JPH0747853A - Control device for vehicle - Google Patents

Abstract

PURPOSE:To change a direction of a vehicle when a driver operates a steering wheel further in a turn direction with lateral force of a wheel in a limit condition while compatibly attaining both ensuring turnability in the beginning of turning and preventing generation of a spin condition of the vehicle during turning. CONSTITUTION:Based on two wheel model, a target yaw rate Yt is set, and on-vehicle equipment is feedback controlled so that the actual yaw rate agrees with the target yaw rate. A limit time detecting means 64 for detecting the time when lateral force of a wheel is in a limit, and the first target yaw rate correcting means 65 for correcting the target yaw rate Yt so as to decrease, when lateral force of the wheel is in the limit, are provided. Further, the second target yaw rate correcting means 66 for correcting the target raw rate Yt, when further increased a steering angle in a condition that lateral force of the wheel is in the limit, so as to be changed in a condition of small change ratio according to increase of a steering angle, as compared with the time when lateral force of the wheel is not in the limit, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle controller for feedback controlling an on-vehicle device so that an actual yaw rate matches a target yaw rate.

[0002]

2. Description of the Related Art Conventionally, as a vehicle control device, as disclosed in, for example, Japanese Patent Publication No. 4-68167, a steering angle sensor for detecting a steering angle, a vehicle speed sensor for detecting a vehicle speed, and both of the above sensors. A target yaw rate setting means for setting a target yaw rate from the steering angle and the vehicle speed detected by, a yaw rate sensor for detecting an actual yaw rate generated in the vehicle body, and a clutch means provided in the power transmission path,
A so-called yaw rate feedback control device is known in which the clutch means is operated to adjust the amount of torque transmission to each drive wheel so that the actual yaw rate matches the target yaw rate. This yaw rate feedback control device can freely change the steering characteristic of the vehicle, and can exert effects such as compensation of the response delay of the vehicle and suppression of the influence of disturbance such as cross wind.

[0003]

In such a yaw rate feedback control device, the target yaw rate is usually set based on the two-wheel model.
In this case, the friction limit between the wheels and the road surface cannot be taken into consideration, and an excessive yaw rate becomes a target at the turning limit, and as a result, the vehicle exhibits oversteering characteristics. Because the attitude of the vehicle is determined by the yaw angle and the turning angle that are determined by the generated yaw rate,
This is because the turning angle depends on the centripetal force during turning, and the centripetal force has a limit due to the friction between the wheel and the road surface. An ordinary vehicle has an equilibrium point due to its balance and is set so as to exhibit understeering characteristics. However, in a vehicle that performs yaw rate feedback control, the yaw rate can be set freely, so if a target yaw rate that does not consider the friction limit between the wheels and the road surface is set, the centripetal force does not increase and the turning angle becomes constant. On the other hand, there is a problem that the yaw angle increases and it is easy to fall into a spin state in which only the attitude of the vehicle changes.

However, if the environment such as the friction coefficient of the road surface (hereinafter referred to as μ if necessary) is constant, it is possible to set the target yaw rate and thus the steering characteristics in advance, but it is possible to use the vehicle. The environment to be exposed varies from high μ road to ice burn, so it cannot be narrowed down to one. For example, when the target yaw rate is set in accordance with the turning of about 0.3 gravity acceleration which is the friction limit on the low μ road, a strong understeering characteristic is shown on the high μ road,
Turnability becomes worse.

Therefore, in view of such a point, the present inventors set the target yaw rate based on the two-wheel model, and at the same time, the friction limit between the wheels and the road surface during turning, that is, the lateral force of the wheels, is set. Proposing a vehicle control device that can both ensure the turning performance at the initial stage of turning and prevent the occurrence of the spin state of the vehicle during turning by changing the target yaw rate before and after reaching the limit We are doing (Japanese Patent Application 5-1
70517 specification and drawings). That is, the proposed control device reduces the target yaw rate when the lateral force of the wheel becomes the limit by the limit time detection means that detects when the lateral force of the wheel becomes the limit. Target yaw rate correction means for correcting the

On the other hand, even when the lateral force of the wheels is in the limit state, the driver may further operate the steering wheel in the turning direction. This operation is based on the demand that it is desired to change only the direction of the vehicle even if it is impossible to change the traveling direction of the vehicle due to the sideslip of the wheels. However, in the above-mentioned proposal, the target yaw rate is corrected by the target yaw rate correction means when the lateral force of the wheel becomes the limit, and the target yaw rate is corrected by the target yaw rate correction means. It does not increase as the steering angle of the wheels increases, and cannot meet the driver's demand.

