Driving assistance device and method, and computer program

Abstract

To appropriately decelerate an own vehicle while preventing the own vehicle from behaving unstably due to the deceleration.SOLUTION: A driving support device (100) automatically decelerates an own vehicle (1) according to a relative relation between the own vehicle and a preceding vehicle. The driving support device comprises: control means (13, 16, 17) for changing the deceleration of the own vehicle by a first change amount or a second change amount which is larger than the first change amount when automatically decelerating the own vehicle; and estimation means (11) for estimating whether or not the own vehicle will behave unstably due to the deceleration by the deceleration means. When the estimation means estimates that the own vehicle will behave unstably, the control means changes the deceleration by the first change amount when automatically decelerating the own vehicle.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical fields of a driving assistance device and method, and a computer program. [Background technology]

[0002] One example of this type of device has been proposed: a device that controls the distance between the vehicle itself and a preceding vehicle, which calculates the collision risk felt by the driver when the preceding vehicle cuts in or the target following distance is changed, and the higher the calculated collision risk, the greater the jerk to slow down the vehicle itself (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-120363 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if a relatively large jerk is set only because the collision risk is relatively high, and the host vehicle suddenly decelerates, the behavior of the host vehicle may become unstable. In other words, there is room for improvement in the technology described in Patent Document 1.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an objective of providing a driving assistance device and method, as well as a computer program, that can appropriately decelerate the vehicle while suppressing unstable behavior of the vehicle. [Means for solving the problem]

[0006] A driving assistance device according to one aspect of the present invention is a driving assistance device that automatically decelerates a host vehicle using a deceleration means of the host vehicle in accordance with a relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle, and includes: a control means that, when automatically decelerating the host vehicle, changes the deceleration of the host vehicle by a first change amount or a second change amount that is greater than the first change amount; and an estimation means that estimates that a behavior of the host vehicle will become unstable due to deceleration by the deceleration means, and the control means estimates that the behavior of the host vehicle will become unstable when it is estimated by the estimation means. Ta In this case, when the host vehicle is automatically decelerated, the deceleration is changed by the first change amount. The estimation means determines whether or not there is a specified curve ahead of the vehicle, the specified curve having a curvature that will cause the behavior of the vehicle to become unstable when a braking force is applied to the vehicle, and if there is the specified curve ahead of the vehicle, the estimation means estimates that deceleration by the deceleration means will cause the behavior of the vehicle to become unstable.

[0007] A driving assistance method according to one aspect of the present invention is a driving assistance method for a driving assistance device that automatically decelerates a host vehicle using a deceleration means of the host vehicle in accordance with a relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle, and when automatically decelerating the host vehicle, changes the deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount, the method including: an estimation step of estimating that a behavior of the host vehicle will become unstable due to deceleration by the deceleration means; and a determination step of determining whether the behavior of the host vehicle will become unstable in the estimation step. Ta In the case where the vehicle is automatically decelerated, the control step of changing the deceleration by the first change amount is included, and in the estimation step, It is determined whether or not there is a specified curve ahead of the vehicle, the specified curve having a curvature that will cause the behavior of the vehicle to become unstable when a braking force is applied to the vehicle, and if there is the specified curve ahead of the vehicle, it is estimated in the estimation process that deceleration by the deceleration means will cause the behavior of the vehicle to become unstable.

[0008] A computer program according to one aspect of the present invention causes a computer of a driving assistance device that automatically decelerates a host vehicle using a deceleration means of the host vehicle in accordance with a relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle to function as: a control means that changes the deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount when automatically decelerating the host vehicle; and an estimation means that estimates that deceleration by the deceleration means will cause behavior of the host vehicle to become unstable. When it is estimated by the estimation means that the behavior of the host vehicle will become unstable, the control means changes the deceleration by the first change amount when automatically decelerating the host vehicle. The estimation means determines whether or not there is a specified curve ahead of the vehicle, the specified curve having a curvature that will cause the behavior of the vehicle to become unstable when a braking force is applied to the vehicle, and if there is the specified curve ahead of the vehicle, the estimation means estimates that deceleration by the deceleration means will cause the behavior of the vehicle to become unstable. Effect of the Invention

