JP5413677B2 - Vehicle travel control device and vehicle travel control method - Google Patents

Description

  The present invention relates to a vehicle travel control device and a method thereof.

  2. Description of the Related Art Conventionally, vehicle travel control that controls the motion state of a vehicle in order to avoid the vehicle from contacting an obstacle according to the travel state of the vehicle and the operation state of the driver is known. For example, Patent Document 1 discloses a method of realizing a steering angle larger than a normal steering angle corresponding to a steering operation by controlling a steering gear ratio. When there is a possibility of contact with a front obstacle, the steering gear ratio is controlled according to the size index including the width of the obstacle, and a large steering angle can be obtained even with a small steering operation. Thereby, it becomes possible to assist the avoidance action with respect to an obstruction.

JP 2005-254835 A

  However, according to the technique disclosed in Patent Document 1, when the driver performs an avoidance operation after sufficiently approaching the obstacle, the driver's steering operation amount increases, and as a result, for assisting. Since the amount of control intervening in the vehicle is large, the stability of the vehicle may be impaired.

  This invention is made | formed in view of this situation, The objective is to suppress the situation where stability of a vehicle is impaired by the control intervention corresponding to a driver's avoidance operation.

  In order to solve such a problem, the present invention provides a vehicle based on a lap rate yaw moment that is a yaw moment that is applied to the vehicle so that the lap rate decreases when the risk potential exceeds the first risk threshold. Is given a yaw moment. Further, when the risk potential exceeds a second risk threshold value that is larger than the first risk threshold value, based on a steering angle yaw moment that is a yaw moment to be applied to the vehicle in accordance with a change in the steering angle caused by the driver's operation. Yaw moment is applied.

  According to the present invention, even when the driver does not perform the avoidance operation, the control based on the lap rate yaw moment works according to the risk potential of the vehicle, so that the control shifts to the control based on the steering angle yaw moment. However, it is possible to suppress a situation in which the amount of control to intervene is small and the stability of the vehicle is impaired.

Explanatory drawing which shows typically the vehicle C to which the vehicle travel control apparatus 10 concerning 1st Embodiment was applied. The block diagram which shows the structure of the vehicle travel control apparatus 10 typically The block diagram which shows the structure of the reference | standard yaw moment calculation part 22 Illustration of lap rate R Flowchart showing calculation procedure of reference yaw moment γb in vehicle travel control Explanatory drawing of 2nd judgment time Tttc2 Explanatory drawing showing correction terms α and β Explanatory drawing of accelerator opening gain Ga Illustration of vehicle speed gain Gv Explanatory drawing explaining the control form in the process in which the own vehicle C approaches the obstacle Ob Explanatory drawing explaining the control form in the process in which the own vehicle C approaches the obstacle Ob Explanatory drawing which shows transition with respect to time T regarding each parameter at the time of performing the lap rate yaw moment control when the driver does not perform the steering operation Explanatory drawing which shows transition with respect to time T regarding each parameter when not performing lap rate yaw moment control when a driver does not perform a steering wheel operation Explanatory drawing of the steering angle yaw moment γs when the lap rate yaw moment control is not performed and when the lap rate yaw moment control is performed Explanatory drawing explaining the effect by cooperative yaw moment γc Explanatory drawing of target yaw moment γf with accelerator opening gain Ga

(First embodiment)
FIG. 1 is an explanatory diagram schematically illustrating a vehicle C to which the vehicle travel control device 10 according to the first embodiment of the present invention is applied, and FIG. 2 schematically illustrates the configuration of the vehicle travel control device 10. FIG. The vehicle travel control device 10 is a travel control device that controls the motion state of the vehicle C in order to avoid an obstacle (for example, a preceding vehicle) Ob present in the vehicle traveling direction, and includes various sensors 11 to 14. The system, the controller 20 and the actuator 30 are mainly configured. In this specification, when identifying front, rear, left and right wheels, “fl”, “fr”, “rl”, and “rr” are added to the reference numerals or symbols. In this case, “fl” indicates the left front wheel, “fr” indicates the right front wheel, “rl” indicates the left rear wheel, and “rr” indicates the right rear wheel. In the present embodiment, the following description will be given as steered wheels that steer the left and right front wheels fl and fr according to the steering operation of the driver. However, the present invention is not limited to this, and for example, all wheels fl to rr can be steered. A so-called four-wheel steering vehicle may be used.

  The external sensor 11 detects the position (including direction and distance) of an object existing in front of the vehicle, and outputs position information Io. In the present embodiment, the external sensor 11 uses a laser radar, but instead of the laser radar, a millimeter wave radar, a camera, vehicle-to-vehicle communication, or the like may be used, or a combination of these methods may be used. . The laser radar as the external sensor 11 is attached to the front end portion of the vehicle C, irradiates the front of the vehicle with laser light, and receives the reflected light from an object existing ahead (for example, a reflector of a preceding vehicle) with a light receiving system. Receive light. The laser radar detects the position of the object with reference to the vehicle C by calculating the time difference between the laser emission time and the reflected light reception time and the laser scanning position.

  The steering angle sensor 12 detects the rotation angle of the steering wheel ST operated by the driver as the steering angle θs (steering angle detection means). This steering angle θs detects the steering angle together with the steering direction such as the left direction or the right direction with reference to the neutral state of the handle ST corresponding to the straight traveling. The wheel speed sensor 13 detects the speed (vehicle speed) V of the vehicle C by detecting the rotational speed of the rear wheel of the vehicle C. The accelerator opening sensor 14 detects the amount of depression of the accelerator pedal AP, that is, the accelerator opening θa.

The controller 20 has a function of controlling the entire system in an integrated manner, and performs various processes related to traveling control by operating according to the control program. As the controller 20, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. The controller 20 performs various calculations based on various information detected by the detection system, and outputs a control signal corresponding to the calculation result to the actuator 30 to control the motion state of the vehicle C (running) control).

