Unified method for quantifying driving risks by comprehensively considering each element of people, vehicles, and roads

Abstract

The steps of obtaining an initial driving safety field model of driving risk according to the energy transfer principle, decomposing the initial driving safety field model in the longitudinal direction and the lateral direction, and creating a unified driving safety field model based on the information of vehicle j and traffic environment information, and calculating the field force F by vehicle j to any position point i in the traffic environment where vehicle j is located. ji and calculating the field force F ji and recognizing the driving risk that point i receives due to the influence of vehicle j based on the above. Based on the fact that driving risk is determined by the comprehensive interaction between the various elements that affect driving safety, the method proposes a unified modeling concept for the driving safety field that can accurately reflect the interaction relationship between each vehicle in the road traffic environment.

Description

[Technical field]

[0001] The present invention relates to the technical field of smart car use, and in particular to a unified method for quantifying driving risks by comprehensively considering the factors of people, vehicles, and roads. [Background technology]

[0002] Quantifying driving risk is the basis for developing driving safety assistance technology and autonomous driving technology. Previous studies usually use parameters describing collisions to quantify driving risk, and mainly include risk assessment methods based on accident analysis, vehicle kinematics, and artificial potential energy fields. Research on smart safety technology for automobiles has already entered a period of high growth. Overall, driving risk assessment can be divided into two categories: 1) one-dimensional driving risk assessment, which is the assessment of risk in the longitudinal direction and longitudinal risk while the vehicle is moving, and 2) two-dimensional driving risk assessment, which considers both the longitudinal and lateral directions while the vehicle is moving.

[0003] Although scholars at home and abroad have done a lot of research on driving risk assessment, there are still many shortcomings. Usually, the driving risk assessment method of vehicle driving angle is based on vehicle state information and relative motion relationship information between the two vehicles, and a risk assessment model is constructed by vehicle kinematics and dynamics theory. Meanwhile, a new method represented by artificial potential energy field is adopted. Although the two methods have their own advantages, they both have common defects, namely, the risk factors considered are not comprehensive, the application scenario is single, and they cannot cope with the complex and changing traffic environment, so the same smart car requires multiple independent risk assessment models. In addition, they ignore the impact of the driver's own physiological and psychological characteristics, road and traffic environment factors, etc. on driving risk, and the risk occurrence mechanism between the person, vehicle, and road has not been fully studied, so the practical use of the traditional method is relatively limited.

[0004] In order to improve the scientific, time-effective and accurate nature of driving risk assessment, it is necessary to construct an initial driving safety field model of the risk that a vehicle poses to the outside world based on the kinetic energy of the vehicle while it is moving, and propose a driving risk description method based on quantum field theory by analyzing the mutual influence relationship between each element in the traffic environment, taking into account the vehicle's driving viewing angle, quantitatively describing the driving risk from the perspective of traffic management, and analyzing the impact of each attribute of the traffic environment, the establishment of road traffic facilities and the driver's behavior on driving safety, and propose to form a comprehensive driving risk unified form that simultaneously considers the attributes of the vehicle itself and the interaction in the traffic flow, and build a unified driving safety field model that reflects the interactive relationship between people, vehicles and roads. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a unified method for quantifying driving risk that comprehensively takes into account each of the elements of pedestrians, vehicles, and roads in order to solve or reduce at least one of the above-mentioned shortcomings of the prior art. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides: According to the principle of energy transfer, an initial driving safety field model of the driving risk is obtained as shown in formula (3); the initial driving safety field model is decomposed in the longitudinal direction and the lateral direction, and a first unified driving safety field model is generated as shown in formula (69) or a second unified driving safety field model is generated as shown in formula (74) based on the information of the vehicle j and the traffic environment information; and a field force F by the vehicle j to any position point i of the traffic environment where the vehicle j is located is calculated. ji and calculating the field force F ji and recognizing the driving risk that point i is subject to due to the influence of vehicle j based on JPEG0007671078000001.jpg77170

[0007] In the above formula, x ji represents the longitudinal distance of vehicle j from any point i in the environment, and y ji represents the lateral distance of vehicle j from point i, r0 represents the headway distance of the driver of vehicle j, and r max represents the maximum separation between vehicles in the free flow, and r min represents the minimum separation between vehicles in the free flow, i.e., the distance between the center of mass of vehicle j and the position point i when a collision occurs, and E j is the speed of vehicle j, v j The kinetic energy E is determined by j,0 and the relative kinetic energy determined by multiple traffic environment factors, E j,fac is the kinetic energy E j,0 and the relative kinetic energy determined by traffic environment elements, including road surface friction coefficient, road curvature, road inclination, environmental visibility, lane and road speed limit rules; if any of the speed of vehicle j and the traffic environment elements is ignored, the value of the kinetic energy corresponding to the element is 0; k x is the product of the speed of vehicle j and the longitudinal slope adjustment coefficient of each of the traffic environment elements, and k x,fac represents the speed of vehicle j and the longitudinal gradient adjustment coefficient of each of the traffic environment elements, and k y is the product of the speed of vehicle j and the lateral slope adjustment coefficient of each of the traffic environment elements, and k y,fac represents the speed of vehicle j and the lateral gradient adjustment coefficient of each of the traffic environment elements, and when any of the speed of vehicle j and the traffic environment elements is ignored, a unified quantification method for driving risk is provided that comprehensively takes into account each of the pedestrian-vehicle-road elements, in which the value of the gradient adjustment coefficient corresponding to the element is 1. Effect of the Invention

