JP2016218935A - Curve section identification system, curve section identification method and curve section identification program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curve section identification system capable of improving the accuracy in identifying curve section.SOLUTION: The curve section identification system is constituted by including: a feature point acquisition section that acquires a feature point which represents a feature point on a road; a line segment acquisition section that acquires a line segment which extends from the interest feature point to another feature point or to a point on the line, which connects neighboring feature points before and after the interest feature point; a curve section identification section that, when a crossing angle of the line segments is larger than a criteria, identifies a curve section based on the interest feature point; and a line segment length adjustment section that changes the length of the line segment based on the density of the feature points on the road.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a curve section specifying system, a curve section specifying method, and a curve section specifying program.

  Conventionally, a technique for specifying a curve section is known. For example, in Patent Document 1, a plurality of continuous nodes on the road ahead of the observation point are acquired, the length of the link connecting the nodes is smaller than the threshold, and the angle at which the links intersect is larger than the threshold. A configuration is disclosed in which it is determined that the curve starts when the determination is continued twice.

JP 2006-4029 A

The conventional technique is a configuration for determining whether or not a curve has started based on the intersection angle of links connecting nodes. Therefore, the determination result of whether or not the curve has started depends on the setting position of the node adjacent to the curve start point. The node is determined according to the shape of the curve, but when a plurality of curves having the same curvature are compared, the relative positional relationship of the nodes is not necessarily the same in all the curves. Therefore, in the prior art, even if the curves have the same curvature, it is determined whether the curves are based on various determination indexes. However, a link connecting nodes in a certain curve is not always appropriate as a reference for determining whether or not the node is included in the curve.
The present invention has been made in view of the above problems, and an object thereof is to improve the accuracy of specifying a curve section.

  In order to achieve the above object, the curve section specifying system is configured such that a shape point acquisition unit that acquires a shape point indicating a road shape and a line connecting other shape points or adjacent shape points from a focused shape point. A line segment acquisition unit that acquires a line segment extending to the point before and after the focused shape point, and a curve segment that specifies a curve segment based on the focused shape point when the intersection angle of the line segment is larger than the criterion A specific unit, and a line segment length adjusting unit that changes the length of the line segment indicating the road section based on the density of shape points on the road.

  In order to achieve the above object, the curve section specifying method includes a shape point acquisition step of acquiring a shape point indicating the shape of the road, and other shape points or adjacent shape points from the focused shape points. A line segment acquisition step for acquiring a line segment extending to a point on the connecting line before and after the focused shape point, and a curve section is specified based on the focused shape point when the intersection angle of the line segment is larger than the criterion It is configured to include a curve segment specifying step and a line segment length adjusting step for changing the length of the line segment indicating the road segment based on the density of shape points on the road.

  Furthermore, in order to achieve the above object, the curve section specifying program obtains a shape point indicating the shape of the road and obtains a shape point from the focused shape point to another shape point or adjacent shape points. A line segment acquisition function that acquires a line segment extending to a point on the connecting line before and after the focused shape point, and a curve section is specified based on the focused shape point when the intersection angle of the line segment is larger than the criterion The computer realizes a curve section specifying function and a line segment length adjusting function for changing the length of the line segment indicating the road section based on the density of shape points on the road.

  That is, in the curve section specifying system, method, and program, a line segment that extends from a focused shape point to another shape point or a point on a line connecting adjacent shape points is defined. The line segment is defined so as to extend before and after the focused shape point. Then, the curve section is specified by the intersection angle of the line segment.

  The line segment defined as described above includes not only the line segment extending from the focused shape point to the adjacent shape point, but also the line segment extending from the focused shape point to the non-adjacent shape point. A line segment extending to a line connecting the shape points is included. Therefore, the line segment for determining whether or not it is a curve section is not limited to a line segment connecting adjacent shape points.

  The length of the line segment depends on the density of shape points on the road. Since the shape points on the road indicate the shape of the road, the density of the shape points is denser on the road where the shape change is large than on the road where the shape change is small. Accordingly, the density of the shape points in the curve section having a small curvature radius is higher than that in the curve section having a large curvature radius. Therefore, by changing the length of the line segment based on the density of the shape points, it is possible to define a determination index (line segment) that changes in accordance with the shape of the curve (curvature radius). Therefore, in the curve section specifying system, method, and program, the accuracy of specifying the curve section can be improved.

It is a block diagram which shows a curve area identification system. (2A) is a curve section specifying process, and (2B) is a flowchart of a start / end candidate point acquisition process. (3A) is a flowchart of the dividing process, and (3B) is a diagram showing a histogram of distances between shape points. (4A), (4B), and (4C) are diagrams showing determination of a curve section by an intersection angle. It is a figure which shows the determination of the curve area by the distance between shape points.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of curve section identification system:
(2) Curve section identification processing:
(3) Start / end candidate point acquisition processing:
(4) Division processing:
(5) Other embodiments:

(1) Configuration of curve section identification system:
FIG. 1 is a block diagram showing a configuration of a curve section specifying system 10 according to the present invention. The curve section specifying system 10 includes a control unit 20 including a CPU, a RAM, a ROM, and the like, and a recording medium 30, and the control unit 20 can execute a program stored in the recording medium 30 and the ROM. In the present embodiment, the curve section specifying program 21 can be executed as this program. The curve section specifying program 21 acquires the current position of the vehicle and causes the control unit 20 to execute a function of specifying a curve section existing ahead of the current position of the vehicle.