[0009] In the driving support device and method, and the computer program, in addition to the relative relationship between the host vehicle and the preceding vehicle, the behavior stability of the host vehicle is also taken into consideration. Therefore, the driving support device and method, and the computer program can appropriately decelerate the host vehicle while suppressing the host vehicle's behavior from becoming unstable due to deceleration of the host vehicle. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a configuration of a driving assistance device according to an embodiment. [Diagram 2] 4 is a flowchart showing an operation of the driving assistance device according to the embodiment. [Diagram 3] FIG. 1 is a block diagram showing a configuration of a computer according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of a driving support device will be described with reference to Figs. 1 and 2. In Fig. 1, a driving support device 100 according to the embodiment is mounted on a vehicle 1 (not shown). The driving support device 100 can make the vehicle 1 travel so as to follow a preceding vehicle, which is another vehicle traveling ahead of the vehicle 1 on the course. That is, the driving support device 100 is configured to be capable of executing a following type of ACC (Adaptive Cruise Control). The driving support device 100 is configured to be capable of executing a deceleration support control that automatically decelerates the vehicle 1 using, for example, a braking device 30 of the vehicle 1 in order to control, for example, a distance between the vehicle 1 and the preceding vehicle according to a relative relationship between the vehicle 1 and the preceding vehicle during execution of the following type of ACC.

[0012] In this embodiment, a mode in which deceleration assist control is performed while adaptive ACC is being executed is given as an example, but the present invention is not limited to this.

[0013] In order to realize the above-mentioned deceleration assistance control, the driving assistance device 100 is configured to include an external environment recognition unit 11, a preceding vehicle information calculation unit 12, a stable behavior determination unit 13, a required deceleration calculation unit 14, an alarm implementation determination unit 15, a jerk suppression implementation determination unit 16, an acceleration control unit 17, and an end determination unit 18, which are implemented as processing blocks logically realized within the driving assistance device 100 or as processing circuits physically realized therein.

[0014] Here, the sensors 20 equipped in the vehicle 1 include sensors for recognizing the outside world of the vehicle 1, such as radar, LiDAR (Light Detection and Ranging), and cameras, and sensors for detecting the motion state of the vehicle 1, such as a speed sensor, an acceleration sensor, and a yaw rate sensor.

[0015] The external environment recognition unit 11 acquires measurement results by a sensor included in the sensor 20 for recognizing the external environment of the vehicle 1. The external environment recognition unit 11 may also acquire, for example, ITS (Intelligent Transport System) information. The external environment recognition unit 11 may also acquire information from other vehicles traveling around the vehicle 1, for example, by vehicle-to-vehicle communication.

[0016] The external environment recognition unit 11 recognizes the external environment of the vehicle 1 based on the acquired measurement results, ITS information, etc. Examples of the external environment include objects such as other vehicles and obstacles, weather conditions such as temperature and rainfall, and information related to the road surface such as white lines and road surface temperature. Note that various existing methods can be applied to the method of recognizing the external environment, and therefore detailed explanations thereof will be omitted.

[0017] When the external environment recognition unit 11 recognizes a preceding vehicle (i.e., another vehicle traveling ahead on the path of the vehicle 1), the preceding vehicle information calculation unit 12 calculates preceding vehicle information related to the preceding vehicle.

[0018] Specifically, the preceding vehicle information calculation unit 12 may calculate, for example, reliability as the preceding vehicle information. Here, the "reliability" may be an index indicating the likelihood that a preceding vehicle is present. Such reliability may be calculated based on, for example, the results of a determination as to whether or not (i) the preceding vehicle is detected by multiple types of sensors included in the sensor 20, (ii) the preceding vehicle is continuously detected by at least one sensor included in the sensor 20, and (iii) the preceding vehicle is continuously subject to the above-mentioned deceleration support control.

[0019] Alternatively, the "reliability" may be an index indicating the likelihood that the preceding vehicle is in the same lane as the lane in which the vehicle 1 is traveling. Such a reliability may be calculated, for example, based on (i) a comparison result between the position of the preceding vehicle predicted from the recognition result of the external environment recognition unit 11 and the predicted path of the vehicle 1, or (ii) a determination result as to whether or not the preceding vehicle is present within the white line (in other words, the dividing line that defines the lane) recognized by the external environment recognition unit 11, or the like.

[0020] The stable behavior determination unit 13 determines whether or not the behavior of the vehicle 1 will become unstable when a relatively large braking force is applied to the vehicle 1, based on the recognition results of the external environment recognition unit 11 (e.g., white lines, road surface temperature, etc.), the measurement results of the sensors for detecting the motion state of the vehicle 1 included in the sensor 20 (e.g., speed, yaw rate, acceleration, etc.), the estimated friction coefficient of the road surface, etc.

