JP2005306121A - Vehicle posture control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle posture control device capable of realizing a superior vehicle posture control even if a vehicle posture control performed by controlling a steering action and a vehicle posture control by controlling a braking mechanism. <P>SOLUTION: A relation between a load applied to a tire W and a critical force Fmax of the tire W is attained in advance and stored in an inner memory of a micro-computer constituting a control amount distributing device 29. The control amount distributing device 29 reads out the critical force Fmax corresponding to a load of the predetermined tire W to calculate a lateral force margin ΔFx=Fmax cosθ-F cosθ and a braking force margin ΔFy=Fmax sinθ-F sinθ. Then, a distribution of a control amount by a steering system control device 17 and a control amount by a running system control device 25 is determined in response to the lateral force margin ΔFx and the braking force margin ΔFy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle attitude control device that uses both vehicle attitude control by control of a steering mechanism and vehicle attitude control by control of a braking mechanism.

  For example, the steering wheel and the steering mechanism for steering the steering wheel are mechanically separated to detect the steering wheel operating angle, and based on the detection result, the torque from the steering actuator is applied to the steering mechanism. A system (so-called steer-by-wire (SBW) system) that achieves steering of a steering wheel by providing the steering wheel has been proposed.

  In the vehicle steering apparatus having such a configuration, since the relationship between the operation of the steering wheel and the operation of the steering mechanism can be freely changed by electrical control, vehicle attitude control by the steering mechanism can be performed. . For example, by obtaining the target yaw rate corresponding to the steering wheel operating angle and controlling the operation of the steering mechanism so that the yaw rate that changes according to the vehicle attitude approaches the target yaw rate, the vehicle attitude control (steering by the steering mechanism) Attitude control) can be achieved.

On the other hand, as another means for controlling the attitude of the vehicle, there is a method of individually controlling the braking pressures of the four wheels. For example, the target braking pressure of each wheel is obtained based on the yaw rate generated in the vehicle, and the braking pressure of each wheel is individually set so that the braking pressure of each wheel detected by the braking pressure sensor approaches the target braking force. By controlling the vehicle position control, vehicle posture control (brake posture control) by braking each wheel can be achieved.
JP 2003-165317 A

  However, in the vehicle attitude control using both the steering attitude control and the brake attitude control, there is a problem that the attitude of the vehicle cannot be controlled well because the steering attitude control and the brake attitude control are not performed in an appropriate balance. . For example, if the control amount by the steering attitude control is set large even though there is not enough room for the grip in the lateral direction of the tire (right and left direction orthogonal to the traveling direction) because the vehicle is cornering, A side slip occurs.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle attitude control device capable of realizing good vehicle attitude control even when vehicle attitude control by control of a steering mechanism and vehicle attitude control by control of a braking mechanism are used in combination. Is to provide.

  The invention described in claim 1 for achieving the above object includes a steering attitude control means (17) for controlling the attitude of the vehicle by controlling the steering mechanism (2, 4, 6, 7) of the vehicle, the vehicle The braking posture control means (25) for controlling the posture of the vehicle by controlling the braking mechanism (23, 24) of the vehicle and the tire (W) mounted on each wheel (5FL, 5FR, 5RL, 5RR) of the vehicle. Based on the stress detecting means (14) for detecting the acting stress and the stress detected by the stress detecting means, the lateral force margin (ΔFx) and the braking force margin (ΔFy) of the tire mounted on a predetermined wheel. On the basis of the lateral force margin amount and the braking force margin amount obtained by the margin amount calculating means, and the control amount by the steering posture control means and the braking posture control means. Is a vehicle posture control system which comprises a control quantity distribution determining means for determining the distribution (29) of the control amount.

The lateral force margin is a grip margin with respect to the lateral direction of the tire (left and right direction orthogonal to the traveling direction).
The braking force margin is the grip margin with respect to the braking direction of the tire.
In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.

