Method for threat assessment for automatic lane change assistance

Abstract

The application provides a threat evaluation method for automatic lane changing assistance, which comprises the following steps: when lane changing is needed, it is needed to judge whether the longitudinal distance between the vehicle and the target vehicle in front of or / and behind the vehicle on the target lane meets the requirement in the lane changing process, and whether the safety limit distance time between the vehicle and the target vehicle in front of or / and behind the vehicle on the target lane meets the requirement in the lane changing process; when the judgment result of any one is no, it is considered that there is a threat in the lane changing process, and when the judgment results of all are yes, it is considered that there is no threat in the lane changing process. In this way, the problems of incomplete consideration of the existing lane changing threat judgment, influence of lane changing safety and experience and the like are solved.

Description

[Technical Field]

[0001] This invention relates to the field of lane change assistance, and more particularly to a threat assessment method for automatic lane change assistance. [Background Technology]

[0002] The Society of Automotive Engineers (SAE) is a highly influential academic organization in the American and global automotive industry, and one of the world's leading resources for information on automotive, marine, and aerospace transportation technologies. It publishes a large number of standards, technical reports, parameter (tool) books, and special publications annually, and maintains a vast database. The classification standard for autonomous driving, with automation levels increasing from L0 to L5, was proposed by SAE in J3016 in 2014.

[0003] In recent years, with the increasing number of SAE Level 2 autonomous driving projects, the number of vehicles equipped with lane change assist has been gradually increasing. Lane change assist is a driving assistance system that uses radar sensors to monitor the area to the side and rear of the vehicle. It can detect the current position, speed, and direction of other vehicles in adjacent lanes within a certain range, assisting the driver in completing a lane change maneuver. Lane change assist is included in Driver Indicator Lane Change (ILC), Automatic Lane Change Assist (ALC), and Navigate on Autopilot (NOA). When the vehicle is in assisted driving mode (i.e., lane centering assist is activated) and the vehicle speed is greater than a certain value, the driver presses the left or right turn signal stalk. The Automatic Lane Change Assist (ALC) system can then assess the environment and smoothly steer the vehicle into the adjacent lane.

[0004] Since lane change assist is a comfort feature, to ensure safety during lane changes, most mass-produced lane change assist functions on the market currently use Time-To-Collision (TTC) based on targets in front of and behind the target lane for lane change threat assessment. TTC refers to the time required for two vehicles to collide if they continue along the same path at their current speeds. Threat Assessment (TA) refers to the complex spatial and temporal relationships between the vehicle and other road users. It uses rule-based expert systems to calculate various threat metrics or probabilistic models to determine the degree of threat posed by other road users to the vehicle's driving safety, thereby providing guidance for vehicle operation.

[0005] However, existing lane change threat assessment methods have the following problems:

[0006] 1) Only calculates whether a collision will occur between this vehicle and vehicles in the target lane, without considering the impact of changing to a new lane on the driving and riding experience of vehicles behind in the target lane;

[0007] 2) The situation where the safe distance between the initial lane and the target was not calculated in advance, and the current lane change process is interrupted, requiring a return to the initial lane;

[0008] 3) In summary, while there are already threat assessment methods based on TTC in lane change assist functions, in actual use, fewer conditions are considered, which may affect the driving and riding experience of traffic participants and the safety of lane change.

[0009] Therefore, there is an urgent need to propose a new technical solution to address the above problems. [Summary of the Invention]

[0010] One of the objectives of this invention is to provide a threat assessment method for automatic lane change assist, which can solve the problems of incomplete consideration of factors in existing lane change threat assessment, affecting lane change safety and experience.

[0011] To achieve the above objectives, the present invention provides a threat assessment method for automatic lane change assistance, comprising: when a lane change is required, determining whether the longitudinal distance between the vehicle and a target vehicle in front of and / or behind the vehicle in the target lane meets the requirements during the lane change process, and determining whether the safe distance time between the vehicle and the target vehicle in front of and / or behind the vehicle in the target lane meets the requirements during the lane change process; if the result of any one of the determinations is negative, then a threat is considered to exist during the lane change process; if the results of all determinations are positive, then no threat is considered to exist during the lane change process.

