JP3431061B2 - Vehicle steering control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering control device capable of changing a transmission ratio between a steering amount of a steering wheel and a turning amount of wheels.

[0002]

2. Description of the Related Art Conventionally, there has been known a vehicle steering control device provided with a transmission ratio variable mechanism capable of changing a transmission ratio between a steering amount of a steering wheel and a steering amount of wheels. For example,
Japanese Unexamined Patent Publication No. 4-283168 is provided with a road surface state detection sensor for detecting a road surface state, and a transmission ratio is set according to a road surface state (a frictional state between a road surface and wheels) detected by the road surface state detection sensor and a vehicle speed. By setting it, proper turning performance is always obtained according to the road surface condition and the vehicle speed.

[0003]

Conventionally, the transmission ratio is changed according to the road surface condition thus detected.
Since the entire road surface is detected as a uniform road surface condition and the subsequent processing is executed, when driving on a straddling road where the frictional state with the road surface is different on the right wheel side and the left wheel side, hydroplaning occurs and drive If the frictional state between the wheel and the driven wheel is different from the road surface, a suitable transmission ratio may not be set and the vehicle behavior may become unstable.

The present invention has been made to solve such a problem, and an object thereof is to appropriately set the transmission ratio even in a situation where the frictional state of the road surface is not uniform, and to control and stabilize the vehicle. To provide a steering control device for a vehicle, which can sufficiently secure the property.

[0005]

Therefore, a vehicle steering control device according to a first aspect of the present invention is a vehicle steering control device that steers wheels according to a steering operation.
Transmission ratio setting means for setting the transmission ratio of the steering amount to the turning amount, and wheel speed detection for detecting the wheel speed of the right wheel and the left wheel
Means and the wheel speed of the right wheel detected by the wheel speed detection means
The larger the wheel speed difference between the
And a changing means for changing the transmission ratio set by the constant means to a small value . In addition, the vehicle steering control device
In the setting, the changing means is configured such that the wheel speed difference is from the first wheel speed difference.
Transmission increases as the speed increases up to the second wheel speed difference
It is preferable to change the ratio to a smaller value.

In a straddling road where the road surface conditions on the right wheel side and the left wheel side are different, the frictional state between the road surface and the wheels is different on the right wheel side and the left wheel side. Therefore, the changing means compares the frictional states of the right wheel side and the left wheel side, and as a result, if there is a predetermined difference between the two frictional states, the transmission ratio set by the transmission ratio setting means is changed. To do. At this time, changing the transmission ratio to a larger value (slow) suppresses a change in vehicle behavior due to steering, and changing the transmission ratio to a smaller value (quick) makes it easier to control the attitude of the vehicle.

A vehicle steering control device according to claim 2 is
A vehicle steering control device for steering wheels according to steering, comprising transmission ratio setting means for setting a transmission ratio of a steering amount to a steering amount according to a traveling state of a vehicle, and wheels for driving wheels and driven wheels. The transmission ratio set by the transmission ratio setting means is changed based on the comparison result of the wheel speed detection means for detecting the speed and the wheel speed of the drive wheel and the driven wheel speed detected by the wheel speed detection means. And a changing means for performing the change.

When hydroplaning occurs, the wheel speeds of the driving wheels and the driven wheels become different.
Therefore, the changing means compares the wheel speeds of the driving wheel and the driven wheel, and as a result, if there is a predetermined difference between the two wheel speeds, the transmission ratio set by the transmission ratio setting means is changed. . At this time, for example, by changing the transmission ratio to a smaller value (quick), posture control becomes easier to perform,
Alternatively, by changing the transmission ratio to a larger value (slow), changes in vehicle behavior due to steering are suppressed.

A vehicle steering control device according to claim 3 is
A vehicle steering control device for steering wheels according to steering, comprising transmission ratio setting means for setting a transmission ratio of a steering amount to a steering amount according to a traveling state of a vehicle, and wheels for driving wheels and driven wheels. Determination means for determining hydroplaning based on speed, vehicle behavior detection means for detecting vehicle behavior,
After escaping from the hydroplaning, a change unit is provided for changing the transfer ratio set by the transfer ratio setting unit to a smaller value based on the detection result of the vehicle behavior detecting unit.

