JP3314698B2 - Steering force assist device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the steering retention force required for a driver on a curved road, while directing the driver appropriate steering operation for the curved road accurately by applying appropriate controlling torque to retain the steering in response to the requirement for supplementary steering retention force. SOLUTION: A curvature calculation means 4A calculates the curvature of the driving lane ahead of the vehicle in the running direction, then a vehicle speed detection means 32 detects the vehicle speed of a running vehicle 1. Then, a control torque calculation means 5 calculates the control torque for steering retention based on the curvature of the running lane calculated by the curvature calculation means 4A and the vehicle speed of a running vehicle 1 detected by a vehicle speed detection means 32. A control means 6 controls a steering actuator 21 of the vehicle so that the control torque determined by a control torque calculation means 5 is generated in the direction assisting the turn of the running vehicle 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an automobile,
The present invention relates to a steering force assisting device that reduces a driver's steering force in a curve by applying a steering torque to a steering in accordance with a curve condition on a road surface ahead in a traveling direction.

[0002]

2. Description of the Related Art In order to assist a steering operation of a vehicle, a power steering device has been developed and spread, and a hydraulic power steering device (hereinafter abbreviated as "power steering" as appropriate) is widely spread. is there. In such a power steering, a torsion bar that twists according to a steering operation force applied to a steering wheel is interposed on a steering shaft, and a control valve is operated according to the torsion of the torsion bar to operate the power steering. The hydraulic pressure is controlled, and steering is assisted in an appropriate direction with an assist force corresponding to the steering operation force.

Therefore, if the torsional stiffness of the torsion bar interposed in the steering shaft is too high, the assisting force becomes insufficient with respect to the steering operation force, and the control valve cannot be operated accurately. Or to ensure power steering performance,
The rigidity of the torsion bar is suppressed.

[0004]

However, if the torsional rigidity of the torsion bar is suppressed as described above, the rigidity of the steering system is reduced, so that the feeling of rigidity at the time of steering operation is insufficient, and the steering feeling becomes poor. There is a problem of causing a decrease. However, as long as the power steering device that operates in response to the torsion bar relies on assisting the steering force, it is difficult to solve such a problem.

On the other hand, from the viewpoint different from the power steering, a technology capable of assisting the steering force has been developed. In other words, the position and attitude of the vehicle with respect to the road on which it is traveling are grasped, and based on this, the automatic driving control technology that automatically performs the accelerator operation and the steering operation of the vehicle, and the steering operation to guide the driver's driving A technology (driving guidance device) for assisting the vehicle has been developed.

[0006] In the case of automatic driving control, it is necessary to drive a car without relying on a driver at all, and various conditions are required for its practical use, such as the provision of basic facilities (infrastructure) such as roads. Is assumed. On the other hand, in the case of the driving guide device, the driver drives the automobile, and the driving guide device informs the driver of a driver's driving error and assists driving in a direction to eliminate the mistake. Therefore, the driving guidance device has many technologies that can be realized even in the current road environment,
It is desired to develop a more practical driving guide device.

[0007] On a curved road, lateral acceleration acts on the vehicle in a direction opposite to the turning direction, and the driver must steer the steering wheel against this lateral acceleration.
The driver is also required to have a large steering force according to the magnitude of the acting lateral acceleration. Therefore, it is conceivable to provide a steering control torque to the steering through the steering actuator to reduce the driver's steering force on a curved road.

In this case, how to apply the steering maintaining control torque is an issue. In other words, depending on the manner in which the steering control torque is given to assist the driver, the driver's steering operation may be hindered and the driver may feel uncomfortable, and the steering control torque does not cause the driver to feel uncomfortable. It is desirable to give it as natural as possible.

It is desired that the steering control torque be applied so as to guide the driver's steering operation along a curved road. The present invention has been made in view of the above-described problem, and reduces a driver's steering force on a curved road by applying an appropriate steering control torque in response to a steering force assistance request. An object of the present invention is to provide a steering force assisting device capable of accurately guiding a steering operation along a curved road to a driver.

