On the design of reconfigurable two layer hierarchical control systems with MPC

This paper deals with the design of a hierarchical two-layer controller. At the high level, a robust MPC regulator works at a slow frequency rate and computes the ideal control signals needed to suitably control the plant. At the low level, a number of already controlled actuators drive the plant at a faster time rate and track the desired control signals as accurately as they can, in accordance to their dynamics. The discrepancy between the ideal control actions computed at the high level and those actually provided to the plant gives rise to a robustness issue for the overall control system. To tackle this problem, we propose to model such a discrepancy as a disturbance term to be rejected in the design of the high level controller by means of the small-gain approach. Moreover, setting an optimization procedure at each time step, the proposed algorithm also allows for an easy reconfiguration of the control system in the occurrence of an actuator addition/replacement.