JPH0542943Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an anti-skid control device that prevents wheels from locking during braking of a vehicle, and in particular, an anti-skid control device that uses the longitudinal acceleration of the vehicle body to obtain an estimated vehicle speed. The present invention relates to an anti-skid control device.

[Prior Art] In order to control the wheel speed to an appropriate slip rate in an anti-skid control device, it is essential to calculate the vehicle body speed with high precision. The one described in JP-A-57-11149 is known.

This conventional device includes a longitudinal acceleration sensor that detects the longitudinal acceleration of the vehicle body, integrates the detected value of this longitudinal acceleration sensor from the moment the brake pedal is depressed, and subtracts the integrated value from the wheel speed when the brake pedal is depressed. The vehicle speed calculating means calculates the estimated vehicle speed, and the brake pressure is controlled based on the estimated vehicle speed.

[The problem that the idea attempts to solve]

However, in the conventional device described above, the vehicle speed is simply estimated by integrating the longitudinal acceleration, and the brake pressure is controlled based on this, so for example, the offset or gain of the longitudinal acceleration sensor itself is If this occurs, if there is a disconnection or short circuit between the sensor and the controller, or if the sensor is improperly installed on the vehicle, the estimated vehicle speed cannot be determined accurately, so the estimated vehicle speed≫ In the case of the actual vehicle speed, a no-brake state occurs, and in the case of the estimated vehicle speed <<the actual vehicle speed, the wheels may lock prematurely.

Therefore, this invention was made in view of the problems of the prior art, and it accurately determines whether the longitudinal acceleration detection sensor is in an abnormal state, and if it is in an abnormal state, at least The problem we are trying to solve is to reliably eliminate situations where brake pressure is incorrectly controlled based on sensor detection values, thereby preventing a decline in braking performance and enhancing fail-safe functions. There is.

[Means to solve the problem]

Therefore, in order to solve the above problems, in this invention, as shown in FIG. Estimated vehicle speed calculating means for calculating an estimated vehicle speed by integrating the detected longitudinal acceleration value using the detected speed value as an initial value, and controlling brake pressure of the wheels based on the calculated estimated vehicle speed value and the detected wheel speed value. In the anti-skid control device, the anti-skid control device includes a stop detecting means for detecting a stop, and when the stop detecting means detects a stop, the detected value of the longitudinal acceleration detecting means is determined in advance to detect an abnormality in the detected value. an abnormal state determining means for determining whether or not the abnormal state exceeds a predetermined value set corresponding to the predetermined value and continues for a predetermined time; and calculation stop command means for commanding the estimated vehicle speed calculation means to stop the calculation.

[Effect]

In this invention, when a stop is detected by the stop detecting means, the abnormal state determining means detects that the detected value of the longitudinal acceleration detecting means exceeds a predetermined value (for example, a value equivalent to the maximum inclination angle at which the vehicle can stop) and It is determined whether the condition is an abnormal condition that continues for a predetermined period of time. When an abnormal state is confirmed by this, the calculation stop command means instructs the estimated vehicle speed calculation means to stop calculating the estimated vehicle speed related to the longitudinal acceleration. With this, it is possible to reliably eliminate at least a situation in which an inaccurate vehicle speed is calculated according to a detected longitudinal acceleration value that includes an error.

〔Example〕

An embodiment of this invention will be described below with reference to FIGS. 2 to 6.

FIG. 2 shows a four-wheel skid control system that controls the front wheel brake pressure independently for the left and right wheels, and controls the rear wheel brake pressure commonly for the left and right wheels.

In the figure, 2 indicates a hydraulic brake;
4 indicates an anti-skid control device for this brake 2. The brake 2 is a brake pedal 6,
It has a master cylinder 8 and wheel cylinders 10FL to 10RR for front left to rear right wheels. The brake 2 may be either a drum type or a disc type.

