JP2520114B2 - Pseudo vehicle speed calculation device for anti-skidding control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for controlling brake fluid pressure in order to prevent wheel lock in such a manner that maximum braking efficiency is achieved, and in particular, it is essential. The present invention relates to a pseudo vehicle speed calculation device.

(Prior Art) An anti-skid control device (see, for example, Japanese Patent Laid-Open No. 59-213552) reduces brake fluid pressure when the wheel peripheral speed (wheel speed) has a predetermined slip relationship with the vehicle speed. Configured to prevent wheel locking.

However, at this time, if the measurement result of the Doppler radar or the like that can directly detect the actual vehicle speed is used as the vehicle speed, the Doppler radar or the like is expensive and not practical, so the pseudo vehicle speed is obtained from the wheel speed and used as the vehicle speed. Is normal.

In the conventional pseudo vehicle speed calculation device represented by this, as shown in FIG. 3, after the braking start t ₀ , the wheels tend to lock and the wheel speed V _w suddenly _deviates from the actual vehicle speed V _c (the wheel speed itself). Is not a model of the vehicle speed), that is, from the instant t ₁ when the wheel deceleration α _w exceeds the reference value −α ₀ , the wheel speed V _w (t ₁ ) = V ₁ at this time is used as the initial value for constant reduction. The pseudo vehicle speed V _i with the speed gradient k ₀ is calculated. In the region where V _i ≦ V _w , the larger value is closer to the actual vehicle speed, so V _i = V _w .

By reducing the brake fluid pressure P _w as shown in the figure (anti-skid control), the wheel speed V _w recovers toward the actual vehicle speed V _c , and in response to this, the brake fluid pressure P _w is raised again to reduce the wheel deceleration α _w. After the next skid cycle start instant t ₂ that exceeds the reference value −α ₀ again, the wheel speed V _w (t ₂ ) = V ₂ at this time is used as the initial value. The pseudo vehicle speed V _i with the deceleration gradient determined as described above is obtained. After that, the pseudo vehicle speed V _i is obtained in the same manner as described above at every instant t _{3 of} start of the skid cycle, and as a result, the pseudo vehicle speed V _i becomes as shown by the alternate long and short dash line in FIG.

However, in the conventional pseudo vehicle speed calculation method, the pseudo vehicle speed gradient k ₀ is constant during the first skid cycle, and the following problems occur.

That is, the pseudo vehicle speed V _i is set to the actual vehicle speed in determining the gradient k _0.
In order to approximate V _c , it is necessary to consider the road surface friction coefficient μ and the brake pedal depressing force that are related to the actual vehicle speed V _c , but these are not constant, and this is always the case in the conventional method in which the gradient k ₀ is constant. There will be excess and deficiency.

If the gradient k ₀ is significantly smaller than the decreasing gradient of the actual vehicle speed V _c , the pseudo vehicle speed V _i is too high, and the slip determination of the wheel performed by comparing this with the wheel speed V _w is an erroneous determination that there is excessive slip (wheel lock). Then, the brake fluid pressure is reduced more than necessary to cause a reduction in braking efficiency (in the worst case, braking is impossible).

On the other hand, if k ₀ is significantly larger than the decrease gradient of the actual vehicle speed V _c , the pseudo vehicle speed V _i is too low, and the slip determination of the wheel makes an erroneous determination that there is no wheel slip (wheel lock), and the brake fluid pressure is reduced. (Anti-skid control) Inability to get out of the locked state.

Therefore, the road surface friction coefficient and the brake pedal depressing force appear as vehicle acceleration / deceleration, and if these are integrated and used as a pseudo vehicle speed change data, a pseudo vehicle speed theoretically close to the actual vehicle speed can be obtained. As disclosed in Japanese Patent Publication No. 57-11149,
Conventionally, a technique has been proposed in which the vehicle body deceleration is integrated with the wheel speed at the start of braking as an initial value to obtain a pseudo vehicle speed.

