JP2017061280A - Steering support control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both alleviation of steering discomfort when switching to manual steering according to the driver's intention and improvement of safety when switching to manual steering when an uncontrollable condition is satisfied. SOLUTION: A position deviation calculation unit that calculates a lateral position deviation between the own vehicle and a steering tracking target based on a detection signal by a sensor, and a target value calculation unit that calculates a control target value for steering based on the lateral position deviation. A steering drive unit that drives the steering mechanism based on the control target value, and a control unit that controls the operation of the steering control system formed by having the sensor, the position deviation calculation unit, the target value calculation unit, and the steering drive unit. When an operation input instructing to stop the steering control realized by the steering control system is performed, the control unit reduces the control target value to the minimum value over the first period and owns the vehicle. When the steering control impossible condition is satisfied while traveling on a curved road, the control target value is reduced to the minimum value over a second period longer than the first period. [Selection diagram] Fig. 3

Description

  The present invention relates to a technical field of a steering assist control device mounted on a vehicle.

JP 2006-298059 A

As a steering assist function, for example, a follow-up steering control function is known in which the lateral position of the host vehicle is made to follow a predetermined follow-up target such as a preceding vehicle (see, for example, Patent Document 1).
For example, in follow-up steering control for a preceding vehicle, the position of the preceding vehicle is detected by an autonomous sensor such as a camera that captures the front of the own vehicle, and a positional deviation in the lateral direction between the position of the preceding vehicle and the own vehicle is calculated. Then, a control target value for steering is calculated based on the position deviation, and the steering mechanism is driven based on the control target value.

  In follow-up steering control, it is assumed that the preceding vehicle as the follow-up target deviates from the sensor capture range such as the camera field of view or that the follow-up steering control becomes impossible due to a sensor failure or the like. The In this case, the steering control should be stopped from the viewpoint of fail-safe.

  When the follow-up steering control is stopped in response to the establishment of an uncontrollable condition such that the follow-up target cannot be captured as described above, the control abort timing should be taken into consideration. Specifically, if the own vehicle immediately stops control while driving on a curved road, that is, if the application of steering torque is stopped, the vehicle abruptly advances toward the outside of the curve due to the self-aligning torque of the tire. Resulting in. Since the driver may feel anxiety and danger due to such a sudden change in the behavior of the vehicle, there is a time lag between the occurrence of the stop cause and the stop of the application of the steering torque when the follow-up steering control is stopped. Switching from automatic steering to manual steering should be done safely.

However, the follow-up steering control can be stopped according to the driver's operation.
Thus, if the time lag as described above is provided when the steering control according to the operation is stopped, there is a possibility that the driver may feel uncomfortable when he / she wants to perform the steering operation himself / herself.

  The present invention has been made in view of the above circumstances, and alleviates steering discomfort at the time of switching to manual steering according to the driver's intention, and safety at the time of switching to manual steering according to the establishment of an uncontrollable condition. It aims at coexistence with improvement of property.

  A steering assist control device according to the present invention includes a position deviation calculation unit that calculates a lateral position deviation between the host vehicle and a steering tracking target based on a detection signal from a sensor, and a control target value for steering based on the lateral position deviation. A target value calculation unit for calculating the control value, a steering drive unit for driving a steering mechanism based on the control target value, the sensor, the position deviation calculation unit, the target value calculation unit, and the steering drive unit. A control unit that controls the operation of the steering control system, and the control unit sets the control target value when an operation input is given to stop the steering control realized by the steering control system. When the vehicle is traveling on a curved road and the steering control disabling condition is satisfied while the vehicle is traveling on a curved road, the control target value is set to a second value longer than the first period. Over time to minimum Those causing little of.

  Thus, when the steering control according to the operation is stopped, the period during which the control target value is reduced to the minimum value can be shortened, and the period during which the steering torque not depending on the driver is applied can be shortened. The In addition, when steering control is stopped according to the establishment of an uncontrollable condition while driving on a curved road, the period during which the control target value decreases to the minimum value can be made longer, and the vehicle caused by self-aligning torque The behavior change is suppressed.

  In the above-described steering assist control device according to the present invention, the control unit, after the elapse of a maintenance period in which the control target value is maintained at the value at the time when the impossible condition is satisfied, in the second period, It is desirable to decrease gradually.

  By providing such a maintenance period, the return timing of the rudder by the self-aligning torque is delayed.

  In the above-described steering assist control device according to the present invention, it is desirable that the control unit notifies the driver during the maintenance period.

