Path re-planning method and system based on accurate cost calculation of AMHS system

Abstract

The invention relates to the technical field of path planning of carrying crown blocks, in particular to a path re-planning method based on accurate cost calculation of an AMHS system. The method comprises the following specific steps: S1, acquiring a real-time traffic condition in a current state in an AMHS system; s2, calculating the path cost of each OHT crown block at the current moment based on the obtained real-time data; and S3, when the OHT crown block runs to the branching point, according to the path cost calculated in the step S2, selecting the path with the minimum current cost in the plurality of alternative paths in a dynamic change manner. According to the method, on the basis of multiple existing alternative paths, data such as the number of vehicles, the speed of the crown blocks, the distance between the crown blocks and the working state in the alternative paths are obtained based on the real-time traffic condition of the AMHS system, and the path cost at the current moment is accurately calculated through a cost formula designed in the technical scheme; and it is ensured that the crown block can select the path with the minimum current cost from the multiple alternative paths with the dynamically-changed cost at the branch node.

Description

Technical Field

[0001] The invention relates to the technical field of overhead crane path planning, and in particular to a path replanning method based on accurate cost calculation of an AMHS system. Background Art

[0002] In the semiconductor manufacturing process, the safety, reliability and efficiency of the automated material handling system (AMHS) play a very important role in achieving large-scale production, improving production speed and shortening processing cycles. How to enable the overhead transport crane (OHT) in the AMHS system to smoothly and quickly transport the loaded materials to the target location through the laid tracks is of utmost importance.

[0003] At present, in practical applications, the solution to the possible congestion problem during the overhead crane transportation process is usually based on some scheduling strategies and path planning methods. The path planning is completed before the overhead crane is transported to reduce the occurrence of congestion. AMHS scheduling has the characteristics of large-scale, real-time, random and multi-objective. These methods usually do not consider the congestion caused by these state changes during the real-time movement of the overhead crane.

[0004] Based on the existing scheduling strategies and path planning, this technical solution replans the path at the fork in the road by accurately calculating the current cost according to the real-time overhead crane speed, vehicle spacing and number of overhead cranes on the path, thereby greatly reducing the congestion rate during the overhead crane transportation process. Summary of the invention

[0005] The purpose of the present invention is to propose a path replanning method based on accurate cost calculation of AMHS system in view of the problems existing in the background technology.

[0006] The technical solution of the present invention is a path replanning method based on accurate cost calculation of the AMHS system, comprising the following specific steps:

[0007] S1. Obtain the real-time traffic situation in the current state of the AMHS system;

[0008] S2, calculating the path cost of each OHT overhead travelling vehicle at the current moment based on the obtained real-time data;

[0009] S3. When the OHT overhead travelling vehicle reaches the divergence point, the path with the lowest current cost among the multiple candidate paths is dynamically selected according to the path cost calculated in step S2.

[0010] Preferably, the real-time traffic conditions obtained in step S1 include:

[0011] The current position, speed, running path, alternative paths and number of vehicles in the alternative paths, OHT crane speed, spacing between OHT cranes and working status.

[0012] The OHT crane runs according to the currently planned path; when the OHT crane runs to a key node, and there are two or more optional paths at the node, the crane transportation path needs to be replanned until it reaches the destination. For the path replanning of the current target crane, the time cost in each optional path is calculated, and the path with the smallest time cost is selected. When the crane transportation path needs to be replanned, the path with the faulty vehicle is first excluded, and the remaining paths are planned; after the fault in the faulty vehicle path is eliminated, the path is re-added to the alternative path and participates in the path replanning.

[0013] During the transportation process of an overhead crane (OHT), the transportation links are constantly changing, and the optimal path at a certain moment may not be the optimal path at the next moment. Therefore, it is necessary to adjust the paths of different operating conditions in a timely manner and replan the paths of the overhead crane. The dynamic path planning part of the overhead crane is based on the statically selected path combination. These alternative path combinations are multiple better paths obtained through some path planning algorithms. Each alternative path is composed of key nodes n on the path. k Composition, for example, the yth path Whenever there are two or more optional paths for the overhead crane at a key node, the overhead crane transportation path needs to be replanned until it reaches the destination. represents a one-way connection set between two adjacent nodes, where N represents the loading / unloading points of equipment (storage warehouses and processing equipment) and the intersection of tracks. Assume that the crane task is a node (n start ,n end ) between the transport, use the specific time cost to calculate the change of cost in the dynamic transportation process. i is the node where the overhead travelling vehicle is currently located, n i+1 Represents the next node adjacent to it, for all n i ∈p y , if (n i ,n i+1 ) is a legal connection, then (n i ,n i+1 )∈E. Among them, (n i ,n i+1 ) A legal connection means that there is a path between two adjacent nodes. At this time, the two nodes belong to E, which means that if there is a path between any two adjacent nodes, then the path is unidirectional.

