Anti-blocking scheduling strategy for variable orbit-based oht handling system

Abstract

The present application relates to a kind of based on variable orbit OHT handling system anti-blocking scheduling strategy, according to task scheduling method, OHT trolley allocation scheme is determined, and according to path planning method, the shortest path and variable orbit point in path are determined;According to travel time prediction method, the time of trolley through each variable orbit point is predicted, and sorting is carried out;Trolley executes task according to planned path, and variable orbit is changed according to through order and trolley state, and waits for trolley to pass in advance;When trolley reaches target station point, station orbit moves to working state, limit block works, trolley starts to load or unload, and when trolley completes loading or unloading and the standby track of station orbit is free of trolley, limit block releases, and station orbit moves to idle state.Last, when trolley completes task, update system state.This method uses variable orbit and station orbit, solves the low resource utilization rate in prior art based on fixed orbit, station point congestion problem.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of intelligent control, in particular to an OHT handling system anti-blocking scheduling strategy based on variable track. BACKGROUND

[0002] With the rapid development of semiconductor manufacturing technology, the size of wafers is increasing, and the weight is increasing. In the case that manual handling cannot meet the manufacturing system handling requirements, overhead hoist transport (OHT) has been widely used in automatic material handling systems of 300mm wafer manufacturing plants because it does not occupy ground space, the trolley speed is fast, and it does not need a buffer zone. It can improve the handling efficiency and avoid waste of resources. Therefore, reasonable OHT trolley scheduling is of great significance to improve the overall efficiency of the semiconductor manufacturing system under the integrated layout.

[0003] In order to ensure the punctuality of materials and improve the efficiency of the system, the OHT trolley anti-blocking traffic management problem needs to be considered. However, by checking the existing literature related to intelligent handling system scheduling, the research object is mainly the automated guided vehicle (AGV), and there are few studies on OHT handling system scheduling problems. The research mainly focuses on the design and scheduling problems of OHT handling system under fixed track, such as Chinese patent CN112650211A, and there are few relevant research literature on OHT handling system scheduling problem based on variable track. SUMMARY

[0004] In order to solve the technical defects in the prior art, the present application proposes an OHT handling system anti-blocking scheduling strategy based on variable track, which considers the OHT handling system scheduling problem based on variable track in the system by using variable track and station track, and solves the low resource utilization and station point blocking problem based on fixed track in the prior art.

[0005] The present application is implemented by the following technical solutions:

[0006] The OHT handling system anti-blocking scheduling strategy based on variable track includes the following steps:

[0007] Step 1: When the OHT handling system meets the task allocation trigger condition, obtain system information;

[0008] Step 2: Determine the OHT trolley task allocation scheme according to the task scheduling method;

[0009] Step 3: Determine the shortest path and variable track points in the path according to the path planning method;

[0010] Step 4: According to the travel time prediction method, the time of the OHT car passing each track change point is predicted;

[0011] Step 5: According to the passing sequence optimization method, the passing sequence of the OHT car at each track change point is sorted;

[0012] Step 6: The OHT car executes the task according to the planned path, and the variable track changes the track in advance according to the passing sequence and the state of the car, and waits for the OHT car to pass;

[0013] Step 7: Determine whether the OHT car has arrived at the target station, if yes, go to step 8, if no, go to step 6;

[0014] Step 8: The station track moves to the working state, the limit block works, and the OHT car starts loading or unloading;

[0015] Step 9: Determine whether the OHT car has completed loading or unloading, if yes, go to step 10, if no, wait for t seconds and go to step 9;

[0016] Step 10: Determine whether the standby track of the station track is empty of the OHT car, if yes, the limit block is released and the station track moves to the idle state, if no, wait for t seconds and go to step 10;

[0017] Step 11: Determine whether the OHT car has completed the task, if yes, go to step 13, if no, go to step 6;

[0018] Step 12: Update the system state and go to step 1.

[0019] Further, the task allocation trigger condition includes periodic triggering and event triggering.

[0020] Further, the system information includes task information, OHT car information, and path information.

[0021] Further, the task scheduling method includes a heuristic rule-based task scheduling method and an intelligent optimization algorithm-based task scheduling method.

[0022] Further, the path planning method includes the following steps:

[0023] Step 3.1: According to the Dijkstra algorithm, the path planning of the task on the system path is completed, and the path sequence of the shortest path of the task is recorded in the task shortest path table, that is, the path number sequence of the shortest path;

[0024] Step 3.2: According to the path sequence of the task shortest path, it is judged whether there is a variable point in the path sequence of the task shortest path, if there is a variable point, the path is marked in the task shortest path table, and the position of the variable point in the path is recorded, otherwise the path is not marked in the task shortest path table.

