JP2002162225A - Road surface inclination estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate the inclination of a road surface even in the case that a vehicle runs on a slope while the vehicle turns. SOLUTION: The slip angle β of a vehicle body is calculated (S20), the longitudinal acceleration Gx' of the vehicle body is calculated after correction in which the centripetal acceleration of the vehicle body caused by the slip angle βof the vehicle body eliminates influence given to the longitudinal acceleration Gx of the vehicle body (S30), the estimation longitudinal acceleration Vwd is calculated on the basis of a value which is a larger value of the wheel speeds Vwf and Vwfr of right and left wheels when the vehicle is not braked (S40, 50), when the vehicle is in a braked state, the estimation longitudinal acceleration Vwd of the vehicle body is calculated on the basis of a value which is the largest value of four-wheel wheel speeds Vwi (S40, 60), and the inclination θof the road surface is calculated on a difference between the longitudinal acceleration Gx' of the vehicle body after correction and the estimation longitudinal acceleration Vwd of the vehicle body (S100).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface gradient estimating apparatus, and more particularly, to a road surface gradient estimating a road surface gradient based on a detected longitudinal acceleration of a vehicle body and a longitudinal acceleration of the vehicle body estimated from wheel speeds. It relates to an estimation device.

[0002]

2. Description of the Related Art As one of devices for estimating the gradient of a road surface in a vehicle such as an automobile, for example, Japanese Patent Application Laid-Open No. Hei 5-27297
As described in Japanese Patent Application Publication No. 4 (1999) -2004, wheel speed and longitudinal acceleration of a vehicle body are detected, longitudinal acceleration of the vehicle body is estimated based on the wheel speed, and the longitudinal acceleration of the detected vehicle body and the estimated longitudinal acceleration of the vehicle body are calculated. BACKGROUND ART A road surface gradient estimating device configured to estimate a road surface gradient based on a difference is conventionally known.

Generally, a longitudinal acceleration detecting means such as a longitudinal acceleration detecting sensor for detecting the longitudinal acceleration of a vehicle body includes an inertial weight, and detects the longitudinal acceleration of the vehicle body by detecting a force acting on the inertial weight in the longitudinal direction of the vehicle. When the vehicle climbs or descends a slope, the vehicle body is inclined with respect to the horizontal direction, so that the inertial weight acts on the inertial weight in the direction along the road surface of gravity, and this component Is proportional to the slope of the road. This component is detected by the longitudinal acceleration detection sensor without being distinguished from the true longitudinal acceleration of the vehicle, whereas the longitudinal acceleration of the vehicle body estimated based on the wheel speed is not affected by the gradient of the road surface. Therefore, the difference between these longitudinal accelerations corresponds to the component of the gravity acting on the inertial weight in the direction along the road surface.

According to the road surface gradient estimating device described in the above publication, the road surface gradient is estimated based on the difference between the detected longitudinal acceleration of the vehicle body and the estimated longitudinal acceleration of the vehicle body. The gradient of the road surface can be estimated.

[0005]

Generally, when the vehicle runs on a slope while turning, the vehicle body has a slip angle, and the direction of the centrifugal force acting on the vehicle is viewed from above the vehicle. Since the vehicle is tilted with respect to the lateral direction, a component of the centrifugal force in the longitudinal direction of the vehicle acts on the inertial weight of the longitudinal acceleration detecting means. A component in the vehicle longitudinal direction of the centripetal acceleration is included. However, the component of the centripetal acceleration in the longitudinal direction of the vehicle does not result from acceleration or deceleration of the vehicle or the gradient of the road surface, nor does it change in accordance with the gradient of the road surface. In addition, there is a problem that the gradient of the road surface cannot be accurately estimated when the vehicle runs on a slope while turning.

When the vehicle travels on a slope while turning, the rotational direction of the steered wheels is different from the longitudinal direction of the vehicle body, and the wheel speed of the steered wheels does not match the actual longitudinal speed of the vehicle body. The longitudinal acceleration of the vehicle body, which is estimated based on the wheel speed of the steered wheels and the wheel speed of the wheels including the steered wheels, does not match the actual longitudinal acceleration of the vehicle body. Can not.

