JP6825528B2 - Vehicle driving support device - Google Patents

Description

The present invention relates to a vehicle driving support device that controls driving of its own vehicle along a target traveling line based on a traveling locus of another vehicle in front of the own vehicle.

One of the conventionally known vehicle driving support devices (hereinafter, referred to as "conventional device") generates a traveling locus of a steering tracking target vehicle selected from the vehicles in front traveling in front of the own vehicle. (See, for example, "Patent Document 1".).

The conventional device detects the position of the steering tracking target vehicle by using the surrounding sensor every time a predetermined time (calculation cycle) elapses, and the traveling locus of the steering tracking target vehicle based on the detected position of the steering tracking target vehicle. To generate. The conventional device performs steering control so as to drive the own vehicle along a target traveling line determined based on the generated traveling locus. The steering control performed so as to drive the own vehicle along the target traveling line based on the traveling locus of the steering tracking target vehicle is also referred to as "steering tracking control".

Various methods have been proposed as a method for generating a traveling locus of a steering tracking target vehicle. For example, the conventional device obtains time-series data (position coordinate data) of the detected position of the steering follower vehicle (for example, the x-coordinate value and the y-coordinate value of the xy coordinate defined based on the current position of the own 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, curvature and curvature change rate) representing the shape of a traveling locus from a coefficient of the function formula f (x) representing a curve, and uses the acquired locus shape parameter for steering follow-up control. use.

Japanese Patent Publication No. 2011-514580

The detection position of the steering tracking target vehicle detected by this calculation may have an error. In this case, the shape of the generated traveling locus changes under the influence of the error of the detection position this time, so that the accuracy of the locus shape parameter may deteriorate.

On the other hand, the conventional device uses, for example, a filter, increases the coordinate range of the detection position used for generating the traveling locus, and increases the number of detection positions. As a result, the change of the locus shape parameter is restricted so that the locus shape parameter acquired this time does not change significantly as compared with the locus shape parameter acquired last time due to the error of the detection position this time.

However, if the change in the locus shape parameter is excessively restricted, the following may occur.

For example, as shown in (A) of FIG. 5 and (B) of FIG. 5, a situation in which the own vehicle SV traveling in the straight section R1 of the traveling lane follows the steering tracking target vehicle TV entering the curve section R2. Occurs. In this case, at the curve section entrance P1, the curvature change rate Cv'of the traveling locus of the actual steering follow-up target vehicle TV is from the curvature change rate Cv'(= 0) of the straight section R1 to the curvature of the curve section entrance (P1). The rate of change greatly changes up to Cv'(= D1).

Therefore, when the own vehicle SV travels at the curve section entrance P1, in order for the conventional device to acquire the ideal locus shape parameter (curvature change rate Cv'(= D1)) with high accuracy, it is necessary to start from time t1. It is necessary to increase the locus shape parameter (curvature change rate Cv') of the curve section entrance P1 of the traveling locus L1 from 0 to D1 until the inter-vehicle time T elapses.

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

Since this ideal parameter change amount increases as the inter-vehicle time T becomes shorter, even when the inter-vehicle time T is short, if the change of the locus shape parameter is excessively restricted, the change of the locus shape parameter per calculation cycle changes. , The ideal parameter change amount (= (D1 / T) × Tcy)) may be smaller.

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

The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to be able to accurately acquire the locus shape parameter representing the shape of the traveling locus of the steering follow-up target vehicle in a situation where the own vehicle enters the curved section from the straight section of the traveling lane. Therefore, it is an object of the present invention to provide a vehicle driving support device (hereinafter, also referred to as "the device of the present invention") capable of enhancing the reliability of steering follow-up control.

The first aspect of the apparatus of the present invention is
A vehicle speed detection unit (16) that detects the vehicle speed of the own vehicle (SV),
The maximum curvature change rate estimation unit (10) for estimating the maximum curvature change rate of the traveling lane in which the own vehicle travels (step 730 in FIG. 7) and
Position information acquisition units (10, 17) that acquire position information including position information indicating the vertical distance and lateral position of the front vehicle traveling in the front region of the own vehicle with respect to the own vehicle (step 715 in FIG. 7)
The steering follow-up target vehicle (TV) is specified from one or more of the preceding vehicles (step 720 in FIG. 7), and the steering follow-up target vehicle identification unit (10).
A position information storage unit (10, RAM) that stores the position information of the specified steering tracking target vehicle every time a predetermined time elapses, and
Using the saved position information, a traveling locus (L1) of the specified steering tracking target vehicle is generated, and a locus shape parameter including a curvature change rate representing the shape of the generated traveling locus is acquired (FIG. 7). Step 755) Travel locus generator (10) and
Steering follow-up control for changing the steering angle of the own vehicle is executed so that the own vehicle travels along the target traveling line set based on the traveling locus (step 755 in FIG. 7). )When,
With
The traveling locus generator
The value (ε) of the ratio of the curvature change rate (Cv'(t-1)) acquired before the predetermined time to the maximum curvature change rate (Dmax) was calculated from the present time (step 725 in FIG. 7).
Using the vehicle speed of the own vehicle and the position information, the inter-vehicle time (T) of the current own vehicle with the steering follow-up target vehicle is calculated (step 730 in FIG. 7).
When both the first condition that the value of the ratio is equal to or more than the predetermined threshold value and the second condition that the inter-vehicle time is equal to or less than the threshold time are satisfied (“Yes” in step 735 of FIG. 7). Judgment),
The degree to which the position information detected behind the current position of the own vehicle is reflected in the traveling locus is reflected in the traveling locus, and the position information detected in front of the current own vehicle is reflected in the traveling locus. The traveling locus is generated so as to be smaller than the degree (step 750).
It is configured as follows.

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

When the first condition and the second condition are satisfied, the degree to which the position information detected behind the current position of the own vehicle is reflected in the traveling locus is reflected in the traveling locus, and the position information detected in front of the current own vehicle is the traveling locus. The traveling locus is generated so as to be smaller than the degree reflected in.

