Operation support apparatus

Abstract

To enable a vehicular lateral velocity to converge to a target lateral velocity in a short period of time at the end of steering support.SOLUTION: A steering angle is controlled in accordance with steering angle profiles (Q1, Q2) representing a temporal change pattern of a steering angle for avoiding a lane departure. The steering angle profiles (Q1, Q2) are constituted by a first steering profile (Q1) that steers a vehicle (1) headed to a direction of lane departure toward a direction of avoiding lane departure and a second steering angle profile (Q2) that continues the first steering profile, then a change rate of steering angle at an initial steering in the first steering profile (Q1), a steering angle and a change rate of the steering angle at the end of steering in the first steering profile, a steering angle and a change rate of the steering angle at the initial steering in the second steering profile (Q2), and a steering angle and change rate of the steering angle at the end of steering in the second steering profile, are all caused to be zero.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device. [Background technology]

[0002] A lane departure prevention control device is known that calculates a target steering angle required to prevent the vehicle from leaving its lane, sets the steering force required when feedback-controlling the steering angle to the target steering angle as a first steering force, sets the steering force required when feedforward-controlling the steering angle based on the target steering angle and vehicle state quantities as a second steering force, changes the ratio between the first steering force and the second steering force depending on the driving state to set the target steering force, and applies a steering force to the steering mechanism based on the target steering force (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-36757 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when lane departure prevention control is performed, including such known lane departure prevention control devices, there is generally a problem that, when the lane departure prevention control is terminated, it takes time for the vehicle's lateral speed to converge to the target lateral speed, for example. [Means for solving the problem]

[0005] In order to solve such problems, according to the present invention, there is provided a steering system that includes a steering device that performs steering assistance for a steering angle of a vehicle, a sensor that can detect a lateral position of the vehicle, a lateral speed of the vehicle, and a lateral acceleration of the vehicle, and a processor, This processor performs steering assistance by controlling the steering angle by following a steering angle profile that indicates the pattern of change over time of the steering angle to avoid lane departure, the steering angle profile is composed of a first steering angle profile and a second steering angle profile that is continuous with the first steering angle profile and changes the steering angle in the opposite direction to the first steering angle profile, A driving assistance device is provided in which the rate of change of the steering angle at the beginning of steering in a first steering angle profile, the steering angle and rate of change of the steering angle at the end of steering in the first steering angle profile, the steering angle and rate of change of the steering angle at the beginning of steering in a second steering angle profile, and the steering angle and rate of change of the steering angle at the end of steering in the second steering angle profile are set to zero. [Effects of the Invention]

[0006] When the steering assist is terminated, the lateral speed of the vehicle can be converged to the target lateral speed in a short time. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the functional configuration of a vehicle. [Figure 2] 2A and 2B are diagrams showing the roadway as viewed from above. [Figure 3] FIG. 3 is a time chart showing changes in the steering angle, etc. [Figure 4] FIG. 4 is a time chart showing changes in the steering angle, etc. [Figure 5] FIG. 5 is a diagram showing the calculation formula. [Figure 6] 6A, 6B and 6C are diagrams showing maps of control time, maximum lateral acceleration and starting position, respectively. [Figure 7] FIG. 7 is a flowchart for executing lane departure avoidance control. DETAILED DESCRIPTION OF THE INVENTION

[0008] FIG. 1 shows the functional configuration of vehicle 1. Vehicle 1 can be driven either manually or automatically. Referring to FIG. 1, reference numeral 10 denotes a vehicle drive unit for applying driving force to the drive wheels of vehicle 1, 11 denotes a braking device for braking vehicle 1, and 12 denotes an electronic control unit mounted in vehicle 1. As shown in FIG. 1, electronic control unit 12 is a digital computer and includes a CPU (processor) 14, memory 15 consisting of ROM and RAM, and input / output ports 16, all connected to each other by a bidirectional bus 13. A communication device 17 for communicating with the outside is connected to electronic control unit 12.

[0009] Meanwhile, vehicle 1 is equipped with a steering device 19 equipped with a power steering mechanism to assist steering angle operation using steering wheel 18. This steering device 19 is controlled by an output signal from electronic control unit 12, and steering angle control is performed in response to the output signal from electronic control unit 12. Vehicle 1 is also equipped with a steering angle sensor 20 for detecting the steering angle, and the output signal from this steering angle sensor 20 is input to electronic control unit 12. Vehicle 1 is also equipped with a sensor 21 for detecting the lateral position (lateral position) of vehicle 1, the lateral speed (lateral velocity) of vehicle 1, and the lateral acceleration (lateral acceleration) of vehicle 1, and the output signal from this sensor 21 is input to electronic control unit 12. In the example shown in FIG. 1 , sensor 21 is a front camera capable of detecting boundary lines representing the boundaries on both sides of the lane in which vehicle 1 is traveling, and the lateral position of vehicle 1 from the boundary line, the lateral speed of vehicle 1, and the lateral velocity of vehicle 1 are calculated based on image data captured by front camera 21.

[0010] The vehicle 1 is also equipped with various sensors 22, such as sensors that detect the state of the vehicle 1 and sensors that detect the periphery of the vehicle 1. For example, sensors that detect the state of the vehicle 1 include an acceleration sensor, a speed sensor, an azimuth sensor, and a geomagnetic sensor. Sensors that detect the periphery of the vehicle 1 include a camera that captures images of the sides and rear of the vehicle 1, and a lidar (LIDAR), radar, clearance sonar, etc. that detect the front, sides, and rear of the vehicle 1. Meanwhile, in the example shown in FIG. 1 , the vehicle drive unit 10 of the vehicle 1 is composed of an electric motor driven by a secondary battery or an electric motor driven by a fuel cell. A drive signal for the electric motor is output from an electronic control unit 12, and the drive wheels are driven and controlled by the electric motor in accordance with this electric motor drive signal.