  In the present embodiment, the actuator 30 is a brake actuator that controls the brake fluid pressure supplied to each of the wheel cylinders 15fl, 15fr, 15rl, and 15rr. When a brake pedal (not shown) is depressed by the driver, the depression force of the brake pedal by the driver is boosted by the electric booster power. The input boosted by the electric booster is converted into braking fluid pressure by the master cylinder. The actuator 30 supplies the brake fluid pressure to the wheel cylinders 15fl to 15rr provided corresponding to the individual wheels according to the brake fluid pressure boosted by the master cylinder. Each wheel is provided with a known hydraulic brake mechanism mainly composed of, for example, a brake pad, a caliper, and a disc rotor, and the brake mechanism according to the brake hydraulic pressure supplied to the wheel cylinders 15fl to 15rr. As a result of the operation, braking force is applied to the individual wheels.

  The actuator 30 can independently control the brake hydraulic pressure related to the wheel cylinders 15fl to 15rr corresponding to the individual wheels. Thereby, the braking force in each wheel is adjusted individually. The actuator 30 controls the brake hydraulic pressure supplied to the wheel cylinders 15fl to 15rr by operating according to the amount of depression of the brake pedal by the driver or according to a control command from the controller 20. That is, the controller 20 can apply a braking force to each wheel independently through the control of the actuator 30, thereby controlling the yawing motion of the vehicle C.

  Further, the controller 20 can alert the driver by controlling the notification device (notification means) 40 to perform predetermined notification. As the notification device 40, for example, a display device such as a liquid crystal display or an output device such as a speaker can be used.

  When the controller 20 grasps this functionally, the obstacle detection unit 21, the reference yaw moment calculation unit 22, the accelerator gain calculation unit 23, the vehicle speed gain calculation unit 24, the surrounding obstacle detection unit 25, and the yaw moment calculation unit 26 The application direction calculation unit 27 and the braking force control unit 28 are provided.

  Based on the position information Io read from the external sensor 11, the obstacle detection unit 21 sets an object (for example, a preceding vehicle) that exists on the course of the vehicle C and may come into contact with the vehicle C as an obstacle Ob. Detect (obstacle detection means). For example, when a preceding vehicle exists on the course of the vehicle C, the external sensor (laser radar) 11 outputs position information Io regarding a pair of reflectors provided in the preceding vehicle. The obstacle detection unit 21 estimates the vehicle width of the preceding vehicle and the representative position (for example, the center position in the vehicle width direction) from a map or a predetermined arithmetic expression based on the distance between the pair of reflectors. The obstacle detection unit 21 detects this as an obstacle Ob on the condition that, for example, a preceding vehicle exists on its own route. Information (obstacle information) Do regarding the detected obstacle Ob is output to the reference yaw moment calculator 22.

  The reference yaw moment calculator 22 calculates a reference value (hereinafter referred to as “reference yaw moment”) γb of the yaw moment applied to the vehicle C based on the obstacle information Do and the steering angle θs. The calculated reference yaw moment γb is output to the yaw moment calculator 26. Further, the reference yaw moment calculator 22 can output predetermined notification information (image information or audio information) from the notification device 40 by outputting the notification signal Sw to the notification device 40.

FIG. 3 is a block diagram illustrating a configuration of the reference yaw moment calculation unit 22. The reference yaw moment calculation unit 22 includes a risk potential calculation unit 22a, a comparison unit 22b, an avoidance limit calculation unit 22c, a lap rate calculation unit 22d, a lap rate yaw moment calculation unit 22e, a cooperative yaw moment calculation unit 22f, and a steering angle yaw moment calculation. It has a portion 22g.

  Here, the risk potential calculation unit 22a, the comparison unit 22b, and the avoidance limit calculation unit 22c serve as a risk potential detection unit that detects a risk potential RP that indicates the degree of approach of the vehicle C to the obstacle Ob. Yes.

The risk potential calculation unit 22a calculates the risk potential RP based on the obstacle information Do. This risk potential RP means that the greater the value, the greater the degree of approach to the obstacle Ob. In the present embodiment, the predicted contact time Tttc is used as an index representing the risk potential RP. The predicted contact time Tttc is a predicted arrival time of the vehicle C to the obstacle Ob, which is calculated based on the distance between the obstacle Ob and the vehicle C and the relative speed of the vehicle C with respect to the obstacle Ob. In relation to the predicted contact time Tttc, the risk potential RP corresponds to a subtraction value (absolute value) obtained by subtracting the predicted contact time Tttc from a first determination time Tttc1 described later. That is, the risk potential RP decreases as the contact prediction time Tttc increases, and the risk potential RP decreases as the contact prediction time Tttc decreases.
Becomes larger. The calculated predicted contact time Tttc is output to the comparison unit 22b.

The comparison unit 22b determines the current state of the risk potential RP by comparing the calculated predicted contact time Tttc with predetermined first to third determination times Tttc1 to Tttc3. And the comparison part 22b selects the control mode of the yaw moment given to the vehicle C according to this judgment result. In this embodiment, three control modes including a lap rate yaw moment control, a coordinated yaw moment control, and a steering angle yaw moment control are prepared, and the comparison unit 22b sets a control flag Flag according to the determined control mode. The control flag Flag is set to “1” when the lap rate yaw moment control is selected, is set to “2” when the cooperative yaw moment control is selected, and the steering angle yaw moment control is selected. In the case of “3”, “3” is set. Of the first to third determination times Tttc1 to Tttc3 compared with the predicted contact time Tttc, the second determination time Tttc2 is calculated by the avoidance limit calculation unit 22c.

  The lap rate calculating unit 22d calculates the lap rate R based on the obstacle information Do (lap rate calculating means). As shown in FIG. 4, the lap rate R is the ratio of the region y in the vehicle width direction occupied by the obstacle Ob in the region x corresponding to the vehicle width set in the traveling direction of the vehicle C (R = (y / x )). That is, the lap rate R decreases as the vehicle C moves in the lateral direction with respect to the obstacle Ob existing on the path of the vehicle C, and the obstacle Ob deviates from the path of the vehicle C. It becomes zero at the timing when the object Ob is avoided. The calculated lap rate R is output to the lap rate yaw moment calculator 22e. The lap rate R can be calculated based on the predicted path and obstacle information Do (the vehicle width and representative position of the preceding vehicle) by predicting the path of the host vehicle C based on the steering angle θs. is there.

