JP2865502B2 - Brake control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake control method for controlling a brake pressure in accordance with a slip ratio of a wheel with respect to a road surface, and more particularly, to switching from normal control to limiting control for controlling brake pressure. In this case, the present invention relates to a brake control method in which the brake pressure is reduced at a maximum reduction rate from that time point and, after the brake pressure reaches a predetermined value, the amount of increase or decrease of the brake pressure is determined based on the slip rate.

[0002]

2. Description of the Related Art For example, in an automobile, a motorcycle, or the like, a slip ratio of a wheel with respect to a road surface is detected in order to obtain an optimum braking state, and a brake pressure corresponding to a brake operation amount is determined based on the slip ratio. Is changed from the normal control for changing the brake pressure to the limit control for controlling the brake pressure to a predetermined value in order to converge to a predetermined slip ratio.

[0003]

However, when converging to a predetermined slip ratio, if the rate of increase or decrease of the brake pressure is set small with emphasis on the convergence, the responsiveness deteriorates, and especially at the beginning of the limit control, the road surface is reduced. Increases the slip ratio of the wheel (hereinafter, referred to as deep slip). On the other hand, if the change rate of the brake pressure is set to be large with emphasis on responsiveness, the deep slip can be prevented, but overshooting is repeated and convergence deteriorates.

The present invention has been made to solve this kind of problem, and an object of the present invention is to provide a brake control method having good convergence and responsiveness when controlling an operation amount of a brake pressure. Aim.

[0005]

In order to achieve the above object, the present invention provides a brake control method for controlling a brake pressure according to a slip ratio of a wheel with respect to a road surface, wherein the slip ratio is set to a predetermined value. upon reaching, the process of switching the limit control for controlling the brake pressure in order to converge the slip rate to a predetermined value from the normal control to brake the wheels by increasing or decreasing the brake pressure according to the operation amount, the from the normal control < after switching to br /> limit control, and the process of reducing the brake pressure to a predetermined brake pressure at the maximum reduction rate, where the brake pressure reaches the predetermined braking pressure,-out based on the slip ratio, the maximum Convergence smaller than the absolute value of the decrease rate
The brake pressure increase / decrease rate is determined in consideration of
Controlling the brake pressure to be increased or decreased .

[0006]

In the brake control method of the present invention, since the brake pressure is reduced at the maximum reduction rate after switching from the normal control to the limit control, deep slip is prevented, and good responsiveness is obtained. When the brake pressure reaches a predetermined value, switching is performed so as to determine the brake pressure based on the slip ratio. Therefore, the control method is switched so that sufficient responsiveness can be obtained in the early stage of the limit control, and after the brake pressure has decreased to a predetermined value, the amount of increase or decrease of the brake pressure is determined with emphasis on convergence based on the slip ratio. Therefore, it is possible to quickly converge to a predetermined slip ratio without a risk of overshooting or the like.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a brake control method according to the present invention will be described below in detail with reference to the accompanying drawings.

In this embodiment, an example of a brake control device mounted on a motorcycle body to which a brake control method is applied will be described.

FIG. 1 is a schematic configuration diagram of a brake control device 10 according to the present embodiment. The brake control device 10
Is the modulator 1 by the control unit 12.
By controlling No. 4, an optimum braking force is obtained by controlling the brake pressure.

The control unit 12 detects a wheel speed Vw via wheel speed sensors 16 and 16a provided near the front wheel (driven wheel) Wf and the rear wheel (drive wheel) Wr, and outputs a pulse of the wheel speed Vw. The signal is introduced into the control unit 12. Control unit 1
2 includes a plurality of arithmetic circuits (not shown).

The brake device 18 comprises a master cylinder 24 driven by a brake lever 22 provided on a steering wheel 20 and a caliper cylinder 2 for braking the front wheel Wf.
6, the master cylinder 24 and the caliper cylinder 26
Are connected to each other via a modulator 14.
The master cylinder 24 adjusts the oil pressure under the action of the brake lever 22 and transmits the adjusted oil to a cut valve, which will be described later. On the other hand, the caliper cylinder 26 adjusts the disk plate based on the oil pressure controlled by the cut valve. 28 to provide a braking force.

