Programmable-Logic-Controller and SCADA-Based Automation of an Industrial Process

Abstract

ABSTRACT Industrial processes once controlled manually or by fixed relay logic are increasingly automated using programmable logic controllers and supervisory control and data acquisition systems, which promise greater throughput, consistency, and reliability and the ability to monitor and adjust the process from a central station. This study automates a representative industrial process using a programmable logic controller and a supervisory system and evaluates the improvement against manual and relay-based operation. The process was controlled by a programmable logic controller, which read its sensors and drove its actuators according to a program implementing the control logic, while a supervisory system displayed the state of the process, recorded its data, and allowed an operator to monitor and adjust it from a central station, and the throughput, the consistency of the cycle, the rate of defects, and the downtime were measured and compared with manual and relay-based operation. Automation improved the process on every measure: the throughput rose substantially as the controller executed the cycle faster and without pause, the cycle time fell and became consistent, the rate of defects dropped as the controller performed each step precisely and identically, and the downtime decreased as the supervisory system enabled faults to be detected and addressed quickly. The flexibility of the programmable controller, whose behaviour is changed by altering its program rather than rewiring, and the visibility and control afforded by the supervisory system were further advantages over fixed relay logic. The study shows that programmable-logic-controller and supervisory automation substantially improves the throughput, consistency, and reliability of an industrial process, and it discusses the sources of these gains and the considerations in adopting such automation.

KEYWORDS: Programmable logic controller, SCADA, Industrial automation, Process control, Throughput, Cycle consistency, Downtime, Supervisory control, Relay logic