JP2990438B2 - Vehicle anti-lock control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an antilock control method for preventing a wheel from being locked when a brake of a traveling vehicle is operated.

(Prior Art) In general, an anti-lock control device for a vehicle represents a wheel speed (rotation speed) detected by a wheel speed sensor for the purpose of ensuring the steerability and running stability of the vehicle during braking and shortening the braking distance. The control mode of the brake fluid pressure is determined based on the electric signal, and the hold valve composed of the normally-open solenoid valve and the decay valve composed of the normally-closed solenoid valve are opened / closed, thereby pressurizing, holding or holding the brake fluid pressure. The pressure is reduced by a control unit including a microcomputer.

FIG. 6 is a block diagram showing a conventional three-system (three-channel) antilock control device for performing such antilock control. The outputs of the wheel speed sensors 1 to 4 are sent to arithmetic circuits 5 to 8. Wheel speeds Vw1 to Vw4
Are obtained. And left front wheel speed
Vw1 and the right front wheel speed Vw2 are sent to the first and second control logic circuits 9 and 10 as the first system speed Vs1 and the second system speed Vs2, respectively, while the left rear wheel speed Vw3
The low-speed wheel speed of the right rear wheel speed Vw4 is selected by the low select circuit 11 and sent to the third control logic circuit 12 as the third system speed Vs3.

Signals representing the wheel speeds Vw1 to Vw4 are sent to a pseudo vehicle speed calculating circuit 13 including a high select circuit 14 and a filter circuit 15. The arithmetic circuit 13 selects the highest wheel speed VwH among the four wheel speeds Vw1 to Vw4 by the high select circuit 14 (four wheel select high), and the filter circuit 15 selects the highest wheel speed VwH. Each control logic circuit 9, 10, 10
Output to 12. In each of the control logic circuits 9, 10, and 12, the system speeds Vs1 to Vs3 are respectively set as control target wheel speeds (hereinafter, referred to as system speeds “Vs”) of the respective channels, and the system speed Vs and the pseudo vehicle speed Vv are referred to as the system speeds. ON / OFF control of the hold valve HV and the decay valve DV is performed as a reference.

By the way, in the antilock control method as described above, the pseudo vehicle speed Vv occupies an important factor as a reference speed of the antilock control. For example, when the vehicle is braked, the four wheel speeds Vw1 to Vw4 are simultaneously controlled. If the vehicle speed falls, the pseudo vehicle speed Vv calculated based on the highest wheel speed VwH of these four wheel speeds also falls as shown in FIG.
The difference between Vv and the actual vehicle speed increases. Therefore, when control is performed based on the pseudo vehicle speed Vv, there is a problem that stable control becomes impossible.

(Object of the Invention) Accordingly, the present invention provides an anti-lock control method capable of preventing the simulated vehicle speed Vv from deviating from the actual vehicle speed by performing simultaneous control of the four wheel speeds and performing stable control. Aim.

(Constitution of the Invention) In the present invention, the following limit of the pseudo vehicle speed Vv is defined as the difference between the pseudo vehicle speed Vv and the highest wheel speed VwH of the four wheels, the acceleration of the highest wheel speed VwH, A map representing the relationship with the deceleration is prepared. The scale of this map is changed according to the magnitude of the friction coefficient of the road surface. Then, by reading the map, the following limit is calculated each time so that the difference between the pseudo vehicle speed Vv and the actual vehicle speed is reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a three-channel antilock control device to which the antilock control method according to the present invention is applied. Most of the configuration in FIG. 1 is common to the configuration in FIG. 6 described above, and thus the same reference numerals are given to the common portions, and redundant description will be omitted.

In the configuration shown in FIG.
A high select circuit 14 selects the highest wheel speed VwH among the four wheel speeds Vw1 to Vw4 (four wheel select high), and a variable deceleration-side following limit for the four wheel select high speed VwH. A variable filter circuit 16 for limiting the range of deceleration. In addition, the above high select circuit
A differentiation circuit 17 for calculating the acceleration / deceleration dVwH / dt of the four-wheel select high speed VwH obtained from 14, a subtraction circuit 18,
A road surface μ determination circuit 19 and a map reading circuit 20 are provided. The subtraction circuit 18 is a circuit for calculating a difference E (= Vv−VwH) between the pseudo vehicle speed Vv and the four-wheel select high speed VwH, and the road surface μ determination circuit 19 is for determining the magnitude of the deceleration gradient of the pseudo vehicle speed Vv. This is a circuit for determining a friction coefficient μ (hereinafter referred to as a road surface μ) of a traveling road surface based on the above. Further, as shown in FIG. 2, the map reading circuit 20 calculates the difference between the acceleration / deceleration dVwH / dt obtained from the differentiating circuit 17 and the speed difference E (= Vv−VwH) obtained from the subtracting circuit 18. This is a circuit for reading out the following limit from a map representing the following limit on the deceleration side of the pseudo vehicle speed Vv. When reading the map, based on the determination result of the road surface μ provided from the road surface μ determination circuit 19, one of the low μ road and the high μ road shown in FIGS. 3 (A) and 3 (B) is used. Set the scale of the map. The tracking limit of the pseudo vehicle speed Vv obtained by the map reading circuit 20 is output to the filter circuit 16 again to calculate the tracking limit of the pseudo vehicle speed Vv.