[0014] If at node n i(i=i0, i0∈{0,1,2,…,k} represents the subscript number of the current node) needs to be replanned, and the time cost at this time is considered to be the remaining section of the yth path (n i ,n end ) on the cost t(p y )=cost(y)+cost(y'), where cost(y) is the initial time cost and cost(y') is the real-time cost.

[0015] For the path replanning of the current target overhead crane, the path with the faulty vehicle is processed first, and then replanning is performed after the path with the faulty vehicle is eliminated:

[0016] In (n i ,n i+1 ) between the nodes decelerates or stops, which will increase the time cost between these nodes. i ,n end ) time cost (y') is:

[0017]

[0018] d safe The maximum safe distance. When the distance between the front and rear vehicles is less than this distance, the rear vehicle starts to slow down. Indicates that at the current node (n i ,n i+1 ) There is an overhead crane between the machine and node n where the goods are picked up and placed. i+1 The distance between (if there are multiple distance nodes, select distance node n i+1 farthest), if the current node (n i ,n i+1 ) If there is no pick-up or release location or no overhead crane is available at this point, the value is 0; d i Indicates (n i ,n i+1 ) of node n i+1 The distance to the node where the current target crane is located; M i Indicates that (n i ,n i+1 ) The number of vehicles on v i,max is the crane at node (n i ,n i+1 ) between the maximum travel speed that can be achieved; Indicates the current node (n i ,n i+1 ) is the speed of the jth overhead crane on the node (j is also the number of the distance from the current target overhead crane in the node from far to near); a 减 is the deceleration of the overhead crane; Indicates deceleration from maximum speed to current speed the time spent; Indicates the time it takes to accelerate from the current speed to the maximum speed; a 加 is the acceleration; Indicates that the distance between the jth car and the j+1th car is greater than d safe The time required, in is the distance between the jth car and the j+1th car, and when season Indicates that at node (n i ,n i+1 ) The remaining time for the j-th overhead crane to pick up and release goods. The value is 0 when there is no pick-up or release of goods.

[0019] In the formula, b and c represent coefficients, which are 0 or 1. (1) When there is only one vehicle between two adjacent nodes, or the distance between the jth vehicle and the vehicles in front and behind is greater than or equal to d safe When the car is accelerating, b = 0 and c = 1; if the car is decelerating, b = 1 and c = 0. (2) When there are multiple cars between two adjacent nodes and the distance between them is less than d safe When the jth overhead crane is in a decelerating state, b=1, c=0; if the crane is in an accelerating state, b=c=0.

[0020] In summary, the real-time cost calculation formula on the yth alternative path is t(p y )=cost(y)+cost(y'), where cost(y) is the theoretical initial time cost of the alternative path. is a node (n i ,n end ) between two adjacent nodes, v i,max represents the maximum speed that the overhead travelling vehicle can reach between these two adjacent nodes. Therefore, when the overhead travelling vehicle performs path replanning at the divergence point, it compares the real-time path cost t(p y ) to select the path with smaller time cost.

[0021] The following adjustments are made to address the limitations of the formula:

[0022] ① From the formula of cost(y'), it can be concluded that the cost depends on the instantaneous speed of the jth overhead travelling vehicle. When the speed of the crane on the path is v i,max (At this time, the distance between the overhead cranes must be greater than or equal to d safe ), cost(y')=0. In this case, if there are multiple paths with zero cost, it is necessary to compare the total time cost t(p y). If the total time cost t(p y ) are the same, choose the path with the least number of vehicles; otherwise, choose the path with the total time cost t(p y )The smallest path.