  A vehicle in which the curve section specifying system 10 is used includes a GPS receiving unit 41, a vehicle speed sensor 42, a gyro sensor 43, a transmission unit 44, and a braking unit 45. The GPS receiver 41 receives radio waves from GPS satellites and outputs a signal for calculating the current position of the vehicle via an interface (not shown). The vehicle speed sensor 42 outputs a signal corresponding to the rotational speed of the wheels provided in the vehicle. The control unit 20 acquires this signal via an interface (not shown) and acquires the vehicle speed. The gyro sensor 43 detects angular acceleration about turning in the horizontal plane of the vehicle, and outputs a signal corresponding to the direction of the vehicle. The control unit 20 acquires this signal and acquires the traveling direction of the vehicle. The control unit 20 acquires the current position of the vehicle by specifying the travel locus of the vehicle based on output signals from the vehicle speed sensor 42 and the gyro sensor 43 and the like. The output signal of the GPS receiver 41 is used for correcting the current position of the vehicle specified by the vehicle speed sensor 42, the gyro sensor 43, and the like.

  The transmission unit 44 includes a stepped torque converter having a plurality of speed stages such as a total of 6 speeds for forward and a total of 1 speed for reverse, and adjusts the rotational speed with a gear ratio corresponding to each speed. Can be transmitted to the wheels of the vehicle. The control unit 20 outputs a control signal for switching the gear position via an interface (not shown), and the transmission unit 44 can acquire the control signal and switch the gear position. Therefore, the control unit 20 can decelerate the vehicle by outputting a control signal to the transmission unit 44 to change the gear position and apply an engine brake to the vehicle. In the present embodiment, the gear ratio is configured to become smaller as the gear position becomes higher gear, such as forward 1st speed to forward 6th speed.

  The braking unit 45 includes a device that controls the pressure of the wheel cylinder that adjusts the degree of deceleration by the brake mounted on the wheel of the vehicle, and the control unit 20 outputs a control signal to the braking unit 45 to output the wheel cylinder. It is possible to adjust the pressure. Therefore, when the control unit 20 outputs a control signal to the braking unit 45 to increase the pressure of the wheel cylinder, the braking force by the brake is increased and the vehicle is decelerated.

  As described above, the control unit 20 can decelerate the vehicle by outputting control signals to the transmission unit 44 and the braking unit 45. In the present embodiment, the control unit 20 can execute a deceleration control program (not shown). By the processing of the deceleration control program, the control unit 20 sets the vehicle speed to the target speed before entering the curve section. Decelerate so that: Here, the target speed is determined according to the curvature of the curve section. For example, the target speed is determined so that the vehicle can travel at a constant vehicle speed in a constant curvature portion of a curve section. In this configuration, the control unit 20 performs deceleration control by, for example, decelerating the vehicle by a constant acceleration linear motion before the entrance of the constant curvature portion and decelerating the vehicle speed to the target speed at the entrance of the constant curvature portion. I do.

  Map information 30a is recorded in the recording medium 30 in advance. The map information 30a includes node data indicating the position of a node set at an intersection on the road on which the vehicle travels, shape interpolation point data for specifying the shape of the road between the nodes, link data indicating the connection between the nodes, It contains facility data indicating facilities that exist around the road. In the present embodiment, the nodes and shape interpolation points are shape points indicating the shape of the road. That is, the shape points in the present embodiment indicate the position of the road, and the straight line connecting the shape points indirectly indicates the direction of the road.

  In the present embodiment, the control unit 20 executes a process of specifying a curve section existing ahead of the vehicle by the curve section specifying program 21 in order to perform the deceleration control as described above. The curve section specifying program 21 includes a shape point acquiring unit 21a, a line segment acquiring unit 21b, a curve section specifying unit 21c, and a line segment length adjusting unit 21d.

  The shape point acquisition unit 21a is a program module that causes the control unit 20 to realize a function of acquiring a shape point indicating the shape of the road. That is, the control unit 20 acquires the current position of the vehicle based on the processing of the GPS reception unit 41, the vehicle speed sensor 42, and the gyro sensor 43 by the processing of the shape point acquisition unit 21a, and refers to the map information 30a to determine the vehicle's current position. Get the shape point that exists ahead.

  The line segment acquisition unit 21b is a program module that causes the control unit 20 to realize a function of acquiring a line segment indicating the direction of the road based on the shape point. Specifically, the control unit 20 acquires a line segment extending from a focused shape point to a point on a line connecting other shape points or adjacent shape points before and after the focused shape point. That is, when a shape point is acquired by the process of the shape point acquisition unit 21a, the control unit 20 sets one of the acquired shape points as a target shape point by the process of the line segment acquisition unit 21b.

  And the control part 20 determines the length of a line segment by the process of the line segment length adjustment part 21d mentioned later. Further, the control unit 20 specifies a line connecting adjacent shape points. And the control part 20 makes the intersection of the circle | round | yen centering on the shape point of interest and the length of a line segment a radius, and the line which connects between adjacent shape points as an end point of a line segment. Since the end point is acquired before and after the target shape point, the control unit 20 acquires a line segment extending from the target shape point to each end point. The control part 20 performs the process which acquires a line segment as mentioned above about a some shape point, changing a focused shape point sequentially.

  The curve section specifying unit 21c is a program module that causes the control unit 20 to realize a function of specifying a curve section based on the intersection angle of the line segment and the distance between the shape points. Specifically, the curve section specifying unit 21c specifies the end points of the curve section based on the intersection angle of the line segment, and the shape point is determined when the distance between the shape points is larger than a threshold value depending on the curvature radius of the curve section. The control unit 20 realizes a function of specifying the end point of the curve section based on the above and specifying the curve section based on the both end points.

  That is, the line segment acquired for each shape point is a line connecting the points (or other shape points) on the line connecting the shape points to each other, and thus indicates the direction of the road (at least approximately). ing. Therefore, if the control unit 20 analyzes the intersection angle of the line segment, it can be specified whether or not the road at the position corresponding to the line segment is a curve section. Therefore, the control unit 20 acquires the intersection angle of the line segment acquired before and after the target shape point by the process of the curve section specifying unit 21c. Further, the control unit 20 determines that the target shape point is included in the curve section when the intersection angle of the line segment is larger than the determination criterion.