[0025] Further, the task shortest path table includes the starting point of the task, the end point of the task, the name of the OHT car, the path sequence of the task shortest path, the path marker of the path containing the variable point, the position of the variable point in the path, and the information of the time of the OHT car passing through each variable point.

[0026] Further, the variable point is the center point of the variable track.

[0027] Further, the variable track is a track in the system that can change direction by rotating the disc to form a passageway with other different tracks.

[0028] Further, the travel time prediction method comprises the following steps:

[0029] Step 4.1: According to the shortest path of the task and the position of the variable point, the travel time of the OHT car to reach each variable point without traffic congestion is predicted;

[0030] Step 4.2: Predict the traffic flow of each path in the path sequence of the task shortest path, and define the traffic congestion level of the path;

[0031] Step 4.3: According to the traffic congestion level of each path, the traffic congestion time of the OHT car passing through each path is predicted;

[0032] Step 4.4: The predicted travel time of the OHT car to reach each variable point without traffic congestion and the traffic congestion time of the OHT car passing through each path are integrated to predict the time of the OHT car passing through each variable point.

[0033] Further, the traffic congestion level includes four levels of "smooth", "light congestion", "moderate congestion" and "serious congestion", the larger the path traffic flow value, the more serious the traffic congestion, the higher the path traffic congestion level, and the longer the traffic congestion time.

[0034] Further, the through sequence optimization method is to sort the through sequence of the OHT car at each variable point according to the predicted time of the OHT car passing through each variable point by using the rule of first-in first-through.

[0035] Further, the variable track is connected by selecting a suitable track according to the task shortest path planned by the OHT car, that is, selecting a suitable entrance and exit.

[0036] Further, the work station track is a movable track beside the work station, which is composed of a working track, a standby track and a limiting block, and can be switched to an idle state and a working state by sliding in the slide.

[0037] Further, the idle state of the work station track is that the working track of the work station track is directly connected with other tracks of the system to form a passageway, the limiting block is loosened, and the standby track is in an idle state.

[0038] Further, the working state of the work station track is that the working track of the work station track is moved to the work station, the work station point of the working track, the center point of the work station and the center point of the OHT trolley coincide, the limiting block works, the standby track is connected with other tracks of the system to form a passageway, and it is ensured that other OHT trolleys will not be blocked when the OHT trolley is loading or unloading.

[0039] Compared with the prior art, the present application has at least the following beneficial effects or advantages:

[0040] The present application proposes an anti-blocking scheduling strategy for an OHT conveying system based on a variable track, which considers the scheduling problem of the OHT conveying system based on a variable track in the system by using a variable track and a work station track, and solves the problems of low resource utilization rate and work station point blocking in the prior art based on a fixed track. BRIEF DESCRIPTION OF DRAWINGS

[0041] The present application will be further described in detail below with reference to the accompanying drawings:

[0042] Figure 1 The flow chart of the anti-blocking scheduling strategy for the OHT conveying system based on a variable track of the present application;

[0043] Figure 2 The schematic diagram of the variable track of the present application;

[0044] Figure 3 (a) and (b) are respectively the idle state and the working state of the work station track of the present application. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0046] Since the OHT scheduling system is relatively complex, the following assumptions are made for the conveying system:

[0047] 1. The running speed of the OHT trolley is constant, and the acceleration and deceleration effects are ignored.

[0048] 2. Once the OHT starts to transport and deliver, it cannot change the path and adjust the task unloading sequence autonomously.

[0049] 3. Each OHT trolley can only load, unload or wait at the station point, and is not allowed to stop at a non-station point. If multiple OHT trolleys need to stop at the same station point, they need to wait in line.

[0050] 4. To avoid collisions or congestion, only one OHT trolley is allowed to pass or stop at each node at the same time.

[0051] 5. The system path network is one-way and single-lane, and does not support overtaking or parallelism.

[0052] 6. The unloading time of the multi-load AGV is fixed, and if multiple AGVs are at the same loading and unloading point, they need to wait in line.

[0053] 7. In the traffic control process, the path re-planning method is not used to avoid the motion conflict of the OHT system.

[0054] Figure 1 The flowchart of the anti-blocking scheduling strategy of the variable orbit-based OHT transport system described in the present application comprises the following steps:

[0055] Step 1: When the OHT transport system meets the task allocation trigger condition, obtain the system information.

