JPH11198844A - Steering effort controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain good steering characteristics by generating steering assist effort so that steering holding power may be minimum in an optimum steering angle necessary for traveling with a detected road curvature and at a vehicle speed detected by a vehicle speed detecting means. SOLUTION: A controller 15 calculates an optimum steering angle passing through a corner based on an inputted road curvature ρand a vehicle speed detected value V, calculates steering assist torque for minimizing steering holding power to travel at a corner with a vehicle speed detected value V based on the steering angle and the vehicle speed detected value V, and outputs pulse current corresponding to the steering assist motor 13. Where the steering assist torque command value of the controller 15 and the actual steering assist torque are equal to each other and there occurs no delay, it acts as power steering in the case of running without steering effort control, and the steering assist torque is determined based on the steering torque of the steering torque sensor 17 and the vehicle speed detected value V of the vehicle speed sensor 18. The current corresponding to it is outputted to a steering assist motor 13 to generate steering assist torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering force control device that changes a neutral value of a steering torque according to a road curvature in order to appropriately encourage a driver to steer.

[0002]

2. Description of the Related Art A conventional steering force control is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-273301.

In this conventional example, a white line at a predetermined forward gazing point distance is photographed by a CCD camera and supplied to an arithmetic processing unit, and the vehicle speed detected by a vehicle speed sensor is supplied to the arithmetic processing unit. A vehicle which performs automatic steering by calculating the relative displacement amount of the white line and the vehicle and its temporal change amount, calculating the control gain, and calculating the steering angle by θ = KPPe + Ke ・ de / dt. An automatic driving device is described.

[0004]

However, in the above-mentioned conventional steering force control device, a target position is provided in a lane, and when the own vehicle position is deviated therefrom, the steering angle is automatically controlled. Since it is configured to displace the vehicle to the target position, for example, even if the vehicle is traveling at the target position, it is not satisfactory at that position, and it is difficult to make fine corrections such as a little more right and a little left Issues.

[0005] Taking the straight running as an example, the relationship between the steering angle and the steering torque of a normal vehicle is shown by a solid line LU in FIG. The torque is set to increase, and the slope of the straight line LU is determined by the self-aligning torque.

However, in an autonomous vehicle, when the steering wheel is turned, an actuator such as a motor separates the self-aligning torque from the self-aligning torque.
The steering wheel is forcibly returned to the neutral position. When the power of this motor is strong, the slope becomes steep so that the steering torque increases sharply with the increase of the steering angle, as shown by the straight line LA shown by the dotted line in FIG. 12, and the driver generates a small steering torque. It becomes difficult to do. Conversely, if the power of the motor is weak, the lane following performance of automatic driving will be reduced.

That is, it is difficult to finely correct the steering wheel in an automatically driven vehicle, or even if it is possible, a driver is required to have a larger force than a normal vehicle. This is also a problem when avoiding an obstacle in front during automatic driving. In this case, the driver's steering torque may be detected and measures such as automatic driving cancellation may be taken. However, when automatic driving is again performed, a switch operation for setting is necessary again, which is troublesome, especially in the lane. There is an unsolved problem in that repeated changes cause driver stress.

Accordingly, the present invention has been made in view of the above-mentioned unsolved problems of the conventional example. Instead of performing automatic driving, it is the driver who only steers, and the road curvature is reduced. Accordingly, the steering torque is minimized at the correct steering angle so that the driver can easily steer correctly.
The driver can freely steer by generating a steering assist force around the steering angle so that the vehicle normally exhibits the same steering characteristics as the steering characteristics generated around the neutral steering angle in a straight running state. It is an object of the present invention to provide a steering force control device capable of realizing performance of reducing a load on a driver by prompting a driver to perform appropriate steering with a steering force.

[0009]

In order to achieve the above object, a steering force control device according to a first aspect of the present invention includes a curvature detecting means for detecting a road curvature ahead, a vehicle speed detecting means for detecting a vehicle speed, A steering torque generating means for generating a steering torque based on the road curvature detected by the road curvature detecting means and the vehicle speed detected by the vehicle speed detecting means, wherein the steering torque generating means comprises: The vehicle is configured to generate a steering assist force such that the steering holding force is minimized at an appropriate steering angle required for traveling at the vehicle speed detected by the vehicle speed detecting means with the road curvature detected by the detecting means. Features.

