JPH04334661A - Steering angle control device - Google Patents

Abstract

PURPOSE:To perform appropriate control in conformity with a driver's will without making steering angle correction over-sensitive by correcting the control steering angle of a front wheel or a rear wheel with a specified delay in relation to accelerator operation in the case of performing the auxiliary steering of the front wheel or the rear wheel on the basis of the steering state. CONSTITUTION:The steering state of a steering wheel in a vehicle A is detected by a steering state detecting means B, and the operation of an accelerator is detected by an accelerator operation detecting means C. At least one of a front wheel FW and a rear wheel RW is auxiliary-steered by steering mechanism D. In this case, a steering angle control means E performs steering control on the basis of the output of the steering state detecting means B so that the steering mechanism D performs auxiliary steering with a control steering angle corresponding to a specified control rule. A front wheel auxiliary steering angle or a rear wheel steering angle is then corrected by the correcting means F of the steering angle control means E with a specified delay in relation to the accelerator operation detected by the accelerator operation detecting means C. Steering angle correction is thereby performed in conformity with a driver's will without becoming over-sensitive.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention 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.

0002

2. Description of the Related Art As a steering angle control device for a vehicle, a control device has been proposed that corrects the control steering angle in the case of acceleration or deceleration during turning in a vehicle having an auxiliary steering mechanism. (Sho 63-121571). In this one,
The steering angle correction switches the rear wheel steering angle control to prevent vehicle behavior such as changes in the direction of increasing or decreasing the turning radius during turns, and to eliminate understeer and tuck-in.

0003

[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, but behavior such as understeer characteristics of the vehicle due to accelerator operation occurs. Since there is a time delay between the two, when correcting the steering angle to reduce understeer, if you move the rear wheels with the amount of accelerator operation in this way,
The steering angle is corrected before understeer of the vehicle occurs, and the correction control becomes oversensitive. That is, if the steering angle is corrected to immediately respond to an accelerator operation, the steering angle will be corrected before the understeer characteristic occurs, which may cause the vehicle to twitch. Therefore, oversensitive steering angle correction causes the vehicle to wobble, resulting in a decrease in stability, and may cause a sense of discomfort.

[0004] An object of the present invention is to make steering angle correction during acceleration and/or deceleration not too sensitive and to be compatible with the driver's intention, thereby correcting the steering angle with control that causes as little discomfort as possible. The object of the present invention is to provide a steering angle control device that can increase the effectiveness of the steering angle control system.

[0005]

[Means for Solving the Problems] For this purpose, the steering angle control device of the present invention, as conceptually shown in FIG. a steering mechanism that performs auxiliary steering on at least one side; an accelerator operation detection means that detects an accelerator operation; and based on the output of the steering state detection means, the steering mechanism can perform steering control with a control steering angle according to a predetermined control law. A steering angle control means, the control means having a correction means for correcting the front wheel auxiliary steering angle or the rear wheel steering angle with a predetermined delay with respect to the accelerator operation detected by the accelerator operation detection means. This is what happens.

[0006]

[Operation] The steering angle control means is based on the output from the steering state detection means that detects the steering state of the steering wheel.
A steering mechanism for auxiliary steering of the front wheels or rear wheels is used to steer the front wheels or rear wheels with a controlled steering angle according to a predetermined control law, and the steering angle correction means adjusts the front wheel auxiliary steering angle or the rear wheel steering angle according to the accelerator operation. When performing the correction, the front wheel or rear wheel control steering angle is corrected so that the correction is performed with a predetermined delay relative to the accelerator operation. As a result, even if understeer characteristics occur due to accelerator operation, it is possible to match the occurrence timing with the actual steering angle correction timing, and avoid oversensitive steering angle correction, thereby preventing vehicle wandering. It is possible to reduce changes such as
It also makes it possible to achieve this through appropriate control that matches the driver's intentions.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an embodiment of the steering angle control device of the present invention.
indicates the front wheel, and 2 indicates the rear wheel. This embodiment shows a configuration in which not only the rear wheels but also the front wheels are actively assisted steered. The front wheels 1 can be mainly steered as usual by transmitting a steering input to a steering wheel (handle) 3 via a steering gear 4, and the case of the steering gear 4 is stroked by an actuator 5 in an auxiliary steering mechanism. This enables auxiliary steering up to a maximum of α degrees relative to the main steering angle. Also, the rear wheel 2 is driven by a maximum β due to the stroke of the actuator 6 in the auxiliary steering mechanism.
This enables auxiliary steering up to a degree. Here, in this embodiment, it is assumed that α degrees < β degrees.

