Vehicle control device and vehicle control method

Abstract

In one aspect of a vehicle control device and a vehicle control method according to the present invention: a storage unit stores, from the present time to a predetermined time in the past, lane information including the position and orientation of a host vehicle relative to the traveling lane of the host vehicle, acquired by an external environment recognition sensor, travel behavior information relating to travel behavior of the host vehicle, and road information including the curvature of the traveling lane; a degree of deviation between odometry information obtained using the stored information, and the lane information, is obtained; an initial value of the odometry is determined on the basis of the lane information and the degree of deviation; and lane keeping control is executed on the basis of either the odometry result or the lane information. As a result, even if the external environment recognition sensor outputs inaccurate demarcation line information, highly accurate demarcation line information can be used for lane keeping control.

Description

Vehicle control device and vehicle control method

[0001] The present invention relates to a vehicle control device and a vehicle control method.

[0002] The driving control method and driving control device disclosed in Patent Document 1, when a state in which lane markings have been detected changes to a state in which lane markings are no longer detected, estimates virtual markings based on the positions of previously detected markings, and controls the driving so that the vehicle is positioned in a predetermined position relative to the virtual markings.

[0003] International Publication No. 2018 / 012179

[0004] However, before and after sections where external recognition sensors such as cameras do not detect lane markings, even if they detect lane markings, they may output inaccurate lane marking information that does not match the actual position or posture of the vehicle.If this inaccurate lane marking information is used for lane keeping control, it may become difficult to stay within the lane.

[0005] Therefore, an object of the present invention is to provide a vehicle control device and a vehicle control method that can use highly accurate lane line information for lane keeping control even when an external environment recognition sensor outputs inaccurate lane line information.

[0006] Therefore, in one aspect, the vehicle control device according to the present invention includes: a memory unit that stores lane information including the position and attitude of the host vehicle relative to the host vehicle's driving lane, which is acquired by an external environment recognition sensor; driving behavior information regarding the driving behavior of the host vehicle; and road information including the curvature of the driving lane, from the present time up to a predetermined time in the past; a deviation calculation unit that calculates the deviation between odometry information calculated from the lane information, the driving behavior information, and the road information stored in the memory unit, and information based on the lane information; an odometry initial value determination unit that determines an initial value of odometry based on the lane information and the deviation; an odometry unit that calculates odometry based on the initial value, the deviation, the lane information, the driving behavior information, and the road information; and a lane keeping control unit that executes lane keeping control of the host vehicle based on either the odometry result by the odometry unit or the lane information.

[0007] Furthermore, the vehicle control method according to the present invention stores, in a memory unit, lane information including the position and attitude of the host vehicle relative to the lane in which the host vehicle is traveling, acquired by an external environment recognition sensor, driving behavior information regarding the driving behavior of the host vehicle, and road information including the curvature of the driving lane, from the present time up to a predetermined time in the past; calculates a deviation between odometry information calculated from the lane information, the driving behavior information, and the road information stored in the memory unit, and information based on the lane information; determines an initial value of the odometry based on the lane information and the deviation; calculates an odometry based on the initial value, the deviation, the lane information, the driving behavior information, and the road information; and performs lane keeping control of the host vehicle based on either the calculated odometry or the lane information.

[0008] According to the present invention, even if the external environment recognition sensor outputs inaccurate lane marking information, highly accurate lane marking information can be used for lane keeping control.

[0009] 1 is an overall configuration diagram showing one aspect of a vehicle control system; FIG. 2 is a flowchart showing a first embodiment of lane keeping control; FIG. 3 is a flowchart showing the first embodiment of lane keeping control; FIG. 4 is a time chart illustrating changes in the deviation degree when passing through an intersection; FIG. 5 is a diagram showing a scene of passing through an intersection; FIG. 6 is a time chart illustrating changes in measured lateral position and estimated lateral position; FIG. 7 is a flowchart showing a second embodiment of lane keeping control; FIG. 8 is a flowchart showing the second embodiment of lane keeping control; FIG. 9 is a flowchart showing a third embodiment of lane keeping control; FIG. 10 is a flowchart showing the third embodiment of lane keeping control; FIG. 11 is a flowchart showing a fourth embodiment of lane keeping control;

[0010]

[0023] Hereinafter, an embodiment of a vehicle control device and a vehicle control method according to the present invention will be described with reference to the drawings. Fig. 1 is an overall configuration diagram showing one aspect of a vehicle control system mounted on a vehicle 10. The vehicle 10 is a four-wheeled automobile equipped with a pair of left and right front wheels 11, 12 and a pair of left and right rear wheels 13, 14.