[0021] For example, when the lateral grip force of the vehicle 1 exceeds the road surface friction force due to at least one of braking and turning of the vehicle 1, the behavior of the vehicle 1 becomes unstable. In particular, when braking and turning of the vehicle 1 are performed simultaneously, the behavior of the vehicle 1 is likely to become unstable.

[0022] For example, when a first condition is established that "the turning state quantity related to the vehicle 1 is equal to or greater than a first predetermined value," the stable behavior determination unit 13 may determine that the behavior of the vehicle 1 will become unstable if a relatively large braking force is applied to the vehicle 1. The turning state quantity can be estimated based on the yaw rate, lateral acceleration, turning curvature (i.e., the value obtained by dividing the yaw rate by the speed), etc., of the vehicle 1. Various existing aspects can be applied to the method of estimating the turning state quantity, and therefore detailed explanations thereof will be omitted.

[0023] The stable behavior judgment unit 13 may judge that the behavior of the vehicle 1 will become unstable if a relatively large braking force is applied to the vehicle 1 when a second condition is met, for example, "the estimated friction coefficient of the road surface is less than or equal to a second predetermined value and / or the road surface temperature is less than or equal to a third predetermined value."

[0024] The stable behavior judgment unit 13 may judge that the behavior of vehicle 1 will become unstable if a relatively large braking force is applied to vehicle 1 when a third condition is met, for example, "a curve having a curvature of a fourth predetermined value or more exists ahead of the planned course of vehicle 1."

[0025] The stable behavior determination unit 13 may determine that the behavior of the vehicle 1 will become unstable if a relatively large braking force is applied to the vehicle 1 when one of the above first to third conditions is satisfied. Alternatively, the stable behavior determination unit 13 may determine that the behavior of the vehicle 1 will become unstable if a relatively large braking force is applied to the vehicle 1 when a plurality of the above first to third conditions are satisfied.

[0026] When decelerating the vehicle 1 by the above-mentioned deceleration support control, the required deceleration calculation unit 14 calculates the required deceleration according to the relative relationship between the vehicle 1 and the preceding vehicle (e.g., relative position, relative speed, etc.). The required deceleration may be, for example, a deceleration for making the relative speed between the vehicle 1 and the preceding vehicle zero within a range of the inter-vehicle distance determined from the relative position between the vehicle 1 and the preceding vehicle. The required deceleration calculation unit 14 further determines whether or not a collision between the vehicle 1 and the preceding vehicle can be avoided when the deceleration of the vehicle 1 is changed to the calculated deceleration by a predetermined jerk.

[0027] The warning implementation determination unit 15 determines whether or not to issue a warning based on, for example, the relative positional relationship between the vehicle 1 and the preceding vehicle, the magnitude of the deceleration calculated by the required deceleration calculation unit 14, and the like.

[0028] The jerk suppression implementation determination unit 16 determines whether or not jerk suppression can be relaxed based on at least one of the reliability as an example of the preceding vehicle information calculated by the preceding vehicle information calculation unit 12, the determination result of the stable behavior determination unit 13, and the determination result of the required deceleration calculation unit 14.

[0029] Here, "jerk suppression" will be explained. In the above-mentioned deceleration support control, a limit is placed on the jerk (in other words, the jerk). Therefore, the fluctuation per unit time of the deceleration (i.e., the negative acceleration) when the vehicle 1 is decelerated by the deceleration support control is suppressed. In this manner, the setting of a limit on the jerk is referred to as "jerk suppression" in this embodiment. By implementing jerk suppression, for example, it is possible to improve the stability of the behavior of the vehicle 1 and suppress the passengers of the vehicle 1 from feeling uncomfortable. Relaxing jerk suppression means relaxing or eliminating the limit placed on the jerk.

[0030] The acceleration control unit 17 transmits information indicating the physical quantities to be realized (e.g., braking force, output torque, engine speed, etc.) to one or more components that actually change the behavior of the vehicle 1, such as the braking device 30 of the vehicle 1 or an engine control device (not shown).

[0031] In addition, when the vehicle 1 is equipped with another system that performs control related to acceleration and deceleration of the vehicle 1 in addition to the driving assistance device 100, and an arbitration unit that arbitrates between the driving assistance device 100 and the other system is present in the vehicle 1, the acceleration control unit 17 may transmit information indicating the deceleration required by the above-mentioned deceleration assistance control to the arbitration unit. In this case, the arbitration unit may transmit information indicating the physical quantity to be realized to one or more components that actually change the behavior of the vehicle 1.

