Predictive compensation for network-induced time-varying delays

The goal of this paper is to provide a control design methodology that can assure the closed-loop performances of a physical plant, while compensating the time-varying delays introduced by the communication network that links the controller with the remote process. Firstly, the error caused by the time-varying delays is modeled as a disturbance and a method of bounding the disturbances is presented. Then, a robust one step ahead predictive controller based on flexible control Lyapunov functions is designed, which explicitly takes into account the bounds of the disturbances caused by time-varying delays and guarantees also the input-to-state stability of the system in a non-conservative way. Moreover, it is shown that by choosing an appropriately Lyapunov function, the MPC algorithm amounts solving a single, low-complexity linear program each sampling instant. The modeling method and the control strategy were tested on a DC motor controlled through Ethernet. A comparison with a state-of-the-art Lyapunov-based predictive controller shows that the proposed control scheme can handle better the performance/physical constraints and the strict limitations on the computational complexity.