Vehicle driving control system

Abstract

To provide a travel control device configured to control traveling of a vehicle such that the vehicle travels along a traffic lane within the traffic lane and capable of gradually decreasing a control amount according to the magnitude relation between a target control amount and an actual control amount when control termination conditions are satisfied.SOLUTION: A vehicle travel control device 100 includes a control unit configured to calculate a target steering angle related to turning for allowing a vehicle 102 to travel along a traffic lane within the traffic lane, calculate a target correction amount of a steering angle for allowing the actual steering angle to become the target steering angle, and control an automatic steering device 46 such that the correction amount of the steering angle becomes the target correction amount. The control unit is configured to gradually decrease the target correction amount of the steering angle when determining that travel control needs to be terminated. The control unit changes the degree of reduction in the target correction amount according to the magnitude relation between the target steering angle closest to the timing when it is determined that travel control needs to be terminated and the actual steering angle.SELECTED DRAWING: Figure 1

Description

[[TECHNICAL FIELD]]

[0001] The present invention relates to a travel control device for vehicles such as automobiles. [[BACKGROUND ART]]

[0002] As one type of travel control device for vehicles such as automobiles, a travel control device that controls the travel of a vehicle such that the vehicle travels along a lane within the lane is well known. As travel control devices of this type, lane departure prevention devices and lane keeping devices are known.

[0003] The lane departure prevention device detects the position of the vehicle relative to a lane, and when it is determined based on the detected position of the vehicle that there is a risk of the vehicle departing from the lane, performs lane departure prevention control that automatically steers the steered wheels such that the risk of the vehicle departing from the lane is reduced. In the present application, the lane departure prevention control is referred to as LDA (abbreviation for Lane Departure Alert with Control).

[0004] The lane keeping device sets a target trajectory for the vehicle to travel along the lane within the lane based on the lane or the travel trajectory of a preceding vehicle, and performs lane keeping control that automatically steers the steered wheels such that the vehicle travels along the target trajectory. In the present application, the lane keeping control is referred to as LTA (abbreviation for Lane Tracing Assist).

[0005] In both cases of LDA and LTA, when a control termination condition for these controls is satisfied, such as when a white line cannot be detected, it is necessary to shift from automatic steering to steering by the driver, so the control amount of automatic steering is gradually decreased at a preset reduction rate. For example, Patent Document 1 below describes a steering assist control device that, in a situation where a vehicle is traveling on a curved road, when a condition for disabling automatic steering is satisfied, gradually decreases the target value of automatic steering to a minimum value over a predetermined period of time. [[PRIOR ART DOCUMENTS]] [[PATENT DOCUMENTS]]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-061280 [Overview of the project]

[0007] [Problems the invention aims to solve] As described above, in both LDA and LTA, when the control termination condition is met, the control amount of the automatic steering must be gradually reduced. However, the preferred reduction rate of the control amount varies depending on the vehicle's condition when the control termination condition is met. For example, when the target control amount is larger than the actual control amount, the control is terminated in a situation where control needs to be continued, so a small reduction rate of the control amount is preferable. Conversely, when the actual control amount is larger than the target control amount, the control is terminated in a situation where control is not necessary, so a large reduction rate of the control amount is preferable.

[0008] However, in conventional driving control systems, once the control termination condition is met, the amount of automatic steering control is gradually reduced at a preset reduction rate. Therefore, it is not possible to gradually reduce the control amount according to the relative magnitudes of the target control amount and the actual control amount.

[0009] The present invention provides a driving control device that controls the driving of a vehicle so that the vehicle drives along the lane within the lane, and which, when the control termination condition is met, can gradually reduce the control amount according to the relationship between the target control amount and the actual control amount.

[0010] [Means for solving the problem and the effects of the invention] According to the present invention, the vehicle (102) includes a target information acquisition device (16) for acquiring information on targets in front of the vehicle (102), an automatic steering device (46), and a control unit (such as a driver assistance ECU 10) configured to perform vehicle driving control. The driving control involves identifying a lane (110) based on the information acquired by the target information acquisition device, calculating a target control amount (target steering angle θt) for turning so that the vehicle can travel along the lane within the lane, and performing the actual control amount (steering angle θt) for turning. The vehicle is controlled to travel within a lane and along the lane by calculating a target correction amount of the steering angle (target correction amount of steering angle Δθt) to make the target control amount a target control amount, and controlling the automatic steering device so that the correction amount of the steering angle becomes the target correction amount (S10~S30). The vehicle driving control device (100) is provided which is configured to gradually reduce the target correction amount of the steering angle (S60~S80) when the control unit determines that it is necessary to terminate the driving control (S40).

[0011] The control unit is further configured to change the degree of reduction of the target correction amount to a different degree depending on the relative magnitudes of the target control amount and the actual control amount closest to the point in time when it is determined that it is necessary to terminate the driving control (S50).

[0012] According to the above configuration, when it is determined that driving control needs to be terminated, the target correction amount of the steering angle is gradually reduced. However, the degree to which the target correction amount is reduced varies depending on the relative magnitudes of the target control amount and the actual control amount closest to the point in time when it is determined that driving control needs to be terminated. Therefore, the degree to which the target correction amount is reduced can be variably set according to the relative magnitudes of the target control amount and the actual control amount.

[0013] [Aspects of the Invention] In one embodiment of the present invention, the control unit (such as the driver assistance ECU 10) is configured to increase the degree of reduction of the target correction amount when the actual control amount is greater than the target control amount, compared to when the target control amount is greater than the actual control amount.

[0014] According to the above embodiment, when the actual control amount is greater than the target control amount, the degree of reduction in the target correction amount is greater than when the target control amount is greater than the actual control amount. Therefore, the risk of unnecessary driving control continuing for a long time when the actual control amount is greater than the target control amount can be reduced. Conversely, when the actual control amount is greater than the target control amount, the degree of reduction in the target correction amount is not increased. Therefore, the risk of driving control ending prematurely when the actual control amount is greater than the target control amount can be reduced.

