Data structure and process data traversal in a manufacturing cell controller

For manufacturing cells used in flexible manufacturing systems (FMS), a cell control system functions autonomously in coordinating the operations of all equipment and a material handling robot in the cell. Since the sequential approach to cell control cannot handle multiple and simultaneous tasks, a cell controller is developed in a concurrent programming environment. The data structures required by the cell control operation are defined, including that for the product, the AGV, the robot, the processes and the system I/O. All data structures are stored in a public memory area that is accessible to all processes. Control tasks are achieved by traversing these data structures and dynamically constructing a control command with the necessary process data in run-time. It is shown that an autonomous control system using multi-tasking and software interrupt techniques is useful for the real-time control of cell production, and software modularity provides a good flexibility to adapting system changes. The relation of the cell control data structure and the overall manufacturing system's database is also briefly discussed.