JP2001071886A - Yawing kinetic momentum control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a yawing kinetic momentum control device for a vehicle for maintaining stability in an under steer state generated by a turning motion at an over speed on a road surface with a low friction coefficient such as a road covered with ice and snow, improving the under steer state, and restraining an over steer state generated afterwards. SOLUTION: An attainable maximum value for a yawing kinetic momentum is calculated based on a first target yawing kinetic momentum calculated based on at least a steering angle and a vehicle speed, and a value detected or estimated by a road surface friction coefficient state detecting/estimating mean. A second target yawing kinetic momentum is calculated by restricting the first target yawing kinetic momentum with the maximum value. When an under steer state is determined, a target yawing kinetic momentum is set to the first target yawing kinetic momentum or a value at least larger than the second target yawing kinetic momentum, and when an over steer state is determined, the target yawing kinetic momentum is set to the second target yawing kinetic momentum, thereby switching the target yawing kinetic momentum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a yaw momentum control device for a vehicle.

[0002]

2. Description of the Related Art A conventional yawing momentum control device for a vehicle is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-144653.

This publication describes a configuration in which a target yaw momentum, which is always limited by a maximum yaw momentum set from a road friction coefficient state, is set as a target in setting a target yaw momentum.

On the other hand, the vehicle described in Japanese Patent Application Laid-Open No. 8-2766841 controls the target yaw momentum limited by the maximum yaw momentum calculated by the road surface friction coefficient when the vehicle is in the understeer state, so that the vehicle is in the oversteer state. In some cases, a reference yaw momentum calculated based on a steering wheel angle and a vehicle speed is controlled as a target. Further, the determination of the steering state is performed for the reference first target yawing momentum.

[0005]

However, in the prior art described in the above-mentioned Japanese Patent Application Laid-Open No. 7-144653, understeering occurs when turning at an overspeed on a low friction coefficient road surface such as an icy snowy road. However, since the target yaw momentum decreases according to the friction coefficient,
The understeer state is maintained, and it becomes difficult for control to intervene in the oversteer direction.

On the other hand, in the prior art described in Japanese Patent Application Laid-Open No. Hei 8-2766841, in the running state (the turning motion at a low friction coefficient on the road surface at an overspeed), when the vehicle is in an understeer state, the road surface friction coefficient is low. Since the target yaw momentum limited by the maximum yaw momentum calculated in step (1) is controlled as the target, the understeer state is maintained as in the above case, and there is no understeer suppression effect. Further, since the determination of the steering state is performed with respect to the reference first target yawing momentum, the actual yawing momentum is larger than the maximum value calculated from the road surface friction coefficient and is smaller than the reference first target yawing momentum. When the understeer is determined to be small and the actual yawing momentum is oversteering, the target yawing momentum is limited to the maximum value as in the prior art described in Japanese Patent Laid-Open No. 7-144653. Therefore, the oversteer suppression effect is obtained, but the actual yawing momentum is larger than the maximum value and the first
When the oversteer is larger than the target yaw momentum and the actual yaw momentum is oversteer, the target yaw momentum becomes the reference first target yaw momentum unlike the prior art described in Japanese Patent Application Laid-Open No. 7-144653. Therefore, the effect of suppressing oversteer is reduced.

The present invention has been made in view of such a conventional problem. Even if an understeer state occurs due to a turning motion at an overspeed on a low friction coefficient road surface such as an icy and snowy road, the present invention has been made. Ability (stability)
It is an object of the present invention to provide a yaw momentum control device for a vehicle that can improve an understeer state and suppress a subsequent oversteer state while maintaining the above condition.

[0008]

Means for solving the above problems are as follows.
It is as follows.

According to the first aspect of the present invention, an actual yawing momentum detecting means for detecting a yawing momentum actually occurring in the vehicle, and an input physical quantity detecting means for detecting an input acting on the vehicle or a physical quantity occurring in the vehicle. Means, target yaw momentum calculation means for calculating a target yaw momentum to be achieved by the vehicle based on an input detection value acting on the vehicle detected by the input physical quantity detection means or a physical quantity detection value occurring in the vehicle, Target yawing momentum control means for controlling the actual yawing momentum detected by the actual yawing momentum detecting means to coincide with the target yawing momentum calculated by the target yawing momentum calculating means. In the device, the road friction coefficient state that detects or estimates the state of the road friction coefficient during traveling And a detection estimation means, the said target yawing momentum calculating means, a first target yawing momentum calculating means based on at least the steering wheel angle and vehicle speed,
A yawing momentum maximum value calculating unit that calculates a maximum value of a yawing momentum that can be steadily realized based on the road surface friction state detection value detected or estimated by the road surface friction coefficient state detection estimating unit or the estimated value thereof; A second target yawing momentum calculating means for limiting the first target yawing momentum by the maximum value, and a steering state for determining whether the actual yawing momentum of the vehicle is in an understeer state smaller than the target yawing momentum or in an oversteer state larger than the target yawing momentum. Determining means for setting the target yawing momentum to a target yawing momentum larger than a first target yawing momentum or at least a second target yawing momentum when in an understeer state;
A target yawing momentum switching means for setting the second target yawing momentum when the vehicle is in the oversteer state.

