Vehicle control method and vehicle control device

Abstract

In this vehicle control method, a controller (16) is controlled so as to execute: vehicle speed determination processing (S2) of determining whether or not a speed of an own vehicle decreases under a predetermined speed threshold value; lateral deviation detection processing (S10) of detecting lateral deviation of the own vehicle with respect to a traffic lane center or a traffic lane boundary; target track generation processing (S13) of generating, when determination has been made that the vehicle speed decreases under the speed threshold value, a first target travelling track of the own vehicle so as to suppress change in lateral deviation after a vehicle-speed decreased point in time, which is a point in time when a vehicle speed decreases under the speed threshold value; object-to-avoid detection processing (S1) of detecting an object to avoid for the own vehicle to avoid; and avoidance processing (S14) of avoiding the object to avoid by adjusting deceleration of the own vehicle while travelling along the first target travelling track after the vehicle-speed decreased point in time.

Description

[Technical field]

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

[0002] For example, Patent Document 1 listed below describes a driving control device that causes a host vehicle to travel while avoiding objects around the host vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 024315 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if a large change in steering angle occurs when automatically avoiding an object, the steering wheel may move significantly, causing an uncomfortable feeling to the occupants. An object of the present invention is to suppress excessive changes in steering angle that occur when automatically avoiding an object. [Means for solving the problem]

[0005] A vehicle control method according to one aspect of the present invention includes a process for detecting a vehicle speed reduction point when the vehicle speed of the host vehicle decreases below a predetermined speed threshold, a process for detecting a lateral deviation of the host vehicle with respect to a lane center or a lane boundary line, a process for generating a first target driving trajectory of the host vehicle so as to maintain the lateral deviation detected at the time when the vehicle speed decreases, and a process for detecting an object to be avoided that the host vehicle should avoid. By suppressing steering control that reduces the degree of approach of the host vehicle to the object to be avoided when it is determined that the vehicle speed will decrease below the speed threshold compared to when it is not determined that the vehicle speed will decrease below the speed threshold, After the vehicle speed is reduced, the controller is caused to execute a process of adjusting the acceleration / deceleration of the host vehicle while traveling along the first target traveling trajectory to avoid the object to be avoided. Effect of the Invention

[0006] According to the present invention, it is possible to suppress excessive changes in steering angle that occur when automatically avoiding an object. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a vehicle control device according to an embodiment; [Figure 2A] FIG. 1 is an explanatory diagram of a problem with conventional vehicle control. [Figure 2B] FIG. 2 is an explanatory diagram of an example of a vehicle control method according to an embodiment; [Diagram 3] 2 is a block diagram illustrating an example of a functional configuration of a controller illustrated in FIG. 1. [Figure 4A] FIG. 11 is an explanatory diagram of an example of a target travel trajectory when the speed is not decreasing. [Figure 4B] FIG. 11 is an explanatory diagram of an example of a target driving trajectory in a speed reduction state. [Figure 4C] 11A and 11B are diagrams illustrating an example of object avoidance control in a speed decreasing state. [Diagram 5] 4 is a flowchart of an example of a vehicle control method according to an embodiment. [Figure 6] 11 is a flowchart of a first example of a speed reduction state detection process. [Figure 7] 13 is a flowchart of a second example of a speed reduction state detection process. [Figure 8] 13 is a flowchart of a third example of a speed reduction state detection process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (composition) FIG. 1 is a diagram showing an example of a schematic configuration of a vehicle equipped with a vehicle control device according to an embodiment. The host vehicle 1 includes a vehicle control device 10 that controls the traveling of the host vehicle 1. The vehicle control device 10 detects the traveling environment around the host vehicle 1 using a sensor, and supports the traveling of the host vehicle 1 based on the surrounding traveling environment. The traveling support control of the host vehicle 1 by the vehicle control device 10 may include, for example, autonomous traveling control that automatically drives the host vehicle 1 without the involvement of a driver. In addition, the traveling support control by the vehicle control device 10 may include driving support control that partially controls the steering angle, driving force, or braking force of the host vehicle 1 to support the driver of the host vehicle 1.

[0009] The vehicle control device 10 includes an object sensor 11, a vehicle sensor 12, a positioning device 13, a map database (map DB) 14, a navigation device 15, a controller 16, and an actuator 17. The object sensor 11 includes a plurality of different types of object detection sensors mounted on the host vehicle 1, such as a laser radar, a millimeter wave radar, a sonar, a camera, and a LIDAR, for detecting objects around the host vehicle 1.

[0010] The vehicle sensor 12 detects various information (vehicle signals) obtained from the host vehicle 1. The vehicle sensor 12 includes, for example, a vehicle speed sensor, a wheel speed sensor, a three-axis acceleration sensor, a steering angle sensor that detects a steering angle, a gyro sensor that detects an angular velocity generated in the host vehicle 1, a yaw rate sensor that detects a yaw rate, an accelerator sensor that detects an accelerator opening degree of the host vehicle, and a brake sensor that detects an amount of brake operation by the driver.

