JP2000302019A - Car body speed presuming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the risk that the presumptive car body speed appears at an erroneous value in case a failure has occurred in a means to sense the fore- and-aft speed of the car body. SOLUTION: The wheel speed Vwfi after a filter processing is calculated (S20), and that value among the obtained wheel speeds Vwfi which is nearest the actual car body speed is decided as the reference wheel speed (car body speed before the change rate limiting correction) Vwc (S30). The presumptive car body deceleration Gb based upon the brake operation amount is calculated on the basis of the master cylinder pressure Pm (S40), and the incremental limitation amount ΔVwu of the car body speed is calculated on the basis of the fore-and-aft acceleration Gx and presumptive deceleration Gb of the car body (S50) while the decremental limitating amount ΔVwd of the car speed is calculated on the basis of the fore-and-aft acceleration Gx and presumptive deceleration Gb of the car body (S60), and using Vbaf as the previous value of Vba, the middle value of the Vwc, Vbaf-ΔVwd, and Vbaf+ΔVwu is decided as the car body speed Vba after the change rate limiting correction (S70).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to estimating a vehicle speed of a vehicle, and more particularly to a vehicle speed estimating device for estimating a vehicle speed based on wheel speeds.

[0002]

2. Description of the Related Art In a vehicle such as an automobile, a vehicle speed estimating device for estimating a vehicle speed used for vehicle behavior control by controlling braking / driving force of wheels or anti-skid control is disclosed in As described in the related art of Japanese Patent Application Laid-Open No. 10-138905, the vehicle speed is detected along with the longitudinal acceleration of the vehicle body, the vehicle speed is estimated based on the detected wheel speed, and the estimated vehicle speed is calculated based on the detected wheel speed. 2. Description of the Related Art A vehicle speed estimating apparatus configured to correct a change rate by limiting the rate of change based on a detected longitudinal acceleration of a vehicle body is conventionally known.

[0003] Generally, the detected wheel speed includes an error component such as a sudden change component when passing through unevenness of a road surface, a component of acceleration / deceleration slip, and noise. According to this, since the estimated rate of change of the vehicle speed is limited based on the longitudinal acceleration of the vehicle, it is possible to estimate the vehicle speed at which the influence of the error component as described above is small.

[0004]

However, in the conventional vehicle speed estimating apparatus as described above, if an abnormality such as a disconnection, a short circuit, or a relatively large zero point offset occurs in a sensor for detecting the longitudinal acceleration of the vehicle body, Since the estimated rate of change of the vehicle speed is limited based on the abnormal longitudinal acceleration, the estimated vehicle speed has an abnormal value, which causes a problem that the behavior control of the vehicle is inappropriately performed.

The problem is that, for example, the longitudinal acceleration of the vehicle body is detected, the vehicle speed and the longitudinal acceleration of the vehicle body are estimated based on the wheel speed, and the offset value of the estimated longitudinal acceleration of the vehicle body with respect to the detected longitudinal acceleration of the vehicle body Is calculated, and the rate of change of the estimated vehicle body speed is limited by a limit value based on the estimated longitudinal acceleration and the offset value of the vehicle body described in Japanese Patent Application Laid-Open No. H10-138905. It is not completely eliminated by the estimator.

According to the present invention, a wheel speed and a longitudinal acceleration of a vehicle body are detected, a vehicle speed is estimated based on the detected wheel speed, and a change rate of the estimated vehicle speed is limited based on the detected longitudinal acceleration of the vehicle body. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems in the conventional vehicle speed estimation device configured as described above, and a main problem of the present invention is to estimate and estimate the deceleration of a vehicle due to a braking operation. By limiting the rate of change of the vehicle speed also by the deceleration, it is possible to reduce the possibility that the vehicle speed is estimated to be an abnormal value when an abnormality occurs in the means for detecting the longitudinal acceleration of the vehicle.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a motor vehicle comprising: a wheel speed detecting means for detecting a wheel speed; and a wheel detected by the wheel speed detecting means. And a vehicle speed estimating device for estimating the vehicle speed based on the speed.
Means for detecting the longitudinal acceleration of the vehicle body, means for detecting the amount of braking operation by the driver, means for estimating the deceleration of the vehicle body based on the amount of braking operation, and determining the rate of change of the estimated vehicle body speed of the vehicle body. Correction means for correcting the estimated vehicle speed by limiting based on the longitudinal acceleration and the deceleration of the vehicle body.