[0011] Next, two typical examples of lane departure avoidance control will be described with reference to FIGS. 2A and 2B, which illustrate the behavior of vehicle 1 when lane departure avoidance control is performed. In FIGS. 2A and 2B, 30 indicates a lane as viewed from above, 31 and 32 indicate boundary lines, e.g., white lines, that define the boundaries on both sides of lane 30, and Y0 indicates a departure determination position that is a distance ΔY away from the edge of white line 31 on the lane 30 side. Boundary lines include not only solid white lines but also dashed white lines and yellow lines. Boundary lines also include not only lines but also non-high-grade road edges such as dirt and gravel, and three-dimensional road edges such as curbs and guardrails. FIG. 2A illustrates a case in which vehicle 1 traveling straight along the centerline of lane 30, deviates toward white line 31 for some reason and approaches the white line 31. In this case, for example, if the outer front end of vehicle 1 approaches white line 31 and exceeds departure determination threshold Y0, lane departure avoidance control is initiated and vehicle 1 is returned toward the center of lane 30. On the other hand, FIG. 2B shows a case in which vehicle 1, turning in the center of curved lane 30 along the center line of lane 30, is bulging outward from the curve of lane 30 and approaching white line 31. In this case as well, for example, if the outer front end of vehicle 1 approaches white line 31 and exceeds departure determination threshold Y0, lane departure avoidance control is initiated and vehicle 1 is returned toward the center of lane 30.

[0012] 3 and 4 show changes over time in the steering angle A, lateral acceleration G, lateral velocity V, and lateral position Y of the vehicle 1 when lane departure avoidance control according to the present invention is performed. The steering angle A represents an angle relative to the steering angle when the vehicle 1 is traveling along the center line of the lane 30, i.e., zero. For example, in the case shown in FIG. 4, when the vehicle 1 is traveling along a curved section along the center line of the lane 30, the steering angle is set to a certain steering angle α necessary to turn the vehicle 1. In the present invention, the steering angle A of the vehicle 1 represents an angle relative to this steering angle α, i.e., zero. In addition, in the present invention, the lateral position Y represents the position of the outer front end of the vehicle 1 relative to the edge of the white line 31 on the lane 30 side. When lane 30 is curved, lateral position Y indicates the position of the outer front end of vehicle 1 relative to the edge of lane 30 in a direction perpendicular to a tangent to the edge of white line 31 on the lane 30 side, as shown in Fig. 2B. Meanwhile, in the present invention, lateral velocity V represents the rate of change of lateral position Y relative to the edge of white line 31 on the lane 30 side, and lateral acceleration G represents the change per unit time of lateral velocity V. Fig. 3 shows the changes over time in steering angle A, lateral acceleration G, lateral velocity V, and lateral position Y of vehicle 1 when lane departure avoidance control as shown in Fig. 2A is performed, and Fig. 4 shows the changes over time in steering angle A, lateral acceleration G, lateral velocity V, and lateral position Y of vehicle 1 when lane departure avoidance control as shown in Fig. 2B is performed.

[0013] First, an overview of the present invention will be described with reference to Figure 3. In the present invention, lane departure avoidance control is initiated when lateral position Y, which indicates the outer front end of vehicle 1, approaches white line 31 and passes departure determination position Y0. When lane departure avoidance control is initiated, an optimal time change pattern of lateral acceleration G corresponding to the situation of vehicle 1, i.e., lateral acceleration profiles P1 and P2, is created within electronic control unit 12 of vehicle 1. Based on these lateral acceleration profiles P1 and P2, an optimal time change pattern of steering angle A, i.e., steering angle profiles Q1 and Q2, is created. Once steering angle profiles Q1 and Q2 are created, steering angle A is controlled, for example, by PID control, so that steering angle A changes in accordance with steering angle profiles Q1 and Q2.

[0014] The steering angle A is a value obtained by multiplying the lateral acceleration G by a constant determined for the vehicle 1. Therefore, as can be seen from Fig. 3, the steering angle profiles Q1 and Q2 have shapes in which the heights of the lateral acceleration profiles P1 and P2 from a reference line GX of zero lateral acceleration are enlarged or reduced by the same proportion throughout the lateral acceleration profiles P1 and P2. Furthermore, because a control delay occurs in the control of the steering angle A, as can be seen from Fig. 3, the lateral acceleration G changes with a time delay of Δt relative to a change in the steering angle A. In the case shown in Fig. 2A, as shown in Fig. 3, when lane departure avoidance control starts, the lateral acceleration G and the time rate of change of the lateral acceleration G are zero, and therefore the time rate of change of the lateral velocity V is also zero.

[0015] During lane departure avoidance control, the magnitude and rate of change of lateral acceleration G have a significant impact on the bodily sensations of occupants of vehicle 1, such as the driver. Therefore, the bodily sensations of occupants of vehicle 1 are influenced by the magnitude and rate of change of lateral acceleration G. For example, if the lateral acceleration G becomes too large during lane departure avoidance control, it will cause fear in occupants of vehicle 1, so the lateral acceleration G cannot be made too large during lane departure avoidance control. Also, if the rate of change of lateral acceleration G becomes large during lane departure avoidance control, it will cause fear in occupants of vehicle 1, so the rate of change of lateral acceleration G during lane departure avoidance control cannot be made large either. In the present invention, these factors are taken into consideration to create optimal lateral acceleration profiles P1 and P2 that do not cause fear in occupants of vehicle 1.

