JP2018149974A - Traffic lane deviation hindering device - Google Patents

Abstract

According to a friction coefficient of a road surface on which a vehicle is traveling, a departure suppressing operation for appropriately suppressing a departure of the vehicle from a traveling lane is appropriately performed. A lane departure restraint device (17) applies a braking force to a wheel (121) so that a restrained yaw moment capable of restraining the departure of the vehicle (1) from the currently traveling lane is applied to the vehicle. When the road surface friction coefficient (μ) is smaller than a predetermined threshold value (K), the deviation suppression means (172) for applying the braking force to the front wheels (121FL, 121FR) is applied to the braking force applied to the vehicle. The deviation is such that the first ratio (r1) that is the ratio is greater than the second ratio (r2) that is the ratio of the braking force applied to the rear wheels (121RL, 121RR) to the braking force applied to the vehicle. Control means (173) for controlling the suppression means. [Selection] Figure 2

Description

  The present invention relates to a technical field of a lane departure suppressing device capable of suppressing a vehicle departure from a currently traveling lane.

  As a lane departure restraint device, when the vehicle may deviate from the driving lane, the braking force applied to the wheels is controlled to give the vehicle a yaw moment that can suppress the vehicle deviating from the driving lane. A lane departure suppression device is known (see, for example, Patent Document 1).

  Furthermore, although it is not a prior art document describing a lane departure device, there is Patent Document 2 as a prior art document related to the present invention. Patent Document 2 describes a device that determines a friction coefficient of a road surface by a combination of the presence / absence of operation of an anti-skid brake system and the magnitude of braking deceleration during braking of a vehicle.

Japanese Patent No. 4601946 JP 2006-137267 A

  The lane departure suppressing device described in Patent Document 1 applies braking force to wheels in order to suppress the departure of the vehicle from the traveling lane without considering the friction coefficient of the road surface on which the vehicle is traveling. . However, if the lane departure suppressing device applies a relatively strong braking force to the rear wheels of a vehicle traveling on a road surface having a relatively small friction coefficient, the rear wheels may be locked. As a result, the behavior of the vehicle may become unstable.

  The present invention provides a lane departure suppression device capable of appropriately performing a departure suppression operation for appropriately suppressing a departure of a vehicle from a traveling lane according to a friction coefficient of a road surface on which the vehicle is traveling. This is the issue.

  One aspect of the lane departure suppressing device of the present invention is a departure suppressing means for applying braking force to wheels so that a suppression yaw moment that can suppress a vehicle departure from a currently traveling lane is applied to the vehicle. And a first ratio that is a ratio of a braking force applied to a front wheel of the wheels to a braking force applied to the vehicle when a friction coefficient of a road surface of the traveling lane is smaller than a predetermined threshold, Control means for controlling the deviation suppressing means so as to be larger than a second ratio that is a ratio of the braking force applied to the rear wheel to the braking force applied to the vehicle.

  According to one aspect of the lane departure restraint device of the present invention, when the road surface friction coefficient is relatively small (that is, smaller than a predetermined threshold), the second is the ratio of the braking force applied to the rear wheel. The ratio is relatively small. For this reason, even if the friction coefficient of the road surface is relatively small, the braking force applied to the rear wheel is small as compared with the comparative example in which the second ratio is not relatively small. For this reason, possibility that a rear wheel will lock becomes small. As a result, the destabilization of the behavior of the vehicle is suppressed. Therefore, one aspect of the lane departure restraint device of the present invention appropriately performs a departure restraining operation for appropriately restraining the departure of the vehicle from the traveling lane according to the friction coefficient of the road surface on which the vehicle is traveling. Can do.

  Preferably, the control means controls the deviation suppressing means so that the first ratio increases and the second ratio decreases as the friction coefficient decreases. Also in this case, the deviation suppressing operation for appropriately suppressing the deviation of the vehicle from the traveling lane is appropriately performed according to the friction coefficient of the road surface on which the vehicle is traveling.