[0012] In one embodiment, when a lane change is required, it is also necessary to determine whether the safe distance time between the target vehicle behind the vehicle in the current lane and the target vehicle in front of the vehicle in the target lane meets the requirements during the lane change process, and to determine whether the safe distance time between the target vehicle in front of the vehicle in the current lane and the target vehicle behind the vehicle in the target lane meets the requirements during the lane change process.

[0013] In one embodiment, if the longitudinal distance between the vehicle and the target vehicle is greater than the headway of the following vehicle during the lane change process, the longitudinal distance between the vehicle and the target vehicle is considered to meet the requirements; otherwise, the longitudinal distance between the vehicle and the target vehicle is considered not to meet the requirements, and the headway of the following vehicle is determined based on the product of the speed of the following vehicle and the reserved following time between the vehicle and the target vehicle.

[0014] In one embodiment, the safe distance time is the time required for the longitudinal distance between the two vehicles to change from the current longitudinal distance to the safe distance. The safe distance is a preset distance value. When the safe distance time is greater than the preset time threshold, it is considered that the safe distance time between the vehicle and the target vehicle or between the two target vehicles meets the requirements. Otherwise, it is considered that the safe distance time between the vehicle and the target vehicle or between the two target vehicles does not meet the requirements. The preset time threshold is related to the lane change time.

[0015] Compared with existing technologies, this invention, when conducting threat assessment for automatic lane change assistance, not only considers the safe distance time between the vehicle and the target vehicle in front of or / and behind it in the target lane, but also considers the longitudinal distance between the vehicle and the target vehicle in front of or / and behind it in the target lane. This solves the problems of incomplete consideration in existing lane change threat assessment, which affects lane change safety and experience. [Attached Image Description]

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0017] Figure 1 This is a scenario example diagram illustrating the threat assessment of automatic lane change assistance in this invention;

[0018] Figure 2 This is a flowchart illustrating one embodiment of the threat assessment method for automatic lane change assistance in this invention.

Detailed Implementation Methods

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms "connected," "linked," and "connected" used herein to indicate electrical connection refer to direct or indirect electrical connection.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," "coupled," etc., should be interpreted broadly; for example, they can refer to direct connection or indirect connection through an intermediate medium, which can be electronic components, functional circuits, etc. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] This invention proposes a lane change threat assessment method for automatic lane change assistance, which can help the lane change assistance control system determine whether a lane change can be completed safely without affecting the driving experience of other road users.

[0023] Figure 1 This is a scenario example diagram illustrating the threat assessment for automatic lane change assistance in this invention. Figure 1 As shown, Host-Car represents the current vehicle; RT1 is the nearest target vehicle directly in front of the current vehicle, and RRT1 is the nearest target vehicle directly behind the current vehicle. RT3 and RRT3 are located in the left lane of the current vehicle's lane (referred to as the current lane); RT3 is the nearest target vehicle to the left front of the current vehicle; RRT3 is the nearest target vehicle to the left rear of the current vehicle. Similarly, RT4 and RRT4 are located in the right lane of the current vehicle's lane; RT4 is the nearest target vehicle to the right front of the current vehicle; RRT4 is the nearest target vehicle to the rear of the current vehicle.

[0024] Figure 2 This is a flowchart illustrating one embodiment of the threat assessment method 200 for automatic lane change assistance in this invention. Figure 2 As shown, the threat assessment method 200 includes the following steps.

[0025] Step 210: Determine the intended lane change direction and identify the target lane.

[0026] If there is an intention to change lanes to the left, proceed to step 220 to determine if there is a threat to the left lane change. At this time, the lane to the left of this lane is the target lane. If there is a threat, in step 240, the lane change is considered to be threatening, and the threat assessment method 200 ends. If there is no threat, proceed to step 250, the left lane change is considered to be non-threatening, and the threat assessment method 200 ends, after which automatic lane change assistance can be performed.

