JP2000159134A - Steering control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the uncomfortableness of steering while restricting a change of the steering torque due to a backlash by controlling the drive of a transmission ratio variable mechanism on the basis of the backlash to be generated between gears in the case of performing the steering from the steering maintaining condition. SOLUTION: A transmission ratio variable mechanism 30 for driving a gear mechanism for connecting an input shaft 20 provided with an input angle sensor 21 for detecting the steering position of a steering wheel 10 and an output shaft 40 with an actuator 31 changes the transmission ratio between the steering angle of the steering wheel 10 and the steering angle of wheels FW1, FW2. Drive of the actuator 31 can be controlled so as to sufficiently reduce the backlash immediately after starting the steering from the steering maintaining condition by adding a value of f.K.θpO based on a coefficient K of steering condition, a coefficient (f) of the actuator 31 in the rotating direction and backlash angle θpO corresponding to the backlash as a correction value for obtaining θpO or -θpO in the only case of starting the steering from the steering maintaining condition to the output angle target value.

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 for controlling a variable transmission ratio mechanism for changing a transmission ratio between a steering angle of a steering wheel and a steering angle of a steered wheel.

[0002]

2. Description of the Related Art Hitherto, a transmission ratio variable mechanism for changing a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel has been known. For example, Japanese Patent Application Laid-Open No. Sho 62-214058 discloses that an input shaft connected to a steering wheel and an output shaft connected to a steering gear box are provided.
A steering device linked via a variable transmission ratio mechanism is disclosed. The transmission ratio variable mechanism is constituted by a planetary gear mechanism, and the rotation of the input shaft is transmitted to the output shaft via the planetary gear mechanism.By rotating the gears constituting the planetary gear mechanism by the actuator, This mechanism is capable of changing the transmission ratio at which the rotation of the input shaft is transmitted as the rotation of the output shaft.

[0003]

As shown in FIG. 5, the gears constituting the planetary gear mechanism include a driving gear 101 driven by an actuator and a driving gear 10
1 and a driven gear 102 that meshes with the driving gear 101. A backlash B exists between the driving gear 101 and the driven gear 102. When the steering is started from the state in which the steering wheel is maintained in the state where the backlash B exists, the actuator starts to rotate with the start of the steering, whereby the drive gear 101 starts to rotate. Here, assuming that the drive gear 101 starts rotating in the direction of arrow a, the gap that forms the backlash B with the rotation of the drive gear 101 gradually decreases, and the drive gear 1
As the rotation of 01 proceeds, the teeth 101h of the drive gear 101 come into contact with the teeth 102h of the driven gear 102. At this time, the teeth 101h of the drive gear 101 collide with the teeth 102h of the driven gear 102 at a certain speed, and the impact due to this collision is perceived as a slight change in the steering torque by the driver holding the steering wheel. It gives a feeling of steering discomfort.

An object of the present invention is to solve such a problem, and an object of the present invention is to suppress a change in steering torque due to backlash when steering is started from a steering holding state, and to provide a steering system. An object of the present invention is to provide a vehicle steering control device that can reduce uncomfortable feeling.

[0005]

SUMMARY OF THE INVENTION Accordingly, a vehicle steering control device according to the present invention includes a vehicle provided with a variable transmission ratio mechanism for changing a transmission ratio between a steering angle of a steering wheel and a steering angle of a steered wheel. A steering control device, comprising: a steering state detecting unit that detects a steering state of a steering wheel; a driving unit that drives a transmission ratio variable mechanism; and a transmission ratio variable mechanism when steering is performed from a steering maintaining state. And control means for performing drive control of the drive means based on the backlash generated between the constituent gears.

Immediately after steering is performed from the steering-holding state, the control means drives the variable transmission ratio mechanism by the driving means so as to sufficiently reduce backlash.
Subsequently, the drive control of the variable transmission ratio mechanism is continued with the backlash substantially eliminated. By first driving the variable transmission ratio mechanism so as to sufficiently eliminate backlash, a change in steering torque due to backlash is sufficiently suppressed.

[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 vehicle steering system 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. Is detected.

The variable transmission ratio mechanism 30 includes a gear mechanism for connecting the input shaft 20 and the output shaft 40. The gear mechanism is driven by an actuator 31 so that the steering angle of the steering wheel 10 and the wheel FW1, It has a function of changing a transmission ratio G (G = steering angle / steering angle) between the FW2 and the 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 is supplied with detection signals of a vehicle speed sensor 60 for detecting a vehicle speed in addition to the input angle sensor 21 and the output angle sensor 41, and based on these signals, sets a transmission ratio and sets the set transmission. The drive control of the transmission ratio variable mechanism 30 is performed according to the ratio.