  As a result, it is possible to notify the driver of the control stop before the rudder return by the self-aligning torque is started.

  In the steering assist control apparatus according to the present invention described above, the control unit correlates the length of the maintenance period or the gradual decrease characteristic of the control target value in the second period with the lateral acceleration acting on the host vehicle. It is desirable to set according to the index value.

  Since the magnitude of the self-aligning torque depends on the lateral acceleration (lateral G), the length of the sustain period or the gradual decrease characteristic is set according to the correlation index value of the lateral acceleration as described above. Therefore, it is possible to further improve safety.

  In the steering assist control apparatus according to the present invention described above, it is preferable that the control unit sets the length of the maintenance period or the gradual decrease characteristic of the control target value in accordance with the presence or absence of steering by the driver.

  When the driver is keeping the steering, the start of manual steering is relatively quick, and when the driver is not holding, the starting of manual steering is relatively slow. For this reason, it is possible to alleviate the driver's uncomfortable feeling of steering when switching to manual steering by setting the length of the maintenance period and the gradual decrease characteristic according to the presence or absence of steering.

  Advantageous Effects of Invention According to the present invention, it is possible to achieve both of mitigation of uncomfortable steering when switching to manual steering according to the driver's intention and improvement of safety when switching to manual steering according to establishment of an uncontrollable condition. Can do.

It is the block diagram which showed the principal part of the vehicle-mounted system containing the steering assistance control apparatus of embodiment. It is explanatory drawing about the horizontal direction deviation of the own vehicle and steering tracking object. It is a figure for demonstrating the steering control stop method of embodiment. It is the flowchart which showed the procedure of the process corresponding to the case where tracking steering control is stopped according to operation. It is the flowchart which showed the procedure of the process corresponding to when follow-up steering control becomes impossible during curve road driving.

<1. Configuration of Steering Support Control Device of Embodiment>
Embodiments will be described below with reference to the accompanying drawings. FIG. 1 shows a main part of an in-vehicle system 1 including a steering assist control device of an embodiment.
The steering assist control apparatus according to the embodiment includes at least an imaging unit 10 and a steering ECU (Electronic Control Unit) 21. FIG. 1 shows a steering mechanism 30 as an object on which steering assistance control is performed by this steering assistance control device, and a vehicle speed sensor 15, a yaw rate sensor 16, and a rudder angle sensor 17 are used as sensors used for steering assistance control. Show. Further, a display unit 22 and a sound generation unit 23 are shown as related parts of the steering assist control.

The imaging unit 10 includes an imaging unit 11 </ b> L, an imaging unit 11 </ b> R, an image processing unit 12, and a driving support control unit 13 that are installed so as to be able to capture the traveling direction (front) in the host vehicle.
A vehicle speed sensor 15 that detects a vehicle speed, a yaw rate sensor 16 that detects a yaw rate, and a rudder angle sensor 17 that detects a steering rudder angle are connected to the imaging unit 10. The image processing unit 12 and the driving support control unit 13 are connected to these units. A detection signal from the sensor can be input.

  The imaging units 11L and 11R are arranged at a predetermined interval in the vehicle width direction, for example, in the vicinity of the upper part of the windshield of the host vehicle so that distance measurement by a so-called stereo method is possible. The optical axes of the imaging units 11L and 11R are parallel, and the focal lengths are the same. Also, the frame periods are synchronized and the frame rates are the same. The number of pixels of the image sensor is, for example, about 1280 pixels in the horizontal direction × about 960 pixels in the vertical direction.

  Electrical signals (captured image signals) obtained by the image sensors of the image capturing units 11L and 11R are each A / D converted into digital image signals (captured image data) representing luminance values with a predetermined gradation in pixel units. . The captured image data is, for example, color image data. Accordingly, three data (luminance values) of R (red), G (green), and B (blue) are obtained for each pixel. The gradation of the luminance value is, for example, 256 gradations.

The image processing unit 12 is configured by a microcomputer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory) as a work area, and the like, according to a program stored in the ROM. Perform various processes.
The image processing unit 12 stores each frame image data as captured image data obtained by the imaging units 11L and 11R imaging the front of the host vehicle in the internal memory. Based on the two captured image data as each frame, various processes for recognizing an object existing in front of the host vehicle as an external environment are executed. For example, a lane formed on a road (a line that divides a travel lane: for example, a white line or an orange line), a three-dimensional object such as a preceding vehicle or an obstacle is recognized. Further, based on the detected lane information, the traveling path of the host vehicle (the traveling path of the host vehicle) is estimated.

