Software Quality in Ladder Programming

This paper aims to measure the software quality for programmable logic controllers (PLCs) especially in ladder programming. The proposed quality metrics involve the criteria of simplicity, reconfigurability, reliability, and flexibility. A fuzzy inference algorithm is developed to select the best controller design among different ladder programs for the same application. A single tone membership function is used to represent the quality metric per each controller. The fitness of each controller is represented by the minimum value of all evaluated criteria. Thereafter, a min-max fuzzy inference is applied to take the decision (which controller is the best). The developed fuzzy assessment algorithm is applied to a conveyor belt module connected to a PLC to perform a repeated sequence. The decision making to select the best ladder program is obtained using the fuzzy assessment algorithm. The obtained results affirmed the potential of the proposed algorithm to assess the quality of the designed ladder programs