JP5900309B2 - Lane maintenance support device - Google Patents

Description

  The present invention relates to a lane keeping assist device.

  In the case of vehicles, particularly automobiles, steering is performed in a direction opposite to the direction of departure from the lane (that is, the direction toward the center of the lane) in order to support lane maintenance while driving, that is, to prevent lane departure. There is a tendency to increase the number of lane keeping assist torques to be applied. Since the steering force in the direction in which the lane keeping assist torque is applied becomes light, the driver is naturally urged to return to the lane center position. Of course, the magnitude of the assist torque for maintaining the lane is set to a size that can be overcome by the driver so as not to hinder the steering performed when the driver actively changes the lane.

  In general, when a steering wheel is operated, hysteresis is set to reduce the steering torque in the steering angle decreasing direction as compared with the steering torque in the steering angle increasing direction. The hysteresis is set in consideration of the self-aligning torque, the mechanical resistance of the steering system, and the like. This hysteresis setting enhances the steering function and ensures a good steering sensation so that there is no significant difference in steering feeling perceived by the driver between the steering angle increasing direction and the steering angle decreasing direction. Will be obtained.

  Patent Document 1 discloses that the hysteresis width is reduced as the steering angle increases. Patent Document 2 discloses a technique in which the hysteresis width is changed in accordance with the gripping force of the wheel, that is, the lateral G. Patent Document 3 discloses that an actual force, that is, a physical force and a perceptive force perceived by a human differ depending on the magnitude of the force exerted by a human upper limb.

JP 2009-227125 A JP 2011-201388 A JP 2008-125520 A

  By the way, it has been found that in a vehicle that performs control for applying lane keeping assist torque, a phenomenon that the steering wheel feels worse is caused. Specifically, when the lane keeping assist torque is applied, the steering torque exerted by the driver can be reduced by that amount compared to the case where the lane keeping assist torque is not applied. Become.

  On the other hand, the steering force perceived by the driver is particularly felt according to the force exerted by the arm (upper limb) that operates the steering handle. And when the driver is exerting a small force, the driver is more likely to change the steering force even if the amount of physical change in the steering force is the same than when the force is large. You will perceive.

  For this reason, even if the width of the hysteresis in a state where the assist torque for maintaining the lane is not applied is set to be preferable as a driver's steering feeling, the width of the hysteresis remains the same for maintaining the lane. When shifting to the state where the assist torque is applied, the steering wheel feels that the return of the steering wheel has deteriorated.

  The present invention has been made in consideration of the above circumstances, and can prevent or suppress the driver from feeling uncomfortable with respect to steering due to the presence or absence of the assist torque for maintaining the lane. It is to provide a maintenance support device.

In order to achieve the above object, the following solution is adopted in the present invention. That is, as described in claim 1, that is,
In the lane keeping assist device in which the assist torque for maintaining the lane in a direction that prevents the own vehicle from deviating from the traveling lane is applied in a size that the driver can overcome,
Hysteresis is set so that the steering torque in the steering angle decreasing direction becomes smaller than the steering torque in the steering angle increasing direction,
When the lane keeping assist torque is applied, the width of the hysteresis is made smaller than when the lane keeping assist torque is not applied.
It is like that. The above solution prevents or suppresses a situation in which the driver feels that the return of the steering wheel has deteriorated when a transition is made from a state where the assist torque for maintaining the lane is not applied to a state where it is applied. Will be.

A preferred mode based on the above solution is as described in claim 2 and the following. That is,
Even if the correlation between the physical steering torque and the magnitude of the perceived steering torque perceived by the driver is the same when the physical steering torque is small, the perception is the same even when the physical steering torque is the same. It is set as a characteristic set to increase the amount of change in steering torque,
The difference in the width of the hysteresis between when the lane keeping assist torque is applied and when it is not applied is compared with the characteristic so that the amount of change in the perceptual steering torque is substantially the same. Set,
(Corresponding to claim 2). In this case, it is possible to sufficiently exhibit the effect corresponding to the first aspect in consideration of human perception characteristics regarding force.

A changeover switch that is manually operated by the driver and that selects a control execution state for applying the lane keeping assist torque and a control prohibiting state for prohibiting the application of the lane keeping assist torque,
When the control execution state is selected by the changeover switch, the width of the hysteresis is made smaller than when the control prohibition state is selected.
(Corresponding to claim 3). In this case, it is possible to prevent or suppress the uncomfortable feeling related to the steering caused by the operation of the changeover switch while enabling the changeover switch to select execution or prohibition of the lane keeping control according to the driver's preference.

