Vehicle redundant braking system, electronic control unit and control method thereof

Abstract

The present application provides a vehicle redundant braking system, an electronic control unit thereof and a control method. The redundant braking system is coupled with a main braking system of a vehicle. The electronic control unit comprises a receiving module configured to receive a state signal indicative of a state of the main braking system and sensor signals indicative of a driver's input to a brake pedal and a vehicle speed condition; an activating module configured to activate a brake assist function of the redundant braking system when it is determined based on the state signal that the main braking system enters a mechanical backup state; and a brake assist module configured to determine to execute a corresponding one of a plurality of brake assist modes based on the sensor signals after the brake assist function is activated, wherein the plurality of brake assist modes comprises a standby mode, a first assist adjustable mode, a second assist adjustable mode, and a brake pressure maintaining mode.

Description

Technical Field

[0001] This application relates to the technical field of vehicle braking, and more particularly to a vehicle redundant braking system, an electronic control unit and control method for the redundant braking system, and a corresponding machine-readable storage medium. Background Technology

[0002] Automotive safety refers to the performance of a vehicle in avoiding accidents and ensuring the safety of pedestrians and passengers while in motion. Automotive safety includes passive safety features such as airbags and seat belts, as well as active safety features such as automatic emergency braking. The performance of a vehicle's braking system (sometimes called the braking system) is an important safety indicator characterizing active safety.

[0003] With the development of autonomous driving, higher demands are being placed on the active safety of vehicles. To address this, a solution has been proposed: equipping vehicles with two braking systems—a main braking system and a redundant braking system as a backup in case of main braking system failure. This redundant backup braking system can provide braking assistance to autonomous vehicles when the main braking system fails, thus significantly improving their active safety. However, existing redundant backup braking systems are designed for many autonomous driving scenarios and do not fully consider the braking assistance needs of drivers in driving modes. For example, if the main braking system fails and the vehicle is in driver-only mode, existing redundant backup braking systems cannot provide sufficient braking assistance. Summary of the Invention

[0004] Against this backdrop, the present invention aims to provide an improved technical solution that, when the vehicle is in driver driving mode and the main braking system fails, provides one of a variety of braking assistance modes according to different inputs to the brake pedal by the driver and different vehicle speeds, thereby providing precise braking assistance and further improving the active safety of the vehicle.

[0005] According to one aspect of the present invention, an electronic control unit for a redundant braking system of a vehicle is provided, the redundant braking system being coupled to the vehicle's main braking system. The electronic control unit includes: a receiving module configured to receive a status signal indicating the state of the main braking system and sensor signals indicating driver input to the brake pedal and vehicle speed; an activation module configured to activate the brake assist function of the redundant braking system when the main braking system is determined to be in a mechanical backup state based on the status signals; and a brake assist module storing multiple brake assist modes for implementing the brake assist function. The brake assist module is configured to, after the brake assist function is activated, determine, based on the sensor signals, which brake assist mode to execute, and the assist module is further configured to switch between the multiple brake assist modes according to changes in driver input to the brake pedal and changes in vehicle speed. The multiple brake assist modes include: a standby mode, a first adjustable assist mode, a second adjustable assist mode, and a brake pressure holding mode.

[0006] According to another aspect of the present invention, a redundant braking system for a vehicle is provided, comprising: two braking circuits configured to be fluidly connected to two braking circuits of the vehicle's main braking system, respectively; four valves connected between the main brake cylinder of the main braking system and four brake wheel cylinders of the vehicle; a motor configured to generate brake assist for pumping some or all of the brake fluid in the main brake cylinder into the four brake wheel cylinders; and an electronic control unit as described above, which electrically controls the four valves and the motor and performs the brake assist function when the main braking system is in a mechanical backup state.

[0007] According to another aspect of the present invention, a control method for a redundant braking system for a vehicle is provided. Optionally, the method is executed by an electronic control unit as described above or a redundant braking system as described above. The method includes: receiving a status signal indicating the state of the vehicle's main braking system and sensor signals indicating the driver's input to the brake pedal and the vehicle speed; activating the brake assist function of the redundant braking system when it is determined based on the status signal that the main braking system has entered a mechanical backup state; after the brake assist function is activated, determining a corresponding brake assist mode among multiple brake assist modes to be executed based on the sensor signals; and switching the brake assist mode among the multiple brake assist modes according to changes in the driver's input to the brake pedal and changes in the vehicle speed; wherein the multiple brake assist modes include: a standby mode, a first adjustable assist mode, a second adjustable assist mode, and a brake pressure holding mode.