The lap rate yaw moment calculator 22e calculates a lap rate yaw moment γr on the condition that the control flag Flag set in the comparator 22b is “1” (lap rate yaw moment calculator). This lap rate yaw moment γr is a yaw moment applied to the vehicle C so that the lap rate R decreases.

The cooperative yaw moment calculator 22f calculates the cooperative yaw moment γc on the condition that the control flag Flag set in the comparator 22b is “2” (cooperative yaw moment calculator). This cooperative yaw moment γc is a yaw moment that is applied to the vehicle C in cooperation with the aforementioned lap rate yaw moment γr and a steering angle yaw moment γs described later.

The steering angle yaw moment calculation unit 22g calculates the steering angle yaw moment γs on the condition that the control flag Flag set in the comparison unit 22b is “3” (steering angle yaw moment calculation means). This rudder angle yaw moment γs is a yaw moment applied to the vehicle C in accordance with a change in the steering angle θs.

  When the yaw moments γr, γc, and γs are calculated in any of these calculation units 22e to 22g, the calculated values are output to the yaw moment calculation unit 26 as the reference yaw moment γb.

  The accelerator gain calculation unit 23 calculates an accelerator gain Ga based on the accelerator opening θa. The calculated accelerator gain Ga is output to the yaw moment calculator 26.

  The vehicle speed gain calculation unit 24 calculates a vehicle speed gain Gv based on the vehicle speed V. The calculated vehicle speed gain Gv is output to the yaw moment calculator 26.

  The surrounding obstacle detection unit 25 detects the presence or absence of an object (hereinafter referred to as “ambient obstacle”) around the obstacle Ob based on the position information Io from the external sensor 11. If present, the position is detected (surrounding obstacle detection means). The detection result of the surrounding obstacle detection unit 25 is output to the application direction calculation unit 27.

  The yaw moment calculator 26 calculates a final yaw moment (hereinafter referred to as “target yaw moment”) γf to be applied to the vehicle C based on the reference yaw moment γb, the accelerator gain Ga, and the vehicle speed gain Gv. The calculated target yaw moment γf is output to the application direction calculation unit 27.

  The applying direction calculating unit 27 sets the sign of the target yaw moment γf, that is, the direction in which the target yaw moment γf is applied based on the information on the surrounding obstacles and the target yaw moment γf (applying direction calculating means). The target yaw moment γf to which the sign is set is output to the braking force control unit 28.

  The braking force control unit 28 determines the target braking fluid pressure of each wheel based on the target yaw moment γf to which the sign is set, and controls the actuator 30 based on the determined target braking fluid pressure. Thereby, the target yaw moment γf is applied to the vehicle C (yaw moment applying means).

  Hereinafter, the procedure of the vehicle travel control according to the present embodiment will be described. First, in the controller 20, the obstacle detection unit 21 detects the obstacle Ob based on the position information Io from the external sensor 11.

  FIG. 5 is a flowchart showing the calculation procedure of the reference yaw moment γb. In step 1 (S1), the risk potential calculation unit 22a detects the risk potential RP. Specifically, the risk potential calculation unit 22a calculates a predicted contact time Tttc as an index indicating the risk potential RP.

In step 2 (S2), the comparison unit 22b determines whether or not the predicted contact time Tttc is smaller than the first determination time Tttc1. Here, the first determination time Tttc1 is a contact prediction time at a position where the driver starts avoiding behavior in the normal driving with respect to the obstacle Ob ahead, and an optimal value is set in advance through experiments and simulations. Yes. That is, in this step 2, in the process in which the vehicle C approaches the obstacle Ob, the current risk potential RP is the first risk potential (first risk threshold value) at the position where the driver starts avoidance behavior in normal driving. It is determined whether or not Rf1 has been exceeded. By setting the first determination time Tttc1 from the viewpoint as described above, it is possible to reduce the user's uncomfortable feeling to the avoidance action by the subsequent control intervention.

If an affirmative determination is made in step 2, that is, if the predicted contact time Tttc is smaller than the first determination time Tttc1, the process proceeds to step 3 (S3). On the other hand, if a negative determination is made in step 2, that is, if the predicted contact time Tttc is equal to or longer than the first determination time Tttc1, the routine is exited.

In step 3, the comparison unit 22b determines whether or not the predicted contact time Tttc is greater than the third determination time Tttc3. Here, the third determination time Tttc3 is a time obtained by adding a predetermined cooperative time (fixed value) to a second determination time Tttc2 described later, and is set to a time shorter than the first determination time Tttc1. ing. Therefore, the third determination time Tttc1 is arbitrarily set to a time between the first determination time Tttc1 and the second determination time Tttc2. In other words, in this step 3, in the process in which the vehicle C approaches the obstacle Ob, the current risk potential RP is larger than the first risk potential Rf1 and smaller than the second risk potential Rf2 described later. It is determined whether or not the third risk potential (third risk threshold) Rf3 is exceeded.

If a negative determination is made in step 3, that is, if the predicted contact time Tttc is equal to or shorter than the third determination time Tttc3, the process proceeds to step 4 (S4). On the other hand, if an affirmative determination is made in step 3, that is, if the predicted contact time Tttc is greater than the third determination time Tttc3, the process proceeds to step 5 (S5). In this case, the comparison unit 22b sets the control flag Flag to “
Set to 1 ”.

In step 4, the comparison unit 22b determines whether or not the predicted contact time Tttc is greater than the second determination time Tttc2. Here, the second determination time Tttc2 is a predicted contact time at a final position where the obstacle Ob can be avoided by the maximum braking force and the maximum turning force of the vehicle C. The second determination time Tttc2 is determined according to the relative speed Va of the vehicle C with respect to the obstacle Ob. For example, as shown in FIG. 6, the second determination time Tttc2 increases proportionally from zero when the relative speed Va increases from zero, and thereafter reaches a certain value when the relative speed Va reaches a certain value. It becomes. The avoidance limit calculation unit 22c holds a map or an arithmetic expression that defines the relationship between the relative speed Va and the second determination time Tttc2 as shown in FIG. 6, and the second determination is made according to the relative speed Va. The time Tttc3 is determined. That is, in this step 4, in the process in which the vehicle C approaches the obstacle Ob, the final position where the current risk potential RP can avoid the obstacle Ob by the maximum braking force and the maximum turning force that the vehicle C has. It is determined whether or not the second risk potential (second risk threshold) Rf2 is exceeded. Note that a map or an arithmetic expression that defines the relationship between the relative speed Va held by the avoidance limit calculation unit 22c and the second determination time Tttc2 is set in advance through experiments, simulations, or the like.