FIG. 4A is a diagram schematically illustrating an arrangement example of shape points on a road, and the shape points are indicated by black circles. In this embodiment, the shape point is arranged at the center of the road. The alternate long and short dash line is a line connecting the shape points. In this example, it is assumed that the shape point of _interest acquired by the control unit 20 by the processing of the line segment acquisition unit 21b is a point P _i1 and the line segments are line segments L _f1 and L _b1 . In this case, the control unit 20 acquires an intersection angle A (an angle formed by a line obtained by extending the rear line segment forward and a front line segment) based on the directions of the line segments L _f1 and L _b1 . When the intersection angle A is larger than the determination criterion, it is determined that the shape point P _i1 is included in the curve section.

  When the target shape point that is not determined to be included in the curve section and the target shape point that is determined to be included in the curve section are adjacent to each other, the control unit 20 sets the latter target shape point as the end point of the curve section. Get as. It should be noted that the determination criterion for the intersection angle only needs to be defined so that the target shape point is a curve section when the intersection angle of the line segment is larger than the determination criterion, and is determined in advance based on statistics.

  Furthermore, the distance between the shape points depends on the density of the shape points. That is, if the density of the shape points is dense, the distance between the shape points becomes short, and if the density of the shape points is coarse, the distance between the shape points becomes long. In general, since the shape point is a point indicating the shape of the road, the density of the shape points is rough in a section where the change in the shape of the road is relatively small. Therefore, the density of the shape points becomes coarse in the section where the radius of curvature is large.

  If the road has a small radius of curvature and a zone with a large radius of curvature (a zone that can be regarded as not substantially a curve, including an infinite radius of curvature (including a straight zone)), a zone with a small radius of curvature Due to the proximity of a section with a large radius of curvature, the intersection angle of the line indicating the direction of the road may be a value indicating a curve. FIG. 5 is a diagram schematically showing an example of arrangement of shape points on the road, and the shape points are indicated by black circles. In this embodiment, the shape point is arranged at the center of the road. The alternate long and short dash line is a line connecting the shape points.

The road shown in FIG. 5 shows an example in which a curve section R ₂ exists between the straight sections R ₁ and R ₃ and a curve section R ₄ exists between the straight sections R ₃ and R ₅ . In this example, it is assumed that the shape point of _interest acquired by the control unit 20 by the processing of the line segment acquisition unit 21b is a point P _i2 and the line segments are line segments L _f2 and L _b2 . In this case, the end point P _eb2, P _EF2 of the line segment L _f2, L _b2 is, due to the presence on the road of the curve segment is not a line segment L _f2, L _b2 are crossing angle B 0 (or approximate value of 0) . As a result, in this example, the intersection angle B of the line segments L _f2 and L _b2 becomes larger than the criterion. Therefore, if only the determination based on the intersection angle B of the line segments L _f2 and L _b2 is determined, the shape point P _i2 is determined to be included in the curve section, and the curvature radius is large with the sections R ₂ and R ₄ having a small curvature radius. The section R ₃ is specified as one large curve section.

  Therefore, when the distance between the shape points is larger than the threshold value by the process of the curve section specifying unit 21c, the control unit 20 determines that the periphery of these shape points is a section having a large curvature radius. That is, since the density of shape points becomes coarse in the straight section as described above, in this embodiment, if the distance between the shape points is equal to or greater than the threshold value, the shape points are between the shape points in the straight road section. A threshold is set in advance so that it can be regarded as a distance (details will be described later). Therefore, the control unit 20 acquires the distance between the shape points of interest based on the map information 30a by the process of the curve section specifying unit 21c, and determines whether or not the distance is larger than the threshold value. And when the distance between shape points is larger than a threshold value, the control part 20 considers that the said shape points are not a curve area. Therefore, if one of the focused shape points is adjacent to the curve section, the shape point becomes the end point of the curve section.

  According to the present embodiment as described above, when a section with a small curvature radius of a road and a section with a large curvature radius (section that can be regarded as substantially not a curve) are continuous, the curve section is excluded by excluding the latter. Can be identified. Therefore, in this embodiment, it is possible to accurately distinguish the curve section and the straight section. As a result, it is possible to specify the presence of a straight road on a road or the like where a straight section continues immediately after the curve section, and further continues the curve section, and the accuracy of specifying the curve section can be improved.

  The line segment length adjustment unit 21d is a program module that causes the control unit 20 to realize a function of changing the length of a line segment based on the density of shape points on the road. That is, when the length of the line segment acquired by the control unit 20 by the process of the line segment acquisition unit 21b is limited to a specific length, the curve section can be accurately specified based on the intersection angle of the line segment. It becomes difficult.

Specifically, FIG. 4B schematically shows a road having a relatively small radius of curvature. Also in this example, the shape point is indicated by a black circle, and the shape point is arranged at the center of the road. In this example, the actual start point of the curve section (clothoid section) is the shape point P _i4 . Here, when the shape point P _i3 behind (behind the curve section) the shape point P _i4 is the target shape point, the line segment acquired by the control unit 20 through the processing of the line segment acquisition unit 21b is the line segment. Assume an example of L _f3 and L _b3 . In this example, since the radius of curvature of the curve section is small, the road shape changes early in front of the shape point P _i3 , and the line segment L _f3 is inclined with respect to the line segment L _b3 (0 ° or 0 °). Is not an approximation). As a result, the crossing angle C between the line segments L _f3 and L _b3 becomes larger than the criterion. Therefore, if the lengths of the line segments L _f3 and L _b3 are the values shown in FIG. 4B, it is erroneously determined that the shape point P _i3 is included in the curve section.

