TR2018-177

A smart actuation architecture for wireless networked control systems



Along with the forth industry revolution, implementing industrial control systems over mainstream wireless networks such as WirelessHART, WiFi, and cellular networks becomes necessary. Well-known challenges, such as uncertain time delays and packet drops, induced by networks have been intensively investigated from various perspectives: control synthesis, network design, or control and network co-design. The status quo is that industry remains hesitant to close the loop at the control-to-actuation side due to safety concerns. This work offers an alternative perspective to address the safety concern, by exploiting the design freedom of system architecture. Specifically, we present a smart actuation architecture, which deploys (1) a remote controller, which communicates with physical plant via wireless network, accounting for optimality, adaptation, and constraints by conducting computationally expensive operations; (2) a smart actuator, which co-locates with the physical plant, executing a local control policy and accounting for system safety in the view of network imperfections. Both the remote and the local controllers run at the same time scale and cooperate through an unreliable network. We propose a policy iteration-based procedure to co-design the local and remote controllers when the latter employs the model predictive control policy. Semi-global asymptotic stability of the resulting closed-loop system can be established for certain classes of plants. Extensive simulations demonstrate the advantages of the proposed architecture and co-design procedure.