JPS63232061A - Artificial car speed generating device for antiskid control system - Google Patents

Abstract

PURPOSE:To enable the worst situation to be avoided like being unable to brake, by constituting a device deciding a G sensor to be abnormal and calculating an artificial car speed being based on a wheel speed in the time of this abnormality, when a wheel speed restoration amount by an antiskid control is lower than a detection slip amount. CONSTITUTION:In the case of an antiskid control circuit 4 which inputs output signals of a brake switch 5, G sensor 6 and a wheel speed sensor 7 when a vehicle is in operation, a device reduces a pressure of brake fluid by an actuator 3 performing an antiskid control when a slip of a wheel 1 is detected from a difference between an artificial car speed, calculated being based on deceleration of the vehicle, and a wheel speed. While here the device, detecting a restoration amount of the wheel speed from a minimum value by a pressure reducing control, decides the G sensor 6 to be in abnormality when the restoration amount after the setting time from a pressure reducing control or in the time of pressure reincrease is lower than the detection slip amount at this point of time. And when this abnormality is decided, the artificial car speed is calculated being based on the wheel speed in place of deceleration of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pseudo vehicle speed generating device for an anti-skid control device that controls brake fluid pressure to achieve maximum braking efficiency while preventing wheels from locking. be.

(Prior Art) An anti-skid control device prevents the wheels from locking by reducing the brake fluid pressure when the circumferential speed of the wheels (wheel speed) has a slip relationship of more than a predetermined value with respect to the vehicle speed. In this case, Doppler radar, etc. that directly detects the actual vehicle speed is expensive and impractical, so every time the wheels tend to lock and the wheel speed suddenly deviates from the actual vehicle speed, that is, the wheel deceleration exceeds the deceleration reference value. Usually, a pseudo vehicle speed with a predetermined deceleration gradient is determined based on the wheel speed value at this time, and this is used as the vehicle speed.

To explain this pseudo vehicle speed generation technology and anti-skid control technology, wheel speed V is shown in FIG. and wheel acceleration/deceleration α
8 defined by the combination of (negative is deceleration). +
A++ Bol Bl four regions are set, V, >Vmu xo, 85 (Vt is the pseudo vehicle speed, 0.85 is based on the characteristics on frozen roads (a) and the characteristics on dry roads (b) in Figure 6. As shown, the value of the wheel slip rate S at which the road surface friction coefficient μ is maximum, that is, the coefficient corresponding to the ideal slip rate S (1 = 15%, V, Xo, and 85 are the target wheels to obtain the ideal slip rate S0. speed), and −bl<α8≦+al(+
(al is the acceleration reference value, -bl is the deceleration reference value). In this area, the brake fluid pressure is increased in the direction of the master cylinder fluid pressure, but in other areas AI+Bl+Bo, the brake fluid pressure is maintained or reduced as shown in the diagram, thereby preventing the wheels from locking. Ensure maximum braking efficiency is achieved.

This anti-skid control action, together with the pseudo vehicle speed generation action, will be described in detail for the case where the wheel speed vw is as shown in FIG. 5 (where vc is the actual vehicle speed shown for reference). instant t0
Brake fluid pressure P due to the start of braking. At the beginning of the rise, of course A
o? In the IN range, the brake fluid pressure 9 is equal to the master cylinder fluid pressure. α due to the start of wheel lock. ≦−b
V, (t) = V, (t
+)-ko(t-t,), the instant t and subsequent pseudo vehicle speed V are determined as shown by the dashed line in FIG. Then, from the instant t5 at which α8≦−bl occurs due to the start of the next wheel lock, the pseudo vehicle speed V is determined as follows. That is, first, + is determined for the deceleration gradient of the approximated vehicle speed Vm, and based on this, Vt (t) = V, l (ts) - k+
The pseudo vehicle speed V is obtained from the calculation of (t-ts). From then on,
A similar calculation is performed every time α, ≦-bl, and the pseudo vehicle speed V is calculated.

is determined as shown in Figure 5. However, when v, I > Vt, v
Since , , is closer to the actual vehicle speed, it is assumed that V, =V. In addition, the above-mentioned coefficient 0.8 is added to the pseudo vehicle speed Vi obtained in this way.
The target wheel speed V, Xo, 85 obtained by multiplying by 5 is the fifth
It will look like the figure.

