Vehicle driving assistance method and driving assistance device

Abstract

To provide a driving support method and driving support device for a vehicle, capable of inhibiting a vehicle from being unable to follow a travel track.SOLUTION: In a driving support method for a vehicle, a travel track along which a vehicle is caused to travel by autonomous travel control is generated. A track curvature at a passage position ahead of the vehicle is acquired from the travel track. On the basis of the acquired track curvature and a current travel state of the vehicle, a vehicle curvature in the case of traveling through the passage position is predicted, and a difference between the acquired track curvature and the predicted vehicle curvature is calculated. When the vehicle travels through the passage position, the difference is used to cause the vehicle to travel by the autonomous travel control so that the vehicle curvature is in agreement with the track curvature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method and device for assisting the operation of a vehicle. [Background technology]

[0002] It is known that a target driving state after a predetermined time is predicted according to delay elements in controlling the vehicle's motion, such as detection delay in sensors, signal communication delay, and actuator response delay, and commands that result in the target driving state are output to the actuators that control the vehicle's motion, thereby controlling the vehicle's motion (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 152977 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the conventional technology described above, commands are output earlier by a predetermined amount of time corresponding to the delay element, compensating for the delay element. However, it cannot compensate for the difference between the target driving trajectory and the actual driving trajectory in the width direction of the road. Therefore, when the curvature of the driving trajectory changes multiple times in a relatively short period of time, the difference between the target driving trajectory and the actual driving trajectory in the width direction of the road becomes large, and there is a problem that the vehicle may not be able to follow the driving trajectory even if the aforementioned delay element is taken into consideration.

[0005] The problem that this invention aims to solve is to provide a vehicle driving assistance method and a driving assistance device that can prevent a vehicle from losing its ability to follow its driving trajectory. [Means for solving the problem]

[0006] This invention generates a driving trajectory for a vehicle driven by autonomous driving control, obtains the curvature of the trajectory at a point the vehicle will pass in front of it from the driving trajectory, predicts the curvature of the vehicle when it passes the point based on the obtained curvature of the trajectory and the vehicle's current driving state, calculates the difference between the obtained curvature of the trajectory and the predicted curvature of the vehicle, and, when the vehicle passes the point, uses this difference to drive the vehicle by autonomous driving control so that the curvature of the vehicle becomes equal to the curvature of the trajectory. The predetermined distance between passing points for obtaining the curvature of the trajectory is set based on the vehicle's speed and the period for obtaining the curvature of the trajectory. This will solve the above problems. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the situation in which a vehicle loses the ability to follow its driving trajectory. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram showing a driver assistance system including a driver assistance device according to the present invention. [Figure 2] Figure 1 is a plan view showing an example of a driving scenario in which the driver assistance system shown performs driver assistance. [Figure 3A] Figure 1 is a plan view showing an example of a driving trajectory generated by the driver assistance system. [Figure 3B] Figure 1 is a plan view showing another example of a driving trajectory generated by the driver assistance system. [Figure 4A] This diagram shows the definition of the curvature of a vehicle. [Figure 4B] This is an example of an equation of motion for predicting the curvature of a vehicle. [Figure 5] Figure 1 is a flowchart showing an example of the processing procedure in the driver assistance system. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. The following description assumes that vehicles travel on the left side of the road in countries with left-hand traffic regulations. In countries with right-hand traffic regulations, vehicles travel on the right side of the road, so the terms "left" and "right" in the following description should be interpreted symmetrically.

[0010] [Configuration of the driver assistance system] Figure 1 is a block diagram illustrating the driver assistance system 10 according to the present invention. The driver assistance system 10 is an in-vehicle system that drives the vehicle to a destination set by the vehicle's occupants (including the driver) through autonomous driving control. Autonomous driving control refers to the autonomous control of the vehicle's driving actions using a driver assistance device described later, and such driving actions include all driving actions such as acceleration, deceleration, starting, stopping, steering to the right or left, lane changes, and swerving. Furthermore, autonomous control of driving actions means that the driver assistance device controls the driving actions using the vehicle's devices. In other words, the driver assistance device intervenes and controls these driving actions within a predetermined range. For driving actions that are not intervened in, the driver performs manual operation.

[0011] As shown in Figure 1, the driver assistance system 10 includes an imaging device 11, a distance measuring device 12, a vehicle status detection device 13, map information 14, a vehicle position detection device 15, a navigation device 16, a vehicle control device 17, a display device 18, and a driver assistance device 19. The devices constituting the driver assistance system 10 are connected by a CAN (Controller Area Network) or other in-vehicle LAN and can exchange information with each other.

[0012] The imaging device 11 is a device that recognizes objects around the vehicle using images, and is, for example, a camera equipped with an image sensor such as a CCD, an ultrasonic camera, or an infrared camera. Multiple imaging devices 11 can be installed on a single vehicle, for example, they can be placed on the front grille, below the left and right door mirrors, and near the rear bumper. This reduces blind spots when recognizing objects around the vehicle.