The present invention has been made in view of the above points, and an object of the present invention is to further improve the above-mentioned proposal to secure the turning ability at the initial stage of turning and to prevent the turning. When the driver further operates the steering wheel in the turning direction while the lateral force of the wheels is in the limit state while achieving both prevention of the spin state of the vehicle, the direction of the vehicle is changed according to the driver's request. It is intended to provide a vehicle control device that can change

[0008]

In order to achieve the above object, the invention according to claim 1 sets a target yaw rate on the basis of a two-wheel model, and an in-vehicle device is set so that an actual yaw rate matches the target yaw rate. In a control device for a vehicle that performs feedback control, a limit time detection unit that detects when the lateral force of the wheel is at its limit, and the target yaw rate when the lateral force of the wheel is at the limit by the detection result of the detection unit. The first target yaw rate correcting means for correcting the steering angle, the steering angle detecting means for detecting the steering angle of the steered wheels, the limit time detecting means and the steering angle detecting means, and the lateral force of the wheel is received. When the steering angle further increases in the limit state, the target yaw rate is corrected so that the rate of change with the increase of the steering angle is smaller than that when the lateral force of the wheel is not the limit. A configuration and a second target yaw rate correcting unit.

The invention according to claim 2 is a subordinate to the invention according to claim 1, and shows a specific mode of the limit time detection means and the first target yaw rate correction means which are the components thereof. That is, the limit time detection means has a lateral acceleration calculation unit that calculates a lateral acceleration calculation value from the steering angle of the steered wheels and the vehicle speed,
The first target yaw rate correction is for detecting the limit time of the lateral force of the wheel based on the difference between the lateral acceleration calculation value calculated by the calculation unit and the lateral acceleration actual measurement value detected by the lateral acceleration sensor. The means corrects the target yaw rate in inverse proportion to the difference between the calculated lateral acceleration value and the actually measured lateral acceleration value.

Here, when the lateral force of the wheel reaches the limit, 2
In correcting the target yaw rate set based on the wheel model so as to be small, the target yaw rate is corrected in inverse proportion to the difference between the lateral acceleration calculated value and the lateral acceleration measured value as in the invention of claim 2. In this case, since the steering angle element is included in both the numerator and the denominator of the target yaw rate calculation formula, it is difficult for the target yaw rate to decrease even if the steering wheel is returned from the state where the lateral force of the wheel is at its limit. The invention according to claim 3 is to solve this.

That is, the invention according to claim 3 sets a target yaw rate on the basis of a two-wheel model, and in a vehicle control device for feedback controlling an on-vehicle device so that an actual yaw rate matches the target yaw rate, And a target yaw rate correction means for correcting the target yaw rate to be small when the lateral force of the wheels becomes the limit based on the detection result of the detection means. Equipped with. The limit time detection unit has a lateral acceleration calculation unit that calculates a lateral acceleration calculation value from the steering angle of the steered wheels and the vehicle speed, and the lateral acceleration calculation value calculated by the calculation unit and the lateral acceleration sensor are detected. The target time limit of the lateral force of the wheel is detected based on the difference between the measured lateral acceleration and the target yaw rate correction means, which is inversely proportional to the difference between the calculated lateral acceleration and the measured lateral acceleration. , The target yaw rate is corrected. Further, when the steering angle is reduced while the lateral force of the wheels is at the limit, the steering angle detecting means for detecting the steering angle of the steered wheels, the signals from the limit time detecting means and the steering angle detecting means are received, and The target yaw rate correction means is provided with a correction correction means for performing correction while keeping a constant difference between the calculated lateral acceleration value and the actually measured lateral acceleration value.

[0012]

With the above construction, in the invention according to claim 1,
In the initial stage of turning, the vehicle-mounted device is feedback-controlled so that the actual yaw rate matches the target yaw rate set based on the two-wheel model, so that the vehicle can smoothly turn in the turning direction. Then, when the friction between the wheel and the road surface becomes the limit during turning, that is, when the lateral force of the wheel becomes the limit, that time is detected by the limit time detection means, and the signal of the detection means is received. The first target yaw rate correction means corrects the target yaw rate small, and feedback control is performed so that the corrected target yaw rate matches the actual yaw rate. Therefore, the actual yaw rate or yaw angle does not become excessive, and the vehicle does not fall into the spin state.

In addition, when the driver further operates the steering wheel in the turning direction in a state where the lateral force of the wheels is at the limit, the target yaw rate is changed by the second target yaw rate correction means as the steering angle increases. The ratio is corrected so as to change in a smaller state than when the lateral force of the wheel is not the limit, and feedback control is performed so that the actual yaw rate matches the corrected target yaw rate. As a result, the direction of the vehicle can be changed while reflecting the driver's intention while preventing the occurrence of the spin state of the vehicle.

According to the third aspect of the present invention, the target yaw rate is corrected by the target yaw rate correcting means in inverse proportion to the difference between the calculated lateral acceleration value and the actually measured lateral acceleration value when the lateral force of the wheel reaches the limit. Even when the steering angle element is included in both the numerator and the denominator of the target yaw rate calculation formula, when the driver operates the steering wheel in the returning direction from the state where the lateral force of the wheel is at the limit, the correction correction means The difference between the lateral acceleration calculated value and the lateral acceleration measured value is kept constant,
Since the target yaw rate correction means corrects the target yaw rate based on this, the target yaw rate decreases as the steering angle decreases.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention applied to a torque distribution control device for a four-wheel drive vehicle. In this figure, 1 and 2 are left and right front wheels, 3 and 4 are left and right rear wheels, 5 is an engine, and the output of the engine 5 is transmitted equally to the front wheel side and the rear wheel side. Input to the transfer 6 having a center differential via the transmission 7.