According to a second aspect of the present invention, in the vehicle yawing momentum control apparatus according to the first aspect, the road surface frictional state detecting and estimating means includes a lateral acceleration detecting means for detecting a lateral acceleration acting on the vehicle. It is characterized by having.

According to a third aspect of the present invention, in the vehicle yawing momentum control device according to the second aspect, the steering state determining means includes an actual yawing momentum and a road surface friction detected or estimated by the road surface friction coefficient state detecting and estimating means. The steer state is determined based on a state detection value or a second target yaw momentum limited by a maximum yaw momentum that can be constantly achieved based on the estimated value.

According to a fourth aspect of the present invention, in the vehicle yawing momentum control device according to the first aspect, the target yawing momentum switching means includes a steering state determination means i.
When the oversteer judgment is completed and the understeer judgment is made, the second target yawing momentum is set to the control target yawing momentum without switching to the first target yawing momentum for a set time.

According to a fifth aspect of the present invention, in the vehicle yawing momentum control device according to any one of the first to fourth aspects, the target yawing momentum switching means switches a target yawing momentum according to a steering state, and then filters a first-order lag or the like. The control target yawing momentum is set.

[0014]

According to the first aspect of the present invention, the actual yawing momentum detecting means detects the yawing momentum actually generated in the vehicle, and the target yawing momentum calculating means detects the yawing momentum by the input physical quantity detecting means. The target yaw momentum to be achieved by the vehicle is calculated based on the input detection value acting on the vehicle or the physical value detected in the vehicle, and the target yaw momentum control means calculates the target yaw momentum calculated by the target yaw momentum calculation means. The yawing momentum is controlled so that the actual yawing momentum detected by the actual yawing momentum detecting means matches the yawing momentum.

In the calculation of the target yawing momentum in the yawing momentum control of the vehicle, the first target yawing momentum calculating means calculates the first target yawing momentum based on at least the steering wheel angle and the vehicle speed, and calculates the maximum yawing momentum. The calculating means calculates a steady-state maximum yaw momentum based on the road friction state detection value detected or estimated by the road friction coefficient state detection estimating means or the estimated value, and calculates the second target yaw momentum. The calculating means calculates the second target yawing momentum by limiting the first target yawing momentum with the maximum value. The steering state determining means determines whether the actual yawing momentum of the vehicle is an understeer state smaller than the target yawing momentum or an oversteering state larger than the target yawing momentum. If the target yawing momentum switching means is in the understeering state, the first state is determined. Is set as the target yawing momentum or at least larger than the second target yawing momentum, while the second target yawing momentum is set as the target yawing momentum when the vehicle is in the oversteer state.

In other words, in the understeer state, the target yaw momentum is set to a value larger than the maximum value without limiting the target yaw momentum to the oversteer side early, and in the oversteer state, the target yaw momentum is reduced. Control is performed so as to shift to the understeer side by limiting the maximum value. Here, if the target yawing momentum is always limited to a maximum value on a road surface having a low friction coefficient such as an icy road, the maximum value is set low, and the understeer state is not improved. On the other hand, if the target yaw momentum is set without limiting the maximum value, a large yaw momentum is generated, resulting in a very unstable vehicle behavior.

Thus, by switching the target yaw momentum according to the steering state, even if an understeer state occurs due to overspeed turning on a low friction coefficient road surface such as an icy road. While maintaining stability, the understeer state can be improved, and the oversteer state that occurs thereafter can be suppressed.

According to the present invention, the lateral acceleration acting on the vehicle is detected by the lateral acceleration detecting means in the road friction coefficient state detecting and estimating means.

That is, the lateral acceleration generated in the turning state of the vehicle intervenes with the vehicle speed, the coefficient of friction between the tire and the road surface, the side slip angle of the tire, the maximum cornering power and cornering force associated therewith, and the like. Is an evaluation index of the vehicle behavior that occurs secondarily to the vehicle.

Therefore, the road surface friction state detection / estimation means can more accurately detect or estimate the road surface friction state by taking the lateral acceleration detection value into account.

