JP3408307B2 - Method of generating pseudo vehicle body speed and anti-lock brake method using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating a pseudo vehicle body speed in an antilock brake device for a vehicle, and particularly to a method for generating a pseudo vehicle body speed in an antilock brake device which is adapted to handle low wheel speeds. Regarding anti-lock braking method.

[0002]

2. Description of the Related Art Conventionally, in an anti-lock brake device for preventing wheel lock during sudden braking of a vehicle such as an automobile, a pulse signal generated by an electromagnetic induction type pickup is used to control the wheel speed of each of the four wheels. It is obtained by calculating every predetermined cycle from the cycle and the radius of gyration of the wheel. Then, the pseudo vehicle body speed is generated based on the maximum wheel speed, the slip ratio is calculated from the pseudo vehicle body speed and the wheel speed, and the brake hydraulic pressure of the wheel cylinder is controlled based on the slip ratio (for example, (See Japanese Unexamined Patent Publication No. 64-63451).

[0003]

However, in such a conventional pseudo vehicle speed generation method in the antilock brake device, the wheel speed is obtained by using the pulse signal generated by the electromagnetic induction type pickup, and the wheel speed is calculated based on this. Since the pseudo vehicle body speed is generated, the induced voltage is low and the S /
There is a problem that the N ratio is also reduced and the accuracy is lowered.

As a result, the wheel speed obtained by the calculation and the actual wheel speed do not match, the pseudo vehicle body speed based on the wheel speed does not match the actual vehicle body speed, and is easily affected by the external magnetic field. There is a fear.

In view of the above conventional problems, an object of the present invention is to provide a method for generating a pseudo vehicle body speed that can always obtain a stable pseudo vehicle body speed regardless of the vehicle speed.

[0006]

In order to achieve the above object, a method for generating a pseudo vehicle body speed according to the present invention is such that a wheel speed is obtained at a cycle of a predetermined time and a pseudo vehicle body speed is calculated by a predetermined calculation based on the wheel speed. In the pseudo vehicle body speed generating method for generating the speed, the pseudo vehicle body speed obtained for each cycle is compared with a predetermined speed, and after the pseudo vehicle body speed becomes smaller than the predetermined speed, the pseudo vehicle body speed is A new pseudo vehicle body speed is generated by setting the vehicle body deceleration obtained in the cycle immediately before the cycle in which is less than the predetermined speed as a constant value and subtracting the constant value from the pseudo vehicle body speed obtained in the previous cycle. Is characterized by.

When the pseudo vehicle body speed is higher than the predetermined speed, the maximum wheel speed among the four wheels and the speed obtained by subtracting the vehicle body deceleration obtained in the previous cycle from the pseudo vehicle body speed obtained in the previous cycle. A new pseudo vehicle body speed can be generated by the speed whichever is larger.

[0008]

According to the present invention, after the pseudo vehicle body speed becomes lower than the predetermined speed, a new vehicle body deceleration obtained in the immediately preceding cycle and a pseudo vehicle body speed obtained in the previous cycle are newly added. A pseudo vehicle body speed is generated.

Therefore, once the speed becomes smaller than the predetermined speed, the new pseudo vehicle body speed is generated independently of the wheel speed, so that the pseudo vehicle body speed is stable without being influenced by the external magnetic field or the like. The vehicle speed can be obtained.

In addition to the above operation, when the speed is greater than the predetermined speed, the maximum wheel speed of the four wheels and the speed obtained by subtracting the vehicle body deceleration obtained in the previous cycle from the pseudo vehicle body speed obtained in the previous cycle. Any higher speed will generate a new pseudo-body speed.

