JP3412395B2 - Vehicle motion control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a braking force to each wheel regardless of whether or not the vehicle is in a braking state caused by the operation of a brake pedal when the vehicle is turning and the like. The present invention relates to a vehicle motion control device that stabilizes a motion state.

[0002]

2. Description of the Related Art As a conventional technique of this type, for example, one disclosed in Japanese Patent Laid-Open No. 4-372446 is known. This is a brake fluid pressure control device that applies a braking force to each wheel of a vehicle at least in accordance with an operation of a brake pedal, a vehicle state amount estimation means that estimates a motion state amount of the vehicle, and a vehicle state amount estimation means. When the vehicle motion state quantity estimated by is greater than a predetermined threshold value, the start determination means determines that control is required, and when the start determination means determines that control is required, the yaw moment of the vehicle is corrected to a stable side. And a motion control means for controlling the brake fluid pressure control device.

Further, this device is further provided with a vehicle speed sensor for detecting the speed of the vehicle, a yaw rate sensor for detecting the turning state of the vehicle, and a lateral acceleration sensor for detecting the lateral acceleration of the vehicle. The vehicle state quantity estimating means calculates the theoretical yaw rate based on the information from the vehicle speed sensor and the lateral acceleration sensor, and calculates the deviation between the actual yaw rate and the theoretical yaw rate based on the information from the yaw rate sensor.

[0004]

However, in this case, since the threshold value of the vehicle motion state quantity for starting the control is constant, the following problems occur.

When the vehicle is traveling on a low μ road, a high μ
It becomes unstable with a smaller vehicle motion state quantity (yaw rate deviation) than when traveling on a road. Therefore, if the threshold value of the vehicle motion state quantity is set to a large value, the responsiveness of the control start becomes poor. On the contrary, when the threshold value is set to a small value, the control may start even when the vehicle is traveling on a high μ road surface, even if it is not necessary to start the control, and the reliability deteriorates.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention is directed to a road surface.
The control start region in the vehicle motion quantity is changed according to μ
The Rukoto, and its technical challenges.

[0007]

In order to solve the above technical problems, a vehicle motion control apparatus according to a first aspect of the present invention applies a braking force to each wheel of the vehicle at least in response to an operation of a brake pedal. A brake fluid pressure control device, a vehicle state quantity estimating means for estimating a movement state quantity of the vehicle at the time of turning, and a vehicle movement state quantity estimated by the vehicle state quantity estimating means exceeds a control start threshold value. A start determination means for determining that control is required, and when the start determination means determines that control is required, the brake fluid pressure control device is controlled to correct the yaw moment of the vehicle to a stable side, and the vehicle is controlled. In a vehicle motion control device including a motion control means for applying a braking force to each wheel, a road surface friction coefficient estimating means for estimating a road surface friction coefficient and the road surface friction coefficient estimating means The difference between the start threshold value setting means for setting the control start threshold value so as to be smaller as the determined road surface friction coefficient is lower, and the control start threshold value as the road surface friction coefficient estimated by the road surface friction coefficient estimating means is higher. End threshold setting means for setting a control end threshold for the vehicle motion state quantity so as to increase the vehicle motion state quantity, and the vehicle motion state quantity estimated by the vehicle state quantity estimating means during the control by the motion control means When the value is below the control end threshold set by the means, the end determination means for determining the control end is required, and the motion control means, when the end determination means determines that the control end is required, the brake fluid. It was decided to end the control of the pressure control device. A vehicle motion control device according to claim 2 of the present invention is a brake fluid pressure control device that applies a braking force to each wheel of the vehicle in accordance with at least an operation of a brake pedal, and a motion state of the vehicle during turning. A vehicle state quantity estimating means for estimating a quantity, a start determining means for determining that control should be started when the vehicle motion state quantity estimated by the vehicle state quantity estimating means exceeds a control start threshold, and the start determining means. When it is determined that control is required, the brake fluid pressure control device is controlled so as to correct the yaw moment of the vehicle to a stable side, and a motion control unit that applies a braking force to each wheel of the vehicle is provided. In a vehicle motion control device, a road surface friction coefficient estimating means for estimating a road surface friction coefficient, and the road surface friction coefficient estimated by the road surface friction coefficient estimating means are set to be smaller as the road surface friction coefficient is lower. A start threshold value setting means for setting a start threshold value, a lateral acceleration sensor for detecting a lateral acceleration of the vehicle, and a steering angle sensor for detecting a steering angle of a wheel are provided, and the road surface friction coefficient estimating means is before starting the control and When the steering angle of the wheel detected by the steering angle sensor is equal to or greater than a predetermined value, the lateral acceleration of the vehicle detected by the lateral acceleration sensor is larger than 1.
A value obtained by multiplying a predetermined constant k is used as the road surface friction coefficient.

Here, the case where the vehicle motion state quantity exceeds the control start threshold value means that the absolute value of the vehicle motion state quantity exceeds the control start threshold value. As the vehicle motion state quantity, a vehicle body side slip angle, a vehicle body side slip angular velocity, etc. can be used. Then, the vehicle motion state quantity is controlled
When the value is below the end threshold, the vehicle motion state quantity is
Mean when the logarithmic value falls below the absolute value of the control end threshold
To do .

According to the first aspect, the control start region in the vehicle motion state is set so that the lower the road surface friction coefficient is, the smaller the road surface friction control coefficient is. Therefore, when the road surface friction coefficient is low, the response of the control start is improved and When the road surface friction coefficient is high, unnecessary control can be prevented from being started.

[0010]

When the road surface friction coefficient is high, the wheel lock pressure is higher than when the road surface friction coefficient is low, so that the braking force applied to the wheels by the motion control is generally large. Therefore, in this case, if the control is terminated early (the control is abruptly terminated), the yaw moment of the vehicle may suddenly change. Where there is, since the road surface friction coefficient is set large the difference between the higher the control start threshold and the control end threshold value, it is possible to delay the termination of the control higher road surface friction coefficient (ends loosely controlled As a result, sudden changes in the yaw moment of the vehicle can be avoided.

