JP2019059441A - Vehicle driving support device - Google Patents

Abstract

A vehicle for increasing the reliability of steering follow-up control by accurately acquiring a trajectory shape parameter representing the shape of the travel trajectory of a steering follow-up target vehicle in a situation in which the own vehicle enters from a straight section of a driving lane into a curved section. Provide a driving assistance device. A driving support ECU calculates a ratio (ε) between a curvature change rate acquired a predetermined time before the current time and a maximum curvature change rate, and calculates the current steering follow-up target vehicle (SV) of the vehicle (SV) at the current time. Calculate the time (T) between the vehicle and the TV). The driving support ECU satisfies both the first condition that the value of the ratio (ε) is equal to or greater than a predetermined threshold value (εth) and the second condition that the inter-vehicle time is equal to or less than the threshold time (Tth). In this case, the degree to which the position information detected behind the current position of the vehicle (SV) is reflected in the travel locus (L1) is determined by the position information detected ahead of the current vehicle (SV). A travel locus (L1) is generated so that the degree of reflection in (L1) is smaller. [Selection drawing] Fig. 2

Description

  The present invention relates to a vehicle driving support device that performs control of causing a host vehicle to travel along a target travel line based on the travel locus of a preceding vehicle that is another vehicle traveling in a front area of the host vehicle.

  One of the conventionally known vehicle driving support devices (hereinafter referred to as "conventional devices") generates a traveling trace of a steering following target vehicle selected from among preceding vehicles traveling in front of the own vehicle. (For example, refer to "patent document 1").

  The conventional device detects the position of the steering following target vehicle using a surrounding sensor every time a predetermined time (calculation cycle) elapses, and the traveling locus of the steering following target vehicle based on the detected position of the steering following target vehicle Generate The conventional device performs steering control so that the host vehicle travels along a target travel line determined based on the generated travel locus. The steering control that is performed to cause the host vehicle to travel along a target travel line based on the travel trajectory of the target vehicle is also referred to as "steering follow control".

  Various methods have been proposed as a method of generating a travel locus of a target vehicle following a steering. For example, the conventional device detects the time-series data (position coordinate data) of the detected position of the vehicle following the steering (for example, x coordinate value and y coordinate value of xy coordinates defined on the basis of the current position of the host vehicle). Buffer in RAM. The conventional device creates a curve representing a traveling locus by performing curve fitting using the buffered position coordinate data.

  The conventional device acquires a locus shape parameter (for example, a curvature and a rate of change of curvature) representing the shape of a traveling locus from the coefficient of the functional expression f (x) representing a curve, and uses the acquired locus shape parameter for steering following control. use.

JP 2011-514580 gazette

  The detected position of the steering-following target vehicle detected by the present calculation may have an error. In this case, since the shape of the generated travel locus changes under the influence of the error of the currently detected position, there is a possibility that the accuracy of the trajectory shape parameter may be deteriorated.

  On the other hand, the conventional device uses, for example, a filter, or increases the coordinate range of the detected position used for generating the traveling locus and the number of detected positions. As a result, the change of the trajectory shape parameter is limited so that the currently obtained trajectory shape parameter is not changed significantly compared to the previously acquired trajectory shape parameter due to the error of the current detection position.

  However, if the change of the trajectory shape parameter is excessively limited, the following may occur.

  For example, as shown in (A) of FIG. 5 and (B) of FIG. 5, the situation in which the host vehicle SV traveling on the straight section R1 of the traveling lane follows the steering following target vehicle TV entering the curve section R2. Will occur. In this case, the curvature change rate Cv 'of the travel locus of the actual vehicle following the target vehicle at the curve section entrance P1 is the curvature change rate Cv' (= 0) of the straight section R1 to the curvature of the curve section entrance (P1) It greatly changes up to the rate of change Cv '(= D1).

  Therefore, when the host vehicle SV travels along the curve section entrance P1, in order to obtain an ideal trajectory shape parameter (curvature change rate Cv '(= D1)) with high accuracy by the conventional device, from time t1 Before the inter-vehicle time T elapses, it is necessary to increase the locus shape parameter (curvature change rate Cv ′) of the curve section entry P1 of the traveling locus L1 from 0 to D1.

  That is, an ideal locus shape parameter change amount per operation cycle (an amount of change with respect to the previously acquired locus shape parameter of the locus shape parameter acquired this time) from the time t1 until the inter-vehicle time T elapses D1 / T) × Tcy (arithmetic cycle) (hereinafter referred to as “ideal parameter change amount”) ”.

  The ideal parameter change amount increases as the inter-vehicle time T decreases. Therefore, even if the inter-vehicle time T is short, if the change in the trajectory shape parameter is excessively limited, the change in the trajectory shape parameter per operation cycle It may be smaller than the ideal parameter change amount (= (D1 / T) × Tcy).

  In this case, when the vehicle SV travels in the curve section R2, the trajectory shape parameter is likely to be smaller than the ideal trajectory shape parameter. Therefore, when the host vehicle SV travels around the curve section entrance P1, a delay in steering response occurs. As a result, the reliability of the steering follow-up control is reduced.

  The present invention was made to address the problems described above. That is, one of the objects of the present invention is to accurately obtain a locus shape parameter representing the shape of the traveling locus of the target vehicle following a steering in the situation where the host vehicle enters a curve section from the straight section of the traveling lane. Accordingly, it is an object of the present invention to provide a vehicle driving support device (hereinafter, also referred to as “the present invention device”) capable of enhancing the reliability of the steering follow-up control.

The first aspect of the device of the present invention is
A vehicle speed detection unit (16) for detecting the vehicle speed of the host vehicle (SV);
A maximum curvature change rate estimation unit (10) for estimating the maximum curvature change rate of the traveling lane on which the vehicle travels (step 730 in FIG. 7);
A position information acquisition unit (10, 17) for acquiring position information including position information indicating a longitudinal distance and a lateral position with respect to the host vehicle of a front vehicle traveling in a front area of the host vehicle (Step 715 in FIG. 7);
A steering following target vehicle (TV) is specified from one or more of the preceding vehicles (step 720 in FIG. 7) and a steering following target vehicle specifying unit (10),
A position information storage unit (10, RAM) for storing the position information of the specified target vehicle following the steering, each time a predetermined time has elapsed;
The travel locus (L1) of the specified target vehicle following the steering is generated using the stored position information, and a locus shape parameter including a curvature change rate representing the shape of the generated travel locus is acquired (FIG. 7 Step 755) A traveling locus generation unit (10),
The steering control unit executes steering follow-up control to change the steering angle of the host vehicle so that the host vehicle travels along the target travel line set based on the travel locus (step 755 in FIG. 7). )When,
Equipped with
The travel locus generation unit
Calculating a value (ε) of a ratio between the curvature change rate (Cv ′ (t−1)) and the maximum curvature change rate (Dmax) acquired the predetermined time before the current time (step 725 in FIG. 7);
An inter-vehicle time (T) between the current vehicle and the steering following target vehicle is calculated using the vehicle speed of the vehicle and the position information (step 730 in FIG. 7).
If both the first condition that the value of the ratio is equal to or greater than the predetermined threshold and the second condition that the inter-vehicle time is equal to or less than the threshold time ("Yes" in step 735 of FIG. 7) Judgment with),
The degree to which the position information detected behind the current position of the host vehicle is reflected in the travel locus is reflected in the travel locus as the position information detected in front of the host vehicle at the current point Generating the travel locus so as to be smaller than the degree of travel (step 750);
Configured as.

  According to this, there is a high possibility that the host vehicle is traveling near the entrance of the curve section, and an ideal locus shape necessary for obtaining an ideal locus shape parameter with high accuracy at the entrance of the curve section The first condition and the second condition are satisfied when the possibility that the parameter change amount is large is high.

