JP2010188801A - Center of gravity position estimating device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a center of gravity position estimating device for a vehicle capable of estimating the longitudinal position (center of gravity-distance between axles of front and rear wheels of a vehicle) of the center of gravity of the vehicle even during traveling of the vehicle without requiring a particular sensor for detecting axle loads. <P>SOLUTION: The center of gravity position estimating device for the vehicle presumes the center of gravity in a longitudinal direction of the vehicle based on braking force of the front wheel, braking force of the rear wheel and deceleration degree of the vehicle when size of difference of a wheel speed of the front wheel of the vehicle and a wheel speed of the rear wheel becomes a predetermined size during braking of the vehicle or when EBD control is executed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for estimating the position of the center of gravity of a vehicle such as an automobile, and more particularly to an apparatus for estimating the position in the front-rear direction of the center of gravity of the vehicle while the vehicle is traveling.

  2. Description of the Related Art In recent vehicles such as automobiles, various behavior control, motion control, or travel control has been executed in order to stabilize motion during travel of the vehicle. In these controls, the braking / driving force or steering angle of each wheel of the vehicle is controlled using a vehicle body motion or tire model so that the vehicle motion state (yawing / rolling, etc.) is stabilized. For example, in the case of VSC (Vehicle Stability Control), in order to stabilize the movement of the vehicle in the yaw direction, the braking / driving force difference or the steering angle of the left and right wheels of the vehicle is controlled. Yaw moment control is achieved.

  In executing the vehicle behavior, motion or travel control as described above, the position of the center of gravity of the vehicle, that is, the distance from the center of gravity of the vehicle to the axles of the front and rear wheels is often required as a parameter for such control. . The position of the center of gravity of such a vehicle is given approximately as a constant because there is little variation in the number of passengers and the load capacity of a typical private automobile. However, in the case of a vehicle having a large variation in the amount and position of the load on the vehicle, such as a medium to large vehicle such as a truck or bus, the position of the center of gravity of the vehicle depends on the amount and arrangement (loading state) of the load on the vehicle. If this happens, the difference between the characteristics of the vehicle motion model set by the motion control device and the actual motion characteristics of the vehicle will increase. Therefore, in order to perform control more accurately in a vehicle in which the amount and position of the load on the vehicle are large, the position of the center of gravity of the vehicle is detected or estimated during use or traveling of the vehicle. It is preferable that it can be used in behavior, motion or running control. Therefore, in the prior art, for example, in Patent Document 1, axle weight meters are provided in the vicinity of the front and rear axles of the vehicle, and the position of the center of gravity is detected from the axle weight distribution based on the measured value of the axle weight meter. It has been proposed to use the values for vehicle braking control. Further, in Patent Document 2, the position of the center of gravity of the vehicle is estimated from the slip ratio of the front and rear wheels (it is estimated that the center of gravity is biased to the side where the slip ratio is small), and the estimation result is used for the rear wheel steering control of the 4WS vehicle. It has been proposed to reflect this.

JP2007-223365

JP-A-5-229446

  As described in Patent Document 1 above, if a special sensor such as an axle weight meter is attached to the axles of the front and rear wheels of the vehicle and the load applied to each axle is detected directly, it depends on the loading state of the vehicle. It is possible to estimate the position in the front-rear direction of the changing vehicle center of gravity. In that case, however, a design and assembly for attaching a special sensor in the vicinity of the axle is required. Therefore, if it is possible to estimate the longitudinal position of the center of gravity of the vehicle from the detection value of a sensor normally used in a motion control device such as a VSC without requiring such a special sensor, the installation of a special sensor is not possible. This eliminates the need for labor and cost.

  Thus, one object of the present invention is to determine the position of the vehicle center of gravity in the longitudinal direction (vehicle center of gravity − even when the vehicle is running, based only on the detection values of existing sensors used in motion control devices such as VSC or ABS. An object of the present invention is to provide a vehicle center-of-gravity position estimation device capable of estimating the distance between the front and rear wheels.