When a range deviated by a predetermined width in the left-right direction from the physical lane center position in the travel lane of the host vehicle is set as a dead zone, and the physical lane center position of the host vehicle is within the dead zone, the lane maintaining assist torque Is not granted,
When the physical lane center position of the host vehicle is outside the dead zone, the width of the hysteresis is made smaller than when the physical lane center position is outside the dead zone.
(Corresponding to claim 4). In this case, while preventing the situation where the lane keeping assist torque is unnecessarily applied by setting the dead zone, it is possible to prevent a sense of incongruity related to steering regardless of whether the physical lane center position of the host vehicle is within the dead zone or Can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the situation which gives the driver discomfort regarding steering due to the presence or absence of the assist torque for maintaining the lane can be prevented or suppressed.

The block diagram which shows the example of a control system of the lane maintenance assistance apparatus to which this invention was applied. An example of changing the width of the hysteresis and the difference between the physical steering torque and the perceived steering torque are shown. The figure for demonstrating determination of a target yaw rate. The figure which shows the example of a setting of the front gaze time T in FIG. The characteristic view which shows the example of a setting of the target steering torque according to a target yaw rate. The characteristic view which shows the example of a setting of the reference | standard hysteresis width according to steering angular velocity. The flowchart which shows the example of control of this invention. The characteristic view which shows the 2nd Embodiment of this invention and shows the example of a setting of assist torque for lane keeping.

  FIG. 1 is a block diagram showing an example of a control system of the present invention mounted on a vehicle (automobile). In FIG. 1, U is a controller (control unit) configured using a microcomputer. The controller U has a storage means M, and stores various characteristic diagrams and the like used for executing the control described later in addition to the program necessary for the control.

  The controller U receives signals from various sensors and devices S1 to S6. S1 is a steering angle sensor that detects an operation amount of a steering wheel operated by a driver, that is, a steering angle (a steering angle including an operation direction). For example, S2 is a torque sensor that is attached to the steering shaft and detects the steering torque in accordance with the amount of twisting of the steering shaft.

  S3 is a camera that captures the front of the host vehicle, and is used to detect the left and right white line positions that divide the lane in which the host vehicle is traveling, and to detect the lateral position of the host vehicle relative to the left and right white line positions. (It also detects the center position of the physical lane). S4 is a vehicle speed sensor that detects the vehicle speed. S5 is a navigation device for detecting the current position of the host vehicle and using the map information to detect the current road condition where the host vehicle is traveling, the road condition ahead, and the like. . S6 is a change-over switch that is manually operated by the driver to select ON (execution) and OFF (execution prohibition) of lane keeping control described later.

  The controller U controls the motor S11 and display means S12 such as a display or a lamp. The motor S11 is incorporated in the steering system and performs power assist. That is, in the embodiment, the power steering mechanism is an electric type in which an assist force is generated by the motor S11. The steering assist force is changed by adjusting (changing) the supply current. The display means S12 is for informing the driver of the ON / OFF state of the changeover switch S6.

  FIG. 2 schematically shows the contents of the present invention, and FIG. 2 (a) shows physical steering torque, steering angle, and hysteresis. In FIG. 2 (a), the broken line indicates the characteristic without the lane keeping assist torque, and the steering angle with respect to the steering torque in the direction in which the steering angle increases at the same steering angle. The steering torque in the direction of decreasing is set small, and the difference ΔTphy indicates the width of hysteresis.

  In FIG. 2 (a), the solid line shows the characteristics in the state where the lane keeping assist torque is applied. When the steering angle is the same, the steering torque is increased with respect to the steering torque in the direction in which the steering angle increases. The steering torque in the direction in which the angle decreases is set small, and the difference ΔT′phy indicates the width of the hysteresis. This ΔT'phy is made smaller than ΔTphy when there is no lane keeping assist torque.

  FIG. 2B shows the correlation between the physical steering torque and the steering torque perceived by a human (driver). As apparent from FIG. 2B, even when the amount of change in the physical steering torque is the same, the amount of change in the perceived steering torque is smaller when the physical steering torque is large than when it is small. It becomes.

  In a state where the physical steering torque is large (in other words, when there is no lane keeping assist torque), the amount of change in the perceived steering torque corresponding to the amount of change in the physical steering torque corresponding to the hysteresis width ΔTphy is ΔTper. . In a state where the physical steering torque is smaller (in other words, when there is a lane keeping assist torque), the amount of change in the perceived steering torque corresponding to the amount of change in physical steering torque corresponding to the hysteresis width ΔT′phy is Δ T'per. Then, ΔT′per = ΔTper = small relationship is established.

