Driving force control method and driving force control device

Abstract

To improve, in a case where steering control is performed based on a traveling track detected by a sensor detecting a surrounding environment of an own vehicle, stability of the steering control when distance of the traveling track an environment recognition sensor can detect is shortened.SOLUTION: A drive force control method comprises steps of: detecting a traveling track in the front of an advancing direction of an own vehicle with a sensor (S2); detecting a first distance from the farthest point within a range where the sensor can detect the traveling track to the own vehicle (S4); setting a front gazing point away from the own vehicle by a second distance in the traveling track detected by the sensor in the front of the advancing direction of the own vehicle (S8); setting a target drive force which is to be generated in the own vehicle (S10); and controlling, when the first distance is less than the second distance, a driving source so that the drive force of the driving source becomes a correction driving force which is obtained by reduction correction of the target drive force (S11, S12).SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Patent document 1 describes a steering control device that detects lane marks from an image captured in front of the vehicle, sets a forward gaze point at a point a forward gaze distance ahead of the vehicle's lane, and controls the vehicle's steering device so that the vehicle heads toward the forward gaze point. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-312505 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if steering control is performed based on the road detected by the sensor in this manner, stable steering control may not be possible if the distance at which the sensor can detect the road becomes shorter than the forward gaze distance. The present invention aims to improve the stability of steering control when steering control is performed based on a road detected by a sensor that detects the environment around the vehicle, when the distance over which the sensor can detect the road becomes shorter. [Means for solving the problem]

[0005] In one embodiment of the driving force control method of the present invention, a sensor detects the road ahead in the direction of travel of the vehicle, detects a first distance which is the distance from the farthest point within the range in which the sensor can detect the road to the vehicle, sets a forward gaze point a second distance away from the vehicle within the road detected by the sensor ahead in the direction of travel of the vehicle, controls the steering mechanism of the vehicle based on the set forward gaze point, sets a target driving force to be generated in the vehicle, and if the first distance is greater than or equal to the second distance, controls the driving source so that the driving force of the driving source of the vehicle becomes the target driving force, and if the first distance is less than the second distance, controls the driving source so that the driving force of the driving source becomes a corrected driving force obtained by reducing or correcting the target driving force. [Effects of the Invention]

[0006] According to the present invention, when steering control is performed based on a road detected by a sensor that detects the environment around the vehicle, the stability of steering control can be improved when the distance over which the sensor can detect the road becomes shorter. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a vehicle equipped with a driving assistance device according to an embodiment. [Figure 2] 3A and 3B are diagrams illustrating an example of steering control by the driving assistance device according to the embodiment. [Figure 3] 2 is a block diagram illustrating an example of a functional configuration of a controller in FIG. 1. FIG. [Figure 4] 4 is a block diagram showing an example of a functional configuration of a driving force correction amount calculation unit shown in FIG. 3. FIG. [Figure 5] 4 is a flowchart illustrating an example of a driving force control method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are designated by identical or similar reference numerals, and redundant explanations will be omitted. Each drawing is a schematic view, and may differ from the actual product. The embodiments shown below exemplify devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention is not limited to the devices and methods exemplified in the following embodiments. The technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0009] (composition) The host vehicle 1 is equipped with a driving assistance device 10 that assists in driving the host vehicle 1. The driving assistance device 10 detects the driving environment around the host vehicle 1 and automatically controls the driving of the host vehicle 1 based on the detected driving environment, thereby assisting the occupant (e.g., the driver) of the host vehicle 1 in driving the host vehicle 1. For example, the driving assistance provided by the driving assistance device 10 for the vehicle 1 may include steering assistance control that automatically controls at least the steering angle. For example, the driving assistance provided by the driving assistance device 10 may include lane departure prevention assistance. Furthermore, the driving assistance provided by the driving assistance device 10 may include autonomous driving control that automatically drives the vehicle 1 without the involvement of a passenger. The driving assistance device 10 includes a positioning device 11, a map database 12, an external sensor 13, a vehicle sensor 14, a controller 15, and an actuator 16. In the drawings, the map database is referred to as a "map DB."

[0010] The positioning device 11 measures the current position of the vehicle 1. The positioning device 11 may include, for example, a Global Positioning System (GNSS) receiver. The GNSS receiver is, for example, a Global Positioning System (GPS) receiver, and receives radio waves from multiple navigation satellites to measure the current position of the vehicle 1. The map database 12 stores road map data. For example, the map database 12 may store high-precision map data (hereinafter simply referred to as "high-precision map") suitable as map information for autonomous driving. The high-precision map is map data with higher precision than map data for navigation (hereinafter simply referred to as "navigation map"). The road map data stored in the map database 12 may be a navigation map.

[0011] The external sensor 13 detects various information (ambient environment information) about the driving environment around the host vehicle 1, for example, objects around the host vehicle 1. The external sensor 13 detects the ambient environment of the host vehicle 1, such as objects present around the host vehicle 1, the relative positions between the host vehicle 1 and the objects, the distance between the host vehicle 1 and the objects, and the direction in which the objects exist. The external sensor 13 outputs the detected ambient environment information to the controller 15 as ambient information. For example, the external sensor 13 detects the relative positions of other vehicles and targets around the vehicle 1 relative to the vehicle 1. Here, targets include, for example, traffic lights installed on the road on which the vehicle 1 is traveling, lines on the road surface (lane markings, etc.), curbs on the shoulders of the road, guardrails, etc.