[0015] In another embodiment of the present invention, the control unit (such as the driver assistance ECU 10) is configured to increase the degree of reduction of the target correction amount when it determines that the actual control amount is greater than the target control amount and the difference between the actual control amount and the target control amount exceeds a first reference value.

[0016] According to the above embodiment, when the actual controlled amount is larger than the target controlled amount and the difference between the actual controlled amount and the target controlled amount is determined to exceed the first reference value, the degree of reduction of the target correction amount is increased. Therefore, in situations where the difference between the actual controlled amount and the target controlled amount is small and there is little need to increase the degree of reduction of the target correction amount, the degree of reduction of the target correction amount can be increased without changing the degree of reduction of the target correction amount, while in situations where there is a high need to increase the degree of reduction of the target correction amount, the degree of reduction of the target correction amount can be increased.

[0017] In another embodiment of the present invention, the control unit (such as the driver assistance ECU 10) is configured to reduce the degree of reduction of the target correction amount when it determines that the target control amount is greater than the actual control amount and that the difference between the target control amount and the actual control amount exceeds a second reference value.

[0018] According to the above embodiment, when the target control amount is larger than the actual control amount and the difference between the target control amount and the actual control amount is determined to exceed a second reference value, the degree of reduction of the target correction amount is reduced. Therefore, in situations where the difference between the target control amount and the actual control amount is small and there is little need to reduce the degree of reduction of the target correction amount, the degree of reduction of the target correction amount can be reduced without changing the degree of reduction of the target correction amount, while in situations where there is a high need to reduce the degree of reduction of the target correction amount, the degree of reduction of the target correction amount can be reduced.

[0019] In another embodiment of the present invention, the control unit (such as the driver assistance ECU 10) is configured to increase the degree of reduction of the target correction amount as the difference between the actual control amount and the target control amount increases.

[0020] According to the above embodiment, the greater the difference between the actual control amount and the target control amount, the greater the degree of reduction in the target correction amount can be. Therefore, even if the difference between the actual control amount and the target control amount is large, the automatic steering by the automatic steering system can be terminated earlier.

[0021] In another embodiment of the present invention, the control unit (such as the driver assistance ECU 10) is configured to reduce the degree of reduction of the target correction amount as the difference between the target control amount and the actual control amount increases.

[0022] According to the above embodiment, the greater the difference between the target control amount and the actual control amount, the smaller the degree of reduction in the target correction amount. Therefore, the greater the difference between the target control amount and the actual control amount, the longer the automatic steering by the automatic steering system can be maintained.

[0023] In another embodiment of the present invention, the control unit (such as the driving support ECU 10) is configured to reduce the degree of reduction of the target correction amount by reducing the rate of reduction of the target correction amount and delaying the start of the reduction of the target correction amount.

[0024] According to the above embodiment, the degree of reduction in the target adjustment amount can be reduced by reducing the rate of reduction of the target adjustment amount, delaying the start of the reduction of the target adjustment amount, or both.

[0025] In another aspect of the present invention, when it is determined that a lane is curved and the target correction amount is a correction amount for moving the vehicle outward of the curve with respect to the lane, the control unit (such as driving assistance ECU 10) is configured not to change the degree of reduction of the target correction amount.

[0026] Generally, when it is determined that a lane is curved and the target correction amount is a correction amount for moving the vehicle outward of the curve with respect to the lane, the target correction amount is smaller than that when it is determined that a lane is curved and the target correction amount is a correction amount for moving the vehicle inward of the curve with respect to the lane, so the necessity of changing the degree of reduction of the target correction amount is lower.

[0027] According to the above aspect, when it is determined that a lane is curved and the target correction amount is a correction amount for moving the vehicle outward of the curve with respect to the lane, the change of the degree of reduction of the target correction amount can be omitted.

[0028] In another aspect of the present invention, the control unit (such as driving assistance ECU 10) is configured to estimate a risk of the vehicle deviating from a lane based on information acquired by a target information acquiring device, and calculate a target control amount relating to turning as a target control amount for reducing the risk when it is determined that the risk exists.

[0029] According to the above aspect, the risk of the vehicle deviating from the lane is estimated, and when it is determined that the risk exists, the target control amount relating to turning is calculated as the target control amount for reducing the risk. Therefore, the risk of the vehicle deviating from the lane can be reduced through travel control.

[0030] In another aspect of the present invention, the control unit (such as driving assistance ECU 10) is configured to set a target trajectory for the vehicle to travel along the lane within the lane based on information acquired by a target information acquiring device, and calculate a target control amount relating to turning as a target control amount for causing the vehicle to travel along the target trajectory.

[0031] According to the above embodiment, a target trajectory is set for the vehicle to travel along the lane within the lane, and a target control amount related to turning is calculated as a target control amount for driving the vehicle along the target trajectory. Therefore, the vehicle can be driven along the target trajectory as closely as possible through driving control.

[0032] In this application, "lane" refers to the area in which a vehicle travels, as defined by white lines, curbs, road boundaries, etc. Furthermore, "target control quantity for turning" and "actual control quantity for turning" refer to the target value and actual value of the control quantity that changes the direction of travel of the vehicle, respectively. Moreover, as will be explained later, the "control quantity" may be the steering angle, the vehicle's lateral acceleration, the vehicle's yaw rate, the estimated lateral acceleration of the vehicle (product of vehicle speed and vehicle yaw rate), the vehicle's yaw moment, etc.

