CN112364961A

CN112364961A - RFID (radio frequency identification) acquisition method for workshop scheduling

Info

Publication number: CN112364961A
Application number: CN202011351169.3A
Authority: CN
Inventors: 程强; 高元杰; 初红艳; 张彩霞; 杨聪彬
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-02-12

Abstract

The invention discloses a workshop scheduling-oriented RFID acquisition method, which records relative position information between a workpiece and equipment through mutual cooperation of a plurality of RFID readers and deduces real-time information of each equipment and each workpiece in a workshop. The method comprises the steps of classifying workpieces, distributing RFID readers to each device, detecting the RFID readers to obtain information of the workpieces and the devices, and carrying out dispatching again in a period according to the difference of an original scheduling plan in actual processing conditions, so that the robustness and the efficiency of workshop dispatching scheduling are improved.

Description

RFID (radio frequency identification) acquisition method for workshop scheduling

Technical Field

The invention relates to the field of intelligent manufacturing scheduling, in particular to a workshop scheduling-oriented RFID acquisition method.

Background

In the scheduling problem of the current intelligent manufacturing industry, most scheduling is based on static scheduling, that is, assuming some conditions, such as processing time of a certain procedure for machining a certain workpiece by a known machine or transportation time considering the processing time, and then performing the static scheduling under the condition assumption. The simplified scheduling mode can rapidly make a scheduling and production scheduling plan, and improves the production efficiency to a certain extent.

However, in the actual production process, various problems may occur, and the assumed conditions are not all satisfied, for example, when the workpiece is installed, the workpiece is installed by a worker, the proficiency of each worker is different, the installation time is different, and for example, when the workpiece is transported, the transportation environment causes blockage, the machine tool is in fault during machining, and the like, the influence caused at this time is often expressed that the time when the workpiece reaches the machine tool and the actual machining time of the machine tool are changed. Therefore, it is not practical to continue scheduling according to the original scheduling plan. How to quickly determine the time when a workpiece reaches equipment and the machine state and reschedule the subsequent scheduling of the rest part under the conditions that all scheduling plans of the original scheduling cannot be met and part of the original scheduling plans is executed is very important.

Disclosure of Invention

The invention provides a workshop scheduling-oriented RFID acquisition method. The method comprises the following specific steps:

step 1: and performing type division on blanks in the workshop, sequentially attaching electronic tags according to the divided blanks of different types, and initializing the contents of the electronic tags.

Step 2: an encoding rule is designed for storing workpiece information.

And step 3: and the RFID reader-writer is arranged between the equipment and is used for detecting the time when the workpiece leaves the processing equipment.

And 4, step 4: and arranging a wireless local area network in a workshop, and performing data interconnection and intercommunication between the RFID readers through the wireless local area network.

And 5: and defining related events, and modifying the coded value of the workpiece electronic tag when the related events occur.

Step 6: and the upper computer acquires all the RFID signal information, decodes the RFID signal information and sends the RFID signal information to the control platform, and the control platform performs equipment allocation on the workpieces according to the idle priority processing rule of the processing equipment in the period to complete the scheduling task.

Furthermore, in order to better manage the workpieces, all the workpieces are attached with electronic tags, and tag contents are initialized according to workpiece classification results.

Further, in order to record information into an electronic tag of a workpiece, an RFID code is designed, as an example, the 1 st and 2 nd digits 01 represent the type of the workpiece, such as a box. The 3 rd and 4 th digits 09 denote the sequence number, i.e., the 9 th workpiece of this type. The 5 th to 8 th bits are the workpiece arrival time at the equipment, i.e. 10 minutes 10 th arrival time. The last 4 bits are the time the workpiece left the tool, i.e., 10 points 30 apart on the day.

0 1 0 9 1 0 1 0 1 0 3 0

Furthermore, workshop arrangement of the RFID readers is completed, each production line device is provided with one RFID reader, each workpiece can be detected in each production process, the monitoring range of the readers is set, one RFID reader can only monitor one production line device, mutual interference among a plurality of RFID readers is avoided, and in principle, the working range of each RFID reader can only be set as the working range of the processing device. An RFID reader-writer is also arranged between the equipment and is used for detecting the time when the workpiece leaves the processing equipment.