  When recognizing a three-dimensional object in front of the host vehicle, the image processing unit 12 uses the triangulation principle based on the principle of triangulation from the corresponding positional deviation amount for a pair of captured image data (stereo images) obtained by the imaging units 11L and 11R. The data (distance image) representing the three-dimensional distance distribution is generated based on the distance information. Then, based on this data, compared with well-known grouping processing and pre-stored three-dimensional road shape data, three-dimensional object data, etc., lane data, side walls such as guardrails and curbs that exist along the road Three-dimensional object data such as data and vehicles are extracted.

  In the three-dimensional object data, the distance to the three-dimensional object and the temporal change (relative speed with respect to the host vehicle) of this distance are obtained. A vehicle traveling at a speed (for example, 0 km / h or more) is extracted as a preceding vehicle. A vehicle having a speed of approximately 0 km / h among the preceding vehicles is recognized as a stopped preceding vehicle.

  Further, as the three-dimensional object information and the preceding vehicle information, the position information of the left end point and the right end point on the rear surface of the three-dimensional object or the preceding vehicle is stored, and the approximate center between the left end point and the right end point on the rear surface is a three-dimensional object. Alternatively, it is stored as the center position of the preceding vehicle.

Further, as for the preceding vehicle information, the preceding vehicle position represented as a coordinate position on the XZ coordinate system with the Z axis as shown in FIG. 2 as the vehicle longitudinal direction and the X axis as the vehicle lateral direction (lateral direction). Information on the preceding vehicle distance (inter-vehicle distance), the preceding vehicle speed ("change amount of the inter-vehicle distance" + "own vehicle speed"), and the preceding vehicle acceleration (differential value of the preceding vehicle speed) is also calculated and stored.
The three-dimensional object position other than the preceding vehicle, the lane position, and the own vehicle traveling path position are also calculated and stored as coordinate positions on the XZ coordinate system.

Image recognition results of the preceding vehicle, the three-dimensional object, the lane, and the like by the image processing unit 12 are used for various driving support controls.
Regarding the steering assist control of the present embodiment, information related to the detected lane (including the own vehicle traveling path, etc.), preceding vehicle information, and the like are input to the driving support control unit 13.

The driving support control unit 13 performs various driving support controls based on input information representing the image recognition result by the image processing unit 12.
For example, the driving support control unit 13 sets the steering angle independently of the driver (driver) based on the lane ahead of the host vehicle, thereby maintaining the host vehicle at the center of the traveling path of the host vehicle. It is possible to perform control and steering assist control (steering control) such as lane departure control for preventing deviation from the own vehicle traveling path (deviation of the own vehicle with respect to the lane of the own vehicle traveling path).
In addition, the driving support control unit 13 according to the present embodiment performs follow-up steering control for causing the preceding vehicle to follow the lateral position of the host vehicle as driving support control related to steering.

  The driving support control unit 13 determines various steering control operation conditions, and executes the steering control when the operation conditions are satisfied. Whether the steering control is operable is determined based on the operation information SD of the driver, information from the image processing unit 12, information from each sensor, and the like. Here, as the operation information SD of the driver, operation information such as an on / off operation of an ACC (Adaptive Cruise Control) switch or a steering control execution switch is comprehensively shown here.

During the steering control, the driving support control unit 13 calculates a target steering instruction current value based on the input information and outputs the target steering instruction current value to the steering ECU 21.
In particular, during the follow-up steering control described above, the driving support control unit 13 calculates, for example, the target steering angle θ _TG based on the following [Equation 1], and obtains a steering command current value corresponding to the target steering angle θ _TG .

θ _TG = G (v) × x / z [Formula 1]

Where x is the lateral position deviation between the host vehicle and the preceding vehicle (see FIG. 2; hereinafter, also simply referred to as “lateral position deviation”), z is the inter-vehicle distance from the preceding vehicle, and G (v) is dependent on the host vehicle speed. Rudder angle correction gain. The term “x / z” is a term that simply represents the angle θ _S (the yaw angle required to follow the preceding vehicle) shown in FIG. 2 based on a trigonometric function. The steering angle correction gain G (v) is a function according to the host vehicle speed, taking into account that the relationship between the yaw rate and the steering angle changes depending on the host vehicle speed.
Note that the lateral position deviation x is the image processing unit 12 as the preceding vehicle information (information on the preceding vehicle position) described above when the host vehicle position is the origin position in the XZ coordinate system as shown in FIG. Is calculated and input to the driving support control unit 13.