If an affirmative determination is made in step 4, that is, if the predicted contact time Tttc is greater than the second determination time Tttc3, the process proceeds to step 6 (S6). In this case, the comparison unit 22b sets the control flag Flag to “2”. On the other hand, if a negative determination is made in step 4, that is, if the predicted contact time Tttc is equal to or shorter than the second determination time Tttc3, the process proceeds to step 7 (S7). In this case, the comparison unit 22b sets the control flag Flag to “3”.

In step 5, the lap rate yaw moment calculator 22e calculates a lap rate yaw moment γr based on the following equation.

Here, Tttc_rf1 is the aforementioned first determination time Tttc1, and a subtraction value (absolute value) obtained by subtracting the contact predicted time Tttc from Tttc_rf1 is a value corresponding to the risk potential RP.
R is the current lap rate calculated by the lap rate calculating unit 22d. Gr is a ramp rate gain, and is a gain for converting the aforementioned subtracted value (absolute value), that is, an integrated value of the risk potential RP and the lap rate R into a yaw moment. As can be seen from the equation, the lap rate yaw moment γr is a value calculated based on the lap rate R and the risk potential RP. The lap rate yaw moment γr has a tendency to increase as the lap rate R increases or the risk potential RP increases.

  Note that the lap rate yaw moment calculation unit 22e has an increase and decrease limiter function. Specifically, the lap rate yaw moment calculation unit 22e changes the lap rate yaw moment γr over time, specifically, the lap rate yaw moment γr calculated in the current processing cycle and the previous processing cycle. A difference (absolute value) from the calculated lap rate yaw moment γr is calculated. When the difference is greater than or equal to the determination value, the lap rate yaw moment calculation unit 22e determines the current lap rate yaw moment γr so that the change width from the previous lap rate yaw moment γr falls within the range of the determination value. Correct. For example, the calculated current lap rate yaw moment γr is corrected as an addition value of the previous lap rate yaw moment γr and the determination value. Thereby, it is possible to suppress a sudden yaw moment change from occurring in the vehicle C.

In step 6, the cooperative yaw moment calculator 22f calculates the cooperative yaw moment γc based on the following equation.

  In the equation, γr is the aforementioned lap rate yaw moment, and the cooperative yaw moment calculator 22f can calculate this using a method similar to the calculation method by the lap rate yaw moment calculator 22e. Further, γs is a steering angle yaw moment that will be described later, and the cooperative yaw moment calculation unit 22f can calculate this using a method similar to the calculation method by the steering angle yaw moment calculation unit 22g described later.

  FIG. 7 is an explanatory diagram showing the correction terms α and β. In the equation, α and β are correction terms, and the correction term α is a correction term that contributes to the lap ratio yaw moment γr. The correction term α is a value determined according to the current risk potential RP, and has a tendency as shown in FIG. Specifically, the correction term α is zero when the risk potential RP is smaller than the first risk potential Rf1, and is one when the risk potential RP is equal to or higher than the second risk potential Rf2. Further, the correction term α linearly increases from zero to 1 in accordance with the increase in the risk potential RP when the risk potential RP is between the first risk potential Rf1 and the second risk potential Rf2.

On the other hand, the correction term β is a correction term that contributes to the steering angle yaw moment γs. The correction term β is a value determined according to the current risk potential RP, and has a tendency as shown in FIG. Specifically, the correction term β is 1 when the risk potential RP is equal to or lower than the third risk potential Rf3, and is 0 when the risk potential RP is equal to or higher than the second risk potential Rf2. Further, the correction term β linearly decreases from 1 to zero as the risk potential RP increases when the risk potential RP is between the third risk potential Rf3 and the second risk potential Rf2.

  The cooperative yaw moment γc is a yaw moment obtained by coordinating the lap rate yaw moment γr and the steering angle yaw moment γs according to the risk potential RP. This cooperation has such a relationship that as the risk potential RP increases, the ratio of the lap rate yaw moment γr decreases and the ratio of the steering angle yaw moment γs increases.

In step 7, the rudder angle yaw moment calculator 22g calculates the rudder angle yaw moment γs based on the following equation.

  Here, dθs is a steering angular velocity obtained by time differentiation of the steering angle θs read from the steering angle sensor 12, and d (dθs) is a steering angular acceleration obtained by time differentiation of the steering angular velocity dθs. is there. τ1 is a first yaw moment gain, which is a gain with respect to the steering angular velocity dθs of the feedforward control according to the risk potential RP. τ2 is a second yaw moment gain, which is a gain with respect to the steering angular acceleration d (dθs). As can be seen from the equation, the steering angle yaw moment γs is calculated based on the steering angular velocity dθs and the steering angular acceleration d (dθs).

  In this way, when any one of the lap rate yaw moment γr, the cooperative yaw moment γc, and the steering angle yaw moment γs is calculated according to the risk potential RP, the calculated value is used as the reference yaw moment γb. 26.

  On the other hand, the accelerator gain calculation unit 23 sets the accelerator opening gain Ga based on the accelerator opening θa read from the accelerator opening sensor 14. The accelerator opening gain Ga is a value set according to the accelerator opening θa, and is set so that the value decreases as the accelerator opening θa increases. In the present embodiment, as shown in FIG. 8, the accelerator opening gain Ga is set to a maximum value when the accelerator opening θa is from zero to a predetermined value, and then becomes zero as the accelerator opening θa increases. And thereafter tends to be zero regardless of the accelerator opening θa. The accelerator gain calculation unit 23 holds a map or an arithmetic expression that defines the relationship between the accelerator opening gain Ga and the accelerator opening θa, and calculates the accelerator opening gain Ga according to the accelerator opening θa.