[0023] ②Formula It is believed that the overhead crane is always in the acceleration stage, but in fact the overhead crane speed reaches v i,max After that, it will travel at a constant speed. Therefore, we must first determine the distance that the overhead crane accelerates away. Within, whether the overhead crane has reached v i,max Using the formula Calculate current speed Acceleration to v i,max The distance traveled, when When the time cost is Otherwise, the time cost is

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] Based on the existing multiple alternative paths, the present invention obtains data such as the number of vehicles in the alternative paths, the speed of the overhead crane, the distance between the overhead cranes, and the working status based on the real-time traffic conditions of the AMHS system, and accurately calculates the path cost at the current moment through the cost formula designed by the technical solution, ensuring that the overhead crane can select the path with the lowest current cost among the multiple alternative paths with dynamically changing costs at the divergence node. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of some nodes and overhead crane in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] The present invention proposes a path replanning method based on accurate cost calculation of the AMHS system, which includes the following specific steps:

[0029] S1. Obtain the real-time traffic situation in the current state of the AMHS system;

[0030] S2, calculating the path cost of each OHT overhead travelling vehicle at the current moment based on the obtained real-time data;

[0031] S3. When the OHT overhead travelling vehicle reaches the divergence point, the path with the lowest current cost among the multiple candidate paths is dynamically selected according to the path cost calculated in step S2.

[0032] Preferably, the real-time traffic conditions obtained in step S1 include:

[0033] The current position, speed, running path, alternative paths and number of vehicles in the alternative paths, OHT crane speed, spacing between OHT cranes and working status.

[0034] The OHT crane runs according to the currently planned path; when the OHT crane runs to a key node, and there are two or more optional paths at the node, the crane transportation path needs to be replanned until it reaches the destination. For the path replanning of the current target crane, the time cost in each optional path is calculated, and the path with the smallest time cost is selected. When the crane transportation path needs to be replanned, the path with the faulty vehicle is first excluded, and the remaining paths are planned; after the fault in the faulty vehicle path is eliminated, the path is re-added to the alternative path and participates in the path replanning.

[0035] Specifically: When an OHT overhead crane fails, it will be reported to the server in real time, and the server will obtain the fault type of the OHT overhead crane; when the warning type is a minor warning, the system can be restored immediately, and the OHT overhead crane can continue to operate; when the warning type is a major fault, it means that it will affect the normal operation of the OHT overhead crane, such as a motor problem or a mechanical structure problem; in this case, manual intervention of the OHT overhead crane is required, which takes a long time, so the path where the vehicle is located is listed as a faulty vehicle path, and this path is excluded first during path planning; after the fault in the faulty vehicle path is eliminated, the path is re-added to the alternative path and participates in path replanning.

[0036] The details are as follows:

[0037] like Figure 1 As shown, assume that the task is issued by machine (1-3), the target machine is (7-8), OHT1 is the current task crane, and assume a 减 =2.5m / s 2 , a 加 =2m / s 2 , d safe =3m, the track length between the two nodes is as marked in the figure, and the optional paths are (discard some paths that are too long, and record the initial cost of the path as cost(y), the real-time cost as cost(y'), and the total cost as t(p y )):

[0038] {10,31,42,53,64,75,126,177,228,259,26 10 ,28 11}—t(p 1 )=cost(1)+cost(1')

[0039] {10,31,42,53,144,155,166,177,228,259,2610 ,28 11}—t(p 2 )=cost(2)+cost(2')

[0040] {10,31,42,53,64,75,86,97,108,119,12 10 ,17 11 ,twenty two 12 ,25 13 ,26 14 ,28 15}—t(p 3 )=cost(3)+cost(3')

[0041] {10,31,42,53,64,75,86,97,108,199,20 10 ,twenty one 11 ,twenty two 12 ,25 13 ,26 14 ,28 15}—t(p 4 )=cost(4)+cost(4')

[0042] {10,31,42,53,64,75,126,137,148,159,16 10 ,17 11 ,twenty two 12 ,25 13 ,26 14 ,28 15}—t(p 5 )=cost(5)+cost(5')

[0043] To simplify the example, the calculation of the same part is omitted, and only the cost of the road section between nodes (5,22) is calculated. When actually calculating the cost, it is necessary to calculate all the costs from the current node to the target node on the path and compare and exclude them. Assume that OHT5 is 3m / s, OHT6 is 3m / s, OHT7 is in the state of picking up and releasing goods and the remaining time T=5s, the distance between the picking up and releasing goods position and the next node is 1.5m, OHT8 is 3m / s, OHT11 is 0.5m / s in the acceleration state, OHT15 and OHT16 are both 0.5m / s in the deceleration state and the distance is 1m, and OHT17 is 1m / s in the acceleration state.