As a result, it is allowed that the locus shape parameter acquired at the present time is significantly changed as compared with the locus shape parameter acquired before the predetermined elapsed time (that is, the limitation of the change of the locus shape parameter is relaxed). Therefore, even when the own vehicle is traveling near the entrance of the curve section, it is possible to obtain an accurate traveling locus. As a result, it is possible to reduce the possibility that the steering response is delayed when the own vehicle enters the curved section from the straight section of the traveling lane.

A second aspect of the apparatus of the present invention is
Vehicle speed detection unit (16) that detects the vehicle speed of the own vehicle,
The maximum curvature change rate estimation unit (10) for estimating the maximum curvature change rate of the traveling lane in which the own vehicle travels (step 730 in FIG. 9) and
The position information acquisition unit (10) that acquires the position information including the position information indicating the vertical distance and the lateral position of the front vehicle traveling in the front region of the own vehicle with respect to the own vehicle (step 715 in FIG. 9)
A steering follow-up target vehicle identification unit (10) for specifying a steering follow-up target vehicle from one or more of the preceding vehicles (step 720 in FIG. 9)
It has a Kalman filter (10), and every time a predetermined time elapses, it calculates target track information including a trajectory shape parameter including a curvature change rate representing the shape of the travel trajectory of the specified steering tracking target vehicle (step of FIG. 9). 910) The traveling locus generation unit (10) calculates a value of the ratio of the curvature change rate and the maximum curvature change rate acquired before the predetermined time from the present time (step 725 in FIG. 9), and the self. Using the vehicle speed and the position information, the inter-vehicle time of the own vehicle at the present time with the steering follow-up target vehicle is calculated (step 730 in FIG. 9), and the maximum curvature change rate and the said Substituting the inter-vehicle time and the predetermined time, if the value of the ratio is smaller than the first threshold (εth1), substitute 3 for N in the following formula, and the value of the ratio is the first threshold or more and the second threshold ( When it is smaller than εth2), 2 is substituted for the N, and when the value of the ratio is equal to or greater than the second threshold value, 1 is substituted for the N, thereby changing the curvature change rate per predetermined time. Calculate the standard deviation of the quantity (σΔcv') (step 905 in FIG. 9).
Input values including the position information of the specified steering tracking target vehicle as observation values and the standard deviation as process noise are input to the Kalman filter, and the target track information is calculated according to the principle of the Kalman filter. With the traveling locus generation unit configured as shown in (step 910 of FIG. 9),
Based on the target track information, the travel control unit (10) that executes steering follow-up control for changing the steering angle of the own vehicle (step 755 in FIG. 9)
To be equipped.
(a formula)
σΔcv'= {(Dmax / N) ÷ T} × Tcy
(ΣΔcv'is the 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 the inter-vehicle time. Tcy. Is the predetermined time.)

According to the above (calculation formula), as the value of the above ratio increases, N decreases, and the process noise input to the Kalman filter, "standard deviation σΔcv'of the amount of change in the rate of change in curvature per predetermined time" increases. .. Further, as the inter-vehicle time becomes smaller, the same "standard deviation σΔcv'of the amount of change in the curvature change rate per predetermined time" increases.

According to the principle of the Kalman filter, when the input process noise (“standard deviation of the amount of change in the curvature change rate per predetermined time (σcv ′)”) becomes large, the observed value is easily reflected in the output value.

As a result, when the own vehicle enters the curve section entrance from the straight section, the restriction on the change of the locus shape parameter is relaxed. As a result, it is possible to reduce the possibility that the steering response is delayed when the own vehicle enters the curved section from the straight section of the traveling lane.

In the above description, in order to help the understanding of the present invention, the names and / or symbols used in the embodiments are added in parentheses to the configurations 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 name and / or reference numeral.

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 lane keeping control. FIG. 3A is a plan view for explaining lane keeping control. FIG. 3B is a mathematical formula for explaining the relationship between the coefficient of the cubic function of the traveling locus and the curvature and the like. FIG. 3C is a mathematical formula 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 the generation of the traveling locus. 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 explaining 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 the generation of a traveling locus 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 included in the vehicle driving support device according to the first embodiment of the present invention. FIG. 8 is a schematic view showing an outline of the operation of the Kalman filter included in the vehicle driving support device according to the second embodiment of the present invention. FIG. 9 is a flowchart showing a routine executed by the CPU of the driving support ECU included in the vehicle driving support device according to the second embodiment of the present invention.

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

(Constitution)
The first implementing device is applied to a vehicle (automobile) as shown in FIG. The vehicle to which the first implementation device is applied may be referred to as "own vehicle" to distinguish it from other vehicles. The first executing device 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 a “DS ECU”.

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

The DSECU is connected to the sensors (including switches) listed below and is adapted 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 the 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 the operation amount (accelerator opening degree) of the accelerator pedal 11a of the own vehicle, and outputs a signal representing the accelerator pedal operation amount AP.
The brake pedal operation amount sensor 12 detects the operation amount of the brake pedal 12a of the own vehicle and outputs a signal indicating the brake pedal operation amount BP.

The steering angle sensor 14 detects the steering operation angle, which is the rotation angle of the steering wheel SW of the own vehicle, and outputs a signal representing the steering operation angle θ.
The steering torque sensor 15 detects the steering torque applied to the steering shaft US of the own vehicle by operating 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 own vehicle and outputs a signal indicating the vehicle speed SPD.

The surrounding sensor 17 includes a radar sensor 17a, a camera sensor 17b, and a target recognition unit 17c. The surrounding sensor 17 acquires information on at least the road in front of the own vehicle and the three-dimensional object existing on the road. The three-dimensional object represents, for example, a moving object such as a pedestrian, a bicycle or an automobile, and a fixed object such as a utility pole, a tree or a guardrail. Hereinafter, these three-dimensional objects may be referred to as "targets".