At instant t, vw≦V! The brake fluid pressure P remains at B + *bi until the instantaneous wheel lock tg becomes Xo and 85.
8 is maintained despite the increase in master cylinder fluid pressure, and this pressure retention makes it possible to determine the road friction condition, and if the brake fluid pressure continues to rise, the anti-skid control that should be performed due to the pressure reduction will cause a response delay. Make sure that there are no

From instant t2, the brake fluid pressure P is in the 8° range, and the brake fluid pressure P is reduced to prevent wheel locking (anti-skid control). As a result, the wheel rotates upward due to the recovery of road friction force, and α
, >+al at the instant t, then α. The brake fluid pressure remains in the A IpI region until instant t4 when ≦+al, and the brake fluid pressure pw is maintained during this period. This pressure holding makes it possible to determine the road surface friction state, and prevents a delay in canceling the anti-skid control that should be performed due to an increase in the brake fluid pressure due to a continuous decrease in the brake fluid pressure.

At instant t4, wheel speed V. Assuming that the speed has recovered to the actual vehicle speed, A from this moment on. Brake fluid pressure P8
By increasing the pressure, it is possible to prevent braking distance from becoming longer due to unnecessary brake fluid pressure increase restrictions. With this pressure increase, α is again
, ≦-b1, and the next skid cycle is started, and the same control as described above is repeated, and eventually the brake fluid pressure pw is controlled to keep the slip ratio S near the ideal slip ratio S0. This ensures maximum braking efficiency while preventing wheel lock.

However, in the calculation method of the pseudo vehicle speed Vi as described above, 1
Pseudo vehicle speed V in the second skid cycle! Since the deceleration gradient is set to a constant value such as 0 as described above, the pseudo vehicle speed V in this skid cycle may not approximate the actual vehicle speed V. In particular, the wheel speed Vw may also change due to a decrease in the brake fluid pressure P. However, if the vehicle speed cannot be recovered to near the actual vehicle speed VC due to a low-friction road or a low-speed gear with large wheel rotational inertia being selected, the pseudo vehicle speed V will be set to a value significantly smaller than the actual vehicle speed VC. In this case, there is a risk that anti-skid control (reduction of brake fluid pressure P1) may not be performed due to a misjudgment that the wheels are not locked even though they are talking, and the wheels may remain locked. will occur.

To solve this problem, a calculation method has been proposed in Japanese Patent Application Laid-Open No. 57-11149, etc., in which the wheel speed at the start of braking is used as an initial value, and the value obtained by subtracting the integral value of vehicle deceleration from this value is used as a pseudo vehicle speed. .

(Problem to be Solved by the Invention) However, in the device that calculates the pseudo vehicle speed based on the vehicle deceleration in this way, the G sensor that detects the vehicle deceleration may be malfunctioning or disconnected, causing the vehicle deceleration to be significantly lower than the actual vehicle deceleration. When detecting the vehicle speed, the pseudo vehicle speed is calculated as a value significantly larger than the actual vehicle speed. In this case, based on the erroneous judgment that the amount of wheel slip detected from the difference between the pseudo vehicle speed and the wheel speed is large even though no wheel slip has occurred, unnecessary brake fluid pressure reduction is performed, This will lead to the worst case scenario where you are unable to brake.

(Means for Solving the Problems) The present invention provides that, even when the brake fluid pressure is reduced during the above-mentioned abnormality, the wheel speed is originally near or far from the actual vehicle, and the amount of recovery is small, whereas the pseudo vehicle speed is lower than the actual vehicle speed. Based on the fact that the detected slip amount calculated from the difference between this and the wheel speed is significantly higher than the above-mentioned wheel recovery amount, based on the difference between the pseudo vehicle speed calculated based on the vehicle deceleration and the wheel speed. In an anti-skid control device that detects the amount of wheel slip and reduces the brake fluid pressure of the wheel when wheel slip occurs, the amount of recovery of the wheel speed from the minimum value due to the reduction of the brake fluid pressure is detected. wheel speed recovery amount detection means, when the wheel speed recovery amount is lower than the detected slip amount at the time when a set time has elapsed since the pressure reduction or when the pressure is increased again, the calculation of the pseudo vehicle speed is calculated based on the vehicle deceleration. Instead, a switching means for switching based on the wheel speed can be provided.

(Function) The anti-skid control device detects the amount of wheel slip from the difference between the simulated vehicle speed and the wheel speed, and when wheel slip occurs, reduces the brake fluid pressure in the wheels to prevent wheel lock while achieving maximum braking efficiency. make sure you get it.

The pseudo vehicle speed is calculated as follows.

That is, the wheel speed recovery amount detection means detects the amount of wheel speed recovery due to the above-mentioned pressure reduction of the brake fluid pressure. If the G sensor that detects vehicle deceleration is normal, the wheel speed recovery amount will not become lower than the detected slip amount when the set time elapses from the pressure reduction or when the pressure is increased again, and in this case, the switching means A pseudo vehicle speed is calculated based on vehicle deceleration.

