JPH06107157A - Automatic braking device - Google Patents

Abstract

PURPOSE:To provide an automatic braking device that is able to eliminate any deviation in output between two sensors and to promote the shortening of a braking distance by way of compensating the other side output with either of the wheel-car speed sensor output or the ground speed sensor output. CONSTITUTION:An error between output out of a wheel-car speed sensor 1 and that out of an optical car speed sensor 4 is calculated as a compensation factor by a compensation factor calculating part 6, and at the time of braking a vehicle, it is compensated on the basis of this compensation factor, thereby calculating each slip factor of wheels. If so, such an optimum slip factor that a braking effect is raised can be found out in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic braking device for a vehicle equipped with a ground speed sensor, and more particularly to a technique for improving braking accuracy in an antilock braking system.

[0002]

2. Description of the Related Art Antilock brake system (AB
S) is a system that automatically controls the brake pressure so as to maximize the frictional force between the wheel and the road surface in order to minimize the braking distance. As is well known, since the frictional force between the wheel and the road surface depends on the slip ratio [(vehicle body speed-wheel vehicle speed) / vehicle body speed], the slip ratio should be controlled with high accuracy so that the frictional force becomes maximum. Is essential for ABS.

However, in the conventional ABS, since the ground speed required for calculating the slip ratio is an estimated value which is pseudo-calculated from the wheel vehicle speed, the slip ratio calculation error is large. That is, in the conventional ABS, as shown in FIG. 5, the detection signal from the wheel vehicle speed sensor 1 is sent to the ECU (El).
When the electronic control unit 2 is received and the brake is depressed, the switch S4 is closed and E
The CU 2 automatically controls the brake hydraulic system 3,
The ground speed required to calculate the slip ratio for operating as the anti-lock brake system has been pseudo-calculated from the wheel vehicle speed inside the ECU 2. In order to solve the above control accuracy problem, an attempt is made to measure the accurate ground speed using a ground speed sensor and calculate the slip ratio from this ground speed and the wheel car speed to control the brake hydraulic system. Preprints 91219
91-10 P3.173-3.176).

[0004]

However, even in the above system, if there is a deviation between the wheel vehicle speed sensor output and the ground speed sensor output, an accurate slip ratio cannot be calculated. Even if this deviation does not exist in the initial state, the wheel vehicle speed is calculated from the wheel rotation speed, so if tire wear or replacement occurs, the detected wheel vehicle speed will change, so the deviation Occurs, and an accurate slip ratio cannot be calculated.

The present invention is to solve the above-mentioned problems, and of the wheel vehicle speed sensor output and the ground speed sensor output,
An object of the present invention is to provide an automatic braking device capable of shortening the braking distance by correcting the output of one of the outputs to eliminate the deviation between the outputs of both sensors, enabling accurate calculation of the slip ratio. To do.

[0006]

In order to achieve the above object, the invention according to claim 1 calculates the slip ratio of a wheel during braking of a vehicle and automatically controls a brake system based on the slip ratio. In the device, a wheel vehicle speed sensor that detects the vehicle speed from the wheel rotation speed, an optical vehicle speed sensor that detects the vehicle speed by receiving light from the road surface, and a wheel vehicle that is detected by the wheel vehicle speed sensor. Correction means for calculating an error between the speed and the optical vehicle speed detected by the optical vehicle speed sensor before the brake is depressed as a correction coefficient, and at the time of braking the vehicle, the wheel vehicle speed, the optical vehicle speed and the correction The slip ratio of the wheel is calculated from the correction coefficient calculated by the means, and the brake system is controlled based on the slip ratio.

According to a second aspect of the present invention, the correction means comprises:
Error calculating means for calculating an error between the wheel vehicle speed detected by the wheel vehicle speed sensor and the optical vehicle speed detected by the optical vehicle speed sensor, and a storage means for storing the value calculated by the error calculating means as a correction coefficient. It is composed of and.