According to the third aspect of the present invention, the steering state determining means determines a steady state based on the actual yawing momentum and the road friction coefficient state detection value or estimated value detected or estimated by the road friction coefficient state detection estimating means. The steering state is determined by comparing the second target yawing momentum limited by the maximum value of the yawing momentum that can be realized in a practical manner.

This makes it possible to control the behavior of the vehicle so as to approach the maximum value of the achievable yaw momentum.

For example, the understeer state is determined by the steer state determination means, and control is performed so as not to limit the maximum value. When the behavior (actual yawing momentum) of the vehicle becomes equal to or more than the maximum value, the maximum value limit is set. , Stable control can be performed without shifting to an extreme oversteer state.

According to the fourth aspect of the present invention, in the target yawing momentum switching means, when the steer state discriminating means completes the oversteer judgment and the understeering judgment is made, the set time is not switched to the first target yawing momentum. The second target yawing momentum is set to the target yawing momentum.

That is, when the target yawing momentum is switched so that the actual yawing momentum is adjusted to the target, there is a high possibility that oversteer and understeer are frequently repeated. For this reason, it is desirable that the setting of the target yawing momentum larger than the first target yawing momentum or at least the second target yawing momentum for suppressing the understeer is effective only at the time of entering a corner or at the beginning of a lane change.

Therefore, when the understeer determination is made after the oversteer determination is completed, the yaw motion of the vehicle is stabilized while the second target yaw momentum is kept for a certain set time, and then the first target yaw momentum or at least the second target yaw momentum is determined. By switching to the target yaw momentum larger than the target yaw momentum, the frequent switching of the control is suppressed, and stable control can be executed.

In the invention described in claim 5, in the target yawing momentum switching means, after switching the target yawing momentum according to the steer state, a filter such as a first-order lag is applied to set the next target yawing momentum.

Therefore, the change due to the switching of the target yawing momentum is reduced by the filter processing,
Smooth control can be realized.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is an overall configuration diagram showing an embodiment of the present invention. Reference numerals 1FL and 1RR in the figure denote front left and rear right wheels, respectively, and 1FR and 1RL denote front right and rear left wheels, respectively. Then, wheel cylinders 2FL to 2RR corresponding to the respective brake cylinders are attached to 1FL to 1RR of each wheel. Each of the wheel cylinders 2FL to 2RR is a so-called disc brake which presses a pad against a disc rotor to perform braking.

The master cylinder 5 generates two systems of master cylinder pressure in response to the depression of the brake pedal 4. The connection structure between the wheel cylinders 2FL to 2RR is such that the front left wheel cylinder 2FL and the rear right wheel cylinder 2RR are connected to one system of the master cylinder 5, and the front right wheel cylinder 2FR and the rear left wheel This is a piping structure called diagonal split piping or X piping for connecting the cylinder 2RL. In this embodiment, a proportioning valve 20R is provided between the rear left and right wheel cylinders 2RL and 2RR and the master cylinder 5.
L, 20RR interposed. The proportioning valves 20RL and 20RR are designed to increase the rate of increase of the braking force on the front wheels in order to bring the braking force distribution of the front and rear wheels closer to the so-called ideal braking force distribution in response to changes in the wheel load during braking. It is smaller than that on the side, and the existing one can be used.

On the other hand, for each system of the master cylinder pressure of the master cylinder 5, master cylinder disconnection valves 6A and 6B for connecting and disconnecting the master cylinder 5 and the wheel cylinders 2FL and 2RR or 2FR and 2RL are interposed. Further, a pressure-intensifying pump 3 for pressurizing the brake fluid in the master cylinder reservoir 5a is separately provided, and the discharge pressure of the pressure-intensifying pump 3 is branched into two, and the two systems of the master cylinder pressure from the master cylinder 5 are used. Then, they are merged downstream from the master cylinder on-off valves 6A and 6B, that is, on the wheel cylinders 2FL to 2RR side. Further, between the respective merging points and the pressure-intensifying pump 3, the pressure-increasing pump intermittent valves 7A and 7B are interposed.

Then, one system of the master cylinder 5 or one system branched from the pressure increasing pump 3 is regarded as one system of the brake fluid pressure source, and the wheel cylinders 2FL, 2RR or 2FR, 2RL connected thereto are regarded as one system. Pressure control valve 8FL, 8RR or 8FR, 8RL corresponding to each upstream side of
Intervene. The brake fluid pressure at the brake fluid pressure source is also referred to as a line pressure for convenience. Each of these pressure increase control valves 8FL, 8RR or 8FR, 8RL is provided with a check valve 9FL, 9RR or 9FR, 9RL in a respective bypass flow passage so that the wheel cylinder 2FL is released when the brake pedal is released. , 2RR or 2FR, 2RL is immediately returned to the master cylinder 5 side.