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

The surrounding sensor 17 acquires these values based on the xy coordinates defined in advance (see FIG. 2). The x-axis is a coordinate axis that extends along the front-rear direction of the own vehicle SV so as to pass through the center position in the width direction of the front end portion of the own vehicle SV and has the front as a positive value. The y-axis is a coordinate axis that is orthogonal to the x-axis and has a positive value in the left direction of the own vehicle SV. The origin of the x-axis and the origin of the y-axis are the center positions in the width direction of the front end portion of the own vehicle SV. The x-coordinate position of the xy coordinate is called the vertical distance Dfx, and the Y-coordinate position is called the horizontal position Dfy.

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

The radar sensor 17a shown in FIG. 1 includes a radar wave transmission / reception unit and a processing unit. The radar wave transmitter / receiver radiates, for example, a radio wave in the millimeter wave band (hereinafter, referred to as "millimeter wave") to a peripheral region of the own vehicle SV including at least the front region of the own vehicle SV, and the radiated millimeter. The reflected wave generated by the wave being reflected by the part of the three-dimensional object (immediately, the reflection point) is received. The radar sensor 17a may be a radar sensor that uses radio waves (radar waves) in a frequency band other than the millimeter wave band.

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

Further, the processing unit of the radar sensor 17a sets the vertical distance Dfx of the target, the orientation θp of the target with respect to the own vehicle SV, and the own vehicle SV based on the reflection point information of the reflection point belonging to the recognized target. The relative speed Vfx with respect to the target, the vehicle speed of the target, etc. (hereinafter referred to as "radar sensor detection information") are calculated.

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

The image processing unit determines the presence or absence of a target existing in the photographing area based on the pair of left and right image data captured. If it is determined that the target object exists, the image processing unit, the orientation theta _p of the _target, the vertical distance Dfx of the target, and the relative velocity Vfx like of the vehicle SV and its target (hereinafter, " It is called "camera sensor detection information").

The target recognition unit 17c is connected to the processing unit of the radar sensor 17a and the image processing unit of the camera sensor 17b in a communicable state so as to receive the "radar sensor detection information" and the "camera sensor detection information". It has become. The target recognition unit 17c recognizes the target (n) using at least one of the “radar sensor detection information” and the “camera sensor detection information”, “target ID, vertical distance Dfx (n), horizontal”. "Target information including position Dfy (n), relative velocity Vfx (n), etc." is determined (acquired). The target target recognition unit 17c transmits the determined target information to the DSPE every time a predetermined time elapses.

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

Information indicating the shape of the own vehicle traveling lane, the positional relationship between the own vehicle traveling lane and the own vehicle in the lane width direction, and the like may be given from the navigation ECU 90.

The operation switch 18 shown in FIG. 1 is a switch operated by the driver of the own vehicle SV. By operating the operation switch 18, the driver can select whether or not to execute the lane keeping control including the steering follow-up control described later. Further, the driver can select whether or not to execute the inter-vehicle distance control (following inter-vehicle distance control) described later by operating the operation switch 18.

The yaw rate sensor 19 detects the yaw rate of the own vehicle SV and outputs the 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. By driving the engine actuator 31, the engine ECU 30 can change the torque generated by the internal combustion engine 32, thereby controlling the driving force of the own vehicle SV and changing the acceleration of the own 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 a friction brake mechanism 42 provided on the left, right, front and rear wheels. The brake actuator 41 adjusts the hydraulic pressure of the hydraulic oil supplied to the wheel cylinder built in the brake caliper 42b of the friction brake mechanism 42 in response to an instruction from the brake ECU 40, and the brake pads (not shown) are pressed by the hydraulic pressure of the brake disc 42a. Press against to generate friction braking force. Therefore, the brake ECU 40 can control the braking force of the own vehicle SV to change the acceleration (in this case, deceleration) of the own vehicle SV by controlling the brake actuator 41.

The steering ECU 60 is a well-known control device for an electric power steering system, and is connected to a 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, and a steering gear mechanism (not shown)". The steering motor 62 generates torque by the electric power supplied from the motor driver 61, and this torque can generate steering assist torque and steer the left and right steering wheels. That is, the steering motor 62 can change the steering angle (also referred to as "steering angle" or "steering angle") of the own vehicle SV.

The meter ECU 70 is connected to a digital display type meter (not shown). Further, the meter ECU 70 is also connected to the hazard lamp 71 and the stop lamp 72, and the lighting state of these can be changed according to the instruction from the DSP ECU.

The alarm ECU 80 is connected to the buzzer 81 and the display 82. The alarm ECU 80 can sound the buzzer 81 in response to an instruction from the DSECU to alert the driver, and also turn on the alert mark (for example, a warning lamp) on the display 82. can do.

The navigation ECU 90 is connected to a GPS receiver 91 that receives a GPS signal for detecting the current position of the own vehicle SV, a map database 92 that stores map information, and a touch panel display 93. The navigation ECU 90 identifies the current position of the own vehicle SV based on the GPS signal (when the own vehicle SV is traveling on a road having a plurality of lanes, which lane the own vehicle SV is traveling in). Includes information).

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

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

<Outline of operation>
Next, the outline of the operation of the first executing device will be described. The DSECU of the first implementation device 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 follow-up inter-vehicle distance control) is the inter-vehicle distance between the vehicle in front and the vehicle SV traveling in front of the vehicle SV in the area in front of the vehicle SV based on the target information. (That is, it is a control that causes the own vehicle SV to follow the preceding vehicle while maintaining the vertical distance Dfx (n) of the vehicle in front of the own vehicle SV at a predetermined target inter-vehicle distance. The following vehicle-to-vehicle distance control itself is well known (see, for example, Japanese Patent Application Laid-Open No. 2014-148293, Japanese Patent Application Laid-Open No. 2006-315491, Japanese Patent No. 4172434, Japanese Patent No. 4929777, etc.). Therefore, it will be briefly described below.