The steering force control device according to claim 2 is
In the invention according to claim 1, the steering torque generating means is characterized in that the steering torque generating means sets the appropriate steering angle to a neutral position of a steering characteristic between a steering angle and a steering torque.

Further, in the steering force control device according to a third aspect, in the invention according to the second aspect, the steering torque generating means is configured to determine a steering assist force while learning the steering characteristics. It is characterized by:

Further, in the steering force control device according to a fourth aspect, in the invention according to the first aspect, the steering torque generating means may include a steering assist force set according to a road curvature.
It is characterized in that it is set to be maximum at an appropriate steering angle, and to decrease as the distance from the appropriate steering angle increases.

Still further, in the steering force control apparatus according to claim 5, in the invention according to claim 4, the rate at which the steering assist force is set to be smaller as the distance from the proper steering angle is increased is increased as the road curvature is increased. It is characterized by having been set to.

[0014]

According to the first aspect of the present invention, the steering torque generating means has an appropriate steering angle required for traveling at the vehicle speed detected by the vehicle speed detecting means by the road curvature detected by the road curvature detecting means. Since the steering assist force is generated to minimize the steering force, the driver only needs to steer to the steering angle at which the steering force is minimized, so that the mental burden due to driving is reduced and In addition, when steering the steering wheel at the will of the operator, there is obtained an effect that the steering force control has no influence and good steering performance can be realized.

According to the second aspect of the present invention, the steering torque generating means sets the proper steering angle to a neutral position of the steering characteristic between the steering angle and the steering torque, so that the steering assist force according to the road curvature is obtained. In the generated state, a steering feeling similar to the neutral position of the steering characteristics of the steering angle and the steering torque, that is, the steering characteristics similar to the steering characteristics when traveling straight ahead can be obtained, and the operation of avoiding an obstacle ahead can be easily performed. The driver can feel that the self-aligning torque around the steering angle required to pass through the corner is increased, and the driver can feel more secure.

According to the third aspect of the present invention, the steering torque generating means is configured to determine the steering assist force while learning the steering characteristics. When a deviation occurs in the steering characteristics due to variations in the production of the vehicle, the deviation can be corrected, and the effect of maintaining the optimum steering characteristics according to the running conditions and the vehicle conditions can be obtained.

According to the fourth aspect of the present invention, the steering torque generating means sets the steering assist force set in accordance with the road curvature to a maximum at an appropriate steering angle, and to decrease as the distance from the appropriate steering angle increases. Therefore, the guide function for surely recognizing an appropriate steering angle to the driver can be further strengthened, and the effect of reducing the steering load can be obtained.

According to the fifth aspect of the present invention, the rate at which the steering assist force is set to be smaller as the steering angle departs from the appropriate steering angle is set to become larger as the road curvature becomes larger, so that the road curvature becomes larger. , The steering angle increases, and the driver's sense of tension increases, so that the effect that the optimum steering angle can be more easily understood is obtained.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In the drawing, a steering wheel 1 is connected to an upper end of a steering shaft 2, and the steering shaft 2 is rotatably supported by a fixed portion. .

The lower end of the steering shaft 2 is connected via a universal joint 3, a column shaft 4 and a universal joint 5 to a pinion shaft 7 having a pinion 6 attached to the lower end.

The pinion 6 meshes with a rack 8 extending horizontally in the vehicle width direction to form a steering gear, and the rotational motion from the steering wheel 1 to the steering shaft 2 is a linear motion (translational motion) of the rack 8. Is converted to

The ends of the horizontally extending rack 8 are respectively connected to knuckles and steered wheels 10 via tie rods 9.
The left and right steered wheels 10 are steered by the rack 8 moving horizontally (translational movement).

The assist pinion 1 is mounted on the rack 8.
The assist pinion 11 is connected via a speed reducer 12 to a rotation shaft of a steering assist motor 13 serving as a drive source, and the steering assist motor 13 is subjected to duty control output from a control unit 15 described later. The control is performed so as to generate a steering assist force corresponding to the steering torque by the generated pulse current.

