A Multi-AGV Scheduling Method and System Based on Task Time Window

Abstract

This invention discloses a multi-AGV scheduling method and system based on task time windows, relating to the field of AGV scheduling technology. A specific embodiment of this invention includes: dividing the time it takes for an AGV to pass through a road network intersection into individual time windows, ensuring that only one AGV passes through the intersection within each time window. This time window is the "task time window" for the AGV to successfully pass through the intersection and complete its task. This patent introduces the concept of "task time window" into the AGV scheduling collision avoidance problem, dividing the time of the AGV at the road network node into multiple task time windows according to the safe task time interval. Each task time window can schedule one vehicle to pass through the road network node. The node speed scheduling collision avoidance method based on "task time windows" can reduce the system's computational load while ensuring the safe and fast movement of AGVs. This patent has a significant effect on improving the operational safety and transportation efficiency of AGVs in logistics systems.

Description

Technical Field

[0001] This invention belongs to the field of AGV scheduling technology, and in particular relates to a multi-AGV scheduling method and system based on task time windows. Background Technology

[0002] In flexible manufacturing systems, with the development of computer and automation technologies, logistics management systems are gradually shifting towards automated management. This is primarily marked by the emergence of Automated Guided Vehicles (AGVs) and computer-based logistics management and control systems. An AGV is an automated transport vehicle equipped with electromagnetic or optical guidance devices, capable of traveling along a predetermined path and possessing safety protection and transfer functions. It requires no driver and is primarily powered by a continuously rechargeable battery. It can automatically navigate to a given task and destination location to complete the task. AGVs have a high degree of automation and their applications extend beyond simply transporting workpieces in manufacturing workshops; they can also perform transport tasks in warehouses, ports, airports, and other locations.

[0003] However, path planning in multi-AGV vehicle systems is quite complex, requiring consideration not only of collision avoidance mechanisms between AGVs but also their cooperation and communication. In multi-AGV systems, collisions can occur due to: 1. AGV malfunctions; 2. Two or more AGVs competing for the same path segment; 3. Path intersections. Existing AGV scheduling and collision avoidance methods are mainly divided into two categories: the first is predictive methods, which anticipate potential obstacles and conflicts encountered by AGVs during operation. However, this method is not comprehensive and unsuitable for real-time dynamic environments. The second is reactive methods, which, while applicable to real-time path planning for multiple AGVs, suffer from poor computational performance due to time constraints. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a multi-AGV scheduling method based on task time windows suitable for use in aerospace manufacturing plants. This patent introduces the concept of "task time windows" into the AGV scheduling collision avoidance problem, dividing the time an AGV spends at a road network node into multiple task time windows according to safe task time intervals. Each task time window allows one AGV to pass through the road network node. This node speed scheduling collision avoidance method based on "task time windows" can reduce the system's computational load while ensuring the safe and rapid movement of AGVs. This patent significantly improves the operational safety and transportation efficiency of AGVs in logistics systems.

[0005] In view of this, according to one aspect of the present invention, a multi-AGV scheduling method based on a task time window is provided, comprising:

[0006] Step S1: When the AGV is about to enter the road network node, obtain the coordinate position, running speed and acceleration a of the AGV within a certain range from the road network node;

[0007] Step S2: When the AGV vehicle passes through the intersection, the time T it passes through the intersection is recorded. i The distance L between the vehicle and the stop line j Guide speed V i Acceleration a and initial velocity V of AGV 0j The following relationships exist:

[0008]

[0009] Based on the above formula, the formulas for the guiding speed given by deceleration and acceleration can be derived:

[0010] Deceleration strategy:

[0011] Acceleration strategy;

[0012] Starting from the idle task time domain start time T0 of the preceding road network node, with the safe task time interval t s To separate the current node's idle task time domain T at intervals g The task time window is divided into i segments, and only one AGV can pass through each task time window. The end time T of each task time window is... i For T i =T0+i*t s The resulting task time windows are [T0,T1], [T1,T2], ..., [T...]. i-1 ,T i ], Tg-t s ≤T i ≤T g This serves as an alternative time window for AGVs to pass through road network nodes.