[0013] The distance measurement device 12 is a device for calculating the relative distance and relative speed between the vehicle and the object, such as a laser radar, millimeter wave radar, etc. (such as LRF), a LiDAR (light detection and ranging) unit, a radar device such as an ultrasonic radar, or a sonar. The distance measurement device 12 can be provided in plural on one vehicle, and can be arranged, for example, in front of, on the right side, on the left side, and at the rear of the vehicle. Thereby, the relative distance and relative speed with respect to the object around the vehicle can be accurately calculated.

[0014] The objects detected by the imaging device 11 and the distance measurement device 12 are road lane boundary lines, center lines, road surface markings, median strips, guardrails, curbstones, side walls of highways, road signs, traffic signals, crosswalks, construction sites, accident sites, traffic restrictions, etc. In addition, the objects include obstacles that may affect the running of the vehicle, such as automobiles (other vehicles) other than the host vehicle, motorcycles, bicycles, pedestrians, etc. The detection results of the imaging device 11 and the distance measurement device 12 are acquired at predetermined time intervals by the driving support device 19 as necessary.

[0015] Further, the detection results of the imaging device 11 and the distance measurement device 12 can be integrated or synthesized (so-called sensor fusion) by the driving support device 19, whereby the insufficient information of the detected object can be supplemented. For example, the position information of the object can be calculated by the driving support device 19 based on the self-position information, which is the position where the vehicle travels, acquired by the self-vehicle position detection device 15, and the relative position (distance and direction) between the vehicle and the object. The calculated position information of the object is integrated by the driving support device 19 with the detection results of the imaging device 11 and the distance measurement device 12, as well as a plurality of information such as the map information 14, to become the running environment information around the vehicle. Also, using the detection results of the imaging device 11 and the distance measurement device 12 and the map information 14, the objects around the vehicle can be recognized and their movements can be predicted.

[0016] The vehicle state detection device 13 is a device for detecting the driving state of the vehicle, and examples include a vehicle speed sensor, acceleration sensor, yaw rate sensor (e.g., gyro sensor), steering angle sensor, and inertial measurement unit. There are no particular limitations on these devices, and known devices can be used. Furthermore, the arrangement and number of these devices can be appropriately set within a range that allows for proper detection of the vehicle's driving state. The detection results of each device are acquired by the driver assistance device 19 at predetermined time intervals as needed.

[0017] Map information 14 is information used for generating driving routes, controlling driving actions, etc., and includes road information, facility information, and their attribute information. Road information and road attribute information include information such as road width, road curvature radius, shoulder structures, road traffic regulations (speed limits, whether lane changes are permitted), road merging and branching points, and locations where the number of lanes increases or decreases. Map information 14 is high-resolution map information that allows tracking of movement trajectories for each lane, and includes two-dimensional and / or three-dimensional position information at each map coordinate, road and lane boundary information at each map coordinate, road attribute information, lane uphill / downhill information, lane identification information, and connecting lane information.

[0018] High-resolution map information includes road and lane boundary information that indicates the boundary between the road on which vehicles travel and other areas. The road on which vehicles travel is the road for which vehicles travel, and the form of the road is not particularly limited. Boundaries exist on both the left and right sides with respect to the direction of travel of the vehicle, and their form is not particularly limited. Boundaries are, for example, road markings or road structures. Examples of road markings include lane boundaries and center lines, and examples of road structures include median strips, guardrails, curbs, tunnels, and highway side walls. In addition, at points where the road boundary cannot be clearly identified, such as within an intersection, a boundary is set in advance on the road. This boundary is fictitious and does not represent an actual existing road marking or road structure.

[0019] Map information 14 is stored in a readable format on a recording medium provided in the driver assistance device 19, an in-vehicle device, or a server on the network. The driver assistance device 19 acquires the map information 14 as needed.

[0020] The vehicle position detection device 15 is a positioning system for detecting the current position of the vehicle, and is not particularly limited; known systems can be used. The vehicle position detection device 15 calculates the current position of the vehicle from, for example, radio waves received from GPS (Global Positioning System) satellites. Alternatively, the vehicle position detection device 15 may estimate the current position of the vehicle from vehicle speed information and acceleration information obtained from the vehicle state detection device 13, which is a vehicle speed sensor, acceleration sensor, and gyro sensor, and calculate the current position of the vehicle by comparing the estimated current position with map information 14.

[0021] The navigation device 16 is a device that calculates a driving route from the vehicle's current position detected by the vehicle position detection device 15 to a destination set by the occupants (including the driver), by referring to map information 14. The navigation device 16 searches for a driving route for the vehicle to reach the destination from its current position using road information and facility information from the map information 14. The driving route includes at least information on the road the vehicle is traveling on, the lane it is traveling in, and the direction of travel, and is displayed, for example, as a linear route. Depending on the search conditions, multiple driving routes may exist. The driving route calculated by the navigation device 16 is output to the driver assistance device 19.