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

First, when the inter-vehicle distance control is required, the DSECU is referred to as a vehicle to be tracked based on the target information of the target (n) acquired by the surrounding sensor 17 (hereinafter referred to as "inter-vehicle distance target vehicle"). To be identified). More specifically, the DSECU determines (identifies) the inter-vehicle distance target vehicle from among other vehicles (that is, the vehicles in front) traveling in the front region of the own vehicle SV as follows.

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

When the DESCU specifies the inter-vehicle distance target vehicle (a), the DESCU calculates the target acceleration Gtgt according to any of the following equations (1) and (2). In equations (1) and (2), Vfx (a) is the relative speed of the inter-vehicle distance target vehicle (a), k1 and k2 are predetermined positive gains (coefficients), and ΔD1 is the “inter-vehicle distance target”. It is an inter-vehicle deviation (ΔD1 = Dfx (a) −Dtgt) obtained by subtracting the “target inter-vehicle distance Dtgt” from the “vertical 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 own 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 inter-vehicle distance target vehicle cannot be specified due to the absence of the vehicle in front, the DESCU adjusts the vehicle speed SPD of the own vehicle SV to match the "target vehicle speed set by using the operation switch 18." In addition, the target acceleration Gtgt is determined based on the target vehicle speed and the vehicle speed SPD.

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

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

The division lane maintenance control determines the target travel line (target travel route) based on the division lines such as the white line and the yellow line, and the steering angle of the own vehicle SV so that the own vehicle SV travels along the target travel line. It is a control to adjust. The division lane maintenance control is sometimes referred to as "LTC (Lane Trace Control)". In the following, the lane markings will be described as white lines.

The steering follow-up control identifies one of the vehicles in front 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 travel line according to the travel locus of the steering follow-up target vehicle. It is a control to adjust. Steering follow-up control and division lane maintenance control may also be collectively referred to as "TJA (Traffic Jam Assist)", and may also be referred to as "steering support control" because they are controls that assist the driver's steering operation. .. Hereinafter, description will be added in the order of division lane maintenance control and then steering follow-up control.

<< Section lane maintenance control >>
When at least one of the left white line and the right white line is recognized by the camera sensor 17b in the front direction of the own vehicle SV for a predetermined distance or more, the DSECU has a target traveling 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 front direction of the own vehicle SV over a predetermined distance or more, the DSECU has the center position of the left white line and the right white line in the lane width direction. The line passing through (that is, the central line) is set as the target traveling line Ld.

On the other hand, in the DSECU, when only one of the left white line and the right white line is recognized in the front direction of the own vehicle SV for a predetermined distance or more, the recognized white line and the left white line are recognized. The position of the unrecognized white line (the other white line) is estimated based on the lane width acquired at the time when both the right white line and the right white line are recognized. Then, the DESCU sets the center line of one recognized white line and the estimated other white line as the target traveling line Ld.

Further, the DSECU is a steering motor so that the lateral position of the own vehicle SV (that is, the position of the own vehicle SV in the lane width direction with respect to the own vehicle travel lane) is maintained near the set target travel line Ld. By applying steering torque to the steering mechanism using 62, the steering angle of the own vehicle SV is changed to support the steering operation of the driver (for example, JP-A-2008-195402, JP-A-2009-). 190464, JP2010-6279, and Patent No. 4349210, etc.). The specific steering control method will be described later.

<< Steering follow-up control >>
When there is no white line recognized in the front direction of the own vehicle SV for more than a predetermined distance, the DSECU is suitable as a steering follow-up target vehicle from among other vehicles (front vehicles) traveling in the front region of the own vehicle SV. Select a vehicle. Then, the DSECU generates a traveling locus of the steering follow-up target vehicle (hereinafter, also referred to as a "preceding vehicle locus") so that the own vehicle SV travels according to a 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 this example, the DESCU sets the preceding vehicle locus itself as the target traveling line Ld. However, the DSECU may set a line displaced in the lane width direction by a predetermined distance from the preceding vehicle locus as the target traveling line Ld.

Next, a method of determining the steering follow-up target vehicle, a method of generating a preceding vehicle trajectory, and a method of steering follow-up control will be described.

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

2. 2. Generation of the preceding vehicle locus The DSECU generates the traveling locus L1 (that is, the preceding vehicle locus) of the steering follow-up target vehicle TV. More specifically, as shown in FIG. 3A, the traveling locus L1 is a cubic function of the following equation (3) at the above-mentioned xy coordinates at the current position of the own vehicle SV. It is known that the curve represented can be accurately approximated.

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 (x = x0, x0 is an arbitrary value) on the curve).
Cv: When the steering follow-up target vehicle TV was present at the current position (x = 0) of the own vehicle SV (that is, the steering follow-up target vehicle TV was present at the position (x = 0, y = dv)). When) the curvature of the traveling locus L1.
θv: The direction of the traveling locus L1 (tangential direction of the traveling locus L1) and the traveling direction of the own vehicle SV (x-axis) when the steering follow-up target vehicle TV is present at the current position (x = 0) of the own vehicle SV. Angle deviation from (+ direction). This angle deviation θv is also called “yaw angle”.
dv: The distance dv between the current position (x = 0, y = 0) of the own vehicle SV and the traveling locus L1 in the y-axis direction (substantially in the lane width direction). This distance dv is also referred to as the "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 FIG. 3 (B), the traveling locus L1 is set as a cubic function f (x) = ax ³ + bx ² + cx + d, and the relationship shown in FIG. 3 (B) is further set. Using the equations and conditions, 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. 3 (C), the above equation (3) is derived.

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

-The DSECU acquires the target information of the steering tracking target vehicle TV (hereinafter, may be referred to as "target (b)") every time a predetermined measurement time elapses, and obtains the target information. The position coordinate data representing the position (vertical distance Dfx (n) and horizontal position Dfy (n)) of the steering tracking target vehicle TV at the time of acquisition is stored (buffered) in the RAM. In order to reduce the amount of data to be saved as much as possible, the DSPE saves only a certain number of position coordinate data from the latest position coordinate data of the steering tracking target vehicle TV, and sequentially discards the old position coordinate data. You may.

