System and method for determining a collision risk situation of an autonomous vehicle

Abstract

Method for determining a risk situation of a collision of an autonomous vehicle, comprising: Detecting a preceding vehicle by a sensor unit (10) located in front of a traveling vehicle (S10) and measuring a variable factor having a distance or a relative speed between the traveling vehicle and the preceding vehicle (S20); Determining, by a controller, whether it is possible to avoid the collision with the preceding vehicle by turning a traveling direction by the traveling vehicle based on the variable factor, and determining whether it is possible to avoid the collision with the preceding vehicle by braking by the traveling vehicle based on the variable factor; and Determination of a risk situation by the control system if the collision is unavoidable due to steering or braking (S30), wherein determining whether it is possible to avoid the collision by steering comprises determining by the controller that the collision is unavoidable by steering when γreq > γmax (S315), where γreq is a yaw rate requirement required for the moving vehicle to avoid collision with the preceding vehicle, and γmax is a yaw rate limit obtained by turning the traveling direction of the moving vehicle on a road surface on which the moving vehicle is located, and wherein determining whether it is possible to avoid the collision by steering further comprises: Calculating the γmax by the controller based on a friction coefficient of the road surface on which the traveling vehicle is driven and a speed of the traveling vehicle (S311); Calculating θreq and γreq by the controller (S313); and Comparing a value of ymax with a value of γreq by the controller, where θreq is a lateral angle requirement required for the moving vehicle to avoid collision with the vehicle in front.

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a system and a method for determining a collision risk situation of an autonomous vehicle for preventing a collision between a moving autonomous vehicle and a preceding vehicle, and in particular to a method for determining a collision risk situation of an autonomous vehicle which takes into account situations in which a collision cannot be prevented by steering or braking. Description of the state of the art

[0002] An autonomous vehicle is a vehicle that recognizes a road and drives automatically without driver control of a brake, steering wheel, accelerator pedal, etc. A device and algorithm are developed to recognize a driving environment for safe driving, generate a driving path, detect an obstacle or a vehicle ahead, and avoid a collision with the obstacle or the vehicle ahead. However, an autonomous vehicle has limitations in recognizing a risky situation and determining whether emergency braking is necessary without relying on a human's decision-making ability in a situation where a driver is not in the vehicle.

[0003] A technology developed in the prior art teaches a method and an apparatus for determining an emergency braking situation of a vehicle and provides a method and an apparatus for determining an emergency braking situation of an autonomous vehicle by calculating a risk index in a risk index calculation unit based on an obstacle detected by a sensor unit, correcting the risk index by a risk index correction unit, and determining whether emergency braking is required.

[0004] However, in the current technology, the risk index calculation only detects a situation where a collision with a vehicle ahead can be avoided by braking, and the risk index correction process is performed under the assumption that a collision can be avoided by braking. Thus, an accident cannot be prevented in an area where a collision cannot be avoided by braking.

[0005] Furthermore, DE 10 2013 224 508 A1 discloses a method and a device for automatically assessing the risk of collision between a vehicle and an object, wherein this assessment comprises the automatic determination of at least one risk value characteristic of the collision risk, based at least on the relative position and the relative speed between the vehicle and the object.A first hazard value (BTN) is determined based on the current distance of the vehicle from a last possible braking position in which a collision of the vehicle with the object can be avoided by braking the vehicle, and a second hazard value (STN) is determined based on the current distance of the vehicle from a last possible avoidance position in which a collision of the vehicle with the object can be avoided by steering the vehicle, whereby the assessment of the collision risk is based on the first hazard value (BTN) and the second hazard value (STN).

[0006] DE 10 2013 225 769 A1 further describes a device and a method for preventing a collision with a vehicle. Information required to calculate the time until a collision is collected. This information includes a distance and / or a relative speed. Furthermore, a braking avoidance section, in which the collision with a vehicle ahead is avoided by braking, and a steering avoidance section, in which the collision with a vehicle ahead is avoided by steering, are calculated. PRESENTATION OF THE INVENTION

[0007] It is an object of the present invention to provide a method and a system for determining a risk situation of a collision with an autonomous vehicle, which takes into account an area in which a collision with a vehicle in front is unavoidable by changing a direction of travel of a moving vehicle by steering or by reducing a speed of a moving vehicle by braking as a risk situation.

[0008] According to the present invention, a method and a system for determining a collision risk situation of an autonomous vehicle provide the features in patent claims 1 and 6, respectively. Embodiments of the invention are found in the subclaims.