(Problems to be solved by the invention) However, in this technique, when an output error (gain change) of a G sensor that detects a vehicle deceleration or a calculation error (offset) of a control circuit occurs, the vehicle deceleration is integrated. The calculated pseudo vehicle speed deviates greatly from the actual vehicle speed, and an accurate pseudo vehicle speed cannot be calculated. Then, when the simulated vehicle speed becomes significantly higher than the actual vehicle speed, the anti-skid control device reduces the brake fluid pressure more than necessary as described above, and causes an extremely bad situation where braking is impossible. Further, when the simulated vehicle speed becomes significantly lower than the actual vehicle speed, the anti-skid control device cannot perform the original anti-skid control as described above, and it becomes impossible to escape from the wheel lock state.

(Means for Solving the Problems) The present invention has taken safety measures so that at least the worst situation of the above-mentioned braking failure does not occur, that is, the pseudo vehicle speed is prevented from accidentally becoming significantly higher than the actual vehicle speed. In order to provide a simulated vehicle speed calculation device, the brake fluid pressure is applied when the wheel speed has a predetermined slip relationship with the simulated vehicle speed obtained by integrating the vehicle body deceleration with the wheel speed at the start of braking as the initial value. In the anti-skid control device for reducing the vehicle body deceleration, the vehicle body deceleration monitor means for detecting that the vehicle body deceleration becomes equal to or higher than a predetermined deceleration, and the peak value of the wheel acceleration generated as the brake fluid pressure is reduced is equal to or less than a predetermined acceleration. The wheel acceleration monitor means for detecting that the vehicle speed is detected, and the pseudo vehicle speed is obtained from the wheel speed by stopping the integration when the detection is performed by both of these monitor means. Characterized in structure in which a switching means for switching.

(Operation) The anti-skid control device obtains the pseudo vehicle speed by integrating the vehicle body deceleration whose initial value is the wheel speed at the start of braking,
When the wheel speed has a predetermined slip relationship with respect to the pseudo vehicle speed, the brake hydraulic pressure is reduced to prevent the wheel from being locked and achieve the maximum braking efficiency.

By the way, when the pseudo vehicle speed becomes significantly higher than the actual vehicle speed and the braking becomes impossible, the brake fluid pressure is increased even though the vehicle body deceleration is on a high friction road such that the deceleration becomes a predetermined deceleration or more. A phenomenon occurs in which the peak value of the wheel acceleration that occurs with the decompression of is less than the predetermined acceleration. The vehicle body deceleration monitor means detects the former phenomenon to detect that the vehicle is on a high friction road, and the wheel acceleration monitor means detects the latter phenomenon. When all of these phenomena are met, that is, when the simulated vehicle speed becomes significantly higher than the actual vehicle speed and braking becomes impossible, the switching means suspends the calculation of the simulated vehicle speed due to the integration of the vehicle body deceleration that causes it.
Instead, the pseudo vehicle speed is calculated from the wheel speed. Therefore, even if the gain change of the G sensor for detecting the vehicle body deceleration or the offset of the control circuit occurs and the simulated vehicle speed obtained by the integration of the vehicle body deceleration becomes significantly higher than the actual vehicle speed, the simulated vehicle speed is obtained from the wheel speed. By switching, it is possible to avoid the worst situation in which the pseudo vehicle speed becomes significantly higher than the actual vehicle speed and braking becomes impossible.

(Example) Hereinafter, the present invention will be described in detail based on examples of the drawings.

FIG. 1 (a) shows an anti-skid control device including a pseudo vehicle speed calculation device according to an embodiment of the present invention, in which 1 is a wheel to be anti-skid controlled, 2 is its wheel cylinder, and 3 is an anti-skid actuator. Are shown respectively.
The actuator 3 is provided by being inserted into a brake fluid pressure (P _w ) circuit from a brake master cylinder (not shown) to the wheel cylinder 2, and the brake fluid pressure P _w is appropriately maintained and reduced by electronic control by the fluid pressure control controller 4. In other cases, the wheel 1 is increased by increasing the master cylinder hydraulic pressure.
The lock shall be prevented.

The rotation speed of the wheel 1 is detected by the rotation sensor 5, and this is input to the wheel speed calculation circuit 6. This circuit 6 calculates the rotation peripheral speed (wheel speed) of the wheel 1 from the rotation speed and the rotation radius of the wheel 1.
V _w is calculated and supplied to the controller 4, and also supplied to the differentiating circuit 7 and the integrating circuit 8. Differentiating circuit 7 determines the wheel speed V _w
Is differentiated with respect to time to obtain wheel acceleration / deceleration α _w (negative is deceleration), and this is input to the controller 4.

