A Heterogeneous Autonomous Vehicle Platooning Method for Energy Saving

Abstract

This invention proposes an energy-saving heterogeneous autonomous vehicle platooning method, belonging to the field of vehicle platooning technology. This method rationally arranges the number, type, arrangement order, speed, and spacing of vehicles in the platoon before executing a transportation task, enabling more efficient and energy-saving completion of the task. Through simulation, it uses aerodynamic principles to calculate the fuel-saving rate under different platooning strategies to analyze the optimal platooning strategy for heterogeneous autonomous vehicles, reducing fuel consumption and transportation costs. Furthermore, it provides the optimal joining position when an external vehicle attempts to join the platoon.

Description

Technical Field

[0001] This invention relates to the field of vehicle platooning technology, specifically a method for platooning multiple heterogeneous autonomous vehicles. Background Technology

[0002] The research on autonomous vehicle platooning originates from the research on task planning and cooperation problems in multi-agent systems. As an important technical hotspot and cutting-edge topic in vehicle-road cooperative systems, it mainly focuses on how multiple autonomous vehicles can maintain a relatively stable motion state with nearby autonomous vehicles by adjusting their own speed and steering in complex and ever-changing traffic environments, while meeting task requirements and adapting to the constraints of the surrounding environment, thereby realizing cooperative driving behavior among multiple autonomous vehicles through wireless communication.

[0003] Current research on heterogeneous autonomous vehicle platooning includes: cooperative platooning methods, environmental perception in autonomous driving systems, vehicle following methods suitable for platooning, and collaborative execution of computational tasks in autonomous vehicle platooning. Most studies employ wireless communication and signal control to develop platooning methods. Regarding energy conservation, some research focuses on heterogeneous platoons composed of different autonomous vehicles, using MATLAB to establish a two-stage ecological platoon control strategy to improve fuel efficiency. However, due to the volatility of road conditions and network fluctuations, the acquisition of surrounding information can be inaccurate, and the aforementioned control methods do not provide a strategy that favors energy conservation in terms of the platoon's arrangement.

[0004] In summary, the problem with existing technologies is that neither offline planning and control nor real-time control strategies take into account the formation strategies of the fleet regarding factors such as arrangement order, vehicle spacing, and vehicle speed. They also fail to combine aerodynamic simulation to provide a formation method that is conducive to reducing fleet costs and improving energy efficiency. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide an energy-saving heterogeneous autonomous vehicle platooning method. This method reduces the fuel consumption of the platoon and improves its stability and road traffic capacity through a reasonable platooning strategy. During the transportation mission, the addition of external vehicles requires recalculation of the platooning strategy to ensure that the addition of external vehicles does not affect the efficiency of the original platoon.

[0006] The technical solution adopted by the present invention to achieve the above objectives is: a heterogeneous autonomous driving vehicle platooning method for energy saving, applied to a transportation task system, the transportation task system including multiple freight vehicles performing transportation tasks to be formed into a platoon and a control center for managing freight vehicles, the multiple freight vehicles performing transportation tasks to be formed into a platoon and the control center are communicatively connected.

[0007] The method includes the following steps:

[0008] Step 1: Freight vehicles waiting to be formed into a queue to perform transportation tasks send a queueing application to the control center, and send basic vehicle information to the control center at the same time as sending the queueing application.

[0009] Step 2: The control center determines whether the freight vehicle meets the platooning requirements based on the vehicle's basic information. If it does not meet the requirements, the platooning application is rejected and the control center reschedules the freight vehicle. If it meets the requirements, the control center determines whether each freight vehicle is a heterogeneous vehicle. If it is a heterogeneous vehicle, the complete platooning strategy is determined. If it is a homogeneous vehicle, there is no need to determine the vehicle arrangement order in the platooning strategy.

[0010] Among them, the formation strategy is to determine the economic speed range, the vehicle arrangement order, and the vehicle spacing.