The present invention detects a wheel speed and a longitudinal acceleration of a vehicle body, estimates a longitudinal acceleration of the vehicle body based on the wheel speed, and calculates a longitudinal acceleration of the vehicle body based on a difference between the detected longitudinal acceleration of the vehicle body and the estimated longitudinal acceleration of the vehicle body. The present invention has been made in view of the above-described problems in a conventional road surface gradient estimating device configured to estimate a road surface gradient, and a main object of the present invention is to provide a vehicle body for estimating a road surface gradient. By removing the error component due to the turning of the vehicle from the longitudinal acceleration,
Even when the vehicle is traveling on a slope while turning, the gradient of the road surface is accurately estimated.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there are provided means for detecting longitudinal acceleration of a vehicle body, means for estimating longitudinal acceleration of a vehicle body based on wheel speeds, and a method for detecting lateral acceleration of a vehicle body. Means for estimating the slip angle of the vehicle body, calculating a correction amount for the longitudinal acceleration of the vehicle body detected based on the lateral acceleration of the vehicle body and the slip angle of the vehicle body, and calculating the detected longitudinal acceleration of the vehicle body. A road surface gradient estimating device comprising: means for correcting with a correction amount; and means for estimating a road surface gradient based on a difference between the corrected longitudinal acceleration of the vehicle and the estimated longitudinal acceleration of the vehicle. Item 1) or means for detecting the longitudinal acceleration of the vehicle body, longitudinal acceleration estimating means for estimating the longitudinal acceleration of the vehicle body based on the wheel speed, and the detected longitudinal acceleration of the vehicle body is estimated. A road surface gradient estimating device having means for estimating the gradient of the road surface based on the difference from the longitudinal acceleration of the body, wherein the longitudinal acceleration estimating means estimates the longitudinal acceleration of the vehicle body based on the wheel speed of the non-steered wheels. Road surface gradient estimating device (structure of claim 2), or means for detecting the longitudinal acceleration of the vehicle body, longitudinal acceleration estimating means for estimating the longitudinal acceleration of the vehicle body based on the wheel speed, Means for estimating a road gradient based on a difference between the estimated longitudinal acceleration of the vehicle and a road surface gradient estimating device, wherein the longitudinal acceleration estimating means calculates a longitudinal velocity of the vehicle at the center of gravity of the vehicle based on the wheel speed. The present invention is achieved by a road surface gradient estimating device (a third aspect of the present invention) that estimates and estimates the longitudinal acceleration of a vehicle body based on the longitudinal speed.

According to the first aspect of the present invention, a correction amount for the longitudinal acceleration of the vehicle detected based on the lateral acceleration of the vehicle and the slip angle of the vehicle is calculated, and the detected longitudinal acceleration of the vehicle is calculated as the correction amount. The gradient of the road surface is estimated based on the difference between the corrected longitudinal acceleration of the vehicle and the estimated longitudinal acceleration of the vehicle. Therefore, as in the case where the vehicle travels on a slope while turning, the slip angle When the direction of the centripetal acceleration of the vehicle is tilted with respect to the lateral direction of the vehicle when viewed from above the vehicle, the effect is removed from the detected value of the longitudinal acceleration of the vehicle, thereby making it more accurate than in the past. The gradient of the road surface is estimated.

As will be described later in detail, even when the vehicle is traveling on a slope while turning, the wheel speed of the non-steered wheels has a better relationship with the front-rear speed of the vehicle body than the wheel speed of the steered wheels. The longitudinal acceleration of the vehicle body estimated based on the wheel speeds of the non-steered wheels is smaller than the longitudinal acceleration of the vehicle body estimated based on the wheel speeds of the steered wheels and the wheel speeds of the wheels including the steered wheels. Close to longitudinal acceleration.

According to the above configuration, the longitudinal acceleration of the vehicle body is estimated based on the wheel speed of the non-steered wheels.
The gradient of the road surface is estimated more accurately than when the longitudinal acceleration of the vehicle body is estimated based on the wheel speeds of the steered wheels or the wheel speeds of the wheels including the steered wheels.

