UBC Theses and Dissertations
Supervisory computer control of a flexible manufacturing cell Kean, Thomas Maxwell
A combined software and hardware package has been developed which coordinates the activities of a Unimation PUMA 560 industrial robot and an ORAC CNC training lathe in a Flexible Manufacturing Cell environment under the supervision of a DEC VAX 11/750 computer. The hardware component is used to provide an intermediate interface between the VAX 11/750 software and the standard manual controls of the ORAC lathe. The interface to the PUMA robot is strictly software oriented and makes use of the Supervisor communication protocol provided by the robot's VAL II controller. The software package has been designed as a hierarchial, multi-tasking system to facilitate modular development and a logical division of labour. The hierarchy consists of three main levels, with the individual machine controllers providing the lowest level. At the middle layer is a number of subprocesses which execute on the VAX 11/750 and are each responsible for the direct supervision of one machine controller. This supervision involves both sending commands and receiving status messages in the native language of the individual controllers. At the top layer of the hierarchy is a single process which is responsible for the overall coordination of the workcell activities. Each subtask in the hierarchy communicates with its vertical neighbours through a series of communication protocols and command vocabularies developed for that purpose. Each subtask is also provided with a structured interface to the operator's console. This interface is implemented by a separate VAX process that provides a status window environment for each machine that is active in the cell, but also intercepts text messages and prompts so that they may be displayed to the operator one at a time. Two different software packages have been developed for the top layer of the hierarchy. The ORCAM package is dedicated to the task of automatically manufacturing turned components from a CAD database. The FMC package provides a flexible interface to each of the supported machines and may be used to supervise any number of user-defined tasks.
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