[0032] The termination determination unit 18 determines whether or not to terminate the deceleration support control based on the relative relationship between the vehicle 1 and the preceding vehicle estimated from the recognition result of the external environment recognition unit 11 while the above-mentioned deceleration support control is being performed.

[0033] Next, the operation of the driving assistance device 100 will be described with reference to the flowchart of FIG.

[0034] 2, the external environment recognition unit 11 recognizes the external environment (step S101). Next, the preceding vehicle information calculation unit 12 calculates preceding vehicle information based on the recognition result of the external environment recognition unit 11 (step S102).

[0035] In parallel with or before or after the process of step S102, the stable behavior determination unit 13 determines whether or not the behavior of the vehicle 1 becomes unstable when a relatively large braking force is applied to the vehicle 1 (step S103). After the process of step S102, the required deceleration calculation unit 14 calculates the required deceleration according to the relative relationship between the vehicle 1 and the preceding vehicle (step S104). At this time, the required deceleration calculation unit 14 determines whether or not a collision between the vehicle 1 and the preceding vehicle can be avoided when the deceleration of the vehicle 1 is changed up to the calculated deceleration by performing jerk suppression (i.e., with a limit on the jerk). Next, the warning implementation determination unit 15 determines whether or not to issue a warning (step S105).

[0036] Next, the jerk suppression implementation determination unit 16 determines whether or not jerk suppression can be relaxed based on at least one of the reliability as an example of the preceding vehicle information calculated by the preceding vehicle information calculation unit 12, the determination result of the stable behavior determination unit 13, and the determination result of the required deceleration calculation unit 14 (step S106).

[0037] In the process of step S106, if it is determined that jerk suppression can be relaxed (step S106: Yes), the jerk suppression implementation determination unit 16 does not implement jerk suppression, and transmits a signal indicating the jerk with jerk suppression relaxed to the acceleration control unit 17 (step S107). Here, examples of cases in which it is determined that jerk suppression can be relaxed include a case in which the reliability is relatively high and it is difficult to avoid a collision between the vehicle 1 and the preceding vehicle by implementing jerk suppression, and a case in which it is determined that the behavior of the vehicle 1 will not become unstable when a relatively large braking force is applied to the vehicle 1.

[0038] If it is determined in the process of step S106 that mitigation of jerk suppression is not possible (step S106: No), the jerk suppression implementation determination unit 16 implements jerk suppression and transmits a signal indicating the suppressed jerk to the acceleration control unit 17 (step S108). Examples of cases in which it is determined that mitigation of jerk suppression is not possible include a case in which the reliability is relatively high and a collision between the vehicle 1 and a preceding vehicle can be avoided by implementing jerk suppression, and a case in which it is determined that the behavior of the vehicle 1 becomes unstable when a relatively large braking force is applied to the vehicle 1.

[0039] In the processing of steps S107 and S108, the jerk indicated by the signal transmitted from the jerk suppression execution determination unit 16 to the acceleration control unit 17 may be the jerk when decelerating the vehicle 1 this time, or may be a limit value of the jerk. When information indicating the limit value of the jerk is transmitted from the jerk suppression execution determination unit 16 to the acceleration control unit 17, the acceleration control unit 17 can arbitrarily set the acceleration within a range not exceeding the limit value.

[0040] The acceleration control unit 17 controls the acceleration to decelerate the vehicle 1 based on the jerk indicated by the information transmitted from the jerk suppression implementation determination unit 16 (step S109). Thereafter, when the end determination unit 18 determines to end the deceleration support control, the operation shown in FIG. 2 is ended.

[0041] (Technical effect) When the vehicle 1 is traveling following a preceding vehicle by using a following type ACC, if the preceding vehicle decelerates, the driving support device 100 decelerates the vehicle 1 so that the vehicle 1 does not get too close to the preceding vehicle. The deceleration of the vehicle 1 by the driving support device 100 is performed automatically regardless of the driver's intention. Therefore, the jerk caused by the deceleration of the vehicle 1 by the driving support device 100 is suppressed so that the driver does not feel uncomfortable.