According to the first aspect of the present invention, the distribution between the control amount by the steering posture control means and the control amount by the braking posture control means is determined based on the lateral force margin amount and the braking force margin amount of the tire. Thereby, the favorable attitude | position control which fully utilized the grip performance of the tire is realizable.
For example, if the braking force margin is small while the lateral force margin is large because braking is being performed by the braking mechanism, the control amount by the steering posture control unit is larger than the control amount by the braking posture control unit. If the control amount is distributed in this way, it is possible to achieve good posture control that fully utilizes the grip performance of the tire without causing a slip in the tire traveling direction. In addition, when the vehicle is cornering, when the lateral force margin is small and the braking force margin is large, the control amount by the braking posture control means is controlled to be larger than the control amount by the steering posture control means. If the amount is distributed, it is possible to realize good posture control that makes full use of the grip performance of the tire without causing a side slip of the tire.

  The distribution of the control amount by the control amount distribution determination unit includes a distribution in which one of the control amount by the braking posture control unit and the control amount by the steering posture control unit is zero.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram for explaining a configuration of a vehicle steering apparatus provided with a vehicle attitude information detecting apparatus according to an embodiment of the present invention. This vehicle steering device eliminates the mechanical coupling between the steering wheel 1 and the steering mechanism, and the operation of the steering actuator 2 driven in accordance with the rotation operation of the steering wheel 1 is performed on the steering shaft supported by the housing 3. 4 is converted into a linear motion in the vehicle width direction, and the steering is achieved by converting the linear motion of the steered shaft 4 into the steered motion of the front left and right wheels 5FL, 5FR for steering. A by-wire (SBW) system.

  The steering actuator 2 includes, for example, an electric motor such as a brushless motor. The driving force (rotational force of the output shaft) of the steering actuator 2 is applied to the axial direction (vehicle width direction) of the steered shaft 4 by a motion conversion mechanism (for example, a ball screw mechanism) provided in association with the steered shaft 4. ) Linear motion. This linear motion of the steered shaft 4 is transmitted to the tie rods 6 provided so as to protrude from both ends of the steered shaft 4, and further causes the knuckle arm 7 connected to the king pin P to be rotated via the tie rod 6. Thereby, the steering of the wheels 5FL and 5FR supported by the knuckle arm 7 is achieved. The steering shaft 4, the tie rod 6, the knuckle arm 7 and the like constitute a steering mechanism for steering the steering wheels 5FL and 5FR.

The steering wheel 1 is connected to a rotating shaft 8 that is rotatably supported with respect to the vehicle body. A reaction force actuator 9 for applying an operation reaction force to the steering wheel 1 is attached to the rotating shaft 8. The reaction force actuator 9 includes an electric motor such as a brushless motor having an output shaft integrated with the rotary shaft 8.
An elastic member 10 such as a spiral spring is coupled to the end of the rotating shaft 8 on the opposite side of the steering wheel 1 from the vehicle body. The elastic member 10 returns the steering wheel 1 to the straight-ahead steering position by the elastic force when the reaction force actuator 9 is not applying torque to the steering wheel 1.

In order to detect an operation input value of the steering wheel 1, an operation angle sensor 11 for detecting an operation angle of the steering wheel 1 is provided in association with the rotary shaft 8. The rotating shaft 8 is provided with a torque sensor 12 for detecting an operation torque applied to the steering wheel 1.
On the other hand, in order to detect the output value of the steering actuator 2, a turning angle sensor 13 for detecting the turning angle (tire angle) of the steering wheels 5 FL and FR is provided in relation to the turning shaft 4. It has been. The steered angle sensor 13 can be configured by a potentiometer or the like that detects the operation amount of the steered shaft 4 by the steering actuator 2.

  Further, a plurality of stress sensors 14 as stress detecting means are provided inside each tire W mounted on the front left and right wheels 5FL, 5FR and the rear left and right wheels 5RL, 5RR. Specifically, as shown in FIG. 2, the tire W includes a tread portion 51 that contacts a road surface, and a pair of sidewall portions 52 that are coupled to both side portions of the tread portion 51. Then, for example, sixteen stress sensors 14 are arranged on the circumference at substantially equal angular intervals (center angle 22.5 degrees) inside one sidewall portion 52 (for example, the outer sidewall portion 52). Has been.

  Each stress sensor 14 detects a stress acting on a portion of the sidewall portion 52 where the stress sensor 14 is disposed, and wirelessly transmits a sensor portion such as a strain gauge and a detection signal of the sensor portion. And a power storage unit that converts the rotational motion of the tire W into electrical energy and stores the electrical energy, and is operated by the electrical energy stored in the power storage unit.