Further, the discharge sides of the individual pressure reducing pumps 11A and 11B are connected to the respective systems of the braking fluid pressure sources, and their suction sides are connected to the wheel cylinders 2FL and 2FL.
Pressure reducing control valve 10FL, 10RR between 2RR or 2FR, 2RL
Or interpose 10FR and 10RL. The two pressure reducing pumps 11A and 11B also serve as one pump motor. In addition, each pressure reducing control valve 10FL, 10RR or 10FR, 1
Reservoirs 18A and 18B for preventing interference are connected between ORL and the decompression pumps 11A and 11B.

Each of these pressure control valves is a two-position switching valve which is switched by a drive signal from a control unit to be described later. For fail-safe operation, for example, the master cylinder on-off valves 6A and 6B are always opened and increased. The pressure pump on-off valves 7A and 7B are normally closed, the pressure increase control valves 8FL and 8RR or 8FR and 8RL are always open, and the pressure reduction control valve 10
FL, 10RR or 10FR, 10RL are always closed,
Each solenoid 6A _sol , 6B by the drive signal in the first period
_sol , 7A _sol , 7B _sol , 8FL _sol , 8RR
_sol , 8FR _sol , 8RL _sol , 10FL _sol , 10
RR _sol, 10FR _{so l,} when 10RL _sol is energized, switched to the reverse of the opening and closing state. The pressure increasing pump 3 and the pressure reducing pumps 11A and 11B are also driven and controlled by drive signals from the control unit.

Accordingly, in this braking fluid pressure circuit, when controlling the braking force for performing the vehicle behavior control described later, the braking fluid pressure (hereinafter also referred to as wheel cylinder pressure) of each of the wheel cylinders 2FL to 2RR is increased. In this case, for example, the master cylinder on-off valves 6A and 6B are closed,
The pressure increasing pump 3 is driven in a state where the pressure increasing pump intermittent valves 7A and 7B are open, and the generated pressure is controlled by the pressure reducing control valves 10FL to 10FL.
10RR is controlled to open to discharge the brake fluid in each wheel cylinder 2FL-2RR.

The opening control of each of the pressure increase control valves 8FL to 8RR and the pressure reduction control valves 10FL to 10RR will be described later.
Further, in order to reduce the reaction force to the brake pedal 4, when the brake pedal 4 is depressed, the master cylinder on-off valves 6A and 6B may be opened. Also, increasing the braking force and increasing the braking fluid pressure (wheel cylinder pressure) are the same as reducing the braking force and decreasing the braking fluid pressure (wheel cylinder pressure). Hereafter, both are treated synonymously.

On the other hand, as shown in FIG. 2, each of the wheels 1FL to 1RR has a corresponding wheel speed in order to detect a wheel speed (hereinafter, also referred to as a wheel speed) corresponding to the rotation speed of the wheel. The limit is a wheel speed sensor 12FL that outputs a signal.
12RR is installed.

The vehicle includes a yaw rate sensor 13 for detecting the actual yaw rate dψ generated in the vehicle, a steering angle sensor 14 for detecting the steering angle θ of the steered wheels from the steering angle of the steering wheel, and an acceleration sensor 15 for detecting acceleration and longitudinal acceleration, the or line pressure sensor 16 for detecting the line pressure P _MC of two systems, for detecting a brake pedal stroke η detects the depression state of the brake pedal 4 as needed A brake stroke sensor 19 and the like are attached, and detection signals of each sensor and switch are all input to a control unit 17 described later. The actual yaw rate dψ from the yaw rate sensor 13 and the steering angle θ from the steering angle sensor 14 have, for example, positive and negative directions, but between them, for example, the steering when the steering wheel is turned to the right. The direction and the direction of the clockwise yaw rate generated at that time are set so as to match each other. In the present embodiment, the steering angle θ> 0 and the yaw rate dψ> 0 in the left turn are set. is there.

The brake stroke sensor 19
Is a theoretical signal "0" indicating an OFF state when the brake pedal is not depressed, and is a digital signal which increases stepwise as the stroke of the brake pedal increases.

The control unit 17 receives a detection signal from each of the above-described sensors and switches and outputs a control signal to each of the switching valves, and a control signal output from the microcomputer. And a drive circuit for converting the control signal to a drive signal for each control valve solenoid. The microcomputer includes an input interface circuit having an A / D conversion function, an output interface circuit having a D / A conversion function, an arithmetic processing unit including a microprocessor unit MPU, and the like.
The storage device includes an OM, a RAM, and the like. In addition,
The microcomputer outputs a reference rectangular wave control signal of pulse width modulated digital data, and each drive circuit is configured to merely convert and amplify it to a drive signal suitable for each actuator operation. ing.