[0011] The positioning device 13 includes a global positioning system receiver and receives radio waves from multiple navigation satellites to measure the current position of the vehicle 1. The global positioning system receiver may be, for example, a global positioning system receiver. The positioning device 13 may be, for example, an inertial navigation system. The map database 14 may store high-precision map data (hereinafter simply referred to as "high-precision map") suitable as a map for autonomous driving. High-precision maps are map data with higher precision than map data for navigation (hereinafter simply referred to as "navigation map"), and include lane-by-lane information that is more detailed than road-by-road information. For example, lane-by-lane information includes lane node information indicating reference points on lane reference lines (e.g., lane center lines) and lane link information indicating lane section configurations between lane nodes. Lane node information includes lane node identification numbers, position coordinates, the number of connected lane links, and identification numbers of connected lane links. Lane link information includes lane link identification numbers, lane type, lane width, lane boundary type, lane shape, lane division shape, and lane reference line shape.

[0012] The navigation device 15 recognizes the current position of the vehicle by the positioning device 13, and obtains map information for the current position from the map database 14. The navigation device 15 sets a route (hereinafter sometimes referred to as a "navigation route") on a road-by-road basis to the destination input by the occupant, and provides road guidance to the occupant along this navigation route. The navigation device 15 also outputs information about the navigation route to the controller 16. The controller 16 may automatically drive the vehicle to travel along the navigation route during autonomous driving control.

[0013] The controller 16 is an electronic control unit (ECU) that controls the running of the host vehicle 1. The controller 16 includes a processor 20 and peripheral components such as a storage device 21. The processor 20 may be, for example, a CPU or an MPU. The storage device 21 may include a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The storage device 21 may include a register, a cache memory, and memories such as a ROM and a RAM used as a main storage device. The functions of the controller 16 described below are realized, for example, by the processor 20 executing a computer program stored in the storage device 21. The controller 16 may be formed of dedicated hardware (for example, a programmable logic device such as an FPGA) for executing each information processing described below.

[0014] The actuator 17 operates the steering wheel, accelerator opening, and brake device of the host vehicle 1 in response to a control signal from the controller 16 to generate vehicle behavior of the host vehicle 1. The actuator 17 includes a steering actuator that controls the steering angle of the host vehicle 1, an accelerator opening actuator that controls the accelerator opening of the host vehicle 1, and a brake control actuator that controls the braking operation of the brake device.

[0015] Next, a description will be given of an example of control of the host vehicle 1 by the controller 16. Fig. 2A is an explanatory diagram of a problem with conventional vehicle control. Now, assume that a target travel trajectory of the host vehicle 1 is set along the lane center 2c of the lane 2, and the host vehicle 1 travels along this target travel trajectory and stops at a target stop position P1. The target stop position P1 may be, for example, a preceding vehicle 3 or a position a predetermined distance before a stop line (not shown). Parked vehicles 4a and 4b exist on the lane 2 ahead of the host vehicle 1 as objects to be avoided by the host vehicle 1. For this reason, the host vehicle 1 is caused to travel so as to approach the target travel trajectory along the lane center 2c while maintaining a distance from the parked vehicles 4a and 4b. For example, the host vehicle 1 travels along a trajectory T. In the example of trajectory T, in order to maintain a distance from parked vehicle 4a, the vehicle travels with a deviation in the lane width direction (hereinafter sometimes referred to as "lateral deviation") from lane center 2c (i.e., target driving trajectory) as shown by arrow 5a. After passing parked vehicle 4a, the vehicle steers to the left to eliminate the lateral deviation as shown by arrow 5b. Also, in order to maintain a distance from parked vehicle 4b just before target stop position P1, the vehicle steers to the left as shown by arrow 5c, generating a lateral deviation from the target driving trajectory. After passing parked vehicle 4b, the vehicle steers to the right to eliminate the lateral deviation as shown by arrow 5d.

[0016] In this way, when steering to eliminate lateral deviation after passing the parked vehicle 4b, the change in steering angle may be large. For example, when the host vehicle 1 is stopped at the target stop position P1, the vehicle speed of the host vehicle 1 becomes extremely low (for example, less than 2.0 m / s). At such an extremely low speed, the change in steering angle required to eliminate lateral deviation may be large. This is because at an extremely low speed where the lateral speed is small, the turning radius of curvature becomes small. As a result, the steering wheel may move significantly, causing discomfort to the occupants.

[0017] 2B is an explanatory diagram of an example of a vehicle control method according to an embodiment. In the vehicle control method according to the embodiment, it is determined whether the vehicle speed of the host vehicle 1 will decrease below a predetermined speed threshold. In addition, a lateral deviation Yoff of the host vehicle 1 with respect to the lane center 2c is detected. A lateral deviation Yoff of the host vehicle 1 with respect to the lane boundary line of the lane 2 may be detected. When it is determined that the vehicle speed will decrease below the speed threshold, a target driving trajectory X of the host vehicle is generated so as to suppress a change in the lateral deviation Yoff after the vehicle speed decrease time point T1, which is the time point at which the vehicle speed decreases below the speed threshold. For example, a vehicle speed reduction time point T1 may be detected or estimated, and a lateral deviation Yoff of the host vehicle 1 with respect to the lane center 2c or a lane boundary line at the vehicle speed reduction time point T1 may be detected. Then, a target driving trajectory X of the host vehicle may be generated so as to maintain the lateral deviation Yoff detected at the vehicle speed reduction time point T1. When the host vehicle 1 detects an object to be avoided (a parked vehicle 4b in the example of FIG. 2B), after the vehicle speed reduction time T1, the host vehicle 1 avoids the object by adjusting the deceleration of the host vehicle 1 while traveling along the target traveling trajectory X.