In addition to the actuators 5 and 6 mentioned above, the front and rear wheel auxiliary steering system is provided with an oil pump 7 as a pressure source common to both systems, and further includes a diverter valve 12, a steering angle control valve 14,
15 will be provided. The oil pump 7 sucks oil in the reservoir 8 and discharges it to the main circuit 9, and the dividing valve 12 thereby 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 12 includes a shuttle spool 12
a is resiliently supported in a neutral position by springs 12b and 12c, and pressure chambers 12d are provided at both ends of the spool 12a.
, 12e. These pressure chambers 12d and 12e are formed by orifices 12 with different diameters formed in the spool 12a.
It communicates with the main circuit 9 through ports 12g and 12g, and also communicates with the auxiliary steering circuits 11 and 10 through horizontal holes 12h and 12i formed in the spool 12a and output ports 12j and 12k. Thus, the degree of communication between the horizontal holes 12h and 12i with the output ports 12j and 12k is adjusted in accordance with the stroke of the spool 12a which responds to the pressure in the pressure chambers 12d and 12e, respectively, and performs the following flow dividing function.

That is, for example, focusing on the circuit 10, the required flow rate Qf of the circuit 10 is determined by the front wheel auxiliary steering actuator 5.
The product Qf of the piston pressure-receiving area SA and the piston moving speed v is expressed as = SA × v, and further the actuator 5
If the stroke of is d and the front wheel steering frequency is f, then the moving speed is v = 2π x f x d, so the required flow rate Qf of the circuit 10 is Qf = SA x 2π x f x d. In addition, the required flow rate Qr of the circuit 11 is found in the same way, and the discharge amount Qo of the pump 7 is calculated as Qo = Qf +Qr
Then, the distribution ratio to obtain the required flow rates Qf and Qr is calculated by dividing the diameter of the orifices 12g and 12f by Qf /Qo
, Qr /Qo. In this way, the pump discharge amount Qo is connected to the diverter valve through the circuit 10.
, 11 at required flow rates Qf and Qr. Furthermore, when the pressure in the circuit 10 or 11 decreases due to a change in flow rate, the spool 12a of the diverter valve 12 moves to the right or left in the figure to reduce the opening degree of the horizontal hole 12i or 12h, thereby preventing the flow rate distribution ratio from collapsing. It is possible to prevent pressure fluctuations in one system from affecting other systems. The steering angle control is performed using the steering angle control valves 14 and 1 under the above-mentioned configuration in which the pressure fluctuations of both systems do not interfere with each other.
This is done under the control of 5.

The steering angle control valves 14 and 15 are each composed of a pressure control valve, and are interposed between the auxiliary steering circuits 10 and 11 and the common drain circuit 13, and the actuators 5 and 6. The steering angle control valve 14 for front wheel auxiliary steering assumes the neutral position shown in the figure when the solenoids 14a and 14b are off (when not energized), returns the entire amount of oil from the circuit 10 to the drain circuit 13, and returns the oil from the circuit 10 to both chambers 5a of the actuator 5. , 5b are kept under no pressure. At this time, the actuator 5 is operated by the built-in spring 5c.
, 5d, the steering gear 4 is kept in a neutral position where the front wheels 1 are not assisted in steering. Solenoid 14a
When turned on (energized), the valve 14 pressurizes the chamber 5a and pressurizes the chamber 5b.
is drained, the actuator 5 is extended, and the steering gear 4 is moved to the right in the figure, thereby auxiliary steering the front wheels 1 in the left steering direction within the α degree. Furthermore, valve 1
4 is the chamber 5 when the solenoid 14b is turned on (when energized).
b 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.

