JP4340991B2 - Vehicle steering assist device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steering assist device for a vehicle, and for example, relates to a steering assist device suitable for being mounted on an automobile which is a typical vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in automobiles that are representative vehicles, a steering assist system that assists a driver's driving operation (steering) in order to travel safely in a traveling lane has been proposed, for example, Japanese Patent Laid-Open No. 9-66853. Has proposed a device that generates a steering reaction force in a direction in which a deviation from a traveling lane can be suppressed based on a captured image in front of the host vehicle.
[0003]
As a specific means for steering assistance (complementary steering) in such a steering assistance device, a method of positively applying a steering torque to the steering mechanism of the vehicle as in the above-described conventional example, or a steering characteristic indirectly. Conventionally known is a method in which the driver changes the torque required for operating the steering wheel (ie, changes the weight of the steering wheel operation) by adjusting the spring characteristics and damping characteristics of the steering mechanism of the vehicle. ing.
[0004]
[Problems to be solved by the invention]
However, in the conventional method described above, steering assist control is performed regardless of the visibility of the road on which the vehicle is traveling. In addition, it is expected that the driver feels bothered by the automatic steering assistance or that the driver feels uncomfortable.
[0005]
Therefore, an object of the present invention is to provide a vehicle steering assist device that performs appropriate steering assist according to the visibility of a road ahead of the host vehicle.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a steering assist device for a vehicle according to the present invention is characterized by the following configuration.
[0007]
That is, a steering reaction force applying means for applying a steering reaction force to the steering mechanism of the vehicle, a visibility estimating means for estimating the visibility of the road ahead of the vehicle , a camera for photographing the front of the vehicle, and a steering angular velocity are detected. The steering reaction force applying means is controlled so that a deviation amount of the vehicle with respect to the travel lane is reduced based on an estimation result by the steering angular velocity detecting means, an estimation result by the visibility estimating means, and a captured image of the camera. Control means for controlling the steering reaction force application means, and when the estimation result indicates that the visibility of the road ahead of the vehicle is good , the steering angular velocity detection means detects proportional to the steering angular velocity, to confer first steering torque in the direction of the deviation amount is small with respect to the traffic lane to the steering mechanism, a predetermined steering reaction force characteristics of the steering mechanism doubt Select varying steering characteristics change control, the when the estimation result indicating that poor visibility of the vehicle front road was proportional to the predicted amount of deviation with respect to the driving lane after a lapse of a predetermined time headway, and selects the Azukasuru steering torque application control with the second steering torque direction shift amount with respect to the traffic lane becomes small to the steering mechanism.
[0008]
In the above apparatus configuration, as a method for estimating that the visibility estimation means that the road ahead of the vehicle is not good, the operation state of the fog lamp switch of the vehicle is detected, and the detected operation state is in the on state. Or when the operation state of the wiper switch of the vehicle is detected and the detected operation state is on, it may be estimated that the visibility of the road ahead of the vehicle is not good (or the raindrop sensor uses a raindrop sensor). It can be estimated that the visibility is not good).
[0009]
A yaw rate sensor for detecting a yaw rate of the vehicle; and the control means sets the predicted deviation amount to a target locus calculated based on the captured image, a lateral deviation of the vehicle with respect to the target locus, and a yaw angle. And calculating the second steering torque, and multiplying the difference between the standard yaw rate calculated based on the captured image and the actual yaw rate detected by the yaw rate sensor by the steering angular velocity, the first steering It is good to calculate the torque .
[0010]
Preferably, the information processing apparatus further includes an awakening state determination unit that determines an awakening state with respect to the driving operation of the driver, and the control unit indicates that the estimation result by the visibility estimation unit indicates that the road ahead of the vehicle has good visibility. Even in such a case, the steering torque application control may be selected when the wakefulness determination means determines that the driver's wakefulness is low.
