In this introductory chapter we review the background and reasons behind the development of the IEC 61499 standard. Specifically we will: review the design of current-day control systems and consider the impact of new technology. Look at the reasons for starting the development of the IEC 61499 standard. Consider the reasons why function blocks are still an important concept to process and system engineers. Show how function blocks have some of the characteristics of object oriented software. And finally show how IEC 61499 models can be used in the control system development life-cycle.

This chapter reviews how to create type definitions for function blocks and subapplications and show how these can be used to create function block instances and copies of subapplications. Specifically it (1) review different forms of function block definition (2) show how events and data interfaces can be defined (3) examine how algorithms are constructed and linked to the event execution (4) consider how instances of function blocks behave (5) review where subapplications can be used and compare their behaviour and properties with composite function blocks.

As discussed in chapters 1 and 2, a fundamental property of lEC 61499 function block networks is that the execution of all software within every function block is, in some way, event triggered. In this chapter we will review a special set of standard function blocks that are provided for event behaviour. These function blocks can be used to model the control, generation and detection of events. This chapter will describe the standard event function blocks that: allow events to be split to produce new events; allow events to be merged; permit the propagation of particular events; select between two or more events; delay an event by a given period; generate streams of events; and create events from Boolean edge detection.

In this final chapter we will review how the IEC 61499 standard is likely to develop in the future and its possible impact on the design of systems and support tools. This chapter will review: current limitations of part 1 of the IEC 61499 standard; proposals for IEC 61499 part 2 that covers 'Engineering Task Support' ; requirements of a standard file exchange format for porting; and future developments.

This appendix gives a brief overview of the XML language and the reasons why it has been chosen as a file exchange format for IEC 61499 library elements, for example, for exchanging function block definitions between engineering support systems and other IEC 61499 compliant applications.

A PID algorithm is used in 'closed loop' control where there is a requirement to control a process that may be subject to disturbances caused by external factors or by unpredictable changes to the process. In the example discussed in this chapter, the PID function block is constructed by connecting instances of three function blocks: FB_INT, FB_DEV and FB_CALC. These are created from DERIVATIVE_REAL, INTEGRAL_REAL and PID_CALC function block types, respectively. The DERIVATIVE_REAL and INTEGRAL_REAL blocks provide derivative and integration functionality for inputs of REAL data type and are based on definitions given as examples in the IEC 1131-3 PLC software standard. The PID_CALC block encapsulates the PID algorithm and calculates a new output value that is proportional to a weighted summation of the error, the derivative of the error and the integral of the error.