  According to the research and development by the inventors of the present invention, the longitudinal position of the center of gravity of the vehicle can be estimated based on the relationship of forces acting on the vehicle during braking (particularly, balance of force moments) in the running vehicle. Was found. Thus, in one aspect, the apparatus for estimating the position of the center of gravity of the vehicle according to the present invention is such that the difference between the wheel speed of the front wheel and the wheel speed of the rear wheel during braking of the vehicle is a predetermined magnitude. The center of gravity position in the longitudinal direction of the vehicle is estimated based on the braking force of the front wheels, the braking force of the rear wheels, and the deceleration of the vehicle. As will be described in more detail later in the section of the embodiment, load movement occurs on the front wheel side during braking of the vehicle, and in general, when the friction coefficient of the road surface is sufficiently high, the rear wheel The wheel speed of the wheel is reduced faster than the wheel speed of the front wheel. In this case, when the difference between the wheel speed of the front wheel and the wheel speed of the rear wheel reaches a predetermined value, the braking force of the front wheel, the braking force of the rear wheel and the deceleration of the vehicle, that is, normal VSC or The position in the front-rear direction of the center of gravity of the vehicle can be estimated based on the relationship between forces acting on the vehicle, from values that can be detected by sensors used in ABS or the like. Utilizing such knowledge, according to the present invention, in the vehicle in which the loading state varies greatly, the longitudinal position of the center of gravity of the vehicle is estimated without requiring a special sensor for directly detecting the axle load. It becomes possible to do.

  In the configuration of the device of the present invention described above, more specifically, the load center position during braking of the vehicle calculated based on the braking force of the front wheels, the braking force of the rear wheels, and the deceleration of the vehicle, and the vehicle The center-of-gravity position in the front-rear direction may be estimated based on the center-of-gravity height that is assumed when a load is loaded on the vehicle. In general, in a vehicle, the height of a position on which a load or an occupant is placed is expected to be limited to a certain extent due to the structure of a loading platform or a seat of the vehicle. Further, as will be described later in the section of the embodiment, when the braking force of the front wheels, the braking force of the rear wheels, and the deceleration of the vehicle are used, the load center position, that is, the vehicle load on the road surface is determined. It is possible to determine the center point that acts, thereby demarcating the existence area in the front-rear direction of the vehicle center of gravity. Thus, the presence of the center of gravity position of the vehicle in the current loading state or riding state is considered by considering the height of the center of gravity assumed from the structure of the loading platform or seat of the vehicle in relation to the force acting on the vehicle body. The position is estimated in the front-rear direction and the vertical direction.

More specifically, when the road surface friction coefficient μ is sufficiently large and can be approximated to μ to 1.0, the longitudinal distance Lf between the center of gravity of the vehicle and the front wheel shaft is the deceleration Gx and the braking force of the front wheels. Using Fxf, rear wheel braking force Fxr, center of gravity height H, gravity acceleration G and wheelbase L,
Lf = L · {Fxr / (Fxf + Fxr)} (Gx / G) + H (Gx / G) (1)
May be calculated as follows. The front wheel braking force Fxf and the rear wheel braking force Fxr may be calculated from control amounts corresponding to the braking force applied to the braking device of each wheel. For example, in the case of a hydraulic or pneumatic brake device, the braking force of each wheel is a value obtained by multiplying the brake pressure supplied to each wheel wheel cylinder by the brake coefficient of each wheel. It should be understood that an expression similar to the expression (1) using a control amount such as a brake pressure as a variable may be used, and such a case also belongs to the scope of the present invention.

  In addition, in the configuration of the above-described device, the case where the friction coefficient μ of the road surface is sufficiently large and can be approximated to μ to 1.0 can be simply described as follows. When the rear wheels are in a slip state before the front wheels reach the slip state (with the brake force set to be higher than the braking force) or when the vehicle is equipped with a so-called electronic braking force distribution control device (EBD) Is known to be in a state of starting to limit the increase in the braking force of the rear wheels. Therefore, in the above-described device of the present invention, when the front wheel does not reach the slip state (when the ABS device is mounted on the vehicle, when the ABS control for the front wheel is not executed), or When the electronic braking force distribution control device executes the restriction on the increase in the braking force of the rear wheel, the estimation of the center of gravity position of the vehicle may be executed.

