CONTROL METHOD OF MIXED TRAFFIC FLOW ON FREEWAY RAMP BASED ON CONTROLLABLE CONNECTED AND AUTONOMOUS VEHICLES (CAVs)

Abstract

A control method of mixed traffic flow on freeway ramp based on controllable connected and autonomous vehicles (CAVs) is provided. A ramp is divided into a normal driving section, a vehicle platoon formation section and an accelerating and merging section. A vehicle platoon is formed by a leading CAV and human-driven vehicles (HDVs). Time interval [t.sub.min, t.sub.max] for the vehicle platoon to completely reach the merging point S is calculated. CAVs on the main lane and ramp are cooperatively controlled, and a merging gap is reserved for the ramp vehicle platoon. The vehicle platoon is allowed to accelerate and merge into the main lane. By means of the Internet-of-Vehicle (IoV) technology, the traffic situation on the main lane and downstream merging zone can be obtained in advance, and speeds of the CAVs are cooperatively controlled to lead the ramp vehicles to safely merge into the main lane.

Claims

1. A control method of mixed traffic flow on freeway ramp based on controllable connected and autonomous vehicles (CAVs), comprising: (S1) dividing a ramp into a normal driving section, a vehicle platoon formation section and an accelerating and merging section; and marking a leading vehicle determination point A, a vehicle platoon formation completion point B and a merging point S on the ramp; (S2) forming a vehicle platoon consisting of a leading CAV and at least one HDV on the vehicle platoon formation section; (S3) calculating a time interval [t.sub.min, t.sub.max] for the vehicle platoon to fully reach the merging point S; (S4) performing cooperative control between a CAV on a main lane and the leading CAV on the ramp to provide a merging gap for the vehicle platoon on the ramp; and (S5) allowing the vehicle platoon to accelerate and merge into the main lane.

2. The control method of claim 1, wherein in step (S2), when the vehicle platoon is formed, a positional relationship between the leading CAV and an immediately-following HDV is expressed as:
L.sub.A+.sub.0.sup.tv.sub.leading_cav(t)dt=v.sub.follower(t)dt+L.sub.H; wherein: L.sub.A represents a position of the leading vehicle determination point A; v.sub.leading_cav(t) represents a speed of the leading CAV at time t; v.sub.follower(t) represents a speed of the immediately-following HDV at the time t; and L.sub.H represents a vehicle car-following distance within the vehicle platoon.

3. The control method of claim 2, wherein in step (S3), the time interval is calculated through steps of: calculating a minimum speed and a maximum speed of the leading CAV on the ramp; and calculating a time when the leading CAV on the ramp reaches the merging point S, and calculating a time when a last HDV of the vehicle platoon reaches the merging point S to calculate the time interval.

4. The control method of claim 3, wherein a speed of the leading CAV on the ramp satisfies the following conditions:
L.sub.A+v.sub.mint=v.sub.max+L.sub.H; and
v.sub.mint=L.sub.BL.sub.A; wherein: v.sub.min represents the minimum speed of vehicles on the ramp; v.sub.max represents the maximum speed of the vehicles on the ramp; L.sub.B represents a position of the vehicle platoon formation completion point B on the ramp; and t represents a travel time of the vehicles on the ramp.

5. The control method of claim 3, wherein the time when the leading CAV on the ramp reaches the merging point S is calculated according to an actual platoon formation completion point B; case 1: when the actual vehicle platoon formation completion point B coincides with the vehicle platoon formation completion point B marked on the ramp, the time t.sub.cav_to_S when the leading CAV on the ramp reaches the merging point S is expressed as: $\frac{L_{S} - L_{B} - \frac{v_{\max}^{2} - v_{\min}^{2}}{2 a_{cav 1}}}{v_{\max}} + \frac{v_{\max} - v_{\min}}{a_{cav 1}} = t_{cav_to_S};$ and case 2: when the actual vehicle platoon formation completion point B is located between the leading vehicle determination point A and the vehicle platoon formation completion point B, the time t.sub.cav_to_S when the leading CAV reaches the merging point S is expressed as: $\frac{L_{S} - L_{Current_LeadingCav_Pos} - \frac{v_{\max}^{2} - v_{\min}^{2}}{2 a_{cav 1}}}{v_{\max}} + \frac{v_{\max} - v_{\min}}{a_{cav 1}} = t_{cav_to_S};$ wherein: L.sub.B represents a position of the vehicle platoon formation completion point B on the ramp; L.sub.S represents a position of the merging point S on the ramp; .sub.cav1 represents an acceleration of the leading CAV; and L.sub.Current_LeadingCav_Pos represents a position of the leading CAV on the ramp when the vehicle platoon is successfully formed.