In the microcomputer, not only the generation and output of the main control signals necessary for the various controls as described above, but also the drive control signals for the pressure reducing pump required for the pressure reducing control in the vehicle behavior control, for example. In addition, control signals to the actuator relay switch element that controls the power supply to the actuator itself are also generated and output in parallel.

Next, the operation will be described.

FIGS. 2 to 5 show flowcharts of an example of a control program executed by the controller. This process is performed by a periodic interrupt at a fixed time interval in an operation system (not shown).

[Vehicle Behavior Control] FIGS. 2 and 3 are flowcharts for performing vehicle behavior control.

In step 101, the steering angle θ, the longitudinal and lateral accelerations Xg and Yg, and the yaw rate dψ are fetched from various sensors indicating the vehicle speed and other running conditions.

In step 102, the side slip acceleration ddβ of the vehicle is calculated from the lateral acceleration Yg, the pseudo vehicle speed Vi, and the yaw rate γ by the following equation.

Ddβ = Yg−V · γ In step 103, a reference first target yaw rate dψ ^* ₀ is calculated from the steering angle θ and the pseudo vehicle speed Vi.

In step 104, the maximum yaw rate dψ ^* max that can be achieved on the road surface is calculated by the following equation.

Dψ ^* max = K · μ / V At step 105, the absolute value of the first target yaw rate dψ ^* ₀ set at step 103 and the maximum yaw rate dψ ^* max set at step 104 are compared, and By selecting, the value obtained by applying the limit is set as the second target yaw rate d１ ^* ₁ .

In step 106, an understeer state judgment flag us described later in steps 201 to 207 is set.

In step 107, if the steer state is judged to be understeer by the us flag, step 10
At 8, the target yaw rate dψ ^* to be the reference for control
₂ is the first target yaw rate dψ ^* ₀ . If the us flag indicates that the vehicle is in the oversteer state, the target yaw rate dψ ^* ₂ to be controlled is set to the second target yaw rate dψ ^* ₁ in step 109.

In step 110, the first-order lag processing is performed by the following equation.

Dψ ^* ₃ = f (t ₀ , dψ ^* ₂ ) In step 111, a correction is made based on the slip angle β and the vehicle skid speed dβ.

Dψ ^* ₄ = f (dψ ^* ₃ , β, dβ) In step 112, the target yaw momentum dψ
^* ₄ and a corrected yaw momentum based on a deviation between the actual yaw momentum dψ and a control amount are calculated.

In step 113, braking force control is performed based on the calculated control amount.

That is, in step 101, the steering angle θ, the longitudinal and lateral accelerations Xg, Yg, and the yaw rate dψ are fetched from various sensors representing the wheel speed and other running conditions. Further, a pseudo vehicle speed Vi is calculated. In the present embodiment, a filter is applied to the wheel speed Vw of each wheel, Vwfi (i = 1 to 4) closer to the vehicle speed is calculated for each wheel, and each Vwfi is determined according to conditions such as braking / non-braking. Vw closest to the vehicle speed by selecting the largest one from
f (referred to as a vehicle-side intermediate value), and a method used in a normal ABS for obtaining the pseudo vehicle speed Vi based on the Vwf, and a value obtained by integrating the input values of the front and rear G sensors. To calculate the pseudo vehicle speed Vi. Alternatively, the road surface friction coefficient μ may be estimated from the mean square of the G sensor or from Yg.

Next, at step 102, the side slip acceleration ddβ of the vehicle is calculated from the lateral acceleration Yg, the pseudo vehicle speed Vi, and the yaw rate γ. The vehicle side slip speed dβ is calculated by integrating the vehicle side slip acceleration d (dβ).
Is calculated as the ratio dβ / Vi of the pseudo vehicle speed Vi, which is the longitudinal speed of the vehicle, and the side slip speed dβ of the vehicle.

In step 103, a first target yaw rate dψ ^* _{0 as} a reference is calculated from the steering angle θ and the pseudo vehicle speed Vi. First target yaw rate d ^*
₀ is a yaw rate realized when a predetermined cornering force is exerted on each wheel and neutral steer is obtained, and is calculated by having a map determined from the steering angle θ and the pseudo vehicle speed Vi. May be.

In step 104, the target can be achieved on the road surface.
Maximum yaw rate dψ^*max to dψ ^*max = K ・ μ / V
Calculation. Here, the proportionality constant K is closer to 1 than 1
It is a large constant. In the present control device, the road surface
Since the effect can be exhibited at the turning limit of μ,
When Yg representing the road surface μ is defined as a μ value, dψ^*max = K ・
Yg / V may be used.

