JP5358487B2 - Vehicle turning control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve head-turning ability and responsiveness of steering during normal turning. <P>SOLUTION: The turning control device 1 for a vehicle can generate a yaw moment to a vehicle body by applying braking force to right and left wheels based on the traveling state of the vehicle. The turning control device includes: a lateral G-norm yaw rate computing part 14 that calculates the lateral G-norm yaw rate based on the detection signal of a lateral G-sensor 5 and a vehicle speed sensor 4; a steady norm yaw rate computing part 12 that determines the steady norm yaw rate based on the detection signal of a steering angle sensor 3 and the vehicle speed sensor 4; a correction part 15 that calculates the limit norm yaw rate by correcting the lateral G-norm yaw rate in an increase direction based on the steady norm yaw rate; an FB control amount computing part 19 that calculates the yaw rate deviation between the limit norm yaw rate and an actual yaw rate detected by the yaw rate sensor 6 to determine the braking force control amount in such a direction that the yaw rate deviation is offset; and a brake device 10 that controls the braking force based on the braking force control amount determined by the FB control amount computing part 19. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a vehicle turning control device that controls turning of a vehicle using braking.

  This kind of turning control device is specified in a direction in which the deviation between the lateral G standard yaw rate calculated based on the lateral acceleration (hereinafter referred to as lateral acceleration) of the vehicle and the vehicle speed and the actual yaw rate of the vehicle is close to zero. It is known that the vehicle behavior is stabilized by braking control of the wheels.

  Further, as another turning control device, the left and right braking force of the front wheel and the left and right braking force of the rear wheel are made different according to the turning state (for example, the steering angle and the change rate of the steering angle) during braking. It is known to assist the yaw moment and improve the turning ability by controlling in this way (see, for example, Patent Document 1).

  Further, a corrected yaw moment is calculated by adding the first yaw moment calculated based on the steering angular velocity or the steering angular acceleration and the second yaw moment calculated based on the steering angle, the vehicle speed, and the yaw rate. It is known to improve the turning performance by controlling the left and right braking forces of the front wheels to be different and the left and right braking forces of the rear wheels to be different (see, for example, Patent Document 2). .

Japanese Patent No. 2572860 JP 2005-153716 A

  However, in the turning control device described in Patent Document 1, since the yaw moment is always assisted at the time of turning at the time of braking, there is a case where the yaw moment becomes excessive and stability is reduced, which is not realistic.

  On the other hand, in the turning control device described in Patent Document 2, the first yaw moment is greatly reflected at the time of sudden turning (when the steering angular velocity and the steering angular acceleration are large). Although improved, it is not effective during normal turning. Therefore, a turning control device that can improve the turning ability during normal turning is desired.

  Therefore, the present invention provides a turning control device for a vehicle that can improve the turning ability during normal turning.

The vehicle turning control apparatus according to the present invention employs the following means in order to solve the above problems.
The invention according to claim 1 is a steering amount detection means (for example, a steering angle sensor 3 in an embodiment described later) for detecting a steering amount of the vehicle, and a vehicle speed detection means (for example, described later) for detecting or estimating the vehicle speed of the vehicle. Vehicle speed sensor 4) in the embodiment, lateral acceleration detection means (for example, lateral G sensor 5 in the embodiment described later) for detecting the lateral acceleration of the vehicle, and yaw rate detection means (for detecting the yaw rate of the vehicle). For example, a vehicle turning control device (e.g., a yaw rate sensor 6 in an embodiment to be described later), which can generate a yaw moment on the vehicle body by applying braking force to the front, rear, left and right wheels based on the traveling state of the vehicle (e.g., A vehicle turning control device 1) in an embodiment to be described later,
A control amount calculation unit (for example, a lateral in the embodiment described later) that calculates a first reference yaw rate (for example, a lateral G reference yaw rate ω_low in an embodiment described later) based on detection signals of the lateral acceleration detection means and the vehicle speed detection means. G norm yaw rate calculation unit 14),
Based on detection signals from the steering amount detection means and the vehicle speed detection means, a correction reference value setting means (for example, a steady reference yaw rate ω_high in a later-described embodiment) that increases as the vehicle speed becomes lower is obtained. A steady-state normative yaw rate calculation unit 12) in an embodiment described later;
A correction unit (for example, correction in an embodiment described later) that corrects the first reference yaw rate in an increasing direction based on the correction reference value to calculate a second reference yaw rate (for example, a limit reference yaw rate ω_TAR in an embodiment described later) Part 15),
A braking force control amount calculation unit that calculates a yaw rate deviation between the second normative yaw rate and the actual yaw rate detected by the yaw rate detection means, and determines a braking force control amount in a direction to cancel the yaw rate deviation (for example, implementation described later) FB control amount calculation unit 19) in the example,
Braking control means for controlling the braking force based on the braking force control amount determined by the braking force control amount calculation unit (for example, a brake device 10 in an embodiment described later),
The correction unit determines a correction amount so that the second reference yaw rate decreases as the vehicle speed increases,
A required torque detecting means (for example, an accelerator opening sensor 7 in an embodiment described later) for detecting the magnitude of the required torque based on the accelerator opening or the accelerator pedal operation amount;
The correction unit determines a correction amount so that the second reference yaw rate increases as the vehicle speed decreases when the detection signal of the required torque detection unit is smaller than a predetermined value;
The correction unit determines a correction amount based on a load movement amount in the front-rear direction of the vehicle so that the second reference yaw rate decreases as the forward load movement amount increases .
In the correction unit, the friction coefficient between the wheel and the road surface is larger than the threshold, the steering amount is larger than the threshold, the lateral acceleration reduction rate is larger than the threshold, or the yaw rate reduction rate is larger than the threshold. When it is determined , the vehicle turning control device determines the correction amount so that the second reference yaw rate is smaller than before the determination .

According to a second aspect of the present invention, in the first aspect of the invention, the correction unit is configured such that the second norm increases as the turning speed or the turning amount calculated based on a detection signal of the steering amount detection unit increases. The correction amount is determined so as to increase the yaw rate.