  When the first condition and the second condition are satisfied, the degree to which the position information detected behind the current position of the host vehicle is reflected in the travel locus is the position information detected ahead of the host vehicle at the current position is the travel locus The travel locus is generated so as to be smaller than the degree of reflection on.

  As a result, the trajectory shape parameter acquired at the present time is allowed to be largely changed as compared with the trajectory shape parameter acquired before the predetermined elapsed time (that is, the restriction on the change of the trajectory shape parameter is relaxed). Therefore, even when the host vehicle travels in the vicinity of the entrance of the curve section, it is possible to obtain a highly accurate traveling locus. As a result, when the host vehicle enters a curve section from the straight section of the traveling lane, the possibility of a delay in steering response can be reduced.

The second aspect of the device of the present invention is
A vehicle speed detection unit (16) for detecting the vehicle speed of the host vehicle;
A maximum curvature change rate estimation unit (10) for estimating the maximum curvature change rate of the traveling lane on which the vehicle travels (step 730 in FIG. 9);
Obtaining position information including position information indicating a longitudinal distance and a lateral position of a front vehicle traveling in a front area of the host vehicle with respect to the host vehicle (Step 715 in FIG. 9) position information acquiring unit (10);
A steering-following target vehicle identification unit (10) that identifies a steering-following target vehicle from among the one or more preceding vehicles (step 720 in FIG. 9);
A target travel path information including a Kalman filter (10) and trajectory shape parameters including a curvature change rate representing the shape of the travel trajectory of the specified vehicle following the steering is calculated each time a predetermined time elapses (step in FIG. 9) 910) a traveling locus generating unit (10), which calculates a value of a ratio between the curvature change rate and the maximum curvature change rate acquired the predetermined time before the current time (step 725 in FIG. 9); Using the vehicle speed of the vehicle and the position information, the inter-vehicle time of the vehicle at the current time to the target vehicle following the vehicle is calculated (step 730 in FIG. 9), and the maximum curvature change rate When the inter-vehicle time and the predetermined time are substituted, and the value of the ratio is smaller than the first threshold (εth1), 3 is substituted for N in the following formula, and the value of the ratio is not less than the first threshold and the second threshold ( If smaller than ε th 2) By substituting 2 for the N and substituting 1 for the N when the value of the ratio is greater than or equal to the second threshold, the standard deviation of the amount of change in the curvature change rate per predetermined time ( calculate σΔcv ′) (step 905 in FIG. 9);
An input value including the position information of the specified target vehicle following the steering as an observed value and the standard deviation as a process noise is input to the Kalman filter, and the target runway information is calculated according to the principle of the Kalman filter. The travel locus generating unit configured as (step 910 in FIG. 9);
Running control unit (10) that executes steering follow-up control that changes the steering angle of the host vehicle based on the target travel path information (step 755 in FIG. 9);
Equipped with
(a formula)
σΔcv '= {(Dmax / N) ÷ T} × Tcy
(ΣΔcv ′ is a standard deviation of the amount of change in the curvature change rate per predetermined time. Dmax is the maximum curvature change rate. N is 3, 2 or 1. T is an inter-vehicle time. Is the predetermined time)

  According to the above (calculation formula), N becomes smaller as the value of the ratio becomes larger, and “the standard deviation σΔcv ′ of the amount of change in curvature change rate per predetermined time” which is the process noise input to the Kalman filter increases. . Furthermore, as the inter-vehicle time decreases, the “standard deviation σΔcv ′ of the amount of change in curvature change rate per predetermined time” increases.

  According to the principle of the Kalman filter, when the input process noise ("the standard deviation of the variation of curvature change rate per predetermined time (σ cv ')") becomes large, the observed value is easily reflected in the output value.

  As a result, when the host vehicle enters the curve section entrance from the straight section, the restriction on the change of the trajectory shape parameter is relaxed. As a result, when the host vehicle enters a curve section from the straight section of the traveling lane, the possibility of a delay in steering response can be reduced.

  In the above description, in order to facilitate understanding of the present invention, the names and / or symbols used in the embodiments are attached in parentheses to the configuration of the invention corresponding to the embodiments described later. However, each component of the present invention is not limited to the embodiment defined by the above-mentioned name and / or code.

FIG. 1 is a schematic configuration diagram of a vehicle driving support device according to a first embodiment of the present invention. FIG. 2 is a plan view for explaining the lane keeping control. FIG. 3A is a plan view for explaining the lane keeping control. FIG. 3B is a mathematical expression for explaining the relationship between the coefficient of the cubic function of the traveling locus and the curvature and the like. FIG. 3C is an equation for explaining the relationship between the coefficient of the cubic function of the traveling locus and the curvature and the like. FIG. 4 is a plan view for explaining travel locus generation. FIG. 5A is a plan view of a road and a vehicle for explaining the operation of the vehicle driving support device according to the first embodiment of the present invention. FIG. 5B is a plan view of a road and a vehicle for illustrating the operation of the vehicle driving support device according to the first embodiment of the present invention. FIG. 6 is a plan view for explaining travel locus generation of the vehicle driving support device according to the first embodiment of the present invention. FIG. 7 is a flowchart showing a routine executed by the CPU of the driving support ECU provided in the vehicle driving support device according to the first embodiment of the present invention. FIG. 8 is a schematic view showing an operation of a Kalman filter provided in a vehicle driving assistance device according to a second embodiment of the present invention. FIG. 9 is a flowchart showing a routine executed by the CPU of the driving support ECU provided in the vehicle driving support device according to the second embodiment of the present invention.

  Hereinafter, a vehicle driving support device (hereinafter, also referred to as “first embodiment device”) according to a first embodiment of the present invention will be described with reference to the drawings. The first embodiment device is also a vehicle travel control device. In all the drawings of the embodiment, the same or corresponding parts are denoted by the same reference numerals.

(Constitution)
The first embodiment is applied to a vehicle (automobile) as shown in FIG. The vehicle to which the first embodiment device is applied may be called "own vehicle" to distinguish it from other vehicles. The first embodiment includes a driving support ECU 10, an engine ECU 30, a brake ECU 40, a steering ECU 60, a meter ECU 70, an alarm ECU 80, and a navigation ECU 90. In the following, the driving support ECU 10 is also simply referred to as “DSECU”.

  These ECUs are electric control units (Electric Control Units) each having a microcomputer as a main part, and are connected to be able to transmit and receive information mutually via a CAN (Controller Area Network) not shown. The microcomputer includes a CPU, a ROM, a RAM, a non-volatile memory, an interface I / F, and the like. The CPU implements various functions by executing instructions (programs, routines) stored in the ROM. Some or all of these ECUs may be integrated into one ECU.

  The DSECU is connected to the sensors (including switches) listed below to receive detection signals or output signals of those sensors. Each sensor may be connected to an ECU other than the DSECU. In that case, the DSECU receives the detection signal or output signal of the sensor from the ECU to which the sensor is connected via the CAN.

The accelerator pedal operation amount sensor 11 detects an operation amount (accelerator opening degree) of the accelerator pedal 11a of the host vehicle, and outputs a signal representing an accelerator pedal operation amount AP.
The brake pedal operation amount sensor 12 detects an operation amount of the brake pedal 12a of the host vehicle, and outputs a signal representing the brake pedal operation amount BP.

The steering angle sensor 14 detects a steering operation angle which is a rotation angle of the steering wheel SW of the host vehicle, and outputs a signal representing the steering operation angle θ.
The steering torque sensor 15 detects a steering torque applied to the steering shaft US of the host vehicle by the operation of the steering wheel SW, and outputs a signal representing the steering torque Tra.
The vehicle speed sensor 16 detects the traveling speed (vehicle speed) of the host vehicle and outputs a signal representing the vehicle speed SPD.