[0011]
【The invention's effect】
According to the present invention described above, it is possible to provide a vehicle steering assistance device that performs appropriate steering assistance in accordance with the visibility of the road ahead of the host vehicle.
[0012]
That is, according to the first aspect of the invention, the control function that actively or indirectly supports the driving operation of the driver can be appropriately switched according to the visibility of the road ahead of the host vehicle. Thus, it is possible to realize safe steering assistance that minimizes the driver from feeling uncomfortable.
[0013]
Moreover, according to the invention of Claim 2 and Claim 3, the visibility of a road ahead can be reliably estimated by the existing apparatus structure generally provided in vehicles, such as a motor vehicle.
[0014]
According to the invention of claim 4, the control amount to be output can be reliably calculated.
[0015]
According to the fifth aspect of the present invention, when it is determined that the driver's awakening state is low, the driving operation is actively supported, so that driving assistance can be performed more safely.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which a steering assist device for a vehicle according to the present invention is applied to an automobile which is a typical vehicle will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a diagram showing an overall configuration of an automobile equipped with a vehicle steering assist device according to the present embodiment.
[0018]
In the figure, reference numeral 2 denotes a CCD (Charge Coupled Device) camera for photographing the front of the host vehicle (vehicle 100). Reference numeral 3 denotes a vehicle speed sensor that detects the host vehicle speed V. Reference numeral 4 denotes a wiper switch that allows the driver to adjust the operation speed (cycle) of a wiper (not shown) and to turn the operation on and off. Reference numeral 5 denotes a raindrop sensor that detects the pressure of raindrops contacting the vehicle 100. Reference numeral 6 denotes a wiper switch that allows a driver to turn on and off a fog lamp (not shown). A steering angle sensor 7 detects the steering angle of the vehicle 100. Reference numeral 8 denotes a yaw rate sensor that detects the yaw rate φ generated in the vehicle 100. Since these sensors themselves are common at present, a detailed description in this embodiment will be omitted.
[0019]
Based on the detection results of these sensors, the control unit 1 generates a control torque T in the steering actuator (electric motor) 10 provided in the steering mechanism shown in FIG.
[0020]
FIG. 2 is a diagram illustrating an automobile steering mechanism equipped with the vehicle steering assist device according to the present embodiment, and shows a mechanism for applying a control torque T to the steering mechanism of the vehicle 100.
[0021]
The steering mechanism itself shown in the figure is a general steering mechanism of an automobile, and as a basic operation, a rotation operation of the steering wheel 11 by a driver is performed in a rack-and-drive via the torsion bar 12 and the steering column 14. The pinion mechanism 16 converts the operation into the vehicle width direction, whereby the left and right front wheels (not shown) are steered. The torque sensor 13 detects a steering torque generated by a rotation operation of the steering wheel 11. With respect to the steering mechanism having such a configuration, the rotational torque of the steering actuator 10 that is an electric motor (corresponding to the control torque T output from the control unit 1) is the rotational torque for the steering column 14 via the reduction gear 15. Communicated.
[0022]
In the present embodiment, a configuration is adopted in which the rotational torque of the steering actuator 10 is transmitted as rotational torque to the steering column 14 as described above, but the control torque T is applied to any part of the steering mechanism shown in FIG. For example, the control torque T may be applied to the steering wheel 11 itself or to the operation in the vehicle width direction by the rack and pinion mechanism 16.
[0023]
Next, control processing of the steering actuator 10 performed by the control unit 1 using the detection results of the sensors shown in FIG. 1 will be described with reference to FIG.
[0024]
FIG. 3 is a block diagram for explaining a control process performed by the control unit of the vehicle steering assist device according to the present embodiment, in which a microcomputer (not shown) provided in the control unit 1 stores control stored in advance. It is a figure which outlines the function implement | achieved by running a program.
[0025]
In the present embodiment, the control unit 1 assists the driver in driving the vehicle 100 while appropriately switching between torque application control and steering characteristic change control described below. First, torque application control and steering characteristic change control will be described.