FIG. 1 is a block diagram illustrating a configuration of a vehicle according to the present embodiment. FIG. 2 is a flowchart showing the flow of the deviation suppression operation of the present embodiment. Each of FIG. 3A to FIG. 3C is a graph showing the relationship between the friction coefficient and the ratio of the braking force applied to the front wheels and the ratio of the braking force applied to the rear wheels.

  Hereinafter, an embodiment of a lane departure restraint device of the present invention will be described with reference to the drawings. Below, description is advanced using the vehicle 1 by which embodiment of the lane departure suppression apparatus of this invention was mounted.

(1) Configuration of Vehicle 1 The configuration of the vehicle 1 of this embodiment will be described with reference to the block diagram of FIG. As shown in FIG. 1, the vehicle 1 includes a brake pedal 111, a master cylinder 112, a brake pipe 113FL, a brake pipe 113RL, a brake pipe 113FR, a brake pipe 113RR, a left front wheel 121FL, and a left rear wheel 121RL. A right front wheel 121FR, a right rear wheel 121RR, a wheel cylinder 122FL, a wheel cylinder 122RL, a wheel cylinder 122FR, a wheel cylinder 122RR, a brake actuator 131 which is a specific example of “braking device”, and a steering wheel 141, vibration actuator 142, vehicle speed sensor 151, wheel speed sensor 152, yaw rate sensor 153, acceleration sensor 154, camera 155, display 161, speaker 162, “lane deviation suppression” And a ECU (Electronic Control Unit) 17 which is one example of a location. "

  The brake pedal 111 is a pedal that is depressed by a driver to brake the vehicle 1. The master cylinder 112 adjusts the pressure of the brake fluid (or any fluid) in the master cylinder 112 to a pressure corresponding to the depression amount of the brake pedal 111. Hereinafter, for the convenience of explanation, “the pressure of the brake fluid” is referred to as “hydraulic pressure”. The hydraulic pressure in the master cylinder 112 is transmitted to the wheel cylinders 122FL, 122RL, 122FR, and 122RR via the brake pipes 113FL, 113RL, 113FR, and 113RR, respectively. Therefore, a braking force corresponding to the hydraulic pressure transmitted to the wheel cylinders 122FL, 122RL, 122FR, and 122RR is applied to the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR, respectively.

  The brake actuator 131 can adjust the hydraulic pressure transmitted to each of the wheel cylinders 122FL, 122RL, 122FR, and 122RR regardless of the depression amount of the brake pedal 111 under the control of the ECU 17. Therefore, the brake actuator 131 can adjust the braking force applied to each of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR regardless of the depression amount of the brake pedal 111.

  The steering wheel 141 is an operator operated by a driver to steer the vehicle 1 (that is, steer the steered wheels). In the present embodiment, the steered wheels are the left front wheel 121FL and the right front wheel 121FR. The vibration actuator 142 can vibrate the steering wheel 141 under the control of the ECU 17.

  The vehicle speed sensor 151 detects the vehicle speed Vv of the vehicle 1. The wheel speed sensor 152 detects wheel speeds Vw of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR. The yaw rate sensor 153 detects the yaw rate γ of the vehicle 1. The acceleration sensor 154 detects the acceleration G of the vehicle 1 (specifically, the longitudinal acceleration Gx and the lateral acceleration Gy). The camera 155 is an imaging device that captures an external situation in front of the vehicle 1. Detection data indicating the detection result of the acceleration sensor 154 from the vehicle speed sensor 151 and image data indicating an image captured by the camera 155 are output to the ECU 17.

  The display 161 can display arbitrary information under the control of the ECU 17. The speaker 162 can output any sound under the control of the ECU 17.

  The ECU 17 controls the overall operation of the vehicle 1. Particularly in the present embodiment, the ECU 17 performs a deviation suppressing operation for suppressing the deviation of the vehicle 1 from the currently traveling lane. Therefore, the ECU 17 functions as a control device for realizing a so-called LDA (Lane Departure Alert) or LDP (Lane Departure Prevention).