According to the first aspect of the present invention, the second reference yaw rate is calculated by correcting the first reference yaw rate calculated based on the lateral acceleration and the vehicle speed in the increasing direction, and the yaw rate between the second reference yaw rate and the actual yaw rate is calculated. Since the yaw moment can be generated by controlling the braking force in the direction to cancel the deviation, the turning ability is improved even during normal turning, and the steering response is improved.
In addition, since the correction amount is determined so that the second reference yaw rate decreases as the vehicle speed increases, it is possible to prevent the stability of the vehicle behavior from deteriorating in the high speed range.
Further, when the detection signal of the required torque detection means is smaller than a predetermined value, the correction amount is determined so that the second standard yaw rate increases as the vehicle speed decreases. improves.

According to the invention of claim 2, the responsiveness of the steering when such avoidance operation or lane change from the previous lateral obstacle can be improved.

It is a control block diagram in the Example of the turning control apparatus of the vehicle which concerns on this invention. It is a block diagram of the correction | amendment part in an Example. It is a figure explaining the relationship between a lateral G standard yaw rate, a rudder angle standard yaw rate, and a limit standard yaw rate. It is a figure explaining the calculation method of distribution coefficient HB1. It is a figure explaining the calculation method of correction coefficient HS1. It is a flowchart which shows the correction coefficient HS2 determination process. It is a figure explaining the calculation method of correction coefficient HS3. It is a block diagram of braking force control amount calculation in an Example.

Embodiments of a vehicle turning control device according to the present invention will be described below with reference to the drawings of FIGS.
FIG. 1 is a control block diagram of the vehicle turning control device according to the embodiment.
The vehicle turning control device 1 includes a brake control unit 2 and a brake device 10.
The brake control unit 2 determines the braking force control amount for the front, rear, left and right wheels according to the traveling state of the vehicle. The brake device 10 determines each wheel based on the braking force control amount for each wheel determined by the brake control unit 2. To control the braking force.

  The brake control unit 2 includes a steering angle sensor 3 that detects the steering angle (steering amount) of the steering wheel of the vehicle, a vehicle speed sensor 4 that detects the vehicle speed, acceleration in the left-right direction (vehicle width direction) of the vehicle, that is, lateral acceleration (hereinafter referred to as a lateral acceleration). , A lateral acceleration sensor (hereinafter abbreviated as lateral G sensor) 5, a yaw rate sensor 6 that detects the yaw rate of the vehicle, and an accelerator opening sensor 7 that detects the accelerator opening of the vehicle. A detection signal corresponding to the value is input, and an electric signal corresponding to the calculated friction coefficient is input from the μ calculation unit 8 that calculates the friction coefficient between the vehicle wheel and the road surface.

  The brake control unit 2 includes a steering angle reference yaw rate calculation unit 11, a steady reference yaw rate calculation unit 12, a steady yaw rate deviation calculation unit 13, a lateral G reference yaw rate calculation unit 14, a correction unit 15, a limit yaw rate deviation calculation unit 16, and a control amount calculation. The control amount calculation unit 17 includes a feedforward control amount calculation unit (hereinafter abbreviated as FF control amount calculation unit) 18 and a feedback control amount calculation unit (hereinafter abbreviated as FB control amount calculation unit). 19).

The steering angle standard yaw rate calculation unit 11 calculates the steering angle standard yaw rate based on the steering angle detected by the steering angle sensor 3 and the vehicle speed detected by the vehicle speed sensor 4. Since the steering angle is increased when the driver wants to actively bend the vehicle, the steering angle standard yaw rate is increased. That is, when the rudder angle standard yaw rate calculated based on the rudder angle is large, it can be estimated that the driver's steering intention to bend the vehicle is large.
The steady state reference yaw rate calculation unit 12 calculates a steady state reference yaw rate gain Kv corresponding to the vehicle speed with reference to the steady state reference yaw rate gain table 21, and calculates the steady state reference yaw rate ω_high by multiplying the steering angle reference yaw rate by the steady state reference yaw rate gain Kv. To do. The steady state reference yaw rate gain table 21 in this embodiment has a vehicle speed on the horizontal axis and a steady state reference yaw rate gain Kv on the vertical axis. The steady state reference yaw rate gain Kv converges to 1 as the vehicle speed increases, and the steady state reference yaw rate decreases as the vehicle speed decreases. The gain Kv is set to be large. In this embodiment, the steady-state normative yaw rate ω_high constitutes a correction reference value, and the steady-state normative yaw rate ω_high has a higher gain as the vehicle speed is lower.
The steady yaw rate deviation calculation unit 13 subtracts the steering angle standard yaw rate from the steady standard yaw rate ω_high to calculate a steady yaw rate deviation Δωff.

The lateral G standard yaw rate calculation unit 14 calculates the lateral G standard yaw rate ω_low based on the lateral G detected by the lateral G sensor 5 and the vehicle speed detected by the vehicle speed sensor 4. The lateral G standard yaw rate ω_low is a yaw rate that can be generated at the current lateral G, and is represented by ω_low = Gy / V, for example. Here, Gy is a lateral acceleration detection value detected by the lateral G sensor 5, and V is a vehicle body speed detected by the vehicle speed sensor 4.
The correction unit 15 calculates the limit reference yaw rate ω_TAR based on the steady reference yaw rate ω_high and the lateral G reference yaw rate ω_low. A method for calculating the limit reference yaw rate ω_TAR in the correction unit 15 will be described in detail later.
The limit yaw rate deviation calculator 16 subtracts the yaw rate (actual yaw rate) detected by the yaw rate sensor 6 from the limit reference yaw rate ω_TAR to calculate the limit yaw rate deviation Δωfb.

  The control amount calculation unit 17 calculates a feedforward control amount (hereinafter abbreviated as FF control amount) based on the steady yaw rate deviation Δωff in the FF control amount calculation unit 18, and sets the limit yaw rate deviation Δωfb in the FB control amount calculation unit 19. Based on this, a feedback control amount (abbreviated as FB control amount) is calculated, a total control amount is calculated by adding the FF control amount and the FB control amount, and is output to the brake device 10 as a command value. A method of calculating the total control amount in the control amount calculation unit 17 will be described in detail later.