[0011] The process for determining the economic speed range is as follows:

[0012] Based on the distance d of the transportation task m Based on the task requirements, the longest time t m Calculate the lower limit of speed v min The maximum speed v of freight vehicles on highways (1) To limit the speed limit v max Complete the determination of the economic speed range v;

[0013]

[0014] v max ≤v (1)

[0015] v min ≤v≤v max

[0016] The process for determining the vehicle arrangement order is as follows:

[0017] Based on the full load capacity of each freight vehicle, they are divided into small freight vehicles, medium freight vehicles, and large freight vehicles. The number of vehicles (n), the full load capacity (m), and the frontal area (A) of each vehicle are also considered. w Driving speed u a The rolling drag coefficient f is imported into the simulation module of the control center, and the drag coefficient c of each vehicle when it is traveling in the convoy is determined through aerodynamic simulation. d and the drag coefficient c′ when driving alone d The fuel-saving rate μ is calculated using the following formula, and the optimal vehicle arrangement order in the formation is determined by comparing the results.

[0018]

[0019] Where i represents the i-th vehicle, m i c represents the full load mass of the i-th vehicle. di Let A represent the drag coefficient of the i-th vehicle when it is traveling within the convoy. wi Let c' represent the frontal area of ​​the i-th vehicle when it is traveling within the convoy. di Let A′ represent the air resistance coefficient when the i-th vehicle is traveling alone. wi Let g represent the frontal area of ​​the i-th vehicle when it is traveling alone, and g represent the acceleration due to gravity.

[0020] The process for determining the vehicle spacing is as follows: Since all freight vehicles are autonomous vehicles, the braking distance of each vehicle is not considered. The spacing between each vehicle is calculated based on the communication delay and driving speed between each vehicle.

[0021] Vehicle spacing is d, communication delay is t, safety factor is a, and driving speed is u. a u a Let v be the upper limit of the economic speed. max ;

[0022] d = au a t

[0023] Step 3: The control center issues platooning instructions and formation strategies to the freight vehicles performing the transportation mission;

[0024] Step 4: The freight vehicles performing the transportation task receive the platooning instructions and platooning strategy, and begin to execute the platooning operation task;

[0025] Step 5: Team formation complete, ready to begin the transportation mission.

[0026] The basic vehicle information includes the vehicle's length, width, height, frontal area, and full load capacity.

[0027] The energy-saving heterogeneous autonomous driving vehicle platooning method further includes: a method for joining a heterogeneous vehicle fleet, applied to vehicles applying to join the fleet and the lead vehicle in the fleet, wherein the joining method includes:

[0028] Step 1: The vehicle to be joined sends a request to join the target fleet's lead vehicle, and the lead vehicle collects the basic vehicle information of the vehicle to be joined;

[0029] Step 2: Import the vehicle's basic information into the simulation module in the control center to calculate the optimal position for joining the queue and the optimal distance between the vehicle and the vehicles in front and behind.

[0030] Among them, the optimal vehicle spacing is consistent with the original vehicle spacing of the convoy; there are two ways to join the convoy, one is to join the convoy inside the convoy, and the other is to join the convoy at the rear of the convoy; the simulation module calculates and analyzes the convoy air resistance coefficient and fuel saving rate after the vehicle to be joined joins the convoy at different positions inside the convoy and at the rear of the convoy, and analyzes the optimal joining position;

[0031] If the optimal position is to join the convoy, the vehicle to be joined needs to move towards this position. The vehicles in front of this position maintain their original speed, while the vehicles behind begin to decelerate and make way for a safe distance before the target vehicle joins the convoy. The safe distance is the vehicle spacing d mentioned above. The vehicle to be joined needs to maintain the same acceleration as the vehicle behind to catch up with the vehicle in front. Calculate the safe distance and decelerate in advance to match the speed of the vehicle in front. If the optimal position is to join the rear of the convoy, the vehicle to be joined starts to accelerate from behind to catch up with the convoy. Calculate the safe distance and decelerate in advance to match the speed of the vehicle in front.

