JPH089323B2 - Pseudo vehicle speed calculator for anti-skid controller - 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, since a Doppler radar or the like that directly detects the actual vehicle speed as the vehicle speed is expensive and not practical, for example, a pseudo vehicle speed is obtained from the wheel speed as described in JP-A-57-11149 and used as the vehicle speed. It is normal to do.

In the conventional pseudo vehicle speed calculation device represented by this, as shown in FIG. 3, the wheels tend to lock after the braking start t ₀ and the wheel speed V _w suddenly _deviates from the actual vehicle speed V _c (the wheel speed itself is When it does not imitate the vehicle speed), that is, wheel deceleration α
_{From the} instant t ₁ when _w exceeds the reference value −α ₀ , the wheel speed at this time is
A pseudo vehicle speed V _i with a constant deceleration gradient k ₀ is obtained with V _w (t ₁ ) = V ₁ as an initial value. In the region where V _i ≦ V _w , the larger one 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 to the maximum, and the wheel deceleration rate α _w Is again over the reference value -α ₀ , the wheel speed V _w (t ₂ ) = V ₂ at this time is used as the initial value after the next skid cycle start instant t _2. 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 such a conventional pseudo vehicle speed calculation method, the pseudo vehicle speed gradient k ₀ is constant during the first skid cycle, which causes the following problems.

That is, in determining the gradient k ₀ , the simulated vehicle speed V _{i is changed} to the actual vehicle speed V _c
In order to approximate to, the road surface friction coefficient μ and the brake pedal depression force that are related to the actual vehicle speed V _c must be taken into consideration, but these are not constant, and in the conventional method in which the gradient k ₀ is constant, this is always excessive or insufficient. Cause

If the gradient 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 judgment of the wheel made by comparing this with the wheel speed V _w is an erroneous judgment that there is excessive slip (wheel lock). Then, the brake hydraulic pressure is increased 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 smaller than the decrease gradient of the actual vehicle speed V _c , the pseudo vehicle speed V _i is too high 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, the pseudo vehicle speed theoretically close to the actual vehicle speed can be obtained. As disclosed in Japanese Laid-Open Patent Publication No. 57-11149, a technique has been conventionally proposed in which the vehicle speed at the start of braking is used as an initial value to integrate the vehicle body acceleration / deceleration to obtain a pseudo vehicle speed.

(Problems to be solved by the invention) However, in this technique, when the braking continues for a long time and the integration of the vehicle body acceleration / deceleration to be performed during this period is performed for a long time, the output error (gain (Change) and a calculation error (offset) of the control circuit, the pseudo vehicle speed largely deviates from the actual vehicle speed, and the pseudo vehicle speed cannot be accurately calculated according to the theory.

(Means for Solving the Problem) In view of this problem, the present invention resets the above integration every predetermined time and obtains a pseudo vehicle speed by integrating the vehicle body acceleration / deceleration with the wheel speed at the time of resetting as an initial value. The timer means for doing so is provided.

By the way, in this case, if the above predetermined time is constant,
There are concerns about the following problems when the wheel speed is low. That is, the wheel speed V _w, as shown in Figure 4 may now be explained lower pseudo vehicle speed as indicated by the dotted line by integration of the acceleration of the vehicle G wheel speed V _w = V ₀ of the brake at the start t ₀ as an initial value V _i = V ₀ −∫ ₀ ^t
Calculate G · dt. The instant t _{10 when} this integration lasts for a predetermined T time
Thereafter, the integral is reset at this instant, and the pseudo vehicle speed V _i = V ₁₀ −∫ ₀ ^t G as shown by the dotted line from the integration of the vehicle body acceleration / deceleration G whose initial value is the wheel speed V _w = V ₁₀ at the time of the reset.・ Calculate dt. After that, even at the instant t ₂₀ when the time T elapses, the integral is reset and the instantaneous vehicle speed V _w = V ₂₀ is used as the initial value to integrate the vehicle body acceleration / deceleration to simulate the vehicle speed V _i = V ₂₀ −∫ ₀ ^t G ・ dt Ask for. Even if the difference between the wheel speed V _w and the actual vehicle speed V _c is small in the pseudo vehicle speed calculated in this way, the predetermined time T is too long in the low wheel speed range, so the wheel slip ratio There is a tendency to increase the calculated value of. That is, if the gain change and the offset error amount are the same in the predetermined time T, the value of V _i becomes small at a low vehicle speed, so that the error amount has a greater influence on the slip ratio than at a high vehicle speed. Therefore, there is a concern that the wheel slip may be erroneously judged to be large in the low wheel speed range, and the brake fluid pressure P _w may be unnecessarily reduced at an instant t ₁₆ in FIG.

