A trajectory planning method for autonomous driving vehicles in mixed traffic environment

Abstract

The present invention provides a method for trajectory planning of an autonomous driving vehicle for fixed signal timing in a mixed environment of manual and automatic driving, including: collecting vehicle information entering the intersection control area; judging the type of the entering vehicle, if it is a manually driven vehicle, using the Newell following model to predict the trajectory of the vehicle, if it is an automatic driving vehicle, using the segmented trajectory planning method to plan the trajectory of the automatic driving vehicle; storing the vehicle's trajectory information, and when the next vehicle is detected to enter, updating the current vehicle information and starting vehicle trajectory planning. The present invention belongs to a heuristic algorithm, which realizes the trajectory planning of the autonomous driving vehicle in a mixed environment, improves the planning efficiency while ensuring safety, and can realize vehicle trajectory planning for signal intersections with different traffic flows, signal phases and vehicle penetration rates.

Description

Technical Field

[0001] The present invention relates to the technical field of road traffic control, and in particular to a method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment. Background Art

[0002] As the core part of urban roads, signalized intersections are the key to improving the efficiency of urban road traffic and have always been the focus of attention. Under the vehicle-road cooperative system, by planning and guiding the trajectory of autonomous driving vehicles at the entrance of the intersection, the congestion of signalized intersections can be effectively alleviated, thereby improving the overall traffic capacity of urban roads.

[0003] In a mixed traffic flow environment of manually driven vehicles and self-driving vehicles, self-driving vehicles are controllable vehicles. For signal-controlled intersections, the trajectory planning of self-driving vehicles requires that the vehicle pass through the intersection as quickly as possible while ensuring safety. Typical self-driving vehicle trajectory planning models mostly control the acceleration (deceleration) of the vehicle to change the position and speed of the vehicle in real time, thereby achieving the purpose of controlling the vehicle trajectory. However, such optimal vehicle control models generally require the establishment of complex nonlinear objective functions and constraints, which are difficult to solve and have low computational efficiency. For vehicle trajectory planning, detailed acceleration adjustment can theoretically obtain the optimal driving trajectory under certain goals, but considering the actual control effect of the vehicle and the complexity of calculation, the optimal control model is not the best choice for vehicle trajectory control. In addition, although the traffic efficiency of road intersections can be improved by controlling self-driving vehicles, the popularization of self-driving vehicles will take some time. In the future, road traffic will appear in a state where self-driving vehicles and manually driven vehicles are mixed.

[0004] Therefore, how to provide a trajectory planning method for an autonomous driving vehicle in a mixed traffic flow environment is an urgent problem that technicians in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method for trajectory planning of an autonomous driving vehicle for fixed signal timing in a mixed traffic flow environment of manual and autonomous driving vehicles, which realizes the trajectory planning of autonomous driving vehicles at signalized intersections in a mixed traffic flow environment, and improves the traffic efficiency of signalized intersections while meeting safety constraints.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment comprises the following steps;

[0008] S1. When the signalized intersection control area detects that the current vehicle n enters, the entry information of the vehicle n is collected, including the entry time, entry speed and entry position, and the vehicle entry information is used as the input parameter of trajectory planning;

[0009] S2. Planning the trajectory of the nth vehicle within the time interval according to the input parameters and the vehicle type: when it is detected that the incoming vehicle is a manually driven vehicle, entering S3; when it is detected that the incoming vehicle is an autonomous driving vehicle, entering S4;

[0010] S3. For manually driven vehicles entering the control area of ​​the signalized intersection, the trajectory of the manually driven vehicle is predicted using the Newell following model to obtain the vehicle's speed and position information;

[0011] S4. For an autonomous driving vehicle entering the control area of ​​a signalized intersection, based on the predicted trajectory information of the preceding vehicle and whether the preceding vehicle and the currently entering autonomous driving vehicle meet the minimum safety distance constraint, a segmented trajectory planning method is used to plan the trajectory of the autonomous driving vehicle, and the vehicle driving speed and trajectory information are obtained by planning;

[0012] S5. When the n+1th vehicle is detected entering the intersection control area, the planned trajectory information of vehicle n is used as the trajectory information of the preceding vehicle, the entry information of the n+1th vehicle is used as the information of the current entering vehicle, and the corresponding storage list is updated. S1 is continued to be executed to start the trajectory planning of the n+1th vehicle.

