Fault-Tolerant IEC 61499 Applications
This chapter focuses on applications whose executions are distributed among multiple execution devices, whether programmable logic controllers, embedded platforms, or full-fledged computers. It presents a design pattern for tolerating partial faults in International Electrotechnical Commission (IEC) 61499 applications. The chapter explains the design pattern and shows how it can be implemented on an existing IEC 61499 execution environment, and how some of the dependability properties of the resulting IEC 61499 application can be determined. Measures that tolerate the more probable faults may need to be used if the application is required to achieve a certain level of reliability. When the application has real-time requirements, the fault-tolerant measures used must be limited to those that adopt the forward-recovery approach. The fault prevention approach consists of building a system in such a way as to prevent the occurrence of faults. Distributed IEC 61499 control applications are subject to failures of one of the execution devices running the distributed application.