JP2017016259A - Road curvature estimation device and lane deviation avoidance system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road curvature estimation device and a lane deviation avoidance system which have high accuracy in curvature estimation and are superior in response.SOLUTION: A road curvature estimation device (3) is characterized by comprising: an image acquisition unit (7) which acquires an image obtained by imaging the front of user's vehicle; a curvature estimation unit (9) which uses the image to estimate a curvature of a lane on which the vehicle is traveling; a vehicle speed acquisition unit (7) which acquires a vehicle speed of the vehicle; a maximum allowable change rate acquisition unit (13) which acquires a maximum allowable change rate corresponding to the vehicle speed acquired by the vehicle speed acquisition unit, from a prescribing unit which prescribes a maximum allowable change rate of the curvature for each vehicle speed; and a correction unit (15) which, if a change rate in the curvature calculated by the curvature estimation unit exceeds the maximum allowable change rate, corrects the curvature calculated by the curvature estimation unit so that the change rate becomes the maximum allowable change rate or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a road curvature estimation device and a lane departure avoidance system.

  A method is known in which the front of the host vehicle is imaged and the curvature of the lane is estimated from the shape of the lane recognized in the captured image (see Patent Document 1). The curvature estimated by this method includes noise. In particular, the curvature noise increases when the white line is thin or when there is a lot of road surface noise.

  In the technique described in Patent Document 1, the curvature estimation accuracy is calculated by obtaining the curvature of the lane at a position before the present and setting the maximum allowable change amount of the curvature according to the curvature.

Japanese Patent No. 4517958

  In the technique described in Patent Document 1, it is necessary to obtain the curvature at a position before the present time in order to set the maximum allowable change amount. For this reason, the processing burden on the apparatus is large, and the responsiveness when estimating the curvature at the current position may be reduced.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a road curvature estimation device and a lane departure avoidance system with high accuracy of curvature estimation and excellent responsiveness.

  The road curvature estimation apparatus of the present invention includes an image acquisition unit that acquires an image obtained by capturing the front of the host vehicle, a curvature estimation unit that uses the image to estimate the curvature in the lane in which the host vehicle is traveling, and the vehicle speed of the host vehicle. The maximum allowable change rate acquisition unit for acquiring the maximum allowable change rate corresponding to the vehicle speed acquired by the vehicle speed acquisition unit from the specified unit that specifies the maximum allowable change rate of curvature for each vehicle speed, and the curvature And a correction unit that corrects the curvature calculated by the curvature estimation unit so that the change rate is equal to or less than the maximum allowable change rate when the change rate in the curvature calculated by the estimation unit exceeds the maximum allowable change rate.

  The road curvature estimation apparatus of the present invention corrects the curvature when the change rate in the curvature exceeds the maximum allowable change rate. The rate of change in the corrected curvature is less than the maximum allowable rate of change. As a result, the influence of noise on the curvature can be reduced, and the accuracy of curvature estimation can be increased.

  Moreover, the road curvature estimation apparatus of the present invention acquires the maximum allowable change rate corresponding to the vehicle speed from the specified unit. Therefore, the processing burden for obtaining the maximum allowable change rate is light. As a result, the responsiveness when estimating the curvature is good.

1 is a block diagram illustrating a configuration of a lane departure avoidance system 1. FIG. It is a flowchart showing the whole process which the parameter estimation apparatus 3 performs. It is a top view showing parameters, such as lateral velocity Vw and lateral position P. It is a flowchart showing the curvature change guard process which the parameter estimation apparatus 3 performs. It is a graph showing the regulation data which prescribed | regulated the relationship between the vehicle speed V and the maximum permissible change rate G. FIG. 6A is an explanatory diagram illustrating correction when C1 before correction is larger than C2, and FIG. 6B is an explanatory diagram illustrating correction when C1 before correction is smaller than C2. It is a flowchart showing the whole process which the control apparatus 5 performs. 4 is a flowchart showing a control start determination executed by the control device 5. 4 is a flowchart illustrating a process during control executed by the control device 5. It is a flowchart showing the control end determination which the control apparatus 5 performs.

Embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
1. Configuration of Lane Departure Avoidance System 1 The configuration of the lane departure avoidance system 1 will be described with reference to FIG. The lane departure avoidance system 1 is an in-vehicle system mounted on a vehicle. In the following, a vehicle equipped with the lane departure avoidance system 1 is defined as the own vehicle. The lane departure avoidance system 1 includes a parameter estimation device 3 and a control device 5.