By the way, when the G sensor is abnormal, the wheel speed recovery amount becomes lower than the detected slip amount when a set time elapses from the pressure reduction or when the pressure is increased again, and this causes the switching means to calculate the pseudo vehicle speed at the abnormality. is performed based on wheel speed instead of vehicle deceleration. Therefore, even if there is an abnormality in the G sensor, the pseudo vehicle speed will not become significantly larger than the actual vehicle speed, and it is possible to avoid the worst case where braking becomes impossible due to an unnecessary decrease in brake fluid pressure.

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

FIGS. 1(a) and 1(b) show an anti-skid control device equipped with a pseudo vehicle speed generating device according to an embodiment of the present invention, and this device controls the brake fluid pressure 9 directed to the wheel cylinder 2 of the wheel worker by an actuator. It is assumed that the anti-skid control of the wheels 1 is performed by appropriately reducing the pressure using the electronic control in step 3.

An anti-skid control circuit 4 is provided to electronically control the actuator 3, and the following information is input to this circuit. That is, a brake switch 5 that closes when the brake is applied, a G sensor 6 that detects the deceleration g of the vehicle, and a wheel speed sensor 7 that emits a pulse signal of a frequency corresponding to the rotation speed of the wheel 1 are provided. The brake switch 5 inputs the brake activation signal to the anti-skid control circuit 4 and the integration circuit 8, and the G sensor 6 integrates the signal related to the vehicle deceleration g (however, the G sensor 6 integrates the signal related to the vehicle deceleration g (however, it integrates the signal from the brake activation start moment t0 to any subsequent moment). value) is input to the anti-skid control circuit 4. Further, the pulse signal from the wheel speed sensor 7 is manually inputted to the wheel speed calculation circuit 9, and this circuit calculates the wheel speed v8 from the pulse signal and the rotation radius of the wheel 1 and sends it to the anti-skid control circuit 4.
Enter.

The anti-skid control circuit 4 performs the function shown in FIG. 1(b) based on the above input information and calculates the pseudo vehicle speed V.

In addition to calculating this pseudo vehicle speed, anti-skid control of the wheels 1 is performed by a well-known operation based on this pseudo vehicle speed.

First, the pseudo vehicle speed calculation function shown in FIG. 1(b) will be explained with reference to FIG. 2. In step 10, it is determined whether the brake switch 5 is ON or not. If it is not ON, braking is not in progress and anti-skid control is started. Since it is not necessary to calculate the vehicle speed or the pseudo vehicle speed, in step 11, the switching flag CHGFLG, which will be described later, is set.
is reset to 0, and timer T (described later) is also reset to O.
The read wheel speed value 9 is temporarily set to the wheel speed minimum value V, min, which will be described later, and the control is terminated.

If braking is in progress, that is, after instant t0 in FIG. 2, it is checked in step 12 whether CHGFLG is 1 or not, but since CHGFLG=O due to the execution of step 11, the control reaches step 13. In step 13,
It becomes something like this.

By the way, when the G sensor 6 detects a significantly smaller vehicle deceleration than the actual one due to an abnormality, the pseudo vehicle speed V determined as above is significantly larger than the actual vehicle speed, as seen at the beginning of braking in Fig. 2. Become. Therefore, this pseudo vehicle speed V
and wheel speed V. Anti-skid control is performed in the same manner as described above with reference to FIG. 5 based on the amount of wheel slip detected from the difference between
~L) is executed unnecessarily even though the wheels are not in a slip state, and the wheel speed recovery amount Δright due to pressure reduction (instantaneous tz) during the anti-skid control is small. Further, the above-mentioned large pseudo vehicle speed Vt increases the detected slip amount Δv2 obtained from the difference between this and the wheel speed v1, and as a result, ΔV<Δv2 as shown in FIG. 2.

In order to determine the abnormality of the G sensor 6 using this, see Figure 1 (
In b), it is determined in the next step 14 whether or not to start decompression. Sten 7” 1l (7) only once at the start of decompression
Execution Niyori CHGFLG = 01T = 0, Vw lIi
, l=vw, and next time, in step 15, it will be determined whether or not the pressure is being reduced. If the pressure is being reduced, or if the pressure has not been increased again in step 16 even if the pressure is not being reduced, step 17.
At step 18, the minimum wheel speed value v817 after the start of pressure reduction is updated.

Then, in step 19, the elapsed time after the start of decompression is measured by the timer T as shown in FIG. 2, and in step 20, it is checked whether or not the timer T indicates the set time T0. Note that the set time T0 is, for example, about 1.5 seconds, which corresponds to the longest skid cycle. When T < 70, the control is terminated and the above loop is repeated until T
When ≧T0 (instant t in Fig. 2), step 2
1, wheel speed recovery amount ΔVl=Vw Vw *! , and calculate the instantaneous detected slip amount ΔV,=V
Mo-v1 is calculated.