The steering shaft 2 has
Actual steering angle θ of tearing wheel 1 _RSteering angle to detect
A sensor 14 is provided and detected by the steering angle sensor 14.
The actual steering angle θ is, for example, positive for a right-turn state and positive for a left-turn state.
Output to the controller 15 described later as a negative voltage signal.
Is forced.

The pinion shaft 7 is provided with a torque detecting mechanism 16. This torque detecting mechanism 16
Is constituted by a torsion bar (not shown) connecting the lower end of the pinion shaft 7 and the upper end of the pinion 6, and a steering torque sensor 17 disposed on the outer periphery thereof.

The steering torque sensor 17 detects the steering torque from the amount of twist of the torsion bar, and turns the steering wheel 1 to the right according to the magnitude of the steering torque (counterclockwise with respect to the input from the pinion 6). ) To supply a torque detection value T, which is a voltage signal of a positive value and a negative value signal when the steering wheel 1 is turned left (clockwise with respect to the input from the pinion 6), to a control unit 15 described later.

The vehicle is provided with a vehicle speed sensor 18 for detecting the vehicle speed. The vehicle speed sensor 18 detects the vehicle speed in the front-rear direction of the vehicle, and detects a vehicle speed detected by a voltage signal corresponding to the magnitude of the vehicle speed. V is supplied to a control unit 15 described later.

Further, the vehicle is equipped with a road curvature detecting device 19 as road curvature detecting means for detecting a road curvature ahead. One example of the road curvature detection device 19 is as follows.
For example, as described in JP-A-8-5388, a distance between a white line located on the left side of the vehicle, which represents the three-dimensional shape of the road, the vehicle position, and the vehicle attitude, and the vehicle center (the mounting position of the imaging device). , A parameter B representing the yaw angle of the vehicle with respect to the tangential direction of the white line, a parameter D representing the pitch angle of the vehicle with respect to the road plane, and a parameter E representing the distance between the white lines. The white line drawn on the road to the horizontal plane (X
-Z), a white line model approximated by a quadratic equation in the vertical plane (XY) is considered by a linear equation, and this is projected on an xy coordinate system planar screen through an optical lens having a focal length f. Of each parameter A to E
Is converted into a white line model on the road surface image using the parameters a to e newly defined in association with the above, and the road curvature ρ is calculated based on this, and is output to the controller 15 described later.

Then, in the control unit 15,
Based on the input road curvature ρ and the vehicle speed detection value V, an optimum steering angle θ is calculated when passing through the corner, and the vehicle travels on the corner with the vehicle speed detection value V based on the calculated steering angle θ and the vehicle speed detection value V. For this purpose, a steering assist torque Ta that minimizes the steering holding force is calculated, and a pulse current corresponding to the steering assist torque Ta is output to the steering assist motor 13.

Next, FIG. 2 shows a steering force control processing procedure in which the operation of the above embodiment is executed by the control unit 15.
Will be described with reference to the flowchart of FIG. This steering force control process is executed as a main program. First, in step S1, the actual steering angle θ _R detected by the steering angle sensor 14 is calculated.
After the steering torque detection value T _R detected by the steering torque sensor 17, the vehicle speed detection value V detected by the vehicle speed sensor 18, and the road curvature ρ detected by the road curvature detection device 19 are read, the process proceeds to step S 2.

[0031] The step S2, is calculated by referring to a steering assist torque TA normal steering torque calculation map shown in FIG. 3 for a steering torque detection value T _R and the vehicle speed detection value V is set in advance based.

Here, the steering torque calculation map is
It is stored in advance in the memory constituting the roller 15 and
As shown in FIG. 3, the horizontal axis represents the steering torque detection value T._DOn the vertical axis
Take the steering assist torque TA and set the vehicle speed detection value V as a parameter.
The steering torque detection value T _DSteer as it increases
The auxiliary torque TA increases, and the inclination of the auxiliary torque TA increases.
It is set so that it becomes smaller as it gets better.