[0009] The method comprises: detecting a preceding vehicle located in front of a moving vehicle by a sensor unit and measuring a variable factor representing a distance or a relative speed between the moving vehicle and the preceding vehicle;and determining whether it is possible to avoid a collision by steering, wherein a risk situation determining unit determines whether it is possible to avoid the collision with the preceding vehicle by turning a traveling direction by the traveling vehicle based on the variable factor, or determining whether it is possible to avoid the collision by braking, wherein the risk situation determining unit determines whether it is possible to avoid the collision with the preceding vehicle by braking by the traveling vehicle based on the variable factor, in which, when it is impossible to avoid the collision by steering or braking, the risk situation determining unit determines the situation as a risk situation.;

[0010] The process of determining whether it is possible to avoid the collision by steering includes determining, by the risk situation determination unit, that it is impossible to avoid the collision by steering when γreq > γmax (γreq is a yaw rate requirement required for the traveling vehicle to avoid the collision with the preceding vehicle, and γmax is a yaw rate limit obtained by turning the traveling direction of the traveling vehicle on a road surface on which the traveling vehicle is located).

[0011] The process of determining whether it is possible to avoid the collision by braking may include determining by the risk situation determination unit that it is impossible to avoid the collision by braking when Sreq <Sbrk ist, aufweisen (Sreq ist eine Distanzanforderung, die erforderlich ist, um durch das fahrende Fahrzeug die Kollision mit dem vorausfahrenden Fahrzeug zu vermeiden, und Sbrk ist eine Bewegungsdistanz, nachdem das fahrende Fahrzeug das Bremsen ausgeführt hat).

[0012] The process of determining whether it is possible to avoid the collision by steering further includes: calculating the ymax by a calculation unit based on a friction coefficient of the road surface on which the traveling vehicle is driven and a speed of the traveling vehicle; calculating θreq (θreq is a lateral angle requirement required for the traveling vehicle to avoid the collision with the preceding vehicle) and calculating γreq; and comparing a value of ymax with a value of γreq by the risk situation determination unit.

[0013] In addition, the process of determining whether it is possible to avoid the collision by braking may include: calculating the Sreq based on the distance by a calculation unit; calculating Sbrk by the calculation unit based on the relative speed and a time change until the collision calculated based on the relative speed; and comparing a value of the Sreq with a value of the Sbrk by the risk situation determination unit.

[0014] Calculating γreq may further include: calculating a time change until the collision based on the distance and the relative speed by the calculation unit; and correcting the time change by reflecting state information related to the traveling vehicle by a correction unit, and the state information related to the traveling vehicle may be at least one of the speed of the traveling vehicle, a speed of the preceding vehicle, and the friction coefficient of the road surface on which the traveling vehicle is located.Calculating the Sreq may further comprise correcting the distance by reflecting state information regarding the traveling vehicle by a correction unit, and the state information regarding the traveling vehicle may be the speed of the traveling vehicle and / or a speed of the preceding vehicle and / or the friction coefficient of the road surface.

[0015] According to the present invention including the above configuration, a situation in which it is impossible to avoid a collision by steering or braking is determined, and thus an accident risk of an autonomous vehicle can be reduced. Further, according to the present invention, when a risk situation is determined, a time and a distance to an actual collision can be corrected to ensure driving stability. Furthermore, according to the present invention, when a risk situation is determined, a condition of a road surface on which a moving vehicle is traveling is taken into account, and thus the accuracy in determining the risk situation can be improved. SHORT DESCRIPTION OF THE CHARACTERS

[0016] The above and other features of the present invention will now be described in detail with reference to exemplary embodiments thereof shown in the accompanying drawings, which are given below by way of illustration only and thus do not limit the present invention, and in which: Fig. 1 is a diagram illustrating a system for determining a collision risk situation of an autonomous vehicle according to an exemplary embodiment of the present invention; Fig. 2 is a diagram illustrating a method for determining a collision risk situation of an autonomous vehicle according to an exemplary embodiment of the present invention; Fig. 3 is a diagram illustrating behavior of an autonomous vehicle and a preceding vehicle according to an exemplary embodiment of the present invention; Fig. 4 is a flowchart illustrating a risk situation determination process in which steering avoidance or braking avoidance is performed according to an exemplary embodiment of the present invention; Fig. 5 is a flowchart illustrating a process for calculating a yaw rate request γreq according to an exemplary embodiment of the present invention; and Fig. 6 is a flowchart illustrating a process for calculating a distance request Sreq according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] It is to be understood that the term "vehicle" or "commuter" or other similar term, as used herein, includes motor vehicles in general, such as passenger cars including sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from sources other than petroleum). A hybrid vehicle, as referred to herein, is a vehicle that has two or more power sources, for example, both gasoline-powered and electric-powered vehicles.