[0018] Therefore, in the period after the vehicle speed decreasing time point T1, lateral movement to avoid the object to be avoided (parked vehicle 4b in the example of FIG. 2B) is suppressed. Therefore, the change in the steering angle to avoid the object to be avoided when the vehicle speed is low can be suppressed. As a result, the rotation of the steering wheel can be suppressed. Also, if the vehicle has avoided an object to be avoided (e.g., a parked vehicle 4a) prior to the vehicle speed reduction time T1, the target travel trajectory X is set to maintain the lateral deviation Yoff at the vehicle speed reduction time T1. This eliminates the need to return to the lateral position within the lane before the avoidance action, thereby suppressing changes in the steering angle when the vehicle is traveling at a low speed. As a result, the rotation of the steering wheel can be suppressed.

[0019] The following describes in detail the functions of the controller 16. Fig. 3 is a block diagram of an example of the functional configuration of the controller 16. The controller 16 includes an object detection unit 30, a vehicle position estimation unit 31, a map acquisition unit 32, a detection integration unit 33, an object tracking unit 34, an in-map position calculation unit 35, and a vehicle control unit 36. The object detection unit 30 detects the positions, postures, sizes, speeds, etc. of objects around the vehicle 1, such as vehicles (cars and motorcycles), pedestrians, obstacles, etc., based on the detection signal from the object sensor 11. The object detection unit 30 outputs a detection result that expresses the two-dimensional position, posture, size, speed, etc. of an object on a zenith diagram (also called a plan view) of the vehicle 1 viewed from the air, for example.

[0020] The vehicle position estimation unit 31 measures the absolute position of the vehicle 1, i.e., the position, attitude, and speed of the vehicle 1 relative to a predetermined reference point, based on odometry using the measurement results by the positioning device 13 and the detection results from the vehicle sensor 12. The map acquisition unit 32 acquires map information indicating the structure of the road on which the vehicle 1 is traveling from the map database 14.

[0021] The detection integration unit 33 integrates the multiple detection results obtained by the object detection unit 30 from each of the multiple object detection sensors, and outputs one two-dimensional position, orientation, size, speed, etc. for each object. Specifically, from the object behavior obtained from each object detection sensor, the most reasonable object behavior that will have the least error is calculated, taking into account the error characteristics of each object detection sensor. Specifically, by using known sensor fusion technology, the detection results obtained from multiple types of sensors are comprehensively evaluated to obtain more accurate detection results. The object tracking unit 34 tracks the object detected by the object detection unit 30. Specifically, based on the detection results integrated by the detection integration unit 33, the object tracking unit 34 verifies (associates) the identity of the object between different times from the behavior of the object output at different times, and predicts the behavior of the object, such as its speed, based on the association.

[0022] The in-map position calculation unit 35 estimates the position and attitude of the host vehicle 1 on the map from the absolute position of the host vehicle 1 obtained by the host vehicle position estimation unit 31 and the map information acquired by the map acquisition unit 32. The in-map position calculation unit 35 also identifies the road on which the host vehicle 1 is traveling, and further identifies the lane 2 on which the host vehicle 1 is traveling on that road and its adjacent lanes 4, and calculates the lateral position of the host vehicle 1 within the lane 2 (vehicle width direction position, in-lane lateral position). The vehicle control unit 36 ​​drives the actuator 17 to control the traveling of the vehicle 1 based on the prediction result of the object behavior by the object tracking unit 34, the calculation result of the position and attitude of the vehicle 1 by the map position calculation unit 35, and input from an occupant (e.g., the driver). The vehicle control unit 36 ​​includes a route setting unit 40, a path generation unit 41, a speed reduction time determination unit 42, and a control command value calculation unit 43.

[0023] The route setting unit 40 sets a target route (hereinafter simply referred to as a "route") for the vehicle 1 to travel on a lane-by-lane basis, based on the current position of the vehicle 1 calculated by the intra-map position calculation unit 35 and the destination input by the occupant (or based on the navigation route set by the navigation device 15). This route is a statically set target route, and is set based on the lane shape of the high-precision map stored in the map database 14 and the shape of the lane boundary line detected by the object sensor 11. For example, the center of the lane of the road along which the vehicle 1 will travel when moving from the current position to the destination may be set as the route.

[0024] The path generating unit 41 judges whether the host vehicle 1 will perform a driving action such as a lane change, and sets a target path (hereinafter, simply referred to as a "path") along which the host vehicle 1 should travel based on the result of the judgment. This path is dynamically set according to the driving action of the host vehicle 1. For example, when the host vehicle 1 is made to change lanes in response to traffic conditions, the path generating unit 41 generates a travel route along which the host vehicle 1 moves from the lane before the lane change to the lane after the lane change based on a vehicle model of the host vehicle 1. On the other hand, when the host vehicle 1 is not made to change lanes, a path that matches the route is generated. The path P generated by the path generating unit 41 may be point sequence data as shown in the following formula (1). P=[P L ,P L+1 ,…,P L+M ]…(1) In addition, P in formula (1) L+M is data on a point on a path M [m] from the current position. The path P is information that represents the shape of the path that the host vehicle 1 should follow, and does not include information on the vehicle speed. L+i is expressed by, for example, position (x, y), orientation (θ), and curvature (κ). Position (x, y) indicates the coordinates in the map coordinate system, and orientation (θ) indicates the path direction (tangent direction) at each point.

