JPH04123980A - Steering angle controller - Google Patents

Abstract

PURPOSE:To perform such a control that is less in a sense of incompatibility including drift or the like in a vehicle by constituting it to make a steering angle for a controlled system wheel controllable so as to be compensated according to a variation in engine speed, in steering angle control for steering at least one side of front wheels or rear wheels in an auxiliary manner. CONSTITUTION:An auxiliary steering angle control means A drives and controls an auxiliary steering mechanism C steering front wheels or rear wheels in an auxiliary manner on the basis of output out of a steering state detecting means B detecting the steering state of a handwheel, thereby performing a job for auxiliary steerage conformed to handwheel operation. In this case, a steering angle compensating means D is installed in the auxiliary steering angle control means A in addition. When engine speed being derected by an engine speed detecting means E is varied to some extent, a control steering angle for the front wheels or the rear wheels is made so as to be compensated according to the engine speed. With this constitution, a variation in drift or the like in a vehicle is made relievable as compared with such that compensates the steering angle by way of detecting an accelerator manipulated variable, and in the case where an understeer reduction at time of turning acceleration is promoted, such a proper control that is less in any incompartible feeling is made so as to be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a steering angle control device, and more particularly to a steering angle control device for a vehicle that performs auxiliary steering of front wheels or rear wheels based on steering wheel operation.

(Prior Art) As a steering angle control device for a vehicle, a control device has been proposed that controls the control steering angle to be corrected in the case of acceleration or deceleration during turning in a vehicle that uses an auxiliary steering mechanism ( Unexamined Japanese Patent Publication 1986
-121571 publication). With this, LJI, rear wheel steering angle control is switched by steering angle correction, and turning '-
Changes in the direction of increasing or decreasing the diameter of the vehicle'd FJ+ [) Tsunoichi U2, understeer, and tuck-in are being tried to be eliminated.

(Problem to be Solved by the Invention) However, in the above-mentioned steering angle control device, such steering angle correction is performed depending on the accelerator opening, or understeer or tuck-in behavior of the vehicle occurs due to accelerator operation. Since there is a time delay between the two, when correcting the steering angle to reduce understeer and tuck-in, if the rear wheels are controlled in accordance with the amount of accelerator operation,
The steering angle is corrected before understeer or tuck-in of the vehicle occurs, and the correction control becomes oversensitive. Oversensitive steering angle correction can cause the vehicle to wobble, causing a sense of discomfort.

An object of the present invention is to make steering angle correction during acceleration and/or deceleration consistent with the driver's feeling without making it too sensitive, and thereby to increase the effectiveness of steering angle correction with control that causes less discomfort. The aim is to provide a steering angle control device that can

(Means for Solving the Problem) For this purpose, the steering angle control device of the present invention, as shown in the concept in the first part, has a first stage of steering state detection for detecting the steering state of the steering wheel, and a steering state detection stage for detecting the steering state of the steering wheel, and a stage for detecting the steering state of the front wheel or rear wheel of the vehicle. an auxiliary steering mechanism that performs auxiliary steering at least in a direction; an engine rotational speed detection means that detects an engine rotational speed; and an auxiliary steering mechanism that provides assistance with a controlled steering angle according to the steering wheel operation based on the output of the steering state detection means. Auxiliary steering angle control means that is capable of steering control and has a steering angle correction means for correcting a controlled steering angle of a front wheel or a rear wheel in accordance with a change in the engine rotation speed detected by the engine rotation speed detection means. It is equipped with the following.

(Operation) The auxiliary steering angle control means controls the auxiliary steering mechanism for auxiliary steering of the front wheels or rear wheels based on the output from the steering state detection means that detects the steering state of the steering wheel to control the steering angle according to the steering wheel operation. However, when the engine rotation speed detected by the engine rotation detection means that detects the engine rotation speed changes, the steering angle correction means corrects the control steering angle of the front wheels or the rear wheels according to the engine rotation speed. .

Here, the engine speed changes depending on the accelerator operation, but due to the inertia of the engine itself, the engine speed is generated with a predetermined response delay with respect to the accelerator operation.

This prevents the steering angle correction from being too sensitive, and compared to a system that detects the amount of accelerator operation and corrects the steering angle, changes such as vehicle wobbling can be reduced, and it is possible to reduce changes such as vehicle wobbling during corner acceleration. Even when aiming to reduce understeer or tuck-in during deceleration, it is possible to achieve this with appropriate control with less discomfort.

(Example) Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 shows an embodiment of the steering angle control device of the present invention, in which 1 indicates the front wheels;
2 indicates the rear wheels. This embodiment shows a configuration in which not only the rear wheels but also the front wheels are actively assisted steered. Front wheel 1
By transmitting the steering input to each steering wheel (handle) 3 via the steering gear 4, main steering is enabled as usual, and the case of the steering gear 4 is stroked by the actuator 5 in the auxiliary steering mechanism. Allows for auxiliary steering up to a maximum of α degrees relative to the main steering angle. Furthermore, the stroke of the actuator 6 in the auxiliary steering mechanism of the rear wheels 2 enables auxiliary steering up to a maximum of β degrees. Here, in this example, α degree>
Assume β degree.

In addition to the above-mentioned actuator 5.6, the front/rear wheel auxiliary steering system is provided with an oil pump 7 as a pressure source common to both systems, and is further provided with a diversion valve 12 and a steering angle control valve 1.4.15. . The oil pump 7 sucks oil in the reservoir 8 and discharges it into the main circuit 9, and the diversion valve 12 distributes the oil in the main circuit 9 to the front wheel auxiliary steering circuit 10 and the rear wheel auxiliary steering circuit 11.