A front differential 12 is connected to the transfer 6 via a front wheel side propeller shaft 11, and left and right front wheels 1 and 2 are connected to the front differential 12 via drive shafts 13, respectively. A rear differential 15 is connected to the transfer 6 via a rear wheel side propeller shaft 14, and the rear differential 15 is connected to the left and right rear wheels 3, 3.
4 are connected to each other via a drive shaft 16.

Further, reference numerals 21, 22, 23 and 24 denote brake devices provided on the respective wheels 1 to 4, and the hydraulic pressure (brake pressure) supplied to these brake devices 21 to 24 is a brake hydraulic circuit 25. Independently controlled by. Reference numeral 26 is a throttle valve provided in the intake system of the engine 1, 27 is a throttle motor for adjusting the opening of the throttle valve 26, and the throttle motor 27 is controlled by an engine controller 28. The engine controller 28 receives an accelerator signal from an accelerator sensor 29 that detects an accelerator operation amount of the driver, and outputs an operation control signal to the throttle motor 27, so that the throttle valve 26 corresponding to the accelerator operation amount of the driver. The engine output is changed so that the engine output torque required to change the torque distribution is obtained in response to the control signal from the torque distribution controller 30.

Further, 31 is a rudder angle sensor as rudder angle detecting means for detecting the rudder angle of the front wheels 1 and 2 which are steered wheels, and 32.
Is a lateral acceleration sensor for detecting the lateral acceleration of the vehicle, 3
3 is a longitudinal acceleration sensor that detects the longitudinal acceleration of the vehicle, 34 is a wheel speed sensor that detects the rotational speeds of the wheels 1 to 4, 35 is a rotational speed sensor that detects the engine rotational speed, 3
6 is a brake pressure sensor that detects the brake pressure of each of the wheels 1 to 4 (brake devices 21 to 24), 37 is a gear position sensor that detects the gear position (shift stage) of the transmission 7, and 38 is the boost pressure of the engine 5. A boost pressure sensor 39 for detecting a yaw rate sensor 39 for detecting a yaw rate of the vehicle.
The signal of 39, together with the signal of the accelerator sensor 29,
It is input to the torque distribution controller 30. The torque distribution controller 30 controls the torque distribution to the wheels 1 to 4 by using the engine controller 28 and the brake hydraulic circuit 25 (more specifically, pressure increasing solenoid valves 46 and 47 and pressure reducing solenoid valves 48, which will be described later). 49) is controlled.

Next, the structure of the brake hydraulic circuit 25 will be described with reference to FIG.

In FIG. 2, 41 is a first hydraulic line for the brake device 21 of the left front wheel 1, 42 is a second hydraulic line for the brake device 22 of the right front wheel 2, and each hydraulic line 41, Pressure control valves 43 and 44 for controlling the supply of the brake pressure are provided in the valve 42, respectively.

In each of the pressure control valves 43 and 44, cylinders 43a and 44a are divided into variable volume chambers 43c and 44c and control chambers 43d and 44d by pistons 43b and 44b. The variable volume chambers 43c and 44c use the brake pressure generated in the master cylinder 45 as the brake device 2
1 and 22 are supplied. The piston 43b,
44b is biased by springs 43e, 44e in the direction in which the volumes of the variable volume chambers 43c, 44c increase, and resists the bias of the springs 43e, 44e by the control pressure introduced into the control chambers 43d, 44d. The variable volume chambers 43c and 44c are moved in the direction of contraction, and the variable volume chambers 43c and 44c are moved by the contraction direction.
Check valves 43f and 44f for closing the braking pressure inlet of c
Is equipped with. Therefore, the control pressure is introduced into the control chambers 43d and 44d so that the pistons 43b and 44b move to the spring 43.
When moving against e and 44e, the master cylinder 45 and the variable volume chambers 43c and 44c are disconnected from each other, and the braking pressure generated in the variable volume chambers 43c and 44c is supplied to the brake devices 21 and 22. Will be done.

On the other hand, in order to operate the pressure control valves 43 and 44, pressure increasing solenoid valves 46 and 47 and pressure reducing solenoid valves 48 and 49 are provided, respectively. Solenoid valve for boosting pressure 4
6 and 47 are control chambers 43d and 44d of the pressure control valves 43 and 44 from the oil pump 50 via the relief valve 51.
Are arranged on the control pressure supply lines 52 and 53, and the depressurizing solenoid valves 48 and 49 are arranged on the drain lines 54 and 55 led from the control chambers 43d and 44d.
The solenoid valves 46 to 49 are controlled to open and close by a signal from the torque distribution controller 30, the pressure increasing solenoid valves 46 and 47 are opened, and the pressure reducing solenoid valves 48 and 4 are opened.
Control chamber 4 of pressure control valves 43, 44 when 9 is shut off
Control pressure is introduced to 3d and 44d, and the solenoid valve for increasing pressure 46,
The control pressure in the control chambers 43d and 44d is discharged when 47 is shut off and the pressure reducing solenoid valves 48 and 49 are opened.