[0032] Step 3: The lead vehicle sends the joining instruction, joining location, and the distance between vehicles after joining to the vehicle to be joined, and waits for the joining operation to be completed;

[0033] Step 4: Once the vehicle to be added receives the joining instruction, its joining location, and the distance between vehicles after joining, the process of joining the fleet begins;

[0034] Step 5: The convoy joining operation is completed, and the convoy continues to perform its transportation task. Through the above design scheme, this invention can bring the following beneficial effects: By rationally arranging the number, type, arrangement order, driving speed, and vehicle spacing of the convoy before performing the transportation task, the transportation task can be completed more efficiently and energy-savingly; by using the simulation module to calculate the fuel-saving rate under different formation strategies based on aerodynamic principles, the optimal formation strategy for heterogeneous autonomous vehicles can be analyzed, thereby reducing the fuel consumption of heterogeneous convoys and lowering transportation costs; and by providing the optimal joining position when an external vehicle attempts to join the convoy. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and are used to understand the invention. They do not constitute an improper limitation of the invention. In the drawings:

[0036] Figure 1 A flowchart of a method for forming a queue of heterogeneous autonomous vehicles provided as an example of the present invention;

[0037] Figure 2 A flowchart illustrating the method for adding a vehicle to a queue, as provided in this invention example. Detailed Implementation

[0038] This invention provides a method for platooning heterogeneous autonomous vehicles for energy conservation. By using a reasonable platooning strategy, the method can reduce the fuel consumption of the platoon and improve its stability and road traffic capacity. During the transportation mission, the addition of external vehicles requires recalculation of the platooning strategy so that the addition of external vehicles does not affect the efficiency of the original platoon.

[0039] The freight vehicles performing transportation tasks are all autonomous vehicles, equipped with information collection modules and vehicle-to-everything (V2X) communication modules; the control center that manages the freight vehicles is equipped with communication modules, simulation modules, computing modules, and decision-making modules.

[0040] Information collection module: Used to receive basic vehicle information from external vehicles, including the vehicle's length, width, height, frontal area, and full load weight.

[0041] Vehicle-to-everything (V2X) communication module: used for communication between vehicles and between the control center and vehicles.

[0042] Simulation Module: Used to perform simulations. After receiving basic vehicle information from external vehicles, the simulation module imports this information into the preprocessed computational domain model, completing the setup of the complete computational domain model. It then runs the fluid simulation test function in the star-ccm+ platform and waits for the results to converge (residual value less than 10). -3 Once convergence is confirmed, the drag coefficient and frontal area of ​​each vehicle in the heterogeneous convoy are obtained. Preprocessing refers to the setting of conditions such as speed and pressure boundaries before the simulation module receives basic vehicle information from external vehicles. This allows the simulation module to complete the simulation process more quickly and obtain the desired drag coefficient when it receives other parameter information. (The simulation module is mainly used to conduct simulation experiments to obtain the drag coefficient of the heterogeneous convoy. The inputs are the length, width, and height of the vehicles, vehicle speed, vehicle spacing, and vehicle frontal area; the outputs are the drag coefficients of individual vehicles and vehicles traveling in a convoy.)

[0043] The simulation module includes the star-ccm+ platform, which builds a computational domain model. This model consists of a velocity inlet boundary, a pressure outlet boundary, a normal wall boundary, and a heterogeneous vehicle convoy model. The heterogeneous vehicle convoy model comprises various types of heterogeneous vehicles spaced at a safe distance of 5 meters. The velocity inlet boundary is set to a vehicle speed of 90 km / h, and the pressure outlet boundary is set to a pressure of 1*10. 3 pa, Ordinary wall boundary setting: The wall surface is set as a sliding surface.