[0011] Here, front wheels 11, 12 are steerable wheels whose tire angles are changed by a steering device 20 provided in vehicle 10. Steering device 20 is a device that is equipped with a steering actuator and is thereby capable of autonomously steering the steerable wheels. Specifically, steering device 20 is a steer-by-wire system in which a steering operation input member such as a steering wheel is mechanically separated from the steerable wheels, or an electric power steering device in which a steering operation input member and the steerable wheels are mechanically connected and which is equipped with a steering actuator such as a motor that generates a steering force.

[0012] The vehicle 10 also includes a sensor unit 30 and a vehicle control device 40 having a lane keeping control function. The lane keeping function is a driving assistance function that assists the vehicle 10 in preventing it from deviating from its lane, and the vehicle control device 40 controls the steering angle of the front wheels 11, 12 to maintain the lane, as will be described later. The sensor unit 30 detects external information about the vehicle 10 and the driving behavior of the vehicle 10, and includes, for example, an external environment recognition sensor 31, a yaw rate sensor 32, a vehicle speed sensor 33, a GPS (Global Positioning System) receiving unit 34, a steering angle sensor 35, a lateral G sensor 36, and the like.

[0013] The external environment recognition sensor 31 is a device that acquires external information about the vehicle 10 (host vehicle), in other words, information about the driving environment of the road on which the vehicle 10 is traveling, and includes, for example, a camera, radar, LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging), etc. The information about the driving environment of the road acquired by the external environment recognition sensor 31 includes information about lane markers that separate lanes, such as white lines painted on the road surface, and lane information including the position and attitude of the vehicle 10 with respect to the lane in which the vehicle 10 is traveling.

[0014] Furthermore, the yaw rate sensor 32 detects the yaw rate of the vehicle 10, the vehicle speed sensor 33 detects the traveling speed of the vehicle 10 (hereinafter also referred to as vehicle speed), the steering angle sensor 35 detects the steering angle of the steered wheels of the vehicle 10, and the lateral G sensor 36 detects the lateral G (lateral acceleration) of the vehicle 10. The yaw rate, vehicle speed, steering angle, and lateral G are information related to the traveling behavior of the vehicle 10. Furthermore, the GPS receiver 34 receives signals from GPS satellites to measure the latitude and longitude of the position of the vehicle 10, i.e., the vehicle's position.

[0015] The vehicle control device 40 is an electronic control device equipped with a computer as a control unit, and acquires various detection signals from the sensor unit 30 and outputs a steering command for keeping the vehicle in the lane to the steering actuator of the steering device 20. Here, the vehicle control device 40 performs lane keeping control using information on the position and attitude of the vehicle 10 with respect to the traveling lane based on the recognition results of the marking lines by the external environment recognition sensor 31, but if the detection accuracy of the marking lines by the external environment recognition sensor 31 decreases, the vehicle control device 40 performs lane keeping control using information on the position and attitude of the vehicle 10 with respect to the traveling lane obtained by odometry (self-position estimation).

[0016] The vehicle control device 40 has, as functional units for lane keeping control, a section line recognition unit 41, a behavior measurement unit 42, a road information acquisition unit 43, a memory unit 44, an odometry unit 45, a deviation calculation unit 46, an odometry initial value determination unit 47, a lane keeping control unit 48, and an actuator control unit 49. The section line recognition unit 41 recognizes the section lines of the lane in which the vehicle is traveling based on information measured by the external environment recognition sensor 31, thereby measuring the position and attitude of the vehicle 10 relative to the traveling lane, and outputs lane information including the position and attitude of the vehicle 10 relative to the traveling lane.

[0017] The behavior measurement unit 42 measures the yaw rate, vehicle speed, steering angle, lateral G, and vehicle position of the vehicle 10 based on output signals from the yaw rate sensor 32, vehicle speed sensor 33, GPS receiver 34, steering angle sensor 35, lateral G sensor 36, etc. The road information acquisition unit 43 acquires information such as road curvature used for odometry correction from the position information of the vehicle 10 obtained by the GPS receiver 34 and map information. The road information acquisition unit 43 can acquire road information from an external source using road-to-vehicle communication, etc.

[0018] The storage unit 44 stores in chronological order in the memory the lane information including the position and attitude of the vehicle 10 relative to the driving lane output by the section line recognition unit 41, driving behavior information regarding the driving behavior of the vehicle 10 measured by the behavior measurement unit 42, and road information including road curvature information acquired by the road information acquisition unit 43, which are acquired at predetermined intervals from the present to a predetermined time in the past. The odometry unit 45 performs odometry to estimate the position and attitude of the vehicle 10 relative to the current driving lane by using past lane information as an initial value and accumulating subsequent driving behavior, and outputs odometry information including estimated values ​​of the position and attitude of the vehicle 10 relative to the driving lane.