FIG. 4C schematically shows a road having a relatively large radius of curvature. Also in this example, the shape point is indicated by a black circle, and the shape point is arranged at the center of the road. In this example, the actual start point of the curve section (clothoid section) is the shape point P _i5 . Here, it is assumed that when the shape point P _i5 is the shape point of _interest , the line segments acquired by the control unit 20 through the processing of the line segment acquisition unit 21b are the line segments L _f5 and L _b5 . In this example, since the curvature radius of the curve section is large, the change in the road shape is small in front of the shape point P _i5 , and the line segment L _f5 is hardly inclined with respect to the line segment L _b5 . As a result, the crossing angle (180-D) between the line segments L _f5 and L _b5 becomes smaller than the criterion. Therefore, if the lengths of the line segments L _f5 and L _b5 are the values shown in FIG. 4C, it is erroneously determined that the shape point P _i5 is not included in the curve section.

  As described above, the length of the line segment acquired by the control unit 20 by the process of the line segment acquisition unit 21b is limited to a specific length (for example, the length of the line segment connecting adjacent shape points). Then, it becomes difficult to accurately specify the curve section based on the intersection angle of the line segment. Therefore, in the present embodiment, the control unit 20 acquires a line segment extending from the focused shape point to a point on a line connecting adjacent shape points by the processing of the line segment acquisition unit 21b. Such line segments include not only line segments extending from the target shape point to adjacent shape points, but also line segments extending from the target shape point to non-adjacent shape points, and lines connecting the target shape point to other shape points. An extending line segment is included. Therefore, the line segment for determining whether or not it is a curve section is not limited to a line segment connecting adjacent shape points.

  Further, the control unit 20 adjusts the length of the line segment according to the density of the shape points on the road by the process of the line segment length adjusting unit 21d. That is, the control unit 20 acquires the density of shape points existing within a predetermined range ahead of the vehicle with reference to the map information 30a by the process of the line segment acquisition unit 21b, and performs line processing according to the density. The length of the minute is determined and transferred to the process of the line segment acquisition unit 21b. As a result, when the control unit 20 acquires a line segment by the processing of the line segment acquisition unit 21b, the control unit 20 acquires a line segment having the length of the transferred line segment. The relationship between the density of shape points and the length of line segments can be specified by various rules, but in this embodiment, the configuration in which the length of line segments becomes longer as the density of shape points is coarser is adopted. (Details will be described later).

  In any case, by changing the length of the line segment according to the density of the shape points, it is possible to define a determination index (line segment) that changes according to the shape of the curve (curvature radius). Therefore, as shown in FIGS. 4B and 4C, even if an appropriate criterion (the length of a line segment) for determining a curve section changes due to a change in the radius of curvature, the length changes according to the change. It becomes possible to define a line segment as follows. For this reason, according to this embodiment, the specific precision of a curve area can be improved.

  Note that the threshold value for the distance between the shape points may be determined so that when the distance between the shape points is larger than the threshold value, the shape point can be regarded as not a curve section. It depends on the variable value. That is, when the radius of curvature is large, the value for determining that it is not a curve section may vary depending on the curvature radius of the curve section adjacent to the straight section. With this configuration, the control unit 20 compares the distance between the shape points with the threshold value even when the existence of the straight section existing between the curve sections cannot be accurately specified based on the intersection angle of the line segments. By doing so, it is possible to accurately specify the existence of the straight section. Therefore, it is possible to improve the accuracy of specifying the curve section.

(2) Curve section identification processing:
Next, the curve section specifying process will be described in detail. FIG. 2A is a flowchart showing the curve section specifying process. In this embodiment, the control unit 20 executes the curve section specifying process at a predetermined start timing (for example, every 100 ms). In the curve section specifying process, the control unit 20 executes a start / end candidate point acquisition process (step S100). The start / end candidate point acquisition process is a process of tentatively determining a curve section candidate based on the intersection angle of a line segment, and will be described in detail later. Here, the start point of the curve section candidate is referred to as a start candidate point, and the end point of the curve section candidate is referred to as an end candidate point.

  Next, the control part 20 performs a division | segmentation process (step S105). The division processing identifies a shape point having a distance between shape points that is greater than a threshold in the curve section candidate, and divides the curve section candidate by excluding at least one of the shape points from the curve section candidate. It is processing. If there is no shape point whose distance between the shape points is greater than the threshold, no division is performed. After the division process is executed, the end points of the section that is set as the curve section (a plurality of sections obtained by the division when divided) are the start point and the end point of the curve section.

  When the dividing process is performed, the control unit 20 executes a clothoid fitting process (step S110). The clothoid fitting process is a process of acquiring a clothoid curve and a line having a constant curvature that most closely matches the position of the shape point. The clothoid fitting process can be realized in various modes. For example, when the control unit 20 specifies a part with the minimum curvature from the shape points existing between the end points of the curve section (the part becomes a section with a constant curvature), and a part other than the part is a clothoid section It is possible to adopt a configuration in which clothoid fitting processing is performed by deriving clothoid curves from shape points at both ends of the section.

  In any case, when the clothoid fitting process is executed, information indicating the clothoid curve and information indicating the position and curvature of the section having a constant curvature are obtained in the curve section ahead of the vehicle. Therefore, the control unit 20 specifies the curve section indicated by these pieces of information (step S115). Although various methods can be adopted as a mode for specifying the curve section, in this embodiment, since it is used for vehicle deceleration control, the vehicle speed is set to be equal to or lower than the target speed before entering the curve section. It is possible to adopt a configuration in which information necessary for control, for example, information indicating the start point of the curve section, the start point of the constant curvature portion, the curvature, and the like is specified as information indicating the curve section. Of course, when the curve section is specified, the control unit 20 outputs a control signal to the transmission unit 44 and the braking unit 45 based on information indicating the curve section, and executes vehicle deceleration control.

(3) Start / end candidate point acquisition processing:
Next, the start / end candidate point acquisition process will be described in detail. FIG. 2B is a flowchart showing start / end candidate point acquisition processing. In the start / end candidate point acquisition process, the control unit 20 acquires a front shape point by the process of the shape point acquisition unit 21a (step S100). In the present embodiment, the range from which the shape points are acquired is determined in advance. For example, a configuration in which a predetermined distance (such as 2 km) from the current position of the vehicle is a range to be acquired can be employed. When there is a branch in the range, a configuration in which a range of a predetermined distance from the current position of the vehicle along the planned travel route of the vehicle or a range between the current position and the branch is an acquisition target may be employed. .