  The method for obtaining the target steering command current value in the follow-up steering control is not limited to the above method, and other methods such as the method described in Patent Document 1 described above are employed. You can also

Here, the driving support control unit 13 determines whether or not a predetermined steering control disabling condition is satisfied during execution of the steering control. For example, during follow-up steering control, a preceding vehicle that has been detected by the image processing unit 12 (that is, a preceding vehicle that has been the subject of follow-up until that time) is not detected, or a sensor (this In the example, it is assumed that the imaging units 11L, 11R, the vehicle speed sensor 15 and the like required for detecting the preceding vehicle are out of control. In the embodiment, occurrence of a causal event that disables such steering control is set in advance as a condition for disabling steering control.
When the disabled condition is satisfied, the driving support control unit 13 stops the steering control. The behavior when the steering control is stopped will be described later.

The steering ECU 21 is configured by a microcomputer, and controls the electric motor 42 in the steering mechanism 30 based on a steering instruction current value from the driving support control unit 13 and a detection signal from the steering angle sensor 17.
The steering ECU 21 obtains a steering command current value for obtaining a steering assist torque according to the steering angle based on information on the steering angle obtained from the detection signal of the steering angle sensor 17, The electric motor 42 is driven based on the command current value. Thereby, power steering control for assisting steering by the driver is realized.
The driver can perform the steering operation even when the steering control is performed by the driving support control unit 13, but when the manual steering is performed during the steering control, the steering is performed. The ECU 21 adds the steering command current value from the driving support control unit 13 and the steering command current value for power steering control obtained as described above, and the electric motor 42 is driven based on the total current value. The

For example, the steering mechanism 30 to be subjected to steering control is configured as follows.
In the steering mechanism 30, a steering shaft 32 is rotatably supported on a body frame (not shown) via a steering column 33. One end of the steering shaft 32 extends toward the driver's seat, and a steering wheel 34 is attached to one end of the steering shaft 32. The other end of the steering shaft 32 extends to the engine room side, and a pinion shaft 35 is connected to the other end of the steering shaft 32.
A steering gear box 36 extending in the vehicle width direction is disposed in the engine room, and a rack shaft 37 is inserted into and supported by the steering gear box 36 so as to be reciprocally movable. A rack (not shown) is provided in the middle of the rack shaft 37, and a rackion and pinion type steering gear mechanism is formed by engaging a pinion (not shown) provided on the pinion shaft 35 with the rack. It is configured.

  Further, both left and right ends of the rack shaft 37 protrude from the steering gear box 36, and a front knuckle 39 is connected to the end of the rack shaft 37 via a tie rod 38. The front knuckle 39 rotatably supports left and right wheels 40L and 40R as steering wheels, and is supported by a vehicle body frame via a king pin (not shown) so as to be continuously hit. Accordingly, when the steering wheel 34 is operated to rotate the steering shaft 32 and the pinion shaft 35, the rack shaft 37 moves in the left-right direction by the rotation of the pinion shaft 35, and the front knuckle 39 is moved to the king pin (not shown). And the left and right wheels 40L, 40R are steered in the left-right direction.

Further, the pinion shaft 35 and electric motor 42 via the assist transmission mechanism 41 is provided continuously at the electric motor 42, the assist and the steering torque applied to the steering wheel 34, so that the target steering angle theta _TG The appropriate steering torque is added.

Here, the driving support control unit 13 performs various notifications regarding driving support in addition to the driver's support by adding the steering torque as described above. Specifically, the driving support control unit 13 supplies display information and pronunciation instruction information to the display unit 22 and the sound generation unit 23.
The display unit 22 comprehensively shows, for example, a display control unit and a display device using a microcomputer. The display device is, for example, various meters such as a speedometer and a tachometer provided in a meter panel installed in front of the driver, MFD (Multi Function Display), and other devices for presenting information to the driver. In the display unit 22, regarding the steering assistance, a warning display and a display for making the driver perceive the operation / stop of the steering control are performed.

  The sound generation unit 23 comprehensively shows a sound generation control unit using, for example, a microcomputer and a sound generation device such as an amplifier / speaker. The sound generation unit 23 outputs a warning sound and a notification sound for making the driver perceive the operation / stop of the steering control.

