Intelligent workshop production logistics scheduling system solution based on the Internet of Things
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1 Project background
The Internet of Things technology is the basis for the transformation and upgrading of the manufacturing industry and the realization of intelligent manufacturing. In the process of promoting the implementation of smart manufacturing, the Internet of Things is expanding from partial processes in the industrial field to workshops and factories, from improving quality and efficiency to promoting the transformation of manufacturing and logistics business models. Intelligent manufacturing takes the intelligent workshop as the carrier to realize seamless end-to-end collaboration in all aspects of design, supply, manufacturing and service. Intelligent logistics can carry out perception, thinking, reasoning, route planning and decision-making, etc. It is an important link to connect supply and manufacturing between intelligences, and it is also the cornerstone of building a smart factory. Currently, smart manufacturing and smart logistics are in the process of integration. How to manage the complex processes of manufacturing and logistics, coordinate production scheduling and logistics scheduling to achieve the integration of smart manufacturing and smart logistics is a major challenge.
Through the installation of sensors, RFID readers and communication modules on the equipment, and the installation of sensors and communication modules on the conveyor line and RGV/AGV, etc., to meet the needs of automatic production scheduling and automatic logistics scheduling in smart workshops, Haide Controls has developed intelligent The workshop production logistics scheduling system realizes the integration of intelligent manufacturing and intelligent logistics. The system has been implemented in a demonstration application in an oral liquid production enterprise. It is the first intelligent workshop production logistics scheduling system project in the domestic pharmaceutical industry. The workshop was put into operation in May 2017. The second intelligent workshop production logistics scheduling system project being developed and implemented by Hyde Controls is expected to be completed in May 2018.
The goals and constraints of the intelligent workshop production logistics scheduling system are shown in Figure 1.
The objectives include three aspects: maximizing resource utilization, minimizing inventory, and minimizing production cycle. Because of the conflict between these goals, it is impossible to achieve the best state of each goal at the same time, so it is necessary to strike a balance between each goal.
In addition to the above three objectives, the production scheduling and logistics scheduling requirements of the smart workshop must be met, which mainly include three characteristics and requirements: flexibility, multiple constraints and variability.
Figure 1 The objectives and constraints of the intelligent workshop production logistics scheduling system
2 System architecture
The intelligent workshop production logistics scheduling scheme based on the Internet of Things adopts a three-tier system architecture: the scheduling layer, the monitoring layer and the execution layer. Among them, the scheduling layer performs production scheduling, route planning and instruction analysis, and issues production and transportation tasks to the PLC execution layer; the execution layer receives tasks from the scheduling layer and transports the work-in-progress from the starting point to the end; the monitoring layer is responsible for data collection and transmission , And dynamically monitor the production logistics system at the same time. as shown in picture 2.
Figure 2 System architecture
3 key technology
The key technologies of the intelligent workshop production logistics scheduling system include workshop production scheduling theory and models, production scheduling methods, path planning algorithms, roller table control methods based on single-section roller table control, AGV/RGV scheduling methods, buffer dynamic construction methods, faults Re-scheduling methods, batch constraint satisfaction algorithms, etc.
(1) Workshop production and logistics model
Based on graph theory and the extended event-driven process chain, the production and logistics of the smart workshop are modeled, including equipment elements, logistics elements, transportation tool elements, personnel elements, logical elements, etc., to establish a multi-dimensional and multi-view integrated model, Have a comprehensive understanding of workshop production and logistics conditions, and provide model and data support for production scheduling and logistics scheduling.
(2) Production scheduling method
Based on the theory of constraints and pull production and other production scheduling ideas, considering the production cycle of each process, a production scheduling method suitable for smart workshops is proposed. Using dynamic real-time scheduling method and dynamic rescheduling method, combined with dynamic planning model, according to the intelligent workshop production scheduling requirements, optimal assignment of production tasks.
(3) Flexible roller table control method based on single-section roller table control
For the roller conveyor scenario, in order to improve the flexibility of the transportation system, a method based on single-section roller conveyor control is adopted, that is, each transportation task passes through the path planning and instruction analysis module, and all its instruction sequences are given, and then the PLC execution module is given. Execute, and avoid path conflicts at the upper level. This method can flexibly realize various scheduling and transportation requirements.