[0033] In the above description, to aid in understanding the present invention, the names and / or reference numerals used in the embodiments of the invention corresponding to those embodiments described later are indicated in parentheses. However, the components of the present invention are not limited to the components of the embodiments corresponding to the names and / or reference numerals indicated in parentheses. Other objects, other features and incidental advantages of the present invention will be readily apparent from the description of embodiments of the present invention, which will be described with reference to the following drawings. [Brief explanation of the drawing]

[0034] [Figure 1] This is a schematic diagram showing a driving control device according to an embodiment. [Figure 2] This is a flowchart of the LDA routine in the embodiment. [Figure 3] This diagram shows the relationship between the vehicle's direction of departure and the control direction of the steering angle θ in LDA (Lane Departure Adaptation). [Figure 4] This figure shows the relationship between the steering angle difference θdif and the correction coefficient Ka. [Figure 5]This diagram illustrates the relationship between the magnitude of the steering angle difference θdif and the reference value θdifc, and the relationship between the gradual decrease in the target correction amount Δθt after the LDA termination condition is met. [Figure 6] This diagram illustrates the operation of an embodiment when a vehicle is traveling on a curve. [Figure 7] This is a flowchart showing the essential parts of the modified LDA routine. [Figure 8] This diagram shows the relationship between the direction in which the vehicle deviates from the target trajectory and the control direction of the steering angle θ in LTA (Lane Trajectory Adjustment). [Figure 9] This figure shows another example of the relationship between the steering angle difference θdif and the correction coefficient Ka. [Figure 10] This figure shows an example of a nonlinear reduction gradient for the magnitude of the target correction amount Δθt when a vehicle is traveling on a lane whose curvature changes as it moves. [Modes for carrying out the invention]

[0035] A vehicle driving control device according to an embodiment of the present invention will be described in detail below with reference to the attached figures.

[0036] As shown in Figure 1, the driving control device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driver assistance ECU 10. The vehicle 102 may be a vehicle capable of autonomous driving and is equipped with a drive ECU 20, a brake ECU 30, an electric power steering ECU 40, and a meter ECU 50. ECU means an electronic control unit that mainly consists of a microcomputer. In the following description, the vehicle 102 will be referred to as "our vehicle 102" as needed to distinguish it from other vehicles, and electric power steering will be referred to as EPS.

[0037] Each ECU's microcomputer includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU implements various functions by executing instructions (programs, routines) stored in ROM. Furthermore, these ECUs are interconnected via CAN (Controller Area Network) 104, enabling data exchange (communication). Therefore, detection values ​​from sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0038] The driver assistance ECU 10 is a central control unit that performs vehicle driver assistance control such as LDA and LTA. In this embodiment, the driver assistance ECU 10 works in cooperation with other ECUs to perform LDA and LTA, as will be described in detail later.

[0039] The driver assistance ECU 10 is connected to a camera sensor 12 and a radar sensor 14. The camera sensor 12 and radar sensor 14 each include multiple camera devices and multiple radar devices, respectively. The camera sensor 12 and radar sensor 14 function as a target information acquisition device 16 that acquires information on targets at least in front of the vehicle 102.

[0040] Each camera device of the camera sensor 12, although not shown in the figure, includes a camera unit that photographs the area around the vehicle 102 and a recognition unit that analyzes the image data obtained from the camera unit to recognize road markings, other vehicles, and other objects. The recognition unit supplies information about the recognized objects to the driver assistance ECU 10 at predetermined intervals.

[0041] Each radar device of the radar sensor 14 is equipped with a radar transceiver and a signal processing unit (not shown). The radar transceiver emits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves (i.e., reflected waves) reflected by three-dimensional objects (e.g., other vehicles, bicycles, etc.) within the emission range. The signal processing unit acquires information representing the relative distance and relative speed between the vehicle and the three-dimensional object, and the relative position (direction) of the three-dimensional object relative to the vehicle, at predetermined intervals based on the phase difference between the emitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from the emission of millimeter waves to the reception of reflected waves, and supplies this information to the driver assistance ECU 10. LiDAR (Light Detection And Ranging) may be used instead of or in addition to the radar sensor 14.

[0042] Furthermore, a setting control 18 is connected to the driver assistance ECU 10, and the setting control 18 is positioned to be operated by the driver. Although not shown in Figure 1, in this embodiment, the setting control 18 includes an LDA switch and an LTA switch, and the driver assistance ECU 10 executes LDA when the LDA switch is ON and executes LTA when the LTA switch is ON. Note that the LDA switch or LTA switch may be omitted.

[0043] The drive ECU 20 is connected to a drive unit 22, which accelerates the vehicle 102 by applying driving force to the drive wheels, which are not shown in Figure 1. Under normal circumstances, the drive ECU 20 controls the drive unit 22 so that the driving force generated by the drive unit 22 changes in accordance with the driver's driving operation, and when it receives a command signal from the driver assistance ECU 10, it controls the drive unit 22 based on the command signal.

[0044] The braking ECU 30 is connected to a braking device 32 that decelerates the vehicle 102 by applying braking force to the wheels, which are not shown in Figure 1. Under normal circumstances, the braking ECU 30 controls the braking device 32 so that the braking force generated by the braking device 32 changes in accordance with the driver's braking operation. When it receives a command signal from the driver assistance ECU 10, it performs automatic braking by controlling the braking device 32 based on the command signal.

[0045] The EPS / ECU 40 is connected to the EPS device 42. Based on the steering torque Ts and vehicle speed V detected by the driving operation sensor 60 and vehicle condition sensor 70 (described later), the EPS / ECU 40 controls the steering assist torque by controlling the EPS device 42 in a manner known in the art, thereby reducing the driver's steering burden. Furthermore, by controlling the EPS device 42, the EPS / ECU 40 can steer the steering wheels 44 as needed. Therefore, the EPS / ECU 40 and the EPS device 42 function as an automatic steering system 46 that automatically steers the steering wheels 44 as needed.

[0046] A warning device 52 is connected to the meter ECU 50. The warning device 52 is activated when it is determined that there is a risk of the vehicle 102 deviating from its lane, and issues a warning that the vehicle is in danger of deviating from its lane. The warning device 52 may be any of the following: a visual warning device such as a display or warning lamp, an auditory warning device such as a warning buzzer, or a tactile warning device such as seat vibration, or any combination thereof.

