Patent Publication Number: US-2022212673-A1

Title: Lane shape recognition system and lane shape recognition method

Description:
TECHNICAL FIELD 
     The present disclosure is related with a lane shape recognition system and a lane shape recognition method. 
     BACKGROUND ART 
     Recently, the apparatus which recognizes the lane shape where the own vehicle travels and utilizes the recognized shape is becoming popular. 
     The recognized lane shape is used for detecting a preceding vehicle or an object which exists in front of the driving lane of the own vehicle. For example, in the following distance controller which keeps following distance with the preceding vehicle appropriately, the recognized lane shape is used for selecting the preceding vehicle appropriately. In the collision damage reduction system which performs a warning or an automatic braking when an object which may cause collision exists in front of the own vehicle, the recognized lane shape is used for choosing an object which may cause collision (for example, PLT 1). 
     In the lane departure preventing system which prevents the own vehicle from deviating from the driving lane, the recognized lane shape is used for anticipation of lane deviation (for example, PLT 2), or is used for the determination of the automatic steering amount. 
     As the means to recognize the lane shape, the method to approximate the right and left white lines by a straight line or a polynomial using the image processing result of the lane image imaged by the camera is known (for example, PLT 3 and PLT 4). 
     CITATION LIST 
     Patent Literature 
     
         
         PLT 1: JP 2016-134093 A 
         PLT 2: JP 2015-189411 A 
         PLT 3: JP 2003-157499 A 
         PLT 4: JP 2012-22574 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional lane shape recognition device, it is not clear how far the lane shape approximated by the curve coincides with the actual lane shape with good accuracy (that is, the effective range of the approximated curve). 
     On the other hand, it is desired to use the curve which approximates the lane shape up to a distant place as much as possible. However, when the accuracy of the approximated curve with respect to the actual lane shape is low, if the approximated curve is used up to the distant place too much compared with the accuracy, the preceding vehicle or the object may be selected erroneously. 
     Thus, it is desired to provide a lane shape recognition system and a lane shape recognition method which can determine an effective range of the approximated curve corresponding to the lane shape. 
     Solution to Problem 
     A lane shape recognition system according to the present disclosure, including: 
     a mark object detection unit that detects relative positions of a series of marks or objects which are continuously arranged in front of an own vehicle, with respect to the own vehicle; 
     an approximated curve calculation unit that calculates a curve which approximates the relative positions of the series of marks or objects; and 
     a curve effective range determination unit that, when a plurality of the curves are calculated, mutually compares shapes of the plurality of curves, and determines the curves corresponding to lane shape and an effective range of the curves. 
     A lane shape recognition method according to the present disclosure, including: 
     a mark object detection step that detects relative positions of a series of marks or objects which are continuously arranged in front of an own vehicle, with respect to the own vehicle; 
     an approximated curve calculation step that calculates a curve which approximates the relative positions of the series of marks or objects; and 
     a curve effective range determination step that, when a plurality of the curves are calculated, mutually compares shapes of the plurality of curves, and determines the curves corresponding to lane shape and an effective range of the curves. 
     Advantage of Invention 
     According to the lane shape recognition system and the lane shape recognition method of the present disclosure, by mutually comparing the shapes of plurality of curves, it can be determined whether each curve corresponds to the lane shape. Even if two curves correspond to the lane shape in the range where the information on the relative positions used for approximation exists, if the curves deviates from the lane shape in the range where the information on the relative positions used for approximation does not exist, the shapes of two curves does not correspond mutually. According to the above configuration, by mutually comparing the shapes of plurality of curves, the effective range of each curve corresponding to the lane shape can be determined. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration diagram of the lane shape recognition system according to Embodiment 1; 
         FIG. 2  is a hardware configuration diagram of the information processing apparatus according to Embodiment 1; 
         FIG. 3  is a figure for explaining the own vehicle coordinate system according to Embodiment 1; 
         FIG. 4  is a figure for explaining the approximated curve calculation processing and the curve effective range determination processing according to Embodiment 1; 
         FIG. 5  is a figure for explaining the selection processing of two curves corresponding to the lane shape according to Embodiment 1; 
         FIG. 6  is a figure for explaining the determination processing of the effective range by curve width on the farther side according to Embodiment 1; 
         FIG. 7  is a figure for explaining the approximated curve calculation processing and the curve effective range determination processing according to Embodiment 1; 
         FIG. 8  is a figure for explaining the determination processing of the effective range by curve width on the closer side according to Embodiment 1; 
         FIG. 9  is a figure for explaining the determination processing of the effective range by curvature difference on the farther side according to Embodiment 1; 
         FIG. 10  is a figure for explaining the determination processing of the effective range by curvature difference on the closer side according to Embodiment 1; 
         FIG. 11  is a flowchart for explaining processing according to Embodiment 1; 
         FIG. 12  is a flowchart for explaining the selection processing of two curves corresponding to the lane shape according to Embodiment 2; 
         FIG. 13  is a figure for explaining the approximated curve calculation processing and the curve effective range determination processing according to Embodiment 2; and 
         FIG. 14  is a figure for explaining the selection processing of two curves corresponding to the lane shape according to Embodiment 2. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     1. Embodiment 1 
     A lane shape recognition system and a lane shape recognition method according to Embodiment 1 will be explained with reference to drawings.  FIG. 1  is a schematic configuration diagram of the lane shape recognition system. The lane shape recognition system is provided with processing units such as a mark object detection unit  1 , an approximated curve calculation unit  2 , a curve effective range determination unit  3 , and a vehicle control unit  4 . 
     1-1. Information Processing Apparatus 
     In the present embodiment, each processing unit  1  to  4  of the lane shape recognition system is provided in the information processing apparatus  30 , and is realized by processing circuits provided in the information processing apparatus  30 . Specifically, as shown in  FIG. 2 , the lane shape recognition system is provided, as processing circuits, with an arithmetic processor (computer)  90  such as a CPU (Central Processing Unit), storage apparatuses  91  which exchange data with the arithmetic processor  90 , an input and output circuit  92  which inputs and outputs signals between the arithmetic processor  90  and the external apparatus, and the like. 
     As the arithmetic processor  90 , DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), IC (Integrated Circuit), FPGA (Field Programmable Gate Array), various kinds of logical circuits, various kinds of signal processing circuits, and the like may be provided. As the arithmetic processor  90 , a plurality of the same type ones or the different type ones may be provided, and each processing may be shared and executed. As the storage apparatus  91 , RAM (Random Access Memory), ROM (Read Only Memory), flash memory, and the like are provided. The input and output circuit  92  is provided with a communication circuit, an A/D converter, a driving circuit, and the like. As the external apparatus, a front monitoring apparatus  9 , a vehicle control apparatus  10 , a guide apparatus  11 , and the like are provided. 
     Then, the arithmetic processor  90  runs software items (programs) stored in the storage apparatus  91  such as a ROM and collaborates with other hardware devices, such as the storage apparatuses  91 , the input and output circuit  92 , and the external apparatus, so that the respective functions of the processing units  1  to  4  provided in the information processing apparatus  30  are realized. Setting data items such as each threshold value and an allowable width range to be utilized in the processing units  1  to  4  are stored, as part of software items (programs), in the storage apparatus  91  such as a ROM. 
     1-2. Front Monitoring Apparatus  9   
     The front monitoring apparatus  9  is an apparatus which detects information on marks or objects which exist in front of the own vehicle. In the present embodiment, as the front monitoring apparatus  9 , one or more of a camera, a radar, and the like are used. As the camera, an optical camera, such as a monocular camera or a stereo camera, are used. As the radar, a millimeter wave radar, a laser radar (LiDAR (Light Detection and Ranging)), an ultrasonic radar, or the like are used. In the present embodiment, especially, it is configured to monitor the front of the own vehicle, a front camera which images the front of the own vehicle, and a front radar which irradiates radio wave to the front of the own vehicle are provided. The kind, the number, and the arrangement of camera and radar may be set arbitrarily. 
     1-3. Mark Object Detection Unit  1   
     The mark object detection unit  1  detects relative positions of a series of marks or objects which are continuously arranged in front of the own vehicle, with respect to the own vehicle. The mark object detection unit  1  detects the marks or the objects which exist in front of the own vehicle, and detects the relative positions of the marks or the objects with respect to the own vehicle, based on the signal transmitted from the front monitoring apparatus  9 . 
     For example, if the camera is provided as the front monitoring apparatus  9 , the mark object detection unit  1  performs an image recognition processing to the image data imaged by the camera, detects the marks or the objects which exist in front of the own vehicle, and detects the relative positions of the marks or the objects with respect to the own vehicle. Various kinds of well-known methods are used for the image recognition processing. 
     If the millimeter wave radar is provided as the front monitoring apparatus  9 , the mark object detection unit  1  detects the objects which exist in front of the own vehicle, and detects the relative positions of the objects with respect to the own vehicle, based on the detection information of the millimeter wave radar. 
     If the laser radar is provided as the front monitoring apparatus  9 , the mark object detection unit  1  detects the marks or the objects which exist in front of the own vehicle, and detects the relative positions of the marks or the objects with respect to the own vehicle, based on the detection information of the laser radar. 
     If a plurality of the front monitoring apparatuses  9  are provided, the mark object detection unit  1  may integrate the detection information on the marks or the objects by the plurality of front monitoring apparatuses  9  to detect the marks or the objects in front of the own vehicle, and detect the relative positions of the marks or the objects. 
     Then, the mark object detection unit  1  determines the marks or the objects which are continuously arranged in front of the own vehicle, as one group. For example, marks or objects continuously extended toward the front of the own vehicle, or a plurality of marks or objects arranged in a line with intervals toward the front of the own vehicle are determined as one group. Various kinds of well-known methods are used for this determination. 
     For example, if the optical camera is provided as the front monitoring apparatus  9 , the mark object detection unit  1  detects a series of road surface lane markings continuously arranged in front of the own vehicle by the image recognition processing, and detects the relative positions of each part of the series of road surface lane markings. In the road surface lane markings, a white line of a solid line or a dashed line is included. In the white line, colors other than white, for example, a yellow line and the like, are included. The mark object detection unit  1  may detect a series of roadside objects continuously arranged in front of the own vehicle by the image recognition processing. In the roadside objects, a guardrail, a center pole, a guide post, a curbstone, a wall, a roadside tree, and the like are included. 
     For example, if the millimeter wave radar is provided as the front monitoring apparatus  9 , the mark object detection unit  1  detects a series of roadside objects continuously arranged in front of the own vehicle, and detects the relative position of each part of the series of roadside objects, based on the detection result of the objects by the millimeter wave radar. 
     For example, if the laser radar is provided as the front monitoring apparatus  9 , the mark object detection unit  1  detects a series of roadside objects or road surface lane markings continuously arranged in front of the own vehicle, and detects the relative position of each part of the series of roadside objects or road surface lane markings, based on the detection result of the objects by the laser radar. In the detection information of the laser radar, the information on brightness of reflected light reflected from the object is also included, and the road surface lane markings are detected from the difference of brightness. 
     For example, as shown in  FIG. 3 , the relative position of the mark or the object with respect to the own vehicle is a position information in a coordinate system (hereinafter, referred to as an own vehicle coordinate system) in which the front and back direction of the own vehicle is set as the first axis X, and the right and left direction of the own vehicle is set as the second axis Y. The front side in the front and back direction X is positive, and the backside is negative. The right side in the right and left direction Y is positive, and the left side is negative. The origin of the own vehicle coordinate system is set to the right and left center point in the front end of the own vehicle. As shown in  FIG. 3 , the relative position (X, Y) of the mark or the object in the own vehicle coordinate system is detected. The mark object detection unit  1  detects the relative position of each part of the series of marks or objects. 
     The mark object detection unit  1  detects the relative position of the object in front of the own vehicle which is not determined as the series of marks or objects. In the front object, a preceding vehicle, an obstacle, and the like are included. 
     1-4. Approximated Curve Calculation Unit  2   
     The approximated curve calculation unit  2  calculates a curve which approximates the relative positions of the series of marks or objects. In the present embodiment, the approximated curve calculation unit  2  calculates, as the curve, a polynomial in which a position X in the front and back direction of the own vehicle is set as an independent variable, and a position Y in the right and left direction of the own vehicle is set as a dependent variable. In the present embodiment, the curve is a third-order polynomial as shown in the next equation. 
         Y=C 0+ C 1× X+C 2× X   2   +C 3× X   3   (1)
 
     Since the lane is configured by a straight line, a transition section, and a circular arc according to law and ordinance, such as Road Construction Ordinance, it can be approximated with good accuracy by the third-order polynomial. 
     The approximated curve calculation unit  2  calculates the curve for each the series of marks or objects. The approximated curve calculation unit  2  approximates the relative positions of respective parts of the one series of marks or objects, to the polynomial by the least square method and the like. Each order coefficients C0, C1, C2, C3 of the polynomial are calculated by the least square method and the like. 
     If the optical camera is used as the front monitoring apparatus  9 , the approximated curve calculation unit  2  calculates the curve for each the series of road surface lane markings. If the millimeter wave radar is used as the front monitoring apparatus  9 , the approximated curve calculation unit  2  calculates the curve for each the series of roadside objects. If the millimeter wave radar is used as the front monitoring apparatus  9 , the approximated curve calculation unit  2  calculates the curve for each the series of roadside objects or the series of road surface lane markings. 
       FIG. 4  shows an example if the optical camera is used as the front monitoring apparatus  9 . As the series of marks, a white line  20  of solid line extending toward the front on the left side of the own vehicle is detected, and a white line  21  of dashed line extending toward the front on the right side of the own vehicle is detected. About each part of the white line of solid line on the left side, the relative positions with respect to the own vehicle are detected. About each part of the white line of broken line on the right side, the relative positions with respect to the own vehicle are detected. 
     The approximated curve calculation unit  2  calculates a third-order polynomial  22  (each order coefficient C0L, C1L, C2L, C3L) which approximates the white line  20  of solid line on the left side, as shown in the equation (2), and calculates a third-order polynomial  23  (each order coefficient C0R, C1R, C2R, C3R) which approximates the white line  21  of broken line on the right side, as shown in the equation (3). 
         Y=C 0 L+C 1 L×X+C 2 L×X   2   +C 3 L×X   3   (2)
 
         Y=C 0 R+C 1 R×X+C 2 R×X   2   +C 3 R×X   3   (3)
 
     1-5. Curve Effective Range Determination Unit  3   
     &lt;Problem of Approximated Curve&gt; 
     In the detected series of marks or objects, one which does not correspond to the lane shape in front of the own vehicle may be included. If the detected series of marks or objects corresponds to the lane shape in front of the own vehicle, in a range (hereinafter, also referred to as a range of interpolation) where the information on the relative positions used for approximation exists, there is a high possibility that the relative positions calculated using the approximated curve corresponds to the lane shape. However, in a range (hereinafter, also referred to as a range of extrapolation) where the information on the relative positions used for approximation does not exist, there is a high possibility that the relative positions calculated using the approximated curve deviates from the lane shape. Accordingly, it is desired to determine whether the approximated curve corresponds to the lane shape, and to determine a range where the approximated curve corresponds the lane shape. 
     &lt;Mutual Comparison of Curves&gt; 
     Then, when a plurality of series of marks or objects are detected and a plurality of curves are calculated, the curve effective range determination unit  3  mutually compares shapes of the plurality of curves, and determines the curves corresponding to lane shape and an effective range of the curves. 
     For example, when two curves correspond to the lane shape, the shapes of two curves corresponds mutually. According to the above configuration, by mutually comparing the shapes of plurality of curves, it can be determined whether each curve corresponds to the lane shape. Even if two curves correspond to the lane shape in the range of interpolation, if the curve deviates from the lane shape in the range of extrapolation, the shapes of two curves does not correspond mutually. According to the above configuration, by mutually comparing the shapes of plurality of curves, the effective range of each curve corresponding to the lane shape can be determined. 
     In the present embodiment, as explained in the following, the curve effective range determination unit  3  mutually compares the shapes of plurality of curves in the range of interpolation, and determines the curves corresponding to the lane shape; and also including the range of extrapolation, determines the effective range of the curves corresponding to the lane shape. 
     1-5-1. Determination of Two Curves corresponding to Lane Width 
     The curve effective range determination unit  3  sets a combination of the two curves from the plurality of curves. And, in an overlapping range RXO in the front and back direction of the own vehicle where a range in the front and back direction where the series of marks or object used for each approximation of the two curves are disposed overlaps between the two curves, the curve effective range determination unit  3  calculates a width W between the two curves in the right and left direction. 
     When the width W in the right and left direction deviates from a preliminarily set allowable width range RWP corresponding to the lane width, the curve effective range determination unit  3  determines that the two curves are not a combination corresponding to the lane shape. And, when the width W in the right and left direction falls within the allowable width range RWP, the curve effective range determination unit  3  determines that the two curves correspond to the lane shape. 
     When two curves correspond to the left edge and the right edge of the lane, at least in the range of interpolation, the width W in the right and left direction of two curves corresponds to the lane width. According to the above configuration, in the range (the range of interpolation) where the information on the relative positions used for approximation exists, when the width W in the right and left direction of two curves falls within the allowable width range RWP corresponding to the lane width, it can be determined that the two curves correspond to the lane shape; and when the width Win the right and left direction deviates from the allowable width range RWP, it can be determined that the two curves are not the combination corresponding to the lane shape. 
     For example, in the example shown in  FIG. 4 , since two curves of a left side curve  22  and a right side curve  23  are calculated, these two curves are set as the combination for determination. When three or more curves are calculated, a plurality of combinations of two curves are set (for example, settable number), and it is determined for each combination of two curves whether it corresponds to the lane shape. One curve is selected one by one from the left side curves of the own vehicle, and one curve is selected one by one from the right side curves; and the combinations of two curves may be set. 
     Then, in the example of  FIG. 4 , the range in the front and back direction X of the relative positions of the left side white line  20  of solid line used for approximation of the left side curve  22  becomes a range from the closest position XminL closest to the own vehicle to the farthest position XmaxL farthest from the own vehicle. The range in the front and back direction X of the relative positions of the right side white line  21  of broken line used for approximation of the right side curve  23  becomes a range from the closest position XminR closest to the own vehicle to the farthest position XmaxR farthest from the own vehicle. The overlapping range RXO overlapping between the left side range from the closest position XminL to the farthest position XmaxL and the right side range from the closest position XminR to the farthest position XmaxR becomes a range from the closest position XminR of right side to the farthest position XmaxR of right side. 
     Then, as shown in  FIG. 5 , the curve effective range determination unit  3  increases the position X in the front and back direction by a step interval ΔX from the closest position XminR of right side to the farthest position XmaxR of right side; and at each position X in the front and back direction, calculates the width W in the right and left direction between the left side curve  22  and the right side curve  23  using the next equation, and determines whether the width W in the right and left direction falls within the allowable width range RWP. 
         W =( C 0 R−C 0 L )+( C 1 R−C 1 L )× X +( C 2 R−C 2 L )× X   2 +( C 3 R−C 3 L )× X   3   (4)
 
     The allowable width range RWP is set to a range from the lower limit allowable width Wmin to the upper limit allowable width Wmax. The lower limit allowable width Wmin and the upper limit allowable width Wmax are set corresponding to the variation range of general lane width or the specification of lane width, for example. 
     In the example of  FIG. 4  and  FIG. 5 , the width W in the right and left direction falls within the allowable width range RWP over the whole overlapping range RXO. Accordingly, the curve effective range determination unit  3  determines that the left side curve  22  and the right side curve  23  correspond to the lane shape. On the other hand, when the width W in the right and left direction does not fall within the allowable width range RWP even at a part of the overlapping range RXO, the curve effective range determination unit  3  determines that the two curves are not the combination corresponding to the lane shape. Alternatively, when the width W in the right and left direction does not falls within the allowable width range RWP in part more than the predetermined ratio (for example, 20%) of the overlapping range RXO, the curve effective range determination unit  3  may determine that the two curves are not the combination corresponding to the lane shape. 
     When determining that there is two or more of the combinations of two curves corresponding to the lane shape, the curve effective range determination unit  3  may determine the combination of two curves whose width W in the right and left direction is the closest to the center value of the allowable width range RWP in the overlapping range RXO, as the final two curves, and may exclude other combinations of two curves. 
     1-5-2. Determination of Effective Range of Curves 
     As determination of effective range of the curves, there are following “determination of effective range by curve width” and “determination of effective range by curvature difference.” 
     1-5-2-1. Determination of Effective Range by Curve Width 
     In the range (the range of interpolation) where the information on the relative positions used for approximation exists, the correspondence degree of the curve to the lane shape is high. But, in the range (the range of extrapolation) where the information on the relative positions used for approximation does not exist, a possibility that the correspondence degree of the curve to the lane shape is deteriorated becomes high. 
     Accordingly, in the range of interpolation, it is highly possible that the width W in the right and left direction between two curves corresponds to the lane shape. But, as it is separated from the range of interpolation, there is a possibility that the width W in the right and left direction does not correspond to the lane shape. Then, in the determination of the effective range by curve width explained in the following, the effective range of two curves is determined by change of the width Win the right and left direction between two curves. 
     The curve effective range determination unit  3  sets a front and back reference position X 0  within the overlapping range RXO in the front and back direction of the own vehicle where a range in the front and back direction where the series of marks or object used for each approximation of the two curves are disposed overlaps between the two curves. Then, the curve effective range determination unit  3  calculates a width in the right and left direction Y of the own vehicle between the two curves at the front and back reference position, as a reference width W 0 . In the present embodiment, as the two curves used for determination of the effective range, the two curves determined corresponding to the lane shape in the determination of two curves corresponding to the lane width are used. 
     The curve effective range determination unit  3  determines a range in the front and back direction X where an absolute value of deviation ΔW between a width W in the right and left direction Y between two curves at the position of the front and back direction X, and the reference width W 0  becomes smaller than a width deviation threshold value JDW, as an effective range by width determination RXEW. 
     According to this configuration, on the basis of the reference width W 0  within the overlapping range RXO in the front and back direction, the range in the front and back direction X where the accuracy of the width W in the right and left direction is maintained is determined as the effective range. Therefore, the effective range of the curves corresponding to the lane shape can be determined with good accuracy. 
     In the present embodiment, as explained in the following, the determination of the effective range by width determination RXEW is divided into a determination on the farther side than the front and back reference position X 0 , and a determination on the closer side than the front and back reference position X 0 . 
     &lt;Determination on Farther Side&gt; 
     In the position close to the own vehicle, the detection accuracy of the relative positions of marks or objects is high, and the correspondence degree of the curve to the lane shape is high. However, as it is separated from the own vehicle to the front, the detection accuracy of the relative positions of marks or objects is deteriorated, and when it enters within the range of extrapolation, there is a possibility that the correspondence degree of the curve to the lane shape is deteriorated. Accordingly, the width Win the right and left direction between two curves in the position close to the own vehicle corresponds to the lane shape. But, as it is separated from the own vehicle to the front, there is a possibility that the width W in the right and left direction does not correspond to the lane shape. 
     In the present embodiment, the curve effective range determination unit  3  sets a position in the front and back direction X closest to the own vehicle within the overlapping ranges RXO, as the front and back reference position X 0 ; and calculates a width in the right and left direction of the own vehicle between two curves at the front and back reference position X 0 , as the reference width W 0 . 
     The curve effective range determination unit  3  determines, as a width determination upper limit position XWmax, a position in the front and back direction where the absolute value of width deviation ΔW between the width W in the right and left direction between two curves at the position X in the front and back direction, and the reference width W 0  becomes larger than the width deviation threshold value JDW, when the position X in the front and back direction is gradually separated from the front and back reference position X 0  (in this example, gradually increased). Then, the curve effective range determination unit  3  determines a range from the front and back reference position X 0  to the width determination upper limit position XWmax, as the effective range by width determination RXEW. 
     According to this configuration, on the basis of the reference width W 0  which is close to the own vehicle and has high accuracy, a farther side range where the accuracy of the width W in the right and left direction is maintained is determined. Accordingly, the effective range of the curves corresponding to the lane shape can be determined with good accuracy. 
     For example, in the example in  FIG. 4 , as mentioned above, the overlapping range RXO becomes the range from the closest position XminR of right side to the farthest position XmaxR of right side, and the front and back reference position X 0  is set to the closest position XminR of right side. Then, using the equation (4), at the front and back reference position X 0  (the closest position XminR of right side), the width W in the right and left direction is calculated, and it is set as the reference width W 0 . 
     Then, as shown in  FIG. 6 , the curve effective range determination unit  3  increases the position X in the front and back direction by the step interval ΔX from the front and back reference position X 0  to the front upper limit position XFmax; and calculates the width W in the right and left direction between the left side curve  22  and the right side curve  23  at each position X in the front and back direction using the equation (4), and calculates the absolute value of width deviation ΔW between the calculated width W in the right and left direction and the reference width W 0  using the next equation. The front upper limit position XFmax is an upper limitation value that prevents the effective range from becoming too long. 
       Δ W=|W−W 0|  (5)
 
     Then, the curve effective range determination unit  3  determines a position X in the front and back direction (in this example, just before position) where the absolute value of width deviation ΔW exceeded the width deviation threshold value JDW, as the width determination upper limit position XWmax; and determines a range from the front and back reference position X 0  to the width determination upper limit position XWmax, as the effective range by width determination RXEW. Even when the position X in the front and back direction is increased to the front upper limit position XFmax, and when the absolute value of width deviation ΔW does not exceed the width deviation threshold value JDW, the curve effective range determination unit  3  sets the front upper limit position XFmax as the width determination upper limit position XWmax (XWmax=XFmax). 
     &lt;Determination on Closer Side&gt; 
     In the example shown in  FIG. 4  and  FIG. 6 , the white line is detected close to the own vehicle, and the closest position (the front and back reference position X 0 ) of the overlapping range RXO becomes close to the own vehicle. Accordingly, the range of extrapolation close to the own vehicle is short, and there is no problem even if this range of extrapolation is not used. However, as shown in the example of  FIG. 7 , when the closest position of the detected white line is far from the own vehicle, the closest position (the front and back reference position X 0 ) of the overlapping range RXO becomes far from the own vehicle, and the range of extrapolation close to the own vehicle becomes long. In this case, it is conceivable to determine the curve effective range also on the closer side, and utilize the curve. 
     Then, the curve effective range determination unit  3  determines, as the width determination lower limit position XWmin, a position X in the front and back direction where the absolute value of width deviation ΔW between a width W in the right and left direction between two curves at the position X in the front and back direction, and the reference width W 0  becomes larger than the width deviation threshold value JDW, when a position X in the front and back direction is gradually brought close from the front and back reference position X 0 ; and adds a range from the width determination lower limit position XWmin to the front and back reference position X 0 , to the effective range by width determination RXEW. 
     For example, in the example of  FIG. 7 , as shown in  FIG. 8 , the curve effective range determination unit  3  decreases the position X in the front and back direction by the step interval ΔX from the front and back reference position X 0  to the front lower limit position XFmin (for example, 0); calculates the width W in the right and left direction between the left side curve  22  and the right side curve  23  at each position X in the front and back direction using the equation (4); and calculates the absolute value of width deviation ΔW between the calculated width W in the right and left direction and the reference width W 0  using the equation (5). 
     Then, the curve effective range determination unit  3  determines a position X in the front and back direction (in this example, just before position) where the absolute value of width deviation ΔW exceeded the width deviation threshold value JDW, as the width determination lower limit position XWmin; and adds a range from the width determination lower limit position XWmin to the front and back reference position X 0 , to the effective range by width determination RXEW. Accordingly, the final effective range by width determination RXEW becomes a range from the width determination lower limit position XWmin to the width determination upper limit position XWmax. Even when the position X in the front and back direction is decreased to the front lower limit position XFmin, and when the absolute value of width deviation ΔW does not exceed the width deviation threshold value JDW, the curve effective range determination unit  3  sets the front lower limit position XFmin as the width determination lower limit position XWmin (XWmin=XFmin). 
     1-5-2-2. Determination of Effective Range by Curvature Difference 
     In the range (the range of interpolation) where the information on the relative positions used for approximation exists, the correspondence degree of the curve to the lane shape is high. But, in the range (the range of extrapolation) where the information on the relative positions used for approximation does not exist, there is a possibility that the correspondence degree of the curve to the lane shape is deteriorated. 
     Accordingly, in the range of interpolation, it is highly possible that the curvatures of two curves correspond to the lane shape, and correspond mutually. But, as it is separated from the range of interpolation, it is highly possible that curvatures of two curves does not correspond mutually. Then, in the determination of the effective range by curvature difference explained in the following, the effective range of two curves is determined by a deviation between the curvatures of two curves. 
     The curve effective range determination unit  3  determines a range in the front and back direction X where an absolute value of deviation Δρ between the curvatures of two curves becomes smaller than a curvature deviation threshold value JDP, as an effective range by curvature determination RXEP. 
     According to this configuration, the range in the front and back direction X where the curvatures of two curves correspond mutually is determined. Accordingly, the effective range of the curves corresponding to the lane shape can be determined with good accuracy. 
     In the present embodiment, as explained in the following, the determination of the effective range by curvature determination RXEP is divided into a determination on the farther side than the front and back reference position X 0 , and a determination on the closer side than the front and back reference position X 0 . 
     &lt;Determination on Farther Side&gt; 
     In the position close to the own vehicle, the detection accuracy of the relative positions of marks or objects is high, and the correspondence degree of the curve to the lane shape is high. However, as it is separated from the own vehicle to the front, the detection accuracy of the relative positions of marks or objects is deteriorated, and when it enters within the range of extrapolation, there is a possibility that the correspondence degree of the curve to the lane shape is deteriorated. Accordingly, the curvatures of two curves in the position close to the own vehicle correspond to the lane shape and correspond mutually. But, as it is separated from the own vehicle to the front, there is a possibility that the curvatures of two curves do not correspond mutually. 
     Similar to the determination of the effective range by curve width, the curve effective range determination unit  3  sets a position in the front and back direction X closest to the own vehicle within the overlapping ranges RXO, as the front and back reference position X 0 . In the present embodiment, as the two curves used for determination of the effective range by curvature difference, the two curves determined corresponding to the lane shape in the determination of two curves corresponding to the lane width are used. 
     The curve effective range determination unit  3  determines, as a curvature determination upper limit position XPmax, a position in the front and back direction where the absolute value of curvature deviation Δρ between the curvatures of two curves at the position X in the front and back direction becomes larger than a curvature deviation threshold value JDP, when the position X in the front and back direction is gradually separated from the front and back reference position X 0  (in this example, gradually increased). Then, the curve effective range determination unit  3  determines a range from the front and back reference position X 0  to the curvature determination upper limit position XPmax, as the effective range by curvature determination RXEP. 
     According to this configuration, on the basis of the front and back reference position X 0  close to the own vehicle, the range on the farther side where the curvatures of two curves correspond mutually is determined. Accordingly, the effective range of the curves corresponding to the lane shape can be determined with good accuracy. 
     For example, in the example in  FIG. 4 , as shown in  FIG. 9 , the curve effective range determination unit  3  increases the position X in the front and back direction by the step interval ΔX from the front and back reference position X 0  to the front upper limit position XFmax; and at each position X in the front and back direction, calculates the curvature ρL of the left side curve  22  using the equation (6), calculates the curvature ρR of the right side curve  23  using the equation (7), and calculates the absolute value of curvature deviation Δρ between two curvatures ρL, ρR using the equation (8). 
       ρ L= 2× C 2 L+ 6× C 3 L×X   (6)
 
       ρ R= 2× C 2 R+ 6× C 3 R×X   (7)
 
       Δρ=|ρ L−ρR|   (8)
 
     Then, the curve effective range determination unit  3  determines a position X in the front and back direction (in this example, just before position) where the absolute value of curvature deviation Δρ exceeded the curvature deviation threshold value JDP, as the curvature determination upper limit position XPmax; and determines a range from the front and back reference position X 0  to the curvature determination upper limit position XPmax, as the effective range by curvature determination RXEP. Even when the position X in the front and back direction is increased to the front upper limit position XFmax, and when the absolute value of curvature deviation Δρ does not exceed the curvature deviation threshold value JDP, the curve effective range determination unit  3  sets the front upper limit position XFmax as the curvature determination upper limit position XPmax (XPmax=XFmax). 
     &lt;Determination on Closer Side&gt; 
     Similar to the determination of the effective range by curve width mentioned above using the example of  FIG. 7 , a determination on the closer side in the determination of the effective range by curvature difference is explained. 
     The curve effective range determination unit  3  determines, as a curvature determination lower limit position XPmin, a position X in the front and back direction where the absolute value of the deviation Δρ between the curvatures of two curves at the position X in the front and back direction becomes larger than the curvature deviation threshold value JDP, when a position X in the front and back direction is gradually brought close from the front and back reference position X 0 ; and adds a range from the curvature determination lower limit position XPmin to the front and back reference position X 0 , as the effective range by curvature determination RXEP. 
     For example, in the example of  FIG. 7 , as shown in  FIG. 10 , the curve effective range determination unit  3  decreases the position X in the front and back direction by the step interval ΔX from the front and back reference position X 0  to the front lower limit position XFmin (for example, 0); and at each position X in the front and back direction, calculates the curvature ρL of the left side curve  22  using the equation (6), calculates the curvature ρR of the right side curve  23  using the equation (7), and calculates the absolute value of curvature deviation Δρ between two curvatures ρL, ρR using the equation (8). 
     Then, the curve effective range determination unit  3  determines a position X in the front and back direction (in this example, just before position) where the absolute value of curvature deviation Δρ exceeded the curvature deviation threshold value JDP, as the curvature determination lower limit position XPmin; and adds a range from the curvature determination lower limit position XPmin to the front and back reference position X 0 , as the effective range by curvature determination RXEP. Accordingly, the final effective range by curvature determination RXEP becomes a range from the curvature determination lower limit position XPmin to the curvature determination upper limit position XPmax. Even when the position X in the front and back direction is decreased to the front lower limit position XFmin, and when the absolute value of curvature deviation Δρ does not exceed the curvature deviation threshold value JDP, the curve effective range determination unit  3  sets the front lower limit position XFmin as the curvature determination lower limit position XPmin (XPmin=XFmin). 
     1-5-2-3. Integration of Two Determination Results of Effective Ranges 
     The curve effective range determination unit  3  sets an overlapping range between the effective range by width determination RXEW and the effective range by curvature determination RXEP, as the final effective range. That is to say, the curve effective range determination unit  3  sets a range between any larger (farther) one of the width determination lower limit position XWmin and the curvature determination lower limit position XPmin, and any smaller (closer) one of the width determination upper limit position XWmax and the curvature determination upper limit position XPmax, as the final effective range. Accordingly, since the curve effective range is determined from two viewpoints of the width of two curves and the deviation between the curvatures of two curves, the determination accuracy can be improved. 
     1-6. Vehicle Control Unit  4   
     The vehicle control unit  4  performs one or both of a traveling control of vehicle and a guidance of traveling information of vehicle to the driver, based on information on the curve within the effective range. For example, as the traveling control of vehicle, the vehicle control unit  4  sets an area between two curves within the effective range as the driving lane of the own vehicle, and performs a collision prevention traveling control with a preceding vehicle or an obstacle which exists in the driving lane, a tracking travel control to a preceding vehicle, a lane keeping traveling control to the driving lane, or the like. The vehicle control unit  4  calculates commands related to the traveling control, such as an acceleration and deceleration command, a brake command, and a steering angle command, and transmits to the vehicle control apparatus  10 . For example, the vehicle control apparatus  10  is a controller which integrates each controller, transmits a command for changing driving force to a controller of driving force source such as an engine and a motor, transmits an operating command of brake to a controller of brake, and transmits a command of steering angle to a controller of electric power steering. 
     For example, as the guidance of traveling information of vehicle, the vehicle control unit  4  sets an area between two curves within the effective range as the driving lane of the own vehicle, and performs a guidance of collision warning with a preceding vehicle or an obstacle which exists in the driving lane, a guidance of deviation warning from the driving lane, a guidance of the driving lane, or the like. The vehicle control unit  4  transmits information related to these guidance to the guide apparatus  11 . The guide apparatus  11  controls a loudspeaker, a display, a lamp, a vibration device, or the like, and informs each guidance to the driver. 
     1-7. Flowchart 
     Next, processing of the lane shape recognition system and the lane shape recognition method according to the present embodiment is explained with reference to the flowchart of  FIG. 11 . The processing represented in the flowchart in  FIG. 11  is recurrently implemented, for example, every predetermined operation cycle while the arithmetic processor  90  implements software (a program) stored in the storage apparatus  91 . 
     In the step S 1 , as mentioned above, the mark object detection unit  1  detects relative positions of a series of marks or objects which are continuously arranged in front of the own vehicle, with respect to the own vehicle. In the present embodiment, the mark object detection unit  1  detects the marks or the objects which exist in front of the own vehicle, and detects the relative positions of the marks or the objects with respect to the own vehicle, based on the signal transmitted from the front monitoring apparatus  9 . Then, the mark object detection unit  1  determines the marks or the objects continuously arranged in front of the own vehicle, as one group. 
     Next, in the step S 2 , as mentioned above, the approximated curve calculation unit  2  calculates a curve which approximates the relative positions of the series of marks or objects. In the present embodiment, the approximated curve calculation unit  2  calculates, as the curve, a polynomial in which a position X in the front and back direction of the own vehicle is set as an independent variable, and a position Y in the right and left direction of the own vehicle is set as a dependent variable. In the present embodiment, the curve is a third-order polynomial. 
     Next, in the step S 3 , the curve effective range determination unit  3  determines whether a plurality of curves are calculated, advances to the step S 4  when the plurality of curves are calculated, and ends a series of processing when a plurality of curves are not calculated. In the step S 4  to the step S 8 , as mentioned above, the curve effective range determination unit  3  mutually compares shapes of the plurality of curves, and determines the curves corresponding to the lane shape and the effective range of the curves. 
     In the present embodiment, in the step S 4 , as mentioned above, as the determination of two curves corresponding to the lane width, the curve effective range determination unit  3  sets a combination of the two curves from the plurality of curves; and, in an overlapping range RXO in the front and back direction of the own vehicle where a range in the front and back direction where the series of marks or object used for each approximation of the two curves are disposed overlaps between the two curves, calculates a width W between the two curves in the right and left direction. When the width W in the right and left direction deviates from a preliminarily set allowable width range RWP corresponding to the lane width, the curve effective range determination unit  3  determines that the two curves are not a combination corresponding to the lane shape. And, when the width W in the right and left direction falls within the allowable width range RWP, the curve effective range determination unit  3  determines that the two curves correspond to the lane shape. When three or more curves are calculated, a plurality of combinations of two curves are set, and it is determined for each combination of two curves whether it corresponds to the lane shape. 
     Next, in the step S 5 , the curve effective range determination unit  3  advances to the step S 6  when determining that there is a combination of two curves corresponding to the lane shape, and ends a series of processing when determining that there is no combination. 
     In the step S 6 , as mentioned above, as the determination of the effective range by curve width, the curve effective range determination unit  3  sets a front and back reference position X 0  within the overlapping range RXO in the front and back direction of the own vehicle where a range in the front and back direction where the series of marks or object used for each approximation of the two curves are disposed overlaps between the two curves. Then, the curve effective range determination unit  3  calculates a width in the right and left direction Y of the own vehicle between the two curves at the front and back reference position, as a reference width W 0 . The curve effective range determination unit  3  determines a range in the front and back direction X where an absolute value of deviation ΔW between a width W in the right and left direction Y between two curves at the position of the front and back direction X, and the reference width W 0  becomes smaller than a width deviation threshold value JDW, as an effective range by width determination RXEW. In the present embodiment, as mentioned above, the determination on farther side and the determination on closer side are performed. 
     In the step S 7 , as mentioned above, as the determination of the effective range by curvature difference, the curve effective range determination unit  3  determines a range in the front and back direction X where an absolute value of deviation Δρ between the curvatures of two curves becomes smaller than a curvature deviation threshold value JDP, as an effective range by curvature determination RXEP. In the present embodiment, as mentioned above, the determination on farther side and the determination on closer side are performed. 
     In the step S 8 , as mentioned above, the curve effective range determination unit  3  sets an overlapping range between the effective range by width determination RXEW and the effective range by curvature determination RXEP, as the final effective range. 
     Then, in the step S 09 , as mentioned above, the vehicle control unit  4  performs one or both of a traveling control of vehicle and a guidance of traveling information of vehicle to the driver, based on information on the curve within the effective range. 
     2. Embodiment 2 
     Next, the lane shape recognition system and the lane shape recognition method according to Embodiment 2 will be explained. The explanation for constituent parts the same as those in Embodiment 1 will be omitted. The basic configuration and processing of the lane shape recognition system according to the present embodiment are the same as those of Embodiment 1. Embodiment 2 is different from Embodiment 1 in processing which determines two curves corresponding to the lane shape from a plurality of curves in the curve effective range determination unit  3 . 
     In the curves corresponding to the lane shape, change tendencies of the position Y in the right and left direction with respect to the change of the position X in the front and back direction correspond with each other. Accordingly, when a plurality of the series of marks or objects are detected and a plurality of curves are calculated, by excluding a curve whose change tendency of the right and left direction with respect to the change of the front and back direction is different from others, two curves corresponding to the lane shape can be selected from the plurality of curves. 
     Then, in the present embodiment, the curve effective range determination unit  3  sets a front and back reference position for right and left deviation X 0 RL in the front and back direction of the own vehicle. About each of the plurality of curves, the curve effective range determination unit  3  calculates a position Y in the right and left direction of the own vehicle at the front and back reference position for right and left deviation X 0 RL, as a right and left reference position Y 0 RL. About each of the plurality of curves, the curve effective range determination unit  3  calculates a right and left deviation ΔY 0 RL which is a deviation between a position Y of the curve in the right and left direction, and the right and left reference position Y 0 RL, at each position X in the front and back direction. Then, when changing a position X in the front and back direction from the front and back reference position for right and left deviation X 0 RL, the curve effective range determination unit  3  excludes the curve whose the right and left deviation ΔY 0 RL deviates from a median ΔY 0 RL_M of the right and left deviations ΔY 0 RL of the plurality of curves by a right and left deviation threshold value JDRL or more, from the plurality of curves, until becoming two curves; and determines that the remaining two curves correspond to the lane shape. 
     According to this configuration, by calculating the right and left deviation ΔY 0 RL between the right and left reference position Y 0 RL and the position Y of the curve in the right and left direction at each position X in the front and back direction. The change tendency of the right and left direction with respect to the change of the front and back direction can be calculated. Then, by excluding the curve whose right and left deviation ΔY 0 RL deviates from the median ΔY 0 RL_M of the right and left deviations ΔY 0 RL of the plurality of curves by the right and left deviation threshold value JDRL or more, from the plurality of curves, the curve whose change tendency of the right and left direction with respect to the change of the front and back direction is different from others can be excluded. Then, the two curves corresponding to the lane shape can be selected. 
     Using the flowchart of  FIG. 12  and the examples of  FIG. 13  and  FIG. 14 , the selection process of the curve corresponding to the lane shape by the right and left deviation is explained.  FIG. 13  and  FIG. 14  are the examples in which the millimeter wave radar is used as the front monitoring apparatus  9 . 
     In the step S 21 , as mentioned above, the mark object detection unit  1  detects relative positions of a series of marks or objects which are continuously arranged in front of the own vehicle, with respect to the own vehicle. In the step S 22 , as mentioned above, the approximated curve calculation unit  2  calculates a curve which approximates the relative positions of the series of marks or objects. 
     For example, in the example shown in  FIG. 13 , a plurality of guide poles  24  arranged in a line with a constant interval along with the left side roadside of the driving lane of the own vehicle are detected as a series of objects, a plurality of guide poles  25  arranged in a line with a constant interval along with the right side roadside of the driving lane are detected as a series of objects, and a wall  26  arranged along the lane on the right side of the plurality of guide poles  25  of the right side roadside is detected as a series of objects. 
     Then, the first curve  27  which approximated the relative positions of the plurality of guide poles  24  of left side is calculated, the second curve  28  which approximated the relative positions of the plurality of guide poles  25  of right side is calculated, and the third curve  29  which approximated the relative positions of the wall  26  of right side is calculated. 
     In the step S 23 , the curve effective range determination unit  3  determines whether three or more curves are calculated. When determining that three or more curves are calculated, the curve effective range determination unit  3  advances to the step S 24  and sets the front and back reference position for right and left deviation X 0 RL in the front and back direction of the own vehicle. The front and back reference position for right and left deviation X 0 RL may be set to a preliminarily set position in the front and back direction, or may be set within an overlapping range in the front and back direction of the own vehicle where a range in the front and back direction where the series of marks or object used for each approximation of the plurality of curves are disposed overlaps between the plurality of curves (for example, the closest position closest to the own vehicle). In the example of  FIG. 14 , the front and back reference position for right and left deviation X 0 RL is set to 0 in the front and back direction. 
     Then, in the step S 25 , about each of the plurality of curves, the curve effective range determination unit  3  calculates a position Y in the right and left direction at the front and back reference position for right and left deviation X 0 RL, as the right and left reference position Y 0 RL. In the example of  FIG. 14 , about the first curve  27 , the right and left reference position Y 0 RL 27  of the first curve is calculated; about the second curve  28 , the right and left reference position Y 0 RL 28  of the second curve is calculated; and about the third curve  29 , the right and left reference position Y 0 RL 29  of the third curve is calculated. 
     In the step S 26 , the curve effective range determination unit  3  increases the position X in the front and back direction from the previous value by the step interval ΔX. The initial value of the position X in the front and back direction is set to the front and back reference position for right and left deviation X 0 RL. 
     Then, in the step S 27 , about each of the plurality of curves, the curve effective range determination unit  3  calculates the position Y in the right and left direction using the curve, at the position X in the front and back direction which was set in the step S 26 . In the example of  FIG. 14 , about the first curve  27 , the position Y 27  in the right and left direction of the first curve is calculated; about the second curve  28 , the position Y 28  in the right and left direction of the second curve is calculated; and about the third curve  29 , the position Y 29  in the right and left direction of the third curve is calculated. 
     In the step S 28 , about each of the plurality of curves, the curve effective range determination unit  3  calculates the right and left deviation ΔY 0 RL which is a deviation between the right and left reference position Y 0 RL and the position Y of the curve in the right and left direction, as shown in the next equation. In the example of  FIG. 14 , about the first curve  27 , the right and left deviation ΔY 0 RL 27  of the first curve is calculated; about the second curve  28 , the right and left deviation ΔY 0 RL 28  of the second curve is calculated; and about the third curve  29 , the right and left deviation ΔY 0 RL 29  of the third curve is calculated. 
       Δ Y 0 RL=Y−Y 0 RL   (9)
 
     In the step S 29 , the curve effective range determination unit  3  calculates the median ΔY 0 RL_M of the right and left deviations ΔY 0 RL of the plurality of curves. The median is a value located in the middle when data is arranged in ascending order. In the example of  FIG. 14 , the median ΔY 0 RL_M among the right and left deviation ΔY 0 RL 27  of the first curve, the right and left deviation ΔY 0 RL 28  of the second curve, and the right and left deviation ΔY 0 RL 29  of the third curve is calculated. 
     Then, in the step S 30 , about each of the plurality of curves, the curve effective range determination unit  3  calculates the absolute value of deviation ΔYD between the median ΔY 0 RL_M and the right and left deviation ΔY 0 RL, as shown in the next equation. In the example of  FIG. 14 , the absolute value of deviation ΔYD of the first curve, the absolute value of deviation ΔYD of the second curve, and the absolute value of deviation ΔYD of the third curve are calculated. 
       Δ YD=|ΔY 0 RL _ M−ΔY 0 RL|   (10)
 
     In the step S 31 , about each of the plurality of curves, the curve effective range determination unit  3  determines whether the absolute value of deviation ΔYD is larger than the right and left deviation threshold value JDRL. Then, in the step S 32 , when there is the curve whose absolute value of deviation ΔYD is larger than the right and left deviation threshold value JDRL, the curve effective range determination unit  3  advances to the step S 33  and excludes the curve larger than the right and left deviation threshold value JDRL from the curve candidate. When there is no curve whose absolute value of deviation ΔYD is larger than the right and left deviation threshold value JDRL, it advances to the step S 26 . In the step S 34 , when the number of the curves after exclusion is two, the curve effective range determination unit  3  ends the series of processing. Or, when the number is three or more, it advances to the step S 26 . 
     In the example of  FIG. 14 , when the position X in the front and back direction becomes XDT, the absolute value of deviation ΔYD of the third curve becomes larger than the right and left deviation threshold value JDRL, the third curve  29  is excluded from the curve candidate, and the first curve  27  and the second curve  28  are determined as the two curves corresponding to the lane shape. 
     When the curve whose right and left deviation ΔY 0 RL deviates from the median ΔY 0 RL_M by the right and left deviation threshold value JDRL is the last curve on the left side or the right side of the own vehicle, the curve effective range determination unit  3  may not exclude this curve from the curve candidate. The determination whether it is the left side curve or the right side curve is determined by whether the position Y of the curve in the right and left direction when the position X in the front and back direction is 0 is located on the left side or the right side of the own vehicle. In this example, it is determined as the right side when Y&gt;0, and it is determined as the left side when Y&lt;0. 
     In the present embodiment, in the flowchart of  FIG. 11  of Embodiment 1, the processing of the step S 4  is changed, and the processing of other steps are the same. In the present embodiment, in the step S 4 , as mentioned above, the curve effective range determination unit  3  sets a front and back reference position for right and left deviation X 0 RL in the front and back direction of the own vehicle; and about each of the plurality of curves, calculates a position Y in the right and left direction of the own vehicle at the front and back reference position for right and left deviation X 0 RL, as a right and left reference position Y 0 RL. About each of the plurality of curves, the curve effective range determination unit  3  calculates a right and left deviation ΔY 0 RL which is a deviation between a position Y of the curve in the right and left direction, and the right and left reference position Y 0 RL, at each position X in the front and back direction. Then, when changing a position X in the front and back direction from the front and back reference position for right and left deviation X 0 RL, the curve effective range determination unit  3  excludes the curve whose the right and left deviation ΔY 0 RL deviates from a median ΔY 0 RL_M of the right and left deviations ΔY 0 RL of the plurality of curves by a right and left deviation threshold value JDRL or more, from the plurality of curves, until becoming two curves; and determines that the remaining two curves correspond to the lane shape. 
     3. Embodiment 3 
     Next, the lane shape recognition system and the lane shape recognition method according to Embodiment 3 will be explained. The explanation for constituent parts the same as those in Embodiment 1 will be omitted. The basic configuration and processing of the lane shape recognition system according to the present embodiment are the same as those of Embodiment 1. In the present embodiment, processing of the approximated curve calculation unit  2  is different from Embodiment 1. 
     In the present embodiment, the approximated curve calculation unit  2  calculates a third-order curve (in this example, a third-order polynomial) within a specific range in a front and back direction of the own vehicle, and calculates a second-order curve (in this example, a second-order polynomial) within a range in the front and back direction other than the specific range. 
     For example, the next equation shows the case where the white line  20  of solid line on the left side of  FIG. 4  of Embodiment 1 is approximated. In the present embodiment, the specific range is set to a range in the front and back direction X of the relative positions of the series of marks or objects (in this example, a range from the closest position XminL closest to the own vehicle to the farthest position XmaxL farthest from the own vehicle). 
     1) In the case of X&lt;XminL 
         Y=C 0 L+C 3 L×X  min  L   3 +( C 1 L− 3× C 3 L×X  min  L   2 )× X +( C 2 L+ 3× C 3 L×X  min  L )× X   2  
 
     2) In the case of XminL&lt;=X&lt;=XmaxL 
         Y=C 0 L+C 1 L×X+C 2 L×X   2   +C 3 L×X   3    
     3) In the case of XmaxL&lt;X 
         Y=C 0 L+C 3 L×X max  L   3 +( C 1 L− 3× C 3 L×X max  L   2 )× X +( C 2 L+ 3× C 3 L×X max  L )× X   2    (11)
 
     Instead the second-order curve, a lower-order curve than the third-order curve (for example, a clothoid curve, a circular arc, or the like) may be used. 
     OTHER EMBODIMENTS 
     Lastly, other embodiments of the present disclosure will be explained. Each of the configurations of embodiments to be explained below is not limited to be separately utilized but can be utilized in combination with the configurations of other embodiments as long as no discrepancy occurs. 
     (1) In each of the above-mentioned Embodiments, there was explained the case where the approximated curve calculation unit  2  calculates a polynomial as the curve. However, embodiments of the present disclosure are not limited to the foregoing case. That is to say, the approximated curve calculation unit may approximate using various kinds of curves, as long as the relative positions of the series of marks or objects can be approximated. For example, the approximated curve calculation unit  2  may approximate using a clothoid curve which uses a starting point, a starting point direction angle, a starting point curvature, and a change rate of curvature as parameters. 
     (2) In each of the above-mentioned Embodiments, there was explained the case where the curve effective range determination unit  3  increases or decreases the position X in the front and back direction by the step interval ΔX, and calculates each calculation value, such as the width W in the right and left direction, the absolute value of width deviation ΔW, the absolute value of curvature deviation Δρ, and the right and left deviation ΔY 0 RL, at each position X in the front and back direction. However, embodiments of the present disclosure are not limited to the foregoing case. That is to say, the curve effective range determination unit  3  may change the position X in the front and back direction with unequal intervals, and may calculate each calculation value at each position X in the front and back direction. For example, the curve effective range determination unit  3  may change the position X in the front and back direction to the closest position of the overlapping range RXO, the farthest position of the overlapping range RXO, and the extreme value of curve, and may calculate each calculation value. 
     (3) In the above Embodiment 1, there was explained the case where the curve effective range determination unit  3  determines whether two curves are the combination corresponding to the lane shape based on the width W in the right and left direction of two curves in the overlapping range RXO. In the above Embodiment 2, there was explained the case where about each of the plurality of curves, the curve effective range determination unit  3  calculates the right and left deviation ΔY 0 RL which is a deviation between the position Y of the curve in the right and left direction, and the right and left reference position Y 0 RL, and excludes the curve whose right and left deviation ΔY 0 RL deviates from the median ΔY 0 RL_M of the right and left deviations ΔY 0 RL of the plurality of curves by the right and left deviation threshold value JDRL or more, from the plurality of curves, until becoming two curves. However, the curve selecting method of Embodiment 1 and the curve selecting method of Embodiment 2 may be combined and performed. For example, when a plurality of combinations of two curves corresponding to the lane shape are selected by the curve selecting method of Embodiment 1, the curves may be excluded until becoming two curves, by the curve selecting method of Embodiment 2. 
     (4) In each of the above-mentioned Embodiments, there was explained the case where the curve effective range determination unit  3  performs both of the determination of the effective range by curve width, and the determination of the effective range by curvature difference, and sets an overlapping range between the effective range by width determination RXEW and the effective range by curvature determination RXEP, as the final effective range. The curve effective range determination unit  3  may perform only the determination of the effective range by curve width, and may set the effective range by width determination RXEW as the final effective range final as it is. Alternatively, the curve effective range determination unit  3  may perform only the determination of the effective range by curvature difference, and may set the effective range by curvature determination RXEP as the final effective range as it is. 
     Although the present disclosure is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations to one or more of the embodiments. It is therefore understood that numerous modifications which have not been exemplified can be devised without departing from the scope of the present disclosure. For example, at least one of the constituent components may be modified, added, or eliminated. At least one of the constituent components mentioned in at least one of the preferred embodiments may be selected and combined with the constituent components mentioned in another preferred embodiment. 
     REFERENCE SIGNS LIST 
       1 : Mark object detection unit,  2 : Approximated curve calculation unit,  3 : Curve effective range determination unit,  4 : Vehicle control unit,  9 : Front monitoring apparatus, JDP: Curvature deviation threshold value, JDRL: Right and left deviation threshold value, JDW: Width deviation threshold value, RWP: Allowable width range, RXO: Overlapping range, W 0 : Reference width, X: Front and back direction, X 0 : Front and back reference position, X 0 RL: Front and back reference position for right and left deviation, Y: Right and left direction, Y 0 RL: Right and left reference position, ΔY 0 RL: Right and left deviation, ΔY 0 RL_M: Median of right and left deviation