  The ambient sensor 17 includes a radar sensor 17a, a camera sensor 17b, and a target recognition unit 17c. The surrounding sensor 17 is configured to obtain information on at least a road ahead of the host vehicle and a three-dimensional object present on the road. The three-dimensional object represents, for example, moving objects such as pedestrians, bicycles and automobiles, and fixed objects such as telephone poles, trees and guardrails. Hereinafter, these three-dimensional objects may be referred to as "targets".

  The surrounding sensor 17 detects the presence or absence of a target based on the information detected from a three-dimensional object by at least one of the radar sensor 17a and the camera sensor 17b, the target ID of the recognized target (n), the vertical distance Dfx (n) , Information of a target (n) including the lateral position Dfy (n) and the relative velocity Vfx (n) (hereinafter referred to as "target information") is calculated and output.

  In addition, the surrounding sensor 17 acquires these values based on the predetermined xy coordinate (refer FIG. 2). The x-axis extends along the front-rear direction of the host vehicle SV so as to pass through the widthwise center position of the front end of the host vehicle SV, and is a coordinate axis having the front as a positive value. The y-axis is a coordinate axis orthogonal to the x-axis and having the left direction of the host vehicle SV as a positive value. The origin of the x axis and the origin of the y axis are center positions in the width direction of the front end of the vehicle SV. The x-coordinate position of the x-y coordinate is called a vertical distance Dfx, and the y-coordinate position is called a horizontal position Dfy.

The vertical distance Dfx (n) of the target (n) is the front end of the host vehicle SV and the rear end of the target (n) (for example, a front vehicle which is another vehicle traveling in the front region of the host vehicle SV) The signed distance in the central axis direction (x-axis direction) of the host vehicle SV between them.
The lateral position Dfy (n) of the target (n) is orthogonal to the central axis of the vehicle SV at "the central position of the target (n) (for example, the center position in the vehicle width direction of the rear end of the preceding vehicle)". Is the signed distance in the direction (y-axis direction).
The relative velocity Vfx (n) of the target (n) is the difference (= Vs-Vj) between the velocity Vs of the target (n) and the velocity Vj (= SPD) of the host vehicle SV. The velocity Vs of the target (n) is the velocity of the target (n) in the central axis direction (x-axis direction) of the host vehicle SV.

  The radar sensor 17a shown in FIG. 1 includes a radar wave transmitting / receiving unit and a processing unit. The radar wave transmitting / receiving unit emits, for example, a millimeter wave band radio wave (hereinafter referred to as “millimeter wave”) at least in the peripheral region of the vehicle SV including at least the front region of the vehicle SV. A wave receives a reflected wave generated by being reflected by a portion (immediately, a reflection point) of a solid. The radar sensor 17a may be a radar sensor that uses radio waves (radar waves) in frequency bands other than the millimeter wave band.

  The processing unit of the radar sensor 17a uses reflection point information including the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, the time from the transmission of the millimeter wave to the reception of the reflected wave, and the like. Based on the determination of the presence or absence of a target.

  Furthermore, the processing unit of the radar sensor 17a determines the vertical distance Dfx of the target, the heading θp of the target with respect to the host vehicle SV, and the host vehicle SV, based on the reflection point information of the reflection points belonging to the recognized target. The relative velocity Vfx with the target, the vehicle speed of the target, and the like (hereinafter referred to as “radar sensor detection information”) are calculated.

  The camera sensor 17 b includes a stereo camera and an image processing unit. The stereo camera captures the scenery of the “left side area and the right side area” in front of the host vehicle SV and acquires a pair of left and right image data.

The image processing unit determines the presence or absence of a target present in the imaging area based on the photographed left and right pair of image data. When it is determined that a target exists, the image processing unit determines the azimuth θ _p of the target, the vertical distance Dfx of the target, the relative velocity Vfx between the vehicle SV and the target, etc. Camera sensor detection information) is calculated.

  The target recognition unit 17 c is connected in a communicable state with the processing unit of the radar sensor 17 a and the image processing unit of the camera sensor 17 b, and receives “radar sensor detection information” and “camera sensor detection information”. It has become. The target recognition unit 17c uses the “target ID, vertical distance Dfx (n) of the target (n) recognized using at least one of the“ radar sensor detection information ”and the“ camera sensor detection information ”, and the horizontal distance Target information including the position Dfy (n) and the relative velocity Vfx (n) is determined (acquired). The target recognition unit 17c transmits the determined target information to the DSECU each time a predetermined time has elapsed.

  Furthermore, the image processing unit of the camera sensor 17b is based on the pair of left and right image data, lane markings (such as lane markers, hereinafter simply referred to as "white lines") such as white lines on the left and right of the road. recognize. Then, the image processing unit determines the shape (for example, curvature radius) of the host vehicle SV traveling lane, which is the lane in which the host vehicle SV is traveling, and the positional relationship between the host vehicle SV traveling lane and the host vehicle SV for a predetermined time. It is calculated and sent to DSECU every time e. The positional relationship between the host vehicle SV traveling lane and the host vehicle SV is, for example, a lane between a central position (that is, a central line) of the left white line and the right white line of the host vehicle traveling lane and the central position in the vehicle width direction of the host vehicle SV. It is represented by the distance in the width direction, the angle between the direction of the center line and the x-axis direction of the vehicle SV (that is, the yaw angle), or the like.

  Information indicating the shape of the host vehicle travel lane, the positional relationship between the host vehicle travel lane and the host vehicle in the lane width direction, and the like may be provided from the navigation ECU 90.

  The operation switch 18 shown in FIG. 1 is a switch operated by the driver of the host vehicle SV. The driver can select whether to execute lane keeping control including steering follow-up control described later by operating the operation switch 18. Furthermore, the driver can select whether to execute an inter-vehicle distance control (following inter-vehicle distance control) described later by operating the operation switch 18.

  The yaw rate sensor 19 detects a yaw rate of the host vehicle SV and outputs an actual yaw rate YRt.

  The engine ECU 30 is connected to the engine actuator 31. The engine actuator 31 is an actuator for changing the operating state of the internal combustion engine 32, and includes at least a throttle valve actuator for changing the opening degree of the throttle valve. Engine ECU 30 can change the torque generated by internal combustion engine 32 by driving engine actuator 31, thereby controlling the driving force of host vehicle SV to change the acceleration of host vehicle SV. it can.

  The brake ECU 40 is connected to the brake actuator 41. The brake actuator 41 is provided in a hydraulic circuit between a master cylinder (not shown) and the friction brake mechanism 42 provided on the left and right front and rear wheels. The brake actuator 41 adjusts the hydraulic pressure of the hydraulic fluid supplied to the wheel cylinder built in the brake caliper 42b of the friction brake mechanism 42 according to the instruction from the brake ECU 40, and the hydraulic pressure of the hydraulic fluid supplied to the wheel cylinder is not shown. To generate friction braking force. Accordingly, by controlling the brake actuator 41, the brake ECU 40 can control the braking force of the host vehicle SV to change the acceleration (in this case, the deceleration) of the host vehicle SV.

  The steering ECU 60 is a control device of a known electric power steering system, and is connected to the motor driver 61. The motor driver 61 is connected to the steering motor 62. The steering motor 62 is incorporated in a "steering mechanism including a steering wheel SW, a steering shaft US, a steering gear mechanism (not shown) and the like". The steering motor 62 generates a torque by the power supplied from the motor driver 61, and can generate a steering assist torque or steer the left and right steered wheels by this torque. That is, the steering motor 62 can change the steering angle (also referred to as “steering angle” or “steering angle”) of the host vehicle SV.

  The meter ECU 70 is connected to a digital display meter not shown. Furthermore, the meter ECU 70 is also connected to the hazard lamp 71 and the stop lamp 72, and can change the lighting state of these according to an instruction from the DSECU.

