A method for unmanned aerial vehicle supervision of construction vehicles entering and exiting a highway construction zone

Abstract

The application discloses a kind of construction vehicle in and out of highway construction area's unmanned aerial vehicle supervision method, it is related to traffic control technical field, including the construction area vehicle guidance control system based on unmanned aerial vehicle detection is built;Construction vehicle and social vehicle traffic demand accurate collection and simulation deduction are constructed;Construction vehicle scheduling plan and influence grade determination based on parking wave theory;Social vehicle hierarchical guidance control mechanism based on influence grade determination;The present application is based on the full field of view of unmanned aerial vehicle detection technology, real-time advantage, constructs a set of construction vehicle in and out scene, dynamically matches control level, realizes the control system of "construction vehicle scheduling-social traffic guidance" two-way cooperation, accurately adapts to the control demand of highway high speed, large flow, to guarantee the traffic safety of construction area, maximizes to reduce the interference to social traffic.

Description

Technical Field

[0001] This invention relates to the field of traffic control technology, and in particular to a method for monitoring construction vehicles entering and exiting highway construction zones using unmanned aerial vehicles (UAVs). Background Technology

[0002] With the continuous expansion of my country's expressway network and the intensive maintenance cycle of roads built in the early stages, expressway construction operations are becoming increasingly frequent, and the semi-closed operation mode of "construction while traffic continues" has become the norm in the industry. Although most expressway construction adopts fully enclosed management, and construction vehicles can enter the construction area through temporary roads built on national and provincial highways, in scenarios where there are no national or provincial highway connections or terrain conditions restrict access, construction vehicles still need to drive directly from the expressway into the work area, which inevitably causes interference with normal traffic flow.

[0003] Highways are characterized by high speeds and large traffic volumes. Construction vehicles, as heavy machinery, inherently suffer from large blind spots, large turning radii, and poor starting and stopping flexibility. Their entry and exit behaviors severely interfere with the high-speed flow of other vehicles. On the one hand, sudden weaving can lead to insufficient anticipation by following vehicles, inducing high-intensity rear-end collisions and minor accidents at critical points such as the transition zone upstream of lane closures. On the other hand, the occupation of lanes and slow movement of construction vehicles can quickly disrupt the orderly flow of traffic, spreading local delays into large-scale congestion through a "cluster effect." This contradiction between safety risks and traffic efficiency has become a bottleneck restricting traffic management in construction areas.

[0004] To alleviate the aforementioned problems, existing technologies have attempted various control measures, such as establishing multi-departmental coordination mechanisms, setting up temporary isolation facilities, and assigning personnel for on-site duty and patrols. However, these traditional methods exhibit significant limitations when dealing with the complex environment of highways: First, the scheduling of construction vehicles lacks precision. The platooning schemes for construction vehicles entering and leaving the work area rely heavily on manual experience and fail to rationally configure scheduling schemes based on real-time traffic flow, easily leading to significant intermingling and conflicts with public traffic, posing certain safety hazards. Second, the detection coverage of public traffic flow is incomplete and the response is untimely. Traditional ground patrols suffer from narrow field of vision and low efficiency, failing to quickly grasp key information such as traffic density and speed in different sections from upstream, resulting in traffic guidance lagging behind the dynamic changes in highway traffic flow, making it difficult to achieve early warning and diversion. Third, the control and guidance methods are relatively singular, failing to form a coordinated linkage system between "construction vehicle scheduling" and "public traffic flow guidance." Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a drone-based monitoring method for construction vehicles entering and exiting highway construction zones. Targeting the core characteristics of highways—high speeds and large traffic volumes—this method precisely matches the entry and exit needs of construction vehicles with the traffic flow needs of the general public. Through scientific scheduling of construction vehicles and efficient guidance of the general public's traffic flow, it achieves coordinated management and control, fundamentally reducing the incidence of conflicts and accidents and avoiding large-scale congestion.

[0006] To address the problems of the prior art, the technical solution of the present invention is as follows: A method for monitoring construction vehicles entering and exiting highway construction zones using unmanned aerial vehicles (UAVs) includes the following steps: S1. Build a vehicle guidance and control system for construction areas based on UAV detection, including a detection unit, an early warning and control unit, a back-end control unit and an instruction issuing unit. The units are interconnected and transmit data through communication links. The detection unit includes a vehicle-mounted dispatch terminal and a drone equipped with a high-definition camera. The vehicle-mounted dispatch terminal is installed inside the construction vehicle and has a built-in positioning module. The vehicle-mounted dispatch terminal establishes a data connection with the back-end control unit through a wireless communication module, which is used for the construction vehicle to report entry and exit demand information and location tracking data in real time. The drone equipped with the high-definition camera is deployed inside or near the construction area at a drone airport. The drone airport can meet the parking and battery swapping needs of multiple drones. The drone is interconnected with the back-end control unit in real time through a 4G or 5G wireless network, which is used to conduct real-time detection of social traffic flow in the entire warning area and obtain traffic flow parameters. The early warning and control unit includes a variable message display screen, a drone loudspeaker, an internet navigation map terminal, and on-site personnel. The variable message display screen is deployed at the corresponding cross-sections of each control zone within the construction warning area and is connected to the back-end control unit via wired or wireless means to receive and display tiered guidance information. The drone loudspeaker is integrated into the drone and is dispatched to the corresponding cross-section with the drone, enabling real-time voice guidance through the drone's onboard audio broadcast module. The internet navigation map terminal and the back-end control unit communicate via a data interface to push information, providing construction warnings or diversion suggestions to upstream vehicles. The on-site personnel are deployed at predetermined cross-sections and are equipped with handheld terminal devices to receive back-end instructions. The background control unit is used to receive construction vehicle positioning data and social traffic flow video data collected by the detection unit, perform data analysis and fusion, input the data into the simulation model for online simulation and output traffic flow parameters under different scheduling schemes; the instruction issuing unit establishes communication connections with each component of the early warning and control unit, and issues graded guidance instructions to the early warning and control unit according to the simulation results; The construction warning area is divided into a first-level control area, a second-level control area, and a third-level control area in the reverse direction of traffic. There are corresponding control sections between each control area. The first-level control area is located in the near-end area, the second-level control area is located in the middle area, and the third-level control area is located in the far-end area. Variable information display screens are deployed on each control section for hierarchical release of control information. S2. Constructing a method for accurately collecting and simulating the traffic demand of construction vehicles and other vehicles: S21. Collect data on the number and type of construction vehicles through vehicle-mounted dispatch terminals and electronic fences. Use drones equipped with high-definition cameras to collect real-time data on social vehicle traffic demand at the far end of the construction warning zone for the most recent detection cycle (3-5 minutes), as detailed below: When construction vehicles enter the work area, the driver reports the number and type of vehicles through the vehicle dispatch terminal. For multi-vehicle convoys, the lead vehicle reports all vehicle information. The system uses an electronic fence deployed upstream of the warning zone and the vehicle positioning module to automatically trigger identity verification and quantity statistics. The system compares the verification data automatically collected by the electronic fence with the data reported by the terminal in real time. When the verification result matches the reported data, the request is confirmed to be valid. If there is a discrepancy such as missed or over-reported data, the system immediately issues a correction reminder and notifies the management personnel to verify simultaneously. The electronic fence is deployed at a distance from the starting point of the warning zone to allow sufficient time for the drone to be dispatched to the detection section. The social vehicle traffic demand data collection is achieved by dispatching drones to hover over the far end of the warning zone for real-time detection. High-definition cameras are used to collect social vehicle traffic data within the most recent detection cycle to obtain the average speed, lane-level flow, and vehicle type information of social vehicles. S22. By receiving social vehicle data and construction vehicle data from the background control unit, the simulation model is dynamically simulated to obtain traffic flow parameters (density, speed, and flow rate) of construction vehicles entering / leaving the construction work area and upstream non-interlacing areas.