  The parameter estimation device 3 is a known computer including a CPU, a RAM, a ROM, and the like. The parameter estimation device 3 performs processing to be described later using a program stored in the ROM, and estimates various parameters. The parameter estimation device 3 functionally includes a sensor value acquisition unit 7, a parameter estimation unit 9, a filter processing unit 11, a maximum allowable change rate acquisition unit 13, and a correction unit 15. The function of each unit will be described later.

  The control device 5 is a known computer including a CPU, RAM, ROM, and the like. The control device 5 executes processing to be described later by a program stored in the ROM, and calculates a required torque (steering torque).

  In addition to the lane departure avoidance system 1, the host vehicle includes an image sensor 17, a yaw rate sensor 19, a wheel speed sensor 21, other in-vehicle sensors 23, a defining unit 25, and an electric power steering device 27.

  The image sensor 17 captures the front of the host vehicle and creates image data. The yaw rate sensor 19 detects the yaw rate of the host vehicle. The wheel speed sensor 21 detects the vehicle speed V of the host vehicle. The other in-vehicle sensor 23 detects various state quantities of the host vehicle. The regulation unit 25 is a storage device such as a hard disk drive, for example, and stores regulation data described later.

In addition to the normal function, the electric power steering device 27 acquires the required torque from the control device 5 and performs automatic steering according to the required torque.
The sensor value acquisition unit 7 is an example of an image acquisition unit and a vehicle speed acquisition unit. The parameter estimation unit 9 is an example of a curvature estimation unit. The parameter estimation device 3 is an example of a road curvature estimation device. The control device 5 is an example of a steering torque calculation device.

2. Processing Performed by Parameter Estimating Device 3 Processing that is repeatedly performed by the parameter estimating device 3 every fixed time Δt will be described with reference to FIGS. In step 1 of FIG. 2, the sensor value acquisition unit 7 acquires a sensor value. Specifically, the sensor value acquisition unit 7 acquires an image obtained by imaging the front of the host vehicle using the image sensor 17, acquires the yaw rate of the host vehicle using the yaw rate sensor 19, and uses the wheel speed sensor 21. The vehicle speed V is acquired, and various state quantities of the host vehicle are acquired using the other on-vehicle sensors 23.

In step 2, the parameter estimation unit 9 estimates the lateral position P, the lateral velocity Vw, and the curvature C using the sensor values acquired in step 1.
As shown in FIG. 3, the lateral position P is a lane boundary line 29, 31 that divides a lane 35 in which the host vehicle 33 is traveling, and is closer to the host vehicle 33 (the lane boundary line 29 in FIG. 3). This is the distance in the lateral direction (direction perpendicular to the traveling direction of the lane 35) with the portion 33A closest to the lane boundary line of the host vehicle 33. As shown in FIG. 3, when the portion 33A is in the lane 35 (on the right side of the lane boundary 29), the lateral position P is a positive value, and the portion 33A is outside the lane 35 (lane boundary The lateral position P is a negative value. The parameter estimation unit 9 estimates the lateral position P from the position of the lane boundary line in the image acquired in step 1.

  The lateral speed Vw is a lateral component of the lane 35 of the vehicle speed V as shown in FIG. The parameter estimation unit 9 estimates the lateral velocity Vw as follows. First, the parameter estimation unit 9 calculates the yaw angle θ of the host vehicle based on the positions and orientations of the lane boundary lines 29 and 31 in the image acquired in step 1. As shown in FIG. 3, the yaw angle θ is an angle formed by the traveling direction α of the host vehicle 33 and the lane boundary lines 29 and 31.

  When the yaw angle θ changes, the positions and orientations of the lane boundary lines 29 and 31 in the image change accordingly. The parameter estimation unit 9 includes a map that prescribes the relationship between the position and orientation of the lane boundary lines 29 and 31 in the image and the yaw angle θ, and determines the position and orientation of the lane boundary lines 29 and 31 in the image. By inputting into the map, the yaw angle θ is calculated.

  Next, the parameter estimation unit 9 calculates the lateral speed Vw by multiplying the vehicle speed V by sin θ. Regarding the positive and negative values of the lateral speed Vw, the lateral speed Vw in the direction from the center of the lane 35 toward the direction closer to the host vehicle 33 (the lane boundary 29 in FIG. 3) is positive. The lateral velocity Vw in the opposite direction is a negative value.