The configurations and functions of the steering angle control valve 15 and actuator 6 for rear wheel auxiliary steering 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 connected to the solenoids 15a, 1
5b, and the actuator 6 includes chambers 6a, 6b and built-in springs 6c, 6d. Further, a stroke sensor 19 that detects the stroke of the rear wheel actuator 6 is provided. When both of the solenoids 15a and 15b are off (when not energized), the valve 15 makes both chambers 6a and 6b unpressurized, and when the solenoid 15a is on (when energized), the chamber 6a is pressurized. When the solenoid 15b is turned on (
When energized), the rear wheels 2 are steered in the respective directions within the β degree by pressurizing the chamber 6b. Rear wheel 2 is
As mentioned above, the vehicle is steered by a mechanism that steers the rear wheels.

Each of the solenoids 14a, 14b, 15a, 15b of the steering angle control valves 14, 15 is controlled on/off by a controller 16, and this controller 16 detects the steering angle (steering wheel angle) θ of the steering wheel 3. A signal from the steering angle sensor 17 that detects the vehicle speed V, a signal from the vehicle speed sensor 18 that detects the vehicle speed V, a signal from the stroke sensor 19, a signal from the accelerator sensor 20 that detects the accelerator opening TH, and a lateral acceleration that detects the lateral acceleration Yg. Sensor (
The signals etc. from the lateral g sensor) 21 are respectively input. The lateral g sensor can detect a physical quantity equivalent to lateral g that corresponds to lateral acceleration. The above controller 16
supplies a control signal to an input detection circuit, an arithmetic processing circuit, a storage circuit that stores a program for steering angle control executed by the arithmetic processing circuit, arithmetic results, etc., and the steering angle control valves 14 and 15. It is configured with an output circuit, etc., and calculates the front and rear wheel auxiliary steering angles based on the above input information, and controls the steering angle control valves 14 and 15.
Signals IFa, IFb, IRa, and IRb are outputted to turn on and off the solenoids 14a, 14b, 15a, and 15b, and the front and rear wheels are individually auxilially steered to the calculated steering angle.

Here, regarding the above steering angle calculation, basically, the steering condition of the steering wheel (steering wheel angle θ
The control steering angle values δf and δr for the front and rear wheels are calculated according to the steering wheel angular velocity, dθ/dt, etc.), or the vehicle speed V. For example, the steering wheel angular velocity dθ/dt (handle steering angular velocity) is also used as a parameter for the steering state. In this case, each operation can be performed using the following equation. δf = Kf (v) ×θ + Tf
(V) ×dθ/dt … 1
δr = Kr (v) ×θ + Tr
(V) ×dθ/dt … 2
Here, Kf (v), Tf (V) constitute control constants in front wheel steering angle control, and Kr (V), T
r (V) constitutes a control constant in rear wheel steering angle control. Specifically, Kf (V) and Kr (v) are multiplication coefficients of θ, which are proportional constants that change depending on the vehicle speed, and Tf (V) and Tr (V) are dθ/d.
It is a multiplication coefficient of t, and similarly here, it is a differential constant that changes depending on the vehicle speed. These equations 1 and 2 are control calculation equations in which the first term is a proportional term and the second term is a differential term. To briefly explain, during the steering transition period (period where θ is small and dθ/dt is large), This calculation formula uses the differential term to obtain sharp vehicle turning performance, while the proportional term is used to obtain stability during the steering period (period where θ is large and dθ/dt is small). .

Furthermore, regarding rear wheel steering angle control, the controller 16 uses the auxiliary steering mechanism for the rear wheels to increase the rear wheel steering angle in the same phase direction as the front wheels 1 until, for example, a predetermined steering wheel angle is reached. When the steering angle is greater than or equal to a predetermined steering angle, control can be executed to increase the rear wheels 2 in the opposite phase direction (to decrease the in-phase steering angle when in the same phase state).

[0016] The controller 16 is also configured to be sensitive to steering angle correction depending on the driving state when at least one of the rear wheels or the front wheels is controlled by the auxiliary steering mechanism during acceleration and/or deceleration during a turn. without saying,
In addition, a means for controlling the steering of the controlled wheels with a certain delay with respect to accelerator operation during turning is also configured so as to match the driver's intention. That is,
When the controller 16 corrects the front wheel auxiliary steering angle or the rear wheel steering angle in accordance with the accelerator operation when turning in such a driving range, the controller 16 corrects the steering angle with a predetermined delay with respect to the accelerator operation. conduct.