  A detection signal wirelessly transmitted by each stress sensor 14 is received via an antenna 15 by a yaw rate detection device 16 that detects a yaw rate that changes according to the vehicle posture. The yaw rate detection device 16 includes, for example, a microcomputer and, as will be described later, based on the stress detected by each stress sensor 14, the lateral force acting on each tire W (the tire W A left-right force orthogonal to the traveling direction) Fx and a braking / driving force (driving or braking force) Fy are detected. Then, based on the detected lateral force Fx and braking / driving force Fy, the direction and magnitude F of the friction force acting on each tire W are obtained, and further, the obtained direction and magnitude F of each obtained friction force are obtained. Based on the above, the yaw rate γ generated in the vehicle is detected.

  The yaw rate γ detected by the yaw rate detection device 16 is input to a steering system control device 17 (steering attitude control means) including an electronic control unit (ECU) including a microcomputer. Further, detection signals from the operation angle sensor 11, the torque sensor 12, and the turning angle sensor 13 and detection signals from the vehicle speed sensor 18 for detecting the vehicle speed are input to the steering system control device 17. .

  The steering system control device 17 obtains a target yaw rate based on the operation angle detected by the operation angle sensor 11 and / or the operation torque detected by the torque sensor 12, and the control amount distribution described later, and further, this target yaw rate. And the yaw rate γ detected by the yaw rate detector 16, the target turning angle is calculated. The vehicle attitude control (steering attitude control) is performed by controlling the steering actuator 2 via the drive circuit 19 so that the steering angle detected by the steering angle sensor 13 approaches the target steering angle. .

Further, the steering system control device 17 determines the operation direction of the steering wheel 1 based on the operation angle detected by the operation angle sensor 11, the operation torque detected by the torque sensor 12, and the vehicle speed detected by the vehicle speed sensor 18. The reaction force actuator 9 is controlled via the drive circuit 20 so that an appropriate reaction force in the reverse direction is generated.
The braking pressure corresponding to the depressing force of the brake pedal 21 is generated by the master cylinder 22, and this braking pressure is amplified by the braking pressure control unit 23 and applied to each brake device 24 of each wheel 5FL, 5FR, 5RL, 5RR. The brake devices 24 are distributed so as to apply a braking force to the wheels 5FL, 5FR, 5RL, and 5RR. The braking pressure control unit 23 is controlled by a traveling system control device 25 (braking posture control means) including a microcomputer, whereby the braking pressures of the wheels 5FL, 5FR, 5RL, 5RR are individually controlled. It has become so.

The traveling system control device 25 includes a braking pressure sensor 26 that individually detects the braking pressures of the wheels 5FL, 5FR, 5RL, and 5RR by the brake devices 24, and rotational speeds of the wheels 5FL, 5FR, 5RL, and 5RR ( A wheel speed sensor 27 for individually detecting the wheel speed) is connected.
The traveling system control device 25 is connected to the steering system control device 17 via a line 28.

  The traveling system control device 25 acquires the detected values of the yaw rate γ and the vehicle speed from the steering system control device 17 via the line 28, and is detected by the acquired yaw rate γ and the detected values of the vehicle speed and the wheel speed sensors 27. The target braking pressure of each wheel 5FL, 5FR, 5RL, 5RR is obtained based on the wheel speed and the control amount distribution described later. Then, the braking pressure control unit 23 is controlled so that each braking pressure detected by each braking pressure sensor 26 approaches each target braking pressure, and the braking pressure of each wheel 5FL, 5FR, 5RL, 5RR is individually controlled. Thus, vehicle attitude control (brake attitude control) is performed. Note that the braking pressure control unit 23 is configured to be able to generate a braking pressure by a built-in pump even when the brake pedal 21 is not operated.

  Further, the direction and magnitude F of the frictional force acting on each tire W detected by the yaw rate detection device 16 is determined based on the control amount distribution device 29 (margin amount calculation means, control amount distribution determination means) including a microcomputer. To be input. Based on the direction and magnitude F of the friction force acting on the predetermined tire W, the control amount distribution device 29 controls the control amount by the steering posture control of the steering system control device 17 and the brake posture control of the traveling system control device 25. Determine the distribution with the control amount. Then, the steering system control device 17 and the traveling system control device 25 obtain the target yaw rate and the target braking pressure according to the control amount distribution determined by the control amount distribution device 29, respectively.