The braking device 2 for the left and right rear wheels 3, 4
Although not shown in the drawings, the same structure as that of the brake devices 21 and 22 for the front wheels 1 and 2 is adopted for 3 and 24, and each brake device 21 to 24 has such a structure.
Independent braking pressure can be applied to the.

Next, the control contents of the torque distribution controller 30 will be described with reference to the flowchart shown in FIG.

In FIG. 3, after starting, first, in step S1, wait for a predetermined measurement timing,
In step S2, the various sensors 29, 31 to 39 shown in FIG.
From each signal from, the accelerator opening as a momentum, steering angle, lateral acceleration, longitudinal acceleration, each wheel speed, engine speed, brake pressure of each wheel, gear position, boost pressure, actual yaw rate of the vehicle is measured. .

Subsequently, the required torque is calculated in step S3. The calculation of the required torque is performed using a map for calculating the engine output torque, which is prepared in advance for each gear position and has the accelerator opening and the engine speed as a function. Then, in step S4, the distribution amounts of the driving torques of the four wheels 1 to 4 are set, and in step S5, the required driving torques of the wheels 1 to 4 are calculated using the distribution amounts. The distribution amount is the drive torque difference ΔT1 between the left and right wheels, as will be described later.
And the driving torque difference ΔT2 between the front and rear wheels.

Thereafter, in step S6, the engine output is controlled via the engine controller 28, and
In step S7, each wheel 1 is passed through the brake hydraulic circuit 25.
Control the brake pressure of ~ 4. In the control of the engine output, the output torques on the drive shafts 13 and 16 are set to the wheels 1 to 4
The throttle opening is controlled so that it becomes the maximum value of the required drive torque of the above.
Actual output torque to drive shafts 13 and 16 and wheels 1 to 4
The brake pressure is controlled independently for each wheel so as to give a brake torque corresponding to the difference from the required drive torque. After these both controls are completed, the process returns to step S1.

The setting of the distribution amount is performed according to the flow chart shown in FIG.

That is, first, in step S11, the target yaw rate Yt is calculated by the method described later, and in step S12, the target yaw rate Yt and the yaw rate sensor 3 are calculated.
The deviation ΔY from the actual yaw rate Y detected in 9 is calculated, and the differential value dΔY of the yaw rate deviation is calculated in step S13. This differential value dΔY is calculated by dividing the difference between the current yaw rate deviation ΔY and the previous yaw rate deviation ΔY0 by the cycle time Δt (about 7 ms). Then, in step S14, the yaw rate deviation ΔY of this time is replaced with the yaw rate deviation ΔY0 of the previous time.

Subsequently, in step S15, a dead zone having a predetermined width e1 centered at 0 is set for the yaw rate deviation ΔY, as shown in FIG. Then, in step S16, the drive torque difference ΔT1 between the left and right wheels is calculated by PD calculation of the yaw rate deviation ΔY. That is, the drive torque difference ΔT
1 is calculated by the following formula: ΔT1 = PG1 × ΔY + DG1 × dΔY. However, PG1 is a proportional coefficient, DG1
Is the differential coefficient.

Then, in step S17, the side slip angle difference dβ between the front and rear wheels is calculated. The calculation formula is dβ = | θ | − | Y × C / V |. However, θ is the steering angle, Y is the yaw rate, and V is the vehicle speed. C is a coefficient, by the following equation, C = (1 + SF × V 2) are those calculated × Lw. However, SF is a stability factor and Lw is a wheel base.

Subsequently, in step S18, the torque distribution ratio s of the front and rear wheels is calculated using a map as shown in FIG.
In this map, the torque distribution ratio s of the front and rear wheels changes according to the side slip angle difference dβ of the front and rear wheels, and a dead zone of a predetermined width e2 is provided around the time when the side slip angle difference dβ is zero. . When the torque distribution ratio s is 0, the front and rear wheels are evenly distributed, the rear wheel driving torque is maximized at +0.5, and the front wheel driving torque is set at 0, and the reverse relationship is set at -0.5. There is.

Subsequently, in step S19, the drive torque difference ΔT2 between the front and rear wheels is calculated. The calculation formula is ΔT2 = s × TRQ. That is, the driving torque difference ΔT2 between the front and rear wheels is an integrated value of the torque distribution ratio s between the front and rear wheels and the engine output torque TRQ. Then return.

In the calculation of the drive torque difference ΔT1 between the left and right wheels in the control of the distribution amount setting described above, the brake hydraulic circuit 25 (brake pressure) as an in-vehicle device so that the actual yaw rate Y matches the target yaw rate Yt. Also, the engine controller 28 (throttle opening) is feedback-controlled.

The calculation of the target yaw rate Yt, which is a characteristic part of the present invention, is performed according to the flow chart shown in FIG.

That is, first, in step S21, the measured lateral acceleration value Gl detected by the lateral acceleration sensor 32 is read, and then in step S22, the measured lateral acceleration value Gl.
Filtering is performed to remove high-frequency noise from the. This filtering process is performed by a low pass filter.