From this point of view, in order to increase the reset frequency of integration at low wheel speeds, the present invention adds integration time changing means for shortening the above predetermined time when the wheel speed at reset is small.

(Operation) The anti-skid control device obtains the pseudo vehicle speed by integrating the vehicle body acceleration / deceleration with the wheel speed at the instant of the start of braking as the initial value, and when the wheel speed has a predetermined slip relationship with this pseudo vehicle speed, the brake fluid is applied. Achieve maximum braking efficiency while reducing pressure to prevent wheel locking.

When the pseudo vehicle speed is obtained as described above, the timer means resets the above integration every predetermined time and obtains the pseudo vehicle speed by integrating the vehicle body acceleration / deceleration with the wheel speed at the reset as an initial value. For this reason, even when the braking continues for a long time and the above integration is performed for a long time, the change in the gain of the G sensor for detecting the vehicle body acceleration / deceleration and the occurrence of the offset do not cause the pseudo vehicle speed to be greatly deviated from the actual vehicle speed. Enable anti-skid control if possible.

In addition, the integration time changing means, depending on the wheel speed at reset,
When this is small, the above predetermined time is shortened to increase the reset frequency of integration. Therefore, the integration time will not be too long in the low wheel speed range, and it is possible to prevent erroneous determination that the wheel slip is large even if the wheels are not locked, and unnecessary anti-skid control improves braking efficiency. It can be prevented from getting worse.

(Example) Hereinafter, the present invention will be described in detail based on an illustrated example.

FIG. 1 shows an anti-skid control device equipped with the device 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. The actuator 3 is provided by being inserted into a brake hydraulic pressure (P _w ) circuit from a brake master cylinder (not shown) to the wheel cylinder 2, and is electronically controlled by the hydraulic pressure controller 4 to appropriately maintain the brake hydraulic pressure P _w ,
The wheel 1 is prevented from being locked by reducing the pressure (in other cases, increasing the pressure toward the master cylinder hydraulic pressure).

The wheel speed V _w of the wheel 1 is detected by the wheel speed sensor 5, and this is supplied to the controller 4, the differentiating circuit 6 and the integrating circuit 7. A differentiating circuit 6 differentiates the wheel speed V _w with _respect to time to obtain a wheel acceleration deceleration α _w (negative is deceleration), and this is calculated by the controller 4
To enter.

Further, a signal from a G sensor 8 for detecting the vehicle body acceleration / deceleration G and the time measurement result of the timer 9 are input to the integration circuit 7. The timer 9 is set by the signal from the controller 4 for a predetermined time T at the same time as the braking is started, and is then decremented in a constant cycle. Time T or
It is assumed that 1 / 2T or 0 is set, and then the time counting operation of decrementing at a constant cycle is repeated. When the braking is not being performed, the timer 9 keeps the timer output at 0 by the controller 4.

The output of the timer 9 is the product decomposition path 7 while this is positive, and the pseudo vehicle speed is calculated by the integration of the vehicle body acceleration / deceleration G with the wheel speed V _w when the timer output rises as the initial value, and V _w −∫ ₀ ^t G ・ dt. It is assumed that the calculation of V _i is performed, the integration circuit 7 is reset while the output of the timer 9 is 0, and V _i = V _w is set by ∫ ₀ ^t G · dt = 0. The output of the timer 9 is also input to the controller 4, and the controller 4 determines the wheel speed V _w when the timer output becomes 0.
_Is compared with set values V _s1 and V _s2 (described later in FIG. 2), and V
_{If w} ≥ V _s1 , set the timer 9 to the same T as when braking started
If V _s2 ≤ V _w <V _s1 , set timer 9 to half If V _w <V _s2 , the set time of the timer 9 is set to 0.

Then, the controller 4 controls the pseudo vehicle speed from the integration circuit 7.
Based on V _i , the wheel speed V _w from the wheel speed sensor 5, and the wheel acceleration / deceleration α _w from the differentiating circuit 6, the actuator 3 is subjected to anti-skid control as described in JP-A-59-213552. It shall be performed on the wheel 1 through the wheel.

The pseudo vehicle speed calculation operation in the above embodiment will be described below with reference to FIG.

When braking is started at an instant t ₀ in FIG. 2, the timer 9 is set to a predetermined time T by a signal from the controller 4, the output is kept positive during this time, and an instant t _{10 when the} time T elapses.
Becomes 0 at. During the instant t _{0 to} t _{10 when} the output of the timer 9 is positive, the integrator circuit 7 integrates the vehicle body acceleration / deceleration G with the wheel speed V _w = V ₀ at the start of braking as an initial value, and V ₀ −∫ ₀ ^t The pseudo vehicle speed V _i is calculated from G · dt.