  The curvature C is the curvature of the lane boundary lines 29 and 31 (in other words, the curvature of the lane 35) when the lane 35 is viewed from above. The parameter estimation unit 9 estimates the curvature C from the shape of the lane boundary lines 29 and 31 appearing in the image acquired in step 1. In addition, about the positive / negative of the value of the curvature C, the curvature C when the lane 35 bends in the left direction as it goes up in FIG. 3 is made into a positive value, and the curvature C when turning in the opposite direction is made into a negative value. .

  Returning to FIG. 2, in step 3, the filter processing unit 11 performs a filter process using the Kalman filter on the lateral position P, lateral velocity Vw, and curvature C estimated in step 2.

  In step 4, the maximum allowable change rate acquisition unit 13 and the correction unit 15 perform curvature change guard processing on the curvature C estimated in step 2. This process will be described with reference to FIGS.

The regulation unit 25 stores the regulation data shown in FIG. 5 in advance. The specified data is data that specifies the maximum allowable change rate G for the change rate in the curvature C for each vehicle speed V. The rate of change in curvature C is as follows. The value of the curvature C at some time _{t 1} is C _{(t 1),} the value of the curvature C at a later point in time _{t 2} is assumed to be C _{(t 2).} The rate of change in the curvature C (t ₂ ) is represented by K (C (t ₂ ) −C (t ₁ )) / (t ₂ −t ₁ ). Here, K is a constant.

In the prescribed data, the relationship between the vehicle speed V and the maximum allowable change rate G is such that the greater the vehicle speed V, the smaller the maximum allowable change rate G.
The regulation data can be created as follows based on the regulations such as the Road Structure Ordinance. The road structure ordinance prescribes the road curvature radius (minimum curve radius) and the road design speed in association with each other. According to the road structure ordinance, the minimum distance of the clothoid section is 1/3 of the radius of curvature.

  The distance of the clothoid section to the curved road having a predetermined radius of curvature R is set to 1/3 of the radius of curvature R, and the curvature change rate (unit: 1 / m / s) in the clothoid section is calculated, and this is the maximum allowable change. Let G be the rate. On the other hand, the vehicle speed V is a vehicle speed obtained by adding a certain margin (for example, 30 km / h) to the design speed on the road having the curvature radius R defined by the road structure ordinance. And the data which matched said maximum permissible change rate G and said vehicle speed V are made into regulation data.

  In step 11 of FIG. 4, the maximum allowable change rate acquisition unit 13 acquires the maximum allowable change rate G corresponding to the vehicle speed V acquired in step 1 from the regulation unit 25. For example, when the vehicle speed V is 50 (km / h), the corresponding maximum allowable change rate G is 0.0104 (1 / m / s), and when the vehicle speed V is 60 (km / h), The corresponding maximum allowable change rate G is 0.0052 (1 / m / s).

  In step 12, the value of curvature C estimated in the previous step 2 (hereinafter referred to as the previous value C2) from the value of curvature C estimated in the previous step 2 (hereinafter referred to as current value C1). ) Is subtracted, and the correction unit 15 calculates the difference Δ. The difference Δ corresponds to the rate of change in the current value C1. The previous value C2 is an example of the curvature C estimated in the past. When the previous value C2 is the current value, the previous value C2 may have been corrected later, or may not have been corrected.

  In step 13, the correction unit 15 determines whether the absolute value of the difference Δ calculated in step 12 is larger than the maximum allowable change rate G acquired in step 11. If the absolute value of the difference Δ is larger than the maximum allowable change rate G, the process proceeds to step 14. On the other hand, in other cases, the curvature change guard process is terminated without correcting the current value C1.

  In step 14, the correction unit 15 determines whether or not the current value C1 is greater than the previous value C2. If the current value C1 is larger than the previous value C2, the process proceeds to step 15. If the current value C1 is smaller than the previous value C2, the process proceeds to step 16.

In step 15, the correction unit 15 corrects the current value C1 to a value “previous value C2 + G”. An example of this correction is shown in FIG. 6A.
In step 16, the correction unit 15 corrects the current value C1 to a value “previous value C2-G”. An example of this correction is shown in FIG. 6B.

  Returning to FIG. 2, in step 5, the sensor value acquired in step 1 and the parameter estimated in step 2 are output to the control device 5. If the curvature C is corrected in step 4, the corrected curvature C is output. If the correction is not made in step 4, the curvature C estimated in step 2 is output as it is.

