Study on voting safe function block and safety system
Voting mechanism based safe function block compatible with IEC 61499 is proposed. The voting safe function block can vote the discrete or continuous parameters and get a reliable value. A new safe communication approach is proposed for not only error sensing but also error correcting. The approach use a triple data field copies to address error correcting problem, and more safety is achieved in communication by this way. By using voting safe function block, a more safe system based on common control devices is designed. Furthermore, a markov model is established to describe safety and reliability of the voting safe function block based safe system. At the end, simulation under given parameters is done, which is about PFD, PFS and MTTF factors.