[0012]

According to the second aspect of the present invention, the road surface friction coefficient is set to be slightly higher than the lateral acceleration of the vehicle before the start of control and when the steering angle of the wheel detected by the steering angle sensor is equal to or greater than a predetermined value. Therefore, even when the lateral acceleration of the vehicle is increasing without reaching the limit state, it is possible to avoid underestimating the road surface friction coefficient, and as a result, it is possible to avoid unnecessary start of control as much as possible. .

[0014]

[0015]

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment of the motion control device of the present invention. The engine EG of this embodiment is an internal combustion engine equipped with a throttle control device TH and a fuel injection device FI. In the throttle control device TH, The main throttle opening of the main throttle valve MT is controlled according to the operation of the accelerator pedal AP. In addition, the electronic control unit E
The sub-throttle valve ST of the throttle control device TH is driven to control the sub-throttle opening according to the output of the CU, and the fuel injection device FI is driven to control the fuel injection amount. The engine EG of the present embodiment is connected to the wheels DL and DR at the rear of the vehicle via a gear change control device GS and a differential gear DF, and a so-called rear wheel drive system is configured. It is not limited to.

Next, regarding the braking system, the wheels NL, N
Wheel cylinders Wfl, Wf for R, DL, DR respectively
r, Wrl, Wrr are mounted, and a brake fluid pressure control device PC is connected to these wheel cylinders Wfl and the like. In addition, the wheel NL indicates a driven wheel on the front left side when viewed from the driver's seat, the wheel NR indicates a driven wheel on the front right side, and the wheel DL
Indicates the drive side on the rear left side, and the wheel DR indicates the drive wheel on the rear right side. The brake fluid pressure control device PC of this embodiment is configured as shown in FIG. 3, which will be described later.

Wheel speed sensors WS1 to WS4 are provided on the wheels NL, NR, DL, DR, and these are connected to an electronic control unit ECU, and the rotational speed of each wheel, that is, the number of pulses proportional to the wheel speed. Is inputted to the electronic control unit ECU. Further, the brake switch BS that is turned on when the brake pedal BP is depressed, and the steering angle δf of the wheels NL and NR in front of the vehicle.
Front wheel steering angle sensor SSf for detecting the vehicle lateral acceleration Gy
The lateral acceleration sensor YG that detects the vehicle speed, the yaw rate sensor YS that detects the vehicle yaw rate γ, and the like are the electronic control unit ECU.
It is connected to the. In the yaw rate sensor YS,
The changing speed of the vehicle rotation angle (yaw angle) around the vertical axis passing through the center of gravity of the vehicle, that is, the yaw angular speed (yaw rate) is detected and output to the electronic control unit ECU as the actual yaw rate γ.

Since the actual yaw rate γ can be estimated based on the wheel speed difference Vfd (= Vwfr-Vwf1) between the left and right wheels NL and NR on the driven wheel side, the wheel speed sensor WS.
The yaw rate sensor YS can be omitted by utilizing the detection outputs of 1 and WS2. Further, a steering angle control device (not shown) may be provided between the wheels DL and DR on the rear side of the vehicle.
A wheel D is driven by a motor (not shown) according to the output of U.
It is also possible to control the steering angles of L and DR.

The electronic control unit ECU of this embodiment is shown in FIG.
As shown in FIG. 3, a microcomputer MCP including a processing unit CPU, a memory ROM, a RAM, an input port IPT, an output port OPT, and the like, which are connected to each other via a bus, is provided. Wheel speed sensor WS
The output signals of 1 to WS4, the brake switch BS, the front wheel steering angle sensor SSf, the yaw rate sensor YS, the lateral acceleration sensor YG, and the like are input to the input port I via the amplifier circuit AMP.
It is configured to be input from the PT to the processing unit CPU. In addition, the output port OPT is configured to output control signals to the throttle control device TH and the brake fluid pressure control device PC via the drive circuit ACT. In the microcomputer MCP, the memory ROM stores programs for various processes including the flowcharts shown in FIGS. 4 to 10, and the processing unit CPU executes the programs while the ignition switch (not shown) is closed. ,
The memory RAM temporarily stores the variable data necessary for executing the program. Note that a plurality of microcomputers may be configured for each control such as throttle control or by appropriately combining related controls, and the microcomputers may be electrically connected to each other.

FIG. 3 shows an example of the brake fluid pressure control device PC in this embodiment, in which the master cylinder MC and the fluid pressure booster HB are driven according to the operation of the brake pedal BP. An auxiliary hydraulic pressure source AP is connected to the hydraulic pressure booster HB, and these are connected to the low pressure reservoir RS together with the master cylinder MC.

The auxiliary hydraulic pressure source AP has a hydraulic pump HP and an accumulator Acc. The hydraulic pump HP is driven by the electric motor M to boost and output the brake fluid in the low-pressure reservoir RS, and the brake fluid is supplied to the accumulator Acc via the check valve CV6 to accumulate the pressure. The electric motor M is driven in response to the hydraulic pressure in the accumulator Acc falling below a predetermined lower limit value, and stops in response to the hydraulic pressure in the accumulator Acc exceeding a predetermined upper limit value. In addition, accumulator Acc and low pressure reservoir RS
A relief valve RV is interposed between the and. Thus, the so-called power hydraulic pressure is appropriately supplied from the accumulator Acc to the hydraulic booster HB. The hydraulic booster HB receives the output hydraulic pressure of the auxiliary hydraulic pressure source AP, adjusts the output hydraulic pressure of the master cylinder MC as a pilot pressure, and adjusts the booster hydraulic pressure in proportion to the output hydraulic pressure. It is boosted.