Preferably, when the wheel to be controlled is a rear wheel,
In relation to the accelerator opening degree, when the accelerator opening degree increases, the rear wheels are steered in a direction that makes a small turn towards the inside of the turn, and when the accelerator opening degree becomes small, the rear wheels are steered in a direction that makes a small turn towards the outside of the turn.

Furthermore, in the above, the controller 16 preferably adjusts the correction amount based on not only the accelerator opening but also the lateral g.
, change depending on vehicle speed, etc. For example, the relationship between the accelerator opening and the rear wheel steering angle is changed depending on the vehicle speed, and in this case, as the vehicle speed increases, the rear wheel steering angle with respect to the accelerator opening is increased. In addition, a physical quantity equivalent to lateral g is detected, and the relationship between the rear wheel steering angle and the accelerator opening is changed depending on the lateral g. In this case, the larger the lateral g, the larger the rear wheel steering angle relative to the accelerator opening.

Preferably, the controller 16 determines the turning direction not in the direction of the steering wheel angle but in the direction of the physical quantity equivalent to lateral g.

Further, the controller 16 can correct the front wheel auxiliary steering angle instead of or in addition to the above correction of the rear wheel steering angle. In this case as well, the acceleration/deceleration during a turn is detected by the accelerator opening, and the front wheels are auxilially steered with a certain delay relative to the accelerator opening. Cut more,
Conversely, when the accelerator opening is returned, the front wheels are turned back toward the outside of the turn.

FIG. 3 is a flowchart showing an example of a control program for steering angle correction processing during turning. This program is an example in which the control steering angle of the rear wheels is corrected, and is executed within the controller 16.

First, in step 100, a check is made to see if the vehicle is turning. Here, the determination as to whether the vehicle is turning can be made based on, for example, the steering wheel angle θ and the vehicle speed V. In this case, it is detected from the vehicle speed value V and the steering wheel angle value θ based on the signals from the vehicle speed sensor 18 and the steering angle sensor 17 at the time of execution of step 100 whether or not the vehicle is in a turning area on a preset map. Distinguish by. Note that turning judgment does not need to be based on such a map, and instead of using vehicle speed and steering wheel angle maps, lateral acceleration (lateral g
) is detected and used for turning judgment in step 1.
The turning judgment may be made based on 00.

As a result of the above determination, if the answer is No and the vehicle is not turning, the program is terminated as is, while if the answer is Yes
When it is determined that the vehicle is turning, in the next step 101, a check is performed regarding changes in the accelerator opening degree to see if the steering angle correction during the turn is in a condition that requires correction. That is, below, we will mainly explain acceleration correction (correction during deceleration can also be performed using the same control procedure), but for such acceleration correction, the accelerator opening change rate may be set to a value of 0 or a preset value. Using the determined positive threshold value as a determination value, it is determined whether a state in which dTH/dt exceeds it is established. Here, the rate of change can be determined based on the output of the accelerator sensor 20 by the difference between the previous detected value and the current detected value in the calculation cycle of the control program. In step 101 described above, acceleration during a turn is detected based on the accelerator opening and an acceleration determination is made.

[0024] In step 101, such changes in the accelerator opening degree are monitored, and if the result is No, the program is immediately terminated. Therefore, when not turning, or even when turning, when exiting this program after passing through step 101 as described above, the rear wheel is rotated with a predetermined delay with respect to the accelerator opening for correction during acceleration. A series of correction processing consisting of return correction is not performed. Therefore, in such a case, the steering angle control is performed using, for example, the values calculated by a steering angle control calculation program (not shown) that calculates the front and rear wheel control steering angles δf and δr according to a normal control law as they are δf.
This value is also applied to the front and rear wheel steering angle control output program (not shown) as the δr value, and control is executed. More specifically, no steering angle correction is performed, and the steering angle control is performed using the control steering angle values δr and δf as shown in Equations 1 and 2, for example.

That is, in normal control, the control steering angles of the front and rear wheels are given by the following equations, which are rewritten using the Laplace operator S in light of equations 1 and 2, respectively. δf = (Kf + Tf S) θ
… 3
δr = (Kr + Tr S) θ
… 4
(Kf, Kr: proportional constants, Tf, Tr: differential constants) The above control does not change whether the vehicle is traveling straight or turning. Note that in the example of the above equation, the change in the control constant due to a change in vehicle speed is omitted. Thus, when no correction is performed, normal steering angle control is executed.

