On the synchronization problem for the stabilization of networked control systems over nondeterministic networks

In recent years, networked control systems have gained the attention of the control community, since they allow re-using the preexisting infrastructure therefore reducing deployment time and costs. Unfortunately, they also introduce new control challenges due to the nondeterministic network behavior. Predictive and model-based approaches can be used to compensate both delays and packet dropouts. However, a common timeframe among the involved components -sensors, actuators, plants and controllers- is required. This brings normally the necessity of keeping inner-clocks synchronized, which at the current state of art can be hard to realize. In this paper, a possible solution for the synchronization problem is presented. The idea is to keep using predictive techniques but utilizing a unique inner-clock on the system side. Assuming that actuator and sensor are directly connected to the system, the packets are time stamped, the delays are bounded, the maximum round-trip-time is known, and a limited amount of information is lost, it is possible to use model predictive control to stabilize the closed loop system by compensating delays and packet dropouts.