  Further, the vehicle speed gain calculation unit 24 sets the vehicle speed gain Gv based on the vehicle speed V read from the wheel speed sensor 13. The vehicle speed gain Gv is a value set according to the vehicle speed V, and is set such that the value decreases as the vehicle speed V increases. In the present embodiment, as shown in FIG. 9, the vehicle speed gain Gv is set to a maximum value when the vehicle speed V is zero to a predetermined value, and then decreases to 1 as the vehicle speed V increases, and thereafter The vehicle tends to be 1 regardless of the vehicle speed V. The vehicle speed gain calculation unit 24 holds a predetermined map or calculation formula that defines the relationship between the vehicle speed gain Gv and the vehicle speed V, and calculates the vehicle speed gain Gv according to the vehicle speed V.

The yaw moment calculator 26 calculates a target yaw moment γf from the following equation based on the reference yaw moment γb, the accelerator opening gain Ga, and the vehicle speed gain Gv.

  As can be seen from the equation, the target yaw moment γf is calculated as a value obtained by multiplying the reference yaw moment γb by the accelerator opening gain Ga and the vehicle speed gain Gv.

  The applying direction calculating unit 27 sets a direction in which the target yaw moment γf is applied based on the information on the surrounding obstacles from the surrounding obstacle detecting unit 25 and the target yaw moment γf. In the present embodiment, the applying direction calculating unit 27 gives a plus sign when giving a counterclockwise yaw moment, and gives a minus sign when giving a clockwise yaw moment. The application direction calculation unit 27 determines to apply a clockwise yaw moment when the center point of the host vehicle C is shifted to the right with respect to the center point of the front obstacle Ob in the vehicle width direction. Therefore, a minus sign is assigned to the target yaw moment γf. On the other hand, when the center point of the host vehicle C is shifted to the left with respect to the center point of the front obstacle Ob in the vehicle width direction, the application direction calculating unit 27 determines to apply a counterclockwise yaw moment. . Therefore, a plus sign is assigned to the target yaw moment γf. Further, when the application direction calculation unit 27 determines to apply the yaw moment in a certain direction, the application direction calculation unit 27 provides the application in the case where there are surrounding obstacles in the application direction and no surrounding obstacles exist in the opposite direction. Reverse direction.

The braking force control unit 28 determines the target braking hydraulic pressures Psfl, Psfr, Psrl, Psrr of each wheel based on the target yaw moment γf to which the sign is set. First, the braking force control unit 28 sets the target braking fluid pressures Psfl, Psfr, Psrl, Psrr of each wheel to the braking fluid pressures Pmf, Pmr as shown in the following equation.

Here, Pmf is the brake fluid pressure for the front wheels. On the other hand, Pmr is the braking fluid pressure for the rear wheels, and is calculated based on the braking fluid pressure Pmf for the front wheels in consideration of the braking force distribution of the front and rear wheels. For example, if the driver is operating the brake, the brake fluid pressures Pmf and Pmr for the front and rear wheels are calculated as the brake operation amount (
The value corresponds to the master cylinder hydraulic pressure.

When the target yaw moment γf is output at the timing when the current risk potential RP exceeds the first risk potential Rf1, the braking force control unit 28 determines the front wheel target braking hydraulic pressure difference ΔPsf based on the target yaw moment γf. Then, the rear wheel target braking hydraulic pressure difference ΔPsr is calculated. Specifically, the target braking hydraulic pressure differences ΔPsf and ΔPsr between the front wheels and the rear wheels are calculated based on the following formulas 6 and 7.

  Here, Expression 6 is an arithmetic expression of the target braking hydraulic pressure differences ΔPsf and ΔPsr when the absolute value of the target yaw moment γf is smaller than the setting threshold γ1. On the other hand, Expression 7 is an arithmetic expression of the target braking hydraulic pressure differences ΔPsf and ΔPsr when the absolute value of the target yaw moment γf is equal to or larger than the setting threshold γ1. In each numerical formula, T is a tread of the vehicle C, and in the present embodiment, the same value is used for the front and rear wheels for convenience. Kbf and Kbr are conversion coefficients for the front wheels and the rear wheels when the braking force is converted into the braking hydraulic pressure, and are set in advance according to the brake specifications.

As shown in each equation, the braking force control unit 28 distributes the braking force generated by the wheels according to the magnitude of the target yaw moment γf. Specifically, when the target yaw moment γf is smaller than the setting threshold value γ1, the braking force control unit 28 sets the front wheel target brake hydraulic pressure difference ΔPsf to zero and sets only the rear wheel target brake hydraulic pressure difference ΔPsr as the target yaw moment. Calculation is performed according to γf. Thus, the yaw moment is generated according to the difference in braking force between the left and right rear wheels. Further, as shown in Formula 6, when the target yaw moment γf is initially applied, the yaw moment control intervenes by setting the target brake hydraulic pressure difference ΔPsf, ΔPsr to be the rear wheel eccentricity compared to the front wheel. It is possible to reduce the user's uncomfortable feeling. On the other hand, when the target yaw moment γf is equal to or larger than the setting threshold γ1, the braking force control unit 28 calculates the front wheel target braking hydraulic pressure difference ΔPsf according to the target yaw moment γf, and sets the rear wheel target braking hydraulic pressure difference ΔPsr to a predetermined value. Calculate as a value. Thereby, the yaw moment is generated according to the braking force difference between the left and right front and rear wheels.

Then, the braking force control unit 28 calculates the final target braking hydraulic pressures Psfl to Psrr of each wheel based on the calculated target braking hydraulic pressure differences ΔPsf and ΔPsr as shown in the following equation.

Here, Expression 8 is an arithmetic expression in the case where the sign given by the giving direction calculation unit 27 is positive, that is, in the case where the counterclockwise yaw moment is given. On the other hand, Expression 9 is an arithmetic expression in the case where the sign provided by the application direction calculation unit 27 is negative, that is, when a clockwise yaw moment is applied. As can be seen from each equation, the braking force control unit 28 calculates the target braking fluid pressures Psfl to Psrr of each wheel in consideration of the brake operation by the driver, that is, the braking fluid pressures Pmf and Pmr.