[0047] The driving operation sensor 70 and the vehicle condition sensor 80 are connected to CAN 104. Information detected by the driving operation sensor 70 and the vehicle condition sensor 80 (referred to as sensor information) is transmitted to CAN 104. The sensor information transmitted to CAN 104 can be used as appropriate by each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to CAN 104 from that specific ECU.

[0048] The driving operation sensor 70 includes a drive operation amount sensor and a brake operation amount sensor. Furthermore, the driving operation sensor 70 includes a steering angle sensor, a steering torque sensor, and the like. The vehicle state sensor 80 includes a wheel speed sensor, a longitudinal acceleration sensor, a lateral acceleration sensor, and a yaw rate sensor. In this embodiment, the steering angle sensor and the steering torque sensor detect the steering angle θ and steering torque Ts, respectively, with the values ​​when the vehicle 102 is in a right + turning state being considered positive.

[0049] In this embodiment, the ROM of the driver assistance ECU 10 stores a program for LDA corresponding to the flowchart shown in Figure 2. The CPU executes the LDA of this embodiment according to this program.

[0050] <LDA routine of the embodiment> Next, the LDA routine of the embodiment will be described with reference to the flowchart shown in Figure 2. The LDA according to the flowchart shown in Figure 2 is repeatedly executed by the CPU of the driver assistance ECU 10 in each control cycle when the LDA switch of the setting control unit 18 (not shown in Figure 1) is turned ON.

[0051] First, in step S10, the CPU calculates a target steering angle θt to prevent the vehicle from deviating from the lane, based on the positional relationship of the vehicle 102 with respect to the lane detected by the camera sensor 12. The target steering angle θt may be calculated in any manner known in the art, such as the method described in Japanese Patent Application Publication No. 2022-39311.

[0052] For example, as shown in Figure 3(A), when there is a risk that vehicle 102 will deviate from lane 110 and cross the left white line 112L, the target steering angle θt is calculated as the steering angle that imparts a rightward yaw moment Ms to vehicle 102, bringing it closer to the right white line 112R. Conversely, as shown in Figure 3(B), when there is a risk that vehicle 102 will deviate from lane 110 and cross the right white line 112R, the target steering angle θt is calculated as the steering angle that imparts a leftward yaw moment Ms to vehicle 102, bringing it closer to the left white line 112L. Furthermore, the absolute value of the difference Δθ between the target steering angle θt and the actual steering angle θ detected by the steering angle sensor increases as the risk of the vehicle deviating from the lane increases.

[0053] In step S20, the CPU determines whether or not a steering angle correction is necessary by checking, for example, whether the absolute value of the difference Δθ between the target steering angle θt and the actual steering angle θ, i.e., the target steering angle correction amount Δθt, is greater than or equal to a reference value Δθc (a positive constant). If the CPU makes a negative determination, it terminates this control; if it makes a positive determination, it proceeds to step S30.

[0054] In step S30, the CPU outputs a command signal to the EPS / ECU 40, thereby controlling the steering angle by the automatic steering device 46 so that the actual steering angle θ becomes the target steering angle θt, that is, so that the correction amount Δθ of the steering angle θ becomes the target correction amount Δθt. The target steering angle θt, the correction amount Δθ of the steering angle, and the target correction amount Δθt are assumed to take positive values ​​when the vehicle is turning to the right, similar to the steering angle θ.

[0055] In step S40, the CPU determines whether the termination condition for LDA has been met. If the CPU determines it is not met, it terminates this control; if it determines it is met, it proceeds to step S50.

[0056] In this case, the termination conditions of the LDA may be deemed to have been met if any of the following situations are determined. A: The driving control device 100 does not function properly due to a malfunction of the camera sensor 12, an abnormality in the EPS device 42, or an abnormality in the wheel speed sensor. B: The driver performed steering operations or turned off the LDA switch, such as override steering or operating the turn signals. C: There are situations on the road where LDA cannot be continued, such as the disappearance of white lines or obstacles on the road.

[0057] In step S50, the CPU calculates the difference between the target steering angle θt and the actual steering angle θa, θdif = (θt - θa)signθt, with the sign of the target steering angle θt being signθt. Based on the difference in steering angles θdif, the CPU calculates the correction coefficient Ka by referring to the map corresponding to the solid line in Figure 4.

[0058] As shown in Figure 4, when the absolute value of the steering angle difference θdif is less than or equal to the reference value θdifc (a positive constant), the correction coefficient Ka is 1. When the steering angle difference θdif is a positive value greater than the reference value θdifc, the correction coefficient Ka is less than 1 and decreases as the steering angle difference θdif increases. Conversely, when the steering angle difference θdif is a negative value less than -θdifc, the correction coefficient Ka is greater than 1 and increases as the steering angle difference θdif decreases (as the absolute value of the difference θdif increases).

[0059] In step S60, the CPU reduces the target correction amount Δθt by calculating the target correction amount Δθt of the steering angle θ according to equation (1) below. In equation (1) below, Δθts is the target correction amount Δθt at the time when a positive judgment was made in step S40. Kb is a basic reduction coefficient greater than 0 and less than 1. t is the elapsed time from the time when a positive judgment was made in step S40. Δθt=Δθts-KaKbΔθts·t…(1)

[0060] In step S70, the CPU, similar to step S30, outputs a command signal to the EPS-ECU 40, thereby controlling the steering angle so that the amount of correction Δθ of the steering angle θ by the automatic steering device 46 becomes the target correction amount Δθt.

[0061] In step S80, the CPU determines whether the absolute value of the target correction amount Δθt is less than or equal to a preset minimum value Δθmin (a positive constant). If the CPU determines it is negative, it returns to step S60; if it determines it is positive, it terminates the control.

[0062] As can be seen from the above explanation, if the termination conditions of LDA are not met, a negative determination is made in step S40, and steps S10 to S40 are executed repeatedly. Therefore, when there is a risk that vehicle 102 will deviate from its lane, the direction of travel of the vehicle changes in a direction that reduces the risk of lane departure, thus preventing lane departure.