The modulator 14 of the front wheel Wf includes a motor driver 32 for energizing and deactivating a DC motor 30 constituting the modulator 14 to control the driving of the DC motor 30. This motor driver 3
2 is electrically connected to the control unit 12,
The signal derived from the control unit 12 is introduced. A pinion 34 is connected to a drive shaft of the DC motor 30, and a gear 36 meshes with the pinion 34. Gear 3
A crankshaft 38 is fixed to the center of 6, and one end of a crankpin 42 is connected to the crankshaft 38 via a crank arm 40. A crank arm 44 is connected to the other end of the crank pin 42, and a potentiometer 46 for detecting a deviation angle of the crank pin 42 is connected to the crank arm 44.

A cam bearing 48 is rotatably mounted on the outer periphery of the crank pin 42.
8 is pressed upward via a return spring 50. An expander piston 52 which moves up and down under the cam bearing 48 is brought into contact with the upper surface of the cam bearing 48, and the cut valve 54 is opened and closed under the action of the expander piston 52 moving up and down. You. The cut valve 54 is disposed in the cut valve housing 56 so as to be vertically displaceable. On the upper surface of the cut valve 54, an input port 58 communicating with the master cylinder 24 is provided. An output port 60 communicating with the caliper cylinder 26 is provided at a portion where the panda piston 52 is connected. The input port 58 and the output port 60 communicate with each other via a communication hole 62 defined on the outer peripheral surface of the cut valve 54.

On the other hand, the modulator 14a of the rear wheel Wr
The master cylinder 24a connected to the brake pedal 23 of the rear wheel Wr communicates with the caliper cylinder 26a connected to the disk plate 28a of the rear wheel Wr.
The modulator 14a is the same as the modulator 14 described above.
And the detailed description thereof is omitted.

The brake control device 1 constructed as described above
The operation of 0 will be described in relation to the brake control method according to the present embodiment.

At the time of manual control in which the brake pressure is changed in accordance with the operation amount of the brake lever 22, the resilient force of the return spring 50 holds the crank pin 42 at a preset upper limit position.
Is maintained in a state in which the expander piston 52 is pushed up. As a result, the cut valve 54 is pushed up by the expander piston 52, and connects the input port 58 and the output port 60.

The master cylinder 24 is urged by gripping the brake lever 22, and the brake pressure generated by the master cylinder 24 is transmitted to the caliper cylinder 26 via the input port 58 and the output port 60. A braking force is applied to the disc plate 28.

On the other hand, when the antilock control is performed, the amount of increase or decrease of the brake pressure (caliper pressure) is obtained from a fuzzy map (see FIG. 2) based on the wheel acceleration / deceleration α and the slip ratio λ. Control unit 1
2 supplies a drive signal to the motor driver 32. As a result, the rotation direction and the rotation amount of the DC motor 30 are controlled. Therefore, a pinion 34 attached to a rotating shaft (not shown) is rotated, and a gear 36 meshing with the pinion 34 and a crank arm 40 fixed to the gear 36 via a crankshaft 38 are rotated. 40
Is displaced from the upper limit position toward the lower limit position. The cam bearing 48 descends due to the deviation of the crank pin 42, and the expander piston 52
Is applied to the torque of the DC motor 30, so that the expander piston 52
Presses the cam bearing 48 and immediately descends.

When the expander piston 52 is lowered by a predetermined amount, the cut valve 54 is seated, thereby shutting off the connection between the input port 58 and the output port 60. Therefore, when the expander piston 52 further lowers further, the volume on the output port 60 side increases, and the hydraulic pressure applied to the caliper cylinder 26 decreases, and, for example, the braking force of the front wheel Wf decreases.

