A variable headway adjustment and adaptive vehicle trajectory control method

Abstract

The application discloses a variable vehicle head time interval adjustment and adaptive vehicle trajectory control method, and relates to the technical field of vehicle control, and comprises the following steps: S1, acquiring safety vehicle distance rules, speed limits and vehicle state information; S2, constructing a speed-density segmented function according to the safety vehicle distance rules, the speed limits and the vehicle state information; S3, constructing a relationship model of ideal vehicle head time interval and speed; S4, determining an acceleration trajectory generation model according to the relationship model of ideal vehicle head time interval and speed; and S5, constructing an optimization model, and cooperatively optimizing parameters in the speed-density segmented function and the acceleration trajectory generation model, so as to complete vehicle trajectory control. The application provides a vehicle head time interval change method and a vehicle acceleration trajectory generation strategy for an automatic driving vehicle, can take into account the safety vehicle distance rules with segmented rule characteristics and the improvement of traffic operation efficiency, and provides an implementation approach for the automatic driving vehicle to meet existing safety vehicle distance regulations.

Description

Technical Field

[0001] This invention relates to the field of vehicle control technology, specifically to a method for variable headway adjustment and adaptive vehicle trajectory control. Background Technology

[0002] Equipped with onboard monitoring equipment and vehicle-to-everything (V2X) communication modules, autonomous vehicles possess strong environmental perception capabilities. Under advanced control methods, they can quickly respond to changes in their surroundings and tolerate shorter headway distances. In mixed traffic situations involving both autonomous and driver-driven vehicles, autonomous vehicles are often assigned shorter headway distances to improve road capacity. However, before specific autonomous driving regulations are enacted, autonomous vehicles on highways must adhere to existing safe following distance rules. For example, on Chinese highways, following distances are typically required to be no less than 50 meters at speeds below 100 km / h and no less than 100 meters at speeds above 100 km / h, thus constraining available following distances by speed segments. Existing fixed headway or spacing strategies struggle to simultaneously achieve: ① meeting segmented minimum following distance requirements; ② improving traffic efficiency in high-speed zones; and ③ enhancing traffic capacity.

[0003] Therefore, this application proposes a variable headway adjustment strategy. Given the challenges of implementing vehicle-to-everything (V2X) connectivity, and the fact that self-perception-based intelligent driving systems are already in operation, this invention, based on the proposed variable headway strategy, designs an adaptive vehicle trajectory control method that maintains queue stability and improves traffic efficiency. Summary of the Invention

[0004] To address the above problems, this invention proposes a variable headway adjustment and adaptive vehicle trajectory control method.

[0005] The technical solution of the present invention is: a method for variable headway adjustment and adaptive vehicle trajectory control, comprising the following steps:

[0006] S1. Obtain safe following distance rules, speed limits, and vehicle status information;

[0007] S2. Construct a speed-density piecewise function based on safe following distance rules, speed limits, and vehicle status information;

[0008] S3. Construct a model of the relationship between ideal headway and speed;

[0009] S4. Based on the relationship model between ideal vehicle headway and speed, determine the acceleration trajectory generation model;

[0010] S5. Construct an optimization model and collaboratively optimize the parameters in the velocity-density piecewise function and acceleration trajectory generation model to complete vehicle trajectory control.

[0011] Furthermore, in S2, the functional expression for velocity and density corresponding to the horizontal line in the piecewise velocity-density function is:

[0012] ;

[0013] in, Let the vehicle speed be a function of the ideal density. Speed ​​limits are set for this section of road;

[0014] In S2, the function expression for velocity and density corresponding to the non-horizontal lines in the piecewise velocity-density function is as follows:

[0015] ;

[0016] ;

[0017] ;

[0018] in, For line segments The slope, The intercept is... The velocity corresponding to one end of the line segment. The velocity corresponding to the other end of the line segment. For vehicle speed The density is calculated based on the ideal vehicle spacing and vehicle length. For vehicle speed The density is calculated based on the ideal vehicle spacing and vehicle length. For speed The corresponding density.

[0019] Furthermore, S3 includes the following sub-steps:

[0020] S31. Calculate the ideal frontage distance;

[0021] S32. Based on the ideal frontage distance, construct a model relating the ideal frontage distance to the speed.

[0022] Furthermore, in S31, the ideal front-end spacing... The expression is:

[0023] ;

[0024] in, For line segments The slope, The intercept is... For vehicle speed.