According to the first aspect of the invention, the deceleration of the vehicle body is estimated based on the amount of braking operation by the driver, and the rate of change of the estimated vehicle speed is limited based on the longitudinal acceleration of the vehicle body and the deceleration of the vehicle body. As a result, the estimated vehicle body speed is corrected, so that the means for detecting the longitudinal acceleration of the vehicle body becomes abnormal, and the detected longitudinal acceleration of the vehicle body becomes an abnormal value, and the estimated rate of change of the vehicle body speed is changed. Even if the vehicle speed is not properly limited by the longitudinal acceleration of the vehicle, the estimated rate of change of the vehicle speed is limited based on the vehicle deceleration based on the braking operation amount, so that the corrected vehicle speed becomes an abnormal value. Is reduced.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the above-mentioned structure, the degree of restriction based on the deceleration of the vehicle body is determined by detecting the longitudinal acceleration of the vehicle body. The degree of restriction is based on the longitudinal acceleration of the vehicle body when the means for performing the operation is normal.

In general, the actual deceleration of the vehicle body caused by the braking operation by the driver differs depending on the running condition of the vehicle, such as the load on the vehicle and the road surface condition. Therefore, the deceleration of the vehicle body based on the amount of braking operation by the driver is estimated. The accuracy is lower than the accuracy of the deceleration detection by the normal longitudinal acceleration detecting means. Therefore, the degree of limitation based on the deceleration of the vehicle body is limited based on the longitudinal acceleration of the vehicle body when the means for detecting the longitudinal acceleration of the vehicle body is normal. If the degree is set equal to the degree, the rate of change of the vehicle body speed may be unnecessarily excessively limited based on the deceleration of the vehicle body.

According to the second aspect of the present invention, the degree of restriction based on the deceleration of the vehicle body is lower than the degree of restriction based on the longitudinal acceleration of the vehicle body when the means for detecting the longitudinal acceleration of the vehicle body is normal. When the means for detecting the longitudinal acceleration of the vehicle body is normal, the rate of change of the vehicle body speed is reliably prevented from being unnecessarily excessively limited based on the deceleration of the vehicle body.

According to the present invention, in order to effectively attain the above-mentioned main object, the means for detecting the braking operation amount detects the master cylinder pressure. The sensor is configured to be a sensor.

According to the third aspect of the invention, since the braking operation amount is the master cylinder pressure which increases and decreases due to the driver's braking operation, the braking operation amount is reliably detected, and thereby the braking operation amount is determined based on the driver's braking operation amount. The deceleration of the vehicle is reliably estimated.

[0014]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the vehicle body speed estimating means filters the detected wheel speed, and executes the filtered wheel speed. It is configured to estimate the vehicle body speed based on the following (preferred mode 1).

According to another preferred embodiment of the present invention, in any one of the first to third aspects, the detected longitudinal acceleration of the vehicle body is Gx, and the detected longitudinal acceleration is based on a braking operation amount by the driver. Assuming that the deceleration of the vehicle body is Gb and Vwdc is a positive constant, the correction means sets the vehicle speed reduction limit amount ΔVwd per unit time to a value obtained by subtracting Vwdc from the smaller value of Gx and -Gb. Thus, the estimated reduction rate of the vehicle speed is limited based on the longitudinal acceleration Gx of the vehicle body and the deceleration Gb of the vehicle body (preferred mode 2).

According to another preferred embodiment of the present invention, in any one of the first to third aspects, the detected longitudinal acceleration of the vehicle body is Gx, and the detected longitudinal acceleration is based on a braking operation amount by the driver. Assuming that the deceleration of the vehicle body is Gb and Vwuc is a positive constant, the correction means sets the increase limit amount ΔVwu of the vehicle body speed per unit time to a value obtained by adding Vwuc from the larger value of Gx and -Gb. Thus, the estimated increase rate of the vehicle body speed is limited based on the longitudinal acceleration Gx of the vehicle body and the deceleration Gb of the vehicle body (preferred mode 3).

According to another preferred aspect of the present invention, in the configuration according to the second aspect, the means for estimating the deceleration of the vehicle body based on the amount of braking operation is provided in various running conditions of the vehicle. It is configured to estimate the deceleration of the vehicle body to a value smaller than the actual deceleration of the vehicle body that occurs for various braking operation amounts (preferred mode 4).

