JPH11321683A - Steering control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering control device for vehicle capable of improving the steering operability in case of suddenly changing the behavior of the vehicle. SOLUTION: A value of yaw rate γs is estimated on the basis of the input angle θh and the car speed V (S 104), and in the case where a deviation between the estimated yaw rate γs and the real yaw rate γ exceeds a threshold value γth (YES in S 106), a value of the transmission ratio Gold set in the last routine is set as a transmission ratio G again (S 122), and change of the transmission ratio G is prohibited.

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 angle of a steering wheel and a turning angle of a wheel.

[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 angle of a steering wheel and a turning angle of a wheel. For example,
In Japanese Patent Application Laid-Open No. 62-46773, the transmission ratio is set according to the vehicle speed within a small steering angle where the steering angle of the steering wheel is near zero, and the change of the transmission ratio is prohibited in a steering range exceeding the small steering angle. . Thus, even when the vehicle speed changes during cornering, stable handling performance can be obtained without changing the transmission ratio.

[0003]

On the other hand, in a situation where the vehicle tends to skid and the vehicle behavior suddenly changes, there is a high possibility that the vehicle will spin or drift out. A counter operation may be performed to suppress the change. In such a situation, the vehicle speed often changes due to a brake operation or the like. Therefore, when the counter operation is performed in response to the sudden change in the vehicle behavior as described above, when the steering angle passes near zero, the set transmission ratio changes in accordance with the change in the vehicle speed, and the steering for rebuilding the vehicle body is performed. Operation was sometimes difficult.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a vehicle steering control device capable of improving steering operability at the time of a sudden change in vehicle behavior. is there.

[0005]

SUMMARY OF THE INVENTION Accordingly, a vehicle steering control device according to the present invention is a vehicle steering control device having a transmission ratio variable mechanism for changing a transmission ratio between a steering angle and a turning angle. A transmission ratio setting means for setting a transmission ratio of the transmission ratio variable mechanism, a behavior state detecting means for detecting a behavior state of the vehicle, and a behavior state of the vehicle when the behavior state of the vehicle suddenly changes, Prohibition means for prohibiting change of the transmission ratio set by the transmission ratio setting means.

[0006] In the case where the tendency of the vehicle to skid increases during traveling and the behavior of the vehicle changes suddenly, the change of the transmission ratio is prohibited by the prohibiting means. Thus, even when the vehicle speed changes, the transmission ratio is not changed and is maintained at a constant value.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the accompanying drawings.

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

The input shaft 20 and the output shaft 40 are connected via a variable transmission ratio 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. Wheels FW1,
FW2 is connected.

An input shaft 20 is provided with an input angle sensor 21 for detecting a steering position of the steering wheel 10.
0 is an output angle sensor 4 for detecting the rotational position of the output shaft 40
1 is provided. The rotation angle of the output shaft 40 is
1 and the stroke position of the rack shaft 51 corresponds to the turning angle of the wheels FW1 and FW2. Therefore, the rotation angle of the output shaft 40 is detected by the output angle sensor 41, so that the wheels FW1 and FW2 are detected. Is detected.

The variable transmission ratio mechanism 30 is provided with a gear mechanism for connecting the input shaft 20 and the output shaft 40. The gear mechanism is driven by an actuator 31 to change the steering angle between the steering angle and the steering angle. It has a function of changing the transmission ratio G (G = steering angle / steering angle).

The drive control of the variable transmission ratio mechanism 30 is performed by a steering control device 70. The steering control device 70 includes, in addition to the detection results of the input angle sensor 21 and the output angle sensor 41, a vehicle speed sensor 61 for detecting a traveling speed of the vehicle, and a yaw rate sensor 62 for detecting a yaw rate generated in the vehicle.
The transmission ratio is set based on these signals, and the transmission ratio variable mechanism 30 is set in accordance with the set transmission ratio.
Drive control is performed.

Here, each process executed by the steering control device 70 will be described with reference to the flowchart of FIG.

This flowchart is started by turning on an ignition switch. First, the process proceeds to step (hereinafter, step is referred to as “S”) 102, where the input angle θh detected by the input angle sensor 21 and the output angle sensor 41
, The yaw rate γ detected by the yaw rate sensor 62 and the output angle θp detected by the yaw rate sensor 62 are read.

The relationship between the input angle θh and the yaw rate γ during traveling at a predetermined vehicle speed Vn shows a characteristic schematically shown in FIG. 3, and this characteristic changes according to the magnitude of the vehicle speed V. The steering control device 70 calculates the input angle θh and the yaw rate γ
Is provided according to the magnitude of the vehicle speed V. In S104, a map is selected based on the vehicle speed V read in S102, and a map corresponding to the input angle θh based on the selected map is provided. Map search for the value of yaw rate γs,
The value of the yaw rate γs applied to the vehicle is estimated.

In a situation where the tendency of the vehicle to skid becomes excessive and the vehicle behavior suddenly changes, the deviation between the yaw rate γ detected in S102 and the yaw rate γs estimated in S104 becomes large. For example, when the vehicle has a tendency to spin, the value of the detected yaw rate γ rapidly increases compared to the estimated yaw rate γs, and when the vehicle tends to drift out, the value of the detected yaw rate γs is detected compared to the estimated yaw rate γs. The value of the yaw rate γ suddenly decreases.