[0027] If there is an intention to change lanes to the right, proceed to step 230 to determine if there is a threat to the right lane change. At this time, the rightmost lane of this lane is the target lane. If there is a threat, in step 240, the lane change is considered to be threatening, and the threat assessment method 200 ends. If there is no threat, proceed to step 260, the right lane change is considered to be non-threatening, and the threat assessment method 200 ends, after which automatic lane change assistance can be performed.

[0028] In one embodiment, if the driver presses the left turn signal stalk, it is assumed that the driver intends to change lanes to the left; if the driver presses the right turn signal stalk, it is assumed that the driver intends to change lanes to the right. Of course, in other embodiments, such as in autonomous driving mode, the intended lane change direction can be determined automatically.

[0029] Combination Figure 1 and Figure 2 As shown, step 220, which determines whether a lane change to the left poses a threat, specifically includes the following steps.

[0030] Step 221: To ensure that the Host-Car will not collide with the target vehicle RT3 in the left lane (the current target lane) and to ensure the comfort of the occupants, determine whether the longitudinal distance between the Host-Car and the target vehicle RT3 in the left lane meets the requirements during the lane change, and whether the safe distance time between the Host-Car and the target vehicle RT3 in the left lane meets the requirements during the lane change. If all judgments are yes (Y), proceed to step 222 for further judgment; if any judgment result is no (N), proceed to step 240.

[0031] Step 222: To ensure that the Host-Car will not collide with the target vehicle RRT3 behind it in the left lane and to ensure the comfort of the occupants of the target vehicle RRT3, determine whether the longitudinal distance between the Host-Car and the target vehicle RRT3 behind it in the left lane meets the requirements during the lane change, and determine whether the safe distance time between the Host-Car and the target vehicle RRT3 behind it in the left lane meets the requirements during the lane change. If all the judgment results are yes (Y), proceed to step 223 for further judgment; if any judgment result is no (N), proceed to step 240.

[0032] Step 223: To ensure sufficient lane-changing space and prevent the vehicle from being sandwiched between target vehicle RRT3 behind it in the target lane and target vehicle RT1 in front of it in its current lane during the lane change, determine whether the safe distance between target vehicle RT1 in front of it in its current lane and target vehicle RRT3 in the left lane behind it meets the requirements during the lane change. If the result is yes (Y), proceed to step 224 for further evaluation; if the result is no (N), proceed to step 240.

[0033] Step 224: To ensure sufficient lane-changing space and prevent being sandwiched between target vehicle RT3 in front of the target vehicle in the target lane and target vehicle RRT1 in front of the vehicle in the current lane during the lane change, and to reserve retreat space while ensuring the comfort of the occupants of target vehicle RRT1 in the current lane during retreat, determine whether the safe distance between target vehicle RRT1 in the current lane and target vehicle RT3 in front of the vehicle in the left lane meets the requirements during the lane change. If the determination result is yes (Y), proceed to step 250; if the determination result is no (N), proceed to step 240.

[0034] It's important to note that the above description of steps 221, 222, 223, and 224 is merely for simplicity. In reality, the execution order of steps 221, 222, 223, and 224 is not fixed; they can be executed in parallel, such as simultaneously, or in a different order, such as executing steps 223 and 224 first, followed by steps 221 and 222. Step 250 proceeds only when all the judgments in steps 221-224 are true (i.e., all requirements are met), indicating that the lane change to the left is deemed harmless and the lane change request can be executed. Conversely, if any judgment in steps 221-224 is false (i.e., the requirements are not met), step 240 proceeds, indicating that the lane change is deemed threatening and the lane change request is not executed. In an improved embodiment, additional judgment conditions can be added to step 220 of determining whether a left lane change poses a threat to determine whether other requirements are met. Only when all requirements are met is the left lane change considered to be without threat.