[0025] The speed reduction time determination unit 42 determines when the host vehicle 1 starts to decelerate toward the target stop position and the current vehicle speed v of the host vehicle 1 is equal to or lower than a predetermined speed threshold V THThe speed reduction time determination unit 42 detects or estimates a vehicle speed reduction time T1, which is the time when the vehicle speed has decreased to less than 100 km / h. First, the speed reduction time determination unit 42 determines whether or not there is an object ahead of the host vehicle 1 that can be a stopping target. Stopping targets include all objects in front of which the host vehicle 1 should stop, such as a vehicle ahead on the lane 2 in which the host vehicle 1 is traveling, a stop line, a pedestrian, a crosswalk, and the like. If there is an object ahead of the host vehicle 1 that can be a stopping target, the speed reduction time determination unit 42 sets a target stopping position at a position a predetermined distance before the stopping target.

[0026] Next, the speed reduction time determination unit 42 determines whether the host vehicle has started to decelerate toward the target stop position. The speed reduction time determination unit 42 may determine that the host vehicle has started to decelerate toward the target stop position when, for example, the following formula (2) is satisfied. L <v 2 / (2a) …(2) In formula (2), L is the distance from the current position of the host vehicle 1 to the target stop position, v is the current vehicle speed of the host vehicle 1, and a is a predetermined deceleration (set value). The speed reduction time determination unit 42 determines that the host vehicle has started decelerating toward the target stop position when the distance from the current position to the target stop position becomes shorter than the distance required to stop the host vehicle at a constant deceleration a.

[0027] If the above formula (2) is satisfied, the speed reduction time determination unit 42 sets the deceleration start flag Fd to “True” and thereafter does not evaluate (2) and determines that the vehicle is decelerating toward the target stop position until the next deceleration start cancellation condition (A) or (B) is satisfied. (A) After it was determined that deceleration had begun, the host vehicle stopped at the target stopping position. (B) After it was determined that deceleration had begun, the target stopping position was changed or canceled. For example, the preceding vehicle, which was the stopping target, moved forward. The target stopping position was canceled when the traffic light on which the stop line, which was the stopping target, was installed changed from a stop indication (red light) to a proceed indication (green light). When the deceleration start cancellation condition (A) or (B) is satisfied, the speed reduction time determination unit 42 cancels the determination that the host vehicle 1 has started decelerating toward the target stop position, and sets the deceleration start flag Fd to “False.”

[0028] Next, the speed reduction time determination unit 42 determines whether the host vehicle 1 is about to stop. For example, when the current vehicle speed v of the host vehicle 1 is greater than or equal to a predetermined speed threshold V TH If the detected velocity falls below this value, it is determined that the host vehicle 1 is about to stop. When it is determined that the host vehicle 1 is about to stop after it is determined that the host vehicle 1 has started to decelerate toward the target stop position, the speed reduction time determination unit 42 detects a speed reduction state of the host vehicle 1. The speed reduction time determination unit 42 detects the time when the speed reduction state is first detected as the vehicle speed reduction time T1. The speed reduction time determination unit 42 determines whether the current vehicle speed v is greater than or equal to the speed threshold value V based on the current vehicle speed v and the deceleration of the host vehicle 1. TH The time when the vehicle speed v falls below the speed threshold V is estimated after it is determined that the host vehicle 1 has started to decelerate toward the target stop position. TH The time when the vehicle speed falls below this value may be estimated as the vehicle speed decrease time T1. That is, the “speed reduction state” is when the host vehicle 1 starts to decelerate toward the target stop position and the vehicle speed v falls below the speed threshold V TH The "vehicle speed reduction time point T1" is a time point when the vehicle speed v falls below the speed threshold V after the host vehicle 1 starts decelerating toward the target stop position. TH This is the point at which the level drops below

[0029] The speed reduction time determination unit 42 records the deviation of the host vehicle 1 in the lane width direction from the path P at the vehicle speed reduction time T1 as the lateral deviation Yoff. If the path P is generated along the center of the lane, the lateral deviation Yoff is the lateral deviation of the host vehicle 1 from the lane center. The lateral deviation from the lane boundary line may be recorded instead of the lane center. The speed reduction time determination unit 42 sets the recorded flag Fr, which indicates that the lateral deviation Yoff has been recorded, to "True." The speed reduction time determination unit 42 can determine whether or not a speed reduction state has been detected for the first time based on whether the recorded flag Fr is "False" or "True." On the other hand, when it is not determined that deceleration has started or that the vehicle is about to stop, the speed reduction time determination unit 42 does not detect a speed reduction state of the host vehicle 1. At this time, the recorded flag Fr is set to "False."

[0030] Next, the control command value calculation unit 43 calculates a control command value such that the host vehicle 1 moves along the path P generated by the path generation unit 41 while maintaining a distance from surrounding objects. The control command value calculation unit 43 calculates a speed command value for the host vehicle 1 based on the distance to the target stop position, and the relative speed and relative acceleration with respect to the stop target. Then, based on the speed command value and the path P, the control unit 43 calculates the target position, attitude, speed and curvature of the host vehicle at each time t+i×dt (i is an integer from 1 to N) for N steps from the current time t until t+N×dt seconds later, thereby calculating the target driving trajectory X of the host vehicle 1.