[0056] When the OHT transport system calls the anti-blocking scheduling strategy of the variable orbit-based OHT transport system, it will first check whether the task allocation trigger condition is met. When the task allocation trigger condition is met, the task information in the system is obtained, including task information, OHT trolley information and path information. The task information includes the transport starting point, the transport ending point, the task generation time and the task deadline, etc., the OHT trolley information includes the trolley state, the speed, etc., and the path information includes the number, the position and the traffic flow of the orbit, etc.

[0057] In the embodiment of the present application, the task allocation trigger condition includes periodic triggering and event triggering, wherein the periodic triggering is triggered periodically at a fixed time interval, and the event triggering is triggered when a set event occurs. In the embodiment of the present application, the set event includes that the number of tasks in the task set to be allocated reaches a certain value.

[0058] It should be noted that the task allocation triggering condition can also be either periodic triggering or event triggering. The set event in the event triggering does not have to be the set event in the embodiment of the present invention. For example, the set event can also be the generation of new tasks in the set of tasks to be allocated.

[0059] Step 2: Determine the task allocation scheme for the OHT vehicle based on the task scheduling method.

[0060] When the OHT (Outdoor Handling) system meets the task allocation trigger condition, it assesses the set of idle carts and the set of tasks to be allocated within the system. The set of idle carts consists of idle OHT carts that have completed their previous task and have not been assigned a new task; the set of tasks to be allocated consists of all tasks generated in the system that have not yet been assigned to OHT carts for handling. If neither the set of idle carts nor the set of tasks to be allocated is empty, tasks in the allocable task set are assigned to idle carts according to the task scheduling method, thus determining the OHT cart task allocation scheme. If either the set of idle carts or the set of tasks to be allocated is empty, there are no idle carts to handle tasks or tasks that do not require cart allocation, therefore no task scheduling is needed, and the system waits for the next time the task allocation trigger condition is met.

[0061] In this embodiment of the invention, the task scheduling method includes a task scheduling method based on heuristic rules and a task scheduling method based on intelligent optimization algorithms. The heuristic rules include, but are not limited to, those based on task priority, shortest distance, and least time; the intelligent optimization algorithms include, but are not limited to, genetic algorithms, ant colony algorithms, and particle swarm optimization algorithms.

[0062] Step 3: Determine the shortest path and the turning points in the path according to the path planning method.

[0063] Once the tasks are assigned, an optimal path needs to be found from the starting point to the destination. Because the system contains variable tracks, the shortest path and the track change points within the path need to be determined using path planning methods.

[0064] like Figure 2 As shown in this embodiment of the invention, the variable track is a track in the system that can form a path with other different tracks by changing its direction through a turntable. The center point of the variable track is the track-changing point.

[0065] The path planning method includes the following steps:

[0066] Step 3.1: Based on Dijkstra's algorithm, complete the path planning of the task on the system path, and record the path sequence of the shortest path of the task in the shortest path table, that is, the path number sequence of the shortest path;

[0067] When a task is assigned a trolley, according to the Dijkstra algorithm, the path planning of the task on the system path is completed, and the path sequence of the shortest path of the task is recorded in the task shortest path table, that is, the path number sequence of the shortest path.

[0068] In the embodiment of the application, the task shortest path table includes the starting point of the task, the end point of the task, the name of the OHT trolley, the path sequence of the shortest path of the task, the path marker of the path containing the track change point, the position of the track change point in the path, and the time of the OHT trolley passing each track change point.

[0069] Step 3.2: According to the path sequence of the shortest path of the task, it is judged whether there is a track change point in the path sequence of the shortest path of the task, if there is a track change point, the path is marked in the task shortest path table, and the position of the track change point in the path is recorded, otherwise the path is not marked in the task shortest path table.

[0070] Because the path sequence of the planned shortest path of the task contains a variable track, in order to facilitate the prediction of the time of the OHT trolley reaching the track change point of the variable track, it is necessary to record the track change point information in the path sequence of the shortest path of the task. That is, according to the path sequence of the shortest path of the task, it is judged whether there is a track change point in the path sequence of the shortest path of the task, if there is a track change point, the path is marked in the task shortest path table, and the position of the track change point in the path is recorded, otherwise the path is not marked in the task shortest path table.

[0071] Step 4: According to the travel time prediction method, the time of the OHT trolley passing each track change point is predicted.