[0026]
<Torque application control>
In general, in a steering mechanism of an automobile, a steering reaction force characteristic that attempts to return to a forward state when a turning operation is performed on the steering wheel 11 is physically created in advance, for example, as shown in FIG. ing. In the torque application control, the driver is likely to feel uncomfortable because it directly intervenes by applying the steering torque to the steering mechanism having the steering reaction force characteristic regardless of the steering wheel steering by the driver. .
[0027]
Hereinafter, a specific procedure for executing the torque application control will be described. In the torque application control, first, a lane marking (for example, a white line) of the currently running lane is detected based on a photographed image by the CCD camera 2 by general image processing, and is calculated based on the detected lane marking. The lateral deviation (ie, course deviation) dy0 and yaw angle φ of the host vehicle with respect to the current target trajectory (for example, a trajectory connecting the center of the running lane) TR is detected, and the change in the target trajectory TR at the forward gazing point y1 is detected. Estimate ΔY. Since the method for obtaining these values is generally common, detailed description thereof is omitted.
[0028]
Based on the estimated change ΔY, the predicted value (future lateral deviation) dy1 of the lateral position deviation dy0 at the forward gazing point y1 is calculated. For example, the current lateral position y0 of the host vehicle 100 in the global coordinate system XY shown in FIG. 6, the lateral position Y0 of the target locus TR, the lateral position (front gazing point) y1 of the host vehicle after the vehicle head time t has elapsed, When the lateral position Y1 of the target trajectory TR at the time is set, the predicted value dy1 can be calculated by the following equation in the traveling state of the vehicle 100 shown in FIG.
[0029]
dy1 = Y1-y1 = (ΔY + Y0) − (y0−φ × L) = ΔY + (Y0 + y0) + φ × L = ΔY + (dy0 + φ × L),
However, in the above formula, the forward gaze distance L = the host vehicle speed V × t (t is the time required for the host vehicle 100 to reach the front gaze point y1 (vehicle head time)).
[0030]
The control torque (control amount) T1 in the torque application control is
T1 = dy1 × K1 (where K1 is a control gain),
It is.
[0031]
<Steering characteristic change control>
Unlike the torque application control described above, the steering characteristic change control generates a steering torque in accordance with the steering of the steering wheel 11 by the driver, so that the driver does not feel uncomfortable.
[0032]
Hereinafter, a specific procedure for executing the steering characteristic change control will be described. In the steering characteristic change control, first, a lane marking (for example, a white line) of the currently running lane is detected by general image processing based on a photographed image by the CCD camera 2 and is calculated based on the detected lane marking. The standard yaw rate (dφ /) to be detected when the vehicle accurately traces the calculated road shape (curvature) based on the road curvature 1 / R of the running road and the detected vehicle speed V. dt) 0 is calculated by the following equation. Here, (dφ / dt) represents the first derivative of the yaw angle φ, and in FIG. 7, it is indicated by a symbol with a dot on φ (the same applies to θ).
[0033]
(Dφ / dt) 0 = (1 / R) × V,
On the other hand, the actual yaw rate (dφ / dt) 1 is detected by the yaw rate sensor 8 as the measured value for the standard yaw rate (dφ / dt) 0 calculated as described above, and the steering angular velocity (dθ / dt) is obtained by the steering angle sensor 7. To detect.
[0034]
Since the difference between the obtained standard yaw rate (dφ / dt) 0 and the actual yaw rate (dφ / dt) 1 causes a shift in the trajectory of the host vehicle 100, the amount of change in the damping component of the steering characteristics according to the difference. (In terms of the driver's experience, so-called the weight of the handle is controlled), it is possible to suppress the occurrence of locus deviation.