Therefore, even if it becomes difficult to obtain the speed due to the locking of the wheels due to the sudden change of the road surface friction coefficient μ, the pseudo vehicle body speed can be obtained.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In FIG. 1, wheel speed sensors 12 and 16 that generate wheel speed pulses in accordance with the rotations of the right front wheel 10 and the left front wheel 14, which are the steered wheels, respectively, and the right rear wheel 20 and the left rear wheel, which are the driving wheels. Wheel speed sensors 24 and 26, which generate wheel speed pulses in accordance with the rotation of the wheel 22, are provided, and each sensor composed of these electromagnetic induction type pickups is a control unit (hereinafter referred to as ECU) including a microcomputer as well known. 4)
It is connected to 0.

Further, as shown in FIG. 2, a wheel cylinder 50 arranged on each wheel and a master cylinder 52 for generating a brake fluid pressure when a driver depresses a brake pedal are provided in a main fluid passage 54. The wheel cylinders 5 are connected to each other in the middle of the main liquid passage 54.
Actuator units 60 for switching and controlling the brake fluid pressure of 0 are respectively provided.

In the actuator unit 60, a switching control valve 62 for controlling the increase / decrease in the hydraulic pressure of the wheel cylinder 50, a reservoir 64 for storing the brake fluid when the wheel cylinder 50 is depressurized, and a reservoir 64 in the reservoir 64. And a pump 66 for returning the stored brake fluid to the main fluid passage 54.

The operation of this embodiment having the above configuration will be described below.

In the ECU 40, as shown in the control flow chart of FIG. 3, first, after initialization, in step S1, each wheel speed sensor 12, 16, 24 ,.
Right front wheel 10, left front wheel 14, right rear wheel 2 according to the output of 26.
0 and each wheel speed of the left rear wheel 22 (V _W FR, V _W F
L, V _W RR, V _W RL) and each wheel acceleration / deceleration are calculated. Next, in step S2, the maximum wheel speed max (V _W FR, V _W FL, V _W R among the wheel speeds is calculated.
R, V _W RL) is selected, and the pseudo vehicle body speed V _{i (n)} is calculated based on this maximum wheel speed.

Details of the steps for obtaining the pseudo vehicle body speed V _{i (n)} and the vehicle deceleration ΔV _{i (n)} will be further described with reference to FIG. 4 showing the subroutine.

In FIG. 4, V _i LO means a low speed range judgment flag, and the pseudo vehicle body speed is a predetermined value (for example, 10 km /
h) Below is programmed to be on. Further, in this flowchart, the subscript (n) means the value obtained in the current execution cycle, and the (n-1) means the value obtained in the previous execution cycle.

In the subroutine of step S2, the pseudo vehicle body speed V _{i (n-1)} obtained in the previous execution cycle in step S21 is a predetermined speed (for example, 10 km described above _).
/ H) is larger than that, and if larger, the process proceeds to step S23 to turn off the low speed region determination flag V _i LO. If it is smaller, the process proceeds to step S22 and the flag V
_The iLO is turned on and the process proceeds to step S24. And
In this step S24 after steps S22 and S23, it is determined whether the low speed region determination flag V _i LO is on or off, and when it is off, that is, the pseudo vehicle body velocity V _{i (n-1) in} the previous cycle is When the speed is equal to or higher than the predetermined speed (steps S21 and S23), the process proceeds to step S25.

Here, the pseudo vehicle body speed V in this cycle
_{i (n)} is calculated by the following equation.

[0022]

## EQU1 ## V _{i (n)} = max {V _{i (n-1)} −ΔV _{i (n-1)} , max (V _W FR, V _W FL, V _W RR, V _W RL)} where ΔV _{i (n-1)} is the vehicle body deceleration obtained in the previous cycle as described later, and the pseudo vehicle body speed V _{i (n) in} this cycle is the maximum wheel speed max (V _W FR, V _W FL, V _W RR, V _W RL),
Alternatively, it is calculated as the larger speed of the speeds obtained by subtracting the vehicle body deceleration ΔV _{i (n-1)} obtained in the previous cycle from the pseudo vehicle body speed V _{i (n-1)} obtained in the previous cycle.