Controller 4 in the instant t ₁₀ is in response to the output of the timer 9 becomes 0, to re-set the timer 9 if it is still in braking. By the way, upon this resetting, the controller 4 compares the wheel speed V _w = V ₁₀ at the instant t ₁₀ with the set values V _s1 , V _s2, and if V _s1 > V _w ≧ V _s2 as shown in FIG. Predetermined time for timer 9 Set. On the other hand, at the instant t ₁₀ , the integrating circuit 7 causes the timer 9 to
Is reset by the output of 0, ∫ ₀ ^t G ・ d
With t = 0, V _i = V _w = V ₁₀ . Then the integrating circuit 7 is the integral of the acceleration of the vehicle G that the wheel speed V ₁₀ of the reset t ₁₀ by resetting the timer 9, the initial value, determine the pseudo vehicle speed V _i by ^{_{V 10 -∫ 0 t G · dt}} , this Calculation Continues until time instant ₁₅ .

Even after the instant t ₁₅ , the pseudo vehicle speed V _i is calculated in the same manner as described above unless the conditions are different from the above, and the instant t ₁₅
V ₁₅ In between ~t ₂₀ to the wheel speed V _w = V ₁₅ of the instant t ₁₅ and the initial value
−∫ ₀ ^t G ・ dt is used to obtain the pseudo vehicle speed V _i and the instantaneous t ₂₀
Between t ₂₅ and t ₂₅ , the wheel speed at the instant t ₂₀ is V _w = V ₂₀ and the initial value is V ₂₀
The pseudo vehicle speed V _i is obtained by the calculation −∫ ₀ ^t G · dt.

By the way, at the instant t ₂₅ , the wheel speed at this time V _w = V ₂₅
Is less than the set value V _s2 , the controller 4 sets the reset time of the timer 9 to 0 and does not reset the timer 9. Therefore, the timer 9 continues to reset the integrating circuit 7 after the instant t _{25 and} sets the pseudo vehicle speed V _i to the wheel speed V _w .

Thus, in the case of FIG. 2, the pseudo vehicle speed V _i is obtained as shown by the dotted line, but the timer 9 resets the integration circuit 7 every predetermined time, and the vehicle body acceleration / deceleration G of the wheel speed at the time of the reset is set as the initial value. Since the pseudo vehicle speed V _i is obtained by the integration, even when the integration is continued for a long time, the change in the gain of the G sensor 8 or the occurrence of the offset does not cause the pseudo vehicle speed V _i to be greatly deviated from the actual vehicle speed V _c , and the high accuracy is obtained. If possible anti-skid control.

In addition, while the wheel speed at reset is less than the set value V _{s1, Or} the above predetermined time during which the wheel speed is lower and less than the set value V _s2 is set to 0, the reset frequency of the integration circuit 7 is increased as the wheel speed decreases, and in the low wheel speed range. It is possible to prevent the erroneous determination that the wheel slip is large even though the wheels are not locked because the integration time is too long. Therefore, the unnecessary anti-skid described above with reference to FIG. 4 does not occur in FIG. 2, and deterioration of braking efficiency can be prevented.

(Effects of the Invention) As described above, the pseudo vehicle speed calculation device of the present invention is configured to reset the integral of the vehicle body acceleration / deceleration every predetermined time and shorten the predetermined time when the wheel speed at the time of reset is small as described above. By resetting, the gain change and the offset generation of the G sensor 8 for detecting the vehicle acceleration / deceleration will not occur.
It is possible to prevent the V _i from being significantly deviated from the actual vehicle speed V _c , and also to correct the excessive integration time in the low wheel speed range by changing the above-mentioned predetermined time, thereby preventing erroneous determination of wheel lock. be able to.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of an anti-skid control device including a pseudo vehicle speed calculation device of the present invention, FIG. 2 is an operation time chart of the device shown in FIG. 1, and FIG. 3 is an operation time of a conventional pseudo vehicle speed calculation device. The chart and FIG. 4 are operation time charts similar to those of FIG. 2 showing the problems in obtaining the pseudo vehicle speed by integrating the vehicle deceleration. 1 ... wheel, 2 ... wheel cylinder 3 ... actuator 4 ... hydraulic pressure controller 5 ... wheel speed sensor, 6 ... fine powder circuit 7 ... integration circuit, 8 ... G sensor 9 ... timer

Claims (1)

[Claims] 1. An anti-skid control device for reducing a brake fluid pressure when a wheel speed has a predetermined slip relationship with a pseudo vehicle speed obtained by integrating a vehicle body acceleration / deceleration with an initial value of the wheel speed at the moment of starting braking. Timer means for resetting the integral every predetermined time to obtain the pseudo vehicle speed by integrating the vehicle body acceleration / deceleration whose initial value is the wheel speed at the time of resetting; A pseudo vehicle speed calculation device for an anti-skid control device, characterized by further comprising integration time changing means for shortening the predetermined time.