The above-mentioned flow dividing valve 12b connects the shuttle spool 12a to the spring 12.
+), 12C to be elastically supported in a neutral position, and pressure chambers 1.2d,
1.2e. These pressure chambers 12d, 12e
For example, orifices 1 with different diameters formed in the spool 12a
2f and 12g to the main circuit 9, and horizontal holes 12h and 12i also formed in the spool 1.2a.
and the auxiliary steering circuit 11.1 via the output capo H2j12k.
Pass it to 0. Accordingly, the degree of communication between the horizontal holes 12h and 12i and the output capos H2j and 12 is adjusted according to the stroke of the spool 12a which responds to the pressure in the pressure chambers 1.2d and 12e, respectively, and performs the following flow dividing function. shall be taken as a thing.

That is, for example, focusing on the circuit 10, the required flow rate Qf of the circuit 10 is the product Qf-8Axv of the piston pressure receiving area SA of the front wheel auxiliary steering actuator 5 and the piston moving speed V.
Further, the stroke of the actuator 5 is expressed as d,
If the front wheel steering frequency is f, the moving speed is V-2πXf
Since Xd, the required flow rate Q of the circuit 10 is Qf-3A
×2πXfXd. In addition, the required flow rate Qr of the circuit 11
The discharge amount Q of the pump 7 is also found in the same way. Q.

−Q t ”−Q , , then the required required flow rate Qf,
Q.

The distribution ratio to obtain the above can be obtained by setting the diameters of the orifices 1.2g and 12f corresponding to Q, /Qo, and Qr/Q. The diverter valve 12 can thus distribute and supply the pump delivery Q, to the required flow rates Q, . . . Qr to the circuit 1.0.11. Furthermore, when the pressure in the circuit 10 or 11 drops due to a change in flow rate, the spool of the diverter valve 12],
2a goes to the right or left in the figure, and the horizontal hole 12i or 12h
It is possible to prevent the flow distribution ratio from collapsing by reducing the opening degree of the flow rate distribution ratio, thereby preventing pressure fluctuations in one system from affecting other systems.

The steering angle control is performed using the steering angle control valve 14 under the above-mentioned configuration in which pressure fluctuations in both systems do not interfere with each other.
．． This is done under the control of No. 15.

The steering angle control valves 14.15 each consist of a pressure control valve, which are interposed between the auxiliary steering circuit 1.0.1.1 and the common drain circuit I3 and the actuator 5.6.

The steering angle control valve 14 for front wheel auxiliary steering includes a solenoid 14a.
, When off for 14 hours (when not energized), it is at the neutral position shown in the figure and the entire amount of oil from the circuit 10 is returned to the drain circuit 13.
Both chambers 5a and 5b of the actuator 5 are kept in an unpressurized state. At this time, the actuator 5 is a built-in spring 5c.

5d, the steering gear 4 is kept at a neutral position where the front wheels 1 are not assisted in steering. When the solenoid 14a is turned on (energized), the valve 14 pressurizes the chamber 5a, drains the chamber 5b, causes the actuator 5 to extend, and moves the steering gear 4 to the right in the figure, thereby moving the front wheel 1 to the α degree. Perform auxiliary steering in the left steering direction within Further, when the solenoid l''14b is turned on (energized), the valve 14 closes the chamber 5b.
is pressurized, the chamber 5a is drained, the actuator 5 is retracted, and the steering gear 4 is moved to the left in the figure, thereby auxiliary steering the front wheels 1 in the right steering direction within α degrees.

The steering is performed based on steering wheel operation according to a control mode as described below.

The front wheels 1 are assisted and steered by such a mechanism.

Steering angle control valve 15 and actuator 6 for rear wheel auxiliary steering
The configuration and functions thereof are also similar to those of the steering angle control valve 14 and actuator 5 described above.

That is, the steering angle control valve 15 is operated by solenoids 15a, 15b.
The actuator 6 includes chambers 6a, 6b and a built-in spring 6c6d. Further, a stroke sensor 19 for detecting the stroke 2 of the rear wheel actuator 6 is provided.

When each of the solenoids 1.5a and 15b are off (not energized), the valve 15 brings both chambers 6a and 6b into an unpressurized state, and when the solenoid 15a is on (when energized), the valve 15 keeps the chamber 6a in an unpressurized state. Due to pressurization, and when solenoid 151) is turned on (
When energized), the rear wheels 2 are steered in the respective directions within the β degree by pressurizing the chamber 6b.

The rear wheels 2B are steered by the mechanism for steering the rear wheels as described above.

Each solenoid 14a of the above steering angle control valve 14.15
14b1.5a and 15b are on/off controlled by a controller 16, which includes a signal from a steering angle sensor 17 that detects the steering angle θ of the steering wheel 3, and a vehicle speed sensor that detects the vehicle speed. A signal from a stroke sensor 18, a signal from a stroke sensor 19, a signal from an engine rotation speed (N) sensor 20 that detects the engine rotation speed, and the like are input, respectively.

The controller 16 includes an input detection circuit, an arithmetic processing circuit, a storage circuit that stores a steering angle control program executed by the arithmetic processing circuit, arithmetic results, etc., and a steering angle control valve 14.15. It is composed of an output circuit that supplies a control signal, etc., and calculates the front and rear wheel auxiliary steering angles based on the above input information, and each solenoid 14a, 14 of the steering angle control valve 14.15.
b, signal I that controls on and off 1.5a and 15b
F+++ l Fb+ I Ra and IRb are output, and the front and rear wheels are auxilially steered individually to the calculated steering angle.