6. The control method of claim 5, wherein the time when the last HDV of the vehicle platoon reaches the merging point S is calculated based on a Newell car-following model, expressed as: $t_{n} = t_{cav_to_S} + {.Math.}_{i = 2}^{n} (_{n} + \frac{d_{n}}{v_{\max}});$ wherein: t.sub.n represents a response time of a n.sup.th HDV of the vehicle platoon; d.sub.n represents a minimum following distance of the n.sup.th HDV of the vehicle platoon; and n represents a n.sup.th vehicle of the vehicle platoon, and n1.

7. The control method of claim 6, wherein in the time interval [t.sub.main, t.sub.max], t.sub.main represents a minimum time required for the last HDV of the vehicle platoon to reach the merging point S when the vehicle platoon is successfully formed, and is calculated as: $t_{\min} = {\begin{matrix} \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B}}{v_{\max}} (case 1, L_{B} = L_{B^{}}) \\ \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B^{}}}{v_{\max}} (case 2, L_{B} L_{B^{}}) \end{matrix};$ t.sub.max represents a maximum time required for the last HDV of the vehicle platoon to reach the merging point S when the vehicle platoon is successfully formed, and is calculated as: $t_{\max} = {\begin{matrix} \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B}}{v_{\min}} (case 1, L_{B} = L_{B^{}}) \\ \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B^{}}}{v_{\min}} (case 2, L_{B} L_{B^{}}) \end{matrix};$ wherein: N represents the number of vehicles in the vehicle platoon on the ramp; and l represents a length of the vehicles.

8. The control method of claim 3, wherein in step (S4), when a position of the CAV on the main lane is within a range [M.sub.S-v.sub.mainlane_maxt.sub.max, M.sub.S-v.sub.mainlane_maxt.sub.min], a speed of the CAV on the main lane is adjusted to provide a safe merging gap for the vehicle platoon on the ramp, wherein v.sub.mainlane_max represents a maximum speed limit for the main lane, and M.sub.S represents a distance from a starting point of the main lane to the merging point S.

9. The control method of claim 8, wherein in step (S4), the speed v.sub.mainlane_cav of the CAV on the main lane is expressed as:
L.sub.mainlane_cav+.sub.0.sup.t.sup.Nv.sub.mainlane_cav(t)dt<M.sub.S; wherein: L.sub.mainlane_cav represents a position of the CAV on the main lane when the vehicle platoon is successfully formed on the ramp; t.sub.N represents a time required for a last vehicle in the vehicle platoon to travel to the merging point S; and v.sub.mainlane_cav(t) represents a speed of the CAV on the main lane at time t.

10. The control method of claim 8, wherein in step (S4), a distance L.sub.mainlane_cav_followdist between the CAV on the main lane and its preceding vehicle is expressed as:
L.sub.mainlane_cav_followdist>(N1)L.sub.H+N.Math.l; wherein: N represents the number of vehicles in the vehicle platoon on the ramp; and l represents a length of the vehicles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0056] FIG. 1 schematically shows a freeway traffic scene according to an embodiment of the present disclosure.

[0057] FIG. 2 schematically shows the analysis of formation conditions of vehicle platoon on the ramp according to an embodiment of the present disclosure.

[0058] FIG. 3 schematically shows the case 1 when the vehicle platoon is formed according to an embodiment of the present disclosure.

[0059] FIG. 4 schematically shows the case 2 when the vehicle platoon is formed according to an embodiment of the present disclosure.

