Reconciling programmable logic controllers (PLCs) with mechatronics control software

Abstract

Programmable logic controllers (PLCs) have established a firm place as control elements for mechanical systems. Because their dominant programming model is ladder logic, based on relay logic, they are usually viewed as an entirely different class of device than computer-based controllers programmed in algorithmic languages such as C. The result separates, somewhat hostile communities of people, those who use PLCs and those who use computers. Through the use of a task/state design and implementation model for mechanical system control software (mechatronic software) these two seemingly disparate means of implementing mechatronic system control can be reconciled. Because the design model relates closely to its computational realization, control system designs can be transported between PLCs and computers relatively easily. This reconciliation is possible because the algorithmic software design is based on fully non-blocking code leading to a scanning computational structure. This structure is completely consistent with the rung-scanning algorithm used by PLCs.