[0013] AGV speed limit V max To determine the time window and suggested speed Vj for the j-th AGV vehicle to complete the passage task, the constraints are as follows:

[0014] Step S3: For the j-th AGV, select the task time window [T] m T m +t s (m≤i) serves as an alternative time window for passing through the intersection, determining whether the AGV vehicle can pass through within this alternative time window at a speed not exceeding the speed limit V. max If the conditions are met, the recommended speed is used to pass through the intersection; otherwise, stopping or the next task time window is selected as the new alternative time window. Where T... mThis represents the end time of the task time window occupied by the (j-1)th AGV vehicle passing through the road network node.

[0015] Optionally, the distance L of the j-th AGV from the intersection stop line j for:

[0016]

[0017] The coordinates of the traffic light are (x L y L The coordinates of the j-th AGV entering the intersection are (x, y). V y V ).

[0018] Optionally, it also includes: determining T i Is the current time still within the idle task time domain? If so, proceed to the next step. Otherwise, to prevent it from colliding with other AGVs and causing danger, guide it to stop in front of the road network node.

[0019] Optionally, it also includes: determining whether the j-th AGV travels at its original speed earlier than T. m Constantly passing through road network nodes, i.e.

[0020]

[0021] If so, in order to prevent it from colliding with the vehicle in front, it should be slowed down and guided to ensure that it is within [T] m T m +t s The time window guides traffic through road network nodes at the following speed:

[0022]

[0023] In the formula, a is the acceleration of the AGV vehicle, and t is the acceleration of the AGV vehicle. i Let t be the time it takes for vehicle j to pass through a road network node according to the task time window. i =T m -T0.

[0024] Optionally, determine whether the j-th AGV travels at its original speed earlier than T. m The AGV must pass through road network nodes at all times; otherwise, in order to improve the efficiency of the AGV, accelerated guidance should be implemented to ensure that it passes through T. i The guidance speed is as follows: (The text abruptly ends here, so the translation stops as well.)

[0025]

[0026] Optionally, determine whether the suggested speed is lower than the AGV's maximum speed limit V. max If so, then the j-th AGV entering the intersection will proceed at the recommended speed V.j Driving can be done during the mission time window [T] m T m +t s Through road network nodes

[0027] Optionally, determine whether the suggested speed is lower than the AGV's maximum speed limit V. max If not, assign the next task time window [T] to the j-th vehicle. m +t s Tm+2t s Determine T by using road network nodes. i Is the time still within the idle task time domain?

[0028] According to another aspect of the present invention, a multi-AGV scheduling system based on task time windows is also provided, comprising: a road network electronic map module, a real-time task scheduling calculation module, a wireless communication module, and an AGV on-board unit. The AGV on-board unit further comprises a sensor module, a GPS coordinate module, and a wireless communication module. When an AGV is about to enter a road network node, within a certain range from the road network node, the AGV scheduling system receives vehicle coordinates and vehicle speed and acceleration fed back from the AGV vehicle communication module. Based on this, the AGV scheduling system parameterizes the above data and inputs it into the multi-AGV scheduling algorithm model based on task time windows for calculation. The algorithm module assigns a reasonable task time window that does not conflict with other AGV vehicles to each AGV vehicle about to pass through the road network node, and uses the assigned task time window to perform reverse calculation to give a reasonable AGV vehicle driving speed strategy. The AGV vehicles smoothly pass through each road network node according to the running strategy calculated by the scheduling system.

[0029] The advantages of this invention are: (1) It introduces the concept of "task time window" into the field of AGV scheduling, divides the node passage time into multiple independent "task time windows", and can realize precise speed guidance through the intersection.

[0030] (2) The present invention schedules AGV vehicles through the “task time window” algorithm, which can significantly reduce the computational load while ensuring their safe operation, making them more suitable for the complex environment of aerospace manufacturing.