Next, FIG. 2 is a map prepared for determining the following limit of the above-described pseudo vehicle speed Vv. In this map, the speed difference E between the pseudo vehicle speed Vv and the four-wheel select high speed VwH is represented by a horizontal axis. The axis is the acceleration of the four-wheel select high speed VwH.
The deceleration dVwH / dt is set on the vertical axis. In the map, the scale of the horizontal axis and the vertical axis is changed according to the determination result output from the road μ determination circuit 19. That is, when it is determined that the traveling road surface is a low μ road, the scale for a low μ road shown in FIG. 3A is set, and when it is determined that the traveling road surface is a high μ road, FIG. The scale for the high μ road shown in (B) is set. However, the relationship between the coefficients a and b representing the magnifications of the scales respectively attached to the horizontal axis and the vertical axis of both scales shown in FIGS. 3A and 3B is a <b. When determining the road surface μ in the road surface μ determination circuit 19, for example, a method of determining the road surface μ based on the magnitude of the deceleration gradient of the pseudo vehicle speed Vv, which is known per se, may be employed.

FIG. 4 is a flowchart showing a method of setting the following limit. First, in step S1, the differentiation circuit
In step 17, the acceleration / deceleration dVwH / dt of the four-wheel select high speed is calculated, and in the next step S2, the speed difference E between the pseudo vehicle speed Vv and the four-wheel select high speed VwH is calculated in the subtraction circuit 18. In the next step S3, the road surface μ determination circuit 19 determines the road surface μ of the traveling road. That is, it is determined whether or not the road is a low μ road. If the determination result is “YES”, the scale of the low μ road shown in FIG. 3A is set as the scale of the map in step S4. . When the result of the determination in step S3 is "NO", the scale for the high μ road shown in FIG. 3 (B) is set in step S5. In the next step S6, one of the scales for the low μ road and the high μ road set in step S4 or S5 is applied to the map shown in FIG. The following limit of the vehicle speed Vv is read. And
The following limit of the variable filter circuit 16 is calculated according to the read value, whereby the pseudo vehicle speed Vv is represented by a broken line as shown in FIG. That is, the fifth
At point a in the figure, there is no speed difference between the four-wheel select high speed VwH and the pseudo vehicle body speed Vv, and the acceleration / deceleration dVwH / dt of the speed VwH is small. Therefore, the following limit read from the map of FIG. This is a large value. At a point b after a predetermined period elapses from the point a, a speed difference is generated between the speed VwH and the speed Vv, and the deceleration dVwH / dt of the speed VwH is large, so that the following limit is the value set at the point a. A smaller value is read. Thereafter, this reading operation is repeated in order at points c, d, e,... Every predetermined period, and the following limit of the pseudo vehicle speed Vv is calculated each time so that the difference between the pseudo vehicle speed Vv and the actual vehicle speed becomes small. And set.

(Effects of the Invention) As is apparent from the above description, in the present invention, a map representing the following limit of the pseudo vehicle body speed Vv is prepared, and the following limit is changed by reading this map.
Even when the four wheels are simultaneously locked, the difference between the actual vehicle speed and the pseudo vehicle speed Vv can be reduced, thereby stabilizing the control.

Further, in the present invention, when reading the map, the scale of the map is changed according to the change of the road surface μ, so that all road surface conditions from the low μ road to the high μ road are on the same map. The following limit of the simulated vehicle speed Vv adapted to the following can be read and set. Therefore, even when the road surface condition changes, more stable and highly reliable control can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a three-system anti-lock control device to which the present invention is applied, FIG. 2 is a map showing a follow-up limit of a pseudo vehicle speed, and FIGS. 3 (A) and (B) are scales used for the map. FIG. 4 is a flowchart showing a method of setting a tracking limit, FIG. 5 is a timing chart showing the operation of the present invention, and FIG. 6 is a three-channel applied to the implementation of a conventional antilock control method. FIG. 7 is a block diagram showing an antilock control device, and FIG. 7 is a diagram showing a pseudo vehicle speed in a conventional method. 1-4 wheel speed sensors 5-8 arithmetic circuits 9, 10, 12 control logic circuits 11 low select circuits 13 pseudo body speed arithmetic circuits 14 high select circuits 15, 16 Filter circuit 17 Differentiator circuit 18 Subtraction circuit 19 Road surface μ judgment circuit 20 Map readout circuit

Continuation of the front page (56) References JP-A-55-31688 (JP, A) JP-A-60-45456 (JP, A) JP-A-63-68454 (JP, A) JP-A-61-229658 (JP) JP-A-3-96466 (JP, A) JP-A-63-269664 (JP, A) JP-A-1-218956 (JP, A) JP-A-1-275253 (JP, A) 1-204856 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60T 8/32-8/66

Claims (1)

(57) [Claims] At the time of braking, the highest wheel speed VwH among the four wheel speeds is selected, and when the deceleration of the highest wheel speed VwH is less than a predetermined value, the highest wheel speed VwH is simulated. When the deceleration of the highest wheel speed VwH exceeds a predetermined value, the pseudo vehicle speed Vv at that time is set as an initial value, and the pseudo vehicle speed Vv is decreased at the predetermined deceleration. In the anti-lock control method for controlling the brake pressure by comparing the simulated vehicle speed Vv with each wheel speed, the difference between the simulated vehicle speed Vv and the fastest wheel speed VwH, and the deceleration of the fastest wheel speed VwH And determining the deceleration of the predetermined value based on the determined road friction coefficient.