Here, regarding the above-mentioned steering angle calculation, basically, the control steering angle value δ1 of the front and rear wheels is calculated according to the steering state of the steering wheel (steering wheel angle θ, steering angular velocity θ, etc.), or furthermore, the vehicle speed ■. Calculate δ1, but for example, handle angular velocity θ(
If the steering wheel steering angular velocity) is also used as a steering state parameter, each calculation can be performed using the following formula.
(VI Xθ ・(1,) δr −K r
(v) Xθ-”'-Tr (V) Xθ
...(2) Here, ■<□i+"'f(or configure the control constant for front wheel steering angle control, Kr(i+Tr(v
) constitutes a control constant in rear wheel steering angle control. Specifically, K□vtlKr, are multiplication coefficients of θ, and here they are proportional constants that change depending on the vehicle speed, Trtvz Tr, respectively.
((ri) is a multiplication coefficient of θ, and here, it is also a differential constant that changes depending on the vehicle speed.

In these (IL) equations, the first term is a proportional term, and the second term is
This is a phase reversal control calculation formula in which the term is a differential term. To explain it simply, the differential term is used to obtain sharpness during the steering transition period (period where θ is small and θ is large), while sharpness is obtained during the steering period (when θ is large). This is an arithmetic expression that realizes a steering characteristic that uses a proportional term to obtain stability during periods when θ is large and small.

Furthermore, regarding the steering angle control of the rear wheels, the control roller 16
The auxiliary steering mechanism for the rear wheels increases the rear wheel steering angle in the same phase direction as the front wheels 1 up to a predetermined steering angle, and increases the rear wheel steering angle in the opposite phase direction when the steering angle exceeds the predetermined steering angle.
When in the same phase state, control can be executed to reduce the same phase steering angle.

In addition, when the controller 16 controls the steering of at least one of the rear wheels or the front wheels using the auxiliary steering mechanism during acceleration and/or deceleration during a turn, the controller 16 is configured to make the steering angle correction depending on the driving state sensitive. It also includes means for controlling the steering angle of the wheels to be controlled to be corrected in accordance with the rate of change in the engine speed so as to match the driver's feeling without any problems.

That is, the controller 16 executes steering angle correction control for correcting the steering angle of the front wheels or rear wheels in accordance with changes in the engine speed when turning in such an engine operating range.

Preferably, for acceleration correction, basically when the rate of increase in engine speed exceeds a reference value, the "acceleration state" is detected.
, and make corrections to gradually steer the rear wheels in a direction opposite to that of the front wheels, or instead of or in conjunction with "-"
Correction is made to perform auxiliary steering of the fiiT wheel in the same direction as the front wheel steering direction.

Preferably, the controller I-roller 16 is also configured to carry out acceleration release processing when the "acceleration state" described in "-" is released, and when the "acceleration state" is released, the rear wheels are gradually moved to the normal state. The control steering angle is returned to the logic control steering angle, and the front wheel auxiliary steering angle is gradually prevented from returning to the normal driving lodge steering angle. Furthermore, in detecting the "acceleration" judgment when accelerating during a turn based on the engine speed, even if the rate of increase in the engine speed caused by downshifting during a turn exceeds a reference value, in that case, it is determined that the "acceleration state" is detected. Therefore, the control described in item 1-1 does not perform this.

Regarding deceleration correction, desirably: 1 The controller 16 basically determines that it is in a "deceleration state" when the rate of decrease in engine speed exceeds a reference value, and moves the rear wheels in the same phase direction as the front wheels. Correction is made to gradually steer the vehicle, or alternatively or in addition to this, to perform auxiliary steering of the front wheels in the opposite direction to the front wheel steering direction during deceleration. Preferably, in addition to such correction, a deceleration release process is executed, and the deceleration state described in 2.
When this is released, the rear wheels are gradually returned to the control steering angle of the normal driving logic, and the front wheel auxiliary steering angle is gradually returned to the normal driving logic.

Furthermore, as in the case of acceleration correction, such deceleration correction is prohibited under certain conditions, and even if the rate of decrease in engine speed caused by upshifting during a turn exceeds a reference value, it is determined that it is not a "deceleration state". and the above control is not performed.

FIG. 3 is a flowchart showing an example of a control program for steering angle correction processing during turning acceleration. This program is an example in which the control steering angle is corrected for both the front and rear wheels, and is executed in the controller 16 according to a predetermined calculation cycle.

First, in step 100, a check is made to see if the vehicle is turning. Here, the determination of turning is made based on, for example, the steering wheel angle θ and the vehicle speed ■, and the vehicle speed value ■ and the steering wheel angle value based on the signals from the vehicle speed sensor 18 and the steering angle sensor 17 at the time of execution of step 100. Based on θ, it is determined whether or not the vehicle is in the turning area of map-hi as shown in FIG. 4 each time it is detected.

In this example, the speed value and steering wheel angle map are also shown as having hysteresis characteristics. For example, the characteristics of the turning judgment ON line and OFF line are set as shown in the figure, and even with the same vehicle speed V value, When entering the turning area, control hunting is prevented by not determining that the vehicle has entered the turning area unless the steering wheel angle θ is larger than when exiting from the turning area to the non-turning area. In addition, it is not necessary to use a map like this for turning judgment; for example, instead of using the vehicle speed and steering wheel angle maps, the average value of lateral acceleration (lateral g) is detected and this is used for turning judgment in step 100. It may also be possible to make a turning judgment.