Next, a method for calculating the limit reference yaw rate ω_TAR in the correction unit 15 will be described with reference to FIGS. 2 to 7.
As shown in FIG. 2, the correction unit 15 includes a distribution coefficient HB1 calculation unit 31, a reference limit standard yaw rate calculation unit 32, a correction coefficient HS1 calculation unit 33, a correction coefficient HS2 calculation unit 34, and a correction coefficient HS3 calculation unit 35. Yes.
In the correction unit 15, the reference limit standard yaw rate calculation unit 32 calculates the reference limit standard yaw rate ω_t1 based on the distribution coefficient HB1 calculated by the distribution coefficient HB1 calculation unit 31, the steady standard yaw rate ω_high, and the lateral G standard yaw rate ω_low. . Further, the reference limit normative yaw rate ω_t1 is multiplied by the correction coefficients HS1 and HS2 calculated by the correction coefficient HS1 calculation unit 33 and the correction coefficient HS2 calculation unit 34, and the correction coefficient HS3 calculated by the correction coefficient HS3 calculation unit 35 is added. Thus, the limit reference yaw rate ω_TAR is calculated.
ω_TAR = ω_t1 × HS1 × HS2 + HS3 Formula (1)
This limit normative yaw rate ω_TAR is a yaw rate target value in feedback control.

  More specifically, the reference limit normative yaw rate calculating unit 32 relates the lateral G normative yaw rate ω_low, which is the target value in the feedback control in the conventional steering assist brake control, to the steady normative yaw rate ω_high calculated based on the steering angle. The reference limit normative yaw rate ω_t1 is calculated by correcting in the increasing direction. As a result, both the control for stabilizing the yaw moment generated in the vehicle body and the control for improving the response of steering are achieved.

  Here, the increase correction of the lateral G standard yaw rate will be described with reference to FIG. FIG. 3 shows temporal changes in the rudder angle standard yaw rate and the lateral G standard yaw rate until the steering wheel is rotated from the straight traveling state and held at a predetermined steering angle. Thus, the rudder angle standard yaw rate is usually larger than the lateral G standard yaw rate. Therefore, as a method for correcting the lateral G standard yaw rate to be increased, the lateral G standard yaw rate is corrected so as to be close to the rudder angle standard yaw rate. The concept of the distribution coefficient between the reference yaw rate and the rudder angle reference yaw rate was adopted.

In this embodiment, as a method of further developing this and increasing the lateral G standard yaw rate, correction is made so as to approach the steady standard yaw rate ω_high calculated based on the rudder angle standard yaw rate.
More specifically, in this embodiment, based on the distribution coefficient HB1 calculated by the distribution coefficient HB1 calculation unit 31, the lateral G standard yaw rate ω_low, and the steady standard yaw rate ω_high, the reference limit standard yaw rate ω_t1 is calculated from the equation (2). calculate.
ω_t1 = HB1 × ω_high + (1−HB1) × ω_low (2)
Here, the distribution coefficient HB1 is a numerical value from 0 to 1. When HB1 = 0, the reference limit standard yaw rate ω_t1 becomes the lateral G standard yaw rate ω_low, and when HB1 = 1, the reference limit standard yaw rate ω_t1 is a steady standard. Yaw rate ω_high.

Next, the distribution coefficient HB1 calculated by the distribution coefficient HB1 calculation unit 31 will be described with reference to FIG.
The distribution coefficient HB1 depends on the distribution coefficient HB1a calculated according to the vehicle speed, the distribution coefficient HB1b calculated according to the yaw rate change rate, the distribution coefficient HB1c calculated according to the yaw rate deviation integration, and the steering speed. It is calculated by multiplying the distribution coefficient HB1d calculated in the above.
HB1 = HB1a × HB1b × HB1c × HB1d (3)
Each distribution coefficient HB1a, HB1b, HB1c, and HB1d is calculated with reference to the distribution coefficient tables 40, 41, 42, and 43 shown in FIG. The distribution coefficient tables 40, 41, 42, and 43 in this embodiment will be described.

  In the distribution coefficient table 40 for calculating the distribution coefficient HB1a, the horizontal axis is the vehicle speed, and the vertical axis is the distribution coefficient HB1a. The distribution coefficient table 40 is constant at HB1a = 1 in the low vehicle speed range, and gradually decreases as the vehicle speed increases when the vehicle speed exceeds a predetermined value, and constant at HB1a = 0 in the high speed range. It becomes. As a result, when the vehicle speed is low, the limit reference yaw rate ω_TAR that is a target value in the FB control amount calculation unit 19 is increased to improve the turning performance and followability. When the vehicle speed is high, the FB control amount calculation unit 19 sets the target The stability of the vehicle behavior can be ensured by not increasing the limit reference yaw rate ω_TAR as a value.

  In the distribution coefficient table 41 for calculating the distribution coefficient HB1b, the horizontal axis is the yaw rate change rate, and the vertical axis is the distribution coefficient HB1b. This distribution coefficient table 41 is constant at HB1b = 1 in a region where the yaw rate change rate is small, and when the yaw rate change rate exceeds a predetermined value, the distribution coefficient HB1b gradually decreases as the yaw rate change rate increases. In the region where the rate of change is large, HB1b = 0 is constant. Here, the yaw rate change rate is a temporal change in the actual yaw rate detected by the yaw rate sensor 6 and can be calculated by differentiating the actual yaw rate with time. For example, a large yaw rate change rate appears when the vehicle is strenuously sluggish or when the vehicle behavior is unstable. In such a case, the limit reference yaw rate ω_TAR that is the target value in the FB control amount calculation unit 19 should not be increased. Therefore, when the yaw rate change rate is large, the distribution coefficient HB1b is set to a small value and the limit reference yaw rate ω_TAR is not increased. Like that.