Subsequently, in step S23, a lateral acceleration calculated value Glt based on the two-wheel model is calculated. The calculation formula is Glt = {V ² / (1 + A 0 × V ² )} × θ / L (1) Here, V is the vehicle speed, θ is the steering angle, L is the wheel base, and A0 is the stability factor. In step S23, the lateral acceleration calculated value Glt is calculated from the steering angle θ and the vehicle speed V.
A lateral acceleration calculation unit 62 for calculating is calculated.

After the calculation of the lateral acceleration calculated value Glt, the lateral acceleration calculated value Glt is filtered in step S24. This filter processing is performed in order to cancel the output delay characteristic and the vehicle delay characteristic due to the steering operation with respect to the lateral acceleration measured value Gl, in addition to removing the noise.

Subsequently, in step S25, the lateral acceleration calculated value G
It is determined whether lt and the lateral acceleration measured value Gl have the same sign. The lateral acceleration calculated value Glt and the lateral acceleration measured value Gl are
The signs are opposite between turning left and turning right, but the signs of both are opposite when the steering wheel is operated in the opposite direction to the turning direction during turning. Is. Therefore, the determination in step S25 is to determine whether it is the normal turning operation state or the counter steering state.

Then, the determination in step S25 is YES.
In other words, in the normal turning operation state, in step S26, the absolute value of the lateral acceleration calculated value Glt and the lateral acceleration measured value G are obtained.
It is determined whether or not the difference between the absolute value of l and a predetermined value Gl0 or more. When the determination is NO, the correction value Ac is set to 0 in step S27, while when the determination is YES, the correction value Ac is calculated in step S28 by the following equation: Ac = K {(| Glt |-| Gl | ) -Gl0} is calculated. However, K is a positive coefficient. Then, in step S29, the correction process for the correction value Ac is performed.

On the other hand, when the determination in step S25 is NO, that is, in the counter steer state, the maximum value Acmax is set to the correction value Ac in step S30.

After setting the correction value Ac in any of the steps S27 to S30, in step S31 the correction value Ac and the pre-correction stability factor A0 are added to calculate a new stability factor A. Then, in step S32, the stability factor A after the correction is subjected to a limit process for restricting its maximum value, and then the step S32 is performed.
At 33, the target yaw rate Yt based on the two-wheel model is calculated by the following equation (2): Yt = {V / (1 + A × V ² )} × θ / L (2) Then, in step S34, the target yaw rate Yt is corrected, and then the process returns.

According to the first half of the above flow chart, that is, the control flow of steps S21 to S26,
3 to 3, the limit time detection means 64 for detecting the time when the lateral force of the wheels 1 to 4 becomes the maximum based on the difference between the lateral acceleration calculated value Glt and the lateral acceleration measured value Gl is configured. In the latter half, that is, in the control flow of steps S26, S28, S31 to S33, the stability factor A is increased when the lateral force of the wheel reaches the limit based on the detection result of the limit time detection means 64, so that the target yaw rate becomes normal. First target yaw rate correction means 65 for correction so as to be smaller than time
Is configured.

The correction process of the target yaw rate Yt in step S34 is performed according to the flowchart shown in FIG. In addition, the correction value Ac in step S29 described above
The correction process is performed according to the flowchart shown in FIG.

That is, as the correction process of the target yaw rate Yt, first in FIG. 8, the steering angular velocity Δθ and the rate of change ΔGl of the measured lateral acceleration value are calculated in step S41. The steering angular velocity Δθ is calculated by dividing the difference between the previous value and the current value of the steering angle θ detected by the steering angle sensor 31 by the cycle time. In addition, the rate of change ΔG of the lateral acceleration measured value
l is calculated by dividing the difference between the previous value of the lateral acceleration measured value Gl detected by the lateral acceleration sensor 32 and the current value by the cycle time.

Subsequently, in step S42, it is determined whether or not the steering angles θ of the front wheels 1 and 2 which are the steered wheels have the same sign as the steering angular velocity Δθ. In step S43, the absolute value of the steering angular velocity Δθ is equal to or greater than a predetermined value Δθ0 Or not. Both of these determinations determine whether or not the steering wheel is further steered by a predetermined value or more in the turning direction of the vehicle. If both of the determinations are YES, it is further determined in step S44 whether or not the absolute value of the change rate ΔGl of the measured lateral acceleration value is equal to or greater than the predetermined value ΔGl0. Here, the fact that the change rate ΔGl of the lateral acceleration measured value does not change beyond the predetermined value ΔGl0 when the steering wheel is further steered in the turning direction of the vehicle to a predetermined value or more means that the lateral force of the wheels 1 to 4 is extremely limited. It means that Therefore, step S44 has a function as a limit time detecting means for detecting the time when the lateral force of the wheels 1 to 4 reaches the limit, like step S26 in FIG. Instead of the judgment formula, step S
26 judgment formulas may be used.

When the determination in step S44 is NO, that is, together with the determinations in steps S42 and S43,
After all, when the steering angle further increases with the lateral force of the wheels reaching the limit, the coefficient K is calculated according to the vehicle speed v in step S45, and the yaw rate correction value ΔYt is calculated according to the steering angle θ in step S46. To do. Then, step S47
Is the integrated value of the coefficient K and the yaw rate correction value ΔYt (K
.DELTA.Yt) is added to the target yaw rate Yt, this is newly set as the target yaw rate Yt, and the process returns.

