Brake control device and brake control method

Abstract

To provide a technique by which responsiveness of a brake control for performing driving support based on steering information is improved.SOLUTION: A brake control device 10 includes: an acquisition unit 26 configured to acquire a steering angle and first steering angular speed that have passed through a first low-pass filter; a brake processing unit 28 configured to determine whether to apply braking force to wheels by a brake device 16 when an absolute value of the steering angle is equal to or greater than a predetermined angle and an absolute value of the first steering angular speed is equal to or greater than a predetermined speed; and a control unit 30 configured to drive the brake device 16 in accordance with the determination by the brake processing unit 28. The acquisition unit 26 acquires a second steering angular speed that includes higher frequency components than the first steering angular speed. The brake processing unit 28 determines to execute predetermined preload control when an absolute value of the second steering angular speed is equal to or greater than the predetermined speed. The control unit 30 executes preload control on the brake device 16 to improve the responsiveness of the brake device 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to brake control that applies braking force to wheels based on steering angle information of a vehicle steered by a driver. [Background technology]

[0002] Patent Document 1 discloses a device that performs vehicle behavior stabilization control, which stabilizes vehicle behavior by applying a braking control amount to one of the front or rear outer wheels during a turn. This vehicle behavior control device applies a preliminary brake pressure to one of the front or rear inner wheels during a turn when a turning operation in the opposite direction to the current turning motion of the vehicle is detected during execution of vehicle behavior stabilization control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-28201 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology disclosed in Patent Document 1, brake control is executed when steering in a turn, but brake control is not executed in situations other than steering in a turn. For example, it is desirable to be able to provide driving assistance with good response by brake control when a sudden turn occurs.

[0005] An object of the present invention is to provide a technology for improving the responsiveness of brake control that assists driving based on steering information. [Means for solving the problem]

[0006] In order to solve the above problem, a brake control device according to one embodiment of the present invention includes an acquisition unit that acquires a steering angle and a first steering angular velocity that have passed through a first low-pass filter; a brake processing unit that determines whether to apply braking force to a wheel by a brake device when the absolute value of the steering angle is equal to or greater than a predetermined angle and the absolute value of the first steering angular velocity is equal to or greater than a predetermined velocity; and a control unit that drives the brake device in accordance with the determination by the brake processing unit. The acquisition unit acquires a second steering angular velocity that includes higher-frequency components than the first steering angular velocity. The brake processing unit determines to execute predetermined preload control when the absolute value of the second steering angular velocity is equal to or greater than the predetermined velocity. The control unit executes preload control on the brake device to improve the responsiveness of the brake device.

[0007] Another aspect of the present invention is a brake control method, each step of which is executed by a brake control device, including the steps of acquiring a steering angle and a first steering angular velocity that have passed through a first low-pass filter, acquiring a second steering angular velocity that includes higher frequency components than the first steering angular velocity, determining to execute preload control that improves responsiveness of a brake device if the absolute value of the second steering angular velocity is equal to or greater than a predetermined velocity, and determining to apply braking force to a wheel by the brake device if the absolute value of the steering angle is equal to or greater than the predetermined angle and the absolute value of the first steering angular velocity is equal to or greater than the predetermined velocity. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique for improving the responsiveness of brake control that assists driving based on steering information. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating a functional configuration of a brake system. [Figure 2] 4A and 4B are diagrams for explaining the operation of the brake control device to execute pre-load control and main pressure control based on steering angle information. [Figure 3] 3 is a flowchart of a brake control method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1 is a diagram showing the functional configuration of a brake system 1. Each function of the brake system 1 can be configured in terms of hardware using circuit blocks, memory, and other LSIs, and can be realized in terms of software using system software or application programs loaded into memory. Therefore, it will be understood by those skilled in the art that each function of the brake system 1 can be realized in various ways using only hardware, only software, or a combination thereof, and is not limited to any one of these. The brake system 1 is provided in a vehicle, and the vehicle may be capable of autonomous driving.

[0011] The brake system 1 includes a brake control device 10, a steering angle sensor 12, an on-board sensor 14, and a brake device 16. The brake system 1 automatically applies braking force based on the detection result of the steering angle sensor 12, and performs assistance to stabilize vehicle driving.

[0012] The steering angle sensor 12 detects the rotation angle of the steering wheel and detects the steering angle of the driver. The steering angle sensor 12 transmits the detection results to the brake control device 10. The on-board sensors 14 are, for example, wheel speed sensors and brake pressure sensors, and transmit the detection results to the brake control device 10. The wheel speed sensors detect the rotation speed of the wheels. The brake pressure sensors detect the brake pressure applied by the brake device 16. The brake pressure sensors are provided in the master cylinder or wheel cylinders.