-The DESCU uses the position coordinate data of the steering tracking target vehicle TV stored in the RAM as "the position and traveling direction of the own vehicle SV and the current position and traveling direction of the own vehicle SV" at the time of acquiring the respective position coordinate data. Based on "the difference between and,", the current position is converted into the position coordinate data of the xy coordinates with the origin (x = 0, y = 0). The x-coordinate and y-coordinate of the converted position coordinate data (hereinafter, may be referred to as "converted position coordinate") are set 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. 4 are This is an example of the converted position coordinates of the steering tracking target vehicle TV acquired in this way.

The DSECU generates the traveling locus L1 of the steering tracking target vehicle TV by executing the curve fitting process using the changed position coordinates of the steering tracking target vehicle TV. The curve used for this fitting process is a cubic curve (curve represented by the above-mentioned cubic function f (x)). The fitting process is performed by the weighted least squares method. That is, the DSECU determines the coefficients a, b, c, and d of the cubic function f (x) so that the "sum of squares ydif_all of the deviations weighted by the weight gi" expressed by the equation (4) is minimized. To do.

3. 3. Execution of steering follow-up control The DSECU sets the generated travel locus L1 to the target travel line Ld. Further, the DESCU is necessary for steering follow-up control when the traveling locus L1 is set to the target traveling line Ld based on the coefficient of the cubic function of Eq. (3) and the relational expression shown in (C) of FIG. Information (sometimes called "target track information") is acquired. The target track information includes the curvature Cv of the travel locus L1, the yaw angle θv with respect to the travel locus L1, the center distance dv with respect to the travel locus L1, and the like.

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) every time a predetermined time elapses. In the equation (5), Klta1, Klta2 and Klta3 are predetermined control gains. Further, the DSECU controls the steering motor 62 by using the steering ECU 60 so that the actual steering angle θ matches the target steering angle θ *. As described above, the steering control by the steering follow-up control is executed.

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

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) every time a predetermined time elapses. In this case, the DESCU calculates the target steering torque Tr * for obtaining the target yaw rate YRc * based on the target yaw rate YRc * and the actual yaw rate YRt using the look-up table. Then, the DSECU controls the steering motor 62 by using the steering ECU 60 so that the actual steering torque Tra matches the target steering torque Tr *. Steering control by steering follow-up control is also executed by the above. As can be understood from the above, if the target runway information can be acquired, the DSPE can execute the steering follow-up control when the travel locus L1 is set to the target travel line Ld without calculating the target travel line Ld itself. it can.

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

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

Then, the DESCU calculates the target steering angle θ * by replacing dv with dL, replacing θv with θL, and replacing Cv with CL in the equation (5) (or equation (6)). , The steering motor 62 is controlled so that the actual steering angle θ matches the target steering angle θ *. As described above, the steering control by the division lane maintenance control is executed.

When the target traveling line Ld cannot be set based on at least one of the left white line and the right white line and the preceding vehicle locus cannot be generated (including the case where the steering follow-up target vehicle cannot be determined), the DSECU has a lane. 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 lane keeping control.

Next, with reference to FIG. 5, the “method for relaxing the limitation on the change of the locus shape parameter” executed by the DSECU of the first implementation device will be described.

As shown in FIG. 5A, the own vehicle SV is traveling in the straight section R1 at time t1. The DSECU generates the traveling locus L1 of the steering tracking target vehicle TV traveling in front of the own vehicle SV, and executes the steering tracking control. At time t1, the steering follow-up target vehicle TV is traveling at the curve section entrance P1 in which the curvature change rate Cv'is D1. The inter-vehicle time T of the own vehicle SV with the steering follow-up target vehicle TV is calculated by "inter-vehicle distance ÷ vehicle speed of the own vehicle SV".

In this case, as shown in FIG. 5B, the locus shape parameter of the traveling locus L1 when the own vehicle SV travels at the curve section entrance P1 at the time “t1 + inter-vehicle time T” after the time t1. Ideally, (curvature change rate Cv') is D1.

Therefore, in order to acquire the ideal locus shape parameter (curvature change rate Cv'= D1) at the time when the own vehicle SV travels at the curve section entrance P1, the DSECU takes time from the time t1 to the inter-vehicle time T. , It is necessary to increase the trajectory parameter (curvature change rate Cv') of the traveling locus L1 from the curvature change rate Cv'(= 0) at time t = t1 to the curvature change rate Cv'(= D1).

In this case, the "ideal locus shape parameter change amount (ideal parameter change amount) per predetermined time (calculation cycle)" is "(D1 / T) x Tcy (predetermined time (calculation cycle))". This ideal parameter change amount increases as the inter-vehicle time T becomes shorter.

On the other hand, the DSPE should relax the restriction on the change of the locus shape parameter by determining whether or not the "parameter change restriction relaxation condition" composed of the following conditions 1 and 2 is satisfied. Determine if it is in.

(Parameter change restriction relaxation conditions)
Condition 1: The following curve determination parameter ε is equal to or greater than the predetermined threshold value εth.
As the curve determination parameter ε, the DESCU has a value ε of the ratio of the locus shape parameter (curvature change rate Cv'(t-1)) acquired in the previous time before a predetermined time from the present time to the maximum curvature change rate Dmax of the traveling lane. (= Cv'(t-1) / maximum curvature change rate Dmax) is acquired.
The larger the curve determination parameter ε, the larger the curvature change rate Cv', so it is highly possible that the curvature change rate Cv'has changed significantly. That is, it can be determined that there is a high possibility that the own vehicle SV is in a situation of entering the curved section R2 from the straight section R1 of the traveling lane.
Condition 2: The inter-vehicle time T of the own vehicle SV with the steering follow-up target vehicle is equal to or less than the threshold time Tth.