[0008] The present invention has the following advantages by adopting the above technical proposal. 1. The present invention proposes a driving safety field modeling method that takes into account the influence of driving risks caused by people, cars, and roads in a road traffic environment, and can accurately reflect the interaction relationship between each vehicle in the road traffic environment, and organically combines the vertical and horizontal risks during vehicle driving in the form of a field, and not only converts the vertical and horizontal risks from the discrete form in the traditional method to a continuous form, but also visualizes and displays them in the form of a risk distribution map. 2. The present invention improves the accuracy of the description of the interrelationship between vehicles while ensuring the continuity of risk distribution. 3. The present invention provides a method for quantifying driving risks, which can identify driving risks in advance and take corresponding safety measures to prevent traffic accidents from occurring. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of the relationship between field forces and potential energy in a traffic environment. [Diagram 2] FIG. [Diagram 3] FIG. 1 is a schematic diagram showing a state in which a vehicle j is normally traveling within a lane. [Figure 4] FIG. 1 is a schematic diagram showing a state in which a vehicle j is traveling on lane 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described in detail with reference to the drawings and examples.

[0011] The present invention uses the following driving risk field model and the field force F in the traffic environment shown in FIG. ji and potential energy U ji The present invention aims to provide a method for quantifying driving risks, by analyzing the influence of each element of people, vehicles, and roads in a road traffic environment on driving risks based on the relationship between them, thereby ascertaining the mechanism by which driving risks occur, identifying driving risks in advance, taking corresponding safety measures, and preventing the occurrence of traffic accidents.

[0012] As known to those skilled in the art, driving risk does not exist independently, but generally occurs between vehicles and between the vehicle itself and the traffic environment. In order to evaluate the safety state of the traffic environment, in the embodiment of the present invention, the risk is represented by a field, and the driving risk is defined as the field interaction between each research object, which describes the perception of risk in the traffic environment by people, specifically, the risk between two objects in the traffic environment is represented by the field as follows:

[0013] JPEG0007671078000002.jpg14170

[0014] In Equation (1) and Equation (2), j represents a field source, i represents a point in the traffic environment, and U ji represents the potential energy field due to the field source at point i, and in the traffic environment, U ji is the self-attribute M of the field source j j , velocity v j and the distance r between the field source j and point i ji is a function of F ji is the potential energy field U ji is the gradient of the field at point i, i.e., the field force at point i. The negative sign indicates the direction of descent along the field gradient. If the attributes and motion state of field source j are constant, the closer to field source j, the greater the field force F ji is large.

[0015] In the embodiment of the present invention, the field describing the risk in the traffic environment is called the "driving safety field". Let r represent the distance of point i from vehicle j in the traffic environment. The greater the distance of point i from vehicle j, the greater the field force F ji is small, and the potential energy U jiis also small. Compared with the electric field method, when modeling the driving safety field, the model can quantify the driving risk under certain conditions. However, the physical electric field is not particularly suitable for describing the driving risk. For example, in the electric field, the potential energy at an infinite distance is zero, and charged particle A is acted upon by the electric field force of charged particle B at any position other than infinity, except that charged particle A is not acted upon by charged particle B at an infinite distance, and when the distance between charged particle A and charged particle B is infinitesimal, the electric field force between them is infinite. Of course, these two phenomena have no corresponding scenario in traffic. Therefore, for the above problem, in the embodiment of the present invention, a new modeling is carried out on the driving safety field.