[0019] The deviation calculation unit 46 calculates the deviation (deviation≧0) between the odometry information and the lane information from the deviation amount between the estimated position and the measured position and / or the deviation amount between the estimated attitude and the measured attitude. Specifically, the deviation calculation unit 46 can set the deviation to a larger value as the absolute value of the position error, which is the difference between the position of the vehicle 10 with respect to the lane of the vehicle 10 obtained from the odometry information (estimated position) and the position of the vehicle 10 with respect to the lane of the vehicle 10 included in the lane information (measured position), increases. Note that the deviation calculation unit 46 calculates the position error as, for example, the difference between the center of the lane and the lateral position of the vehicle 10.

[0020] Furthermore, the deviation calculation unit 46 can set the deviation to a larger value as the absolute value of the attitude error, which is the difference between the attitude of the vehicle 10 with respect to the lane in which the vehicle 10 is traveling obtained from the odometry information (estimated attitude) and the attitude of the vehicle 10 with respect to the lane in which the vehicle 10 is traveling included in the lane information (measured attitude), becomes larger. Note that the deviation calculation unit 46 obtains the attitude error as, for example, the difference in the yaw angle of the vehicle 10 with respect to the lane marking of the vehicle 10. Furthermore, the deviation calculation unit 46 can set the deviation from both the position error (lateral position error) and the attitude error (yaw angle error).

[0021] The odometry initial value determination unit 47 is a functional unit that determines lane information to be used as an initial value for the odometry when the deviation degree increases, that is, when the reliability of the lane information from the external environment recognition sensor 31 decreases and the system transitions to lane keeping control based on the odometry information. Here, the odometry initial value determination unit 47 performs a retroactive search that goes back in time until the deviation degree becomes equal to or less than a threshold, and determines the lane information when the deviation degree becomes equal to or less than the threshold as the initial value for the odometry.

[0022] The lane keeping control unit 48 sets a command for the steering angle (tire angle) of the steered wheels (front wheels 11, 12) so that the vehicle 10 keeps traveling near the center of the traveling lane or so that the vehicle 10 does not deviate from the traveling lane, based on either the odometry information (in other words, the odometry result) or the lane information from the external environment recognition sensor 31. In other words, the lane keeping control unit 48 determines whether the lane information from the external environment recognition sensor 31 is reliable based on the degree of deviation, and if the lane information is reliable (in other words, if it is determined that execution of odometry is unnecessary), it performs lane keeping control using the lane information from the external environment recognition sensor 31, and if the lane information is unreliable (in other words, if it is determined that execution of odometry is necessary), it performs lane keeping control using the odometry information.

[0023] The actuator control unit 49 then obtains a steering angle command (in other words, a lane keeping control command) from the lane keeping control unit 48, and performs driving assistance by controlling a steering actuator (steering motor) in the steering device 20 that generates a steering force that changes the steering angle of the front wheels 11, 12.

[0024] The lane keeping control performed by the vehicle control device 40 will be described in more detail below. The flowcharts in Figures 2 and 3 show a first embodiment of the procedure for lane keeping control (vehicle control method) performed by the vehicle control device 40. In step S101, the vehicle control device 40 reads road information including vehicle speed and yaw rate information, which are driving behavior information of the vehicle 10, lane information (information on the position and attitude of the vehicle 10 with respect to the driving lane), obtained by the external environment recognition sensor 31, and the curvature of the driving lane (road curvature) obtained by referring to map information based on the vehicle's position.

[0025] The lane information obtained by the external environment recognition sensor 31 is not limited to lane information based on section lines detected by a camera, and may be lane information based on section lines detected by LiDAR. Also, instead of detecting dividing lines such as white lines painted on the road surface by the external environment recognition sensor 31, the external environment recognition sensor 31 can detect road structures such as guardrails and curbs to obtain lane information.

[0026] Next, in step S102, the vehicle control device 40 stores in memory in chronological order the driving behavior information, lane information, and road information of the vehicle 10 that were read in at each predetermined calculation cycle in step S101 within a period from the present to a predetermined time in the past. Note that the period for storing the lane information, driving behavior information, and road information may be at least a period appropriate for a retrospective search for the initial values ​​of the odometry, that is, at least a period of time expected to allow a search for an appropriate initial value.