[0013] The brake device 16 is a hydraulic brake device that applies frictional force to the wheels, and is driven under the control of the brake control device 10 to apply braking force to the vehicle. The brake device 16 includes a master cylinder connected to the brake pedal, a wheel cylinder that moves a piston linked to the brake pad, and the like.

[0014] The brake control device 10 includes a communication unit 20, a first filter unit 22, a second filter unit 24, an acquisition unit 26, a brake processing unit 28, and a control unit 30. The communication unit 20 has an in-vehicle communication function and receives detection results from the steering angle sensor 12 and the in-vehicle sensor 14.

[0015] The first filter unit 22 is a software application having a first low-pass filter function, and the second filter unit 24 is a software application having a second low-pass filter function. The first filter unit 22 and the second filter unit 24 send steering angle information obtained by removing high-frequency components from the sensor value received from the steering angle sensor 12 to the acquisition unit 26.

[0016] The first filter unit 22 removes high-frequency components from the steering angle and steering angular velocity transmitted from the steering angle sensor 12. The first filter unit 22 removes high-frequency components equal to or greater than a first threshold from the steering angular velocity received from the steering angle sensor 12 without being subjected to noise removal processing, to obtain a first steering angular velocity.

[0017] The second filter unit 24 removes high-frequency components equal to or greater than a second threshold from the steering angular velocity transmitted from the steering angle sensor 12 to obtain a second steering angular velocity. The second threshold may be set to a cutoff frequency several times greater than the first threshold. Because the second threshold is set to be greater than the first threshold, the second steering angular velocity includes higher-frequency components than the first steering angular velocity. The second steering angular velocity may be a sensor value that has not passed through a low-pass filter, but using the second filter unit 24 makes it possible to remove a minimum amount of noise.

[0018] The acquisition unit 26 acquires the steering angle and the first steering angular velocity that have passed through a first low-pass filter, and acquires the second steering angular velocity that have passed through a second low-pass filter. The acquisition unit 26 also acquires the wheel speed and the brake pressure as detection results from the on-board sensor 14.

[0019] The brake processing unit 28 determines to apply braking force to the wheels by the brake device 16 when the absolute value of the steering angle is equal to or greater than a predetermined angle and the absolute value of the first steering angular velocity is equal to or greater than a predetermined velocity. The brake processing unit 28 determines the amount of braking to each wheel according to a preset control map. This control map defines the distribution of braking force to each wheel in the main pressure application control, and defines the distribution between the left and right front wheels and the left and right rear wheels. The control unit 30 activates the brake device 16 in accordance with the determination by the brake processing unit 28. This control of applying braking force based on the steering angle and the first steering angular velocity is called main pressure application control. As a result, when abrupt steering or the like occurs, the brake control device 10 can activate the brake device 16 to stabilize driving.

[0020] If the absolute value of the second steering angular velocity is equal to or greater than a predetermined velocity, the brake processing unit 28 determines to execute predetermined preload control. The brake processing unit 28 sends the determination result to the control unit 30. The predetermined preload control is a control that improves the responsiveness of the brake device 16. In this pressurization control, the pressure is applied by monitoring not only the first steering angular velocity but also the steering angle, so that sudden steering can be accurately determined. On the other hand, the preload control is executed based only on the second steering angular velocity, so that a quick response can be made. Furthermore, the second steering angular velocity contains more high-frequency components than the first steering angular velocity, so that it can be detected earlier than the first steering angular velocity.

[0021] The predetermined speed used for the first steering angular velocity in determining whether to perform the pressurization control is the same as the predetermined speed used for the second steering angular velocity in determining whether to perform the preload control, so that it can be determined that the second steering angular velocity has reached or exceeded the predetermined speed earlier than the first steering angular velocity has reached or exceeded the predetermined speed.

[0022] The control unit 30 receives the determination result of the brake processing unit 28 and executes preload control on the brake device 16. As the preload control, the control unit 30 drives the brake device 16 to apply a predetermined preliminary brake pressure and / or reduces the idle stroke of the master cylinder of the brake device 16.

[0023] In pre-pressure control, the control unit 30 drives the brake device 16 to apply a predetermined preliminary brake pressure, which actually pressurizes each wheel cylinder of the brake device 16, improving the responsiveness of the brake device 16. The preliminary brake pressure is determined through experiments, etc., and is set to a very small value that causes almost no change in wheel speed and does not cause the occupant to feel any deceleration, and is smaller than the brake pressure applied in the main pressure control. The preliminary brake pressure is allocated to the front and rear wheels at a preset ratio.

