A comparison of sequential function chart and object-modelling PLC programming

This paper analyses the use of two control software design methodologies for developing a solution to control an automated manufacturing cell. Two separate approaches, sequential function charts and an object-modelling tool called enterprise controls are compared and contrasted with a view to establishing the effectiveness of each approach. These experiences are illustrated by comparing software to operate a simple clamp. Enterprise controls provided a simpler solution, which reduced both the time taken for implementation of process changes as well as the need for these to be carried out by trained personnel. The experience showed that the object modelling approach provides benefits to manufacturers by aiding manufacturing flexibility, though this comes with a processor overhead. Concerns remain as to whether or not enterprise controls will be accepted by practicing control engineers in industry. Further work to quantify these benefits is planned.