[0016] Furthermore, the present invention takes into consideration the following two points when creating optimal lateral acceleration profiles P1, P2 that do not instill fear in the occupants of the vehicle 1. First, the lateral acceleration profiles P1, P2 can be created easily, and second, the lateral velocity V can be converged to zero in a short period of time when lane departure avoidance control is completed. Note that the lateral velocity V to be converged to can be set to a value other than zero, and even in this case, the lateral velocity V can be converged to the desired lateral velocity V in a short period of time.

[0017] To meet these requirements, the present invention configures the lateral acceleration profiles P1 and P2 to include a first lateral acceleration profile P1 and a second lateral acceleration profile P2 that is continuous with the first lateral acceleration profile P1, as shown in Fig. 3. The first lateral acceleration profile P1 is generated according to the situation of the vehicle 1, and the second lateral acceleration profile P2 is generated based on the generated first lateral acceleration profile P1. Therefore, the present invention also configures the steering angle profiles Q1 and Q2 to include a first steering angle profile Q1 and a second steering angle profile Q2 that is continuous with the first steering angle profile Q1, as shown in Fig. 3. In this case, the first steering angle profile Q1 is formed to have a change pattern that changes the steering angle A so that the vehicle 1 heading in the lane departure direction moves toward the lane departure avoidance direction, and the second steering angle profile Q2 is formed to have a change pattern that changes the steering angle A in the opposite direction to the first steering angle profile Q1 so that the vehicle 1 heading in the lane departure avoidance direction moves toward lane 30. In Fig. 3, T1 indicates a control time during which steering control is performed based on the first steering angle profile Q1, and T2 indicates a control time during which steering control is performed based on the second steering angle profile Q2. In the example shown in Fig. 3, the control time T1 and the control time T2 are the same time.

[0018] As described above, in the present invention, the first lateral acceleration profile P1 is first created. Therefore, the first lateral acceleration profile P1 will be described first. The control time T1, which indicates the range of the first lateral acceleration profile P1, is the same as the control time T1 during which steering control is performed based on the first steering angle profile Q1. Empirically, there exists an optimal control time for this control time T1 depending on the lateral acceleration G and the lateral velocity V. Therefore, in an embodiment according to the present invention, this control time T1 is set in advance in the form of a control time map as a function of the lateral acceleration G and the lateral velocity V, as shown in FIG. 6A. Note that FIG. 6A shows several representative numerical examples for the lateral acceleration G and the lateral velocity V.

[0019] On the other hand, the first lateral acceleration profile P1 has a maximum lateral acceleration G1 at the center, that is, when a time T1 / 2 has elapsed after the start of lane departure avoidance control. Regarding this maximum lateral acceleration G1, there is an empirically optimal maximum lateral acceleration G1 that corresponds to the lateral acceleration G and the lateral velocity V within a range that does not cause fear to the occupants of the vehicle 1. Therefore, in this embodiment of the present invention, this maximum lateral acceleration G1 is also set in advance in the form of a maximum lateral acceleration map as a function of the lateral acceleration G and the lateral velocity V, as shown in FIG. This first lateral acceleration profile P1 is created so that the maximum lateral acceleration G1 is set to the value of the maximum lateral acceleration map, the lateral acceleration G and the rate of change of the lateral acceleration G are zero at the start of lane departure avoidance control, the rate of change of the lateral acceleration G at the maximum lateral acceleration G1 is zero, the lateral acceleration G and the rate of change of the lateral acceleration G are zero when the control time T1 has elapsed after the start of lane departure avoidance control, for example, the target lateral velocity Vc at the end of lane departure avoidance control is zero, and the lateral velocity Vb when the control time T1 has elapsed is a certain percentage, for example, 1 / 3, of the lateral velocity Va at the start of lane departure avoidance control.

[0020] 3, the first steering angle profile Q1 is formed into a change pattern in which the steering angle A becomes a maximum steering angle A1 midway between the initial stage of steering and the end stage of steering in the first steering angle profile Q1, the steering angle A and the rate of change of the steering angle A at the initial stage of steering in the first steering angle profile Q1 are zero, and the steering angle A and the rate of change of the steering angle A at the end stage of steering in the first steering angle profile Q1 are zero. Note that in this embodiment of the present invention, the first lateral acceleration profile P1 is created using a sextic function.

[0021] In this way, when the first lateral acceleration profile P1 is created so that the lateral acceleration G and the rate of change of the lateral acceleration G are zero at the start of lane departure avoidance control, the rate of change of the lateral acceleration G at maximum lateral acceleration G1 are zero, and the lateral acceleration G and the rate of change of the lateral acceleration G are zero when the control time T1 has elapsed after the start of lane departure avoidance control, the lateral acceleration G slowly increases and smoothly reaches the maximum lateral acceleration G1 when lane departure avoidance control is started, and then the lateral acceleration G smoothly decreases and slowly reaches zero. Furthermore, the change pattern of the first lateral acceleration profile P1 is symmetrical between the first half and the second half of the first lateral acceleration profile P1, with the maximum lateral acceleration G1 as the boundary. As a result, the occupants of the vehicle 1 do not feel a sense of fear when the lateral acceleration G increases and when the lateral acceleration G decreases, and a natural feeling of discomfort can be provided.