3. Processing Performed by Control Device 5 The processing that the control device 5 repeatedly executes at predetermined time intervals will be described with reference to FIGS. In step 21 in FIG. 7, sensor values and parameters (lateral position P, lateral velocity Vw, and curvature C) are acquired from the parameter estimation device 3.

  In step 22, it is determined whether or not the control execution flag is on. Note that the control execution flag is turned on or off by a process described later. When the control execution flag is off, the process proceeds to step 23, and when it is on, the process proceeds to step 25.

  In step 23, control start determination is performed. This control start determination will be described with reference to FIG. In step 31 of FIG. 8, it is determined whether or not the lateral speed Vw is greater than a preset threshold value T1. When the lateral speed Vw is larger than the threshold value T1, the process proceeds to step 32, and when it is equal to or less than the threshold value T1, the control start determination is terminated.

  In step 32, it is determined whether or not the lateral position P is smaller than a preset threshold value T2 (see FIG. 3). When the lateral position P is smaller than the threshold value T2, the process proceeds to step 33, and when it is equal to or larger than the threshold value T2, the control start determination is terminated.

In step 33, the control execution flag is turned on.
Returning to FIG. 7, in step 24, it is determined whether or not the control execution flag is ON. If the control execution flag is on, the process proceeds to step 25. If the control execution flag is off, the process ends.

  In step 25, a process during control is executed. This in-control process will be described with reference to FIG. In step 41 of FIG. 9, the target value of the lateral position P and the target value of the lateral speed Vw are set under the assumption that the lane in which the host vehicle is traveling is a straight line. The target value of the lateral position P is a value larger than a threshold value T2 and a threshold value T3 described later. The target value of the lateral velocity Vw has a sufficiently small absolute value.

Next, a required torque (hereinafter referred to as FF (feed forward) amount) required to reach the target value of the lateral position P and the target value of the lateral speed Vw is calculated.
In step 42, the required torque (hereinafter referred to as the amount of FF for the curvature) required for traveling according to the curvature C acquired in step 21 is calculated.

  In step 43, the difference between the target value of the lateral position P and the lateral velocity Vw and the actual value is calculated, and a required torque (hereinafter referred to as FB (feedback) amount) for reducing the difference is calculated.

  In step 44, the final required torque is calculated by adding the FF amount calculated in step 41, the curvature FF amount calculated in step 42, and the FB amount calculated in step 43.

In step 45, the required torque calculated in step 44 is output to the electric power steering device 27.
Returning to FIG. 7, in step 26, control end determination is performed. This control end determination will be described with reference to FIG. In step 51 of FIG. 10, it is determined whether or not the lateral position P is larger than a preset threshold value T3 (see FIG. 3). If the lateral position P is greater than the threshold value T3, the process proceeds to step 52. If the lateral position P is less than or equal to the threshold value T3, the control end determination is terminated.

  In step 52, it is determined whether or not a condition that the lateral speed Vw is within a preset range R for a predetermined time is satisfied. If the condition is satisfied, the process proceeds to step 53. If the condition is not satisfied, the control end determination is ended.

In step 53, the control execution flag is turned off.
4). Effects Produced by Parameter Estimation Device 3 and Lane Departure Avoidance System 1 (1A) Parameter estimation device 3 corrects current value C1 when difference Δ in curvature C (an example of a change rate) exceeds maximum allowable change rate G. The difference Δ between the corrected current value C1 and the previous value C2 is the maximum allowable change rate G. As a result, the influence of noise on the curvature C can be reduced and the estimation accuracy of the curvature C can be increased.

  (1B) The parameter estimation device 3 acquires the maximum allowable change rate G corresponding to the vehicle speed V from the regulation unit 25. Therefore, the processing load for obtaining the maximum allowable change rate G is light. As a result, the responsiveness when estimating the curvature C is good.

  (1C) The lane departure avoidance system 1 calculates the required torque using the curvature C corrected as necessary as described above. As a result, it is possible to secure the responsiveness of the required torque with respect to the change in curvature, and to suppress the noise of the curvature C from affecting the automatic steering.

(1D) The relationship between the vehicle speed V and the maximum allowable change rate G is such that the greater the vehicle speed V, the smaller the maximum allowable change rate G. This relationship coincides with the relationship between the vehicle speed V when the host vehicle actually travels in the lane and the rate of change of the curvature C in the lane. As a result, the maximum allowable change rate G can be set to an appropriate value according to the vehicle speed V.
<Other embodiments>
As mentioned above, although embodiment of this invention was described, this invention can take a various form, without being limited to the said embodiment.