In this way, the determination by the larger one of the speeds is performed, for example, when the friction coefficient (μ) of the road surface suddenly changes from high μ to low μ during braking and all the wheels tend to lock. This is effective because it is difficult to obtain the wheel speed.

Next, in step S26, the pseudo vehicle body speed V _{i (n)} of the current cycle obtained in step S25 is subtracted from the pseudo vehicle body speed V _{i (n-1)} of the previous cycle to obtain the current cycle. The vehicle deceleration ΔV _{i (n)} is obtained, and this is set as the estimated vehicle body deceleration ΔV in step S27.

On the other hand, in the judgment at step S24,
If the low speed region determination flag V _i LO is on, the process proceeds to step S28. Then, in this step S28, the pseudo vehicle body speed V _{i (n) of} this cycle is obtained by the following equation.

[0026]

## EQU00002 ## _{V.sub.i (n)} = V.sub.i _(n-1)-. DELTA.V where .DELTA.V is the estimated vehicle deceleration set in step S27.

As described above, when the pseudo vehicle body speed enters the low speed below the predetermined speed, the pseudo vehicle body speed V obtained in the previous cycle.
_{i (n-1)} and estimated vehicle body deceleration ΔV immediately before entering the low speed range
The pseudo vehicle body speed V _{i (n)} of this cycle is obtained from the difference between That is, the control routine for the pseudo vehicle body speed is 5 ms.
Each time it is executed, it is updated based on the pseudo vehicle body speed of the previous cycle and the estimated vehicle body deceleration of the straight line that enters the low speed range.

After the pseudo vehicle body speed calculation processing in step S2, the process proceeds to step S3, and the slip ratio of each wheel is calculated from the pseudo vehicle body speed obtained in step S2 and each wheel speed obtained in step S1. . Then, the process proceeds to step S4, and the pressure reduction threshold value for starting the pressure reduction of the brake hydraulic pressure of the wheel cylinder is set to, for example, 15% of the wheel slip ratio (85% at the pseudo vehicle body speed).

Further, in step S5, step S
The wheel step rate obtained in 3 is compared with the pressure reduction threshold value set in step S4. Here, when the slip ratio is larger than the pressure reducing threshold value, the process proceeds to step S7, and the brake fluid pressure reducing control is performed. That is, a switching signal is sent from the ECU 40 to the switching control valve 62 of the actuator unit 60, the master cylinder 52 and the wheel cylinder 50 of the rear wheel are cut off, and the wheel cylinder 5
0 and the reservoir 64 are communicated with each other.

When the wheel slip ratio is smaller than the pressure reduction threshold value in step S5, the process proceeds to step S6, where it is determined whether the wheel acceleration / deceleration obtained in step S1 is larger than a predetermined holding level. If it is higher than the predetermined holding level, the hydraulic pressure in the wheel cylinder 50 is likely to be insufficient, so the routine proceeds to step S8, where the brake hydraulic pressure increase control is performed. In this case, the switching control valve 62 of the actuator unit 60 is driven so that the master cylinder 52 and the wheel cylinder 50 are in communication with each other.

On the contrary, when the wheel acceleration / deceleration is smaller than the predetermined holding level in step S6, step S9
Then, the brake fluid pressure holding control is performed. In this case, the switching control valve 62 is driven to a position where the wheel cylinder 50 blocks the communication with the master cylinder 52 and the reservoir 64, respectively.

Thus, after the control in any of steps S7, S8 or S9 is performed, the process proceeds to step S10,
Here, the time is adjusted for 5 ms and the process returns to step S1. In other words, the above-mentioned cycle is executed every 5 ms as described above.

The state of the above control will be further described with reference to the characteristic diagram shown in FIG.