[0072] When the system determines the shortest path and the track change point in the path according to the path planning method, the time of the OHT trolley passing each track change point is predicted according to the travel time prediction method.

[0073] The travel time prediction method comprises the following steps:

[0074] Step 4.1: According to the shortest path of the task and the position of the track change point, the travel time of the OHT trolley reaching each track change point without traffic congestion is predicted;

[0075] According to the shortest path of the task and the position of the track change point, the distance from the starting point of the task to the position of the track change point can be obtained, and according to the speed of the OHT trolley, the travel time of the OHT trolley reaching each track change point without traffic congestion can be predicted.

[0076] Step 4.2: Predict the traffic flow of each path in the path sequence of the shortest path of the task, and define the traffic congestion level of the path;

[0077] Because the OHT trolley may encounter traffic congestion in performing the task, so that the travel time of the OHT trolley to each track-changing point is increased, it is necessary to predict the traffic flow of each path in the path sequence of the shortest path of the task, define the traffic congestion level of the path, and thus calculate the traffic congestion time.

[0078] In the embodiment of the present application, the traffic congestion level includes four levels of "smooth", "light congestion", "moderate congestion" and "serious congestion", the larger the path traffic flow value is, the more serious the traffic congestion condition is, the higher the path traffic congestion level is, and the longer the traffic congestion time is.

[0079] Step 4.3: According to the traffic congestion level of each path, the traffic congestion time of the OHT trolley passing through each path is predicted.

[0080] According to the traffic congestion level of each path in the shortest path of the task, the traffic congestion time of the OHT trolley passing through each path is predicted. When the traffic congestion level is "smooth", there is no traffic congestion, that is, the traffic congestion time is 0; when the traffic congestion level is "light congestion", there is slight traffic congestion, and the traffic congestion time is less; when the traffic congestion level is "moderate congestion" and "serious congestion", the traffic congestion is relatively serious, and the traffic congestion time is relatively more. The specific value of the traffic congestion time is related to the length of each path and the number of OHT trolleys on the path.

[0081] Step 4.4: The time of the OHT trolley passing through each track-changing point is predicted by comprehensively predicting the travel time of the OHT trolley to each track-changing point without traffic congestion and the traffic congestion time passing through each path.

[0082] The time of the OHT trolley passing through each track-changing point is predicted by comprehensively predicting the travel time of the OHT trolley to each track-changing point without traffic congestion and the traffic congestion time passing through each path. That is, the travel time of the OHT trolley to each track-changing point without traffic congestion and the traffic congestion time passing through each path are added, and the time of the OHT trolley passing through each track-changing point is obtained.

[0083] Step 5: The passing sequence of the OHT trolley at each track-changing point is sorted according to the passing sequence optimization method.

[0084] For the variable track in the system, there may be multiple OHT trolleys passing through each time period, so it is necessary to sort the passing sequence of the OHT trolley at each track-changing point according to the passing sequence optimization method, so that the variable track can be changed in advance to improve the system efficiency while avoiding conflicts.

[0085] In the embodiment of the present application, the first-come-first-pass rule is used to sort the passing sequence of the OHT trolley at each track-changing point according to the predicted time of the OHT trolley passing each track-changing point by using the sequential optimization method.

[0086] It should be noted that the sequential optimization method includes but is not limited to the first-come-first-pass rule, and the passing sequence of the OHT trolley can also be optimized according to the urgency of the task.

[0087] Step 6: The OHT trolley executes the task according to the planned path, and the variable track changes the track in advance according to the passing sequence and the state of the trolley, and waits for the OHT trolley to pass.

[0088] The trolley starts to execute the task according to the task scheduling method and the path planning method, and the variable track changes the track in advance according to the passing sequence and the state of the trolley, and waits for the OHT trolley to pass; wherein the state of the trolley refers to whether the trolley normally executes the task according to the shortest path sequence, if the OHT trolley fails to pass the track-changing point at the originally predicted time point due to failure or other reasons, the variable track needs to re-sort the passing sequence of the OHT trolley.

[0089] In the embodiment of the present application, the track-changing is that the variable track selects a suitable track to connect according to the shortest path of the OHT trolley, that is, selects a suitable entrance and exit.

[0090] Step 7: It is judged whether the OHT trolley reaches the target work position, if yes, step 8 is entered, if no, step 6 is entered.

[0091] It is judged whether the OHT trolley reaches the target work position, if yes, the loading or unloading is started, step 8 is entered, if no, the task is executed according to the shortest path scheme, step 6 is entered.