[0027] Next, in step S103, the vehicle control device 40 determines whether to turn off the odometry execution flag by determining whether all of the following three conditions are met: First condition: The odometry execution flag is on. Second condition: The external environment recognition sensor 31 has redetected the lane marking. Third condition: The deviation degree is smaller than a predetermined value and continues for a predetermined time or longer.

[0028] The odometry implementation flag is set to ON when lane keeping control is performed using odometry information (odometry result), and is set to OFF when lane keeping control is performed using lane information obtained by the external environment recognition sensor 31. Therefore, the process in step S103 is a process for determining whether or not to return from lane keeping control using odometry information to lane keeping control using lane information obtained by the external environment recognition sensor 31.

[0029] If all three of the above conditions are met, the vehicle control device 40 turns off the odometry implementation flag in step S104. In other words, when the vehicle control device 40 is using the odometry information for lane keeping control, if the external environment recognition sensor 31 detects a dividing line, the deviation is stable and small, and the vehicle control device 40 determines that the reliability of the recognition result by the external environment recognition sensor 31 is sufficiently high, the vehicle control device 40 returns to lane keeping control using the lane information from the external environment recognition sensor 31.

[0030] On the other hand, if any one of the above three conditions is not satisfied, the vehicle control device 40 bypasses step S104 and proceeds to step S105. Therefore, when the odometry execution flag is on, if at least one of the second condition and the third condition is not satisfied, the odometry execution flag is kept on.

[0031] Furthermore, by setting the third condition, "the deviation degree remains smaller than a predetermined value for a predetermined period of time or more," as the condition for turning off the odometry implementation flag, in cases where inaccurate lane information is obtained immediately after the external environment recognition sensor 31 re-detects the lane markings, lane keeping control based on the odometry information (in other words, the odometry implementation flag is turned on) can be continued, and lane keeping can be achieved with high accuracy without being affected by inaccurate lane information.

[0032] In step S105, the vehicle control device 40 determines whether the odometry execution flag is off or on. If the odometry execution flag is off, that is, if lane keeping control is being performed using lane information from the external environment recognition sensor 31, the vehicle control device 40 proceeds to step S106 (see FIG. 3).

[0033] In step S106, the vehicle control device 40 calculates the degree of deviation between the odometry information and the lane information from a position error, which is the difference between the position information included in the odometry information and the position information included in the lane information, and / or an attitude error, which is the difference between the attitude information included in the odometry information and the attitude information included in the lane information. Note that the position information is calculated, for example, as a lateral position (amount of lateral deviation) with respect to the lane center, and the attitude information is calculated, for example, as a yaw angle with respect to the lane center (the angle between the front-rear axis of the vehicle and the lane center).

[0034] Here, the vehicle control device 40 performs odometry, which estimates the current position and attitude by setting past lane information (position and attitude) for a predetermined time as initial values ​​and accumulating subsequent vehicle behaviors based on the information saved in step S102. The vehicle control device 40 then calculates a deviation (deviation≧0) from the error between the current position determined by odometry and the position included in the current lane information. The vehicle control device 40 can also calculate the deviation based on an attitude error (yaw angle error) calculated using a procedure similar to that for the position error.

[0035] Furthermore, the vehicle control device 40 can calculate the deviation degree from both the position error (lateral position error) and the attitude error (yaw angle error). When calculating the deviation degree from both the position error (lateral position error) and the attitude error (yaw angle error), the vehicle control device 40 can set a high deviation degree when, for example, both the position error (lateral position error) and the attitude error (yaw angle error) are equal to or greater than a predetermined value.

[0036] Furthermore, the vehicle control device 40 can set the time used as the initial value of the odometry for calculating the deviation degree in step S106 to a time a certain time in the past from the current time, and the higher the vehicle speed, the more lane information from a time in the past can be used as the initial value of the odometry. Since the higher the vehicle speed, the easier it is for the external environment recognition sensor 31 to recognize the lane markings, the vehicle control device 40 can calculate the deviation degree taking into account the ease of recognizing the lane markings by setting the initial value of the odometry to lane information from a time in the past as the vehicle speed increases.

[0037] However, if the odometry simply accumulates (integrates) vehicle behavior, errors in estimating the position and attitude of the vehicle 10 increase if the road on which the vehicle 10 is traveling is curved. Therefore, the vehicle control device 40 corrects the odometry information based on road curvature information. Specifically, the vehicle control device 40 calculates the change in the yaw angle of the road from the previous processing to the current processing, for example, based on the road curvature and the distance traveled by the vehicle 10 from the previous processing to the current processing. Then, by adding up the change in the yaw angle of the road when integrating the yaw rate of the vehicle 10, odometry can be performed that takes the road shape into account.