[0025] Furthermore, in S32, the ideal headway versus speed model includes the ideal headway... The expression is:

[0026] ;

[0027] in, For line segments The slope, The intercept is... For vehicle speed;

[0028] In S32, the net headway is a crucial factor in the relationship between ideal headway and speed. The expression is:

[0029] ;

[0030] in, For ideal front-end spacing, For the length of the vehicle, This refers to the minimum distance between vehicles when they are stationary.

[0031] Furthermore, in S4, the expression for the acceleration trajectory generation model is as follows:

[0032] ;

[0033] in, Let acceleration be a function of time t. As the first weighting coefficient, This is the second weighting coefficient. Let be the speed of the vehicle in front at time t. Let be the speed of the vehicle at time t. Let t be the position of the vehicle in front at time t. Let be the position of this vehicle at time t. This is the ideal net headway for this vehicle.

[0034] Furthermore, in S5, the expression for the optimization model is: ,in, The speed corresponding to the maximum traffic volume in each segmented speed range. For speed The corresponding ideal density.

[0035] Furthermore, the constraints for optimizing the model include velocity range, density range, consistency principle, and queue stability condition;

[0036] Expression for speed range ;in, The speed corresponding to the maximum traffic volume in each segmented speed range. The minimum prescribed driving speed within the segmented speed range, This corresponds to the maximum driving speed;

[0037] The expression for the density range is: ;in, The minimum vehicle spacing specified for adjacent high-speed segments. The minimum vehicle spacing specified for adjacent low-speed segments. For the length of the vehicle, For speed The corresponding ideal density;

[0038] The expression for the consistency principle is: and ;in, As the first weighting coefficient, This is the second weighting coefficient. for Smaller velocity change values, for and( The slope of the line connecting the two sides. for and( The slope of the line connecting the two sides. The speed corresponding to the maximum traffic volume in each segmented speed range. For speed The corresponding ideal density;

[0039] The expression for queue stability is: and Where M is a large integer, The net headway is defined in the ideal headway-speed relationship model.

[0040] The beneficial effects of this invention are as follows: This invention provides an automatic vehicle headway variation method and a vehicle acceleration trajectory generation strategy, which can simultaneously meet the safety distance regulations with segmented rules and improve traffic operation efficiency, providing an implementation path for automatic vehicles to meet existing safety distance regulations. Furthermore, this invention is geared towards adaptive control systems and can be applied to trajectory control of automatic vehicles in mixed traffic conditions. Attached Figure Description

[0041] Figure 1 A flowchart of a variable headway adjustment and adaptive vehicle trajectory control method;

[0042] Figure 2 This is a schematic diagram illustrating the relationship between velocity and density. Detailed Implementation

[0043] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, the present invention provides a method for variable headway adjustment and adaptive vehicle trajectory control, comprising the following steps:

[0045] S1. Obtain safe following distance rules, speed limits, and vehicle status information;

[0046] S2. Construct a speed-density piecewise function based on safe following distance rules, speed limits, and vehicle status information;

[0047] S3. Construct a model of the relationship between ideal headway and speed;

[0048] S4. Based on the relationship model between ideal vehicle headway and speed, determine the acceleration trajectory generation model;

[0049] S5. Construct an optimization model and collaboratively optimize the parameters in the velocity-density piecewise function and acceleration trajectory generation model to complete vehicle trajectory control.

[0050] The purpose of this application is to provide a method for changing the ideal headway of an autonomous vehicle and an adaptive cruise control strategy that takes into account the following distance regulations on highways. This addresses the problem of how to design a desired headway strategy that varies with speed under the premise that the following distance is subject to regulatory constraints, and embeds it into a longitudinal vehicle acceleration control framework that can achieve queue stability, thereby improving the maximum flow rate and traffic capacity in high-speed areas.

[0051] In S1, obtain the safe following distance rules and speed constraints, including speed limits. Minimum driving speed (Corresponding to the Chinese highway regulation of 60km / h), speed in the segmented vehicle spacing constraint (Corresponding to the Chinese highway safety following distance rule of 100km / h), the controlled vehicle's length, position (which can be the rear bumper), speed, and the position (which can be the rear bumper) and speed information of the vehicle in front in the same lane.

[0052] In this embodiment of the invention, in S2, the function expression for the velocity and density corresponding to the horizontal line in the velocity-density piecewise function is as follows:

[0053] ;

[0054] in, Let the vehicle speed be a function of the ideal density. Speed ​​limits are set for this section of road;

[0055] In S2, the function expression for velocity and density corresponding to the non-horizontal lines in the piecewise velocity-density function is as follows:

[0056] ;

[0057] ;

[0058] ;

[0059] in, For line segments The slope, The intercept is... The velocity corresponding to one end of the line segment. The velocity corresponding to the other end of the line segment. For vehicle speed The density is calculated based on the ideal vehicle spacing and vehicle length. For vehicle speed The density is calculated based on the ideal vehicle spacing and vehicle length. For speed The corresponding density.