  By the way, in the vehicle, when more loads are placed behind the loading platform of the vehicle, the load on the rear wheel increases, and as a result, the front wheel speed and the rear wheel speed of the vehicle increase. In some cases, the deceleration of the vehicle becomes considerably large without the magnitude of the difference between the vehicle and the vehicle being a predetermined size, that is, without the rear wheels being locked. In that case, the position of the center of gravity of the vehicle is considered to have “moved” considerably to the rear of the vehicle. Therefore, in the apparatus of the present invention described above, the vehicle deceleration is performed when the magnitude of the difference between the front wheel speed and the rear wheel speed of the vehicle does not reach a predetermined value during braking of the vehicle. When the value reaches a predetermined value, it may be estimated that the position of the center of gravity is located at the rearmost position of the range in the front-rear direction in which the presence of the center of gravity is assumed. The front-rear direction range in which the presence of the center of gravity position is assumed may be determined in advance from the structure of the vehicle.

  Therefore, according to the apparatus of the present invention described above, in a vehicle in which the loading state greatly fluctuates, a sensor for detecting the axle load is not required during its use or traveling, and the vehicle longitudinal direction is determined. Can be estimated. The parameters used for estimating the position of the center of gravity are the same as those used for the vehicle motion control device such as the wheel speed of each wheel, the braking force (or brake pressure) of each wheel, and the vehicle deceleration. For vehicles equipped with, it is possible to estimate the position of the center of gravity in the front-rear direction of the current vehicle using only existing sensors, and to reflect the estimation result in motion control. It is expected that better motion control can be provided.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention.

FIG. 1A is a schematic diagram of a vehicle on which a vehicle center-of-gravity position estimation apparatus that is a preferred embodiment of the present invention is mounted. FIG. 1B is a diagram schematically showing the configuration of the vehicle braking system. FIG. 1C shows a vehicle center-of-gravity position estimation apparatus, which is a preferred embodiment of the present invention, in the form of a block diagram. FIG. 2A is a diagram illustrating the principle of estimating the center of gravity of the vehicle according to the present invention, and shows the force acting on the vehicle during braking. 2B is a graph showing the braking force distribution of the front and rear wheels, and FIG. 2C is a schematic diagram of the vehicle showing an assumed range (shaded area) of the center of gravity position of the vehicle. 2B, the alternate long and short dash lines (a), (b), and (c) indicate the center-of-gravity position estimation lines (a) and (b) in which the center of gravity is indicated by the broken line in FIG. b) and (c) are ideal braking force distribution lines in the case of being on, and the solid line in FIG. 2B is the braking force distribution lines of the front and rear wheels during actual normal braking. The white circles on the solid line indicate the braking force distribution at which the EBD control operation starts when the center of gravity is on the center of gravity position estimation line (a) or (b). 2 (B) and 2 (C), (a) shows an ideal braking force distribution line and a center-of-gravity position estimation line when the vehicle is in an idle state. FIG. 3 shows the processing flow of the vehicle center-of-gravity position estimation apparatus of the present invention in the form of a flowchart.

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings. In the figure, the same reference numerals indicate the same parts.

Configuration of Device FIG. 1 (A) shows a vehicle 10 in which the preferred embodiment of a vehicle center-of-gravity position estimation apparatus according to the present invention for estimating the center of gravity of the longitudinal direction of the vehicle such as an automobile is mounted schematically. The vehicle 10 may be any known type of vehicle, and includes a pair of front wheels 12f and a pair of rear wheels 12r, and a loading platform 14 on which an arbitrary load S is placed. In the illustrated example, for the sake of simplicity, it is depicted as a truck having a cargo bed with an open upper part at the rear of the vehicle. However, the vehicle on which the vehicle center-of-gravity position estimation device of the present invention is mounted has a box-type cargo bed. It may be a vehicle having a truck on the rear, a vehicle having a loading platform in the front, a bus, or any other load.