  In any case, the control unit 20 acquires the current position of the vehicle based on the output signals of the GPS reception unit 41, the vehicle speed sensor 42, and the gyro sensor 43, and refers to the map information 30a to obtain the range of the shape point acquisition target. Is identified. And the control part 20 acquires the position and number of the shape points which exist in the said range.

  Next, the control unit 20 acquires the density of shape points by the processing of the line segment length adjustment unit 21d (step S205). That is, the control unit 20 specifies the distance along the road in the range based on the shape point acquisition target range, and divides the number of shape points acquired in step S200 by the distance to determine the shape point. Get the density.

  Next, the control unit 20 acquires the length of the line segment based on the density of the shape points by the process of the line segment length adjustment unit 21d (step S210). In the present embodiment, a configuration is adopted in which the length of the line segment becomes longer as the density of the shape points is coarser, and the correspondence between the density of the shape points and the length of the line segment is preliminarily set (function, table, etc. Determined by). In this embodiment, when the shape of the road (curvature of the curve) changes, the determination accuracy of whether or not it is a curve section does not decrease, or the determination accuracy of whether or not it is a curve section decreases. The correspondence between the density of shape points and the length of the line segment is defined so that the degree becomes small. Therefore, the control unit 20 specifies the length of the line segment corresponding to the density acquired in step S205 based on the correspondence relationship, and acquires it as the length of the line segment.

  Specifically, in the correspondence relationship, the density and the length of the line segment are associated with each other so that the length of the line segment becomes longer as the density of the shape points is coarser. When the density of shape points is rough, if the section is a curve section, the section has a large radius of curvature. Therefore, if the length of the line segment is fixed to be short, it is difficult to determine that the line segment is a curve section based on the intersection angle of the line segment as shown in FIG. 4C. However, if the length of the line segment becomes longer as the density of the shape points is coarser, it is possible to specify a curve section having a large curvature radius with high accuracy.

  On the other hand, a section where the density of shape points is dense is a section having a small radius of curvature if the section is a curve section. Therefore, if the length of the line segment is fixed to a long state, as shown in FIG. 4B, a section that is not a curve section is a curve section because the crossing angle of the line segment is larger than the criterion. There is a case where it is erroneously determined. However, if the length of the line segment is shortened as the density of the shape points is denser, it is possible to specify a curve section having a small curvature radius with high accuracy.

  In the present embodiment, the length of the line segment acquired based on the correspondence relationship between the density and the length of the line segment is used to determine the intersection angle for all the shape points acquired in step S200. The That is, when the shape point acquisition target range is a curve section, it can be considered that the density of the shape points over the curve section represents the curvature of the entire curve section. Therefore, in the present embodiment, the control unit 20 uses the length of the line segment for determination on all the shape points acquired in step S200.

  In the above correspondence relationship, the minimum value of the length of the line segment changes for each shape point. That is, the distance from the target shape point (target shape point) from which the length of the line segment is acquired to the nearest shape point is the minimum value of the length of the line segment. Since the end points of line segments are shape points and points on the road that indicate the shape of the road (including lines between shape points and shape points themselves), define a line segment that is shorter than the length between adjacent shape points. Even so, the direction coincides with a line segment connecting adjacent shape points. Therefore, even if a line segment shorter than the line segment from the target shape point to the nearest shape point is defined, the determination result by the intersection angle of the line segment is not affected. Therefore, in this embodiment, the distance from the target shape point to the nearest shape point is the minimum value of the length of the line segment.

  Next, the control unit 20 sets a target shape point by the process of the line segment acquisition unit 21b (step S215). In the present embodiment, the target shape point is set so that the shape point is sequentially scanned forward from the current position of the vehicle. Accordingly, steps S215 to S255 are a loop process, and when step S215 is executed for the first time in the loop process, the control unit 20 determines the current position of the vehicle from the shape points acquired in step S200. The shape point closest to the front is set as the target shape point. Thereafter, when step S215 is executed for the Nth time (N is an integer equal to or greater than 2), the control unit 20 determines the shape closest to the current position of the vehicle from among the shape points acquired in step S200. Let the point be the shape point of interest.

Next, the control unit 20 acquires a line segment extending back and forth from the shape point of interest by the process of the line segment acquisition unit 21b (step S220). That is, the control unit 20 specifies a line connecting the shape points acquired in step S200 (a chain line shown in FIG. 4A). Further, the control unit 20 extends from the target shape point to each end point with the intersection of the circle having the radius of the length of the line segment as the center and the line connecting the shape points as the end point of the line segment. Get line segments before and after shape points. As a result, for example, if the _target shape point is P _i1 in FIG. 4A, line segments L _f1 and L _b1 are acquired.

  Next, the control part 20 acquires an intersection angle by the process of the curve area specific | specification part 21c (step S225). That is, the control unit 20 extends the rear line segment forward among the line segments acquired in step S220, and acquires the obtained angle (angle A in the example shown in FIG. 4A) as the intersection angle. .

  Next, the control unit 20 determines whether the intersection angle is larger than the determination criterion and the flag is turned off by the process of the curve section specifying unit 21c (step S230). That is, the control unit 20 compares the intersection angle with the determination criterion, and determines whether or not the intersection angle is larger than the determination criterion. In the present embodiment, a flag that is set to ON when the target shape point is included in the curve section candidate (initial value is OFF) is prepared in advance, and the control unit 20 sets the flag to OFF. It is determined whether or not.

  In step S230, when it is determined that the intersection angle is larger than the criterion and the flag is off, that is, when the target shape point is not included in the curve section candidates, the intersection angle is larger than the criterion. If it is determined, the control unit 20 acquires the target shape point as a start candidate point by the processing of the curve section specifying unit 21c, and turns on the flag (step S235). The start candidate point becomes an end point of the curve section through a division process described later.