[0022] The vehicle control device 17 is an on-board computer such as an electronic control unit (ECU), which electronically controls on-board equipment that governs the vehicle's operation. The vehicle control device 17 includes a vehicle speed control device 171 that controls the vehicle's speed and a steering control device 172 that controls the vehicle's steering operation. The vehicle speed control device 171 and the steering control device 172 autonomously control the operation of these drive and steering devices in response to control signals input from the driver assistance device 19. As a result, the vehicle can autonomously drive according to the set driving path. Information necessary for autonomous control by the vehicle speed control device 171 and the steering control device 172, such as the vehicle's speed, acceleration, steering angle, and attitude, is obtained from the vehicle state detection device 13.

[0023] The drive systems controlled by the vehicle speed control device 171 include electric motors and / or internal combustion engines that serve as driving sources, power transmission systems including drive shafts and automatic transmissions that transmit output from these driving sources to the drive wheels, and drive systems that control the power transmission systems. The braking systems controlled by the vehicle speed control device 171 are, for example, braking systems that brake the wheels. The vehicle speed control device 171 receives control signals from the driver assistance system 19 according to the set driving speed. Based on the control signals received from the driver assistance system 19, the vehicle speed control device 171 generates signals to control these drive systems and transmits these signals to the drive systems, thereby autonomously controlling the vehicle's driving speed.

[0024] On the other hand, the steering control device 172 controls the steering wheel according to the steering angle of the steering wheel, and examples include steering actuators such as motors attached to the steering column shaft. Based on the control signals input from the driver assistance device 19, the steering control device 172 autonomously controls the operation of the steering wheel so that the vehicle drives while maintaining a predetermined lateral position (the position of the vehicle in the left-right direction) relative to the set driving path. This control uses at least one of the detection results of the imaging device 11 and the distance measuring device 12, the driving state of the vehicle acquired by the vehicle state detection device 13, map information 14, and information on the current position of the vehicle acquired by the vehicle position detection device 15.

[0025] The display device 18 is a device for providing necessary information to the vehicle occupants, and is, for example, a liquid crystal display or a projector such as a head-up display (HUD) provided on the instrument panel. The display device 18 may also include an input device for the vehicle occupants to input instructions to the driver assistance device 19. Examples of input devices include a touch panel that accepts input by the user's finger or stylus pen, a microphone that acquires instructions by the user's voice, and a switch mounted on the vehicle's steering wheel. The display device 18 may also include a speaker as an output device.

[0026] The driver assistance device 19 controls the vehicle's movement by controlling and coordinating the devices that make up the driver assistance system 10, and drives the vehicle to a set destination. The destination is set, for example, by the vehicle's occupants. The driver assistance device 19 is, for example, a computer and comprises a CPU (Central Processing Unit) 191 which is a processor, a ROM (Read Only Memory) 192 which stores programs, and a RAM (Random Access Memory) 193 which functions as an accessible storage device. The CPU 191 is an operating circuit that executes the programs stored in the ROM 192 and realizes the functions of the driver assistance device 19.

[0027] The driver assistance device 19 has a driver assistance function that drives the vehicle to a set destination by autonomous driving control. The driver assistance device 19 has a route generation function that generates a driving route, an environment recognition function that recognizes the driving environment around the vehicle, and a driving control function that generates a driving trajectory and drives the vehicle along the driving trajectory. In addition, the driver assistance device 19 has an acquisition function that acquires the curvature of the trajectory at the passing point and a prediction function that predicts the curvature of the vehicle at the passing point. The program stored in ROM 192 contains programs to realize these functions, and these functions are realized when the CPU 191 executes the program stored in ROM 192. Figure 1 shows, for convenience, extracted functional blocks that realize each function.

[0028] [Functions of each function block] The functions of each functional block shown in Figure 1, namely the support unit 20, generation unit 21, recognition unit 22, control unit 23, acquisition unit 24, and prediction unit 25, will be described below. In the following description, the vehicle itself will simply be referred to as the vehicle.

[0029] The support unit 20 has a driving assistance function that drives the vehicle to a set destination through autonomous driving control. Figure 2 is a plan view showing an example of a driving scene in which the driving assistance device 19 autonomously controls the vehicle's movement using the driving assistance function of the support unit 20. The road shown in Figure 2 is a three-lane road with lanes L1, L2, and L3, and vehicles traveling on the road are assumed to be traveling from the bottom to the top of the diagram. In addition, there is an intersection ahead of the road shown in Figure 2, and vehicles traveling in lane L1 can turn left at the intersection, vehicles traveling in lane L2 can go straight at the intersection, and vehicles traveling in lane L3 can turn right at the intersection.

[0030] In the driving scenario shown in Figure 2, the destination (not shown) is set at a location beyond the aforementioned intersection, and the vehicle V1 is heading towards this destination. The vehicle V1 is traveling in lane L1 at position P1. In lane L1, other vehicles V2 and V3 are parked on the shoulder, in lane L2, other vehicles V4 and V5 are traveling straight, and in lane L3, other vehicles V6 and V7 are stopped for a right turn. In the driving scenario shown in Figure 2, other vehicle V4 is assumed to be traveling at a lower speed than the vehicle V1.