[0063] Furthermore, when the LDA termination condition is met, a positive determination is made in step S40, and steps S50 to S80 are repeatedly executed until the absolute value of the target correction amount Δθt is less than or equal to the minimum value Δθmin. This gradually reduces the magnitude of the target correction amount Δθt according to the basic reduction coefficient Kb and correction coefficient Ka. The correction coefficient Ka is calculated in step S50 based on the difference in steering angles θdif.

[0064] As shown in Figure 4, when the absolute value of the steering angle difference θdif is less than or equal to the reference value θdifc, the correction coefficient Ka is set to 1. Therefore, as shown in Figure 5(A), the magnitude of the target correction amount Δθt is gradually reduced by the basic gradual reduction gradient based on the basic reduction coefficient Kb.

[0065] In contrast, when the magnitude of the target steering angle θt is greater than the magnitude of the actual steering angle θa, and the difference in steering angles θdif is a positive value greater than the reference value θdifc, that is, when the amount of correction for the steering angle θ is insufficient, the correction coefficient Ka is set to a value less than 1 and which decreases as the difference in steering angles θdif increases. Therefore, as shown in Figure 5(B), the magnitude of the target correction amount Δθt is gradually reduced by a gradual reduction gradient smaller than the basic gradual reduction gradient (dashed line gradient).

[0066] Conversely, when the magnitude of the actual steering angle θa is greater than the magnitude of the target steering angle θt, and the difference in steering angles θdif is a negative value less than -θdifc, that is, when the amount of correction to the steering angle θ is excessive, the correction coefficient Ka is set to a value greater than 1 and increases as the difference in steering angles θdif decreases (as the absolute value of the difference θdif increases). Therefore, as shown in Figure 5(C), the magnitude of the target correction amount Δθt is gradually reduced by a gradient that is greater than the basic gradient (dashed line gradient).

[0067] <Operation of the Embodiment> Next, the operation of the embodiment will be described with reference to Figure 6. As shown in Figure 6, suppose that vehicle 102 is traveling in lane 110, road 114 curves to the right, and the curvature of lane 110 gradually increases and then gradually decreases. In Figure 6, P1 to P5 indicate the position of the vehicle as it moves.

[0068] As vehicle 102 moves from position P1 to position P2, the curvature of lane 110 at the vehicle's position increases as the vehicle moves, creating a risk that the vehicle may deviate from lane 110 to the outside of the curve. A target steering angle θt is calculated to prevent the vehicle from deviating from the lane (S10), and the steering angle is controlled so that the actual steering angle θ becomes the target steering angle θt, that is, so that the steering angle correction amount Δθ becomes the target correction amount Δθt (S30). Therefore, as shown as position P3 in Figure 6, the vehicle is prevented from deviating from lane 110.

[0069] However, when the LDA termination condition is met (S30) while the vehicle 102 is located at or before / after position P2, the magnitude of the target correction amount Δθt is gradually reduced. Therefore, when the gradual reduction gradient of the magnitude of the target correction amount Δθt is large, the magnitude of the yaw moment Ms required to prevent the vehicle 102 from deviating from lane 112 decreases rapidly. As a result, as shown as position P3' in Figure 6, it may become impossible to reduce the risk of the vehicle deviating from lane 110.

[0070] In contrast, according to this embodiment, the correction coefficient Ka is set to a value less than 1 and decreases as the difference in steering angle θdif increases, so the magnitude of the target correction amount Δθt is gradually reduced at a gradient smaller than the basic gradient. Therefore, the magnitude of the yaw moment Ms that prevents the vehicle 102 from deviating from lane 112 is prevented from decreasing too quickly, thereby reducing the risk of the vehicle deviating from lane 110.

[0071] As vehicle 102 moves from position P3 to position P4, the curvature of lane 110 at the vehicle's position decreases as the vehicle moves, and steering angle control is performed to reduce the risk of the vehicle deviating from lane 110 to the inside of the curve, and the LDA termination condition is met before vehicle 102 reaches position P4 (S30). Furthermore, the difference in steering angle θdif at the time the LDA termination condition is met is a negative value smaller than -θdifc, and the amount of correction of the steering angle θ is excessive.

[0072] The magnitude of the target correction amount Δθt is gradually reduced, but when the rate of reduction of the magnitude of the target correction amount Δθt is small, the yaw moment Ms required to prevent the vehicle 102 from deviating from lane 112 remains excessive. As a result, there is a higher risk that the vehicle will deviate from lane 110 into the adjacent lane 116 on the inside of the curve, as shown as position P4' in Figure 6.

[0073] In contrast, according to this embodiment, the correction coefficient Ka is set to a value greater than 1 and to increase as the difference in steering angle θdif increases, so the magnitude of the target correction amount Δθt is reduced by a gradient that is greater than the basic gradient. Therefore, it is possible to prevent a situation in which the magnitude of the yaw moment Ms required to prevent the vehicle 102 from deviating from lane 112 is excessive, thereby reducing the risk of the vehicle deviating from lane 110 into the adjacent lane 114 on the inside of the curve.

[0074] Figure 6 shows an example where there is a risk of vehicle 102 deviating from the curved lane 110, and the LDA termination condition is met. However, even when there is a risk of vehicle deviating from the straight lane 110, and the LDA termination condition is met, the risk of the vehicle deviating from the lane 110 can be similarly reduced.

[0075] <Variation> In the above embodiment, when the vehicle 102 is traveling on a curve, the risk of lane departure is set variably based on the difference in steering angle θdif, without distinguishing whether the vehicle is on the outside or inside of the curve. However, the magnitude of the target correction amount Δθt when the vehicle 102 is at risk of deviating to the inside of the curve is smaller than the magnitude of the target correction amount Δθt when the vehicle is at risk of deviating to the outside of the curve.