  In the distribution coefficient table 42 for calculating the distribution coefficient HB1c, the horizontal axis is the yaw rate deviation integrated value, and the vertical axis is the distribution coefficient HB1c. In the distribution coefficient table 42, HB1c = 1 is constant in a region where the yaw rate deviation integrated value is small, and when the yaw rate deviation integrated value exceeds a predetermined value, the distribution coefficient HB1c gradually decreases as the yaw rate deviation integrated value increases. In a region where the yaw rate deviation integrated value is large, HB1c = 0 and becomes constant. Here, the yaw rate deviation integrated value is a value obtained by integrating the deviation between the limit reference yaw rate and the actual yaw rate detected by the yaw rate sensor 6, that is, the limit yaw rate deviation Δωfb from the start of steering. For example, even if the limit yaw rate deviation Δωfb is small, if the state continues for a long time, the yaw rate deviation integrated value becomes large. In such a case, although there is a possibility that the vehicle is slowly in a spin state, the limit reference yaw rate ω_TAR that is the target value in the FB control amount calculation unit 19 should not be increased. Therefore, when the yaw rate deviation integrated value is large, the distribution coefficient HB1c is set to a small value so that the limit reference yaw rate ω_TAR is not increased.

In the distribution coefficient table 43 for calculating the distribution coefficient HB1d, the horizontal axis is the steering speed, and the vertical axis is the distribution coefficient HB1d.
The distribution coefficient table 43 is set so that the distribution coefficient HB1d increases as the turning speed increases, and the distribution coefficient HB1d increases when the turning speed is positive than when the turning speed is negative. ing. Here, the steering speed is a value determined based on the time change amount of the steering angle detected by the steering angle sensor 3 and the steering angle, and is calculated by differentiating the steering angle with time and comparing it with the steering angle. Can do. When the steering speed is positive, when the steering wheel is rotated in a direction away from the neutral position (straight direction position), a time change amount in the same direction is generated, and the steering wheel is neutral. When the amount of time change in the same direction has occurred while rotating to the position (straight-running position), and when the turning speed is negative, the steering wheel is in the neutral position (straight-running position) When the time change amount is generated in the direction toward the neutral position while rotating in the direction away from the neutral position, and in the direction away from the neutral position while rotating in the direction to return the steering wheel to the neutral position. This is when there is a time change amount.

When the turning speed is positive, it can be estimated that the driver's willingness to bend the vehicle greatly is large. Therefore, the distribution coefficient HB1d is increased as the turning speed increases (the maximum value is HB1d = 1), the limit reference yaw rate ω_TAR is increased. Thereby, the response of steering is improved. On the other hand, when the turning speed is negative, it can be estimated that the driver wants to converge the operation. Therefore, the distribution coefficient HB1d is decreased as the absolute value of the turning speed increases (the minimum value is HB1d). = 0), and the limit reference yaw rate ω_TAR is not increased.
As a result, the steering responsiveness during an avoidance operation from a front obstacle or a lane change is improved.
The distribution coefficient HB1d may be calculated based on the turning angle (steering amount) instead of the turning speed. This is because it can be estimated that the greater the turning angle, the greater the willingness of the driver to actively bend the vehicle. In this case, the turning angle is synonymous with the steering angle.

Next, the correction coefficient HS1 calculated by the correction coefficient HS1 calculation unit 33 will be described with reference to FIG.
The correction coefficient HS1 is a correction coefficient that is assumed when the driver performs an operation of bending the vehicle by turning the steering wheel with the vehicle as a preload.
As shown in FIG. 5, the correction coefficient HS1 is calculated by multiplying the correction coefficient HS1a calculated according to the steering speed and the correction coefficient HS1b calculated according to the vehicle front load.
HS1 = HS1a × HS1b (4)
The vehicle front load is a load moving amount forward of the vehicle, and can be estimated based on, for example, a longitudinal acceleration sensor (not shown) that detects acceleration in the longitudinal direction of the vehicle. In this case, the longitudinal acceleration sensor can be said to be load movement amount estimation means for estimating the load movement amount in the front-rear direction.

The correction coefficients HS1a and HS1b are calculated with reference to the correction coefficient tables 44 and 45 shown in FIG. The correction coefficient tables 44 and 45 in this embodiment will be described.
In the correction coefficient table 44 for calculating the correction coefficient HS1a, the horizontal axis is the steering speed, and the vertical axis is the correction coefficient HS1a. The correction coefficient HS1a table 44 is constant at HS1a = 1 in a region where the steering speed is low, and when the steering speed exceeds a predetermined value, the correction coefficient HS1a gradually decreases as the steering speed increases. In a large region, HS1a = 0 is constant.
In the correction coefficient table 45 for calculating the correction coefficient HS1b, the horizontal axis represents the front load (the amount of load movement forward of the vehicle), and the vertical axis represents the correction coefficient HS1b. This correction coefficient HS1b table 45 is constant at HS1b = 1 in a region where the preload is small. When the preload exceeds a predetermined value, the correction coefficient HS1b gradually decreases as the preload increases. In a large region, HS1b = 0 is constant.

As described above, if the vehicle is preloaded and the steering wheel is turned, it becomes easier to bend the vehicle, but the vehicle behavior tends to become unstable as the front load increases, and the vehicle behavior becomes unstable as the steering speed increases. Easy to be. The correction coefficient HS1 is a correction coefficient for adjusting the limit reference yaw rate ω_TAR during such steering.
As a result of calculating the correction coefficient HS1 as described above, since the correction coefficient HS1 is 1 in a region where the steering speed is low and the preload is low, the limit reference yaw rate ω_TAR can be increased, and the turning performance is improved. be able to. On the other hand, since the correction coefficient HS1 becomes smaller than 1 as the steering speed and the preload increase, the limit reference yaw rate ω_TAR can be reduced, and the stability of the vehicle behavior can be ensured. .