Electromagnetic switching valves SA1 and SA2 are provided in the front wheel hydraulic passages connecting the master cylinder MC and the vehicle front wheel cylinders Wfr and Wfl, respectively, and these control passages Pfr and Pfl are provided. Via the electromagnetic open / close valves PC1, PC5 and the electromagnetic open / close valves PC2, PC6, respectively.
It is connected to the. Further, an electromagnetic opening / closing valve SA3 and electromagnetic opening / closing valves PC1 to PC8 for supply / discharge control are provided in a hydraulic pressure path connecting the hydraulic booster HB and the wheel cylinders Wfr, etc., and proportional to the rear wheels. A pressure reducing valve PV is provided. The auxiliary hydraulic pressure source AP is connected to the downstream side of the electromagnetic opening / closing valve SA3 via the electromagnetic opening / closing valve STR. In FIG. 3, the front and rear pipes are divided into a hydraulic control system for the front wheels and a hydraulic control system for the rear wheels, but so-called X pipes may be used.

In the hydraulic system on the front wheel side, the solenoid opening / closing valve PC1
And PC2 are connected to the solenoid on-off valve STR. The electromagnetic opening / closing valve STR is a 2-port / 2-position electromagnetic opening / closing valve, which is in a closed state at a closed position when not in operation, and directly connects the electromagnetic opening / closing valves PC1 and PC2 to the accumulator Acc at an open position when operating. The electromagnetic switching valve SA1 and the electromagnetic switching valve SA2 are 3
The solenoid directional control valve in the port 2 position is in the first position shown in FIG. 3 when not in operation, and both the wheel cylinders Wfr and Wfl are communicatively connected to the master cylinder MC, but the solenoid coil is energized to the second position. When switched to, the communication between the wheel cylinders Wfr and Wfl is cut off with the master cylinder MC, and the electromagnetic opening / closing valves PC1 and PC5 are respectively disconnected.
It communicates with the solenoid on-off valves PC2 and PC6.

Check valves CV1 and CV2 are connected in parallel to the electromagnetic opening / closing valves PC1 and PC2, and the inflow side of the check valve CV1 is placed in the control passage Pfr and the check valve CV2.
The inflow sides of are connected to the control passage Pf1, respectively. As for the check valve CV1, the electromagnetic switching valve SA1 is in the operating position (second position).
In the above case, when the brake pedal BP is released, the brake fluid pressure of the wheel cylinder Wfr is allowed to flow to the output of the hydraulic booster HB, but the reverse flow is blocked. The same applies to the check valve CV2.

Next, the rear wheel side hydraulic system will be explained.
The electromagnetic opening valve SA3 is a 2-port 2-position electromagnetic on-off valve, which is in the open position shown in FIG.
3, PC4 is a hydraulic booster HB via a proportional pressure reducing valve PV.
Communicate with. At this time, the electromagnetic opening / closing valve STR is closed and the communication with the accumulator Acc is cut off. When the solenoid opening / closing valve SA3 is switched to the closed position during operation, the solenoid opening / closing valves PC3, PC4 are disconnected from the hydraulic booster HB, and are connected to the solenoid opening / closing valve STR via the proportional pressure reducing valve PV. The on-off valve STR communicates with the accumulator Acc when activated.

Further, check valves CV3 and CV4 are connected in parallel to the solenoid on-off valves PC3 and PC4. The inflow side of the check valve CV3 is the wheel cylinder Wrr and the inflow side of the check valve CV4 is the wheel cylinder Wrl. Connected to each. These check valves CV3 and CV4 are provided for quickly causing the brake hydraulic pressure of the wheel cylinders Wrr and Wrl to follow the decrease in the output hydraulic pressure of the hydraulic booster HB when the brake pedal BP is released. Thus, the flow of the brake fluid in the direction of the electromagnetic opening / closing valve SA3 is allowed and the flow in the opposite direction is blocked. Further, the check valve CV5 is provided in parallel with the electromagnetic opening / closing valve SA3, and even when the electromagnetic opening / closing valve SA3 is in the closed position, the brake pedal BP can be further pressed.

The electromagnetic opening / closing valves SA1 and SA2, the electromagnetic opening / closing valves SA3 and STR, and the electromagnetic opening / closing valves PC1 to PC8.
Is driven and controlled by the above-mentioned electromagnetic control unit ECU, and various controls including the above-mentioned braking and steering control are performed.
For example, during brake steering control that is performed when the brake pedal BP is not operated, since the brake hydraulic pressure is not output from the hydraulic booster HB and the master cylinder MC, the electromagnetic opening / closing valves SA1 and SA2 are set to the second position. The solenoid on-off valve SA3 is in the closed position, and the solenoid on-off valve ST
R is in the open position. As a result, the output power hydraulic pressure of the auxiliary hydraulic pressure source AP is transferred to the wheel cylinder Wfr via the electromagnetic opening / closing valve STR and the electromagnetic opening / closing valves PC1 to PC8 in the open state.
And so on. Then, the solenoid on-off valve PC
By appropriately opening and closing 1 to PC8, the brake fluid pressure in each wheel cylinder is changed to a sudden pressure increase, a pulse pressure increase (slow pressure increase), a pulse pressure decrease (slow pressure decrease), a rapid pressure decrease, and a holding state. Thus, the oversteer suppression control and / or the understeer suppression control is performed.

In the present embodiment configured as described above, when the electronic control unit ECU performs a series of processes such as braking steering control and anti-skid control, the ignition switch (not shown) is opened. The execution of the program corresponding to the flowcharts of FIGS. FIG. 4 shows the motion control operation of the vehicle. First, in step 101, the microcomputer MCP is initialized and various calculated values are cleared. Next step 102
In addition, the detection signals of the wheel speed sensors WS1 to WS4 are read, and the detection signal of the front wheel steering angle sensor SSf (steering angle δf), the detection signal of the yaw rate sensor YS (actual yaw rate γ), and the detection signal of the lateral acceleration sensor YG ( That is, the actual lateral acceleration, which is represented by Gya), is read.