Next, the process proceeds to step S3, where it is determined whether or not to perform the steering force control based on, for example, whether or not a steering force control selection switch provided in the vicinity of the driver's seat is turned on. If not, step S4
Then, a pulse current having a current value corresponding to the calculated steering assist torque TA is output to the steering assist motor 13 so as to have a direction corresponding to the steering direction, and the process returns to step S1.

If the result of the determination in step S3 indicates that the steering force control is to be performed, the process proceeds to step S5 to refer to the steering angle calculation map shown in FIG. 4 based on the detected vehicle speed V and the road curvature ρ. Then, the optimum steering angle θ for passing through the corner of the road curvature ρ at the vehicle speed detection value V is calculated.

Here, the steering angle calculation map is stored in a memory constituting the controller 15 in advance. As shown in FIG. 4, the vehicle speed detection value V is plotted on the horizontal axis and the steering angle θ is plotted on the vertical axis. It is represented by a parabolic characteristic curve LA using the curvature ρ as a parameter, and is set to shift downward as the road curvature ρ decreases, that is, as the corner radius increases.

Next, the process proceeds to step S6, and based on the calculated optimum steering angle θ and the detected vehicle speed V, the corner of the road curvature ρ is determined by referring to the steering torque calculation map shown in FIG. , The steering assist torque Ta required when passing at the steering angle θ is calculated.

Here, the steering torque calculation map is stored in advance in a memory constituting the controller 15 similarly to the steering angle calculation map. As shown in FIG. 5, the abscissa indicates the vehicle speed detection value V, and the ordinate indicates the ordinate. Is represented by a characteristic curve LB that is parabolic in a low vehicle speed range and linear at a predetermined vehicle speed or more, and shifts downward as the optimal steering angle θ decreases, with the optimal steering angle θ as a parameter. It is set as follows.

Next, the process proceeds to step S7, where it is determined whether or not the road curvature ρ is positive. If ρ> 0, it is determined that the vehicle is turning right, and the process proceeds to step S8, and the process proceeds to step S2. From the steering assist torque TA calculated in step S
A value obtained by subtracting the steering assist torque Ta calculated in step 6 is calculated as a new steering assist torque TA, and then the above-described step S is performed.
4, when ρ ≦ 0, it is determined that the vehicle is turning left, and the process proceeds to step S9, in which the steering assist torque TA calculated in step S6 is added to the steering assist torque TA calculated in step S2. The new steering assist torque TA
Then, the process proceeds to step S4.

[0039] Thus, now, when the actual steering assist torque TA _R generated by command value and the steering assist motor 13 of the steering assist torque TA output from the controller 15 shall not occurred equally delayed, the steering force control When the vehicle is not running normally, it acts as a power steering. In step S2, a steering assist torque TA is obtained based on the steering torque T of the steering torque sensor 17 and the vehicle speed detection value V of the vehicle speed sensor 18, and the steering assist torque TA is calculated. by outputting a corresponding current to the steering assist motor 13 to generate steering assist torque TA _R.

As shown in FIG. 6, the relationship between the steering angle θ _R , the realized steering torque T, and the steering assist torque TA does not perform the steering assist represented by the straight line L0 shown by the dashed line. The actual steering torque with respect to the steering torque in the case is represented by a straight line L2 shown by a broken line
Is obtained by subtracting the steering assist torque TA represented by the following equation.

On the other hand, even when the steering force control is performed, the relationship shown in FIG. 6 does not change when the vehicle travels straight in which the road curvature ρ is “0”. However, when the vehicle travels in a corner having a road curvature ρ by performing the steering force control, a uniform steering assist torque TA is applied regardless of the steering angle so that the required steering force at that time becomes “0”. I do.

That is, when the steering force control process shown in FIG. 2 is executed, the process shifts from step S3 to step S5 to refer to the steering angle calculation map shown in FIG. 4 based on the detected vehicle speed V and the road curvature ρ. To calculate the optimum steering angle θ for traveling through a corner, and calculate the optimum steering angle θ and the vehicle speed detection value V.
The steering torque T is calculated with reference to the steering torque calculation map of FIG. 5 based on the above, and the steering assist torque Ta is generated so that the steering torque T becomes “0”.

