Manufacturing Control system

Manufacturing Control systemManufacturing Control - Managing and controlling the physical activities in the factory aiming to execute the manufacturing plans. Normally, a manufacturing control comprises the short-term process plan and the shop floor activities.

Three indicators for testing a manufacturing control system

• Agility - Capability to react in a short period of time to the occurrence of unexpected disturbances (i.e. production environment changes).

• Flexibility - Capability to adapt to new, different or changing environments. In manufacturing world, several flexibility classifications are presented in literature, like mix, changeover, volume, product and sequencing.

• Re-configurability - Ability to support different manufacturing system configurations, i.e. different production systems scenarios, with a small customization task.

Traditional Manufacturing Control Approaches

Centralized Control Structures

is characterized by a single decision node, where all the planning and processing information functions are concentrated.

• Advantage: a better management and control optimization

• Disadvantage: low, speed of response, control complexity, tolerance to faults and expandability, specially for large systems.

Hierarchical Control Structures In the hierarchical architecture, a complex problem is decomposed in

several simpler and smaller problems, and distributed among multiple control layers. This architecture is characterized by the existence of some control levels, distributed in a tree structure, allowing the distribution of decision-making among these hierarchical levels. The relations between hierarchical levels are based on the master-slave concept.

• Advantage: The main advantages of this architecture are the robustness, the predictability and the efficiency that are better than in centralized architectures.

• Disadvantage: the appearance of disturbances in the system reduces significantly its performance.

Heterarchical Control Structures The heterarchical architecture, also designated by

autonomous agent approach in the agent domain, is characterized by the high level of autonomy and co-operation, being the client-server structure with fixed relations no more applied.

• Advantage: allow a high performance against disturbances, The expandability of the system is an easier task, because it is enough to modify only the functioning of some modules or add new modules to the control system.

• Disadvantage: is a novel technology, needs more research works, at the time the implementation of this control structure is not common

Sensors in manufacturing control system

For any manufacturing control system a kind of drawback of an excessive dependence on up-to-date information about the products and other elements which move within the system is essential.

To address these issues, wireless identification technologies have been developed and introduced over the last decades.Bluetooth and WiFI

• Bluetooth and Wifi

• Wireless sensors

• Bar code

• RFID

Bar code in compare to RFID in manufacturing control context

• When a part is complex, it may lack a convenient and scan able location for bar codes. RFID tags can be placed anywhere on the part, and scanned from any orientation.

• Unlike bar codes, RFID tags can store data for continuous production updates.

• Unlike bar codes, RFID tags are unaffected by the dust and grime common to industrial environments.

• RFID tags can provide monitoring of the arrival, continuous presence, and departure of specific parts to/from a cell, allowing for better management of routes and locations in the assembly environment.

Radio-frequency identification

• Radio-frequency identification (RFID) is the wireless non-contact use of radio-frequency electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects.

• Tags • Antenna • Reader

RFID

RFID-Based Manufacturing Control System

Conclusion

• This work has discussed the multi-agent architecture proposed to support the design and implementation of an RFID-enabled distributed control and monitoring system for a manufacturing shop. The agents that compose the architecture have been conceived to cover flexibility, agility and re-configurability posed by all the distributed “Station Control Agent” which it is inspired and the communication mechanisms needed for the agents to carry out an RFID-based distributed control and monitoring system have been defined.