[0038] In step S107, the vehicle control device 40 determines whether the deviation calculated in step S106 is equal to or greater than a first threshold (first threshold > 0). Here, the deviation equal to or greater than the first threshold indicates that the reliability of the lane information provided by the external environment recognition sensor 31 is low enough that it is unsuitable for use in lane keeping control. Therefore, if the deviation is equal to or greater than the first threshold, the vehicle control device 40 proceeds to step S108, switches the odometry implementation flag from off to on, and transitions to lane keeping control using odometry information.

[0039] In the next step S109, the vehicle control device 40 performs a retroactive search going back in time until the deviation degree becomes equal to or less than a second threshold (first threshold > second threshold > 0), and determines the lane information at time Tr when the deviation degree becomes equal to or less than the second threshold as the initial value of the odometry.The vehicle control device 40 then performs odometry to estimate the current position and attitude by accumulating the driving behavior from the initial value to the present.

[0040] Next, in step S110, the vehicle control device 40 performs lane keeping control based on the odometry information with the lane information at time Tr as the initial value. That is, in step S110, the vehicle control device 40 inputs the odometry information with the lane information at time Tr as the initial value to the lane keeping control unit 48.

[0041] The recognition result immediately before the external environment recognition sensor 31 stops detecting the lane markings is often inaccurate, and the odometry information that uses such inaccurate recognition results as initial values ​​also becomes inaccurate. For this reason, if information obtained by odometry that uses as initial values ​​the recognition result immediately before the external environment recognition sensor 31 stops detecting the lane markings, it may become difficult to maintain driving within the lane.

[0042] Therefore, when the vehicle control device 40 transitions to lane keeping control using odometry information based on the fact that the external environment recognition sensor 31 can no longer detect the lane markings with high accuracy, the accuracy of the odometry information is ensured by setting the initial value of the odometry to the most recent information among past lane information that showed sufficient accuracy. This allows the vehicle to stably maintain driving within the lane during lane keeping control using odometry information.

[0043] On the other hand, if the vehicle control device 40 determines in step S107 that the deviation degree is less than the first threshold and that the reliability of the lane information obtained by the external environment recognition sensor 31 is high, the vehicle control device 40 proceeds to step S111. Then, in step S111, the vehicle control device 40 keeps the odometry implementation flag off and performs lane keeping control based on the lane information obtained by the external environment recognition sensor 31. In other words, in step S111, the vehicle control device 40 inputs the lane information obtained by the external environment recognition sensor 31 to the lane keeping control unit 48.

[0044] Furthermore, if the vehicle control device 40 determines in step S105 (see FIG. 2) that the odometry execution flag is on and that lane keeping control using odometry information is in progress, the process proceeds to step S112, where the vehicle control device 40 updates the position and attitude information input to the lane keeping control unit 48 at the previous time (the time one cycle ago) with the odometry. Then, in the next step S113, the vehicle control device 40 inputs the updated position and attitude information to the lane keeping control unit 48.

[0045] After performing the input process of the position and attitude information with respect to the traveling lane in any of step S110, step S111, and step S113, vehicle control device 40 proceeds to step S114 and calculates a lane keeping control command value. Next, in step S115, vehicle control device 40 operates the steering actuator of steering device 20 in accordance with the lane keeping control command value, thereby controlling the steering angle of front wheels 11, 12 so that vehicle 10 maintains the traveling lane.

[0046] That is, when the deviation is small and it is determined that the lane information from the external environment recognition sensor 31 is reliable, the lane information from the external environment recognition sensor 31 is used for lane keeping control (step S111). After that, when the measurement accuracy of the lane information from the external environment recognition sensor 31 decreases and the deviation increases, the odometry information from the odometry whose initial value has been reset by retroactively is used for lane keeping control (step S110).

[0047] When the measurement accuracy of the lane information by the external environment recognition sensor 31 continues to be low, the previous odometry information is updated with the odometry information and used for lane keeping control (step S113). When the measurement accuracy of the lane information by the external environment recognition sensor 31 is restored and the deviation degree is maintained at a stable low level, the lane keeping control using the lane information by the external environment recognition sensor 31 is resumed (step S111).