In step S106, the deviation | γs−γ | between the estimated value of the yaw rate and the actually measured value is compared with a threshold value γth. As a result, the value of the deviation | γs−γ |
If it is smaller than th, the process proceeds to S108, where a map search is performed based on the vehicle speed V read in S102 from the map showing the relationship between the vehicle speed V and the transmission ratio G shown in FIG. Set the ratio G.

On the other hand, in step S106, the deviation | γs−γ
If it is determined that the value of | is equal to or greater than the threshold value γth, the process proceeds to S122, in which the transmission ratio G according to the vehicle speed V is not set, and the transmission ratio Gold set in the previous routine is not executed.
Is again set as the transmission ratio G set in this routine. In a situation where the vehicle behavior suddenly changes, such as when the vehicle tends to spin or drift out, S1
At 22, the value of the transmission ratio Gold set in the previous routine is also set in this routine, and the change of the transmission ratio G is prohibited.

After S108 or S122, S11
The process proceeds to 0, and based on the set transmission ratio G and the input angle θh read in S102, θpm = (1 / G) · θh is calculated, and an output angle target value θpm is set.

At S112, the output angle target value θpm set at S110 and the output angle θ read at S102.
The deviation e from p is calculated as e = θpm−θp.

In the following S114, the actuator 31 is set so that the deviation e becomes zero without overshooting.
Is determined. As an example of this processing, PI is calculated based on an arithmetic expression of Is = C (s) · e.
By appropriately setting the parameters of the D control, the control signal Is can be determined. Note that “s” in the expression is a Laplace operator.

In S116, the control signal Is determined in S114 is output to the actuator 31, and the actuator 31 is driven according to the control signal Is.

At S118, the value of the transmission ratio G set in the current routine is stored as Gold.

Thereafter, the program proceeds to S120, in which it is determined whether or not the ignition switch (IG) has been turned off.
In this case, the process returns to S102, and the above-described processing from S102 is repeatedly executed until “Yes” is determined in S120.

As described above, in a situation where the vehicle behavior suddenly changes, the value of the transmission ratio G is maintained at a constant value even when the vehicle speed V changes in S106 and S122.
Correction steering when the vehicle behavior suddenly changes can be facilitated.

The process for maintaining the value of the transmission ratio G at a constant value ends immediately when the result of the determination in S106 is "No", and the normal process of setting the transmission ratio G according to the vehicle speed V is performed. The process returns to the transmission ratio setting process.

As another condition for returning to the normal transmission ratio setting process, other than the time immediately after the determination of “No” in S106, the time for determining “No” is not used. If the vehicle has continued for a certain period of time (when the vehicle behavior has been stabilized for a certain period of time), “Yes
s ", a case where a predetermined sufficient time has elapsed, a case where the vehicle speed V = 0 and the vehicle stops, and the like. Further, when returning to the normal transmission ratio setting process during traveling, a method of gradually shifting the value of the transmission ratio G with time so as to prevent a sudden change in the value of the transmission ratio G may be adopted. it can.

In the embodiment described above, the case where the behavior state of the vehicle is detected by the yaw rate sensor 62 is exemplified. However, the lateral acceleration generated in the vehicle may be detected by the lateral acceleration sensor. It is. In this case, by comparing the detected lateral acceleration with the lateral acceleration estimated based on the input angle θh and the vehicle speed V, it is determined whether the vehicle behavior has suddenly changed.

[0029]

As described above, according to the vehicle steering control apparatus of the present invention, when the behavior state of the vehicle is suddenly changed, the change of the transmission ratio set by the transmission ratio setting means is prohibited. Since the means is provided, the transmission ratio is maintained at a constant value even when the vehicle speed changes in a situation where spin or drift out occurs. This makes it possible to avoid a situation in which the transmission ratio changes with a change in the vehicle speed in a situation where the vehicle behavior changes suddenly as in the past, and it is possible to improve the steering operability when the vehicle behavior changes suddenly. Become.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a steering device.

FIG. 2 is a flowchart purely showing processing executed by the steering control device.

FIG. 3 shows an input angle θh during traveling at a predetermined vehicle speed Vn.
4 is a map showing a relationship between the yaw rate γ and the yaw rate γ.

FIG. 4 is a map that defines a relationship between a vehicle speed V and a transmission ratio G;

[Description of Signs] 30 ... Transmission ratio variable mechanism, 31 ... Actuator, 62 ...
Yaw rate sensor, 70: steering control device.

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Takahiro Ogi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (1)

[Claims] 1. A vehicle steering control device provided with a transmission ratio variable mechanism for changing a transmission ratio between a steering angle and a turning angle, wherein the variable transmission ratio mechanism is provided in accordance with a running state of a vehicle. Transmission ratio setting means for setting the transmission ratio; behavior state detection means for detecting the behavior state of the vehicle; and when the behavior state of the vehicle changes suddenly, changing the transmission ratio set by the transmission ratio setting means is prohibited. A vehicle steering control device comprising prohibition means.