” As a result of the second judgment, if the answer is No and the vehicle is not turning, the program is terminated. However, if the answer is Yes and it is determined that the vehicle is turning, in the next step 101, the increase rate of the engine rotation speed N is determined. When is larger than a predetermined value, a check is executed to determine the change in engine speed that will bring the acceleration state to such an extent that steering angle correction during turning acceleration is required.

That is, using a preset threshold value ΔNo for the rate of change in engine speed as a discriminant value, dN/dt>ΔN
o Determine whether or not it holds true. Here, the rate of change of the engine speed is determined based on the output of the engine speed sensor 20.
The difference between the detected value a few cycles ago and the current detected value is calculated in the calculation cycle of the control program. Note that when applying such a difference to the above processing, it is desirable to use a difference with a reasonably long span in order to avoid being affected by noise and the like.

In step 101, the difference thus obtained is compared with the set threshold value ΔNo, and an acceleration judgment is made based on whether the difference value is larger.

Here, since the "acceleration" judgment is made based on the rate of change in engine speed, the threshold value ΔNo used for comparison can also be set to ζ as follows. Let's make a comparison now] 7. If the threshold ΔNO is used as a control parameter such as vehicle speed, it is possible to perform more detailed control 2 in steering angle correction for understeer reduction control during turning acceleration. , follow °
ζ When aiming at such control, it is desirable to change the ANo value depending on, for example, the vehicle speed ■, the gear position of the transmission, or both.

FIG. 5 shows an example of the characteristics of the change in the threshold value ΔNo of the engine rotational speed, which is a criterion for determining acceleration, with respect to the vehicle speed ■ and the gear position. As shown in the figure (a), regarding the vehicle speed ■, the threshold value ΔNo is set with a tendency as shown in the figure, so that it takes a smaller value as the vehicle speed range becomes high, medium speed, and low. ing. Regarding the gear position, as shown in FIG. 3B, the threshold value ΔNo is set to have a large value at a low gear position, as shown in the figure.

If the engine speed change rate threshold ΔNo applied in step 101 is set low, even if the rate of increase is the same, when ΔNo is set high, the acceleration state will be Even if the rate of change is determined to be negative, it is determined to be acceleration in step 101, and as a result, steering angle correction is executed as described later. Therefore, the ΔNo characteristic in FIG. This means that it is possible to prevent understeer with a small R, and at high speeds, it is possible to raise No to the threshold value to generate weak understeer. The basic idea is to do this, and when changing it depending on the gear position, set the NO to the threshold value higher when the vehicle is in a lower gear at the same vehicle speed to reduce the difference in sensitivity depending on the gear. You can also do it.

As a result of the judgment in step 101, if the answer is No, the process proceeds to step 110, where the acceleration flag FA is set to the value 1.
Determine whether it is equal to or not. The flag FA is a flag whose value is set to 1 in step 108 during acceleration correction processing, which will be described later, and whose value is set to 0 in step 117 during acceleration cancellation processing, which will be described later. As the initial value of the acceleration flag FA, a value O is set in an initialization process (not shown) that is performed when the power is turned on.

In step 110, the value of such flag FA is monitored, and when the result is No (FA'-0 state)
exits this program. Therefore, even when the vehicle is turning, when the program is terminated after passing through step 101110 as described in -1-1, a series of correction processes consisting of the acceleration correction and the subsequent return correction when the acceleration is released will not be performed.

Therefore, in such a case, the steering angle control is, for example, as described in (1) above.
, Front and rear wheel control steering angle δ2. according to equation (2). The calculated value in the steering angle control value calculation program (not shown) that calculates δ1 is directly applied as δ, value, δ, value to the front and rear wheel steering angle control output program (not shown) to execute the control. Become. More specifically, Fig. 6 is a diagram showing the basic concept of the control logic for the front and rear wheels in the case of acceleration correction targeted at acceleration.
If shows an increasing change as shown in (a) of the same figure, the rear wheel steering angle and front wheel steering angle of (0) and (d) of the same figure will change from time L to L2 to 3 as well. No steering angle correction is performed, and the time and control steering angle value δ1 is the same as before. The steering angle control will be performed with δ.

In addition, in the example shown in Fig. 6, the steering wheel angle θ is kept constant without being changed, and regarding changes in vehicle speed, changes in control constants due to changes in vehicle speed are omitted for the sake of explanation. This is an indication.

Thus, when no correction is performed, normal steering angle control is performed.

On the other hand, as a result of the comparative judgment in step 101,
If it is determined that the difference value is larger (if the answer is Yes), it is determined that acceleration is to be performed, and step 10 mentioned above is performed.
In order to switch to acceleration steering angle correction control including the setting process of the acceleration flag FA in step 8, the process proceeds as follows.

When controlling the steering angle during turning acceleration, whether or not the acceleration state is at a timing when the correction should be applied is determined not by the accelerator opening, but by looking at changes in the engine rotation speed, as described above. With this control, which can judge based on the increase rate and correct the control steering angle by switching the steering angle control from normal driving, changes in engine speed are caused by the influence of the engine's own inertia, and this is due to the accelerator operation. Since this occurs with a predetermined response delay, it is possible to appropriately reduce understeer during acceleration without impairing the driver's feeling. In other words, when reducing understeer during corner acceleration by correcting the steering angle, the steering angle correction must be made more sensitive than when correcting the steering angle by detecting the amount of accelerator operation and switching control. Therefore, it is possible to reduce the discomfort caused by the vehicle's sway due to oversensitivity, and it is possible to reliably reduce understeer with control that does not cause any discomfort to the driver.