The maximum curvature change rate Dmax of the traveling lane under condition 1 is acquired as follows. The DESCU acquires the vehicle speed of the own vehicle SV. The DESCU estimates the design vehicle speed of the road based on the vehicle speed of the own vehicle SV. A lookup table (also called a "map") that defines the relationship between the design vehicle speed determined based on the Road Structure Ordinance and the clothoid parameter A (maximum allowable clothoid parameter) MaP (v) estimates the design vehicle speed of the road. Is applied to obtain the clothoid parameter A. Then, the DSPE calculates the reciprocal of the clothoid parameter A, and sets the reciprocal of the calculated clothoid parameter A as the maximum curvature change rate Dmax.

If condition 1 is satisfied, it is highly possible that the own vehicle SV is traveling near the curve section entrance P1. When condition 2 is satisfied, the "ideal parameter change amount" required for acquiring the ideal trajectory shape parameter may increase when the own vehicle SV is traveling near the curve section entrance P1. high. That is, when the conditions 1 and 2 are satisfied, it is highly possible that the own vehicle SV is traveling near the curve section entrance P1 and the "ideal parameter change amount" is large.

Therefore, in this case, when the DESCU generates the traveling locus by using the equation (4) in the curve fitting, the weight gi is changed according to the detection area of the position coordinate data, so that the locus shape parameter is changed. Relax the restrictions. That is, the locus shape parameter acquired at the time of this calculation is made to change significantly as compared with the previous locus shape parameter.

Specifically, when both the condition 1 that the inter-vehicle time T is equal to or less than the threshold time Tth and the condition 2 that the curve determination parameter ε is equal to or more than the predetermined threshold εth are satisfied, the DSPE is at present. By making 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, the restriction on the change of the locus shape parameter is relaxed.

For example, as shown in FIG. 6, the term "g1" in which the converted position coordinates (xi, yi) = (x1, y1) to (x4, y4) acquired behind the current position of the own vehicle SV are substituted. (Y1-f (x1)) ² ”to item“ g4 (y4-f (x4)) ² ”each weight g1 to g4 is set to a second value (eg, 1) smaller than the first value (eg, 1). , 0). The first value is a value set in the normal time (when at least one of the condition 1 and the condition 2 is not satisfied), and the second value is from the first value in the normal time. It is a small value.

The term "g5 (y5-f (x5)) ² " to which the converted position coordinates (xi, yi) = (x5, y5) to (x6, y6) acquired in front of the current position of the own vehicle SV are substituted. The respective weights g5 to g6 of the item “g6 (y6-f (x6)) ² ” are set to the first value (for example, gi = 1).

The traveling locus generated in this way is the traveling locus L1. The traveling locus L1p is the traveling locus generated by setting the weights g1 to g6 to the first value (1) without changing the weights g1 to g6.

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 is relatively small. There is. Further, the traveling locus L1 is generated so that the converted position coordinates (x1, y1) and (x2, y2) acquired in the curve section R2 have a relatively large influence on the shape of the traveling locus. .. As a result, the curvature change rate Cv'of the traveling locus L1 at the curve section entrance P1 becomes larger than the traveling locus L1p, and the restriction on the change of the locus shape parameter is relaxed.

By relaxing the restriction on the change of the locus shape parameter, the DSECU may be able to acquire the ideal locus shape parameter (curvature change rate Cv') at the time when the own vehicle SV travels at the curve section entrance P1. Will be higher. As a result, it is possible to reduce the possibility that the steering response is delayed when the own vehicle SV travels on P1 near the curve section entrance P1.

<Specific operation>
Next, the specific operation of the CPU of the DSECU (sometimes referred to simply as "CPU") will be described. The CPU executes the steering follow-up control routine shown by the flowchart of FIG. 7 every time a predetermined time elapses. 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 executed.

Therefore, when the inter-vehicle distance control is executed, when the predetermined timing is reached, the CPU starts the process from step 700 in FIG. 7 and proceeds to step 705, and whether or not the execution condition of the steering follow-up control is satisfied. Is determined.

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 to execute the lane keeping control by operating the operation switch 18.
Condition A2: The vehicle speed SPD of the own 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 traveling line Ld based on "at least one of the left white line and the right white line" recognized by the camera sensor 17b cannot be set.

If the execution condition of the steering follow-up control is not satisfied, the CPU determines "No" in step 705, proceeds to step 710, and cancels (stops) the steering follow-up control. After that, the CPU proceeds to step 795 and temporarily ends this routine.

On the other hand, when the execution condition of the steering follow-up control is satisfied, the CPU determines "Yes" in step 705 and proceeds to step 715, and after performing steps 715 to 730 described below in order, Proceed to step 735.

Step 715: The CPU uses the surrounding sensor 17 to detect the vehicle in front. Specifically, the CPU acquires the target information of all the target (n) acquired by the surrounding sensor 17. Based on the acquired target information, the CPU recognizes the target (n) existing in a predetermined area in front of the own vehicle SV as the front vehicle.
Step 720: The CPU identifies the steering follow-up target vehicle TV for which the travel locus L1 is to be generated. Specifically, the CPU acquires the vehicle speed of the own vehicle SV from the vehicle speed sensor 16 and acquires the yaw rate of the own vehicle SV from the yaw rate sensor 19. The CPU predicts the traveling course of the own vehicle SV from the acquired vehicle speed and yaw rate. Next, the vehicle in front closest to the predicted "traveling course of the own vehicle SV" is selected as the "steering follow-up target vehicle TV for which the traveling locus L1 is generated".

Step 725: The CPU acquires the previous curvature change rate Cv'(t-1) of the position corresponding to the current position of the own vehicle SV on the traveling locus L1 generated when this routine was executed last time. .. The CPU acquires the "maximum curvature change rate Dmax of the traveling lane (road)" by applying the design vehicle speed estimated based on the vehicle speed of the own vehicle SV to the above-mentioned map. The CPU calculates the 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 the inter-vehicle time T of the own vehicle SV with the steering follow-up target vehicle TV.

