A real-time virtual machine and process control workstation

Digital process control systems have typically been based on either a large central computer that performs all the control functions or on small, specialized stand-alone computers called programmable controllers. Recent introduction of powerful microcomputer hardware has enabled the distribution of advanced control technology. Some benefits offered by this approach are increased throughput, improved response time, additional operator communication flexibility and greatly enhanced reliability at a lower cost. The present thesis involves the development of an efficient, cost-effective software system which transforms readily available, general-purpose microcomputer hardware into a "state-of-the-art" process control workstation. The main features of this workstation include- (a) User-friendly operator interface allowing dynamic, menu-driven configuration of all system defining parameters; (b) Turn-key support for common control strategies and capabilities for incorporation of user-written algorithms; (c) Interprocessor communication interface permitting operation within a distributed control hierarchy; (d) Real-Time Virtual Machine facilities which provide an environment conducive to the efficent execution of cooperating process control programs and therefore eliminate the unnecessary overhead and expense associated with the use of conventional operating systems and high-level language extensions. Structured software has been developed to implement the previously described workstation functionalities with hardware based on DECS LSI-11 family of microcomputers. The resulting system provides a unique, turn-key solution for cost-effective distribution of advanced control technology. The developed system can be utilized as a stand-alone laboratory instrument or incorporated into a distributed process control hierarchy. It can be applied to the control of small industrial processes or used as an effective tool for training engineering students.