  On the other hand, when the intersection angle is larger than the determination criterion and the flag is not determined to be off in step S230, the control unit 20 determines that the intersection angle is smaller than the determination criterion by the processing of the curve section specifying unit 21c, and It is determined whether or not the flag is on (step S240). That is, the control unit 20 compares the intersection angle with the determination criterion, and determines whether or not the intersection angle is smaller than the determination criterion. Further, the control unit 20 determines whether or not the flag is on.

  In step S240, when it is determined that the intersection angle is smaller than the determination criterion and the flag is turned on, that is, the shape point that is the target shape point in the previous loop processing is included in the curve section candidates. When it is determined that the intersection angle is smaller than the determination criterion in the state, the control unit 20 acquires the target shape point as an end candidate point by the processing of the curve section specifying unit 21c, and turns off the flag (step S250). The end candidate point becomes an end point of the curve section through a division process described later.

  On the other hand, if the intersection angle is smaller than the determination criterion and the flag is not determined to be ON in step S240, the target shape point is not included in the curve section or the target shape point is within the curve section (end point) Step S250 is skipped.

  When step S235 or step S250 is executed or step S250 is skipped, the control unit 20 determines whether or not the determination of the intersection angle has been completed for all the shape points by the processing of the curve section specifying unit 21c. (Step S255). That is, the control unit 20 determines that the determination of the intersection angle has been completed for all of the shape points when the processing from step S215 to S250 has been completed using all of the shape points acquired in step S200 as the target shape point. .

  In step S255, when it is not determined that the determination of the intersection angle has been completed for all of the shape points, the control unit 20 repeats the processes in and after step S215. On the other hand, when it is determined in step S255 that the determination of the intersection angle has been completed for all the shape points, the control unit 20 ends the start / end candidate point acquisition process. Through the above process, in the process of scanning the shape point forward, a section from the shape point whose intersection angle exceeds the determination criterion to the shape point whose intersection angle falls below the determination criterion is set as a candidate for the curve section.

(4) Division processing:
Next, the division process will be described in detail. FIG. 3A is a flowchart showing the division process. In the dividing process, the control unit 20 acquires a start candidate point and an end candidate point by the process of the curve section specifying unit 21c (step S300). That is, the control unit 20 acquires the positions of the start candidate point and the end candidate point acquired in steps S235 and S250.

Next, the control part 20 acquires the distance between shape points about each shape point of the area from a start candidate point to an end candidate point by the process of the curve area specific | specification part 21c (step S305). That is, the control unit 20 regards the section from the start candidate point to the end candidate point as a curve section candidate, and acquires the distance between the shape points as an index as to whether or not the candidate should be divided for each shape point. When this processing is performed, for example, in the example shown in FIG. 5, when the start candidate point is the shape point P _i6 and the end candidate point is the shape point P _i7 , the section between these points becomes the candidate of the curve section. The distance between the shape points in the candidate (from Ls to Le shown in FIG. 5) is acquired.

Next, the control unit 20 acquires a threshold value based on the standard deviation of the distance between the shape points by the processing of the curve section specifying unit 21c (step S310). Here, the threshold is set so that the shape point can be regarded as a distance between the shape points in the straight road section, and in the present embodiment, the threshold is configured to depend on the standard deviation of the distance between the shape points. Has been. That is, since the shape points are dense in the curve section and the shape points are coarse in the straight section, when the histogram distribution of the distance between the shape points is acquired in the section where the curve section and the straight section are adjacent, in the histogram distribution, The distribution of the distance between the shape points in the curve section is separated from the distribution of the distance between the shape points in the straight section. Figure 3B is a diagram showing an example of such a histogram, small distribution D ₁ of the inter-shape point distance corresponds to the distribution between the shape point distance in the curve section, a large distribution D ₂ between the shape point distance curve This corresponds to the distribution of the distance between the shape points in the section.

  And since the shape point to be processed is a candidate for the curve section, comparing the distribution of the distance between the shape points in the curve section and the distribution of the distance between the shape points in the straight section, the distribution of the distance between the shape points in the curve section is Relatively more. Therefore, if the standard deviation of the distribution of distance between the shape points in the entire distribution or the curve section is obtained, the distance between the shape points in the curve section and the distance between the shape points in the straight section are calculated by multiplying the standard deviation by a constant. It can be distinguished from the distribution of distances. Therefore, in the present embodiment, the control unit 20 acquires the standard deviation of the distribution of the distance between the shape points, and acquires the threshold value by multiplying the standard deviation by a constant (for example, 2).

  In addition, since the said threshold value is acquired based on the standard deviation of the distance between shape points, it depends on distribution of the distance between shape points. Since the distribution of the distance between the shape points depends on the density of the shape points in the curve section, the threshold value depends on the radius of curvature of the curve section. Therefore, the threshold value can be different for each curve section. Further, since the threshold is specified based on the standard deviation of the distribution of the distance between the shape points in each curve section candidate, it is suitable for each curve section candidate (that is, the curve section and the straight section in each curve section candidate). Can be determined).

  Next, the control unit 20 acquires the distance between the points of interest through the process of the curve section specifying unit 21c (step S315). Also here, the control unit 20 sequentially scans the shape points from the current position of the vehicle toward the front. In other words, the control unit 20 executes processing for acquiring the distance between the points of interest with reference to the map information 30a by using the two adjacent shape points as the points of interest while sequentially moving the points of interest forward. Steps S315 to S335 are a loop process, and when step S315 is executed for the first time in the loop process, the control unit 20 moves from the shape points acquired in step S200 in front of the current position of the vehicle. The closest shape point and the shape point adjacent to the front of the shape point are set as the points of interest. Thereafter, when step S215 is executed for the Nth time (N is an integer equal to or greater than 2), the control unit 20 determines the Nth and (N + 1) with respect to the current position of the vehicle from among the shape points acquired in step S200. ) The point closest to the shape is the point of interest.