[0022] On the other hand, as described above, in this embodiment of the present invention, the first lateral acceleration profile P1 is generated using a sextic function. In this case, if the first lateral acceleration profile P1 were generated using, for example, a quartic function, the change pattern of the first lateral acceleration profile P1 would be more upwardly pointed at the maximum lateral acceleration G1 than in the case shown in FIG. 3 and would not be flat near the maximum lateral acceleration G1, as shown in FIG. 3. When the first lateral acceleration profile P1 has such an upwardly pointed shape at the maximum lateral acceleration G1, the lateral acceleration G changes suddenly near the maximum lateral acceleration G1, which can frighten the occupants of the vehicle 1. Furthermore, the maximum lateral acceleration G1 tends to increase when the lateral velocity V in the lane departure direction is high. In contrast, when the change pattern of the first lateral acceleration profile P1 is flat near the maximum lateral acceleration G1, as shown in FIG. 3, the lateral acceleration G changes slowly near the maximum lateral acceleration G1, which does not frighten the occupants of the vehicle 1. Therefore, it is significant that the first lateral acceleration profile P1 is generated using a sextic function. The first lateral acceleration profile P1 can also be created using a function of sixth order or higher.

[0023] Meanwhile, as described above, in the present invention, the second lateral acceleration profile P2 is generated based on the generated first lateral acceleration profile P1. Next, a method for generating this second lateral acceleration profile P2 will be described. In the example shown in FIG. 3, the second lateral acceleration profile P2 has a change pattern that generates lateral acceleration G in the opposite direction to that of the first lateral acceleration profile P1, i.e., a change pattern that is located on the opposite side of the first lateral acceleration profile P1 with respect to the zero lateral acceleration reference line GX. The second lateral acceleration profile P2 has a shape in which the height of the first lateral acceleration profile P1 from the zero lateral acceleration reference line GX is reduced by the same percentage throughout the first lateral acceleration profile P1. In this case, the reduction percentage is G2 / G1, which is the value obtained by dividing the maximum lateral acceleration G2 at the center of the second lateral acceleration profile P2 by the maximum lateral acceleration G1 at the center of the first lateral acceleration profile P1.

[0024] Therefore, the second steering angle profile Q2 also has a change pattern in which the steering angle A is in the opposite direction to that of the first steering angle profile P1, that is, a change pattern located on the opposite side of the first steering angle profile Q1 with respect to the reference line AX of the zero steering angle, and the second steering angle profile Q2 has a shape in which the height of the first steering angle profile Q1 from the reference line AX of the zero steering angle is reduced by the same proportion over the entire first steering angle profile Q1. Furthermore, in this case, as can be seen from Fig. 3, the first steering angle profile Q1 has a maximum steering angle A1 at the center between the initial stage and the end of steering in the first steering angle profile Q1, and the second steering angle profile Q2 has a change pattern in which the steering angle A is a maximum steering angle A2 at the center between the initial stage and the end of steering in the second steering angle profile Q2, and the steering angle A at the initial stage of steering and the rate of change of the steering angle A are zero in the first steering angle profile Q1, and the steering angle A at the end of steering and the rate of change of the steering angle A are zero in the second steering angle profile Q2.

[0025] In this case, in the embodiment according to the present invention, the reduction ratio G2 / G1 is calculated based on the amount of change in the lateral speed V. That is, as shown in FIG. 3, if the lateral velocity Va at the start of lane departure avoidance control, i.e., the velocity difference between the lateral velocity Va at the initial point of the first lateral acceleration profile P1 and the lateral velocity Vb at the end of the first lateral acceleration profile P1, is denoted as ΔV1, and the velocity difference between the lateral velocity Vb at the initial point of the second lateral acceleration profile P2 and the target lateral velocity Vc (=0) at the end of the second lateral acceleration profile P2 is denoted as ΔV2, then the integral of the lateral acceleration G from the initial point to the end point of the first lateral acceleration profile P1, i.e., the area enclosed by the first lateral acceleration profile P1 and the reference line GX of zero lateral acceleration, corresponds to the amount of change in the lateral velocity V that changes within the control time T1, i.e., the velocity difference ΔV1, and the integral of the lateral acceleration G from the initial point to the end point of the second lateral acceleration profile P2, i.e., the area enclosed by the second lateral acceleration profile P2 and the reference line GX of zero lateral acceleration, corresponds to the amount of change in the lateral velocity V that changes within the control time T2, i.e., the velocity difference ΔV2.

[0026] In this case, the ratio of the area surrounded by the second lateral acceleration profile P2 and the reference line of zero lateral acceleration to the area surrounded by the first lateral acceleration profile P1 and the reference line of zero lateral acceleration represents the reduction ratio G2 / G1, and therefore the ratio of the change in lateral velocity V, ΔV2 / ΔV1, represents this reduction ratio G2 / G1. Therefore, if the second lateral acceleration profile P2 is created by reducing the first lateral acceleration profile P1 by the reduction ratio G2 / G1, i.e., by the reduction ratio ΔV2 / ΔV1, and the second steering angle profile P2 is created from the created second lateral acceleration profile P2, when the steering angle is controlled, for example, by PID control, so as to change in accordance with the second steering angle profile Q2, the lateral velocity V will decrease by ΔV2 from the lateral velocity Vb, and therefore the lateral velocity V will change from the lateral velocity Vb to the target lateral velocity Vc (=0).

[0027] In this manner, in this embodiment of the present invention, if the speed difference between the vehicle lateral velocity Va at the beginning of steering in the first steering angle profile Q1 and the vehicle lateral velocity Vb at the end of steering in the first steering angle profile Q1 is defined as V1, and the speed difference between the vehicle lateral velocity Vb at the beginning of steering in the second steering angle profile Q2 and the vehicle target lateral velocity Vc (=0) at the end of steering in the second steering angle profile Q2 is defined as ΔV2, the ratio ΔV2 / ΔV1 of the speed difference ΔV2 to the speed difference ΔV1 is defined as the reduction rate G2 / G1. In this case, in this embodiment of the present invention, this ratio ΔV2 / ΔV1 is preset. That is, as described above, when creating the first lateral acceleration profile P1, for example, the target lateral velocity Vc at the end of lane departure avoidance control is set to zero, and a certain rate, for example, one-third, of the lateral velocity Va at the start of lane departure avoidance control is set as the lateral velocity Vb when the control time T1 has elapsed. That is, in the embodiment according to the present invention, the relationship between the lateral speed Va, the lateral speed Vb, and the target lateral speed Vc is set in advance, and therefore the ratio ΔV2 / ΔV1 is set in advance.