[0008] According to another aspect of the invention, a machine-readable storage medium is provided that stores executable instructions, which, when executed, cause one or more processors to perform the control method described above.

[0009] The foregoing provides a summary of the main aspects of the invention to enable a basic understanding of these aspects. This summary is not intended to limit the scope of any or all aspects of the invention. The purpose of this summary is to present some implementations of these aspects in a simplified form as a prelude to the detailed description that follows. Attached Figure Description

[0010] The technical solution of the present invention will become clearer from the following detailed description taken in conjunction with the accompanying drawings. It is to be understood that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0011] Figure 1 This is a schematic diagram of a redundant braking system according to an embodiment of the present invention.

[0012] Figure 2 This is according to one embodiment of the present invention. Figure 1 A schematic block diagram of the electronic control unit of the redundant braking system.

[0013] Figure 3 It is based on one embodiment of the present invention. Figure 2 The flowchart shows the brake assist control process implemented by the electronic control unit in the system.

[0014] Figure 4 A braking assist model according to one embodiment of the present invention is illustrated schematically.

[0015] Figure 5 yes Figure 3 An example of a graph used in the brake assist control process.

[0016] Figure 6 An example of an adjustable boost amplification factor is illustrated.

[0017] Figure 7 yes Figure 3 Another example of a graph used in the brake assist control process.

[0018] Figure 8 This is a flowchart of a control method for a redundant braking system for a vehicle according to an embodiment of the present invention. Detailed Implementation

[0019] Embodiments of the present invention relate to a solution in which a redundant braking system, serving as a backup system to the main braking system, provides braking assistance when the vehicle is in driver-driven mode.

[0020] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0021] Figure 1 The diagram schematically illustrates a redundant braking system 20 of a vehicle (not shown) according to an embodiment of the present invention, which is hydraulically coupled to the vehicle's main braking system 10. The main braking system 10 is, for example, an integrated power braking system.

[0022] See Figure 1 In one embodiment, the redundant braking system 20 and the main braking system 10 can be hydraulically coupled by providing hydraulic interfaces HI_1-HI_4 between the two braking systems 10 and 20, so that the two braking systems are formed as spatially separated structural units. These hydraulic interfaces HI_1-HI_4 are separable from each other. The two braking systems 10 and 20 are hydraulically coupled through these hydraulic interfaces HI_1-HI_4 and via four hydraulic lines BC_1-BC_4.

[0023] See also Figure 1 The main braking system 10 includes: an electronic control unit 11, a main brake cylinder 12, a stroke sensor 13, a pedal stroke simulator 14, a motor 15, a plunger 16, plunger control valves 17A-17B, a circuit separation valve 18A-18B, and a pressure forming valve 19A-19D.

[0024] The master brake cylinder 12 stores brake fluid and is used for the fluid connection of the four wheel cylinders CFL, CRR, CRL, and CFR for the four wheels FL, RR, RL, and FR. The stroke sensor 13 measures the actuation stroke of the lever OL connected to the brake pedal BP and sends the measured stroke signal to the electronic control unit 11. The pedal stroke simulator 14 simulates the stroke of the pedal BP and sends a signal indicating the simulation result to the electronic control unit 11. The motor 15 electronically controls the plunger 16. The motor 15 is capable of individually controlling each of the pressure forming valves 19A-19D, enabling individual control of the pressure regulation of each wheel cylinder. It is understood that, for clarity, Figure 1 Only the main components of the main braking system 10 are shown. The main braking system 10 may also include other components not shown. For example, the main braking system 10 also includes four pressure reduction valves (i.e., discharge valves) corresponding to the pressure forming valves 19A-19D.

[0025] When the main braking system 10 is operating normally, that is, when the braking assist function of the main braking system 10 is normal, the main braking system 10 realizes the braking assist function by means of the electronic control unit 11.

[0026] It is worth noting that this invention does not limit how the electronic control unit 11 of the main braking system 10 implements the brake assist function. The embodiments of this invention relate to how the electronic control unit 21 of the redundant braking system 20 implements the brake assist function when the brake assist function of the main braking system 10 fails and the vehicle is in driver-driven mode.

[0027] See also Figure 1 The redundant braking system 20 includes an electronic control unit 21; a motor 22; two pressure generators 23A and 23B; and four valves 24A, 24B, 25A, and 25B.