According to the third aspect of the invention, the longitudinal speed of the vehicle at the center of gravity of the vehicle is estimated based on the wheel speed, and the longitudinal acceleration of the vehicle is estimated based on the longitudinal speed. The gradient of the road surface is estimated more accurately than when the acceleration is estimated based on the wheel speeds of the steered wheels or the wheel speeds of the wheels including the steered wheels.

[0013]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the detected longitudinal acceleration and lateral acceleration of the vehicle body are Gx and Gy, respectively, and the slip angle of the vehicle body is determined. Is β, and the correction amount is Gy ·
The longitudinal acceleration Gx of the vehicle body is calculated by the correction amount Gy
-It is configured to be corrected by adding tanβ (preferred mode 1).

According to another preferred embodiment of the present invention, in the configuration of the above-described preferred embodiment 1, the means for estimating the longitudinal acceleration of the vehicle body based on the wheel speed is adapted to the wheel speed of the driven wheel when the vehicle is not braking. The longitudinal acceleration of the vehicle body is estimated based on the vehicle speed, and the longitudinal acceleration of the vehicle body is estimated based on the maximum value of the wheel speeds of the four wheels or the wheel speed of the rear wheels during braking of the vehicle (preferred mode 2).

According to another preferred aspect of the present invention, in the configuration of the second aspect, the vehicle is a front-wheel steering rear-wheel drive vehicle, and the longitudinal acceleration estimating means includes a left-right front wheel when the vehicle is not braking. It is configured to estimate the longitudinal acceleration of the vehicle body based on the higher one of the wheel speeds of the vehicle, and to estimate the longitudinal acceleration of the vehicle body based on the highest wheel speed of the four wheel speeds when braking the vehicle. Aspect 3).

According to another preferred aspect of the present invention, in the configuration of the second aspect, the vehicle is a front wheel drive vehicle for front wheel steering, and the longitudinal acceleration estimating means determines whether the vehicle is braking. It is configured to estimate the longitudinal acceleration of the vehicle body based on the higher wheel speed of the wheel speeds of the left and right rear wheels regardless of the above (preferred mode 4).

According to another preferred aspect of the present invention, in the configuration of the third aspect, the longitudinal acceleration estimating means estimates the longitudinal velocity of the vehicle body at the center of gravity of the vehicle based on the wheel speed of the driven wheel. Then, it is configured to estimate the longitudinal acceleration of the vehicle body based on the longitudinal speed (preferred mode 5).

According to another preferred aspect of the present invention, in the configuration of the third aspect, the longitudinal acceleration estimating means includes a four-wheel corresponding to each wheel at the center of gravity of the vehicle based on the wheel speed of the four wheels. Estimate the longitudinal speed of one vehicle body, estimate the longitudinal acceleration of the vehicle based on the lowest longitudinal speed of the four longitudinal speeds when the vehicle is not braking, and based on the highest longitudinal speed of the four longitudinal speeds when braking the vehicle It is configured to estimate the longitudinal acceleration of the vehicle body (preferred mode 6).

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which several preferred embodiments are shown.

First Embodiment FIG. 1 is a schematic diagram showing a first preferred embodiment of a road surface gradient estimating apparatus according to the present invention applied to a rear wheel drive vehicle.

In FIG. 1, 10FL and 10FR denote left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR denote left and right rear wheels which are driving wheels of the vehicle, respectively. The left and right front wheels 10FL and 10FR, which are both driven wheels and steered wheels, are driven via tie rods 18L and 18R by a rack-and-pinion type power steering device 16 driven in response to steering of the steering wheel 14 by the driver. Steered.

The braking force of each wheel is controlled by the hydraulic circuit 22 of the braking device 20 so that the wheel cylinders 24FR, 24FL, 24RR,
The control is performed by controlling the braking pressure of 24RL. Although not shown in the figure, the hydraulic circuit 2
2 includes various valve devices such as an oil reservoir, an oil pump, and a pressure increasing / decreasing control valve for increasing / decreasing a pressure in a wheel cylinder. Is controlled by a master cylinder 28 that is driven in accordance with the pressure control valve, and is controlled by opening and closing the pressure increasing / decreasing control valve by an electric control device 30 as will be described later in detail, if necessary.

