JP2855006B2 - 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 by averaging a coefficient of friction on a road surface by sequentially comparing slip ratios when the acceleration / deceleration of a wheel is substantially zero.

[0002]

2. Description of the Related Art For example, in an automobile or a motorcycle, a brake control device is used for controlling a brake.

In this brake control device, a slip ratio between a wheel and a road surface is calculated from a speed of a running vehicle and a rotational speed of a wheel, and optimal braking is performed on the vehicle based on the calculated slip ratio. Things are known.

[0004]

In this case, the slip ratio between the wheel and the road surface and the friction coefficient (μ) in the rotational direction of the wheel are as follows:
Generally, there is a relationship shown in FIG. This characteristic is expressed by μ-S
It is called a curve and changes depending on the road surface conditions such as rain, snow or sand. On the other hand, the relationship between the coefficient of friction (μ) in the lateral direction of the wheel (in the direction perpendicular to the direction of rotation) and the slip ratio is shown in FIG. Road), the value of μ in the lateral direction is lower than that of a road surface having a high friction coefficient such as an asphalt road surface (hereinafter referred to as a high μ road).

Therefore, for example, the μ of the road surface is estimated on the basis of the wheel speeds of the front and rear wheels of the motorcycle and information from a G sensor and the like, and the target slip ratio is further estimated, and braking is performed so as to converge on the target slip ratio. It is possible. However, it has been pointed out that the value of μ varies considerably due to, for example, a change in the braking state due to front wheel and / or rear wheel braking or a sudden change in the road surface state, so that high-precision brake control is not performed. I have.

An object of the present invention is to provide a brake control method capable of calculating μ in an accurate and short time, thereby enabling optimal brake control. I do.

[0007]

In order to achieve the above object, the present invention provides a process for determining a brake braking force when the acceleration / deceleration of a wheel is substantially zero, and a method of calculating a friction coefficient of a road surface from the determined braking force. And the acceleration / deceleration is substantially zero.
When the slip rate obtained at the time of (c) converges with the slip rate obtained last time, performing an averaging process including the present friction coefficient in the friction coefficient up to the previous time; and Is approximately 0, the slip ratio obtained is
A step of stopping the friction coefficient averaging process and starting a new averaging process from the current friction coefficient when the slip ratio does not converge to the slip ratio obtained last time.

[0008]

In the brake control method according to the present invention, the brake braking force when the acceleration / deceleration of the wheel is substantially zero is measured or calculated, and the friction coefficient of the road surface is calculated from the brake braking force. It is not necessary to take into account the acceleration / deceleration of the data, so that the arithmetic processing is performed simply and in a short time. Furthermore, by averaging the respective friction coefficients, a more accurate friction coefficient is obtained, and the brake control is performed with high accuracy. When the slip rate does not converge to the previous slip rate, that is, when the road surface condition is , The averaging process of the friction coefficient up to the previous time is reset, and the averaging process is newly started from the current friction coefficient, whereby the calculation of the friction coefficient with high accuracy becomes possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A brake control method according to the present invention will be described in detail below with reference to the accompanying drawings in connection with an apparatus for carrying out the method.

In FIG. 2, reference numeral 10 denotes a motorcycle. The motorcycle 10 includes a main body 12, a handle 14, a front wheel 16, and a rear wheel 18.

The motorcycle 10 has a brake control device 20 for implementing the brake control method according to the present embodiment.
As shown in FIG. 1, the brake control device 20 includes an antilock modulator 22. A DC motor 24 constituting the modulator 22 has a pinion 26 pivotally mounted thereon. 28 mesh. The gear 28 is supported by a crankshaft 30,
One end of a crank pin 34 is eccentrically connected to the crank shaft 30 via a crank arm 32. The other end of the crank pin 34 is connected to an expander piston (described later) via a crank arm 36. A potentiometer 38 as a means for detecting a position is attached.

A cam bearing 4 is provided on the crank pin 34.
The lower end of the cam bearing 40 is constantly pressed in the direction of the upper limit position under the action of the return spring 44 housed in the spring housing 42. An expander piston 46 contacts the upper end side of the cam bearing 40, and the expander piston 46 moves up and down with the up and down movement of the cam bearing 40 to open and close the cut valve 48.