Here, the processing executed by the steering control device 70 will be described with reference to 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 values of the output angle θp detected by the vehicle speed V and the vehicle speed V detected by the vehicle speed sensor 60 are read.

In the following S104, a map showing the relationship between the vehicle speed V and the input angle θh and the transmission ratio G shown in FIG.
A map search is performed based on the vehicle speed V and the input angle θh read in 02, and a transmission ratio G corresponding to the vehicle speed V and the input angle θh is set.

In S106, θpm = (1 / G) · θh is calculated based on the transmission ratio G set in S104 and the input angle θh read in S102, and an output angle target value θpm is set. I do.

In the following S108, the correction value θα of the output angle target value θpm set by the processing described later is read, and in the next S110, the output angle target value θpm set in S106 is read in S108. By adding the correction value θα, the value of each output target value θpm is updated.

In S112, the deviation e between the output angle target value θpm updated in S110 and the output angle θp detected by the output angle sensor 41 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.
The control signal Is can be determined by appropriately setting the parameters of the D control. Note that “s” in the expression is a Laplace operator.

At S116, the control signal Is determined at S114 is output to a drive circuit (not shown) for driving the actuator 31. This allows the drive circuit to operate the actuator 31 in accordance with the control signal Is.
Drive.

Then, the program proceeds to S118, in which it is determined whether or not the ignition switch (IG) has been turned off.
If “No”, the process returns to S102, and “Ye” in S118.
Until the determination is "s", the above-described processing from S102 onward is repeatedly executed.

By repeating such processing, the vehicle speed V
And the transmission ratio G according to the input angle θh, and the wheels FW1, FW2 according to the input angle θh based on the set transmission ratio G.
Steering control is performed.

Next, the process of setting the correction value θα 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 S202, in which the steering speed H of the steering wheel 10 is set. The steering speed H may be set to a value obtained by calculating dθh / dt from the value of the input angle θh read in S102, or may be set based on the transition of the input angle θh and its time interval.

In the following S204, it is determined whether the steering speed Hold stored in the previous routine is Hold = 0, that is, whether the steering wheel 10 is in the steering holding state. If the steering wheel 10 is in the steering state, “No” is determined in S204, the process proceeds to S206, and the steering state coefficient K
Is set to K = 0. Note that this steering state coefficient K
Are used in the setting process of the correction value θα described later.

On the other hand, if the steering wheel 10 is in the steering holding state in the previous routine, the process proceeds to S208,
It is determined whether the steering speed H set in S202 in this routine is H> 0. Here, the direction in which the sensor output of the input angle sensor 21 increases is right steering, and the direction in which the sensor output decreases is left steering. If Yes is determined in S208, steering in the right direction is started from the steering holding state. That is, in this case, the process proceeds to S210, and the value of the steering state coefficient K is set to K = 1.

If "No" is determined in step S208, the process proceeds to step S212.
This includes both the case where the steering in the leftward direction is started from the held state and the case where the steering is continuously maintained. Therefore, in S212, it is determined whether or not the steering speed H set in S202 in this routine is H <0. Here, if it is determined as “Yes”, it means that steering to the left has been started from the steering holding state, and in this case, the process proceeds to S214, and the value of the steering state coefficient K is set to K = −
Set to 1. If “No” is determined in S212, the steering holding state is continued, and in this case, the process proceeds to S216, and the value of the steering state coefficient K is set to K = 0.
Set to.

After setting the value of the steering state coefficient K in this manner, the process proceeds to S218, and stores the value of the steering speed H set in S202 as Hold. The stored steering speed Hold is used in the next routine.

At S220, the value of the transmission ratio G set at S104 is read. At S222, the value of the transmission ratio G set at S104 is compared with the value of the base transmission ratio Gbase. The base transmission ratio Gbase is a transmission ratio in a state where the actuator 31 of the transmission ratio variable mechanism 30 is stopped, and is set to be an intermediate value of the transmission ratio variable width here. Therefore, when Gbase ≧ G, speed-up control is performed, and when Gbase <G, deceleration control is performed. In the speed-up control and the deceleration control, the rotation direction of the actuator 31 in the transmission ratio variable mechanism 30 is reversed, and the drive gear 1 is used to sufficiently reduce the backlash B (see FIG. 5).
01 is rotated in a different direction.