The anti-skid control device 4 includes wheel speed sensors 12FL and 12 for detecting the wheel speed of each wheel.
FR, 12R, a longitudinal acceleration sensor 13 as a longitudinal acceleration detection means for detecting acceleration in the longitudinal direction of the vehicle, a brake switch 14 that outputs a switch signal in response to a depression operation of the brake pedal 6, and each of these detections. A controller 15 commands brake pressure control based on the signal, an actuator section 16 adjusts the hydraulic pressure of the wheel cylinders 10FL to 10RR individually based on the control signal output from the controller 15, Warning indicator 17
It is composed of.

Each of the wheel speed sensors 12FL to 12R is composed of an electromagnetic pickup. Among these, sensor 1
2FL and 12FR are attached to the front left and right wheels, and the sensor 12R is attached to the final reduction gear, respectively, thereby generating sine wave voltage signals v ₁ and v with frequencies proportional to the respective rotational speeds of the front left and right wheels and the average rotational speed of the two rear wheels. ₂ and _v3 are output to the controller 15, respectively. Further, the longitudinal acceleration sensor 13 is provided at a predetermined position on the vehicle body, detects acceleration in the longitudinal direction, and outputs an acceleration signal g(t) in the form of an analog voltage corresponding to this to the controller 15, with the acceleration being considered positive. do. Furthermore, the brake switch 14 is provided at a predetermined position that is linked to the operation of the brake pedal 6, and becomes a logic H level (or logic "1") when the brake pedal 6 is depressed, and becomes a logic high level (or logic "1") when the pedal is released. A switch signal S having an L level (or logic "0") is output to the controller 15.

As shown in FIG. 2, the controller 15 inputs the voltage signals v 1 to v ₃ supplied from the wheel speed sensors 12FL to 12R to its input stage and converts them into a wheel speed signal V _W1 which is a voltage signal proportional to the frequency of the voltage signals v ₁ to v 3 supplied from the wheel speed sensors 12 FL to 12 R. A wheel speed calculation circuit 18 is equipped which individually converts (frequency [F] - voltage [V] conversion) into ~V _W3 . The output side of this wheel speed calculation circuit 18 has its output signal V _W1 ~
It reaches the microcomputer 22 via the A/D converters 20A to 20C for each _VW3 , and also reaches the input end of the select low switch 24.

The select low switch 24 selects (select low) the lowest value of the input wheel speed signals V _W1 to V _W3 as the signal closest to the actual vehicle speed considering wheel spin, and selects this as the minimum wheel speed signal.
V is configured to output as _WL . Furthermore, the output side of this select low switch 24 is
It reaches the initial value input terminal of the integrator 26 for estimating the vehicle speed, and also reaches the microcomputer 22 via the A/D converter 28.

Further, the output end of the longitudinal acceleration sensor 13 is connected to the microcomputer 22 via an integrator 26 and an A/D converter 30 in the controller 15, and is also directly connected to the microcomputer 22 via an A/D converter 31. It reaches 22. Further, the switch signal S from the brake switch 14 is supplied to the microcomputer 22, and
It is applied to the integrator 26 as a control input to determine whether or not to perform an integral calculation.

That is, when the switch signal S reaches the logic H level, the integrator 26 uses the minimum wheel speed signal V _WL (t ₀ ) at the time t ₀ at which it rises as an initial value, and converts it into the longitudinal acceleration detection signal g(t). On the other hand, the calculation based on V _ref (t) = V _WL (t ₀ ) + ∫g(t)dt ...(1) is performed to output the estimated vehicle speed signal V _ref , and the switch signal S is set to logic L level. When it reaches the initial value V WL (t), it is reset to the initial value V _WL (t).

Here, the wheel speed sensors 12FL to 12R and the wheel speed calculation circuit 18 form a wheel speed detection means, and the brake switch 14 and the integrator 26 form an estimated vehicle speed calculation means.

The microcomputer 22 includes at least an interface circuit, an arithmetic processing unit, and a storage device. The arithmetic processing unit reads each detection signal via the interface circuit, performs predetermined arithmetic and processing (see Figs. 3 to 5) according to a pre-stored program, and controls the actuator drive circuit as necessary. Control signals are individually output to 36. The storage device stores in advance fixed data such as programs and control maps necessary for the execution of the arithmetic processing device, and is also capable of temporarily storing the processing results.