[0018] Although an example embodiment is described as using a plurality of units to perform the example process, it is understood that the example processes may also be performed by one or more modules. Furthermore, it is understood that the term controller / controller refers to a hardware device that includes a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more processes described further below.

[0019] Furthermore, the control logic of the present invention may be embodied as a non-transitory computer-readable medium on a computer-readable medium containing executable program instructions executed by a processor, controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, CD-ROMs, magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable recording medium may also be distributed in network-coupled computer systems such that the computer-readable medium is stored and executed in a distributed manner, e.g., through a telematics server or a controller area network (CAN).

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” “an,” and “the” are intended to include the plural, unless the context clearly indicates otherwise. It is further understood that the terms “comprising” and / or “having,” when used in this specification, indicate the presence of the specified features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any or all combinations of one or more of the associated listed elements.

[0021] Unless expressly stated herein or obvious from the context, the term "approximately" is understood within a range of normal tolerance, for example, within 2 standard deviations of the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless the context otherwise indicates, all numerical values stated herein are modified by the term "approximately."

[0022] The present invention will be described in detail below with reference to the contents described in the accompanying drawings. However, the present invention is not limited to exemplary embodiments. The same reference numerals provided in each drawing denote elements that perform substantially the same functions.

[0023] The object and effect of the present invention can be naturally understood or can become clearer from the following description, and the object and effect of the present invention are not limited to the following description. In the description of the present invention, a detailed explanation of a publicly known technology related to the present invention may be omitted to avoid unnecessarily obscuring the subject matter of the present invention.

[0024] Fig. 1 illustrates a system 100 for determining a collision risk situation of an autonomous vehicle of the present invention. Referring to Fig. 1, the system 100 for determining a collision risk situation of an autonomous vehicle of the present invention may include a sensor unit 10, a calculation unit 20, a correction unit 30, or a risk situation determination unit 40. The vehicle may be configured to operate any of the units of the system.

[0025] The sensor unit 10 may be configured to acquire driving environment information of a traveling vehicle based on image information, laser detection information, received radar information, and the like, using a device such as a camera, a laser scanner, and a radar. However, the device included in the sensor unit 10 is not limited to this and may include any sensors that can detect an environment around a vehicle. The calculation unit 20 may be configured to execute a series of calculation processes for determining a collision risk situation of an autonomous vehicle based on an equation specification based on the driving environment information of the traveling vehicle acquired by the sensor unit 10, and derive a result value for determining the collision risk situation of the autonomous vehicle.In particular, the calculation unit 20 can be operated by a controller of the system.

[0026] The correction unit 30 may be configured to correct a change in time until the collision and a distance to the collision by detecting the driving environment information, such as a speed of the traveling vehicle, a speed of the preceding vehicle, or a friction coefficient of a road on which the traveling vehicle is traveling, from the sensor unit 10 during the process of deriving the result value by the calculation unit 20, thereby improving the accuracy of determining the risk situation. The risk situation determination unit 40 may be configured to receive the information from the sensor unit 10, the calculation unit 20, or the correction unit 30 and determine whether the traveling vehicle can avoid the collision with the preceding vehicle.

[0027] The method for transmitting the information by the sensor unit 10, the calculation unit 20, the correction unit 30 or the risk situation determination unit 40 may be carried out by a communication method such as CAN (Controller Area Network) communication, but is not limited thereto. Fig. 2 is a diagram illustrating a method for determining a collision risk situation of an autonomous vehicle of the present invention.

[0028] Referring to Fig. 2, the sensor unit 10 may be configured to detect a preceding vehicle located in front of a traveling vehicle or a subject vehicle (S10), and then measure a distance or a relative speed between the traveling vehicle and the preceding vehicle, which is a variable factor of the vehicle (S20). The risk situation determination unit 40 may then be configured to perform a risk situation determination operation S30 by determining whether the traveling vehicle is able to avoid the collision with the preceding vehicle by turning a traveling direction based on the variable factor, or by determining whether the traveling vehicle can avoid the collision with the preceding vehicle by braking based on the variable factor.If the collision is unavoidable due to the steering or braking of the vehicle, the risk situation determination unit 40 may be configured to determine the situation as a risk situation.