[0007] S3. Construction vehicle scheduling plan and impact level determination based on parking wave theory: Based on traffic flow parameters obtained from S2 simulation, the specific scenario type of construction vehicle passage demand is determined: S31. When the scene is determined to be a driving scene, the system calculates the deceleration wave speed caused by the construction vehicle driving in based on the parking wave theory. The calculation of the deceleration wave speed takes into account the average speed of social vehicles in the interlacing area, the traffic density, and the speed change of the construction vehicle during the driving process. Based on the deceleration wave speed and the deceleration time required for the construction vehicle to decelerate from the initial speed to the driving speed, the distance of the deceleration wave propagating upstream is calculated. S32. When the scenario is determined to be a departure scenario, the system optimizes the departure scheduling plan for construction vehicles with the goal of minimizing the total delay. For each departure scheduling requirement, all feasible scheduling batches and combinations of the number of vehicles in each batch are enumerated. Based on the parking wave theory, the acceleration wave speed, propagation distance, single delay and total delay under each plan are calculated. By comparing the total delay values ​​of all enumerated plans, the plan with the minimum total delay is selected as the optimal departure scheduling plan for construction vehicles and executed. S33. When it is determined that there are simultaneous entry and exit demands, the system calibrates and obtains the distance between the entrance and exit sections of the construction area. It compares the propagation distance of the accelerated wave of the optimal exit plan with this distance. If the propagation distance of the accelerated wave is less than the distance between the entrance and exit of the construction area, the system simultaneously executes entry and exit scheduling. If the propagation distance of the accelerated wave is greater than or equal to the distance between the entrance and exit of the construction area, it is determined that there is a risk of overlap between the exit traffic wave and the entry traffic wave. The system issues a temporary exit instruction to the vehicles waiting to exit through the vehicle terminal, and displays a no-exit sign at the exit. Priority is given to ensuring that the vehicles entering complete the entry operation before starting the exit scheduling process. According to the degree of impact of the traffic wave propagation distance on the passage of social vehicles, the impact level is quantified into three levels: Level 1, Level 2, and Level 3. S4. Based on the determined impact level, use variable message signs, drones, and internet navigation maps to conduct graded guidance and control of social vehicles.

[0008] Furthermore, towards the work area The cross sections are set sequentially in the upstream direction. , section , section Sections 3, 2, and 1, leading to the work area. The cross sections are set sequentially in the downstream direction. , section ; work area To the cross-section The space between them is a vertical buffer zone. , section To the cross-section The area between them is the upstream transition zone. Section 1 to Section 2 The area between these points is a construction warning zone. work area To the cross-section The area between them is the downstream transition zone. ; Construction warning area The control zones are divided into different levels: the area between section 1 and section 2 is the first-level control zone. The area between section 2 and section 3 is a secondary control zone. Section 3 and section The area between them is a Level 3 control zone. ; Section Used to determine the deceleration position of construction vehicles, from section 1 to section 2. The area between them is the upstream non-interlacing region, cross-section To the cross-section The area between them is an interwoven region.

[0009] Furthermore, in step S22, the traffic flow parameters obtained by the simulation model under the scenario of construction vehicles entering the construction work area are as follows: Average speed of social vehicles entering the upstream non-interlacing area ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); Average speed of social vehicles entering the weaving area ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); Construction vehicles at the cross-section initial velocity ( km / h ), in cross-section speed of entry ( km / h deceleration and acceleration ( ).

[0010] Furthermore, in S22, the simulation model dynamically calculates the traffic flow parameters for different scheduling schemes under the scenario of construction vehicles leaving the construction work area, as follows: Average speed of social vehicles leaving the upstream non-interlacing area ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); Average speed of social vehicles exiting the intersection ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); Construction vehicles at the cross-section initial departure speed ( km / h ), return to normal speed ( km / h ), acceleration ( ).

[0011] Furthermore, in S31, in the scenario where construction vehicles enter the construction work area, the propagation distance of the deceleration wave is... The calculation formula is as follows: ; in, To slow down the wave speed, for Construction vehicles from the cross-section Decelerate to cross section The time is calculated using the following formula: ; ; in, express The length of the entire construction vehicle team.

[0012] Furthermore, based on the propagation distance of the deceleration wave When construction vehicles enter a construction work area, the rules for determining the level of impact on other vehicles are as follows: when At that time, it was determined to be a Level 1 impact; when At that time, it was determined to be a level two impact; when At that time, it was determined to be a level three impact.