Further, the designed codes are used, the electronic tag code values of the workpieces read by the devices are continuously received from the RFID reader-writer through the wireless local area network in a periodic polling mode, the electronic tag code values are compared with the electronic tag code values of the workpieces stored in the previous control platform, if the electronic tag code values are different, decoding is carried out according to the coding rules, and the decoded information is returned to the control platform. Meanwhile, the control platform can also issue an instruction to the reader-writer through the local area network, and the RFID reader-writer can modify the coding value in the electronic tag of the workpiece.

Further, the code value in the workpiece electronic tag is modified by adopting different methods through the occurrence of the following different events:

when the RFID reader-writer of a certain device of the production line reads the electronic tag of a certain workpiece, the workpiece is considered to enter the device and start to be processed, the time point is recorded as the processing starting time, and the time when the workpiece in the electronic tag code reaches the device is modified as the time point.

And when the reader-writer of the RFID reader-writer of the equipment can not detect the information of the workpiece, the workpiece is regarded as leaving the current equipment, the current working procedure processing is completed, and the next working procedure is started. And the RFID reader-writer between the two devices reads the workpiece, and the time for the workpiece in the electronic tag code to leave the devices is modified into the time for the R FID reader-writer between the two devices to read the workpiece.

After the last process is finished, the time for the workpieces in the last process to leave the equipment is modified for all the workpieces through a general RFID reader-writer.

Further, after the workpiece information is obtained, scheduling is performed according to a periodic re-scheduling method, which mainly includes:

and establishing a rescheduling period based on the periodic polling time T, wherein the period length is lambda and forms a certain multiple relation with the periodic polling time length, the lambda depends on the number X of the remaining tasks scheduled in the current workshop, and X is the sum of all processes of the remaining workpieces, and the following formula is shown, wherein C is a constant and is obtained based on experience.

Then, establishing a constraint condition:

1) the available state of the machine in the current period is determined by the actual scheduling scheme of the previous period, and when the machining of the machine in the scheduling scheme determined in the previous period continues until the next period starts, the machine is in a busy state for a certain period of time at the beginning of the next period, and cannot machine a newly arrived workpiece.

2) All newly arrived workpieces in the current cycle can be processed in the current cycle.

3) The time that a workpiece can be processed earliest in the current cycle depends on the maximum value of the current rescheduling time of the workpiece and the finishing time of the last process that the workpiece has finished.

4) The machine can only process one workpiece at a time.

5) The machine is not allowed to stop once it starts working.

6) Different processes of the same workpiece are sequentially constrained, and the processes of different workpieces are not sequentially constrained.

After the constraint conditions are determined, in each period, the management and control platform polls the RFID reader-writer to acquire the read workpiece data, the time when the workpiece leaves the equipment for the first time is regarded as the time when the workpiece reaches the current period, and the time when the workpiece leaves the equipment for the non-first time is regarded as the time when the machine finishes the current task processing. And then, according to which machine is idle, allocating the workpiece to the machine for processing to perform task scheduling, and realizing the function of acquiring the workpiece information according to the RFID technology and guiding workshop scheduling.

Drawings

The invention is further described with reference to the accompanying drawings and specific embodiments.

FIG. 1 Overall flow sheet

FIG. 2 is an acquisition process diagram based on RFID technology

FIG. 3 is a communication diagram of the control platform and the RFID reader

FIG. 4 is a diagram of periodic rescheduling based on RFID technology

Detailed Description

According to fig. 1, in actual production, analysis is performed by ignoring certain factors based on assumed conditions, so that a production scheduling plan can be generated quickly, and efficiency can be improved greatly. At the moment, the whole processing task can be processed by processing according to the initial scheduling plan, and then scheduling is carried out according to the current scheduling. However, this is not always the case, and when an unpredictable change occurs, which results in that the initial scheduling cannot be continued, we need to quickly adjust the remaining tasks, and the RFID technology can help us to more quickly obtain the overall situation of the current scheduling. Therefore, the dispatching task can be carried out within a period according to the RFID technology, and the rest dispatching task requirements are completed.

