Development, implementation and use of an IEC 61499 function block library for embedded closed loop control

A wide range of industrial processes and applications are controlled by closed loop control systems. Such processes consist of the plant that needs to be controlled and of controlling elements such as actuators, sensors, regulators or controllers. Due to decreasing hardware costs controllers are more and more integrated into sensors, actuators or other field devices. The result is increased modularity, scalability and more intelligence of the control networks that can be built out of these new mechatronic devices. To be able to program such systems in a convenient and intuitive way the function block (FB) oriented IEC 61499 standard for modeling and engineering of distributed industrial process measurement and control systems was developed. First prototypes were successfully applied to the area of distributed discrete controllers. For the area of closed loop control there seems to be a natural link between block diagram descriptions of closed loop control elements and the FB concepts of IEC 61499. But up to now efforts for mapping and implementing the wide range of block diagram element of closed loop control theory to IEC 61499 constructs were outstanding. The goal of this paper is to investigate the possibilities for applying the concept of the IEC 61499 standard to the field of closed loop control. Therefore, computer aided design and engineering tools for closed loop control systems that are currently used by control engineers for design and control of centralized automatic control systems are analyzed regarding their capabilities. Based on this information, new FB types are identified to cover the core functionality that is necessary for the implementation in closed loop control systems. Based on this analysis a library of FB types for closed loop control applications was developed and applied. The usage and limitations of IEC 61499 for distributed closed loop control is demonstrated on a real experiment - the control of a challenging seesaw problem