The wheels 10FR to 10RL are provided with wheel speed sensors 32FR to 32RL for detecting the wheel speed Vwi (i = fr, fl, rr, rl) of the corresponding wheel as a peripheral speed. The vehicle 12 has a vehicle speed sensor 34 for detecting a vehicle speed V, a yaw rate sensor 36 for detecting a yaw rate γ of the vehicle, a longitudinal acceleration sensor 38 for detecting a longitudinal acceleration Gx, and a lateral acceleration sensor 40 for detecting a lateral acceleration Gy.
Is provided. The yaw rate sensor 36 and the lateral acceleration sensor 40 detect the yaw rate and the lateral acceleration, respectively, with the right turning direction of the vehicle being positive, and
Detects the longitudinal acceleration with the vehicle acceleration direction being positive.

As shown, wheel speed sensors 32FR-32
A signal indicating the wheel speed Vwi detected by the RL, a signal indicating the vehicle speed V detected by the vehicle speed sensor 34, a signal indicating the yaw rate γ detected by the yaw rate sensor 36,
The longitudinal acceleration Gx detected by the longitudinal acceleration sensor 38
And a signal indicating the lateral acceleration Gy detected by the lateral acceleration sensor 40 are input to the electric control device 30.

Although not shown in detail in FIG. 1, the electric control device 30 has, for example, a CPU, a ROM, a RAM, and an input / output port device, which are generally connected to each other by a bidirectional common bus. Microcomputer with a typical configuration.

The electric control device 30 calculates the slip angle β of the vehicle body based on the vehicle speed V and the like according to the flowchart shown in FIG. 2 as described later, and converts the detected longitudinal acceleration Gx of the vehicle body into the lateral acceleration Gy of the vehicle body. Then, the corrected longitudinal acceleration Gx 'of the vehicle body is calculated by the correction based on the correction amount based on the slip angle β of the vehicle body, and the estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the wheel speed Vwi. Acceleration G
The gradient θ of the road surface is estimated and calculated based on the difference between x ′ and the estimated longitudinal acceleration Vwd of the vehicle body.

Although not shown in the figure, the electric control device 30 calculates a spin state quantity indicating the degree of spin of the vehicle and a drift out state quantity indicating the degree of drift out of the vehicle based on the running state of the vehicle. Calculating the target slip ratio of each wheel of the behavior control based on the amount of spin state and the amount of drift-out state, and controlling the braking force of each wheel so that the slip ratio of each wheel becomes the target slip ratio. Stabilizes the behavior of

The behavior control of the vehicle itself does not form the gist of the present invention, and the behavior control may be performed in any manner known in the art. It may be applied to any control of the vehicle other than the behavior control.

Next, the road gradient estimation routine in the first embodiment will be described with reference to the flowchart shown in FIG. The 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, the wheel speed Vwi
Is read, and in step 20, the deviation of the lateral acceleration, that is, the vehicle slip acceleration Vyd, is calculated as the deviation Gy-γV between the lateral acceleration Gy and the product γV of the vehicle speed V and the yaw rate γ. The vehicle slip speed Vy is calculated by integrating the side slip acceleration Vyd, and the slip angle β of the vehicle body is calculated as the ratio Vy / Vx of the vehicle body slip speed Vy to the vehicle front-rear speed Vx (= vehicle speed V). .

In step 30, the corrected longitudinal acceleration Gx 'of the vehicle body in which the influence of the centripetal acceleration of the vehicle body on the longitudinal acceleration Gx of the vehicle body due to the slip angle β of the vehicle body is eliminated according to the following equation 1 is eliminated. Is calculated. Gx ′ = Gx + Gy · tanβ (1)

In step 40, for example, it is determined whether or not the vehicle is in a braking state by determining whether or not a stop lamp switch (not shown) is on, and a negative determination is made. If so, in step 50, the estimated longitudinal acceleration Vwd of the vehicle body is calculated as a differential value based on the larger one of the wheel speeds Vwfl and Vwfr of the left and right front wheels. The estimated longitudinal acceleration Vwd of the vehicle body is calculated as a differential value based on the largest value among the wheel speeds Vwi of the four wheels.