[0013] Furthermore, in step S32, the optimal scheduling scheme for construction vehicles in the scenario of construction vehicles leaving is determined by the following steps: S321. For all scheduling schemes Any scheduling scheme It can be represented as ,in: For the number of scheduling, The number of vehicles dispatched each time. The sum is the total number of vehicles ; Calculate the time it takes for a single vehicle to leave the construction area and return to normal speed. : ; S322, Calculate the first i Total time for this scheduling Because each dispatch may involve more than one vehicle, it's necessary to calculate the total acceleration time for all vehicles in the same dispatch. Since the vehicles depart in convoy, the travel time intervals are also a factor. Small enough, so The travel times of the two vehicles overlap. Calculation formula: ; S323, Calculate the first i The accelerated wave generated by this scheduling propagates over a distance of... The formula is calculated by multiplying the wave velocity by the total acceleration time of this scheduling: ; Formula for calculating wave speed: ; S324, Calculate the first i Single delay of the sub-scheduling , This is the product of the squared propagation distance and the three correction coefficients, where... For speed correction factor, This is the road correction factor. (Environmental correction factor), calculation formula: ; S325, Calculate the first k Total delay of all scheduling schemes , for m The sum of single-time delays for each scheduling operation is calculated using the following formula: ; contrast K Total delay of the plan The scheme with the smallest D is selected as the optimal departure scheduling scheme.

[0014] Furthermore, based on the propagation distance of the accelerated wave When construction vehicles leave the construction work area, the rules for determining the degree of impact on other vehicles are as follows: when At that time, it was determined to be a Level 1 impact; when At that time, it was determined to be a level two impact; when At that time, it was determined to be a level three impact.

[0015] Furthermore, for scenarios where construction vehicles simultaneously enter and exit, the construction vehicle dispatching plan is as follows: Spacing between entrances and exits of the construction area As the criterion for judgment, For construction vehicles to enter the cross section and the section of the road The straight-line distance is equal to the upstream transition zone. Vertical buffer zone Work area and downstream transition zone length The sum; If construction vehicles leave the planned area The system determines that the simultaneous entry and exit control strategy can be implemented, and the construction vehicles at the entry end can enter normally. If construction vehicles leave the planned area If the decision is made to suspend the dispatch of construction vehicles, priority will be given to ensuring that the vehicles entering the field complete their entry. Once the last construction vehicle has entered the field, the dispatch of vehicles leaving the field will be initiated.

[0016] Furthermore, the social vehicle classification and control mechanism based on the impact level determination is as follows: When the impact level of construction vehicles on social vehicles is Level 1, one drone is deployed at section 3 to issue early warnings and control to vehicles with abnormal traffic trajectories through the drone's loudspeaker; the variable message display screen only publishes construction operation information at section 3; and the Internet navigation map simultaneously pushes construction location warnings to social vehicles upstream. When the impact level is level 2, two drones are dispatched to cover section 2 and section 3 respectively, and the construction operation information is broadcast to passing vehicles through the drone's loudspeaker equipment; the variable message signs deployed in control zones at all levels broadcast the operation information and speed limit reminders; and the Internet navigation map pushes the construction vehicle flow ahead into the operation zone to upstream social vehicles.

[0017] When the impact level is level 2, three drones are dispatched to fully cover sections 1, 2, and 3. Multi-section early warning announcements are made through drone loudspeaker equipment, and variable message signs are deployed in control areas at all levels to push information on the entry and exit of construction and operation vehicles. Internet navigation maps push diversion suggestions to social vehicles at the upstream ramp entrances. On-site personnel are coordinated to assist in traffic control near section 3.

[0018] Compared with the prior art, the advantages of the present invention are as follows: 1. This invention abandons the traditional scheduling method that relies on manual experience. It uses a vehicle-mounted scheduling terminal combined with electronic fences to accurately collect dynamic information of construction vehicles, relies on drones to obtain social traffic flow parameters in real time, and uses online simulation to quantify the traffic flow interference impact of different formation and batch scheduling schemes. Based on parking wave theory, it calculates the traffic wave propagation range and total traffic delay, and selects the best departure scheduling scheme with the goal of minimizing the total delay. It can also intelligently identify conflict risks and adaptively adjust the scheduling order in the case of overlapping entry and exit scenarios. It configures the entry and exit sequence and formation of construction vehicles according to the real-time social traffic flow dynamics to avoid interweaving conflicts and avoid the safety hazards caused by manual scheduling from the source.

[0019] 2. This invention adopts a multi-level control zone drone dynamic inspection scheme to replace the traditional ground inspection mode. It can collect key traffic parameters such as traffic density and speed of upstream sections in real time with full coverage and lane level. Combined with online simulation and prediction of traffic flow disturbance and congestion evolution trend caused by construction vehicles entering and leaving, it relies on variable message signs, navigation maps, drone voice broadcasts and other methods to carry out advance warning and diversion, effectively solving the problem of traffic guidance lagging behind the dynamic changes of highway traffic flow, and improving the timeliness and accuracy of construction zone control.

[0020] 3. This invention establishes a three-level differentiated gradient control mechanism based on the impact level of traffic waves, integrating multiple methods such as dynamic inspection by drones, layered prompts on screens, remote navigation warnings, and on-site manual guidance to achieve coordinated linkage between "construction vehicle scheduling" and "social traffic flow guidance," effectively balancing traffic safety and efficiency in construction areas. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the overall process of the drone monitoring method for construction vehicles entering and exiting highway construction zones according to the present invention.

[0022] Figure 2 This is a schematic diagram of the installation and deployment of the vehicle guidance and control system of the present invention.

[0023] Figure 3 This is a flowchart of the method for accurately collecting and simulating the traffic demand of construction vehicles and other vehicles according to the present invention.

[0024] Figure 4 This is a schematic diagram of the construction vehicle entering the construction work area according to the present invention.

[0025] Figure 5 This is a schematic diagram of the construction vehicle of the present invention leaving the construction work area.

[0026] Figure 6 This is a schematic diagram illustrating that the simultaneous entry and exit of vehicles do not affect each other, according to the present invention.

[0027] Figure 7 This is a schematic diagram illustrating the mutual influence of simultaneous entry and exit in this invention.