[0024] In preload control, the control unit 30 reduces the ineffective stroke of the master cylinder of the braking device 16, thereby eliminating the ineffective stroke and improving the responsiveness of the braking device 16. To reduce the ineffective stroke of the master cylinder of the braking device 16, the control unit 30 moves the piston of the master cylinder to the pressurizing side.

[0025] 2A to 2D are diagrams for explaining the operation of the brake control device 10 to execute preload control and main pressure control based on steering angle information. The horizontal axis of the graphs shown in Fig. 2A to 2D represents time, and is the same for all times t1, t2, and t3. The vertical axis of Fig. 2A represents the steering angle, the vertical axis of Fig. 2B represents the steering angular velocity, the vertical axis of Fig. 2C represents PFR (actual hydraulic pressure in the wheel cylinder of the right front wheel), and the vertical axis of Fig. 2D represents PRL (actual hydraulic pressure in the wheel cylinder of the left rear wheel).

[0026] As shown in Figure 2(a), the steering angle 31 suddenly increases and becomes almost constant at time t3. In other words, the driver is trying to turn the vehicle by performing a sudden steering operation. The steering angle 31 shown in Figure 2(a) has passed through a first low-pass filter.

[0027] FIG. 2(b) shows the first steering angular velocity 32 and the second steering angular velocity 34. The second steering angular velocity 34 rises earlier than the first steering angular velocity 32. At time t1, the second steering angular velocity 34 becomes equal to or greater than the predetermined velocity S, and preload control is executed. At time t2, the first steering angular velocity 32 becomes equal to or greater than the predetermined velocity S, and the steering angle becomes equal to or greater than the predetermined angle θ, and main pressurization control is executed. In this way, the preload control is started at an earlier timing than the main pressurization control.

[0028] 2(c) and 2(d) show a first brake assistance result 36 when preload control is not executed, and a second brake assistance result 38 when preload control is executed. The start of the first brake assistance result 36 is determined based on the steering angle 31 and the first steering angular velocity 32, and the start of the second brake assistance result 38 is determined based on the second steering angular velocity 34.

[0029] In the first brake support result 36 shown in Figures 2(c) and 2(d), main pressurization control is executed from time t2, and PFR and PRL rise a little later. At time t3, main pressurization control ends and PFR and PRL fall.

[0030] In the second brake assist result 38 shown in Figures 2(c) and 2(d), preload control is started at time t1, and PFR and PRL are slightly increased and maintained at a constant pressure. In this preload control, the control unit 30 drives the brake device 16 to apply a predetermined preliminary brake pressure. In the preload control, the same preliminary brake pressure may be applied to the wheel cylinders of the front and rear wheels.

[0031] Main pressure application control is initiated at time t2, but PFR and PRL do not begin to rise until a short time after time t2. Main pressure application control ends at time t3, and PFR and PRL decrease. In this way, when the driver makes an abrupt turn, the brake control device 10 automatically applies braking force to stabilize the vehicle's running. Furthermore, compared to the first brake support result 36 in which pre-load control is not executed, PFR and PRL in the second brake support result 38 rise quickly from time t2 when main pressure application control is initiated. This makes it easier to stabilize the vehicle's running.

[0032] Returning to Figure 1, the brake processing unit 28 determines to terminate the preload control if a predetermined termination condition is met after the preload control is started but before the main pressurization control begins. Also, the preload control terminates once the main pressurization control begins.

[0033] The brake processing unit 28 determines to end the preload control when the time since the start of the preload control exceeds a predetermined time. This allows the preload control to be ended if the main pressurization control does not start at all after the start of the preload control. The predetermined time is set to a few seconds or less.

[0034] The brake processing unit 28 terminates the preload control when the absolute value of the second steering angular velocity becomes equal to or less than a predetermined termination speed that is smaller than a predetermined speed. The predetermined termination speed is determined by experiment or the like, but is set to a value slightly smaller than the predetermined speed, which can prevent the preload control from being frequently turned on and off.

[0035] The control unit 30 terminates the preload control according to the determination result of the brake processing unit 28 when the time since the start of the preload control exceeds a predetermined time, or when the absolute value of the second steering angular velocity becomes equal to or less than a predetermined termination speed that is smaller than the predetermined speed.

[0036] 3 is a flowchart of the brake control method of the embodiment. The first filter unit 22 passes the detection result of the steering angle sensor 12 through a first low-pass filter, and the acquisition unit 26 acquires the steering angle and the first steering angular velocity (S10).