[0016] Figure 1 shows the relationship between field force and potential energy. In Figure 1, a curve in the coordinate system represents the field force F that a vehicle j exerts on any point i in the environment. ji represents the risk range, and the induced risk range is bounded by the distance r ji is max That is, r ji ≧r max If , then point i is not acted upon by vehicle j, i.e., F ji = 0. On the other hand, the potential energy U ji Also ji = 0, which corresponds to a scenario in which the distance between vehicles in the traffic environment is large enough that the driver's actions are not influenced by other vehicles (e.g., a free-flow scenario). The distance r between point i and vehicle j satisfies ji As becomes smaller (i.e., r ji <r max ), the field force F ji and potential energy U ji begins to increase, and r ji The smaller is the field force F ji and potential energy U ji is large, but the distance r between point i and vehicle j is ji is min is less than r ji <r min In this case, the field force F jiwill not increase, which corresponds to a scenario where a collision occurs in a traffic environment. In the embodiment of the present invention, the coordinates of the midpoint i and the vehicle j are both calculated as their geometric centers, and the distance between the point i and the vehicle j cannot be 0 because the traffic participants have a certain appearance size. For ease of analysis, r ji is min Field force less than F ji F max Set to.

[0017] The method for quantifying driving risk according to an embodiment of the present invention includes several aspects. (1) Method for quantifying risk to the vehicle itself (1.1) Risk from the perspective of traffic management In the embodiment of the present invention, the initial driving safety field model is simply modified according to FIG. 1 to become a new initial driving safety field model, that is, Equation (3) is obtained. JPEG0007671078000003.jpg14170

[0018] In the formula, E j,0 represents the kinetic energy of vehicle j. ji ∈[0,r min ), then F ji The value of E j,0 r0 is the driver's gaze range for the risk and is related to the driver's following distance. r max is the free flow vehicle headway, which represents the maximum impact of risk and is also called the maximum vehicle headway in free flow. min represents the minimum separation between vehicles in the free stream, i.e., the distance between the center of mass of vehicle j and the position point i when a collision occurs.

[0019] When a driver is driving behind the vehicle in front, he is restricted by the current traffic environment. According to traffic flow theory, the driver's distance r0 can be seen from the relationship between the macro traffic flow rate and flow speed corresponding to the process of driving behind the vehicle in front, as shown in Equation (4). JPEG0007671078000004.jpg14170

[0020] where the driver's overall sharpness is γ, γ∈[-0.03,0]s 2 / m, the mean reaction time is τ, where τ = 1 s, l is the effective vehicle length, where l = 6 m, and v is the flow velocity of the traffic flow.

[0021] According to the Road Traffic Manual, at free flow speed, the maximum value of traffic flow q max satisfies the following formula (5). q max =3100-54v f (5)

[0022] In the formula, v f is the free flow velocity, and therefore the vehicle spacing in the free flow r max is shown as equation (6). JPEG0007671078000005.jpg14170

[0023] As can be seen from FIG. 1 and equation (3), r min is max and the value of r0, according to equation (7). JPEG0007671078000006.jpg14170

[0024] F ji is ji ∈(0,r min )∪(r max , +∞) is a given value, and r ji ∈[r min ,r max ] only if r ji In this example, we mainly focus on the change in r ji ∈[r min ,r max ]The analysis will be performed on the interval.

[0025] When a vehicle j moves freely at a constant speed in a boundary-free environment, if we consider it as a mass point, the vehicle may travel in any direction, so the driving risk caused by the vehicle j in the environment satisfies isotropy in a plane. Therefore, the field force F ji,0 is shown as equation (8). JPEG0007671078000007.jpg14170

[0026] In the formula, x ji represents the distance between vehicle j and any point i in the environment in the longitudinal direction, and y ji represents the distance between vehicle j and point i in the lateral direction.

[0027] Generated driving safety field force F ji,0 The gradient change of is given by equation (9). JPEG0007671078000008.jpg14170

[0028] When the mass and velocity of vehicle j are known, the field force generated by vehicle j at each position in the road traffic environment can be calculated by equation (9). In a spacious road traffic environment, the driving safety field is related only to the distance and has an inverse functional relationship with the distance, and the closer to the vehicle, the greater the driving safety field force experienced.

[0029] In an actual road traffic environment, the movement of a vehicle has a direction, so the risk that a vehicle poses to the outside world is not isotropic. Usually, whether based on human subjective sensation or objective collision probability, during the movement of a vehicle, the risk to the outside world is greater in the positive direction of the movement direction than in the negative direction, and this phenomenon is similar to the Doppler shift effect of waves. The viewpoint that the risk that vehicle j poses to the outside world is greater in the positive direction of the movement direction than in the negative direction of the movement direction may be described as the gradient descent degree of the field force of the driving safety field being related to the vehicle's movement direction, that is, when vehicle j approaches point i, the gradient descent of the field force of the driving safety field becomes gentler, and by setting the longitudinal gradient adjustment coefficient and the lateral gradient adjustment coefficient, the following formula (10) is obtained.