[0028] Figure 8 This is a schematic diagram illustrating a scenario where construction vehicles are only allowed to enter the construction work area under the present invention, where simultaneous entry and exit interfere with each other. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] A method for monitoring construction vehicles entering and exiting highway construction zones using unmanned aerial vehicles (UAVs) includes the following steps: S1. Establish a vehicle guidance and control system for construction areas based on drone detection, including a detection unit, an early warning and control unit, a back-end control unit, and an instruction issuing unit; The detection unit includes an on-board dispatch terminal installed in the construction vehicle, an electronic fence deployed upstream of the construction warning zone, and a drone equipped with a high-definition camera; The early warning and control unit includes a variable message display screen, a loudspeaker integrated with drones, and a linked internet navigation map; The construction warning area is divided into Level 1, Level 2, and Level 3 control zones according to the control level. Variable message signs and drones are deployed in each control zone. S2. Constructing a method for accurately collecting and simulating the traffic demand of construction vehicles and other vehicles: S21. Collect data on the number and type of construction vehicles through vehicle-mounted dispatch terminals and electronic fences. Use drones equipped with high-definition cameras to monitor social vehicle traffic demand data in real time at the far end of the construction warning area for one cycle (3-5 minutes). S22. By receiving social vehicle data and construction vehicle data from the background control unit, the simulation model is dynamically simulated to obtain traffic flow parameters (density, speed, and flow rate) of construction vehicles entering / leaving the construction work area and upstream non-interlacing areas.

[0031] S3. Construction vehicle scheduling plan and impact level determination based on parking wave theory: Determine the entry and exit scenarios of construction vehicles; S31. In the scenario of construction vehicles entering, based on the traffic flow parameters of construction vehicles entering obtained by simulation, the speed of the deceleration wave caused by the entry of construction vehicles is calculated based on the parking wave theory, and the distance of the deceleration wave propagating upstream is further obtained. S32. In the scenario of construction vehicles leaving, based on the traffic flow parameters of construction vehicles leaving obtained from simulation, the acceleration wave speed, propagation distance, single delay and total delay of different scheduling schemes are calculated based on the parking wave theory. The scheme with the minimum total delay is selected as the optimal scheduling scheme execution plan for construction vehicles. S33. Based on the traffic wave propagation distance of the implementation plan, the degree of impact on social vehicles is determined as Level 1, Level 2, or Level 3; S4. Based on the determined impact level, use variable message signs, drones, and internet navigation maps to conduct graded guidance and control of social vehicles.

[0032] To the work area The cross sections are set sequentially in the upstream direction. , section , section Sections 3, 2, and 1, leading to the work area. The cross sections are set sequentially in the downstream direction. , section ; work area To the cross-section The space between them is a vertical buffer zone. , section To the cross-section The area between them is the upstream transition zone. Section 1 to Section 2 The area between these points is a construction warning zone. work area To the cross-section The area between them is the downstream transition zone. ; Construction warning area The control zones are divided into different levels: the area between section 1 and section 2 is the first-level control zone. The area between section 2 and section 3 is a secondary control zone. Section 3 and section The area between them is a Level 3 control zone. ; Section Used to determine the deceleration position of construction vehicles, from section 1 to section 2. The area between them is the upstream non-interlacing region, cross-section To the cross-section The area between them is an interwoven region.

[0033] like Figure 1 As shown, this invention constructs a construction area vehicle guidance and control system based on drone detection. It utilizes drones equipped with high-definition cameras to comprehensively detect the traffic demand data of social vehicles, and employs an onboard dispatch terminal to detect the number and type of construction vehicles entering and exiting. The multi-source data collected in real-time is input into a simulation model for dynamic simulation, obtaining traffic flow, speed, and density data for weaving areas and upstream non-weaving areas under different dispatch schemes for construction vehicle entry / exit scenarios. Then, it determines whether it is an entry scenario. If so, it calculates the deceleration wave speed caused by the construction vehicle's entry based on parking wave theory and further obtains the distance the deceleration wave propagates upstream. If not, it determines the optimal dispatch scheme for construction vehicles, calculating the acceleration wave speed, propagation distance, and corresponding total delay under different dispatch schemes based on parking wave theory. The optimal dispatch scheme is selected as the execution scheme with the goal of minimizing the total delay. Based on the traffic wave propagation distance of the execution scheme, the degree of impact on social vehicles is classified into three levels: Level 1, Level 2, and Level 3. Based on the determined impact level, drones, variable message signs, and internet navigation maps are used to conduct graded guidance and control of social vehicles.

[0034] The following details the methods for monitoring drones used by construction vehicles entering and exiting highway construction zones: 1. Establish a vehicle guidance and control system for construction areas based on drone detection: like Figure 2 As shown, this system consists of a detection unit, an early warning and control unit, a background control unit, and an instruction issuing unit; Within the detection unit, the onboard dispatch terminal for construction vehicles has a built-in 4G wireless communication module, providing comprehensive coverage of all construction vehicles in the construction area. This ensures real-time reporting of entry and exit needs, while also providing coverage outside the warning zone. Electronic fences are deployed every kilometer to double-verify the number of construction vehicles entering and exiting, and to determine the scheduling time for drone inspections.

[0035] The inspection of social vehicles uses drones equipped with high-definition cameras to conduct precise inspections at one section of the warning zone. The drone airport is located inside the construction area and can meet the needs of parking 3+1 drones and temporary battery swapping.

[0036] In the early warning and control unit, drones are deployed within the construction warning zone to provide real-time voice guidance to social vehicles or construction vehicles.

[0037] Variable message display screens are deployed at sections 1, 2, and 3 to display information such as work information, speed limit reminders, and the flow of work vehicles entering and leaving the work area.

[0038] Internet navigation maps are used to push construction warnings or diversion routes to vehicles.

[0039] On-site personnel are located at section 3 to guide and control construction vehicles and traffic flow.

[0040] In the back-end control unit, real-time interconnection with vehicle-mounted dispatch terminals and drones is achieved through a 4G network to ensure data transmission. At the same time, online simulation is used to pre-analyze and obtain traffic flow parameters (density, speed, and flow) of construction vehicles entering / leaving the construction work area and upstream non-interlacing areas. In the instruction issuance unit, graded guidance instructions are simultaneously issued to drones, variable message signs, internet navigation maps, and on-site personnel terminals through the 4G network to ensure the timeliness of instruction issuance.