  The braking of the front wheels and the rear wheels of the vehicle 10 is performed by a braking system device 40 in a normal mode as schematically shown in FIG. In short, the braking system device 40 may be a so-called electronically controlled pneumatic / hydraulic braking device, pneumatic braking device, or hydraulic braking device, and operates in response to the depression of the brake pedal 44 by the driver. Wheel cylinders 42i (i = fl, fr, rl, rr, etc.) equipped to each wheel by a fluid pressure circuit (pneumatic circuit and / or hydraulic circuit) 46 communicating with a brake valve (or master cylinder) 45 to be operated .)), Ie the braking force on each wheel. In the fluid pressure circuit 46, various types of wheel cylinders for each wheel selectively communicate with an air compressor, an air tank, a braking force booster, an oil pump, an oil reservoir, etc. (not shown) in a normal manner. In normal operation, in response to depression of the brake pedal 44, the pressure of the brake booster, the air tank or the master cylinder is reduced. It is supplied to each wheel cylinder 42i. However, when adjusting the braking force of each wheel individually or independently to execute ABS control, motion control such as VSC, or other arbitrary braking force distribution control, it is based on a command of the electronic control unit 50. The various valves are operated, and the brake pressure in the wheel cylinder of each wheel is controlled to match the target pressure based on the detection value of the corresponding pressure sensor. The electronic control unit 50 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port unit connected to each other by a bidirectional common bus and a driving circuit. Brake pedal depression amount θb from a given depression amount sensor (not shown), wheel speed Vwi from a wheel speed sensor (not shown) provided for each wheel, and in the wheel cylinder of each wheel from a wheel cylinder pressure sensor The detected values such as the pressure Pbi and the acceleration / deceleration Gx from the front / rear G sensor 62 are input (in addition to those shown in the figure, various control such as lateral acceleration and yaw rate to be executed in the vehicle of the present embodiment). Various detection signals representing the values of various parameters required may be input).

  Note that the braking system device 40 described above is particularly configured to be able to execute front and rear wheel braking force distribution control (EBD) under the control of the electronic control device 50. As is well known in this field, when a vehicle is braked, the load shifts to the front wheel side due to the inertial force of the vehicle motion, so the vertical load on the rear wheel is reduced, and the braking force on the rear wheel is reduced accordingly. The limit of is reduced. Therefore, the braking system device 40 is generally located between the front and rear wheels by a load movement to the front wheel side even during normal operation (that is, when the brake pressure of the front and rear wheels is equal). In order to cope with a dynamic change in load distribution, the braking force of the front wheels is adjusted to be larger than the braking force of the rear wheels at a predetermined rate. However, if the ratio of the braking force of the front and rear wheels is constant, it cannot be completely prevented that the braking force of the rear wheel reaches its limit (the rear wheel locks). Therefore, when the braking force of the rear wheel is close to its limit, specifically, when the rear wheel speed is lower than the front wheel speed and the magnitude of the difference exceeds a predetermined value, the rear wheel Front and rear wheel braking force distribution (EBD) control is executed so as to limit the increase in the braking force of the rear wheels in order to prevent the locked state.

  FIG. 1C shows the vehicle center-of-gravity position estimation apparatus of the present invention incorporated in the electronic control unit 50 in the form of a block diagram. The vehicle center-of-gravity position estimation device 50a reads the brake pedal depression amount θb, the acceleration / deceleration Gx, the wheel brake pressure Pbi, the wheel speed Vwi or EBD operation information, and the ABS operation information of each wheel, into a program described in detail later. By the processing operation according to this, the front-rear axis distance Lf between the front wheel axis and the center of gravity or the rear wheel axis-center-of-gravity distance Lr is estimated and calculated as the center of gravity position, and the calculation result can be used in the motion control device 50b such as VSC. Like that.