[0010]

Therefore, in the steering force assisting device according to the present invention, the curvature calculating means includes an image information from the imaging means.
Calculate the road curvature ahead of the running direction of the vehicle based on the information ,
Vehicle speed detecting means detects the vehicle speed of the own vehicle. Then, the control torque calculating means calculates a lateral acceleration acting on the own vehicle based on the curvature of the traveling lane calculated by the curvature calculating means and the vehicle speed of the own vehicle detected by the vehicle speed detecting means, and calculates the calculated lateral acceleration.
A steering control torque is calculated according to the magnitude of the acceleration .
The control means controls the steering actuator of the vehicle such that the steering torque of the magnitude calculated by the control torque calculating means is added to the steering to which the steering torque is applied from the driver according to the curve situation ahead. In this case , more preferably, the calculated steering control torque is limited to a magnitude that the driver can overcome. It is also preferable that the steering control torque applied from the steering actuator to the steering be added to the steering torque from the driver and transmitted to the steered wheels via the power steering device.

According to this structure, when the host vehicle approaches a curve ahead in the traveling direction, the vehicle responds to a lateral acceleration predicted to act on the vehicle separately from the steering torque applied by the driver in a direction that assists the vehicle to turn along the curve. The steering control torque is applied by the steering actuator, so that the driver's steering force on the curved road is reduced, and the steering operation along the curved road is accurately guided to the driver.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 10 show a steering force assisting device as an embodiment of the present invention. This steering force assisting device is provided to reduce a driver's steering wheel steering load due to lateral acceleration acting on the vehicle when the vehicle is traveling on a curved road in a vehicle. When the vehicle approaches the curved road after recognizing the situation described above, as shown in FIG. 1, a steering torque (this steering torque is different from the steering torque applied by the driver by the steering actuator 21 provided in the vehicle). In order to distinguish the steering torque (hereinafter also referred to as a steering wheel) 20 of the driver, the burden on the steering wheel (hereinafter, also referred to as a steering wheel) 20 is reduced.

Of course, the steering control torque itself is also
It has the effect of correcting the behavior of vehicles on curved roads,
The main purpose of this steering control torque is to reduce the burden on the driver to maintain the steering wheel, and to correct the position of the vehicle so that it turns along a curve, the control torque for steering was added. Therefore, the operation is to be performed by the driver's steering operation whose burden is reduced.

Accordingly, as shown in FIG. 1, the present steering force assisting device includes a camera 2 as an image pickup means for picking up an image of a road condition in front of the vehicle 1 in order to recognize the position of the own vehicle with respect to the traveling lane. An image information processing means 3 for appropriately processing image information from image information from the camera 2 to recognize left and right white line positions on the front road, and a driving lane (traveling lane) based on the white line position image information by the image information processing means 3. ) Is provided with a curvature calculation means 4A for calculating the curvature ρ.

Although the lateral acceleration G can be calculated from the curvature ρ and the vehicle speed V, the lateral acceleration G corresponds to a determination parameter relating to a driver's burden on a curved road. Further, the curvature calculating means 4A includes a traveling lane estimation means 4 for estimating a relative position of a traveling lane (traveling lane) with respect to the own vehicle.
It is provided as a functional element within. Further, the present steering force assisting device includes a vehicle speed sensor 3 for detecting a vehicle speed V of the vehicle 1.
2, the vehicle speed V detected by the vehicle speed sensor 32, and the curvature ρ of the traveling lane calculated by the curvature calculating means 4A.
A control torque calculating means 5 for calculating a steering torque Tg based on the lateral acceleration G acting on the vehicle 1 based on the lateral acceleration G, that is, the degree of the driver's burden on a curved road. The steering actuator 21 that can apply a steering control torque Tg to the steering system separately from the applied steering torque, and the steering control torque Tg calculated by the control torque calculation means 5 is used to control the vehicle against the lateral acceleration G. A control means (controller) 6 for controlling the steering actuator 21 so as to generate in a direction that assists turning is provided.

