JP2007001501A - Camber angle control device and camber angle control method for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camber angle control device for a vehicle capable of reducing a vehicle body rolling angle at the time of turning without providing a vehicle height adjustment mechanism. <P>SOLUTION: A suspension mounting position angle θ° for making the vehicle body rolling angle θ to zero is calculated according to the detected lateral G (step S2) and a camber angle ψ1 at an inner side of turning is made to a large angle in a negative direction than a camber angle ψ<SB>0</SB>at an outer side of turning based on the calculated suspension mounting angle θ° (step S3). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of a camber angle control device and a camber angle control method for a vehicle that independently control a camber angle inside a turn and a camber angle outside a turn.

In a conventional camber angle control device for a vehicle, the limit performance of the tire is improved by changing the camber angle during turning. The camber angle control has advantages such as being particularly effective in improving the limit lateral G, and that the lateral force generation by the camber is more responsive than the lateral force generation by the side slip angle (see, for example, Non-Patent Document 1). .
http://www.fast-cars.ch/Mercedes-Benz_F400_Carving_pictures.htm (Daimler concept car F400)

  Although camber angle control contributes to improving the performance of tires in the limit region, in the normal region, the camber angle of the tire on the outside of the turn is tilted in the negative direction. There is a problem that the tilting roll behavior becomes large. On the other hand, in the above prior art, vehicle height adjustment by hydraulic pressure is used to control the roll angle, but this leads to a complicated system and an increase in weight.

  The present invention has been made paying attention to the above-described problem, and an object of the present invention is to provide a camber angle control device and camber angle control for a vehicle that can reduce a vehicle body roll angle during turning without providing a vehicle height adjustment mechanism. It is to provide a method.

In order to achieve the above object, in the camber angle control device for a vehicle of the present invention,
In the camber angle control means of the vehicle provided with the camber angle control means for independently controlling the camber angle inside the turn and the camber angle outside the turn,
The camber angle control means sets the camber angle inside the turn to a larger angle than the camber angle outside the turn when the vehicle turns.

  According to the present invention, by setting the camber angle inside the turn larger than the camber angle outside the turn, the mounting position (height) of the suspension inside the turn can be lowered, and the vehicle height adjusting mechanism is provided. In addition, the vehicle body roll angle during turning can be kept small.

  The best mode for realizing a camber angle control device for a vehicle according to the present invention will be described below based on Examples 1 and 2.

First, the configuration will be described.
FIG. 1 is a block diagram illustrating the configuration of a camber angle control device for a vehicle according to a first embodiment. The camber angle control device for a vehicle according to the first embodiment includes a steering angle detection unit 1 and a control device unit (camber angle control means). ) 2, vehicle state detection unit 3, right front wheel (FR) camber actuator 4-1, left front wheel (FL) camber actuator 4-2, right rear wheel (RR) camber actuator 4-3, left rear wheel (RL) ) Camber actuator 4-4.

  The driver inputs the steering angle by rotating the steering wheel. The steering angle input by the driver is detected by the steering angle detector 1 and transmitted to the controller 2. Various vehicle states detected by the vehicle state detection unit 3 are also transmitted to the control device unit 2. The various vehicle states used here refer to one or more of vehicle speed, yaw rate, and lateral G, which are vehicle states related to vehicle motion control (lateral acceleration detecting means).

  The control unit 2 generates a target camber angle for each wheel from the steering angle and the vehicle state quantity (vehicle speed, yaw rate, lateral G), and issues a command corresponding to the generated target camber angle to the camber actuator 4-1, Tell 4-2, 4-3,4-4 respectively. The camber actuators 4-1, 4-2, 4-3,4-4 cause the camber angle of the wheel to follow the command value from the control device unit 2.

Here, as shown in FIGS. 2, 3 and 4, the steering angle θ _d , the turning angle δ _f , the turning inner front wheel camber angle φ _fi , the turning outer front wheel camber angle φ _fo , the turning inner rear wheel camber angle φ _ri , The turning outer rear wheel camber angle φ _ro is positive in the direction in which the steering wheel 5 is rotated counterclockwise, positive in the direction in which the front wheel 6 is rotated counterclockwise when viewed from above the vehicle, and counterclockwise from the rear wheel 7 as viewed from the rear of the vehicle. The direction to turn clockwise is positive.

When turning the vehicle, the control device unit 2 increases the ground height of the suspension mounting portion on the inside of the turn by setting at least the camber angle φ _i on the inside of the turn to be larger in the positive or negative direction than the camber angle φ _o on the outside of the turn. Lower and restrain the roll of the sprung body.