Principle of center-of-gravity position estimation As schematically shown in FIG. 2A, when a vehicle having a mass M is being braked at a deceleration Gx, the vehicle is in contact with the road surface of the front and rear wheels of the vehicle. The braking forces Fxf and Fxr act in parallel with the road surface, respectively, and the axle load drag forces Fzf and Fzr act vertically upward with respect to the road surface. At the center of gravity C of the vehicle, inertial force M · Gx and gravity M · G (G is gravitational acceleration) act as shown in the figure. Therefore, the balance of the moment of force around the ground contact area of the front wheel is
M · G · Lf = M · Gx · H + Fzr · L (2)
It is represented by Here, Lf is the front-rear direction distance between the front wheel axis and the center of gravity, and H is the height of the center of gravity. That is, the distance between the front wheel shaft and the center of gravity Lf is
Lf = Fzr · L / (M · G) + H (Gx / G) (3)
Given by. In this equation (3), the vehicle mass M is
M = (Fxf + Fxr) / Gx (4)
The drag Fzr of the axial load of the rear wheel is given by the friction coefficient μ of the road surface,
Fzr = Fxr / μ (5)
Given by. Thus, the distance Lf between the front wheel shaft and the center of gravity is
Lf = L · Fxr / {(Fxf + Fxr) μ} (Gx / G) + H (Gx / G) (6)
It will be given by. In this equation (6), the deceleration Gx is acquired from the detected value of the front / rear acceleration / deceleration sensor, and the braking forces Fxf and Fxr are calculated using the front wheel brake pressure Pbf and the rear wheel brake pressure Pbr,
Fxf = Kf · Pbf; Fxr = Kr · Pbr (7)
Obtained by Therefore, according to the equation (6), if the road surface friction coefficient μ and the center of gravity H are given, the front wheel shaft-center of gravity distance Lf can be calculated from the braking force of the front and rear wheels and the deceleration of the vehicle. The position can be estimated. The first term of equation (6) is the intersection C ′ between the straight line descending toward the road surface along the resultant force of gravity and inertial force in FIG. The point C ′ of the distance Lf ′ is the center position (load center position) of the load acting on the road surface from the vehicle being braked (ie, Fzf · Lf ′ = Fzr · ( L-Lf ′) is a position where Lf ′ is established. When the center of gravity height H is considered as one variable, the straight line represented by the equation (6) indicated by the broken line in FIG. 2A represents a linear region where the center of gravity position can exist. (Center of gravity position estimation line).

If the vehicle is equipped with a device for estimating or detecting the road surface friction coefficient, the estimated value or the detected value of the road surface friction coefficient μ in the above formula (6) may be used. However, when the braking force of the rear wheel is saturated or when the EBD control is activated or the value of (front wheel speed-rear wheel speed) is larger than a predetermined value when the braking force of the front wheel is not saturated. Sometimes approximately μ-1.0 (8)
Can be set. The reason for this is as follows.

  As already described, in a vehicle that is being braked, the load shifts to the front wheels due to the inertial force, and the distribution of the ground load on the front wheels increases. The braking force distribution of the front and rear wheels (distribution of the braking force proportional to the ground load distribution of the front and rear wheels) ideally corresponding to the change in the dynamic load distribution between the front and rear wheels due to the load movement to the front wheel side is shown in FIG. B) is given by an “ideal braking force distribution curve” as exemplified by the one-dot chain lines (a) to (c). The ideal braking force distribution curve shifts toward the rear wheel as the center of gravity position is behind the vehicle, that is, the presence of the center of gravity position estimation line (a) → (b) → (c) in FIG. Corresponding to the change in position, the ideal braking force distribution curve changes as (a) → (b) → (c). Further, in each of the ideal braking force distribution curves, the upper side of the curve in the figure is a region where the braking force of the rear wheel tends to be saturated before the braking force of the front wheel, and the lower side of the curve is the front wheel. This is an area where the braking force tends to be saturated before the braking force of the rear wheels.

  With reference to the ideal braking force distribution in consideration of the dynamic distribution of the vertical load of the front and rear wheels as described above, the actual braking force distribution (solid line in FIG. 2B) is normal braking (ABS and When the motion control is not executed), the normal dry road surface that follows the ideal braking force distribution curve as much as possible, that is, the road surface on which the condition of the equation (8) is approximately satisfied. In order to prevent the braking force of the rear wheel from reaching the saturation region as much as possible, as shown in FIG. 2B, in a region where the braking force is not large, it is generally set to be lower than the ideal braking force distribution curve. is there. In that case, as shown in the relationship between the one-dot chain line (a) or (b) in FIG. 2B and the solid line, the region where the braking force is small (lower left in the figure), that is, the friction coefficient is small. On the road surface, the front wheels tend to be locked first (the solid line is below the ideal braking force distribution curve) and the braking force is large (upper right in the figure), that is, on the road surface with a large friction coefficient, The wheel tends to be locked first (the solid line exceeds the ideal braking force distribution curve). In other words, when the braking force of the rear wheels is saturated while the braking force of the front wheels is not saturated, the region where the braking force is large, that is, the friction coefficient of the road surface is sufficiently large. It can be considered that the condition is approximately satisfied. However, in reality, when the braking force of the front wheels is likely to be saturated, the ABS is activated, and when the braking force of the rear wheels is likely to be saturated (before the braking force of the front wheels) (FIG. 2B). When the EBD is activated when the EBD control (or ABS) is activated and the rear wheel lock is avoided, but the front wheel ABS is not activated. The braking force of the rear wheels is almost saturated, and it is assumed that Equation (8) is approximately established with respect to the friction coefficient of the road surface. Thus, as described above, when the EBD control is activated or when the value of (front wheel speed−rear wheel speed) becomes larger than a predetermined value, the friction coefficient μ in the equation (6) is not directly detected. In addition, the condition of equation (8) can be used.