[0041] The construction warning zone is divided into different control areas according to the control level: the area between section 1 and section 2 is the Level 1 control area (generally 500 meters); the area between section 2 and section 3 is the Level 2 control area (generally 700 meters); and the area between section 3 and the starting point of the warning zone is the Level 3 control area (generally 800 meters). Sections 1, 2, and 3 are used to deploy variable message signs. Used to determine the deceleration position of construction vehicles, cross-section Located at the end of the upstream transition zone, it is used to determine the location where construction vehicles enter the construction work area; cross-section Located at the end of the longitudinal buffer zone, cross-section Located at the end of the downstream transition zone, it is used to determine the position where construction vehicles leave the construction work area; cross-section. The location to restore construction vehicles to normal speed.

[0042] Based on the impact level of on-site construction vehicles entering / leaving the construction area on other vehicles, different numbers of drones are dispatched to achieve precise guidance and control of other vehicles. The specific dispatch plan is shown in Table 1. When the impact level is Level 1 (low), one drone is dispatched to guide and control vehicles at section 3. When the impact level is Level 2 (medium), two drones are dispatched to guide and control vehicles at sections 2 and 3. When the impact level is Level 3 (high), three drones are dispatched to guide and control vehicles at sections 1, 2, and 3.

[0043] Table 1. Drone scheduling schemes under different impact levels

[0044] 2. Construct a method for accurately collecting and simulating the traffic demand of construction vehicles and other vehicles. like Figure 3 As shown, regarding the collection of construction vehicle traffic demand, when a construction vehicle enters the construction area, it arrives upstream of the construction area. The system initiates an entry request from the kilometer marker (located upstream of the electronic fence). Drivers specify the number and type of vehicles via their onboard dispatch terminal; for multi-vehicle convoys, the lead vehicle submits the request. Simultaneously, the system utilizes equipment deployed outside the warning zone... An electronic fence covering a distance of 5 kilometers (5 kilometers is recommended, allowing sufficient time for drones to be dispatched to section 1 for data detection) automatically triggers identity verification and quantity statistics via the vehicle-mounted positioning module, and compares the results with the data reported by the terminal in real time. When the verification matches, the request is confirmed to be valid. If there are discrepancies such as missed or over-reported data, the system will immediately remind the driver to make corrections and have the management personnel verify them simultaneously. When construction vehicles leave the construction area, they can directly initiate a departure request in advance through the vehicle-mounted dispatch terminal.

[0045] Regarding the collection of social vehicle traffic demand, when a construction vehicle needs to enter the work area, after it enters the electronic fence, the system immediately dispatches a drone equipped with a high-definition camera to the warning zone section 1 to conduct real-time detection of social vehicles and obtain social vehicle traffic demand data for the most recent period (3-5 minutes). When a construction vehicle needs to leave the work area, the driver needs to report the demand in advance through the vehicle dispatch terminal. The system then simultaneously dispatches a drone equipped with a high-definition camera to the warning zone section 1 to detect social vehicles in real time and collect social vehicle traffic demand data for the most recent period (3-5 minutes), providing real-time basic data support for simulation.

[0046] Then, the social vehicle data and the double-verified construction vehicle data are input into the simulation model for dynamic simulation, simulating the impact of construction vehicles entering / exiting on social traffic flow, and outputting traffic flow parameters (density, speed, and volume) in the weaving area and the upstream non-weaving area in seconds: In the scenario where construction vehicles enter the construction work area, the upstream non-interlacing area (section 1 to section 2) is obtained. The average speed of social vehicles ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); obtain the area of ​​entry into the weaving zone (section) To the cross-section The average speed of social vehicles ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); obtain information on construction vehicles at the cross-section initial velocity ( km / h ), in cross-section speed of entry ( km / h deceleration and acceleration (Negative values ​​are generally recommended; values ​​between 1.5 and 2.0 are typically suggested.) ); In the scenario where construction vehicles leave the construction work area, the data on vehicles leaving the upstream non-interlacing area (section) under different scheduling schemes is obtained. To the cross-section The average speed of social vehicles ( km / h Traffic density (vehicles / km·lane), cross-sectional flow (vehicles / hour); obtain exit from the weaving area (section) To the cross-section (Average speed of social vehicles and traffic density) (vehicles / km·lane), cross-sectional flow (vehicles / hour); obtain information on construction vehicles at the cross-section initial departure speed ( km / h ), return to normal speed ( km / h The design speed of the highway can be taken as 100 km / h. km / h ), acceleration (For positive values, a value of 0.5 is generally recommended.) This provides data support for subsequent calculations of traffic wave speed, propagation distance, single delay, and total delay.

[0047] 3. Construction vehicle scheduling plan and impact level determination based on parking wave theory This step combines Figures 4 to 8 As shown, based on the parking wave theory (a parking wave refers to the wave formed behind a vehicle when it stops at a red light, caused by changes in vehicle density and speed, which often manifests as queuing when vehicles are waiting for a signal), and combined with three scenarios of construction vehicles entering and leaving the construction work area, and simultaneously entering and leaving the construction work area, the traffic flow parameters (density, speed, and flow rate) in different weaving areas and upstream non-weaving areas obtained from simulation are used as the basis to calculate the acceleration wave speed, propagation distance, single delay, and total delay generated by construction vehicles leaving the construction work area under different scheduling schemes.

[0048] This study takes minimizing total delay as its core objective. By comparing the calculation results of various scheduling schemes, the optimal construction vehicle departure scheduling scheme with the minimum total delay is selected and implemented. At the same time, based on the propagation distance of a single traffic wave, the degree of impact of social vehicles on the passage of construction vehicles is accurately divided into three levels: Level 1, Level 2, and Level 3, providing a clear and scientific decision-making basis for subsequent graded guidance and control work in the construction operation area.