[0031] In this case, the driver assistance device 19 generates a driving route to the destination using the driver assistance function of the support unit 20, and drives the vehicle V1 along the generated driving route using autonomous driving control. This autonomous driving control is mainly controlled by the functions of the generation unit 21, recognition unit 22, control unit 23, acquisition unit 24, and prediction unit 25.

[0032] The generation unit 21 has a route generation function that generates a driving route for the vehicle to travel from its current location to its destination. The generation unit 21 also has a function that sets lanes for the vehicle to travel along the driving route. The driver assistance device 19 uses the navigation device 16, based on the route generation function of the generation unit 21, to generate a driving route for the vehicle to travel from its current location to its destination using autonomous driving control. The driver assistance device 19 also sets lanes for the vehicle to travel along the generated driving route. The driver assistance device 19 acquires information on the generated driving route and the set lanes from the navigation device 16 as needed.

[0033] In the driving scenario shown in Figure 2, the driver assistance system 19 generates a driving route from the current position P1 of the vehicle V1 to the destination. In the driving scenario shown in Figure 2, the driving route is a straight path along the road. Also, in the driving scenario shown in Figure 2, the vehicle V1 is set to lane L2 in order to proceed straight through the intersection ahead to reach the destination.

[0034] The recognition unit 22 has an environmental recognition function that recognizes the driving environment around the vehicle. The driver assistance device 19 recognizes the driving environment around the vehicle using the imaging device 11 and the distance measuring device 12 based on the environmental recognition function of the recognition unit 22. The driving environment is information used to determine whether the vehicle can maintain its current driving state or whether it needs to change its driving state, and includes information such as the type and location of objects, the type and location of obstacles if any exist, road conditions such as road surface conditions, and weather. The driver assistance device 19 recognizes the driving environment by performing appropriate processing such as pattern matching and sensor fusion on the detection results of the imaging device 11 and the distance measuring device 12. The driver assistance device 19 may also recognize obstacles that are in a range undetectable by the vehicle's detection device using fixed-point cameras installed on the road, servers that provide traffic information, vehicle-to-vehicle communication with other vehicles, etc.

[0035] In the driving scenario shown in Figure 2, it is assumed that infrastructure such as roadside cameras are unavailable, and the vehicle cannot connect to external servers or vehicle-to-vehicle communication. In this case, the driver assistance system 19 recognizes other vehicles V2 parked in front of the vehicle V1, other vehicles V4 and V5 traveling in lane L2, and other vehicle V6 stopped in lane L3, based on the detection results of the imaging device 11 and the distance measuring device 12. However, in the driving scenario shown in Figure 2, the area in front of other vehicles V2 and V6 is a blind spot for the detection device, and other vehicles V3 and V7 cannot be recognized.

[0036] The control unit 23 has a driving control function that generates a driving trajectory for the vehicle to travel along the generated driving path and controls the vehicle's driving motion to follow the generated driving trajectory. The driver assistance device 19 generates a driving trajectory for the vehicle to travel along the driving path using the driving control function of the control unit 23 and autonomously controls the vehicle's driving motion via the vehicle control device 17 (particularly the vehicle speed control device 171 and the steering control device 172) so that the vehicle follows the generated driving trajectory. In generating the driving trajectory, information such as the shape and width of the road and the curvature of the curves included in the map information 14 is taken into consideration, as well as the overall length and width of the vehicle body V1 and the minimum turning radius of the vehicle V1.

[0037] In the driving scene shown in Figure 2, the driver assistance device 19 generates a driving trajectory T1 that enters lane L2 from lane L1 while avoiding the other recognized vehicles V2 and V4. Then, via the vehicle control device 17, it autonomously controls the driving motion of its own vehicle V1 and drives along the driving trajectory T1 from position P1 to P2.

[0038] The driver assistance system 19 recognizes from the detection results of the distance measuring device 12 that, while traveling to position P2, another vehicle V4 is traveling at a lower speed than the own vehicle V1. In this case, if the driver assistance system 19 detects space for the own vehicle V1 to enter between the other vehicles V4 and V5, it overtakes the other vehicle V4 and continues driving in lane L2.

[0039] In the driving scene shown in Figure 2, there is space for vehicle V1 to enter between other vehicles V4 and V5, so the driver assistance device 19 generates a driving trajectory T2 that overtakes other vehicle V4. Then, through autonomous driving control, the vehicle drives along the driving trajectory T2 from position P2 to P3 and overtakes other vehicle V4.

[0040] The driving trajectories T1 and T2 shown in Figure 2 are trajectories involving turns with relatively small turning radii. Specifically, they involve turns with a turning radius of about 10R, which can occur when turning right or left at an intersection. Furthermore, since the curvature of the driving trajectories T1 and T2 changes multiple times, the driver assistance device 19 rotates the steering wheel by one or more revolutions via the steering control device 172 to follow the driving trajectories T1 and T2. In such driving scenarios, if control is performed to follow the driving trajectory using the vehicle's current driving state (feedback control), the difference between the driving trajectories T1 and T2 and the trajectory actually traveled by the vehicle V1 may become large, and the vehicle V1 may not be able to follow the driving trajectories T1 and T2. Therefore, the driver assistance device 19 in this embodiment performs control to follow the driving trajectory using the vehicle's future driving state (feedforward control).