  The alarm ECU 80 is connected to the buzzer 81 and the display 82. The alarm ECU 80 can alert the driver by ringing the buzzer 81 in response to an instruction from the DSECU, and makes the indicator 82 light a mark for alerting (for example, a warning lamp) can do.

  The navigation ECU 90 is connected to a GPS receiver 91 for receiving a GPS signal for detecting the current position of the vehicle SV, a map database 92 storing map information and the like, a touch panel display 93 and the like. The navigation ECU 90 determines the position of the vehicle SV at the current time based on the GPS signal (in the case where the vehicle SV is traveling on a road having a plurality of lanes, which lane the vehicle SV is traveling) Identify information).

  The navigation ECU 90 performs various arithmetic processing based on the position of the vehicle SV and the map information and the like stored in the map database 92, and performs route guidance using the display 93 based on the arithmetic processing result.

  The map information stored in the map database 92 includes road information. The road information includes parameters indicating the shape of the road in each section of the road (for example, the curvature radius or curvature of the road indicating the degree of how the road bends). The curvature is the reciprocal of the radius of curvature.

<Overview of operation>
Next, an outline of the operation of the first embodiment will be described. The DSECU of the first embodiment can execute inter-vehicle distance control and lane keeping control. Hereinafter, “inter-vehicle distance control and lane keeping control” will be described.

<Inter-vehicle distance control (ACC: adaptive cruise control)>
The inter-vehicle distance control (that is, the following inter-vehicle distance control) is an inter-vehicle distance between the own vehicle SV and a forward vehicle traveling in front of the own vehicle SV in the area ahead of the own vehicle SV based on target information. (That is, control is performed to cause the own vehicle SV to follow the preceding vehicle while maintaining the longitudinal distance Dfx (n) of the preceding vehicle with respect to the own vehicle SV at a predetermined target inter-vehicle distance. The following inter-vehicle distance control itself is known (see, for example, JP-A-2014-148293, JP-A-2006-315491, JP-A-4172434, and JP-A-4929777). Therefore, it will be briefly described below.

  The DSECU executes inter-vehicle distance control when inter-vehicle distance control is requested by the operation of the operation switch 18.

  First, when the inter-vehicle distance control is requested, the DSECU calls a vehicle to be followed based on the target information of the target (n) acquired by the surrounding sensor 17 (hereinafter referred to as “inter-vehicle distance target vehicle” Identified). More specifically, the DSECU determines (specifies) an inter-vehicle distance target vehicle among other vehicles (that is, forward vehicles) traveling in the front region of the host vehicle SV as follows.

Step 1A: The DSECU acquires, from the vehicle speed sensor 16 and the yaw rate sensor 19, the vehicle speed SPD of the vehicle SV and the yaw rate Yrt of the vehicle SV, which are motion state quantities of the vehicle SV.
Step 2A: The DSECU predicts the traveling path of the host vehicle SV in xy coordinates based on the vehicle speed SPD and the yaw rate Yrt.
Step 3A: The DSECU determines that the predicted absolute value of the distance in the lane width direction from the travel route of the own vehicle SV predicted from among other vehicles (ie, forward vehicles) having a positive value of the vertical distance Dfx (n) The other vehicle within the first reference threshold of is determined (selected / set) as an inter-vehicle distance target vehicle (a). The first reference threshold is set to decrease as the vertical distance Dfx (n) increases. When there are a plurality of other vehicles determined, the DSECU specifies the other vehicle with the minimum vertical distance Dfx (n) as the target inter-vehicle distance (a).

  When the inter-vehicle distance target vehicle (a) is specified, the DSECU calculates the target acceleration Gtgt in accordance with either of the following equations (1) and (2). In the equations (1) and (2), Vfx (a) is the relative velocity of the target inter-vehicle distance (a), k1 and k2 are predetermined positive gains (coefficients), and ΔD1 is the target of inter-vehicle distance An inter-vehicle deviation (ΔD1 = Dfx (a) −Dtgt) obtained by subtracting the “target inter-vehicle distance Dtgt” from the longitudinal distance Dfx (a) of the vehicle (a). The target inter-vehicle distance Dtgt is calculated by multiplying the target inter-vehicle time Ttgt set by the driver using the operation switch 18 by the vehicle speed SPD of the host vehicle SV (that is, Dtgt = Ttgt · SPD).

When the value (k1 · ΔD1 + k2 · Vfx (a)) is positive or “0”, the DSECU determines the target acceleration Gtgt using the following equation (1). ka1 is a positive gain (coefficient) for acceleration, and is set to a value of “1” or less.
When the value (k1 · ΔD1 + k2 · Vfx (a)) is negative, the DSECU determines the target acceleration Gtgt using the following equation (2). kd1 is a positive gain (coefficient) for deceleration, and is set to "1" in this example.

Gtgt (for acceleration) = ka1 · (k1 · ΔD1 + k2 · Vfx (a)) (1)
Gtgt (for deceleration) = kd1 · (k1 · ΔD1 + k2 · Vfx (a)) (2)

  When the target vehicle distance can not be specified due to the absence of the preceding vehicle, the DSECU is configured such that the vehicle speed SPD of the host vehicle SV matches the "target vehicle speed set using the operation switch 18". Then, the target acceleration Gtgt is determined based on the target vehicle speed and the vehicle speed SPD.

  The DSECU controls the engine actuator 31 using the engine ECU 30 so that the acceleration of the host vehicle SV matches the target acceleration Gtgt, and controls the brake actuator 41 using the brake ECU 40 as necessary.

<Lane maintenance control>
When the lane keeping control is requested by the operation of the operation switch 18, the DSECU executes the lane keeping control only during the execution of the inter-vehicle distance control. Lane maintenance control mainly includes section lane maintenance control and steering follow-up control.

  Section lane maintenance control determines a target travel line (target travel path) based on the division lines such as the white line and the yellow line, and the steering angle of the host vehicle SV so that the host vehicle SV travels along the target travel line. Control to adjust the Partition lane maintenance control may be referred to as LTC (Lane Trace Control). In the following, the dividing lines are described as white lines.

  The steering follow-up control identifies one of the preceding vehicles as the steering follow-up target vehicle, and the steering angle of the own vehicle SV so that the own vehicle SV travels along the target traveling line according to the traveling trajectory of the steering follow-up target vehicle. Control to adjust the Steering follow-up control and section lane maintenance control may also be generically referred to as "TJA (Traffic Jam Assist)", and may be referred to as "steering support control" because the control assists the driver's steering operation. . Hereinafter, the description will be added in the order of section lane maintenance control and then steering follow-up control.

<< Section Lane Maintenance Control >>
If at least one of the left white line and the right white line is recognized by the camera sensor 17b over a predetermined distance in the forward direction of the host vehicle SV, the DSECU determines a target travel line based on at least one of the left white line and the right white line. Set Ld.

  More specifically, when both the left white line and the right white line are recognized in the forward direction of the host vehicle SV over a predetermined distance, the DSECU measures the center position in the lane width direction of the left white line and the right white line. The line passing through (ie, the center line) is set as the target travel line Ld.

  On the other hand, when only one white line of the left white line and the right white line is recognized over the predetermined distance in the forward direction of the host vehicle SV, the DSECU recognizes the recognized white line and the left white line. The position of the unrecognized white line (the other white line) is estimated based on the lane width acquired when both the right white line and the right white line were recognized. Then, the DSECU sets the center line of the recognized one white line and the estimated other white line as the target travel line Ld.

  Furthermore, the steering motor is controlled so that the DSECU maintains the lateral position of the host vehicle SV (that is, the position of the host vehicle SV in the lane width direction with respect to the host vehicle travel lane) in the vicinity of the set target travel line Ld. The steering angle of the host vehicle SV is changed by applying a steering torque to the steering mechanism using 62, thereby supporting the driver's steering operation (for example, Japanese Patent Application Laid-Open Nos. 2008-195402 and 2009-). 190464, JP-A-2010-6279, and Patent No. 4349210, etc.). A specific steering control method will be described later.