[0076] Therefore, as shown in Figure 7, in step S42 preceding step S50, it may be determined whether or not there is a risk of the vehicle 102 deviating to the inside of the curve. If a negative determination is made, step S50 is executed, and if a positive determination is made, in step S44, the correction coefficient Ka is set to 1, and then step S60 is executed.

[0077] Generally, when it is determined that the lane is curved and the target correction amount is a correction amount that moves the vehicle to the outside of the curve relative to the lane, the target correction amount is smaller and the necessity of changing the degree of reduction of the target correction amount is lower than when it is determined that the lane is curved and the target correction amount is a correction amount that moves the vehicle to the inside of the curve relative to the lane.

[0078] According to the above modification, when it is determined that the lane is curved and the target correction amount Δθt is a correction amount that moves the vehicle to the outside of the curve relative to the lane, changing the degree of reduction of the target correction amount can be omitted.

[0079] <In case of LTA> When the LTA switch of the setting operation device 18 is on, LTA is executed. In step S10, the CPU sets a target trajectory of the vehicle based on the lane detected by the camera sensor 12 or the trajectory of the preceding vehicle. Further, the CPU calculates a target steering angle θt for reducing the deviation of the vehicle position from the target trajectory. The target steering angle θt may be calculated by any method known in the art, for example, according to the method described in Japanese Laid-Open Patent Publication No. 2017-35925.

[0080] For example, as shown in FIG. 8(A), when there is a possibility that a reference position such as the center of gravity of the vehicle 102 deviates leftward from the target trajectory 120 by more than a reference value, the target steering angle θt is calculated as a steering angle for applying a yaw moment Ms in the right-turn direction to the vehicle 102 to bring the reference position of the vehicle closer to the target trajectory 120. Conversely, as shown in FIG. 8(B), when there is a possibility that the vehicle 102 deviates rightward from the target trajectory 120 by more than a reference value, the target steering angle θt is calculated as a steering angle for applying a yaw moment Ms in the left-turn direction to the vehicle 102 to bring the vehicle closer to the target trajectory 120. Also, the absolute value of the difference Δθ between the target steering angle θt and the actual steering angle θ detected by the steering angle sensor increases as the degree of the vehicle deviating from the target trajectory becomes higher.

[0081] In step S40, the CPU determines whether the LTA termination condition has been met. If the CPU determines it is not met, it terminates this control; if it determines it is met, it proceeds to step S50.

[0082] In this case, the termination conditions for the LTA may be deemed to have been met if any of the following situations are determined. D: The driving control device 100 does not function properly, such as due to a malfunction of the camera sensor 12, an abnormality in the EPS device 42, or an abnormality in the wheel speed sensor. E: The driver performed a steering operation or turned off the LTA switch, such as override steering or turn signal operation. F: There are situations where it is impossible to set a target trajectory and continue the LTA on the road, such as when white lines disappear or obstacles are present on the road.

[0083] The other steps from step S20 onward are performed in the same manner as in the embodiments or modifications described above. Therefore, in the case of LTA as well as in the case of LDA, the risk of the vehicle deviating from its lane when the LTA termination condition is met can be reduced compared to the case where the correction coefficient Ka is not variably set based on the difference in steering angle θdif.

[0084] As can be seen from the above explanation, according to the embodiment and modified examples, the gradual decrease gradient of the target correction amount Δθt is changed depending on whether the amount of correction of the steering angle θ at the time the LDA or LTA termination condition is met is insufficient or excessive. Therefore, in both cases, where the amount of correction of the steering angle θ is insufficient or excessive, the risk of the vehicle deviating from the lane can be reduced compared to the case where the gradual decrease gradient of the target correction amount Δθt is not changed.

[0085] In particular, according to the embodiment and its modifications, when the actual control amount (the magnitude of the actual steering angle θa) is greater than the target control amount (the magnitude of the target steering angle θt), the degree of reduction in the target correction amount is greater than when the target control amount is greater than the actual control amount (see Figure 5). Therefore, when the actual control amount is greater than the target control amount, the risk of unnecessary driving control continuing for a long time can be reduced. Conversely, when the actual control amount is greater than the target control amount, the degree of reduction in the target correction amount is not increased. Therefore, when the actual control amount is greater than the target control amount, the risk of driving control ending prematurely can be reduced.

[0086] More specifically, when the actual controlled amount is larger than the target controlled amount and the difference between the actual controlled amount and the target controlled amount is determined to exceed the first reference value, the degree of reduction of the target correction amount is increased (see Figure 5(C)). Therefore, in situations where the difference between the actual controlled amount and the target controlled amount is small and there is little need to increase the degree of reduction of the target correction amount, the degree of reduction of the target correction amount can be increased without changing the degree of reduction of the target correction amount, while in situations where there is a high need to increase the degree of reduction of the target correction amount, the degree of reduction of the target correction amount can be increased.

[0087] Furthermore, the greater the difference between the actual controlled amount and the target controlled amount, the greater the reduction in the target correction amount (see Figure 4). Therefore, the greater the difference between the actual controlled amount and the target controlled amount, the greater the reduction in the target correction amount can be, allowing the automatic steering by the automatic steering system to be terminated earlier even when the difference between the actual controlled amount and the target controlled amount is large.

[0088] Conversely, when the target control amount is larger than the actual control amount and the difference between the target control amount and the actual control amount is determined to exceed a second reference value, the degree of reduction in the target correction amount is reduced (see Figure 5(B)). Therefore, in situations where the difference between the target control amount and the actual control amount is small and there is little need to reduce the degree of reduction in the target correction amount, the degree of reduction in the target correction amount can be reduced without changing the degree of reduction in the target correction amount, while in situations where there is a high need to reduce the degree of reduction in the target correction amount can be reduced.

[0089] Furthermore, the greater the difference between the target control amount and the actual control amount, the smaller the degree of reduction in the target correction amount (see Figure 4). Therefore, since the degree of reduction in the target correction amount is smaller the greater the difference between the target control amount and the actual control amount, the longer the automatic steering by the automatic steering system can be maintained.