Next, the operation will be described.
[Target camber angle generation method]
A method for generating a target camber angle in the control unit 2 will be described.
First, parameters related to the movement in the roll direction are shown below. Unusual parameters are also shown in FIGS. For reference, some of the parameters show typical values in a sedan type passenger car. Hereinafter, a vehicle having this vehicle parameter is referred to as a reference vehicle.
Driver steering angle: θ _d [rad]
Front wheel turning angle: δ _f [rad]
Rear wheel turning angle: δ _r [rad]
Front wheel ground camber angle: φ _f [rad]
Rear wheel camber angle: φ _r [rad]
Vehicle side slip angle: β [rad]
Front wheel skid angle: β _f [rad]
Rear wheel skid angle: β _r [rad]
Front wheel cornering power: C _f [N / rad]
Rear wheel cornering power: C _r [N / rad]
Front wheel lateral force: F _f [N]
Rear wheel lateral force: F _r [N]

Vehicle speed: v [m / s]
Car weight: m [kg] (Reference vehicle: 1,800 [kg])
Yaw rate: γ [rad / s]
Horizontal G: α [m / s ² ]
Distance between center of gravity and roll center: h _CG-RC [m] (Reference vehicle: 0.55 [m])
Vehicle lateral displacement: y [m]
Body roll angle: θ [rad]
Roll stiffness: k _r [Nm / rad] (Reference vehicle: 120,000 [Nm / rad])
Roll damping: C _r [Nm / (rad / s)] (Reference vehicle: 8,000 [Nm / (rad / s)])
Sprung moment of inertia: I _r [kgm ² ] (Reference vehicle: 675 [kgm ² ])
Sprung mass: m _u [kg] (Reference vehicle: 1,600 [kg])
Suspension spring constant: k _s [N / m] (Reference vehicle: 2,200 [N / m])
Suspension damping coefficient: C _s [N / (m / s)] (Reference vehicle: 6,000 [N / (m / s)])
Front wheel tread: tr [m] (Reference vehicle: 1.5 [m])
Inner ring center axis displacement: d _h [m]
Suspension mounting angle: θ '[rad]
Suspension mounting distance: tr '[m]
Tire radius: R [m] (Reference vehicle: 0.325 [m])
Inner ring wheel ground camber angle: φ _i [rad]
Outer wheel wheel ground camber angle: φ _o [rad]
Stabilizer roll rigidity (front and rear total): k _{r_st} [Nm / rad] (reference vehicle: 52,000 [Nm / rad])

The motion around the roll center of the vehicle can be expressed by the following equation (1) assuming that the roll moment due to gravity is small. In the following description, one dot (·) added above each parameter indicates a first-order differential value, and two dots (··) indicate a second-order differential value.

If the ground camber angle of the wheel is always zero, rigidity Kr and viscosity Cr of roll rotation direction of the suspension can be expressed as follows in the vertical stiffness Ks and viscosity C _s.

When the camber angle of the front-turning wheel is φ, the following inner wheel center axis displacement dh is expressed by equation (4), and the suspension attachment position angle θ ′ is expressed by equation (5).

The change in the suspension attachment position angle θ ′ affects the movement around the roll center, and the balance of the force around the roll center is as shown in Equation (6).

By transforming Equation (6), Equation (7) is obtained, and by moving the camber angle φ so that θ ′ becomes Equation (8), the right side of Equation (7) becomes zero and the roll angle θ does not occur. .

Here, in order for Equation (8) to hold, θ ′ may be set to an angle corresponding to the lateral G as shown in Equation (9). In order to realize θ ′, the camber angle φ _i inside the turn may be set as shown in Expression (10).

That is, the camber angle φ _i inside the turning is obtained from the lateral G using the equations (9) and (10). If the maximum lateral G is 8 [m / s ² ] in the reference vehicle, the maximum value of θ ′ is about 3.1 [deg] from Equation (9), and the maximum camber angle φ _i is 40 when Equation (10) is used. [deg] grade.
Turning front wheel camber angle: φ _fi [rad]
Turning front wheel camber angle: φ _fo [rad]
Back side camber angle of turning: φ _ri [rad]
Back outer camber angle: φ _ro [rad]

The proportionality coefficient of the lateral force and D for the camber angle, shown subscript _{f i, f o, r i} , r o are each turning inner front wheel, front outside wheel, the turning inner rear wheel, the turning outer rear wheel. The sum of the right and left proportional coefficients is set to D _f and D _r for the front and rear wheels, respectively. Similarly, the total cornering power of the left and right wheels is C _f and C _r respectively for the front and rear wheels, but for the cornering power of each wheel, it is assumed that subscripts f _i , f _o , r _i , and _ro are added. And can be expressed as the formulas (11) and (12).