[0031] (3) The mobile communication module involved in this invention has good performance and low configuration price. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the working principle of a multi-AGV scheduling method and system based on a task time window, according to an embodiment of the present invention.

[0033] Figure 2Here is a flowchart of a multi-AGV scheduling method based on task time windows according to an embodiment of the present invention;

[0034] Figure 3 Here is a roadside unit structure block diagram of a multi-AGV scheduling method and system based on task time windows according to an embodiment of the present invention;

[0035] Figure 4 The diagram below shows the on-board unit structure of a multi-AGV scheduling method and system based on task time windows, according to an embodiment of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 and Figure 2 As shown, this invention provides a multi-AGV scheduling method based on task time windows, including:

[0038] Step S1: When the AGV is about to enter the road network node, obtain the coordinate position, running speed and acceleration a of the AGV within a certain range from the road network node;

[0039] Step S2: When the AGV vehicle passes through the intersection, the time T it passes through the intersection is recorded. i The distance L between the vehicle and the stop line j Guide speed V i Acceleration a and initial velocity V of AGV 0j The following relationships exist:

[0040]

[0041] Based on the above formula, the formulas for the guiding speed given by deceleration and acceleration can be derived:

[0042] Deceleration strategy:

[0043] Acceleration strategy;

[0044] Starting from the idle task time domain start time T0 of the preceding road network node, with the safe task time interval t s To separate the current node's idle task time domain T at intervals g The task time window is divided into i segments, and only one AGV can pass through each task time window. The end time T of each task time window is...i For T i =T0+i*t s The resulting task time windows are [T0,T1], [T1,T2], ..., [T...]. i-1 ,T i ], Tg-t s ≤T i ≤T g This serves as an alternative time window for AGVs to pass through road network nodes.

[0045] AGV speed limit V max To determine the time window and suggested speed Vj for the j-th AGV vehicle to complete the passage task, the constraints are as follows:

[0046] Step S3: For the j-th AGV, select the task time window [T] m T m +t s (m≤i) serves as an alternative time window for passing through the intersection, determining whether the AGV vehicle can pass through within this alternative time window at a speed not exceeding the speed limit V. max If the conditions are met, the recommended speed is used to pass through the intersection; otherwise, stopping or the next task time window is selected as the new alternative time window. Where T... m This represents the end time of the task time window occupied by the (j-1)th AGV vehicle passing through the road network node.

[0047] Furthermore, the distance L of the j-th AGV from the intersection stop line j for:

[0048]

[0049] The coordinates of the traffic light are (x L y L The coordinates of the j-th AGV entering the intersection are (x, y). V y V ).

[0050] Furthermore, it also includes: determining T i Is the current time still within the idle task time domain? If so, proceed to the next step. Otherwise, to prevent it from colliding with other AGVs and causing danger, guide it to stop in front of the road network node.

[0051] Furthermore, it also includes: determining whether the j-th AGV travels at its original speed earlier than T. m Constantly passing through road network nodes, i.e.

[0052]

[0053] If so, in order to prevent it from colliding with the vehicle in front, it should be slowed down and guided to ensure that it is within [T]m T m +t s The time window guides traffic through road network nodes at the following speed:

[0054]

[0055] In the formula, a is the acceleration of the AGV vehicle, and t is the acceleration of the AGV vehicle. i Let t be the time it takes for vehicle j to pass through a road network node according to the task time window. i =T m -T0.

[0056] Furthermore, determine whether the j-th AGV travels at its original speed earlier than T. m The AGV must pass through road network nodes at all times; otherwise, in order to improve the efficiency of the AGV, accelerated guidance should be implemented to ensure that it passes through T. i The guidance speed is as follows: (The text abruptly ends here, so the translation stops as well.)