[0041] The acquisition unit 24 has an acquisition function that acquires the curvature of the trajectory at the point where the vehicle passes in front of it, based on the driving trajectory. The driving support device 19 acquires the passing point of the generated driving trajectory and the curvature of the trajectory at that passing point using the acquisition function of the acquisition unit 24. When the driving trajectory is generated by the driving control function of the control unit 23, the driving support device 19 pre-sets the passing point of the vehicle V1 and the curvature of the trajectory at each passing point. The interval at which the passing points are set can be set to an appropriate interval within the range in which the vehicle V1 can follow the driving trajectory. For example, the passing point and curvature are set at least for the inflection points of the driving trajectory. Also, when driving along a gentle curve along the road, the interval is set to be relatively wide, and when driving that does not depend on the shape of the road, such as changing lanes or overtaking, the interval is set to be narrower than when driving along the road.

[0042] Examples of driving trajectories generated by the driver assistance device 19 are shown in Figures 3A and 3B. Driving trajectory T3 shown in Figure 3A is a driving trajectory with a relatively large change in curvature, while driving trajectory T4 shown in Figure 3B is a driving trajectory with a smaller change in curvature compared to driving trajectory T3. In driving trajectories T3 and T4, the passing position and the curvature of the trajectory are set at the inflection points of the trajectory.

[0043] In travel trajectories T3 and T4, the passing positions are set using the X and Y coordinates of the plane on which the vehicle V1 is traveling. For example, in travel trajectory T3, the current position of the vehicle V1 is (x0, y0), and the next passing position is set to (x1, y1). Note that the passing positions do not need to be set in a Cartesian coordinate system; they can be set using a polar coordinate system or any other appropriate method. Furthermore, the curvature of the trajectory is defined as the reciprocal of the radius of curvature of the circle of curvature at the passing position, representing the travel trajectory as a curve. An appropriate value is set within a range that does not cause discomfort to the occupants of the vehicle V1, taking into consideration the minimum turning radius of the vehicle V1 and the shape of the road on which the vehicle V1 is traveling. For example, in travel trajectory T3, the curvature at the current position (x0, y0) is κ r0 Therefore, the curvature at the passing position (x1, y1) is κ r1 That is the case.

[0044] Furthermore, the driver assistance device 19 sets a predicted section of a predetermined length in front of the vehicle and acquires the curvature of the trajectory at predetermined distance intervals within the predicted section. The predetermined length can be set to an appropriate length within the range in which the feedforward control by the driver assistance device 19 can be performed appropriately. On the other hand, the predetermined distance is set based on the vehicle's travel speed and the period for acquiring the curvature of the trajectory, and the period can be set to an appropriate period within the range in which the feedforward control by the driver assistance device 19 does not cause discomfort to the occupants of the vehicle.

[0045] For the trajectory T3 shown in Figure 3A, a predicted interval Z is set from the current position (x0, y0) to the passing position (x6, y6), and a period is set that allows the curvature of the trajectory to be obtained at least at each inflection point of the trajectory T3, taking into account the vehicle's speed. Similarly, for the trajectory T4 shown in Figure 3B, a predicted interval Z is set from the current position (x0, y0) to the passing position (x3, y3), and a period is set that allows the curvature of the trajectory to be obtained at least at each inflection point of the trajectory T4, taking into account the vehicle's speed.

[0046] When the driver assistance device 19 acquires the curvature of the trajectory, if the amount of change in the curvature of the trajectory between the first passing position and the second passing position located a predetermined distance ahead of the first passing position is greater than the first threshold, the device sets a shorter period for acquiring the curvature of the trajectory than when the amount of change in the curvature of the trajectory is less than or equal to the first threshold. The device then acquires the curvature of the trajectory again between the first passing position and the second passing position. Conversely, if the amount of change in the curvature of the trajectory between the first passing position and the second passing position is less than the second threshold, which is less than the first threshold, the device sets a longer period than when the change in the curvature of the trajectory is greater than or equal to the second threshold. In this way, by changing the period for acquiring the curvature according to the amount of change in the curvature of the trajectory, it is possible to suppress situations in which the vehicle cannot follow the driving trajectory, while also suppressing situations in which the vehicle's behavior changes frequently due to unnecessary feedforward control, causing discomfort to the occupants.

[0047] For example, in the travel trajectory T3 shown in Figure 3A, between the current position (x0, y0) and the passing position (x1, y1), κ r1 -κ r0Only the curvature changes. When this change amount is greater than the first threshold value, the period for obtaining the curvature of the trajectory is set shorter, and between the current position (x0, y0) and the passing position (x1, y1), the curvature of the trajectory is further obtained. In contrast, κ r1 -κ r0 If it is less than or equal to the first threshold value, the period for obtaining the curvature of the trajectory is not changed, and the acquisition of the curvature of the trajectory is continued. The first threshold value is set to a value such that when the change amount of the curvature is greater than that value, the host vehicle cannot follow the traveling trajectory, taking into account the motion performance such as the minimum turning radius of the vehicle.

