Allen-Bradley PLC5 Development Services by Valiant Technologies, Inc.

Allen-Bradley PLC5 Development Services

We have over five years experience in developing the ladder control logic for the PLC5 class of Allen-Bradley controllers. Specifically, Dr. Nelson designed, developed, and integrated the PLC5 ladder control logic for the Defense Nuclear Agency (DNA) Large Blast Thermal Simulator (LBTS) at the White Sands Missile Range in the central deserts of New Mexico.

This development effort required the real-time monitoring of some 100 sensors and controls to create approximately 200 safety interlock conditions for nearly 75 independently timed events. Since the LBTS is an experimental test-bed, the ladder logic was designed to deal with daily modifications and thus has a number of custom internal test and evaluation structures. These internal checks prevent catastrophic sequences from being executed by the system, where the term catastrophic implies a substantial explosion and fire in the test chamber.

The LBTS posed a number of unique problems for the PLC5 systems since the experiments are performed daily, require minor modifications for each one, and the system had to be integrated into the overall LBTS structure. Just the timing for the experiment is problematic since the countdown can last for hours, the execution sequence minutes, and the actual experiment only a few seconds.

In order to meet the strict documentation requirements of the Defense Nuclear Agency and manage the development of this highly complicated experimental test-bed, Dr. Nelson developed an external documentation and code development system for the PLC5 logic. With this system, he was able to create self-contained source code structures that are easily read, commented, and documented (something not possible with the standard Allen-Bradley tools). This structure, along with the creation of a representative PLC5 pseudo-code language, allowed for the creation of complete system documentation such that the entire control system could be rebuilt from it. This structure allowed the ladder logic to be developed by the systems engineers, reviewed by the development review team, and then entered by key-punch personnel.

Our experience base with other advanced real-time systems makes Valiant uniquely equipped to deal with even the most difficult programmable logic controller implementations, including the reverse engineering, documenting, and reengineering of existing systems.

06/20/00 ern