[0049] 3.1 Determine the optimal scheduling scheme for construction vehicles based on the driving scenario Since the speed at which construction vehicles enter the work area affects the construction progress, it is recommended that construction vehicles enter the work area directly upon arrival. Therefore, this invention does not design a scheduling scheme for the scenario of construction vehicles entering the work area, but designs a scheduling scheme for the scenario of construction vehicles leaving the work area. By calculating the total delay of different scheduling schemes, the optimal scheduling scheme with the minimum total delay is selected and executed.

[0050] Based on simulation, traffic flow parameters (density, speed, and flow rate) of social vehicles leaving the construction work area are obtained under different scheduling schemes. The optimal scheduling scheme for construction vehicles leaving the work area is determined by minimizing the total delay. For each group of scheduling needs, all scheduling schemes of "scheduling batches (number of times) + number of vehicles per batch" are enumerated. Based on the parking wave theory, the acceleration wave speed, propagation distance, single delay, and total delay of different scheduling schemes are calculated respectively. By comparing all options, the total delay is selected. The minimum solution is used as the optimal scheduling plan for construction vehicles; the optimal departure scheduling plan is determined using the following steps: For all scheduling schemes Any scheduling scheme It can be represented as ,in: For the number of scheduling, The number of vehicles dispatched each time. The sum is the total number of vehicles First, calculate the time it takes for a single vehicle to leave the construction area and return to normal speed. The calculation formula is shown in equation (1); then calculate the first... i Total time for this scheduling (That is, the total time from the first vehicle leaving the work area to the last vehicle completing acceleration in this dispatch). Because the number of vehicles dispatched each time may be more than one, it is necessary to calculate the total time for all vehicles in the same dispatch to complete acceleration. Since the vehicles leave in convoy, the driving time interval is... Small enough, so The travel times of the two vehicles overlap. The calculation formula is shown in equation (2); then calculate the next step. i The accelerated wave generated by this scheduling propagates over a distance of... The product of wave speed and total acceleration time of this scheduling is calculated using equation (3), and the wave speed is calculated using equation (4); then the first... i Single delay of the sub-scheduling , The product of the squared propagation distance and the three correction coefficients ( For speed correction factor, This is the road correction factor. (This is the environmental correction factor), the calculation formula is shown in equation (5); finally, the first... k Total delay of all scheduling schemes , for m The sum of single-time delays for each scheduling event is calculated using equation (6); (Compare) K Total delay of the plan The scheme with the smallest D is selected as the optimal departure scheduling scheme.

[0051] (1); (2); (3); (4); (5); (6); As shown in Table 2, there are 4 possible scenarios for the 3 construction vehicles to leave the construction area. Scenario 2 has the shortest total delay of 60 seconds, so Scenario 2 is selected for scheduling.

[0052] Table 2. Examples of methods for determining the optimal scheduling scheme for a given scenario.

[0053] For scenarios where construction vehicles enter and exit simultaneously, the distance between entrances and exits should be considered. (i.e., construction vehicles enter the cross-section) and the section of the road The straight-line distance is equal to the upstream transition zone. Vertical buffer zone Work area and downstream transition zone length Using the sum of the values ​​of the acceleration waves (the distance between the entrance and exit) as the criterion, if the propagation distance of the acceleration wave from the exit route is less than the distance between the entrance and exit, then the exit effect does not cover the entry position, and the two do not interfere with each other; if the propagation distance of the acceleration wave is greater than the distance between the entrance and exit, then the exit effect will be superimposed on the entry effect, causing a serious conflict; therefore, there are the following two situations: Scenario 1: For example Figure 6 As shown, if the propagation distance of the exit route is less than the distance between the entrances and exits of the construction area (i.e., If the total delay is minimized, the optimal solution with the least delay will be selected for the outbound dispatching, and it will be determined that the simultaneous inbound and outbound control strategy can be implemented, and the construction vehicles at the inbound end will enter normally. Scenario 2: For example Figure 7 As shown, if there is no exit route with a propagation distance less than the distance between the entrances and exits of the construction area (i.e., If the impact of vehicles leaving the site is determined to be superimposed on the impact of vehicles entering the site, it is likely to cause widespread congestion or accidents. Therefore, the dispatching of construction vehicles is suspended. Figure 8 As shown, the back-end system sends a "suspension of departure" instruction to the departing vehicle through the vehicle terminal, and at the same time displays a "no departure" sign at the exit, giving priority to ensuring that the incoming vehicle can complete its entry. After the last construction vehicle enters, the departure scheduling is initiated (using the minimum total delay scheme).

[0054] 3.2 Impact Level Determination Since the effects of dispatching batches do not overlap, regardless of the dispatching scheme used, only the distance of a single dispatch is considered. Therefore, the classification of the impact level directly depends on the propagation distance of the traffic wave caused by a single dispatch of construction vehicles. The system obtains traffic flow data (density, speed, density) of the weaving area and the upstream non-weaving area of ​​the construction work area based on simulation. It calculates the deceleration wave velocity (reflecting the propagation speed of the interference of construction vehicle deceleration on the social traffic flow behind) according to the parking wave theory, and calculates the upstream propagation distance of the deceleration wave by combining the deceleration duration of the construction vehicles.

[0055] For scenarios involving construction vehicles entering the site, such as Figure 4 As shown, construction vehicles start from the end of the upstream transition zone. When the cross-section enters the construction area, the deceleration wave velocity is calculated according to formula (7). Calculate according to formula (8) Construction vehicles from the cross-section Decelerate to cross section time (in express The length of the entire convoy of construction vehicles is equal to The total length of all vehicles plus the total distance between them is used to calculate the propagation distance of the deceleration wave according to formula (9). ,according to Determine the level of impact.

[0056] (7); (8); (9); For scenarios where construction vehicles leave, such as Figure 5 As shown, based on the optimal departure scheduling scheme determined in 3.1 Determine the level of impact.

[0057] The impact level of construction vehicles entering and leaving the construction work area is determined by using traffic wave propagation distance as the core indicator, combined with the calculation starting point and threshold range for different scenarios, forming a differentiated grading standard.