[0031] The target travel trajectory X is a sequence of points on a trajectory that represents the future state of the host vehicle 1 for a certain period of time, and is expressed, for example, by the sequence of points given by the following equation (3). X=[X t ,X t+dt ,X t+2dt …,X t+N×dt ]…(3) X t+T is the target state of the vehicle after T seconds, and is expressed by position (x, y), orientation (θ), velocity (v), and curvature (κ). In addition, the control command value calculation unit 43 calculates a predicted trajectory Xp of the vehicle 1. The predicted trajectory Xp is a trajectory that predicts the future state of the vehicle, and is a trajectory that attempts to get as close as possible to the target trajectory while avoiding obstacles using the current position of the vehicle 1 as a base point. The components of each point of the predicted trajectory Xp are the same as the components of each point of the target driving trajectory X.

[0032] An example of a method for calculating the target running trajectory X by the control command value calculation unit 43 will be described below. The control command value calculation unit 43 calculates a point X on the target trajectory at time t+T. t+T The previous point X t+Tーdt By repeating the distance calculation based on t ,X t+dt ,X t+2dt…,X t+N×dt Specifically, the previous point X t+Tーdt The position and orientation of point X after a displacement D along path P from t+T It is calculated as follows. The displacement D is calculated by the following equation (4). D=v t+Tーdt ×dt …(4) v t+Tーdt :Point X of the target trajectory in the previous step t+Tーdt Speed dt: step time

[0033] The control command value calculation unit 43 calculates the point X t+T The speed command value is calculated from the distance from the target stop position. For example, the control command value calculation unit 43 may obtain a speed command value V that minimizes an evaluation function F of the following equation (5) by optimization calculation.

number

[0034] When the speed reduction time determination unit 42 detects a speed reduction state of the host vehicle 1 (i.e., when it is determined that the host vehicle 1 is about to stop after determining that the host vehicle 1 has started to decelerate toward the target stop position), the control command value calculation unit 43 calculates the target travel trajectory X's point X' based on the lateral deviation Yoff at the vehicle speed reduction time T1 as shown in the following equation (6). t+T Correct the following.

number

[0035] The effect of this correction is shown in Figures 4A and 4B. Figure 4A is an explanatory diagram of an example of a target driving trajectory when the vehicle 1 is not in a speed reduction state. In this case, the target trajectory point X is generated so as to be completely along the path P. In the example of Figure 4A, it is generated along the lane center 2C. After avoiding the parked vehicle 4a on the left side, the predicted trajectory Xp is generated so as to return to the lane center 2c. If the vehicle 1 is traveling at an extremely low speed just before the target stop position P1 and turns along the predicted trajectory Xp, the steering wheel may move significantly, as described above, which may cause the occupants to feel uncomfortable. 4B, when the vehicle 1 approaches the target stop position P1 and a speed reduction state is detected, the target travel trajectory X is corrected so as to maintain the lateral deviation Yoff. This allows the vehicle to stop without eliminating the lateral deviation Yoff that occurred when avoiding the parked vehicle 4a, thereby suppressing the movement of the steering wheel.

[0036] Please refer to Fig. 3. The control command value calculation unit 43 performs vehicle control of the host vehicle 1 using the generated target driving trajectory X. In the vehicle control, for example, the steering and vehicle speed of the host vehicle 1 are controlled. In vehicle control, the predicted trajectory Xp of the host vehicle 1 for N×dt seconds is controlled by a control input (acceleration / deceleration command value dV in and steering command value dK in This control can be realized by using a general model predictive control. For example, the control command value calculation unit 43 calculates a predicted trajectory of the host vehicle 1 when a control input U is input to the host vehicle 1 at a discrete time t+T. XP Point Xp t+T and point X on the target trajectory t+TThe control input U at time t+T is calculated so that an evaluation function defined according to the difference between and the degree of approach of the host vehicle 1 to the object to be avoided becomes small. When a speed reduction state of the host vehicle 1 is not detected, the evaluation function J1 at each time t+T is defined as, for example, the following equation (7).

[0037]

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[0038] The first term of the evaluation function J1 is the predicted position Xp t+T increases when the target object i is approaching. A i,t+T is the state quantity Xp t+T is a function of the state quantity Xp t+T is the current state quantity Xp t and a function of the control input U. i,t+T A control input U is calculated to minimize In addition, the second term of J1 is the predicted state Xp t+T and the target running trajectory X t+T The first term is the cost for the difference between U and the target trajectory. The third term is the cost for the absolute value of U. By summing these up to create an evaluation function, a control input is calculated that achieves both avoidance of the object to be avoided (first term), tracking of the target trajectory (second term), and stabilization of the control input (third term).

[0039] Here, when approaching a side object to be avoided (parked vehicle 4b) as shown in FIG. 4C, A i,t+T increases. A i,t+T To reduce this, the predicted position is XPt+T Since it is necessary to shift to the left, the steering command value dK in At this time, if the vehicle 1 is traveling at a very low speed just before the target stop position P1, it is necessary to steer the vehicle 1 to the left. Therefore, the steering command value dK in becomes a large value, which may cause the passengers to feel uncomfortable.

[0040] Therefore, in the present invention, when a speed reduction state of the host vehicle 1 is detected as the host vehicle approaches the target stop position P1, the control input U is calculated by an optimization calculation that minimizes the evaluation function J2 of the following equation (8).