[0044] The calculation module is used to calculate the fuel-saving rate μ using a fuel-saving rate model. (The calculation module is mainly used to calculate the fleet deployment strategy, including vehicle deployment order (determined by calculating the fuel-saving rate), vehicle spacing, and vehicle speed range. The inputs to the calculation module are gravitational acceleration, the full load mass of each type of vehicle, frontal area, number of vehicles, rolling resistance coefficient, vehicle speed, drag coefficient of each vehicle when driving alone, and drag coefficient when driving in a fleet. The output is the fuel-saving rate of the heterogeneous fleet. The calculation model is a fuel-saving rate model derived from existing aerodynamic theories.)

[0045] Decision module: Used to analyze the feasibility of forming a queue and joining a queue, and the decision is issued by the control center.

[0046] This invention mainly includes the following two aspects:

[0047] In a first aspect, this application provides a method for assembling a queue of multiple heterogeneous vehicles, applied to freight vehicles and a control center for managing freight vehicles, the method comprising:

[0048] Step 1: When the communication module in the control center receives a convoy application from a freight vehicle to perform a transportation task, the information collection module simultaneously receives the basic vehicle information of all freight vehicles.

[0049] Step 2: The decision-making module of the control center needs to determine whether the vehicles meet the platooning requirements based on the basic information of each freight vehicle. If they do not meet the requirements, the platooning application is rejected and the freight vehicles are rescheduled by the control center. If they meet the requirements, it is necessary to determine whether each vehicle is a heterogeneous vehicle. If they are heterogeneous vehicles, the complete platooning strategy is calculated in the calculation module. If they are homogeneous vehicles, there is no need to calculate the vehicle arrangement order in the platooning strategy.

[0050] The formation strategy is calculated by the calculation module, including determining the economic speed range, vehicle arrangement order, and vehicle spacing (the economic speed range is calculated based on the specific task and the maximum speed on the highway; the vehicle spacing is calculated based on the communication latency and the upper limit of the economic speed range; the vehicle arrangement order is derived from the fuel-saving rate calculated by the calculation module; the formation strategy with the highest fuel-saving rate is taken as the arrangement order of the heterogeneous fleet).

[0051] Based on the distance d of the transportation task m Based on the task requirements, the longest time t m Calculate the lower limit of speed v min The maximum speed v of freight vehicles on highways (1) To limit the speed limit v max Complete the determination of the economic speed range v;

[0052]

[0053] v max ≤v (1)

[0054] v min ≤v≤v max

[0055] Based on their full load capacity, freight vehicles are categorized into small, medium, and large freight vehicles. Small freight vehicles have a full load capacity of less than 4500 kg, medium freight vehicles between 4500 kg and 12000 kg, and large freight vehicles above 12000 kg. The number of vehicles (n), full load capacity (m), and frontal area (A) are also considered. w Driving speed u a The rolling resistance coefficient f and the gravitational acceleration g are given, along with the air resistance coefficient c of the i-th vehicle when it is traveling within the convoy. di The frontal area A of the i-th vehicle when it is traveling in the convoy wi The air drag coefficient c′ of the i-th vehicle when it is driving alone di The frontal area A′ of the i-th vehicle traveling alone wi The value of i ranges from 1 to n. The simulation module outputs the drag coefficient c of each freight vehicle as it travels within the convoy. d The drag coefficient c′ when driving alone d The fuel-saving rate μ is calculated using the following formula, and the formation order with the highest fuel-saving rate is determined by comparison.

[0056]

[0057] Where i represents the i-th vehicle, m i c represents the full load mass of the i-th vehicle. di Let A represent the drag coefficient of the i-th vehicle when it is traveling within the convoy. wi Let c' represent the frontal area of ​​the i-th vehicle when it is traveling within the convoy. di Let A′ represent the air resistance coefficient when the i-th vehicle is traveling alone. wi Let g represent the frontal area of ​​the i-th vehicle when it is traveling alone, and g represent the acceleration due to gravity.

[0058] The process for determining the vehicle spacing is as follows: Since all freight vehicles are autonomous vehicles, the braking distance of each vehicle is not considered. The spacing between each vehicle is calculated based on the communication delay and driving speed between each vehicle.