[0013] Preferably, in S1: the signalized intersection control area is an area on the entrance road at a fixed distance from the stop line, and the intersection adopts a fixed signal timing method for signal control.

[0014] Preferably, S3 includes:

[0015] S31, based on the trajectory information of the preceding vehicle n-1 and the entry information of the current vehicle n, the Newell following model is used to predict the driving position and driving speed of the current vehicle:

[0016] Determine whether the distance between vehicle n and the preceding vehicle n-1 always satisfies the minimum safety distance constraint x when the manually driven vehicle n accelerates first and then travels at a constant speed. n (t)≤x n-1 (t-τ n )-d n If yes, go to step 32; if no, adjust the predicted trajectory so that the distance between vehicle n and the preceding vehicle n-1 is the minimum safe distance, x n (t) represents the position of vehicle n at time t, τ n represents the time displacement of vehicle n, d nrepresents the spatial displacement of vehicle n;

[0017] S32: Determine whether vehicle n passes through the intersection at the same green light phase as the preceding vehicle n-1. If so, predict the predicted trajectory of the vehicle and update the trajectory of vehicle n at time t as the predicted trajectory.

[0018] Preferably, the predicted trajectory of the vehicle is:

[0019]

[0020]

[0021] In the formula, and represents the predicted trajectory of the vehicle considering safety constraints, represents the time when the vehicle reaches the stop line considering safety constraints, According to t fm The distance and speed relationship between vehicle n and the preceding vehicle n-1 at time t is established by establishing a system of equations to obtain fm and t fa :

[0022]

[0023]

[0024] Update the current prediction trajectory and

[0025] Preferably, the S32 further includes: if the vehicle n and the preceding vehicle n-1 do not pass through the intersection at the same green light phase, it indicates that the vehicle n will decelerate and stop before the stop line, and the driving trajectory of the vehicle is:

[0026]

[0027]

[0028] In the formula, and represents the predicted trajectory of the vehicle considering signal control and safety constraints, t d Indicates the moment when the vehicle starts to decelerate, t s Indicates the moment when the vehicle speed decreases to 0, t d The calculation formula is:

[0029]

[0030] t d With t s The relationship is:

[0031]

[0032] Update the predicted trajectory of vehicle n and

[0033] Preferably, S4 includes:

[0034] S41: Based on the entry speed and entry time of vehicle n, an initial trajectory of vehicle n is generated according to a driving mode of first accelerating and then driving at a constant speed;

[0035] S42: Generate a spatiotemporal safety trajectory based on the trajectory information of the preceding vehicle n-1; determine whether the initial trajectory of vehicle n collides with the spatiotemporal safety trajectory of the preceding vehicle n-1; if so, the initial trajectory does not satisfy the spatiotemporal safety constraint, and enter S43; if not, enter S44;

[0036] S43, when the initial trajectory of vehicle n does not meet the safety constraint, start forward trajectory planning and adjust the trajectory;

[0037] S44. Determine whether the signal phase is green when the vehicle travels to the stop line according to the current planned trajectory. If so, the current trajectory is the final planned trajectory of vehicle n; if not, start the backward trajectory planning and adjust the vehicle trajectory by changing the time when the vehicle reaches the stop line.

[0038] Preferably, in S42, a spatiotemporal safety trajectory S is generated according to the trajectory information of the preceding vehicle n-1. n-1 The calculation formula for the position and driving speed is:

[0039]

[0040]

[0041] In the formula, τ c represents the minimum headway of the autonomous vehicle, s represents the safe distance between autonomous vehicles, and l c represents the length of the autonomous vehicle, represents the position of the spatiotemporal safety trajectory of vehicle n-1 at time t, It represents the speed of vehicle n-1’s spatiotemporal safety trajectory at time t.

[0042] Preferably, the S43 includes:

[0043] In t fa Change the vehicle's acceleration to a , a <0, so that the vehicle trajectory and the space-time safety trajectory of the preceding vehicle are at t fm The position and velocity at the same time are the same, which can be expressed as:

[0044]

[0045]

[0046] After that, the acceleration of the vehicle trajectory is consistent with the acceleration of the space-time safety trajectory of the preceding vehicle. At this time, the vehicle trajectory increases by a t on the basis of the initial trajectory. fa Time to t fm The deceleration period and

[0047] t fm The merged segment after the moment;

[0048] According to the space-time safety trajectory of the vehicle and the preceding vehicle, fm Under the condition that the position and velocity are the same at the same time, establish a system of equations and solve for t fm and t fa :

[0049]

[0050]

[0051] Update the planned trajectory of vehicle n and And enter S44.