  (1) The correction unit 15 determines that the current value C1 has a larger absolute value than the previous value C2 (the curvature C changes in a direction in which the absolute value increases compared to the curvature C estimated in the past). ) Performs the above correction, but the current value C1 may not be corrected when the absolute value is smaller than the previous value C2.

  In this case, since the frequency of correction is reduced, the processing load on the parameter estimation device 3 can be reduced. Note that, when the absolute value of the curvature C changes in a decreasing direction, the control of the automatic steering becomes weaker with time, so that the influence of the noise of the curvature C is relatively small without correction.

(2) The parameter estimation device 3 may acquire the maximum allowable change rate G corresponding to the vehicle speed V from a facility outside the host vehicle.
(3) The method of correcting the current value C1 may be another method. For example, in step 15, the corrected current value C1 may be a value “previous value C2 + δ”, and in step 16, the corrected current value C1 may be a value “previous value C2-δ”. it can. This δ is, for example, a positive number and can be set to a value smaller than the maximum allowable change rate G. In this case, the difference Δ between the corrected current value C1 and the previous value C2 is a value δ smaller than the maximum allowable change rate G.

  (4) The parameter estimation device 3 may calculate the rate of change from the curvature C estimated three or more times continuously. If the rate of change exceeds the maximum allowable rate of change G, part or all of the curvature C of three or more times can be corrected.

  (5) The curvature C may be corrected for the curvature C other than the current value C1. For example, the curvature C that has been estimated in the past may be detected afterwards when the rate of change exceeds the maximum allowable change rate G, and the curvature C may be corrected.

  (6) The functions of one constituent element in the above embodiment may be distributed as a plurality of constituent elements, or the functions of a plurality of constituent elements may be integrated into one constituent element. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. 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 only by the wording described in the claim are embodiment of this invention.

  (7) In addition to the parameter estimation device 3 described above, a system including the parameter estimation device 3 as a component, a program for causing a computer to function as the parameter estimation device 3, a medium on which the program is recorded, a curvature estimation method, etc. The present invention can also be realized in various forms.

DESCRIPTION OF SYMBOLS 1 ... Lane departure avoidance system, 3 ... Parameter estimation apparatus, 5 ... Control apparatus, 7 ... Sensor value acquisition unit, 9 ... Parameter estimation unit, 11 ... Filter processing unit, 13 ... Maximum allowable change rate acquisition unit, 15 ... Correction unit , 17 ... Image sensor, 19 ... Yaw rate sensor, 21 ... Wheel speed sensor, 23 ... Other in-vehicle sensors, 25 ... Regulation unit, 27 ... Electric power steering device, 29, 31 ... Lane boundary line, 33 ... Own vehicle, 35 ... lane

Claims (5)

An image acquisition unit (7) for acquiring an image of the front of the host vehicle;
A curvature estimation unit (9) for estimating a curvature in a lane in which the host vehicle is traveling using the image;
A vehicle speed acquisition unit (7) for acquiring the vehicle speed of the host vehicle;
A maximum allowable change rate acquisition unit (13) for acquiring the maximum allowable change rate corresponding to the vehicle speed acquired by the vehicle speed acquisition unit from a prescribed unit that specifies the maximum allowable change rate of the curvature for each vehicle speed;
A correction unit that corrects the curvature calculated by the curvature estimation unit so that the change rate is equal to or less than the maximum allowable change rate when the change rate in the curvature calculated by the curvature estimation unit exceeds the maximum allowable change rate. 15)
A road curvature estimation device (3), comprising: The road curvature estimation device according to claim 1,
The correction unit corrects the curvature calculated by the curvature estimation unit so that the change rate becomes the maximum allowable change rate. The road curvature estimation device according to claim 1 or 2,
The correction unit performs correction on the condition that the curvature estimated by the curvature estimation unit changes in a direction in which the absolute value of the curvature increases compared to the curvature estimated in the past. Road curvature estimation device. The road curvature estimation device according to any one of claims 1 to 3,
The road curvature estimation apparatus according to claim 1, wherein the relationship between the vehicle speed and the maximum allowable change rate in the prescribed unit is a relationship in which the maximum allowable change rate is smaller as the vehicle speed is higher. The road curvature estimation apparatus according to any one of claims 1 to 4,
A steering torque calculation device (5) for calculating a steering torque for traveling along the lane using the curvature estimated by the road curvature estimation device;
A lane departure avoidance system (1) comprising:

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