Next, the correction coefficient HS2 calculated by the correction coefficient HS2 calculation unit 34 will be described.
This correction coefficient HS2 is a lane change on a road surface (hereinafter abbreviated as a high μ road) having a high coefficient of friction between the wheel and the road surface (hereinafter abbreviated as a μ) (operation for steering and immediately returning to the original traveling direction). It is a correction coefficient that assumes the case of performing.
The correction coefficient HS2 has a maximum value of 1 and subtracts a predetermined decrease count value from the initial value when the following condition is satisfied, and a predetermined increase count value toward 1 when neither of the following conditions is satisfied: Is a gain configured to add As conditions, (a) when it is determined that the friction coefficient μ is high (or when longitudinal or lateral acceleration corresponding to road running with a high friction coefficient is detected), (b) when the steering angle is large. When it is determined, (c) when it is determined that the lateral G decrease rate is large, (d) when it is determined that the yaw rate decrease rate is large, a predetermined decrease count value is subtracted. In addition, the said conditions should just be what combined at least 1 or multiple arbitrarily among (a) to (d). In particular, considering the vehicle behavior convergence at the time of a high friction coefficient, it is preferable to use a combination of (a) and (b) to (d).
The friction coefficient μ is calculated by the μ calculator 8. The lateral G reduction rate is the lateral G reduction rate and can be calculated based on the lateral G detected by the lateral G sensor 5. The yaw rate reduction rate is an actual value detected by the yaw rate sensor 6. This is the rate of decrease of the yaw rate.

An example of processing for determining the correction coefficient HS2 will be described with reference to the flowchart of FIG.
First, in step S01, it is determined whether or not the friction coefficient μ is larger than the threshold value μth.
If the determination result in step S01 is “YES” (μ> μth), the process proceeds to step S02, where the steering angle δ is larger than the threshold value δth (δ> δth), or the lateral G decrease rate ΔG is the threshold value. It is determined whether it is greater than ΔGth (ΔG> ΔGth), or whether the yaw rate reduction rate γ is greater than the threshold value γth (γ> γth), which satisfies at least one of them.
When the determination result in step S02 is “YES”, the process proceeds to step S03, the correction coefficient HS2 is determined by the subtraction process, and the execution of this routine is temporarily ended. In this subtraction process, a predetermined subtraction count value is subtracted from the initial value of the correction coefficient HS2, so that the correction coefficient HS2 converges to zero.
On the other hand, if the determination result in step S01 is “NO” (μ ≦ μth) and if the determination result in step S02 is “NO”, the process proceeds to step S04, and the correction coefficient HS2 is determined by the addition process. Then, the execution of this routine is temporarily terminated. In this addition process, a predetermined increase count value is added so that the correction coefficient HS2 converges to 1.
The initial value of the correction coefficient HS2 is a predetermined value between 0 and 1.

  When the lane change is performed on a high μ road, if the yaw rate and the lateral G rapidly decrease, a large yaw rate may be generated in a direction opposite to the direction desired to travel by steering. At this time, if the limit reference yaw rate ω_TAR is increased, the traceability of the vehicle with respect to steering may be deteriorated. The correction coefficient HS2 is for suppressing this. That is, when the friction coefficient μ, the steering angle, the lateral G reduction rate, and the yaw rate reduction rate are large, the limit reference yaw rate ω_TAR is not increased by setting the correction coefficient HS2 to a small value. Improve yaw rate convergence.

Next, the correction coefficient HS3 calculated by the correction coefficient HS3 calculation unit 35 will be described with reference to FIG.
This correction coefficient HS3 is a correction coefficient that assumes when the driver has tacked in. Tuck-in is a phenomenon in which the vehicle enters the inside of the turn as a preload when the accelerator pedal is suddenly returned during turning, but depending on the driver, there are cases where the turning operation is actively performed using this. . However, in the turning operation using this tuck-in, the vehicle behavior becomes unstable when the accelerator is released from when the required torque to the vehicle is large (in other words, when the accelerator opening is large) or when the vehicle speed is high. easy. The correction coefficient HS3 is a correction coefficient for adjusting the limit reference yaw rate ω_TAR at the time of tuck-in.
As shown in FIG. 7, the correction coefficient HS3 is calculated by multiplying the correction coefficient HS3a calculated according to the vehicle speed and the correction coefficient HS3b calculated according to the required torque of the vehicle.
HS3 = HS3a × HS3b (6)
The required torque of the vehicle can be calculated from the accelerator opening detected by the accelerator opening sensor 7.

The correction coefficients HS3a and HS3b are calculated with reference to the correction coefficient tables 51 and 52 shown in FIG. The correction coefficient tables 51 and 52 in this embodiment will be described.
In the correction coefficient table 51 for calculating the correction coefficient HS3a, the horizontal axis represents the vehicle speed, and the vertical axis represents the correction coefficient HS3a. The correction coefficient HS3a table 51 indicates that HS3a is a positive constant value in a region where the vehicle speed is lower than a predetermined value, and the correction coefficient HS3a gradually decreases as the vehicle speed increases when the vehicle speed exceeds the predetermined value. When the vehicle speed exceeds a predetermined speed V0, a negative value is obtained. In a region where the vehicle speed is very high, HS3a is a negative constant value.

  In the correction coefficient table 52 for calculating the correction coefficient HS3b, the horizontal axis represents the required torque of the vehicle, and the vertical axis represents the correction coefficient HS3b. In the correction coefficient HS3b table 52, HS3b is a positive value in a region where the required torque is smaller than the predetermined value T0, and a correction coefficient HS3b = 0 in a region where the required torque is equal to or greater than the predetermined value T0. Here, the predetermined value T0 is an extremely small value, for example, set to a required torque corresponding to when the accelerator opening is close to zero.

By setting the correction coefficient tables 51 and 52 as described above, when the required torque is equal to or greater than the predetermined value T0 (that is, when it is determined that the vehicle is not in the tack-in state), the correction coefficient HS3 is used regardless of the vehicle speed. Becomes 0, and the limit reference yaw rate ω_TAR can be prevented from being corrected.
Further, when the required torque is equal to or less than the predetermined value T0 (that is, when it is determined that the vehicle is in the tuck-in state), when the vehicle speed is lower than V0, the correction coefficient HS3 becomes a positive value, and therefore the limit reference yaw rate ω_TAR When the vehicle speed is V0 or higher, the correction coefficient HS3 becomes a negative value, so that the limit reference yaw rate ω_TAR can be reduced. Further, when the vehicle speed is lower than V0 and the required torque is the same, the limit reference yaw rate ω_TAR can be increased by setting the correction coefficient H3 to a larger positive value as the vehicle speed decreases. Thereby, the turnability at the time of tuck-in when the vehicle speed is low and medium can be improved. On the other hand, when the vehicle speed is V0 or higher and the required torque is the same, the limit reference yaw rate ω_TAR can be reduced by setting the correction coefficient H3 to a larger negative value as the vehicle speed increases.