Here, the coefficient K increases as the vehicle speed v increases in the low vehicle speed region, and increases in the medium / high vehicle speed region.
It is set to decrease with the increase of. Also,
The yaw rate correction value ΔYt is set so as to increase linearly as the steering angle θ increases. However, the integrated value of the coefficient K and the yaw rate correction value ΔYt (K · ΔY
The corrected target yaw rate Yt obtained by adding t) is changed in a state in which the change rate with the increase of the steering angle is smaller than that when the lateral force of the wheel is not the limit.

On the other hand, when the determination at step S42 or S43 is NO, or when the determination at step S44 is YES, the target yaw rate Yt is not corrected and the routine returns.

By the correction processing of the target yaw rate Yt as described above, when the steering angle is further increased in a state where the lateral forces of the wheels 1 to 4 are maximized according to the invention described in claim 1, the above first The target yaw rate Yt corrected by the target yaw rate correction means 65 is corrected again so that the rate of change with the increase of the steering angle is smaller than that when the lateral force of the wheel is not the limit. The second target yaw rate correction means 66 is configured.

Further, as the correction processing of the correction value Ac, in FIG. 9, first, at step S51, the steering angular velocity Δθ is set.
After calculating, it is determined in step S52 whether the flag F is 1. When the flag F is 1, it means that the steering wheel is operated in the direction opposite to the turning direction of the vehicle, that is, in the returning direction.

When the determination in step S52 is NO, it is determined in step S53 whether the signs of the steering angle θ and the steering angular velocity Δθ are different, and in step S54 whether the absolute value of the steering angular velocity Δθ is equal to or greater than a predetermined value Δθ1. Each is judged. Both of these determinations determine whether or not the steering wheel has been returned to the direction opposite to the turning direction of the vehicle. When the handle is being returned, the flag F is set to 1 in step S55, and then the correction value A is set in step S56.
Set the previous value to c instead of the current value and return. On the other hand, when the handle is not returned,
In step S60, the correction value Ac remains unchanged and the process returns.

When the determination in step S52 is YES, it is determined in step S57 whether the signs of the steering angle θ and the steering angular velocity Δθ are the same. In step S58, the absolute value of the steering angular velocity Δθ is equal to or greater than the predetermined value Δθ2. Whether or not each is determined.
Both of these determinations are made after the return operation to determine whether or not the handle has passed the neutral position and has been operated for cutting. Then, when the steering wheel is being cut, after resetting the flag F to 0 in step S59,
In step S60, the correction value Ac remains unchanged and the process returns.

On the other hand, when the steering wheel has not been turned, the target yaw rate Y is determined in step S61.
It is determined whether the absolute value of the deviation between t and the actual yaw rate Y is less than or equal to a predetermined value α, that is, whether the actual yaw rate Y has converged to the target yaw rate Yt. This judgment is N
When it is O, the count CNT is reset to 0 in step S65 and then the process proceeds to step S56 while the determination is Y.
In the case of ES, the count CNT is incremented by 1 in step S62, and then it is determined in step S63 whether the count CNT is a predetermined number of times Ct or more. If the determination is NO, the process proceeds to step S56, while if the determination is YES, the count CNT is set to 0 in step S64.
After resetting, shifts to step S59.

By the correction processing of the correction value Ac as described above, the first target yaw rate correction is performed when the steering angle is reduced in a state in which the lateral force of the wheels 1 to 4 is maximized according to the invention of claim 3. Correction correction means 67 for correcting the correction value Ac with respect to the means 65, that is, keeping the difference between the calculated lateral acceleration value Glt and the measured lateral acceleration value Gl constant.
Is configured. Keeping the correction value Ac at the previous value is maintained until the steering wheel is depressed or until the actual yaw rate Y converges to the target yaw rate Yt for a predetermined time.

Next, the operation and effect of the first embodiment will be described. At the initial stage of turning, the steering angle θ is determined based on the two-wheel model.
Since the difference between the lateral acceleration measurement value Glt calculated from the vehicle speed V and the lateral acceleration actual measurement value Gl detected by the lateral acceleration sensor 32 is small, the correction value Ac is set to 0, and the target yaw rate Yt is set to the two-wheel model. Based on this, it is set to a relatively large value. Then, the drive torques of the left and right wheels are feedback-controlled so that the actual yaw rate Yt matches the target yaw rate Yt, so that the vehicle can smoothly turn in the turning direction, and the turning performance at the initial turning is improved. You can

On the other hand, when the lateral force of the wheel becomes the maximum during turning, the difference between the lateral acceleration measured value Glt and the lateral acceleration measured value Gl becomes larger than a predetermined value Gl0, and the stability factor A is at the beginning of turning. Since the target yaw rate Yt becomes smaller than that at the time when the correction value Ac is added, the target yaw rate Yt becomes smaller than that at the beginning of turning, and feedback control is performed so that the actual yaw rate Y matches the target yaw rate Yt. Therefore, the actual yaw rate Y or the yaw angle does not become excessive, the vehicle can be prevented from falling into the spin state, and the safety can be improved.