In this program, from step 101 to step 1,
Proceeding to step 02, a determination is made as to whether it is immediately after a downshift. This is a determination process provided to prevent the increase in engine speed caused by downshifting from affecting the acceleration judgment. If the answer is Yes (engine speed), steps 103 to 109 described below
Skip this and exit this program. In this way, when the engine speed increases due to a downshift during a turn, it is not determined that the vehicle is in an acceleration state, and no correction control is performed in this program.

When the answer to step 102 is No, the process proceeds to the steno knob 103 and below to start the correction process.

In this program example, this can have the following contents. First, in step 103, each time this step is executed, the front and rear wheel control steering angles (
Calculate correction amount) δ1 (+1), δ, (A).

δ, (A) − δr (A) +Δδ,. (A)
...(3) δr (A) −δ , (8)
+ Δ δ ゎ. (A) ...(
4) Here, δ, (Δ
) value and δ, (A) value are the current value of the correction value, and the first term on the right side is the previous value. That is, the first term is the previous value δt (A )
, and δ, the previous value for rear wheel control steering angle correction applied as a subtraction correction value to the values, δ, (A). Note that if the calculation process in step]03 is the first one, the value 0 (initial value) is applied as the previous value δ, (Δ), δ, (^).

Also, Δδ of the second term on the right side of each equation. (A), and Δ
δ,. (A) is the amount of change in the front wheel steering angle and the amount of change in the rear wheel steering angle per calculation time in the supplementary iIE during acceleration, respectively (the time in Fig. 6 (C) and (d) is also 1 ~ also see 2-ma)
, are applied as addition values to the δr (A) value, δ, (^) value of the first term, respectively. If so, since the amount of change during steering angle correction is set, the steering angle correction in the direction of increasing steering as shown in Fig. 6(d) during front wheel acceleration correction (front wheel main steering The steering speed for auxiliary steering of the front wheels in the same direction as the direction is Δδ. In (A), the steering angle correction (
Steering speed (speed to return the rear wheels to the same phase) (steering the rear wheels in the opposite phase direction to the front wheels, including returning the in-phase steering angle)
is the above Δδ. (A), and therefore functions as a constant for setting the steering speed of auxiliary steering based on the acceleration of the front and rear wheels.

The above Δδ. The values of (A) and Δδ1° (A) can also be used as control parameters depending on the vehicle speed (■).

When changing these values depending on the vehicle speed (2), it is desirable to consider changes in vehicle behavior and select characteristics such that the change in behavior is large at low speeds and small at high speeds.

”2 (3), (calculated value δt (A) using formula 41,
δ, (A) will remain at its calculated value unless it is suppressed to a predetermined value in the next limit check, and will be used as the current value of the additional correction value for the front wheels, and as the calculated correction value for the rear wheels. Since these values are applied as the current values in step 109, which will be described later, they each function as control values that determine the amount of additional steering of the front wheels and the amount of steering in the opposite phase direction of the rear wheels when correction is performed by acceleration.

Once the process in step 103 has been completed, the correction amount is checked in the next steps 104 to 107. That is, regarding the front wheel side correction value, in step 104, the calculated value δt(A) is set to the predetermined discrimination value δrthax(8)(
If the answer is No, step 105 is skinned, while if the answer is Yes, the δr (A) value is determined in step 105.
Binary value δ. The calculated value δ, (A
) is the predetermined discriminant value δ, , , , X(A) ((C)
) Check whether the answer is <No
If the answer is Yes, skip step 107;
s, in step 107 the δt (A) value is changed to the above value δ
, , 88 (eight), and proceed to step 108.

Here, δffft1lN (8), δr + saga (8)
is a value determined to predefine the maximum steering amount of the front wheels and rear wheels at the time of correction. That is, these are the front wheel steering angle at the correction start point (time t, 1), respectively, as shown in FIG.
A control value set based on the rear wheel steering angle, and δr
□, X(A) is the maximum steering amount (maximum return amount) for steering the rear wheels (returning the same phase) in the case of correction due to acceleration, and δ + max (A) (+f is the Maximum steering amount (maximum increase amount) to steer the front wheels (increase the steering angle)
(Note that these are selected as being within the most steerable range according to the stroke of the actuator 5.6).

Therefore, if the calculated values δ, (A) and δr(B) exceed them, the δr-X(ALδr-yu(8))
Since this is a value that will be applied to step 109 described later by resetting (steps 105 and 107) as described above,
It functions to determine each steering amount at the time of correction.

δ above. The settings of □(A) and δrmax(^) can also be changed, for example, depending on the vehicle speed ■. When setting the control parameters according to the vehicle speed ■, δ is set with the intention of eliminating understeer in small and medium R turns at medium and low speeds and realizing weak understeer characteristics in large R turns, as mentioned earlier. , X(A) value, δ
1. It is desirable that the ff1aX (c) value be set larger at low speeds.

Next, in step 108, the previously mentioned acceleration flag F7 is set to the value 1, and in the subsequent step 109, the front and rear wheel control steering angles are corrected according to the following equation, and the program ends.

