Fault-tolerant controllers in adjacent wireless networked control systems using 802.11

Wireless Networked Control Systems is an interesting research field for industrial automation applications. A workcell model based on the 802.11 standard as a communication protocol for Wireless Networked Control Systems is presented in this paper. The standard protocol is investigated without modifications. Fault-Tolerance at the controller level of neighboring workcells is studied. When adjacent controllers are interconnected, the amount of control data traffic is increased since each sensor sends its real-time information to all controllers. Also, watchdog messages between these controllers must be continuously propagated to ensure that all controllers have complete knowledge of the status of neighboring ones. In this research, a fault-tolerant model of two adjacent workcells is proposed and simulated using OPNET. Interfering noise considerations are also investigated. Fault-free and fault-tolerant results are presented and compared to previous works, showing correct performance within specified network requirements. All results are based on a 95% confidence analysis.