[0060] FIG. 5 schematically shows cooperative control of the CAV on the main lane according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0061] The present disclosure will be further described below with reference to the embodiments, which are merely illustrative of this application rather than a limitation to this application.

[0062] This application provides a control method of mixed traffic flow on freeway ramp based on controllable connected and autonomous vehicles (CAVs), which includes the following steps.

[0063] (S1) Referring to FIGS. 1-2, the ramp is divided into a normal driving section, a vehicle platoon formation section and an accelerating and merging section, and a leading vehicle determination point A, a vehicle platoon formation completion point B, and a merging point S are marked on the ramp. The position of the leading vehicle determination point A is L.sub.A; L.sub.B represents the position of the vehicle platoon formation completion point B, L.sub.S represents the position of the merging point S on the ramp, M.sub.S represents the position of the merging point S on the main lane.

[0064] (S2) A leading CAV and at least one HDV form a vehicle platoon on the vehicle platoon formation section.

[0065] When the vehicle platoon is formed by two vehicles in an extreme scenario, a positional relationship between the leading CAV and the immediately-following HDV is expressed as:

L.sub.A+.sub.0.sup.tv.sub.leading_cav(t)dt=.sub.0.sup.tv.sub.follower(t)dt+L.sub.H;

[0066] where L.sub.A represents the position of the leading vehicle determination point A;

[0067] v.sub.leading_cav(t) represents a speed of the leading CAV at time t;

[0068] v.sub.follower(t) represents a speed of the immediately-following HDV at time t;

[0069] L.sub.H represents a vehicle car-following distance within the vehicle platoon.

[0070] When the actual vehicle platoon formation completion point B coincides with the vehicle platoon formation completion point B marked on the ramp, the positional relationship between the leading CAV and the immediately-following HDV is expressed as:

[00006] $L_{A} + \frac{v_{A_cav}^{2} - v_{\min}^{2}}{2 a_{cav 2}} + v_{\min} t_{1} = \frac{v_{\max}^{2}}{2 a_{hdv 1}} + v_{\max} t_{2} + \frac{v_{\max}^{2} - v_{\min}^{2}}{2 a_{hdv 2}} + L_{H};$

[0071] where v.sub.A_cav represents a speed of the leading CAV when arriving at the leading vehicle determination point A;

[0072] .sub.cav2 represents a deceleration of the leading CAV;

[0073] .sub.dv1 represents an acceleration of the immediately-following HDV;

[0074] .sub.dv2 represents a deceleration of the immediately-following HDV;

[0075] t.sub.1 represents a travel time of the leading CAV at a constant speed;

[0076] t.sub.2 represents a travel time of the immediately-following HDV at a constant speed.

[0077] (S3) A time interval [t.sub.min, t.sub.max] (owing to the difference in speeds of the vehicles in the vehicle platoon) for the vehicle platoon to completely arrive at the merging point S is calculated as follows.

[0078] (S31) Firstly, a minimum speed of the vehicles on the ramp is calculated.

[0079] When the acceleration and deceleration process of the leading CAV and the immediately-following HDV are not considered, the speed of the leading CAV on the ramp is expressed as:

L.sub.A+v.sub.mint=v.sub.maxt+L.sub.H; and

v.sub.mint=L.sub.BL.sub.A;

[0080] where v.sub.min represents the minimum speed of the vehicles on the ramp;

[0081] v.sub.max represents the maximum speed of the vehicles on the ramp, where the vehicles refer to the CAV and the HDVs;

[0082] L.sub.B represents the position of the vehicle platoon formation completion point B;

[0083] t represents the travel time of vehicles on the ramp.

[0084] (S32) The time when the leading CAV reaches the merging point S and the time when the last HDV of the vehicle platoon reaches the merging point S are calculated respectively.