[0012] The external environment sensor 13 may include a monocular camera such as a full HD color camera. The camera captures an image including a recognition target in the environment surrounding the vehicle 1, and outputs the captured image to the controller 15 as external environment information. The external sensor 13 may also include a distance measuring device such as a laser range finder (LRF), radar, or LiDAR (Light Detection and Ranging) laser radar. The distance measuring device detects the relative position of the vehicle, which is determined by the relative distance and direction to an object present around the vehicle. The distance measuring device outputs the detected distance data to the controller 15 as external information.

[0013] The vehicle sensors 14 detect various information (vehicle information) obtained from the host vehicle 1. The vehicle sensors 14 include, for example, a vehicle speed sensor that detects the traveling speed (vehicle speed) V of the host vehicle 1, a wheel speed sensor that detects the rotational speed of each tire equipped on the host vehicle 1, a three-axis acceleration sensor (G sensor) that detects the acceleration (including deceleration) in three axial directions of the host vehicle 1, a steering angle sensor that detects the steering angle of the steering wheel, a turning angle sensor that detects the turning angle δt of the steered wheels, a gyro sensor that detects the angular velocity generated in the host vehicle 1, a yaw rate sensor that detects the yaw rate γ, an accelerator sensor that detects the operation amount α of the accelerator pedal of the host vehicle 1, and a brake sensor that detects the brake operation amount by the driver.

[0014] Controller 15 is an electronic control unit (ECU) that performs driving assistance control of host vehicle 1. In driving assistance control of host vehicle 1, controller 15 sets a target steering angle δtar, which is a target value for the steering angle δt of the steered wheels of host vehicle 1, based on the surrounding driving environment, and controls the steering mechanism so that the steering angle δt becomes the target steering angle δtar. Controller 15 also sets a larger target driving force Fx based on the accelerator pedal operation amount Ac by the driver, so that the larger the accelerator pedal operation amount Ac, the larger the target driving force Fx. Note that when autonomous driving control is performed by driving assistance device 10, the target driving force Fx is set based on the surrounding driving environment detected by external sensor 13. Controller 15 controls the driving force of the drive source of host vehicle 1 based on the set target driving force Fx. The controller 15 includes a processor 20 and peripheral components such as a storage device 21. The processor 20 may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0015] The storage device 21 may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device 21 may include memories such as a register, a cache memory, a ROM (Read Only Memory) used as a main memory device, and a RAM (Random Access Memory). The functions of the controller 15 described below are realized by, for example, the processor 20 executing a computer program stored in the storage device 21. The controller 15 may be formed of dedicated hardware for executing each of the information processes described below. For example, the controller 15 may include a functional logic circuit configured in a general-purpose semiconductor integrated circuit. For example, the controller 15 may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

[0016] The actuator 16 includes a drive source connected to the wheels of the host vehicle 1. The actuator 16 includes, for example, a drive motor, an internal combustion engine, or a brake actuator that generates a drive torque or a braking torque on the wheels of the host vehicle 1. In the following, in this embodiment, as an example, the actuator 16 includes a drive motor. The actuator 16 generates a drive force for driving the host vehicle 1 or a braking force for braking the host vehicle 1 in response to a control signal (target drive force Fx) from the controller 15. The actuator 16 also includes a steering mechanism that steers the steered wheels of the host vehicle 1. The actuator 16 steers the steered wheels of the host vehicle 1 in response to a control signal (target steering angle δtar) from the controller 15.

[0017] Next, the steering control of the controller 15 during driving assistance control of the host vehicle 1 will be described with reference to FIG. Dashed lines L1 and L2 indicate lane boundary lines (line marks) on the left and right sides of the road (driving lane) of the host vehicle 1. In addition, a solid line Ttrg indicates a target line (hereinafter referred to as a "target driving trajectory") along which the host vehicle 1 is driven by the driving assistance control of the driving assistance device 10. For example, in lane departure prevention assistance, the controller 15 controls the steering angle δt of the host vehicle 1 based on the surrounding driving environment so that the host vehicle 1 travels at a predetermined position in the lane width direction on the road. In this case, for example, a line offset inward by a predetermined distance in the lane width direction from the lane boundary lines L1 and L2 becomes the target driving trajectory Ttrg. For example, the target driving trajectory Ttrg may be the center of the road (center of the lane). Furthermore, for example, when autonomous driving control is performed by the driving assistance device 10, the controller 15 generates a target driving trajectory Ttrg for the vehicle 1 based on a driving route set by a navigation device or the like and the surrounding driving environment.