At this time, assuming that the steering assist torque TA calculated in step S2 is not considered, for example, when the vehicle speed detection value V is 100 km / h and the vehicle runs on the right corner of 300R, the necessary steering angle θ Assuming that _R is 10 ° and the required steering torque T is 0.4 Nm, FIG.
By executing the steering force control processing of FIG. 7, the steering characteristic representing the relationship between the steering torque and the steering angle is shifted to the right as shown by the solid line in FIG. 7 with respect to the normal steering force characteristic shown by the dashed line in FIG. Now that cut 10 ° steering wheel, the steering torque T _R is "0", the steering angle is the neutral position of the steering force characteristics.

Therefore, the driver can recognize that the steering angle at which the steering wheel is turned 10 ° to the left is the optimum steering angle when passing through this corner, and the driver can adjust the steering angle around the optimum steering angle. Since the steering can be performed with exactly the same steering force characteristics as a normal vehicle, the operation of avoiding an obstacle ahead can be performed as desired by the driver.

Actually, in the process of FIG.
From step S7 to step S8, where the positive right steering assist torque TA calculated in step S2 is set to step S8.
Since the steering assist torque Ta calculated in 6 is subtracted,
As shown by the solid line in FIG. 8, the optimum steering angle θ ₁ as shown by the straight line L11 with respect to the steering torque when the steering assist control shown by the dashed line L10 is not performed.
As a result, the steering torque is "0", that is, the steering holding force is "0", and the steering characteristics before and after the steering torque are substantially the same as the steering characteristics when the steering angle is "0", that is, the straight traveling.

In the first embodiment, the optimum steering angle θ and the steering assist torque Ta are calculated using the steering angle calculation map shown in FIG. 4 and the steering holding torque calculation map shown in FIG.
However, in practice, there is a difference between the calculated value using the map and the actual value due to road surface friction coefficient μ, tire characteristics, and variations during production of the vehicle, and the like. In addition, as described below, it is preferable that the deviation between the calculated value using the map and the actual value is compensated by obtaining the steering angle calculation map and the steering torque calculation map by learning.

That is, when the vehicle is represented by a general two-wheel model, the equation of motion is represented by the following equations (1) and (2). Where m: vehicle mass, γ: yaw rate, β: vehicle body slip angle, θ: steering angle, Cf: front wheel cornering power, C
r: rear wheel cornering power; Lf: distance between front wheel and center of gravity; Lr: distance between rear wheel and center of gravity; I: vehicle yaw moment of inertia; N: steering gear ratio; Represents

Here, it is γ ′ = β ′ = 0 because the user wants to know the stationary characteristic. At this time, the relationship between the yaw rate γ and the steering angle θ is expressed by the following equation. Here, Ks is a stability factor, and Ks =
(M / L ²⁾ represented by (LrCr-LfCf) / CfCr) .

On the other hand, between the road curvature ρ and the yaw rate γ, there is a relationship of γ = ρV (4). It can be expressed as.

Next, the relationship between the steering torque T and the steering angle θ is determined. Here, the steering torque T is proportional to the self-aligning torque, and the self-aligning torque is proportional to the cornering force of the front wheels during normal driving. It can be expressed as. From the above equations (1) and (2) By substituting the equations (3) and (7) into the equation (6), Becomes

The basis of the steering angle calculation map shown in FIG. 4 is the equation (5), and the basis of the steering torque calculation map shown in FIG. 5 is the equation (8). First, the steering angle θ
And the relationship between steering torque T. This relationship is learned when no control is performed. Here, it is assumed that the unknown parameters are P, N, and Ks, and the other parameters that are initially set are correct.

In a state where it can be determined that the vehicle is "steady" during normal running, the relationship between the steering angle θ and the steering torque T is sampled as data, and P, N, and Ks are identified by the least square method every moment. In this manner, a mathematical expression corresponding to the steering torque calculation map of FIG. 4 can be obtained, and an arbitrary vehicle speed detection value V
And the steering torque T can be obtained at the steering angle θ.

On the other hand, from equation (5), the road curvature ρ and the steering angle θ
Can be defined. Here, the unknown parameters are N and Ks. This parameter identification may be either control or non-control.

In the state considered to be "steady" as in the case described above, data of the road curvature ρ and the steering angle θ are collected, and N and Ks are identified every moment by the least square method or the like. N and Ks obtained here may be different from N and Ks obtained from the relationship between the steering angle θ and the steering torque T.

