US-12623662-B2 - 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 min , t 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.

Inventors

• Xiangmo ZHAO
• Wenjing Wang
• Yukun Ding
• Congli Zhang
• Ze Li
• Xia Wu
• Siyuan Gong
• Haigen MIN
• Yihan Sun
• Kang Sun
• Wuqi WANG
• Guohui Zheng

Assignees

• CHANG'AN UNIVERSITY

Dates

Publication Date

20260512

Application Date

20230905

Priority Date

20220923

Claims (9)

1. 1 . A control method of mixed traffic flow on a 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 human-driven vehicle (HDV) on the vehicle platoon formation section; (S3) calculating a time interval [t min , t 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; 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 A + ∫ 0 t v leading ⁢ _ ⁢ cav ( t ) ⁢ dt = ∫ 0 t v follower ( t ) ⁢ dt + L H ; wherein L A represents a position of the leading vehicle determination point A; v leading_cav (t) represents a speed of the leading CAV at time t; v follower (t) represents a speed of the immediately-following HDV at the time t; and L H represents a vehicle car-following distance within the vehicle platoon.
2. 2 . The control method of claim 1 , wherein in step (S3), the time interval is calculated through steps of: calculating a minimum speed of the leading CAV 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.
3. 3 . The control method of claim 2 , wherein a speed of the leading CAV on the ramp satisfies the following conditions: L A + v min ⁢ t = v max ⁢ t + L H ; and ⁢ v min ⁢ t = L B - L A ; wherein: v min represents the minimum speed of vehicles on the ramp; v max represents the maximum speed of the vehicles on the ramp; L 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.
4. 4 . The control method of claim 2 , 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 cav_to_S when the leading CAV on the ramp reaches the merging point S is expressed as: L S - L B - v max 2 - v min 2 2 ⁢ a cav ⁢ 1 v max + 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 cav_to_S when the leading CAV reaches the merging point S is expressed as: L S - L Current ⁢ _ ⁢ LeadingCav ⁢ _ ⁢ Pos - v max 2 - v min 2 2 ⁢ a cav ⁢ 1 v max + v max - v min a cav ⁢ 1 = t cav ⁢ _ ⁢ to ⁢ _ ⁢ S ; wherein: L B represents a position of the vehicle platoon formation completion point B on the ramp; L S represents a position of the merging point S on the ramp; α cav1 represents an acceleration of the leading CAV; and L Current_LeadingCav_Pos represents a position of the leading CAV on the ramp when the vehicle platoon is successfully formed.
5. 5 . The control method of claim 4 , 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 + ∑ i = 2 n ⁢ ( τ n + d n v max ) ; wherein: τ n represents a response time of a n th HDV of the vehicle platoon; d n represents a minimum following distance of the n th HDV of the vehicle platoon; and n represents a n th vehicle of the vehicle platoon, and n≠1.
6. 6 . The control method of claim 5 , wherein in the time interval [t main , t max ], t 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 = { ( N - 1 ) ⁢ ( L H + l ) + L S - L B v max ⁢ ( case ⁢ 1 , L B = L B ′ ) ( N - 1 ) ⁢ ( L H + l ) + L S - L B ′ v max ⁢ ( case ⁢ ⁢ 2 , L B ≠ L B ′ ) ; t 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 = { ( N - 1 ) ⁢ ( L H + l ) + L S - L B v min ⁢ ( case ⁢ 1 , L B = L B ′ ) ( N - 1 ) ⁢ ( L H + l ) + L S - L B ′ v min ⁢ ( case ⁢ 2 , L B ≠ L B ′ ) ; wherein: N represents the number of vehicles in the vehicle platoon on the ramp; and l represents a length of the vehicles.
7. 7 . The control method of claim 2 , wherein in step (S4), when a position of the CAV on the main lane is within a range [M S -v mainlane_max t max , M S -v mainlane_max t 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 mainlane_max represents a maximum speed limit for the main lane, and M S represents a distance from a starting point of the main lane to the merging point S.
8. 8 . The control method of claim 7 , wherein in step (S4), the speed v mainlane_cav of the CAV on the main lane is expressed as: L mainlane ⁢ _ ⁢ cav + ∫ 0 t N v mainlane ⁢ _ ⁢ cav ( t ) ⁢ dt < M S ; wherein: L mainlane_cav represents a position of the CAV on the main lane when the vehicle platoon is successfully formed on the ramp; t N represents a time required for a last vehicle in the vehicle platoon to travel to the merging point S; and v mainlane_cav (t) represents a speed of the CAV on the main lane at time t.