[0035]
Therefore, the control torque (control amount) T2 in the steering characteristic change control for suppressing the occurrence of the locus deviation is:
T2 = K2 × (dθ / dt) × | (dφ / dt) 0− (dφ / dt) 1 | = K2 × (dθ / dt) × | (1 / R) × V− (dφ / dt) 1 | (Where K2 is the control gain),
It is.
[0036]
<Switching control>
In this embodiment, the visibility of the road ahead of the host vehicle is estimated based on the state of the wiper switch 4 (or raindrop sensor 5) and the fog lamp switch 6, and the steering characteristic change control is executed when it is determined that the visibility is good. When it is determined that the visibility is poor, torque application control is executed.
[0037]
As described above, the reason why the control method is switched according to the visibility of the road ahead of the host vehicle is that the driver tends to feel uncomfortable with the torque application control and uncomfortable with the steering characteristic change control. Therefore, the torque application control is automatically executed under a driving condition in which the driver can easily drive the vehicle with his / her own judgment (intention) and the visibility of the road ahead of the host vehicle is sufficiently secured. In this case, the driver is expected to feel bothersome or feel uncomfortable with the driving operation. Therefore, in the present embodiment, the steering characteristic change control is executed in a traveling situation where the visibility is sufficiently secured, and it is difficult to perform an accurate driving operation as compared with the case where the visibility is sufficient. The torque application control is executed only when the visibility which would be desired for automatic operation support is poor.
[0038]
Further, in the present embodiment, when the control method is appropriately switched according to the visibility of the road ahead of the host vehicle as described above, the steering state (straight center frequency f0) when traveling on a straight road and the current steering state (steering) If the driver is in a low arousal state as a result of the estimation, the estimated frequency of the road ahead of the host vehicle is good. The driver's driving operation is directly supported by stopping the steering characteristic change control and executing the torque application control. Here, for the center frequency f of the driver's operation on the steering wheel 11, for example, a plurality of detection results of the steering angle sensor 7 are stored over a predetermined period, and general arithmetic processing (fast Fourier transform processing, etc.) is performed on these detection results. ).
[0039]
<Steering drive function>
The control amount T1 in the torque application control calculated as the control torque (control amount) T as described above or the control amount T2 in the steering characteristic change control is output to the steering actuator 10 by the steering drive function in the control unit 1.
[0040]
FIG. 4 is a block diagram of the steering drive mechanism provided at the final stage of the control unit 1.
[0041]
As shown in FIG. 4, the calculated control torque (control amount) T is subjected to steering friction correction in the control unit 1 and then converted into a current command value corresponding to the corrected control torque T ′. A current I corresponding to the current command value is supplied from the motor drive circuit to the steering actuator 10 which is an electric motor. These corrections and conversions may be performed by referring to a lookup table or the like stored in advance in the memory.
[0042]
Next, a procedure of control processing executed by a microcomputer (not shown) of the control unit 1 in order to realize the above-described control function will be described with reference to FIGS.
[0043]
FIGS. 8 and 9 are flowcharts showing a control process executed by the control unit of the vehicle steering assist apparatus according to the present embodiment, which is started when, for example, the ignition key switch of the vehicle 100 is turned on.
[0044]
In the same figure, step S1: the detection result by each sensor shown in FIG.1 and FIG.2 is updated.
[0045]
Steps S2 to S4: Calculate the standard deviation σ0 of the forward gaze distance L, the lateral position deviation dy0, and the lateral position deviation dy0 to be used for calculating the control torque T1 in the torque application control described above.
[0046]
Step S5: A lane marking (for example, a white line) of the currently running lane is detected by general image processing based on a photographed image by the CCD camera 2, and a road on the running road calculated based on the detected lane marking is detected. The road curvature 1 / R is calculated.
[0047]
Step S6: It is determined whether the currently running road is a straight road by determining whether the calculated road curvature 1 / R is substantially zero. If the determination is YES (straight road), the process proceeds to step S7, and if NO (not a straight road), the process proceeds to step S9.