On the upper part of the expander piston 46,
A cut valve storage unit 50 containing a cut valve 48 is provided, and an input port 5 of the cut valve storage unit 50 is provided.
A master cylinder 56 is connected to 2 via a passage 54, while a caliper cylinder 62 for wheel braking is connected to an output port 58 of the cut valve housing 50 via a passage 60. The master cylinder 56 and the caliper cylinder 62 are connected to the passage 54, the modulator 22 and the passage 60.
And this path is filled with hydraulic oil. The master cylinder 56 adjusts the hydraulic pressure under the action of the brake lever 64, drives the caliper cylinder 62 via the cut valve 48, and
6 and a disk plate 66 disposed on the rear wheel portion 18
To the braking force.

Potentiometer 38 and DC motor 2
4 is connected to the motor controller 70. The motor controller 70 supplies the angle information of the crank pin 34 from the potentiometer 38, that is, the position of the expander piston 46 and the terminal current value of the DC motor 24 to the control unit 72.

The control unit 72 has a function of calculating the caliper pressure (braking braking force) based on the motor torque obtained from the terminal current value of the DC motor 24 and the position of the expander piston 46, and the calculated caliper pressure. The function of calculating the coefficient of friction (μ) of the road surface,
The control unit 72 is connected to a wheel acceleration / deceleration detection sensor 76 mounted on the disk plate 66.

Next, the operation of the brake control device 20 configured as described above will be described in relation to the brake control method according to the present embodiment.

During normal braking, the return spring 44
The resilient force holds the crank pin 34 at a preset upper limit position, and the cam bearing 40 mounted on the crank pin 34 is maintained in a state where the expander piston 46 is pushed up. As a result, the cut valve 48 is pushed up by the expander piston 46, and the input port 52 and the output port 58 communicate with each other.

Then, the master cylinder 56 is urged by gripping the brake lever 64, and the brake oil pressure generated by the master cylinder 56 is applied to the passage 5
4, transmitted to the caliper cylinder 62 through the input port 52, the output port 58, and the passage 60, and a braking force is applied to the disk plate 66.

Next, when a drive signal is supplied from the control unit 72 to the motor controller 70 to perform the brake control, the rotation direction and the rotation amount of the DC motor 24 are controlled. Therefore, a pinion 26 mounted on a rotating shaft (not shown) is rotated, and a gear 28 meshing with the pinion 26 and a crankshaft 30
Then, the crank arm 32 fixed via the shaft rotates, and the crank pin 34 engaged with the crank arm 32 is displaced from the upper limit position toward the lower limit position. The cam bearing 40 descends due to the deviation of the crank pin 34, and the brake oil pressure acting on the expander piston 46 acts so as to be added to the torque of the DC motor 24, so that the expander piston 46 presses the cam bearing 40. And descend immediately.

When the expander piston 46 descends by a predetermined amount, the cut valve 48 is seated, whereby the connection between the input port 52 and the output port 58 is shut off. Therefore, when the expander piston 46 further lowers further, the volume on the output port 58 side increases, and the hydraulic pressure applied to the caliper cylinder 62 decreases.
Braking force is reduced.

Here, the calculation processing of the friction coefficient (μ) of the road surface is performed based on the flowchart shown in FIG. First, the front wheel portion 16 will be described. A sensor 76 mounted on a disc plate 66 constituting the front wheel portion 16 is described.
When it is detected that the wheel acceleration / deceleration (α) of the front wheel section 16 has become almost 0 (step S1), the slip ratio (λ) at that time is calculated. Next, the process proceeds to step S3 or S4 depending on whether the front wheel section 16 is in the acceleration state or the deceleration state (step S2). When the wheel acceleration / deceleration (α) becomes substantially 0 from the deceleration state of the front wheel portion 16 (see FR1 in FIG. 4),
The wheel speed of the front wheel portion 16 becomes smaller than the vehicle speed V, and the slip ratio (λ) becomes larger. Then, this slip ratio (λ) is set to a preset maximum slip ratio (λM
AX) and if λ <λMAX (step S
3, YES), this λ is set to λMAX (step S5).