At this time, the formula of the force balance in the lateral direction of the vehicle in the horizontal plane (xy plane) and the formula of the balance of moments around the center of gravity are as shown in formulas (13) and (14), respectively.

When the vehicle is in the vicinity of the limit side G, the tire can have a higher limit when the camber angle outside the turn is in the negative direction. Here, assuming that the camber angle outside the turn is a negative direction, C _fo and C _ro have large values according to the camber angle outside the turn, so C _f and _Cr are large in Equations (13) and (14). And the side slip angle of the tire decreases.

Therefore, when the tire has a side slip angle close to the limit value, the limit side G can be improved by increasing the camber angle on the outer side of the turn according to the driver's steering. The camber additional steering angle dφ ratio of relative turning-increasing turning angle dδ tire at this time by the k _.delta..phi, controlled to be Equation (15).

At this time, k _δφ is obtained by solving Equation (13) and Equation (14) for the tire slip angle β _f · β _r , and the partial differentiation of β _f and β _r by δ as shown in Equation (16) and Equation (17). Set so that the value of is negative. Alternatively, by numerical calculation, β _f and β _r are set to have a negative minute displacement with respect to the minute displacement of δ.

The camber angle on the inside of the turn is set in the same way, and is changed to reduce the tire skid angle.

  With the above configuration, the rolling behavior of the vehicle is improved in the normal region, and the limit characteristics of the tire are improved near the limit.

[Camber angle setting control processing]
FIG. 8 is a flowchart showing the flow of the camber angle setting control process executed by the control device unit 2 of the first embodiment, and each step will be described below.

In step S1, it is determined whether or not the front wheel side slip angle β _f is equal to or less than a predetermined maximum side slip value β _fmax close to the tire limit value. If YES, the process proceeds to step S2, and if NO, the process proceeds to step S4.

  In step S2, the suspension attachment position angle θ ′ at which the vehicle body roll angle θ is zero is calculated according to the lateral G using the equation (9), and the process proceeds to step S3 (suspension attachment position angle calculation means).

In step S3, the camber angle φ _i on the inside of the turn that realizes the suspension attachment position angle θ ′ obtained in step S2 is calculated by the equation (10), and the process proceeds to return.

  In step S4, the camber cut increasing angle dφ according to the driver's steering (tire turning turning angle dδ) is calculated by the equation (15), and the process proceeds to return.

That is, when the tire slip angle β _f of the front wheels is equal to or less than the maximum slip value β _fmax , the flow proceeds from step S1 to step S2 to step S3 in the flowchart of FIG. The camber angle φ _i inside the turning so as to be zero is calculated. Therefore, in the normal region where the side slip angle of the tire is within the limit range, the vehicle body roll angle θ during turning can be kept small, and the roll behavior of the vehicle is improved.

If the tire slip angle β _{f of the} front wheel exceeds the maximum slip value β _fmax , the process proceeds from step S1 to step S4. In step S4, the camber angle φ that decreases the tire slip angle β _f according to the driver's steering. The additional angle dφ is calculated. Therefore, in the vicinity of the tire skid angle limit, the tire skid angle can be reduced and the tire limit characteristics can be improved.

Next, the effect will be described.
In the camber angle control device for a vehicle according to the first embodiment, the effects listed below can be obtained.

(1) When the vehicle turns, the control device 2 lowers the mounting position (height) of the suspension inside the turn so that the camber angle φ _i inside the turn is larger than the camber angle φ _o outside the turn. Therefore, the vehicle body roll angle θ during turning can be kept small without providing a vehicle height adjustment mechanism.

(2) A vehicle state detection unit 3 that detects the lateral G of the vehicle, and a suspension attachment position angle calculating unit that calculates a suspension attachment position angle θ ′ that makes the vehicle body roll angle θ zero according to the detected lateral G ( The control device unit 2 controls the camber angle φ _i inside the turning and the camber angle φ _o outside the turning based on the calculated suspension attachment position angle θ ′. Therefore, the vehicle body roll angle θ during turning can be brought close to zero.

(3) The control unit 2 determines that the steering angle (the tire turning steering) when the front wheel side slip angle β _f is equal to or greater than the maximum side slip value β _fmax near the tire limit, that is, the wheel side slip angle β _f is in the saturation region. In accordance with the angle dδ), the camber angle φ _{i on the} inside of the turn and the camber angle φ _o on the outside of the turn are changed in the direction in which the side slip angle β _f decreases. Therefore, the limit characteristics of the tire in the vicinity of the tire limit are increased, and the limit lateral G can be improved.