[0035] In one embodiment, in steps 221-222, if the longitudinal distance between the host car and the target car is greater than the headway gap of the following vehicle during the lane change, then the longitudinal distance between the host car and the target car is considered to meet the requirement; otherwise, the longitudinal distance between the host car and the target car is considered not to meet the requirement. Specifically, the headway gap of the following vehicle is determined based on the product of the speed of the following vehicle in both the host car and the target car and the reserved following time.

[0036] In one example, the headway is the product of the speed of the vehicle behind and the allowable following time. It represents the minimum distance that should be maintained between the two vehicles to reduce the discomfort of the following vehicle. The formula is as follows:

[0037] x headwayGap =t headwaygap ×v reartarget (3)

[0038] Where x headwayGapTo allow for headway, t headwaygap To allow time for following the vehicle, v reartarget This represents the speed of the vehicle behind.

[0039] In one embodiment, in steps 221-224, if the safe distance time is greater than a preset time threshold, the safe distance time between the vehicle and the target vehicle, or between two target vehicles, is considered to meet the requirements; otherwise, the safe distance time between the vehicle and the target vehicle, or between two target vehicles, is considered not to meet the requirements. The preset time threshold is related to the lane-changing time, for example, it is the sum of the lane-changing time and a fixed time. The safe distance time is the time required for the longitudinal distance between two vehicles (e.g., the vehicle and the target vehicle, or two target vehicles) to first change from the current longitudinal distance to the safe distance. The safe distance is a preset distance value, such as 1 meter, 2 meters, or 3 meters.

[0040] Figure 1 In the middle, the motion state of all vehicles [xv x a x The x and lane information are provided by the upstream perception fusion module, where x is the relative longitudinal distance between the target vehicle (RT) and the current vehicle, with the current vehicle as the reference and forward as positive, in meters; v x The longitudinal velocity relative to the ground, in m / s, a x This is the longitudinal acceleration of the vehicle relative to the ground.

[0041] All vehicles at any given moment can be simplified to uniformly accelerated linear motion with a velocity v. x acceleration a x The displacement s has the following relationship:

[0042]

[0043] The safe distance between two vehicles can be calculated as follows. Here, we use the target vehicle RT3 and the host car as an example. The positional relationship between the two vehicles over a certain period can be expressed as:

[0044]

[0045] in, Let RT3 be the longitudinal distance between the target vehicle RT3 and the host car after a certain time t. This can be referred to as the safe distance between the target vehicle RT3 and the host car. Let RT3 be the longitudinal velocity of the target vehicle at the current moment. Let RT3 be the longitudinal acceleration of the target vehicle at the current moment. The current longitudinal speed of the Host-Car. Let x be the longitudinal acceleration of the Host-Car at the current moment. This represents the longitudinal distance between the target vehicle and the host car at the current moment.

[0046] If The above equation can be viewed as a quadratic equation in one variable with the collision time t as the unknown. From its physical meaning, we know that when the equation has no solution, the two cars will not collide; when a solution exists, the solution that is greater than or equal to 0 and closest to the origin is the time when the target car RT3 collides with the host car.

[0047] Automatic lane change assist, being a comfort feature, and operating at relatively high speeds, requires sufficient safety margin. A certain distance should be maintained, x end This can be referred to as the safe distance. At this point, the calculated t is the safe distance between the Host-Car and the target vehicle (RT3) for the first time. The required time, i.e. the safe distance time, ensures that within the time interval t∈[0,t], the distance between the host car and the target car RT3 is always greater than the safe distance.

[0048] In steps 221 and 222, the safety distance is set to x. end1 In steps 223 and 224, the safety distance is set to x. end2 And x end1 <x end2 The advantage of this setup is that when the vehicle is only suppressed or overtaken by a vehicle in the target lane or its own lane (in other words, when the vehicle is not sandwiched), it still has a relatively large margin for maneuver in lane changing. Therefore, in steps 221 and 222, the smaller x is taken. end The value is set to allow for a small safety margin, ensuring flexibility in lane changes. However, when the vehicle is simultaneously sandwiched between a vehicle in front of the target lane and a vehicle behind in its own lane (i.e., the situation described in step 224), or between a vehicle behind the target lane and a vehicle in front in its own lane (i.e., the situation described in step 223), the risk of lane changing is greater, or the margin for error is smaller. Therefore, to address this sandwiching tendency from both sides, a larger x value is set in steps 223 and 224. end This reduces the likelihood of triggering a lane change in such situations.