[0048] As another example, in the traveling trajectory T4 shown in FIG. 3B, between the current position (x0, y0) and the passing position (x1, y1), κ r1 -κ r0 Only the curvature changes. When this change amount is less than the second threshold value, the period for obtaining the curvature of the trajectory is set longer. For example, the curvature of the passing position (x3, y3) is not obtained. In contrast, κ r1 -κ r0 If it is greater than or equal to the second threshold value, the period for obtaining the curvature of the trajectory is not changed, and the acquisition of the curvature of the trajectory is continued. The second threshold value can be set to an appropriate value within the range where the host vehicle can appropriately follow the traveling trajectory.

[0049] The prediction unit 25 has a function of predicting the curvature of the vehicle when passing through a passing position based on the current traveling state of the vehicle. The driving support device 19 predicts the curvature of the vehicle when passing through a passing position by the prediction function of the prediction unit 25. The current traveling state of the vehicle includes the traveling speed, acceleration, yaw rate, steering angle, etc. obtained from the host vehicle state detection device 13. Also, the current position of the host vehicle V1 obtained from the host vehicle position detection device 15 is included in the traveling state.

[0050] As shown in Figure 4A, the curvature of a vehicle is defined by the steering angle δ and the wheelbase L, which is the distance between the front and rear axles of the vehicle. The steering angle δ is the angle formed by a straight line X1 parallel to the longitudinal direction of the vehicle (perpendicular to the front or rear axle of the vehicle) and a straight line X2 parallel to the circumferential direction of the front wheels. Since the steering angle is proportional to the rotation angle of the steering wheel, the curvature of the vehicle can also be determined as the rotation angle of the steering wheel per unit length of the straight line X1 parallel to the longitudinal direction of the vehicle. In the driving assistance device 19 of this embodiment, autonomous driving control is performed by feedforward control, so the vehicle passes through a set passing position, and by matching the curvature of the vehicle at that time with the curvature of the trajectory, the difference in the road width direction between the set driving trajectory and the trajectory actually traveled by the vehicle is compensated.

[0051] The curvature of the vehicle when traveling through the passing position is predicted using, for example, a model using the Freinet coordinate system. The model may be nonlinear or a linear approximation. As an example of a model, the nonlinear state equation is shown in Figure 4B. In the equation shown in Figure 4B, s and t represent the longitudinal and transverse positions of the vehicle V1 in the plane on which it travels, respectively, θ represents the yaw angle of the vehicle V1, and V represents the speed of the vehicle V1. In the equation, κ is the curvature of the vehicle, and κ r κ is the curvature of the trajectory. Therefore, assuming that the travel speed and yaw angle (V, θ) of the vehicle V1 at a certain passing position in front of the vehicle V1 are the current travel speed and yaw angle obtained from the vehicle state detection device 13, the passing position (s, t) in front of the vehicle V1 and the curvature (κ) of that passing position can be expressed using the equation shown in Figure 4B. r By substituting ) into the formula, the curvature (κ) of the vehicle V1 at the passing position can be determined.

[0052] The driving support device 19, using the driving control function of the control unit 23, calculates the difference between the curvature of the acquired trajectory and the predicted curvature of the vehicle, and when the vehicle is traveling to the passing position, it uses this difference in curvature to drive the vehicle so that the curvature of the vehicle is equal to the curvature of the trajectory. For example, in the driving trajectory T3 shown in Figure 3A, if the curvature of the vehicle when it passes the passing position (x1, y1) is predicted to be κ1, then κ1-κ r1The system calculates that when the vehicle is traveling at the passing position (x1, y1), κ1 is κ r1 The vehicle's driving motion is autonomously controlled to achieve this.

[0053] Furthermore, when a predicted section Z is set, the driver assistance device 19 predicts the curvature of the vehicle when it travels through each passing position in the predicted section Z based on the vehicle's current driving state. For each passing position, it calculates the difference between the curvature of the trajectory at that position and the predicted curvature of the vehicle. Using this difference, it autonomously controls the vehicle's driving motion so that the curvature of the vehicle matches the curvature of the trajectory when traveling through the predicted section.

[0054] [Processing in driver assistance systems] Referring to Figure 5, the procedure for information processing by the driver assistance device 19 will be explained. Figure 5 is an example of a flowchart showing the information processing performed in the driver assistance system 10 of this embodiment. The processes described below are executed at predetermined time intervals by the CPU 191, which is the processor of the driver assistance device 19.

[0055] First, in step S1, the route generation function generates a driving route to the set destination. In the following step S2, the environment recognition function detects obstacles around the vehicle V1. In the following step S3, it is determined whether the vehicle V1 can travel along the driving trajectory. If it is determined that the vehicle V1 cannot travel along the driving trajectory due to obstacles, the routine execution is terminated, and the driver is prompted to switch to manual operation via the display device 18. On the other hand, if it is determined that the vehicle V1 can travel along the driving trajectory, the process proceeds to step S4.