[0085] Calculating the time when the leading CAV arrives at the merging point S according to the actual vehicle platoon formation completion point B:

[0086] case 1: according to FIG. 3, when the actual vehicle platoon formation point B coincides with the vehicle platoon formation completion point B marked on the ramp, the time t.sub.cav_to_s when the leading CAV reaches the merging point S is expressed as:

[00007] $\frac{L_{S} - L_{B} - \frac{v_{\max}^{2} - v_{\min}^{2}}{2 a_{cav 1}}}{v_{\max}} + \frac{v_{\max} - v_{\min}}{a_{cav 1}} = t_{cav_to_S};$

and
case 2: according to FIG. 4, when the actual vehicle platoon formation completion point B is located between the leading vehicle determination point A and the vehicle platoon formation completion point B, the time t.sub.cav_to_s when the leading CAV reaches the merging point S is expressed as:

[00008] $\frac{L_{S} - L_{Current_LeadingCav_Pos} - \frac{v_{\max}^{2} - v_{\min}^{2}}{2 a_{cav 1}}}{v_{\max}} + \frac{v_{\max} - v_{\min}}{a_{cav 1}} = t_{cav_to_S}$

where L.sub.B represents the position of the vehicle platoon formation completion point B on the ramp;

[0087] L.sub.S represents a position of the merging point S on the ramp;

[0088] .sub.cav1 represents an acceleration of the leading CAV; and

[0089] L.sub.Current_LeadingCav_Pos represents a position of the leading CAV on the ramp when the vehicle platoon is successfully formed.

[0090] The time when the last HDV of the vehicle platoon reaches the merging point S is calculated based on the Newell car-following model, expressed as:

[00009] $t_{n} = t_{cav_to_S} + {.Math.}_{i = 2}^{n} (_{n} + \frac{d_{n}}{v_{\max}});$

[0091] where t.sub.n represents a response time of the n.sup.th HDV of the vehicle platoon;

[0092] d.sub.n represents a minimum following distance of the n.sup.th HDV of the vehicle platoon; and

[0093] n represents the n.sup.th vehicle of the vehicle platoon, and n1.

[0094] (S33) Finally, calculating a time interval of vehicle platoon completely arriving at merging point S:

[0095] [t.sub.min, t.sub.max] represents the time interval of vehicle platoon completely arriving at the merging point S, where it is assumed that a distance of two adjacent vehicles in the vehicle formation is the same, tmin represents a minimum time required for the last HDV of the vehicle platoon to reach the merging point S when the vehicle platoon is successfully formed, and is calculated as:

[00010] $t_{\min} = {\begin{matrix} \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B}}{v_{\max}} (case 1, L_{B} = L_{B^{}}) \\ \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B^{}}}{v_{\max}} (case 2, L_{B} L_{B^{}}) \end{matrix};$

[0096] t.sub.max represents maximum time, and is calculated as:

[00011] $t_{\max} = {\begin{matrix} \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B}}{v_{\min}} (case 1, L_{B} = L_{B^{}}) \\ \frac{(N - 1) (L_{H} + l) + L_{S} - L_{B^{}}}{v_{\min}} (case 2, L_{B} L_{B^{}}) \end{matrix};$

[0097] where L.sub.B represents a position of the vehicle platoon formation completion point B on the ramp;

[0098] L.sub.S represents a position of the merging point S on the ramp;

[0099] N represents the number of vehicles in the vehicle platoon on the ramp;

[0100] L.sub.H represents a vehicle car-following distance within the vehicle platoon; and

[0101] l represents a length of vehicles.

[0102] N represents the number of vehicles in the vehicle platoon and is calculated by the collaborative calculation of CAVs and roadside equipment. The specific algorithm steps are as follows:

[0103] Step (1), referring to FIG. 2, when a vehicle travels to the leading vehicle determination point A, the roadside equipment first determines its vehicle type. If the vehicle is a CAV, determining it as the leading vehicle and executing step (2); if the vehicle is a HDV, executing step (3).

[0104] Step (2), judging whether there are other leading CAVs in the vehicle platoon formation section at this time, if so, the first leading CAV in the vehicle platoon formation section and its rear vehicles automatically form platoon successfully. At this time, N=Count represents the number of vehicles in the current vehicle platoon, and the value of Count is determined by the vehicle counter at point A during the vehicle platoon forming period. After obtaining the number of vehicles of previous vehicle platoon N, reassign Count a value, set Count=1, go back to step (1); if not, assign Count a value, set Count=1, go back to step (1) and continue execution, and loop through step (4).