[0028] As described above, in this embodiment of the present invention, the second lateral acceleration profile P2 is created based on the first lateral acceleration profile P1. Therefore, the lateral acceleration profiles P1 and P2 from the start of lane departure avoidance control to the end of lane departure avoidance control can be easily created. Furthermore, in this embodiment, the lateral acceleration G and the rate of change of the lateral acceleration G are set to zero at the end of the first lateral acceleration profile P1, the initial stage of the second lateral acceleration profile P2, and the end of the second lateral acceleration profile P2. Therefore, the lateral velocity V is temporarily held at the lateral velocity Vb at the end of the first lateral acceleration profile P1 and the initial stage of the second lateral acceleration profile P2, and is at least temporarily held at the lateral velocity Vc, i.e., zero, at the end of the second lateral acceleration profile P2.

[0029] Incidentally, in the latter half of lane departure avoidance control, when lateral acceleration G is occurring or lateral velocity V is changing, if control is initiated to converge lateral velocity V to a target final lateral velocity Vb, e.g., zero, the lateral acceleration G and lateral velocity V at this time typically vary considerably due to control delays and the like. However, if the lateral acceleration G and lateral velocity V vary at the start of control, it is difficult to converge lateral velocity V to the target final lateral velocity Vb, e.g., zero, while adjusting the lateral acceleration G and lateral velocity V. Even if lateral velocity V can converge to the target final lateral velocity Vb, e.g., zero, it takes time to converge. However, in the present invention, the rates of change of lateral acceleration G and lateral acceleration G are set to zero at the initial stage of second lateral acceleration profile P2, and lateral velocity V is maintained at a constant value at lateral velocity Vb. This allows smooth adjustment of lateral acceleration G and lateral velocity V, which in turn allows lateral velocity V to converge to the target final lateral velocity Vb, e.g., zero, in a short time.

[0030] Next, a method for generating the first lateral acceleration profile P1 and the second lateral acceleration profile P2 when lane departure avoidance control as shown in Figure 2B is performed will be described with reference to Figure 4. In this case, the method for generating the first lateral acceleration profile P1 is substantially the same as that shown in Figure 3, but the method for generating the second lateral acceleration profile P2 is slightly different from that shown in Figure 3.

[0031] First, a brief description will be given of how to create the first lateral acceleration profile P1 shown in Figure 4. In the case shown in Figure 4, when lane departure avoidance control is initiated, centrifugal force acts on the vehicle 1, causing a change in lateral velocity V and the generation of lateral acceleration G. However, the rate of change of lateral acceleration G at the start of lane departure avoidance control is set to zero. In the case shown in Figure 4, as in the case shown in Figure 3, the first lateral acceleration profile P1 reaches a maximum lateral acceleration G1 when time T1 / 2 has elapsed after the start of lane departure avoidance control. Furthermore, this first lateral acceleration profile P1 is created so that the maximum lateral acceleration G1 is set to the value of the maximum lateral acceleration map shown in FIG. 6B, the lateral acceleration G at the start of lane departure avoidance control is G0, the rate of change of the lateral acceleration G is zero, the rate of change of the lateral acceleration G at the maximum lateral acceleration G1 is zero, the lateral acceleration G and the rate of change of the lateral acceleration G are zero when a control time T1 has elapsed after the start of lane departure avoidance control, for example, the target lateral velocity Vc at the end of lane departure avoidance control is zero, and the lateral velocity Vb when the control time T1 has elapsed is a certain percentage, for example, 1 / 3, of the lateral velocity Va at the start of lane departure avoidance control.

[0032] On the other hand, in the case shown in FIG. 4, in order to generate the second lateral acceleration profile P2, the first lateral acceleration profile P1r for generating the profile P2 shown by the dashed line in FIG. The first lateral acceleration profile P1r is also created at the same time. This first lateral acceleration profile P1r also has a maximum lateral acceleration G1 when time T1 / 2 has elapsed after the start of lane departure avoidance control. Furthermore, this first lateral acceleration profile P1r is created so that the maximum lateral acceleration G1 is set to the value of the maximum lateral acceleration map shown in FIG. 6B, the lateral acceleration G and the rate of change of the lateral acceleration G at the start of lane departure avoidance control are zero, the rate of change of the lateral acceleration G at the maximum lateral acceleration G1 is zero, the lateral acceleration G and the rate of change of the lateral acceleration G when control time T1 has elapsed after the start of lane departure avoidance control are zero, for example, the target lateral velocity Vc when lane departure avoidance control is zero, and the lateral velocity Vb when control time T1 has elapsed is a certain percentage, for example, 1 / 3, of the lateral velocity Va when lane departure avoidance control is started.