[0059] Vehicle spacing is d, communication delay is t, safety factor is a, and driving speed is u. a u a Let v be the upper limit of the economic speed. max

[0060] d = au a t

[0061] Where the safety factor a is 2 and the driving speed u a Taking a speed of 90 km / h and a communication delay of 100 ms, the calculated vehicle spacing d is 5 m.

[0062] Step 3: The communication module of the control center sends platooning instructions and formation strategies to the freight vehicles performing the transportation task;

[0063] Step 4: The communication module of the freight vehicle performing the transportation task receives the platooning instruction and platooning strategy and begins the platooning operation;

[0064] Step 5: Team formation complete, ready to begin the transportation mission.

[0065] Secondly, the present invention provides a method for joining a heterogeneous vehicle fleet, applicable to vehicles applying to join the fleet and the lead vehicle in the fleet, the joining method comprising:

[0066] Step 1: The communication module of the vehicle to be added sends a request to join the target fleet's navigator vehicle. The navigator vehicle then collects the target vehicle's basic vehicle information through its information collection module.

[0067] Step 2: Import the vehicle's basic information into the simulation module to calculate the optimal position for joining the queue and the optimal distance between the vehicle and the vehicles in front and behind.

[0068] The optimal vehicle spacing is consistent with the original platoon spacing and does not require additional calculation. There are two ways to join the platoon: joining the inner platoon or joining the rear of the platoon. Since the lead vehicle is not easy to replace, the method of external vehicles joining the platoon as lead vehicles is not considered for the time being. The simulation module needs to calculate and analyze the platoon air resistance coefficient and fuel saving rate after the vehicle to be joined joins the platoon at different positions inside the platoon and at the rear of the platoon, and analyze the optimal joining position.

[0069] If the optimal position is to join the convoy, the vehicle to be joined needs to move closer to this position. The vehicle in front of this position maintains its original speed, and the vehicle behind begins to decelerate to make way for a safe distance (i.e., the vehicle spacing d) before the target vehicle joins the convoy. The vehicle to be joined needs to maintain the same acceleration as the vehicle behind to catch up with the vehicle in front. Calculate the safe distance and decelerate in advance to match the speed of the vehicle in front.

[0070] If the best position is to join the rear of the convoy, the vehicle that joins should start accelerating from behind to catch up with the convoy. Calculate the safe distance and slow down in advance to match the speed of the vehicle in front.

[0071] Step 3: The communication module on the lead vehicle sends the join command, join location, and vehicle spacing after joining to the vehicle to be joined, and waits for the join operation to be completed;

[0072] Step 4: The communication module on the vehicle to be joined receives the joining instruction and joining information, and begins to execute the joining operation of the fleet;

[0073] Step 5: Once the convoy operation is complete, the convoy will continue its transportation mission.

[0074] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains.

[0075] Figure 1 The method for platooning heterogeneous autonomous vehicles provided in this invention includes the following steps:

[0076] In this transportation mission, one small truck, one medium truck and one heavy truck are on duty, and the speed limit for freight vehicles on the mission section is 90km / h.

[0077] Step 1: The communication module of the freight vehicle sends a team formation request to the control center and simultaneously sends the basic information of the freight vehicle performing the task to the control center;

[0078] Step 2: The control center determines that the information of the three vehicles meets the mission requirements, and judges them as a heterogeneous convoy based on their length, width and height dimensions, and transfers the basic information of the heterogeneous convoy to the calculation module.

[0079] Step 3: The calculation module solves the vehicle spacing and economic speed range of the three vehicles, transmits the information to the lead vehicle and the other two vehicles, and imports the basic information into the simulation module to obtain the air resistance coefficient of the convoy under different vehicle arrangement orders through simulation experiments.

[0080] Among them, the arrangement order with the highest fuel saving rate, calculated by aerodynamic simulation, is medium-sized trucks in the first place, small trucks in the middle, and heavy trucks in the last place, with a fuel saving rate of 12.60%.