Next, in step 103, the wheel speed Vw ** of each wheel is calculated, the vehicle speed is estimated in step 104 based on these calculation results, and the estimated vehicle speed Vso ** is obtained for each wheel. Further, if necessary, normalization is performed in order to reduce an error based on a difference between inner and outer wheels when the vehicle is turning. That is, the normalized estimated vehicle speed NVso ** is NVso
It is calculated as ** = Vso ** (n) -ΔVr ** (n). Here, ΔVr ** (n) is a correction coefficient for turning correction, and is set as follows, for example. That is, the correction coefficient ΔVr ** (** indicates each wheel FR, etc., particularly FW indicates two front wheels, RW indicates two rear wheels).
Is the turning radius R of the vehicle and γ · VsoFW (= lateral acceleration Gy
Based on a), it is set according to a map (not shown) for each wheel except the reference wheel. For example, based on ΔVrFL, this is set to 0, but ΔVrFR is set according to the inner-outer wheel difference map, ΔVrRL is set according to the inner-inner wheel difference map, and ΔVrRR is set according to the outer-inner wheel difference map and the inner-outer wheel difference map. .

Then, in step 105, the actual slip of each wheel is calculated based on the wheel speed Vw ** of each wheel and the estimated vehicle speed Vso (or the normalized estimated vehicle speed NVso **) obtained in steps 103 and 104. The rate Sa ** is calculated as Sa ** = (Vso-Vw **) / Vso.

Next, in step 106, a road surface friction coefficient (hereinafter referred to as road surface μ) estimation processing, which will be described later, is performed. Next, at step 107, the lateral slip angular velocity of the vehicle body is Dβ =
It is calculated as Gy / Vso-γ. Note that Gy is the lateral acceleration of the vehicle, Vso is the estimated vehicle speed, Gy / Vso is the theoretical yaw rate, and γ is the actual yaw rate. Next, at step 108, the vehicle body side slip angle β is obtained as β = ∫Dβdt. Here, the vehicle body side slip angle β represents the slip of the vehicle body with respect to the traveling direction of the vehicle as an angle, and the vehicle body side slip angular velocity Dβ is a differential value dβ / dt of the vehicle body side slip angle β. The vehicle body side slip angle β can also be obtained as β = tan ⁻¹ (Vy / Vx) based on the ratio of the vehicle speed Vx in the traveling direction and the vehicle speed Vy in the lateral direction perpendicular thereto.

Next, the routine proceeds to step 109, where the brake steering control mode is set, the start / end judgment of the brake steering control is performed as described later, the target slip ratio to be used for the brake steering control is set, and then step 117 described later. With the hydraulic servo control, the brake hydraulic pressure control device PC is controlled according to the motion state of the vehicle, and the braking force for each wheel is controlled. This braking steering control is superimposed on the control in all control modes described later. After that, the routine proceeds to step 110, where it is judged whether or not the anti-skid control start condition is satisfied, and if the start condition is satisfied and it is judged that the anti-skid control should be started at the time of braking steering, at step 111, the braking steering control and The control mode is set to perform both antiskid control.

When it is determined at step 110 that the anti-skid control start condition is not satisfied, the routine proceeds to step 112, at which it is determined whether the front-rear braking force distribution control start condition is satisfied, and the front-rear braking control is performed. When it is determined that the braking force distribution control is started, the process proceeds to step 113, the control mode is set to perform both the braking steering control and the front-rear braking force distribution control, and if not satisfied, the process proceeds to step 114 and the traction control start condition. It is determined whether or not is satisfied. When it is determined that the traction control is started during the braking steering control, the control mode for performing both the braking steering control and the traction control is set in step 115, and when neither control is determined to be started during the braking steering control. In step 116, the control mode is set to perform only the braking steering control. Then, based on these control modes, hydraulic servo control is performed in step 117, and then the process returns to step 102. Incidentally, based on steps 111, 113, 115 and 116, the throttle control device T can be operated according to the motion state of the vehicle, if necessary.
The H sub-throttle opening is adjusted, the output of the engine EC is reduced, and the driving force is limited.

In the anti-skid control mode, the wheels are prevented from locking during braking of the vehicle.
The braking force applied to each wheel is controlled. In the front-rear braking force distribution control mode, the distribution of the braking force applied to the rear wheels to the braking force applied to the front wheels is controlled so that the stability of the vehicle is maintained during braking of the vehicle. In the Tocclarsion control mode, braking force is applied to the drive wheels and throttle control is performed to prevent the drive wheels from slipping when the vehicle is driven, and these controls the drive force for the drive wheels. It

Here, the road surface μ estimation processing in step 106 will be described with reference to FIGS. 5 and 10.

First, at step 201, the maximum absolute value Gyp of the lateral acceleration Gy for the past t1 seconds is obtained based on the information from the lateral acceleration sensor YG. Then step 2
At 02, it is determined whether or not the braking steering control is being performed or within t2 seconds after the control is finished. If not, it is determined in step 203 whether the absolute value of the front wheel steering angle δf is less than or equal to the predetermined value δk. If so, it is considered that the vehicle is traveling substantially straight, and the road surface μ is set to G0 (for example, 1G) in step 204. When it is determined in step 203 that the absolute value of the front wheel steering angle δf is larger than the predetermined value δk (during turning and before control), the road surface μ is set to k · Gyp (where k is greater than 1 in step 205). (Slightly larger value). On the other hand, step 2
If it is determined in 02 that the braking steering control is being performed or within t2 seconds after the control is finished, the road surface μ is set to Gyp (Gyps) at the control start instant in step 206. Note that steps 204 and 20
Reference numerals 5 and 206 denote A, B, and C of FIG. 10, respectively.

Next, details of the braking steering control mode processing in step 109 of FIG. 4 will be described with reference to FIG. Here, the braking steering control includes oversteer suppressing control and understeer suppressing control, and a target slip ratio corresponding to the oversteer suppressing control and / or the understeer suppressing control is set for each wheel.

First, in step 301, a control reference straight line is calculated as described later. The control reference straight line is a start reference straight line of the oversteer suppression control (hereinafter referred to as a control start reference straight line; a control start threshold of claim 1) and an end reference straight line of the oversteer suppression control (hereinafter referred to as a control end reference straight line; claim 2). Control end threshold value) and a start / end reference straight line for oversteer suppression pre-control (hereinafter referred to as pre-control start / end reference straight line; pre-control start threshold value in claim 4).