[0030] JPEG0007671078000009.jpg14170

[0031] In the formula, k x,0 represents the longitudinal gradient adjustment coefficient of the speed of vehicle j, and k y,0 is the lateral gradient adjustment factor for the speed of vehicle j. Of course, the parameter kx,0 and k y,0 directly affects the distribution of the driving safety field. In the specification, the "longitudinal direction" corresponds to x and the "lateral direction" corresponds to y. The "positive direction" is the direction in which the vehicle j travels in the direction indicated by the center line of the lane.

[0032] If vehicle j travels in the positive direction of x, then according to the Doppler shift principle, x,0 and k y,0 are defined as follows, respectively: JPEG0007671078000010.jpg42170

[0033] In the formula, x j is the x-coordinate of vehicle j, and v j is the velocity of vehicle j in the x direction, and point i may be another vehicle or another point, and represents a given point in the environment, x i is the given coordinate of the point i in the x direction, and v i = 0, and conversely, if i represents a vehicle, then x i is the x-coordinate of the vehicle, and v i is its speed, and v max is the speed of risk propagation, and the risk that a moving object poses to the outside world is usually related to the attributes of the moving object itself.

[0034] (1.2) Risks from the perspective of vehicle travel When a vehicle is driving in a traffic environment, traffic perturbations occur because the driver responds to stimuli caused by changes in the external traffic environment. Therefore, according to equation (8), from the driver's perspective, the risk that vehicle j receives in the traffic environment is described by the driving safety field as shown in equation (15). JPEG0007671078000011.jpg35170

[0035] JPEG0007671078000012.jpg21170

[0036] It is clear from equation (17) that the calculation formula for the longitudinal slope adjustment coefficient is the same from the traffic control visual angle and the vehicle driving visual angle, but in reality, the vehicle driving visual angle is v i Since is constantly changing, its value differs from the gradient adjustment coefficient in the case of the traffic management angle.

[0037] Similarly, we may analyze the impact of a particular vehicle j in the traffic environment on the entire traffic flow from the traffic flow angle. When the average speed of the vehicle flow of the traffic flow is denoted as,, Equation (11) may be rewritten as follows: JPEG0007671078000013.jpg15170

[0038] JPEG0007671078000014.jpg24170

[0039] (1.3) Overall Driving Risk As can be seen from the analysis of (1.1) and (1.2), there are certain limitations when observing a specific vehicle from either the traffic management angle or the vehicle driving angle. Therefore, in the embodiment of the present invention, the vehicle driving angle is mainly assumed, and the driving risk is quantitatively described from the traffic management angle, and the expression form of the comprehensive driving risk that simultaneously considers the attributes of the vehicle itself and the interaction in the traffic flow is unified as formula (20). JPEG0007671078000015.jpg50170

[0040] In the formula, E j represents the risk source element of vehicle j while it is running, and k x represents the longitudinal trend of risk while vehicle j is traveling, and k y represents the lateral change tendency of the risk that vehicle j experiences while traveling.

[0041] Note that if i represents a specific target (e.g., vehicle i, rider i, pedestrian i, stationary obstacle i, etc.), then F ji represents the force of the safety field corresponding to the risk that vehicle j poses to i, and k x Parameter v in i is the actual velocity of target i.

[0042] (2) Analysis and quantification of risk constraints of road traffic facilities and driver behavior In order to improve driving safety, road traffic facilities and regulations include facilities to prevent vehicle driving trajectories from crossing by forcibly stopping one vehicle, facilities to reduce driving risks by warning or increasing the right-of-way of the other vehicle and slowing down the vehicle's traffic speed, and facilities to control driving risks by dividing traffic flows traveling in the same or different directions and guiding the direction of vehicle movement.

[0043] (2.1) Impact of road transport facilities on traffic risks (2.1.1) Longitudinal constraints of traffic signals The embodiment of the present invention mainly focuses on two states: when the traffic light is on from yellow to red, and when the red light is off and the green light is on. Chinese standard GB 14886-2016 specifies that the yellow light time of a traffic light must be 3s to 5s, and if a vehicle is far enough away from the intersection when the yellow light is on, it will have at least 3s to decelerate to the parking line. Then, a vehicle that has enough time to decelerate to the parking line will have an equivalent restraint resistance F sj will be subject to the following. JPEG0007671078000016.jpg42170

[0044] (2.1.2) Longitudinal restraints on pedestrian crossings By networking the road traffic environment, vehicles can easily obtain information about the traffic environment, so in the embodiment of the present invention, the crosswalk is regarded as a facility that limits the vehicle's driving speed to reduce driving risks. Before passing the crosswalk line, a moving vehicle needs to reduce its speed to improve driving safety because the closer it gets to the crosswalk line, the greater the traffic control resistance becomes. According to China's traffic regulations, the speed at which a vehicle passes over the crosswalk line must not exceed 30km / h, so before vehicle j passes over the crosswalk line, cj is the equivalent restraint resistance F generated by a pedestrian crossing cj is defined as receiving JPEG0007671078000017.jpg32170