The actuator drive circuit 36 sends hydraulic pressure control signals for each control system to the actuator section 16 in response to control signals supplied from the microcomputer 22.
I ₁ to I ₃ (each of these signals actually consists of two signals instructing hydraulic pressure and pressure increase, and an oil pump drive signal, as will be described later).

Furthermore, the actuator 16 has a front left side,
Actuators for the front right and rear wheels are individually equipped. Each of the actuators is formed in a well-known manner (for example, see the structure described in Japanese Patent Laid-Open No. 60-252057). That is, from the master cylinder 8 to the wheel cylinder 10FL (~1
0RR) and a solenoid valve on the inflow side that can intermittent the oil flowing into the wheel cylinder 10FL (~10
It includes an electromagnetic on-off valve on the outflow side that can intermittent the flow of oil returning from RR) to the master cylinder 8, and an oil pump for oil recovery. Therefore, each solenoid valve and pump are driven according to the command mode (pressure increase [normal brake], pressure holding, and pressure reduction modes) based on the hydraulic pressure control signal I ₁ (~I ₃ ), and as a result, the cylinder pressure It is possible to increase the pressure (including gradual pressure increase in steps), hold the pressure, and reduce the pressure.

Next, the operation of the above embodiment will be explained with reference to FIGS. 3 to 6.

When the ignition switch is turned on,
The power is turned on and the device starts up.

First, the operation of each part will be explained. Wheel speed sensor 1
2FL to 12R detect AC voltage signals v ₁ to v ₃ corresponding to the wheel speed, and the longitudinal acceleration sensor 13 detects an acceleration signal g( t) is detected.

In the controller 15, the input AC voltage signal
The signals v ₁ to _{v 3} are individually converted into wheel speed signals V _W1 to V _W3 by the wheel speed calculation circuit 18, digitized, and supplied to the microcomputer 22. At the same time, the minimum wheel speed signal V _WL is selected by the select low switch 24, digitized, and then supplied to the microcomputer 22 as well as to the integrator 26. This integrator 26
When the switch signal S is at the logic H level during braking, the calculation based on the equation (1) is performed and an estimated vehicle speed signal V _ref is output. Further, when the brake is not applied, the switch signal S is at the logic L level, and the output signal V _ref of the integrator 26 is always reset to the initial value at that time, so that V _ref =V _WL .

Next, the timer interrupt processing shown in FIGS. 3 to 5, which is executed by the microcomputer 22 at fixed intervals (for example, 20 msec), will be explained.

First, FIG. 3 will be explained. In the step of the figure, the arithmetic processing unit of the microcomputer 22 reads the estimated vehicle speed signal V _ref related to the integrator 26, temporarily stores this value, and moves on to the step. In step, it is determined whether or not the vehicle is stopped by determining whether or not the estimated vehicle body speed V _ref read in step exceeds a predetermined speed (for example, 5 km/h) at which the vehicle is considered to be in a pseudo-stop state.

If this judgment indicates that the vehicle is not stopped, the process moves to step 1, and the longitudinal acceleration sensor 13
Clears the timer T that monitors the abnormal value output time, removes the flag F indicating that an abnormality has occurred in the sensor 13 and its output system, etc. (hereinafter referred to simply as an abnormality in the sensor 13), and returns to the main program. Return. Next, the process moves to step and the display 17 is turned off.

On the other hand, while repeating the timer interrupt processing, if it is determined that the vehicle is stopped at a step,
Go to the step, read the longitudinal acceleration detection signal g(t), and at the step, calculate |g with respect to the reference value _G0 .
Determine whether (t)｜≧G ₀ . Here, the reference value G ₀
is a value corresponding to the output value of the longitudinal acceleration sensor 12 when the vehicle is stopped on a road surface with the maximum inclination angle at which the vehicle can be stopped (for example, if the maximum coefficient of static friction between the road surface and the tires is 1.0, it is possible to stop the vehicle) Maximum tilt angle is 45°
The sensor output value at this time is set to a value corresponding to approximately ±0.7G). Here, the reference value
Considering uphill and downhill, G ₀ is set to +G ₀ in the uphill direction and -G ₀ in the downhill direction, as shown in FIG. 6 and 2.