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[0041] Therefore, A' is calculated by optimization. i,t+T No adjustment is made to make the approach degree A' 0. i,t+T relative velocity (vi-v t+T ), when the vehicle is approaching the object to be avoided i, the vehicle speed is adjusted to match that of the object to be avoided i. As a result, the acceleration / deceleration command value dV in is calculated. The control command value calculation unit 43 calculates a control input U that minimizes the evaluation functions J1 and J2. The control command value calculation unit 43 drives the actuator 17 based on the calculated control input U to control the speed and steering angle of the host vehicle 1.

[0042] (operation) FIG. 5 is a flowchart of an example of a vehicle control method according to the embodiment. In step S1, the controller 16 detects objects around the vehicle 1, stop lines, and the vehicle's own position. In step S2, the speed reduction time determination unit 42 performs a speed reduction state detection process.

[0043] 6 is a flowchart of a first example of a speed reduction state detection process. In step S30, the speed reduction time determination unit 42 determines whether the deceleration start flag Fd is "True" or not. If the deceleration start flag Fd is not "True" (S30:N), the process proceeds to step S31. If the deceleration start flag Fd is "True" (S30:Y), the process proceeds to step S36. In step S36, the speed reduction time determination unit 42 determines whether the deceleration start cancellation condition is satisfied. If the deceleration start cancellation condition is not satisfied (S36: N), the process proceeds to step S33. If the deceleration start cancellation condition is satisfied (S36: Y), the process proceeds to step S37. In step S37, the speed reduction time determination unit 42 sets the deceleration start flag Fd to “False.” After that, the process proceeds to step S31.

[0044] In step S31, the speed reduction time determination unit 42 determines whether the host vehicle has started to decelerate toward the target stop position. If deceleration has started (S31: Y), the process proceeds to step S32. If deceleration has not started (S31: N), the process proceeds to step S35. In step S35, the speed reduction time determination unit 42 determines that the host vehicle 1 has not detected a speed reduction state. The speed reduction state detection process then ends. In step S32, the speed reduction time determination unit 42 sets the deceleration start flag Fd to “True.” After that, the process proceeds to step S33.

[0045] In step S33, the speed reduction time determination unit 42 determines whether or not the host vehicle 1 is about to stop. If the host vehicle 1 is not about to stop (S33: N), the process proceeds to step S35, where it is determined that a speed reduction state of the host vehicle 1 has not been detected, and the speed reduction state detection process ends. If the host vehicle 1 is about to stop (S33: Y), the process proceeds to step S34. The speed reduction time determination unit 42 determines that a speed reduction state of the host vehicle 1 has been detected. The speed reduction state detection process then ends.

[0046] See Figure 5. Attitude If it is detected (S3: Y), the process proceeds to step S11. Attitude If not detected (S3: N), the process proceeds to step S4. The speed reduction time determination unit 42 sets the recorded flag Fr to "False." In step S5, the control command value calculation unit 43 initializes a variable i to "1." In step S6, the control command value calculation unit 43 calculates the point X of the target traveling trajectory X at the time t+i×dt. t+i×dt In step S7, the control command value calculation unit 43 calculates the position of the point X t+i×dt In step S8, the control command value calculation unit 43 increments the value of the variable i by 1. In step S9, the control command value calculation unit 43 determines whether the variable i is greater than N. If the variable i is not greater than N (S9: N), the process returns to step S6. If the variable i is greater than N (S9: Y), the process proceeds to step S10.

[0047] In step S10, the control command value calculation unit 43 calculates the control input U by an optimization calculation that reduces the evaluation function J1 in the above equation (7). After that, the process proceeds to step S21. On the other hand, in step S11, the speed reduction time determination unit 42 determines whether or not a speed reduction state has been detected for the first time (i.e., whether or not the recorded flag Fr is "False"). If a speed reduction state has been detected for the first time (S11: Y), the process proceeds to step S12. If a speed reduction state has already been detected ( S11:N), the process proceeds to step S14. In step S12, the speed reduction time determination unit 42 sets the recorded flag Fr to “True.” In step S13, the speed reduction time determination unit 42 records the lateral deviation Yoff. The processes of steps S14 to S16 are the same as the processes of steps S5 to S7.

[0048] In step S17, the control command value calculation unit 43 calculates the lateral deviation Yoff based on the point X t+T Correct the following. In step S18, the control command value calculation unit 43 increments the value of the variable i by 1. In step S19, the control command value calculation unit 43 determines whether the variable i is greater than N. If the variable i is not greater than N (S19: N), the process returns to step S15. If the variable i is greater than N (S19: Y), the process proceeds to step S20. In step S20, the control command value calculation unit 43 calculates the control input U by an optimization calculation that reduces the evaluation function J2 in the above equation (8). After that, the process proceeds to step S21. In step S21, the control command value calculation unit 43 controls the host vehicle 1 with the control input U. In step S22, it is determined whether the ignition key is turned off. If the ignition key is not turned off (S22: N), the process returns to step S1. If the ignition key is turned off (S22: Y), the process ends.