[0048] Fig. 4 illustrates an example of a change in the deviation (yaw angle error) when the vehicle 10 passes through an intersection, and Fig. 5 is a diagram showing the road conditions at the intersection where the deviation in Fig. 4 was calculated. There are no dividing lines (white lines) in the intersection shown in Fig. 5, but even before the vehicle 10 enters this intersection without dividing lines (white lines), the lane information provided by the external environment recognition sensor 31 becomes inaccurate and the deviation increases.

[0049] In the example shown in Figure 4, time t1 is the point at which the vehicle 10 passes 20 meters in front of the stop line at the intersection. At this time, the detection information of the lane markings by the external environment recognition sensor 31 is accurate, and the deviation is sufficiently small. Then, as the vehicle 10 enters the intersection, it loses sight of the lane markings at time t4. However, from time t3, before time t4, onwards, the deviation becomes equal to or greater than the first threshold, making it undesirable to use the detection results of the lane markings in lane keeping control. Therefore, the vehicle control device 40 verifies the deviation values ​​going back from time t3, and determines the lane information at time t2, when the deviation becomes equal to or less than the second threshold for the first time, as the initial value of the odometry.

[0050] 6 is a time chart showing the effect of retroactive search of the odometry initial value, with the vertical axis representing the lateral position of the vehicle 10 relative to the lane center. Fig. 6 shows an odometry result OD1 in which the lane information at time t2, when the deviation degree becomes equal to or less than the second threshold, is used as the initial value of the odometry, and an odometry result OD2 in which the lane information immediately before the lane marking is lost at time t4 is used as the initial value.

[0051] Then, at time t5 (see FIG. 5 ) when the vehicle 10 has crossed the intersection and passed through the crosswalk at the intersection, the detection accuracy of the lane markings by the external environment recognition sensor 31 is restored, so the deviation between the detection result of the external environment recognition sensor 31 and the odometry result at this time t5 represents the accuracy of the odometry. Here, the odometry result OD1 obtained by performing a backward search of the initial value approximates the detection result of the lane markings by the external environment recognition sensor 31 at time t5.

[0052] In contrast, the odometry result OD2, which uses the lane information immediately before the lane marking was lost as its initial value, deviates significantly from the lane marking detection result by the external environment recognition sensor 31 at time t5. In other words, Figure 6 shows that performing a backward search of the odometry initial value improves the accuracy of the odometry. Therefore, even if the external environment recognition sensor 31 outputs inaccurate lane marking information, the vehicle control device 40 can use the highly accurate lane marking information for lane keeping control, and can stably maintain the vehicle 10 traveling within the lane.

[0053] The flowcharts in Figures 7 and 8 show a second embodiment of the procedure for lane keeping control (vehicle control method) performed by the vehicle control device 40. The second embodiment shown in the flowcharts in Figures 7 and 8 differs from the first embodiment shown in the flowcharts in Figures 2 and 3 in the method for calculating the degree of deviation between the odometry information and the lane information in step S206. Here, steps S201 to S205 and steps S207 to S215 other than step S206 are similar to steps S101 to S105 and steps S107 to S115 described above, and therefore detailed description thereof will be omitted.

[0054] In step S206, the vehicle control device 40 calculates the deviation degree between the odometry information and the lane information using the lateral speed, which is the derivative of the lateral position with respect to the lane center, and / or the yaw rate, which is the derivative of the yaw angle with respect to the lane center. Specifically, the vehicle control device 40 can calculate the deviation degree based on the difference (lateral speed difference) between the current lateral speed obtained by time-differentiating the lateral position of the vehicle 10 with respect to the lane center obtained by the external environment recognition sensor 31, and the lateral speed obtained by time-differentiating the lateral position of the vehicle 10 obtained by odometry using lane information from a predetermined time ago as the initial value. Alternatively, instead of using the lateral speed obtained by time-differentiating the lateral position of the vehicle 10 obtained by odometry using lane information from a predetermined time ago as the initial value, the deviation degree can also be calculated by using the lateral speed calculated by integrating the lateral G of the vehicle 10. When calculating the lateral speed by integrating the lateral G, the detection value by the lateral G sensor 36, the lateral G calculated from the vehicle speed and the yaw rate, or the like can be used. The yaw rate may be a value detected by the yaw rate sensor 32 or a yaw rate calculated from the steering angle and vehicle speed.

