Sensor/Channel Redundancy for Sensor-to-Actuator Networked Control Systems

Nowadays, reliability is becoming more and more important in the design of Networked Control Systems (NCSs). Fault-tolerance is often used to increase system reliability. In this paper, Triple Modular Redundancy (TMR) and Parallel Redundancy Protocol (PRP) are both applied to a Sensor-to-Actuator architecture with 16 sensors, 4 Actuators and one Supervisor. Two of the 16 sensors as well as two of the 4 actuators are wireless while the rest of the nodes are wired. It is first shown that this NCS succeeds in meeting all control system requirements (zero packet loss and bounded end-to-end delay). Reliability models are then developed to help designers choose the appropriate mix of fault-tolerant techniques in order to maximize lifetime while at the same time minimizing the extra cost due to the added redundancy.