<< Steering tracking control >>
If there is no white line recognized over a predetermined distance in the forward direction of the host vehicle SV, the DSECU is suitable as a steering following target vehicle among other vehicles (forward vehicles) traveling in the front region of the host vehicle SV. Select a vehicle. Then, the DSECU generates a traveling locus of the steering following target vehicle (hereinafter, also referred to as “preceding vehicle locus”), and the host vehicle SV travels along the target traveling line determined based on the preceding vehicle locus. The steering torque is applied to the steering mechanism to change the steering angle. In the present example, the DSECU sets the preceding vehicle trajectory itself as the target travel line Ld. However, the DSECU may set a line displaced in the lane width direction by a predetermined distance from the preceding vehicle trajectory as the target travel line Ld.

  Next, the method of determining the target vehicle following the steering, the method of generating the trajectory of the preceding vehicle, and the method of the steering following control will be described.

1. Method of Determining a Steering Follow-Up Target Vehicle As shown in FIG. 2, the DSECU sets a forward vehicle, which is a target (n) for which a preceding vehicle trajectory is to be created, as a steering follow-up target vehicle TV. The method of setting the steering following target vehicle TV will be described in detail later.

2. Generation of Preceding Vehicle Trajectory The DSECU generates a traveling trajectory L1 (that is, a preceding vehicle trajectory) of the steering following target vehicle TV. More specifically, as shown in FIG. 3A, this traveling locus L1 is a cubic function of the following equation (3) in the above-mentioned x-y coordinates at the current position of the vehicle SV: It is known to be accurately approximated by the curve represented.

y = (1/6) Cv 'x ³ + (1/2) Cv x ² + θv x + dv (3)

Cv ′: curvature change rate (curvature change amount per unit distance (Δx) at an arbitrary position on the curve (x = x0, x0 is an arbitrary value)).
Cv: When the steering following target vehicle TV is present at the current position (x = 0) of the host vehicle SV (ie, the steering following target vehicle TV is present at the position (x = 0, y = dv) Curvature of the traveling locus L1).
θv: Direction of the traveling locus L1 (the tangential direction of the traveling locus L1) when the steering following target vehicle TV exists at the current position (x = 0) of the own vehicle SV and the traveling direction of the own vehicle SV (x axis Angular deviation with +). The angular deviation θv is also referred to as “yaw angle”.
dv: a distance dv (substantially in the lane width direction) between the current position (x = 0, y = 0) of the vehicle SV and the traveling locus L1. This distance dv is also referred to as "center distance".
The curvature Cv and the curvature change rate Cv ′ are also referred to as “trajectory shape parameters”.

The above equation (3) is derived as described below. That is, as shown in (B) of FIG. 3, the traveling locus L1 is set to the cubic function f (x) = ax ³ + bx ² + cx + d, and further, the relationship shown in (B) of FIG. Using the equation and the condition, “the relationship between the coefficients (a, b, c and d) of the cubic function and the curvature etc.” shown in FIG. 3C can be derived. Therefore, when the coefficients (a, b, c, and d) of the cubic function are obtained from the relationship shown in FIG. 3C, the above equation (3) is derived.

  Based on this point of view, the DSECU sets the coefficients of the first to fourth terms on the right side of equation (3) (in other words, the coefficients a, b, c, and d of the function f (x) as follows: Ask.

  -The DSECU acquires target information of the steering following target vehicle TV (hereinafter may be referred to as "target (b)") every time a predetermined measurement time elapses, and the target information is obtained. Positional coordinate data representing the position (longitudinal distance Dfx (n) and lateral position Dfy (n)) of the steering following target vehicle TV at the time of acquisition is stored (buffered) in the RAM. In order to minimize the amount of data to be stored, the DSECU saves only a certain number of position coordinate data from the latest position coordinate data of the steering following target vehicle TV, and discards the old position coordinate data sequentially You may

  The DSECU stores the position coordinate data of the steering-following target vehicle TV stored in the RAM on the position and traveling direction of the vehicle SV, and the position and traveling direction of the vehicle SV at the current time when acquiring each position coordinate data. Based on the difference between the two points, and is converted into position coordinate data of xy coordinates with the current position as the origin (x = 0, y = 0). The x and y coordinates of the converted position coordinate data (hereinafter sometimes referred to as "converted position coordinates") are placed as xi and yi, respectively. In this case, (xi, yi) = (x1, y1), (x2, y2), (x3, y3), (x4, y4), (x5, y5), (x6, y6) shown in FIG. These are examples of post-conversion position coordinates of the steering following target vehicle TV acquired in this manner.

  The DSECU executes a curve fitting process using the post-change position coordinates of the steering following target vehicle TV to generate a traveling locus L1 of the steering following target vehicle TV. The curve used for this fitting process is a cubic curve (curve represented by the above-described cubic function f (x)). The fitting process is performed by a weighted least squares method. That is, the DSECU determines the coefficients a, b, c, d of the cubic function f (x) such that “square sum ydif_all of deviation weighted by weight gi” expressed by equation (4) is minimized. Do.

3. Execution of Steering Follow-up Control The DSECU sets the generated traveling locus L1 to the target traveling line Ld. Furthermore, the DSECU is required for steering following control when the traveling locus L1 is set to the target traveling line Ld based on the coefficient of the cubic function of the equation (3) and the relational expression shown in FIG. Information (sometimes called "target travel path information") is acquired. The target travel path information includes the curvature Cv of the travel locus L1, the yaw angle θv with respect to the travel locus L1, and the center distance dv with respect to the travel locus L1.

The DSECU calculates the target steering angle θ * by applying the curvature Cv, the yaw angle θv, and the center distance dv to the following equation (5) each time a predetermined time elapses. In the equation (5), Klta1, Klta2 and Klta3 are predetermined control gains. Furthermore, the DSECU controls the steering motor 62 using the steering ECU 60 so that the actual steering angle θ matches the target steering angle θ *. By the above, steering control by steering following control is performed.

θ * = Klta1 · Cv + Klta2 · θv + Klta3 · dv (5)

Note that the DSECU may calculate the target yaw rate YRc * by applying the curvature Cv, the yaw angle θv, and the center distance dv to the following equation (6) each time a predetermined time elapses. In this case, the DSECU calculates a target steering torque Tr * for obtaining the target yaw rate YRc * using the look-up table, based on the target yaw rate YRc * and the actual yaw rate YRt. Then, the DSECU controls the steering motor 62 using the steering ECU 60 so that the actual steering torque Tra matches the target steering torque Tr *. Also by the above, steering control by steering following control is performed. As understood from the above, if the target running path information can be obtained, the DSECU executes steering following control in the case where the running locus L1 is set to the target running line Ld without calculating the target running line Ld itself. it can.

YRc * = K1 × dv + K2 × θv + K3 × Cv (6)

  The DSECU also uses the equation (5) or (6) when executing the above-described section lane maintenance control. More specifically, the DSECU sets the curvature CL of the target travel line Ld (that is, the center line of the host vehicle travel lane) set based on at least one of the left white line and the right white line, and the vehicle width of the host vehicle SV. The distance dL between the central position in the direction and the target travel line Ld in the y-axis direction (substantially the road width direction) and the deviation between the direction of the target travel line Ld (tangential direction) and the traveling direction of the host vehicle SV The angle θL (yaw angle θL) is calculated.

  Then, the DSECU calculates the target steering angle θ * by replacing dv with dL, replacing θv with θL, and replacing Cv with CL in equation (5) (or equation (6)). The steering motor 62 is controlled such that the actual steering angle θ matches the target steering angle θ *. Thus, the steering control based on the block lane maintenance control is performed.