According to a third aspect of the present invention, the slip rate of the wheels is calculated when the vehicle is being braked, and the automatic braking device that automatically controls the brake system based on the slip rate detects the speed of the vehicle from the rotational speed of the wheels. Wheel vehicle speed sensor, an optical vehicle speed sensor for detecting the vehicle speed by receiving light from the road surface, a wheel vehicle speed detected by the wheel vehicle speed sensor, and an optical vehicle detected by the optical vehicle speed sensor A correction means for correcting the optical vehicle speed by sampling an error from the speed, and at the time of braking of the vehicle, the slip ratio of the wheel is calculated from the wheel vehicle speed and the corrected optical vehicle speed, and the slip ratio is calculated. The brake system is controlled based on.

According to a fourth aspect of the present invention, in the above, a steering angle sensor for detecting a steering angle of the vehicle is provided, and when the steering angle of the vehicle detected by the steering angle sensor is out of a predetermined range, the wheels are wheeled. The error between the vehicle speed and the optical vehicle speed is not stored or sampled. The invention according to claim 5 is provided with a brake sensor for detecting whether or not the brake is stepped on in the above, and when the brake sensor detects that the brake is stepped on, the wheel vehicle speed and the optical vehicle are detected. It does not store or sample the error from the speed.

[0010]

According to the present invention, the error between the wheel vehicle speed and the optical vehicle speed is calculated as a correction coefficient by the correction means, and when the vehicle is braked, the wheel vehicle speed or Since the slip ratio of the wheel is calculated by correcting the optical vehicle speed, the optimum slip ratio for braking can be obtained, and by controlling the brake hydraulic system based on this, the slip ratio between the wheel and the road surface can be controlled. The frictional force can be maximized. According to the structure of claim 3, the error between the wheel vehicle speed and the optical vehicle speed is sampled, and the optical vehicle speed is corrected by the correction means. Therefore, the wheel vehicle speed sensor output and the optical vehicle speed sensor output are obtained. Since and match, the reliability of each sensor output becomes high. According to the configuration of claim 4, when the steering angle of the vehicle is out of the predetermined range, a large error is included in the output of the optical vehicle speed sensor, and therefore, this is not stored or sampled. According to the fifth aspect of the present invention, when the brake pedal is depressed, the output of the optical vehicle speed sensor contains a large error, and therefore this is not stored or sampled.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment embodying the present invention will now be described with reference to FIG.
Will be described with reference to. FIG. 1A shows a normal traveling state,
(B) shows a braking state, and (c) shows an abnormal running state when the steering wheel is turned such as when turning. The normal running state means a state in which the driver is not stepping on the brake and the steering angle of the steering wheel is near 0. This means that the brake sensor (not shown) attached to the brake and the steering wheel or the front wheel shaft are attached. It is determined by the attached steering angle sensor (not shown). The braking state means a state in which the driver is stepping on the brake, and this is determined by a brake sensor (not shown) attached to the brake. The non-normal traveling state means a state in which the steering angle of the steering wheel is not near 0, such as when turning, and this is determined by a steering angle sensor (not shown) attached to the steering wheel or the front wheel shaft.

The present automatic braking system includes a wheel vehicle speed sensor 1 for detecting the vehicle speed from the wheel rotation speed, and an optical vehicle speed sensor for detecting the vehicle speed by receiving light from the road surface which is a ground speed sensor. 4, a correction device 5 that corrects the output of the optical vehicle speed sensor 4, an ECU 2 that calculates the slip ratio of the wheels and controls the brake hydraulic system 3.
It is composed of a brake hydraulic system 3 for braking. The correction device 5 includes a correction coefficient calculation unit 6 that calculates a correction coefficient from the detected speed data, and a storage device 7 that stores the calculation result. The switch S1 is provided in a line that sends a signal from the wheel vehicle speed sensor 1 to the correction coefficient calculation unit 6, the switch S2 is provided in a line that sends a signal from the correction coefficient calculation unit 6 to the storage device 7, and the switch S3 is stored. The switch S4 is provided on a line for transmitting a signal from the device 7 to the correction coefficient calculation unit 6, and is provided between the ECU 2 and the brake hydraulic system 3 to turn the brake O on.
It is opened / closed by N / OFF and steering angle.