A switch (SW) 23 for selecting the operation of the steering force assisting device is provided. Therefore, if you want to operate this device, turn on the switch 23,
If you do not want to operate this device, turn off switch 23,
It can be selected according to the driver's preference.
Further, for example, in the instrument panel (instrument panel), when the switch 23 is turned on, or when a steering control torque for reducing the load is applied, an operation display unit 24 for displaying the torque is provided. Have been.

The image information processing means 3, travel lane estimating means 4 (curvature calculating means 4A), control torque calculating means 5, and controller 6 are an electronic control unit having a CPU, an input / output interface, a ROM, a RAM, and the like. Is configured as First, the calculation of the degree of the size of the curve on which the vehicle travels, that is, the calculation of the curvature ρ of the traveling lane will be described.

In the image information processing means 3, first, as shown in FIG. 2, an original image 41 from the camera 2 is taken in, a road white line is extracted from the original image 41, and an image of the extracted road white line is converted into a vertical image. The image is converted into a two-dimensional image 42 as viewed from above. Next, the recognition of the white lines 12L and 12R is shown in FIG.
This will be described with reference to FIG. Here, the recognition of the white line 12L as the roadside line at the left end of the traveling lane will be described. However, the same applies to the case where the white line 12R at the right end of the traveling lane is used as a reference. I will call it.

Next, in the image information recognizing means 3, FIG.
As shown in FIG. 1A, a camera 2 provided on a vehicle 1 uses a camera 2 to cover a flat area (eg, 5 m to 30 m).
m), the image in the vertical direction on the screen is partially omitted from the image information. Then, a plurality of horizontal lines 11 are set at equal intervals on this screen. The capture of the black-and-white image information is updated every minute control cycle. As shown in FIG. 3B, on each horizontal line 11, the left and right positions of the white line position on the previous screen are required. (Here, the left and right 50 pixels [do
t]) is set as a white line search area (processing target area) 10. For the first screen, the white line position on the straight road is used as the previous screen data.

Then, as shown in FIG. 3C, the brightness of each horizontal line is differentiated in the horizontal direction from the left. Reference numeral 14 in the figure is a guardrail. By the way, a normal road surface has low luminance and a small change in luminance. On the contrary,
Since the brightness of the white line 12 is very high compared to the normal road surface, the brightness change is positive at the boundary point from the normal road surface to the white line 12, and the brightness change is positive. Differential data is obtained such that the luminance change becomes negative at the boundary point to. An example of such differential data is shown in FIG.

Then, for each data of each horizontal line 11, peaks of the differential values appear in the order of plus and minus from the left, and the interval between the peaks is the white line 12
Is extracted as a candidate for a white line, and a combination that falls within a reasonable degree (interval between a positive peak and a negative peak is within 30 dots, for example) is extracted.
As shown in FIG. 3E, the midpoint M is set to the white line candidate point 15.
Save as

Then, among these white line candidate points 15,
Only the point closest to the screen center is left as the final candidate point.
This means that, for example, when the vehicle 1 is traveling on the left side, the search area 1
The right side of 0 is a road surface with little change in normal luminance, and the white line candidate point 15 closest to this normal road surface can be determined as the white line 12. Therefore, further to the left of the white line 12,
Objects that cause noise (for example, guardrails 14)
Is present, the white line 12 can be reliably recognized from the image information captured by the camera 2.

Finally, as shown in FIG. 3F, the vertical continuity of the white line candidate points 15 in each horizontal line data is sequentially verified from the bottom of the screen. First, the inclination between the upper and lower ends of the white line 12 on the previous screen is calculated in advance.
Then, assuming that the lowest point 15A is the white line 12, it is verified whether or not the candidate point 15B on the horizontal line 11 which is only one line above is within the range of ± 50 dots of the inclination of the previous white line 12.

