Terminal constraints are usually employed in predictive control formulations to provide closed-loop stability guarantees. However, such guarantees are lost if the associated optimization problem is not feasible from the beginning or if it becomes infeasible due to the onset of faults, for example. This work presents an approach involving setpoint management and relaxation of operational constraints to address infeasibility problems in predictive control. It is assumed that infeasibility may occur either at the beginning of the control task, due to an adverse initial condition, or as the result of an actuator fault that reduces the range of admissible control values. The proposed approach involves the parametrization of the maximal output admissible set (MAS) employed as terminal constraint in the control law. This parametrization avoids the need to repeat the MAS determination during the infeasibility handling procedure. For illustration purposes, a case study involving a simulation model is presented.
Predictive control; Constraints; Feasibility; Setpoint management