  The braking force control unit 28 outputs the calculated target braking hydraulic pressures Psfl to Psrr of each wheel to the actuator 30 as command values. Then, the brake fluid pressure supplied to each of the wheel cylinders 15fl to 15rr is adjusted so that the actuator 30 achieves the target brake fluid pressures Psfl to Psrr of each wheel. Thereby, the braking force of each wheel is controlled independently, and the yawing motion is controlled according to the target yaw moment γf.

  In addition, the reference yaw moment calculation unit 22 outputs the notification signal Sw to the notification device 40 from when the risk potential RP exceeds the first risk potential Rf1 until the lap rate R becomes zero, whereby the notification device 40, predetermined notification information (image information or audio information) is output.

  FIG. 10 is an explanatory diagram illustrating a control mode in the process in which the host vehicle C approaches the obstacle Ob. This figure shows a state in which the driver performs a steering operation on the obstacle Ob from a certain timing when the risk potential RP is smaller than the third risk potential Rf3. As shown in the figure, when the host vehicle C approaches the obstacle Ob ahead, the risk potential RP exceeds the first risk potential Rf1 and is smaller than the third risk potential Rf3, that is, When the vehicle C (C11) is present in the area indicated by A1, the target yaw moment γf corresponding to the lap rate yaw moment γr is applied to the vehicle C11. Next, when the risk potential RP exceeds the third risk potential Rf3 and is smaller than the second risk potential Rf2, that is, when the vehicle C (C12) exists in the area indicated by A2, the cooperative yaw moment A target yaw moment γf corresponding to γc is applied to the vehicle C12. When the risk potential RP exceeds the second risk potential Rf2, that is, when the vehicle C (C13) exists in the area indicated by A3, the target yaw moment γf corresponding to the steering angle yaw moment γs is To C13.

  FIG. 11 is an explanatory diagram illustrating a control mode in the process in which the host vehicle C approaches the obstacle Ob. This figure shows a state in which the driver performs a steering operation from a certain timing when the risk potential RP exceeds the second risk potential Rf2. As shown in the figure, when the host vehicle C approaches the obstacle Ob ahead, the risk potential RP exceeds the first risk potential Rf1 and is smaller than the second risk potential Rf2, that is, A1. When the vehicle C (C21, C22) is present in the area shown in FIG. 2, a target yaw moment γf corresponding to the lap rate yaw moment γr is applied to the vehicles C21, C22. When the risk potential RP exceeds the second risk potential Rf2, that is, when the vehicle C (C23) exists in the region indicated by A3, the target yaw moment γf corresponding to the steering angle yaw moment γs is To C23.

  In the case shown in FIG. 11, the target yaw moment γf corresponding to the cooperative yaw moment γc is given to the vehicle C22 when the risk potential RP exceeds the third risk potential Rf3, as shown in parentheses in the figure. However, since the steering wheel operation is not performed by the driver, the target yaw moment γf corresponding to the lap rate yaw moment r is substantially applied to the vehicle C22. Note that in a scene where the steering operation is not performed even if the third risk potential Rf3 is exceeded, that is, a scene where the steering angle yaw moment γs remains zero, the correction term α for the lap rate yaw moment γr is always treated as zero. Is preferred.

Thus, in the present embodiment, when the risk potential RP of the vehicle C exceeds the first risk potential Rf1, the target yaw moment γf is given to the vehicle C based on the lap rate yaw moment γr (lap rate yaw moment). control). Further, when the risk potential RP of the vehicle C exceeds the second risk potential Rf2, the target yaw moment γf is given to the vehicle C based on the steering angle yaw moment γs (steering angle yaw moment control).

  FIG. 12 shows a change with respect to time T regarding the yaw moment γ, the yaw angle θy, the lateral movement amount Dy, and the lap rate R of the vehicle C when the lap rate yaw moment control is executed when the driver does not operate the steering wheel. Yes. FIG. 13 shows a transition with respect to time T related to the yaw moment γ, yaw angle θy, lateral movement amount Dy, and lap rate R of the vehicle C when the lap rate yaw moment control is not executed when the driver does not operate the steering wheel. Yes.

  According to the present embodiment, even when the driver does not notice the obstacle Ob in front and does not perform the avoidance operation, the risk potential RP of the vehicle C exceeds the first risk potential Rf1, so that the obstacle Ob Since the control (lap rate yaw moment control) for avoiding the operation works, the avoidance action for the obstacle Ob can be assisted. As can be seen from FIG. 13, when the lap rate yaw moment control is not performed, the lap rate R does not change. On the other hand, as can be seen from FIG. 12, when the lap rate yaw moment control is performed, the yaw angle θy is changed by the yaw moment γ being applied to the vehicle C. Thereby, since the lateral movement amount Dy is generated in the vehicle C, the lap rate R is reduced, and the avoidance action for the obstacle Ob can be autonomously performed.

  FIG. 14 is an explanatory diagram of the steering angle yaw moment γs when the lap rate yaw moment control is not performed (see (a)) and when the lap rate yaw moment control is performed (see (b)). As a premise that the steering angle yaw moment control is executed, as shown in FIG. 14, the steering angle yaw moment γs is compared with the case where the lap rate yaw moment control is not performed. And become a small value. Therefore, even when the driver performs a steering operation while the vehicle C is sufficiently close to the obstacle Ob, the amount of assist by the control is small (because the obstacle can be avoided even if the assist amount is small). The situation where the stability of the vehicle C is impaired can be suppressed.

  In the present embodiment, when the risk potential RP of the vehicle C exceeds the third risk potential Rf3, the target yaw moment γf is given to the vehicle C based on the cooperative yaw moment γc (cooperative yaw moment control).

  FIG. 15 is an explanatory diagram for explaining the effect of the cooperative yaw moment γc. When the coordinated yaw moment control is not performed, the lap rate yaw moment control is switched to the steering angle yaw moment control. Because the yaw moment is applied according to different parameters, the vehicle behavior changes such as the amount of yaw moment applied changing excessively or the assist amount in a decreasing trend increasing again at the control switching timing. However, the driver may feel uncomfortable. In this regard, according to the present embodiment, the lap rate yaw moment control is shifted to the rudder angle yaw moment control via the coordinated yaw moment control. Therefore, it is possible to smoothly shift to the steering angle yaw moment control without applying an excessive yaw moment. Thereby, the change of the vehicle behavior at the time of control switching can be suppressed, and a user's discomfort can be reduced.

