Arbitrated Networked Control Systems


Distributed cyber-physical architectures typically consist of multiple control applications mapped onto spatially distributed embedded systems (DES) with sensors and actuators that communicate via shared buses such as CAN and FlexRay. These Cyber-Physical Systems (CPS) provide considerable flexibility in designing the network in terms of mapping control tasks to processors and determining various scheduling parameters and protocols. We refer to such systems as arbitrated networked control systems (ANCS) to emphasize the fact that the arbitration policy in the network also needs to be determined, and these policies together with the embedded system topology can be co-designed with the control system. By making use of real-time calculus, suitable information can be extracted about the delays due to communication and computation. This information in turn can be incorporated to result in a co-design of both the embedded systems network and the control system. One example of such a co-design is the use of a hybrid protocol and an adaptive control architecture. We design the protocol using the fact that any communication delay needs to be minimal during the transient mode of a control application, but can be larger during its steady-state mode. In particular, a time-triggered protocol is used during the transient mode and an event-triggered protocol during the steady-state mode. An adaptive controller is designed for each mode and suitable switching strategies are imposed to switch between the modes. The resulting multi-modal co-design is shown to be stable, schedulable, and realize efficient performance from multiple control applications.