On the other hand, as a result of the determination in step 101, if it is determined that acceleration is occurring (if the answer is Yes), the steering angle during acceleration including the setting process of the amount of steering angle to be returned during acceleration. The process proceeds to step 102 and subsequent steps in order to switch to correction control.

When controlling the steering angle during turning acceleration, first check the accelerator opening to determine whether the acceleration state requires correction. In doing so, instead of adjusting the steering angle in response to the accelerator operation, the rear wheels are returned with a certain delay in response to changes in the accelerator opening as described later (including returning the in-phase steering angle, the steering angle is adjusted in the opposite direction to the front wheels). With this control, which can cause the rear wheels to return in the opposite direction, it is appropriate to reduce understeer during acceleration so that it does not go against the driver's intention to press the accelerator pedal more with the intention of accelerating. It can also be executed. When reducing understeer during turning acceleration, when this is done by correcting the steering angle, the steering angle correction does not become too sensitive compared to simply moving the rear wheels with the amount of accelerator operation.
Therefore, it is possible to reduce the discomfort caused by the vehicle's sway due to oversensitivity, and it is also possible to reliably reduce understeer with control that is more comfortable for the driver.

To explain below, in this program, when the program proceeds from step 101 to step 102, a correction steering angle amount setting process is executed. An example of this process is as shown in FIG. 4, and in this example, the amount of return of the rear wheels for correction is also changed depending on the lateral g and vehicle speed.

First, in step 200, the maximum value δmax of the steering angle to be returned from the in-phase steering angle is set in accordance with the accelerator opening TH. FIG. 5 shows an example of the relationship between the accelerator opening TH and the returned rear wheel steering angle, and the δmax value is determined by searching a table of such characteristics. The δmax determines the maximum steering amount (maximum return amount) for steering the rear wheels (returning the same phase) at the time of correction, and functions as a basic value in the following processing, and its value is dependent on the accelerator opening TH. It is desirable to increase the value accordingly (the upper limit is selected as being within the maximum steerable range of β in Fig. 2 described above), but in that case, Fig. 5
It does not have to be a linear characteristic as shown in FIG. In addition, if the accelerator opening is 0%, if the accelerator opening is TH.
It may be possible to have characteristics such as starting from
Experiments have shown that it is better to have a characteristic that has a value (not 0) in a range greater than or equal to a predetermined accelerator opening, as shown in the figure, to better match the driver's intentions. There is.

δmax, which is the basic value for steering angle correction
Once the value has been retrieved, in the next step 201, a gain G1 is retrieved in order to set what percentage of δmax should be the amount of steering angle to be returned according to the magnitude Yg of the lateral g. FIG. 6 shows an example of the characteristics that can be applied in this case.
It shows how the magnitude of the rear wheel steering angle to be returned, determined by , changes with lateral g. As shown in Figure 6, the gain G
It is desirable for 1 to take a larger value as the lateral g increases (this is because the higher the g, the more understeer characteristics occur, so in order to reduce understeer, such characteristics should be adopted). ).

Here, the gain G1 is also desirably set to 0 when the lateral g is small, and therefore, it is preferable that the gain G1 is set to a characteristic that starts from a predetermined Yg value, for example, about 0.6 g. If the vehicle is started from too low a g, the movement of the vehicle will increase when the accelerator is operated, which can easily lead to a sense of discomfort, but by doing the above, it is possible to prevent such a sense of discomfort from occurring. Further, although FIG. 6 shows an example of a linear characteristic, the table characteristic does not necessarily have to be linear in this case as well.

In the next step 202, a gain G2 is similarly determined in accordance with the vehicle speed V to set the percentage of the δmax to be returned to. Similarly to the gain G1 according to the lateral g, FIG. 7 also shows how to change the magnitude of the rear wheel steering angle to be returned as determined in FIG. This is an example of the characteristics that can be changed. Here, the gain G according to the vehicle speed V
Regarding 2, the characteristic tendency can be selected depending on the type of vehicle to which it is applied. That is, in the case of a normal vehicle, it is generally desirable to have a characteristic that increases as the vehicle speed V increases as shown in Figure 7 (a), but it is desirable to have a characteristic that increases as the vehicle speed V increases, as shown in Fig. 7 (a), but it is desirable to enjoy turning performance like a mid-ship vehicle, and dislike understeer even with a small R. If you want to improve the stability of your vehicle at high speed, you may use such a table by setting the characteristics as shown in FIG. Furthermore, there is no particular problem if the gain G2 is kept constant regardless of the vehicle speed.