  In the present embodiment, the lap rate yaw moment γr is calculated based on the risk potential RP and the lap rate R. As a result, the yaw moment necessary for avoiding the obstacle Ob can be calculated before contact with the obstacle Ob, and therefore the obstacle Ob can be avoided by following the lap ratio yaw moment γr.

  In the present embodiment, the target yaw moment γf applied to the vehicle C is corrected by the accelerator gain Ga according to the accelerator opening θa. Specifically, the accelerator gain Ga has a function of decreasing the target yaw moment γf as the accelerator opening θa increases, as shown in FIG. Thereby, since a driver | operator's willingness to accelerate can be reflected, a user's discomfort can be suppressed.

  In the present embodiment, the target yaw moment γf applied to the vehicle C according to the vehicle speed V is corrected by the vehicle speed gain Gv. Specifically, the vehicle speed gain Gv has a function of increasing the target yaw moment γf as the vehicle speed V decreases. When the vehicle speed V of the vehicle C is low, there is a possibility that the distance between the vehicle C and the obstacle Ob is close at the timing when the target yaw moment γf is applied. Therefore, by setting the vehicle speed gain Gv as described above, it is possible to obtain an effect that the obstacle Ob can be easily avoided.

  In the present embodiment, the application direction calculation unit 27 calculates the direction in which the target yaw moment γf is applied based on the detection results of the obstacle detection unit 21 and the surrounding obstacle detection unit 25. Accordingly, it is possible to select a direction in which the obstacle Ob is effectively avoided, and it is possible to determine the avoidance direction in consideration of surrounding obstacles. Thereby, although the obstacle Ob is avoided, the situation where it avoids in the direction where the surrounding obstacle exists can be suppressed.

  In the present embodiment, the second risk potential Rf2 is calculated as a risk potential at a final position where the obstacle Ob can be avoided by the maximum braking force and the maximum turning force of the vehicle C. Thereby, even when the driver's avoidance operation is delayed, the situation in which the obstacle Ob cannot be avoided can be effectively suppressed.

  In the present embodiment, the third risk potential Rf3 is calculated based on the calculated second risk potential Rf2 and the first risk potential Rf1. As a result, the third risk potential Rf3 can be set at an appropriate position, and the shift to the coordinated yaw moment control can be appropriately made.

  Moreover, according to this embodiment, the alerting | reporting by the alerting | reporting apparatus 40 can urge the driver to call attention to the obstacle Ob existing in the traveling direction. Thereby, the user can be prompted to avoid the obstacle Ob.

  In the above-described embodiment, the comparison unit 22b uses a fixed value that is set in advance for the first risk potential Rf1, but the fixed value depends on the driving tendency of the driver. May be set. For example, the comparison unit 22b learns a driving tendency through a user's driving operation such as an accelerator operation or a steering operation. For example, the accelerator operation or the steering wheel operation is a gentle driving tendency or an agile driving tendency. When the driving tendency of the driver is acquired through such learning, the comparison unit 22b, for example, if the driver has a slow driving tendency, for example, the setting position of the first risk potential Rf1 is closer to the fixed value (obstacle). For example, it is set in a direction away from Ob. On the contrary, when the comparison unit 22b is an agile driver, for example, the setting position of the first risk potential Rf1 is set to the back side (direction approaching the obstacle Ob) from the fixed value. That's right.

  In addition, when the lap rate R is small, the comparison unit 22b may set the setting position of the first risk potential Rf1 to the back side (direction approaching the obstacle Ob) from the fixed value.

  According to such a configuration, since control intervention is performed at a timing according to the driving tendency of the driver, it is possible to realize control with less discomfort for the driver.

(Second Embodiment)
Hereinafter, the vehicle travel control apparatus 10 according to the second embodiment will be described. The vehicle travel control device 10 according to the second embodiment is different from that of the first embodiment in the calculation method of the cooperative yaw moment γc. In addition, about the structure and control operation | movement of the vehicle travel control apparatus 10 concerning this embodiment, it is fundamentally the same as that of 1st Embodiment, suppose that it quotes drawing and related description, and is different below. The explanation will be given mainly.

The cooperative yaw moment calculating unit 22f calculates the cooperative yaw moment γc on the condition that the control flag Flag set in the comparing unit 22b is set to “2”. Specifically, the cooperative yaw moment calculating unit 22f calculates the cooperative yaw moment γc based on the following equation.

  As can be seen from the equation, the cooperative yaw moment calculator 22f calculates the cooperative yaw moment γc based on the larger value of the steering angle yaw moment γs and the lap rate yaw moment γr.

  According to such a configuration, the yaw moment necessary for avoiding the obstacle Ob can be reflected in the cooperative yaw moment γc so as not to be insufficient. Thereby, the obstacle Ob can be avoided effectively.

  As mentioned above, although the vehicle travel control apparatus and method concerning the embodiment of the present invention were explained, the present invention is not limited to the above-mentioned embodiment, and various modifications are possible within the scope of the present invention. Needless to say. In each of the above-described embodiments, the yaw moment is applied to the vehicle C by controlling the braking force of each wheel, but the present invention is not limited to this. For example, when a steering device using a so-called steer-by-wire mechanism in which the steering wheel and the steering wheel are mechanically separated and the steering wheel is driven by an actuator or the like, the steering angle of the steering wheel is arbitrarily set The yaw moment may be applied to the vehicle C by controlling to the vehicle C, or the yaw moment may be applied to the vehicle C by controlling the driving force of each wheel on the condition that the relative distance to the obstacle Ob is large. Alternatively, the yaw moment may be applied to the vehicle C by other methods.