[0057]

[0058] Furthermore, determine whether the suggested speed is lower than the AGV's maximum speed limit V. max If so, then the j-th AGV entering the intersection will proceed at the recommended speed V. j Driving can be done during the mission time window [T] m T m +t s Through road network nodes

[0059] Furthermore, determine whether the suggested speed is lower than the AGV's maximum speed limit V. max If not, assign the next task time window [T] to the j-th vehicle. m +t s Tm+2t s Determine T by using road network nodes. i Is the time still within the idle task time domain?

[0060] like Figure 3 and Figure 4As shown, this invention also provides a multi-AGV scheduling system based on task time windows, including: a road network electronic map module, a real-time task scheduling calculation module, a wireless communication module (the above are roadside units), and an AGV vehicle-mounted unit. The AGV vehicle-mounted unit also includes a sensor module, a GPS coordinate module, and a wireless communication module. When an AGV is about to enter a road network node, within a certain range from the road network node, the AGV scheduling system receives the vehicle coordinates, vehicle speed, and acceleration fed back from the AGV vehicle communication module. Based on this, the AGV scheduling system parameterizes the above data and inputs it into the multi-AGV scheduling algorithm model based on task time windows for calculation. The algorithm module assigns a reasonable task time window that does not conflict with other AGV vehicles to each AGV vehicle about to pass through the road network node, and uses the assigned task time window to perform reverse calculation to give a reasonable AGV vehicle driving speed strategy. The AGV vehicles smoothly pass through each road network node according to the running strategy calculated by the scheduling system.

[0061] This invention provides a multi-AGV scheduling method based on task time windows, applicable to complex environments in aerospace manufacturing. A "task time window" refers to dividing the time it takes for multiple AGVs to pass through a road network intersection into individual "time windows," ensuring that only one AGV passes through the intersection within each "time window." This "time window" is the "task time window" in which the AGV successfully completes its task. In this method, the AGV scheduling module obtains information such as the AGV's initial velocity, acceleration, and position through the AGV's onboard unit, and then uses the task scheduling module and electronic map module to obtain the task time allocation plan and node location for each node in the road network. Based on the above data, the AGV scheduling system incorporates data such as the task time allocation plan of each node in the road network, the location coordinates of each node, the speed and acceleration of AGV vehicles, and the location coordinates of AGVs in the road network into a multi-AGV scheduling algorithm model based on task time windows for calculation. This provides reasonable running speed instructions for AGV vehicles. Finally, the system uses a communication module to transmit the scheduling information, including vehicle running speed instructions, to AGV vehicles that are about to pass through each road network node, ensuring that AGVs do not collide or interfere with other AGV vehicles during their operation in the road network, thus guaranteeing their safe, fast, and efficient operation in the road network.

[0062] Specifically, the AGV scheduling system determines the coordinates and initial task time domains of each node in the road network using a pre-set electronic map and initialization data. Through the system's communication module, it collects data such as the speed and acceleration of AGVs within a certain range of each road network node, as well as the AGV's position coordinates within the road network. This data is then fused with node coordinates and task time windows. Subsequently, the AGV scheduling system parameterizes this data and inputs it into a multi-AGV scheduling algorithm model based on task time windows for computation. Finally, it outputs the travel speed and acceleration at which AGVs can safely and reasonably pass through road network nodes, avoiding collisions and interference between different AGVs in the road network, ultimately ensuring the safe and efficient operation of AGVs within the road network.

[0063] Example

[0064] The constraints involved in the multi-AGV scheduling algorithm model based on task time windows include:

[0065] The task time windows of each node in the road network are independent of each other, and the task time window allocated to the AGV is located in the idle task time domain of the node to be passed.

[0066] The final travel speed and acceleration of the AGV shall not exceed the design travel speed limit and acceleration speed limit.