Therefore, if |g(t)|<G ₀ in the step,
Assuming that the output value g(t) is normal, the process moves to the above-mentioned step ~, and if |g(t)|≧G ₀ , the output value g
(t) is abnormal, but in order to see whether the abnormality is temporary, we move on to step . Then, in a step, the timer T is incremented, and in a step, it is determined whether or not the count value of the timer T is T≧T ₀ with respect to the reference value T ₀ .
Here, the reference value T ₀ is a value corresponding to a time t _D at which it can be determined that the abnormal output of the sensor 13 is permanent.

Therefore, if T<T ₀ in step, it is determined that it cannot yet be determined that the sensor is abnormal, and the flag F is kept cleared in step. On the other hand, if T≧T ₀ in step, it is assumed that there is a sensor abnormality, and the process moves to step 1, sets flag F, lights display 17 in step 11 to issue a warning, and then returns to the main program. .

In other words, by performing the process shown in Figure 3,
If the flag F=0, it is recognized that the longitudinal acceleration sensor 13 is in a normal state, and if F=1, it is recognized that the sensor 13 is in an abnormal state where some kind of failure has occurred.

Next, the process shown in FIG. 4 will be explained. In the step shown in the figure, the arithmetic processing unit determines the contents of the flag F determined as shown in FIG. In other words,
If F=0, which corresponds to the normal state in the step, then
Move to step , and output the estimated vehicle speed signal.
V _ref and wheel speed signal V _Wi (i=1 to 3) are read in sequence, and these values are temporarily stored.

Next, the process moves to step, and based on the value V _wi read in step, wheel acceleration/deceleration V〓V _wi is calculated from the difference from the wheel speed V _wi related to the previous control cycle, and the process moves to step. In this step, the slip ratio S _i is calculated based on the formula: Si=V _ref -V _wi /V _ref ×100 (i=1 to 3), and this is temporarily stored before returning to the main program.

On the other hand, when it is determined that F=1 in step while repeating the timer interrupt processing, the processing in steps ~ is performed instead. That is, in the step, the wheel speed signals V _wi are sequentially read, and in the step, the maximum value V _WH is selected (high select) from among the signals V _wi read in the step. Furthermore, in the step, the maximum value V _WH related to the step
is set as the estimated vehicle speed V _ref . After this, the above-mentioned steps are performed.

In other words, by performing the process shown in FIG. 4, when the sensor 13 is in a normal state, the estimated vehicle speed V _ref is calculated based on the detected value g(t), and the estimated vehicle speed V ref is calculated based on the detected value g(t). A slip rate S _i is calculated. On the other hand, if the sensor 13 is in an abnormal state, its detected value g(t) cannot be used, so instead, the estimated vehicle speed according to the wheel speed V _wi is used.
V _ref and slip rate S _i are calculated. Here, the reason why the high selection is performed during this alternative calculation is to estimate a vehicle speed as high as possible to avoid a no-brake state.

Next, the process shown in FIG. 5 will be explained. This process is performed based on the wheel acceleration/deceleration _Vwi and the slip rate S _i that have been updated and stored in the step of FIG. 4 described above. AS indicates a control flag, and L indicates a pressure reduction timer, which is cleared when the anti-skid control ends (step) (step 17).

Therefore, in step, the slip rate S _i <S ₀ (S ₀ is the reference slip rate, for example, 15%), in step, the decompression timer L = 0, in step "NO", and in step, the wheel acceleration/deceleration V〓 _wi <α ₁ (α ₁ is the reference value on the acceleration side: positive value), step V _wi > α ₂
( _α2 is a reference value on the deceleration side: a positive value) When "YES" is satisfied in the steps one after another, the process moves to the step and the rapid pressure mode (normal brake) is commanded. Therefore, the hydraulic pressure control signal I _i supplied to the actuator section 16 is in a predetermined pressure increase mode,
Oil from the master cylinder 8 can flow into the wheel cylinders 10FL (~10RR). In other words, when the brake pedal 6 is depressed, the brake pressure increases and the vehicle enters a braking state. On the other hand, when the brake pedal 6 is not operated, the vehicle is in a non-braking state.