[0049] To calculate whether a pincer attack situation exists between target vehicles RT1 and RRT3, and between target vehicles RT3 and RRT1, on the vehicle itself, there are two calculation methods. Method one involves calculating the safe distance x between the vehicle and RT1 separately. end The safe distance between this vehicle and RRT3 (x) end The safe distance between this vehicle and RT3 (x)end The safe distance between this vehicle and RRT1 (x) end And calculate their safe distance time limits. Then, determine whether a sandwich situation exists based on the magnitude of each safe distance time limit and the corresponding rules. Method 2, i.e., steps 223 and 224, determines whether the safe distance time limit between the target vehicle RT1 in front of the vehicle in this lane and the target vehicle RRT3 in front of the vehicle in the left lane meets the requirements during the lane change, and whether the safe distance time limit between the target vehicle RRT1 in the rear of the vehicle in this lane and the target vehicle RT3 in front of the vehicle in the left lane meets the requirements during the lane change. This judgment method is based on the fact that between RT1 and RRT3, and between RT3 and RRT1, as long as the safe distance x end If the distance is less than a certain value, it constitutes a sandwich situation. In this case, the permissible longitudinal distance between this vehicle and RT1, RRT3, RT3, and RRT1 can vary greatly. Calculating the safe distance between this vehicle and other vehicles using Method 1 requires setting a complex x-value. end Combinations of values ​​can cover all possibilities, greatly increasing the complexity, implementation difficulty, probability of error, and computational load of the algorithm. However, here we directly calculate the safe distance time between RT1 and RRT3, and between RT3 and RRT1, avoiding the aforementioned situation. We can determine whether other vehicles constitute a pincer attack on our vehicle through simple rules. The algorithm is simpler, easier to implement, less prone to errors, and the computational load is greatly reduced. The algorithm also responds promptly.

[0050] When the target vehicles (i.e., one or more of RT1, RT3, RT4, RRT1, RRT3, and RRT4) in the current, rear, left, and right directions do not exist, the vehicle's state parameters [xv] are... x a x The following rules are set: the distance is set to infinity or a fixed, very large value; in this embodiment, it is set to a distance greater than 500m; the vehicle speed remains the same as the current vehicle, and the acceleration is set to 0. This ensures that the distance between the target vehicle and the current vehicle is always a fixed value, the safe distance limit time is infinite, and the lane-changing process is not inhibited. In other words, when a target vehicle does not exist, the judgment results related to that target vehicle are all satisfactory, and the lane-changing process is not inhibited.

[0051] Combination Figure 1 and Figure 2 As shown, step 230, which determines whether a lane change to the right poses a threat, specifically includes the following steps.

[0052] Step 231: To ensure that the Host-Car will not collide with the target vehicle RT4 in the right lane (the current target lane) and to ensure the comfort of the occupants, determine whether the longitudinal distance between the Host-Car and the target vehicle RT4 in the right lane meets the requirements during the lane change, and whether the safe distance time between the Host-Car and the target vehicle RT4 in the right lane meets the requirements during the lane change. If all judgments are yes (Y), proceed to step 232 for further judgment; if any judgment result is no (N), proceed to step 240.

[0053] Step 232: To ensure that the Host-Car will not collide with the target vehicle RRT4 behind it in the right lane and to ensure the comfort of the occupants of the target vehicle RRT4, determine whether the longitudinal distance between the Host-Car and the target vehicle RRT4 behind it in the right lane meets the requirements during the lane change, and determine whether the safe distance time between the Host-Car and the target vehicle RRT4 behind it in the right lane meets the requirements during the lane change. If all the judgment results are yes (Y), proceed to step 233 for further judgment; if any judgment result is no (N), proceed to step 240.

