JPS63170159A - Antiskid controller - Google Patents

Abstract

PURPOSE:To improve the responsiveness of control, by dividing output of an accelerating sensor, detecting body deceleration, into plural levels by a comparator, and setting either larger value of body speed or wheel speed to be estimated and operated on the basis of output of this comparator down to the body side at each point of time. CONSTITUTION:Output of a wheel speed sensor 1 is converted into a digital waveform at a waveform processing part 2 and inputted into a digital processing part 6 for antiskid control use. And, output of an acceleration sensor 3 detecting the deceleration of a car body is removed of its noise component by a filter processing part 4 and then it is inputted into a comparator 5. At this comparator 5, the output of the acceleration sensor 3 is divided into plural levels, and on the basis of the output of this comparator 5, body speed is estimated and operated at the processing part 6, while either larger value of this estimated body speed or the wheel speed by the wheel speed sensor 1 is set down to the body speed at each point of time, thereby making it control a hydraulic modulator 7. With this constitution, hydraulic pressure to be transmitted to a wheel cylinder W/C is controlled.

Description

[Detailed Description of the Invention] [Summary] The present invention attempts to compensate for the vehicle speed during sudden braking, which is inaccurate with the method of estimating the vehicle speed from the wheel speed, by using the vehicle speed estimated from the output of an acceleration sensor. It is.

[Industrial application field]

The present invention relates to an anti-skid control device that estimates and calculates vehicle speed.

[Conventional technology]

The anti-skid control device optimally controls brake hydraulic pressure to prevent wheels from locking and slipping during sudden braking.
In order to calculate the slip rate from the difference between wheel speed and vehicle speed, calculation of vehicle speed is essential.

There are two calculation methods for estimating this vehicle speed.

One is the wheel speed (which is calculated directly from the output of the wheel speed sensor).
This is a method of estimating vehicle speed (Vo) based on Vw).

Generally, in a vehicle that detects the wheel speed of the front and rear four wheels, the fastest wheel speed among them is used, and when the wheel speed decreases as shown in the solid line during braking as shown in Figure 5, the vehicle body speed also increases as shown in the broken line. It is estimated that it has decreased to The pulsations in wheel speed correspond to changes in brake oil pressure as a result of anti-skid control.

Another method is to obtain the vehicle speed by integrating the output of the acceleration sensor.

[Problem that the invention seeks to solve]

By the way, in the method of estimating the vehicle speed from the wheel speed,
If there is no slip between the wheels and the road surface, it is possible to treat wheel speed = vehicle speed, but if slip occurs, such as during sudden braking, the wheel speed (Vw) will drop rapidly, so estimation is based on this. The vehicle speed (Vo) tends to be smaller than the actual vehicle speed. As a result, slip rate S=(V
o-Vw)/Vw becomes apparently smaller, the start of anti-skid control (hydraulic pressure reduction) becomes slower. Fig. 6 is an explanatory diagram of this, showing that even if the wheel speed suddenly decreases, the estimated vehicle speed decreases at a constant slope.

However, this limit deceleration is generally set based on the deceleration (approximately IG) obtained when braking on a road surface with a relatively large coefficient of friction (μ) with the wheels (for example, a concrete road surface). On a small (slippery) road surface, the actual vehicle deceleration is smaller than the above-mentioned limit deceleration, so the estimated vehicle speed becomes smaller than the actual vehicle speed, as shown in Figure 7, and the slip ratio S appears to be smaller again. This will cause problems. However, in order to solve this problem, if the limit deceleration is set for a low μ road, the estimated vehicle speed will be too high on a high μ road, and the timing of increasing the brake oil pressure will be delayed, causing the brake to become excessively loose. This is dangerous.

On the other hand, in the method of calculating the vehicle speed using an acceleration sensor, the sensor signal includes vertical vibrations, horizontal errors, noise, etc., so when these are integrated, the errors are also integrated. Further, since the sensor signal is generally an analog signal, a digital system using a microcomputer requires an expensive interface such as an A/D converter, and an analog system requires an integrator, making it difficult to handle.

The present invention improves the acceleration sensor method and further combines it with the wheel speed sensor method, thereby making it possible to calculate vehicle body speed without the drawbacks of both methods.