If the candidate point 15B falls within this range, it is regarded as a white line. If not, the candidate point 15B is rejected, and the coordinates interpolated from the above-mentioned inclination are regarded as the white line position. By performing the same operation for each horizontal line for this detection, a continuous white line 12 can be recognized. Such white line recognition work is continuously performed at a required cycle, and the recognition of the white line 12 is updated each time.

White line 12 as the roadside line at the right end of the traveling lane
The recognition of R is performed in the same manner. In the estimating means 4, the original image 41 thus recognized in each recognition cycle
The upper white lines 12R and 12L are converted into a two-dimensional image 42,
Based on the road centerline LC _R from traveling lane left to the road central line LC _L which can be estimated from the white line 12L traveling lane right edge of the white line 12R can estimate, and performs the estimation of the road centerline LC. And this road center line LC
Is calculated on the basis of the lateral displacement amount ΔY, the deflection angle β, and the curvature index θ.

The declination β is, as shown in FIG. 4, the angle between the tangent to the curved road center line LC and the vehicle center line direction, and is the first detection point ( It can be calculated from the reference line position information at the perigee in the figure) and the reference line position information at the second detection point (shown as the apogee in the figure) further away from the perigee by a predetermined distance. .

That is, the declination β is calculated as an angle between a straight line connecting the first detection point and the second detection point and the center line of the host vehicle. The declination calculated in this way is a declination at an intermediate point between the first detection point and the second detection point (marked by x in the drawing), and is at least a declination at a point at least a certain distance ahead of the vehicle 1. . In this example, the point closest to the vehicle 1 on the road center line LC based on the image information from the camera 2 is set as the first detection point, and the amount of lateral deviation ΔY is determined by comparing the vehicle center line at this first detection point with the road. The lateral distance from the center line LC (the road width direction, the lateral distance of the camera image) is calculated as a lateral displacement amount (lateral deviation) ΔY.

The curvature calculating means 4A, as shown in FIG. 5, for example, a first point (a point B on the road center line LC in front of the vehicle (this is defined as a curve detection point) behind the point B by a sampling distance L). Given a point A) and a second point (point C) ahead of the curve detection point (point B) by a sampling distance L, a first vector AB from point A to point B;
Angle θ between second point BC and point C from point B to point C
Is calculated as a curvature index (curvature characteristic) at point B.

From the sampling distance L and the curvature index θ, the curvature (road curvature) ρ of the traveling lane is calculated by the following equation. ρ = 2 sin (θ / 2) / L (1) That is, the value of the curvature index θ is an index representing the degree of curvature of the curve at the point B, and the curvature index The larger the θ, the more the point B
Indicates that the curvature ρ of the curve is large, indicating that the curve is steep.

The control torque calculating means 5 calculates the lateral acceleration G acting on the vehicle based on the curvature ρ of the traveling lane calculated in this manner. That is, assuming that the magnitude of the traveling speed of the vehicle detected by the vehicle speed sensor 32 is V, the lateral acceleration G is calculated by the following equation. G = ρ × V ² (2) Then, based on the lateral acceleration G, the steering control torque T
g is set, and in the present device, the steering control torque T
There is a feature in the setting of g.

In other words, the steering control torque Tg is different from the steering torque used for automatic steering, and the main purpose is to reduce the driver's steering force on a curved road, and to maintain the position of the vehicle on the lane. Is due to the driver's steering operation,
The steering maintaining control torque Tg is set to a magnitude that does not hinder the driver's steering operation, that is, a magnitude that the driver can easily overcome.

Therefore, on a curved road, the lateral acceleration G
When the steering control torque Tg is applied in a direction to reduce the burden on the driver due to the lateral acceleration G when the driver operates, if the driver tries to perform the steering operation in the direction deviating from the lane, it is sufficient. You can do this.
Accordingly, emergency steering for retreating the vehicle out of the traveling lane can be easily performed, and even when the steering control torque Tg is applied at the time of lane change on a curved road,
It does not hinder the lane change.