[0033] In the example shown in Figure 4, the second lateral acceleration profile P2 also has a change pattern that generates lateral acceleration G in the opposite direction to that of the first lateral acceleration profile P1r, i.e., a change pattern that is located on the opposite side of the zero lateral acceleration reference line GX from that of the first lateral acceleration profile P1r. The second lateral acceleration profile P2 has a shape obtained by reducing the height of the first lateral acceleration profile P1r from the zero lateral acceleration reference line GX by the same percentage throughout the first lateral acceleration profile P1. In this case, the reduction percentage is G2 / G1, which is the maximum lateral acceleration G2 at the center of the second lateral acceleration profile P2 divided by the maximum lateral acceleration G1 of the first lateral acceleration profile P1r. Therefore, in the example shown in Figure 4, the second lateral acceleration profile P2 is generated by reducing the first lateral acceleration profile P1r by this reduction percentage G2 / G1, i.e., by the reduction percentage ΔV2 / ΔV1. In this case, theoretically, the value of G2 / G1 and the value of ΔV2 / ΔV1 do not perfectly match, but the difference between these values ​​is small, and therefore does not pose a major problem in practice.

[0034] While lane departure avoidance control has been described above using an example in which vehicle 1 is about to deviate from white line 31 on the right side of the vehicle's traveling direction as shown in Figures 2A and 2B, lane departure avoidance control is also performed when vehicle 1 is about to deviate from white line 32 on the left side of the vehicle's traveling direction using lateral acceleration profiles P1, P2 and steering angle profiles Q1, Q2 shown in Figures 3 and 4. In this case, however, the lateral acceleration G represented by lateral acceleration profiles P1, P2 is in the opposite direction to the lateral acceleration G shown in Figures 3 and 4, the steering angle A represented by steering angle profiles Q1, Q2 is in the opposite direction to the steering angle A shown in Figures 3 and 4, and the lateral position Y represents the distance from white line 32.

[0035] Next, a brief description will be given of a method for calculating the first lateral acceleration profile P1 and the first lateral acceleration profile P1r, which represent changes in lateral acceleration G. In an embodiment according to the present invention, the lateral acceleration G is expressed using a sextic function as shown in equation (2) of FIG. 5. Note that t in equation (2) of FIG. 5 represents the elapsed time since lane departure avoidance control was initiated. The jerk J in equation (1) of FIG. 5 represents the rate of change of the lateral acceleration G, and equation (1) of FIG. 5 is obtained by differentiating the lateral acceleration G shown in equation (2) of FIG. 5. Meanwhile, equation (3) of FIG. 5 represents the lateral velocity V, and equation (3) of FIG. 5 is obtained by integrating the lateral acceleration G shown in equation (2) of FIG. 5. Furthermore, equation (4) of FIG. 5 represents the lateral position Y, and equation (4) of FIG. 5 is obtained by integrating the lateral velocity V shown in equation (3) of FIG. 5. By applying boundary conditions to equation (4) in FIG. 5 from equation (1) in FIG. 5, equation (2) in FIG. 5 showing the lateral acceleration G can be calculated.

[0036] Taking the case of calculating the lateral acceleration G representing the first lateral acceleration profiles P1 and P1r in Figure 5 as an example, when t = 0, the jerk J = 0, so a1 = 0, and when t = 0, the lateral acceleration G = 0, so a0 = 0. Also, when t = 0, the lateral velocity V = Va (Figures 3 and 4), so a7 = Va, and when t = 0, the lateral position Y = departure determination position Y0, so a8 = Y0. Therefore, the only five coefficients of lateral acceleration G that have not been determined at this point are a2, a3, a4, a5, and a6. Therefore, by setting up five simultaneous equations, a2, a3, a4, a5, and a6 will be determined.

[0037] Next, regarding this simultaneous equation, the equation in equation (1) of FIG. 5 where jerk J=0 when t=T1 / 2 is defined as the first equation. In this case, control time T1 is obtained from the control time map shown in FIG. 6A, and the same applies to the following equations. Meanwhile, the equation in equation (2) of FIG. 5 where lateral acceleration G=maximum lateral acceleration G1 when t=T1 / 2 is defined as the second equation. In this case, maximum lateral acceleration G1 is obtained from the maximum lateral acceleration map shown in FIG. 6B. Meanwhile, the equation in equation (1) of FIG. 5 where jerk J=0 when t=T1 is defined as the third equation. Meanwhile, the equation in equation (2) of FIG. 5 where lateral acceleration G=0 when t=T1 is defined as the fourth equation. Finally, the equation in equation (3) of FIG. 5 where lateral velocity V=Va / 3 when t=T1 is defined as the fifth equation. By solving the simultaneous equations consisting of the first to fifth equations, a2, a3, a4, a5, and a6 are determined, and the lateral acceleration G can be calculated using equation (2) in FIG.

[0038] In equation (4) of Figure 5, the departure determination position Y0 of the lateral position Y at t = 0 is initially set to an arbitrary value. Therefore, even if a2, a3, a4, a5, and a6 are determined, the lowest point of the curve showing the change in lateral position Y usually does not become zero, as shown in Figures 3 and 4. In an embodiment according to the present invention, a curve showing the change in lateral position Y when the lateral acceleration G and lateral velocity V at the start of lane departure avoidance control are variously changed is calculated, and the departure determination position Y0 is found from the value when the lowest point of the calculated curve becomes zero. This departure determination position Y0 is preset in the form of a start position map as a function of the lateral acceleration G and lateral velocity V, as shown in Figure 6C. In practice, depending on the driving state of the vehicle 1 at the start of lane departure avoidance control or the surrounding conditions such as the movement of other vehicles, it may be preferable to control the steering angle A so that the vehicle 1 heading in the lane departure direction heads in the lane departure avoidance direction after slightly passing the white line 31, or it may be preferable to control the steering angle A so that the vehicle 1 heading in the lane departure direction heads in the lane departure avoidance direction before reaching the white line 31. In this case, in order to control the steering angle A in this way, it is also possible to shift the departure determination position Y0 obtained from the start position map toward the white line 31 or toward the center of the lane 30.