  In order to perform the deviation suppression operation, the ECU 17 includes, as processing blocks logically realized in the ECU 17, a data acquisition unit 171, an LDA control unit 172 as a specific example of “deviation suppression means”, and “control A ratio adjusting unit 173 that is a specific example of “means”. The operations of the data acquisition unit 171, the LDA control unit 172, and the ratio adjustment unit 173 will be described in detail later with reference to FIG. 2 and the like, but the outline thereof will be briefly described below. The data acquisition unit 171 acquires detection data indicating a detection result of the acceleration sensor 154 and image data indicating an image captured by the camera 155 from the vehicle speed sensor 151. Based on the detection data and image data acquired by the data acquisition unit 171, the LDA control unit 172 determines that the left front wheel 121 FL and the left rear wheel 121 RL when the vehicle 1 may deviate from the currently traveling lane. Using the braking force applied to at least one of the right front wheel 121FR and the right rear wheel 121RR, a suppression yaw moment that can suppress the deviation of the vehicle 1 from the traveling lane is applied to the vehicle 1. The brake actuator 131 is controlled. In the present embodiment, “suppression of the deviation of the vehicle 1 from the traveling lane” refers to the suppression yaw as compared with the deviation distance of the vehicle 1 from the traveling lane that is assumed when the restraining yaw moment is not applied. This means that the actual departure distance of the vehicle 1 from the traveling lane when the moment is applied is reduced. The ratio ratio adjusting unit 173 applies the front wheel (that is, the left front wheel 121FL and the right wheel) to the braking force applied to the vehicle 1 based on the friction coefficient μ of the road surface on which the vehicle 1 is traveling when the suppression yaw moment is applied. The ratio r1 of the braking force applied to at least one of the front wheels 121FR) and the braking force applied to the rear wheels relative to the braking force applied to the vehicle 1 (that is, at least one of the left rear wheel 121RL and the right rear wheel 121RR). The ratio r2 is adjusted. The ratios r1 and r2 are specific examples of “first ratio” and “second ratio”, respectively. In the following description, the braking force applied to the vehicle 1 is referred to as “total braking force”, the braking force applied to the front wheels is referred to as “front wheel braking force”, and the braking force applied to the rear wheels is This is referred to as “rear wheel braking force”.

(2) Details of Departure Suppression Operation Next, the lane departure suppression operation performed by the ECU 17 will be described with reference to the flowchart of FIG.

  As shown in FIG. 2, first, the data acquisition unit 171 acquires detection data indicating the detection result of the acceleration sensor 154 and image data indicating an image captured by the camera 155 from the vehicle speed sensor 151 (step S10).

  Thereafter, the LDA control unit 172 analyzes the image data acquired in step S10, so that the lane edge of the traveling lane in which the vehicle 1 is currently traveling (in this embodiment, a white line is used as an example of the lane edge). ) Is specified in the image captured by the camera 155 (step S20).

  Thereafter, the LDA control unit 172 calculates the radius of curvature R of the traveling lane in which the vehicle 1 is currently traveling based on the white line identified in step S20 (step S21). Note that the radius of curvature R of the traveling lane is substantially equivalent to the radius of curvature of the white line. For this reason, the LDA control unit 172 may calculate the curvature radius of the white line specified in step S20, and may handle the calculated curvature radius as the curvature radius R of the traveling lane. However, the LDA control unit 172 uses the position information of the vehicle 1 specified using GPS (Global Positioning System) and the map information used for the navigation operation, and the radius of curvature R of the traveling lane in which the vehicle 1 is currently traveling. May be calculated.

  The LDA control unit 172 further calculates the current lateral position X of the vehicle 1 based on the white line specified in step S20 (step S22). The “lateral position X” in the present embodiment is a distance from the center of the traveling lane to the vehicle 1 (typically, the vehicle 1) along the lane width direction orthogonal to the direction in which the traveling lane extends (lane extending direction). The distance to the center of the In this case, one of the direction from the center of the traveling lane toward the right side and the direction toward the left side is set as a positive direction, and the other of the direction from the center of the traveling lane toward the right side and the direction toward the left side is The negative direction is preferably set. The same applies to a lateral velocity Vl described later, a yaw moment such as the above-described suppression yaw moment, the above-described lateral acceleration Gy, the above-described yaw rate γ, and the like.