<2. Steering control stop method of embodiment>
FIG. 3 is a diagram for explaining a steering control stop method according to the embodiment.
FIG. 3A shows a change characteristic of the steering instruction current value when the follow-up steering control is stopped based on the operation of the driver.
In the figure, when an operation to instruct the stop of the follow-up steering control is detected at time t1, the driving support control unit 13 sets the steering instruction current value to the minimum value ("0" in this example) over the first period P1. ). Specifically, in the first period P1, the steering command current value is maintained from the time when the stop operation is detected to the required maintenance period Pm1 (maintained at the current value at the time when the operation is detected), and then gradually decreases to the minimum value.
In this example, the first period P1 is set to a period of 1 sec or less, for example.

FIG. 3B shows a change characteristic of the steering instruction current value in the case where the follow steering control is stopped in response to the fact that the control disable condition of the follow steering control is satisfied while the host vehicle is traveling on a curved road.
If the establishment of the uncontrollable condition is time t2 in the figure, the driving support control unit 13 sets the steering instruction current value to the minimum value over a second period P2 longer than the first period P1 from time t2. To decrease. In the case of this example, in the second period P2, the steering command current value is maintained for the required maintenance period Pm2 from the time when the uncontrollable condition is satisfied (when it is determined), and then gradually decreases.

Here, the length of the sustain period Pm and the gradually decreasing slope θ (the slope of the descending line of the steering command current value at the time of gradually decreasing: it can also be referred to as the rate of decrease of the current value per unit time) can be made variable.
In this example, in consideration of the safe switching from the steering control state to the manual steering state when traveling on a curved road, the length of the maintenance period Pm2 and the gradually decreasing slope θ2 in the second period P2 are It is set based on an index value correlated with (lateral acceleration). Specifically, the index value correlated with the lateral G may include, for example, the own vehicle speed at the time when the impossible condition is determined, the curvature of the curved road during traveling, the steering instruction current value, the yaw rate, or the lateral G itself.
For example, when the lateral G is estimated to be large based on an index value correlated with any one of these lateral Gs, the sustain period Pm2 is lengthened and the gradually decreasing slope θ2 is decreased (gradually) according to the magnitude. . That is, the maintenance period Pm2 is lengthened and the gradual slope θ2 is decreased according to the magnitude of the value of the host vehicle speed, the magnitude of the curvature of the curved road during traveling, the magnitude of the steering command current value, and the magnitude of the yaw rate. .

In other words, the magnitude of the lateral G represents the magnitude of the self-aligning torque during traveling on a curved road. For this reason, the maintenance period Pm2 when the lateral G is large is relatively shortened, that is, the period during which the rudder is prevented from returning due to self-aligning torque is shortened, which is a safety factor when switching to manual steering. There is a risk of lowering.
As understood from this point, variably setting the maintenance period Pm2 according to the size of the lateral G, in other words, the size of the self-aligning torque, makes it possible to switch to manual steering more safely. It is desirable to make it.

In addition, if the steering command current value is sharply decreased after the maintenance period Pm2, the steering torque for resisting the self-aligning torque is drastically reduced, and the burden of the steering torque on the driver side is drastically reduced. It will increase. That is, if the driver is holding the steering wheel 34, the steering is suddenly heavy.
Therefore, by variably setting the gradually decreasing inclination θ2 in accordance with the size of the lateral G as described above, it is possible to more firmly prevent the steering weight felt by the driver from abruptly increasing. Thus, switching to manual steering can be performed more safely.

  The curvature of the curved road can be calculated based on the position information of the own vehicle traveling path (position information on the XZ coordinate system described above). Moreover, what is necessary is just to acquire about the side G with the side G sensor provided in the own vehicle.

  In the embodiment, the sustain period Pm2 variably set as described above is longer than the sustain period Pm1 in the first period P1, and the gradual decrease slope θ2 is smaller than the gradual decrease slope θ1. Thereby, the relationship of 2nd period> 1st period P1 is acquired.

Here, in this example, the driver is notified that the follow-up steering control is stopped in the maintenance period Pm2 in the second period P2. The notification is performed through the display unit 22 and the sound generation unit 23 shown in FIG.
By performing such notification in the maintenance period Pm2, it is possible to increase the possibility that manual steering by the driver will be started at a safe timing without the return of the rudder. That is, the safety can be further improved.

<3. Processing procedure>
A specific processing procedure to be executed to realize the steering control stop method as the embodiment described above will be described with reference to the flowcharts of FIGS. 4 and 5.
The processes shown in FIGS. 4 and 5 are executed by the driving support control unit 13 based on a program stored in a predetermined storage device such as a built-in ROM. The process shown in FIGS. 4 and 5 is executed in response to the start of follow-up steering control, for example.