δ , −δ , + δ , (8)
...(5) δ1− δ,
−δ r (8)
...(6) Here, the δ value and δ value on the left side of equations (5) and (6) above are the corrected control steering angle values for the front and rear wheels, respectively, and the first term on the right side is , are calculated in the steering angle control value calculation program described above. Therefore, in the case of acceleration correction, based on 1-12, the first term δ2. For δ1 hani, in the case of the front wheel, this time B[
The calculation δf (
A) (If applicable, the set value δr (8) in step 105 is added and corrected, and in the case of the rear wheel, it is the same (Progera 1 this time, calculated δ in step 103 at the time of execution, (Δ ) value or step 107 if applicable
The set value δr(^) at is corrected by subtraction.

Thus, as a result of executing the front and rear wheel steering angle control output processing based on the corrected control steering angle, as shown in FIG. Gai? The rear wheels are controlled so that they are turned back toward the opposite phase side, so that the rear wheels are not cut more as the il is turned.

In this process, if we pay particular attention to the rear wheels,
On the rear wheel side, in-phase understeer cancellation is performed by the above-mentioned steering angle correction, and Fig. 6 shows an example where the rear wheel steering angle further exceeds the neutral position and is corrected and steered to the opposite phase region. is shown.

Here, I would like to add a further note regarding the vehicle behavior during turning acceleration in 4WS FR cars and 4WD cars.In the case of these vehicles, when turning, when the rear wheels are steered in the same phase, the rear The yaw moment generated by the driving force of the wheels acts in a direction that impedes the turning of the vehicle, increasing the burden on the front tires to maintain the turning, and there is a tendency for strong understeer to occur. In addition, in the case of FF cars, when accelerating, driving force is originally applied to the front, which places a heavy burden on the front tires and tends to cause understeer characteristics. Therefore, the understeer characteristic becomes even stronger (if the vehicle speed increases, the in-phase steering angle of the rear wheel steering angle increases and the above-mentioned tendency is further exacerbated).

On the other hand, if the present control is followed, it is possible to appropriately eliminate understeer such as "double" during turning acceleration.

Namely, when accelerating during a turn, this is detected by the engine rotation speed when determining "acceleration", and the rear wheels can be steered in the opposite phase direction. It is possible to eliminate bushing understeer due to rear wheel drive force and understeer associated with a decrease in front wheel cornering force due to generation of front wheel drive force in FF vehicles, and it is possible to generate the required yawlay 1- at the optimal timing.

Due to the occurrence of yaw rate, the sideslip angle of the front wheels decreases2.
Since the sideways slipping of the rear wheels increases, the burden on the front wheel is reduced, and the rear can generate a larger calling force, and as already mentioned, this can be achieved without causing any discomfort.

After entering the correction during acceleration as after time t1 in FIG. , z), it is assumed that the acceleration state has been canceled, and the process proceeds from step 101 to step 110.

As described above, once the acceleration correction is started, the acceleration flag FA is set to the repetition value 1 every time the step 108 is executed (see FIG. 6(b)). - When the process proceeds to step 110, the answer is Yes, and therefore, the process proceeds to step 111 and subsequent steps to execute the return correction upon cancellation of acceleration.

First, in step 111, the δt (A) value and δr(Δ) value in the case of return correction are calculated using the following equations in accordance with the arithmetic processing in step 109 each time the step is executed.

δ f (A) −δ f (8) −Δ δ
7. (8) ... (7) δ ,, (
To 8) δ , − (8) −△ δ ,, (8)
...(8) Here, the first term on the right side of the "-signing formula is the previous value (in the case of immediately after transitioning to the acceleration cancellation process, the δf (Δ) value applied in step 109 in the immediately preceding cycle) , δ1(8) value). In addition, Δδf+(A) and Δδ□(A) in the second term on the right side are subtracted values, respectively, and indicate the amount of change in front and rear wheel steering angles per calculation time when acceleration is released (Fig. 6 (C), (See also the time in (d) between 2 and tJ).

Calculated value δr (A) using equations (7) and (8) above,
δr (8), ill: and 6md calculated value Δδ,, (A)
, Δ/i, , (A) c. A control value having a function similar to the above-mentioned acceleration correction, for example, Δδf
In terms of the +(A) value and Δδ-+(A) value, these function as constants that set the steering speed of the +iil rear wheels in the case of return control (the front and rear wheels are returned to their original control, that is, normal). The speed at which the vehicle returns to steering angle control using driving logic is determined by these factors.)

The above values of Δδfl(Δ) and ΔδrI(A) are also set so that the vehicle speed is less
It is desirable to change it by

Next, in step 112, the calculated value δ, (8) is the value Δδ.

(Δ), and if the answer is No, skip step 113, while if the answer is Yes, set δt (A) to the value 0 in step 113, and
In step 114, the calculated value δr(A) is changed to the value ΔδrI(A)
If the answer is No, step 115 is skipped, while if the answer is Yes, δ, (/l) is set to the value O in step 115, and the process proceeds to step 116. In step 116, δ, (A) δr
(A) Determine whether or not -〇.If the answer is NO, it is assumed that the return correction is in progress at the time of acceleration cancellation, and step 1 is performed.
09 and terminate this program.

By executing the above processing, the correction amount is returned to its original value as shown in FIG. 6 when acceleration is canceled. However,
In this process, when a Yes answer is obtained in step 116, it is assumed that the return correction has been completed, and step 1 is performed.
17, rewrite the acceleration flag F to the value 0, step 109
Execute and exit this program.