Next, at step 302, the start / end determination of the oversteer suppressing control, which will be described later, is performed. Here, the start / end determination of the oversteering suppression pre-control and the oversteering suppression main control is performed. Then, in step 303, the start / end determination of the understeer suppression control is performed. The start / end determination of the understeer suppression control performed here is performed based on whether or not the control region is in the hatched control area in FIG. That is, in the determination, understeer suppression control is started when the control area is deviated from the ideal state indicated by the one-dot chain line according to the change of the actual lateral acceleration Gya with respect to the target lateral acceleration Gyt, and when the control area is left, the understeer suppression control is performed. Is ended.

Next, at step 304, it is judged if the oversteer suppressing control is under control. If it is not under control, then it is judged at step 305 whether the understeer suppressing control is under control. If not, the process directly returns to the main routine of FIG. When it is determined in step 305 that the understeer suppression control is performed, step 306
Then, the target slip ratio of each wheel is set for understeer suppression control described later. If it is determined in step 304 that the oversteer suppression control has been performed, it is determined in step 307 whether or not the understeer suppression control has been performed. Set for. When it is determined in step 307 that the understeer suppressing control is being performed, the oversteer suppressing control and the understeer suppressing control are simultaneously performed, and the target slip ratio for simultaneous control is set in step 309.

First, the vehicle body side slip angle β and the vehicle body side slip angular velocity Dβ are used to set the target slip ratio for the oversteer suppressing control. The target lateral acceleration G is set in the target step rate in the understeer suppression control.
The difference between yt and the actual lateral acceleration Gya is used. The target lateral acceleration Gyt is calculated based on Gyt = γ (θf) · Vso. Here, γ (θf) is γ (θf) = (θf / N ·
L) · Vso / (1 + Kh · Vso ² ), Kh
Is a stability factor, N is a steering gear ratio, and L is a wheel base.

The target slip ratios of the respective wheels in step 306 are set such that the front wheel on the outside of the turn is set to Stufo, the rear wheel on the outside of the turn is set to Sturo, and the rear wheel on the inside of the turn is Sturi.
Is set to. Regarding the sign of the slip ratio (S) shown here, "t" represents "target" and is compared with "a" which represents "actual measurement" described later. "u" means "understeer suppression control", "f" means "front wheel", "r" means "rear wheel", "o" means "outside", "i" means "inside". Represent each.

The target slip ratio of each wheel in step 308 is set to Stefo for the front wheel on the outside of the turn and set to Stero for the rear wheel on the outside of the turn. Here, "e" represents "oversteer suppression control."

Then, in step 309, the target slip ratio of each wheel is set to Stefo for the front wheel on the outside of the turn, Steuro for the rear wheel on the outside of the turn, and Sturi for the rear wheel on the inside of the turn. It That is, when the oversteer suppression control and the understeer suppression control are performed at the same time, the front wheels on the outside of the turn are set in the same manner as the target slip ratio of the oversteer suppression control, and the rear wheels are set in the same manner as the target slip ratio of the understeer suppression control. Is set. In any case, the front wheels on the inside of the turn (that is, the driven wheels in the rear-wheel drive vehicle) are not controlled for setting the estimated vehicle speed.

The target slip ratio Stefo of the front wheel on the outside of the turn used for the oversteer suppressing control is Stefo = K1.β ** +
The target slip ratio Stero of the rear wheel on the outside of the turn is set as Stero = K3.β ** + K4.Dβ **. Here, K1 to K4 are constants, and the target slip ratios Stefo and Stero for the wheels on the outside of the turn are set.
Is set to a value for controlling the pressurizing direction (the direction in which the braking force is increased).

On the other hand, the target slip ratio for understeer suppression control is set as follows based on the deviation ΔGy between the target lateral acceleration Gyt and the actual lateral acceleration Gya. That is,
The target slip ratio Stufo for the front wheel on the outside of the turn is K7
ΔGy is set, and the constant K7 is set to a value for controlling the pressurizing direction (or the depressurizing direction). Further, the target slip ratios Sturo and Sturi for the rear wheels are K8 and ΔG, respectively.
y and K9 · ΔGy are set, and the constants K8 and K9 are both set to values for controlling the pressurizing direction.

Next, details of the control reference straight line calculation processing in step 301 of FIG. 6 will be described with reference to FIG. Control start reference straight lines A1 and A2 are calculated in steps 401 to 403, control end reference straight lines B1 and B2 are calculated in steps 404 to 406, and pre-control start and end reference straight lines C1 and C2 are calculated in steps 407 to 409. . The calculation processing of each reference straight line will be described below.

First, at step 401, the control start sensitivity coefficient ks is calculated based on the road surface μ calculated in FIG. That is, the control start sensitivity coefficient kS is calculated based on the function of the road surface μ and the control start sensitivity coefficient kS shown in FIG.
The lower is, the smaller it is. When the road surface μ is μ1 or less, the control start sensitivity coefficient kS is set to the lower limit value kS1, and when the road surface μ is μ2 or more, it is set to the upper limit value kS2.

Next, at step 402, an oversteer suppressing control map (FIG. 13) in which the vehicle body side slip angle β is the X axis (horizontal axis) and the vehicle body side slip angular velocity Dβ is the Y axis (vertical axis).
), The starting intercept XS, YS is XS = kS.XSk.
(XS is positive) and YS = kS.YSk (YS is positive). Here, XS0 and YS0 are starting intercept reference values, which are constants.

Subsequently, in step 403, the equation of the control start reference lines A1 and A2 is A1: Dβ11 = (-YS / XS
) Β + YS, A2: Dβ12 = (-YS / XS) β-YS
Is calculated as That is, the starting reference line A1 is the starting intercept XS, YS [that is, (XS,
0) and (0, YS)], and the starting reference straight line A2 passes through the starting intercept -XS, -YS [that is, (-XS, 0) and (0, -YS)]. Low μ (eg, 0.
2G), the starting reference lines A1 and A2 are shown in FIG.
FIG. 14 shows the starting reference straight lines A1 and A2 in the case of (for example, 0.8 G). As is clear from FIGS. 13 and 14, the starting reference straight line width of low μ is smaller than that of high μ. This means that the lower the μ, the earlier the control starts.