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing one embodiment of a vehicle body speed estimating apparatus according to the present invention applied to an FF (front engine front drive) vehicle.

In FIG. 1, 10FL and 10FR are steering wheels and left and right front wheels of the vehicle 12 which are driving wheels, respectively, and 10RL and 10RR are left and right rear wheels which are driven wheels, respectively. Each wheel has a wheel cylinder 14
FL, 14FR, 14RL, and 14RR are provided. The braking force of each wheel is controlled by controlling the braking pressure of the wheel cylinders 14FR, 14FL, 14RR, and 14RL by the hydraulic circuit 18 of the braking device 16.

Although not shown in detail in FIG. 1, the hydraulic circuit 18 includes an oil reservoir, an oil pump, various valve devices, and the like. It is controlled by a master cylinder 22 driven in accordance with a stepping-down operation, and is controlled by an electronic control unit 24 at the time of individual control of each wheel braking force such as a vehicle behavior control by controlling a braking force.

As is well known, left and right front wheels 10FL and 10FR
Is a torque converter and transmission 28, left and right drive shafts 30FL and 30
The engine 26 is rotationally driven through the FR, and the engine 26 is controlled by an engine control device (not shown).

The wheels 10FL to 10RR are provided with wheel speed sensors 32FL to 32RR for detecting the rotational speeds Rfl, Rfr, Rrl, and Rrr of the corresponding wheels, respectively. The electronic control unit 24 has wheel speed sensors 32FL to 32RR. A / D
Via signal processing circuits not shown in FIG. 1 including a converter and a multiplier for multiplying a constant corresponding to the wheel radius, the wheel speeds (peripheral speeds) Vwfl, Vwfr, Vwrl of the wheels 10FL, 10FR, 10RL, 10RR respectively. , Vwrr.

A signal indicating the longitudinal acceleration Gx of the vehicle body is input from the longitudinal acceleration sensor 34 to the electronic control unit 24, and a signal indicating the pressure Pm in the master cylinder 22 is input from the pressure sensor 36. Longitudinal acceleration sensor 3
4 detects the longitudinal acceleration Gx of the vehicle body with the acceleration direction of the vehicle as positive.

The electronic control unit 24 includes, for example, a central processing unit (CPU), a read-only memory (ROM),
It may be a microcomputer having a general configuration including a random access memory (RAM) and an input / output port device, which are connected to each other by a bidirectional common bus.

The electronic control unit 24 stores a vehicle speed calculation flow of FIG. 2 and a braking force control flow (not shown) as described later, and is based on the rotation speeds detected by the wheel speed sensors 32FL to 32RR. Wheel speed Vwi of each wheel
(I = fl, fr, rl, r) based on the vehicle speed V
b, and the braking slip ratio of each wheel is calculated using the vehicle speed Vb as a reference speed. When the braking slip ratio is not within a predetermined range, the braking force is adjusted so that the braking slip ratio of the wheel falls within a predetermined range. The anti-skid control for increasing or decreasing is performed.

When the behavior of the vehicle is unstable, the electronic control unit 24 controls the braking force of each wheel to increase or decrease so that the braking slip rate of each wheel becomes the target slip rate for stabilizing the behavior of the vehicle. Note that the control of the braking force itself for the anti-skid control and the behavior control does not form the gist of the present invention, and is well known in the art, so that the detailed description thereof will be omitted.

Next, a vehicle speed calculation routine in the illustrated embodiment will be described with reference to a flowchart shown in FIG. The arithmetic control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

First, in step 10, a signal indicating the wheel speed Vwi detected by the wheel speed sensors 32FL to 32RR is read. In step 20, for example, each wheel of the past several cycles and the current cycle is read. By performing the filtering process by the moving average process on the speed Vwi, the wheel speed Vwfi (i = fl, f
r, rl, r) are calculated.

In step 30, the wheel speed closest to the actual vehicle speed of the vehicle among the wheel speeds Vwfi after the filter processing is the reference wheel speed Vwc as the vehicle speed before correction.
Is determined. Various methods for determining the reference wheel speed Vwc have conventionally been proposed in the art, and do not form the subject of the present invention. At times, it is determined to be the larger one of the wheel speeds of the driven wheels (the left and right rear wheels in the illustrated embodiment).