In FIG. 5, V _W is the wheel speed, of which V _wt indicated by the alternate long and short dash line indicates the case where the wheel speed sensor is performing the detection operation as usual, and V _wp is, for example, a frequency of 50 to 60 Hz. If a change in the external magnetic field is detected by the wheel speed sensor as a disturbance, then V _wa also represents the actual speed of the wheel at which this disturbance is detected.

As can be seen from this characteristic diagram, when the wheel speed sensor detects a disturbance of the above frequency, the ECU 40 _causes V _wp2 even though the actual wheel speed V _wa is zero.
The wheels are rotating at the speed of V _wp2 , and the pseudo vehicle body speed V _i is generated based on the speed of V _wp2 . In this case, the wheel in normal operation is considered to have a large slip ratio and the pressure reduction control is performed, and the wheel in which disturbance is being detected is considered to have a slip ratio of 0. Therefore, the pressure increase control is performed, so that the wheel behavior and The braking feeling may be deteriorated.

On the other hand, according to the embodiment of the present invention, the pseudo vehicle body speed V _i is the point P at the predetermined speed (for example, 10 km / h).
In a smaller area, the estimated vehicle body deceleration ΔV immediately before entering this area is used to estimate the pseudo vehicle body speed V _i after that, and since it does not depend on the wheel speed sensor, it is not affected by disturbance even if disturbance occurs and is stable. Control becomes possible.

In the above embodiment, after the pseudo vehicle body speed is generated, the brake fluid pressure is controlled based on the slip ratio of each wheel. However, the pseudo vehicle body speed is 10 km / h.
In the extremely low speed range such as below, without being based on the slip ratio,
If it is determined that the pseudo vehicle body speed is lower than the predetermined speed, the brake fluid pressure reduction inhibition control may be immediately performed, or the pressure increase control may be performed. This simplifies the control.

[0038]

As is apparent from the above description, according to the present invention, the detected wheel speed is affected by the disturbance in the extremely low speed region where the S / N ratio of the wheel speed detector is lowered. In addition, a stable pseudo vehicle body speed can be obtained regardless of the vehicle speed, and stable control is possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a system of an antilock brake device in which the present invention is implemented.

FIG. 2 is a configuration diagram showing a brake hydraulic circuit in which the present invention is implemented.

FIG. 3 is a flowchart showing an example of a control procedure of this embodiment.

FIG. 4 is a flowchart showing an example of a control procedure of this embodiment.

FIG. 5 is a characteristic diagram illustrating a control state of the present invention.

[Explanation of symbols]

10,14,20,22 wheels 12, 16, 24, 26 Wheel speed sensor 40 control unit 50 wheel cylinder 62 switching control valve

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Claims (3)

(57) [Claims] 1. A method for generating a pseudo vehicle body speed in which a wheel speed is obtained in a cycle for every predetermined time, and a pseudo vehicle body speed is generated by a predetermined calculation based on the wheel speed, wherein the pseudo vehicle body speed is obtained in each cycle. After the vehicle body speed and the predetermined speed are compared and the pseudo vehicle body speed becomes lower than the predetermined speed, the pseudo vehicle body speed becomes smaller than the predetermined speed.
The body deceleration obtained in the cycle immediately before the vehicle is set to a constant value.
Then, from the pseudo vehicle speed obtained in the previous cycle, the above constant
A method for generating a pseudo vehicle body speed, which is characterized in that a new pseudo vehicle body speed is generated by reducing the value . 2. When the pseudo vehicle body speed is higher than the predetermined speed, the maximum wheel speed of the four wheels and a speed obtained by subtracting the vehicle body deceleration obtained in the previous cycle from the pseudo vehicle body speed obtained in the previous cycle. The pseudo vehicle body speed generation method according to claim 1, wherein a new pseudo vehicle body speed is generated by any one of the larger speeds. 3. When the pseudo vehicle body speed generated by the method according to claim 1 or 2 is smaller than a predetermined speed,
An antilock braking method characterized by performing a pressure reduction inhibition control or a pressure increase control of a brake fluid pressure.