[0029] Fig. 3 is a diagram illustrating behavior of an autonomous vehicle and a preceding vehicle of the present invention. Referring to Fig. 3, a variable factor measured by the sensor unit 10 can be used to determine a risk situation of a collision with an autonomous vehicle of the present invention. Specifically, V represents a speed of a traveling vehicle, VF represents a speed of a preceding vehicle, W is a road width, W' is a width of the preceding vehicle, and ΔS represents a distance between the traveling vehicle and the preceding vehicle. The above V, VF, W, W', and ΔS can be measured by various sensor devices, such as a camera device and a wheel speed sensor of the sensor unit 10.

[0030] Fig. 4 is a flowchart illustrating the risk situation determination operation S30 of the present invention in which steering avoidance or braking avoidance is performed. Referring to Fig. 4, the risk situation determination unit 40 may be configured to determine whether it is possible to avoid the collision by turning and to determine whether it is possible to avoid the collision by braking regardless of the order, and when it is impossible to perform either of the prevention by steering and the prevention by braking, the risk situation determination unit 40 may be configured to determine the situation as a risk situation (S300).

[0031] When determining whether it is possible to avoid the collision by steering, the risk situation determination unit 40 may be configured to determine that the collision by steering is unavoidable if γreq>ymax. Specifically, γreq represents a yaw rate requirement required for the traveling vehicle to avoid collision with the preceding vehicle, and γmax represents a yaw rate limit that can be obtained by turning a traveling direction of the traveling vehicle on a road surface on which the traveling vehicle is located. Specifically, γmax can be calculated by the following Equation 1. γmax=μgV where µ is a friction coefficient of a road surface on which the moving vehicle is driven, g is the acceleration due to gravity and V is the speed of the moving vehicle.

[0032] Determining whether it is possible to avoid the collision by steering may further include process S311 of calculating ymax by the calculation unit 20 with Equation 1 based on a friction coefficient of the road surface on which the traveling vehicle is traveling and a speed of the traveling vehicle, process S313 of calculating θreq and calculating γreq by the calculation unit 20, and process S315 of comparing a value of γmax with a value of γreq (γreq>ymax) by the risk situation determination unit. Specifically, θreq means a lateral angle requirement required for the traveling vehicle to avoid the collision with the preceding vehicle and can be calculated by the following Equation 2. θreq=tan−1(wΔS)

[0033] Referring to Fig. 3, a value of a lateral angle requirement θreq required for the traveling vehicle to avoid collision with the preceding vehicle can be calculated as described below. Specifically, the value of θreq can be calculated using the vehicle width W' of the preceding vehicle and an arctangent value of the distance ΔS between the traveling vehicle and the preceding vehicle, but the value of θreq can be set larger than a deviation angle required to avoid collision by increasing the value of the arctangent result value. This is for safety by setting the lateral angle requirement required to avoid collision with a larger margin than the actually required avoidance angle.

[0034] Accordingly, the value of θreq can be calculated using the road width W greater than W', or it can be calculated using a value between W' and W. In addition, γreq can be calculated by Equation 3 below using the value of θreq. γreq=θreqt=θreqΔt−TSM,(Δt=ΔSΔV),(ΔV=|V−VF|) where t is a time for collision, and TSM is a time for the safety distance to avoid time change, which is corrected by reflecting state information regarding the traveling vehicle, which will be described below. In other words, when γreq calculated by reflecting a current traveling situation measured by the sensor unit 10 is greater than γmax, which is a maximum yaw rate achievable by a linear behavior of the traveling vehicle under a current road surface condition, the traveling vehicle may be determined that it is not possible to avoid the collision with the preceding vehicle by the linear behavior by turning the traveling direction under the current road surface condition, and thus the risk situation determining unit 40 may be configured to determine the situation as a risk situation (S317).

[0035] When determining whether it is possible to avoid a collision by braking, the risk situation determination unit 40 may be configured to determine that a collision by braking is unavoidable when Sreq < Sbrk. Sreq is a distance requirement required for the traveling vehicle to avoid a collision with the preceding vehicle, and Sbrk refers to a moving distance after the traveling vehicle performs braking. Specifically, Sreq and Sbrk can be calculated by the following equations 4 and 5. sreq=ΔS−DSM sbrk=|ΔV|×Δt−12μg×Δt2 where DSM is a distance for a safety margin to avoid time change being corrected by reflecting state information regarding the moving vehicle, which will be described below.