FIG. 4 shows a procedure of processing corresponding to the case where the tracking steering control is stopped according to the operation.
In FIG. 4, the driving support control unit 13 determines whether or not a stop operation of the follow steering control is detected in step S101. If the stop operation is not detected, the driving support control unit 13 executes the determination process of step S101 again. This determination is made based on the operation information SD.

  If it is determined in step S101 that the stop operation has been detected, the driving support control unit 13 proceeds to step S102, and gradually decreases after maintaining the steering instruction current value over the period Pm1. As described above, the sustain period Pm1 is shorter than the sustain period Pm2, and the gradual decrease slope θ1 is greater than the gradual decrease slope θ2.

FIG. 5 shows a procedure of processing corresponding to the case where the follow-up steering control is disabled while traveling on a curved road.
In FIG. 5, the driving support control unit 13 determines whether or not the uncontrollable condition is satisfied in step S201, and if the uncontrollable condition is not satisfied, executes the determination process of step S201 again.
As described above, the determination in step S201 includes predetermined steering control such that the preceding vehicle being detected by the image processing unit 12 is not detected or a sensor required for the follow-up steering control is broken. It is determined whether or not the impossible condition is satisfied.

  If it is determined in step S201 that the uncontrollable condition is satisfied, the driving support control unit 13 proceeds to step S202, and determines whether or not the host vehicle is traveling on a curved road. Whether or not the vehicle is traveling on a curved road can be determined based on, for example, a detection signal from the yaw rate sensor 16 or a detection result of the vehicle traveling path by the image processing unit 12.

If it is determined in step S202 that the vehicle is not traveling on a curved road, the driving support control unit 13 proceeds to step S203, maintains the steering command current value over the period Pm1, and then gradually decreases. That is, when the uncontrollable condition is established while the host vehicle is traveling straight (or stopped), the steering command current value is reduced to the minimum value with the same behavior as when the follow-up steering control according to the operation is stopped.
Note that the behavior when the uncontrollable condition is satisfied when the host vehicle is not traveling on a curved road is not limited to the same behavior as when the follow-up steering control is stopped according to the operation. For example, the first period P1 Other behaviors may be employed, such as reducing the steering command current value to the minimum value over a third period set to satisfy the relationship of <third period <second period P2.
Further, even when the uncontrollable condition is satisfied when the host vehicle is not traveling on a curved road, the driver can be notified during the steering instruction current value maintaining period.

  The driving support control unit 13 ends the process shown in FIG. 5 in response to the execution of the process of step S203.

  On the other hand, when it is determined in step S202 that the vehicle is traveling on a curved road, the driving support control unit 13 proceeds to step S204, starts maintaining the steering instruction current value, and then counts the time in step S205. Start.

  In step S206, the driving support control unit 13 sets the maintenance period Pm2 and the gradual decrease slope θ2 corresponding to the lateral G correlation index value. That is, as described above, the maintenance period Pm2 and the gradually decreasing slope θ2 are set according to the magnitude of the lateral G correlation index value such as the value of the own vehicle speed, the curvature of the curved road during traveling, and / or the steering command current value, respectively. Set.

  Furthermore, in step S207, the driving support control unit 13 notifies the driver through the display unit 22 and / or the sound generation unit 23 that the follow-up steering control is stopped as a control stop notification process.

  In response to the execution of the notification process in step S207, the driving support control unit 13 determines whether or not the maintenance period Pm2 has elapsed in step S208. If the maintenance period Pm2 has not elapsed, the driving support control unit 13 executes the determination process in step S208 again.

  On the other hand, when the determination result that the maintenance period Pm2 has elapsed is obtained, the driving support control unit 13 proceeds to step S209, gradually decreases the steering instruction current value with the set inclination θ2, and ends the process shown in FIG.

In the above, as an example of setting the gradual decrease characteristic of the steering command current value in accordance with the lateral G correlation index value, an example in which the gradual decrease inclination θ2 is set is given. However, as the gradual decrease characteristic, the curvature of the gradual decrease curve (gradual decrease) The curve curvature of the descending line of the steering command current value at the time may be set. Specifically, the curvature of the gradually decreasing curve is reduced according to the size of the lateral G estimated from the lateral G correlation index value.
This makes it possible to moderate the change in the steering weight felt by the driver as the following steering control is stopped while driving on a curved road according to the size of the lateral G, thereby further improving safety. Can do.