DESCRIPTION OF SYMBOLS 10 Vehicle traveling control apparatus 11 External sensor 12 Steering angle sensor 13 Wheel speed sensor 14 Accelerator opening sensor 20 Controller 21 Obstacle detection part 22 Reference yaw moment calculation part 22a Risk potential calculation part 22b Comparison part 22b
22c avoidance limit calculation unit 22d lap rate calculation unit 22e lap rate yaw moment calculation unit 22f cooperative yaw moment calculation unit 22g rudder angle yaw moment calculation unit 23 accelerator gain calculation unit 24 vehicle speed gain calculation unit 25 surrounding obstacle detection unit 26 yaw moment calculation Unit 27 application direction calculation unit 28 braking force control unit 28
30 Actuator 40 Notification device C Vehicle Ob Obstacle γb Reference yaw moment γr Lap rate yaw moment γc Coordinated yaw moment γs Rudder angle yaw moment RP Risk potential Rf1 First risk potential Rf2 Second risk potential Rf3 Third risk potential

Claims (12)

Obstacle detection means for detecting obstacles in the vehicle traveling direction;
Risk potential detection means for detecting a risk potential based on the degree of approach of the vehicle to the detected obstacle;
Steering angle detection means for detecting a steering angle that is an angle of a steering wheel that can be steered by a driver;
A lap rate calculating means for calculating, as a lap rate, a ratio occupied by the detected obstacle in a region corresponding to the vehicle width set in the traveling direction of the vehicle;
A lap rate yaw moment calculating means for calculating a lap rate yaw moment that is a yaw moment to be applied to the vehicle so that the calculated lap rate decreases;
Rudder angle yaw moment calculating means for calculating a rudder angle yaw moment that is a yaw moment to be applied to the vehicle in accordance with the detected change in the steering angle;
A yaw moment calculating means for calculating a target yaw moment to be applied to the vehicle based on the detected risk potential and the calculation results of the lap rate yaw moment calculating means and the rudder angle yaw moment calculating means;
Based on the calculated target yaw moment, yaw moment applying means for applying a yaw moment to the vehicle,
The yaw moment calculating means calculates the lap rate yaw moment as the target yaw moment when the risk potential exceeds a first risk threshold that is a predetermined risk potential, and the risk potential is Vehicle travel characterized in that the steering angle yaw moment is calculated as the target yaw moment when a second risk threshold that is a predetermined risk potential that is greater than the first risk threshold is exceeded. Control device. A coordinated yaw moment calculating means for calculating a coordinated yaw moment obtained by coordinating the rudder angle yaw moment and the lap rate yaw moment;
The yaw moment calculating means exceeds the third risk threshold, which is a predetermined risk potential that is greater than the first risk threshold and smaller than the second risk threshold, and If less than the second risk threshold, the cooperative yaw moment is calculated as the target yaw moment;
The cooperative yaw moment calculating means calculates the cooperative yaw moment so as to decrease the ratio of the lap rate yaw moment and increase the ratio of the rudder angle yaw moment according to an increase in the risk potential. The vehicle travel control device according to claim 1, wherein A coordinated yaw moment calculating means for calculating a coordinated yaw moment obtained by coordinating the rudder angle yaw moment and the lap rate yaw moment;
The yaw moment calculating means exceeds the third risk threshold that is larger than the first risk threshold and smaller than the second risk threshold, and is smaller than the second risk threshold. Calculates the cooperative yaw moment as the target yaw moment,
2. The vehicle travel control device according to claim 1, wherein the cooperative yaw moment calculating unit calculates the larger one of the lap rate yaw moment and the rudder angle yaw moment as the cooperative yaw moment. .   4. The lap rate yaw moment calculating means calculates the lap rate yaw moment based on the detected risk potential and the calculated lap rate. 5. The vehicle travel control device described.   The lap rate yaw moment calculating means is an increase / decrease limiter function that corrects the lap rate yaw moment within a range of the determination value when the width of the change in the lap rate yaw moment with time is equal to or greater than the determination value. The vehicle travel control device according to claim 4, comprising:   2. The yaw moment calculating means calculates the target yaw moment such that the yaw moment increases as the vehicle speed decreases, or the yaw moment decreases as the accelerator opening increases. To 5. The vehicle travel control device according to any one of 5 to 5. A surrounding obstacle detecting means for detecting an obstacle present around the obstacle detected by the obstacle detecting means as a surrounding obstacle;
The apparatus further comprises an application direction calculation unit that calculates a direction of applying the target yaw moment calculated by the yaw moment calculation unit based on detection results of the obstacle detection unit and the surrounding obstacle detection unit. The vehicle travel control apparatus according to any one of claims 1 to 6.   The risk potential detection means calculates, as the second risk threshold, a risk potential at a final position where the detected obstacle can be avoided by a maximum braking force and a maximum turning force of the vehicle. A vehicle travel control device according to any one of claims 1 to 7.   9. The vehicle travel according to claim 8, wherein the risk potential detecting means calculates the third risk threshold based on the calculated second risk threshold and the first risk threshold. Control device.   10. The information processing device according to claim 1, further comprising a notification unit that prompts the driver to call attention when there is no driver avoidance operation even if the detected risk potential exceeds the first risk threshold value. 11. The vehicle travel control device described in the above.   11. The vehicle travel control device according to claim 1, wherein the risk potential detection means sets the position of the first risk threshold based on a driving tendency of a driver. Detecting a risk potential based on the degree of approach of the vehicle to the obstacle in the vehicle traveling direction;
Detecting a steering angle that is an angle of a steering wheel that can be steered by a driver;
Calculating a ratio of the obstacle in the region corresponding to the vehicle width set in the traveling direction of the vehicle as a lap rate;
Applying a yaw moment to the vehicle based on the risk potential,
The step of applying a yaw moment to the vehicle includes
A vehicle based on a lap rate yaw moment that is a yaw moment that is applied to the vehicle so that the lap rate decreases when the risk potential exceeds a first risk threshold that is a predetermined risk potential. Yaw moment is applied to
When the risk potential exceeds a second risk threshold that is a predetermined risk potential that is greater than the first risk threshold, a yaw moment that is applied to the vehicle according to a change in the steering angle. A vehicle travel control method, wherein a yaw moment is applied to a vehicle based on a certain steering angle yaw moment.

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