Thus, the next time the program is executed, the flag F
As a result of rewriting the value of A to 0, the answer at step 110 becomes NO, and therefore, from now on, the steering angle control will be performed using the normal driving logic described above.

Next, the steering angle correction control during turning deceleration will be explained with reference to FIG. 7 and subsequent figures.

FIG. 7 is a flowchart showing an example of a control program in that case, and this program example also corrects both the front and rear wheels.

The processing contents in each step 200 to 217 in the figure are similar to the contents of the corresponding steps 100 to 117 in the case of Fig. 3, and the control process is basically the same as the processing in the case of acceleration correction. Follows procedures.

In FIG. 7, in step 200, it is determined whether or not the vehicle is turning.
In step 201, when the rate of decrease in the engine speed N is greater than a predetermined value, dN/dt<-ΔN is set to a deceleration state in which steering angle correction during turning deceleration is required.

In step 210, the deceleration flag F is determined. It is determined whether or not the value is 1.

As shown in Figure 8, the decision to turn is made based on the vehicle speed.
This is done by detecting whether or not the steering wheel is in the turning area shown in the map-hi from the steering wheel angle θ. Turning may be determined by detecting the average value of lateral g without using such a vehicle speed and steering wheel angle map.

The rate of change in the engine speed N is calculated by calculating the control program by calculating the difference between the detected value several cycles ago and the current detected value, and then comparing this difference value with a preset threshold value. Determine deceleration. It is desirable that the threshold value for comparison be similarly changed depending on the gear position and vehicle speed.

FIG. 9 shows an example of a change in the threshold value of the rate of change in engine speed, which is a criterion for determining deceleration, with respect to vehicle speed and gear position. As will be described later, in the case of deceleration correction, the control is switched by looking at the change in engine speed, and based on the characteristics of the change in engine speed described above, the steering angle is corrected by the accelerator opening. Compared to this, it is possible to reduce tank-in during deceleration without impairing the driver's feeling, but in this way, "deceleration" during a turn is determined based on the rate of change in engine speed, When attempting to reduce tack-in by correcting the steering angle, and using the characteristics shown in Figure 9, the threshold value should be set high at high speeds to prevent error movement, and at low speeds, the threshold value should be lowered. It is also possible to prevent rapid tack-in from small R and high g, and to increase the threshold value when the vehicle is in a low gear at the same vehicle speed to reduce the difference in sensitivity depending on the gear, allowing for fine-grained control. can.

If the answer is No in step 200, the program is terminated, and the program proceeds to steps 200, 201, and 210, and if the answer is No in step 210, the program is terminated directly.

The check as to whether or not the shift-up has just occurred, which is executed in step 202 when YES in step 201, is provided so that the decrease in engine speed caused by the shift-up does not affect the deceleration judgment. . If the answer is Yes, just exit this program and
Therefore, even if the rate of decrease in engine speed caused by the shift amplifier during turning exceeds the base $ value, it will not be judged as a "deceleration state",
No steering angle correction control is performed.

The deceleration correction is performed when steps 203 and subsequent steps are executed.

That is, in step 203, step 10 in FIG.
3, front and rear wheel control steering angles (correction amounts) δt (n), δ, (D) due to deceleration are calculated according to the following formula.

δ, (D) − δ, (D) ten Δδ,. (D) ・
... (9) δ, (D) - δr (D) + Δδro (
D) ・00) Here, the second term on the right side is
This is the amount of change in the front and rear wheel steering angles per one calculation time during deceleration.

Next, in steps 204 to 207, a predetermined value δr−X(
n) , δ, , , (D), perform a limit check and, if applicable, the δrmax(D) value, δr,
, , perform the setting process to the aM(D) value, and then proceed to step 2.
In step 08, the deceleration flag F is set to the value 1, and in step 209
In accordance with the process in step 109 of FIG. 3, the corrected front and rear wheel control steering angle values δ1. δ, the following formula (IILO
After executing the calculation process in step 9, the program ends.

δ, -δ, -δt (D)...
(II) δ1-δ1+δ, (D)
...In the case of surface subtraction correction, the front wheel side is set to (11
δr (D) is applied as a subtraction correction value as in the formula ), and δ and (D) as an addition correction value on the rear wheel side as in the formula (0), respectively, are applied to the two calculations.

With the above control, as shown in FIG.
Slow speed correction is started from z, and during turning deceleration, the front and rear wheel steering angles can be controlled in accordance with the decrease in engine speed as shown in the figure. In other words, when the rate of decrease in engine speed exceeds a reference value, it is determined that the engine is in a deceleration state, and the rear wheels can be gradually steered in the same phase direction as the front wheels. In addition, in the same way as the control during acceleration, steering angle correction during deceleration is not overly sensitive, and it is possible to reduce discomfort such as vehicle wobbling, and to do so appropriately. This makes it possible to reduce tuck-in. Note that in the case of FIG. 10, which shows the basic concept of the control logic for the front and rear wheels in deceleration correction, the above-mentioned
As in the figure, the steering wheel angle is assumed to be constant, and changes in control constants due to changes in vehicle speed are omitted in the figure.

FIG. 10 also shows an example of the situation when the correction amount is limited by the limit check in the correction process described in "-". Then, between time 1.13 and t+a, δ, (0)
, δ, (D) is δ,, a, (D) , δf, , (D
) is regulated by the value.

The δr,...(n), δ,...(D) values can also be changed depending on the vehicle speed, similar to the control in the case of acceleration correction. In that case, in order to prevent sudden tuck-in at medium and low speeds and high g's and to prevent error movements at high speeds, it is desirable to set the characteristics so that they take a large value at low speeds.