  On the other hand, in a state where the physical steering torque is smaller (in other words, when there is a lane keeping assist torque), it corresponds to the amount of change in physical steering torque corresponding to a large hysteresis width ΔTphy when there is no lane keeping assist torque. The amount of change in the perceived steering torque is considerably larger than ΔT′per. That is, when the lane keeping assist torque is changed from the non- assisting state to the existing state, if the hysteresis width is kept as ΔTphy which is a large hysteresis width, the amount of change in the perceived steering torque corresponding to this ΔTphy is The driver becomes too large and the driver feels that the steering wheel has returned poorly.

  In the present invention, the hysteresis width is changed to a smaller hysteresis width ΔT′phy as compared with the case where there is a lane keeping assist torque, and therefore the amount of change in the perceived steering torque corresponding to this is changed. This is the same as or almost the same as the case without the assist torque for maintaining the lane, and does not feel (or is difficult to feel) an uncomfortable feeling about steering.

  In the embodiment, the amount of change in the hysteresis width corresponding to the presence / absence of the lane keeping assist torque is set so that the amount of change in the perceived steering torque is the same. Specifically, first, the perceptual steering torque change amount ΔTper corresponding to the hysteresis width ΔTphy when there is no lane keeping assist torque is determined. Next, the hysteresis width when the lane keeping assist torque is present may be determined so as to be the same perceived steering torque change amount ΔTper (= ΔT′per) as the change amount ΔTper. As a result, the same steering feeling can be obtained when there is no steering lane maintaining assist torque and when there is no lane keeping assist torque.

  Next, an example of determining the lane keeping assist torque for lane keeping will be described. First, in the embodiment, as shown in FIG. 3, a target yaw rate calculation required for guiding to the guidance target point α that is the physical lane center position ahead of the host vehicle X is performed. The distance in the forward direction of the host vehicle to the guidance target point α is defined as VT. In this case, V is the vehicle speed and T is the forward gaze time. The forward gaze time is set as a characteristic as shown in FIG. 4, for example, but the point is the target time until the guidance target point α is reached. Basically, the front gaze time T decreases as the vehicle speed increases. (Upper limit value and lower limit value are set).

  The target yaw rate Υtarget required for guiding to the guidance target point α is obtained by the following equation (1) based on the vehicle speed, the lateral position of the host vehicle, the yaw angle, the curvature of the lane, and the clothoid parameter. In equation (1), V is the vehicle speed, T is the forward gaze time, R is the curvature of the lane, Ψ0 is the yaw angle of the host vehicle X, y0 is the lateral position of the host vehicle X, and A is the clothoid parameter. The curvature R and the like can be determined based on the detection result of the camera S3. For example, the curvature R is obtained based on the map information in the navigation device S5 or information from the infrastructure facility set on the roadside. Can be obtained by an appropriate method.

  When the target yaw rate Υtarget is determined, the target steering torque to be exhibited by the driver is determined by comparing the target yaw rate Υtarget and the vehicle speed with the characteristics shown in FIG. Next, the steering angular velocity is checked against the characteristic diagram shown in FIG. 6 to determine the hysteresis width. Note that a dead zone is set for the hysteresis width in a region where the steering angular velocity is small (for example, 0.00001 rad / s or less) (steering rattling is prevented). This hysteresis width corresponds to the case where a reference value without the lane keeping assist torque is set. When the lane keeping assist torque is present, the hysteresis width decreases so as to reduce the hysteresis width as described with reference to FIG. It is corrected.

  The following steering torque is determined for the final output to the power steering device. First, TBASE is calculated as the steering torque necessary for the turning described with reference to FIG. The target steering torque determined from FIG. 5 described above is Ttarget. When the steering torque by the driver is TDriver, the standard assist torque corresponding to TDriver is determined as TESP. The lane keeping assist torque TLKA is calculated based on the following equation (2).

TLKA = TBASE-TDriver-TESP (2)
The lane keeping assist torque TLKA is additionally applied to the case where there is no lane keeping control. When the lane keeping assist torque TLKA is applied, the hysteresis width is corrected to be smaller than when the lane keeping assist torque TLKA is not applied.

  FIG. 7 is a flowchart showing an example of control for determining the lane keeping assist torque TLKA and the hysteresis width. This flowchart will be described below, but it is assumed that the changeover switch S6 is ON (with lane keeping assist torque control). In the following description, Q indicates a step. Of course, the characteristics shown in FIG. 2 (particularly (b)), FIG. 4, FIG. 6 and FIG. 8 to be described later, and expressions (1) and (2) are stored in the storage means M.