When the CPU proceeds to step 735, it determines whether or not both the condition 1 that the inter-vehicle time T is equal to or less than the threshold time Tth and the condition 2 that the curve determination parameter ε is equal to or greater than the predetermined threshold εth are satisfied. To do.

If at least one of the condition 1 and the condition 2 is not satisfied, the CPU determines "No" in step 735, proceeds to step 740, and based on the position information of the steering tracking target vehicle specified in step 720, the CPU determines "No". The traveling locus L1 is generated. At this time, the CPU does not relax the limitation of the change of the locus shape parameter. After that, the CPU proceeds to step 745.

When both condition 1 and condition 2 are satisfied, the CPU determines "Yes" in step 735, proceeds to step 750, and based on the position information of the steering tracking target vehicle specified in step 720, the CPU determines "Yes". The traveling locus L1 is generated. At this time, the CPU relaxes the limitation of the change of the locus shape parameter. That is, as described above, the locus shape is formed by making the weighting of the position coordinate data behind the current position of the own vehicle SV smaller than the weighting of the position coordinate data ahead of the current position of the own vehicle SV. Relax the restrictions on parameter changes. After that, the CPU proceeds to step 745.

When the CPU proceeds to step 745, it determines whether or not the estimation accuracy of the generated travel locus L1 is low. Specifically, when the time series data of the target information of the previous steering follow-up target vehicle is not sufficient to generate the travel locus L1, the CPU estimates the accuracy of "the travel locus L1 of the previous steering follow-up target vehicle". Judge as low. If this is not the case, the CPU determines that the estimation accuracy of the "traveling locus L1 of the previous steering follow-up target vehicle" is not low.

If the estimation accuracy of the "traveling locus L1 of the previous steering follow-up target vehicle" is not low, the CPU determines "Yes" in step 745 and proceeds to step 755.

When the CPU proceeds to step 755, the generated travel locus L1 is set as the target travel line, and the steering angle of the own vehicle SV is controlled so as to travel the own vehicle SV along the target travel line. That is, the CPU executes steering tracking control using the traveling locus L1 of the steering tracking target vehicle. After that, the CPU proceeds to step 795 and temporarily ends this routine.

On the other hand, if the estimation accuracy of the "traveling locus L1 of the previous steering tracking target vehicle" is low, the CPU determines "No" in step 745, proceeds to step 710, and cancels (stops) steering tracking control. .. After that, the CPU proceeds to step 795 and temporarily ends this routine.

According to the first implementing apparatus described above, in a situation where the own vehicle SV enters the curved section R2 from the straight section R1 of the traveling lane, the trajectory shape representing the shape of the traveling locus L1 of the steering tracking target vehicle used for steering tracking control. The parameters can be acquired with high accuracy, and thus the reliability of the steering follow-up control can be improved.

<Second Embodiment>
Next, the vehicle driving support device (hereinafter, also referred to as "second embodiment") according to the second embodiment of the present invention will be described. The second implementation device differs from the first implementation device only in the following points.
The DSECU of the second implementation device calculates the target runway information by using the Kalman filter 10a provided in the DSECU with the position coordinate data (position coordinates after conversion) (xi, yi) as input values (observed values).
The DSECU of the second implementation device calculates the process noise (σΔcv') in the equation of state of the Kalman filter 10a by 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 the inter-vehicle time. Tcy is the calculation cycle.)
Hereinafter, this difference will be mainly described.

<Outline of operation>
As shown in FIG. 8, the Kalman filter 10a included in the DSPE has position coordinate data (xi, yi), "standard deviation σΔcv'of the amount of change in the curvature change rate Cv'per calculation cycle" as process noise, and The covariance matrix P calculated by the target track information and the well-known Kalman filter principle is calculated with the observed noise σyi as the input value and the output value as the output value.

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

As is well known, the Kalman filter 10a (extended Kalman filter) describes a non-linear dynamic system after considering the state equations and observation equations of the system under the influence of noise, and is currently based on these equations. It is an iterative estimation type filter that estimates the current state quantity from the observed value of the above and the estimated value of the past state quantity (for example, JP-A-2007-505377, JP-A-2014-10872, JP-A-2014). Refer to JP-A-102137, JP-A-2014-2103, JP-A-2017-012650, etc.)

The Kalman filter 10a includes an observation equation having position coordinate data (xi, yi) and observation noise σyi as observed values, and a state equation having target runway information (Cv'Cv, θ, d) and process noise as state quantities. Is used to perform a well-known Kalman filter process according to the well-known Kalman filter principle.

The DESCU has observed values such as current position coordinate data (xi, yi), observed noise σyi, process noise, and past output values (Cv'(t-1), Cv (t-1), θ (t-1)). , D (t-1)) is input to the Kalman filter 10a, and the current target track information (Cv', Cv, θ, dv) is acquired as an output value. At this time, the DSECU of the second implementing device calculates the "standard deviation σΔcv'of the amount of change in the curvature change rate Cv'per calculation cycle" as the process noise using the above-mentioned (calculation formula), and the Kalman filter. Enter in 10a.

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

Based on the idea that the probability of occurrence of the maximum curvature change rate Dmax increases as the curve judgment parameter ε (= Cv'(t-1) / maximum curvature change rate Dmax) increases, N is set according to the curve judgment parameter ε. 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), as the curve determination parameter ε increases, N decreases, and the “standard deviation σΔcv ′ of the amount of change in the curvature change rate Cv ′ per calculation cycle” increases. Further, as the inter-vehicle time T becomes smaller, the "standard deviation σΔcv'of the amount of change in the curvature change rate Cv'per calculation cycle" increases.