  FIG. 3 is a block diagram showing a configuration of the yaw rate detection device 16. The yaw rate detection device 16 receives a detection signal wirelessly transmitted from each stress sensor 14, and based on the detection signal received by the reception unit 161, the lateral force Fx acting on each tire W is obtained. A lateral force detection unit 162 to detect, a braking / driving force detection unit 163 that detects braking / driving force Fy acting on each tire W based on a detection signal received by the reception unit 161, and a lateral force detection unit 162 A yaw rate calculator 164 that calculates a yaw rate γ generated in the vehicle based on the detected lateral force Fx and the braking / driving force Fy detected by the braking / driving force detector 163 is provided.

The lateral force detector 162 and the braking / driving force detector 163 are each acting on the tire W for each tire W based on the stress detected by each stress sensor 14 disposed on each tire W. The force Fx and the braking / driving force Fy are obtained.
The yaw rate calculator 164 acts on the tire W for each tire W based on the lateral force Fx detected by the lateral force detector 162 and the braking / driving force Fy detected by the braking / driving force detector 163. The direction and the magnitude F of the friction force that is present are obtained, and further, the yaw rate γ generated in the vehicle is obtained based on the magnitude F of the friction force acting on each tire W.

That is, the frictional force acting on the tire W is a vector of the left or right lateral force Fx perpendicular to the traveling direction of the tire W and the vector of the braking / driving force Fy in the traveling direction or backward direction of the tire W. As shown in FIG. 4, the lateral force Fx is taken on the horizontal axis and the braking / driving force Fy is taken on the vertical axis, as shown in FIG. Assuming that the positive direction is the left direction of the lateral force Fx and the backward direction (braking direction) of the braking / driving force Fy is the negative direction, the frictional force acting on the tire W is counterclockwise with respect to the positive direction of the horizontal axis. The angle θ formed is
Fy> 0: θ = tan ⁻¹ (Fy / Fx) <180 ° (1-1)
Fy <0: θ = tan ⁻¹ (Fy / Fx)> 180 ° (1-2)
Fy = 0, Fx> 0: θ = 0 (1-3)
Fy = 0, Fx <0: θ = 180 ° (1-4)
Can be asked according to. In addition, the magnitude F of the frictional force is
F = (Fx ² + Fy ² ) ^1/2 (2)
Can be asked according to. The yaw rate calculation unit 164 obtains the direction and magnitude F of the frictional force acting on each tire W according to the above formulas (1-1) to (1-4) and (2). Then, the yaw rate γ generated in the vehicle is obtained according to the following equation (3).

γ = [Lf (F ₁ + F ₂ ) −Lr (F ₃ + F ₄ )] / I (3)
Here, as shown in FIG. 5, Lf is the distance along the vehicle traveling direction between the rotation center of the front left and right wheels 5FL, 5FR and the center of gravity G of the vehicle, and Lr is the rear left and right wheels. It is the distance along the vehicle traveling direction between the rotation center of 5RL and 5RR and the center of gravity G of the vehicle. F ₁ , F ₂ , F ₃ , and F ₄ are magnitudes of frictional forces acting on the tires W mounted on the wheels 5FL, 5FR, 5RL, and 5RR, respectively. I is the yaw moment.

  Since the stress acting on the tire W changes almost simultaneously with the vehicle attitude, the yaw rate γ obtained based on the stress detected by the stress sensor 14 changes without delay with respect to the change in the vehicle attitude. In other words, the yaw rate detection device 16 can detect the yaw rate γ that changes according to the vehicle posture without delay. Therefore, by controlling the steering actuator 2 by the steering system control device 17 based on the detected yaw rate γ, it is possible to realize steering posture control with excellent responsiveness to changes in the vehicle posture.

FIG. 6 is a diagram for explaining the function of the control amount distribution device 29. The control amount distribution device 29 acquires, for example, the direction θ and the magnitude F of the frictional force acting on the tire W mounted on the front wheel 5FL or 5FR from the yaw rate detection device 16, and based on this. Then, the lateral force margin ΔFx and the braking force margin ΔFy are obtained.
Specifically, a relationship between a load applied to the tire W and a limit force of the tire W (force when the tire W starts to slide on the road surface) Fmax is obtained in advance, and the control amount distribution device 29 is configured. It is stored in the built-in memory of the microcomputer. In the control amount distribution device 29, the limit force Fmax corresponding to the load of the tire W mounted on the front wheel 5FL or 5FR is read, and the lateral force margin is calculated based on the following equations (4) and (5), respectively. An amount ΔFx and a braking force margin amount ΔFy are obtained.