[0045] JPEG0007671078000018.jpg59170

[0046] (2.1.3) Longitudinal constraints of road traffic speed limit markings Road speed limit signs have the role of restricting vehicle travel only by speed, and when a driver commits this violation, the risk to the outside world in a short time is smaller than the two other violations of ignoring traffic signals and driving without slowing down in front of a pedestrian crossing line. l,m where v is the minimum speed limit for the lane, l,h If is the maximum speed limit of the lane, the equivalent restraining resistance F that vehicle j experiences from the road traffic speed limit sign is lj becomes: JPEG0007671078000019.jpg32170

[0047] (2.1.4) Lateral constraints of road traffic markings Road traffic markings play the role of driving guidance and behavioral constraints for drivers. Traffic markings include lanes and crosswalk lines, and lanes affect the driver's behavior laterally, and further affect the vehicle's driving process. Lanes do not directly affect the driving risk of the vehicle, and the vehicle will not cross the road traffic markings to directly cause a traffic accident. Generally, road traffic markings are considered to be able to generate virtual lateral constraint forces (such as lane keeping) when the vehicle is traveling. Therefore, the constraint force F that the road traffic markings exert on the vehicle is mj is defined as in equation (32).

[0048] JPEG0007671078000020.jpg12170

[0049] In the formula, k m is a constant coefficient that may be calibrated with the return lateral acceleration at various vehicle speeds, and k my is the lateral slope adjustment factor, which is related to the driver's actions, and r max,m is the range of influence of the road traffic marking line, and r max,m =0.5lw This indicates that the vehicle is not affected by traffic markings when traveling along the lane centerline.

[0050] (2.2) Methods for quantifying the risk of driver actions (2.2.1) Normal driving behavior of the driver Road traffic markings play a restrictive role in the driving risks that a vehicle poses to the road traffic environment, and are shown to restrict the driver's behavior. If the driver and traffic environment factors are not taken into account, the risk that a vehicle poses to the outside world is considered to be isotropic. By analyzing the normal driving behavior of the driver, the risk distribution that a vehicle poses to the traffic environment can be expressed as an ellipse as shown in Figure 2, where A1A2 and B1B2 are the major and minor axes of the ellipse, respectively, and A1A2=2A1j=2jA2=2A j , B1B2=2B1j=2jB2=2B j Moreover, the ellipse shown in Fig. 2 is one contour of the risk field that vehicle j generates in the environment.

[0051] In consideration of ensuring that the driver always complies with the rules while driving and ensures safe driving as much as possible, the driver usually maintains a certain headway while driving the vehicle, and the traffic rules stipulate that the vehicle must not change lanes continuously. At the same time, in accordance with the geometric dimensions of the vehicle, the lengths of the semi-major axis and semi-minor axis of the ellipse in Figure 2 are set as follows, respectively: A j =r max +l1(33) B j =l w +l2+l cj (34)

[0052] In the formula, A j is the semimajor axis of the ellipse, l1 is half the vehicle length, and B j is the semi-minor axis of the ellipse, and l w is 1x the lane width (usually l w =3.5m), l2 is half the vehicle width, and l cjis the distance between the vehicle and the lane center line. Note that the major axis of the ellipse is a function related to the vehicle speed. The slower the vehicle speed, the smaller the major axis. Therefore, in order to avoid the length of the major axis being smaller than the minor axis, r0 ≧ l w It stipulates that:

[0053] Due to the lateral constraint of the lane, obvious differences appeared in the longitudinal and lateral risk distributions during the vehicle's travel. The ellipse shown in Figure 2 takes into account the safe inter-vehicle time, vehicle flow speed, etc. in the longitudinal direction, and the influence of lane constraints in the lateral direction, and then compresses the isotropic circular distribution to form an elliptical risk distribution with dynamically changing major and minor axes, as shown in Figure 2. When compressed in the lateral direction, the outer circle contour is compressed into an inner ellipse contour, and B'1B'2 is shortened to B1B2, but the risk values ​​represented by the two field force contours are the same. Therefore, when the risk of vehicle j occurring is distributed along the blue contour, the following formula is obtained:

[0054] JPEG0007671078000021.jpg45170

[0055] JPEG0007671078000022.jpg19170

[0056] JPEG0007671078000023.jpg67170

[0057] (2.2.2) Driver violations Since the impact of road traffic facilities on driving safety is reflected in the constraints on driving risk, a driver's violation indicates that the driver has intentionally or unconsciously violated the constraints that road traffic facilities impose on driving risk for some reason. Therefore, in an embodiment of the present invention, the vehicle's motion state under the longitudinal speed limit and the lateral position limit is analyzed to determine whether the driver's behavior has a tendency to violate the rules.