  Next, the control unit 20 determines whether or not the distance between the points of interest is larger than the threshold value by the process of the curve section specifying unit 21c (step S320). In other words, the control unit 20 compares the distance between the points of interest acquired in step S315 and the threshold acquired in step S310. If it is not determined in step S320 that the distance between the points of interest is larger than the threshold value, the control unit 20 regards the distance between the points of interest as a curve section and skips steps S325 and S330.

On the other hand, when it is determined in step S320 that the distance between the points of interest is larger than the threshold value, the control unit 20 acquires the points of interest as a straight section (step S325). That is, when the distance between the points of interest is larger than the threshold, the control unit 20 regards the section indicated by the points of interest as a straight section, and sets a flag indicating that the section between these points of interest is a straight section. Associate. For example, in the example shown in FIG. 5, assuming that the point of _interest is the shape points P _i8 and P _i2 and the point of _interest is the shape points P _i2 and P _i9 , assume that the distance between the points of _interest is greater than the threshold. The control unit 20 regards the section between the shape points P _i8 and P _i2 and the section between the shape points P _i2 and P _i9 where the point of _interest is a straight section. As a result, the curve section candidates are divided into the curve sections R ₂ and R ₄ .

Next, the control part 20 specifies the end point of a curve area by the process of the curve area specific | specification part 21c (step S330). That is, the control unit 20 excludes a section regarded as a straight section from the curve section candidates, and specifies a shape point positioned at the end of the remaining shape points as an end point of the curve section. For example, in the example illustrated in FIG. 5, when the section between the shape points P _{i6 to} P _i7 is a candidate for the curve section and the area between the shape points P _{i8 to} P _i9 is regarded as a straight section, the control unit 20 The shape point P _i6 is specified as the start point of the curve section R ₂ , and the shape point P _i8 is specified as the end point of the curve section R ₂ . Further, when the area between the shape points P _{i2 to} P _i9 is regarded as a straight section and the area between the shape points P _{i9 to} P _i7 is not regarded as a straight section, the control unit 20 sets the shape point P _i9 as the curve section R ₄ . The start point and the shape point P _i7 are specified as the end point of the curve section R ₄ .

  When step S330 is performed or when it is not determined in step S320 that the distance between the points of interest is larger than the threshold value, the control unit 20 determines threshold values for all the shape points by the processing of the curve section specifying unit 21c. It is determined whether or not the process has ended (step S335). That is, the control unit 20 determines that the determination of the threshold has been completed for all of the shape points when the processing from step S315 to S3350 is completed with all the shape points acquired in step S200 as the point of interest.

  In step S335, when it is not determined that the determination of the threshold has been completed for all of the shape points, the control unit 20 repeats the processing after step S315. On the other hand, when it is determined in step S355 that the determination of the threshold has been completed for all of the shape points, the control unit 20 ends the division process. With the above processing, the end point of the curve section can be set by excluding the straight section from the curve section candidates.

(5) Other embodiments:
The above embodiment is an example for carrying out the present invention, and various other embodiments can be adopted as long as the length of the line segment is changed based on the density of the shape points. For example, the curve section specifying system 10 may be a terminal mounted on a vehicle or a terminal carried by a vehicle user. In addition, at least some of the functions of the shape point acquisition unit 21a, the line segment acquisition unit 21b, the curve segment specification unit 21c, and the line segment length adjustment unit 21d may be realized by a control entity different from that of the above-described embodiment.

  In addition, some functions, for example, a function using the distance between the shape points as a determination element may be omitted in the curve section specifying unit 21c. In this case, the curve section is specified based on the intersection angle of the line segment. Further, the control executed based on the curve section information is not limited to the deceleration control described above. For example, the curve section information may be used for acceleration control, suspension control, auto cruise control, headlight direction control, and the like.

  The shape point acquisition unit only needs to be able to acquire a shape point indicating the shape of the road, and various aspects can be adopted as the expression form of the shape of the road by the shape point. For example, an aspect (for example, an aspect in which a plurality of shape points indicate an arc or clothoid curve) indicating a road shape (corresponding to a center line or a boundary line) may be used. In addition, a plurality of positions on the road may be indicated by the positions of the shape points, and a straight line connecting the shape points may indicate the road direction indirectly or locally. The shape point may indicate the shape of the road and may have other meanings. For example, the shape point includes a node indicating the position of the intersection and a shape interpolation point indicating the road shape between the nodes. Also good.

  The line segment acquisition unit only needs to be able to acquire a line segment extending from the focused shape point to another shape point or a point on a line connecting adjacent shape points before and after the focused shape point. That is, since the shape points or the lines between the shape points indicate the shape of the road, whether the line segment acquisition unit acquires a line segment extending from the focused shape point to the relevant line or not is a curve section. It suffices if a line segment can be acquired as an index for determining.

  Since the end points of a line segment are a shape point and a point on the line indicating the shape on the road (including the line between the shape points and the shape point itself), the direction of the road in the direction of the line segment (approximate value) Is shown. For this reason, if the length of the line segment is changed, the range of the length of the line segment changes from the focused shape point, and the shape of the road is evaluated (evaluates whether it is a curve). The range can be changed.

  The curve section specifying unit 21c only needs to be able to specify the curve section based on the focused shape point when the intersection angle of the line segment is larger than the determination criterion. That is, since two line segments are defined so as to extend before and after the focused shape point, it can be considered that the intersection angle of the line segment indicates the degree of bending of the curve. It is possible to specify whether or not the road around the shape point of interest is a curve section.

  Various methods can be adopted as a method for specifying the curve section. When the intersection angle of the line segment is larger than the criterion, the curve section specifying unit 21c includes the focused shape point in the curve section. A configuration may be considered, or a configuration may be considered in which points around the focused shape point are included in the curve section. Note that the criterion for determining the crossing angle is that the road where at least one line segment exists is defined as a curve section when the crossing angle of the line segment is larger than the determination criterion, and is based on statistics and the like. It may be determined.