[0067] The specific scheduling calculation method is as follows:

[0068] When an AGV vehicle passes through an intersection, the time T it takes to pass through the intersection is... i The distance L between the vehicle and the stop line j Guide speed V i ;

[0069] Where L j The location of the traffic light (x) is obtained by the vehicle unit as follows: L y L ) and the GPS location (x) of the j-th vehicle entering the intersection V y V ), calculate the distance L of the j-th vehicle from the stop line at the intersection. j

[0070]

[0071] With a fixed acceleration a and the initial velocity V of the vehicle 0j The following relationships exist:

[0072]

[0073] Based on the above formula, the formulas for the guiding speed given by deceleration and acceleration can be derived:

[0074] Deceleration strategy:

[0075] Acceleration strategy;

[0076] During algorithm execution, the algorithm runs as follows:

[0077] Starting from the start time T0 of the idle task time domain of the preceding road network node, the idle task time domain T of the current node is divided into two parts at intervals of safe task time interval ts. g The task time window is divided into i segments. Only one AGV can pass through each task time window. The end time T of each task time window is... i For T i =T0+i*t s ;

[0078] The resulting task time windows are [T0,T1], [T1,T2], ..., [T...]. i-1 ,T i ], Tg-t s ≤T i ≤T g This serves as an alternative time window for the AGV to pass through road network nodes. The AGV speed limit V is also considered. max The constraints determine the time window for the passing task and the recommended speed V assigned to the j-th AGV. j The specific steps are as follows:

[0079] (1) Determine whether the first AGV vehicle closest to the road network node at time T0 is in a parked state;

[0080] If so, then T0 = T g -t s +tq, where tq is the startup time of the stopped AGV vehicle;

[0081] Otherwise, T0 = T g -t s .

[0082] (2) For the first AGV, the task time window [T0, T1] is its alternative time window for passing through the intersection. Determine whether the AGV can pass through the intersection within this alternative time window at a speed not exceeding the speed limit V. max If the conditions are met, the vehicle passes through the intersection at the recommended speed; otherwise, it stops or chooses the next task time window as a new alternative time window, and so on. For the j-th subsequent vehicle, the task time window [T] is selected. m T m +t s (m≤i) serves as an alternative time window for passing through the intersection, guiding the AGV vehicle through the road network node according to the above logic. Where, T mThis represents the end time of the task time window occupied by the (j-1)th AGV vehicle passing through the road network node.

[0083] (3) Determine T i Is the current time still within the idle task time domain?

[0084] If so, proceed to the next step of the judgment;

[0085] Otherwise, to prevent it from colliding with other AGVs and causing danger, it should be guided to stop in front of the road network node.

[0086] (4) Determine whether the j-th AGV vehicle is moving at its original speed earlier than T. m Constantly passing through road network nodes, i.e.

[0087]

[0088] If so, in order to prevent it from colliding with the vehicle in front, it is necessary to slow down and guide it to ensure that it is within [T] m T m +t s The time window guides traffic through road network nodes at the following speed:

[0089]

[0090] In the formula, a is the acceleration of the AGV vehicle, and t is the acceleration of the AGV vehicle. i Let t be the time it takes for vehicle j to pass through a road network node according to the task time window. i =T m -T0;

[0091] Otherwise, to improve the efficiency of AGV vehicle passage, acceleration guidance is required to ensure its passage within T... i The guidance speed is as follows: (The text abruptly ends here, so the translation stops as well.)

[0092]

[0093] (5) Determine whether the suggested speed obtained from the vehicle speed guidance model is lower than the maximum speed limit V of the AGV. max ,

[0094] If so, the j-th AGV entering the intersection will proceed at the recommended speed V. j Driving can be done during the mission time window [T] m T m +t s The speed command is transmitted to the AGV vehicle via the road network nodes and the communication module.

[0095] Otherwise, assign the next task time window [T] to the j-th vehicle. m +t s T m +2ts [Return to step (3) through the road network node and continue the loop judgment.]