[0028] Two pressure generators 23A and 23B are fluidly connected to two brake circuits BC3 and BC4, with pressure generator 23A fluidly connected to brake circuit BC3 and pressure generator 23B fluidly connected to brake circuit BC4. The two pressure generators 23A and 23B are, for example, each implemented as a piston pump. Motor 22 generates brake assist to drive pressure generators 23A and 23B to pump brake fluid from master brake cylinder 12 into brake wheel cylinders CFL, CRR, CRL, and CFR. Four valves 24A, 24B, 25A, and 25B may include valves 24A and 25A fluidly connected to brake circuit BC3, and valves 24B and 25B fluidly connected to brake circuit BC4. Valves 24A and 25A can be implemented as high-pressure switching valves, capable of switching from a normal shut-off position to a flow-through position under the electrical control of motor 22. Valves 25A and 25B can be implemented as switching valves, which, under the electrical control of motor 22, are flow-through in their initial position and can be steplessly switched to a shut-off position. Thus, switching valves 25A and 25B function as throttling mechanisms, capable of setting different braking pressures via the redundant braking system 20 through corresponding electrical control, for example, by steplessly adjusting the flow cross-section of the pipeline fluidly connected to switching valves 25A and 25B.

[0029] It should be noted that the "electronic control unit" in the claims refers to the electronic control unit 21 of the redundant braking system 20. The "motor" in the claims refers to the motor 22 of the redundant braking system 20.

[0030] See Figure 2 The electronic control unit 21 may include a receiving module 211, an activation module 212, and a brake assist module 213. It is understood that the naming of these modules is functional and not intended to limit their implementation or physical location. For example, these modules may be implemented on the same chip or circuit, or on different chips or circuits.

[0031] The electronic control unit 21 and its various modules can be implemented in hardware, software, or a combination of both. For the hardware implementation, it can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), data signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic units designed to perform their functions, or combinations thereof. For the software implementation, it can be implemented using microcode, program code, or code segments, and can also be stored in a machine-readable storage medium such as a storage component.

[0032] In one embodiment, the electronic control unit 21 is implemented including a memory and a processor. The memory contains instructions that, when executed by the processor, cause the processor to perform the brake assist control method according to an embodiment of the present invention.

[0033] Figure 3 A brake assist control process 300 according to one embodiment of the present invention is shown. This brake assist control process 300 can be implemented by means of the electronic control unit 21 of the redundant braking system 20, and therefore the above description also applies here.

[0034] See Figure 3 In block 302, receiving module 211 receives status signals indicating the state of main braking system 10 and sensor signals indicating the driver's input to brake pedal BP and vehicle speed.

[0035] In one embodiment, the receiving module 211 can receive the aforementioned status signal in the following manner: The main braking system 10 and the redundant braking system 20 are communicatively connected via an onboard bus. The main braking system 10 performs a self-check of its status and sends a status signal indicating the detected status (such as whether the brake assist function of the main braking system 10 is normal, abnormal, or failed) to the onboard bus. Therefore, the receiving module 211 of the redundant braking system 20 can receive the status signal indicating the status of the main braking system 20 from the onboard bus.

[0036] In one embodiment, the receiving module 211 can receive sensor signals representing the driver's input to the brake pedal BP in the following manner. The driver's input to the brake pedal BP can be measured by the aforementioned travel sensor 13 and / or pedal travel simulator 14. Alternatively, the driver's input to the brake pedal BP can also be measured by other sensors, such as a force sensor (not shown) for measuring the force applied by the driver to the brake pedal BP (also referred to as "muscle force" or "driver force"). The measured sensor signals are then transmitted to the vehicle bus. Thus, the receiving module 211 of the redundant braking system 20 is able to receive sensor signals representing the driver's input to the brake pedal BP from the vehicle bus.

[0037] In one embodiment, the receiving module 211 can receive sensor signals indicating vehicle speed in the following manner: Vehicle speed can be measured by wheel speed sensors. The wheel speed sensors transmit the measured sensor signals to the vehicle bus. Thus, the receiving module 211 of the redundant braking system 20 can receive sensor signals indicating vehicle speed from the vehicle bus.

[0038] In block 304, activation module 212 determines whether to activate the brake assist function of redundant braking system 20 based on the received status signal and / or sensor signal.