[0042] For example, if the leading vehicle suddenly decelerates (in other words, applies sudden braking) or another vehicle cuts in between vehicle 1 and the leading vehicle, even if a collision between vehicle 1 and the leading vehicle or the other vehicle can be avoided by suppressing the jerk, the driver may feel uneasy or uncomfortable as vehicle 1 approaches the leading vehicle or the other vehicle. Note that the cutting in can be considered as a new leading vehicle, and therefore the other vehicle can be included in the concept of the "leading vehicle."

[0043] Therefore, it is conceivable to configure the vehicle 1 to decelerate without suppressing the jerk as necessary. However, if a relatively large braking force is applied to the vehicle 1 without suppressing the jerk, the behavior of the vehicle 1 may become unstable depending on, for example, the road surface condition. In response to this, the driving support device 100 takes into consideration the behavior stability of the vehicle 1 in addition to the relative relationship between the vehicle 1 and the preceding vehicle or another vehicle. Therefore, the driving support device 100 can suppress the behavior of the vehicle 1 from becoming unstable due to the deceleration support control.

[0044] Suppressing the jerk associated with the deceleration support control improves the ride comfort of the vehicle 1, but the occupants may feel uneasy due to the vehicle 1 approaching the preceding vehicle. On the other hand, not suppressing the jerk associated with the deceleration support control improves the safety of the vehicle 1, but the occupants may feel uncomfortable due to the deceleration of the vehicle 1 caused by the deceleration support control. The driving support device 100 can achieve both improved safety of the vehicle 1 and improved sense of security for the occupants by switching between jerk suppression and relaxation of the suppression based on the relative relationship between the vehicle 1 and the preceding vehicle, the behavior of the vehicle 1, and the like.

[0045] <Computer Program> An embodiment of a computer program will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration of a computer according to the embodiment.

[0046] 3, a computer 50 includes a CPU (Central Processing Unit) 51, a RAM 52, a HDD (Hard Disk Drive) 53, and an I / O 54. The CPU 51, the RAM 52, the HDD 53, and the I / O 54 are interconnected by a bus 55. The HDD 53 stores a computer program 531 according to this embodiment in advance.

[0047] The processing of the CPU 51 by the computer program 531 will be described. The CPU 51 acquires measurement results by a sensor included in the sensor 20 for recognizing the outside of the vehicle 1. Then, the CPU 51 recognizes the outside environment of the vehicle 1. When a preceding vehicle is recognized by recognizing the outside environment, the CPU 51 calculates preceding vehicle information (e.g., reliability) related to the preceding vehicle. In parallel with or before or after the recognition of the outside environment, the CPU 51 determines whether or not the behavior of the vehicle 1 becomes unstable when a relatively large braking force is applied to the vehicle 1.

[0048] The CPU 51 calculates the necessary deceleration in accordance with the relative relationship between the vehicle 1 and the preceding vehicle. At this time, the CPU 51 determines whether or not a collision between the vehicle 1 and the preceding vehicle can be avoided when the deceleration of the vehicle 1 is changed to the calculated deceleration by implementing jerk suppression. Then, the CPU 51 determines whether or not to issue an alarm.

[0049] The CPU 51 determines whether or not jerk suppression can be relaxed based on at least one of: (i) the reliability as an example of preceding vehicle information; (ii) the determination result as to whether or not the behavior of the vehicle 1 will become unstable; and (iii) the determination result as to whether or not a collision between the vehicle 1 and the preceding vehicle can be avoided if jerk suppression is implemented and the jerk is changed.

[0050] When it is determined that relaxation of jerk suppression is possible, the CPU 51 does not perform jerk suppression, but controls the acceleration based on the jerk after the jerk suppression is relaxed, to decelerate the vehicle 1. On the other hand, when it is determined that relaxation of jerk suppression is not possible, the CPU 51 performs jerk suppression, and controls the acceleration based on the suppressed jerk to decelerate the vehicle 1.

[0051] The computer program 531 may be stored in the HDD 53 by the computer 50 reading the computer program 531 from a recording medium, such as an optical disk, such as a CD-ROM (Compact Disc Read Only Memory), or a USB (Universal Serial Bus) memory, that stores the computer program 531. Alternatively, the computer 50 may store the computer program 531 in the HDD 53 by downloading the computer program 531 via a network, such as the Internet.

[0052] According to the computer program 531, similarly to the driving assistance device 100 described above, it is possible to achieve both improved safety of the vehicle 1 and improved sense of security for the occupants by switching between jerk suppression and relaxation of the suppression based on the relative relationship between the vehicle 1 and the preceding vehicle, the behavior of the vehicle 1, etc.