[0096] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-AGV scheduling method based on task time windows, characterized in that, include: Step S1: When the AGV is about to enter the road network node, obtain the coordinate position, running speed and acceleration a of the AGV within a certain range from the road network node; Step S2: When the AGV vehicle passes through the intersection, the time T it passes through the intersection is recorded. i The distance L between the vehicle and the stop line j Guide speed V i Acceleration a and initial velocity of AGV The following relationships exist: Based on the above formula, the formulas for the guiding speed given by deceleration and acceleration can be derived: Deceleration strategy: ; Acceleration strategy; ; Starting from the idle task time domain start time T0 of the preceding road network node, with the safe task time interval t s To separate the current node's idle task time domain T at intervals g The task time window is divided into i segments, and only one AGV can pass through each task time window. The end time T of each task time window is... i For T i =T0+i*t s The resulting task time windows are [T0,T1], [T1,T2], ..., [T...]. i-1 ,T i ], Tg-t s ≤T i ≤T g This serves as an alternative time window for AGVs to pass through road network nodes. AGV speed limit V max To determine the time window and suggested speed Vj for the j-th AGV vehicle to complete the passage task, the constraints are as follows: Step S3: For the j-th AGV, select the task time window [T] m T m +t s (m≤i) serves as an alternative time window for passing through the intersection. The decision is made to determine whether the AGV vehicle can pass through this alternative time window at a speed not exceeding the speed limit V. max If the conditions are met, the recommended speed is used to pass through the intersection; otherwise, stopping or the next task time window is selected as the new alternative time window. Where T... m This is the end time of the task time window occupied by the (j-1)th AGV vehicle passing through the road network node; Determine whether the j-th AGV travels at its original speed before T. m Constantly passing through road network nodes, i.e. If so, in order to prevent it from colliding with the vehicle in front, it should be slowed down and guided to ensure that it is within [T] m T m +t s The time window guides traffic through road network nodes at the following speed: In the formula, a is the acceleration of the AGV vehicle, and t is the acceleration of the AGV vehicle. i Let j be the time it takes for the j-th vehicle to pass through the road network nodes according to the task time window, i.e. ; Determine whether the j-th AGV travels at its original speed before T. m The AGV must pass through road network nodes at all times; otherwise, in order to improve the efficiency of the AGV, accelerated guidance should be implemented to ensure that it passes through T. i The guidance speed is as follows: (The text abruptly ends here, so the translation stops as well.) 。 2. The method according to claim 1, characterized in that, The j-th AGV is L away from the intersection stop line. j for: The coordinates of the traffic light are (x L y L The coordinates of the j-th AGV entering the intersection are (x... V y V ).

3. The method according to claim 1, characterized in that, Also includes: Determine T i Is the time still within the idle task time domain? If so, proceed to the next step of the judgment; Otherwise, to prevent it from colliding with other AGVs and causing danger, it should be guided to stop in front of the road network node.

4. The method according to claim 1, characterized in that, Determine if the suggested speed is lower than the AGV's maximum speed limit Vmax. If so, the j-th AGV entering the intersection can pass through the road network node within the task time window [Tm, Tm+ts] by traveling at the suggested speed Vj.

5. The method according to claim 4, characterized in that, Determine if the suggested speed is lower than the AGV's maximum speed limit V. max If not, assign the next task time window [T] to the j-th vehicle. m +t s Tm+2t s Determine T by using road network nodes. i Is the time still within the idle task time domain? 6. A multi-AGV scheduling system based on task time windows, characterized in that, For performing any of the methods as described in claims 1-5, comprising: The system includes a road network electronic map module, a real-time task scheduling and calculation module, a wireless communication module, and an AGV on-board unit. The AGV on-board unit also includes a sensor module, a GPS coordinate module, and a wireless communication module. When the AGV is about to enter the road network node, within a certain range from the road network node, the AGV scheduling system will receive the vehicle coordinates, vehicle speed and acceleration fed back by the AGV vehicle communication module. Based on this, the AGV scheduling system will parameterize the above data and input it into the multi-AGV scheduling algorithm model based on task time window for calculation. The algorithm module assigns a reasonable task time window that does not conflict with other AGVs to each AGV vehicle about to pass through a road network node. It then uses the assigned task time window to perform reverse calculations to give a reasonable AGV vehicle driving speed strategy. The AGV vehicles smoothly pass through each road network node according to the operation strategy calculated by the scheduling system.

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