[0039] When the activation module 212 determines, based on the aforementioned status signals, that the main braking system 10 has entered a mechanical backup state, it activates the brake assist function of the redundant braking system 20. The "mechanical backup state" occurs, for example, when the brake assist function of the main braking system 10 fails. For instance, based on the status signals of the main braking system 10, it is determined that the main braking system 10 has lost software control, lost power, or experienced a hardware failure / degradation, and thus it is determined that the main braking system 10 has entered a mechanical backup state.

[0040] The activation module 212 does not activate the braking assist function of the redundant braking system 20 when at least one of the following conditions (1) and (2) is met.

[0041] (1) Based on the above status signals, it is determined that the brake assist function of the main braking system 10 is operating normally. For example, the main braking system 10 sends its status signals to the vehicle bus at a predetermined frequency. Thus, when the main braking system 10 is operating normally, the activation module 212 can receive sensor signals indicating that the main braking system 10 is operating normally at predetermined intervals, and the activation module 212 determines that the brake assist function of the main braking system 10 is operating normally based on this.

[0042] (2) The vehicle speed is lower than the first speed threshold. The first speed threshold is predetermined and can be obtained by using the creep speed or by adjusting the creep speed appropriately. Here, the creep speed refers to the coasting speed of the vehicle assuming it is traveling on flat ground, with the driver not pressing the accelerator or brake pedal. The first speed threshold can also be calibrated through real vehicle experiments. For example, when the vehicle is relatively heavy, the first speed threshold is calibrated to be lower; while when the vehicle is relatively light, the first speed threshold is calibrated to be relatively higher.

[0043] The first speed threshold should be understood as a relatively low speed. When the speed is low, even without brake assist, the vehicle can be safely brought to a stop using only the driver's strength (i.e., the driver's muscle strength). Therefore, when the speed is low enough (i.e., below the first speed threshold), there is no need to activate the brake assist function.

[0044] In block 306, after the brake assist function of the redundant braking system 20 is activated, the brake assist module 213 determines, based on the received sensor signals, to execute one of a variety of brake assist modes. These multiple brake assist modes are predetermined and stored in the brake assist module 213. These multiple brake assist modes include: standby mode (MODE_1), first adjustable assist mode (MODE_2), second adjustable assist mode (MODE_3), and brake pressure holding mode (MODE_4). The limitations of each brake assist mode and the operation methods under each brake assist mode will be described in detail below.

[0045] In one embodiment, the brake assist module 213 stores a brake assist model, which includes the aforementioned multiple brake assist modes and their switching states. The brake assist module 213 uses this brake assist model to determine which brake assist mode to execute or switch to. These switching states correspond to changes in the driver's input to the brake pedal and changes in vehicle speed. These switching states include: bidirectional switching between the first adjustable assist mode and standby mode, the second adjustable assist mode, and the brake pressure holding mode; unidirectional switching from the brake pressure holding mode to the standby mode; unidirectional switching from the brake pressure holding mode to the second adjustable assist mode; and unidirectional switching from the second adjustable assist mode to the standby mode.

[0046] The braking assist model can be represented using a state machine. Figure 4 An example of this state machine is shown. Figure 4 The direction indicated by the "arrow" in the text represents the direction in which mode switching can be performed. For example, see... Figure 4After the brake assist function of the redundant braking system 20 is activated, it enters standby mode (MODE_1). Then, it switches from standby mode (MODE_1) to the first adjustable assist mode (MODE_2). Next, it switches from the first adjustable assist mode (MODE_2) to the second adjustable assist mode (MODE_3). Then, it returns from the second adjustable assist mode (MODE_3) to standby mode (MODE_1). This example scenario could be: after the brake assist function of the redundant braking system 20 is activated, the driver does not apply force to the brake pedal BP (corresponding to "entering standby mode"), then the driver depresses the brake pedal BP (corresponding to "switching to the first adjustable assist mode"), then the driver releases the brake pedal (corresponding to "switching to the second adjustable assist mode"), and finally, the force applied by the driver to the brake pedal BP is zero (corresponding to "returning to standby mode").

[0047] It is understandable that, in addition to the state machine mentioned above, the braking assist model can also be represented in other ways, such as a table containing the various braking assist modes and the switching states between them.

[0048] The following section describes in detail the various braking assist modes and the braking assist control performed by the braking assist module 213 in each braking assist mode.

[0049] Referring to block 3061, in one embodiment, when the sensor signal indicates that the driver has not input any input to the brake pedal BP, the brake assist module 213 determines to execute a standby mode. In standby mode, the brake assist module 213 does not perform any assist control. Here, no input from the driver to the brake pedal BP means, for example, that the driver has not pressed the brake pedal BP.