In step 40, an estimated deceleration Gb of the vehicle body based on the braking operation amount is calculated from a map corresponding to the graph shown in FIG. 3 based on the master cylinder pressure Pm. Note that the estimated deceleration Gb is set to be smaller than the actual deceleration of the vehicle body (the hatched area in FIG. 3) that occurs in various running situations of the vehicle.

In step 50, MAX () is set to the larger one of the values in parentheses, and Vwuc is set to a positive constant according to the following equation (1). Speed increase limit ΔV
wu is calculated. Note that the constant Vwuc is obtained experimentally, for example. ΔVwu = MAX (Gx, -Gb) + Vwuc (1)

Similarly, in step 60, MIN
() Is the smaller of the values in parentheses, and Vwd
With c as a positive constant, the vehicle speed reduction limit amount ΔVwd per cycle time in the flowchart shown in FIG. Note that the constant Vwdc is also obtained experimentally, for example. ΔVwd = MIN (Gx, −Gb) −Vwdc (2)

In step 70, MID () is set to an intermediate value among the values in parentheses, and Vbaf is set to the vehicle speed Vba after the change rate limit correction calculated in the previous cycle according to the following equation (3). Vehicle speed V after change rate limit correction
ba is calculated. Vba = MID (Vwc, Vbaf−ΔVwd, Vbaf + ΔVwu) (3)

In step 80, the vehicle speed Vba after the correction of the change rate limit is used for controlling the braking force, and is rewritten to Vbaf in preparation for the next cycle.

Thus, according to the illustrated embodiment, in step 20, the filtered wheel speed Vwfi is calculated, and in step 30, the value of the filtered wheel speed Vwfi that is closest to the actual vehicle speed is used. Is determined as the reference wheel speed (vehicle speed before correction of the change rate limitation) Vwc.

In step 40, the estimated deceleration Gb of the vehicle body based on the braking operation amount is calculated based on the master cylinder pressure Pm. In step 50, the estimated vehicle deceleration Gx and the estimated vehicle deceleration Gb are calculated based on the vehicle body longitudinal acceleration Gx. The speed increase restriction amount ΔVwu is calculated, and in step 60, the vehicle body speed reduction limit amount ΔVwd is calculated based on the longitudinal acceleration Gx of the vehicle body and the estimated vehicle deceleration Gb, and in step 70, Vwc, Vbaf−ΔVwd , Vbaf + ΔVwu, the vehicle speed Vba after the change rate limit correction is calculated.

Therefore, according to the illustrated embodiment, the rate of change of the vehicle body speed Vba is limited by both the longitudinal acceleration Gx of the vehicle body and the estimated deceleration Gb of the vehicle body. Since the longitudinal acceleration sensor 34 functions as a guard against the limitation due to the acceleration Gx, an abnormality occurs in the longitudinal acceleration sensor 34, and the longitudinal acceleration Gx of the vehicle body detected by the longitudinal acceleration sensor becomes a negative very small value (a very large deceleration value). When this happens, the rate of change of the vehicle body speed Vba is limited not by the abnormal longitudinal acceleration Gx but by the estimated deceleration Gb of the vehicle body.

Therefore, even if the vehicle speed Vwc before the correction is sharply reduced due to the superposition of an error component such as noise on the wheel speed even though the actual vehicle speed is not sharply reduced, the vehicle body after the correction is It is possible to prevent the speed Vba from suddenly dropping, so that the corrected vehicle speed Vba becomes an abnormally smaller value than the actual vehicle speed in a situation where the longitudinal acceleration sensor 34 becomes abnormal. Further, it is possible to prevent inappropriate control of the braking force from being performed.

In particular, according to the illustrated embodiment, the estimated deceleration Gb is calculated to be smaller than the actual deceleration of the vehicle body which occurs for various master cylinder pressures Pm in various driving situations of the vehicle. Since the degree of limitation based on the estimated deceleration Gb is lower than the degree of limitation based on the longitudinal acceleration Gx of the vehicle body when the longitudinal acceleration sensor 34 is normal, when the longitudinal acceleration sensor 34 is normal, the estimated vehicle speed Vb It is possible to reliably prevent the rate of change from being unnecessarily excessively limited based on the estimated deceleration Gb of the vehicle body.