[0018] The dashed-dotted line P1 indicates the current position of the vehicle 1 in the longitudinal direction along the road, and point Ps indicates the lane width direction position of the vehicle 1 at the current position P1. Distance Y is the lateral deviation between the lane boundary line L1 and the lane width direction position Ps. The dashed-dotted line P2 indicates a position forward of the vehicle 1 at the forward gaze distance Df. The solid line Lt is a tangent to the lane boundary line L1 at the current position P1 and is perpendicular to the lane width direction. In Figure 2, the x-axis and y-axis directions represent the direction of the tangent line Lt and the lane width direction, respectively. The controller 15 sets a target position in the lane width direction at a position P2 ahead of the vehicle 1 by a forward gaze distance Df as a basic forward gaze point Pf. In the following description, the lane width direction position Ppre of the lane boundary line L1 at position P2, which is the forward gaze distance Df ahead of the host vehicle 1, will be referred to as the "forward lane boundary line position Ppre." For example, the lane width direction position of the basic forward gaze point Pf1 may be set based on the forward lane boundary line position Ppre. For example, a position that is a target lane width distance Ytrg away from the forward lane boundary line position Ppre in the lane width direction toward the center of the lane may be set as the lane width direction position of the basic forward gaze point Pf1.

[0019] For example, when a point on the target driving trajectory Ttrg is set as the basic forward gaze point Pf as shown in Figure 2, the distance between the target driving trajectory Ttrg and the lane boundary line L1 is set as the target lane width distance Ytrg. Also, when the basic forward gaze point Pf1 is set at the center of the lane, for example, half the length of the lane width is set as the target lane width distance Ytrg. The basic forward gaze point Pf1 may be set based on the lane center position instead of the forward lane boundary line position Ppre. That is, the lane center position at a position P2 that is the forward gaze distance Df ahead of the host vehicle 1 may be used as the reference. By controlling the steering angle δt so that the host vehicle 1 travels toward the basic forward gaze point Pf thus set, the controller 15 can make the host vehicle 1 travel along the target travel trajectory Ttrg. For example, the host vehicle 1 can travel along the lane and in the center of the lane.

[0020] However, the distance over which the external sensor 13 can detect the road (i.e., the distance over which the positions of the lane boundary lines L1, L2 can be detected) may be shortened due to various factors. In the following description, the distance from the limit point at which the external sensor 13 can detect the positions of the lane boundary lines L1, L2 ahead of the host vehicle 1 (i.e., the farthest point within the range detectable by the external sensor 13) to the position of the host vehicle 1 may be referred to as the "recognition distance Dr." For example, on a curved road, the recognition distance Dr may be shortened depending on the curvature of the road. The recognition distance Dr may also be shortened depending on the weather and time of day. As a result, if the recognition distance Dr becomes shorter than the look-ahead distance Df, the basic look-ahead point Pf1 cannot be set. However, if the look-ahead distance Df is shortened to match the recognition distance Dr, the frequency of the tracking control of the lane width direction position of the host vehicle 1 increases, reducing the stability of the control and making it more likely that sudden steering or divergent steering will occur. Furthermore, if the vehicle speed V of the host vehicle 1 increases with the look-ahead distance Df shortened, the resonance frequency of the yaw rotational motion may decrease, potentially destabilizing the control system.

[0021] Therefore, in the embodiment, when the recognition distance Dr is shorter than the forward gaze distance, the controller 15 corrects the target driving force Fx so that the driving force of the drive source is reduced. For example, when the distance difference ΔD obtained by subtracting the recognition distance Dr from the forward gaze distance is large, the controller 15 corrects the target driving force by a large amount of reduction correction compared to when the distance difference ΔD obtained by subtracting the recognition distance Dr from the forward gaze distance is small. This suppresses acceleration of the host vehicle 1 (or decelerates the host vehicle 1), thereby improving the stability of steering control.

[0022] Next, a more detailed description will be given of the functions of the controller 15. In the following description, an example is given in which the camera of the external sensor 13 captures an image of the area ahead in the traveling direction of the vehicle 1 and recognizes the lane (i.e., recognizes lane boundary lines L1, L2), but the present invention is not limited to this and can also be applied to a configuration in which the lane is recognized by radar or LiDAR. 3 is a block diagram showing an example of the functional configuration of controller 15. Controller 15 includes an image recognition unit 30, a forward gaze distance setting unit 31, a gaze point setting unit 32, a target lateral force calculation unit 33, a conversion unit 34, a basic driving force setting unit 35, a driving force correction amount calculation unit 36, and a subtractor 37.

[0023] The image recognition unit 30 recognizes the position and shape of the road (i.e., the positions and shapes of lane boundary lines L1, L2) from captured images generated by the camera of the external sensor 13 capturing an image of the area ahead in the traveling direction of the vehicle 1. The image recognition unit 30 outputs road shape information indicating the position and shape of the recognized road to the gaze point setting unit 32. The road shape information may be, for example, point sequence data that is a set of coordinates of each point on the recognized road. Based on the recognized position of the road, the image recognition unit 30 detects the lane width direction position Ps within the road at the current position P1 of the vehicle 1. The image recognition unit 30 outputs information on the detected lane width direction position Ps to the target lateral force calculation unit 33.

[0024] The image recognition unit 30 also detects the distance from the limit point at which the lane can be recognized based on the captured image to the position of the vehicle 1 as the recognition distance Dr. For example, the image recognition unit 30 may detect the farthest point on the lane that can be recognized based on the captured image, that is the farthest point from the vehicle 1, as the limit point at which the lane can be recognized. Alternatively, the image recognition unit 30 may detect a point that is closer to the vehicle 1 than the farthest point by a predetermined margin distance as the limit point at which the lane can be recognized. The recognition distance Dr is an example of the "first distance" described in the claims. The image recognition unit 30 outputs information on the recognition distance Dr to the forward gaze distance setting unit 31 and the driving force correction amount calculation unit 36 ​​.