At step 105, the absolute value of the first target yaw rate dψ ^* ₀ is compared with the absolute value of the maximum yaw rate dψ ^* max, and the smaller one is selected ^. _Let it be ₁ .

In step 106, an understeer state judgment flag us is set. If the us flag indicates that the steering state is understeer, the target yaw rate dψ ^* ₂ to be controlled is changed to the first target yaw rate dψ ^*.
_Set to ₀ . Here, the meaning of this value can be attained if the absolute value is dψ ^* ₁₀ which is larger than the second target yaw rate dψ ^* ₁ limited by the road surface friction coefficient.

In steps 107 to 109, if the us flag indicates that the vehicle is in the oversteer state, the target yaw rate dψ ^* ₂ to be controlled is set to the second target yaw rate dψ ^* ₁ .

In steps 110 to 113, the target yaw rate set in this way is corrected by first-order lag processing, a slip angle and an angular velocity, and a corrected yaw moment is calculated by feedback control according to the target yaw rate and the actual yaw rate. , To perform the braking force control to realize it.

[0065] Here, the first-order lag system operation in step 110, using a common time constant ^{_{t 0, dψ * 3 = dψ}} * 2 / (1 + t 0 S) S: a Laplace operator. As a result, the change in the target yaw rate at the time of switching can be reduced, and the influence of switching to the vehicle behavior can be reduced.

[Understeer State Determination] FIG. 4 is a flowchart showing understeer state determination.

In step 201, it is determined whether or not moment control is being performed based on a flag vdc indicating whether or not the correction moment control is being performed in steps 301 to 309 in FIG. If the control is not being performed, the process proceeds to step 203, where vdc =
The process proceeds to step 202 during the ON moment control.

In step 202, it is determined whether or not the us flag is ON. If YES, the process proceeds to step 203, and if NO, the process proceeds to step 206.

In step 203, it is determined whether dψ> 0. If YES, the process proceeds to a step 205, and if NO, the process proceeds to a step 204.

In step 204, it is determined whether dψ <dψ ^* _4. If YES, the process proceeds to step 206, where
If NO, proceed to step 207.

In step 205, it is determined whether dψ> dψ ^* _4. If YES, the process proceeds to step 206, where
If NO, proceed to step 207.

At step 206, the us flag is turned off.
And

At step 207, the us flag is turned ON.

That is, step 301 in FIG.
It is determined whether or not the moment control is being performed based on a flag vdc indicating whether or not the correction moment control performed in step 309 is being performed. Here, when the moment control of vdc = OFF is not being performed, the process proceeds to step 203 to always determine the steer state because the vehicle is in a straight running state, a turning initial state, and a steady turning state in a steady and stable state so far. .

On the other hand, during the moment control of vdc = ON, in order to increase the target yaw rate for realizing the under-suppression control according to the present invention only in the under-steer state at the beginning of turning, it is determined by the us flag whether or not a steady state has been achieved. Therefore, the process proceeds to step 202. This is because even if the actual yaw rate and the target yaw rate are related to each other in the under state after the vehicle is once in the oversteer state, the vehicle is excessively turned by the under suppression control in a transitional movement state such as a lane change. When the target yaw rate is too large, overshoot occurs and the vehicle again enters an unstable oversteer state. Therefore, when the understeer state is determined, when the moment control is started from the steady state, if the us flag becomes an oversteer state in which the actual yaw rate is larger than the target yaw rate, the us flag is prohibited until the moment control ends and a stable steady state is reached. The us flag is set in the OFF state. Also, here, the vdc_c counter in Steps 301 to 309 described later is a waiting time when the yaw rate deviation becomes small and almost coincides and becomes stable, and this represents a stabilizing time until the steady state is reached. The present invention has a function of suppressing a hunting phenomenon accompanying the switching of the target yaw rate according to the present invention. Accordingly, if the us flag is OFF, the process proceeds to step 206, and the us flag remains OFF.

On the other hand, in step 202, the us flag is set to O
If the answer is N, steps 203 to 2 are performed to determine whether or not the state has changed to the oversteer state.
Go to 05.

In the following steps 203 to 205, whether or not the vehicle is in the oversteer state is determined by comparing the signed actual yaw rate ψ with the target yaw rate dψ ^* ₄ or dψ ^* ₃ limited by the road surface friction coefficient. Judge.

That is, when dψ> 0 and dψ> dψ ^* _{4, when} dψ <0 and dψ <dψ ^* ₄ , it is determined that the state has changed to oversteer, and the routine proceeds to step 206, where the us flag is set to OFF. On the other hand, if the judgment is not oversteer, step 20
At 7, the us flag remains set to ON.

[Modified yawing moment control] FIG. 5 is a flowchart of the modified yawing moment control performed in steps 301 to 309.