Further, the length of the maintenance period Pm2 and the gradually decreasing inclination θ2 can be set according to the presence or absence of steering by the driver (at least whether or not the steering wheel 34 is gripped). When the driver is keeping the steering, the start of manual steering is relatively quick, and when the driver is not holding, the starting of manual steering is relatively slow. For this reason, when the driver is keeping the steering, the maintenance period Pm2 is shorter and the gradually decreasing slope θ2 is made larger than when the driver is not keeping the steering.
As a result, it is possible to alleviate the driver's uncomfortable feeling when switching to manual steering.
Note that the presence or absence of steering by the driver may be determined, for example, by a sensor provided on the steering wheel 34 (for example, a sensor that can detect contact with the steering wheel 34). Or you may determine the presence or absence of the input of the steering torque by a driver | operator.

<4. Summary of Embodiment>
As described above, the steering assist control apparatus according to the embodiment includes a position deviation calculation unit (for example, an image) that calculates a lateral position deviation between the host vehicle and a steering tracking target based on a detection signal from a sensor (for example, the imaging units 11L and 11R). A processing unit 12), a target value calculation unit (for example, a driving support control unit 13) for calculating a control target value (for example, a steering command current value) for steering based on the lateral position deviation, and a steering mechanism based on the control target value. A control unit (for example, driving support control) that controls the operation of a steering control system that includes a steering drive unit (for example, the steering ECU 21) that drives, a sensor, a position deviation calculation unit, a target value calculation unit, and a steering drive unit. Part 13).
Then, when an operation input for instructing stop of the steering control realized by the steering control system is performed, the control unit decreases the control target value to the minimum value over the first period, and the host vehicle When the condition for disabling steering control is established while traveling on the road, the control target value is decreased to the minimum value over a second period longer than the first period.

Thus, when the steering control according to the operation is stopped, the period during which the control target value is reduced to the minimum value can be shortened, and the period during which the steering torque not depending on the driver is applied can be shortened. The In addition, when steering control is stopped according to the establishment of an uncontrollable condition while driving on a curved road, the period during which the control target value decreases to the minimum value can be made longer, and the vehicle caused by self-aligning torque The behavior change is suppressed.
Therefore, it is possible to achieve both of mitigation of the uncomfortable feeling at the time of switching to manual steering according to the driver's intention and improvement of safety at the time of switching to manual steering according to the establishment of the uncontrollable condition.

  Further, in the steering assist control device of the embodiment, the control unit gradually decreases the control target value to the minimum value after the maintenance period in which the control target value is maintained at the value at the time when the impossible condition is satisfied in the second period. .

By providing such a maintenance period, the return timing of the rudder by the self-aligning torque is delayed.
Therefore, it is possible to start the manual steering by the driver at a safe timing without the return of the rudder, and the safety can be improved.

  Furthermore, in the steering assist control device of the embodiment, the control unit notifies the driver during the maintenance period.

As a result, it is possible to notify the driver of the control stop before the rudder return by the self-aligning torque is started.
Therefore, it is possible to increase the possibility that manual steering is started at a safe timing where there is no return of the rudder, and the safety can be further improved.

  Furthermore, in the steering assist control device of the embodiment, the control unit sets the length of the maintenance period in the second period or the gradual decrease characteristic of the control target value to an index value that correlates with the lateral acceleration acting on the host vehicle. It is set accordingly.

  Since the magnitude of the self-aligning torque depends on the lateral acceleration, the length of the maintenance period or the gradual decrease characteristic is set according to the correlation index value of the lateral acceleration as described above, so that safety can be achieved. Can be further improved.

  Further, in the steering assist control apparatus of the embodiment, the control unit sets the length of the maintenance period or the gradual decrease characteristic of the control target value according to the presence or absence of steering by the driver.

  When the driver is keeping the steering, the start of manual steering is relatively quick, and when the driver is not holding, the starting of manual steering is relatively slow. For this reason, by setting the length of the maintenance period and the gradual decrease characteristic according to the presence or absence of steering, it is possible to alleviate the driver's uncomfortable feeling of steering when switching to manual steering.

<5. Modification>
The present invention is not limited to the specific examples described above, and various modifications can be considered.
For example, in the above, it obtains a steering command current value driving support control unit 13 from the target steering angle theta _TG, but illustrating the configuration of outputting the steering command current value to the steering ECU 21, the steering ECU 21 is driving support control unit 13 based on the output target steering angle theta _TG can be configured to determine a steering command current value. In this case, the steering ECU 21 is responsible for maintaining and gradually reducing the steering command current value. In this case, either the driving support control unit 13 or the steering ECU 21 may determine whether or not the vehicle is traveling on a curved road and whether or not the uncontrollable condition is satisfied.