[0025] The forward gaze distance setting unit 31 sets a forward gaze distance Df, which is the distance from the position of the host vehicle 1 to a position ahead of the host vehicle 1 where the forward gaze point Pf is set. For example, the forward gaze distance setting unit 31 sets a longer forward gaze distance Df when the vehicle speed V of the host vehicle 1 is high compared to when the vehicle speed V is low. For example, the higher the vehicle speed V, the longer the forward gaze distance Df may be set. For example, the forward-looking distance setting unit 31 sets the product obtained by multiplying the vehicle speed V by a predetermined look-ahead time Tprev as the basic forward-looking distance Df0. The basic forward-looking distance Df0 is an example of the "second distance" described in the claims.

[0026] Then, the forward gaze distance setting unit 31 determines whether the recognition distance Dr is less than the basic forward gaze distance Df0. If the recognition distance Dr is equal to or greater than the basic forward gaze distance Df0, the forward gaze distance setting unit 31 sets the basic forward gaze distance Df0 to the forward gaze distance Df. If the recognition distance Dr is less than the basic forward gaze distance Df0, the recognition distance Dr is set to the forward gaze distance Df. Further, the forward gaze distance setting unit 31 calculates a distance difference ΔD obtained by subtracting the recognition distance Dr from the basic forward gaze distance Df0 using the following equation (1). ΔD=max(0,Df0-Dr) …(1)

[0027] In other words, when the recognition distance Dr is less than the basic forward gaze distance Df0, the distance difference ΔD is the difference obtained by subtracting the recognition distance Dr from the basic forward gaze distance Df0, and when the recognition distance Dr is greater than or equal to the basic forward gaze distance Df0, the distance difference ΔD is 0. The forward gaze distance setting unit 31 outputs information about the forward gaze distance Df to the gaze point setting unit 32. It also outputs information about the distance difference ΔD to the target lateral force calculation unit 33 and the drive force correction amount calculation unit .

[0028] The gaze point setting unit 32 sets a forward gaze point Pf based on the forward gaze distance Df and the shape of the road. The gaze point setting unit 32 may set the forward gaze point Pf, for example, in the following manner: First, the gaze point setting unit 32 calculates the forward lane boundary line position Ppre based on the curvature ρ of the lane boundary line L1, the curvature change ρ', the yaw angle deviation Ψ between the vehicle 1 and the lane boundary line L1, and the lateral deviation Y. For example, the gaze point setting unit 32 may calculate the lane width direction position of the forward lane boundary line position Ppre based on the tangent line Lt by calculating the lane boundary line deviation Ypre, which is the distance from the tangent line Lt to the forward lane boundary line position Ppre, based on the following equation (2). Ypre=Y+Ψ×Df+ρ×Df 2 / 2+ρ'×Df 3 / 6 …(2) The gaze point setting unit 32 sets a point that is moved a target lane width distance Ytrg from the forward lane boundary line position Ppre toward the center of the lane as the forward gaze point Pf. For example, when driving in the center of the lane during lane departure prevention assistance, half the lane width may be set as the target lane width distance Ytrg. Also, when the target driving trajectory Ttrg is generated by, for example, autonomous driving control, the distance between the target driving trajectory Ttrg and the lane boundary line L1 may be set as the target lane width distance Ytrg.

[0029] The target lateral force calculation unit 33 calculates a target lateral force Fy that moves the host vehicle 1 from the current position toward the forward gaze point Pf. The target lateral force calculation unit 33 may correct the target lateral force Fy by decreasing it when the recognition distance Dr is short. This is because a short recognition distance Dr may reduce the accuracy of estimating the curvature ρ of the road, thereby reducing the accuracy of controlling the target lateral force Fy. For example, when the recognition distance Dr is less than the basic look-ahead distance Df0, the target lateral force Fy may be corrected by decreasing it. For example, the target lateral force calculation unit 33 may set a smaller target lateral force Fy when the distance difference ΔD obtained by subtracting the recognition distance Dr from the basic gaze forward distance Df0 is large compared to when the distance difference ΔD is small. For example, the target lateral force calculation unit 33 may set a smaller target lateral force Fy as the distance difference ΔD is larger. For example, the target lateral force calculation unit 33 may reduce the target lateral force Fy by a larger reduction correction amount as the distance difference ΔD is larger.

[0030] The conversion unit 34 converts the target lateral force Fy into a target turning angle δtar of the steered wheels based on the following equation (3), and outputs information on the target turning angle δtar to the actuator 16. δtar=C×lx×(1+AV 2 )×Fy / mV 2 …(3) In the above equation (3), C is the conversion coefficient between the steering angle δt of the steered wheels and the steering angle of the steering wheel, and l x is the wheelbase length and A is the steering factor. The steering mechanism of the actuator 16 steers the steered wheels of the host vehicle 1 so that the steering angle δt becomes the target steering angle δtar.