  Regarding the center of gravity height H of the above formula (6), the position of the vehicle carrier is known in advance, and can be estimated in advance from the structure of the vehicle. That is, it is assumed that the center of gravity from the empty product state to the fixed product state (maximum allowable load state) exists in advance in the area indicated by the oblique lines in FIG. Therefore, it is possible to use the height of the assumed center-of-existence area of the assumed center of gravity as the center of gravity height H in Equation (6).

Thus, equation (6) uses the condition of equation (8)
Lf = L.Fxr / (Fxf + Fxr). (Gx / G) + H (Gx / G) (9)
It can be expressed as. Moreover, if Formula (7) is used,
Lf = L.Kr.Pbr / (Kf.Pbf + Kr.Pbr). (Gx / G) + H (Gx / G) (9a)
Can be expressed as

  By the way, as illustrated in the center of gravity position estimation line (c) of FIG. 2 (C), when the center of gravity of the vehicle is located considerably rearward of the vehicle, the distribution of the vertical load of the vehicle is directed to the rear wheel side. As a result, as shown in the curve (c) of FIG. 2B, even if the braking force of the front and rear wheels is considerably increased, that is, the vehicle deceleration is significantly increased, There may be a case where the wheel braking force does not reach the saturation region and the EBD control is not executed. Therefore, when the deceleration of the vehicle becomes considerably large without the braking force reaching the saturation region for both the front and rear wheels, the center of gravity position is the end of the assumed range, that is, the center of gravity position estimation line (c). Can be estimated to be on the line.

Operation of Apparatus The center-of-gravity position estimation apparatus according to the present embodiment may be operated according to the process shown in the form of a flowchart in FIG. The illustrated process may be repeatedly executed at a predetermined cycle time while the vehicle is traveling.

Referring to the figure, in the process, it is first determined whether or not the vehicle is being braked (step 10). Such a determination is made whether the brake pedal depression amount θb exceeds a predetermined value, whether a stop lamp switch (not shown) is ON, whether the deceleration Gx exceeds a predetermined value, or other It may be determined by any method. When it is determined that the vehicle is braking, it is then determined whether the ABS is operating on the front wheels or whether the front wheel braking force has reached the saturation region (step 20). . Here, if it is determined that the ABS is operating on the front wheels, or if it is determined that the front wheel braking force has reached the saturation region, it is determined whether EBD control is being executed. (Step 30). In general, the EBD control is performed when the rear wheel speed is lower than the front wheel speed by a predetermined speed, that is, the value of (front wheel speed−rear wheel speed) is a predetermined value. It starts when it exceeds. Therefore, instead of determining whether or not the EBD control is being executed,
(Front wheel speed-rear wheel speed)> predetermined speed value (10)
It may be directly determined whether or not is established.

  When the EBD control is activated or the condition (10) is satisfied in step 30, the estimation calculation of the distance Lf between the front wheel shaft and the center of gravity is executed using the equation (6), (9) or (9a). Then, a distance Lf between the front wheel shaft and the center of gravity is calculated (step 40).

  On the other hand, when it is determined in step 30 that the EBD control is not operating or the condition (10) is not satisfied, it is determined whether or not the current deceleration Gx exceeds a predetermined threshold ( Step 60). Here, as described above, when the EBD control is not operated, that is, when the deceleration is considerably large although the braking force has not reached the saturation region in both the front wheels and the rear wheels. The center of gravity of the vehicle is estimated to be at the end of the assumed existence range. Therefore, the distance Lf between the front wheel axis and the center of gravity is set to a distance Lfmax between the front wheel axis and the end of the assumed range of the center of gravity (step 70).