The steering control torque Tg is set to a magnitude corresponding to the lateral acceleration G acting on the vehicle. In other words, the control torque calculation means 5 sets the control torque Tg for maintaining the steering so as to be proportional to the lateral acceleration G, as shown in FIG. In FIG. 6, the abscissa regarding the lateral acceleration G indicates that the right direction indicates the effect of the lateral acceleration of the vehicle to the right, and the left direction indicates the effect of the lateral acceleration of the vehicle to the left.
The ordinate relating to the steering-holding control torque Tg indicates left steering in which the upward direction guides the vehicle to the left side of the lane, and rightward steering in which the downward direction guides the vehicle to the right side of the lane.

As shown in FIG. 6, when a lateral acceleration in the right direction acts on the vehicle, a left-hand steering control torque Tg for guiding the vehicle to the left side of the lane is set in accordance with the lateral acceleration G. If lateral acceleration in the left direction acts on the lateral acceleration G
The steering control torque Tg for right steering that guides the vehicle to the right side of the lane is set in accordance with. However, in any case, the magnitude of the steering control torque Tg is limited by a constant value Tgm. Here, when the magnitude of the lateral acceleration G becomes G1, the constant value Tgm is set.
Limited to This limits the driver to a size that can be easily overcome, as described above.

Then, the control torque calculating means 5 multiplies the control torque Tg for steering maintenance thus set by the gain K and outputs the result to the controller 6. Note that this gain K
Is a coefficient determined by the structure of a power steering mechanism (not shown) provided in the steering shaft 40 (shown in FIG. 10). Further, the magnitude of the gain K is adjustable, so that not only does the driver partially bear the steering force as described above, but also the driver completely releases the steering force and the driver releases the steering wheel 20. However, it is also possible to set the level to maintain a constant steering angle.

The steering actuator 21 may be any actuator capable of applying a torque to the steering shaft. For example, as shown in FIG. 10, the steering actuator 21 is installed below the torsion bar (not shown) of the steering shaft 40 (on the power steering side). It may be constituted by the small electric torque motor 41 described above. In this case, the motor 41
The transmission of torque from the steering shaft 40 to the steering shaft 40 is performed via a worm gear 42 comprising a worm 42a and a worm wheel 42b.
A torque limiter 43 is interposed between the steering shaft 40 and the steering shaft 40. The torque limiter 43 allows the driver to easily operate the handle 20 even if the motor 41 is stuck. The maximum torque of the motor 41 is set to a necessary minimum, so that even if a failure occurs in the controller 6, an excessive steering load is not applied to the driver.

The output of the control torque calculation information is provided between the control torque calculation means 5 and the controller 6 such that the control torque actually exerted by the steering actuator 21 is smoothly continued without sudden change. A low-pass filter 25 for performing a smoothing process is provided. Since the steering force assisting device as one embodiment of the present invention is configured as described above, the steering force assisting process is performed, for example, as shown in FIG.

That is, it is determined whether or not the control switch 23 is turned on (step S10). If the control switch 23 is not turned on, the processing for assisting the holding force is not performed. The processing after S20 is performed. That is, first, the curvature of the traveling lane is calculated by the curvature calculating means 4A (step S20), and the control torque calculating means 5 calculates the control torque according to the lateral acceleration calculated based on the curvature of the driving lane (step S20). (S30) The controller 6 operates the steering actuator 21 with a control amount corresponding to the control torque and outputs a display signal to the operation display unit 24 (step S40).

This process will be described with reference to the block diagram of FIG. 9. The driver side makes a proper judgment while visually recognizing the traveling lane, and performs steering operation of the steering wheel. On the other hand, in this steering force assist device,
First, lane recognition for the traveling lane is performed by image recognition through the camera 2, and the curvature of the traveling lane (road curvature)
ρ is calculated, the lateral acceleration G is calculated from the curvature ρ and the vehicle speed V, and the steering control torque Tg is calculated from the lateral acceleration G. Then, the steering actuator 21 is operated based on the steering control torque.