[0031] The basic driving force setting unit 35 sets a basic driving force Fx0, which is an initial value of a target driving force to be generated on the wheels of the host vehicle 1 by the driving source of the actuator 16. For example, the basic driving force setting unit 35 may set the basic driving force Fx0 based on the amount of accelerator pedal operation Ac by the driver and the vehicle speed V. Furthermore, when the driving assistance device 10 performs autonomous driving control of the vehicle 1, the controller 15 may set the basic driving force Fx0 based on the surrounding driving environment detected by the external sensor 13 and the vehicle speed V. The basic driving force setting unit 35 outputs the basic driving force Fx0 to the subtractor 37.

[0032] The driving force correction amount calculation unit 36 ​​calculates a decrease correction amount Cd for decreasing the basic driving force Fx0. 4 is a block diagram showing an example of the functional configuration of the driving force correction amount calculation unit 36. The driving force correction amount calculation unit 36 ​​includes a first correction amount calculation unit 41, a second correction amount calculation unit 42, a third correction amount calculation unit 43, an adder 44, a gain setting unit 45, and a multiplier 46. When the recognition distance Dr is less than the basic forward-looking distance Df0, the first correction amount calculation unit 41 calculates a first decrease correction amount C1 according to the distance difference ΔD obtained by subtracting the recognition distance Dr from the basic forward-looking distance Df0. For example, the first correction amount calculation unit 41 may calculate a larger first decrease correction amount C1 when the distance difference ΔD is large compared to when the distance difference ΔD is small. For example, the larger the distance difference ΔD, the larger the first decrease correction amount C1 may be calculated. When the recognition distance Dr is equal to or greater than the basic forward gaze distance Df0, the first decrease correction amount C1 may be set to 0.

[0033] For example, the first correction amount calculation unit 41 may calculate the first decrease correction amount C1 based on the following equation (4). C1=K1×ΔD …(4) In the above equation (4), K1 is a predetermined gain. For example, the gain K1 may be a fixed value. Note that when the curvature ρ of the road is large, the recognition distance Dr becomes shorter and the distance difference ΔD becomes larger. Therefore, a larger first decrease correction amount C1 is calculated when the curvature ρ of the road is large compared to when the curvature ρ is small. For example, the larger the curvature ρ of the road, the larger the first decrease correction amount C1 is calculated.

[0034] The second correction amount calculation unit 42 calculates a second decrease correction amount C2 corresponding to the difference between the estimated lateral acceleration Gye, which is an estimate of the current lateral acceleration of the host vehicle 1, and the target lateral acceleration Gy. The target lateral acceleration Gy can be calculated by dividing the target lateral force Fy calculated by the target lateral force calculation unit 33 by the mass m of the host vehicle 1. By decreasing the target driving force by the second decreasing correction amount C2, vehicle stability can be improved on curved roads where a difference between the estimated lateral acceleration Gye and the target lateral acceleration Gy is likely to occur. For example, second correction amount calculation unit 42 may calculate a larger second decrease correction amount C2 when the lateral acceleration difference ΔG obtained by subtracting target lateral acceleration Gy from estimated lateral acceleration Gye is large compared to when the lateral acceleration difference ΔG is small. For example, the larger the lateral acceleration difference ΔG, the larger the second decrease correction amount C2 may be calculated.

[0035] However, on curved roads with a large curvature ρ, the recognition distance Dr becomes short and the error in the curvature ρ detected from the image captured by the camera of the external sensor 13 becomes large, so there is a risk that sufficient vehicle stability will not be ensured even if the target driving force is reduced or corrected according to the lateral acceleration difference ΔG. Therefore, when the recognition distance Dr is less than the basic looking-ahead distance Df0, the second correction amount calculation unit 42 increases the second decrease correction amount C2 according to the lateral acceleration difference ΔG. This more strongly suppresses the acceleration of the host vehicle 1 (or more strongly decelerates the host vehicle 1), thereby further improving vehicle stability on curved roads where stability control performance is required.

[0036] The second correction amount calculation unit 42 includes a lateral acceleration estimation unit 42a, a divider 42b, a subtractor 42c, and a gain multiplication unit 42d. Lateral acceleration estimator 42a calculates estimated lateral acceleration Gye based on vehicle speed V and steering angle δt of the steered wheels. Divider 42b calculates target lateral acceleration Gy by dividing target lateral force Fy by mass m of vehicle 1. Subtractor 42c calculates the difference obtained by subtracting target lateral acceleration Gy from estimated lateral acceleration Gye as a lateral acceleration difference ΔG. Gain multiplier 42d multiplies the lateral acceleration difference ΔG by a control gain and calculates the product as a second decrease correction amount C2.

[0037] The control gain is a gain that is larger when the distance difference ΔD is large than when the distance difference ΔD is small. For example, the value of the control gain may be "1" when the distance difference ΔD is 0. When the distance difference ΔD is greater than 0, the control gain may be set to a value greater than "1," and may be set to a larger value when the distance difference ΔD is large compared to when the distance difference ΔD is small. For example, the larger the distance difference ΔD, the larger the control gain may be set. By multiplying the control gain in this way, when the recognition distance Dr is less than the basic forward gaze distance Df0, the target driving force can be reduced and corrected by a larger second reduction correction amount C2. As described above, the greater the curvature ρ of the road, the greater the distance difference ΔD. Therefore, a larger second decrease correction amount C2 is calculated when the curvature ρ of the road is large compared to when the curvature ρ is small. For example, the greater the curvature ρ of the road, the larger the second decrease correction amount C2 is calculated. Furthermore, as described above, the target lateral force Fy may be set to a smaller value when the distance difference ΔD is large than when the distance difference ΔD is small. In this case, the target lateral acceleration Gy is smaller when the curvature ρ is large than when it is small. Therefore, the lateral acceleration difference ΔG obtained by subtracting the target lateral acceleration Gy from the estimated lateral acceleration Gye is larger. Therefore, a larger second decrease correction amount C2 is calculated when the curvature ρ of the road is large than when it is small. For example, the larger the curvature ρ of the road, the larger the second decrease correction amount C2 is calculated.