Further, the coefficient of friction (μ) of the road surface is calculated. This μ is obtained from the equation (1). μ = (K · P + I · α) / WH (1) where K: brake force per unit fluid pressure P: brake fluid pressure (caliper pressure) I: wheel inertia gravity α: wheel acceleration / deceleration WH: wheel sharing load In the present embodiment, when the wheel acceleration / deceleration (α) of the front wheel portion 16 is almost 0, that is, when I · α = 0, the above equation (1) is calculated as follows. It can be represented by an equation. μ = k · P (2) where k is a constant. Here, the brake hydraulic pressure P may be directly measured by a hydraulic pressure gauge, or may be calculated and calculated as described below. That is, the position of the expander piston 46 is detected as the crank angle via the potentiometer 38 by the deviation of the crank pin 34, and the output value of the potentiometer 38 is introduced to the motor controller 70. The output value and the terminal current value of the DC motor 24 are supplied from the motor controller 70 to the control unit 72. In the control unit 72, first, the motor torque (TM) of the DC motor 24 is calculated from the terminal current value, and further the brake fluid pressure P is calculated according to the following equations. TM = KT · (IM-IO) (3) TP = (Z · Z · JM + JC) · ω−TM + TS ± TF (4) P = 4 · TP / (π · D · e · sin θc) (5) Where, TM: Motor torque KT: Motor torque constant IM: Motor current IO: Motor no-load current TP: Caliper pressure torque Z: Reduction ratio JM: Motor inertia mass JC: Crank inertia mass ω: Crank angular acceleration TS: B / USPG torque TF: friction torque D: diameter of expander piston e: crank eccentricity θc: crank angle After the friction coefficient (μ) is calculated (step S6), if this calculation processing is the first time, The process returns to step S1 via steps S7 and S8, and if it is the second time or later, the friction coefficient (μ) is averaged (step S9).

On the other hand, if it is determined in step S2 that the wheel acceleration / deceleration (α) of the front wheel portion 16 has become substantially zero from the acceleration state (NO in step S2 and see FR2 in FIG. 4), the vehicle speed V The wheel speed of the lever portion 16 becomes as close as possible, and the slip ratio (λ) becomes small. Then, this slip ratio (λ) is compared with a preset minimum slip ratio (λMIN), and if λ> λMIN (step S4, YES), this λ is set as λMIN (step S10). Further, after the friction coefficient (μ) of the road surface is calculated, the friction coefficient (μ) is averaged so that n> 1 (steps S6 to S9).

As described above, the slip ratio (λ) at the time when the wheel acceleration / deceleration (α) of the front wheel portion 16 becomes substantially zero (FR1 to FRn) is obtained, and the slip ratio (λ) is sequentially compared. When it is determined that the slip ratio (λ) is converged with respect to the determined slip ratio (λ), each time point (FR1 through FR
The averaging process of the friction coefficient (μ) in n) is performed (see the calculated μ in FIG. 4).

Therefore, as shown in FIG. 5, when the road surface condition changes from a dry asphalt road (high μ road) to a frozen road (low μ road), the slip ratio (λ) at FR5 becomes lower than the slip ratio at FR3. Rate (λ). Therefore, NO is determined in step S3, the slip ratio (λ) is set as λMAX, the averaging process is stopped, and reset (n = 0) is performed (steps S11 and S12). And this F
The averaging process of the friction coefficient (μ) is newly started from R5. Similarly, when the slip ratio (λ) becomes smaller than the minimum slip ratio (λMIN) which is the previous slip ratio in step S4, the slip ratio (λ) is set as λMIN, and the averaging process is stopped. Then, reset (n = 0) is performed (steps S13 and S14).

In this case, in this embodiment, each time point (FR1
To FRn), the friction coefficient (μ) calculated is averaged, so that a value as close as possible to the actual friction coefficient (μ) can be obtained. By adjusting the caliper pressure of the front wheel portion 16 on the basis of this, it is possible to obtain an effect that highly accurate and optimal brake control can be performed. Moreover, by sequentially comparing the slip ratios (λ), when the condition of the road surface changes, the averaging process of the friction coefficient (μ) is stopped and a new averaging process is started. Therefore, there is no problem that the friction coefficient departs from the actual friction coefficient (μ) as in the case where the averaging process is performed irrespective of the change in the road surface state (see the broken line in FIG. 5). An approximate value can be obtained.

Although only the front wheel section 16 has been described, the rear wheel section 18 is similarly operated. At this time, the friction coefficient (μ) at each time point (RR1 to RRn in FIG. 4) is obtained, and the averaging process of each slip ratio (λ) is performed (FIG. 6, step S101 and step S10).
2). Then, the averaged μ of the front wheel portion 16 and the rear wheel portion 1
The average μ of 8 is subjected to a weighted averaging process to calculate μ of the road surface (steps S103 and S104).