[0039] In an embodiment according to the present invention, the control time map shown in Figure 6A, the maximum lateral acceleration map shown in Figure 6B, and the start position map shown in Figure 6C are stored in memory 15 of electronic control unit 12 of vehicle 1, and further, the five simultaneous equations described above for calculating lateral acceleration G are stored in memory 15 of electronic control unit 12 of vehicle 1. In vehicle 1, lane departure avoidance control is performed using these maps and simultaneous equations stored in memory 15. Figure 7 shows a routine executed in electronic control unit 13 for performing lane departure avoidance control according to the present invention.

[0040] 7, first, in step 40, the sensor 21 detects the lateral position Y of the vehicle 1, the lateral velocity V of the vehicle 1, and the lateral acceleration G of the vehicle 1. Next, in step 41, a departure determination position Y0 is obtained from the start position map shown in FIG. 6C based on the detected lateral velocity V and lateral acceleration G. Next, in step 42, it is determined whether the detected lateral position Y of the vehicle 1 exceeds the departure determination position Y0 and the vehicle is likely to deviate from its lane. If it is determined that the lateral position Y of the vehicle 1 does not exceed the departure determination threshold position Y0 and the vehicle is unlikely to deviate from its lane, the processing cycle ends. On the other hand, if it is determined that the lateral position Y of the vehicle 1 exceeds the departure determination position Y0 and the vehicle is likely to deviate from its lane, lane departure avoidance control is initiated, and the process proceeds to step 43, where a control time T1 is obtained from the control time map shown in FIG. 6A and a maximum lateral acceleration G1 is obtained from the maximum lateral acceleration map shown in FIG. 6B based on the lateral velocity V and lateral acceleration G at the start of lane departure avoidance control.

[0041] Next, in step 44, all of the coefficients a0, a1, a2, a3, a4, a5, and a6 in equation (2) of FIG. 5 are calculated based on the lateral velocity V and lateral acceleration G at the start of lane departure avoidance control, thereby obtaining equation (2) of FIG. 5 representing the lateral acceleration G. That is, a first lateral acceleration profile P1 is created. Next, in step 45, it is determined whether the lateral acceleration G0 at the start of lane departure avoidance control is zero, that is, whether the state shown in FIG. 3 is present. If it is determined that the lateral acceleration G0 at the start of lane departure avoidance control is zero, that is, if it is determined that the state shown in FIG. 3 is present, the process proceeds to step 47, where a second lateral acceleration profile P2 is created based on the first lateral acceleration profile P1 created in step 44.

[0042] On the other hand, if it is determined in step 45 that the lateral acceleration G0 at the start of lane departure avoidance control is not zero, that is, if it is determined that the state is as shown in Figure 4, the process proceeds to step 46, where a first lateral acceleration profile P1r is created for creating the profile P2 shown by the dashed line in Figure 4. Next, the process proceeds to step 47, where a second lateral acceleration profile P2 is created based on the first lateral acceleration profile P1r created in step 46. Next, in step 48, steering angle profiles Q1 and Q2 are created from the created first lateral acceleration profile P1 and second lateral acceleration profile P2. Next, in step 49, the steering angle A is controlled, for example, by PID control, so that the steering angle A changes in accordance with the created steering angle profiles Q1 and Q2.

[0043] As described above, the steering angle A is a value obtained by multiplying the lateral acceleration G by a constant determined for the vehicle 1. Therefore, as can be seen from Figures 3 and 4, the steering angle profile has a shape in which the height of the lateral acceleration profile from the reference line GX of zero lateral acceleration is enlarged or reduced at the same rate throughout the lateral acceleration profile. Therefore, when the lateral acceleration G is zero, the steering angle A is also zero, and when the rate of change of the lateral acceleration G is zero, the rate of change of the steering angle A is also zero.

[0044] Expressed using steering angle profiles Q1 and Q2, the driving assistance device according to the present invention includes a steering device 19 that performs steering assistance for the steering angle A of the vehicle 1, a sensor 21 that can detect the lateral position, lateral speed, and lateral acceleration of the vehicle 1, and a processor 15. The processor 15 performs steering assistance by controlling the steering angle A in accordance with the steering angle profiles Q1 and Q2 that indicate a temporal change pattern of the steering angle A to avoid lane departure. The steering angle profiles Q1 and Q2 are composed of a first steering angle profile Q1 and a second steering angle profile Q2 that is continuous with the first steering angle profile Q1 and changes the steering angle in the opposite direction to the first steering angle profile Q1, and the rate of change of the steering angle at the start of steering in the first steering angle profile Q1, the steering angle and rate of change of the steering angle at the end of steering in the first steering angle profile Q1, the steering angle and rate of change of the steering angle at the start of steering in the second steering angle profile Q2, and the steering angle and rate of change of the steering angle at the end of steering in the second steering angle profile Q2 are set to zero.

[0045] In this case, in the embodiment according to the present invention, as can be seen from Figures 3 and 4, the second steering angle profile Q2 is a change pattern located on the opposite side of the first steering angle profile Q1 with respect to the reference line AX of the zero steering angle, and the second steering angle profile Q2 has a shape in which the height of the first steering angle profile Q1 from the reference line AX of the zero steering angle is reduced by the same proportion over the entire first steering angle profile Q1. Also, as can be seen from Figures 3 and 4, the first steering angle profile Q1 is formed in a change pattern that changes the steering angle A so that the vehicle 1 heading in the lane departure direction is directed in the lane departure avoidance direction, and the second steering angle profile Q2 is formed in a change pattern that changes the steering angle A on the opposite side of the first steering angle profile so that the vehicle heading in the lane departure avoidance direction is directed toward lane 30.