  The second embodiment is an example in which the camber angle is limited to less than the maximum value on the mechanism. The configuration is the same as that of the first embodiment shown in FIG.

Next, the operation will be described.
[Target camber angle generation method]
In the second embodiment, when the camber angle φ _i becomes the maximum camber angle φ _imax due to mechanical limitations, the method is not as in the first embodiment but as follows.

When the camber angle φ _i is zero, that is, when θ ′ is zero, the response of the roll angle θ to the lateral G is expressed as follows when the steady-state gain is G _θ , the damping coefficient is ζ, and the natural frequency is ω _n. As a modification of 1), the following equations (18) to (21) can be substituted.

Here, θ ′ is set to the following formula (22), and by substituting formula (6), the equation of motion around the roll center becomes the following formula (23).

At this time, the equation (23) is modified, and the response of the roll angle θ to the lateral G is expressed by the following equation (24) when the steady-state gain is G _θ ′, the damping coefficient is ζ ′, and the natural frequency is ω _n ′. It can be replaced with ~ (27).

θ'は、式(22)と式(24)より導かれる以下の式(29)に従い、横Ｇに応じて決定する。

At this time, the attenuation coefficient ζ ′ can be freely set according to the value of k, and is preferably about 0.7 to 0.8. k can be set as in the following equation (28) using ζ ′.

θ ′ is determined according to lateral G according to the following equation (29) derived from equations (22) and (24).

[Target camber angle generation logic according to target damping coefficient ζ ']
When the mechanical condition of the camber angle φ _i is severe and the camber angle φ _i becomes the maximum camber angle φ _imax during the roll, the response of the roll changes due to the camber angle φ _i becoming the maximum camber angle φ _imax There is a risk that this may be uncomfortable. In the second embodiment, since the lateral G used in normal operation is up to about 0.4 G, when the lateral G is 0.4 G or less, the camber angle φ _i does not become the maximum camber angle φ _imax. The camber angle φ _i is set so that the value of k becomes a value close to 0.7 to 0.8. In the second embodiment, the value of k is obtained assuming that ζ ′ is about 0.7 in the equation (26).

Here, in order to set the attenuation coefficient ζ ′ to 0.7 to 0.8, k may have to be 1 or more. In this case, the value of k is set so that ζ ′ is as large as possible. In the reference vehicle described in the first embodiment, this case is established. When the attenuation coefficient ζ ′ is set to 0,55, k is about 0.50, and the maximum camber angle φ _i can be set to 30 [deg]. it can.

In Example 2, a large area of the tire slip angle beta _f is the same manner as in Example 1, changing to the negative direction according to camber angles phi _i of the turning outer driver steering angle theta _d.

[Camber angle setting control processing]
FIG. 9 is a flowchart showing the flow of the camber angle setting control process executed by the control device unit 2 of the second embodiment. Each step will be described below. In addition, the same step number is attached | subjected to the step which performs the process similar to Example 1 shown in FIG. 8, and description is abbreviate | omitted.

In step S11, k corresponding to a desired damping coefficient ζ ′ (for example, 0.7 to 0.8) such that the camber angle φ _i does not become the maximum camber angle φ _imax during the roll is calculated by the equation (28), and step S12 Migrate to

  In step S12, the suspension attachment position angle θ ′ is calculated according to equation (29) according to k and the lateral G obtained in step S11, and the process proceeds to step S3.

That is, when the tire slip angle β _f of the front wheel is equal to or less than the maximum skid value β _fmax , the flow proceeds from step S1 → step S11 → step S12 → step s13 in the flowchart of FIG. The camber angle φ _i is calculated such that the coefficient ζ ′ becomes a desired value (0.7 to 0.8). Therefore, the camber angle φ _i becomes the maximum camber angle φ _imax , and it is possible to prevent the roll response characteristic of the vehicle from changing. Moreover, the vibration of the roll behavior on the vehicle spring accompanying camber control can be suppressed.

Next, the effect will be described.
In the camber angle control device for a vehicle according to the second embodiment, the following effects can be obtained in addition to the effects (1) to (3) of the first embodiment.

(4) Since the control unit 2 limits the camber angle φ _i inside the turn to less than the maximum value on the mechanism, the roll response of the vehicle is determined by the camber angle φ _i being the maximum camber angle φ _imax during the roll. Can be prevented and the driver can be prevented from feeling uncomfortable.