Further, the speed of auxiliary steering of the front wheels in correction during deceleration and further the speed of steering in deceleration release processing to be described later are Δδ in FIG. (D) value, Δδ, o(n) value, and Δδr+ after time tz in the moving diagram applied in step 211 described below.
(n) value and Δδr+(o) value, but in the same way as in the case of the acceleration correction control described above, such control value can also be used as a parameter for vehicle speed. In that case, these values also It is better to set the characteristics to increase the speed and reduce changes in vehicle behavior at high speeds.

In FIG. 10, the process at the time of deceleration release starts at time t, 14, and in the program of FIG. 7, the return correction at the time of deceleration release is performed when the process proceeds from step 210 to step 211 and subsequent steps.

In step 211, similar to the process in step 113 of FIG. 3, calculation processing of δ, (D) value, and δ, (D) value according to the following equations is executed.

δt (D)-δ1 (0)-Δδr+(o)
・・・03) δr(1))−δr(D) −Δδ,,+
(0) to θ In the above, the second term on the right side is the amount of change in the front and rear wheel steering angles per one calculation time when deceleration is released.

Next, in steps 212 to 217 and 209, the return processing in the case of FIG. 3 (steps 112 to 1171
After the deceleration state is released, the process for returning to normal driving logic control is executed in the same manner as in step 09). That is, the correction amount is returned as shown in FIG. In the illustrated example, the correction amount is returned to zero for the rear wheel side at time t15 and for the front wheel side at time L11+.

In this way, when the deceleration state is released, the rear wheels can be gradually returned to the control steering angle of the normal driving logic, and the front wheels can be gradually returned to the steering angle of the normal driving logic.

As described above, even during turning deceleration, steering angle correction can be performed without being too sensitive, and tuck-in reduction during deceleration can be appropriately achieved with control that does not give an unnatural feeling.

Note that in the present invention, acceleration correction can be performed alone, deceleration correction can be performed alone, or both can be performed. Furthermore, in those cases, the steering angle correction may be performed only on the front wheels, only the rear wheels, or both the front and rear wheels.

(Effects of the Invention) Thus, the steering angle control device of the present invention is capable of controlling the steering angle of a wheel to be controlled according to a change in the engine speed in steering angle control that performs auxiliary steering of at least one of the front wheels or the rear wheels. Since the configuration allows control to correct the steering angle, it is possible to eliminate the need to make the steering angle correction too sensitive, and increase the effectiveness of the steering angle correction control with less discomfort such as vehicle wobbling. Even when trying to reduce understeer or tuck-in during deceleration or turning, this can be achieved appropriately without impairing the driver's feeling.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the rudder angle control device of the present invention, Fig. 2 is a system diagram showing an embodiment of the rudder angle control device of the present invention, and Fig. 3 is a diagram of the acceleration correction process of the control I/roller on the same side. Fig. 4 is a flowchart showing an example of a control program for the control program, Fig. 4 is a diagram showing an example of a map for the turning judgment logic that can be applied to the same program, and Fig. 5 is a flowchart showing an example of a map for the turning judgment logic that can be applied to the same program. FIG. 6 is a diagram showing an example of the characteristics of the threshold value of the number change rate with respect to vehicle speed and gear position; FIG. Figure 7 is a flowchart showing an example of a control program for deceleration correction processing of the controller, Figure 8 is a diagram showing an example of a map for turning judgment logic that can be applied to the same program, and Part 9 is a flowchart showing an example of a control program for the controller's deceleration correction processing. Figure 10 shows an example of the characteristics of the threshold value of engine speed change rate, which is an applicable deceleration judgment criterion, with respect to vehicle speed and gear A/position.
The figure is a diagram showing the basic concept of the control logic for the front and rear wheels, which is used to explain an example of the content of the deceleration correction control by the same program. 1... Front wheel 2... Rear wheel 3... Steering wheel 4... Steering gear 5... Front wheel auxiliary steering actuator 6... Rear wheel auxiliary steering actuator 7... Oil pump 12... Diversion valve 1.4, 1.5... Rudder angle control valve 16... Controller I7... Rudder angle sensor 18... Vehicle speed sensor 20... Engine rotation speed sensor patented person

Claims (1)

[Scope of Claims] 1. Steering state detection means for detecting the steering state of the steering wheel; An auxiliary steering mechanism for auxiliary steering of at least one of the front wheels or rear wheels of the vehicle; Engine speed detection means for detecting the engine speed. and a control means capable of controlling the auxiliary steering by the auxiliary steering mechanism with a controlled steering angle according to the steering wheel operation based on the output of the steering state detection means, the engine rotation speed detected by the engine rotation speed detection means. 1. A steering angle control device comprising: an auxiliary steering angle control means having a steering angle correction means for correcting a controlled steering angle of a front wheel or a rear wheel in accordance with a change in the steering angle of a front wheel or a rear wheel. 2. When the rate of increase in the engine speed is greater than a predetermined value, it is set as an acceleration state, and in this state, the steering angle correction means corrects the steering angle by turning the front wheels toward the additional steering side or the rear wheels toward the opposite phase side. The steering angle control device according to claim 1. 3. When the reduction rate of the engine speed is larger than a predetermined value, the engine is decelerated, and in this state, the steering angle correction means corrects the steering angle by turning the front wheels toward the return side or the rear wheels toward the same phase side. The steering angle control device according to claim 1 or 2.