In the next step 22, it is determined whether the G sensor 6 is abnormal or not based on whether the wheel speed recovery amount Δv1 is greater than or equal to a set value Δv0 taking into account the error and lower than the detected slip amount lVz.

When JV+-Δv2≦Δv0 is abnormal, the switching flag CIIGFLG is set to 1 to indicate this in step 23, and when lv+-AV is normal, CIIGFLG is set to 0 to indicate this in step 24. Reset to .

Thus, the control proceeds from step 12 to step 13 due to CHGPLG=O during normal operation, and the pseudo vehicle speed V! continues to be calculated by integrating the vehicle deceleration g, but in the event of an abnormality, the control proceeds from step 12 to step 25.
The pseudo vehicle speed V is based on the wheel speed v8 instead of the vehicle deceleration g,
The instant t in FIG. 5 and the rest are calculated in the same manner as described above. Therefore, when the G sensor 6 is abnormal, the pseudo vehicle speed V is at the instant t in FIG. After the lever abnormality is determined, the situation will be as shown in the same figure.

The anti-skid control circuit 4 performs the same anti-skid control as described above with reference to FIG. 5 to adjust the brake fluid pressure P based on the pseudo vehicle speed V and the wheel speed V8 determined as described above. is controlled as shown in FIG. At this time, due to the abnormality of the G sensor 6, the brake fluid pressure P, is set to 0 at instant t3, and braking becomes temporarily impossible, but at the abnormality determination instant t.

Since the calculation of the pseudo vehicle speed V, is switched based on the wheel speed V, . . . instead of the abnormal vehicle deceleration g, normal anti-skid control can be performed thereafter.

Therefore, even when the G sensor 6 is abnormal, it is possible to prevent the braking from being disabled from continuing.

Note that while the G sensor 6 is normally detecting the vehicle deceleration g, the wheel speed recovery amount AV is determined after the set time T0 has elapsed from the pressure reduction start instant txt, as shown in FIG.

is larger than the detected slip amount Δv2, and the pseudo vehicle speed V is based on the vehicle deceleration g at step 13 in FIG. 1(b).

The calculation of ti is continued, and the vehicle speed similar to ti becomes as shown in FIG. Since the G sensor 6 is normal, the 1 pseudo vehicle speed V does not show an abnormal value, and anti-skid control can be performed accurately.

Note that, as seen immediately after the next pressure reduction start instant t2□ in FIG.
It is determined whether the G sensor 6 is abnormal or not. For this purpose, the start of pressure increase again is checked in step 26 in FIG. , then control proceeds to step 21.

(Effects of the Invention) Thus, as described above, the pseudo vehicle speed generator/device of the present invention detects when the amount of wheel speed recovered by the anti-skid control is lower than the detected slip amount when the set time from pressure reduction has elapsed or when the pressure is increased again. Since the vehicle deceleration value detected by the G sensor is determined to be abnormal, and the pseudo vehicle speed is calculated based on the wheel speed instead of the vehicle deceleration at the time of abnormality, the pseudo vehicle speed will be abnormal even due to the above abnormality. Therefore, the anti-skid control that is executed based on this can continue to be performed normally, and the worst case of inability to brake can be avoided.

[Brief explanation of the drawing]

FIG. 1(a) is an overall system diagram of an anti-skid control device equipped with a pseudo-vehicle speed generator of the present invention, FIG. 1(b) is a flow chart of the pseudo-vehicle speed calculation function of the anti-skid control circuit on the same side, and FIG. Figure 3 is an operation time chart when the G sensor of the ipsilateral device is abnormal and when it is normal, respectively.
Figure 5 is a general area diagram of anti-skid control, Figure 5 is an operation time chart of general anti-skid control, and Figure 6 is a road surface friction coefficient change characteristic diagram for frozen roads and dry roads. 1... Wheel 2... Wheel cylinder 3... Actuator 4... Anti-skid control circuit 5... Brake switch 6... G sensor 7...
Wheel speed sensor 8...Integrator circuit 9...Wheel speed calculation circuit Patent applicant: Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. The amount of wheel slip is detected from the difference between the pseudo vehicle speed calculated based on the deceleration of the vehicle and the wheel speed, and when wheel slip occurs, the brake fluid pressure of the wheel is reduced. The anti-skid control device includes a wheel speed recovery amount detection means for detecting the amount of recovery of the wheel speed from the minimum value due to the reduction of the brake fluid pressure, and the wheel speed recovery amount detection means detects the amount of recovery of the wheel speed from the minimum value due to the reduction of the brake fluid pressure; Anti-skid control characterized by providing a switching means for switching to calculate the pseudo vehicle speed based on the wheel speed instead of the vehicle deceleration when the wheel speed recovery amount is lower than the detected slip amount at the time. The device's pseudo vehicle speed generator.