[0049] (Modification) (1) In the above embodiment, when either one of the deceleration start cancellation conditions (A) "the vehicle stops at the target stop position" or (B) "the target stop position is changed or canceled" is satisfied, the speed reduction time determination unit 42 cancels the determination that the vehicle 1 has started decelerating toward the target stop position. Alternatively, the determination of the deceleration start cancellation condition (B) may be omitted as shown in the flowchart of FIG. 7. In step S40, the speed reduction time determination unit 42 determines whether the host vehicle 1 is in a stopped state. If the host vehicle 1 is in a stopped state (S40: Y), the process proceeds to step S41. If the host vehicle 1 is not in a stopped state (S40: N), the process proceeds to step S42. In step S41, the speed reduction time determination unit 42 sets the deceleration start flag Fd to "False." In step S42, the speed reduction time determination unit 42 determines whether or not the deceleration start flag Fd is "True." If the deceleration start flag Fd is "True" (S42: Y), the process proceeds to step S45. If the deceleration start flag Fd is not "True" (S42: N), the process proceeds to step S43. The processes of steps S43 to S47 are the same as the processes of steps S31 to S35 in FIG. 6.

[0050] (2) The determination of the above deceleration start cancellation conditions (A) and (B) is a determination to detect that “deceleration to stop is no longer necessary,” and may be substituted by determining whether or not the following equation (9) is satisfied. L>v 2 / (2a)+L TH …(9) L TH :Judgment margin In other words, after it is determined that the vehicle 1 has started to decelerate toward the target stopping position, the situation changes and the margin to the target stopping position becomes L TH If this occurs, the determination that the host vehicle 1 has started to decelerate toward the target stop position may be cancelled.

[0051] (3) Furthermore, the condition of the above formula (9) and the condition of the above formula (1) may be combined to detect a speed reduction state of the host vehicle 1. Fig. 8 is a flowchart of a third example of the speed reduction state detection process. In step S50, the speed reduction time determination unit 42 determines whether or not the host vehicle 1 is decelerating. The speed reduction time determination unit 42 determines that the host vehicle 1 is decelerating when the following formula (10) is established. L <v 2 / (2a)+L TH …(10) If the host vehicle 1 is decelerating (S50: Y), the process proceeds to step S51. If the host vehicle 1 is not decelerating (S50: N), the process proceeds to step S53. In step S51, the speed reduction time determination unit 42 determines whether or not the host vehicle 1 is about to stop. If the host vehicle 1 is about to stop (S51: Y), the process proceeds to step S52. If the host vehicle 1 is not about to stop (S51: N), the process proceeds to step S53. In step S52, the speed reduction time determination unit 42 determines that a speed reduction state of the host vehicle 1 has been detected. In step S53, the speed reduction time determination unit 42 determines that a speed reduction state of the host vehicle 1 has not been detected. In the determination in step S50 of FIG. 8, the margin L TH The condition for determining whether or not the vehicle is decelerating is loosened accordingly, but when combined with the determination in step S51 of whether or not the vehicle is about to stop, the result is the same as in the above embodiment.

[0052] (4) Furthermore, the threshold value for determining whether the host vehicle 1 is about to stop is the vehicle speed V TH Considering this, in step S50 of FIG. 8, the conditional expression L <V TH 2 / (2a)+L TH In this case, it may be determined whether the vehicle 1 is decelerating or not depending on whether the vehicle speed v of the vehicle 1 is greater than or equal to the threshold value V TH Since the above fact is indirectly taken into consideration, step S51 for determining whether or not the vehicle is about to stop may be omitted.

[0053] (Effects of the embodiment) (1) The controller 16 executes a vehicle speed determination process for determining whether the vehicle speed of the host vehicle will decrease below a predetermined speed threshold; a lateral deviation detection process for detecting a lateral deviation of the host vehicle relative to the center of the lane or a lane boundary line; a target trajectory generation process for generating a first target driving trajectory of the host vehicle so as to suppress change in the lateral deviation after a vehicle speed decrease point at which the vehicle speed decreases below the speed threshold if it is determined that the vehicle speed will decrease below the speed threshold; an avoidance object detection process for detecting an avoidance object that the host vehicle should avoid; and an avoidance process for avoiding the avoidance object by adjusting the deceleration of the host vehicle while driving along the first target driving trajectory after the vehicle speed decrease point. This makes it possible to suppress the change in steering angle that occurs when avoiding an object when the vehicle speed is low, thereby preventing the steering wheel from moving too much and causing discomfort to the occupants.

[0054] (2) The controller 16 may execute a process of setting a target stop position ahead of the vehicle and a process of determining whether the vehicle has started to decelerate toward the target stop position, and may execute a target trajectory generation process and an avoidance process when it determines that the vehicle has started to decelerate toward the target stop position and that the vehicle speed will drop below the speed threshold. This makes it possible to suppress steering angle changes only when the vehicle is stopped at the target stop position.

[0055] (3) After determining that the vehicle has started to decelerate toward the target stop position, if the vehicle stops at the target stop position or the target stop position is changed or canceled, the controller 16 does not execute the target trajectory generation process and the avoidance process. This makes it possible to prevent unnecessary suppression of steering angle changes.

[0056] (4) The controller 16 may execute a process of calculating a required distance for the host vehicle to be stopped at the target stop position with a predetermined deceleration according to the current vehicle speed of the host vehicle, and may determine that the host vehicle has started decelerating toward the target stop position when the distance from the host vehicle to the target stop position is less than a distance threshold value set according to the required distance, and may execute a target trajectory generation process and an avoidance process when it determines that the host vehicle has started decelerating toward the target stop position and that the vehicle speed will fall below a speed threshold value. This makes it possible to determine whether the host vehicle is decelerating toward the target stop position.