Therefore, a workshop scheduling-oriented RFID acquisition method is provided, as shown in FIGS. 2 and 3, and the specific steps are as follows.

The method comprises the following steps: classifying according to the type of the workpiece, simultaneously attaching a label, initializing the code through an RFID reader-writer, and increasing the class of the workpiece for the code value of the label of the workpiece.

Step two: in order to record information into the electronic label of the workpiece, an RFID code is designed,

step three: and each equipment accessory of the production line is provided with one RFID reader, and each reader is set with a reasonable working range, so that the RFID readers are not interfered with each other. And an RFID reader-writer is arranged between adjacent devices and used for recording the time when the workpiece leaves the devices, so that the RFID reader-writer is ensured not to interfere with other RFID reader-writers.

Step four: a wireless local area network is provided so that RFID readers can communicate with each other in the same wireless network.

Step five: when different types of readers-writers read the workpiece, the code values are modified according to different methods,

step six: and (3) periodically acquiring the workpiece information read by the RFID by using a polling method and taking the time T as a period. And determining that the scheduling period is as long as possible, and performing periodic rescheduling according to the workpiece information and the equipment information acquired by the RFID in the scheduling period.

The detailed development of the steps is as follows:

the work piece accessible manual work is categorised, pastes electronic tags to work piece unprocessed portion, avoids the label to damage. And carrying out coding initialization in sequence, wherein 1 to 4 bits in a coding value are information of the workpiece and are unique identifiers in the whole production flow. And completing the initialization of the code values for the electronic tags of all the workpieces based on the classification condition.

The following example designs a code, and the 1 st and 2 nd digits 01 represent the type of workpiece, such as a box. The 3 rd and 4 th digits 09 denote the sequence number, i.e., the 9 th workpiece of this type. The 5 th to 8 th bits are the workpiece arrival time at the equipment, i.e. 10 minutes 10 th arrival time. The last 4 bits are the time the workpiece left the tool, i.e., 10 points 30 apart on the day.

0 1 0 9 1 0 1 0 1 0 3 0

In the layout of a workshop, a certain distance exists between devices, and the RFID reader-writer corresponding to a device and the readers-writers of other devices should not interfere with each other, as shown in fig. 2, the working range of the RFID reader-writer of each device is represented by a circle, the inside of the circle is the working range of the RFID reader-writer, and the circles are not intersected with each other. And an RFID reader-writer should be arranged between the processing equipment in the previous process and the processing equipment in the next process, and a plurality of RFIDs are mutually matched to determine the real-time states of the workpiece and the processing equipment.

Through the configuration of the wireless local area network, the control platform and the plurality of RFIDs can communicate with each other, as shown in fig. 3, the control platform can periodically poll the encoded values of the workpieces read by the RFID devices, and can also issue a command for modifying the label values of the workpieces to the RFID reader/writer through the wireless local area network.

When the RFID reader-writer corresponding to the equipment reads a certain workpiece, a signal for reading the workpiece is sent to the background, the background receives the signal and controls the reader-writer to finish the code modification operation according to the current time, the arrival time of the workpiece is recorded into the code through the RFID reader-writer, and meanwhile, the equipment state corresponding to the RFID reader-writer is set to be a busy state.

When the RFID reader-writer beside the equipment reads the workpiece, a signal for reading the workpiece is sent to the background, after the background receives the signal, the reader-writer is controlled to finish the code modification operation according to the current time, the time when the workpiece leaves the equipment is recorded into the code through the RFID reader-writer, and meanwhile, the state of the workpiece in the previous processing equipment is changed from busy to idle.

After the last procedure of all the workpieces is finished, the last RFID reader-writer is required to uniformly encode, a signal for reading the workpieces is sent to a background, after the background receives the signal, the current time is determined as the final completion time of the workpieces, the reader-writer is controlled to finish encoding modification operation, and meanwhile, the state of the workpieces in the previous processing equipment is changed from busy to idle.