Therefore, in the determination of S222, Gbase
If ≧ G (“Yes” in S222), the process proceeds to S224, where the direction coefficient f indicating the rotation direction of the actuator 31 in the speed increase control is set to f = 1, and if Gbase <G (“No” in S222). ) Proceeds to S226 and sets the direction coefficient f indicating the rotation direction of the actuator 31 in the deceleration control to f = −1.

After passing through S224 or S226, S22
In S228, the steering state coefficient K indicating the steering state previously set, the direction coefficient f indicating the rotation direction of the actuator 31, and the backlash angle θp0 set in advance to correspond to the backlash B are determined in S228. Based on this, the correction value θα is set as θα = f · K · θp0.

By setting the correction value θα based on such a routine, the value of the correction value θα becomes θα = θp0 or θα = only when steering is started from the steering holding state.
-Θp0, which value is taken depends on the steering direction of the steering wheel 10 and the rotation direction of the actuator 31. In a steering state other than the state where the steering is started from the steering holding state, θp0 = 0 is set.

Accordingly, in 110 of FIG. 2, the correction processing for adding the correction value θα to the output angle target value θpm is executed only when the steering is started from the steering holding state. In a steering state other than the normal state, the substantial correction processing in S110 is not performed, and the value of the output angle target value θpm set in S106 is not updated.
At 110, it is set as it is.

As described above, the correction value θα is added to the output angle target value θpm only when the steering is started from the steering holding state, so that immediately after the steering is started from the steering holding state, First, the drive of the actuator 31 is controlled so as to sufficiently reduce the backlash B. In the next and subsequent routines, the control can be performed with the backlash B substantially eliminated. For this reason, the fluctuation of the steering torque caused by the backlash B can be sufficiently suppressed, and the feeling of steering discomfort caused by the backlash B can be sufficiently suppressed.

In the above-described embodiment, the case where the output angle target value θpm set in S106 is smaller than the backlash when steering is started from the steering holding state has been described. In some cases, a system larger than the backlash may be configured. In such a case, in a routine immediately after the steering is started from the steering holding state, the actuator 31 is rotationally driven by an angle corresponding to the backlash B,
For example, a process of replacing the value of the deviation e with a predetermined value in S112 may be executed.

In addition to the method of correcting the control variables inside the steering control device 70 as described above, for example, the drive current or drive voltage output from the drive circuit for driving the actuator 31 Similar correction processing can be performed.

After such a correction process is performed in consideration of the occurrence of vibration and the like, a process such as prohibiting another correction process within a predetermined time or further correcting the correction value θα. It is also possible to do.

[0038]

As described above, according to the vehicle steering control apparatus of the present invention, when steering is performed from the steering-holding state, the backlash generated between the gears constituting the variable transmission ratio mechanism is reduced. Based on the above, a configuration including a control unit that controls the driving of the driving unit is adopted. Therefore, immediately after the steering is started from the steering holding state, the drive of the variable transmission ratio mechanism is controlled so as to sufficiently reduce the backlash, and subsequently, the drive of the variable transmission ratio mechanism is performed with the backlash substantially eliminated. Since the control can be performed, a change in the steering torque due to the backlash can be sufficiently suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a vehicle steering system according to an embodiment.

FIG. 2 is a flowchart illustrating a control process executed by the steering control device.

FIG. 3 is a map defining a relationship between a vehicle speed V, an input angle | θh |, and a transmission ratio G;

FIG. 4 is a flowchart illustrating a setting process of a correction value θα.

FIG. 5 is an explanatory diagram showing a backlash that occurs between a drive gear and a driven gear that constitute the variable transmission ratio mechanism.

[Explanation of symbols]

Reference Signs List 10 steering wheel, 20 input shaft, 21 input angle sensor, 30 variable transmission ratio mechanism, 31 actuator, 4
0: output shaft, 60: vehicle speed sensor, 70: steering control device,
100 ... steering device.

Claims (1)

[Claims] 1. A vehicle steering control device provided with a variable transmission ratio mechanism for changing a transmission ratio between a steering angle of a steering wheel and a steering angle of a steered wheel, wherein a steering state of the steering wheel is detected. A steering state detecting unit, a driving unit that drives the transmission ratio variable mechanism, and, based on a backlash generated between gears constituting the transmission ratio variable mechanism when steering is performed from a steering holding state,
A vehicle steering control device comprising: a control unit that performs drive control of the drive unit.