  The line segment length adjustment unit only needs to change the length of the line segment based on the density of shape points on the road. That is, it suffices if the index for determining whether or not it is a curve section is changed according to the density of shape points on the road, and the range to be determined can be changed. Here, the density only needs to indicate the number of shape points per unit distance on the road. The road section for which the density is to be calculated only needs to be defined so as to include a road to be specified as to whether or not it is a curve section, and can be defined by various methods. For example, measure the number of shape points in a section around the shape point of interest (for example, a section within a predetermined distance in the front or rear, front and rear, or a section to a branch), and divide by the distance of the section It is possible to adopt a configuration in which the density is acquired by the above.

  The correspondence between the density and the length of the line segment is such that when the road shape (curvature of the curve) changes, the accuracy of determining whether or not it is a curve section does not decrease, or whether or not it is a curve section It is only necessary to be defined so that the degree of decrease in the determination accuracy is small. As a configuration for this, for example, a configuration in which the length of the line segment becomes longer as the density of the shape points is coarser can be adopted. That is, the section where the density of the shape points is coarse is a section where the change in shape is relatively small. Therefore, if it is a curve section, it is a section having a large curvature radius. In such a section, the length between the shape points is long, and the degree of change in the road bending when changing from one shape point to another is small.

  Therefore, if the length of the line segment is fixed in a short state, the crossing angle of the line segment becomes excessively small, even if it is in a curve section (for example, even in a clothoid section), It becomes difficult to determine that it is a curve section based on the intersection angle. However, if the length of the line segment becomes longer as the density of the shape points is coarser, it is possible to specify a curve section having a large curvature radius with high accuracy.

  On the other hand, the section where the density of the shape points is dense is a section where the change in shape is relatively large, so if it is a curve section, it is a section having a small curvature radius. In such a section, the length between the shape points is short, and the degree of change in the road bending when changing from one shape point to another is large.

  Therefore, if the length of the line segment is fixed in a long state, the crossing angle of the line segment becomes excessively large, and it is not a curve section (for example, even if it is a position before reaching the clothoid section). In some cases, the intersection angle of the line segment is determined to be a curve section due to being larger than the determination criterion. However, if the density of the shape points is coarser, the length of the line segment is longer (that is, the denser the shape points are, the shorter the length of the line segment is). It is possible to specify a small curve section with high accuracy. Note that the change in the length of the line segment may be continuous or stepwise. Further, the relationship between the length of the line segment and the density may be linear or non-linear.

  Furthermore, the length of the line segment can be in various ranges. For example, the distance from the focused shape point to the nearest shape point may be the minimum value of the length of the line segment. good. That is, the end point of the line segment is a shape point and a point on the line indicating the shape on the road (including the line between the shape points and the shape point itself), so the line segment is shorter than the length between the adjacent shape points. Is defined, the direction coincides with a line segment connecting adjacent shape points. Therefore, even if a line segment shorter than the line segment from the focused shape point to the nearest shape point is defined, the determination result by the intersection angle of the line segment is not affected. Therefore, it is preferable that the distance from the focused shape point to the nearest shape point is the minimum value of the length of the line segment. Of course, a maximum value may be provided for the length of the line segment.

  Further, the method of changing the length of the line segment based on the density of the shape points can be applied as a method or program for performing this processing. Further, the above-described curve section identification system, method, and program may be realized as a single device or as a plurality of devices. Moreover, it may be realized using parts shared with each part provided in the vehicle, or may be realized in cooperation with each part not mounted on the vehicle, and includes various aspects. Further, some changes may be made as appropriate, such as a part of software and a part of hardware. Furthermore, the invention is also established as a recording medium for a program for controlling the curve section specifying system. Of course, the software recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium to be developed in the future.

  DESCRIPTION OF SYMBOLS 10 ... Curve area identification system, 20 ... Control part, 21 ... Curve area identification program, 21a ... Shape point acquisition part, 21b ... Line segment acquisition part, 21c ... Curve area identification part, 21d ... Line segment length adjustment part, 30 ... Recording medium, 30a ... map information, 41 ... GPS receiver, 42 ... vehicle speed sensor, 43 ... gyro sensor, 44 ... speed change part, 45 ... braking part

Claims (5)

A shape point acquisition unit for acquiring a shape point indicating the shape of the road;
A line segment acquisition unit for acquiring the line segment extending from the focused shape point to a point on the line connecting the other shaped points or adjacent shape points before and after the focused shape point;
A curve section specifying unit that specifies a curve section based on the shape point of interest when an intersection angle of the line segment is larger than a criterion;
A line segment length adjustment unit that changes the length of the line segment based on the density of the shape points on the road;
Curve section identification system with The length of the line segment is
The longer the density of the shape points, the longer.
The curve section specifying system according to claim 1. The minimum length of the line segment is
The distance from the focused shape point to the nearest shape point,
The curve section specifying system according to claim 1 or 2. A shape point acquisition step of acquiring a shape point indicating the shape of the road;
A line segment acquisition step of acquiring the line segment extending from the focused shape point to another point on the line connecting the other shape points or adjacent shape points before and after the focused shape point;
A curve section specifying step of specifying a curve section based on the shape point of interest when an intersection angle of the line segment is larger than a criterion;
A line segment length adjustment step of changing the length of the line segment based on the density of the shape points on the road;
Curve section identification method including. A shape point acquisition function for acquiring a shape point indicating the shape of the road;
A line segment acquisition function for acquiring the line segment extending from the focused shape point to another point on the line connecting the adjacent shape points or before and after the focused shape point;
A curve section specifying function for specifying a curve section based on the shape point of interest when an intersection angle of the line segment is larger than a criterion;
A line segment length adjustment function for changing the length of the line segment based on the density of the shape points on the road;
Curve section identification program that makes the computer realize.

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