[0038] The third correction amount calculation unit 43 calculates a third decrease correction amount C3 according to the rate of decrease of the recognition distance Dr. The higher the rate of increase of the curvature ρ of the curved road, the higher the rate of decrease of the recognition distance Dr. Therefore, by decreasing and correcting the target driving force by the third decrease correction amount C3 according to the rate of decrease of the recognition distance Dr, the higher the rate of increase of the curvature ρ of the curved road, the more the acceleration of the host vehicle 1 can be suppressed. Alternatively, the host vehicle 1 can be decelerated more strongly. For example, the third correction amount calculation unit 43 may calculate a larger third decrease correction amount C3 when the decrease rate of the recognition distance Dr is high compared to when the decrease rate is low. For example, the higher the decrease rate of the recognition distance Dr, the larger the third decrease correction amount C3 may be calculated.

[0039] For example, the third correction amount calculation unit 43 may calculate the third decrease correction amount C3 based on the following equation (5). C3=-K2×min(0,(Dr2-Dr1) / (t2-t1)) In the above formula (5), Dr1 and Dr2 are the recognition distances Dr at times t1 and t2, respectively, and K2 is a predetermined gain. For example, the gain K2 may be a fixed value.

[0040] The adder 44 calculates the sum (C1+C2+C3) of the first decrease correction amount C1, the second decrease correction amount C2, and the third decrease correction amount C3. The gain setting unit 45 sets a gain K according to the amount Ac of accelerator pedal operation by the driver. A multiplier 46 multiplies the sum (C1+C2+C3) by a gain K to calculate the product as a decrease correction amount Cd. The gain setting unit 45 may set the value of the gain K to "1" when the operation amount Ac is equal to or less than a predetermined operation amount threshold Ath, and may set the value to a value smaller than "1" when the operation amount Ac is greater than the operation amount threshold Ath. This makes it possible to reduce the decrease correction amount Cd when the operation amount Ac is greater than the operation amount threshold Ath. Within a range in which the operation amount Ac is greater than the operation amount threshold Ath, a smaller gain K may be set when the operation amount Ac is large compared to when the operation amount Ac is small. The larger the operation amount Ac, the smaller the gain K may be set.

[0041] For example, the gain K may be set to 1 when the accelerator opening corresponding to the accelerator pedal operation amount Ac is 0%, and the gain K may be set to decrease as the accelerator opening increases, until the gain K becomes 0 when the accelerator opening reaches 100%. In this way, by decreasing the decrease correction amount Cd when the operation amount Ac is greater than the operation amount threshold Ath, it is possible to give priority to the driver's intention to accelerate.

[0042] The gain setting unit 45 may set a gain K according to the rate of change of the accelerator pedal operation amount Ac. For example, the value of gain K may be set to "1" when the operation speed is equal to or less than a predetermined speed threshold, and may be set to a value smaller than "1" when the operation speed is higher than the speed threshold. This makes it possible to reduce the decrease correction amount Cd when the operation speed is higher than the speed threshold. Within a range in which the operation speed is higher than the speed threshold, a smaller gain K may be set when the operation speed is high compared to when the speed is low. For example, the higher the operation amount Ac, the smaller the gain K may be set. Even when gain K is set in this manner, it is possible to reduce the decrease correction amount Cd according to the driver's intention to accelerate.

[0043] 3, the subtractor 37 subtracts the decrease correction amount Cd from the basic driving force Fx0 to calculate a difference as the corrected driving force Fx. The subtractor 37 outputs information about the corrected driving force Fx to the actuator 16. The drive source of the actuator 16 controls the output so that the drive force generated at the wheels of the host vehicle 1 becomes the corrected drive force Fx.

[0044] (operation) FIG. 5 is a flowchart of an example of a driving force control method according to an embodiment of the present invention. In step S1, the camera of the external sensor 13 captures an image of the area ahead in the traveling direction of the host vehicle 1, and generates a captured image. In step S2, the image recognition unit 30 recognizes the road ahead in the traveling direction of the host vehicle 1 from the captured image. In step S3, the image recognition unit 30 detects the lane width direction position Ps of the vehicle 1 at the current position P1 within the road from the captured image. In step S4, the recognition distance Dr is detected.

[0045] In step S5, the forward gaze distance setting unit 31 sets a basic forward gaze distance Df0. In step S6, the forward gaze distance setting unit 31 calculates the distance difference ΔD=max(0, Df0−Dr). In step S7, the forward gaze distance setting unit 31 sets the recognition distance Dr to the forward gaze distance Df if the recognition distance Dr is less than the basic forward gaze distance Df0, or sets the basic forward gaze distance Df0 to the forward gaze distance Df if the recognition distance Dr is equal to or greater than the basic forward gaze distance Df0. In step S8, the gaze point setting unit 32 sets a forward gaze point Pf. In step S9, the target lateral force calculation unit 33 calculates a target lateral force Fy that moves the host vehicle 1 from the current position toward the forward gaze point Pf. The conversion unit 34 converts the target lateral force Fy into a target steering angle δtar of the steered wheels.