[0048]
Step S7, Step S8: In step S6, it is determined that the road that is currently running is a straight road, and is used as a reference value when determining the driver's arousal level in a later-described step. There is a possibility that the center frequency f0 of the steering can be detected. Therefore, first, it is determined whether the standard deviation σ0 of the lateral position deviation dy0 of the host vehicle 100 calculated in step S4 is smaller than the threshold value a for determining the straight traveling state (step S7). When ≦ a), it can be determined that the running state of the vehicle 100 is substantially straight along the target locus TR and the center frequency f0 can be calculated. The center frequency f0 is calculated using the detection result, and the calculated value is stored in the memory. On the other hand, if NO (σ0> a) in the determination in step S7, even if the currently traveling road itself is a substantially straight line, it cannot be determined that the traveling state of the vehicle 100 with respect to the straight road is a straight line. The process proceeds to step S9 without performing the center frequency f0.
[0049]
Step S9 to Step S12: The yaw angle φ is detected, the target trajectory TR is calculated, the future lateral deviation dy1 is calculated (Step S9 to Step S11), and these detected values and calculated values are used as described above. A control torque T1 in the torque application control is calculated (step S12).
[0050]
Steps S13 to S16: The standard yaw rate (dφ / dt) 0 is calculated, the actual yaw rate (dφ / dt) 1 is detected, and the steering angular velocity (dθ / dt) is detected (steps S13 to S15). Using the detected value and the calculated value, the control torque T2 in the steering characteristic change control is calculated as described above (step S16).
[0051]
Step S17: In order to estimate the visibility of the road ahead of the host vehicle as described above, whether the wiper switch 4 and / or the fog lamp switch 6 are turned on, or whether raindrops are detected by the raindrop sensor 5 or not. When the determination is YES, it can be determined that the visibility of the road ahead of the host vehicle is poor. Therefore, the process proceeds to step S21 to execute the torque application control. When the determination is NO, the visibility of the road ahead of the host vehicle is good. However, prior to executing the steering characteristic change control, the process proceeds to step S18 in order to determine the driver's arousal level.
[0052]
Steps S18 and S19: The current steering center frequency f1 is calculated using the detection result of the steering angle sensor 7 (step S18), and the difference between the center frequency f0 calculated in step S8 and the center frequency f1 is calculated. While calculating, the driver's arousal level α according to the difference is estimated by referring to the lookup table shown in FIG. 10 (step S19).
[0053]
Step S20: It is determined whether or not the driver's arousal level α of the driver estimated in step S19 is smaller than a threshold value b that is determined to be a low arousal state. If this determination is YES (α ≦ b), the driver is low. Since it is preferable to execute torque application control although it is possible to determine that the state is awake and it is preferable that the visibility of the road ahead is determined in step S17, the process proceeds to step S21. When NO (α> b), the driver Since it can be determined that the vehicle is sufficiently awake for driving operation and the visibility of the road ahead is good in step S17, the process proceeds to step S22 to execute the steering characteristic change control.
[0054]
Step S21, Step S22: Control torque to be output in the current control cycle (loop) of torque application control by the control torque T1 calculated in Step S12 or steering characteristic change control by the control torque T2 calculated in Step S10 Set (determine) as T.
[0055]
Step S23: Based on the control torque T set in step S21 or step S22, the steering actuator 10 is caused to generate a rotational torque, and the process returns.
[0056]
As described above, according to the above-described embodiment, it is possible to perform appropriate steering support according to the visibility of the road ahead of the host vehicle, and to suppress the driver from feeling uncomfortable.
[0057]
Further, in the present embodiment described above, even when the visibility of the road ahead of the host vehicle is good, when it is determined that the driver's arousal level is not sufficient for the driving operation, the torque application control is performed, so that it is safer. Driving assistance can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an overall configuration of an automobile on which a vehicle steering assist device according to an embodiment is mounted.