(4) AGV/RGV scheduling method
For multiple RGVs on the linear reciprocating roller table, in order to increase the utilization rate of RGV and improve the transportation efficiency, the safety zone is dynamically calculated according to the location of the production equipment and the actual position of the RGV to ensure that the two RGVs are loaded and loaded in their respective areas. Unload, improve the utilization rate or transportation capacity of RGV.
(5) Buffer dynamic construction method
For production equipment that requires work-in-process trays, the buffer zone of work-in-process trays is dynamically established and maintained. At any state and at any time, a reasonable and timely supply of work-in-process trays can be realized to ensure continuous supply without congestion.
(6) Equipment failure/offline/online adaptive
When equipment fails, the relevant work-in-progress will be rescheduled; at the same time, the adaptability of the system will be increased, allowing the equipment to be offline and self-repair from the system; when the equipment is online, the system automatically accepts the equipment to enter.
(7) Batch constraint satisfaction algorithm
For smart workshops with strict batch constraints, batch constraints are added to production scheduling and logistics scheduling to ensure that the new and old batches are divided when batches are switched, and batches are separated when mixed batches are produced.
(8) Manual planning and adaptation
In response to the user’s manual intervention requirements, the system’s adaptability is increased, allowing manual production task assignment and path planning during the automatic operation of the system, and automatically avoid path conflicts and achieve load balancing.
4 Innovation
Based on the Internet of Things technology, the intelligent workshop production logistics scheduling system realizes intelligent production and intelligent logistics. Compared with the production and logistics of traditional manufacturing workshops, the main innovations include the following:
(1) Buffer dynamic scheduling: In order to avoid the supply of WIP pallets, the production equipment that is far away from the WIP pallet dynamically establishes a buffer zone to ensure the timely supply and balanced distribution of WIP pallets;
(2) Path conflict re-scheduling: When the WIP pallet has a path conflict on the path, the relevant WIP pallet can be rescheduled to resolve the conflict;
(3) Equipment failure adaptation: After the production equipment that requires the work-in-process pallet fails, the work-in-process pallet will no longer be supplied to it; after other production equipment fails, the work-in-process delivered to the production equipment on the conveyor line is rescheduled to other available parallel Production equipment;
(4) Equipment online/offline adaptation: After the production equipment goes offline, the work in progress transported to the production equipment on the conveyor line is rescheduled to other available parallel production equipment;
(5) Manual planning and self-adaptation: manual scheduling of target points can be accepted, and path conflicts can be automatically resolved;
(6) Batch control: When the production equipment batch is switched, after the old batch is cleared and the production equipment in the next process is completed, the new batch of work in process is scheduled to ensure that the two batches of work in process are not mixed;
(7) Electronic map: present the status of the entire workshop with an “electronic map”, real-time dynamic display of the online status of production equipment, important interactive signals, and important parameters and alarm information of all equipment;
(8) Information traceability based on electronic tags: Through electronic tags, record the production equipment number, entry time, exit time, etc. of each work-in-process pallet, so as to achieve full process traceability.
5 Benefit analysis
The intelligent workshop production logistics scheduling system developed by Haide Control realizes the integration of intelligent manufacturing and intelligent logistics, provides an ideal solution for the integration of intelligent manufacturing and intelligent logistics for manufacturing enterprises, and improves the production efficiency and logistics efficiency of manufacturing enterprises.
The production mode shifts from manual control of equipment and work-in-progress to control of the intelligent dispatching center, the production process is standardized and controllable, and the physical labor intensity of the workshop production personnel is minimized;
The system automatically ensures that the production is not mixed batches, and realizes the traceability of the whole process;
Improve logistics efficiency, reduce production equipment outages, and increase equipment utilization;
Optimize logistics routes and reduce logistics and transportation costs;
Optimize overall workshop production efficiency and logistics efficiency, and increase workshop productivity.
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