From the determination result of the determination means, it is detected that the vehicle has escaped from the hydroplaning, and when the vehicle behavior is large immediately after the vehicle has escaped from the hydroplaning, the transmission ratio set by the transmission ratio setting means is made smaller. By changing the value (quick), it becomes easier to perform the steering operation for controlling the vehicle behavior.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
An example of a front-wheel drive vehicle will be described with reference to the accompanying drawings.

FIG. 1 shows the configuration of a steering apparatus 100 according to the embodiment.

The input shaft 20 and the output shaft 40 are connected via a transmission ratio variable mechanism 30, and the steering handle 10 is connected to the input shaft 20. The output shaft 40 is connected to a rack shaft 51 via a rack and pinion type gear device 50, and front wheels FL, F are provided on both sides of the rack shaft 51.
R is connected.

Further, the input shaft 20 is provided with an input angle sensor 21 for detecting the steering position of the steering wheel 10, and the output shaft 4
0 is an output angle sensor 4 that detects the rotational position of the output shaft 40.
1 is provided. The rotation angle of the output shaft 40 is the rack shaft 5
Since the stroke position of the rack shaft 51 corresponds to the turning angle of the front wheels FL and FR, the rotation angle of the output shaft 40 is detected by the output angle sensor 41. The steering angle of is detected.

The transmission ratio variable mechanism 30 includes the steering handle 10.
Transmission ratio G between the steering angle of the vehicle and the turning angles of the front wheels FL, FR
It has a function of changing (G = steering angle / steering angle), and is provided with an actuator 31 as a drive source for changing the transmission ratio G.

As shown in FIG. 2, the left front wheel FL and the right front wheel F
Wheel speed sensors 71 to 74 are provided for the R, the left rear wheel RL, and the right rear wheel RR, respectively. In addition to these, a vehicle speed sensor 75 for detecting the traveling speed of the vehicle and a yaw rate applied to the vehicle are detected. A yaw rate sensor 76 and the like are provided. The detection result of each sensor is given to the steering control device 60, and the control signal Is according to the detection result is output from the steering control device 60 to the actuator 31. As described above, the drive control of the variable transmission ratio mechanism 30 is performed by the steering control device 60.

Here, each processing of the steering control device 60 configured as above will be described with reference to the flowchart of FIG.

This flowchart is started by turning on the ignition switch. First, the process proceeds to step (hereinafter, the step is referred to as “S”) 102, and the left front wheel speed WF which is the detection result of each wheel speed sensor 71 to 74.
L, right front wheel speed WFR, left rear wheel speed WRL, right rear wheel speed WRR, vehicle speed V detected by the vehicle speed sensor 75, input angle θh detected by the input angle sensor 21, output angle sensor 4
The values of the output angle θp detected in 1 and the yaw rate γ detected by the yaw rate sensor 76 are read.

After that, the routine proceeds to S200, where a predetermined transmission ratio setting process is executed based on each detection result read in S102, and the transmission ratio G is set according to the traveling state.
The specific process of setting the transmission ratio G will be described in detail later.

At S104, θpm = (1 / G) * θh is calculated based on the transmission ratio G set at S200 and the input angle θh read at S102, and the output angle target value θ is obtained.
Set pm.

In subsequent S106, the deviation e between the output angle target value θpm set in S104 and the output angle θp detected by the output angle sensor 41 is calculated as e = θpm−θp.

In subsequent S108, the actuator 31 is set so that the deviation e is set to 0 without overshooting.
The control signal Is for controlling is determined. As an example of this processing, PI is calculated based on the operational expression of Is = C (s) * e.
The control signal Is can be determined by appropriately setting the D control parameter. In addition, "s" in a formula is a Laplace operator.