Here, the judgment as to whether or not the control end condition of the step is satisfied is determined specifically by determining whether the estimated vehicle speed V _ref is a predetermined value V _ref0 corresponding to the stopped state, and V _ref ≦
It depends on whether V _ref0 or not.

Therefore, sudden braking is applied at an arbitrary time, and the sudden increase in brake pressure causes the wheel speed V _wi to gradually decrease.
When the wheel deceleration V〓 _wi falls below the reference value −α ₂ and thus satisfies V _wi ≦ −α ₂ in the step, the hydraulic pressure control signal I _i is set to a predetermined holding mode in the step to maintain the brake pressure. is commanded.

Since high-pressure braking is performed even during this pressure holding, the slip rate S _i gradually increases, and step S _i ≧ S ₀ and step V _wi < α ₁ are satisfied, and in step 11, L = L ₀ (predetermined integer value) and
AS=1 processing is done, “NO” at step,
If the step is ``YES'', the depressurization mode of the step is commanded. In other words, the hydraulic control signal
I _i enters a predetermined pressure reduction mode, and the hydraulic pressure of the wheel cylinder 10FL (~10RR) decreases.

Due to this pressure reduction, the wheel speed V _wi gradually recovers and changes to approach the vehicle body speed, so the wheel acceleration V _wi gradually increases. Then, in step S _i ≧S ₀ and V〓 _wi ≧α ₁ in step 13, the decompression timer L=0 is processed, “NO” in step 1, “YES” in step 14, and “ When the result is "NO", and when S _i <S ₀ at the step, the result is "NO" at the step,
Thereafter, when processing is performed through steps 14 to 14, the hold mode at step 15 is commanded in the same manner as described above.

By maintaining this hydraulic pressure, the slip ratio S _i <S ₀ and the wheel acceleration/deceleration V〓 _wi become −α ₂ <V〓 _wi <
When _α1 is satisfied, the process proceeds to step 16 through steps 1 to 16, where the hydraulic pressure control signal I _i is set to a predetermined slow pressure increase mode, and the cylinder pressure increases in a substantially slip-like manner.

Thereafter, each wheel cylinder 10FL is operated until braking is completed and the above-mentioned control end conditions are satisfied.
Pressure reduction, holding, slow pressure increase, and holding mode are repeated every ~10RR, resulting in a skid cycle. When the control termination condition is satisfied, the routine returns to the normal braking mode at step 17.

In addition, during braking on a high friction coefficient road, if the slip rate S _i improves to below its standard value S ₀ faster than the recovery of the wheel acceleration V _wi while the pressure is being reduced, the Move to step 18. In this step 18, the decompression timer L=
Go to L-1 and wait. After this wait, the step
The slow pressure increase mode according to step 16 is commanded before the holding mode according to step 15.

Here, the overall operation will be explained along the passage of time based on FIG.

Assuming that the vehicle is currently running at a constant speed, the flag F in the process shown in FIG. 3 has been cleared (stepped), so in the timer interrupt process shown in FIG. 4, the longitudinal acceleration g( Processing related to reading t) is instructed.

Therefore, at time _t0 , a sudden braking state is entered, and a logic H level switch signal S is output from the brake switch 14.
is output from the longitudinal acceleration sensor 13 as shown in FIG.
Suppose that the longitudinal acceleration g(t) is detected as follows. Therefore, the integrator 26 uses this acceleration g(t) to calculate the estimated vehicle speed V _ref using equation (1), and supplies it to the microcomputer 22 . The microcomputer 22 calculates the wheel acceleration/deceleration V _wi based on the estimated vehicle speed V _ref and the wheel speed V _wi (FIG. 4). Then, until the time _t1 when braking is completed, a good braking state is obtained in which wheel lock is prevented by the hydraulic pressure control according to the process shown in FIG. 5 described above.

When the vehicle comes to a stop on a downhill road at time t ₁ (the ignition switch is turned on), the normal brake mode (step) is commanded in the process shown in FIG. 5, while the timer interrupt process shown in FIG. Then, processing is performed through steps. Now, assuming that the longitudinal acceleration sensor 13 is normal, the flag F is maintained clear (step in the figure).