Incidentally, in the counter steer state, the correction value Ac is set to the maximum value Acmax and the target yaw rate Yt is corrected to the minimum value, so that the vehicle turns in a direction in which the turning is suppressed.

FIG. 10 shows the change characteristics of the steering angle θ, the target yaw rate Yt and the lateral acceleration measured value Gl during turning of the vehicle. In the figure, the solid line A shows the change characteristics of the steering angle θ, and the alternate long and short dash line B1 shows the correction characteristics. The solid line B2 shows the change characteristic of the target yaw rate Yt of this embodiment, and the broken line C shows the change characteristic of the lateral acceleration measured value Gl. As can be seen from this figure, in the case of this embodiment,
After the turning start t1, the target yaw rate Yt is corrected after the time t2 when the lateral force of the wheel reaches the limit, and its change characteristic B2 is
It is smaller than the conventional change characteristic B1.

The correction value Ac is set based on the difference between the lateral acceleration measured value Glt and the lateral acceleration measured value Gl. The lateral acceleration measured value Glt is a value proportional to the steering angle θ. There is (see formula (1)). Therefore, the target yaw rate Yt
Since both the numerator and the denominator in the calculation formula (2) include the element of the steering angle θ, the target yaw rate Yt becomes difficult to change as the steering angle θ increases or decreases.

On the other hand, in the present embodiment, when the steering angle θ further increases from the state where the lateral force of the wheel is at the limit, the target yaw rate Yt is corrected by the equation (2). The yaw rate correction value (K · ΔY) that increases with an increase in the steering angle θ with respect to the target yaw rate Yt
t) is added, and feedback control is performed so that the actual yaw rate Y matches the target yaw rate Yt after this addition. Therefore, the direction of the vehicle can be changed according to the steering wheel operation, reflecting the driver's intention, and the usability is improved. This means that in FIG.
When the steering angle θ increases at the 3rd point, the target yaw rate Yt also increases accordingly. Moreover, at this time, the change rate of the target yaw rate Yt with respect to the increase of the steering angle θ is smaller than that when the lateral force of the wheels is not at the limit (between time points t1 and t2), so the vehicle is in the spin state. It is possible to prevent falling.

Further, when the steering angle θ decreases from the state where the lateral force of the wheels is at the limit, that is, when the returning operation is performed, the correction value Ac and thus the stabilizer factor A are made constant by the correction processing of the correction value Ac. Since the target yaw rate Yt is maintained, the target yaw rate Yt decreases as the steering angle θ decreases, and feedback control is performed so that the actual yaw rate Y matches the target yaw rate Yt. As a result, the stability at the time of return steering can be improved.

FIG. 11 shows a four-wheel steering system for a vehicle according to a second embodiment of the present invention. The four-wheel steering system comprises a front wheel steering section 110 for steering the left and right front wheels 101, 102 and left and right rear wheels. The rear wheel steering unit 120 steers 103 and 104.

The front wheel steering unit 110 is connected to a steering shaft 111, a steering handle 112 provided at one end of the steering shaft 111, and a rack and pinion (not shown) at the other end of the steering shaft 111. The rod member 113 extending in the width direction of the vehicle, both ends of the rod member 113, and the left and right front wheels 1
A pair of left and right tie rods 11 connecting 01 and 102
The front wheels 101 and 102 are steered to the left and right by rotating the steering handle 112.

On the other hand, the rear wheel steering unit 120 includes a rod member 121 extending in the vehicle width direction, and a pair of left and right tie rods 122 and 122 connecting both ends of the rod member 121 and the left and right rear wheels 103 and 104, respectively. A hydraulic cylinder 123 having the rod member 121 as an operating rod is provided.
Pressure oil is selectively supplied to the left and right cylinder chambers in the hydraulic cylinder 123 from a hydraulic pump 124 via a control valve (not shown), whereby the rear wheels 103, 104 steer the front wheels 101, 102. The steering is performed in the same direction as the same direction or in the opposite direction and opposite phase.
The switching of the control valve is controlled by a servo controller 125, and a control signal from a main controller 126 including a micro computer or the like is input to the servo controller 125.

The main controller 126 is provided with a signal from a steering angle sensor 131 as a steering angle detecting means for detecting the steering angles of the front wheels 101 and 102 which are steered wheels, and a signal from a yaw rate sensor 132 for detecting a yaw rate of the vehicle. , A signal from a lateral acceleration sensor 133 that detects the lateral acceleration of the vehicle,
A signal from a vehicle speed sensor 134 that detects the vehicle speed from the wheel speed of the driven wheels (rear wheels), and a signal from a rear wheel steering angle sensor 135 that detects the steering angle of the rear wheels 103 and 104 from the axial displacement of the rod member 121. Is entered. Main controller 1
Reference numeral 26 sets a target yaw rate on the basis of the two-wheel model, and the rear wheel steering section 12 sets so that the actual yaw rate detected by the yaw rate sensor 132 matches the target yaw rate.
0 (servo controller 125) has a yaw rate feedback control unit (not shown) for feedback control.

In such a yaw rate feedback control unit, the calculation of the target yaw rate has the same structure as in the case of the first embodiment, and the same operation and effect can be obtained. .