[0033] Therefore, as described above, steps 200~
Once the δmax value, G1 value, and G2 value are determined in step 202, the steering angle (return amount) to be returned is determined, so the following step 20
In step 3, the corrected steering angle amount δo is determined as the steering angle to be returned by calculation using the following equation δo = δmax ×G1 ×G2.

Specifically, when using the characteristic examples shown in FIGS. 5, 6, and 7 (normal case (A)), for example, when the accelerator opening is 100%, δmax is, for example, 1 degree,
For example, the gain G1 is 80 when the lateral g is 0.8 g.
%, gain G2 is, for example, vehicle speed 100km/h.
When it is 70%, the speed is 100km/h and the lateral g is 0.
8g, when correcting the rear wheel steering angle at full throttle, the steering angle to be returned to the rear wheel in step 203 is as follows: δo = 1° x 80% x 70% = 0.56°
It will be calculated.

Returning to FIG. 3, once the steering angle to be returned to is determined as described above, in step 103 following step 102, the rear wheel steering angle is corrected by the amount of return by a predetermined delay with respect to the accelerator operation. In order to achieve this, in this example,
A first-order delay filter is applied to changes in accelerator opening. That is, as mentioned above, the calculated correction amount is δo = δma
If x×G1×G2, then by filtering here, the steering angle δ1 to be returned is expressed by the following equation. δ1 = δo / (1+τS)
... 6 Here, in the above equation 6, τ is a time constant that is inserted to prevent the movement of the rear wheel from becoming too sensitive to the accelerator operation, and its value is selected from this point of view. For example, τ = 1
Approximately 00 to 200 msec is preferable.

In this way, even if the steering angle of the controlled object is corrected according to the following general formula 7 using the above δ1, and the detection mode is based on the accelerator opening, hypersensitivity can be removed and stability can be improved. It is possible to correct the steering angle. δ=(K+TS)θ±δo/(1+τS)
…7 However, the above
This is the case where the normal steering angle control law is (K+TS)θ, where K and T are proportional constants and differential constants according to Equations 1 and 2, and Equations 3 and 4, respectively.

Therefore, in the case of rear wheel steering angle, step 10
The rear wheel steering angle when corrected in step 4 is: δr = (Kr + Tr S) θ±δO / (1
+TS) ... is written as 8. Note that here, since the normal rear wheel steering angle control law is δr = (Kr + Tr S) θ as in equation 4 above, it becomes as shown in equation 8 above, but the normal control law (equation 8
It goes without saying that the first term) is not necessarily limited to this, and even if other control laws are used, Equation 8
It can be similarly implemented by applying the correction according to the second term. Further, the direction of return is determined based on the lateral g direction, and is a direction in which the steering wheel makes a small turn toward the inside of the turn during acceleration (in the normal steering state, it is in the opposite direction). The reason for determining the turning direction based on lateral g rather than the steering wheel angle is to prevent the change in the rear wheel steering angle from being too large, for example when applying countersteering during a turn. , Therefore, when making a judgment based on lateral g, these advantages can also be obtained.

Thus, when the steering angle is corrected according to the above equation 8, the rear wheel steering angle control output process is executed based on the correction control steering angle δr, and as a result, in the acceleration correction,
The rear wheels are steered back toward the opposite phase, but at this time, the steering angle is not corrected properly before the understeer characteristic occurs, and the steering angle is too sensitive, causing the vehicle to wander and become unstable. can be avoided from decreasing. That is,
By applying the correction according to the second term of Equation 8, it is possible to match the timing at which understeer characteristics occur due to accelerator operation and the actual steering angle correction timing based on that operation, so that the vehicle does not detect steering angle correction as a factor. This can prevent twitching. In this case, the value of the above-mentioned time constant T may be changed, for example, depending on the vehicle speed and lateral g (or it can be implemented without changing it in this way). Moreover, this control is accurate control in the sense that it does not go against the driver's intention.