After the problem occurs in the original scheduling, in order to solve the subsequent processing task, the scheduling is performed periodically, so that the stability of the scheduling scheme can be improved, the period length can be selected reasonably according to the task scheduling condition of the current workshop, and the subsequent scheduling task is solved by rescheduling in the period, as shown in fig. 4, the method mainly comprises the following steps:

1) setting a periodic polling time T, establishing a rescheduling period, wherein the period length is lambda and forms a certain multiple relation with the periodic polling time length, lambda depends on the number X of the remaining tasks scheduled in the current workshop, X is the sum of all procedures of the remaining workpieces, and the formula (1) is shown in the specification, wherein C is a constant and is obtained based on experience.

2) The available state of the machine in the current period is determined by the actual scheduling scheme of the previous period, and when the machining of the machine in the scheduling scheme determined in the previous period continues until the next period starts, the machine is in a busy state for a certain time at the beginning of the next period, namely M_statusWhen the value is 0, the newly arrived workpiece cannot be machined, and if the new workpiece can be machined, the value is M _status1. T in formula (2)_iIs the moment when the ith scheduling period starts after the original scheduling fails, M_i-1，finishIs the point in time at which the processing of one cycle on the machine is completed.

3) All newly arrived workpieces in the current period can be processed in the current period, as shown in formula (3), J_statusWhether the workpiece is in a machining state at present or not is 1, namely the workpiece is in an idle state at present.

4) The time that a workpiece can be processed earliest in the current cycle depends on the maximum value of the current rescheduling time of the workpiece and the finishing time of the last process that the workpiece has finished.

5) Equation (4) represents a process in which the machine can only process one workpiece at a time, and equation (5) is a decision variable of workpiece i.

6) Once the machine starts working, it is not allowed to stop, s in equation (6)_i，j，kStarting time point, t, of j-stage machining of workpiece i_i，j，kTo estimate the machining time, e_i，j，kAnd a machining completion time point of the j-step machining of the workpiece i.

e_i，j，k＝s_i，j，k+t_i，j，k i＝1，2，…，n；j＝1，2，…S；

k＝1，2，…，m_j (6)

7) Different processes of the same workpiece are sequentially constrained, and the processes of different workpieces are not sequentially constrained.

And finally, in the current period, firstly determining the state of each equipment at the beginning of the period, acquiring the completion time of each workpiece in the current time window according to the RFID technology, and distributing the workpieces according to the state of each equipment in the current time window.

The allocation mode is based on the idle priority processing rule of the processing equipment, namely equipment with an idle processing state is selected to process the latest arriving workpiece, and if a plurality of equipment capable of processing the workpiece are in the idle state, the equipment with the shortest time for processing the workpiece is selected to process the workpiece.

When the workpiece is machined on the distributed equipment, the completion time of the workpiece can be detected through the RFID technology, the workpiece is distributed again at the moment, the state of the equipment is obtained, the workpiece is distributed to the equipment which is idle and can machine the workpiece, and the operation is repeated continuously in a plurality of periods until the machining task is completed. And the function of acquiring the workpiece information according to the RFID technology in the period and guiding the workshop scheduling is realized.

Claims

1. A RFID acquisition method facing workshop scheduling is characterized by comprising the following steps:

step 1: classifying the types of blanks in a workshop, sequentially attaching electronic tags according to the classified blanks of different types, and initializing the contents of the electronic tags;

step 2: designing a coding rule for storing workpiece information;

and step 3: arranging an RFID reader-writer on each production line device to ensure that each workpiece can be detected in each production process, and arranging the RFID reader-writers between the devices for detecting the time when the workpiece leaves the processing device;

and 4, step 4: arranging a wireless local area network in a workshop, and performing data interconnection and intercommunication between the RFID readers through the wireless local area network;

and 5: defining a related event, and modifying the encoding value of the workpiece electronic tag when the related event occurs;

2. The RFID acquisition method facing workshop scheduling according to claim 1, wherein workpiece classification and workpiece labeling are performed, that is, all workpieces are labeled with electronic tags, and tag contents are initialized according to workpiece classification results.

3. The RFID acquisition method facing workshop scheduling according to claim 1, wherein the customized RFID code has 1 st and 2 nd digits representing workpiece types, 3 rd and 4 th digits representing sequence numbers, 5 th to 8 th digits representing workpiece arrival time and the last 4 th digit representing workpiece departure time.

