Steady-State Availability and Inventory in Fault-Tolerant NCS for Pharmaceutical Process

Fault tolerance is becoming an essential feature in today’s Networked Control Systems (NCSs). The extra cost of redundancy is expected to be compensated by the reduced downtime. Especially in developing countries, large variations in duration of repair can greatly influence downtime. This paper studies the fault-tolerant aspect of an Ethernet-based NCS for pharmaceutical tablet production described in the literature. Markov models are used to calculate the steady state availability. A cost analysis is then conducted to relate availability, cost of downtime, inventory costs and cost of repair strategies. The techniques described in this paper are general and can be applied to different fault-tolerant NCSs.