  The LDA control unit 172 further calculates the deviation angle θ of the vehicle 1 based on the white line specified in step S20 (step S22). The “deviation angle θ” of the present embodiment indicates an angle formed by the traveling lane and the longitudinal axis of the vehicle 1 (that is, an angle formed by the white line and the longitudinal axis of the vehicle 1).

  The LDA control unit 172 further calculates the lateral velocity Vl of the vehicle 1 based on the time series data of the lateral position X of the vehicle 1 calculated from the white line (step S22). However, the LDA control unit 172 may calculate the lateral speed Vl of the vehicle 1 based on at least one of the detection result of the vehicle speed sensor 151 and the calculated deviation angle θ and the detection result of the acceleration sensor 154. The “lateral speed Vl” in the present embodiment indicates the speed of the vehicle 1 along the lane width direction.

  The LDA control unit 172 further sets an allowable deviation distance D (step S23). The allowable deviation distance D indicates an allowable maximum value of the deviation distance of the vehicle 1 from the traveling lane (that is, the deviation distance of the vehicle 1 from the white line) when the vehicle 1 deviates from the traveling lane. For this reason, the departure suppressing operation is an operation of applying a suppressing yaw moment to the vehicle 1 so that the departure distance of the vehicle 1 from the traveling lane is within the allowable departure distance D.

  The LDA control unit 172 may set the allowable deviation distance D from the viewpoint of satisfying a request such as a regulation (for example, a request of NCAP: New Car Assessment Program). In this case, the allowable deviation distance D set from the viewpoint of satisfying the requirements of laws and regulations may be used as the default allowable deviation distance D.

  Thereafter, the LDA control unit 172 determines whether or not the vehicle 1 may deviate from the currently traveling lane (step S24). Specifically, the LDA control unit 172 calculates the future lateral position Xf. For example, the LDA control unit 172 calculates the lateral position X when the vehicle 1 travels a distance corresponding to the forward gaze distance from the current position as the future lateral position Xf. The future lateral position Xf can be calculated by adding or subtracting a multiplication value of the lateral speed Vl and the time Δt required for the vehicle 1 to travel the forward gaze distance from the current lateral position X. . Thereafter, the LDA control unit 172 determines whether or not the absolute value of the future lateral position Xf is greater than or equal to the departure threshold value. When it is assumed that the vehicle 1 is oriented in a direction parallel to the lane extending direction, the departure threshold value is determined based on, for example, the width of the traveling lane and the width of the vehicle 1 (specifically, the width of the traveling lane -The width of the vehicle 1) / 2). In this case, the situation in which the absolute value of the future lateral position Xf coincides with the departure threshold is that the side surface of the vehicle 1 along the lane width direction (for example, the side surface far from the center of the traveling lane) is located on the white line. It corresponds to. The situation where the absolute value of the future lateral position Xf is larger than the departure threshold corresponds to the situation where the side surface of the vehicle 1 along the lane width direction (for example, the side surface far from the center of the traveling lane) is located outside the white line. To do. For this reason, when the absolute value of the future lateral position Xf is not greater than or equal to the departure threshold value, the LDA control unit 172 determines that there is no possibility that the vehicle 1 will deviate from the currently traveling lane. On the other hand, when the absolute value of the future lateral position Xf is greater than or equal to the departure threshold value, the LDA control unit 172 determines that the vehicle 1 may deviate from the currently traveling lane. However, since the vehicle 1 may actually face in a direction that is not parallel to the lane extending direction, any value different from the above example may be used as the departure threshold.