[0046] On the other hand, in an embodiment according to the present invention, as can be seen from Fig. 7, when lane departure avoidance control is initiated, a first lateral acceleration profile P1 showing the temporal change pattern of the lateral acceleration of the vehicle 1 is created, a second lateral acceleration profile P2 is created from the first lateral acceleration profile P1, a first steering angle profile Q1 is created from the first lateral acceleration profile P1, and a second steering angle profile Q2 is created from the second lateral acceleration profile P2. In this case, as can be seen from equation (2) in Fig. 5, the change pattern of the first lateral acceleration profile P1 is expressed by a function of sixth order or higher.

[0047] Furthermore, in an embodiment of the present invention, as can be seen from FIG. 7, if the lateral acceleration G0 of the vehicle 1 when lane departure avoidance control is initiated is zero, a second lateral acceleration profile P2 is created from a first lateral acceleration profile P1 created based on the lateral acceleration G0 of the vehicle 1 when lane departure avoidance control is initiated. If the lateral acceleration G0 of the vehicle 1 when lane departure avoidance control is initiated is not zero, in addition to the first lateral acceleration profile P1 created based on the lateral acceleration G0 of the vehicle when lane departure avoidance control is initiated, another first lateral acceleration profile P1r created assuming that the lateral acceleration G0 of the vehicle when lane departure avoidance control is initiated is zero is created, and a second lateral acceleration profile P2 is created from this another first lateral acceleration profile P1r.

[0048] Note that when lane departure avoidance control based on the first steering angle profile Q1 ends, if the lateral velocity V increases or decreases due to disturbances such as road cant, crosswind, or vehicle speed change, the reduction rate ΔV2 / ΔV1 for the second steering angle profile Q2 can be changed, making this control resistant to disturbances. Also, in Figures 3 and 4, it is possible to make the control time T2 longer than the control time T1. In this case, the reduction rate for the second steering angle profile Q2 is the value obtained by multiplying ΔV2 / ΔV1 by T1 / T2. [Explanation of symbols]

[0049] 1. Your vehicle 15 processors 19 Steering gear 20 Steering angle sensor 21 Sensors

Claims

1. The steering system includes a steering device that performs steering assistance for a steering angle of a vehicle, a sensor that can detect a lateral position of the vehicle, a lateral speed of the vehicle, and a lateral acceleration of the vehicle, and a processor, the processor performs steering assistance by controlling the steering angle in accordance with a steering angle profile that indicates a time-varying pattern of the steering angle to avoid lane departure; the steering angle profile is made up of a first steering angle profile and a second steering angle profile that is continuous with the first steering angle profile and changes the steering angle in a direction opposite to the first steering angle profile, A driving assistance device that sets to zero the rate of change of the steering angle at the beginning of steering in the first steering angle profile, the steering angle and rate of change of the steering angle at the end of steering in the first steering angle profile, the steering angle and rate of change of the steering angle at the beginning of steering in the second steering angle profile, and the steering angle and rate of change of the steering angle at the end of steering in the second steering angle profile.

2. 2. The driving assistance device according to claim 1, wherein the first steering angle profile is formed as a change pattern that changes the steering angle of a vehicle heading in a lane departure direction so as to move the vehicle toward the lane departure avoidance direction, and the second steering angle profile is formed as a change pattern that changes the steering angle in a direction opposite to the first steering angle profile so as to move the vehicle heading in the lane departure avoidance direction toward the lane.

3. 2. The driving assistance device according to claim 1, wherein the second steering angle profile has a change pattern located on the opposite side of the first steering angle profile with respect to a reference line of zero steering angle, and the second steering angle profile has a shape in which the height of the first steering angle profile from the reference line of zero steering angle is reduced by the same reduction rate over the entire first steering angle profile.

4. 4. The driving assistance device according to claim 3, wherein the first steering angle profile is formed to have a change pattern in which the steering angle reaches a maximum at a midpoint between the initial stage of steering and the end stage of steering in the first steering angle profile.

5. 4. The driving assistance device according to claim 3, wherein a speed difference between the lateral velocity of the vehicle at the beginning of steering in the first steering angle profile and the lateral velocity of the vehicle at the end of steering in the first steering angle profile is ΔV1, and a speed difference between the lateral velocity of the vehicle at the beginning of steering in the second steering angle profile and a target lateral velocity of the vehicle at the end of steering in the second steering angle profile is ΔV2, a ratio ΔV2 / ΔV1 of the speed difference ΔV2 to the speed difference ΔV1 is set to the same reduction rate, and the ratio ΔV2 / ΔV1 is set in advance.

6. 2. The driving assistance device according to claim 1, wherein a first lateral acceleration profile indicating a temporal change pattern of the vehicle's lateral acceleration is created when lane departure avoidance control is initiated, the second lateral acceleration profile is created from the first lateral acceleration profile, the first steering angle profile is created from the first lateral acceleration profile, and the second steering angle profile is created from the second lateral acceleration profile.

7. 7. The driving assistance device according to claim 6, wherein the change pattern of the first lateral acceleration profile is expressed by a function of sixth order or higher.

8. 7. The driving assistance device of claim 6, wherein, if the lateral acceleration of the vehicle is zero when lane departure avoidance control is initiated, the second lateral acceleration profile is created from the first lateral acceleration profile created based on the lateral acceleration of the vehicle when lane departure avoidance control is initiated; and, if the lateral acceleration of the vehicle is not zero when lane departure avoidance control is initiated, in addition to the first lateral acceleration profile created based on the lateral acceleration of the vehicle when lane departure avoidance control is initiated, another first lateral acceleration profile created assuming that the lateral acceleration of the vehicle is zero when lane departure avoidance control is initiated is created, and the second lateral acceleration profile is created from this another first lateral acceleration profile.

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