[0058] (2.2.2.1) Longitudinal Speed ​​Limits The risk posed by a perturbation of the traffic environment by a vehicle is related to the speed of the vehicle itself and the average speed of the traffic flow, and similar to equation (20), when the vehicle exceeds the maximum road speed limit or is lower than the minimum road speed limit, the violation risk that the vehicle poses to the road traffic environment may be shown as equation (41):

[0059] JPEG0007671078000024.jpg19170JPEG0007671078000025.jpg51170

[0060] For longitudinal violations, according to equation (22), the field force F of the driving safety field corresponding to the driving risk to the outside world while driving is ji is as follows: JPEG0007671078000026.jpg14170

[0061] (2.2.2.2) Lateral Position Restrictions The role of road traffic marking lines is to restrain and reduce the impact of vehicles on the traffic environment by restraining the lateral movement of the vehicle. As shown in Figure 3, when a vehicle runs stably in the lane formed by lane 2 and lane 3, the elliptical restraining action caused by lane 2 and lane 3 on vehicle j follows equations (33) and (34) in the longitudinal and lateral directions, respectively. However, when a vehicle is on a certain road marking line for a long time, as shown in Figure 4, when vehicle j runs on lane 3, it is considered that lane 3 does not restrain vehicle j, and the elliptical restraining action of the road traffic marking lines on vehicle j is caused by lane 2 and lane 4, and the longitudinal ellipse semimajor axis still follows equation (33), but the transverse ellipse semiminor axis follows equation (46).

[0062] B j =l w +l2+l jc (46) In the formula, l jc is the distance from the centerline of vehicle j.

[0063] (3) Methods for quantifying the risks of road traffic environment elements (3.1) Road surface friction coefficient (3.1.1) Effect of road friction coefficient on braking distance Due to the promotion of Chinese policy regulations, the number of vehicles with ABS systems installed on the front is increasing year by year and is being effectively popularized. By controlling the braking force of the front and rear axle brakes, the synchronous friction coefficient and the road friction coefficient can be made equal. In this preferable case, the minimum braking distance of the vehicle is as follows: JPEG0007671078000027.jpg30170

[0064] JPEG0007671078000028.jpg43170

[0065] JPEG0007671078000029.jpg80170

[0066] JPEG0007671078000030.jpg49170

[0067] JPEG0007671078000031.jpg14170

[0068] JPEG0007671078000032.jpg51170

[0069] where m is the mass of the vehicle, g is the acceleration due to gravity, b is the distance of the rear axle of the vehicle from the center of the vehicle mass, a is the distance of the front axle of the vehicle from the center of the vehicle mass, f is the rolling resistance coefficient, Ψ is the moment distribution coefficient of the rear axle, for front-wheel drive vehicles, Ψ=0, while for rear-wheel drive vehicles, Ψ=1, L is the wheelbase of the vehicle, A is the wind-receiving area of ​​the vehicle, and ρ is the density of air, typically ρ=1.2258Ns 2 m -4 and C D is the drag coefficient of the vehicle, and C lf and C lr are the front and rear air lift coefficients of the vehicle, respectively.

[0070] In addition, after the road friction decreases, if the vehicle needs to decelerate below the maximum vehicle speed limit of the road, if vehicle j travels in the positive direction of x, the overall driving risk that vehicle j poses to the outside world is as follows: JPEG0007671078000033.jpg12170

[0071] JPEG0007671078000034.jpg32170

[0072] (3.2) Road curvature In road design, it is inevitable that the road will bend on a horizontal plane or have undulations in its longitudinal section, so there are a large number of curves with large curvatures. When a vehicle passes through a curve, the vehicle speed v j >v d If so, there is a risk due to the curvature of the road, v j >v j,lim If the road is too strong, the vehicle will skid because the road cannot provide sufficient lateral force to the vehicle. j ∈[v d , v j,lim ], the field force F of the driving safety field of the driving risk due to the road curvature jc is expressed by equation (56), and the risk source increment E after the vehicle speed exceeds the curve design speed is j,c is expressed by equation (57). JPEG0007671078000035.jpg29170

[0073] In steering, the vehicle always tends to move away from the steering center, and the lateral force applied by the ground to the tires provides a centripetal force to the steering of the vehicle, allowing the vehicle to run stably. If the vehicle speed is too high or the steering radius is too small for the ground to provide sufficient centripetal force to the vehicle, the vehicle will enter a dangerous state such as skidding. As a result, when steering, the risk of the vehicle being pulled to the side where the centrifugal force is directed is greater than that of the other side. The steering angle δ of the wheels of vehicle j j is positive in the counterclockwise direction, the longitudinal gradient adjustment coefficient k x,c is expressed by equation (58), and the lateral gradient adjustment coefficient ky,c is expressed by equation (59), and the method for obtaining each parameter in the equation can be calculated from the theory of vehicle dynamics. JPEG0007671078000036.jpg20170

[0074] In the formula, v d represents the design speed of the road, φ represents the road surface friction coefficient, and F jZ represents the vertical support force exerted by the ground on vehicle j, and F jY represents the lateral friction force of vehicle j caused by the road surface, and y i represents the x-coordinate of point i, and y j represents the y-coordinate of vehicle j.