Next, the brake control amount calculation executed in the control amount calculation unit 17 will be described with reference to FIG.
As described above, the control amount calculation unit 17 calculates the FF control amount based on the steady yaw rate deviation Δωff in the FF control amount calculation unit 18, and the FB control amount based on the limit yaw rate deviation Δωfb in the FB control amount calculation unit 19. And the total control amount for each wheel is calculated by adding the FF control amount and the FB control amount.

First, calculation of the FF control amount in the FF control amount calculation unit 18 will be described.
First, based on the steering angle detected by the steering angle sensor 3, the pressure increase distribution is applied to the turning inner wheel on the front wheel side (hereinafter abbreviated as FR turning inner wheel) and the turning inner wheel on the rear wheel side (hereinafter abbreviated as RR turning inner wheel). And a pressure increase coefficient K1fr for the FR turning inner wheel and a pressure increase coefficient K1rr for the RR turning inner wheel are calculated based on the pressure increase distribution. Here, when the load movement due to steering is large, the pressure increase coefficient K1fr for the FR turning inner wheel may be set to be large according to the steering angle.
Based on the pressure increase coefficient K1fr for the FR turning inner wheel and the pressure increase coefficient K1rr for the RR turning inner wheel, calculation of the FF pressure increase amount ΔP1ff for the FR turning inner wheel and calculation of the FF pressure increase amount ΔP2ff for the RR turning inner wheel are performed in parallel. Implemented.

First, calculation of the FF pressure increase amount ΔP1ff for the FR turning inner wheel will be described. By multiplying the pressure increase coefficient K1fr steady yaw rate deviation Δωff calculated in steady-state yaw rate deviation calculation unit 13 calculates the steady-state yaw rate deviation Δω1ff for FR turning inner.

  Next, referring to the pressure increase amount table 60, the brake fluid pressure increase amount ΔP1ffk of the FR turning inner wheel is calculated according to the steady yaw rate deviation Δω1ff with respect to the FR turning inner wheel. In the pressure increase amount table 60, the horizontal axis is the steady yaw rate deviation Δω1ff, and the vertical axis is the brake fluid pressure increase amount ΔP1ffk. In this embodiment, when the steady yaw rate deviation Δω1ff for the FR turning inner wheel is 0 or less, the brake fluid pressure increase amount ΔP1ffk is 0. When the steady yaw rate deviation Δω1ff for the FR turning inner wheel is 0 or more, the steady yaw rate deviation Δω1ff is large. As the pressure increases, the brake fluid pressure increase amount ΔP1ffk increases.

  Next, the limit processing unit 61 performs limit processing so that the brake fluid pressure increase amount ΔP1ffk of the FR turning inner wheel does not exceed the upper limit value. The upper limit value is an arbitrary value calculated by the upper limit value calculation unit 62, and by setting the upper limit value so as not to exceed this value, the sudden increase in the hydraulic pressure increase amount ΔPlffk is suppressed.

  Next, the brake fluid pressure increase amount ΔP1ffk of the FR turning inner wheel subjected to the limit processing is multiplied by a gain corresponding to the vehicle speed to calculate the FF pressure increase amount ΔP1ff for the FR turning inner wheel. The gain corresponding to the vehicle speed is calculated based on the gain table 63. In this gain table 63, the horizontal axis is the vehicle speed, the vertical axis is the gain, the gain = 1 is constant in the region where the vehicle speed is low, and the gain gradually increases as the vehicle speed increases when the vehicle speed exceeds a predetermined value. In a region where the vehicle speed is increasing and the vehicle speed is high, the gain is constant at zero.

  As a result of multiplying the gain according to the vehicle speed as described above, the FF pressure increase amount ΔP1ff of the FR turning inner wheel becomes 0 when the vehicle speed is high. In other words, the FF pressure increase amount ΔP1ff of the FR turning inner wheel is invalidated at a high vehicle speed. Thereby, it is possible to prevent the vehicle behavior from becoming unstable due to the steering assist brake at a high vehicle speed. In this embodiment, the gain table 63 constitutes invalidating means. Instead of multiplying the gain according to the vehicle speed, a limit value that decreases as the vehicle speed increases may be given, and this limit value may be set so that ΔPlff does not exceed.

Since the calculation of the FF pressure increase amount ΔP2ff for the RR turning inner wheel is the same as the calculation of the FF pressure increase amount ΔPfr1 for the FR turning inner wheel, it will be briefly described.
Steady yaw rate deviation Δωff calculated in steady-state yaw rate deviation calculation unit 13, by multiplying the pressure increase coefficient K1rr for RR turning inner calculates the steady-state yaw rate deviation Δω2ff for RR turning inner.
Next, referring to the pressure increase amount table 64, the brake fluid pressure increase amount ΔP2ffk of the RR turning inner wheel is calculated according to the steady yaw rate deviation Δω2ff with respect to the RR turning inner wheel. Since the pressure increase amount table 64 is the same as the pressure increase amount table 60, description thereof is omitted.
Next, the limit processing unit 65 performs limit processing so that the brake fluid pressure increase amount ΔP2ffk of the RR turning inner wheel does not exceed the upper limit value. The upper limit value is calculated by the upper limit value calculation unit 66. The upper limit calculator 66 is the same as the upper limit calculator 62.
Next, the brake fluid pressure increase amount ΔP2ffk of the RR turning inner wheel subjected to the limit process is multiplied by the gain calculated by the gain table 67 to calculate the FF pressure increase amount ΔP2ff for the RR turning inner wheel. Since the gain table 67 is the same as the gain table 63, description thereof is omitted. In this embodiment, the gain table 67 constitutes invalidation means.