  Note that the operation described here is merely an example of an operation for determining whether or not the vehicle 1 may deviate from the currently traveling lane. Therefore, the LDA control unit 172 may determine whether or not the vehicle 1 may deviate from the currently traveling lane using an arbitrary determination criterion. As an example of the situation where “the vehicle 1 may deviate from the travel lane”, the vehicle 1 straddles or steps over the white line in the near future (for example, when traveling a distance corresponding to the above-described forward gaze distance). The situation can be raised.

  As a result of the determination in step S24, when it is determined that there is no possibility that the vehicle 1 deviates from the traveling lane (step S24: No), the deviation suppression operation shown in FIG. 2 ends. Therefore, the operation (step S25 to step S29) performed when it is determined that the vehicle 1 may deviate from the travel lane is not performed. That is, the LDA control unit 172 controls the brake actuator 131 so that the suppression yaw moment is not applied to the vehicle 1 (that is, the braking force that can apply the suppression yaw moment to the vehicle 1 is not applied). Furthermore, the LDA control unit 172 does not warn the driver that the vehicle 1 may deviate from the traveling lane.

  When it is determined that there is no possibility that the vehicle 1 will deviate from the traveling lane, when the deviation suppression operation shown in FIG. 2 is completed, the ECU 17 performs a predetermined period (for example, several milliseconds to several tens of milliseconds). 2) again, the departure suppression operation shown in FIG. 2 is started again. That is, the deviation suppressing operation shown in FIG. 2 is repeatedly performed at a cycle corresponding to a predetermined period.

  On the other hand, as a result of the determination in step S24, when it is determined that the vehicle 1 may deviate from the travel lane (step S24: Yes), the LDA control unit 172 deviates from the travel lane. The driver is warned of the possibility (step S25). For example, the LDA control unit 172 may control the display 161 so as to display an image indicating that the vehicle 1 may deviate from the traveling lane. For example, the LDA control unit 172 may control the vibration actuator 142 so that the driver 1 is notified by vibration of the steering wheel 141 that the vehicle 1 may deviate from the traveling lane. For example, the LDA control unit 172 may control the speaker (so-called buzzer) 162 so as to notify the driver with a warning sound that the vehicle 1 may deviate from the traveling lane.

  When it is determined that the vehicle 1 may deviate from the travel lane, the LDA control unit 172 further controls the brake actuator 131 so as to apply a braking force that can apply the suppression yaw moment to the vehicle 1. (Step S26 to Step S29).

Specifically, when there is a possibility that the vehicle 1 deviates from the travel lane, the vehicle 1 is likely to travel away from the center of the travel lane. For this reason, if the travel locus of the vehicle 1 is changed from a travel locus that travels away from the center of the travel lane to a travel locus that travels toward the center of the travel lane, the vehicle 1 deviates from the travel lane. It is suppressed. For this reason, the LDA control unit 172 sets the detected data, the image data, the specified white line, the calculated curvature radius R, the calculated lateral position X, the calculated lateral velocity Vl, the calculated deviation angle θ, and the set allowable deviation distance D. Based on this, a new travel locus is calculated in which the vehicle 1 traveling away from the center of the travel lane travels toward the center of the travel lane. At this time, the LDA control unit 172 calculates a new travel locus that satisfies the restriction of the allowable deviation distance D set in step S23. Further, the LDA control unit 172 calculates a yaw rate estimated to occur in the vehicle 1 traveling on the calculated new travel locus as the target yaw rate γ _tgt (step S26).

Thereafter, the LDA control unit 172 calculates the yaw moment to be applied to the vehicle 1 in order to cause the vehicle 1 to generate the target yaw rate γ _tgt as the target yaw moment M _tgt (step S27). The target yaw moment M _tgt is equivalent to the suppression yaw moment.

  Thereafter, the ratio adjusting unit 173 estimates the friction coefficient μ of the road surface of the traveling lane in which the vehicle 1 is currently traveling (step S281). As the operation for estimating the friction coefficient μ, an existing operation can be adopted, and a detailed description thereof will be omitted.