[0056] In step S4, the driving control function generates a driving trajectory. In the following step S5, the prediction function sets a predicted section Z in front of the vehicle V1, and in step S6, the acquisition function acquires the curvature of the trajectory at the passing position in front of the vehicle V1. In the following step S7, it is determined whether the amount of change in the curvature of the trajectory between a certain passing position (first passing position) and a passing position located a predetermined distance ahead of that passing position (second passing position) is greater than the first threshold. If the amount of change in the curvature of the trajectory between the two passing positions is greater than the first threshold, the process proceeds to step S8, and the period for acquiring the curvature of the trajectory is set to be shorter. On the other hand, if the amount of change in the curvature of the trajectory between the two passing positions is less than or equal to the first threshold, the process proceeds to step S9.

[0057] In step S9, it is determined whether the change in curvature of the trajectory between a certain passing position (first passing position) and a passing position located a predetermined distance ahead of that position (second passing position) is less than the second threshold. If the change in curvature of the trajectory between the two passing positions is less than the second threshold, the process proceeds to step S10, and the period for acquiring the curvature of the trajectory is set to be longer. On the other hand, if the change in curvature of the trajectory between the two passing positions is greater than or equal to the second threshold, the process proceeds to step S11. In other words, if the change in curvature of the trajectory between the two passing positions is less than or equal to the first threshold and greater than or equal to the second threshold, the period for acquiring the curvature is maintained.

[0058] In step S11, it is determined whether the acquisition of the curvature of the trajectory in predicted section Z has been completed. If it is determined that the acquisition of the curvature of the trajectory in predicted section Z has not been completed, the process proceeds to step S6 to continue acquiring the curvature of the trajectory. On the other hand, if it is determined that the acquisition of the curvature of the trajectory in predicted section Z has been completed, the process proceeds to step S12 to predict the curvature of the vehicle when it is traveling at the position in front of the vehicle V1. In the following step S13, the difference between the acquired curvature of the trajectory and the predicted curvature of the vehicle is calculated, and in the following step S14, the calculated difference is used to control the vehicle autonomously so that the curvature of the vehicle matches the curvature of the trajectory.

[0059] Once the predicted section is completed, the process proceeds to step S15. In step S15, it is determined whether or not the destination has been reached. If it is determined that the destination has been reached, the routine execution ends, and the driver is prompted to switch to manual operation via the display device 18. On the other hand, if it is determined that the destination has not been reached, the process proceeds to step S2, and the above process is repeated until the destination is reached.

[0060] [Embodiments of the present invention] As described above, according to this embodiment, a vehicle driving assistance method is provided in which the processor generates a driving trajectory for driving a vehicle by autonomous driving control, obtains the curvature of the trajectory at a position passed in front of the vehicle from the driving trajectory, predicts the curvature of the vehicle when it is driving at the passing position based on the obtained curvature of the trajectory and the current driving state of the vehicle, calculates the difference between the obtained curvature of the trajectory and the predicted curvature of the vehicle, and when the vehicle is driving at the passing position, uses the difference to drive the vehicle by autonomous driving control so that the curvature of the vehicle becomes equal to the curvature of the trajectory. This makes it possible to suppress the vehicle from losing track of the driving trajectory.

[0061] Furthermore, according to the vehicle driving assistance method of this embodiment, the processor sets a predicted section Z having a predetermined length in front of the vehicle, obtains the curvature of the trajectory at predetermined distance intervals in the predicted section Z, predicts the curvature of the vehicle when it travels through each of the passing positions based on the vehicle's current driving state, calculates the difference between the curvature of the trajectory at each passing position and the predicted curvature of the vehicle, and uses this difference to drive the vehicle in the predicted section Z such that the curvature of the vehicle becomes equal to the curvature of the trajectory. This makes it possible to suppress the vehicle from being unable to follow the driving trajectory in the set predicted section Z.

[0062] Furthermore, according to the vehicle driving assistance method of this embodiment, the processor sets a predetermined distance, which is the interval between the passing positions for acquiring the curvature of the trajectory, based on the vehicle's travel speed and the period for acquiring the curvature of the trajectory. This makes it possible to set the interval for acquiring curvature according to the travel trajectory.

[0063] Furthermore, according to the vehicle driving assistance method of this embodiment, the processor sets the period shorter than when the change in curvature of the trajectory is less than or equal to the first threshold if the change in curvature of the trajectory is greater than the change in curvature of the trajectory is less than or equal to the first threshold, and acquires the curvature of the trajectory between the first and second passing positions. By changing the period for acquiring the curvature according to the change in curvature of the trajectory, it is possible to suppress situations in which the vehicle cannot follow the driving trajectory, while suppressing situations in which the vehicle's behavior changes frequently due to unnecessary feedforward control, causing discomfort to the occupants.