In the antilock control executed as described above, in order to control the target slip ratio λT on the fuzzy map shown in FIG. 2, overshooting prevention, that is, a change rate of the caliper pressure with emphasis on convergence. Is set low, the control that repeatedly increases and decreases the caliper pressure quickly converges to the target slip rate λT as shown by the broken line, but the rate of change in the caliper pressure is low when switching from manual control to antilock control. However, as shown by the solid arrow on the map shown in FIG. 2, there is a problem that the increasing wheel slip ratio λ cannot be controlled, resulting in a deep slip (see FIG. 3).
Conversely, if the caliper pressure increase / decrease rate is set high with emphasis on responsiveness, the deep slip can certainly be prevented, but on the contrary, the slip ratio λ and caliper pressure repeat overshooting, making it difficult to converge. There is a problem (see FIG. 4). That is, when switching from the manual control to the anti-lock control, for example, in the hatched area A on the fuzzy map shown in FIG. Conversely, if the rate of increase and decrease of the caliper pressure is increased with an emphasis on responsiveness, a problem occurs in convergence.

Therefore, the brake control method of the present embodiment has solved the above-mentioned problem as follows. This will be described with reference to the control flowchart of the control unit 12 (FIG. 5).

First, while the vehicle is running, based on the outputs from the wheel speed sensors 16 and 16a and the potentiometer 46, the wheel speed Vw of the front and rear wheels and the deviation angle of the crankpin 42 are detected, and Based on this, the estimated vehicle speed Vr, the wheel acceleration / deceleration α, and the slip ratio λ are calculated (steps S1 and S2).

Subsequently, it is determined whether or not to enter the anti-lock control based on the slip ratio λ, the estimated vehicle speed Vr, the wheel acceleration / deceleration α, and the like.
The S flag is set (step S3).

Subsequently, the ABS flag is set (ON).
It is determined whether or not (step S4). If it is determined that the ABS flag is not set (OFF), steps S1 to S3 are repeated until the antilock control is performed. At this time, the initial flag is always set to ON (step S5).

If it is determined in step S4 that the ABS flag is OFF, manual control is performed, and
The caliper pressure increases in accordance with the operation amounts of the brake lever 22 and the brake pedal 23, and the vehicle body is braked.

On the other hand, when it is determined in step S4 that the ABS flag is ON, the control enters the antilock control.

In this case, it is determined whether or not the crank angle θc read from the potentiometer 46 in step S1 is equal to or greater than an initial release angle θ0 described later (step S6). The initial release angle θ0 refers to an angle at which the output of the motor is operated at a maximum until the crankpin 42 is displaced to the crank angle. Note that the initial release angle θ0 is larger than the cut valve working angle θe at which the cut valve 54 blocks the communication hole 62,
Any value may be used as long as it is smaller than an initial angle θi described later (θe <θ0 <θi). The caliper pressure when switching from the manual control to the antilock control, or the value of the caliper pressure when the crank angle θc is the initial release angle θ0 is variously changed due to expansion of a hose of a brake system or the like.

If the crank angle θc has not reached the initial release angle θ0, it is determined whether or not the initial flag is set (ON) (step S7). If the initial flag is ON, the control target angle is determined. A certain target crank angle θT is set as an initial angle θi that is the maximum deviation angle of the crankpin 42 (step S8).

If the crank angle θc has reached the initial release angle θ0 in step S7, the initial flag is set to OFF (step S9), or if it is determined in step S7 that the initial flag is OFF, Based on the fuzzy map shown in FIG. 2, the caliper pressure increase / decrease amount, that is, the displacement amount Δθ of the crank pin 42 is obtained from the slip ratio λ and the wheel acceleration / deceleration α (step S).
10) A target crank angle θT is obtained by adding the current crank angle θc to the displacement amount Δθ (step S11).

Subsequently, PID control is performed on the DC motor 30 based on the target crank angle θT (step S12).

In this case, in the antilock control, the target crank angle θT is set to the initial angle θi until the crank angle θc becomes the initial release angle θ0 after switching from the manual control to the antilock control. Since the deviation between θT (= θi) and the crank angle θc is large, the DC motor 30 displaces the crankpin 42 at the maximum output, and the cut valve 54 is seated in the cut valve housing 56 so that the master cylinder 24 and the caliper The cylinder 26 is shut off (the crank angle at this time is referred to as a cut valve operating angle θe). Further, the displacement of the crank pin 42 increases the volume of the output port 60 and further reduces the caliper pressure. In this way, when switching from the manual control to the antilock control, by driving the DC motor 30 at the maximum output, the caliper pressure, that is, the reduction of the wheel speed Vw is controlled in a short time, and a deep slip occurs. Can be prevented (see FIG. 6).

