking actuator is operated by outputting a drive signal from the fourth drive circuit and having the second switch circuit select the drive signal output from the fourth drive circuit, and the brake control device, when normal, operates the plurality of electric parking actuators by outputting drive signals from the first drive circuit and the second drive circuit.

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