[0060] A piecewise velocity-density function is constructed to form a basic graph across the entire density range. Given that, under steady-state conditions (vehicles traveling at desired spacing), traffic managers need to improve traffic efficiency while maintaining safe spacing, and that with constant speed, the minimum safe spacing maximizes flow rate, thus improving and ensuring traffic efficiency. Furthermore, it is acceptable for short-term variations in spacing due to traffic flow disturbances to be slightly less than the safe spacing.

[0061] Based on the above two points, within the permissible speed range of highways, the minimum vehicle spacing can be selected as the desired vehicle spacing for the segmented constrained speed values. For example, taking the highway following distance safety regulations in the Implementation Regulations of the Road Traffic Safety Law of the People's Republic of China as an example, the ideal vehicle spacing corresponding to a speed of 100 km / h can be 100 m. Based on this, the constructed speed-density piecewise function is as follows: Figure 2 As shown. Among them, and They are respectively and The corresponding ideal vehicle spacing, Let be the length of the vehicle, and s_0 be the minimum distance between vehicles when stationary. Figure 2 In the middle, point E is at velocity and Between these points, the location with the highest traffic flow calculated from the basic graph is identified, with G representing the location corresponding to the traffic capacity. E and G are key points. To ensure stability, other straight sections can be appropriately adjusted into multiple segmented straight lines.

[0062] In this embodiment of the invention, S3 includes the following sub-steps:

[0063] S31. Calculate the ideal frontage distance;

[0064] S32. Based on the ideal frontage distance, construct a model relating the ideal frontage distance to the speed.

[0065] The relationship between ideal front-end distance and speed is established to prepare for embedding an acceleration control model. The ideal front-end distance can be obtained based on the relationship between front-end spacing and density.

[0066] In this embodiment of the invention, in S31, the ideal front-end spacing is... The expression is:

[0067] ;

[0068] in, For line segments The slope, The intercept is... For vehicle speed.

[0069] In this embodiment of the invention, in S32, the ideal headway and speed relationship model includes the ideal headway. The expression is:

[0070] ;

[0071] in, For line segments The slope, The intercept is... For vehicle speed;

[0072] In S32, the net headway is a crucial factor in the relationship between ideal headway and speed. The expression is:

[0073] ;

[0074] in, For ideal front-end spacing, For the length of the vehicle, This refers to the minimum distance between vehicles when they are stationary.

[0075] In this embodiment of the invention, in S4, the expression for the acceleration trajectory generation model is as follows:

[0076] ;

[0077] in, Let acceleration be a function of time t. As the first weighting coefficient, This is the second weighting coefficient. Let be the speed of the vehicle in front at time t. Let be the speed of the vehicle at time t. Let t be the position of the vehicle in front at time t. Let be the position of this vehicle at time t. This is the ideal net headway for this vehicle.

[0078] The form and related parameters of the acceleration trajectory generation model based on the Helly model are determined, subject to the constraint that a(t) ≤ min(a max ,(v limit -v(t)) / Δt),2*(xp(t+Δt)-x(t)-v(t)*Δt-l_veh–s0) / (Δt) 2 ) and a(t)≥max(a min ,-v(t) / Δt) and xp(t+Δt)=xp(t)+vp(t)*Δt+0.5*ap(t)*Δt*Δt; where c1 and c2 are weighting coefficients. a max and a min These represent the maximum acceleration and the minimum acceleration, respectively, which is also the maximum deceleration.

[0079] In this embodiment of the invention, in S5, the expression for the optimization model is: ,in, The speed corresponding to the maximum traffic volume in each segmented speed range. For speed The corresponding ideal density.

[0080] In this embodiment of the invention, the constraints of the optimization model include speed range, density range, consistency principle, and queue stability condition;

[0081] Expression for speed range ;in, The speed corresponding to the maximum traffic volume in each segmented speed range. The minimum prescribed driving speed within the segmented speed range, This corresponds to the maximum driving speed;

[0082] The expression for the density range is: ;in, The minimum vehicle spacing specified for adjacent high-speed segments. The minimum vehicle spacing specified for adjacent low-speed segments. For the length of the vehicle, For speed The corresponding ideal density;

[0083] The expression for the consistency principle is: and ;in, As the first weighting coefficient, This is the second weighting coefficient. for Smaller velocity change values, for and( The slope of the line connecting the two sides. for and( The slope of the line connecting the two sides. The speed corresponding to the maximum traffic volume in each segmented speed range. For speed The corresponding ideal density;

[0084] ;

[0085] ;

[0086] ;

[0087] ;

[0088] Δv = 0.18, 0.36, 1.8, 3.6;

[0089] The expression for queue stability is: and Where M is a large integer, The net headway is defined in the ideal headway-speed relationship model.