[0058] For scenarios where construction vehicles enter the construction work area, as shown in Table 3, the propagation distance of the deceleration wave is... The calculation starts at section S2, based on With threshold Relationship classification influence level: when When the congestion is classified as Level 1 (low), the queue extends to the Level 3 control zone, where it can dissipate quickly without further control. When the situation is assessed as Level 2 impact (medium), congestion queues extend to the Level 2 control zone, requiring system-wide guidance to dissipate; when When the situation is classified as Level 3 (High), with congestion queues exceeding those in the Level 2 control zone, a comprehensive traffic management plan must be implemented to complete the evacuation within a relatively long period.

[0059] Table 3. Determination of the Impact Level of Construction Vehicle Entry

[0060] For scenarios where construction vehicles leave the construction work area, as shown in Table 4, the propagation distance of the acceleration wave is... The calculation starts at section S3, based on With threshold Relationship classification influence level: when When the impact is classified as Level 1 (low), congestion queues will extend to the buffer zone and dissipate quickly without intervention; when... At that time, it was determined to be a Level 2 impact (medium), with congestion queuing extending to the Level 3 control zone, requiring system-wide coordination and guidance to dissipate; when When the situation is classified as Level 3 (High), and the congestion queue exceeds the Level 3 control zone, a comprehensive traffic management plan must be implemented to complete the evacuation within a relatively long period of time.

[0061] Table 4. Impact Level Determination Table for Construction Vehicle Exit

[0062] 4. A graded guidance and control mechanism for social vehicles based on the level of impact. As shown in Table 5, differentiated guidance and control measures are initiated based on the impact level to achieve precise coordination between construction vehicles and social traffic flow.

[0063] When the impact level of construction vehicles on other vehicles is Level 1, one drone will be deployed at section 3 of the Level 3 control zone. It will only issue a single warning via loudspeaker when it detects abnormalities such as illegal lane changes by other vehicles, without disrupting normal traffic flow. Variable message signs will only display the message "Construction area ahead, please be aware" at section 3; no additional information will be displayed at sections 1 and 2 to avoid over-guiding traffic. Internet navigation maps will be routed upstream. For vehicles within a 5-kilometer radius (5 kilometers recommended), a construction site location warning will be issued, navigation routes will not be adjusted, and normal traffic flow will be maintained.

[0064] When the impact level of construction vehicles on other vehicles is Level 2, two drones are deployed to cover sections 2 and 3 respectively. The drones use loudspeakers to broadcast messages to passing vehicles: "Construction vehicles ahead, please do not change lanes illegally, maintain a safe distance." Variable message signs (VMS) then distribute guidance information in layers: section 1 displays "Construction ahead 2 kilometers, slow down," section 2 displays "Construction vehicles passing, please give way," and section 3 displays "Speed ​​limit 60 km / h." km / h "Keep a safe distance"; Internet navigation maps are moving upstream. Within a 5-kilometer radius (recommended), social vehicles will be prompted to enter the work area by the construction vehicles ahead, without activating the diversion function to avoid causing new congestion.

[0065] When the impact level of construction vehicles on other vehicles is level three, three drones are deployed to provide comprehensive coverage of sections 1, 2, and 3. Multiple sections continuously issue warnings and announcements, with a particular emphasis on reminding large vehicles to "pass through construction vehicles ahead, slow down and give way." Simultaneously, high-definition cameras capture and push images of traffic violations such as cutting in, changing lanes, and overtaking to traffic management departments for enforcement and penalties. Variable message signs at multiple sections provide full-process warnings: section 1 displays "Construction ahead 2 kilometers, drive carefully," and section 2 displays "Construction vehicles passing through, speed limit 60 km / h." km / hSection 3 issued a "No overtaking, keep a distance of 200 meters" notice; Internet navigation maps pushed diversion suggestions to social vehicles at the upstream ramp, guiding vehicles to detour through adjacent roads to reduce traffic pressure in the construction area; On-site personnel received instructions from the backend and assisted in traffic management near Section 3, guiding construction vehicles to enter and exit in an orderly manner to avoid local congestion.

[0066] Table 5. Social Vehicle Tiered Guidance and Control Scheme

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for monitoring construction vehicles entering and exiting highway construction zones using unmanned aerial vehicles (UAVs), characterized in that, Includes the following steps: S1. Build a vehicle guidance and control system for construction areas based on UAV detection, including a detection unit, an early warning and control unit, a back-end control unit and an instruction issuing unit. The units are interconnected and transmit data through communication links. The detection unit includes an on-board dispatch terminal installed in the construction vehicle, an electronic fence deployed upstream of the construction warning zone, and a drone equipped with a high-definition camera; The early warning and control unit includes a variable message display screen, a loudspeaker integrated with drones, an internet navigation map, and on-site personnel. According to the control level, the construction warning area is divided into Level 1 control area, Level 2 control area and Level 3 control area in the opposite direction of traffic. There are corresponding control sections between each control area, and variable message display screens are deployed on each control section for hierarchical release of control information. S2. Constructing a method for accurately collecting and simulating the traffic demand of construction vehicles and other vehicles: S21. Collect construction vehicle traffic data and location tracking data through vehicle-mounted dispatch terminals and electronic fences. Use a drone equipped with a high-definition camera to hover over the far end of the construction warning area to collect social vehicle traffic data within the most recent detection cycle. S22. By receiving social vehicle traffic data and construction vehicle traffic data from the background control unit, the simulation model is dynamically simulated to obtain traffic flow parameters of construction vehicles entering / leaving the construction work area and upstream non-interlacing areas. S3. Construction vehicle scheduling plan and impact level determination based on parking wave theory: Based on traffic flow parameters obtained from S2 simulation, the specific scenario type of construction vehicle passage demand is determined: S31. When it is determined that a construction vehicle has entered the scene, the deceleration wave speed caused by the entry of the construction vehicle is calculated based on the parking wave theory, and the distance the deceleration wave propagates upstream is calculated. S32. When it is determined that the construction vehicle has left the scene, the acceleration wave speed, propagation distance, single delay and total delay of different scheduling schemes are calculated based on the parking wave theory. The scheme with the minimum total delay is selected as the optimal scheduling scheme execution plan for the construction vehicle. S33. When it is determined that there is both entry and exit demand, the degree of impact on social vehicles is determined as Level 1, Level 2, or Level 3 based on the traffic wave propagation distance of the implementation plan. S4. Based on the determined impact level, use variable message signs, drones, and internet navigation maps to conduct graded guidance and control of social vehicles.

2. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 1, characterized in that, To the work area The cross sections are set sequentially in the upstream direction. , section , section Sections 3, 2, and 1, leading to the work area. The cross sections are set sequentially in the downstream direction. , section ; Vertical buffer Work area To the cross-section Between; upstream transition zone : Section To the cross-section between; Construction warning area Section 1 to Section 2 Between, downstream transition zone Work area To the cross-section between; Construction warning area The division of control zones at all levels: Level 1 Control Area Between section 1 and section 2; Level II control zone Between section 2 and section 3, a level 3 control zone Section 3 and Section between; Upstream non-interlacing area: Section 1 to section Between; intersecting areas: cross-section To the cross-section between.

3. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 2, characterized in that, In step S22, the traffic flow parameters obtained by the simulation model under the scenario of construction vehicles entering the construction work area are as follows: Average speed of social vehicles entering the upstream non-interlacing area Traffic density Cross-sectional flow ; Average speed of social vehicles entering the weaving area Traffic density Cross-sectional flow ; Construction vehicles at the cross-section initial velocity In the cross section speed of entry deceleration and acceleration ; Units for each parameter: km / h; Traffic density unit: vehicles / km / lane; Acceleration unit: m / s² 2 End-face flow rate unit: vehicles / hour.

4. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 2, characterized in that, In S22, the simulation model dynamically simulates and obtains the traffic flow parameters for different scheduling schemes under the scenario of construction vehicles leaving the construction work area, as follows: Average speed of social vehicles leaving the upstream non-interlacing area Traffic density Cross-sectional flow ; Average speed of social vehicles exiting the intersection area Traffic density Cross-sectional flow ; Construction vehicles at the cross-section initial departure speed Return to normal speed Acceleration ; Units for each parameter: km / h; Traffic density unit: vehicles / km / lane; Acceleration unit: m / s² 2 End-face flow rate unit: vehicles / hour.

5. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 3, characterized in that, In S31, under the scenario of construction vehicles entering the construction work area, the propagation distance of the deceleration wave is... The calculation formula is as follows: ； in, To slow down the wave speed, for Construction vehicles from the cross-section Decelerate to cross section The time is calculated using the following formula: ； ； in, express The length of the entire construction vehicle team.

6. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 5, characterized in that, Based on the propagation distance of the deceleration wave When construction vehicles enter a construction work area, the rules for determining the level of impact on other vehicles are as follows: when At that time, it was determined to be a Level 1 impact; when At that time, it was determined to be a level two impact; when At that time, it was determined to be a level three impact.

7. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 3, characterized in that, In step S32, the optimal scheduling scheme for construction vehicles in the scenario of construction vehicles leaving is determined by the following steps: S321. For all scheduling schemes Any scheduling scheme It can be represented as ,in: For the number of scheduling, The number of vehicles dispatched each time. The sum is the total number of vehicles ; Calculate the time it takes for a single vehicle to leave the construction area and return to normal speed. : ； S322, Calculate the first i Total time for this scheduling Because each dispatch may involve more than one vehicle, it's necessary to calculate the total acceleration time for all vehicles in the same dispatch. Since the vehicles depart in convoy, the travel time intervals are also a factor. Small enough, so The travel times of the two vehicles overlap. Calculation formula: ； S323, Calculate the first i The propagation distance of the accelerated wave generated by this scheduling The formula is calculated by multiplying the wave speed by the total acceleration time of this scheduling: ； Formula for calculating wave speed: ； S324, Calculate the first i Single delay of the sub-scheduling , This is the product of the squared propagation distance and three correction coefficients, where... For speed correction factor, This is the road correction factor. (Environmental correction factor), calculation formula: ； S325, Calculate the first k Total delay of all scheduling schemes , for m The sum of single-time delays for each scheduling operation is calculated using the following formula: ； contrast K Total delay of the plan The scheme with the smallest D is selected as the optimal departure scheduling scheme.

8. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 7, characterized in that, Based on the propagation distance of the accelerated wave When construction vehicles leave the construction work area, the rules for determining the degree of impact on other vehicles are as follows: when At that time, it was determined to be a Level 1 impact; when At that time, it was determined to be a level two impact; when At that time, it was determined to be a level three impact.

9. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 7, characterized in that, For scenarios where construction vehicles enter and exit simultaneously, the construction vehicle dispatching plan is as follows: Spacing between entrances and exits of the construction area As the criterion for judgment, For construction vehicles to enter the cross section and the section of the road The straight-line distance is equal to the upstream transition zone. Vertical buffer zone Work area and downstream transition zone length The sum; If construction vehicles leave the planned area The system determines that the simultaneous entry and exit control strategy can be implemented, and the construction vehicles at the entry end can enter normally. If construction vehicles leave the planned area If the decision is made to suspend the dispatch of construction vehicles, priority will be given to ensuring that vehicles entering the field complete their entry. Once the last construction vehicle has entered the field, the dispatch of vehicles leaving the field will be initiated.

10. The method for monitoring construction vehicles entering and exiting highway construction areas according to claim 2, characterized in that, The social vehicle classification and control mechanism based on impact level determination is as follows: When the impact level of construction vehicles on other vehicles is Level 1, one drone will be deployed at section 3 to conduct early warning and control of vehicles with abnormal traffic trajectories through the drone's loudspeaker; the variable message display screen will only display construction operation information at section 3. Internet navigation maps simultaneously push construction location warnings to upstream vehicles; When the impact level is level 2, two drones are deployed to cover section 2 and section 3 respectively, and the construction operation information is broadcast to passing vehicles through the drone's loudspeaker equipment; the variable message signs deployed in control zones at all levels broadcast the operation information and speed limit reminders; and the Internet navigation map pushes the construction vehicle flow ahead into the operation zone to upstream social vehicles. When the impact level is level 2, three drones are dispatched to fully cover section 1, section 2, and section 3. Multi-section early warning announcements are made through drone loudspeaker equipment, and variable message display screens deployed in control areas at all levels push information on the flow of construction and work vehicles entering and leaving the work area. Internet navigation maps push diversion suggestions to social vehicles at the upstream ramps; The on-site personnel assisted in traffic control near section 3.

Images