[0046] In step S10, the basic driving force setting unit 35 sets a basic driving force Fx0, which is the initial value of the target driving force to be generated at the wheels of the host vehicle 1 by the driving source. In step S11, the driving force correction amount calculation unit 36 ​​calculates a decrease correction amount Cd for decreasing the basic driving force Fx0. In step S12, the subtractor 37 calculates the difference obtained by subtracting the decrease correction amount Cd from the basic driving force Fx0 as the corrected driving force Fx. In step S13, the drive source of actuator 16 controls the output so that the drive force generated on the wheels of host vehicle 1 becomes corrected drive force Fx. The steering mechanism of actuator 16 steers the steered wheels of host vehicle 1 so that the steering angle δt becomes target steering angle δtar. Then, the process ends.

[0047] (Effects of the embodiment) (1) The controller 15 detects the road ahead in the direction of travel of the vehicle 1 using the external sensor 13, detects a first distance which is the distance from the vehicle 1 to the limit point at which the road can be detected by the external sensor 13, sets a forward gaze point a second distance away from the vehicle 1 within the road ahead in the direction of travel detected by the external sensor 13, controls the steering mechanism of the vehicle 1 based on the set forward gaze point, sets a target driving force to be generated in the vehicle 1, and if the first distance is greater than or equal to the second distance, controls the driving source so that the driving force of the driving source of the vehicle 1 becomes the target driving force, and if the first distance is less than the second distance, controls the driving source so that the driving force of the driving source becomes a corrected driving force obtained by reducing and correcting the target driving force. As a result, when the distance over which the road can be detected by the external sensor 13 becomes shorter and the stability of the control becomes more likely to decrease, the driving force of the driving source of the vehicle 1 is reduced to suppress the acceleration of the vehicle 1 (or the vehicle 1 is decelerated). As a result, the stability of the steering control of the vehicle 1 can be improved.

[0048] (2) The controller 15 may set the target driving force based on the amount of accelerator pedal operation by the driver. This allows, for example, if the distance at which the external sensor 13 can detect the road becomes shorter while steering assist control such as lane departure prevention assist is being executed, the target driving force set based on the amount of accelerator pedal operation by the driver can be reduced or corrected. (3) The controller 15 may detect the surrounding environment of the vehicle 1 using the external sensor 13, and set the target driving force by automatic driving control of the vehicle 1 based on the detection result of the surrounding environment. This allows, for example, if the distance at which the external sensor 13 can detect the road becomes shorter while automatic driving control is being executed to automatically drive the vehicle 1 without the involvement of an occupant, the target driving force set by the automatic driving control can be reduced or corrected.

[0049] (4) The controller 15 may set the second distance to a longer distance when the vehicle speed of the host vehicle 1 is fast compared to when the vehicle speed is slow. This allows an appropriate forward gaze point to be set according to the vehicle speed of the host vehicle 1. (5) When the first distance is less than the second distance, the controller 15 may reduce the target driving force by a larger reduction correction amount to set the corrected driving force when the distance difference obtained by subtracting the first distance from the second distance is large compared to when the distance difference is small. This allows the amount of reduction correction to be set according to the magnitude of the difference between the distance at which the external sensor 13 can detect the road and the forward gaze distance.

[0050] (6) The controller 15 may calculate an estimated lateral acceleration, which is an estimated value of the lateral acceleration occurring in the host vehicle 1, set a target lateral acceleration to be generated in the host vehicle 1, and set a reduction correction amount according to the product obtained by multiplying the lateral acceleration difference obtained by subtracting the target lateral acceleration from the estimated lateral acceleration by a gain that is larger when the distance difference is large compared to when the distance difference is small. In addition, the controller 15 may calculate an estimated lateral acceleration, which is an estimated value of the lateral acceleration occurring in the host vehicle 1, and set a smaller lateral acceleration as the target lateral acceleration to be generated in the host vehicle 1 when the distance difference is large compared to when the distance difference is small, and set a reduction correction amount according to the lateral acceleration difference obtained by subtracting the target lateral acceleration from the estimated lateral acceleration. This makes it possible to further improve vehicle stability on curved roads where stability control performance is required.