  Thereafter, the ratio adjusting unit 173 sets the ratio r1 of the front wheel braking force to the total braking force (that is, the ratio of the front wheel braking force to the total braking force) (step S282). Further, the ratio adjusting unit 173 sets a ratio r2 of the rear wheel braking force to the total braking force (that is, a ratio of the rear wheel braking force to the total braking force) (step S282). The total braking force is typically equivalent to the sum of the front wheel braking force and the rear wheel braking force.

  The magnitude of the braking force applied to the left rear wheel RL is proportional to the hydraulic pressure transmitted to the wheel cylinder 122RL. The magnitude of the braking force applied to the right rear wheel RR is proportional to the hydraulic pressure transmitted to the wheel cylinder 122RR. The magnitude of the braking force applied to the left front wheel FL is proportional to the hydraulic pressure transmitted to the wheel cylinder 122FL. The magnitude of the braking force applied to the right front wheel FR is proportional to the hydraulic pressure transmitted to the wheel cylinder 122FR. Therefore, the ratio r1 is equivalent to the ratio (that is, the distribution ratio) of the hydraulic pressure transmitted to the wheel cylinders 122FL and 122FR corresponding to the front wheels among the hydraulic pressure in the master cylinder 112. Similarly, the ratio r2 is equivalent to the ratio (that is, the distribution ratio) of the hydraulic pressure transmitted to the wheel cylinders 122RL and 122RR corresponding to the rear wheels in the hydraulic pressure in the master cylinder 112.

  The ratio adjusting unit 173 sets the ratios r1 and r2 based on the friction coefficient μ estimated in step S282. Specifically, the ratio adjusting unit 173 sets each of the ratios r1 and r2 to the same first value (specifically, 50%) when the friction coefficient μ is equal to or greater than the predetermined threshold value K. To do. However, the ratio adjustment unit 173 may set the ratios r1 and r2 so that the ratio r1 is smaller than the ratio r2. On the other hand, when the friction coefficient μ is smaller than the predetermined threshold K, the ratio adjusting unit 173 sets the ratio r1 to a second value (for example, a value greater than 50%) that is larger than the first value, The ratio r2 is set to a third value (for example, a value smaller than 50%) that is smaller than the first value. In other words, when the friction coefficient μ is smaller than the predetermined threshold K, the ratio adjusting unit 173 sets the ratios r1 and r2 so that the ratio r1 is larger than the ratio r2. At this time, the ratio adjustment unit 173 preferably sets the ratios r1 and r2 so that the ratio r1 increases and the ratio r2 decreases as the friction coefficient μ decreases.

  In step S282, the ratio adjustment unit 173, for example, based on a map (see FIGS. 3A to 3C) showing the relationship between the friction coefficient μ and each of the ratios r1 and r2, the ratios r1 and r2 May be set. Note that FIG. 3A shows that when the friction coefficient μ is equal to or greater than a threshold value K1 which is an example of the predetermined threshold value K (where 0 <K1 <1), the ratios r1 and r2 are 50%. Shows an example of a map in which the ratio r1 continuously increases and the ratio r2 decreases continuously as the friction coefficient μ decreases. In particular, FIG. 3A shows an example of a map in which the ratio r1 is 100% and the ratio r2 is 0% when the friction coefficient μ is zero. FIG. 3B shows that when the friction coefficient μ is equal to or higher than a threshold value K2 (where 0 <K2 <1), which is an example of the predetermined threshold value K, each of the ratios r1 and r2 is 50%, and the friction coefficient μ is In the case of smaller than the threshold value K2, an example of a map in which the ratio r1 increases stepwise and the ratio r2 decreases stepwise as the friction coefficient μ decreases is shown. In particular, FIG. 3B shows that the ratio r1 becomes 70% and the ratio r2 becomes 30% when the friction coefficient μ is smaller than the threshold K2 and is equal to or larger than the threshold K3 (where 0 <K3 <K2). In the example of the map, the ratio r1 is 100% and the ratio r2 is 0% when the friction coefficient μ is smaller than the threshold value K3. FIG. 3C shows that when the friction coefficient is a threshold value K4 which is an example of the predetermined threshold value K (where K3 = 1), each of the ratios r1 and r2 is 50%, and the friction coefficient μ is smaller than the threshold value K4. In this case, an example of a map in which the ratio r1 continuously increases and the ratio r2 continuously decreases as the friction coefficient μ decreases. In particular, FIG. 3C shows an example of a map in which the ratio r1 is 100% and the ratio r2 is 0% when the friction coefficient μ is zero.