  The DSECU can not set the target travel line Ld based on at least one of the left white line and the right white line, and can not generate a preceding vehicle locus (including the case where it is not possible to determine the steering following target vehicle). Cancel the execution of maintenance control. That is, in this case, the DSECU does not perform lane keeping control. The above is the outline of the lane keeping control.

  Next, with reference to FIG. 5, the “relaxation method of the restriction of the change of the trajectory shape parameter” executed by the DSECU of the first embodiment will be described.

  As shown in FIG. 5A, at time t1, the host vehicle SV is traveling in a straight section R1. The DSECU generates a traveling locus L1 of a steering following target vehicle TV traveling in front of the host vehicle SV, and executes steering following control. At time t1, the steering following target vehicle TV is traveling on the curve section entrance P1 where the curvature change rate Cv 'is D1. The inter-vehicle time T between the host vehicle SV and the steering following target vehicle TV is calculated by “inter-vehicle distance / vehicle speed of the host vehicle SV”.

  In this case, as shown in (B) of FIG. 5, at the time “t1 + inter-vehicle time T” after time t1, the locus shape parameter of the traveling locus L1 when the host vehicle SV travels on the curve section entrance P1. (The curvature change rate Cv ′) is ideally D1.

  Therefore, while the inter-vehicle time T elapses from time t1, the DSECU obtains an ideal trajectory shape parameter (curvature change rate Cv '= D1) at the time when the vehicle SV travels the curve section entrance P1. The trajectory parameter (curvature change rate Cv ') of the traveling track L1 needs to be increased from the curvature change rate Cv' (= 0) at time t = t1 to the curvature change rate Cv '(= D1).

  In this case, “an ideal locus shape parameter change amount (ideal parameter change amount) per predetermined time (calculation cycle)” is “(D1 / T) × Tcy (predetermined time (calculation cycle))”. The ideal parameter change amount increases as the inter-vehicle time T decreases.

  On the other hand, the DSECU should reduce the restriction on the change of the trajectory shape parameter by determining whether or not the "parameter change restriction relaxation condition" consisting of the following conditions 1 and 2 holds. It is determined whether or not

(Parameter change restriction relaxation condition)
Condition 1: The following curve determination parameter ε is equal to or greater than a predetermined threshold value εth.
The DSECU uses the curve determination parameter ε a value ε of the ratio of the locus shape parameter (curvature change rate Cv ′ (t−1)) acquired at the previous time by a predetermined time before the current time and the maximum curvature change rate Dmax of the traveling lane. (= Cv ′ (t−1) / maximum curvature change rate Dmax) is acquired.
Since the curvature change rate Cv ′ is larger as the curve determination parameter ε is larger, there is a high possibility that the curvature change rate Cv ′ is largely changed. That is, it can be determined that there is a high possibility that the host vehicle SV enters the curve section R2 from the straight section R1 of the traveling lane.
Condition 2: The inter-vehicle time T between the host vehicle SV and the steering following target vehicle is equal to or less than the threshold time Tth.

  In addition, the largest curvature change rate Dmax of the travel lane of condition 1 is acquired as follows. The DSECU acquires the vehicle speed of the host vehicle SV. The DSECU estimates a designed vehicle speed of the road based on the vehicle speed of the host vehicle SV. Look-up table (also referred to as "map") MaP (v) that defines the relationship between the design vehicle speed determined based on the road structure and the clothoid parameter A (allowable maximum clothoid parameter) MaP (v), the design vehicle speed of the road To obtain the clothoid parameter A. Then, the DSECU calculates the reciprocal of the clothoid parameter A, and sets the calculated reciprocal of the clothoid parameter A as the maximum curvature change rate Dmax.

  When the condition 1 is satisfied, there is a high possibility that the host vehicle SV is traveling near the curve section entrance P1. When the condition 2 is satisfied, there is a possibility that the "ideal parameter change amount" necessary for acquiring the ideal trajectory shape parameter may increase when the host vehicle SV is traveling near the curve section entrance P1. high. That is, when the condition 1 and the condition 2 are satisfied, there is a high possibility that the host vehicle SV is traveling near the curve section entrance P1, and the possibility that the "ideal parameter change amount" is large is high.

  Therefore, in this case, when the DSECU generates a traveling locus by curve fitting using equation (4), the change of the locus shape parameter is performed by changing the weight gi according to the detection area of the position coordinate data. Relax the restrictions of That is, the trajectory shape parameter acquired at the current calculation time point is made to largely change as compared with the previous trajectory shape parameter.

  Specifically, when the inter-vehicle time T is equal to or less than the threshold time Tth, and the condition 2 is satisfied that the curve determination parameter ε is equal to or more than the predetermined threshold εth, the DSECU The restriction of the change of the trajectory shape parameter is relaxed by setting the weighting of the position coordinate data behind the position of the own vehicle smaller than the weighting of the position coordinate data ahead of the current position of the own vehicle.

For example, as shown in FIG. 6, the term “g1 obtained by substituting the position coordinates (xi, yi) = (x1, y1) to (x4, y4) obtained after the current position of the host vehicle SV after conversion Each of the weights g1 to g4 of (y1-f (x1)) ^{2 to the} term "g4 (y4-f (x4)) ² " is set to a second value (e.g., smaller than a first value (e.g., 1)) , 0). The first value is a value that is set under normal conditions (when at least one of Condition 1 and Condition 2 is not satisfied), and the second value is greater than the first value during normal conditions. It is a small value.

The term "g5 (y5-f (x5)) ² " from which the position coordinates (xi, yi) = (x5, y5) to (x6, y6) after transformation acquired ahead of the current position of the vehicle SV is substituted. Each weight g5 to g6 of the term "g6 (y6-f (x6)) ² " is set to a first value (for example, gi = 1).

  The travel locus generated in this manner is a travel locus L1. Note that the travel locus generated with all the weights g1 to g6 set to the first value (1) without changing the weight is the travel locus L1 p.

  The traveling locus L1 is generated so that the degree of influence of the converted position coordinates (x1, y1) to (x4, y4) acquired in the straight section R1 of the traveling lane on the shape of the traveling locus becomes relatively small. There is. Furthermore, the traveling locus L1 is generated so that the degree of influence of the converted position coordinates (x1, y1) and (x2, y2) acquired in the curve section R2 on the shape of the traveling locus becomes relatively large. . Thereby, the curvature change rate Cv 'of the traveling locus L1 of the curve section entrance P1 becomes larger than the traveling locus L1p, and the restriction of the change of the locus shape parameter is relaxed.

  By relaxing the restriction on the change of the trajectory shape parameter, the DSECU may be able to acquire an ideal trajectory shape parameter (curvature change rate Cv ') when the host vehicle SV travels along the curve section entrance P1. Becomes higher. As a result, when the host vehicle SV travels in the vicinity P1 of the curve section entrance P1, the possibility of a delay in steering response can be reduced.

<Concrete operation>
Next, the specific operation of the CPU of the DSECU (which may be simply referred to as “CPU”) will be described. The CPU executes a steering follow-up control routine shown by the flowchart of FIG. 7 each time a predetermined time has elapsed. The predetermined time is a calculation cycle. The CPU executes inter-vehicle distance control (ACC) by a routine not shown. The CPU executes the routine shown in FIG. 7 only when the inter-vehicle distance control is being performed.

  Therefore, when the inter-vehicle distance control is being executed, the CPU starts the process from step 700 of FIG. 7 at a predetermined timing and proceeds to step 705 to determine whether the steering follow-up control execution condition is satisfied. Determine if

The execution condition of the steering follow-up control is satisfied, for example, when all of the conditions A1 to A3 described below are satisfied.
Condition A1: It is selected by the operation of the operation switch 18 to execute lane keeping control.
Condition A2: The vehicle speed SPD of the host vehicle SV is equal to or higher than a predetermined lower limit vehicle speed and equal to or lower than a predetermined upper limit vehicle speed.
Condition A3: The target travel line Ld based on "at least one of the left white line and the right white line" recognized by the camera sensor 17b can not be set.