[0050] Referring to block 3062, in one embodiment, when the sensor signal indicates that the driver has pressed the brake pedal BP and the force applied by the driver to the brake pedal BP exceeds a pressure threshold, the brake assist module 213 determines to execute a first assist adjustable mode. The pressure threshold is predetermined to accurately identify the driver's braking demand. For example, to distinguish between a driver's unintentional light touch of the brake pedal BP, this pressure threshold is used to determine whether the driver's pressing of the brake pedal can be accurately detected. Here, the pressure threshold should be understood as an extremely small pressure value, even zero or a negative value.

[0051] In the first adjustable assist mode, the brake assist control performed by the brake assist unit 213 includes the following steps: Calculating the driver's desired braking pressure based on sensor signals. For example, the driver's desired braking pressure can be determined based on the operating stroke of the joystick OL or the driver's force applied to the brake pedal. The present invention does not limit how the driver's desired braking pressure is determined based on sensor signals (e.g., sensor signals representing brake pedal travel or driver force), and any embodiment that enables the calculation of the driver's desired braking pressure based on sensor signals is applicable to the present invention. Next, the assist amplification factor corresponding to the driver's desired braking pressure is determined using an assist amplification factor curve, so that the redundant braking system 20 performs vehicle braking assist according to the determined assist amplification factor. The assist amplification factor curve can be pre-plotted and stored in the brake assist unit 213, expressing the correspondence between the assist amplification factor and the driver's desired braking pressure.

[0052] Figure 5 An example of a power assist amplification factor curve is shown, where the horizontal axis represents the ratio (pDriver / pMech_500N) between the driver's desired braking pressure and a fixed braking pressure (e.g., the braking pressure corresponding to the driver pressing the brake pedal with a muscle force of 500N), and the vertical axis represents the power assist amplification factor. The curve shows the correspondence between the power assist amplification factor and the aforementioned braking pressure ratio. Thus, the power assist amplification factor corresponding to the driver's desired braking pressure can be obtained from this power assist amplification factor curve.

[0053] The power assist amplification factor curve can be plotted as follows. First, the starting value of the power assist amplification factor is set to zero, corresponding to a zero braking pressure desired by the driver. Then, based on the vehicle deceleration that a fixed braking pressure should provide, as stipulated in vehicle safety regulations, the power assist amplification factor corresponding to that braking pressure is calculated. For example, according to vehicle safety regulations: on a high-friction surface, when the driver applies a 500N force to the brake pedal, the vehicle should provide 6.44 m / s². 2 The deceleration is calculated to determine the assist amplification factor when the brake pedal force is 500N, thus obtaining a calibration point. Next, a curve is plotted between the zero point and the obtained calibration point to ensure a smooth braking process, resulting in the assist amplification factor curve. This curve can be plotted based on real-vehicle experiments and / or model calculations. After obtaining the assist amplification factor curve, the assist amplification factor corresponding to the driver's desired braking pressure can be determined based on this curve.

[0054] Furthermore, the assist braking coefficient is adjustable. For example, the assist amplification factor can be increased or decreased based on a determined assist braking coefficient. Figure 6 An example of an adjustable power-assisted braking coefficient is shown. See also Figure 6 The horizontal axis represents the driver's force applied to the brake pedal, and the vertical axis represents the vehicle deceleration. L1-L3 represent vehicle deceleration corresponding to different driver forces. L1 represents the vehicle deceleration when relying solely on driver force (i.e., without brake assist), L2 represents the vehicle deceleration calculated based on the aforementioned assist amplification coefficient curve, and L3 represents the vehicle deceleration corresponding to an alternative assist amplification coefficient (which can be understood as an adjustment based on the assist amplification coefficient determined according to the aforementioned assist amplification coefficient curve) provided by the redundant braking system 20's braking assist capability. In one embodiment, after calculating the assist amplification coefficient based on the aforementioned assist amplification coefficient curve, the assist amplification coefficient can be increased (corresponding to a change in vehicle deceleration from L2 to L3) or decreased (corresponding to a change in vehicle deceleration from L2 to L1) based on the actual application scenario.