[0039] I would like to add a further note regarding 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 wheels The yaw moment generated by the driving force acts in a direction that impedes the turning of the vehicle, increasing the load 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, the driving force is originally applied to the front, which puts a heavy burden on the front tires and tends to cause understeer characteristics. In addition, in 4WS, the rear wheels are steered in the same phase, so yaw movement Since the vehicle is exerting force in a direction that cancels out the above, the understeer characteristic becomes even stronger. ).

On the other hand, according to the present control, when accelerating a turn with the aim of improving turning performance, the above-mentioned understeer can be made appropriate and eliminated with accurate correction timing. That is, when accelerating during a turn, this is detected by the accelerator opening when determining acceleration, and the rear wheels can be steered in the opposite phase direction with a predetermined delay.
It can eliminate pushing understeer due to rear wheel drive force in D and FR cars, and understeer caused by reduced front wheel cornering force due to front wheel drive force generation in FF cars, making it possible to generate the required yaw rate at the optimal timing. be. When yaw rate occurs, the sideslip angle of the front wheels decreases and the sideslip of the rear wheels increases, which reduces the load on the front and allows the rear to generate greater calling force, and this can be achieved without causing any discomfort.

It is also conceivable to switch the control of the rear wheels by detecting the rate of change in vehicle speed or the rate of change in engine speed. We are proposing a device that makes corrections according to changes). When detecting vehicle speed and engine speed, when taking into consideration things such as inner wheel slipping during a turn, there may be a phenomenon where the driver's intention and the detected amount do not necessarily match, and this may cause a sense of discomfort. is also expected. With this control, the sense of discomfort from this point is also alleviated.

[0042] Although the above description has mainly focused on correction during acceleration, correction during deceleration can also be performed in the same manner, and since the control during deceleration is in the opposite direction to that during acceleration, there is an effect of suppressing tuck-in. Therefore, even when turning and decelerating, the steering angle can be corrected in accordance with the driver's intention without making it too sensitive.
It is possible to appropriately reduce tuck-in during deceleration with control that does not cause discomfort. 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.

[0043]

As described above, the steering angle control device of the present invention adjusts the steering angle of the controlled wheel in response to accelerator operation in steering angle control that controls at least one of the front wheel auxiliary steering angle and the rear wheel steering angle. Since the correction is configured to be controlled to be performed with a predetermined delay in response to the accelerator operation, it is possible to avoid making the steering angle correction too sensitive, and to achieve control with less discomfort such as vehicle wobbling. To be able to increase the effectiveness of steering angle correction control, and to appropriately realize the reduction of understeer and tack-in during acceleration and deceleration of turns with characteristics that suit the driver's intention and cause as little discomfort as possible. is possible.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a steering angle control device of the present invention.

FIG. 2 is a system diagram showing an embodiment of the steering angle control device of the present invention.

FIG. 3 is a flowchart showing an example of a control program for correction processing of the controller in the same example.

FIG. 4 is a diagram showing an example of a subroutine for determining a corrected steering angle amount using turning logic that can be applied to the same program.

FIG. 5 is a diagram showing an example of the characteristics of the relationship between the accelerator opening degree and the return steering angle amount that can be applied to the same subroutine.

FIG. 6 is a diagram showing an example of characteristics when the return amount is similarly changed according to lateral acceleration.

FIG. 7 is a diagram showing an example of characteristics when the return amount is similarly changed according to the vehicle speed.

[Explanation of symbols]

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 14, 15 Steering angle control valve 16 Controller 17 Rudder angle sensor 18 Vehicle speed sensor 20 Accelerator sensor 21 Lateral acceleration sensor

Claims (1)

[Claims] 1. Steering state detection means for detecting a steering state of a steering wheel; a steering mechanism for auxiliary steering of at least one of a front wheel or a rear wheel of a vehicle; an accelerator operation detection means for detecting an accelerator operation; The control means is capable of controlling the steering by the steering mechanism with a control steering angle according to a predetermined control law based on the output of the detection means, the control means being capable of controlling the steering with a control steering angle according to a predetermined control law, the control means having a predetermined delay with respect to the accelerator operation detected by the accelerator operation detection means. A steering angle control device comprising: a steering angle control means having a correction means for correcting a front wheel auxiliary steering angle or a rear wheel steering angle.