[0053] Aspects of the invention derived from the above-described embodiment will be described below.

[0054] A driving assistance device according to one embodiment of the invention is a driving assistance device that automatically decelerates the host vehicle using a deceleration means of the host vehicle depending on the relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle, and is equipped with a control means that changes the deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount when automatically decelerating the host vehicle, and an estimation means that estimates that deceleration by the deceleration means will cause the behavior of the host vehicle to become unstable, and if the estimation means estimates that the behavior of the host vehicle will become unstable, the control means changes the deceleration by the first change amount when automatically decelerating the host vehicle.

[0055] In the above-mentioned embodiment, the "stable behavior determination unit 13," the "jerk suppression implementation determination unit 16," and the "acceleration control unit 17" correspond to an example of a "control means," the "external environment recognition unit 11" corresponds to an example of an "estimation means," and the "braking device 30" corresponds to an example of a "deceleration means." In the above-mentioned embodiment, the "jerk when jerk suppression is being implemented" corresponds to an example of a "first change amount," and the "jerk when jerk suppression is not being implemented" corresponds to an example of a "second change amount."

[0056] In the driving assistance device, the estimation means may determine whether or not the host vehicle is in a predetermined turning state using a sensor that detects the motion state of the host vehicle, as at least part of estimating that deceleration by the deceleration means will cause the behavior of the host vehicle to become unstable, and the control means may change the deceleration by the first change amount when automatically decelerating the host vehicle if it is determined that the host vehicle is in the predetermined turning state, which is the case when it is estimated that the behavior of the host vehicle will become unstable.

[0057] In the driving assistance device, the estimation means' estimating that deceleration by the deceleration means will cause the behavior of the vehicle to become unstable may include estimating the conditions of the road surface on which the vehicle is traveling, and the estimation means may determine that deceleration by the deceleration means will cause the behavior of the vehicle to become unstable based on any one of (i) whether or not a friction coefficient of the road surface, as the road surface condition, is below a predetermined value, (ii) whether or not a predetermined weather condition is present, or (iii) whether or not a curve is present ahead of the vehicle.

[0058] A driving assistance method according to one embodiment of the invention is a driving assistance method in a driving assistance device that automatically decelerates the host vehicle using a deceleration means of the host vehicle depending on a relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle, and when automatically decelerating the host vehicle, changes the deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount, and includes an estimation step of estimating that deceleration by the deceleration means will cause behavior of the host vehicle to become unstable, and a control step of changing the deceleration by the first change amount when automatically decelerating the host vehicle if it is estimated in the estimation step that the behavior of the host vehicle will become unstable.

[0059] In the driving assistance method, the estimation step may estimate that deceleration by the deceleration means will cause the behavior of the host vehicle to become unstable, and a sensor that detects the motion state of the host vehicle may determine whether the host vehicle is in a predetermined turning state, and in the control step, when it is determined that the host vehicle is in the predetermined turning state, which is a case in which it is estimated that the behavior of the host vehicle will become unstable, the deceleration may be changed by the first change amount when automatically decelerating the host vehicle.

[0060] In the driving assistance method, the estimation process may include estimating the condition of the road surface on which the vehicle is traveling, and the estimation process may determine that deceleration by the deceleration means will cause the behavior of the vehicle to become unstable based on any one of (i) whether a friction coefficient of the road surface, as the road surface condition, is below a predetermined value, (ii) whether a predetermined weather condition is met, or (iii) whether a curve is present ahead of the vehicle.

[0061] A computer program according to one embodiment of the invention causes a computer of a driving assistance device that automatically decelerates a host vehicle using a deceleration means of the host vehicle in accordance with a relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle to function as: a control means that changes the deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount when automatically decelerating the host vehicle; and an estimation means that estimates that deceleration by the deceleration means will cause the behavior of the host vehicle to become unstable.If the estimation means estimates that the behavior of the host vehicle will become unstable, the control means changes the deceleration by the first change amount when automatically decelerating the host vehicle.