[0052] Preferably, the vehicle trajectory adds a t fa Time to t fm The deceleration segment at time t fm The planned trajectory of the vehicle in the merged segment after time is:

[0053]

[0054]

[0055] In the formula, and represents the planned trajectory of the vehicle considering safety constraints, represents the time when the vehicle reaches the stop line considering safety constraints,

[0056] Preferably, the S44 includes:

[0057] In t bm Time bm The vehicle acceleration is changed to a , a <0, then at t ba Change the vehicle acceleration to Make the vehicle reach the stop line at the beginning of the next green light phase:

[0058]

[0059] L n -1 (t) = t g

[0060] In the formula, t g Indicates the time when the green light phase starts, t e represents the time when vehicle n reaches the stop line without considering signal control, c represents the signal cycle length, L n -1 (t) represents the time when vehicle n reaches the stop line;

[0061] After that, the acceleration of the new planned trajectory of the vehicle is the same as the acceleration of the original planned trajectory from t0 to t bm At this time, the new trajectory adds a deceleration segment and an acceleration segment to the original planned trajectory, and the new planned trajectory of the vehicle is:

[0062]

[0063]

[0064] In the formula, and represents the planned trajectory of the vehicle considering signal control and safety constraints; according to the new vehicle trajectory and the original planned trajectory at t bm Under the condition that the position and velocity are the same at all times, establish a system of equations and solve for t bm and t ba :

[0065]

[0066]

[0067] Update vehicle n planning trajectory and

[0068] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects of the present invention include:

[0069] The present invention is aimed at a traffic flow environment where manual and automatic driving vehicles are mixed. In combination with signal timing information and phase information, the central control center plans the trajectory of the automatic driving vehicle at a fixed signal timing intersection, taking into account the predicted trajectory of the preceding vehicle, as well as the reasonable planning of the trajectory of manual and automatic driving vehicles, reducing the parking and delay of vehicles passing through the intersection and improving the traffic efficiency of the entire intersection. While ensuring safety, the planning efficiency is improved, and vehicle trajectory planning can be achieved for signal intersections with different traffic flows, signal phases, and vehicle penetration rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative work.

[0071] Figure 1 The real-time planning flow chart of the trajectory of an autonomous driving vehicle at a signal-controlled intersection in a mixed environment of manual and autonomous driving provided by the example of the present invention is as follows:

[0072] Figure 2 Schematic diagram of a four-entry signalized intersection provided by an embodiment of the present invention:

[0073] Figure 3 A schematic diagram of a situation where a vehicle trajectory violates a safety constraint provided by an embodiment of the present invention:

[0074] Figure 4 A schematic diagram of a vehicle trajectory generated by a forward trajectory planning method provided by an embodiment of the present invention:

[0075] Figure 5 A schematic diagram of a situation in which a vehicle trajectory reaches a stop line during a red light phase provided by an embodiment of the present invention:

[0076] Figure 6 A schematic diagram of a vehicle trajectory generated using a backward trajectory planning method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0077] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] like Figure 1 As shown, the present invention provides a real-time trajectory planning method for an autonomous driving vehicle at a signal-controlled intersection in a mixed environment of manual and autonomous driving, comprising the following steps:

[0079] S1: When the signalized intersection control area detects the entry of the nth vehicle, the entry information of vehicle n is collected, including the entry time, entry speed and entry position, and the vehicle entry information is used as the input parameter of trajectory planning.

[0080] S2: According to the category of vehicle n and the input parameters, the trajectory of vehicle n is planned, wherein the vehicle trajectory is a collection of vehicle driving positions within a period of time. When it is detected that the incoming vehicle is a manually driven vehicle, the process proceeds to step 3; when it is detected that the incoming vehicle is an autonomous driving vehicle, the process proceeds to step 4.

[0081] S3: For manually driven vehicles entering the control area, the trajectory of the manually driven vehicle is predicted using the Newell car-following model, and the predicted vehicle speed and position information is stored.