  If the execution condition of the steering follow-up control is not satisfied, the CPU determines “No” in step 705 and proceeds to step 710 to cancel (cancel) the steering follow-up control. Thereafter, the CPU proceeds to step 795 to end this routine once.

  On the other hand, when the execution condition of the steering follow-up control is satisfied, the CPU makes a “Yes” determination in step 705, proceeds to step 715, and sequentially performs steps 715 to 730 described below. Proceed to step 735.

Step 715: The CPU detects the forward vehicle using the surrounding sensor 17. Specifically, the CPU acquires target information of all targets (n) acquired by the surrounding sensor 17. The CPU recognizes the target (n) present in a predetermined area in front of the host vehicle SV as a front vehicle based on the acquired target information.
Step 720: The CPU specifies a steering-following target vehicle TV to be generated for the traveling locus L1. Specifically, the CPU acquires the vehicle speed of the host vehicle SV from the vehicle speed sensor 16 and acquires the yaw rate of the host vehicle SV from the yaw rate sensor 19. The CPU predicts the traveling route of the host vehicle SV from the acquired vehicle speed and yaw rate. Then, the forward vehicle closest to the predicted “traveling route of the host vehicle SV” is selected as “the steering follow-up target vehicle TV to be generated as the traveling trajectory L1”.

Step 725: The CPU acquires the previous curvature change rate Cv ′ (t−1) of the position corresponding to the current position of the vehicle SV on the traveling locus L1 generated when this routine was previously executed. . The CPU acquires “the maximum curvature change rate Dmax of the traveling lane (road)” by applying the designed vehicle speed estimated based on the vehicle speed of the host vehicle SV to the above-described map. The CPU calculates a curve determination parameter ε (= Cv ′ (t−1) / Dmax) by dividing the previous curvature change rate Cv ′ (t−1) by the maximum curvature change rate Dmax of the traveling road.
Step 730: The CPU calculates an inter-vehicle time T with the steering following target vehicle TV of the host vehicle SV.

  When the CPU proceeds to step 735, it determines whether or not both the condition 1 that the inter-vehicle time T is the threshold time Tth or less and the condition 2 that the curve determination parameter ε is the predetermined threshold εth or more hold Do.

  If at least one of the condition 1 and the condition 2 is not satisfied, the CPU determines “No” in step 735 and proceeds to step 740, and based on the position information of the steering following target vehicle specified in step 720, A traveling locus L1 is generated. At this time, the CPU does not ease the restriction of the change of the trajectory shape parameter. Thereafter, the CPU proceeds to step 745.

  If both condition 1 and condition 2 are satisfied, the CPU makes affirmative determination in step 735, proceeds to step 750, and based on the position information of the steering following target vehicle specified in step 720, A traveling locus L1 is generated. At this time, the CPU relaxes the restriction of the change of the trajectory shape parameter. That is, as described above, the locus shape can be obtained by setting the weight of the position coordinate data behind the current position of the vehicle SV to be smaller than the weight of the position coordinate data ahead of the current position of the vehicle SV. Relax the restriction of parameter change. Thereafter, the CPU proceeds to step 745.

  When the CPU proceeds to step 745, it determines whether or not the estimation accuracy of the generated traveling locus L1 is low. Specifically, when the time-series data of the target information of the previous steering-following target vehicle is not sufficient to generate the traveling locus L1, the CPU estimates the accuracy of the “previous steering-following target vehicle traveling locus L1” Determined to be low. If this is not the case, the CPU determines that the estimation accuracy of the “previous steering following target vehicle's traveling locus L1” is not low.

  If the estimation accuracy of the “previous steering following target vehicle L1” is not low, the CPU makes affirmative determination in step 745 and proceeds to step 755.

  In step 755, the CPU sets the generated travel locus L1 to the target travel line, and controls the steering angle of the host vehicle SV so that the host vehicle SV travels along the target travel line. That is, the CPU executes the steering follow-up control using the travel locus L1 of the target vehicle following the steering. Thereafter, the CPU proceeds to step 795 to end this routine once.

  On the other hand, if the estimation accuracy of the "previous steering follow-up target vehicle's traveling locus L1" is low, the CPU determines "No" in step 745 and proceeds to step 710 to cancel (cancel) the steering follow-up control. . Thereafter, the CPU proceeds to step 795 to end this routine once.

  According to the first embodiment described above, in the situation where the host vehicle SV enters the curve section R2 from the straight section R1 of the traveling lane, a locus shape representing the shape of the traveling locus L1 of the steering following target vehicle used for steering following control The parameters can be obtained with high accuracy, which can enhance the reliability of the steering follow-up control.

Second Embodiment
Next, a vehicle driving support device according to a second embodiment of the present invention (hereinafter, also referred to as a “second embodiment device”) will be described. The second embodiment apparatus is different from the first embodiment apparatus only in the following points.
The DSECU of the second embodiment uses the Kalman filter 10a included in the DSECU as the input value (observed value) for the position coordinate data (position coordinates after conversion) (xi, yi) to calculate the target travel path information.
The DSECU of the second embodiment calculates the process noise (σΔcv ′) in the equation of state of the Kalman filter 10a according to the following formula, and inputs it to the Kalman filter 10a.
(a formula)
σΔcv '= (Dmax / N) ÷ T × Tcy
(N is 3, 2 or 1. T is inter-vehicle time. Tcy is a calculation cycle.)
Hereinafter, this difference will be mainly described.

<Overview of operation>
As illustrated in FIG. 8, the Kalman filter 10 a included in the DSECU includes position coordinate data (xi, yi), “standard deviation σΔcv ′ of change amount per calculation period of curvature change rate Cv ′” as process noise, With the observation noise σ yi as an input value, a covariance matrix P calculated on the basis of the target travel path information and the known Kalman filter principle is calculated as an output value.

  The target travel path information is the curvature change rate Cv 'of the travel path L1, the curvature Cv of the travel path L1, the yaw angle θ with respect to the travel path L1, and the center distance dv with respect to the travel path L1.

  The Kalman filter 10a (extended Kalman filter), as is well known, describes a nonlinear dynamic system, taking into account the state equation of the same system and the observation equation under the influence of noise, and based on those equations It is an iterative estimation type filter that estimates the current state quantity from the observed value of the current state and the estimated value of the past state quantity (for example, JP-A-2007-505377, JP-A-2014-10872, JP-A-2014) -102137, JP-A 2014-2103 and JP-A 2017-012650 etc.)

  The Kalman filter 10a is an observation equation having position coordinate data (xi, yi) as observation values and observation noise .sigma.yi, a state equation having target runway information (Cv'Cv, .theta., D) as state quantities, process noise, etc. To perform the well-known karma filter processing according to the well-known Kalman filter principle.

  The DSECU uses the current position coordinate data (xi, yi), the observation noise σ yi, the process noise and the past output values (Cv ′ (t−1), Cv (t−1), θ (t−1) as observation values. , D (t−1)) are input to the Kalman filter 10 a to acquire current target track information (Cv ′, Cv, θ, dv) as an output value. At this time, the DSECU of the second embodiment calculates “the standard deviation σΔcv ′ of the amount of change per calculation period of the curvature change rate Cv ′” as the process noise using the above (calculation formula) to obtain the Kalman filter. Enter in 10a.

  In the above (calculation formula), it is assumed that the maximum curvature change rate Dmax = N · σΔcv ′. In the case of N = 3, it is the value of the maximum curvature change rate Dmax when the occurrence probability of the maximum curvature change rate Dmax according to the normal distribution is 0.3%.