As a result, the steering torque of the driver and the control torque for steering by the steering actuator 21 are added and transmitted to the steered wheels 22 via the power steering device, and the steered wheels 22 are steered. You do it.
To describe these processes in more detail, it is necessary to calculate the curvature ρ of the traveling lane when calculating the control torque. First, in the present device, the traveling lane estimating means 4 calculates the curvature index θ of the road center line LC ahead of the vehicle. Here, a first point (point A) behind the point B (curve detection point) on the road center line LC based on image information from the camera 2 by a sampling distance L, and a curve detection point (point B) The second point (point C) forward from the point A to the point B, and the angle θ between the second vector BC from the point B to the point C Is calculated as a curvature index (curvature characteristic) at the point B.

That is, in the present apparatus, white line recognition is performed for the white line 12L at the left end of the driving lane and the white line 12R at the right end of the driving lane. It is presumed that the curve is curved with a certain declination.
Recognition of 2R will be described by taking the left white line 12L as an example.

First, as shown in FIG.
On a flat ground, the area in front of the vehicle (for example,
m), the monochrome image information is fetched for each minute control cycle, and a plurality of horizontal lines 11 are set at regular intervals on this screen for each cycle. Then, as shown in FIG.
On each horizontal line 11, a required range of the left and right positions of the white line position in the previous screen (for example, 50 pixels [do
t]) is set as a white line search area (processing target area) 10. In the initial screen, a white line position on a straight road is used as previous screen data.

From the image information, as shown in FIG. 3C, the brightness of each horizontal line is differentiated in the horizontal direction from the left, and the differential data of each horizontal line is obtained as shown in FIG. 3D.
From the left], the peaks of the differential values appear in the order of plus and minus from the left, and the interval between the peaks is considered to be appropriate as the white line 12 (the interval from the plus peak to the minus peak is, for example, within 30 dots). ) Are extracted as white line candidates, and the midpoint thereof is stored as a white line candidate point 15 (see FIG. 3E).

Then, among these white line candidate points 15,
Only the point closest to the screen center is left as the final candidate point.
By limiting the white line candidate point 15 to the one closest to the center of the screen in this way, an object that causes noise (for example, the guardrail 14 or a vehicle in another traveling lane) exists outside the white line 12. Even in this case, the white line 12 can be reliably recognized from the image information obtained by the camera 2.

Finally, as shown in FIG. 3 (f), the continuity of the white line candidate points 15 in each horizontal line data in the vertical direction is sequentially verified from the bottom of the screen. First, the inclination between the upper and lower ends of the white line 12 on the previous screen is calculated in advance. If the lowermost point 15A is the white line 12, the candidate point 15B on the upper horizontal line 11 is calculated by the inclination ± 5 of the previous white line 12.
0 dot is compared, and candidate point 1
If 5B is within this range, it is regarded as a white line. If not, the candidate point 15B is rejected, and the coordinates calculated by interpolation from the above-mentioned inclination are regarded as the position of the white line.

By performing such an operation for each horizontal line, continuous white lines 12 can be recognized. Such white line recognition work is continuously performed at a required cycle, and the recognition of the white line 12 is updated each time.
In this manner, the white lines 12L, 1 on the left and right of the traveling lane are periodically repeated.
Recognition of 2R is performed in the same manner.

Then, the estimating means 4 calculates each road center line L
C _L, roads and averages the LC _R centerline LC (= LC _L + _L
C _R ) is calculated. When the road center line LC is estimated in this manner, a first point (point A), which is a sampling distance L behind the point B (curve detection point) on the road center line LC ahead of the vehicle, and a curve detection point (point B) is given a second point (point C) ahead by a sampling distance L, and a point A
Is calculated as a curvature index (curvature characteristic) at the point B between the first vector AB from the point B to the point B and the second vector BC from the point B to the point C. In addition, the lateral distance (road width direction, lateral distance of the camera image) between the vehicle center line and the road center line LC at the first detection point is calculated as a lateral deviation amount (lateral deviation) ΔY. The angle between the straight line connecting the second detection point and the center line of the host vehicle is calculated as the argument β.