[0075] Taking into account the direct risk and perturbation risk due to the vehicle and the steering process of the vehicle, the overall driving risk that vehicle j poses to the outside world is shown as equation (60). JPEG0007671078000037.jpg12170

[0076] (3.3) Road inclination The driving risk caused by road inclination is mainly manifested in the interaction process between vehicles when going uphill, and in speeding and reduced braking performance due to the conversion of gravitational potential energy into kinetic energy when going downhill. In uphill sections, the field force F of the driving safety field corresponding to the driving risk to the outside world while driving is ji is shown as equation (61). JPEG0007671078000038.jpg13170

[0077] In a downhill section, the risk is that the energy carried by the vehicle is gravitational potential energy in addition to its own kinetic energy, i.e., the risk increases with the increase in the value of the energy carried by the energy source. Let the gradient of the slope be i r Then, the conversion amount of gravitational potential energy when vehicle j travels downhill is E j,s is shown as equation (63), where specific values ​​of the parameters can be determined based on the characteristics and kinematics of the vehicle. JPEG0007671078000039.jpg12170

[0078] Therefore, the field force F of the driving safety field of the driving risk due to the gradient js is shown as equation (64). JPEG0007671078000040.jpg12170

[0079] JPEG0007671078000041.jpg26170

[0080] The field force F of the driving safety field corresponds to the driving risk that the vehicle poses to the outside world when driving downhill. ji is as follows: JPEG0007671078000042.jpg13170

[0081] Obviously, equation (65) is applicable to both uphill and downhill scenarios, and when the vehicle is climbing uphill, F j,s The value of F is 0 and the vehicle is traveling downhill. js is calculated using equation (64).

[0082] (3.4)Environmental visibility When encountering bad weather such as heavy rain, thick fog, and snow and ice, the friction coefficient of the road may decrease, and the driver's visibility may also be strongly affected (sensors of smart driving such as industrial cameras are also interfered with and affected). Bad weather increases the driver's sense of tension and brings driving risks. When driving in rainy weather, the driver's field of vision is easily affected. For example, in light rain, the environmental visibility is low, and in heavy rain, the driver's field of vision is hindered by the operation of the wipers. In addition, due to the limited range of the wiper's water, rain adheres to the windshield and rearview mirror, narrowing the driver's field of vision and the range of visual perception. In a foggy environment, the driver's visibility is seriously affected, making it difficult to maintain a safe distance from surrounding vehicles. In snow and ice weather, snow affects the driver's field of vision, and when snow accumulates, the sun's light shines, making it easy for the driver's eyesight to deteriorate. Therefore, changes in environmental visibility due to weather have an extremely significant impact on driving safety, and the force field of the driving safety field corresponding to the driving risk that a vehicle poses to the traffic environment when driving with a certain environmental visibility is expressed as Equation (66). JPEG0007671078000043.jpg12170

[0083] Wherein, the environmental visibility longitudinal gradient adjustment factor k x,e and the environmental visibility lateral gradient adjustment factor k y,e is related to the driver's actions, vehicle state and environmental conditions. If we only consider the effect of environmental visibility, the effect of environmental visibility on the lateral direction of the vehicle is small, so JPEG0007671078000044.jpg8170

[0084] In the longitudinal direction of the vehicle, the driver's visibility in a good traffic environment D0 and the current environmental visibility D e Considering this, k x,e The value of satisfies the following formula: JPEG0007671078000045.jpg11170

[0085] In the formula, k j,e is a constant related to the driver's actual visual acuity, and k j,e= 1, and for drivers with good eyesight, visibility in a good traffic environment is usually D0 = 500 m, and the current environmental visibility D e adjusts values ​​in real time according to weather conditions.

[0086] (4) Comprehensive risk quantification method for people, vehicles, and roads The aforementioned study used a force field of driving safety field based on equal force to describe the interactive relationship between people, vehicles and roads, that is, to consider how five types of traffic environment elements, namely the direct and perturbation risks that vehicles pose to the outside world, road surface conditions, road curvature, road inclination and environmental visibility, affect the risks that vehicles pose to the outside world, and the effects of normal and illegal driving behaviors of drivers under traffic rules on the risks to vehicles, respectively, and the factors that affect the risks that vehicles pose to the outside world are as shown in Table 1. The restraining effects on vehicle movement of traffic environment elements represented by four types of traffic facilities, namely traffic signals, pedestrian crossings, road traffic speed limit signs and road traffic marking lines, and road boundaries are considered.