[0082] S4: For the autonomous driving vehicle entering the control area, the segmented trajectory planning method is used to plan the trajectory of the autonomous driving vehicle, and the planned vehicle driving speed and trajectory information are stored.

[0083] S5: When the n+1th vehicle is detected to enter the intersection control area, the information of the preceding vehicle and the incoming vehicle is updated, specifically including: using the planned trajectory information of vehicle n as the trajectory information of the preceding vehicle, using the entry information of the n+1th vehicle as the information of the current incoming vehicle, and updating the corresponding storage list. That is, when the n+1th vehicle enters the control area, the list storing the preceding vehicle information is updated to the trajectory information of vehicle n, and the information storing the current planned vehicle is updated to the entry information of the n+1th vehicle. Continue to step 1 to start vehicle trajectory planning.

[0084] Furthermore, if Figure 2 As shown, this embodiment takes a typical four-entry signal-controlled intersection as an example. Each direction includes a left-turn lane, a straight lane and a right-turn lane. The signal intersection control area is the area 300 meters away from the stop line on the entrance lane. The left-turn and straight-through flow of each entrance lane is the same, set to 600veh / h, and the traffic capacity of each lane is set to 3600veh / h. There are four phases in this intersection, namely, the north-south entrance lane straight, the north-south entrance lane left turn, the east-west entrance lane left turn, and the east-west entrance lane straight. Each phase is allocated 20s green light duration and 3s clearing duration in turn. All right-turning vehicles are not controlled by signal lights. The steps required for the embodiment of the present invention are described in detail:

[0085] In one embodiment, the specific execution steps of S1 include:

[0086] When the control area detects the entry of the nth vehicle, the entry information of vehicle n is collected, including the entry time, entry speed and entry position, and the vehicle entry information is used as the input parameter of trajectory planning.

[0087] In one embodiment, the specific execution steps of S2 include:

[0088] According to the category of vehicle n and the input parameters, the trajectory of vehicle n is planned, wherein the vehicle trajectory is a collection of vehicle driving positions within a period of time. When it is detected that the incoming vehicle is a manually driven vehicle, enter S3, and when it is detected that the incoming vehicle is an autonomous driving vehicle, enter S4.

[0089] In one embodiment, the specific execution steps of S3 include: for a manually driven vehicle entering the control area, using the Newell car-following model to predict the trajectory of the manually driven vehicle, and storing the predicted vehicle driving speed and position information.

[0090] S31, based on the trajectory information of the preceding vehicle n-1 and the entry information of the current vehicle n, the Newell following model is used to predict the driving position and driving speed of the current vehicle, specifically: when the manually driven vehicle n is driven in a manner of first accelerating and then driving at a constant speed, whether the distance between the vehicle n and the preceding vehicle n-1 always satisfies the minimum safety distance constraint x n (t)≤x n-1 (t-τ n )-d n If yes, enter S32, the predicted trajectory of the vehicle is:

[0091]

[0092]

[0093] In the formula, x n (t) represents the position of vehicle n at time t, such as x n (10) = 200, which means that the nth vehicle is 200 meters away from the starting point of the signal intersection control area at the 10th second. n (t)≤L,τ n represents the time displacement of vehicle n, d n represents the spatial displacement of vehicle n, v max Indicates the maximum speed allowed on the road, v n (t) represents the speed of vehicle n at time t, v n (t)≤v max , v0 represents the vehicle’s entry speed, t0 represents the vehicle’s entry time, t e represents the time when the vehicle reaches the stop line without considering signal control and safety constraints, x n (t e )=L, is the vehicle's acceleration.

[0094] Otherwise, adjust the predicted trajectory so that the distance between vehicle n and the preceding vehicle n-1 is the minimum safe distance. Specifically: at t fa Change the vehicle's acceleration toa ( a <0), so that the distance between vehicle n and the preceding vehicle n-1 is t fm Always meet x n (t fm )=x n-1 (t fm -τ n )-α n , and when t>t fm When x n (t) = x n-1 (t-τ n )-α n , the predicted trajectory of the vehicle is:

[0095]

[0096]

[0097] In the formula, and represents the predicted trajectory of the vehicle considering safety constraints, represents the time when the vehicle reaches the stop line considering safety constraints, According to t fm The distance and speed relationship between vehicle n and the preceding vehicle n-1 at time t is established by establishing a system of equations to obtain fm and t fa :

[0098]

[0099]

[0100] Update the current prediction trajectory and And enter S32.