[0090] Although the present invention has been described in detail above in terms of specific embodiments and modifications, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments and modifications described above, and that various other embodiments are possible within the scope of the present invention.

[0091] For example, in the embodiment and its modifications, in step S50, the correction coefficient Ka is calculated based on the target steering angle θt and the actual steering angle θ in the current control cycle. However, if, for example, information on the actual steering angle θ is not available at the time it is determined that the control termination condition has been met, the correction coefficient Ka may be calculated based on the target steering angle θt of the current control cycle and the actual steering angle θ of the previous control cycle. That is, the correction coefficient Ka should be calculated based on the target steering angle θt and the actual steering angle θ of the control cycle closest to the time it is determined that the control termination condition has been met.

[0092] Furthermore, in the embodiments and modified examples, the target control quantity for turning and the actual control quantity for turning the vehicle are the target steering angle θt and the steering angle θ, respectively. However, the control quantity may also be the vehicle's lateral acceleration, the vehicle's yaw rate, the estimated vehicle's lateral acceleration (product of vehicle speed and vehicle's yaw rate), or the vehicle's yaw moment. An example of the calculation procedure for the target lateral acceleration of the vehicle in LDA and LTA is described in Japanese Patent Publication No. 2017-65273. An example of the calculation procedure for the target yaw rate and target lateral acceleration of the vehicle in LTA is described in Japanese Patent Publication No. 2010-6279.

[0093] Furthermore, if the controlled variable is the vehicle's lateral acceleration, vehicle's yaw rate, estimated vehicle lateral acceleration, or vehicle's yaw moment, in step S30, the target correction amount Δθt of the steering angle θ is calculated based on the difference between the target controlled variable and the actual controlled variable, and the vehicle is controlled so that the correction amount Δθ of the steering angle θ becomes the target correction amount Δθt.

[0094] Furthermore, the correction coefficient Ka may be calculated from a map similar to the solid line in Figure 4, based on the difference between the target control amount and the actual control amount, or, as in the embodiment, from a map corresponding to the solid line in Figure 4, based on the difference θdif between the target steering angle θt and the actual steering angle θa.

[0095] Furthermore, in the embodiments and modified examples, the correction coefficient Ka is calculated in step S50 from the map corresponding to the solid line in Figure 4 based on the difference in steering angles θdif, and the correction coefficient Ka is 1 when the absolute value of the difference in steering angles θdif is less than or equal to the reference value θdifc. However, the correction coefficient Ka may also be calculated from the map corresponding to the dashed line in Figure 4 based on the difference in steering angles θdif.

[0096] Furthermore, in the embodiments and modified examples, the correction coefficient Ka decreases as the steering angle difference θdif increases in the range greater than or equal to the reference value θdifc, and increases as the steering angle difference θdif decreases in the range less than or equal to the reference value -θdifc. However, the correction coefficient Ka may be a constant value in the range greater than or equal to the reference value θdifc and / or less than or equal to the reference value -θdifc.

[0097] For example, in the first modification example shown in Figure 9(A), when the absolute value of the steering angle difference θdif is less than or equal to the reference value θdifc, the correction coefficient Ka is 1, as in the embodiment. However, when the steering angle difference θdif is greater than the reference value θdifc, the correction coefficient Ka is a positive constant Ka1 less than 1, and when the steering angle difference θdif is less than the reference value -θdifc, the correction coefficient Ka is a positive constant Ka2 greater than 1.

[0098] Furthermore, as shown by the dashed line in Figure 9(A), in the first correction example, when the steering angle difference θdif decreases from a value greater than the reference value θdifc, the correction coefficient Ka may be maintained as a positive constant Ka1 until the steering angle difference θdif becomes smaller than the reference value θdifc, which is θdifc1. In that case, it is possible to maintain a situation where the gradual decrease in the magnitude of the target correction amount Δθt is reduced until the steering angle difference θdif becomes smaller than the reference value θdifc, which is θdifc1.

[0099] Similarly, as shown by the dashed line in Figure 9(A), in the first correction example, when the steering angle difference θdif increases from a value smaller than the reference value -θdifc, the correction coefficient Ka may be maintained as a positive constant Ka2 until the steering angle difference θdif becomes greater than the reference value -θdifc, i.e., θdifc2. In that case, it is possible to maintain a situation where the gradual decrease in the magnitude of the target correction amount Δθt is increased until the steering angle difference θdif becomes greater than the reference value -θdifc, i.e., θdifc2.

[0100] In the second correction example shown in Figure 9(B), the correction coefficient Ka is 1 when the steering angle difference θdif is 0. However, when the steering angle difference θdif is a positive value, the correction coefficient Ka is a positive constant Ka1 less than 1, and when the steering angle difference θdif is a negative value, the correction coefficient Ka is a positive constant Ka2 greater than 1.

[0101] Furthermore, as shown by the dashed line in Figure 9(B), in the second correction example, when the steering angle difference θdif increases from a value smaller than the reference value 0, the correction coefficient Ka may be maintained as a positive constant Ka2 until the steering angle difference θdif becomes greater than the reference value 0, i.e., θdifc2. In that case, it is possible to maintain a situation where the gradual decrease in the magnitude of the target correction amount Δθt is increased until the steering angle difference θdif becomes greater than the reference value 0, i.e., θdifc2.

[0102] Furthermore, in the third correction example shown in Figure 9(C), when the steering angle difference θdif is greater than the reference value -θdifc, the correction coefficient Ka is a positive constant Ka1 less than 1, and when the steering angle difference θdif is less than or equal to the reference value -θdifc, the correction coefficient Ka is a positive constant Ka2 greater than 1.