[0090] A value of 8 can be chosen. The consistency principle ensures that under small velocity disturbances, the change in acceleration will not exhibit inconsistencies in sign, thus preventing acceleration oscillations. Since velocity and density have a linear relationship, consistency can be guaranteed; therefore, consistency can be considered only at the connection points of piecewise linear functions in the model. The stability condition is used to ensure the local stability of vehicles and the stability of the queue. Ensuring queue stability guarantees traffic flow stability. During parameter co-optimization, once the parameters are determined... and Then, the feasible regions of velocity and density can be discretized, and the optimal solution can be determined by enumeration. For different and By combining the above methods, calculate the optimal solution. Compare the different optimal solutions to determine the suitable or optimal one. and The combination of .

[0091] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for variable headway adjustment and adaptive vehicle trajectory control, characterized in that, Includes the following steps: S1. Obtain safe following distance rules, speed limits, and vehicle status information; S2. Construct a speed-density piecewise function based on safe following distance rules, speed limits, and vehicle status information; S3. Construct a model of the relationship between ideal headway and speed; S4. Based on the relationship model between ideal vehicle headway and speed, determine the acceleration trajectory generation model; S5. Construct an optimization model and collaboratively optimize the parameters in the velocity-density piecewise function and acceleration trajectory generation model to complete vehicle trajectory control.

2. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 1, characterized in that, In S2, the function expression for velocity and density corresponding to the horizontal line in the velocity-density piecewise function is as follows: ； in, Let the vehicle speed be a function of the ideal density. Speed ​​limits are set for this section of road; In S2, the functional expressions for velocity and density corresponding to non-horizontal lines in the velocity-density piecewise function are as follows: ； ； ； in, For line segments The slope, The intercept is... The velocity corresponding to one end of the line segment. The velocity corresponding to the other end of the line segment. For vehicle speed The density is calculated based on the ideal vehicle spacing and vehicle length. For vehicle speed The density is calculated based on the ideal vehicle spacing and vehicle length. For speed The corresponding density.

3. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 1, characterized in that, S3 includes the following sub-steps: S31. Calculate the ideal frontage distance; S32. Based on the ideal frontage distance, construct a model relating the ideal frontage distance to the speed.

4. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 3, characterized in that, In S31, the ideal front-end spacing The expression is: ； in, For line segments The slope, The intercept is... For vehicle speed.

5. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 3, characterized in that, In S32, the ideal headway and speed relationship model includes the ideal headway. The expression is: ； in, For line segments The slope, The intercept is... For vehicle speed; In S32, the net headway is in the relationship model between the ideal headway and speed. The expression is: ； in, For ideal front-end spacing, For the length of the vehicle, This represents the minimum distance between vehicles when they are stationary.

6. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 1, characterized in that, In S4, the expression for the acceleration trajectory generation model is as follows: ； in, Let acceleration be a function of time t. As the first weighting coefficient, This is the second weighting coefficient. Let be the speed of the vehicle in front at time t. Let be the speed of the vehicle at time t. Let t be the position of the vehicle in front at time t. Let be the position of this vehicle at time t. This is the ideal net headway for this vehicle.

7. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 1, characterized in that, In S5, the expression for the optimization model is: ,in, The speed corresponding to the maximum traffic volume in each segmented speed range. For speed The corresponding ideal density.

8. The variable headway adjustment and adaptive vehicle trajectory control method according to claim 1, characterized in that, The constraints of the optimization model include speed range, density range, consistency principle, and queue stability condition; The expression for the speed range ;in, The speed corresponding to the maximum traffic volume in each segmented speed range. The minimum prescribed driving speed within the segmented speed range, This corresponds to the maximum driving speed; The expression for the density range is: ;in, The minimum vehicle spacing specified for adjacent high-speed segments. The minimum vehicle spacing specified for adjacent low-speed segments. For the length of the vehicle, For speed The corresponding ideal density; The expression for the consistency principle is: and ;in, As the first weighting coefficient, This is the second weighting coefficient. for Smaller velocity change values, for and( The slope of the line connecting the two sides. for and( The slope of the line connecting the two sides. The speed corresponding to the maximum traffic volume in each segmented speed range. For speed The corresponding ideal density; The expression for the queue stability is: and Where M is a large integer, The net headway is defined in the ideal headway-speed relationship model.

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