In this manner, a mathematical expression corresponding to the steering angle calculation map shown in FIG. 3 can be obtained, and an optimum steering angle θ can be obtained for an arbitrary detected vehicle speed V and road curvature ρ.

It should be noted that the above-mentioned "steady state" is preferably a state where the fluctuation of the steering angle has continued within a predetermined range (for example, within ± 2 °) for a predetermined time (for example, about 20 seconds).

As described above, the equations (8) and (5) corresponding to the steering angle calculation map of FIG. 3 and the steering torque calculation map of FIG. 4 can be obtained by learning. Even when the tire characteristics change or when there is a variation in the production of the vehicle, it is possible to obtain an accurate optimum steering angle θ and steering torque Ta.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the function of guiding the optimum steering angle θ in the first embodiment is further enhanced.

That is, in the second embodiment, as shown in FIG. 9, the steering assist torque Ta at the optimum steering angle θ calculated in the steering force control processing of FIG.
Is maximized at the optimum steering angle θ, and the steering assist torque Ta is gradually reduced as the distance from the optimum steering angle θ increases.

That is, as shown in FIG. 10, in the above-described steering force control processing of FIG. 2, after calculating the steering assist torque Ta in step S6, the process proceeds to step S11, where the current steering angle sensor detects the torque. The deviation Δθ between the detected steering angle θ _R and the optimum steering angle θ is calculated, and then the step S
Then, the process proceeds to step S12, where the following equation (9) is calculated based on the deviation θ and the steering assist torque Ta, and the steering assist torque correction value
After calculating the a _A, except that the process proceeds to step S7 to execute the same processing as FIG.

Ta _A = Ta−K _P · Δθ (9) According to the second embodiment, in the above-described first embodiment, the steering assist corresponding to the steering angle θ and the road curvature ρ. As shown in FIG. 11A, the relationship with the torque Ta is such that the steering assist torque Ta increases as the road curvature increases.
Although it becomes larger, the steering angle θ is maintained at a constant value. However, in the second embodiment, FIG.
As shown in, the steering assist torque Ta _A is the maximum in accordance with the road curvature ρ at the optimal steering angle theta, since the steering angle from the optimum steering angle theta is the steering assist torque Ta _A is to be decreased with distance, driving Can more reliably recognize the optimum steering angle θ.

Further, as shown by a dashed line in FIG. 11B, if the slope η is increased as the road curvature ρ is increased, the driver is more nervous and the steering angle is larger, and the steering is more optimally performed. This is preferable because the angle θ can be easily recognized.
For this purpose, the proportionality constant K _P in the above-mentioned equation (9) is used.
May be set to increase as the road curvature ρ increases.

In the first and second embodiments, the case where the road curvature detecting device for estimating the road curvature using the television camera has been described. However, the present invention is not limited to this. Instead of, for example,
As described in JP-A-81602, the image information of a road ahead captured by a television camera is converted into planar image information, and a first point a predetermined distance before and a second point farther than this are connected based on the image information. The first between the straight line and the center line of the vehicle
The declination β at the intermediate point between the point and the second point is calculated, and the curve radius R (1 / ρ) is estimated based on the declination β and the distance K between the intermediate point and the vehicle. Good.

Also, instead of using a television camera,
When a transmitting device for transmitting the road curvature information is laid on the side of the road, the road curvature and the turning direction may be detected by receiving the road curvature information from the transmitting device.

Further, a relative lateral displacement measuring means for measuring a relative lateral displacement of the vehicle with respect to the road at a predetermined vehicle front gazing point and a steering angle detecting means for detecting at least one of the front wheels and the rear wheels of the vehicle are provided. Alternatively, the road curvature may be obtained by calculation based on the relative lateral displacement and the steering angle.

Further, a navigation system combining map information mounted on a vehicle and a vehicle position detecting device such as a GPS for specifying the position of the vehicle is used to calculate a road curvature ahead of the current position. Is also good.