[0081] The upper limit of the economic speed range is limited to 90 km / h. Based on the task requirement time and freight distance, the lower limit of the speed is calculated to be 80 km / h, resulting in an economic speed range of 80-90 km / h.

[0082] Assuming a platoon communication delay of 100ms, a safety factor of 2, and a driving speed of 90km / h (the maximum economical speed), then the vehicle spacing d = au. a t = 5m;

[0083] Step 4: The control center sends the optimal formation strategy to the lead vehicle's communication module, and the lead vehicle controls the other vehicles to complete the formation operation;

[0084] Step 5: After receiving the information, the navigator vehicle's communication module completes the team formation operation with other vehicles according to the optimal team formation strategy given by the calculation module and begins to execute the task. The navigator vehicle controls its speed within the economic speed range, and the two following vehicles maintain a specified distance from the vehicle in front.

[0085] Figure 2 The method for adding a component to a queue provided in this invention includes the following steps:

[0086] While the convoy was on a transport mission, a small freight vehicle attempted to join the convoy;

[0087] Step 1: Vehicles performing transportation tasks simultaneously discover that they have separated from their original convoy and there is a target convoy performing other tasks ahead. However, the destination of the vehicle waiting to join is the same as that of the target convoy. The vehicle sends a request to join the target convoy through the communication module.

[0088] Step 2: The navigator vehicle's communication module receives requests from other vehicles to join the convoy and sends the target vehicle information to the control center to analyze its likelihood of joining the convoy.

[0089] Step 3: The control center decision module analyzes that the vehicle to be added is consistent with the fleet's mission objective and that its addition will not have a significant impact on the fleet's transportation efficiency. It allows the vehicle to join the fleet. The calculation module imports the basic information of the vehicle to be added into the simulation module to start calculating the queue air resistance coefficient and fuel saving rate at different insertion positions. After calculation and comparison, it is determined that the small truck should be inserted between the small trucks and heavy trucks in the original fleet. The permission to join and the joining position information are sent back to the navigator vehicle.

[0090] Step 4: The lead vehicle's communication module receives the joining permission and joining location information, sends a joining command to the vehicle to be joined, and sends a deceleration command to the heavy truck to give way to the safe distance calculated above so that the vehicle to be joined can join the convoy;

[0091] Step 5: The communication module of the vehicle to be joined receives the instruction and begins to accelerate to catch up with the convoy. When it is about to catch up with the heavy truck, it begins to decelerate to the convoy's speed and reaches the specified safe distance to complete the joining of the convoy and continue to perform the transportation task.