In subsequent S110, the control signal Is determined in S108 is output to the actuator 31, and the actuator 31 is driven according to the control signal Is.

Thereafter, the process proceeds to S112, it is judged whether the ignition switch (IG) is turned off, and "No" is determined.
In the case of, the process proceeds to S102 and the above-mentioned processing is repeatedly executed. Then, such processing is repeatedly executed until “Yes” is determined in S112.

By repeatedly executing such processing, the transmission ratio according to the traveling state of the vehicle is set, and the steering control is performed using the set transmission ratio.

Here, the setting process of the transmission ratio G executed in S200 will be described with reference to the flowchart of FIG.

On a straddle road where the left and right road surface conditions are different, the left and right wheel speed difference ΔWLR tends to increase as the left and right road surface conditions greatly differ. So first S212
To the front left wheel speed WFL, right front wheel speed W
Using FR, the wheel speed difference ΔW between the left and right front wheels, which are the driving wheels
LR is calculated as ΔWLR = | WFL−WFR |.

At S214, based on the basic transmission ratio map which defines the relationship between the vehicle speed V and the basic transmission ratio Go shown in FIG.
A map search is performed based on the vehicle speed V detected in S102, and a basic transmission ratio Go is set according to the vehicle speed V.

In subsequent S215, a map search is performed based on the left / right wheel speed difference ΔWLR calculated in S212 from a correction gain map that defines the relationship between the left / right wheel speed difference ΔWLR and the correction gain α1 shown by the solid line in FIG. Then, the supplementation gain α1 is set according to the left / right wheel speed difference ΔWLR.

Then, in S216, Go * α1 is calculated using the basic transmission ratio Go set in S214 and the correction gain α1 set in S215, and the calculation result is calculated as the transmission ratio G1.
Set as.

Thus, the basic transmission ratio Go is corrected by the correction gain α1 set according to the magnitude of the left and right wheel speed difference ΔWLR, and this corrected value is set as the transmission ratio G.

When the map is defined as the correction gain map as shown by the solid line in FIG. 6, the value of the left / right wheel speed difference ΔWLR becomes large in the region where the left / right wheel speed difference is Δ1 ≦ ΔWLR ≦ Δ2. The basic transmission ratio Go is corrected to the quicker side, and is corrected to the quickest side in the region of Δ2 ≦ ΔWLR. As a result, it is possible to facilitate the attitude control of the vehicle when traveling on a straddle road.

As the correction gain map, a map can be defined as shown by the broken line in FIG. In this case, the left and right wheel speed difference is Δ1 in the map indicated by the broken line.
In the region of ≦ ΔWLR ≦ Δ2, the difference between the left and right wheel speeds ΔWL
The larger the value of R is, the more the basic transmission ratio Go is corrected to the slow side, and the most is corrected to the slow side in the region of Δ2 ≦ ΔWLR. As a result, it is possible to suppress a change in the behavior of the vehicle due to the steering during traveling on the overpass.

As another embodiment of S200, the process shown in the flowchart of FIG. 7 can be executed.

First, in S222, similarly, the left and right wheel speed difference ΔWLR is calculated as ΔWLR = | WFL-WFR |, and in subsequent S224, the basic transmission ratio Go according to the vehicle speed V is set using FIG. To do.

After that, the routine proceeds to S226, where the left and right wheel speed difference ΔWLR calculated at S222 is the predetermined threshold value TH.
It is determined whether it is greater than 1. As a result, if the left and right wheel speed difference ΔWLR is less than or equal to the threshold value TH1, S22
8, the value of the basic transmission ratio Go is set as it is as the transmission ratio G, and this routine is ended.

On the other hand, in S226, the difference in wheel speed between the left and right wheels ΔW
When LR is larger than the threshold value TH1, the process proceeds to S230 and Go * α2 is set using the correction gain α2 defined in advance.
Is calculated, and the calculation result is set as the transmission ratio G.