[0057] (5) The controller may generate a second target driving trajectory based on the lane shape, and generate a first target driving trajectory by moving a position of the second target driving trajectory in the lane width direction according to the lateral deviation detected at the time when the vehicle speed decreases. This makes it possible to calculate a target driving trajectory that maintains the lateral deviation.

[0058] (6) The controller may execute a process of calculating a control input so as to reduce an evaluation function according to a difference between a predicted position of the host vehicle and a first target driving trajectory when control inputs of acceleration / deceleration and steering angle are input to the host vehicle, and a degree of approach of the host vehicle to the object to be avoided, and the evaluation function evaluated when calculating the control input at the first time may include a term obtained by multiplying the degree of approach when a control input calculated at a second time prior to the first time is input to the host vehicle by the relative speed of the object to be avoided with respect to the host vehicle. This makes it possible to avoid the object to be avoided by adjusting the deceleration. [Explanation of symbols]

[0059] 1... host vehicle, 2... lane, 2c... lane center, 3... preceding vehicle, 4a, 4b... parked vehicles, P1... target stopping position, X... target driving trajectory, Xp... predicted trajectory, Yoff... lateral deviation

Claims

1. a vehicle speed determination process for determining whether or not the vehicle speed of the host vehicle decreases to below a predetermined speed threshold; A lateral deviation detection process for detecting a lateral deviation of the host vehicle relative to a lane center or a lane boundary line; a target trajectory generation process for generating a first target traveling trajectory of the host vehicle so as to suppress a change in the lateral deviation after a vehicle speed reduction point at which the vehicle speed is reduced below the speed threshold when the vehicle speed is determined to be reduced below the speed threshold; an avoidance object detection process for detecting an avoidance object to be avoided by the host vehicle; an avoidance process for avoiding the object to be avoided by adjusting a deceleration of the host vehicle while traveling along the first target traveling path after the vehicle speed has decreased, by suppressing a steering control that reduces a degree of approach of the host vehicle to the object to be avoided when it is determined that the vehicle speed will decrease below the speed threshold, compared to when it is not determined that the vehicle speed will decrease below the speed threshold; A vehicle control method comprising: causing a controller to execute the above steps.

2. The controller: A process of setting a target stop position in front of the host vehicle; a process of determining whether the host vehicle has started to decelerate toward the target stop position; 2. The vehicle control method according to claim 1, further comprising the steps of: executing the target trajectory generation process and the avoidance process when it is determined that the vehicle has started to decelerate toward the target stop position and when it is determined that the vehicle speed will drop below the speed threshold.

3. 3. The vehicle control method according to claim 2, characterized in that, after determining that the host vehicle has started to decelerate toward the target stop position, if the host vehicle stops at the target stop position or if the target stop position is changed or canceled, the controller does not execute the target trajectory generation process and the avoidance process.

4. The controller: Executing a process of calculating a required distance for stopping the host vehicle at the target stop position at a predetermined deceleration according to the current vehicle speed of the host vehicle; When a distance from the host vehicle to the target stop position is less than a distance threshold value set according to the required distance, it is determined that the host vehicle has started decelerating toward the target stop position; When it is determined that the deceleration of the host vehicle toward the target stop position has started and when it is determined that the vehicle speed will decrease to less than the speed threshold, the target trajectory generation process and the avoidance process are executed.

4. The vehicle control method according to claim 2 or 3.

5. The vehicle control method according to any one of claims 1 to 4, characterized in that the controller generates a second target driving trajectory based on a lane shape, and generates the first target driving trajectory by moving a lane width direction position of the second target driving trajectory in accordance with the lateral deviation detected at the time point when the vehicle speed decreases.

6. the controller executes a process of calculating the control input so as to reduce an evaluation function according to a difference between a predicted position of the host vehicle and the first target traveling trajectory when control inputs of acceleration / deceleration and steering angle are input to the host vehicle and a degree of approach of the host vehicle to the object to be avoided; The vehicle control method according to any one of claims 1 to 5, characterized in that the evaluation function evaluated when calculating the control input at a first time includes a term obtained by multiplying the degree of approach when the control input calculated at a second time prior to the first time is input to the host vehicle by a relative speed of the object to be avoided with respect to the host vehicle.

7. a vehicle speed determination process for determining whether or not the vehicle speed of the host vehicle decreases to below a predetermined speed threshold; A lateral deviation detection process for detecting a lateral deviation of the host vehicle relative to a lane center or a lane boundary line; a target trajectory generation process for generating a first target traveling trajectory of the host vehicle so as to suppress a change in the lateral deviation after a vehicle speed reduction point at which the vehicle speed is reduced below the speed threshold when the vehicle speed is determined to be reduced below the speed threshold; an avoidance object detection process for detecting an avoidance object to be avoided by the host vehicle; an avoidance process for avoiding the object to be avoided by adjusting a deceleration of the host vehicle while traveling along the first target traveling path after the vehicle speed has decreased, by suppressing a steering control that reduces a degree of approach of the host vehicle to the object to be avoided when it is determined that the vehicle speed will decrease below the speed threshold, compared to when it is not determined that the vehicle speed will decrease below the speed threshold; A vehicle control device comprising: a controller that executes the above-mentioned.

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