[0036] Determining whether it is possible to avoid the collision by braking may further include: process S321 for calculating Sreq by the calculation unit 20 based on the distance; process S323 for calculating Sbrk by the calculation unit 20 based on the relative speed and a time change until the collision calculated based on the relative speed; and process S325 for comparing the value of Sreq and the value of Sbrk (Sreq <Sbrk) durch die Risikosituationsbestimmungseinheit 40.

[0037] In other words, when the moving distance Sbrk after the braking of the traveling vehicle under the current road surface condition is greater than the distance Sreq calculated by reflecting the current driving situation measured by the sensor unit 10, which is required to avoid the collision, it can be determined that the collision with the preceding vehicle is unavoidable due to the braking by the traveling vehicle under the current road surface condition, and thus the risk situation determining unit 40 can be configured to determine the situation as a risk situation (S317).

[0038] As a result, both the process of determining whether it is possible to avoid the collision by steering and the process of determining whether it is possible to avoid the collision by braking can be performed, and therefore, in response to determining that either of the avoidance by steering and the avoidance by braking is impossible, the risk situation determining unit 40 can be configured to determine the situation as the risk situation (S317), and the routine of the present invention can be terminated.

[0039] Although not shown in the drawings, the present invention may further include a mechanism for dealing with a situation in which it is impossible to avoid the collision by the steering or a general braking method after the method for determining a collision risk situation of an autonomous vehicle of the present invention is terminated.

[0040] Fig. Figure 5 is a flowchart illustrating the process S313 for calculating a yaw rate request of the present invention. The method described herein may be executed by a controller. Referring to Fig. 5, the process for calculating γreq may further include: process S3131 for acquiring state information regarding the traveling vehicle by the sensor unit 10; process S3133 for calculating a time change until the collision by the calculation unit 20 based on the distance and the relative speed; and process S3135 for correcting the state information regarding the traveling vehicle and correcting the time change by the correction unit 30.

[0041] The state information regarding the traveling vehicle may be, but is not limited to, the speed of the traveling vehicle and / or the speed of the preceding vehicle and / or the friction coefficient of the road surface. The state information regarding the traveling vehicle may further include the weight of the vehicle, a speed of the vehicle, a tire pressure, a brake pressure, and the like according to a device attached to the sensor unit 10. The state information regarding the traveling vehicle may be stored in the risk situation determination unit 40 as variable data 40. Specifically, γreq can be calculated by the following equation as described above. γreq=θreqt=θreqΔt−TSM,(Δt=ΔSΔV)

[0042] In particular, TSM can be adjusted by the variable data, and a value of Δt expected to be taken until the actual collision is corrected, and it is calculated that γreq is larger than a yaw rate required to actually avoid the collision to ensure safety.

[0043] Fig. 6 illustrates the process S321 for calculating the distance requirement of the present invention. Referring to Fig. 6, the process for calculating Sreq may further include a process S3211 for acquiring state information regarding the traveling vehicle by the sensor unit 10; and a process S3213 for reflecting the state information regarding the traveling vehicle and correcting the distance by the correction unit 30. Sreq may be calculated by the equation described above. sreq=ΔS−DSM

[0044] Specifically, DSM can be adjusted by the same method as that of TMS, and a value of ΔS for the actual collision is corrected, and Sreq is calculated to be smaller than a distance required to actually avoid the collision to ensure safety.