Thereafter, the LDA control unit 172 individually calculates the braking force applied to each of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR (step S283). At this time, the LDA control unit 172 calculates a braking force that can provide the target yaw moment M _tgt and satisfy the conditions of the ratios r1 and r2. Thereafter, the LDA control unit 172 calculates a pressure command value for designating a hydraulic pressure necessary for generating the calculated braking force (step S283). In this case, the LDA control unit 172 individually calculates a pressure command value that specifies the oil pressure inside each of the wheel cylinders 122FL, 122RL, 122FR, and 122RR.

  For example, when it is determined that the vehicle 1 may deviate from the traveling lane across the white line located on the right side with respect to the traveling direction of the vehicle 1, in order to suppress the deviation of the vehicle 1 from the traveling lane In other words, the vehicle 1 may be provided with a restraining yaw moment that can deflect the vehicle 1 toward the left side with respect to the traveling direction of the vehicle 1. In this case, the braking force is not applied to the right front wheel 121FR and the right rear wheel 121RR, while the braking force is applied to at least one of the left front wheel 121FL and the left rear wheel 121RL, or the right front wheel 121FR and the right rear wheel. If a relatively small braking force is applied to at least one of 121RR while a relatively large braking force is applied to at least one of left front wheel 121FL and left rear wheel 121RL, vehicle 1 is deflected toward the left side. A restraining yaw moment that can be applied is applied to the vehicle 1. When it is determined that the vehicle 1 may deviate from the driving lane across the left white line with respect to the traveling direction of the vehicle 1, conversely, braking force is applied to the left front wheel 121FL and the left rear wheel 121RL. On the other hand, if a braking force is applied to at least one of the right front wheel 121FR and the right rear wheel 121RR, or a relatively small braking force is applied to at least one of the left front wheel 121FL and the left rear wheel 121RL, the right If a relatively large braking force is applied to at least one of the front wheel 121FR and the right rear wheel 121RR, a restraining yaw moment capable of deflecting the vehicle 1 toward the right side with respect to the traveling direction of the vehicle 1 is increased. To be granted. That is, in this embodiment, the LDA control unit 172 uses the braking force difference between the left wheel including the left front wheel 121FL and the left rear wheel 121RL and the right wheel including the right front wheel 121FR and the right rear wheel 121RR. A restraining yaw moment is applied.

Thereafter, the LDA control unit 172 controls the brake actuator 131 based on the pressure command value calculated in step S283. Accordingly, a braking force corresponding to the pressure command value is applied to at least one of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR (step S29). As a result, the vehicle 1 is given a restrained yaw moment equivalent to the target yaw moment M _tgt , so that the deviation of the vehicle 1 from the traveling lane is restrained.

(3) Technical Effects of Departure Suppression Operation of the Present Embodiment In the vehicle 1 of the present embodiment, a suppression yaw moment is applied to the vehicle 1 when the vehicle 1 may deviate from the traveling lane. For this reason, the deviation of the vehicle 1 from the traveling lane is suppressed.

  Further, in the present embodiment, the ratios r1 and r2 are set based on the friction coefficient μ. For this reason, the ECU 17 can appropriately perform the deviation suppressing operation for appropriately suppressing the deviation of the vehicle 1 from the traveling lane, regardless of the magnitude of the friction coefficient μ of the road surface on which the vehicle 1 is traveling. Hereinafter, regarding the reason why the deviation suppression operation can be appropriately performed regardless of the friction coefficient μ, the suppression yaw moment that can deflect the vehicle 1 toward the left side with respect to the traveling direction of the vehicle 1 is the vehicle 1. The explanation will be made using an example given to.