[0103] Furthermore, as shown by the dashed line in Figure 9(C), in the third correction example, when the steering angle difference θdif increases from a value smaller than the reference value -θdifc, the correction coefficient Ka may be maintained as a positive constant Ka2 until the steering angle difference θdif becomes greater than the reference value -θdifc, i.e., θdifc2. In that case, it is possible to maintain a situation where the gradual decrease in the magnitude of the target correction amount Δθt is increased until the steering angle difference θdif becomes greater than the reference value -θdifc, i.e., θdifc2.

[0104] Furthermore, in the fourth correction example shown in Figure 9(D), when the steering angle difference θdif is greater than the reference value θdifc, the correction coefficient Ka is a positive constant Ka1 less than 1, and when the steering angle difference θdif is less than or equal to the reference value θdifc, the correction coefficient Ka is a positive constant Ka2 greater than 1.

[0105] Furthermore, as shown by the dashed line in Figure 9(D), in the fourth correction example, when the steering angle difference θdif increases from a value smaller than the reference value θdifc, the correction coefficient Ka may be maintained as a positive constant Ka2 until the steering angle difference θdif becomes larger than the reference value θdifc, i.e., θdifc2. In that case, it is possible to maintain a situation where the gradual decrease in the magnitude of the target correction amount Δθt increases until the steering angle difference θdif becomes larger than the reference value θdifc, i.e., θdifc12.

[0106] Furthermore, in the embodiments, modifications, and the first modification, the first reference value is the reference value θdifc, the second reference value is the reference value -θdifc, and the absolute values ​​of the first and second reference values ​​are the same. However, the absolute values ​​of the first and second reference values ​​may be different from each other.

[0107] Furthermore, in the embodiments and modified examples, the reduction in the rate of decrease of the magnitude of the target correction amount Δθt is achieved by reducing the gradual decrease slope of the magnitude of the target correction amount Δθt. However, the reduction in the rate of decrease of the magnitude of the target correction amount Δθt may also be achieved by delaying the start of the gradual decrease of the magnitude of the target correction amount Δθt, or by both reducing the gradual decrease slope of the magnitude of the target correction amount Δθt and delaying the start of the gradual decrease.

[0108] Furthermore, in the embodiments and modifications, the reduction rate of the magnitude of the target correction amount Δθt is performed at a constant gradient. However, the magnitude of the target correction amount Δθt may be reduced at a reduction rate that changes the reduction gradient.

[0109] In particular, the reduction gradient of the target correction amount Δθt may be changed according to the subsequent change in lane curvature that is known at the time the LDA or LTA termination conditions are met. For example, as shown in Figure 10, if the subsequent lane curvature decreases, the reduction gradient of the target correction amount Δθt may be set to be large immediately after the start of reduction, and then to decrease as time progresses. In Figure 10, the dashed line shows the standard gradient when the correction coefficient Ka is 1. [Explanation of symbols]

[0110] 10…Driver assistance ECU, 12…Camera sensor, 14…Radar sensor, 16…Target information acquisition device, 40…EPS / ECU, 60…Driver operation sensor, 70…Vehicle status sensor, 100…Driving control device, 102…Vehicle, 110…Lane, 112L, 112R…White line, 120…Target trajectory

Claims

1. A target information acquisition device that acquires information about targets in front of the vehicle, Automatic steering system, A control unit configured to control the movement of a vehicle, The aforementioned driving control involves identifying a lane based on information acquired by the target information acquisition device, calculating a target control amount for turning so that the vehicle can travel within the lane and along the lane, calculating a target adjustment amount for the steering angle to make the actual control amount for turning the vehicle equal to the target control amount, and controlling the automatic steering device so that the adjustment amount for the steering angle equals the target adjustment amount, thereby causing the vehicle to travel within the lane and along the lane. In a vehicle driving control device configured to gradually reduce the target correction amount of the steering angle when the control unit determines that it is necessary to terminate the driving control, The control unit is further configured to change the degree of reduction of the target correction amount to a different degree depending on the relative magnitudes of the target control amount and the actual control amount closest to the point in time when it is determined that it is necessary to terminate the driving control.

2. A vehicle driving control device according to claim 1, wherein the control unit is configured such that when the actual control amount is greater than the target control amount, the degree of reduction of the target correction amount is greater than when the target control amount is greater than the actual control amount.

3. A vehicle driving control device according to claim 1, wherein the control unit is configured to increase the degree of reduction of the target correction amount when it determines that the actual control amount is greater than the target control amount and the difference between the actual control amount and the target control amount is greater than or equal to a first reference value.

4. A vehicle driving control device according to claim 1, wherein the control unit is configured to reduce the degree of reduction of the target correction amount when it determines that the target control amount is greater than the actual control amount and the difference between the target control amount and the actual control amount is greater than or equal to a second reference value.

5. A vehicle driving control device according to claim 3, wherein the control unit is configured to increase the degree of reduction of the target correction amount as the difference between the actual control amount and the target control amount increases.

6. A vehicle driving control device according to claim 4, wherein the control unit is configured to reduce the degree of reduction of the target correction amount as the difference between the target control amount and the actual control amount increases.

7. A vehicle driving control device according to claim 4, wherein the control unit is configured to reduce the degree of reduction of the target correction amount by reducing the rate of reduction of the target correction amount and delaying the start of the reduction of the target correction amount.

8. A vehicle driving control device according to claim 1, wherein the control unit is configured not to change the degree of reduction of the target correction amount when it is determined that the lane is curved and the target correction amount is a correction amount that moves the vehicle outward from the curve relative to the lane.

9. A vehicle driving control device according to claim 1, wherein the control unit is configured to estimate the likelihood of the vehicle deviating from the lane based on information acquired by the target information acquisition device, and to calculate a target control amount for turning as a target control amount to reduce the likelihood when it is determined that such a likelihood exists.

10. A vehicle driving control device according to claim 1, wherein the control unit is configured to set a target trajectory for the vehicle to travel along the lane within the lane based on information acquired by the target information acquisition device, and to calculate a target control amount for turning as a target control amount for driving the vehicle along the target trajectory.

Images