[0055] Referring again to box 3062, in this embodiment, when the receiving unit 211 receives a signal indicating that a function related to vehicle stability has been activated, the brake assist unit 213 maintains the assist amplification factor at the value at the moment the function related to vehicle stability is activated. The function related to vehicle stability is, for example, an anti-lock braking system (ABS). The signal indicating that the ABS is activated is provided by the ABS module of the redundant braking system. Thus, the receiving unit 211 can receive the signal from the ABS module indicating that the ABS is activated. In this case, the assist amplification factor is limited, i.e., it is a constant value. When the driver applies greater muscle force to the brake pedal, the braking pressure is still amplified, but by a constant ratio (i.e., the ratio at the moment the function related to vehicle stability is activated).

[0056] Referring to block 3063, in one embodiment, when a sensor signal indicates that the driver has released the brake pedal BP, the brake assist unit 213 determines to execute a second assist adjustable mode. The driver releasing the brake pedal can be determined based on a sensor signal indicating a decrease in the muscle force applied by the driver to the brake pedal.

[0057] In the second adjustable assist mode, the brake assist control performed by the brake assist unit 213 includes the following steps: First, the driver's desired brake pressure reduction slope is calculated based on sensor signals. Next, the actual brake pressure reduction slope is determined based on the driver's desired brake pressure reduction slope and a brake pressure reduction slope threshold, so that the redundant braking system 20 disengages the vehicle brakes according to the determined actual brake pressure reduction slope. For example, when the driver's desired brake pressure reduction slope causes the brake pressure to decrease faster than the brake pressure reduction slope threshold, the actual brake pressure reduction slope is determined as the brake pressure reduction slope threshold. When the driver's desired brake pressure reduction slope causes the brake pressure to decrease more slowly than the brake pressure reduction slope threshold, the actual brake pressure reduction slope is determined as the driver's desired brake pressure reduction slope.

[0058] Using a brake pressure reduction slope threshold to limit the speed at which the vehicle exits the brakes is advantageous. For example, if the driver suddenly releases the brake pedal BP, the driver's desired brake pressure reduction slope will be very large. If the brake pressure reduction slope is not limited, the brake pedal BP will rebound quickly and strike the driver's foot. By using a brake pressure reduction slope threshold as described above, this rapid rebound of the brake pedal can be avoided.

[0059] Figure 7 An example of a graph showing the slope of brake pressure reduction is shown, where the horizontal axis represents time and the vertical axis represents brake pressure. The gray curve represents the driver's desired brake pressure reduction slope, and the black curve represents the brake pressure reduction slope threshold. This black curve can be implemented as a straight line, meaning the brake pressure reduction slope threshold can be set to a constant value. Figure 7 As shown, the gray curve is below the black curve, which indicates that the driver's desired brake pressure withdrawal speed is significantly faster than the brake pressure withdrawal speed obtained based on the brake pressure reduction slope threshold. Therefore, the vehicle brakes should be withdrawn according to the brake pressure reduction slope threshold (i.e., the black curve).

[0060] Referring to box 3064, in one embodiment, when the brake assist mode is in a first assist adjustable mode and the vehicle speed is below a second vehicle speed threshold, a brake pressure holding mode is determined to be executed when a function related to vehicle driving stability (e.g., anti-lock braking system) is activated. Here, the second vehicle speed threshold is predetermined and should be understood as a low vehicle speed. The second vehicle speed threshold may be the same as or different from the first vehicle speed threshold.

[0061] In the brake pressure holding mode, the brake assist unit 213 operates the vehicle brakes according to a predetermined brake pressure, that is, it holds the brake pressure. This predetermined brake pressure is associated with the brake pressure requested by the function related to vehicle driving stability. For example, if the anti-lock braking system is activated and requests a brake pressure of 40 bar, then vehicle brake assist is performed according to a brake pressure of 40 bar. This brake pressure holding mode can be canceled when the driver releases the brake pedal, or when the function related to vehicle driving stability is deactivated.

[0062] In this embodiment, the scenario might be: the vehicle is in the first adjustable assist mode and the vehicle speed has decreased to a low level. At this point, the anti-lock braking system (ABS) is activated, and the vehicle enters the brake pressure holding mode. Once the wheels are detected to have recovered, the vehicle switches back from the brake pressure holding mode to the first adjustable assist mode.

[0063] Figure 8 A control method 800 for a redundant braking system for a vehicle according to an embodiment of the present invention is shown. This method 800 can be executed by the aforementioned redundant braking system 20 or its electronic control unit 21, and therefore the above description is also applicable here.