[0037] The second filter unit 24 passes the detection result of the steering angle sensor 12 through a second low-pass filter, and the acquisition unit 26 acquires a second steering angular velocity (S12). The brake processing unit 28 determines whether the second steering angular velocity is equal to or greater than a predetermined velocity (S14). If the second steering angular velocity is equal to or greater than the predetermined velocity S (Y in S14), the brake processing unit 28 determines to execute preload control, and the control unit 30 executes preload control (S16). This improves the responsiveness of the brake device 16.

[0038] After the preload control is executed, the brake processing unit 28 determines whether the steering angle and the first steering angular velocity exceed the reference values ​​(S18). If the steering angle is equal to or greater than a predetermined angle θ and the first steering angular velocity is equal to or greater than a predetermined velocity S (Y in S18), the brake processing unit 28 determines to execute the main pressurization control, and the control unit 30 executes the main pressurization control (S20). Once the main pressurization control is executed, the control unit 30 ends the preload control (S22).

[0039] If the second steering angular velocity is not equal to or greater than the predetermined velocity S (N in S14), the brake processing unit 28 determines whether preload control is being executed (S24). If preload control is not being executed (N in S24), the process ends without applying the brakes.

[0040] If the preload control is being executed (Y in S24), the brake processing unit 28 determines whether the termination condition of the preload control is satisfied. If the steering angle is not equal to or greater than the predetermined angle θ or the first steering angular velocity is not equal to or greater than the predetermined velocity S (N in S18), the brake processing unit 28 determines whether the termination condition of the preload control is satisfied (S26).

[0041] The termination condition for preload control is satisfied when the time since the start of preload control exceeds a predetermined time, or when the absolute value of the second steering angular velocity becomes equal to or less than a predetermined termination speed that is smaller than the predetermined speed. If the termination condition for preload control is satisfied (Y in S26), the control unit 30 terminates the preload control (S22). If the termination condition for preload control is not satisfied (N in S26), the process terminates while continuing the preload control.

[0042] The present disclosure has been described above based on examples. The present disclosure is not limited to the above examples, and various modifications such as design changes may be made based on the knowledge of those skilled in the art. [Explanation of symbols]

[0043] 1 Brake system, 10 Brake control device, 12 Steering angle sensor, 14 On-board sensor, 16 Brake device, 20 Communication unit, 22 First filter unit, 24 Second filter unit, 26 Acquisition unit, 28 Brake processing unit, 30 Control unit, 32 First steering angular velocity, 34 Second steering angular velocity.

Claims

1. an acquisition unit that acquires the steering angle and the first steering angular velocity that have passed through a first low-pass filter; a brake processing unit that determines to apply a braking force to a wheel by a brake device when the absolute value of the steering angle is equal to or greater than a predetermined angle and the absolute value of the first steering angular velocity is equal to or greater than a predetermined velocity; a control unit that drives a brake device in accordance with the determination of the brake processing unit, the acquisition unit acquires a second steering angular velocity that includes a higher frequency component than the first steering angular velocity, the brake processing unit determines to execute a predetermined preload control if the absolute value of the second steering angular velocity is equal to or greater than a predetermined velocity, The brake control device is characterized in that the control unit executes preload control for the brake device to improve responsiveness of the brake device.

2. 2. The brake control device according to claim 1, wherein the control unit, as the pre-pressure control, drives the brake device to apply a predetermined preliminary brake pressure or reduces an ineffective stroke of a master cylinder of the brake device.

3. 3. The brake control device according to claim 1, wherein the second steering angular velocity is a value that passes through a second low-pass filter having a second threshold value that is set to be greater than the first threshold value of the first low-pass filter.

4. 3. The brake control device according to claim 1, wherein the control unit terminates the preload control when a time since the start of the preload control exceeds a predetermined time, or terminates the preload control when an absolute value of the second steering angular velocity becomes equal to or less than a predetermined termination velocity that is smaller than the predetermined velocity.

5. A brake control method in which each step is executed by a brake control device, acquiring a steering angle and a first steering angular velocity that have passed through a first low-pass filter; acquiring a second steering angular velocity that includes a higher frequency component than the first steering angular velocity; determining, if the absolute value of the second steering angular velocity is equal to or greater than a predetermined velocity, to execute preload control for improving responsiveness of a brake device; and determining to apply braking force to the wheels by a brake device when the absolute value of the steering angle is equal to or greater than a predetermined angle and the absolute value of the first steering angular velocity is equal to or greater than a predetermined velocity.

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