[0101] S32: Determine whether vehicle n passes through the intersection at the same green light phase as the preceding vehicle n-1. If so, it is considered that the vehicle is traveling according to the predicted trajectory in S31. If not, it indicates that vehicle n will decelerate and stop before the stop line. The vehicle's driving trajectory is:

[0102]

[0103]

[0104] In the formula, and represents the predicted trajectory of the vehicle considering signal control and safety constraints, t d Indicates the moment when the vehicle starts to decelerate, t s Indicates the moment when the vehicle speed decreases to 0, td The calculation formula is:

[0105]

[0106] t d With t s The relationship is:

[0107]

[0108] Update the predicted trajectory of vehicle n and

[0109] S4. For the autonomous driving vehicle entering the control area, the segmented trajectory planning method is used to plan the trajectory of the autonomous driving vehicle, and the planned vehicle driving speed and trajectory information are stored.

[0110] S41. Based on the entry speed and entry time of vehicle n, generate the initial trajectory of vehicle n in a driving mode of first accelerating and then driving at a constant speed. Generally, the initial trajectory consists of an acceleration segment and a constant speed segment. The calculation formula for the position and driving speed of vehicle n at time t in the initial trajectory is:

[0111]

[0112]

[0113] In the formula, t e represents the time it takes for the vehicle to reach the stop line following the initial trajectory, x n (t e ).

[0114] S42, generating a spatiotemporal safety trajectory S according to the trajectory information of the preceding vehicle n-1 n-1 To meet the minimum safety distance constraint between vehicle n-1 and vehicle n. Figure 3 As shown, it is determined whether the initial trajectory of vehicle n collides with the spatiotemporal safety trajectory of the preceding vehicle n-1, that is, whether there is If yes, it means that the initial trajectory does not meet the space-time safety constraint, and the process goes to S43; if no, the process goes to S44. n-1 The calculation formula for the position and driving speed is:

[0115]

[0116]

[0117] In the formula, τ c represents the minimum headway of the autonomous vehicle, s represents the safe distance between autonomous vehicles, and l crepresents the length of the autonomous vehicle, represents the position of the spatiotemporal safety trajectory of vehicle n-1 at time t, It represents the speed of vehicle n-1’s spatiotemporal safety trajectory at time t.

[0118] S43. When the initial trajectory of vehicle n does not meet the safety constraints, start forward trajectory planning and adjust the trajectory. The specific method is: fa Change the vehicle's acceleration to a ( a <0), so that the vehicle trajectory and the space-time safety trajectory of the preceding vehicle are at t fm The position and velocity at the same time are the same, which can be expressed as:

[0119]

[0120]

[0121] After that, the acceleration of the vehicle trajectory is consistent with the acceleration of the spatiotemporal safety trajectory. Figure 4 As shown in the figure, the vehicle trajectory adds a deceleration segment and a merging segment on the basis of the initial trajectory, and the planned trajectory of the vehicle is:

[0122]

[0123]

[0124] In the formula, and represents the planned trajectory of the vehicle considering safety constraints, represents the time when the vehicle reaches the stop line considering safety constraints,

[0125] According to the space-time safety trajectory of the vehicle and the preceding vehicle, fm Under the condition that the position and velocity are the same at the same time, establish a system of equations and solve for t fm and t fa :

[0126]

[0127]

[0128] Update the planned trajectory of vehicle n and And go to 4).

[0129] S44, such as Figure 5As shown in , it is determined whether the signal phase is green when the vehicle drives to the stop line according to the current planned trajectory. If so, the current trajectory is the final planned trajectory of vehicle n; if not, the backward trajectory planning is turned on and the vehicle trajectory is adjusted by changing the time when the vehicle reaches the stop line. The specific method is: first, at t bm Change the vehicle acceleration to a ( a <0), then at t ba Change the vehicle acceleration to Make sure the vehicle can reach the stop line just at the beginning of the next green light phase:

[0130]

[0131] L n -1 (t) = t g (twenty two)

[0132] In the formula, t g Indicates the time when the green light phase starts, t e represents the time when vehicle n reaches the stop line without considering signal control, c represents the signal cycle length, L n -1 (t) represents the time when vehicle n reaches the stop line. When planning the backward trajectory of the autonomous vehicle, the signal timing information and phase information are combined to determine whether the vehicle trajectory reaches the signal intersection during the green light period.