[0064] See Figure 8 In block 802, a status signal indicating the state of the vehicle's main braking system and sensor signals indicating the driver's input to the brake pedal and the vehicle speed are received.

[0065] In block 804, when it is determined from the status signal that the main braking system has entered the mechanical backup state, the braking assist function of the redundant braking system is activated.

[0066] In block 806, after the brake assist function is activated, a corresponding one of multiple brake assist modes is determined based on the sensor signal, wherein the multiple brake assist modes include: standby mode, first assist adjustable mode, second assist adjustable mode, and brake pressure holding mode.

[0067] In box 808, the brake assist mode is switched among the multiple brake assist modes according to changes in the driver's input to the brake pedal and changes in vehicle speed.

[0068] The present invention also provides a machine-readable storage medium storing executable instructions that, when executed, cause one or more processors to perform the method 800 described above.

[0069] It is understood that processors can be implemented using electronic hardware, computer software, or any combination thereof. Whether these processors are implemented as hardware or software will depend on the specific application and the overall design constraints imposed on the system. As an example, the processor, any portion of the processor, or any combination of processors provided in this invention can be implemented as a microprocessor, microcontroller, digital signal processor (DSP), field-programmable gate array (FPGA), programmable logic device (PLD), state machine, gate logic, discrete hardware circuitry, and other suitable processing units configured to perform the various functions described in this disclosure. The functionality of the processor, any portion of the processor, or any combination of processors provided in this invention can be implemented as software executed by a microprocessor, microcontroller, DSP, or other suitable platform.

[0070] It is understood that software should be broadly considered as representing instructions, instruction sets, code, code segments, program code, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, running threads, procedures, functions, etc. Software may reside on a computer-readable medium. Computer-readable media may include, for example, memory, which may be, for example, magnetic storage devices (e.g., hard disks, floppy disks, magnetic stripes), optical disks, smart cards, flash memory devices, random access memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), registers, or removable disks. Although memory is shown as separate from the processor in several aspects set forth in this disclosure, memory may also reside within the processor (e.g., in caches or registers).

[0071] While some embodiments have been described above, these embodiments are given by way of example only and are not intended to limit the scope of the invention. The appended claims and their equivalents are intended to cover all modifications, substitutions, and alterations made within the scope and spirit of the invention.

Claims

1. An electronic control unit for a redundant braking system of a vehicle, the redundant braking system being coupled to the vehicle's main braking system, the electronic control unit comprising: The receiving module is configured to receive status signals indicating the state of the main braking system and sensor signals indicating the driver's input to the brake pedal and the vehicle speed. The activation module is configured to activate the braking assist function of the redundant braking system when the main braking system is determined to have entered the mechanical backup state based on the status signal. as well as The brake assist module stores multiple brake assist modes for implementing the brake assist function. The brake assist module is configured to, after the brake assist function is activated, determine, based on the sensor signal, which of the multiple brake assist modes to execute. Furthermore, the assist module is configured to switch between the multiple brake assist modes according to changes in the driver's input to the brake pedal and changes in vehicle speed. The multiple brake assist modes include: standby mode, first adjustable assist mode, second adjustable assist mode, and brake pressure holding mode. Among them, determining to execute one of the multiple braking assist modes based on the sensor signals includes: When the sensor signal indicates that the driver has released the brake pedal, it is determined that the second power assist adjustable mode is to be executed; In the second adjustable assist mode, the brake assist module is configured as follows: The slope of the brake pressure reduction desired by the driver is calculated based on sensor signals; and The actual braking pressure reduction slope is determined based on the driver's desired braking pressure reduction slope and the braking pressure reduction slope threshold, so that the redundant braking system disengages the vehicle braking according to the determined actual braking pressure reduction slope.

2. The electronic control unit as claimed in claim 1, wherein, The activation module is also configured to not activate the brake assist function of the redundant braking system when at least one of the following conditions is met: - Based on the status signal, it is determined that the brake assist function of the main braking system is operating normally; and - The vehicle speed is lower than a first speed threshold, wherein the first speed threshold is the vehicle's creep speed.

3. The electronic control unit as described in any one of claims 1-2, wherein, Determining to execute one of the multiple braking assist modes based on the sensor signals includes: When the sensor signal indicates that the driver has not input the brake pedal, it is determined to be in standby mode, in which the brake assist module does not perform any brake assist operation.