[0087] JPEG0007671078000046.jpg61170

[0088] (4.1) Unified driving safety field model (4.1.1) Field forces Based on the original framework of comprehensive driving risk modeling, the overall framework for forming the risk that a vehicle poses to the outside world is presented as follows: JPEG0007671078000047.jpg24170

[0089] JPEG0007671078000048.jpg7170

[0090] JPEG0007671078000049.jpg7170

[0091] JPEG0007671078000050.jpg51170

[0092] (4.1.2) Potential Energy There is a limit to directly describing the influence of multiple vehicles on a point in a traffic environment. In this embodiment, a complete driving safety field system is constructed to describe the interaction relationship between people, vehicles, and roads in a road traffic environment, and a quantitative description of driving risks is realized.

[0093] In the driving safety field, point P (P∈[r min ,r max ]), the potential energy that a vehicle acquires under the influence of a field source is the potential energy of an object of unit mass m e The work done to move from point P to a point with zero potential energy, r ji ≧r max Therefore, the potential energy U at point P is equal to the work done to move jp is as follows: JPEG0007671078000051.jpg22170

[0094] Therefore, the potential energy U of the field source j that vehicle i receives ji When put into rectangular coordinate system form, we obtain the following equation: JPEG0007671078000052.jpg21170

[0095] The gradient of the potential energy change is: JPEG0007671078000053.jpg19170

[0096] Specific examples are given below. The degree of risk to the vehicle i is judged by the virtual acceleration calculated by Newton's second law, and measures such as warning or active braking can be taken according to the grade. For example, i >3m / s 2 If , vehicle i issues an alarm and i >5m / s 2 In the case of , vehicle i performs slight braking and a i >8m / s 2 If , vehicle i performs emergency braking.

[0097] JPEG0007671078000054.jpg13170The mechanism of driving risk occurrence lies in the comprehensive interaction between various factors affecting driving safety, and the factors affecting driving risk are not limited to the various factors described in the above embodiments. The research purpose of the embodiment of the present invention is to provide a unified modeling concept that can build a corresponding mathematical model in the framework of the unified modeling concept proposed by the embodiment of the present invention when a new factor affecting driving risk appears in a specific scenario.

[0098] It should be noted that the above embodiments are only used to explain the technical solutions of the present invention, and are not intended to limit the same. It is obvious to those skilled in the art that the technical solutions described in the above embodiments can be modified or some of the technical features can be replaced with equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

[Claim 1] A unified method for quantifying driving risk that comprehensively considers each element of people, vehicles, and roads, Obtaining an initial driving safety field model of driving risk as shown in equation (3); Decomposing the initial driving safety field model in the longitudinal and lateral directions, and creating a first unified driving safety field model shown in Equation (69) based on the information of vehicle j and traffic environment information; The field force F due to vehicle j on any point i in the traffic environment where vehicle j is located ｊｉ and calculating The field force F ｊｉ and recognizing the driving risk that point i is subject to due to the influence of vehicle j based on In the above formula, x ｊｉ represents the longitudinal distance of vehicle j from any point i in the environment, and y ｊｉ represents the lateral distance of vehicle j from point i, and r ０ represents the distance between the driver of vehicle j and r ｍａｘ represents the maximum separation between vehicles in the free flow, and r ｍｉｎ represents the minimum separation between vehicles in a free stream, and E ｊ is the speed of vehicle j, v ｊ The kinetic energy E is determined by ｊ,０ and the relative kinetic energy determined by a plurality of traffic environment factors, E ｊ,ｆａｃ is the kinetic energy E ｊ,０ and the relative kinetic energy determined by traffic environment elements, including road surface friction coefficient, road curvature, road inclination, environmental visibility, lane and road speed limit rules; if any of the speed of the vehicle j and the traffic environment elements is ignored, the value of the kinetic energy corresponding to the element is 0; k ｘ is the product of the speed of vehicle j and the longitudinal slope adjustment coefficient of each of the traffic environment elements, and k ｘ,ｆａｃ represents the speed of vehicle j and the longitudinal gradient adjustment coefficient of each of the traffic environment elements; k ｙ is the product of the speed of vehicle j and the lateral slope adjustment coefficient of each of the traffic environment elements, and k ｙ,ｆａｃ represents the speed of vehicle j and the lateral slope adjustment coefficient of each of the traffic environment elements, and when any of the speed of vehicle j and the traffic environment elements is ignored, the value of the slope adjustment coefficient corresponding to the element is 1.

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