4. The RFID acquisition method facing workshop scheduling according to claim 1, wherein the workshop arrangement of RFID readers is completed, each production line device is provided with one RFID reader, each workpiece can be detected in each production process, the monitoring range of the reader is set, one RFID reader is ensured to be capable of monitoring only one production line device, the mutual interference among a plurality of RFID readers is avoided, and in principle, the working range of each RFID reader is only set as the working range of a processing device; and meanwhile, an RFID reader-writer is also arranged between the equipment and is used for detecting the time when the workpiece leaves the processing equipment.

5. The RFID acquisition method facing workshop scheduling according to claim 2, wherein the RFID reader-writer continuously receives the electronic tag coded values of the workpieces read by each device in a periodic polling mode through a wireless local area network, the electronic tag coded values are compared with the electronic tag coded values of the workpieces stored in a previous control platform, if the electronic tag coded values are different, decoding is performed according to the coding rules, and decoded information is returned to the control platform; meanwhile, the control platform can also issue an instruction to the reader-writer through the local area network, and the reader-writer modifies the coding value in the electronic tag of the workpiece.

6. The RFID acquisition method facing workshop scheduling according to claim 1, wherein the modification rule of the electronic tag code value comprises:

when an RFID reader-writer of the production line equipment reads an electronic tag of a certain workpiece, the workpiece is considered to enter the equipment and start to be processed, the time point is recorded as the processing starting time, and the time of the workpiece in the electronic tag code reaching the equipment is modified as the time point;

when the reader-writer of the RFID reader-writer of the equipment can not detect the information of the workpiece, the workpiece is regarded as leaving the current equipment, the current working procedure processing is completed, and the next working procedure is started; the RFID reader-writer between the two devices reads the workpiece, and the time for the workpiece in the electronic tag code to leave the devices is modified into the time for the RFID reader-writer between the two devices to read the workpiece;

7. The RFID acquisition method facing plant scheduling according to claim 1, wherein the guidance of the plant scheduling by using the information obtained by the RFID comprises the following steps:

scheduling is carried out in the mixed flow shop, the number of workpieces is assumed to be n, the number of processes is assumed to be S, and the machinable machine of each process is assumed to be m_jAfter the original scheduling fails to continue scheduling, the remaining workshop scheduling is quickly finished by using the RFID technology;

firstly, establishing a period window and a constraint condition:

1) establishing a rescheduling period based on the periodic polling time T of claim 5, wherein the period length is lambda and is in a certain multiple relation with the periodic polling time length, lambda depends on the number X of the current workshop scheduling residual tasks, and X is the sum of all processes of the residual workpieces, and is shown as the following formula, wherein C is a constant and is obtained based on experience;

2) the available state of the machine in the current period is determined by the actual scheduling scheme of the previous period, and when the machining of the machine in the scheduling scheme determined in the previous period continues until the next period starts, the machine is in a busy state for a certain time at the beginning of the next period, namely M_statusWhen the value is 0, the newly arrived workpiece cannot be machined, and if the new workpiece can be machined, the value is M_status1 is ═ 1; t in formula (2)_iIs the moment when the ith scheduling period starts after the original scheduling fails, M_i-1，finishIs the time point when the processing of one cycle on the machine is finished;

3) all newly arrived workpieces in the current period can be processed in the current period, as shown in formula (3), J_statusWhether the workpiece is in a machinable state at present or not is 1, namely the workpiece is in an idle state at present;

4) the earliest processing time of the workpiece in the current period depends on the maximum value of the current rescheduling time of the workpiece and the finishing time of the last process finished by the workpiece;

5) formula (4) represents a process in which the machine can only process one workpiece at the same time, and formula (5) is a decision variable of the workpiece i;

6) once the machine starts working, it is not allowed to stop, s in equation (6)_i，j，kStarting time point, t, of j-stage machining of workpiece i_i，j，kTo estimate the machining time, e_i，j，kA processing completion time point of the j-process processing of the workpiece i;

e_i，j，k＝s_i，j，k+t_i，j，k i＝1，2，...，n；j＝1，2，...S； (6)

k＝1，2，...，m_j