In step 100, the gradient θ of the road surface is calculated based on the corrected longitudinal acceleration Gx 'of the vehicle body and the estimated longitudinal acceleration Vwd of the vehicle according to the following equation (2). θ = arcsin (Gx′−Vwd) (2)

Thus, according to the illustrated first embodiment,
In step 20, the slip angle β of the vehicle body is calculated,
In step 30, the corrected longitudinal acceleration Gx 'of the vehicle body in which the influence of the centripetal acceleration of the vehicle body on the longitudinal acceleration Gx of the vehicle body due to the slip angle β of the vehicle body is eliminated is calculated. When the vehicle is in the non-braking state, step 5
At 0, the estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the larger one of the wheel speeds Vwfl and Vwfr of the left and right front wheels which are the non-driven wheels. The estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the largest value of the wheel speeds Vwi of the vehicle, and the road surface acceleration is calculated based on the difference between the longitudinal acceleration Gx ′ of the vehicle body corrected in step 100 and the estimated longitudinal acceleration Vwd of the vehicle body. Is calculated.

As shown in FIG. 5, when the vehicle turns, the slip angle β occurs in the vehicle body due to the direction of the vehicle speed Vb being inclined with respect to the front-back direction of the vehicle, and the centripetal acceleration Gc of the vehicle becomes , The detection value Gx of the longitudinal acceleration sensor 38 includes the component of the centripetal acceleration Gc in the longitudinal direction of the vehicle (Gy · tanβ), and the acceleration of the vehicle due to acceleration and deceleration of the vehicle. Assuming that the longitudinal acceleration is Gbx and the longitudinal acceleration of the vehicle body due to the inclination of the road surface is Gix, Gx is Gbx + Gix−Gy · tanβ. Therefore, the conventional road surface gradient estimating device cannot accurately estimate the road surface gradient due to an error due to the component of the centripetal acceleration Gc in the vehicle front-rear direction when the vehicle runs on a slope while turning.

On the other hand, according to the first embodiment shown in the drawing, the component (Gy · tan) of the centripetal acceleration Gc in the longitudinal direction of the vehicle.
The corrected longitudinal acceleration Gx ′ of the vehicle body after β) has been removed, that is, the corrected longitudinal acceleration of the vehicle body indicating the road surface component (Gbx + Gix) of gravity caused by acceleration / deceleration of the vehicle and inclination of the road surface is calculated, Since the gradient of the road surface is estimated based on the corrected longitudinal acceleration Gx 'of the vehicle body, it is possible to more accurately estimate the gradient of the road surface even when the vehicle travels on a slope in a turning state as compared with the related art. it can.

In particular, according to the illustrated first embodiment, when the vehicle is in the non-braking state, the estimated longitudinal acceleration Vwd of the vehicle body is determined based on the larger one of the wheel speeds Vwfl and Vwfr of the left and right front wheels that are the driven wheels. Is calculated, and when the vehicle is in the braking state, the estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the largest value of the wheel speeds Vwi of the four wheels.
For example, regardless of whether the vehicle is in a braking state or not, the estimated longitudinal acceleration Vwd of the vehicle body is determined based on the larger one of the left and right front wheel speeds Vwfl and Vwfr or the largest value of the four wheel speeds Vwi. The estimated acceleration of the vehicle body can be calculated more accurately than in the case where the calculation is performed, whereby the road surface gradient can be estimated with high accuracy.

In the first embodiment, when the vehicle is in the non-braking state, in step 50, the vehicle speed is estimated before and after the estimation based on the larger one of the left and right front wheel speeds Vwfl and Vwfr. The acceleration Vwd is calculated, and when the vehicle is in the braking state, the estimated longitudinal acceleration Vwd of the vehicle body is calculated in step 60 based on the largest value of the four wheel speeds Vwi. At 50, the estimated longitudinal acceleration of the vehicle body is calculated based on the wheel speeds Vwfl and Vwfr of the left and right front wheels, and the estimated longitudinal acceleration Vwd of the vehicle body is calculated as an average value thereof. The estimated longitudinal acceleration of the vehicle body is calculated based on the largest value and the next largest value of Vwi, and the estimated longitudinal acceleration V
wd may be modified to be calculated as their average (Modification 1-1).

Second Embodiment FIG. 3 is a flow chart showing a road gradient estimating routine in a second embodiment of the road gradient estimating apparatus according to the present invention applied to a front wheel drive vehicle.