As described above, when the left / right wheel speed difference ΔWLR is larger than the threshold value TH1, it is also possible to adopt a method of correcting the basic transmission ratio Go using the correction gain α2 defined in advance. In this case, the value of the correction gain α2 can be set to α2 <1 or α2> 1 as in the case of α1, and the same effect as that of α1 can be obtained.

Further, as S200, the process of setting the transmission ratio G can be executed by executing the flowchart of FIG.

When hydroplaning occurs, in the case of a front-wheel drive vehicle, a wheel speed difference occurs between the front wheel that is a driving wheel and the rear wheel that is a driven wheel. Therefore, first, S232
Then, by calculating WF = (WFL + WFR) / 2, the wheel speed WF of the front wheel is obtained as an average value of the wheel speed WFL of the left front wheel and the wheel speed WFR of the right front wheel, and W
By calculating R = (WRL + WRR) / 2, the wheel speed WR of the rear wheel is obtained as an average value of the wheel speed WRL of the left rear wheel and the wheel speed WRR of the right rear wheel.

In subsequent S234, the wheel speed difference WF between the front wheels and the rear wheels is calculated using the wheel speed WF of the front wheels and the wheel speed WR of the rear wheels calculated in S232: ΔWFR = | WF-
Then, in S236, the basic transmission ratio Go according to the vehicle speed V is set in S236.

In subsequent S237, the wheel speed difference ΔWFR between the front and rear wheels calculated in S234 is calculated from the correction gain map which defines the relationship between the wheel speed difference ΔWFR between the front and rear wheels and the correction gain α3 shown by the solid line in FIG. A map search is performed based on, and a supplementary gain α3 is set according to the wheel speed difference ΔWFR between the front wheels and the rear wheels.

Then, the process proceeds to S238, in which the correction gain α3 set in S237 and the basic transmission ratio G set in S236 are set.
Go * α3 is calculated using o, and the calculation result is set as the transmission ratio G.

Thus, the wheel speed difference ΔW between the front wheels and the rear wheels is
The basic transmission ratio Go is corrected by the correction gain α3 set according to the magnitude of FR, and the corrected value is set as the transmission ratio G.

When the map is defined as shown by the solid line in FIG. 9 as the correction gain map in this way, in the region where the wheel speed difference between the front wheels and the rear wheels is Δ3 ≦ ΔWFR ≦ Δ4, the wheel speed difference between the front wheels and the rear wheels is shown. The larger the value of ΔWFR, the more the basic transmission ratio Go is corrected to the quick side, and Δ4 ≦ ΔWFR
Is corrected to the quickest side in the area. This makes it easier to control the attitude of the vehicle when hydroplaning occurs.

Further, as the correction gain map, a map can be defined as shown by a broken line in FIG. In this case, in the region where the wheel speed difference between the front wheels and the rear wheels is Δ3 ≦ ΔWFR ≦ Δ4 in the map shown by the broken line, the basic transmission ratio Go becomes slower as the value of the wheel speed difference ΔWFR between the front wheels and the rear wheels becomes larger. Is corrected to the slowest side in the region of Δ4 ≦ ΔWFR. As a result, it is possible to suppress a change in vehicle behavior caused by steering when hydroplaning occurs.

As a process when hydroplaning occurs, S200 can be executed as shown in FIG.

First, like S232 to S236,
After proceeding to S242, the wheel speed WF of the front wheels and the wheel speed WR of the rear wheels are obtained, and then proceeding to S244, the wheel speed difference ΔWFR between the front wheels and the rear wheels is calculated, and proceeding to S246, the basic transmission ratio according to the vehicle speed V. Set Go.

In subsequent S248, it is determined whether the wheel speed difference ΔWFR between the front wheels and the rear wheels is larger than a predetermined threshold value TH2. As a result, the wheel speed difference between the front wheels and the rear wheels ΔWFR
Is less than or equal to the threshold value TH2, the process proceeds to S250 and S
The basic transmission ratio Go set in 246 is set as the transmission ratio G as it is, and this routine is ended.

On the other hand, if it is determined in S248 that the wheel speed difference ΔWFR between the front wheels and the rear wheels is larger than the threshold value TH2, the correction processing is started.