Next, at step 404, the control end hysteresis coefficient kH is calculated based on the road surface μ calculated in FIG. That is, the end hysteresis coefficient kH is calculated based on the function of the road surface μ and the end hysteresis coefficient kH shown in FIG. 12, and the higher the road surface μ, the larger the end hysteresis coefficient kH. When the road surface μ is μ1 or less, the ending hysteresis coefficient kH is the lower limit value kH1, and when the road surface μ is μ2 or more, it is the upper limit value kH2.

Next, at step 405, the end intercept YE in the above-mentioned oversteer suppression control map is YE.
= (1-kHz) YS (YE is positive). Then, in step 406, the equation of the control end reference straight lines B1 and B2 is B1: Dβ21 = (-YS / XS) β + YE, B
2: Calculated as Dβ22 = (-YS / XS) β-YE. That is, the end reference straight line B1 is a straight line whose slope is equal to A1 and its intercept is YE, and the end reference straight line B2 is a straight line whose slope is equal to A2 and whose intercept is -YE. Low μ
The end reference straight lines B1 and B2 in the case of (eg 0.2 G) are shown in FIG. 13, and the end reference straight line B in the case of high μ (eg 0.8 G).
1 and B2 are shown in FIG. As is clear from FIGS. 13 and 14, the width between the high-μ starting reference line and the ending reference line is
It is larger than that of low μ. This means that the higher the μ, the more gently the control is ended.

Next, at step 407, the pre-control start / end intercept YP in the above-mentioned oversteer suppression control map is calculated as YP = (1-kP) YS (YP is positive). Here, kP is a pre-control start / end sensitivity coefficient and is a constant. Note that kP may be a variable that changes depending on the road surface μ. Then, in step 408, the equation of the pre-control start / end reference straight lines C1 and C2 is C1: Dβ31.
= MAX [(-YS / XS) [beta] + YP, D [beta] 0], C2
: Dβ32 = MIN [(-YS / XS) β-YP, -Dβ
0]. Here, Dβ0 is a constant. Thus, as shown in FIGS. 13 and 14, the reference straight line C1 and the straight line X whose slope is equal to A1 and whose intercept is YP are
It is the larger of the straight line Y = Dβ0 parallel to the axis. Also,
The reference straight line C2 has an inclination of A as shown in FIGS.
It is equal to 2 and the intercept is the smaller of the straight line of -YP and the straight line Y = -Dβ0 parallel to the X axis.

The reference straight lines C1 and C2 for low μ (eg 0.2 G) are shown in FIG. 13, and the reference straight lines C1 and C2 for high μ (eg 0.8 G) are shown in FIG. As is clear from FIGS. 13 and 14, the reference straight line width for low μ is smaller than that for high μ. This means that the lower the μ, the earlier the start of pre-control. Also, -Dβ0 ≤ Dβ ≤ Dβ0
In the area of, the pre-control is not started. This means that the pre-control is not performed when the vehicle body side slip angle changes gently, and unnecessary start of the pre-control is avoided.

Details of the oversteer suppression control start / end determination processing in step 302 of FIG. 6 will be described below with reference to FIG.

In step 501, it is determined whether or not the oversteer suppression main control is being performed (hereinafter referred to as the main control). If the present control is not in progress, the vehicle body side slip angular velocity Dβ calculated in step 107 (hereinafter referred to as the calculated vehicle body side slip angular velocity Dβ) with respect to the vehicle body side slip angle β calculated in step 108 of FIG.
The value Dβ obtained by substituting the calculated vehicle side slip angle β into the equation
It is determined whether or not 11 or more (Dβ ≧ Dβ11). That is,
It is determined whether or not the coordinates (β, Dβ) of the calculated vehicle body side slip angle β and vehicle body side slip angular velocity Dβ are above the start reference line A1. If Dβ ≧ Dβ11, the routine proceeds to step 503, where it is determined that the main control needs to be started.

If Dβ ≧ Dβ11 is not satisfied at step 502, the routine proceeds to step 504, where the calculated vehicle body side slip angular velocity D is calculated.
It is determined whether or not β is equal to or less than a value Dβ12 (Dβ ≦ Dβ12) obtained by substituting the calculated vehicle body sideslip angle β into the equation of the starting reference straight line A2. That is, it is determined whether or not the calculated coordinates (β, Dβ) are below the start reference line A2. D
If β ≦ Dβ12, the process proceeds to step 503, and it is determined that the main control needs to be started. If Dβ ≦ Dβ12 does not occur, the process proceeds to step 507 described later.

If it is determined in step 501 that the main control is in progress, the calculated vehicle body side slip angular velocity D is calculated in step 505.
β is a value Dβ22 or more obtained by substituting the calculated vehicle body side slip angle β into the equation of the end reference straight line B2 and a value Dβ21 or less obtained by substituting the calculated vehicle body side slip angle β in the equation of the end reference straight line B1 for the computed vehicle body side slip angular velocity Dβ (Dβ22 ≦ Dβ ≦ D
β21) is determined. That is, it is determined whether or not the calculated coordinates (β, Dβ) are in the region above the end reference straight line B2 and below the end reference straight line B1. If Dβ22 ≦ Dβ ≦ Dβ21, step 5
In step 06, it is determined that this control needs to be terminated, and Dβ22 ≦ Dβ ≦
If it is not Dβ21, the process proceeds to step 507. As described above, it is determined whether or not the start / end of this control is necessary.

Here, as shown in FIG. 13, in the case of low μ, this control is performed between DE and FG, and FIG.
As shown in, in the case of high μ, this control is performed between HI and HI. The braking force of each wheel is controlled such that the control amount increases as the control start reference straight line deviates to the control region side.

Subsequently, in step 507, it is determined whether or not the main control is required to start (passing step 503). If it is not determined that the main control is required,
In step 508, it is determined whether or not the oversteer suppression pre-control is in progress (hereinafter referred to as pre-control). If the pre-control is not in progress, in step 509, the calculated vehicle body side slip angular velocity Dβ is a value Dβ31 or more obtained by substituting the calculated vehicle body side slip angle β into the equation of the pre-control start reference straight line C1 (Dβ ≧
It is determined whether or not it is Dβ31). That is, the coordinates (β, D) of the calculated vehicle body side slip angle β and vehicle body side slip angular velocity Dβ
It is determined whether or not β) is a region above the pre-control start reference line C1. If Dβ ≧ Dβ31, step 51
The process proceeds to 0 and it is determined that the pre-control needs to be started.