The control according to the flowchart shown in FIG. 3 is also started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.
Also, in FIG. 3, steps corresponding to the steps shown in FIG. 2 are given the same step numbers as those given in FIG. The same applies to a third embodiment (FIG. 4) described later.

In the second embodiment, in step 70 executed after step 30, the estimated vehicle speed Vbw is set to the wheel speeds Vwrl and Vw of the left and right rear wheels that are driven wheels.
Calculation is performed based on the larger value of rr, and for other points, the road surface gradient θ is calculated in the same manner as in the first embodiment.

As shown in FIG. 6 (A), when the vehicle turns, the direction of movement of the front wheels is significantly different from the direction of movement of the center of gravity 102 of the vehicle 12, and therefore, before and after the estimation of the vehicle body obtained by differentiating the wheel speed of the front wheels. The acceleration is the center of gravity 1 of the vehicle 12
02 does not match the longitudinal acceleration of the vehicle body, and therefore from this point, the conventional road surface gradient estimating device cannot estimate the road surface gradient with high accuracy when the vehicle travels on a slope in a turning state. .

As shown in FIG. 6 (B), focusing on the rear wheel which is a non-steered wheel, the rear wheel moves forward at the same speed Vwrx as the front-rear speed Vx of the vehicle body. It can be considered that the vehicle moves laterally at the speed Vwry by skidding so that the moving speed becomes the moving speed of the rear wheel,
Since the wheel speed sensors 32RR and the like detect Vwrx, the estimated longitudinal acceleration V of the vehicle body calculated based on the wheel speeds of the rear wheels
wd is a value reflecting the acceleration due to acceleration and deceleration of the vehicle.

According to the illustrated second embodiment, similarly to the first embodiment described above, the corrected longitudinal acceleration Gx 'of the vehicle body after the component of the centripetal acceleration in the longitudinal direction of the vehicle has been removed is calculated. In addition, the estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the wheel speeds Vwrl or Vwrr of the left and right rear wheels that are non-steered wheels, so the estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the wheel speed of the front wheels that are steered wheels. The road gradient can be estimated more accurately than in the case where

In general, when the vehicle is braked, a braking slip occurs on the wheels, so that the wheel speed of the driven wheel becomes lower than the vehicle speed. When the vehicle is not braked, the wheel speed of the driven wheel does not become higher than the vehicle speed. Therefore, the larger value of the wheel speeds of the right and left rear wheels, which are the driven wheels, has higher correspondence with the front-rear speed of the vehicle body. Therefore, the estimated longitudinal acceleration of the vehicle calculated based on the larger value of the left and right rear wheel speeds is greater than the estimated longitudinal acceleration of the vehicle calculated based on the smaller value of the left and right rear wheel speeds. Acceleration and deceleration are reflected well.

According to the illustrated second embodiment, the estimated longitudinal acceleration Vwd of the vehicle body is determined by the wheel speeds Vwrl and Vwrr of the left and right rear wheels.
, The estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the wheel speeds Vwrl and Vwrr of the left and right rear wheels.
It is possible to accurately estimate the gradient of the road surface as compared with the case where the calculation is performed based on the smaller value of

In the above-described second embodiment, in step 70, the estimated longitudinal acceleration Vwd of the vehicle body is calculated based on the larger one of the wheel speeds Vwrl and Vwrr of the left and right rear wheels as driven wheels. However, the estimated longitudinal acceleration Vwd of the left and right rear wheels may be calculated based on the wheel speeds Vwrl and Vwrr, and the estimated longitudinal acceleration Vwd of the vehicle body may be calculated as an average value thereof ( Correction example 2-1).

Third Embodiment FIG. 4 is a flowchart showing a road gradient estimation routine in a third embodiment of the road gradient estimation device according to the present invention applied to a front wheel drive vehicle.

As shown in FIG. 7, assuming that the slip angles of the left and right wheels are equal and the steering angle is δ, the slip angles βfl and βfr of the left and right front wheels (the slip angle βf of the front wheel 100f) and the rear and right and left Wheel slip angles βrl, βrr (rear wheel 1
00r can be determined by the following equations 3 and 4, respectively.