As the curve determination parameter ε (= Cv ′ (t−1) / maximum curvature change rate Dmax) becomes larger, the generation probability of the maximum curvature change rate Dmax is N based on the thought that the occurrence probability increases. To change like.
N = 3 (ε <first threshold ratio εth1)
N = 2 (first threshold ratio εth1 ≦ ε <second threshold ratio εth2)
N = 1 (second threshold ratio εth2 ≦ ε)

  According to (calculation formula), N becomes smaller as the curve determination parameter ε becomes larger, and “the standard deviation σΔcv ′ of the amount of change per calculation period of the curvature change rate Cv ′” increases. Furthermore, as the inter-vehicle time T decreases, "the standard deviation ?? cv 'of the amount of change per calculation cycle of the curvature change rate Cv' increases.

  According to the Kalman filter principle, the observed value is likely to be reflected in the output value (estimated value) when the input process noise (“the standard deviation σΔcv ′ of the amount of change per calculation period of the curvature change rate Cv ′” increases). . This alleviates the limitation of the change of the trajectory shape parameter. In other words, the trajectory shape parameter acquired at the time of the current calculation changes more than the trajectory shape parameter acquired last time.

  Therefore, when the host vehicle SV enters the curve section R2 from the straight section R1, the restriction on the change of the locus shape parameter is relaxed, and therefore, the locus shape parameter can be acquired with high accuracy. As a result, the reliability of the steering following control can be enhanced.

<Concrete operation>
Next, the specific operation of the CPU of the DSECU of the second embodiment will be described. The CPU is configured to execute the steering follow-up control routine shown by the flowchart of FIG. 9 each time a predetermined time elapses. In the present example, the predetermined time is a calculation cycle.

The routine of FIG. 8 differs from the routine of FIG. 7 only in that steps 735 to 745 are replaced by steps 905 to 915.
Step 905: The CPU substitutes the maximum curvature change rate Dmax, the inter-vehicle time T, and the calculation cycle tcy into (calculation formula) to calculate “the amount of change per calculation cycle (predetermined time) of the curvature change rate Cv ′. Standard deviation σΔcv 'is calculated.
Step 910: The CPU acquires target raceway information as an output value by inputting an input value to the Kalman filter 10a.
Step 915: The CPU determines whether the estimation accuracy of the travel locus (target travel route information) is not low. If the value of the covariance matrix P output from the Kalman filter 10a is smaller than a predetermined value, it is determined that the estimation accuracy of the traveling locus is not low. If the value of the covariance matrix P output from the Kalman filter 10a is equal to or greater than a predetermined value, it is determined that the estimation accuracy of the traveling locus is low.

  As described above, according to the second embodiment, in a situation where the host vehicle SV enters the curve section R2 from the straight section R1 of the traveling lane, the target including the trajectory shape parameter of the steering following target vehicle used for the steering follow-up control Runway information can be acquired with high accuracy. As a result, the reliability of the steering following control can be enhanced.

<Modification>
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention are possible.

  For example, the first embodiment and the second embodiment execute lane keeping control only during execution of following distance control, but do not perform lane keeping control even when following distance control is not in progress. It may be configured to run.

  For example, the first embodiment apparatus and the second embodiment apparatus may acquire position information, speed information, and the like of another vehicle including a steering follow-up target vehicle TV and an inter-vehicle distance target vehicle through inter-vehicle communication. Specifically, for example, the position information of the other vehicle acquired by the other vehicle by the navigation device of the other vehicle is transmitted to the own vehicle SV together with a vehicle ID signal specifying the other vehicle itself, and the own vehicle SV Based on the transmitted information, position information of the steering following target vehicle TV and / or the inter-vehicle distance target vehicle may be acquired.

  For example, the first embodiment and the second embodiment may acquire the maximum curvature change rate Dmax of the traveling lane by using the map information acquired by the navigation ECU 90.

  DESCRIPTION OF SYMBOLS 10 ... Driving assistance ECU, 16 ... Vehicle speed sensor, 17 ... Ambient sensor, 17a ... Radar sensor, 17b ... Camera sensor, 17c ... Target object recognition part, 18 ... Operation switch, 19 ... Yaw rate sensor, 60 ... Steering ECU, 61 ... Motor driver, 62: Steering motor, 80: Alarm ECU, 81: Buzzer, 82: Display, SV: Own vehicle, TV: Steering following target vehicle

Claims (2)

A vehicle speed detection unit that detects the vehicle speed of the host vehicle;
A maximum curvature change rate estimation unit configured to estimate a maximum curvature change rate of a traveling lane on which the vehicle travels;
A position information acquisition unit that acquires position information of a preceding vehicle traveling in a front area of the host vehicle;
A steering-following target vehicle identification unit that identifies a steering-following target vehicle from among the one or more preceding vehicles;
A position information storage unit for storing the position information of the specified target vehicle following the steering, each time a predetermined time has elapsed;
A traveling locus generating unit that generates a traveling locus of the identified target vehicle following the steering using the stored position information, and acquires a locus shape parameter including a curvature change rate representing a shape of the generated traveling locus;
A traveling control unit that executes steering follow-up control that changes a steering angle of the own vehicle so that the own vehicle travels along a target traveling line set based on the traveling locus;
Equipped with
The travel locus generation unit
Calculating a value of a ratio between the curvature change rate and the maximum curvature change rate acquired the predetermined time before the current time,
The inter-vehicle time of the vehicle at the current time with the target vehicle is calculated using the vehicle speed of the vehicle and the position information,
When any of the first condition that the value of the ratio is equal to or more than a predetermined threshold and the second condition that the inter-vehicle time is equal to or less than the threshold time, the vehicle is located behind the current position of the vehicle The degree that the position information detected in step is reflected in the travel locus is smaller than the degree in which the position information detected in front of the host vehicle at the current point is reflected in the travel locus. Generate a running track,
Configured as
Vehicle driving support device. A vehicle speed detection unit that detects the vehicle speed of the host vehicle;
A maximum curvature change rate estimation unit configured to estimate a maximum curvature change rate of a traveling lane on which the vehicle travels;
A position information acquisition unit that acquires position information of a preceding vehicle traveling in a front area of the host vehicle;
A steering-following target vehicle identification unit that identifies a steering-following target vehicle from among the one or more preceding vehicles;
A travel locus generation unit that has a Kalman filter and calculates target travel path information including a trajectory shape parameter including a curvature change rate representing the shape of a travel trajectory of the specified vehicle following a target, each time a predetermined time elapses, The value of the ratio between the curvature change rate and the maximum curvature change rate acquired the predetermined time before the current time is calculated, and the steering of the vehicle at the current time is calculated using the vehicle speed of the vehicle and the position information. The inter-vehicle time with the follow-up target vehicle is calculated, and the maximum curvature change rate, the inter-vehicle time, and the predetermined time are substituted into the following formula, and if the value of the ratio is smaller than the first threshold, 3 is substituted into N, and 2 is substituted into the N when the value of the ratio is greater than or equal to the first threshold and smaller than the second threshold, and 1 when the value of the ratio is greater than or equal to the second threshold. The curvature by substituting Calculating a standard deviation of change per predetermined time of the rate,
An input value including the position information of the specified target vehicle following the steering as an observed value and the standard deviation as a process noise is input to the Kalman filter, and the target runway information is calculated according to the principle of the Kalman filter. The travel locus generation unit configured as described above;
A traveling control unit that executes steering follow-up control that changes a steering angle of the host vehicle based on the target travel path information;
Vehicle driving assistance device comprising:
(a formula)
σΔcv '= {(Dmax / N) ÷ T} × Tcy
(ΣΔcv ′ is a standard deviation of the amount of change in the curvature change rate per predetermined time. Dmax is the maximum curvature change rate. N is 3, 2 or 1. T is an inter-vehicle time. Is the predetermined time)

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