In addition, the FF control amount calculation unit 18 includes an inner ring pressure reduction amount calculation unit 70. The inner wheel pressure reduction amount calculation unit 70 is for restricting the brake fluid pressure of the turning inner wheel in advance on the premise that the vehicle behavior becomes unstable due to braking at high speed or high lateral G.
The inner ring pressure reduction amount calculation unit 70 calculates the pressure reduction rate according to the vehicle speed with reference to the first pressure reduction rate table 71, calculates the pressure reduction rate according to the lateral G with reference to the second pressure reduction rate table 72, The total decompression rate is calculated by multiplying these decompression rates.

  In the first decompression rate table 71, the horizontal axis is the vehicle speed, the vertical axis is the decompression rate, the decompression rate = 0 is constant in the region where the vehicle speed is low, and the vehicle speed increases as the vehicle speed exceeds a predetermined value. The decompression rate gradually increases, and the decompression rate = 1 is constant in the region where the vehicle speed is high.

In the second decompression rate table 72, the horizontal axis is the lateral G, the vertical axis is the decompression rate, and in a region where the lateral G is small, the decompression rate = 0 is constant, and when the lateral G becomes a predetermined value or more, the lateral G As the pressure increases, the pressure reduction rate gradually increases, and in a region where the lateral G is large, the pressure reduction rate = 1 is constant.
As a result, the total decompression rate is set to a value between 0 and 1 according to the vehicle speed and the lateral G when traveling.
Then, the total pressure reduction rate obtained in this way is multiplied by the master cylinder pressure of the brake device 10 and further multiplied by minus 1 to obtain the inner ring pressure reduction amount ΔPd.

Next, calculation of the FB control amount in the FB control amount calculation unit 19 will be described.
In the FB control amount calculation unit 19, based on the limit yaw rate deviation Δωfb calculated by the limit yaw rate deviation calculation unit 16, the FB pressure increase amount ΔP1fb of the FR turning inner wheel, the turning outer wheel on the front wheel side (hereinafter abbreviated as FR turning outer wheel). FB pressure increase amount ΔP3fb of the RR turning inner wheel, FB pressure increase amount ΔP2fb of the RR turning inner wheel, and FB pressure increase amount ΔP4fb of the rear wheel side turning outer wheel (hereinafter abbreviated as RR turning outer wheel) are calculated. In the following turning direction, an example will be described in which the sign of the deviation Δωfb is positive and both the standard yaw rate and the actual yaw rate are positive.

  The FB pressure increase amount ΔP1fb of the FR turning inner wheel is calculated with reference to the pressure increase amount table 80 based on the limit yaw rate deviation Δωfb. In the pressure increase amount table 80, the horizontal axis is the limit yaw rate deviation Δωfb, and the vertical axis is the FB pressure increase amount ΔP1fb. In this embodiment, when the limit yaw rate deviation Δωfb is 0 or less, the FB pressure increase amount ΔP1fb is 0. When the limit yaw rate deviation Δωfb is 0 or more, the FB pressure increase amount ΔP1fb increases as the limit yaw rate deviation Δωfb increases. I will do it.

  The FB pressure increase amount ΔP2fb of the RR turning inner wheel is calculated with reference to the pressure increase amount table 81 based on the limit yaw rate deviation Δωfb. In the pressure increase amount table 81, the horizontal axis is the limit yaw rate deviation Δωfb, and the vertical axis is the FB pressure increase amount ΔP2fb. In this embodiment, when the limit yaw rate deviation Δωfb is 0 or less, the FB pressure increase amount ΔP2fb is 0. When the limit yaw rate deviation Δωfb is 0 or more, the FB pressure increase amount ΔP2fb increases as the limit yaw rate deviation Δωfb increases. I will do it.

  The FB pressure increase amount ΔP3fb of the FR turning outer wheel is calculated with reference to the pressure increase amount table 82 based on the limit yaw rate deviation Δωfb. In the pressure increase amount table 82, the horizontal axis is the limit yaw rate deviation Δωfb, and the vertical axis is the FB pressure increase amount ΔP3fb. In this embodiment, when the limit yaw rate deviation Δωfb is 0 or more, the FB pressure increase amount ΔP3fb is 0. When the limit yaw rate deviation Δωfb is 0 or less, the FB pressure increase amount increases as the absolute value of the limit yaw rate deviation Δωfb increases. ΔP3fb increases.

  The FB pressure increase amount ΔP4fb of the RR turning outer wheel is calculated with reference to the pressure increase amount table 83 based on the limit yaw rate deviation Δωfb. In the pressure increase amount table 83, the horizontal axis is the limit yaw rate deviation Δωfb, and the vertical axis is the FB pressure increase amount ΔP4fb. In this embodiment, when the limit yaw rate deviation Δωfb is 0 or more, the FB pressure increase amount ΔP4fb is 0. When the limit yaw rate deviation Δωfb is 0 or less, the FB pressure increase amount increases as the absolute value of the limit yaw rate deviation Δωfb increases. ΔP4fb increases.

  That is, in the FB control amount calculation unit 19, when the limit yaw rate deviation Δωfb is 0 or more, the actual yaw rate is smaller than the limit reference yaw rate, so the yaw rate is increased (in other words, the limit yaw rate deviation Δωfb is canceled). Next, the FB control amount for each wheel is set. Specifically, the FB pressure increase amount is set in a direction to increase the brake fluid pressure of the FR turning inner wheel and the RR turning inner wheel, and the FB pressure increasing amount is set so as not to increase the brake fluid pressure of the FR turning outer wheel and the RR turning outer wheel. Set.

  On the other hand, when the limit yaw rate deviation Δωfb is 0 or less, the actual yaw rate is larger than the limit reference yaw rate, so that the FB control amount of each wheel in the direction of decreasing the yaw rate (in other words, the direction of canceling the limit yaw rate deviation Δωfb). Set. Specifically, the FB pressure increase amount is set in a direction to increase the brake fluid pressure of the FR turning outer wheel and the RR turning outer wheel, and the FB pressure increasing amount is set so as not to increase the brake fluid pressure of the FR turning inner wheel and the RR turning inner wheel. Set.