[0050]

(Equation 1)

The wheel speed V of each wheel is calculated using the steering angle δ and the like.
The longitudinal velocity V at the position of the center of gravity 102 of the vehicle based on wi
bwi (i = fr, fl, rr, rl) can be calculated.
For example, for the right front wheel, the following equations 5 and 6 are established as shown in FIG.

[0052]

(Equation 2)

From the above equations 5 and 6, the front-rear speed Vbwfr based on the wheel speed of the right front wheel is obtained by the following equation 7, and similarly, the front-rear speed Vbwfl based on the wheel speed of the left front wheel is obtained by the following equation 8. .

[0054]

(Equation 3)

The front-rear speeds Vbwfr and Vbwfl based on the wheel speeds of the right rear wheel and the left rear wheel are given by the following equations 9 and 1 respectively.
It is determined by 0.

[0056]

(Equation 4)

In the third embodiment, the longitudinal speed Vbwi of the vehicle body at the center of gravity 102 of the vehicle is calculated based on the wheel speed Vwi of each wheel in step 35 executed after step 30. When the vehicle is not braking, the estimated longitudinal acceleration Vbwd of the vehicle body is calculated based on the smallest value of the longitudinal speed Vbwi in step 80, and when the vehicle is braked, based on the largest value of the longitudinal speed Vbwi in step 90. The estimated longitudinal acceleration Vbwd of the vehicle body is calculated, and for other points, the gradient θ of the road surface is calculated in the same manner as in the first embodiment.

Thus, according to the illustrated third embodiment,
The front-rear speed Vbwi of the vehicle at the center of gravity 102 of the vehicle is calculated based on the wheel speed Vwi of each wheel. Longitudinal acceleration Vbwd
When the vehicle is braking, the estimated longitudinal acceleration Vbwd of the vehicle body is calculated based on the largest value of the longitudinal speed Vbwi, that is, the value of the smallest braking slip. The longitudinal acceleration can be accurately calculated, whereby the road surface gradient can be estimated more accurately than in the case of the conventional gradient estimating device.

In the third embodiment, when the vehicle is not braked, the estimated longitudinal acceleration Vbwd of the vehicle body is determined in step 80 based on the smallest value of the longitudinal speed Vbwi.
When the vehicle is braked, the estimated longitudinal acceleration Vbwd of the vehicle body is calculated based on the largest value of the longitudinal speed Vbwi in step 90, but in step 80, the estimated longitudinal acceleration Vbwi is calculated. The estimated longitudinal acceleration of the vehicle body is calculated based on the smallest value and the next smallest value, and the estimated longitudinal acceleration Vbwd of the body is calculated as an average value thereof. In step 90, the largest value and the largest value of the longitudinal speed Vbwi are calculated. The estimated longitudinal acceleration of the vehicle body may be calculated based on the next largest value, and the estimated longitudinal acceleration Vbwd of the vehicle body may be corrected to be calculated as an average value thereof (Modification Example 3-1).

In the third embodiment described above, the vehicle is a front wheel drive vehicle, but this embodiment may be applied to a rear wheel drive vehicle or a four wheel drive vehicle (Modification 3-2). ) Further, the estimated longitudinal acceleration Vbwd of the vehicle body may be calculated as an average value of the estimated longitudinal accelerations of the four vehicle bodies calculated based on the longitudinal speed Vbwi (Modification 3-3).
It may be calculated as the average of the second and third largest estimated longitudinal accelerations of the four estimated longitudinal accelerations of the vehicle body calculated based on i (Modification 3-4).

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 are included within the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in each of the illustrated embodiments, the slip angle β of the vehicle body is calculated based on the vehicle speed V or the like, but the slip angle β of the vehicle body may be obtained by detection.

In each of the illustrated embodiments, the vehicle speed V
Is detected by the vehicle speed sensor 34, and the slip angle β of the vehicle body is detected.
The vehicle speed V is used as the vehicle front-rear speed Vx in the calculation of the vehicle body. However, the vehicle front-rear speed Vx used in the calculation of the vehicle body slip angle β is calculated in the previous embodiment in each embodiment. May be modified to use the front-rear speed Vx.

