Effective implementation of algorithm theory into PLCs
Date
2005-10
Authors
Piao, Xianshu, author
Burt, Charles, author
U.S. Committee on Irrigation and Drainage, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
A major constraint for implementation of automated canal control is the complicated, tedious, and potentially error-ridden task of programming the control algorithm and associated overhead into PLCs (Programmable Logic Controllers). A typical control program may easily occupy 100 pages of Ladder logic that must be painstakingly developed and programmed. The most common argument in favor of Ladder logic - that local electricians can get into the program and modify it if needed - is flawed because (1) local electricians do not understand the logic, and (2) Ladder cannot easily perform many mathematical tasks that are simple in other programming languages. In addition, the Ladder programmed on one brand of PLC is not directly programmable onto another brand because each brand has its own variation of the Ladder language. ITRC's approach to canal automation simulation includes building a model with an excellent hydraulic simulation program, characterizing each pool for storage and resonance, Matlab optimization of the control logic's parameters based on hydraulic properties, and writing the logic in ISaGRAF. These services cannot be performed by integrators, who rarely, if ever, understand the theory behind modern canal control. This has been misunderstood by districts when planning their long-term canal automation strategy, putting at stake large investments into the controller and software programming.
Description
Presented at SCADA and related technologies for irrigation district modernization: a USCID water management conference on October 26-29, 2005 in Vancouver, Washington.