Increasing adaptability of assembly process planning and control using Function Block methodology.

摘要

Today's market turbulences cause frequent changes in manufacturing environments. Products diversity, small batch sizes and short life cycles have increased production uncertainties and created highly dynamic shop floors. One essential requirement in such environments is an adaptive process planning system which is sufficiently agile to respond to the great variable of production requirements and to enable easy system reconfigurations at run-time. On the other hand, if distributed knowledge sources and joint product development by dispersed teams is taken into consideration - owing to the business globalization and outsourcing -- information flow in a collaborative environment becomes important.;In this research, a framework and new approach have been introduced to increase the adaptability and autonomy of job-shop Assembly Process Planning (APP) and control using Function Block (FB) technique. Job-shop is characterized by multiple machine types and varying part types and thus experiences a high degree of variability. IEC61499 function block, an international industrial control standard, is chosen as a data transit and execution element. Function block is a reusable functional module with an explicit event-driven model, and provides for data flow and finite state automata based control. In this approach, process-oriented function blocks are built into assembly process plans. To facilitate FB-enabled assembly process planning, basic assembly operations are identified and classified as standard assembly operations. A complete' assembly task is broken down to its basic assembly operations that can be readily assembled by the known assembling technology and the available resources. A generic function block is designed for each basic assembly operation, with a set of embedded algorithms on how to carry out the job by a robot. The algorithms are event-driven and can make adaptive decisions at run-time. Function block methodology is also incorporated to deal with the layout issues of the assembly shop in a frequently changing environment, where essential requirements such as adaptability and proactive responsiveness to the dynamic changes need to be considered in addition to the cost issue of material handling and machine relocation when reconfiguring the shop floor from one layout to the next. In this research, based on the source of uncertainty, the shop floor layout problem is split into two sub-problems and dealt with by two modules: re-layout and find-route. Function blocks can be incorporated in the find-route module to suggest the best sequence of robots for the new routings/conditions.;The proposed FB-enabled APP is further demonstrated through simulations in Matlab Simulink environment through examples of one- and two-robot assembly workstations. The simulation results show that by applying FB methodology, a process plan no longer needs to be re-generated to fit changes in resources, schedule, and product design, etc.;This novel approach enables not only adaptive decision-making but also effective plan execution. Adopting IEC-61499 function blocks, the advantages of Object Oriented (00) technology such as abstraction, encapsulation, and polymorphism can be achieved. A traditionally continuous manufacturing process becomes a set of objected-oriented reusable functional units. Process planners are thus able to generate or adjust a process plan quickly and effectively.;During product development, assembly is a key area that highly impacts a manufacturing system's responsiveness to changes. A good assembly process plan can increase production efficiency and product quality, and decrease the cost and time of the whole product manufacturing process.;Keywords - Job-shop Assembly Process Planning; Dynamic Manufacturing Environment; Adaptive Process Planning System; Manufacturing Uncertainty; Function Block Methodology; Assembly Layout Planning.