In the normal traveling state, as shown in FIG. 1 (a), the switches S1 and S2 are turned on and the wheel vehicle speed sensor 1
And the output from the optical vehicle speed sensor 4 are input to the correction device 5. Correction coefficient calculation unit 6 in the correction device 5
Sequentially calculates an offset error and a gain error of the optical vehicle speed with respect to the wheel vehicle speed as a correction coefficient, and stores the calculated correction coefficient in the storage device 7. In ECU2,
The wheel vehicle speed sensor output and the correction output of the optical vehicle speed sensor (both values are equal) are input, but since the brake is not depressed and the switch S4 is OFF, the control command value from the ECU 2 to the brake hydraulic system 3 is input. Is not output and the braking operation of the wheels is not performed.

In the braking state, as shown in FIG.
Switches S1 and S2 are turned off, and switches S3 and S4
Is turned on. Therefore, only the output from the optical vehicle speed sensor 4 is input to the correction device 5. This correction device 5
In the correction coefficient calculation unit 6 therein, the correction coefficient at the moment when the brake is depressed is read from the storage device 7, and the output of the optical vehicle speed sensor is corrected by this correction coefficient. The vehicle speed sensor output and the correction output of the optical vehicle speed sensor are input to the ECU 2, and the ECU 2 calculates the slip ratio from the two outputs. At this time, since the switch S4 is ON, the ECU 2 sends the brake hydraulic system 3
A control command value is output based on the calculated slip ratio, and an appropriate wheel braking operation is performed. For example, when the slip ratio is smaller than the optimum value (generally around 0.2), the ECU 2 outputs a command value for increasing the brake oil pressure.

In the non-normal traveling state, as shown in FIG. 1 (c), all the switches S1, S2, S3 and S4 are turned off. The correction coefficient is not calculated because the output from the wheel vehicle speed sensor 1 generally includes a large error in an abnormal traveling state. Therefore, the correction coefficient having low reliability is not stored in the storage device 7.

Next, a modification of the above embodiment will be described. 2A shows a normal traveling state, FIG. 2B shows a braking state, and FIG. 2C shows an abnormal traveling state. In FIG. 2, as compared with the above-described embodiment, only the object of correction is changed from the optical vehicle speed of the optical vehicle speed sensor 4 to the wheel vehicle speed of the wheel vehicle speed sensor 1, and other operations, actions and effects are obtained in the above embodiment. Is the same as. Further, in the above embodiment, the correction device 5 is provided separately from the sensors 1, 4 and the ECU 2, but FIG.
As shown in, the function of the correction device 5 may be incorporated in the ECU 2. Also in this case, the operation, action, and effect are similar to those of the above-described embodiment.

Next, a second embodiment will be described with reference to FIG. In the present embodiment, the function of the correction device 5 is incorporated as hardware inside the optical vehicle speed sensor 14. The optical vehicle speed sensor 14 includes an optical vehicle speed detector 24 that detects the speed of the vehicle by receiving light from the road surface, a divider 25 that calculates a correction coefficient, and a sample hold circuit (S / H) 26. And a multiplier 27. In addition, the switch S5 is the divider 25 to S.
It is provided on the line that sends a signal to / H26. In the normal traveling state, the divider 25 divides the optical vehicle speed sensor output and the wheel vehicle speed sensor output, and the switch S5 turns off.
Since the result is N, the division result is sampled as a correction coefficient in S / H 26, and the optical vehicle speed sensor output is corrected by multiplying the optical vehicle speed sensor output by the multiplier 27. The switch S5 is turned off at the moment when the brake is depressed to enter the braking state, and the correction coefficient is held (stored). Therefore, in the braking state, after the correction is performed using the held correction coefficient. Output from the optical vehicle speed sensor 14 to EC
It is output to U2. Since the optical vehicle speed is corrected as described above, the optical vehicle speed has a small error.