When the curvature index θ is calculated in this manner, the traveling lane estimating means 4 calculates the curvature ρ of the traveling lane from the equation (1), and further calculates the vehicle speed V of the vehicle detected by the vehicle speed sensor 32. Is used to calculate the lateral acceleration G acting on the vehicle from equation (2). The calculation of the steering control torque Tg by the control torque calculation means 5 is performed using a map, a table, or an arithmetic expression as shown in FIG. That is, as shown in FIG. 6, when the traveling lane is curved to the left, the lateral acceleration G acting on the vehicle acts in the right direction that hinders the turning of the vehicle. The left-hand steering control torque Tg for turning the vehicle to the left is set. When the driving lane is curved rightward, the right-hand steering for turning the vehicle to the right according to the magnitude of the lateral acceleration G is set. The rudder control torque Tg is set. However, in order to maintain the magnitude of the steering control torque Tg to such an extent that the driver can easily overcome, when the magnitude of the lateral acceleration G is equal to or more than G1, the magnitude of the steering control torque Tg is limited to a constant value Tgm. .

Therefore, by applying the steering control torque Tg, the driver can reduce the steering holding force of the steering wheel 20 on a curved road, and can easily perform the steering operation even when a large lateral acceleration G is applied. Will be performed. Further, the steering control torque Tg is equal to the lateral acceleration G that will act on the curve where the vehicle is about to enter.
Is determined in advance based on the predicted lateral acceleration G, so that the steering control torque Tg can be applied so as to prompt the driver to steer the steering wheel along the curve. For this reason, the steering control torque Tg also has the effect of alerting the driver that the vehicle is approaching a curve, and is effective, for example, for a driver looking aside.

Further, the control torque calculating means 5 can change the gain K of the steering control torque Tg arbitrarily by the driver. Depending on the setting of the gain K, the driver releases the steering wheel. However, a constant steering angle can be maintained by the steering control torque Tg. Furthermore, if the assist of the steering force is relied solely on the hydraulic power steering mechanism, the torsional rigidity of the torsion bar cannot be increased in order to finely control the assist, resulting in a steering feeling with insufficient rigidity. However, in this steering force assisting device, the small electric torque motor 41 provided separately from the hydraulic power steering mechanism assists the driver's steering operation together with the hydraulic power steering mechanism, so that the load on the hydraulic power steering mechanism is reduced,
Thereby, the control ability of the hydraulic power steering mechanism can be reduced. Therefore, the rigidity of the steering system can be set high, and the lack of rigidity can be resolved.

The low-pass filter 25 smoothes the steering control torque Tg and outputs it.
There is also an advantage that the steering control torque generated by the steering actuator 21 is smoothly continued without abrupt change, and steering control of the steering wheel on a curved road can be stably performed. The calculation of the steering control torque Tg by the control torque calculating means 5 is not limited to the characteristic shown in FIG.

In other words, the steering control torque Tg may be any value as long as the lateral acceleration G increases in accordance with the magnitude. In particular, in the region where the lateral acceleration G is small, the steering control torque Tg is used.
Is set to 0, and if the magnitude of the lateral acceleration G becomes larger than this area (dead zone), the control torque Tg for steering maintenance may be set according to the lateral acceleration G. In this case, FIG.
As shown in (2), the steering control torque Tg may be linearly increased with respect to the lateral acceleration G, or may be increased stepwise.

In the present embodiment, the curvature ρ of the traveling lane is estimated from the image information obtained through the camera 2, and the lateral acceleration G is calculated using the curvature ρ of the traveling lane and the vehicle speed V detected by the vehicle speed sensor 32. Although the calculation is performed, the detection of the lateral acceleration by the lateral acceleration sensor may be used separately. In this case, there is an advantage that, even when the recognition of the traveling lane is not normal, the steering control torque can be applied based on the lateral acceleration detected through the lateral acceleration sensor, that is, robustness can be ensured. .