[0054] Step 233: To ensure sufficient lane-changing space and prevent the vehicle from being sandwiched between target vehicle RRT4 behind it in the target lane and target vehicle RT1 in front of it in its current lane during the lane change, determine whether the safe distance between target vehicle RT1 in front of it in its current lane and target vehicle RRT4 in front of it in the right lane meets the requirements during the lane change. If the result is yes (Y), proceed to step 234 for further evaluation; if the result is no (N), proceed to step 240.

[0055] Step 234: To ensure sufficient lane-changing space and prevent being sandwiched between target vehicle RT4 in front of the target vehicle in the target lane and target vehicle RRT1 in the current lane during the lane change, and to allow for retreat space while ensuring the comfort of the occupants of target vehicle RRT1 in the current lane during retreat, determine whether the safe distance between target vehicle RRT1 in the current lane and target vehicle RT4 in front of the vehicle in the right lane meets the requirements during the lane change. If the determination result is yes (Y), proceed to step 260; if the determination result is no (N), proceed to step 240.

[0056] For information regarding the right lane as the target lane, please refer to the description of the left lane as the target lane; it will not be repeated here.

[0057] Thus, when performing threat assessment for automatic lane change assistance, this invention not only considers the safe distance time between the vehicle and the target vehicle in front of or / and behind it in the target lane, but also the longitudinal distance between the vehicle and the target vehicle in front of or / and behind it in the target lane. This solves the problems of incomplete consideration in existing lane change threat assessments, which affect lane change safety and user experience.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0059] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications and variations to the above embodiments within the scope of the present invention.

Claims

1. A threat assessment method for automatic lane change assist, characterized in that, It includes: When it is necessary to change lanes, it is necessary to determine whether the longitudinal distance between the vehicle and the target vehicle in front of or / and behind the vehicle in the target lane meets the requirements during the lane change process, and whether the safe distance time between the vehicle and the target vehicle in front of or / and behind the vehicle in the target lane meets the requirements during the lane change process. When changing lanes, it is also necessary to determine whether the safe distance between the vehicle behind the vehicle in the current lane and the vehicle in front of the vehicle in the target lane meets the requirements during the lane change process, and to determine whether the safe distance between the vehicle in front of the vehicle in the current lane and the vehicle behind the vehicle in the target lane meets the requirements during the lane change process. If any one of the judgments is negative, a threat is considered to exist during the lane change, and the threat assessment method ends; if all judgments are positive, no threat is considered to exist during the lane change, the threat assessment method ends, and automatic lane change assistance is then implemented. If the longitudinal distance between the vehicle and the target vehicle is greater than the headway of the following vehicle during a lane change, the longitudinal distance between the vehicle and the target vehicle is considered to meet the requirements; otherwise, the longitudinal distance between the vehicle and the target vehicle is considered not to meet the requirements. The headway of the following vehicle is determined based on the product of the speed of the following vehicle and the reserved following time between the vehicle and the target vehicle. The safe distance time is the time required for the longitudinal distance between two vehicles to change from the current longitudinal distance to the safe distance. The safe distance is a preset distance value. When the safe distance time is greater than the preset time threshold, it is considered that the safe distance time between the vehicle and the target vehicle or between the two target vehicles meets the requirements. Otherwise, it is considered that the safe distance time between the vehicle and the target vehicle or between the two target vehicles does not meet the requirements. The preset time threshold is related to the lane change time.

2. The threat assessment method according to claim 1, characterized in that, The safe distance between this vehicle and the target vehicle in front of and / or behind this vehicle in the target lane is greater than the safe distance between the target vehicle behind this vehicle in this lane and the target vehicle in front of this vehicle in the target lane, as well as the safe distance between the target vehicle in front of this vehicle in this lane and the target vehicle behind this vehicle in the target lane.

3. The threat assessment method according to claim 1, characterized in that, When a target vehicle does not exist, all judgment results related to that target vehicle are true.

4. The threat assessment method according to claim 1, characterized in that, It also includes: Determine the intended lane change direction and identify the target lane.

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