First, in S252, the map is searched based on the vehicle speed V at this time from the correction gain map shown in FIG. 11, and the correction gain α4 corresponding to the vehicle speed V is set.

In subsequent S254, Go * α4 is calculated using the basic transmission ratio Go set in S246 and the correction gain α4 set in S252, and the calculation result is set as the transmission ratio G, and this routine is executed. finish.

Thus, the wheel speed difference ΔW between the front wheels and the rear wheels is
When FR is larger than the threshold value TH2, the basic transmission ratio Go is corrected by the correction gain α4 set according to the vehicle speed V, so that the speed is quicker at low speed than when hydroplaning does not occur. On the other hand, the transmission ratio G is set to the slower side at high speed. As a result, it becomes easier to control the attitude of the vehicle when hydroplaning occurs during low-speed traveling, and it is possible to suppress changes in vehicle behavior due to steering when hydroplaning occurs during high-speed traveling.

It should be noted that the process shown in the flowchart of FIG. 12 can be executed in S200 within a fixed time immediately after the escape from the hydroplaning.

First, in S262, the basic transmission ratio Go according to the vehicle speed V is set based on the map of FIG. 5, and then in S264, the value of the yaw rate γ read in S102 is a predetermined value. It is determined whether it is larger than the threshold value TH3. When the value of the yaw rate γ is equal to or less than the threshold value TH3, the process proceeds to S266, the basic transmission ratio Go set in S262 is set as it is as the transmission ratio G, and this routine is finished.

On the other hand, if it is determined in S264 that the value of the yaw rate γ is larger than the threshold value TH3, the vehicle behavior is large. In such a case, the routine proceeds to S268, where the basic transmission ratio Go is The value of the correction gain α5 is set so as to more quickly correct. In this case, the value of the correction gain α5 defined in advance as α5 <1 is set, or
Alternatively, as the value of the yaw rate γ increases, the correction gain α5 increases.
It is also possible to set the value of the correction gain α5 according to the magnitude of the yaw rate γ so that the value of is smaller.

In subsequent S270, Go * α5 is calculated using the correction gain α5 set in S268, the calculation result is set as the transmission ratio G, and this routine is ended.

As described above, when the vehicle behavior is large immediately after escape from the hydroplaning, the basic transmission ratio Go is corrected so as to be quicker, thereby facilitating the steering operation for controlling the vehicle behavior. it can. It should be noted that, after a certain period of time elapses from the escape from the hydroplaning, the routine shown in FIG.
The process returns to the predetermined transfer ratio setting process that was executed before the shift to 2.

The correction gains α1 to α4 in each of the embodiments described above can be set in accordance with the corresponding wheel speed difference, vehicle speed, and the like.

Further, the case where the vehicle speed V is detected as the traveling state of the vehicle and the basic transmission ratio Go is set according to the vehicle speed V has been exemplified, but in addition to this, as the traveling state of the vehicle, the vehicle speed V and the input angle θh. Can be detected and the basic transmission ratio Go can be set according to the vehicle speed V and the input angle θh.

Further, the case where the yaw rate γ is directly detected by the yaw rate sensor 76 as the behavior of the vehicle has been illustrated, but the present invention is not limited to this example and may be estimated from the detection results of other sensors.

[0062]

As described above, according to the vehicle steering control apparatus of the first aspect, the transmission ratio setting means sets the friction ratio between the right wheel side and the left wheel side based on the comparison result. Since it is equipped with a changing means for changing the transmission ratio, it is possible to set a suitable transmission ratio according to the road surface condition on the left and right even when traveling on a straddle road, ensuring sufficient maneuverability and stability of the vehicle. can do.

Further, according to the vehicle steering control device of the second aspect, the transmission ratio set by the transmission ratio setting means is calculated based on the result of comparison between the wheel speeds of the driving wheels and the wheel speeds of the driven wheels. Since the changing means for changing is provided, it is possible to set a suitable transmission ratio according to the occurrence of hydroplaning, and it is possible to sufficiently secure the maneuverability and stability of the vehicle.