  As described above, the LDA control unit 172 deflects the vehicle 1 to the left by applying braking force to the left front wheel 121FL and the left rear wheel 121RL while not applying braking force to the right front wheel 121FR and right rear wheel 121RR. The suppression yaw moment that can be applied can be applied. Here, if a relatively large braking force is applied to the left rear wheel 121RL, the left rear wheel 121RL may be locked (in other words, slipped). That is, the lateral force of the left rear wheel 121RL may be reduced. As a result, there is a high possibility that the behavior of the vehicle 1 becomes unstable.

  However, in the present embodiment, when the friction coefficient μ is smaller than the predetermined threshold value K, the ratio r1 is larger than the ratio r2. That is, the ratio r2 becomes relatively small. For this reason, the braking force smaller than the original braking force (that is, the braking force applied when the friction coefficient μ is equal to or greater than the predetermined threshold value K) necessary for applying the suppression yaw moment to the left rear wheel 121RL. Is granted. As a result, the possibility that the left rear wheel 121RL is locked is reduced. That is, the possibility that the lateral force of the left rear wheel 121RL is reduced is reduced. As a result, destabilization of the behavior of the vehicle 1 is suppressed.

  In addition, in order to obtain an appropriate braking force difference by compensating for the decrease in the braking force applied to the left rear wheel 121RL, the ratio r1 becomes relatively large in accordance with the relatively small ratio r2. . As a result, the left front wheel 121FL has a braking force larger than the original braking force necessary for applying the restraining yaw moment (that is, the braking force applied when the friction coefficient μ is equal to or greater than the predetermined threshold K). Is granted. As a result, even if the braking force applied to the left rear wheel 121RL is relatively small and the braking force applied to the left front wheel 121FL is relatively large, the braking force applied to the entire left wheel (that is, , The total braking force) can be kept constant. As a result, it is possible to generate a braking force difference between the right wheel and the left wheel so as to realize a restrained yaw moment. That is, an appropriate restraining yaw moment can be applied to the vehicle 1.

  Thus, according to the present embodiment, even when the vehicle 1 is traveling on a road surface having a friction coefficient μ that is relatively small (that is, smaller than the predetermined threshold value K), that is, it is relatively large (that is, As with the case where the vehicle 1 is traveling on the road surface with the friction coefficient μ), an appropriate suppression yaw moment can be applied to the vehicle 1 without causing instability of the behavior of the vehicle 1. It becomes.

  In addition, in the present embodiment, when the friction coefficient μ is smaller than the predetermined threshold K, the ratio r1 increases and the ratio r2 decreases as the friction coefficient μ decreases. Considering that the smaller the friction coefficient μ is, the higher the possibility that the rear wheel will be locked when a braking force is applied to the rear wheel, the smaller the friction coefficient μ, the larger the ratio r1 and the ratio r2 are. By becoming smaller, the lock of the rear wheel is more appropriately suppressed. As a result, the destabilization of the behavior of the vehicle 1 is more appropriately suppressed.

  The present invention can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and a lane departure restraining device that includes such a change is also included in the technical concept of the present invention. It is.

1 Vehicle 131 Brake actuator 17 ECU
172 LDA control unit 173 Ratio adjustment unit

Claims (1)

Deviation suppression means for applying braking force to the wheels such that a suppression yaw moment that can suppress the deviation of the vehicle from the currently running lane is applied to the vehicle;
The first ratio, which is the ratio of the braking force applied to the front wheels of the wheels to the braking force applied to the vehicle when the friction coefficient of the road surface of the traveling lane is smaller than a predetermined threshold, Control means for controlling the departure suppressing means so as to be larger than a second ratio that is a ratio of a braking force applied to a rear wheel to a braking force applied to the vehicle. Deviation suppression device.

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