[0062] The present invention is not limited to the above-described embodiments, and may be modified as appropriate within the scope that does not contradict the gist or concept of the invention that can be read from the claims and the entire specification. Driving assistance devices and methods, as well as computer programs that involve such modifications, are also included in the technical scope of the present invention. [Explanation of symbols]

[0063] 1...vehicle, 11...external environment recognition unit, 12...preceding vehicle information calculation unit, 13...stable behavior determination unit, 14...required deceleration calculation unit, 15...warning implementation determination unit, 16...jerk suppression implementation determination unit, 17...acceleration control unit, 18...end determination unit, 20...sensor, 30...braking device, 100...driving support device

Claims

1. A driving assistance device that automatically decelerates a host vehicle using a deceleration means of the host vehicle in accordance with a relative relationship between the host vehicle and a preceding vehicle traveling ahead of the host vehicle, a control means for changing a deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount when automatically decelerating the host vehicle; an estimation means for estimating that a behavior of the host vehicle will become unstable due to deceleration by the deceleration means; Equipped with When the estimation means estimates that the behavior of the host vehicle will become unstable, the control means changes the deceleration by the first change amount when automatically decelerating the host vehicle, The estimation means determines whether or not a predetermined curve having a curvature that causes the behavior of the host vehicle to become unstable when a braking force is applied to the host vehicle is present ahead of the host vehicle; When the predetermined curve exists ahead of the host vehicle, the estimation means estimates that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means. A driving assistance device comprising:

2. the estimation means determines, by a sensor that detects a motion state of the host vehicle, whether or not the host vehicle is in a predetermined turning state in which a behavior of the host vehicle becomes unstable when a braking force is applied to the host vehicle; When the host vehicle is in the predetermined turning state, the estimation means estimates that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means.

2. The driving support device according to claim 1 .

3. the estimation means determines whether or not a friction coefficient of a road surface on which the host vehicle is traveling is equal to or less than a predetermined value at which a behavior of the host vehicle becomes unstable when a braking force is applied to the host vehicle; When the friction coefficient is equal to or less than the predetermined value, the estimation means estimates that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means.

3. A driving assistance device according to claim 1 or 2.

4. A driving assistance method for a driving assistance device, comprising: automatically decelerating a host vehicle using a deceleration means of the host vehicle according to a relative relationship between the host vehicle and a preceding vehicle traveling ahead of the host vehicle; and, when automatically decelerating the host vehicle, changing a deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount, comprising: an estimation step of estimating that a behavior of the host vehicle will become unstable due to deceleration by the deceleration means; a control step of changing the deceleration by the first change amount when automatically decelerating the host vehicle when it is estimated in the estimation step that the behavior of the host vehicle will become unstable; Including, In the estimation step, it is determined whether or not a predetermined curve having a curvature that makes the behavior of the host vehicle unstable when a braking force is applied to the host vehicle is present ahead of the host vehicle; When the predetermined curve is present ahead of the host vehicle, it is estimated in the estimating step that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means. A driving assistance method comprising:

5. In the estimation step, a sensor that detects a motion state of the host vehicle is used to determine whether or not the host vehicle is in a predetermined turning state in which a behavior of the host vehicle becomes unstable when a braking force is applied to the host vehicle; When the host vehicle is in the predetermined turning state, it is estimated in the estimation step that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means. The driving assistance method according to claim 4 .

6. In the estimation step, it is determined whether or not a friction coefficient of a road surface on which the host vehicle is traveling is equal to or less than a predetermined value at which a behavior of the host vehicle becomes unstable when a braking force is applied to the host vehicle; When the friction coefficient is equal to or less than the predetermined value, it is estimated in the estimation step that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means.

6. The driving support method according to claim 4 or 5.

7. a computer of a driving support device that automatically decelerates the host vehicle using a deceleration means of the host vehicle in accordance with a relative relationship between the host vehicle and a preceding vehicle traveling in front of the host vehicle, a control means for changing a deceleration of the host vehicle by a first change amount or a second change amount greater than the first change amount when automatically decelerating the host vehicle; an estimation means for estimating that a behavior of the host vehicle will become unstable due to deceleration by the deceleration means; Functioning as a When the estimation means estimates that the behavior of the host vehicle will become unstable, the control means changes the deceleration by the first change amount when automatically decelerating the host vehicle, The estimation means determines whether or not a predetermined curve having a curvature that causes the behavior of the host vehicle to become unstable when a braking force is applied to the host vehicle is present ahead of the host vehicle; When the predetermined curve exists ahead of the host vehicle, the estimation means estimates that the behavior of the host vehicle will become unstable due to deceleration by the deceleration means. A computer program comprising:

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