[0044] ①If the maximum speed of all tracks is 3m / s:

[0045] According to the data in the figure, we can conclude that cost(1)=cost(2)=4.3s, cost(3)=8.3s, cost(4)=8.3s, cost(5)=8.3s. According to the formula, we can get cost(y'):

[0046]

[0047] t(p 1 )=cost(1)+cost(1')=4.3+0.478=4.778s

[0048] t(p 2 )=cost(2)+cost(2')=4.3+0.221=4.521s

[0049] t(p 3 )=cost(3)+cost(3')=8.3+0.299=8.599s

[0050] t(p 4 )=cost(4)+cost(4')=8.3+0.115=8.415s

[0051] t(p 5 )=cost(5)+cost(5')=8.3+1.524=9.824s

[0052] At this time, t(p 2 ) is the optimal path at this time.

[0053] ② If the maximum speed of the track where nodes (5, 6, 7, 8, 9) and (20, 21, 22, 23, 24) are located is 3m / s, and the maximum speed of the turning track and the straight track between the two tracks is 1m / s. At this time, when OHT16 accelerates to the maximum speed, it cannot pull away from OHT15 by more than d safe , so the cost is calculated by dividing it into two processes: acceleration and uniform speed.

[0054]

[0055]

[0056]

[0057] cost4'=0+0+0+0=0s

[0058]

[0059] t(p 1)=cost(1)+cost(1')=8+0.369=8.369s

[0060] t(p 2 )=cost(2)+cost(2')=13+0.044=13.044s

[0061] t(p 3 )=cost(3)+cost(3')=17+0.231=17.231s

[0062] t(p 4 )=cost(4)+cost(4')=13+0=13s

[0063] t(p 5 )=cost(5)+cost(5')=21+1.241=22.241s

[0064] The calculation result is expressed as t(p 1 ) is the optimal path. At this time, it can be seen that under the same path length, the gain of the expressway allows the time cost of some congestion between overhead cranes to be ignored during path replanning. If t(p 1 ), we can observe t(p 2 and t(p 4 ), we will choose t(p 4 ), the cost difference between the two lanes is small, but the number of vehicles is very different. Even so, it is still believed that the overhead travelling vehicle on the expressway will leave in a short time. As shown in the calculation results, t(p 4 ) is less than t(p 2 ), representing t(p 4 ) congestion probability is less than t(p 2 ).

[0065] According to the results presented in ① and ②, when the fast and slow track settings are used, the overhead crane tends to take the path with more fast tracks; when the maximum speed allowed for all tracks is the same, it tends to take the path where the overhead crane is more dispersed.

[0066] After using the method of this embodiment, the overhead crane calculates the additional time cost caused by the mutual influence between the overhead cranes on the alternative paths in dynamic path planning, compares the advantages and disadvantages of multiple optional paths, and finally selects the path with the smallest time cost. This method greatly reduces the probability of congestion of the overhead crane during the material transportation process and improves the overall transportation efficiency of the AMHS system.

[0067] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto, and various changes can be made within the knowledge scope of technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A path replanning method based on accurate cost calculation of AMHS system, characterized in that: The specific steps include: S1. Obtain the real-time traffic situation in the current state of the AMHS system; S2, calculating the path cost of each OHT overhead travelling vehicle at the current moment based on the obtained real-time data; S3. When the OHT overhead travelling vehicle reaches the divergence point, the path with the lowest current cost among the multiple candidate paths is dynamically selected according to the path cost calculated in step S2.

2. The path replanning method based on accurate cost calculation of AMHS system according to claim 1 is characterized in that: The real-time traffic conditions obtained in step S1 include: The current position, speed, running path, alternative paths and number of vehicles in the alternative paths, OHT crane speed, spacing between OHT cranes and working status.

3. The path replanning method based on accurate cost calculation of AMHS system according to claim 1 is characterized in that: The OHT crane runs according to the currently planned path; when the OHT crane runs to a key node and there are more than or equal to two optional paths at the node, the crane transportation path needs to be replanned until it reaches the destination.

4. The path replanning method based on accurate cost calculation of AMHS system according to claim 3 is characterized in that: For the path replanning of the current target overhead crane, the time cost of each optional path is calculated, and the path with the minimum time cost is selected.