According to the vehicle steering control device of the third aspect, the transmission ratio set by the transmission ratio setting means is changed to a larger value in accordance with the vehicle behavior after escape from the hydroplaning. Since the means is provided, it becomes possible to immediately reestablish the vehicle attitude even when the vehicle behavior is great after the vehicle escapes from the hydroplaning.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing the structure of a transmission ratio variable mechanism.

FIG. 2 is a block diagram showing an overall configuration of a steering control device.

FIG. 3 is a flowchart showing a steering control process.

4 is a flowchart showing an example of a transmission ratio setting process in FIG.

FIG. 5 is a basic transmission ratio map defining the relationship between vehicle speed V and basic transmission ratio Go.

FIG. 6 is a correction gain map that defines the relationship between the left and right wheel speed difference ΔWLR and the correction gain α1.

7 is a flowchart showing an example of a transmission ratio setting process in FIG.

8 is a flowchart showing an example of a transfer ratio setting process in FIG.

FIG. 9 is a correction gain map that defines the relationship of the correction gain α3 with respect to the wheel speed difference ΔWFR between the front wheels and the rear wheels.

10 is a flowchart showing an example of a transfer ratio setting process in FIG.

FIG. 11 is a correction gain map that defines the relationship between the vehicle speed V and the correction gain α4.

12 is a flowchart showing an example of a transmission ratio setting process in FIG.

[Explanation of symbols]

10 ... Steering handle, 21 ... Input angle sensor, 30 ... Transmission ratio variable mechanism, 31 ... Actuator, 41 ... Output angle sensor, 60 ... Steering control device, 71-74 ... Wheel speed sensor,
75 ... Vehicle speed sensor, 76 ... Yaw rate sensor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B62D 137: 00 B62D 137: 00 (72) Inventor Kawamuro Toko, Toyota City, Aichi Prefecture Toyota Town, Toyota Motor Corporation ( 56) References JP-A-4-283168 (JP, A) JP-A-3-193560 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 5/04

Claims (4)

(57) [Claims] 1. A steering control device for a vehicle, which steers wheels according to steering, comprising: a transmission ratio setting means for setting a transmission ratio of a steering amount to a steering amount according to a traveling state of a vehicle; and a right wheel. And wheel speed detecting means for detecting the wheel speed of the left wheel
And the wheel speed of the right wheel detected by the wheel speed detection means and the left
The greater the wheel speed difference from the wheel speed of the wheel, the more the transmission ratio setting
A vehicle steering control device comprising: a changing unit that changes the transmission ratio set by the setting unit to a small value . 2. The changing means is characterized in that the wheel speed difference is first.
Large in the range from the wheel speed difference to the second wheel speed difference
The smaller the transmission ratio, the smaller
The vehicle steering control device according to claim 1. 3. A vehicle steering control device for steering wheels according to steering, comprising: a transmission ratio setting means for setting a transmission ratio of a steering amount to a steering amount according to a traveling state of the vehicle; and a drive wheel. And wheel speed detecting means for detecting the wheel speed of the driven wheel, and based on the comparison result of the wheel speed of the driving wheel and the wheel speed of the driven wheel detected by the wheel speed detecting means, the previous transmission ratio setting means A steering control device for a vehicle, comprising: a changing unit that changes the transmission ratio set in step 1. 4. A vehicle steering control device for steering wheels according to steering, comprising: a transmission ratio setting means for setting a transmission ratio of a steering amount to a steering amount according to a traveling state of a vehicle; and a drive wheel. And a determination means for determining hydroplaning based on the wheel speed of the driven wheels, a vehicle behavior detection means for detecting the behavior of the vehicle, and a vehicle behavior detection means based on the detection result of the vehicle behavior detection means after escape from the hydroplaning. A steering control device for a vehicle, comprising: a changing unit that changes the transmission ratio set by the transmission ratio setting unit to a smaller value.