If Dβ ≧ Dβ31 at step 509, the routine proceeds to step 511, where the calculated vehicle side slip angular velocity D is calculated.
β is a value Dβ32 or less (Dβ ≦ Dβ32) obtained by substituting the calculated vehicle body side slip angle β into the equation of the pre-control start reference straight line C2.
It is determined whether or not. That is, the calculated coordinates (β, D
It is determined whether or not β) is a region below the starting reference line C2. If Dβ ≦ Dβ32, the routine proceeds to step 510, where it is determined that the pre-control should be started. If Dβ ≦ Dβ32 is not satisfied, the routine returns to the routine of FIG.

When it is determined in step 508 that the pre-control is being performed, it is determined in step 512 whether Dβ32 <Dβ <Dβ31. That is, the calculated coordinates (β, Dβ)
Is in a region above the pre-control end reference straight line C2 and below the pre-control end reference straight line C1. If Dβ32 <Dβ <Dβ31, the process proceeds to step 513, where it is determined that the pre-control is required, and Dβ32 <
If Dβ <Dβ31 is not satisfied, the process returns to the routine of FIG. still,
If it is determined in step 507 that the main control should be started, the pre-control start / end determination is not performed and the routine returns to the routine of FIG. As described above, it is also determined whether or not the start / end of pre-control is necessary.

The details of the hydraulic servo control processing in step 117 of FIG. 4 will be described with reference to FIG. 9. Here, the slip ratio servo control of the wheel cylinder hydraulic pressure is performed for each wheel.

First, the target slip ratio St ** set in the above-mentioned step 306, 308 or 309 is read in step 601, and these are read as they are as the target slip ratio St ** of each wheel. Although not shown in this flowchart, the target slip ratio St ** is further increased by adding, for example, the slip ratio correction amount ΔSs ** for the anti-skid control mode to the target slip ratio St ** according to various control modes. Will be updated. Similarly, the target slip ratio St ** is added with the slip ratio correction amount ΔSb ** for the front-rear braking force distribution control mode or the slip ratio correction amount ΔSr ** for the traction control mode is added. St ** is updated. And step 6
02, the slip ratio deviation ΔSt ** is calculated for each wheel, and the vehicle body acceleration deviation ΔD is calculated in step 603.
Vso ** is calculated.

In step 602, the difference between the target slip rate St ** of each wheel and the actual slip rate Sa ** is calculated to obtain the slip rate deviation ΔSt ** (ΔSt ** = St *).
* -Sa **). Further, in step 603, the difference between the vehicle body acceleration DVso ** between the reference wheel (non-controlled wheel) and the controlled wheel is calculated, and the vehicle body acceleration deviation ΔDV is calculated.
so ** is required. Actual slip ratio S of each wheel at this time
The calculation of a ** and vehicle body acceleration deviation ΔDVso ** differs depending on the control mode such as anti-skid control and traction control, but the description thereof will be omitted.

Subsequently, the routine proceeds to step 604, where the slip ratio deviation ΔSt ** is compared with a predetermined value Ka, and if it is equal to or larger than the predetermined value Ka, the integral value of the slip ratio deviation ΔSt ** is updated at step 606. That is, this slip ratio deviation ΔS
The value obtained by multiplying t ** by the gain GI ** is added to the previous slip ratio deviation integrated value IΔSt ** to obtain the current slip ratio deviation integrated value IΔSt **. Slip rate deviation | ΔSt *
When * | is less than the predetermined value Ka, the slip ratio deviation integrated value IΔSt ** is cleared (0) in step 605. Next, in steps 607 to 610, if the slip ratio deviation integrated value IΔSt ** is less than or equal to the upper limit value Kb, the lower limit value K
It is limited to a value of c or more, and when the upper limit Kb is exceeded, Kb
Is set to, and when it is below the lower limit value Kc, it is set to Kc, and then the process proceeds to step 611.

In step 611, one parameter Y used for the brake fluid pressure control in each control mode.
** is calculated as Gs **. (. DELTA.St ** + I.DELTA.St **). Here, Gs ** is a gain and is set according to the vehicle body side slip angle β as shown by the solid line in FIG. Further, in step 612, another parameter X ** used for the brake fluid pressure control is calculated as Gd ** · ΔDVso **. The gain Gd ** at this time is a constant value as shown by the broken line in FIG.

Thereafter, the routine proceeds to step 613, where the hydraulic pressure control mode is set for each wheel based on the parameters X **, Y ** according to the control map shown in FIG. Figure 1
In 6, each area of the rapid pressure reduction area, the pulse pressure reduction area, the holding area, the pulse pressure increase area and the rapid pressure increase area is set in advance, and in step 613, according to the values of the parameters X ** and Y **, It is determined to which area it corresponds.
In the non-controlled state, the hydraulic control mode is not set (solenoid off).

When the region determined this time in step 613 is switched from pressure increase to pressure decrease or pressure decrease to pressure increase with respect to the region judged last time, the fall or rise of the brake fluid pressure is made smooth. Since it is necessary, in step 614, the pressure increase / decrease compensation process is performed. For example, when switching from the sudden pressure reduction mode to the pulse pressure increase mode,
The sudden pressure increase control is performed, and the time is determined based on the duration of the immediately previous sudden pressure decrease mode. And step 6
At 15, the solenoids of the solenoid valves constituting the brake fluid pressure control device PC are driven according to the fluid pressure control mode and the pressure increase / decrease compensation processing, and the braking force of each wheel is controlled.

As described above, in the present embodiment, the start reference line, the end reference line in the oversteer suppression main control, and the start / end reference straight line in the oversteer suppression pre-control are changed according to the road surface μ. The start reference line, the end reference line in the suppression main control and the start / end reference line in the understeer suppression pre-control can be changed according to the road surface μ.