4. The electronic control unit as described in any one of claims 1-2, wherein, Determining to execute one of the multiple braking assist modes based on the sensor signals includes: When the sensor signal indicates that the driver has pressed the brake pedal, it is determined that the first adjustable power assist mode is to be executed. In the first adjustable assist mode, the brake assist module is configured as follows: Calculate the driver's desired braking pressure based on sensor signals; and The amplification factor curve is used to determine the assist amplification factor corresponding to the driver's desired braking pressure, so that the redundant braking system can control the vehicle braking according to the determined assist amplification factor. The amplification factor curve is predetermined and includes the correspondence between the driver's desired braking pressure and the power assist amplification factor.

5. The electronic control unit as described in claim 4, wherein, In the first adjustable assist mode, the brake assist module is further configured to: When the receiving module receives a signal indicating that a function related to vehicle driving stability has been activated, it will maintain the amplification factor at the value at the moment when the function related to vehicle driving stability is activated.

6. The electronic control unit as claimed in claim 1, wherein, The actual braking pressure reduction slope is determined based on the driver's desired braking pressure reduction slope and a braking pressure reduction slope threshold, including: When the brake pressure decreases faster than the brake pressure decrease slope threshold desired by the driver, the actual brake pressure decrease slope is determined as the brake pressure decrease slope threshold; and When the brake pressure decreases more slowly than the brake pressure decrease slope threshold desired by the driver, the actual brake pressure decrease slope is determined as the brake pressure decrease slope desired by the driver.

7. The electronic control unit as described in any one of claims 1-2, wherein, Determining to execute one of the multiple braking assist modes based on the sensor signals includes: When the brake assist mode is in the first adjustable assist mode and the vehicle speed is below the second vehicle speed threshold, when a function related to vehicle driving stability is activated, it is determined to execute the brake pressure holding mode. In the brake pressure holding mode, the brake assist module is configured to control the redundant braking system to perform vehicle braking at a predetermined brake pressure.

8. The electronic control unit as claimed in claim 1, wherein, The brake assist module includes a brake assist model, which includes multiple brake assist modes and their switching states. The switching states correspond to changes in the driver's input to the brake pedal and changes in vehicle speed.

9. The electronic control unit as claimed in claim 8, wherein, The switching states include: The first adjustable assist mode can be switched bidirectionally with standby mode, second adjustable assist mode and brake pressure holding mode; One-way switching from brake pressure holding mode to standby mode; One-way switching between brake pressure holding mode and second assist adjustable mode; and The second assist allows for one-way switching between adjustable mode and standby mode.

10. A redundant braking system for a vehicle, comprising: Two braking circuits are configured to be fluidly connected to the two braking circuits of the vehicle's main braking system, respectively. Four valves are connected between the master brake cylinder of the main braking system and the four brake wheel cylinders of the vehicle; A motor configured to generate braking assistance for pumping some or all of the brake fluid from the master brake cylinder into the four brake wheel cylinders. as well as The electronic control unit as described in any one of claims 1-9 performs electrical control over the four valves and the motor, and performs brake assist function when the main braking system enters mechanical backup state.

11. A control method for a redundant braking system for a vehicle, said method being performed by an electronic control unit as claimed in any one of claims 1-9 or a redundant braking system as claimed in claim 10, said method comprising: Receive status signals indicating the status of the vehicle's main braking system and sensor signals indicating the driver's input to the brake pedal and the vehicle speed; When the main braking system is determined to have entered the mechanical backup state based on the status signal, the braking assist function of the redundant braking system is activated. After the brake assist function is activated, a corresponding brake assist mode is determined to be executed among multiple brake assist modes based on the sensor signal. as well as The braking assist mode is switched among the various braking assist modes based on changes in the driver's input to the brake pedal and changes in vehicle speed. The various braking assist modes include: standby mode, first adjustable assist mode, second adjustable assist mode, and brake pressure holding mode. Among them, determining to execute one of the multiple braking assist modes based on the sensor signals includes: When the sensor signal indicates that the driver has released the brake pedal, it is determined that the second power assist adjustable mode is to be executed; In the second adjustable assist mode, the brake assist module is configured as follows: The slope of the brake pressure reduction desired by the driver is calculated based on sensor signals; and The actual braking pressure reduction slope is determined based on the driver's desired braking pressure reduction slope and the braking pressure reduction slope threshold, so that the redundant braking system disengages the vehicle braking according to the determined actual braking pressure reduction slope.

12. A machine-readable storage medium storing executable instructions that, when executed, cause one or more processors to perform the control method of claim 11.

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