Reference numeral 9 is a brake switch, 10 is a G sensor for detecting the vehicle body deceleration α _c , and the brake switch 9 is closed by depressing the brake pedal to supply a signal indicating the start of braking and braking to the controller 4 valve and the integrating circuit 8.

The integrator circuit 8 is a time integration of the vehicle body deceleration α _c with the wheel speed V _w = V ₀ at the start of braking as an initial value. Then, the pseudo vehicle speed V _i is obtained and is input to the controller 4.

Then, the controller 4 performs the function in accordance with the flowchart of FIG. 1 (b) during braking when the brake switch 9 is closed to perform the calculation of the pseudo vehicle speed V _i which is an object of the present invention, and also through the actuator 3, a known method. The anti-skid control is performed on the wheel 1.

First, the pseudo vehicle speed calculation function will be described with reference to FIG. 1 (b). In step 11, the G sensor use prohibition flag GFLG is set to 1
Or not, that is, the vehicle body deceleration α detected by the G sensor 10
It is determined whether or not the use of the pseudo vehicle speed V _{i obtained} by integrating _c is prohibited. If not, the process proceeds to step 12 and it is determined as follows whether or not it should be prohibited.

That is, it is determined in step 12 whether or not the re-increase of the brake fluid pressure P _w is started, and in step 13, whether or not the reduction of the brake fluid pressure P _w is started. If the pressure reduction is started, in step 14, the peak value α _max of the wheel acceleration / deceleration α _w
Is stored and the pressure is set to 0, and if neither pressure increase nor pressure reduction is started, the peak value α _max of the wheel acceleration α _w generated during this period is stored in step 15. Then, in step 16, the calculated value of the integrating circuit 8 Is read as the pseudo vehicle speed V _i and used.

When it is determined in step 12 that the pressure increase is started, it is determined in steps 18 and 19 whether the peak value α _{max of the} wheel acceleration is the predetermined acceleration α ₃₀ or less and the vehicle deceleration α _c is the predetermined deceleration α ₂₀ or more. That is, the above pseudo vehicle speed Is determined to be significantly higher than the actual vehicle speed V _c . If this tendency does not exist, proceed to the function of step 16 from step 18 or 17 to continue the pseudo vehicle speed V _i . And

If there is the above tendency, after setting GFLG = 1 in step 20, the pseudo vehicle speed V _i is changed from the wheel speed V _w to the third value in step 21.
Obtained in the same manner as described above for the instant t ₂ onward in the figure, and this is determined in step 16. Used instead of.

After that, the function proceeds from step 11 to step 21 with GFLG = 1, and continues to obtain the pseudo vehicle speed as described above.

The controller 4 further controls the simulated vehicle speed V _i as described above.
In addition to the above, the well-known anti-skid control is executed for the wheel 1 by a function not shown based on the pseudo vehicle speed V _i , the wheel speed V _w , and the wheel acceleration / deceleration α _w .

The above-mentioned effect is simulated vehicle speed A general description will be given of a case in which there is a tendency to become significantly higher than the actual vehicle speed V _{c as} shown by the dotted line in FIG.

Unconditionally at the beginning of braking after t ₀ The well-known anti-skid control is performed by increasing, maintaining and reducing the brake fluid pressure P _w using the pseudo vehicle speed of. That is, the wheel deceleration α _w is the reference value −α ₀ (the same as in FIG. 3).
The brake fluid pressure P _w is maintained at the instant t ₁ that exceeds the brake fluid pressure P _w at the instant t ₁₁ when the wheel slip ratio becomes equal to or higher than the ideal slip ratio (the slip ratio at which the road friction force is maximum, usually about 15%). _The pressure _w is reduced, and the brake fluid pressure P _w is maintained before and after the instant t ₁₂ of the rotation increase of the wheel 1 thereby to increase the pressure again. The antiskid control similar to that described above is repeated after the start t _{2 of the} next skid cycle in which the wheel deceleration α _w due to this pressure increase again exceeds the reference value −α ₀ .