[0105] Step (3) judging whether there is leading CAV waiting to form in the vehicle platoon formation section at this time, if so, setting the value of the vehicle counter at point A as Count=Count+1, and executing step (4) in sequence; if not, going back to step (1) and continue execution.

[0106] Step (4) judging whether the leading CAV that do not form a vehicle platoon in the vehicle platoon formation section is traveling to vehicle platoon formation completion point B, if so, the leading CAV communicates with the roadside equipment at point B, and the vehicle counter stops counting. At this time, the value of the vehicle counter Count is the number of vehicles in the current vehicle platoon, then going back to step (1).

[0107] (S4) Performing cooperative control between the CAV on a main lane and the leading CAV on the ramp, adjusting the speed of the CAV on the main lane to provide a safe merging gap for the vehicle platoon on the ramp when position of the CAV on the main lane is within the range [M.sub.S-v.sub.mainlane_maxt.sub.max, M.sub.S-V.sub.mainlane_maxt.sub.min], where v.sub.mainlane_max represents a maximum speed limit on the main lane of freeway, M.sub.S represents the distance from the start of the main lane to the merging point S.

[0108] For the CAV within this range, the appropriate merging gap should be reserved for vehicle platoon on the ramp. As shown in FIGS. 4-5, the cooperative control CAV on the main lane must arrive at the merging point S later than the last vehicle of the vehicle platoon on the ramp, v.sub.mainlane_cav represents the speed of the cooperative control CAV on the main lane and satisfies a formula:

L.sub.mainlane_cav+.sub.0.sup.t.sup.Nv.sub.mainlane_cav(t)dt<M.sub.S;

[0109] where L.sub.mainlane_cav represents a position of the cooperative control CAV on the freeway main lane when the vehicle platoon is successfully formed on the ramp;

[0110] t.sub.N represents time required for the last vehicle in the vehicle platoon to travel to the merging point S when the vehicle platoon is successfully formed; and

[0111] v.sub.mainlane_cav(t) represents a speed of the cooperative control CAV on the main lane at the time t.

[0112] On the main lane, a distance L.sub.mainlane_cav_followdist between the cooperative control CAV and its preceding vehicle is expressed as:

L.sub.mainlane_cav_followdist>(N1)L.sub.H+N.Math.l;

[0113] where N represents the number of vehicles in the vehicle platoon on the ramp;

[0114] L.sub.H represents a vehicle car-following distance within the vehicle platoon; and

[0115] l represents a length of vehicles.

[0116] (S5) The vehicle platoon is allowed to accelerate and merge into the main lane.

[0117] This application, a control method of mixed traffic flow on freeway ramp based on controllable CAVs, obtains the traffic situation on the main lane and downstream merging zone of freeway in advance based on vehicle networking technology, utilizes the controllability of the CAVs, and controls the speeds of the CAVs to complete leading the vehicles on the ramp to merge into the main lane of the freeway safely, so as to avoid the situation that the drivers find the time to merge into the main lane only based on their own driving experiences and surrounding driving environment.

[0118] Described above are merely preferred embodiments of this application, which are not intended to limit the technical solutions of this application. It should be understood that various variations and replacements made by those skilled in the art without departing from the spirit and principles of the disclosure shall also fall within the scope of the disclosure defined by the appended claims.

CONTROL METHOD OF MIXED TRAFFIC FLOW ON FREEWAY RAMP BASED ON CONTROLLABLE CONNECTED AND AUTONOMOUS VEHICLES (CAVs)

Inventors

Cpc classification

Classification Explorer

B60W2520/00

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60W2530/00

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

G08G1/167

PHYSICS

Classification Explorer

B60W60/001

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60W30/146

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

G08G1/22

PHYSICS

Classification Explorer

B60W30/18163

PERFORMING OPERATIONS; TRANSPORTING

International classification

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B60W30/18

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

G08G1/00

PHYSICS

Classification Explorer

G08G1/16

PHYSICS

Classification Explorer

B60W60/00

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60W30/14

PERFORMING OPERATIONS; TRANSPORTING

Abstract

Claims

Description