5. The path replanning method based on accurate cost calculation of AMHS system according to claim 3 is characterized in that: When the overhead crane transport route needs to be replanned, the route with the faulty vehicle is first excluded and the remaining routes are planned; after the fault in the faulty vehicle's path is eliminated, the path is re-added to the alternative routes and participates in the route replanning.

6. The path replanning method based on accurate cost calculation of AMHS system according to claim 4 is characterized in that: Each alternative path consists of the key nodes n on the path. k Composition, path y N represents the loading / unloading points of equipment and the intersections of tracks; E represents the one-way connection set of two adjacent nodes, then OHT crane at task node (n start ,n end ) between; n start is the initial node; n end is the terminal node; n i is the node where the OHT overhead travelling vehicle is currently located, n i+1 is the next node adjacent to the current node; For all n i ∈p y , if (n i ,n i+1 ) is a legal connection, then (n i ,n i+1 )∈E; If at node n i Replanning is required at this point, and the time cost at this time is considered to be the remaining section of the yth path (n i ,n end ) on the cost t(p y )=cost(y)+cost(y'), where cost(y) is the initial time cost and cost(y') is the real-time cost.

7. The path replanning method based on accurate cost calculation of AMHS system according to claim 6 is characterized in that: In (n i ,n i+1 ) between the OHT overhead travelling vehicle decelerates or stops, which will increase the time cost between these nodes. i ,n end ) time cost (y') is Among them, d safe The maximum safe distance. When the distance between the front and rear vehicles is less than this distance, the rear vehicle starts to slow down. Indicates that at the current node (n i ,n i+1 ) There is an overhead crane between the machine and node n where the goods are picked up and placed. i+1 The distance between the current node (n i ,n i+1 ) If there is no pick-up or release location or no overhead crane is available at this point, the value is 0; d i Indicates (n i ,n i+1 ) of node n i+1 The distance to the node where the current target crane is located; M i Indicates that (n i ,n i+1 ) The number of vehicles on v i,max is the crane at node (n i ,n i+1 ) between the maximum travel speed that can be achieved; Indicates the current node (n i ,n i+1 ) is the speed of the jth overhead travelling crane; a 减 is the deceleration of the overhead crane; Indicates deceleration from maximum speed to current speed the time spent; Indicates the time it takes to accelerate from the current speed to the maximum speed; a 加 is the acceleration; Indicates that the distance between the jth car and the j+1th car is greater than d safe The time required, in is the distance between the jth car and the j+1th car, and when season Indicates that at node (n i ,n i+1 ) The remaining time for the jth overhead crane to pick up and release goods. If there is no pick-up and release, the value is 0; In the formula, b and c represent coefficients, and their values ​​are 0 or 1; When there is only one car between two adjacent nodes, or the distance between the jth car and the front and rear cars is greater than or equal to d safe When the car is in the accelerating state, b=0, c=1; when the car is in the decelerating state, b=1, c=0; When there are multiple vehicles between two adjacent nodes and the distance between them is less than d safe When , if the jth overhead travelling vehicle is in a decelerating state, then b=1, c=0; if the vehicle is in an accelerating state, then b=c=0; The real-time cost calculation formula on the yth alternative path is t(p y )=cost(y)+cost(y'), where cost(y) is the theoretical initial time cost of the alternative path. d (ni,ni+1) is a node (n i ,n end ) between two adjacent nodes, v i,max represents the maximum speed that the overhead travelling vehicle can reach between the two adjacent nodes; in step S3, by comparing the real-time path cost t(p y ) to select the path with smaller time cost.

8. A path replanning system based on accurate cost calculation of AMHS system, used to implement the steps of any method described in claim 1-7, characterized in that: It includes a data acquisition module, a path re-planning module and a communication unit; The data acquisition module is used to collect the real-time traffic conditions in the current state of the AMHS system; The path re-planning module is used to plan the path with the minimum time cost for the OHT car that needs to re-plan the path according to the data collected by the data acquisition module; The communication unit is used to communicate with the AMHS system and send the planned path information to the control end of the AMHS system.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the path replanning method based on accurate cost calculation of the AMHS system as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the path replanning method based on accurate cost calculation of the AMHS system as described in any one of claims 1 to 7 are implemented.

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