[0064] Furthermore, according to the vehicle driving assistance method of this embodiment, the processor sets the period to be longer than when the change in curvature of the trajectory is greater than or equal to the second threshold if the change in curvature of the trajectory between the first passing position and the second passing position is less than a second threshold which is less than the first threshold. By changing the period for acquiring curvature according to the change in curvature of the trajectory, it is possible to suppress situations in which the vehicle cannot follow the driving trajectory, while suppressing situations in which the vehicle's behavior changes frequently due to unnecessary feedforward control, causing discomfort to the occupants.

[0065] Furthermore, according to this embodiment, a vehicle driving support device 19 is provided, comprising: a generation unit 21 that generates a driving trajectory for driving a vehicle by autonomous driving control; an acquisition unit 24 that acquires the curvature of the trajectory at a passing position in front of the vehicle from the driving trajectory; a prediction unit 25 that predicts the curvature of the vehicle when it travels to the passing position based on the acquired curvature of the trajectory and the vehicle's current driving state; and a control unit 23 that calculates the difference between the acquired curvature of the trajectory and the predicted curvature of the vehicle, and uses the difference to drive the vehicle by autonomous driving control so that the curvature of the vehicle becomes the curvature of the trajectory when the vehicle travels to the passing position. This makes it possible to suppress the vehicle from losing track of the driving trajectory. [Explanation of symbols]

[0066] 10…Driving assistance systems 11…Imaging device 12…Distance measuring device 13... Vehicle status detection device 14…Map Information 15... Vehicle position detection device 16…Navigation system 17... Vehicle control system 171... Vehicle speed control device 172... Steering control device 18...Display device 19…Driving assistance systems 191...CPU (Processor) 192...ROM 193...RAM 20…Support Department 21...Generation part 22...Recognition part 23…Control Unit 24…Acquisition part 25…Prediction Department V1...My vehicle V2, V3, V4, V5, V6, V7...Other vehicles L1, L2, L3... lanes P1, P2, P3…Position T1, T2... Driving trajectory Z... Prediction interval

Claims

1. In a vehicle driving assistance method executed by a processor, The aforementioned processor, Generate a driving trajectory for the vehicle to be driven using autonomous driving control. From the aforementioned travel trajectory, the curvature of the trajectory at the point where the vehicle passes in front of it is obtained. Based on the curvature of the acquired trajectory and the current driving state of the vehicle, the curvature of the vehicle when it travels through the aforementioned passing position is predicted. The difference between the curvature of the acquired trajectory and the predicted curvature of the vehicle is calculated. When the vehicle is traveling through the aforementioned passing position, the autonomous driving control uses the difference to drive the vehicle so that the curvature of the vehicle becomes the curvature of the trajectory. A vehicle driving assistance method comprising setting a predetermined distance, which is the interval between the passing positions for obtaining the curvature of the trajectory, based on the vehicle's driving speed and the period for obtaining the curvature of the trajectory.

2. The aforementioned processor, A predicted section having a predetermined length is set in front of the vehicle. In the prediction section, the curvature of the trajectory at the passing position is obtained at intervals of the predetermined distance. Based on the current driving state of the vehicle, the curvature of the vehicle when it travels through each of the passing positions is predicted. For each of the aforementioned passing positions, the difference between the curvature of the trajectory at that position and the predicted curvature of the vehicle is calculated. The vehicle driving assistance method according to claim 1, wherein when the vehicle travels along the predicted section, the difference is used to drive the vehicle so that the curvature of the vehicle becomes the curvature of the trajectory.

3. The aforementioned processor, If the change in curvature of the trajectory between the first passing position and the second passing position located a predetermined distance forward from the first passing position is greater than the first threshold, the period is set to be shorter than when the change in curvature of the trajectory is less than or equal to the first threshold. A vehicle driving assistance method according to claim 1 or 2, comprising obtaining the curvature of the trajectory between the first passing position and the second passing position.

4. The vehicle driving assistance method according to claim 3, wherein the processor sets the period to be longer than when the change in curvature of the trajectory is greater than or equal to the second threshold if the amount of change in curvature of the trajectory between the first passing position and the second passing position is less than a second threshold which is less than the first threshold.

5. A control unit that generates a driving trajectory for driving a vehicle using autonomous driving control, An acquisition unit that obtains the curvature of the trajectory at the point where the vehicle passes in front of the aforementioned travel trajectory, The system includes a prediction unit that predicts the curvature of the vehicle when it travels through the aforementioned location, based on the curvature of the acquired trajectory and the current driving state of the vehicle. The control unit calculates the difference between the curvature of the acquired trajectory and the predicted curvature of the vehicle. When the vehicle is traveling through the aforementioned passing position, the difference is used to control the vehicle autonomously so that the curvature of the vehicle becomes the curvature of the trajectory. The acquisition unit is a vehicle driving assistance device that sets a predetermined distance, which is the interval between the passing positions for acquiring the curvature of the trajectory, based on the vehicle's travel speed and the period for acquiring the curvature of the trajectory.

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