If, for example, the longitudinal acceleration sensor is erroneously assembled to the vehicle in a direction opposite to the longitudinal direction of the vehicle, the longitudinal acceleration Gx becomes a negative value in a situation where the vehicle is actually accelerating. The vehicle speed increase limit amount Δ
When Vwu is calculated to be Gx + Vwuc, the increase limiting amount ΔVwu becomes a very small positive value or a negative value even though the vehicle is accelerating and the actual vehicle speed is increasing. The increase in the speed Vb is unnecessarily suppressed or prevented.

On the other hand, according to the illustrated embodiment, the increase limit amount .DELTA.Vwu of the vehicle body speed is calculated in step 50 according to the above equation 1, and since the estimated deceleration Gb is 0, MAX (Gx, -Gb ) Also becomes 0, so that the increase limit amount ΔVwu is prevented from becoming a very small positive value or a negative value in the above-described situation, and the estimated increase in the vehicle body speed Vb becomes unnecessary. It can be prevented from being suppressed or prevented.

The vehicle speed increase limit amount ΔVwu is equal to Gx +
When calculated to Vwuc, as shown in FIG. 4, when the vehicle 100 is traveling uphill on a slope 102 having a relatively large gradient, the speed is increased with a relatively small acceleration, and the vehicle 100 acts on the vehicle 100. Even if the magnitude of the component Gi of the gravity behind the vehicle is larger than the actual longitudinal acceleration Gxa of the vehicle and the detected longitudinal acceleration Gx becomes a negative value, the vehicle accelerates and the actual vehicle speed increases. Is increased, the increase limit amount ΔVwu becomes a very small positive value or a negative value, and the increase in the estimated vehicle body speed Vb is unnecessarily suppressed or prevented.

On the other hand, according to the illustrated embodiment, the increase limit amount ΔVwu of the vehicle speed is calculated according to the above equation (1).
Since the estimated deceleration Gb is 0, MAX (Gx, -G
Since b) also becomes 0, it is possible to prevent the increase limit amount ΔVwu from becoming a very small positive value or a negative value even in the above-described uphill situation, and the increase in the estimated vehicle body speed Vb is prevented. Unnecessarily suppressed or prevented can be prevented.

Also, as shown in FIG.
Is decelerated by braking when traveling downhill on a slope 102 having a relatively large gradient, and the component Gi of gravity acting on the vehicle 100 in front of the vehicle is the magnitude of the actual longitudinal acceleration Gxa (negative value) of the vehicle. Even if the detected longitudinal acceleration Gx is equal to or greater than 0 and the detected longitudinal acceleration Gx is 0 or a positive value, the vehicle speed is reduced even if the vehicle speed is reduced and the actual vehicle speed is reduced. The amount ΔVwd becomes 0 or a positive value, and the decrease in the estimated vehicle body speed Vb is unnecessarily suppressed or prevented.

On the other hand, according to the illustrated embodiment, the vehicle speed reduction limit amount ΔVwd is calculated in step 60 according to the above equation 2, and the estimated deceleration Gb is a certain positive value. Since MIN (Gx, -Gb) becomes a negative value, the decrease restriction amount ΔV in the downhill situation as described above.
It is possible to prevent wd from becoming 0 or a positive value, thereby preventing the estimated decrease in the vehicle body speed Vb from being unnecessarily suppressed or prevented.

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments may be included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the above-described embodiment, the filtering process is a moving average process. However, as long as a rapid change in the wheel speed value used for estimating the vehicle body speed can be suppressed, for example, a low-pass filter is used. Any filtering known in the art, such as processing or Butterworth filtering may be used.

In the above embodiment, the master cylinder pressure Pm is detected as the braking operation amount by the driver. However, the depression force or the depression stroke of the brake pedal 20 is detected as the braking operation amount. Alternatively, the braking operation amount may be estimated based on the master cylinder pressure Pm or the stepping force and the stepping stroke.

In the above embodiment, the estimated deceleration Gb of the vehicle body is calculated based on the master cylinder pressure Pm regardless of whether the anti-skid control is performed. Gb in equations 1 and 2 is K
Gb may be replaced so that the coefficient K is variably set to a smaller value as the number of wheels on which anti-skid control is performed is increased within a range of greater than 0 and less than or equal to 1.