In this normal state, the longitudinal acceleration sensor 13
When some abnormality occurs, the detected longitudinal acceleration value g(t)
exceeds the downhill side reference value _-G0 at time _t2 , and this state is also the count-up value of the monitoring timer T.
Assume that a predetermined time t _D corresponding to T ₀ has elapsed. That is, at time t ₃ (=t ₂ +t _D ), the flag F is set to recognize the abnormal state, and the display 17 is turned on (steps to 11 in FIG. 3). Thereby, an abnormality in the longitudinal acceleration sensor 13 can be easily determined, and appropriate measures can be taken thereafter.

On the other hand, when the controller 15 recognizes an abnormality in the sensor 13, the vehicle speed is estimated based on the wheel speed.
The value is automatically switched to the value based on the high select value of V _wi . As a result, even when the vehicle is running, where sensor repair or the like cannot be performed immediately, the worst-case estimation of the vehicle body speed thereafter can be reliably avoided, and the fail-safe function can be enhanced.

In this embodiment, the stop detection means is configured by the processing in step 3 of FIG. A computation stop command means is configured, and performs the steps from FIG. 4 to the processing in FIG.
This constitutes a brake pressure control means.

Note that the controller 15 in the above embodiment
can be configured entirely by a computer, while the microcomputer 2
2 can also be constructed from electronic circuits such as counters, comparators, flip-flops, etc.

Furthermore, although the above embodiment has been described with respect to an anti-skid control device for four-wheel control, the present invention is not necessarily limited thereto, and can also be applied to, for example, an anti-lock brake for rear two-wheel control.

[Effect of idea]

As explained above, this invention provides that, in a stopped state, the detected value of the longitudinal acceleration detection means such as a longitudinal acceleration sensor exceeds a predetermined value set in advance in response to an abnormality in the detected value, and this state If it is determined that the abnormal condition continues for a certain period of time, the calculation of the estimated vehicle speed based on the detected longitudinal acceleration value will be discontinued. Therefore, the above-mentioned predetermined value is set to, for example, the longitudinal acceleration equivalent to the maximum inclination angle at which the vehicle can be stopped. By doing so, it is possible to accurately determine an abnormality in the longitudinal acceleration detection means in a stopped state, and it is possible to reliably eliminate adverse effects such as a decline in braking performance due to performing anti-skid control with many errors in such an abnormal state, and to provide a fail-safe function. This has the effect of expanding the scope of the project.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing how this invention corresponds to the scope of the claims for utility model registration, Fig. 2 is a block diagram showing the configuration of an embodiment of this invention, and Figs. 3 to 5 are each executed on a microcomputer. A schematic flowchart showing the processing procedure, and FIG. 6 is a timing chart showing a control example. In the figure, 2 is a brake, 4 is an anti-skid control device, 10FL to 10RR are wheel cylinders, 1
2FL to 12R are wheel speed sensors, 13 is a longitudinal acceleration sensor, 14 is a brake switch, 15 is a controller, 16 is an actuator section, 22 is a microcomputer, 26 is an integrator, and 36 is an actuator drive circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] Wheel speed detection means for detecting the wheel speed of the wheels; longitudinal acceleration detection means for detecting the longitudinal acceleration of the vehicle body; and the longitudinal acceleration detection value with the wheel speed detection value as an initial value. Estimated vehicle speed calculation means for calculating the estimated vehicle speed by integrating the
The anti-skid control device includes a brake control means for controlling the brake pressure of the wheels based on the estimated vehicle speed calculation value and the detected wheel speed value, and a stop detection means for detecting a stop, and the stop detection means detects a stop. abnormal state determination for determining whether or not the detected value of the longitudinal acceleration detection means exceeds a predetermined value set in advance in response to the abnormality of the detected value and this state continues for a predetermined period of time. An anti-skid control device comprising: means for instructing the estimated vehicle speed calculating means to stop calculating when a predetermined abnormal state is determined by the abnormal state determining means.