ΔFx = Fmax · cos θ−F · cos θ (= Fmax · cos θ−Fx) (4)
ΔFy = Fmax · sin θ−F · sin θ (= Fmax · sin θ−Fy) (5)
Based on the lateral force margin ΔFx and the braking force margin ΔFy thus obtained, the control amount distribution device 29 controls the control amount by the steering posture control of the steering system control device 17 and the brake posture control of the traveling system control device 25. Determine the distribution with the control amount. For example, since braking by the brake device 24 is being performed, the braking force margin amount ΔFy is small (for example, the braking force acting on the tire W (braking / driving force in the reverse direction of the tire W) Fy is the limit control of the tire W) On the other hand, when the lateral force margin ΔFx is large (for example, the lateral force Fx acting on the tire W is less than 20% of the limit lateral force Fmax · cosθ of the tire W). The target control amount is set so that the control amount by the steering posture control becomes larger than the control amount by the brake posture control (for example, the ratio between the control amount by the steering posture control and the control amount by the brake posture control is 6: 4). The control amount is distributed as (x0.6, 0.4).

As described above, according to this embodiment, the distribution of the control amount by the steering posture control and the control amount by the brake posture control is determined based on the lateral force margin amount ΔFx and the braking force margin amount ΔFy. It is possible to achieve good posture control that fully utilizes the grip performance of the tire W.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above embodiment, the distribution of the control amount by the steering posture control and the control amount by the brake posture control is determined based on the lateral force margin amount ΔFx and the braking force margin amount ΔFy. The steering posture control and the brake posture control may be switched based on the force margin amount ΔFx and the braking force margin amount ΔFy, and only more effective posture control may be selectively performed. That is, since braking by the brake device 24 is being performed and the braking force margin amount ΔFy is small and the lateral force margin amount ΔFx is large, the steering posture control is performed by the steering system control device 17 and the vehicle is cornering. Therefore, when the lateral force margin ΔFx is small and the braking force margin ΔFy is large, the brake posture control by the traveling system control device 25 may be performed.

  In addition, various design changes can be made within the scope of matters described in the claims.

It is a conceptual diagram for demonstrating the structure of the vehicle steering device provided with the vehicle attitude | position information detection apparatus which concerns on one Embodiment of this invention. It is a figure for demonstrating arrangement | positioning of a stress sensor. It is a block diagram which shows the structure of a yaw rate detection apparatus. It is a figure for demonstrating how to obtain | require the direction and magnitude | size of the frictional force which is acting on the tire. It is a figure for demonstrating the calculation method of a yaw rate. It is a figure for demonstrating the calculation method of lateral force margin amount and braking force margin amount.

Explanation of symbols

2 Steering actuator (steering mechanism)
4 Steering shaft (steering mechanism)
5FL, 5FR, 5RL, 5RR Wheel 6 Tie rod (steering mechanism)
7 Knuckle arm (steering mechanism)
14 Stress sensor 16 Yaw rate detection device 17 Steering system control device 23 Braking pressure control unit (braking mechanism)
24 Brake device (braking mechanism)
25 Traveling system control device 29 Control amount distribution device W Tire

Claims (1)

Steering attitude control means for controlling the attitude of the vehicle by controlling the steering mechanism of the vehicle;
Braking attitude control means for controlling the attitude of the vehicle by controlling the braking mechanism of the vehicle;
Stress detecting means for detecting stress acting on a tire mounted on each wheel of the vehicle;
Based on the stress detected by the stress detection means, a margin amount calculation means for obtaining a lateral force margin amount and a braking force margin amount of a tire mounted on a predetermined wheel;
Control amount distribution determining means for determining a distribution between the control amount by the steering posture control means and the control amount by the braking posture control means based on the lateral force margin amount and the braking force margin amount obtained by the margin amount calculating means. A vehicle attitude control device comprising:

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