In the above, an example in which the control target value to be maintained or gradually decreased is the steering command current value. However, the control target value in the present invention is, for example, a target steering angle θ _TG , a target steering torque, or the like. And the target value for the steering control calculated based on the lateral position deviation between the steering tracking target and the steering tracking target.

  Note that the maintenance and gradual decrease of the control target value, particularly the maintenance and gradual decrease of the control target value, can be realized by an analog circuit instead of the digital arithmetic processing.

  In the above, the example in which the steering follow target is the preceding vehicle has been described. However, the present invention can also be suitably applied to the case where the vehicle other than the preceding vehicle is the steering follow target, such as the lane of the own vehicle traveling path.

Moreover, although the example which calculates | requires the horizontal direction positional deviation of the own vehicle and the steering follow target based on the stereo image obtained by the imaging parts 11L and 11R was given above, this horizontal direction positional deviation is taken by the monocular camera. The detection result of the steering tracking target by the radar or the position detection result by the GPS sensor can also be obtained by other means. The notation of “GPS” here is not limited to “Global Positioning System” in operation in the United States, but “GNSS (Global Navigation Satellite System)” which is a general “satellite positioning system”. It is used as meaning.
Here, as a method for obtaining the lateral position deviation based on the position detection result by the GPS sensor, for example, when the steering follow target is a preceding vehicle, the own vehicle position is detected by the GPS sensor provided in the own vehicle, As for the preceding vehicle position, a method of obtaining position detection information by a GPS sensor provided in the preceding vehicle by inter-vehicle communication and calculating based on the position information can be mentioned. Alternatively, when the steering tracking target is the lane of the own vehicle traveling path, the own vehicle position is detected by a GPS sensor provided in the own vehicle, and the lane position is acquired from the map information based on the own vehicle position. A method of calculating the lateral position deviation based on the position information of the own vehicle / lane can be mentioned.
Note that when the lateral position deviation is obtained using inter-vehicle communication, the inability to perform steering control includes disruption of inter-vehicle communication, failure of the communication unit, and further failure of the GPS sensor in the communication partner vehicle.

  DESCRIPTION OF SYMBOLS 1 ... In-vehicle system, 10 ... Imaging unit, 11L, 11R ... Imaging part, 12 ... Image processing part, 13 ... Driving support control part, 15 ... Vehicle speed sensor, 16 ... Yaw rate sensor, 17 ... Steering angle sensor, 21 ... Steering ECU , 22 ... Display section, 23 ... Sound generating section, SD ... Operation information, 30 ... Steering mechanism, 32 ... Steering shaft, 33 ... Steering column, 34 ... Steering wheel, 35 ... Pinion shaft, 36 ... Steering gear box, 37 ... Rack Shaft, 38 ... Tie rod, 39 ... Front knuckle, 40L, 40R ... Right and left wheels, 41 ... Assist transmission mechanism, 42 ... Electric motor

Claims (5)

A position deviation calculation unit that calculates a lateral position deviation between the host vehicle and the steering tracking target based on a detection signal from the sensor;
A target value calculation unit for calculating a control target value for steering based on the lateral position deviation;
A steering drive unit that drives the steering mechanism based on the control target value;
A control unit for controlling the operation of a steering control system formed by including the sensor, the position deviation calculation unit, the target value calculation unit, and the steering drive unit;
The controller is
When an operation input for instructing the stop of the steering control realized by the steering control system is performed, the control target value is decreased to the minimum value over the first period, and the host vehicle is traveling on a curved road When the steering control disabling condition is satisfied, the control target value is decreased to a minimum value over a second period longer than the first period. The controller is
2. The steering assist control device according to claim 1, wherein, in the second period, the control target value is gradually decreased to the minimum value after a maintenance period in which the control target value is maintained at a value when the impossible condition is satisfied. The controller is
The steering assist control device according to claim 2, wherein notification is given to the driver during the maintenance period. The controller is
The steering according to claim 2 or 3, wherein the length of the maintenance period or the gradual decrease characteristic of the control target value in the second period is set according to an index value correlated with a lateral acceleration acting on the host vehicle. Support control device. The controller is
The steering assist control apparatus according to any one of claims 2 to 4, wherein a length of the maintenance period or a gradual decrease characteristic of the control target value is set according to presence or absence of steering by a driver.

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