[0092] Step 8: The trolley waits for loading at the target work position, at this time, the work track moves to the working state, the limiting block works, and the OHT trolley starts to load or unload.

[0093] When the OHT trolley reaches the target work position, the work track moves to the working state, the limiting block works, and the OHT trolley starts to load or unload.

[0094] As Figure 3As shown, in the embodiment of the present application, the track where the work station point is located is the working track, the work station track is the movable track arranged on one side of the working track, and the working track, the standby track and the limiting block are included, wherein the limiting block is used for fixing the work station track to prevent it from sliding during the working process, the standby track is parallel to the working track, and the two are connected through the work station track, and the work station track is arranged on the slide. The work station track is switched between the idle state and the working state through the sliding of the work station track on the slide. The idle state of the work station track is that the working track of the work station track is directly connected with other tracks of the system to form a passage, at this time, the limiting block is loosened, the standby track is not communicated with other tracks, and is in the idle state. The working state of the work station track is that the working track of the work station track is moved to the work station, at this time, the work station point of the working track, the center point of the work station and the center point of the OHT trolley coincide, the limiting block works to fix the position of the working track, the standby track is connected with other tracks of the system to form a passage, and it is ensured that the OHT trolley will not block other OHT trolleys during loading and unloading.

[0095] Step 9: whether the OHT trolley completes loading or unloading is judged, if yes, step 10 is entered, if not, T seconds of time are waited, and step 9 is entered.

[0096] Because the OHT trolley loading or unloading needs a certain time, whether the OHT trolley completes loading or unloading needs to be judged to carry out the next step, if the OHT trolley completes loading or unloading, step 10 is entered, otherwise, T seconds of time are waited, and whether the OHT trolley completes loading or unloading is judged again.

[0097] Step 10: whether the standby track of the work station track is without OHT trolley is judged, if yes, step 11 is entered, if not, t seconds of time are waited, and step 10 is entered.

[0098] When the OHT trolley completes loading or unloading, the work station track cannot slide immediately from the working state to the idle state, because although the OHT trolley completes loading or unloading, it cannot be ensured that there is no OHT trolley passing on the standby track of the work station track, if the work station track slides immediately from the working state to the idle state at this time, the OHT trolley on the standby track will be left on the standby track until the next time the work station track is switched from the idle state to the working state, and the OHT trolley on the standby track can leave, which causes the task of the trolley to be delayed. Therefore, whether the standby track of the work station track is without OHT trolley needs to be judged, if yes, step 11 is entered, if not, t seconds of time are waited, and whether the standby track of the work station track is without OHT trolley is judged again.

[0099] Step 11: the limiting block is loosened, and the work station track is moved to the idle state.

[0100] When the standby track of the station track has no OHT trolley, the limiting block of the station track is loosened, and the station track starts to slide, and the working state is changed to the idle state.

[0101] Step 12: judging whether the OHT trolley completes the task or not, if yes, entering step 13, if not, entering step 6;

[0102] judging whether the OHT trolley completes the assigned task or not, if yes, entering step 13, if not, continuing to execute the task, and entering step 6.

[0103] Step 13: updating the system state, and entering step 1.

[0104] When the OHT trolley completes the assigned task, the system task, track and trolley states are updated, and entering step 1 to wait for the next task scheduling.

[0105] The above only describes the preferred embodiments of the present application, and it should be noted that the ordinary skilled in the art can make several improvements without departing from the principles of the present application, and these improvements should be considered as the protection scope of the present application.