In step 301, the deviation of the yawing momentum is calculated by the following equation.

{D} = dψ−dψ ^* _{4 In} step 302, it is determined whether or not the absolute value of the deviation {d} is larger than the set value A. If YES, proceed to step 307, and if NO, proceed to step 303. move on.

In step 303, it is determined whether or not vdc_c is larger than 0.
04, if NO, proceed to step 305.

In step 304, vdc_c is decremented.

At step 305, the moment control operation flag vdc is set to OFF.

In step 306, {d} = 0 is set.

In step 307, a moment control end counter vdc_c is set to X.

At step 308, the moment control operation flag vdc is set to ON.

At step 309, a corrected yawing moment ΔM is calculated.

That is, a flag vdc is set which indicates whether the modified moment control is being controlled. Further, the vdc_c counter in steps 301 to 309 is a waiting time when the yaw rate deviation becomes small and almost coincides and becomes stable, and represents a stabilizing time until the steady state is reached.

First, in step 301, a deviation △ ψ which is a difference between the actual yaw rate dψ and the target yaw rate dψ ^* _4.
Is calculated. Next, in step 302, it is determined whether or not the absolute value of △ ψ is larger than a set value A close to zero. If it is larger than the set value A, it means that the moment control is still being performed in an unstable vehicle motion state.
7, the moment control end counter vdc_c
Is set to a set value X at which the vehicle is stabilized and does not enter the control state again. Then, in step 308, an operation flag vdc indicating that the moment control operation is being performed is set to ON, and in step 309, a correction moment △ M is calculated by multiplying the deviation △ ψ by a control gain.

On the other hand, in step 302, the deviation △ ψ
Is smaller than the set value, the routine proceeds to step 303, where the counter vdc_c is zero, so it is determined whether or not the set time is stable. If this is zero, it is determined that the vehicle motion has become stable, and in step 305, the moment control operation flag vdc is set to OFF. On the other hand, if it is still larger than zero in step 303, the moment control flag vdc is turned on.
Leave as is.

In the next step 306, the control operation frequency when the deviation of the yawing momentum is equal to or less than the predetermined value is reduced, and the deviation equal to or less than the set value A is cleared in order to cope with the error of the sensor. FIG. 7 shows a time chart when this control is executed.

[Regarding the yawing motion at the time of operating the steering wheel] FIG. 6A is a time chart of the steering angle θ, and FIG.
Is a time chart showing the ON / OFF state of the us flag, and (c) is a time chart showing the change in the yawing momentum of the present invention. (D) shows the change in yaw momentum when the conventional technology is applied, and (e) shows the change in yaw momentum of a vehicle to which no technology is applied. Here, in the time chart showing the change of each yawing momentum, a thick line is peculiar to the present invention, a solid line shows a target yawing momentum, and a dashed line shows an actual yawing momentum generated in an actual vehicle.

When the driver operates the steering wheel, in a vehicle to which no technology is applied, unstable behavior such as spin occurs when the maximum yawing momentum is exceeded. Next, in the prior art, although a large change in the yawing momentum such as spin is suppressed, the inward moment of turning is small by regulating the yawing momentum to the maximum value, and the under feeling tends to appear strongly. In the present invention, when the us flag (understeer flag) is ON, the under tendency is suppressed by controlling using the first target yawing momentum dψ ^* ₀ that is larger than the yawing momentum maximum value dψ ^* max. When the us flag is turned off, maximum value regulation is performed to suppress oversteer similarly to the related art. As a result, a large target value is set in the under-state, the under-steer state is eliminated early, and the over-steer state that occurs thereafter is switched to a target value that can be achieved on the actual road surface, thereby suppressing the over-steer state early. And
Stable traveling can be achieved.

Next, the effects will be described.

As described above, according to the embodiment of the present invention, the theoretical yawing momentum calculated from a dry road surface equivalent or a two-wheel model is used to calculate the steering angle θ and the vehicle speed Vi.
Target yaw momentum dψ ^* ₀ calculated based on
And calculating a steady-state maximum yaw momentum dψ ^* max based on the road friction state detection value detected or estimated by the road friction coefficient state detection estimating means or the estimated value, and calculating the first target A second target yawing momentum dψ ^* _{1 in} which the yawing momentum dψ ^* ₀ is limited by the maximum value dψ ^* max is calculated, and the target yawing momentum is determined by the first target yawing momentum or at least the second target when the understeer state is determined. The target yaw momentum is set to be larger than the yaw momentum. On the other hand, when the oversteer state is determined, the target yaw momentum is set to the second target yaw momentum dψ ^* ₁ , and the target yaw momentum is switched. Can be improved.