[0054]

As described above in detail, according to the steering holding force assisting device of the present invention, when the vehicle enters the curved road, Dora
In response to lane curvature and vehicle speed, independent of steering torque
Steering control torque of the same magnitude is applied to the steering actuator.
Since the steering wheel is added to the steering wheel , the driver's steering force on the curved road is reduced, and the steering operation can be easily performed even at a curve or a vehicle speed at which a large lateral acceleration is applied.

As a result, the dependence on the power steering mechanism can be reduced, the torsional rigidity of the torsion bar is increased, and the rigidity of the steering and the like is set high, so that a steering rigidity with a good steering feeling can be obtained. Will be able to In addition, the steering control torque predicts in advance the lateral acceleration that will be applied to the curve where the vehicle is about to enter, and is determined based on the predicted lateral acceleration. Steering control torque can be applied to encourage steering of the steering wheel.
For this reason, this steering control torque also has the effect of alerting the driver that the vehicle is approaching a curve.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of a steering force assisting device as one embodiment of the present invention.

FIG. 2 is a diagram illustrating image processing for driving lane recognition according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating traveling lane recognition according to an embodiment of the present invention in the order of (a) to (f).

FIG. 4 is a schematic plan view illustrating travel lane recognition.

FIG. 5 is an explanatory diagram for describing calculation of a curvature of a traveling lane.

FIG. 6 is a diagram showing an example of a setting map of a steering control torque applied to the steering force assisting device as one embodiment of the present invention.

FIG. 7 is a diagram showing another example of a setting map of the steering control torque applied to the steering force assisting device as one embodiment of the present invention.

FIG. 8 is a flowchart illustrating the operation of the steering force assisting device as one embodiment of the present invention.

FIG. 9 is a block diagram illustrating the operation of the steering force assisting device as one embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating an example of a configuration of a steering actuator provided in the steering force assisting device as one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vehicle 2 Camera 3 Image information processing means 4 Running lane estimation means 4A Curvature calculation means 5 Control torque calculation means 6 Control means (controller) 20 Steering wheel (handle) 21 Steering actuator 22 Steering wheel 23 Switch 24 Operation display part 25 Low-pass filter 32 Vehicle speed sensor 40 Steering shaft 41 Small electric torque motor 42 Worm gear 43 Torque limiter LC Road center line

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-104850 (JP, A) JP-A-6-340264 (JP, A) JP-A-4-138973 (JP, A) JP-A-7-104 81603 (JP, A) JP-A-7-186992 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00-6/06

Claims (3)

(57) [Claims] 1. A steering to which a steering torque is applied by a driver in accordance with a curve situation ahead, an image pickup means for picking up an image of the vehicle in the forward direction, and a road curvature ahead in the drive direction based on image information from the image pickup means. , A vehicle speed detecting means for detecting the vehicle speed of the own vehicle, and acting on the own vehicle based on the curvature calculated by the curvature calculating means and the vehicle speed detected by the vehicle speed detecting means. Lateral acceleration
Control torque calculating means for calculating a steering control torque in accordance with the calculated magnitude of the lateral acceleration; and a steering control torque having the magnitude calculated by the control torque calculating means. A steering force assisting device, further comprising control means for controlling a steering actuator so as to be added. 2. The control torque calculating means according to claim 1 , wherein
Control torque is small enough for the driver to overcome
The steering assisting device according to claim 1, wherein the auxiliary force is limited.
Place. 3. The steering actuator according to claim 1, wherein
The steering control torque added to the steering is controlled by the driver.
It is added to the rudder torque and operated via the power steering device.
3. The method according to claim 1, wherein the power is transmitted to a steering wheel.
On-board steering assist device.