Claims

1. A jam prevention scheduling strategy for a variable orbit based OHT handling system, characterized in that, The method comprises the steps of: Step 1: obtaining system information when the OHT conveying system meets a task allocation trigger condition; Step 2: determining an OHT vehicle task allocation scheme according to a task scheduling method in combination with task information in the system information; Step 3: determining a shortest path from a conveying starting point to a target station point and a variable rail point in the path according to a path planning method, specifically comprising: Step 3.1: completing path planning of the task on a system path according to a Dijkstra algorithm, and recording a path sequence of the shortest path on a task shortest path table; Step 3.2: judging whether a path in the path sequence of the task shortest path exists a variable rail point, and marking the path and recording a position of the variable rail point in the path on the task shortest path table when the variable rail point exists; Step 4: predicting a time of the OHT vehicle passing through each variable rail point according to a travel time prediction method in combination with the shortest path and the variable rail point, specifically comprising: Step 4.1: predicting a travel time of the OHT vehicle reaching each variable rail point without traffic congestion according to the shortest path of the task and the position of the variable rail point; Step 4.2: predicting a traffic flow of each path in the path sequence of the task shortest path, and defining a traffic congestion level of the path; Step 4.3: predicting a traffic congestion time of the OHT vehicle passing through each path according to the traffic congestion level of each path; Step 4.4: predicting the time of the OHT vehicle passing through each variable rail point by comprehensively predicting the travel time of the OHT vehicle reaching each variable rail point without traffic congestion and the traffic congestion time of the OHT vehicle passing through each path; Step 5: for each variable rail point, sorting a passing order of the OHT vehicle at the variable rail point according to a passing order optimization method, i.e., according to the predicted time of the OHT vehicle passing through each variable rail point, and adopting a rule of first-in-first-out; Step 6: the OHT vehicle executes the task according to the shortest path planned in step 3, and the OHT system continuously monitors a state of the vehicle, i.e., whether the vehicle executes the task according to the task shortest path, and if a fault or other interruption reason occurs in the execution, returning to step 4 to re-predict the time of the OHT vehicle passing through each variable rail point, otherwise, making the variable rail advance to the variable rail according to the state of the vehicle and the passing order of each variable rail point obtained in step 5, and waiting for the OHT vehicle to pass; Step 7: the OHT system judges whether the OHT vehicle reaches the target station point, and if yes, entering step 8, otherwise, returning to step 6; Step 8: a rail where the target station point is located is a working rail, a standby rail parallel to the working rail is arranged on one side of the working rail, the working rail moves to the station when the vehicle reaches the target station point, the corresponding standby rail accesses the original rail, and the OHT vehicle starts loading or unloading at this time; Step 9: judging whether the OHT vehicle completes the loading or unloading, and if yes, entering step 10, otherwise, waiting for T seconds to re-judge; Step 10: judging whether the standby rail is free of the OHT vehicle, and if yes, moving the working rail to the original rail, otherwise, waiting for t seconds to re-judge. Step 11: judging whether the OHT trolley completes the task, if yes, updating the system state, returning to step 1, otherwise returning to step 6.

2. The variable orbit based OHT handling system anti-jamming scheduling strategy of claim 1, wherein, The task scheduling method comprises a heuristic rule-based task scheduling method and a task scheduling method based on an intelligent optimization algorithm.

3. The variable orbit based OHT handling system anti-jamming scheduling strategy according to any one of claims 1 to 2, characterized in that, The variable point is a center point of a variable orbit, the variable orbit is arranged in a rotating disc, the rotating disc is arranged at an intersection point of different orbits in the system, and the variable orbit is connected with other different orbits by rotating the rotating disc to change the direction, so that the variable orbit and the other different orbits form a passage.

4. The variable orbit based OHT handling system anti-jamming scheduling strategy of claim 1, wherein, The task shortest path table comprises information of a starting point of a task, an ending point of the task, a name of an OHT trolley for carrying, a path sequence of a task shortest path, a path marker of a path containing a variable point, a position of the variable point in the path, and a time of the OHT trolley passing each variable point.

5. The variable orbit based OHT handling system anti-jamming scheduling strategy of claim 1, wherein, The traffic congestion level comprises four levels of "smooth", "light congestion", "moderate congestion" and "serious congestion", the greater the path traffic flow value, the more serious the traffic congestion condition, the higher the path traffic congestion level, and the longer the traffic congestion time.

6. The variable orbit based OHT handling system anti-jamming scheduling strategy of claim 1, wherein, The track where the work station point is located is a working track, a movable work station track and a corresponding standby track are arranged on one side of the working track, the standby track is parallel to the working track, and the two are connected through the work station track, and the work station track is arranged on a slide; The standby track has a working state and an idle state, the working state is that the work station track slides on the slide to coincide with the work station point, the center point of the work station and the center point of the OHT trolley, the working track is not connected with other tracks, at this time, the OHT trolley performs loading and unloading work, the standby track is connected with other tracks of the system to form a passage, so that the OHT trolley does not block other OHT trolleys when performing loading and unloading work; The idle state is that the working track is directly connected with other tracks of the system to form a passage, and the corresponding standby track is not connected with other tracks and is in an idle state.

7. The variable orbit based OHT handling system anti-jamming scheduling strategy of claim 6, wherein, When the OHT trolley in step 8 performs loading or unloading, the standby track is in a working state, and the working track moves to the original track in step 10, that is, the standby track is in an idle state.

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