In each of the illustrated embodiments, whether the vehicle is in an uphill state or in a downhill state is not taken into consideration. However, the previous estimated value of the road surface gradient, the output torque of the engine and the front and rear of the vehicle are not considered. Based on the relationship with acceleration, etc., it is determined whether the vehicle is in an uphill state or a downhill state, and the wheel speed used for estimating the estimated front-rear speed Vx of the vehicle body is changed according to the determination result. May be done.

[0065]

As is apparent from the above description, according to the present invention, it is possible to remove an error component caused by turning of the vehicle from the longitudinal acceleration of the vehicle body for estimating the gradient of the road surface. Even when the vehicle runs on a slope while turning, the gradient of the road surface can be accurately estimated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first preferred embodiment of a road surface gradient estimating device according to the present invention applied to a rear wheel drive vehicle.

FIG. 2 is a flowchart illustrating a road gradient estimation routine according to the first embodiment.

FIG. 3 is a flowchart showing a road surface gradient estimating routine in a second preferred embodiment of the road surface gradient estimating device according to the present invention applied to a front wheel drive vehicle.

FIG. 4 is a flowchart showing a road surface gradient estimating routine in a third preferred embodiment of the road surface gradient estimating device according to the present invention applied to a rear wheel drive vehicle.

FIG. 5 is an explanatory diagram showing the effect of the centripetal acceleration of the vehicle on the longitudinal acceleration of the vehicle body when the vehicle turns.

FIG. 6 is an explanatory diagram (A) showing a moving direction of a vehicle body and each wheel when the vehicle turns, and an explanatory diagram showing a movement of a rear wheel when the vehicle turns.

FIG. 7 is an explanatory diagram showing a procedure for calculating a slip angle βi of each wheel based on a slip angle β of the vehicle body and the like.

FIG. 8 is an explanatory diagram showing a procedure for calculating a front-rear speed Vbwi at the center of gravity of the vehicle based on the wheel speed Vwi of each wheel.

[Explanation of symbols]

 10FR-10RL ... Wheel 20 ... Brake device 28 ... Master cylinder 30 ... Electrical control device 32FR-32RL ... Wheel speed sensor 34 ... Vehicle speed sensor 36 ... Yaw rate sensor 38 ... Longitudinal acceleration sensor 40 ... Lateral acceleration sensor

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshitaka Hamada 2-1-1 Asahi-machi, Kariya-shi, Aichi F-term (reference) in Aisin Seiki Co., Ltd. 3D045 BB40 CC01 EE02 EE05 GG25 GG27 GG28

Claims (3)

[Claims] 1. Means for detecting longitudinal acceleration of a vehicle body, means for estimating longitudinal acceleration of the vehicle body based on wheel speed, means for detecting lateral acceleration of the vehicle body, means for estimating a slip angle of the vehicle body, Means for calculating a correction amount for the longitudinal acceleration of the vehicle body detected based on the lateral acceleration and the slip angle of the vehicle body, and correcting the detected longitudinal acceleration of the vehicle body with the correction amount; Means for estimating a road gradient based on a difference from the estimated longitudinal acceleration of the vehicle body. Means for detecting the longitudinal acceleration of the vehicle body, means for estimating the longitudinal acceleration of the vehicle body based on the wheel speed, and a difference between the detected longitudinal acceleration of the vehicle body and the estimated longitudinal acceleration of the vehicle body. A road surface gradient estimating device having means for estimating the road surface gradient based on the road surface gradient estimating device, wherein the longitudinal acceleration estimating device estimates the longitudinal acceleration of the vehicle body based on the wheel speeds of the non-steered wheels. Means for detecting the longitudinal acceleration of the vehicle body; means for estimating the longitudinal acceleration of the vehicle body based on the wheel speed; and a difference between the detected longitudinal acceleration of the vehicle body and the estimated longitudinal acceleration of the vehicle body. A road surface gradient estimating device having means for estimating a road surface gradient based on the vehicle speed, wherein the longitudinal acceleration estimating means estimates the longitudinal speed of the vehicle body at the center of gravity of the vehicle based on the wheel speed, and based on the longitudinal speed, A road surface gradient estimating device for estimating longitudinal acceleration.