FIG. 2 is a diagram exemplifying a steering mechanism of an automobile equipped with the vehicle steering assist device according to the embodiment.
FIG. 3 is a block diagram illustrating a control process performed by a control unit of the vehicle steering assist device according to the present embodiment.
4 is a block diagram of a steering drive mechanism provided at the final stage of the control unit 1. FIG.
FIG. 5 is a diagram showing a steering reaction force characteristic in a general automobile steering mechanism.
FIG. 6 is a diagram illustrating torque application control in the present embodiment.
FIG. 7 is a diagram illustrating steering characteristic change control in the present embodiment.
FIG. 8 is a flowchart showing a control process executed by a control unit of the vehicle steering assist apparatus according to the present embodiment.
FIG. 9 is a flowchart showing a control process executed by a control unit of the vehicle steering assist apparatus according to the present embodiment.
FIG. 10 is a diagram illustrating a look-up table referred to in order to estimate a driver's arousal level α.
[Explanation of symbols]
1: control unit,
2: CCD camera,
3: Vehicle speed sensor,
4: Wiper switch,
5: Raindrop sensor,
6: Fog lamp switch,
7: Steering angle sensor,
8: Yaw rate sensor,
10: Steering actuator,
11: Steering wheel,
12: Torsion bar,
13: Torque sensor,
14: Steering column,
15: Reduction gear,
16: Rack and pinion mechanism,
100: vehicle,

Claims (5)

Steering reaction force applying means for applying a steering reaction force to the vehicle steering mechanism;
Visibility estimation means for estimating the visibility of the road ahead of the vehicle;
A camera for photographing the front of the vehicle;
Steering angular velocity detection means for detecting the steering angular velocity;
Control means for controlling the steering reaction force applying means so that a deviation amount of the vehicle with respect to the travel lane is reduced based on an estimation result by the visibility estimating means and a photographed image of the camera ;
The control means includes
When controlling the steering reaction force applying means, if the estimation result indicates that the visibility of the road ahead of the vehicle is good , the amount of deviation from the travel lane proportional to the steering angular speed detected by the steering angular speed detecting means A steering characteristic change control in which a predetermined steering reaction force characteristic of the steering mechanism changes in a pseudo manner by applying a first steering torque in a direction in which the steering mechanism decreases to the steering mechanism ;
When the estimation result indicates that the visibility of the road ahead of the vehicle is not good, the amount of deviation with respect to the traveling lane, which is proportional to the estimated deviation amount with respect to the traveling lane after a predetermined vehicle head time has elapsed, is reduced. vehicle, characterized in that the second steering torque selecting Azukasuru steering torque applied control with the steering mechanism steering assist system.   The visibility estimating means detects an operation state of a fog lamp switch of the vehicle, and estimates that the visibility of a road ahead of the vehicle is not good when the detected operation state is an on state. Item 2. The vehicle steering assist device according to Item 1.   The visibility estimation unit detects an operation state of a wiper switch of the vehicle, and estimates that the visibility of a road ahead of the vehicle is not good when the detected operation state is an on state. Item 2. The vehicle steering assist device according to Item 1. A yaw rate sensor for detecting the yaw rate of the vehicle;
The control means includes
Calculating the second steering torque by calculating the predicted deviation amount based on a target locus calculated based on the captured image, a lateral deviation of the vehicle with respect to the target locus, and a yaw angle ;
2. The first steering torque is calculated by multiplying a difference between a standard yaw rate calculated based on the captured image and an actual yaw rate detected by the yaw rate sensor by the steering angular velocity . A steering assist device for a vehicle. Furthermore, the wake state determination means for determining the wake state for the driving operation of the driver is provided,
The control means, when the estimation result by the visibility estimation means indicates that the visibility of the road ahead of the vehicle is good, when the arousal level determination means determines that the driver's arousal state is low The vehicle steering assist device according to claim 1, wherein the steering torque application control is selected.

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