[0018]

As described above, according to the inventions of claims 1 and 2, even if there is a deviation between the output of the wheel vehicle speed sensor and the output of the optical vehicle speed sensor, the optimum slip ratio is calculated by applying the correction. it can. Therefore, by controlling the brake hydraulic system based on this slip ratio, the frictional force between the wheel and the road surface can be maximized, the braking distance can be shortened, and the performance of the antilock brake system is improved. According to the invention of claim 3, in addition to the same effect as described above, since the error is sampled and the optical vehicle speed is corrected, the wheel vehicle speed and the optical vehicle speed match each other. The output is stable and reliable. According to the inventions of claims 4 and 5, when the steering angle of the vehicle is out of a predetermined range or when the brake is depressed, there is a large error in the optical vehicle speed detected by the optical vehicle speed sensor. Since it is included, the error between the wheel vehicle speed and the optical vehicle speed is not stored or sampled. Therefore, it is possible to prevent the braking operation using the value including the error.

[Brief description of drawings]

FIG. 1 is a block diagram showing an automatic control system according to a first embodiment of the present invention, where (a) shows a normal running state, (b) shows a braking state, and (c) shows an abnormal running state.

FIG. 2 is a block diagram showing an automatic control system according to a modification, in which (a) is a normal traveling state, (b) is a braking state,
(C) shows an abnormal driving state.

FIG. 3 is a block diagram showing still another modified example.

FIG. 4 is a block diagram showing an automatic control system according to a second embodiment.

FIG. 5 is a block diagram showing an automatic control system according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wheel vehicle speed sensor 2 ECU 3 Brake hydraulic system 4,14 Optical vehicle speed sensor 5 Correction device 6 Correction coefficient calculation unit 7 Memory device 24 Optical vehicle speed detection unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Nakamura 10 Odoron-cho, Hanazono Todo-cho, Ukyo-ku, Kyoto-shi, Kyoto Prefecture

Claims (5)

[Claims] 1. An automatic braking device for calculating a slip ratio of wheels during braking of a vehicle and automatically controlling a brake system based on the slip ratio, a wheel vehicle speed sensor for detecting a vehicle speed from a rotational speed of the wheels, An optical vehicle speed sensor that detects the speed of the vehicle by receiving light from the road surface, and a brake applied between the wheel vehicle speed detected by the wheel vehicle speed sensor and the optical vehicle speed detected by the optical vehicle speed sensor are applied. And a correction means for calculating the error before correction as a correction coefficient, and when the vehicle is being braked, the slip ratio of the wheel is calculated from the wheel vehicle speed, the optical vehicle speed, and the correction coefficient calculated by the correction means. An automatic braking device characterized in that the brake system is controlled based on the above. 2. The correcting means calculates an error between the wheel vehicle speed detected by the wheel vehicle speed sensor and the optical vehicle speed detected by the optical vehicle speed sensor, and the error calculating means. The automatic braking device according to claim 1, further comprising: a storage unit that stores the value as a correction coefficient. 3. A wheel vehicle speed sensor for detecting the speed of the vehicle from the rotational speed of the wheel in an automatic braking device for calculating the slip ratio of the wheel during braking of the vehicle and automatically controlling the brake system based on the slip ratio. An optical vehicle speed sensor that detects the speed of the vehicle by receiving light from the road surface, and a sampling of the error between the wheel vehicle speed detected by the wheel vehicle speed sensor and the optical vehicle speed detected by the optical vehicle speed sensor However, a correction means for correcting the optical vehicle speed is provided, and at the time of braking of the vehicle, the slip ratio of the wheel is calculated from the wheel vehicle speed and the corrected optical vehicle speed, and the brake system is calculated based on the slip ratio. An automatic braking device characterized by being controlled. 4. A steering angle sensor for detecting a steering angle of a vehicle is provided, and when the steering angle of the vehicle detected by the steering angle sensor is out of a predetermined range, an error between a wheel vehicle speed and an optical vehicle speed is produced. The automatic braking device according to claim 2 or 3, wherein the automatic braking device is not stored or sampled. 5. A brake sensor for detecting whether or not a brake is depressed is provided, and when the brake sensor detects that the brake is depressed, an error between a wheel vehicle speed and an optical vehicle speed is stored. Alternatively, the automatic braking device according to claim 2 or 3, wherein sampling is not performed.