[Means for solving problems]

In the present invention, when the wheel speed decreases beyond a certain deceleration, the vehicle speed estimated from the acceleration sensor signal and the wheel speed are selected, whichever is greater, and the wheel speed is recovered and estimated from the acceleration sensor signal. After the vehicle speed matches the specified vehicle speed, the wheel speed is selected and used until the wheel speed decreases beyond a certain deceleration. At this time, the signal from the acceleration sensor is divided into several levels depending on its magnitude, and each division is processed at a predetermined deceleration rate.

, [Operation] Fig. 1 is a diagram explaining the principle of the present invention. The estimated vehicle speed (broken line) of the present invention corresponds to the change in wheel speed (solid line) → A → B
-C→. Among these, A-C selects whichever is greater, the vehicle speed estimated from the signal of the acceleration sensor or the wheel speed. After 0 point, the wheel speed is selected, and until the constant deceleration is exceeded again due to pressure increase, the vehicle body speed is selected over the wheel speed. Estimate the speed.

The vehicle speed estimated from the acceleration sensor signal reflects the difference in road surface μ. In other words, if the wheel speed suddenly decreases on a high μ road, it will change in the same way as the conventional estimated vehicle speed (dotted chain line).
If the wheel speed suddenly decreases on the road, it changes to a high value as shown by the broken line (in any case with the conventional wheel speed sensor method, it changes as shown by the dashed line).

On the other hand, since there is a problem in processing the signal from the acceleration sensor, in the present invention, the deceleration of the estimated vehicle speed is made to vary depending on the level of the sensor signal.

FIG. 2 is a characteristic diagram of the acceleration sensor, and FIG. 3 is an input/output characteristic diagram of a comparator which receives the output voltage of the sensor as input. This comparator has input/output characteristics similar to a Gaussian function, and its output becomes an input to the processing section. As shown in FIG. 3, the comparator input (deceleration) from the acceleration sensor changes continuously, but the comparator output to the processing section is C++ 02, 03. It can only take discontinuous values such as... In this way, minute changes in the acceleration sensor signal will not be reflected in the estimated vehicle speed (approximate), making it less susceptible to noise and the like. Further, since the processing unit does not have to process with high precision, the burden is reduced.

〔Example〕

FIG. 4 is a block diagram showing an embodiment of the present invention, where l is a wheel speed sensor, 2 is a waveform processing unit that converts its output into a digital waveform, 3 is an acceleration sensor that detects the deceleration of the vehicle body, and 4 is a A filter processing section removes noise components from the output, 5 is a comparator having the characteristics shown in Fig. 3, 6 is a digital processing section for anti-skid control, 7 is from the mask cylinder M/C to the wheel cylinder W/C This is a modulator that controls the transmitted hydraulic pressure.

The processing unit 6 calculates the wheel speed from the output of the wheel speed sensor 1, but does not use the conventional method of simply estimating and calculating the vehicle speed from this. This is because before point A and after point 0 in Figure 1, the wheel speed is close to the actual vehicle speed (and between (A-C).
) is because the estimated vehicle speed obtained by the acceleration sensor 3 can be used.

The estimated vehicle speed in FIG. 1 is divided into an interval AB and an interval BC. The former deceleration G2 is larger than the latter deceleration G1. Furthermore, on a low μ road surface, the vehicle body deceleration becomes smaller and becomes 0.
The 2nd section is gone and only G1 is left. Although this example has been explained using a slippery road surface as an example, G3 is used on a high μ road surface, and a combination of G3 and G2 is used depending on the road surface.

By inputting the output of the comparator 5 instead of the output of the acceleration sensor 3 to the digital processing unit 6, high accuracy
/D converter becomes unnecessary.

〔Effect of the invention〕

As described above, according to the present invention, the estimation calculation of the vehicle speed during braking can be performed with high precision, so that the responsiveness of anti-skid control can be improved and the control accuracy can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a characteristic diagram of the acceleration sensor, Fig. 3 is an input/output characteristic diagram of the comparator, Fig. 4 is a block diagram showing an embodiment of the present invention, Fig. 5 6 is a partially enlarged view of FIG. 5, and FIG. 7 is an explanatory diagram showing the relationship between estimated vehicle speed and actual vehicle speed. ';ii 'I LJJ

Claims (1)

[Claims] In an anti-skid control device that calculates a slip rate from wheel speed and vehicle speed to control brake oil pressure, a comparator (5) divides the output of an acceleration sensor (3) that detects vehicle deceleration into multiple levels; An anti-skid control device characterized in that the larger value of the estimated vehicle speed calculated based on the output of (5) or the wheel speed is used as the vehicle speed at each point in time.