Next, the calculation process of μ of a four-wheeled vehicle will be described below. 7, a four-wheeled vehicle 90 includes front wheels 92R and 92L and rear wheels 94R and 94L. Then, as shown in the flowchart of FIG. 8, the μ of the front wheel 92R, the front wheel 92L, the rear wheel 94R, and the rear wheel 94L are averaged by the μ calculation routine shown in FIG. 3, and further, the front wheel 92R and the front wheel 92R are processed. 92L and the rear wheel 94R and the rear wheel 94L are respectively weighted and averaged by the front and rear wheel weighted averaging routine shown in FIG. 6, and μR and μL are calculated (steps S201 and S202).

In step S203, it is determined whether μR and μL are close to each other, that is, whether the left and right road surfaces are high μ road and low μ road.
It is determined whether the road is not divided into a road and if it is determined that μR and μL are close to each other (step S20).
3, NO), a weighted averaging process of μR and μL is performed, and μ of the road surface is calculated (steps S204 and S205). On the other hand, when μR and μL are significantly different (step S203, YES), since the left and right road surface conditions have changed (determined as a split road), this μR
Without performing the weighted averaging process between the front wheels 92R, 92L and the rear wheels 94R, 94L based on μR and μL (step S20).
6 and step S207, see between AB in FIG. 9).
In FIG. 9, in B, μR and μL are approximated again, so that a weighted averaging process of μR and μL is performed. Here, whether to perform the weighted averaging process for μR and μL can be variously changed by setting the value of Δμ0.

[0030]

According to the brake control method of the present invention, the brake braking force when the acceleration / deceleration of the wheel is substantially zero is measured or calculated, and the friction coefficient of the road surface is calculated from the brake braking force. It is not necessary to consider the acceleration / deceleration of the wheels in the above, so that the arithmetic processing is performed simply and in a short time. Furthermore, by averaging the respective friction coefficients, a more accurate friction coefficient can be obtained, the brake control is performed with high accuracy, and when the slip rate does not converge to the previous slip rate, that is, when the road surface condition is abrupt. , The averaging process up to the previous time is reset, and a new averaging process is started from the current friction coefficient, thereby enabling a highly accurate calculation of the friction coefficient. Therefore, it is possible to immediately respond to a change in the road surface condition, and optimal brake control is performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for implementing a brake control method according to the present invention.

FIG. 2 is a schematic external view of a motorcycle incorporating the brake control device.

FIG. 3 is a flowchart of a μ calculation routine of the brake control method.

FIG. 4 is a graph showing a relationship between a wheel speed of a wheel, a hydraulic pressure, and a calculated μ.

FIG. 5 is a diagram illustrating a relationship between wheel speed, hydraulic pressure, and μ when a road surface condition changes;

FIG. 6 is a flowchart of a weighted average routine for front and rear wheels.

FIG. 7 is a schematic explanatory view of a four-wheeled vehicle.

FIG. 8 is a flowchart of a weighted averaging routine for left and right wheels.

FIG. 9 is a diagram showing the relationship between μR and μL when the road surface condition changes.

FIG. 10 is a relationship diagram between a road surface μ in a rotation direction and a slip ratio.

FIG. 11 is a relationship diagram between a road surface μ in a lateral direction and a slip ratio.

[Explanation of symbols]

 Reference Signs List 20 brake controller 22 modulator 24 DC motor 34 crank pin 38 potentiometer 40 cam bearing 46 expander piston 56 master cylinder 62 caliper cylinder 66 disk plate 70 motor controller 72 control unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-253557 (JP, A) JP-A-61-256240 (JP, A) JP-A-1-257654 (JP, A) JP-A-4-254 55156 (JP, A) JP-A-3-67770 (JP, A) JP-A-62-283050 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60T 8/58

Claims (2)

(57) [Claims] A step of obtaining a brake braking force when the acceleration / deceleration of the wheel is substantially zero; a step of calculating a friction coefficient of a road surface from the obtained braking force; When the obtained slip rate converges to the slip rate obtained last time, the averaging process including the current friction coefficient is included in the friction coefficient up to the previous time, and the acceleration / deceleration is substantially zero. A step of stopping the friction coefficient averaging process and starting a new averaging process from the current friction coefficient when the slip ratio obtained at the time does not converge with the slip ratio obtained last time. And a brake control method comprising: 2. The method according to claim 1, further comprising the steps of: calculating a friction coefficient for each wheel; and calculating a weighted average of the friction coefficient according to the number of calculations for each wheel. Brake control method.