Claims

1. A method for platooning heterogeneous automated vehicles for energy conservation, applied to a transportation task system, the transportation task system including multiple freight vehicles performing transportation tasks and forming platoons, and a control center managing the freight vehicles, wherein the multiple freight vehicles performing transportation tasks and forming platoons are communicatively connected to the control center, characterized in that, The method includes the following steps: Step 1: Freight vehicles waiting to be formed into a queue to perform transportation tasks send a queueing application to the control center, and send basic vehicle information to the control center at the same time as sending the queueing application. Step 2: The control center determines whether the freight vehicle meets the mission requirements for convoying based on the vehicle's basic information. If it does not meet the mission requirements, the convoy application is rejected and the control center reschedules the freight vehicle. If the task requirements are met, determine whether each freight vehicle is a heterogeneous vehicle. If it is a heterogeneous vehicle, determine the complete formation strategy. If it is a homogeneous vehicle, there is no need to determine the vehicle arrangement order in the formation strategy. Among them, the formation strategy is to determine the economic speed range, the vehicle arrangement order, and the vehicle spacing. The process for determining the economic speed range is as follows: Based on the distance d of the transportation task m Based on the task requirements, the longest time t m Calculate the lower limit of speed v min The maximum speed v of freight vehicles on highways (1) To limit the speed limit v max Complete the determination of the economic speed range v; in max ≤in (1) in min ≤v≤v max The process for determining the vehicle arrangement order is as follows: Based on the full load capacity of each freight vehicle, they are divided into small freight vehicles, medium freight vehicles, and large freight vehicles. The number of vehicles (n), the full load capacity (m) of each vehicle, and the frontal area (A) of each vehicle are also considered. w Driving speed u a The rolling drag coefficient f is imported into the simulation module of the control center, and the drag coefficient c of each vehicle when it is traveling in the convoy is determined through aerodynamic simulation. d and the drag coefficient c′ when driving alone d The fuel-saving rate μ is calculated using the following formula, and the optimal vehicle arrangement order in the formation is determined by comparing the results. Where i represents the i-th vehicle, m i c represents the full load mass of the i-th vehicle. di Let A represent the drag coefficient of the i-th vehicle when it is traveling within the convoy. wi Let c' represent the frontal area of ​​the i-th vehicle when it is traveling within the convoy. di Let A′ represent the air resistance coefficient when the i-th vehicle is traveling alone. wi Let g represent the frontal area of ​​the i-th vehicle when it is traveling alone, and g represent the acceleration due to gravity. The process for determining the vehicle spacing is as follows: Since all freight vehicles are autonomous vehicles, the braking distance of each vehicle is not considered. The spacing between each vehicle is calculated based on the communication delay and driving speed between each vehicle. Vehicle spacing is d, communication delay is t, safety factor is a, and driving speed is u. a u a Let v be the upper limit of the economic speed. max ; d=au a t Step 3: The control center issues platooning instructions and formation strategies to the freight vehicles performing the transportation mission; Step 4: The freight vehicles performing the transportation task receive the platooning instructions and platooning strategy, and begin to execute the platooning operation task; Step 5: Team formation complete, ready to begin the transportation mission.

2. The method for platooning heterogeneous autonomous vehicles for energy conservation according to claim 1, characterized in that: The basic vehicle information includes the vehicle's length, width, height, frontal area, and full load capacity.

3. The method for platooning heterogeneous autonomous vehicles for energy conservation according to claim 1, characterized in that, Also includes: The method for joining a heterogeneous fleet is applied to vehicles applying to join the fleet and the lead vehicle in the fleet. The joining method includes: Step 1: The vehicle to be joined sends a request to join the target fleet's lead vehicle, and the lead vehicle collects the basic vehicle information of the vehicle to be joined; Step 2: Import the vehicle's basic information into the simulation module in the control center to calculate the optimal position for joining the queue and the optimal distance between the vehicle and the vehicles in front and behind. Among them, the optimal vehicle spacing is consistent with the original vehicle spacing of the convoy; there are two ways to join the convoy, one is to join the convoy inside the convoy, and the other is to join the convoy at the rear of the convoy; the simulation module calculates and analyzes the convoy air resistance coefficient and fuel saving rate after the vehicle to be joined joins the convoy at different positions inside the convoy and at the rear of the convoy, and analyzes the optimal joining position; If the optimal position is to join the convoy, the vehicle to be joined needs to move towards this position. The vehicles in front of this position maintain their original speed, while the vehicles behind begin to decelerate and make way for a safe distance before the target vehicle joins the convoy. The safe distance is the vehicle spacing d mentioned above. The vehicle to be joined needs to maintain the same acceleration as the vehicle behind to catch up with the vehicle in front. Calculate the safe distance and decelerate in advance to match the speed of the vehicle in front. If the optimal position is to join the rear of the convoy, the vehicle to be joined starts to accelerate from behind to catch up with the convoy. Calculate the safe distance and decelerate in advance to match the speed of the vehicle in front. Step 3: The lead vehicle sends the joining instruction, joining location, and the distance between vehicles after joining to the vehicle to be joined, and waits for the joining operation to be completed; Step 4: Once the vehicle to be added receives the joining instruction, its joining location, and the distance between vehicles after joining, the process of joining the fleet begins; Step 5: Once the convoy operation is complete, the convoy will continue its transportation mission.

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