Integration of Multiple Fault-Tolerant techniques for FPGA-based NCS Nodes

Fault-Tolerance is quickly becoming a very important issue in the design of industrial automation systems. This paper addresses this issue in the context of temporary failures occurring in harsh industrial environments. The Fault-Tolerant design of sensors and controllers is investigated for both the In-Loop and Sensor-to-Actuator architectures. Processing is implemented on FPGAs whenever possible. Triple Modular Redundancy (TMR) is used to implement sensors for fast varying applications while Temporal Redundancy (TR) is used for sensors for slow varying applications in order to reduce cost without affecting system reliability. Dynamic Partial Reconfiguration (DPR) is used for fault recovery. Reliability models are developed for all Fault-Tolerant blocks to help system designers with the choice of the Fault-Tolerant techniques to be implemented. Two case studies are carried out with different numbers of fast and slow sensors. System reliabilities are calculated for both conventional and hybrid NCS systems. Results show that the proposed technique results in a cost-effective system at the expense of a very slight decrease in reliability.