(Other Embodiments) In the first embodiment, an example in which the yawing momentum of the vehicle is controlled by the brake control is shown. However, the yawing momentum is controlled by other control such as the four-wheel steering control and the traction control. It can also be applied to systems.

[Brief description of the drawings]

FIG. 1 is a diagram showing a brake circuit for controlling a yawing momentum according to a first embodiment.

FIG. 2 is a flowchart illustrating a vehicle behavior control process according to the first embodiment.

FIG. 3 is a flowchart illustrating a vehicle behavior control process according to the first embodiment.

FIG. 4 is a flowchart illustrating an understeer state determination process according to the first embodiment;

FIG. 5 is a flowchart illustrating a correction moment control process according to the first embodiment.

FIG. 6 is a time chart showing the operation of the first embodiment and the operation of the conventional technique.

FIG. 7 is a time chart showing the operation of the first embodiment.

[Explanation of symbols]

Reference Signs List 1 brake pedal 2 booster 3 reservoir 4 master cylinder 5 motor 6,7 pump 8,9 reservoir 10,20 left and right front wheel 30,40 left and right rear wheel 11,21,31,41 wheel cylinder 12,22,32,42 inlet valve ( 13, 23, 33, 43 Outlet valve (electromagnetic) 50 Controller 51, 52, 53, 54 Wheel speed sensor 55 Vehicle acceleration sensor 56 Yaw rate sensor 57 Steering angle sensor 58 Brake SW 59 M / C pressure sensor 70 Accumulator 71 Motor 72 Pump

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) B62D 137: 00 F term (Reference) 3D032 CC17 CC18 DA03 DA23 DA24 DA25 DA29 DA33 DA39 DA82 DA93 DC08 DC09 DC11 DC21 DC33 DD01 DD17 DE06 EA04 EB16 FF01 FF08 GG01 3D045 BB40 EE21 FF42 GG10 GG25 GG26 GG27 GG28 3D046 BB21 EE01 HH08 HH16 HH21 HH23 HH25 HH26 HH36 HH46

Claims (5)

[Claims] 1. An actual yawing momentum detecting means for detecting a yawing momentum actually generated in a vehicle; an input physical quantity detecting means detecting an input acting on the vehicle or a physical quantity occurring in the vehicle; Target yawing momentum calculating means for calculating a target yawing momentum to be achieved by the vehicle based on an input detection value acting on the vehicle detected by the detecting means or a physical value detected in the vehicle; and the target yawing momentum calculating means. A yaw momentum control device for a vehicle, comprising: a target yaw momentum control device that performs control so that the actual yaw momentum detected by the yaw momentum detection device matches the target yaw momentum calculated in the above. Road surface friction coefficient state detection and estimation means for detecting or estimating the state of the friction coefficient, The target yawing momentum calculating means includes a first target yawing momentum calculating means based on at least a steering wheel angle and a vehicle speed; and a road surface friction state detection value detected or estimated by the road surface friction coefficient state detection estimating means or an estimated value thereof. A yawing momentum maximum value calculating means for calculating a maximum value of the yawing momentum that can be steadily realized based on the second target yawing momentum calculating means for limiting the first target yawing momentum by the maximum value; Steering state determination means for determining whether the actual yawing momentum is an understeer state smaller than the target yawing momentum or an oversteer state larger than the target yawing momentum; and the target yawing momentum is a first target yawing momentum or at least when the understeering state. Second target yaw momentum And a target yawing momentum switching means for setting the target yawing momentum to be larger than the target yawing momentum, while setting the target yawing momentum to a second target yawing momentum when the vehicle is in the oversteer state. 2. The vehicle yawing momentum control device according to claim 1, wherein the road surface friction state detection and estimation means includes a lateral acceleration detection means for detecting a lateral acceleration acting on the vehicle. Yaw momentum control device. 3. The yaw momentum control device for a vehicle according to claim 2, wherein the steering state discriminating means detects or estimates the actual yawing momentum and the road friction state detected or estimated by the road friction coefficient state detection estimating means. A yaw momentum control device for a vehicle, wherein a steering state is determined by comparing a second target yaw momentum limited by a maximum value of a yaw momentum that can be steadily realized based on the value. 4. The yaw momentum control device for a vehicle according to claim 1, wherein the target yawing momentum switching means sets the first time when the steer state determination means ends oversteer determination and makes understeer determination. A yaw momentum control device for a vehicle, wherein a second target yaw momentum is set as a control target yaw momentum without switching to the target yaw momentum. 5. The yaw momentum control device for a vehicle according to claim 1, wherein the target yaw momentum switching means switches the target yaw momentum according to a steer state, and then filters the target yaw momentum to control the target yaw momentum. A yaw momentum control device for a vehicle, characterized in that: