JP2018087759A - Curve estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of estimation of a road shape existing in a traveling direction of a vehicle. SOLUTION: By measuring the position of a roadside object which is a stationary object existing on the road acquired from a first radar sensor (10) and a second radar sensor (20) having different search ranges, The radius of curvature is estimated when the road shape is estimated to be a clothoid curve or a circular shape, and it is determined from the measurement result whether the road shape is closer to the clothoid curve or the circular shape. The radius of curvature of the road shape determined to be closer to the determination result is output. [Selection diagram] Figure 1

Description

  The present disclosure relates to a curve estimation device provided in a vehicle.

  An on-vehicle radar device that detects a target around a vehicle by irradiating a radar wave such as a laser wave or a millimeter wave as a transmission wave and receiving a reflected wave over a predetermined angle range around the vehicle is known. Yes.

  And in patent document 1, the position of roadside objects, such as a soundproof wall and a guardrail, is acquired from the various targets detected by the vehicle-mounted radar apparatus, and an approximate straight line is calculated from the positional relationship of the acquired roadside objects. A technique for estimating the road shape is disclosed.

JP 2012-173152 A

  By the way, when a roadside object is detected by an in-vehicle radar device, the in-vehicle radar device is mainly provided for detecting a preceding vehicle, and therefore detects a target existing in a range far from the own vehicle. Do. When it is set to detect a target existing in a far range with respect to the host vehicle, since it is a far detection, the variation in the position of the measured target becomes large. In addition, when it is set to detect a target that exists in a range far from the host vehicle, the range of angles that can be detected by the radar output is limited to a narrow angle. The detectable range is narrowed. From these factors, the detection error of the position of the target detected by the on-vehicle radar device increases, and the curvature radius of the road calculated based on the position of the target greatly fluctuates and the reliability of the measurement is reduced. There was a problem.

  An object of this indication is to improve the reliability of estimation of the road shape which exists in the advancing direction of a vehicle.

The curve estimation device (30) provided in the vehicle includes a first acquisition unit (S100), a second acquisition unit (S100), and a shape estimation unit (S300, S600, S800).
The first acquisition unit has a first range that is within a first angle range that is a predetermined angle range including at least the front of the vehicle and that is within a first distance that is a predetermined distance. First data that is target data detected by a first radar sensor (10) that detects an existing target is acquired.

  The second acquisition unit is within a range of a second angle range that is a narrower angle range than the first angle range including at least the front of the vehicle, and is within a second distance that is longer than the first distance. Second data, which is target data detected by a second radar sensor (20) that detects a target existing in a second range as an area, is acquired.

  The shape estimation unit uses roadside object data, which is stationary data, out of the first data acquired by the first acquisition unit and the second data acquired by the second acquisition unit. Estimate the shape.

According to such a configuration, it is possible to improve the reliability of estimation of the curvature radius existing in the traveling direction of the vehicle.
Note that the reference numerals in parentheses described in this column and in the claims indicate the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present disclosure It is not limited.

It is a block diagram showing the structure of a vehicle control system. It is a figure showing the positional relationship of the own vehicle, the 1st range, and the 2nd range. It is a flowchart of a shape estimation process. It is a figure showing detection of the target by the 1st radar sensor and the 2nd radar sensor. It is a figure showing circle presumption. It is a flowchart of an inclination calculation process. It is a figure showing calculation of lane inclination. It is a flowchart of a clothoid estimation process. It is a figure showing clothoid estimation.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. Embodiment]
[1. Constitution]
A vehicle control system 1 shown in FIG. 1 is mounted on a vehicle and includes a first radar sensor 10, a second radar sensor 20, a curve estimation device 30, and a vehicle control device 40. Hereinafter, a vehicle equipped with the vehicle control system 1 is referred to as a host vehicle.

  The first radar sensor 10 and the second radar sensor 20 detect a target reflecting the radar wave by irradiating the radar wave within a predetermined range and receiving the reflected wave. The first radar sensor 10 and the second radar sensor 20 are well-known ones that generate target data related to the detected target. The first radar sensor 10 and the second radar sensor 20 are installed in the own vehicle so that the beam direction coincides with the front direction of the own vehicle. The target data referred to here includes at least a horizontal angle at which the target is obtained based on the beam direction and a relative speed between the vehicle and the target. The target data is generated by performing known signal processing such as fast Fourier transform processing, digital beam forming processing, and Doppler processing on the received reflected wave. The radar wave here may be a so-called millimeter wave radar using an electromagnetic wave in the millimeter wave band, a laser radar using a laser beam as a radar wave, or a sonar using a sound wave as a radar wave. In any case, the antenna unit that transmits and receives the radar wave is configured to detect the arrival direction of the reflected wave in the horizontal direction. Note that the antenna unit may be an array antenna including a transmission element and a reception element, for example.

  The first radar sensor 10 and the second radar sensor 20 are different in that the search range is different. Specifically, as shown in FIG. 2, the search range of the first radar sensor 10 is a first range D1, and the search range of the second radar sensor 20 is a second range D2. The first range D <b> 1 here is a region within a first distance that is a predetermined distance within a first angular range that is a predetermined angular range around the beam direction of the first radar sensor 10. Specifically, the first angle range may be 150 °, for example, and the first distance may be 10 m. On the other hand, the second range D2 is a region within a second angle range that is a narrower angle range than the first angle range and within a second distance that is longer than the first distance. Specifically, the second angle range may be 30 °, for example, and the second distance may be 50 m.

  The curve estimation device 30 acquires the target data output from the first radar sensor 10 and the second radar sensor 20, and estimates the road shape ahead of the host vehicle based on the acquired target data.

  The curve estimation device 30 is mainly configured by a known microcomputer having a CPU 31 and a semiconductor memory (hereinafter, memory 32) such as a RAM, a ROM, and a flash memory. Various functions of the curve estimation device 30 are realized by the CPU 31 executing a program stored in a non-transitional tangible recording medium. In this example, the memory 32 corresponds to a non-transitional tangible recording medium that stores a program. Also, by executing this program, a method corresponding to the program is executed. Note that the number of microcomputers constituting the curve estimation device 30 may be one or more.

  The curve estimation device 30 realizes a shape estimation process to be described later when the CPU 31 executes a program. The method of realizing various functions of the curve estimation device 30 is not limited to software, and some or all of the elements may be realized using one or a plurality of hardware. For example, when the above function is realized by an electronic circuit that is hardware, the electronic circuit may be realized by a digital circuit including a large number of logic circuits, an analog circuit, or a combination thereof.

  The vehicle control device 40 acquires the road shape estimated by the curve estimation device 30 and controls the host vehicle according to the acquired road shape. Here, the control of the own vehicle is, for example, lane keeping control for realizing traveling along the lane or power steering control for generating assist torque for assisting the steering operation by the driver of the own vehicle. Note that lane keeping control and power steering control are well-known techniques and will not be described.

[2. processing]
Next, the shape estimation process executed by the curve estimation device 30 will be described with reference to the flowchart of FIG. Note that the shape estimation processing may be repeatedly performed every time the first data and the second data are prepared, for example, by the outputs from the first radar sensor 10 and the second radar sensor 20 alternately.

  In S100, the curve estimation device 30 acquires target data from the first radar sensor 10 and the second radar sensor 20. Here, target data acquired from the first radar sensor 10 is referred to as first data, and target data acquired from the second radar sensor 20 is referred to as second data.

  In S200, the curve estimation device 30 extracts, as roadside object data, data representing a stationary object from the target data acquired in S100. Specifically, roadside object data is extracted as follows. That is, first, the moving speed of each target is calculated from the relative speed between each target contained in the target data and the host vehicle. Here, the calculation of the moving speed of each target may be obtained, for example, from the difference between the relative speed of each target with respect to the own vehicle and the moving speed of the own vehicle. Next, the curve estimation device 30 determines that the target is a roadside object when the calculated moving speed of the target is equal to or less than the speed threshold value, and determines that the target is a moving object when the speed threshold value is exceeded. to decide. Here, the speed threshold value is a reference value for distinguishing whether or not the vehicle is moving, and is, for example, 10 km / h. Thus, the data of the target determined to be a roadside object is extracted as roadside object data. For example, it is assumed that a target is detected at the reflection point G1, the reflection point G2, and the reflection point C in the first range D1, as shown in FIG. The reflection point here is a point where the radar wave hits the target and is reflected. In addition, squares and circles such as the reflection point G1, the reflection point G2, and the reflection point C in FIG. 4 represent the reflection points in the following FIG. 5, FIG. 7, and FIG. The curve estimation device 30 calculates the moving speed of each reflection point. The curve estimation device 30 determines whether or not the calculated movement speed of each reflection point is equal to or less than the speed threshold, and the reflection points G1 and G2 whose movement speed is equal to or less than the speed threshold detect roadside objects. And the data of the reflection point G1 and the reflection point G2 are extracted as roadside object data. That is, the roadside object data extracted by the curve estimation device 30 in S200 is data relating to stationary objects such as soundproof walls and guardrails installed on the road on which the host vehicle is traveling. On the other hand, the moving object is a moving object such as another vehicle that travels on a road on which the host vehicle travels.

In S300, the curve estimation device 30 calculates the lane inclination θ based on the roadside object data acquired in S200. Details of the calculation of the lane inclination θ will be described later.
In S400, the curve estimation device 30 determines whether or not the lane inclination θ calculated by the curve estimation device 30 in S300 is equal to or less than a curve threshold θth that is a preset angle. The curve threshold value θth here is an angle serving as a reference for determining whether or not the road shape ahead of the host vehicle is a straight line.

If it is determined in S400 that the lane inclination θ is equal to or less than the curve threshold θth, the process proceeds to S500.
If it is determined in S400 that the lane inclination θ is greater than the curve threshold θth, the process proceeds to S600.

  In S500, the curve estimation device 30 outputs the lane inclination θ assuming that the road shape is a straight line, and ends the process. For example, the curve estimation device 30 may output a flag indicating that the road shape is a straight line together with the output of the lane inclination θ.

  In S600, the curve estimation device 30 performs clothoid estimation. Specifically, the clothoid estimation is to obtain the curvature radius of the road shape on the assumption that the road shape is a clothoid curve. Here, as the curvature radius of the road shape, a representative value Rtyp, a minimum value Rmin, and a maximum value Rmax are obtained. In the following, the representative value Rtyp of the radius of curvature obtained by clothoid estimation will be referred to as clothoid radius Rtyp. Details of clothoid estimation will be described later.

  In S700, the curve estimation device 30 determines whether or not the clothoid radius Rtyp obtained in S600 is equal to or less than a specified value Rth of the curvature radius. The specified value Rth here is a radius of curvature that serves as a reference for determining whether or not the road shape ahead is a curve.

If it is determined in S700 that the clothoid radius Rtyp is greater than the specified value Rth, the process proceeds to S500.
If it is determined in S700 that the clothoid radius Rtyp is equal to or less than the specified value Rth, the process proceeds to S800.

  In S800, the curve estimation device 30 performs circle estimation. Specifically, the circle estimation is to obtain the curvature radius of the road shape assuming that the road shape is a circle. Here, for example, as shown in FIG. 5, the radius of curvature is searched for a circle that applies to the position distribution using the first data extracted from the first range D1 and the second data extracted from the second range D2. The radius of the fitted circle is obtained as the radius of curvature. The search for the applicable circle may be obtained by a method using a known least square method, for example, obtaining a circle having the smallest sum of square errors with respect to roadside object data. In the following, the calculated radius of curvature of the circle is defined as a circle radius Rc. Further, the center position Cc of the circle is obtained from the circle radius Rc.

  In S900, the curve estimation device 30 uses the absolute value of the difference between the clothoid radius Rtyp obtained by the clothoid estimation in S600 and the circle radius Rc obtained by the circle estimation in S800 as the radius difference value Rd, and the radius difference value. It is determined whether Rd is equal to or less than the difference threshold ΔRth. Thereby, it is determined whether the estimated road shape is closer to the clothoid curve or the circular shape.

When it is determined in S900 that the radius difference value Rd is larger than the difference threshold value ΔRth, the curve estimation device 30 proceeds to S1000.
When it is determined in S900 that the radius difference value Rd is equal to or less than the difference threshold ΔRth, the curve estimation device 30 proceeds to S1100.

  In S1000, the curve estimation device 30 selects that the shape close to the estimated road shape is a clothoid curve shape rather than a circular shape, outputs the clothoid radius Rtyp, and ends the process. The curve estimation device 30 outputs, for example, a flag indicating that the curvature radius minimum value Rmin and the curvature radius maximum value Rmax calculated in S600 and the road shape are approximated to a clothoid curve together with the output of the clothoid radius Rtyp. Also good.

  In S1100, the curve estimation device 30 selects that the shape close to the estimated road shape is more circular than the shape of the clothoid curve, outputs the circle radius Rc, and ends the process. For example, the curve estimation device 30 may output a flag indicating that the road shape is approximated to a circular shape together with the output of the circle radius Rc. The center position Cc of the circle calculated in S800 may be output together.

It should be noted that the processing in S100 is performed in the first acquisition unit and the second acquisition unit, the processing in S300 is performed in the inclination calculation unit, the processing in S600 is performed in the clothoid estimation unit, the processing in S800 is performed in the circle estimation unit, S300, The processing in S600 and S800 corresponds to the shape estimation unit, and the processing in S900 corresponds to the selection unit.
<Lane inclination calculation processing>
Here, the details of the lane inclination calculation process executed by the curve estimation device 30 in the previous S300 will be described with reference to the flowchart of FIG. 6 and the lane inclination calculation chart of FIG.

In S310, the curve estimation device 30 calculates the first angle α1 and the second angle α2.
Here, the first angle α1 is an angle formed by the first straight line A1 that is a straight line obtained by linearly approximating the position indicated by the first data detected in S300 and the beam direction of the first radar sensor 10. Say.

  Similarly, the second angle α2 is formed by the second straight line A2 that is a straight line obtained by linearly approximating the position indicated by the second data detected in S300, and the beam direction of the second radar sensor 20. Say.

  Specifically, the same target range T1, T2 is defined as the range within which the distance between the roadside objects included in each of the first range D1 and the second range D2 is equal to or less than a predetermined distance. Linear approximation is performed on the distribution of positions where roadside objects included in each of T2 exist. The first straight line A1 and the second straight line A2 are calculated by linear approximation.

  In S320, the curve estimation device 30 calculates a lane inclination θ that is an absolute value of the difference between the first angle α1 and the second angle α2 obtained in S310. That is, the lane inclination θ is obtained by the equation (1).

The lane inclination θ can be calculated by the lane inclination calculation process described above.
<Clothoid estimation processing>
Here, the details of the lane inclination calculation processing executed by the curve estimation device 30 in the previous S600 will be described with reference to the flowchart of FIG. 8 and the figure representing the clothoid estimation of FIG.

In S610, the curve estimation device 30 acquires the first position Ka, which is the farthest position with respect to the host vehicle, among the positions of the roadside objects included in the first data.
In S620, the curve estimation device 30 acquires a second position Ke that is a position farthest from the host vehicle among the positions of the roadside objects included in the second data.

  In S630, the curve estimation device 30 calculates a roadside length L that is a length along the road shape between the first position Ka and the second position Ke. The roadside length L here is obtained from the sum of the distances between points at which the roadside objects are captured using the roadside object position data included in the roadside object data.

  In S640, the curve estimation device 30 calculates the minimum radius of curvature R in the clothoid curve. Hereinafter, the minimum curvature radius R in the clothoid curve is defined as a clothoid radius R. Here, the clothoid radius R is obtained from the equation (2) based on the clothoid parameter A and the roadside length L. Here, clothoid parameter A is a constant that satisfies equation (3).

  A representative value of the curvature radius R obtained here is a clothoid radius Rtyp. Here, the clothoid radius Rtyp is a value obtained by substituting A = R / 2. Thereby, clothoid radius Rtyp is represented by clothoid radius Rtyp = 4L using roadside length L. The maximum value Rmax of the curvature radius R is obtained by substituting A = R / 3 into the equation (2) and rearranging, and is represented by Rmax = 9L. Similarly, the minimum value Rmin of the curvature radius R is obtained by substituting A = R into the equation (2) and rearranging, and is represented by Rmin = L.

By the clothoid estimation processing described above, the representative value Rtyp, the maximum value Rmax, and the minimum value Rmin of the radius of curvature can be obtained.
[3. effect]
According to the embodiment described in detail above, the following effects can be obtained.

  (A1) According to the present embodiment, by using targets existing in two different search ranges of the first radar sensor 10 and the second radar sensor 20, a target existing in a single search range is searched. Compared with the case of using a radar sensor, a wider range of targets can be detected. Since the road shape existing in the traveling direction of the own vehicle is estimated based on the detected wide range of targets, the reliability of the estimation of the road shape existing in the traveling direction of the own vehicle can be improved.

  (A2) According to this embodiment, the reliability of the curvature radius of the road shape obtained by measurement can be improved. Specifically, the clothoid radius Rtyp is obtained by clothoid estimation, and the circle radius Rc is obtained by circle estimation. The result of the radius of curvature corresponding to the closest to the estimated road shape among the clothoid curve and the circular shape is output. For this reason, since the curvature radius of a closer shape can be measured compared with the case where only one of them is estimated, the reliability of the curvature radius of the road shape obtained by measurement can be improved.

  (A3) According to this embodiment, it is possible to reduce the processing load when it is determined that the estimated road shape is a straight line. Specifically, when it is determined that the calculated lane inclination θ is equal to or less than the curve threshold θth, the lane inclination θ is output assuming that the estimated road shape is a straight line, and the process is terminated. In this case, it is not necessary to perform a process such as clothoid estimation or circle estimation. Thereby, the load concerning processing, such as clothoid estimation and circle estimation, can be reduced.

[3. Other Embodiments]
As mentioned above, although embodiment of this indication was described, this indication is not limited to the above-mentioned embodiment, and can carry out various modifications.

  (B1) In the above embodiment, two radar sensors, the first radar sensor 10 and the second radar sensor 20, are used. However, the form of the radar sensor is not limited to this. For example, the search may be performed by switching between two types of search ranges corresponding to the search range of the first radar sensor 10 and the search range of the second radar sensor 20 using one array antenna. In this case, the configuration can be simplified compared to the case shown in the above embodiment.

  (B2) In the above embodiment, lane inclination calculation, clothoid estimation, and circle estimation are performed in the shape estimation process, but not all of them are included in the same process. That is, the process may include one or more of lane inclination calculation, clothoid estimation, and circle estimation. For example, without calculating the lane inclination, only clothoid estimation and circle estimation may be performed, and one of the estimation results may be output according to the estimated road shape. Further, only clothoid estimation may be performed. That is, clothoid estimation may be performed and the result of clothoid estimation may be output.

  (B3) In the above embodiment, the absolute value of the difference between the clothoid radius Rtyp and the circle radius Rc is set as the radius difference value Rd, and it is estimated by determining whether the radius difference value Rd is equal to or less than the difference threshold value ΔRth. It is determined whether the road shape obtained is closer to a clothoid curve or a circular shape. However, the method of determining whether the estimated road shape is closer to the clothoid curve or the circular shape is not limited to this. For example, if the specified value of the data error, which is the error between the fitted circular shape and the position of each target to be fitted, is set in advance as the error specified value, and the data error is larger than the specified error value, it is closer to the clothoid curve It may be determined.

  (B4) In the above embodiment, the representative value Rtyp, the maximum value Rmax, and the minimum value Rmin of the clothoid radius are obtained by clothoid estimation, but the results obtained by clothoid estimation are not limited to this. For example, Ctyp, which is the center position of the clothoid curve, may be obtained by clothoid estimation. In this case, the center position Ctyp of the clothoid curve may be output together with the radius of curvature as a result of clothoid estimation.

  (B5) A plurality of functions of one constituent element in the above embodiment may be realized by a plurality of constituent elements, or a single function of one constituent element may be realized by a plurality of constituent elements. . Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  (B6) In addition to the curve estimation device 30 described above, a system including the curve estimation device 30 as a constituent element, a program for causing a computer to function as the curve estimation device 30, a non-transitive semiconductor memory or the like in which the program is recorded The present disclosure can also be realized in various forms such as a substantial recording medium and a curve estimation method.

DESCRIPTION OF SYMBOLS 1 ... Vehicle control system, 10 ... 1st radar sensor, 20 ... 2nd radar sensor, 30 ... Curve estimation apparatus, 31 ... CPU, 32 ... Memory, 40 ... Vehicle control apparatus.

Claims (7)

A curve estimation device (30) provided in a vehicle,
A target that is within a first angle range that is a predetermined angle range including at least the front of the vehicle and that is within a first distance that is a predetermined distance, A first acquisition unit (S100) configured to acquire first data which is data of the target detected by the first radar sensor (10) to detect;
The region is within a second angle range that is a narrower angle range than the first angle range including at least the front of the vehicle and within a second distance that is longer than the first distance. A second acquisition unit (S100) configured to acquire second data that is data of the target detected by a second radar sensor (20) that detects a target existing in the second range;
The road of the road on which the vehicle travels using roadside object data that is data of a stationary object among the first data acquired by the first acquisition unit and the second data acquired by the second acquisition unit. A shape estimation unit (S300, S600, S800) configured to estimate a shape;
A curve estimation device comprising: The curve estimation device according to claim 1,
The shape estimation unit is configured to use the roadside object data to estimate a clothoid radius that is a curvature radius of the road, assuming that the road shape of the road is a clothoid curve shape (S600). A curve estimation device further comprising: The curve estimation device according to claim 1 or 2,
The shape estimation unit is configured to estimate a circle radius, which is a curvature radius of the road, using the roadside object data and assuming that the road shape of the road is a circle shape (S800). A curve estimation device further comprising: The curve estimation device according to claim 1,
The shape estimation unit
Using the roadside object data, a clothoid estimation unit configured to estimate a clothoid radius that is a curvature radius of a road on which the vehicle travels is determined as the road shape of the road is a shape of a clothoid curve;
Using the roadside object data, a circle estimation unit configured to estimate a circle radius that is a curvature radius of a road on which the vehicle travels is determined as a circle shape in the road shape of the road;
A selection unit (S900) that selects at least one of the clothoid radius and the circle radius as a parameter representing the shape of the road using the estimated clothoid radius and the circle radius;
A curve estimation device further comprising: The curve estimation device according to claim 4,
The selection unit sets a data error as an error between the circle having the circle radius estimated by the circle estimation unit and the roadside object data used for the estimation, and the data error is larger than a preset error regulation value. In this case, the curve estimation device selects the clothoid radius as a parameter representing the shape of the road, and selects the circle radius as a parameter representing the shape of the road when the data error is equal to or less than the error specified value. The curve estimation device according to claim 4,
The selection unit uses the absolute value of the difference between the circle radius and the clothoid radius as a radius difference value, and when the radius difference value is larger than a difference threshold value that is a predetermined value, the clothoid radius is set to the shape of the road. A curve estimation device that selects the circle radius as a parameter representing the shape of the road when the radius difference value is equal to or smaller than the difference threshold value. A curve estimation device according to any one of claims 1 to 6,
The shape estimation unit sets a straight line obtained by linearly approximating the position of the roadside object indicated by the roadside object data included in the first data as a first straight line, and the roadside object data included in the second data. A slope calculating unit that calculates a lane slope that is a difference between an angle of the first straight line and the second straight line with respect to the vehicle as a second straight line obtained by linearly approximating the position of the roadside object indicated by In addition,
The shape estimation unit estimates the road shape when the lane inclination calculated by the inclination calculation unit is equal to or more than a curve threshold value that is a criterion for determining whether or not the road shape is a curve. A curve estimation device configured as described above.

Images