(5) The control unit 2 controls the camber angle φ _{i on the} inside of the turn and the camber angle φ _o on the outside of the turn so as to suppress the vibration of the damping term (damping coefficient ζ ′) of the roll behavior on the vehicle spring. Therefore, the vibration of the roll behavior on the vehicle spring accompanying the camber control can be suppressed.

(6) The control unit 2 has a camber angle φ _i inside the turn so that the damping term (damping coefficient ζ ′) in the roll motion is as large as possible (0.7 to 0.8) in the normal lateral G region (0.4G). And the camber angle φ _o on the outside of the turn. Therefore, the roll behavior characteristic on the vehicle spring can be maintained at a desired characteristic in the normal lateral G region.

  The best mode for carrying out the present invention has been described based on the first and second embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments. Design changes and the like within a range that does not depart from the gist are also included in the present invention.

  For example, in the second embodiment, the suspension attachment position angle θ ′ is determined according to the lateral G using the expression (29) derived from the expressions (22) and (24). The angle θ ′ may be determined as shown in Expression (22) according to the roll angle θ and k.

1 is a block diagram illustrating a configuration of a camber angle control device for a vehicle according to a first embodiment. It is explanatory drawing of the steering angle of Example 1, and a front-wheel turning angle. It is explanatory drawing of the front-wheel camber angle | corner of Example 1. FIG. It is explanatory drawing of the rear-wheel camber angle of Example 1. FIG. It is explanatory drawing of the parameter regarding a vehicle body roll. It is explanatory drawing of the parameter (spring, damper) regarding a vehicle body roll. It is explanatory drawing of the parameter regarding the vehicle body roll of Example 1. FIG. 6 is a flowchart illustrating a flow of camber angle setting control processing executed by the control device unit 2 according to the first embodiment. 6 is a flowchart illustrating a flow of a camber angle setting control process executed by the control device unit 2 according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering angle detection part 2 Control apparatus part 3 Vehicle state detection part
4-1 Right front wheel camber actuator
4-2 Left front wheel camber actuator
4-3 Right rear wheel camber actuator
4-4 Left rear wheel camber actuator

Claims (8)

In the camber angle control means of the vehicle provided with the camber angle control means for independently controlling the camber angle inside the turn and the camber angle outside the turn,
The camber angle control device is characterized in that the camber angle inside the turn is larger than the camber angle outside the turn when the vehicle turns. The camber angle control device for a vehicle according to claim 1,
Lateral acceleration detecting means for detecting the lateral acceleration of the vehicle;
A suspension attachment position angle calculating means for calculating a suspension attachment position angle for reducing the vehicle body roll angle according to the detected lateral acceleration;
With
The camber angle control device according to claim 1, wherein the camber angle control means controls a camber angle inside the turn and a camber angle outside the turn based on the calculated suspension attachment position angle. The camber angle control device for a vehicle according to claim 1 or 2,
The camber angle control means changes the camber angle inside the turn and the camber angle outside the turn in a direction in which the side slip angle of the wheel decreases according to the steering angle when the side slip angle of the wheel is in a saturation region. A camber angle control device for a vehicle. The camber angle control device for a vehicle according to any one of claims 1 to 3,
The camber angle control means limits the camber angle inside the turn to less than the maximum value in the mechanism. The camber angle control device for a vehicle according to any one of claims 1 to 4,
The camber angle control device for controlling a left and right camber angle so as to suppress vibration of a damping term of a roll behavior on a vehicle spring. The camber angle control device for a vehicle according to any one of claims 1 to 5,
The camber angle control means controls the camber angle inside the turn and the camber angle outside the turn so that the attenuation term in the roll motion is as large as possible in the normal lateral acceleration range. apparatus. The camber angle control device for a vehicle according to any one of claims 1 to 6,
Lateral acceleration detecting means for detecting the lateral acceleration of the vehicle;
Suspension mounting position angle calculating means for calculating a suspension mounting position angle with a vehicle body roll angle of zero according to the detected lateral acceleration;
With
The camber angle control device according to claim 1, wherein the camber angle control means controls a camber angle inside the turn and a camber angle outside the turn based on the calculated suspension attachment position angle. In the camber angle control means for a vehicle that independently controls the camber angle inside the turn and the camber angle outside the turn,
A camber angle control method for a vehicle, characterized in that when the vehicle turns, the camber angle on the inner side of the turn is made larger than the camber angle on the outer side of the turn, and the vehicle body roll angle is reduced.

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