  When the vehicle is not braking, when the ABS is operating on the front wheels, or when the EBD control is not operating and the deceleration does not exceed a predetermined threshold, the estimation calculation of the distance Lf between the front wheel shaft and the center of gravity is Until then, the value of the distance Lf between the front wheel shaft and the center of gravity previously held in the apparatus or the calculated value (Lf (previous value)) of the previous estimation calculation is used as the distance Lf between the front wheel shaft and the center of gravity. It is done.

  The value of the distance Lf between the front wheel shaft and the center of gravity obtained or set as described above may be stored in an arbitrary memory or the like, and may be appropriately used in motion control such as VSC. Further, the distance Lr between the rear wheel shaft and the center of gravity may be given by Lr = L−Lf.

  Thus, according to the above configuration, the position of the center of gravity of the vehicle can be estimated based on the deceleration of the vehicle, the braking force of each wheel, or the brake pressure without using a sensor that detects the axle load.

  Although the above description has been made in relation to the embodiment of the present invention, many modifications and changes can be easily made by those skilled in the art, and the present invention is limited to the embodiment exemplified above. It will be apparent that the invention is not limited and applies to various devices without departing from the inventive concept.

  For example, the rear wheel axis-center-of-gravity distance Lr may be directly calculated first. When the vehicle braking system is an electromagnetic braking device, the braking force value of each wheel may be calculated from a current value or a power value applied to the electromagnetic actuator.

  In the above embodiment, the front and rear wheels are described as performing ABS and EBD control. However, the principle of the present invention is that the rear wheel braking force is applied before the front wheel braking force. When the saturation region is reached, the center of gravity position of the vehicle can be estimated and calculated, and if the presence or absence of saturation of the braking force of the front and rear wheels can be determined from the wheel speeds of the front and rear wheels, the device of the present invention can be achieved. It should be understood that the ABS device or the EBD control device is not an essential component in a vehicle in which the device of the present invention is mounted.

DESCRIPTION OF SYMBOLS 10 ... Vehicle 12f ... Front wheel 12r ... Rear wheel 14 ... Loading platform 40 ... Braking system device 44 ... Brake pedal 42fl, fr, rl, rr ... Wheel cylinder 45 ... Brake valve 50 ... Electronic control device (including center of gravity position estimating device)
S: Load

Claims (7)

  An apparatus for estimating the position of the center of gravity of a vehicle, wherein the braking force of the front wheel when the difference between the wheel speed of the front wheel of the vehicle and the wheel speed of the rear wheel reaches a predetermined value during braking of the vehicle. And a center of gravity position in the front-rear direction of the vehicle based on a braking force of the rear wheel and a deceleration of the vehicle.   2. The apparatus according to claim 1, wherein the position of the center of gravity in the front-rear direction of the vehicle is calculated based on the braking force of the front wheel, the braking force of the rear wheel, and the deceleration of the vehicle. Is estimated on the basis of the center of load and the height of the center of gravity assumed when the load is loaded on the vehicle.   The apparatus according to claim 1, wherein the center-of-gravity position is estimated when the front wheel does not reach a slip state.   4. The device according to claim 1, wherein an electronic braking force distribution control device is mounted on the vehicle, and the electronic braking force distribution control device executes a restriction on an increase in the braking force of the rear wheel. 5. An apparatus for estimating the position of the center of gravity.   5. The apparatus according to claim 1, wherein an ABS apparatus is mounted on the vehicle, and the center-of-gravity position is estimated when the ABS control for the front wheels is not executed. 6. The apparatus according to claim 2, wherein the distance Lf in the front-rear direction between the center of gravity and the axle of the front wheel is determined by the deceleration Gx and the braking force of the front wheel. Using Fxf, the braking force Fxr of the rear wheel, the center of gravity height H, the gravitational acceleration G, and the wheel base L,
Lf = L · {Fxr / (Fxf + Fxr)} (Gx / G) + H (Gx / G)
A device characterized by being calculated by: 7. The apparatus according to claim 1, wherein a difference between a wheel speed of a front wheel and a rear wheel of the vehicle does not reach a predetermined size during braking of the vehicle. When the deceleration of the vehicle reaches a predetermined value, it is estimated that the position of the center of gravity is located at the rearmost position in the front-rear direction range where the vehicle is assumed to exist.

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