After the crank angle .theta.c reaches the initial release angle .theta.0, the caliper pressure, that is, the displacement of the crankpin 42, is determined by a fuzzy map (see FIG. 2) based on the slip ratio .lambda. Find Δθ,
Based on this, the target crank angle θT is set (step S11), and the caliper pressure is repeatedly increased and decreased by displacing the expander piston 52. Therefore, if the fuzzy map is set with emphasis on convergence, the crank pin 42 is not displaced at the maximum output of the DC motor 30 as in the case where the crank angle θc is up to the initial release angle θ0, and there is no danger of overshooting. Absent. In addition, by setting the initial flag, the crank angle θc can be changed to the initial release angle θ0 during the antilock control.
Even if the initial value becomes below, the initial flag is turned off in step S9.
Since it is F, the control based on the fuzzy map can be continued without resetting the target crank angle θT to the initial angle θi by the determination in step S7.

As described above, in this embodiment, the DC motor 30 is operated at the maximum output from the time when the control is switched from the manual control to the antilock control until the initial release angle θ0 is reached.
To prevent deep slip by increasing responsiveness. Also, after the crank angle θc reaches the initial release angle θ0, the brake control is performed based on the fuzzy map (see FIG. 2), so that control with good convergence can be performed.

[0034]

According to the brake control method of the present invention, the following effects can be obtained.

That is, since the brake pressure is reduced at the maximum reduction rate from the point in time when the normal control is switched to the limit control, deep slip is prevented and good responsiveness is obtained. When the brake pressure reaches a predetermined value, switching is performed so as to determine the brake pressure based on the slip ratio and the wheel acceleration / deceleration. Therefore, sufficient responsiveness can be obtained in the early stage of the limit control, and after the brake pressure is reduced to a predetermined value, the increase / decrease amount of the brake pressure is determined in consideration of the convergence based on the slip ratio. Since the control method is switched over, there is no risk of overshooting or the like, and it is possible to quickly converge to a predetermined slip ratio.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a brake control device that executes a brake control method according to the present invention.

FIG. 2 is a fuzzy map for determining an increase / decrease amount of a brake pressure in the brake control method according to the present invention.

FIG. 3 is a diagram showing brake control with emphasis on responsiveness in the brake control method according to the present invention.

FIG. 4 is a diagram showing brake control with emphasis on convergence in the brake control method according to the present invention.

FIG. 5 is a flowchart showing a brake control method according to the present invention.

FIG. 6 is a diagram showing a control result of a brake control method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Brake control device 12 ... Control unit 14, 14a ... Modulator 16, 16a ... Wheel speed sensor 22 ... Brake lever 23 ... Brake pedal 24, 24a ... Master cylinder 26, 26a ... Caliper cylinder 28, 28a ... Disk plate 30 ... DC Motor 42 ... Crank pin 46 ... Potentiometer 52 ... Expander piston 54 ... Cut valve

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tatsuo Hayashi 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-64-47650 (JP, A) JP-A Sho 51-15770 (JP, A) JP-A-62-166148 (JP, A) JP-A-3-50059 (JP, A) JP-A-63-38062 (JP, A) JP-B-51-31350 (JP, A) B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60T 8/58 B60T 8/42

Claims (1)

(57) [Claims] 1. A brake control method for controlling a brake pressure according to a slip ratio of a wheel with respect to a road surface, wherein when the slip ratio reaches a predetermined value, the brake pressure is increased or decreased according to an operation amount to control a wheel. a process of switching the limit control for controlling the brake pressure in order to converge the slip rate to a predetermined value from the normal control to brake, after switching to the limit control from the normal control, a predetermined braking pressure to the brake pressure at the maximum reduction ratio And when the brake pressure reaches the predetermined brake pressure,
-Out based on the slip ratio, than the absolute value of the maximum reduction rate
Determining the rate of increase or decrease of the brake pressure in consideration of the small convergence, and controlling the increase or decrease of the brake pressure based on the rate of increase or decrease .