[0051] (7) The greater the curvature of the road, the shorter the distance over which the road can be detected by the external sensor 13. For this reason, when the curvature of the road detected by the sensor is large compared to when the curvature is small, the controller 15 may set the corrected driving force by reducing the target driving force by a larger amount of reduction correction. This allows the amount of reduction correction to be set according to the distance at which the external sensor 13 can detect the road. (8) If the driver's accelerator pedal operation amount is greater than a predetermined operation amount threshold, or if the rate of change in the driver's accelerator pedal operation amount is greater than a predetermined speed threshold, controller 15 may reduce the amount of correction by which the target driving force is decreased when the first distance is less than the second distance. This allows the driver's intention to accelerate to take priority. (9) The controller 15 may set the corrected driving force by reducing the target driving force by a larger amount when the rate of decrease of the first distance is high compared to when the rate of decrease is low. This allows the acceleration of the vehicle 1 to be more strongly suppressed or the vehicle 1 to be more strongly decelerated the faster the rate of increase of the curvature of the curved road. [Explanation of symbols]

[0052] 1...Own vehicle, 10...Driver assistance device, 11...Positioning device, 12...Map database, 13...External sensor, 14...Vehicle sensor, 15...Controller, 16...Actuator, 20...Processor, 21...Storage device, 30...Image recognition unit, 31...Forward gaze distance setting unit, 32...Gaze point setting unit, 33...Target lateral force calculation unit, 34...Conversion unit, 35...Basic driving force setting unit, 36...Driving force correction amount calculation unit, 37, 42...Subtractor, 41...First correction amount calculation unit, 42...Second correction amount calculation unit, 42a...Lateral acceleration estimation unit, 42b...Divider, 42d...Gain multiplication unit, 43...Third correction amount calculation unit, 44...Adder, 45...Gain setting unit, 46...Multiplier

Claims

1. The sensor detects the road ahead in the direction of travel of the vehicle, detecting a first distance, which is a distance from the farthest point within a range in which the road can be detected by the sensor to the vehicle; a second distance is set to a distance that increases as the vehicle speed of the host vehicle increases, and a predetermined lane width direction position in the road that is the second distance ahead of the host vehicle and detected by the sensor in the direction of travel of the host vehicle is set to a forward gaze point; controlling a steering mechanism of the host vehicle so that the host vehicle travels toward the set forward gaze point; setting a target driving force to be generated in the host vehicle; When the first distance is equal to or greater than the second distance, the drive source of the host vehicle is controlled so that the drive force of the drive source becomes the target drive force, and when the first distance is less than the second distance, the drive source is controlled so that the drive force of the drive source becomes a corrected drive force obtained by reducing and correcting the target drive force. A driving force control method characterized by:

2. 2. The driving force control method according to claim 1, wherein the target driving force is set based on an amount of accelerator pedal operation by a driver.

3. 2. The driving force control method according to claim 1, wherein the host vehicle is an automatically driven vehicle.

4. 4. The driving force control method according to claim 1, wherein the second distance is set to a longer distance when the vehicle speed of the host vehicle is high than when the vehicle speed is low.

5. A driving force control method according to any one of claims 1 to 4, characterized in that when the first distance is less than the second distance, the target driving force is reduced and corrected by a larger reduction correction amount to set the corrected driving force when the distance difference obtained by subtracting the first distance from the second distance is large compared to when the distance difference is small.

6. calculating an estimated lateral acceleration that is an estimated value of the lateral acceleration occurring in the host vehicle; setting a target lateral acceleration to be generated in the host vehicle; the decrease correction amount is set according to a product obtained by multiplying a lateral acceleration difference obtained by subtracting the target lateral acceleration from the estimated lateral acceleration by a gain that is larger when the distance difference is large compared to when the distance difference is small.

6. The driving force control method according to claim 5.

7. calculating an estimated lateral acceleration that is an estimated value of the lateral acceleration occurring in the host vehicle; As a target lateral acceleration to be generated in the host vehicle, a smaller lateral acceleration is set when the distance difference is large compared to when the distance difference is small; setting the decrease correction amount in accordance with a lateral acceleration difference obtained by subtracting the target lateral acceleration from the estimated lateral acceleration; 6. The driving force control method according to claim 5.

8. A driving force control method according to any one of claims 1 to 7, characterized in that when the curvature of the road detected by the sensor is large compared to when the curvature is small, the target driving force is reduced and corrected by a large reduction correction amount to set the corrected driving force.

9. 9. The driving force control method according to claim 1, wherein when the amount of accelerator pedal operation by the driver is greater than a predetermined threshold value for the amount of operation, or when the rate of change in the amount of accelerator pedal operation by the driver is higher than a predetermined threshold value for the rate of change, the correction amount for decreasing the target driving force when the first distance is less than the second distance is reduced.

10. A driving force control method according to any one of claims 1 to 9, characterized in that the target driving force is reduced and corrected by a larger reduction correction amount when the rate of reduction of the first distance is high compared to when the rate of reduction of the first distance is low, thereby setting the corrected driving force.

11. a sensor for detecting a road ahead in the traveling direction of the host vehicle; a steering mechanism for steering the steered wheels of the host vehicle; a drive source that generates a drive force for the host vehicle; a controller that detects a first distance, which is the distance from the farthest point within a range where the road can be detected by the sensor, to the host vehicle, sets a second distance that becomes longer as the vehicle speed of the host vehicle increases, sets a predetermined lane width direction position in the road that is the second distance forward of the host vehicle and forward in the traveling direction of the host vehicle and detected by the sensor, as a forward gaze point, controls the steering mechanism so that the host vehicle travels toward the set forward gaze point, sets a target drive force to be generated in the host vehicle, controls the drive source so that the drive force of the drive source becomes the target drive force when the first distance is equal to or greater than the second distance, and controls the drive source so that the drive force of the drive source becomes a corrected drive force obtained by reducing or correcting the target drive force when the first distance is less than the second distance; A driving force control device comprising:

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