In the first and second embodiments, the case where the assist pinion 11 connected to the auxiliary steering motor 13 is meshed with the rack 8 has been described. However, the present invention is not limited to this. The auxiliary steering motor 13 is connected to the pinion shaft 7 via power transmission means such as gears.
May be connected. In short, the auxiliary steering motor 13
What is necessary is just to be able to transmit the auxiliary steering torque generated in the steering system to the steering system.

Further, in each of the above embodiments, the case where the steering assist force is generated by the steering assist motor 13 has been described. However, the present invention is not limited to this.
A hydraulic power steering device can also be applied.

Further, in each of the above embodiments, the case where the actual steering assist torque actually generated by the steering assist motor 13 has no delay with respect to the command torque from the control unit 15 has been described. If there is a delay between the command torque and the actual steering assist torque generated by the steering assist motor 13, it goes without saying that the delay is compensated for. For example, when the transfer function of the actual steering assist torque / command torque is H (s) and the control transfer function to be realized is Y _c (s), Should be set to.

Further, when there is a possibility of sudden change due to noise on the road curvature detected by the road curvature detecting device 19, a limiter is used or a noise filter composed of a low-pass filter is used. Needless to say, it is preferable to do so.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating an example of a steering force control processing procedure executed by a controller of FIG. 1;

FIG. 3 is a characteristic diagram showing a steering assist torque calculation map showing a relationship between a steering torque detection value and a steering assist torque using a vehicle speed as a parameter.

FIG. 4 is a characteristic diagram showing a steering angle calculation map showing a relationship between a vehicle speed detection value and an optimum steering angle using a road curvature as a parameter.

FIG. 5 is a characteristic diagram showing a steering torque calculation map showing a relationship between a vehicle speed detection value and a steering assist torque using an optimum steering angle as a parameter.

FIG. 6 is a characteristic diagram illustrating a relationship between a steering angle and a steering torque when steering force control is not performed.

FIG. 7 is a characteristic diagram illustrating a relationship between a steering angle and a steering assist torque when steering force control is performed.

FIG. 8 is a characteristic diagram showing a relationship between a steering angle and actual steering assist torque when steering force control is performed.

FIG. 9 is a characteristic diagram illustrating a relationship between a steering angle and a steering torque according to the second embodiment of the present invention.

FIG. 10 is a flowchart illustrating an example of a steering force control processing procedure according to the second embodiment.

FIGS. 11A and 11B are characteristic diagrams showing a relationship between a steering angle and a steering assist torque according to a road curvature, wherein FIG. 11A is a characteristic diagram of the first embodiment, and FIG. 11B is a characteristic diagram of the second embodiment; FIG.

FIG. 12 is a characteristic diagram showing a relationship between a steering angle and a steering torque in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 steering shaft 6 pinion 8 rack 10 steered wheel 11 steering assist pinion 13 steering assist motor 14 steering angle sensor 15 control unit 17 steering torque sensor 18 vehicle speed sensor 19 road curvature detecting device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 13:00

Claims (5)

[Claims] 1. A road curvature detecting means for detecting a curvature of a road ahead, a vehicle speed detecting means for detecting a vehicle speed, and a steering based on a road curvature detected by the road curvature detecting means and a vehicle speed detected by the vehicle speed detecting means. A steering torque control device comprising: a steering torque generating means for generating torque; wherein the steering torque generating means is required to travel at a vehicle speed detected by the road curvature detecting means by the road curvature detected by the road curvature detecting means. A steering force control device configured to generate a steering assist force such that a steering holding force is minimized at an appropriate steering angle. 2. The steering force control device according to claim 1, wherein the steering torque generating means sets the appropriate steering angle to a neutral position of a steering characteristic between the steering angle and the steering torque. 3. The steering force control device according to claim 2, wherein the steering torque generating means is configured to determine a steering assist force while learning the steering characteristics. 4. The steering torque generating means is set such that a steering assist force set in accordance with a road curvature is maximized at an appropriate steering angle and becomes smaller as the steering angle is further away from the appropriate steering angle. The steering force control device according to claim 1, wherein 5. The method according to claim 4, wherein the rate of setting the steering assist force to be smaller as the steering angle is away from the proper steering angle is set to be larger as the road curvature becomes larger.
The steering force control device according to any one of the preceding claims.