Claims

[1] A method for determining a risk situation of a collision of an autonomous vehicle, comprising: Detecting a preceding vehicle by a sensor unit (10) located in front of a moving vehicle (S10) and measuring a variable factor having a distance or a relative speed between the moving vehicle and the preceding vehicle (S20); Determining, by a controller, whether it is possible to avoid the collision with the preceding vehicle by turning a traveling direction by the traveling vehicle based on the variable factor, and determining whether it is possible to avoid the collision with the preceding vehicle by braking by the traveling vehicle based on the variable factor; and Determination of a risk situation by the control system if the collision is unavoidable due to steering or braking (S30), wherein determining whether it is possible to avoid the collision by steering comprises determining by the controller that the collision is unavoidable by steering when γreq > γmax (S315), where γreq is a yaw rate requirement required for the moving vehicle to avoid collision with the preceding vehicle, and γmax is a yaw rate limit obtained by turning the traveling direction of the moving vehicle on a road surface on which the moving vehicle is located, and wherein determining whether it is possible to avoid the collision by steering further comprises: Calculating the γmax by the controller based on a friction coefficient of the road surface on which the traveling vehicle is driven and a speed of the traveling vehicle (S311); Calculating θreq and γreq by the controller (S313); and Comparing a value of ymax with a value of γreq by the controller, where θreq is a lateral angle requirement required for the moving vehicle to avoid collision with the preceding vehicle. [2] The method according to claim 1, wherein determining whether it is possible to avoid the collision by braking comprises determining by the controller that the collision is unavoidable by braking when Sreq < Sbrk (S325), where Sreq is a distance requirement required for the moving vehicle to avoid collision with the preceding vehicle, and Sbrk is a moving distance after the moving vehicle has performed braking. [3] The method according to claim 1 or 2, wherein determining whether it is possible to avoid the collision by braking further comprises: Calculating the Sreq by the controller based on the distance (S321); Calculating Sbrk by the controller based on the relative speed and a time change until the collision calculated based on the relative speed (S323); and Comparing a value of Sreq with a value of Sbrk by the controller (S325). [4] The method according to any one of the preceding claims, wherein calculating the γreq (S313) further comprises: Calculating a time change until the collision based on the distance and the relative speed by the controller (S3133); and Correcting the time change by the controller by reflecting status information regarding the moving vehicle (S3135), wherein the state information regarding the moving vehicle is the speed of the moving vehicle and / or a speed of the preceding vehicle and / or the friction coefficient of the road surface. [5] The method of claim 3 or 4, wherein calculating the Sreq (S321) further comprises: Correcting the distance by the controller by reflecting status information regarding the moving vehicle (S3213), wherein the state information relating to the moving vehicle is the speed of the moving vehicle and / or the speed of the preceding vehicle and / or the friction coefficient of the road surface on which the moving vehicle is driven. [6] System for determining a risk situation of a collision of an autonomous vehicle, the system comprising: a sensor unit (10) configured to detect a preceding vehicle located in front of a traveling vehicle and configured to measure a variable factor comprising a distance or a relative speed between the traveling vehicle and the preceding vehicle; and a control system that is designed to determine whether it is possible to avoid the collision with the preceding vehicle by changing a direction of travel by the preceding vehicle based on the variable factor, and to determine whether it is possible to avoid the collision with the preceding vehicle by braking by the preceding vehicle based on the variable factor; and to determine a risk situation when the collision is unavoidable due to steering or braking, wherein the controller is configured to determine that the collision is unavoidable by the steering when γreq > γmax, where γreq is a yaw rate requirement required to avoid the collision with the preceding vehicle by the traveling vehicle, and ymax is a yaw rate limit obtained by turning the traveling direction of the traveling vehicle on a road surface on which the traveling vehicle is driven, and wherein the control is further configured: ymax based on a friction coefficient of the road surface on which the moving vehicle is driven and a speed of the moving vehicle; to calculate θreq and γreq; and to compare a value of γmax with a value of γreq, where θreq is a lateral angle requirement required for the moving vehicle to avoid collision with the preceding vehicle. [7] The system according to claim 6, wherein the controller is configured to determine that the collision is unavoidable by the braking when Sreq < Sbrk, where Sreq is a distance requirement required to avoid the collision by the running vehicle with the preceding vehicle, and Sbrk is a moving distance after the running vehicle has performed the braking. [8] System according to claim 6 or 7, wherein the controller is further configured: calculate the Sreq based on the distance; Calculate Sbrk based on the relative velocity and a time change until the collision calculated based on the relative velocity; and to compare a value of Sreq with a value of Sbrk. [9] System according to one of claims 6 to 8, wherein in the calculation of the γreq the control is further configured: to calculate a time change until the collision based on the distance and the relative speed; and to correct the temporal change by reflecting status information regarding the moving vehicle, wherein the state information regarding the traveling vehicle is the speed of the traveling vehicle and / or a speed of the preceding vehicle and / or the friction coefficient of the road surface. [10] System according to claim 8 or 9, wherein in calculating the Sreq the controller is further configured: to correct the distance by reflecting status information regarding the moving vehicle, wherein the state information regarding the moving vehicle is the speed of the moving vehicle and / or the speed of the preceding vehicle and / or the friction coefficient of the road surface on which the moving vehicle is driven.

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