Further, in this embodiment, the vehicle body side slip angle β and the vehicle body side slip angular velocity Dβ are used together as the motion state quantities of the vehicle used for the oversteer suppressing control, but the present invention is not limited to this. , Vehicle side slip angle β
Alternatively, the vehicle body side slip angular velocity Dβ may be used.

[0074]

According to the first aspect of the present invention, the control start region in the vehicle motion state is set so that the lower the road surface friction coefficient is, the smaller the road surface friction coefficient becomes. Therefore, when the road surface friction coefficient is low, the control start response is improved. At the same time, when the road surface friction coefficient is high, unnecessary control can be prevented from being started. That
The higher the road friction coefficient, the higher the control start threshold and the control end threshold.
The difference between the road surface friction coefficient is
The higher the value, the later the end of control can be delayed.
Can result in the vehicle's yawmen
It is possible to avoid sudden changes in the car .

[0075]

According to the second aspect, when the steering angle of the wheel detected by the steering angle sensor is equal to or more than the predetermined value before the control is started, the road surface friction coefficient is set to be slightly higher than the lateral acceleration of the vehicle. Therefore, even when the lateral acceleration of the vehicle is increasing without reaching the limit state, it is possible to avoid underestimating the road surface friction coefficient, and as a result, it is possible to avoid unnecessary start of control as much as possible. .

[0077]

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a vehicle motion control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of a motion control device of the present invention.

FIG. 3 is a configuration diagram showing an example of a brake fluid pressure control device in FIG.

FIG. 4 is a flowchart showing the overall motion control of the vehicle in the embodiment of the present invention.

5 is a flowchart showing a road surface μ estimation process in FIG.

FIG. 6 is a flowchart showing a process for the braking steering control of FIG.

FIG. 7 is a flowchart showing a calculation process of a control reference straight line in FIG.

FIG. 8 is a flowchart showing start / end determination processing of oversteer suppression control of FIG.

9 is a flowchart showing a process of hydraulic servo control of FIG.

FIG. 10 is a timing chart illustrating the road surface μ estimation processing of FIG.

FIG. 11 is a graph showing a relationship between a road surface μ and a control start sensitivity coefficient in the present embodiment.

FIG. 12 is a graph showing a relationship between a road surface μ and a control end hysteresis coefficient in the present embodiment.

FIG. 13 is a graph showing a control reference straight line for oversteer suppressing control at low μ in the present embodiment.

FIG. 14 is a graph showing a control reference straight line for oversteer suppression control at high μ in the present embodiment.

FIG. 15 is a graph showing a control region of understeer suppression control of the present embodiment.

FIG. 16 is a graph showing a relationship between a parameter used for brake fluid pressure control and a fluid pressure control mode in the present embodiment.

FIG. 17 is a graph showing a relationship between a vehicle body side slip angle and a gain for parameter calculation in the present embodiment.

[Explanation of symbols]

BP brake pedal NR, NL, DR, DL wheels PC brake fluid pressure controller

Front page continuation (72) Inventor Norio Yamazaki, Aisin Nuhard Co., Ltd., 2-3, Showa-cho, Kariya city, Aichi prefecture (56) Reference JP-A-7-215190 (JP, A) JP-A 5-170087 (JP, A) JP-A-8-58554 (JP, A) JP-A-7-315197 (JP, A) JP-A-3-264846 (JP, A) JP-A-3-224860 (JP, A) A) JP-A-8-80826 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60T 8/00 B60T 8/32-8/96

Claims (2)

(57) [Claims] 1. A brake fluid pressure control device for applying a braking force to each wheel of a vehicle at least in response to an operation of a brake pedal, and a vehicle state quantity estimating means for estimating a motion state quantity of the vehicle during turning. When the vehicle motion state quantity estimated by the vehicle state quantity estimation means exceeds a control start threshold value, start determination means for determining that control is required to start, and when the start determination means determines that control to be started, the vehicle A vehicle motion control device including a motion control means for controlling the brake fluid pressure control device so as to correct the yaw moment of the vehicle to a stable side and applying a braking force to each wheel of the vehicle. And a start threshold value setting unit for setting the control start threshold value so that the road surface friction coefficient estimated by the road surface friction coefficient estimating unit becomes smaller as the road surface friction coefficient becomes lower. Means, road surface friction coefficient estimated by the road surface friction coefficient estimating means
The higher the number, the larger the difference between the control start threshold
End threshold for setting control end threshold for vehicle motion state quantity
During the control by the value setting means and the motion control means, the vehicle state quantity estimation is performed.
The vehicle motion state quantity estimated by the means is set to the end threshold value.
If the value is below the control end threshold set by the
In this case, the motion determining means determines that the control is required to be terminated,
When judged, the control of the brake fluid pressure control device is terminated
A vehicle motion control device characterized by: 2. A brake fluid pressure control device for applying a braking force to each wheel of a vehicle at least in response to an operation of a brake pedal, and a vehicle state quantity estimating means for estimating a motion state quantity of the vehicle during turning. When the vehicle motion state quantity estimated by the vehicle state quantity estimation means exceeds a control start threshold value, start determination means for determining that control is required to start, and when the start determination means determines that control to be started, the vehicle A vehicle motion control device including a motion control means for controlling the brake fluid pressure control device so as to correct the yaw moment of the vehicle to a stable side and applying a braking force to each wheel of the vehicle. And a start threshold value setting unit for setting the control start threshold value so that the road surface friction coefficient estimated by the road surface friction coefficient estimating unit becomes smaller as the road surface friction coefficient becomes lower. Means, a lateral acceleration sensor for detecting a lateral acceleration of the vehicle, and a steering angle sensor for detecting a steering angle of the wheels, wherein the road surface friction coefficient estimating means is detected before the control is started and by the steering angle sensor. When the absolute value of the steering angle of the wheels is equal to or larger than a predetermined value, a value obtained by multiplying the lateral acceleration of the vehicle detected by the lateral acceleration sensor by a predetermined constant k larger than 1 is used as the road surface friction coefficient. Vehicle motion control device.