[0055] The vehicle control device 40 can also calculate the deviation degree based on the difference (yaw rate difference) between the current yaw rate obtained by time-differentiating the yaw angle of the vehicle 10 with respect to the lane center obtained by the external environment recognition sensor 31 and the yaw rate obtained by time-differentiating the yaw angle of the vehicle 10 obtained by odometry using lane information from a predetermined time ago as the initial value. Note that the deviation degree can also be calculated using the detection value by the yaw rate sensor 32 or a yaw rate calculated from the steering angle and vehicle speed, instead of the yaw rate obtained by time-differentiating the yaw angle of the vehicle 10 obtained by odometry using lane information from a predetermined time ago as the initial value. The vehicle control device 40 can also calculate the deviation degree from both the difference from the lateral speed and the difference from the yaw rate. For example, when both the difference from the lateral speed and the difference from the yaw rate are equal to or greater than a predetermined value, the deviation degree can be set to a high value.

[0056] As described above, according to the second embodiment, the degree of deviation between the odometry information and the lane information obtained by the external environment recognition sensor 31 is calculated using the lateral speed (in other words, the rate of change of the lateral position), which is the differential value of the lateral position with respect to the lane center, and / or the yaw rate (in other words, the rate of change of the yaw angle), which is the differential value of the yaw angle with respect to the lane center. Therefore, compared to the first embodiment in which the degree of deviation is calculated from a position error or an attitude error, the occurrence of deviation can be determined at an earlier timing, and lane keeping control using the odometry result can be started earlier, making it possible to responsively deal with a decrease in lane keeping accuracy due to lane information with reduced reliability.

[0057] 9 and 10 show a third embodiment of the procedure for lane keeping control (vehicle control method) performed by the vehicle control device 40. In the third embodiment shown in the flowcharts of FIGS. 9 and 10, the method of setting lane information as an initial value for odometry in step S309 differs from the calculation method in step S106 of the first embodiment shown in the flowcharts of FIGS. 2 and 3. Here, steps S301 to S305 and steps S307 to S315 other than step S309 are similar to steps S101 to S105 and steps S107 to S115, and therefore detailed description thereof will be omitted.

[0058] After calculating the deviation degree from the position error and / or the attitude error in step S306, the vehicle control device 40 determines in step S307 whether the deviation degree is equal to or greater than a third threshold value (third threshold value>0).

[0059] If the deviation degree is equal to or greater than the third threshold, the vehicle control device 40 sets the odometry execution flag to ON in step S308, and then proceeds to step S309. Then, in step S309, the vehicle control device 40 determines the lane information at the time when the deviation degree becomes equal to or greater than the third threshold, in other words, the lane information when the deviation degree switches from being below the third threshold to being above the third threshold, as the initial value of the odometry.

[0060] In other words, after the deviation degree reaches or exceeds the third threshold, the deviation degree continues to increase, and there is a possibility that a period will come when the lane information cannot be used for lane keeping control. Therefore, when the deviation degree exceeds the third threshold, the lane information at that time, i.e., lane information that has a certain level of reliability, is determined as the initial value of the odometry. This allows the lane information when the deviation degree is equal to or less than the third threshold to be used as the initial value of the odometry, and improves the accuracy of the odometry compared to when the lane information immediately before the external environment recognition sensor 31 stops detecting the dividing line is used as the initial value of the odometry, thereby improving the accuracy of lane keeping at intersections, for example.

[0061] 11 and 12 show a fourth embodiment of the procedure for lane keeping control (vehicle control method) performed by the vehicle control device 40. In the fourth embodiment shown in the flowcharts of FIGS. 11 and 12, the method for calculating the deviation degree is the same as in the second embodiment, and the method for determining the initial value of the odometry is the same as in the third embodiment. Therefore, the processing from step S406 for calculating the deviation degree to step S409 for determining the initial value of the odometry will be mainly described, and detailed descriptions of the other steps S401 to S405 and steps S410 to S415 will be omitted.

[0062] In step S406, the vehicle control device 40 calculates the degree of deviation between the odometry information and the lane information using the lateral speed, which is a differential value of the lateral position with respect to the lane center, and / or the yaw rate, which is a differential value of the yaw angle with respect to the lane center. Then, in step S407, the vehicle control device 40 determines whether the degree of deviation based on the lateral speed and / or the yaw rate is equal to or greater than a third threshold value.

[0063] If the deviation is equal to or greater than the third threshold, the vehicle control device 40 sets the odometry execution flag to ON in step S408, and then proceeds to step S409. In step S409, the vehicle control device 40 determines the lane information when the deviation is equal to or greater than the third threshold as the initial value of the odometry.

[0064] The technical ideas described in the above embodiments can be used in appropriate combinations as long as no contradictions arise. Furthermore, although the contents of the present invention have been specifically described with reference to preferred embodiments, it is obvious that a person skilled in the art can adopt various modified embodiments based on the basic technical ideas and teachings of the present invention.