9. 9 . The control method of claim 7 , wherein in step (S4), a distance L mainlane_cav_followdist between the CAV on the main lane and its preceding vehicle is expressed as: L mainlane ⁢ _ ⁢ cav ⁢ _ ⁢ followdist > ( N - 1 ) ⁢ L H + N · l ; wherein: N represents the number of vehicles in the vehicle platoon on the ramp; and l represents a length of the vehicles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of International Patent Application No. PCT/CN2023/074797, filed on Feb. 7, 2023, which claims the benefit of priority from Chinese Patent Application No. 202211165614.6, filed on Sep. 23, 2022. The content of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference. TECHNICAL FIELD This application relates to intelligent transportation, in particular to a control method of mixed traffic flow on freeway ramp based on controllable connected and autonomous vehicles. BACKGROUND With the development of fifth-generation (5G) communication technology, Internet-of-Vehicle (IoV) technology, intelligent vehicles and roadside equipment, connected and autonomous vehicles (CAVs) are emerging. The precision and effectiveness of control strategies can be greatly improved based on the precise perception, trafficability and control performance of CAVs. Meanwhile, the CAVs can also avoid the negative impact of randomness and uncertainty of driving behaviors of traditional human-driven vehicles (HDVs) on the operation of traffic system. As the freeway junction, the ramp merging zone often suffers serious traffic jam and traffic accidents owing to the frequent lane-changing behavior and large randomness of driving behavior. In the case of heavy main lane traffic flow, if the ramp vehicles cannot find an acceptable merging gap, it will lead to the mandatory lane-changing behavior of main lane vehicles, which will further aggravate traffic jam in the merging zone. The existing control methods for traffic flow on freeway ramp are predominated by signal light control. However, in view of the complex traffic scene at the freeway junction, it is difficult to deal with the complex traffic flow in the ramp merging zone through the single signal timing control. Besides, the control of the CAVs is also difficult in the mixed traffic flow control on the ramp. The unreasonable speed control of the CAVs will aggravate the traffic jam on the downstream section of the freeway. SUMMARY In view of the defects in the existing control strategies for traffic jam at the ramp merging zone of the freeway, the present disclosure provides a control method of mixed traffic flow on freeway ramp based on controllable connected and autonomous vehicles (CAVs). Technical solutions of the present disclosure are described as follows. This application provides a control method of mixed traffic flow on freeway ramp based on controllable 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 human-driven vehicle (HDV) on the vehicle platoon formation section;(S3) calculating a time interval [tmin, tmax] 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. In some embodiments, in step (S2), when the vehicle platoon is formed by two vehicles in an extreme scenario, a positional relationship between the leading CAV and an immediately-following HDV is expressed as: LA+∫0tvleading⁢_⁢cav(t)⁢dt=∫0tvfollower(t)⁢dt+LH;wherein: LA represents a position of the leading vehicle determination point A;vleading_cav(t) represents a speed of the leading vehicle at time t;vfollower(t) represents a speed of the immediately-following HDV at the time t; andLH represents a vehicle car-following distance within the vehicle platoon. In some embodiments, in step (S3), the time interval [tmin, tmax] when the vehicle platoon completely passes the merging point is calculated as follows: calculating a minimum speed and a maximum speed of the leading CAV on the ramp; calculating a time when the leading CAV on the ramp reaches the merging point S, and calculating a time when the last HDV of the vehicle platoon reaches the merging point S; and calculating the time interval [tmin, tmax] for the vehicle platoon to completely pass the merging point S based on the time when the last HDV in the vehicle platoon reaches the merging point S. In some embodiments, a speed of the vehicles on the ramp satisfies the following conditions: LA+vmin⁢t=vmax⁢t+LH;and⁢ vmin⁢t=LB-LA;wherein: vmin represents a minimum speed of the vehicles on the ramp;vmax represents a maximum speed of the vehicles on the ramp;LB represents a position of the vehicle platoon formation completion point B; andt represents a travel time of the vehicles on the ramp. In some embodiments, the time when the leading CAV on the ramp reaches the merging point S is calcula