[0133] The acceleration of the new trajectory and the original planned trajectory is from t0 to t bm Keep consistent with each other, generate Figure 6 The new trajectory is shown in Figure 1. At this time, the new trajectory adds a deceleration segment and an acceleration segment to the original planned trajectory, and the new planned trajectory of the vehicle is:

[0134]

[0135]

[0136] In the formula, and represents the planned trajectory of the vehicle considering signal control and safety constraints. bm Under the condition that the position and velocity are the same at all times, establish a system of equations and solve for t bm and t ba :

[0137]

[0138]

[0139] Update vehicle n planning trajectory and

[0140] S5. When the n+1th vehicle is detected to enter the intersection control area, the information of the preceding vehicle and the entering vehicle is updated, and S1 is executed to start vehicle trajectory planning.

[0141] The above is a detailed introduction to the automatic driving vehicle trajectory planning method in a mixed traffic flow environment provided by the present invention. In this embodiment, specific examples are used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0142] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in the present embodiments may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in the present embodiment, but will conform to the widest range consistent with the principles and novel features disclosed in the present embodiment.

Claims

1. A method for trajectory planning of an autonomous driving vehicle in a mixed traffic environment, characterized in that: The method comprises the following steps: S1. When the signalized intersection control area detects that the current vehicle n enters, the entry information of the vehicle n is collected, including the entry time, entry speed and entry position, and the vehicle entry information is used as the input parameter of trajectory planning; S2. Planning the trajectory of the nth vehicle within the time interval according to the input parameters and the vehicle type: when it is detected that the incoming vehicle is a manually driven vehicle, entering S3; when it is detected that the incoming vehicle is an autonomous driving vehicle, entering S4; S3. For manually driven vehicles entering the control area of ​​the signalized intersection, the trajectory of the manually driven vehicle is predicted using the Newell following model to obtain the vehicle's speed and position information; S3 includes: S31, based on the trajectory information of the preceding vehicle n-1 and the entry information of the current vehicle n, the Newell following model is used to predict the driving position and driving speed of the current vehicle: Determine whether the distance between vehicle n and the preceding vehicle n-1 always satisfies the minimum safety distance constraint x when the manually driven vehicle n accelerates first and then travels at a constant speed. n (t)≤x n-1 (t-τ n )-d n If yes, go to step 32; if no, adjust the predicted trajectory so that the distance between vehicle n and the preceding vehicle n-1 is the minimum safe distance, and the position L meters from the stop line is the starting point of the control area, x n (t) represents the position of vehicle n at time t, τ n represents the time displacement of vehicle n, d n represents the spatial displacement of vehicle n; S32: Determine whether vehicle n passes through the intersection at the same green light phase as the preceding vehicle n-1. If so, predict the predicted trajectory of the vehicle and update the trajectory of vehicle n at time t as the predicted trajectory; the predicted trajectory of the vehicle is: In the formula, and represents the predicted trajectory of the vehicle considering safety constraints, represents the time when the vehicle reaches the stop line considering safety constraints, According to t fm The distance and speed relationship between vehicle n and the preceding vehicle n-1 at time t is established by establishing a system of equations to obtain fm and t fa : Update the current prediction trajectory and S4. For an autonomous driving vehicle entering the control area of ​​a signalized intersection, based on the predicted trajectory information of the preceding vehicle and whether the preceding vehicle and the currently entering autonomous driving vehicle meet the minimum safety distance constraint, a segmented trajectory planning method is used to plan the trajectory of the autonomous driving vehicle, and the vehicle driving speed and trajectory information are obtained by planning; S5. When the n+1th vehicle is detected entering the intersection control area, the planned trajectory information of vehicle n is used as the trajectory information of the preceding vehicle, the entry information of the n+1th vehicle is used as the information of the current entering vehicle, and the corresponding storage list is updated. S1 is continued to be executed to start the trajectory planning of the n+1th vehicle.

2. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 1, characterized in that: In S1: the signalized intersection control area is an area on the entrance road that is a fixed distance from the stop line, and the intersection adopts a fixed signal timing method for signal control.

3. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 1, characterized in that: The step S32 further includes: if the vehicle n and the preceding vehicle n-1 do not pass through the intersection at the same green light phase, it indicates that the vehicle n will decelerate and stop before the stop line, and the vehicle's driving trajectory is: In the formula, and represents the predicted trajectory of the vehicle considering signal control and safety constraints, t d Indicates the moment when the vehicle starts to decelerate, t s Indicates the moment when the vehicle speed decreases to 0, t d The calculation formula is: t d With t s The relationship is: Update the predicted trajectory of vehicle n and 4. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 1, characterized in that: The S4 includes: S41: Based on the entry speed and entry time of vehicle n, an initial trajectory of vehicle n is generated according to a driving mode of first accelerating and then driving at a constant speed; S42: Generate a spatiotemporal safety trajectory based on the trajectory information of the preceding vehicle n-1; determine whether the initial trajectory of vehicle n collides with the spatiotemporal safety trajectory of the preceding vehicle n-1; if so, the initial trajectory does not satisfy the spatiotemporal safety constraint, and enter S43; if not, enter S44; S43, when the initial trajectory of vehicle n does not meet the safety constraint, start forward trajectory planning and adjust the trajectory; S44. Determine whether the signal phase is green when the vehicle travels to the stop line according to the current planned trajectory. If so, the current trajectory is the final planned trajectory of vehicle n; if not, start the backward trajectory planning and adjust the vehicle trajectory by changing the time when the vehicle reaches the stop line.

5. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 4, characterized in that: In S42, a spatiotemporal safety trajectory S is generated based on the trajectory information of the preceding vehicle n-1. n-1 The calculation formula for the position and driving speed is: In the formula, τ c represents the minimum headway of the autonomous vehicle, s represents the safe distance between autonomous vehicles, and l c represents the length of the autonomous vehicle, represents the position of the spatiotemporal safety trajectory of vehicle n-1 at time t, It represents the speed of vehicle n-1’s spatiotemporal safety trajectory at time t.

6. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 4, characterized in that: The S43 includes: In t fa Change the vehicle's acceleration to a , a <0, so that the vehicle trajectory and the space-time safety trajectory of the preceding vehicle are at t fm The position and velocity at the same time are the same, which can be expressed as: After that, the acceleration of the vehicle trajectory is consistent with the acceleration of the space-time safety trajectory of the preceding vehicle. At this time, the vehicle trajectory increases by a t on the basis of the initial trajectory. fa Time to t fm The deceleration segment at time t fm The merged segment after the moment; According to the space-time safety trajectory of the vehicle and the preceding vehicle, fm Under the condition that the position and velocity are the same at the same time, establish a system of equations and solve for t fm and t fa : Update the planned trajectory of vehicle n and And enter S44.

7. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 6, characterized in that: The vehicle trajectory adds a t to the initial trajectory. fa Time to t fm The deceleration segment at time t fm The planned trajectory of the vehicle in the merged segment after time is: In the formula, and represents the planned trajectory of the vehicle considering safety constraints, represents the time when the vehicle reaches the stop line considering safety constraints, 8. The method for trajectory planning of an autonomous driving vehicle in a mixed traffic flow environment according to claim 4, characterized in that: The S44 includes: In t bm Change the vehicle acceleration to a , a <0, then at t ba Change the vehicle acceleration to Make the vehicle reach the stop line at the beginning of the next green light phase: L n -1 (t)=t g In the formula, t g Indicates the time when the green light phase starts, t e represents the time when vehicle n reaches the stop line without considering signal control, c represents the signal cycle length, L n -1 (t) represents the time when vehicle n reaches the stop line; After that, the acceleration of the newly planned trajectory of the vehicle is the same as the acceleration of the trajectory planned in S41 or S43 from t0 to t bm At this time, the new trajectory adds a deceleration segment and an acceleration segment to the original planned trajectory, and the new planned trajectory of the vehicle is: In the formula, and represents the planned trajectory of the vehicle considering signal control and safety constraints; according to the new vehicle trajectory and the original planned trajectory at t bm Under the condition that the position and velocity are the same at all times, establish a system of equations and solve for t bm and t ba : Update vehicle n planning trajectory and

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