[0069]

As described above, according to the first or second aspect of the present invention, the feedback control of the vehicle-mounted device is performed so that the actual yaw rate matches the target yaw rate set based on the two-wheel model. By correcting so that the target yaw rate is reduced when the lateral force of the wheels reaches the limit, it is possible to improve the turning performance in the initial stage of turning and prevent the vehicle from falling into the spin state during turning. Therefore, the safety can be improved. Moreover, when the driver further operates the steering wheel in the turning direction with the lateral force of the wheels being at the limit, the target yaw rate changes when the lateral force of the wheels is not at the limit as the rate of change with increasing steering angle. It is corrected so that it changes in a small state,
Since the yaw rate feedback control is performed, there is an effect that the direction of the vehicle can be changed while reflecting the intention of the driver while preventing the occurrence of the spin state.

According to the third aspect of the invention, similarly to the first or second aspect of the invention, it is possible to achieve both the turning ability at the initial stage of turning and the prevention of the spin state of the vehicle during turning, Moreover, when the driver operates the steering wheel in the return direction from the state where the lateral force of the wheels is at the limit, the target yaw rate decreases as the steering angle decreases and the yaw rate feedback control is performed. It also has the effect of improving stability.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a torque distribution control device for a four-wheel drive vehicle according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a brake hydraulic circuit.

FIG. 3 is a flowchart of torque distribution control.

FIG. 4 is a flow chart diagram of distribution amount setting.

FIG. 5 is a diagram showing a map used for setting a dead zone with respect to a yaw rate deviation.

FIG. 6 is a diagram showing a map used for calculating a torque distribution ratio of front and rear wheels.

FIG. 7 is a flowchart of target yaw rate calculation.

FIG. 8 is a flowchart showing a target yaw rate correction process.

FIG. 9 is a flowchart showing a correction value correction process.

FIG. 10 is a diagram showing a change characteristic of each momentum during turning.

FIG. 11 is an overall configuration diagram of a four-wheel steering system for a vehicle according to a second embodiment of the present invention.

[Explanation of symbols]

 25 Brake Hydraulic Circuit (In-Vehicle Equipment) 28 Engine Controller (In-Vehicle Equipment) 31, 131 Steering Angle Sensor (Steering Angle Detection Means) 62 Lateral Acceleration Calculator 64 Extreme Time Detecting Means 65 First Target Yaw Rate Correction Means 66 Second Targets Yaw rate correction means 67 Correction correction means 120 Rear wheel steering unit (vehicle equipment)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B62D 109: 00 111: 00 113: 00 117: 00 125: 00 127: 00 137: 00

Claims (3)

[Claims] 1. A vehicle control device that sets a target yaw rate based on a two-wheel model and feedback-controls an in-vehicle device so that an actual yaw rate matches the target yaw rate. A limit time detecting means for detecting the time, a first target yaw rate correcting means for correcting the target yaw rate to be small when the lateral force of the wheel becomes the limit based on the detection result of the detecting means, and a steering wheel steering wheel. The target yaw rate is changed when the steering angle further increases while the lateral force of the wheel is at the limit, by receiving signals from the steering angle detection means for detecting the angle, the limit time detection means and the steering angle detection means. A vehicle provided with a second target yaw rate correction means for correcting so that the change rate with the increase of the angle is changed in a smaller state than when the lateral force of the wheel is not the limit. Control device. 2. The limit time detection means has a lateral acceleration calculation section for calculating a lateral acceleration calculation value from the steering angle of the steered wheels and the vehicle speed, and the lateral acceleration calculation value and lateral acceleration calculated by the calculation section. The lateral force of the wheel is detected based on the difference between the measured lateral acceleration and the measured lateral acceleration, and the first target yaw rate correction means includes the calculated lateral acceleration and the measured lateral acceleration. 2. The vehicle control device according to claim 1, wherein the target yaw rate is corrected in inverse proportion to the difference between the target yaw rate and the target yaw rate. 3. A vehicle control device for setting a target yaw rate on the basis of a two-wheel model and feedback-controlling an in-vehicle device so that the actual yaw rate matches the target yaw rate, and the lateral force of the wheel is minimized. And a target yaw rate correction means for correcting the target yaw rate so as to reduce the target yaw rate when the lateral force of the wheel becomes the limit based on the detection result of the detection means. The detection means has a lateral acceleration calculation unit that calculates a lateral acceleration calculation value from the steering angle of the steered wheels and the vehicle speed. The lateral acceleration calculation value calculated by the calculation unit and the lateral acceleration measurement value detected by the lateral acceleration sensor are measured. The target yaw rate correction means detects the limit time of the lateral force of the wheel based on the difference between the calculated lateral acceleration and the lateral acceleration calculated value. In order to correct the rate, the steering angle detecting means for detecting the steering angle of the steered wheels, and the signals of the limit time detecting means and the steering angle detecting means are received, and the lateral force of the wheels is in a limit state. When the steering angle decreases, the target yaw rate correction means is provided with a correction correction means for performing correction while keeping a constant difference between the calculated lateral acceleration value and the actually measured lateral acceleration value. Vehicle control device.