Implementation guidelines for closed loop control algorithms on PLCs

The integration of closed loop control algorithms into industrial control systems represents an important topic in the automation domain. Timing constraints have to be taken into account, often leading to a compromise between real-time capabilities of the control and accuracy of the calculated values. Due to its event-based execution model, IEC 61499 bears advantages concerning the closed loop control application implementation. This provides flexibility and allows the implementation of various and more sophisticated feedback algorithms. The work described in this paper is concerned with these different implementation aspects. A detailed analysis is presented concerning their timing characteristics and solutions are proposed for the actual realization of these design variants by applying IEC 61499 function blocks.