By the way, as shown in FIG. If There have a tendency significantly greater than the actual vehicle speed V _c, estimated vehicle deceleration vehicle deceleration alpha _c is the time differential value of the second as shown in FIG show a higher predetermined deceleration alpha ₂₀ (pseudo vehicle speed V _i α
Even though the road is on a high friction road ( _i indicates a predetermined deceleration α ₁₀ or more), the peak of the wheel acceleration α _w generated by the decompression as seen from the depressurization instant t ₂₁ to the repressurization instant t _22. The value α _max disappears at the predetermined acceleration α ₃₀ .

In this case, at instant t ₂₂ to re-increase pressure is started, the pseudo vehicle speed V _i is the wheel speed V switched so _w is calculated from, hereinafter third pseudo vehicle speed as in the instant t ₂₂ after in FIG V _i Is obtained and becomes as shown by the one-dot chain line in FIG.
Anti-skid control using this is performed. Therefore, never instantaneous t ₂₂ hereafter also pseudo vehicle speed V _i is left significantly greater from the actual vehicle speed V _c to as shown by a dotted line in Figure 2 shows the pseudo vehicle speed V _i at moment t ₂₂ after a one-dot chain line as-obtained by approximating the actual vehicle speed V _c, it is possible to perform accurate anti-skid control.

The difference between the pseudo vehicle speed V _i and the wheel speed V _w, i.e. the anti-skid control performed based on the slip ratio calculated from the slip quantity (V _i -V _w) is the (V _i -V _w) originally small V _i
Greatly affected by the error. Therefore, in the case where the pseudo vehicle speed V _i is calculated by integrating the G sensor output α _c as described above, if an error occurs in the G sensor output α _c due to the gain change of the G sensor or the offset of the control circuit, the pseudo sensor accompanying this is simulated. Due to the error of the vehicle speed V _i , the above anti-skid control becomes extremely inaccurate. However, when the high μ road is determined using the same G sensor output α _c as described above, even if the output value α _c of the G sensor has an output error similar to the above, the G sensor output α _c itself from be determined to be high μ road when an α _c> α ₂₀ is compared with a predetermined value alpha _20, affecting enough above error of the G sensor output alpha _c is a problem in the area In addition, it does not impair the effects of the above-mentioned embodiment.

(Effect of the invention) Thus, as described above, the pseudo vehicle speed calculation device of the present invention calculates the actual vehicle speed by integrating the vehicle deceleration by the gain change of the G sensor for detecting the vehicle deceleration and the offset of the control circuit. If there is a tendency to become significantly higher, this tendency is detected from the vehicle body deceleration above a predetermined value and the wheel acceleration peak value below a predetermined value, and the pseudo vehicle speed is switched to be calculated from the wheel speed instead of integrating the vehicle body deceleration. Since the configuration is adopted, it is possible to avoid the worst situation in which the pseudo vehicle speed becomes significantly higher than the actual vehicle speed and braking becomes impossible.

[Brief description of drawings]

FIG. 1 is an embodiment of a pseudo vehicle speed calculation device of the present invention. FIG. 1 (a) is a system diagram shown together with an anti-skid control device, FIG. 1 (b) is a flowchart showing the pseudo vehicle speed calculation function of the controller, and FIG. FIG. 3 is a time chart of a conventional pseudo vehicle speed calculation operation and anti-skid control operation. 1 ... wheel, 2 ... wheel cylinder 3 ... actuator 4 ... hydraulic pressure controller 5 ... rotation sensor, 6 ... wheel speed calculation circuit 7 ... differential circuit, 8 ... integration circuit 9 ... brake switch , 10 …… G sensor

Claims (1)

(57) [Claims] 1. An anti-skid control device for reducing a brake hydraulic pressure when a wheel speed has a predetermined slip relationship with a pseudo vehicle speed obtained by integrating a vehicle body deceleration having a wheel speed at the start of braking as an initial value, Vehicle body deceleration monitoring means for detecting that the vehicle body deceleration is equal to or higher than a predetermined deceleration, and wheel acceleration for detecting that a peak value of wheel acceleration generated due to the reduction of the brake fluid pressure is equal to or lower than a predetermined acceleration. A pseudo vehicle speed calculation device for an anti-skid control device, characterized by comprising monitor means and switching means for stopping the integration and switching to obtain a pseudo vehicle speed from the wheel speed when detection is made by both of these monitor means. .