[0065] For example, instead of transitioning to lane keeping control using odometry results based on a comparison between the deviation degree and a threshold value, the system may transition to lane keeping control using odometry results based on a comparison between the rate of increase of the deviation degree and a speed threshold value.Furthermore, the system may use both a transition determination based on a comparison between the deviation degree and a threshold value and a transition determination based on a comparison between the rate of increase of the deviation degree and a speed threshold value.

[0066] Furthermore, in determining whether to return to lane keeping control using lane information from the external environment recognition sensor 31 in step S103, if a predetermined time or more has elapsed without the third condition being satisfied, that is, "the state in which the deviation degree is smaller than a predetermined value continued for a predetermined time or more," the vehicle control device 40 can forcibly return to lane keeping control using lane information from the external environment recognition sensor 31. Furthermore, the lane keeping control may be an alert control that turns on a warning light or warns the driver with an alarm when the vehicle 10 is about to deviate from its driving lane.

[0067] 10...vehicle, 20...steering device, 30...sensor unit, 31...external environment recognition sensor, 40...vehicle control device, 41...section marking recognition unit, 42...behavior measurement unit, 43...road information acquisition unit, 44...storage unit, 45...odometry unit, 46...deviation degree calculation unit, 47...odometry initial value determination unit, 48...lane keeping control unit, 49...actuator control unit

Claims

1. A vehicle control device comprising: a memory unit that stores lane information including the position and attitude of the host vehicle relative to the host vehicle's driving lane, acquired by an external environment recognition sensor, driving behavior information regarding the driving behavior of the host vehicle, and road information including the curvature of the driving lane, from the present time up to a predetermined time in the past; a deviation calculation unit that calculates the deviation between odometry information calculated from the lane information, the driving behavior information, and the road information stored in the memory unit, and information based on the lane information; an odometry initial value determination unit that determines an initial value of odometry based on the lane information and the deviation; an odometry unit that calculates odometry based on the initial value, the deviation, the lane information, the driving behavior information, and the road information; and a lane keeping control unit that executes lane keeping control of the host vehicle based on either the odometry result by the odometry unit or the lane information.

2. A vehicle control device according to claim 1, wherein, when the deviation degree exceeds a first threshold, the odometry initial value determination unit determines, as the initial value, the lane information at a past time when the deviation degree was below a second threshold that is smaller than the first threshold.

3. A vehicle control device according to claim 1, wherein the odometry initial value determination unit determines the lane information at that time as the initial value when the deviation degree exceeds a third threshold value.

4. A vehicle control device as described in claim 1, wherein the deviation calculation unit calculates the deviation from at least one of: a position error obtained from the position of the host vehicle relative to the host vehicle's traveling lane, obtained from the odometry information, and the position of the host vehicle relative to the host vehicle's traveling lane, included in the lane information; and an attitude error obtained from the host vehicle's attitude relative to the host vehicle's traveling lane, obtained from the odometry information, and the attitude of the host vehicle relative to the host vehicle's traveling lane, included in the lane information.

5. A vehicle control device according to claim 1, wherein the deviation calculation unit determines the deviation from at least one of: a lateral speed difference obtained from the lateral speed included in the driving behavior information and the lateral speed obtained by time-differentiating the lateral position of the host vehicle relative to the host vehicle's driving lane included in the lane information; and a yaw rate difference obtained from the yaw rate included in the driving behavior information and the yaw rate obtained by time-differentiating the yaw angle of the host vehicle's attitude relative to the host vehicle's driving lane included in the lane information.

6. A vehicle control device as described in claim 1, wherein the lane keeping control unit, when it is determined from the odometry result that execution of the odometry is unnecessary, executes the lane keeping control based on the lane information acquired by the external environment recognition sensor, and when it is determined from the odometry result that execution of the odometry is necessary, executes the lane keeping control based on the odometry result.

7. A vehicle control method executed by a control unit mounted on a vehicle, comprising: storing in a memory unit lane information including the position and attitude of the host vehicle relative to the lane in which the host vehicle is traveling, acquired by an external environment recognition sensor, driving behavior information regarding the driving behavior of the host vehicle, and road information including the curvature of the driving lane, from the present time up to a predetermined time in the past; calculating a deviation between odometry information calculated from the lane information, the driving behavior information, and the road information stored in the memory unit, and information based on the lane information; determining an initial value for odometry based on the lane information and the deviation; calculating odometry based on the initial value, the deviation, the lane information, the driving behavior information, and the road information; and executing lane keeping control of the host vehicle based on either the calculated odometry or the lane information.

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