  Based on the above, first, in Q1, signals from various sensors S1 to S6 are read. Next, at Q2, as described in FIG. 3, the target yaw rate Υtaeget is calculated. Next, at Q3, a target steering torque TDtarget to be exhibited by the driver is calculated based on FIG. Thereafter, in Q4, a steering torque TBASE required for turning for guiding to the guidance target point α in FIG. 3 is calculated.

  After Q4, in Q5, the standard assist torque TESP is calculated based on the target steering torque TDtarget calculated in Q3. Thereafter, in Q6, the lane keeping assist torque TLKA is calculated based on the equation (2). Thereafter, in Q7, the reference hysteresis width is determined based on FIG.

  After Q7, at Q8, it is determined whether or not the lane keeping assist torque TLKA is zero. When the determination in Q8 is YES, since the lane keeping assist torque is applied, the reference hysteresis width determined in Q7 is corrected to decrease in Q9. Thereafter, in Q10, the motor S11 is controlled so that the lane keeping assist torque TLKA is added, and is controlled so as to have the determined hysteresis width.

  When the determination in Q8 is NO, the lane keeping assist torque is not present, and in this case, the process proceeds to Q10 without passing through Q9 (the reference hysteresis width is set).

  FIG. 8 shows a second embodiment of the present invention. In the present embodiment, the determination of the lane keeping assist torque is made based on the characteristics shown in FIG. In FIG. 8, a dead zone having a predetermined width (for example, 0.4 to 0.5 m) is set in the left-right direction from the center position of the physical lane, and the assist torque for maintaining the lane is not applied (prohibited) in the dead zone. It is. The lane keeping assist torque is applied only outside the dead zone. In the case of this embodiment, the hysteresis width is set to the reference hysteresis width when in the dead band, and is set to a size obtained by reducing and correcting the reference hysteresis width in a region outside the dead band (how to reduce correction is shown in FIG. 2). Same as description).

  Here, when the control switch of the lane keeping assist torque is switched between the control execution and the control prohibition by the changeover switch S6, the hysteresis width when the control is prohibited is set as the reference hysteresis width. It is corrected to be smaller than the hysteresis width.

  Although the embodiments have been described above, the present invention is not limited to the embodiments, and appropriate modifications can be made within the scope of the claims. The power assist device is not limited to an electric type but may be a hydraulic type. In addition to using the camera S2, the position of the vehicle in the lateral direction with respect to the lane can be detected by using another sensor such as a radar as an alternative or in cooperation, using a high-precision navigation device, It can be selected as appropriate, for example, by obtaining information from the infrastructure facility from the roadside by communication, or by combining them. Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

  The present invention is suitable as a vehicle lane keeping assist device.

U: Controller (control means)
S1: Rudder angle sensor S2: Torque sensor S3: Camera S4: Vehicle speed sensor S5: Navigation device S6: Changeover switch (for ON / OFF of lane keeping control)
S11: Motor (for power assist)

Claims (4)

In the lane keeping assist device in which the assist torque for maintaining the lane in a direction that prevents the own vehicle from deviating from the traveling lane is applied in a size that the driver can overcome,
Hysteresis is set so that the steering torque in the steering angle decreasing direction becomes smaller than the steering torque in the steering angle increasing direction,
When the lane keeping assist torque is applied, the width of the hysteresis is made smaller than when the lane keeping assist torque is not applied.
A lane keeping assist device characterized by that. In claim 1,
Even if the correlation between the physical steering torque and the magnitude of the perceived steering torque perceived by the driver is the same when the physical steering torque is small, the perception is the same even when the physical steering torque is the same. It is set as a characteristic set to increase the amount of change in steering torque,
The difference in the width of the hysteresis between when the lane keeping assist torque is applied and when it is not applied is compared with the characteristic so that the amount of change in the perceptual steering torque is substantially the same. Set,
A lane keeping assist device characterized by that. In claim 1 or claim 2,
A changeover switch that is manually operated by the driver and that selects a control execution state for applying the lane keeping assist torque and a control prohibiting state for prohibiting the application of the lane keeping assist torque,
When the control execution state is selected by the changeover switch, the width of the hysteresis is made smaller than when the control prohibition state is selected.
A lane keeping assist device characterized by that. In any one of Claims 1 thru | or 3,
When a range deviated by a predetermined width in the left-right direction from the physical lane center position in the travel lane of the host vehicle is set as a dead zone, and the physical lane center position of the host vehicle is within the dead zone, the lane maintaining assist torque Is not granted,
When the physical lane center position of the host vehicle is outside the dead zone, the width of the hysteresis is made smaller than when the physical lane center position is outside the dead zone.
A lane keeping assist device characterized by that.

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