According to the principle of the Kalman filter, when the input process noise (“standard deviation σΔcv'of the amount of change in the curvature change rate Cv'per calculation period) becomes large, the observed value is easily reflected in the output value (estimated value). .. As a result, the restriction on the change of the locus shape parameter is relaxed. That is, the locus shape parameter acquired at the time of this calculation changes significantly as compared with the locus shape parameter acquired last time.

Therefore, when the own vehicle SV enters the curve section R2 from the straight section R1, the restriction on the change of the locus shape parameter is relaxed, so that the locus shape parameter can be acquired with high accuracy. As a result, the reliability of steering follow-up control can be improved.

<Specific operation>
Next, the specific operation of the CPU of the DSECU of the second implementation device will be described. The CPU executes the steering follow-up control routine shown by the flowchart of FIG. 9 every time a predetermined time elapses. In this example, the predetermined time is the 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), and substitutes "the amount of change in the curvature change rate Cv'per the calculation cycle (predetermined time)". Calculate the standard deviation σΔcv'”.
Step 910: The CPU acquires the target track information as an output value by inputting an input value to the Kalman filter 10a.
Step 915: The CPU determines whether or not the estimation accuracy of the travel locus (target track information) is low. When the value of the covariance matrix P output from the Kalman filter 10a is smaller than the predetermined value, it is determined that the estimation accuracy of the traveling locus is not low. When 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 implementing apparatus, in a situation where the own 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 follow target vehicle used for the steering follow control. It is possible to acquire track information with high accuracy. As a result, the reliability of steering follow-up control can be improved.

<Modification example>
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible.

For example, the first executing device and the second executing device execute the lane keeping control only during the execution of the following inter-vehicle distance control, but perform the lane keeping control even if the following inter-vehicle distance control is not executed. It may be configured to run.

For example, the first implementation device and the second implementation device may acquire position information, speed information, and the like of other vehicles including the steering follow-up target vehicle TV and the inter-vehicle distance target vehicle by inter-vehicle communication. Specifically, for example, the position information of the other vehicle acquired by the navigation device of the other vehicle is transmitted to the own vehicle SV together with the vehicle ID signal that identifies the other vehicle itself, and the own vehicle SV The position information of the steering follow-up target vehicle TV and / or the inter-vehicle distance target vehicle may be acquired based on the transmitted information.

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

10 ... Driving support ECU, 16 ... Vehicle speed sensor, 17 ... Surrounding sensor, 17a ... Radar sensor, 17b ... Camera sensor, 17c ... Target recognition unit, 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 tracking target vehicle

Claims (2)

A vehicle speed detector that detects the vehicle speed of the own vehicle,
The maximum curvature change rate estimation unit that estimates the maximum curvature change rate of the traveling lane in which the own vehicle travels, and the maximum curvature change rate estimation unit.
A position information acquisition unit that acquires position information of a vehicle in front traveling in the area in front of the own vehicle, and a position information acquisition unit.
A steering tracking target vehicle identification unit that identifies a steering tracking target vehicle from among one or more of the preceding vehicles,
A position information storage unit that stores the position information of the specified steering tracking target vehicle every time a predetermined time elapses,
Using the saved position information, a traveling locus generator that generates a traveling locus of the specified steering tracking target vehicle and acquires a locus shape parameter including a curvature change rate representing the shape of the generated traveling locus, and a traveling locus generator.
A travel control unit that executes steering follow-up control that changes the steering angle of the own vehicle so that the own vehicle travels along a target travel line set based on the travel locus.
With
The traveling locus generator
The value of the ratio of the curvature change rate and the maximum curvature change rate acquired before the predetermined time from the present time is calculated.
Using the vehicle speed of the own vehicle and the position information, the inter-vehicle time of the own vehicle with the steering follow-up target vehicle at the present time is calculated.
When both the first condition that the value of the ratio is equal to or more than the predetermined threshold value and the second condition that the inter-vehicle time is equal to or less than the threshold time are satisfied, the vehicle is behind the current position of the own vehicle. The degree to which the position information detected in the above is reflected in the traveling locus is smaller than the degree to which the position information detected in front of the own vehicle at the present time is reflected in the traveling locus. Generate a running trajectory,
Constructed as
Vehicle driving support device. A vehicle speed detector that detects the vehicle speed of the own vehicle,
The maximum curvature change rate estimation unit that estimates the maximum curvature change rate of the traveling lane in which the own vehicle travels,
A position information acquisition unit that acquires position information of a vehicle in front traveling in the area in front of the own vehicle, and a position information acquisition unit.
A steering tracking target vehicle identification unit that identifies a steering tracking target vehicle from among one or more of the preceding vehicles,
A travel locus generator that has a Kalman filter and calculates target track information including a trajectory shape parameter including a curvature change rate representing the shape of the travel trajectory of the specified steering tracking target vehicle every time a predetermined time elapses. The value of the ratio of the curvature change rate and the maximum curvature change rate acquired before the predetermined time from the present time is calculated, and the vehicle speed of the own vehicle and the position information are used to steer the own vehicle at the present time. Calculate the inter-vehicle time with the tracking target vehicle, substitute the maximum curvature change rate, the inter-vehicle time and the predetermined time into the following formula, and if the value of the ratio is smaller than the first threshold value, use the following formula. Substitute 3 for N, substitute 2 for N when the value of the ratio is equal to or greater than the first threshold, and assign 1 to N when the value of the ratio is greater than or equal to the second threshold. By substituting, the standard deviation of the amount of change in the curvature change rate per predetermined time is calculated.
Input values including the position information of the specified steering tracking target vehicle as observation values and the standard deviation as process noise are input to the Kalman filter, and the target track information is calculated according to the principle of the Kalman filter. With the traveling locus generator configured as
A travel control unit that executes steering follow-up control that changes the steering angle of the own vehicle based on the target track information.
Vehicle driving support device equipped with.
(a formula)
σΔcv'= {(Dmax / N) ÷ T} × Tcy
(ΣΔcv'is the 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 the inter-vehicle time. Tcy. Is the predetermined time.)

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