Abstract：For conventional PLC triple modular redundant (TMR) systemsexists common cause failure (CCF) issue, a PLC heterogeneous triple modular redundant fault-tolerant scheme is presented in this paper. In this scheme, the main controller subsystem is designed in TMR structure with three different PLCs: OMRON CS1D, SIEMENS S7-400 and ROCKWELL Controllogix, the input subsystem, output subsystemand system bus arealso in heterogeneous redundant structure.The redundant data is processed in majority voting system and adopting preset adaptable voting mechanism. A self-diagnostics mechanism support heterogeneous TMR structure is presented to realize fault processing. Taking into account of CCF, availability and reliability of the system are analyzed based on the Markov model. Simulation results show that the heterogeneous redundant can improve reliability effectively.
2014, Vol. 15 