Then, the control amount calculation unit 17 sets a value obtained by adding the FF pressure increase amount ΔP1ff of the FR turning inner wheel, the FB pressure increase amount ΔP1fb of the FR turning inner wheel, and the inner wheel pressure reduction amount ΔPd as a total control amount for the FR turning inner wheel, and sets the RR turning inner wheel. The total control amount for the RR turning inner wheel is obtained by adding the FF pressure increase amount ΔP2ff to the RR turning inner wheel FB pressure increase amount ΔP2fb and the inner wheel pressure reduction amount ΔPd, and the FB pressure increase amount ΔP3fb of the FR turning outer wheel is the total amount of the FR turning outer wheel. As the control amount, the FB pressure increase amount ΔP4fb of the RR turning outer wheel is output to the brake device 10 as the total control amount of the RR turning outer wheel.
The brake device 10 controls the brake pressure of each wheel according to the input control amount of each wheel.

According to the vehicle turning control device of this embodiment, the correction unit 15 corrects the lateral G reference yaw rate ω_low in the increasing direction in relation to the steady reference yaw rate ω_high calculated based on the steering angle, and the limit reference Since the yaw rate ω_TAR is calculated, it is possible to achieve both control for stabilizing the yaw moment generated in the vehicle body and control for improving the steering response. As a result, the turning intention of the driver is reflected with good response, and the steering feel is improved.
Further, since the lateral G standard yaw rate ω_low is corrected to the limit standard yaw rate ω_TAR, the target value in the FB control amount calculation unit 19 can be increased, and the turnability is improved. As a result, the vehicle can be turned along the traveling road, and the road surface following performance (trace performance) is improved.

  Further, according to the vehicle turning control device of this embodiment, the brake pressure is controlled based on the total control amount obtained by adding the FF control amount calculated based on the steering input to the FB control amount calculated based on the vehicle body behavior. Therefore, it is possible to improve the steering response while securing the stability of the vehicle behavior. In addition, the followability of steering is improved. For example, in the process of steering holding after steering input, such as during steady circle turning, fluctuations in the control amount are suppressed and followability is improved.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, in the embodiment described above, the total control amount is calculated by adding the FF control amount and the FB control amount, but it is also possible to calculate the total control amount by multiplying the FF control amount and the FB control amount.
Further, an estimated vehicle speed estimated based on the detection value of the wheel speed sensor may be used instead of the detection value of the vehicle speed sensor.

  Further, in the above-described embodiment, the FF control amount calculation unit 18 invalidates the FF pressure increase amount ΔP1ff of the FR turning inner wheel at the high vehicle speed and the FF pressure increase amount ΔP2ff of the RR turning inner wheel, thereby steering assist at the high vehicle speed. Although the vehicle behavior is prevented from becoming unstable due to braking, the FF pressure increase amount of the turning inner wheel may be invalidated even when the steering speed is extremely high or the ABS is operated.

DESCRIPTION OF SYMBOLS 1 Vehicle turning control apparatus 3 Steering angle sensor (steering amount detection means)
4 Vehicle speed sensor (vehicle speed detection means)
5 Lateral G sensor (lateral acceleration detection means)
6 Yaw rate sensor (yaw rate detection means)
7 Accelerator opening sensor (required torque detection means)
10 Brake device (braking control means)
12 Steady state yaw rate calculation unit (correction reference value setting means)
14 Horizontal G standard yaw rate calculation unit (first standard yaw rate calculation unit)
15 Correction unit 18 FF control amount calculation unit (second braking force control amount calculation unit)
19 FB control amount calculation unit (braking force control amount calculation unit)
63, 67 Gain table (invalidation means)

Claims (2)

Steering amount detection means for detecting the steering amount of the vehicle, vehicle speed detection means for detecting or estimating the vehicle speed of the vehicle, lateral acceleration detection means for detecting lateral acceleration of the vehicle, and detection of the yaw rate of the vehicle A vehicle turning control device capable of generating a yaw moment on a vehicle body by applying a braking force to front, rear, left and right wheels based on a running state of the vehicle,
A first normative yaw rate calculating unit that calculates a first normative yaw rate based on detection signals of the lateral acceleration detecting unit and the vehicle speed detecting unit;
A correction reference value setting means for determining a correction reference value that increases as the vehicle speed decreases based on detection signals of the steering amount detection means and the vehicle speed detection means;
A correction unit that calculates the second reference yaw rate by correcting the first reference yaw rate in an increasing direction based on the correction reference value;
A braking force control amount calculation unit that calculates a yaw rate deviation between the second normative yaw rate and the actual yaw rate detected by the yaw rate detection means, and determines a braking force control amount in a direction to cancel the yaw rate deviation;
Braking control means for controlling the braking force based on the braking force control amount determined by the braking force control amount computing unit,
The correction unit determines a correction amount so that the second reference yaw rate decreases as the vehicle speed increases,
A required torque detection means for detecting the magnitude of the required torque based on the accelerator opening or the accelerator pedal operation amount,
The correction unit determines a correction amount so that the second reference yaw rate increases as the vehicle speed decreases when the detection signal of the required torque detection unit is smaller than a predetermined value;
The correction unit determines a correction amount based on a load movement amount in the front-rear direction of the vehicle so that the second reference yaw rate decreases as the forward load movement amount increases .
In the correction unit, the friction coefficient between the wheel and the road surface is larger than the threshold, the steering amount is larger than the threshold, the lateral acceleration reduction rate is larger than the threshold, or the yaw rate reduction rate is larger than the threshold. When it is determined , the vehicle turning control apparatus determines the correction amount so that the second reference yaw rate is smaller than before the determination .   The correction unit determines a correction amount such that the second reference yaw rate increases as the turning speed or the turning amount calculated based on a detection signal of the steering amount detection unit increases. Item 2. A turning control device for a vehicle according to item 1.

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