In the above embodiment, the acceleration of the vehicle body is not estimated. For example, when the automatic transmission is locked up, the engine speed is calculated based on the engine speed and the throttle opening. Based on the output torque, and when the automatic transmission is not locked up, the estimated longitudinal acceleration Gxe of the vehicle is calculated based on the output torque of the torque converter calculated based on the engine speed and the output speed of the torque converter, thereby increasing the vehicle speed. The above equation 2 for calculating the limit amount ΔVwu may be replaced with the following equation 4. ΔVwu = MAX (Gx, Gxe) + Vwuc (4)

In the above embodiment, the longitudinal acceleration Gx of the vehicle body detected by the longitudinal acceleration sensor 34 is used as it is in the calculation of the increase limit amount ΔVwu and the decrease amount ΔVwd of the vehicle body speed. Has become
For example, as described in JP-A-10-138905, the estimated longitudinal acceleration Gxa of the vehicle body is calculated based on the differential value of the wheel speed, and Gx is corrected based on the deviation between Gx and Gxw, and thus corrected. It may be modified so that the increase restriction amount ΔVwu and the decrease restriction amount ΔVwd are calculated based on the longitudinal acceleration after this.

Further, in the above embodiment, the vehicle is F
Although the vehicle is an F vehicle, the vehicle to which the vehicle speed estimation apparatus of the present invention is applied is an FR (front engine rear drive) vehicle or a 4W
It may be a D car.

[0054]

As is apparent from the above description, according to the first aspect of the present invention, an abnormality occurs in the means for detecting the longitudinal acceleration of the vehicle body, and the detected longitudinal acceleration of the vehicle body is an abnormal value. In a situation where the estimated rate of change of the vehicle speed is not properly limited by the longitudinal acceleration of the vehicle,
Since the estimated change rate of the vehicle speed is limited based on the deceleration of the vehicle body based on the braking operation amount, the possibility that the corrected vehicle speed becomes an abnormal value can be reduced.

According to the second aspect of the present invention, the degree of limitation based on the deceleration of the vehicle body is lower than the degree of limitation based on the longitudinal acceleration of the vehicle body when the means for detecting the longitudinal acceleration of the vehicle body is normal. In addition, it is possible to reliably prevent the rate of change of the estimated vehicle body speed from being unnecessarily excessively limited based on the deceleration of the vehicle body when the means for detecting the longitudinal acceleration of the vehicle body is normal.

According to the third aspect of the present invention, since the braking operation amount is the master cylinder pressure which increases and decreases due to the braking operation of the driver, the braking operation amount is reliably detected, whereby the braking operation amount of the driver is reduced. The deceleration of the vehicle based on the estimated value can be reliably estimated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a vehicle body speed estimation device according to the present invention applied to an FF vehicle.

FIG. 2 is a flowchart illustrating a vehicle speed calculation control routine according to the embodiment;

FIG. 3 shows the master cylinder pressure Pm and the estimated deceleration Gb of the vehicle.
6 is a graph showing the relationship between

FIG. 4 is an explanatory diagram showing a situation in which the speed is increased at a relatively small acceleration when the vehicle is traveling on a slope having a relatively large gradient.

FIG. 5 is an explanatory diagram showing a situation where the vehicle is decelerated by braking when the vehicle is traveling on a slope having a relatively large gradient.

[Explanation of symbols]

 14FL-14RR ... wheel cylinder 18 ... hydraulic control circuit 20 ... brake pedal 24 ... electronic control device 26 ... engine 32FL-32RR ... wheel speed sensor 34 ... front and rear acceleration sensor 36 ... pressure sensor

Claims (3)

[Claims] 1. Wheel speed detecting means for detecting wheel speed,
A vehicle speed estimating device for estimating a vehicle speed based on the wheel speed detected by the wheel speed detecting device; a vehicle speed estimating device for detecting a longitudinal acceleration of the vehicle; Means for detecting the amount, means for estimating the deceleration of the vehicle body based on the braking operation amount, and limiting the rate of change of the estimated vehicle body speed based on the longitudinal acceleration of the vehicle body and the deceleration of the vehicle body. A vehicle speed estimating device having a correcting means for correcting the estimated vehicle speed. 2. The limit based on the longitudinal acceleration of the vehicle body when the means for detecting the longitudinal acceleration of the vehicle body is normal is lower than the limit degree based on the longitudinal acceleration of the vehicle body. Item 2. The vehicle body speed estimation device according to item 1. 3. The vehicle body speed estimating device according to claim 1, wherein the means for detecting the braking operation amount is a sensor for detecting a master cylinder pressure.