Fuzzy Assessment Algorithm for Ladder Programming

This paper* proposes an assessment algorithm to measure the quality in ladder programming for programmable logic controllers (PLCs). The proposed quality metrics involve the criteria of simplicity, reconfigurability, reliability, and flexibility. The value of each metric criterion is normalized between 0 and 1. A fuzzy assessment algorithm is developed to select the best controller design among a set of developed ladder programs for the same application. A single tone membership function is used to represent the metric criterion for each controller between 0 and I. The fitness of each controller is evaluated as the minimum value of all the applied metric criteria. Thereafter, the decision making to select the best logic design is obtained as the maximum value of all fitness values. The developed fuzzy assessment algorithm is applied to real time discrete event systems. These systems are a pneumatic cylinder and a conveyor belt where each of them performs a repeated sequence. The obtained results affirmed the potential of the proposed algorithm to assess the quality of the designed ladder programs. The main contribution of this paper is to define a methodology to measure the quality for programs written in ladder diagrams.