Robust tuning for PID controllers with multiple performance specifications

The problem of PID controller robust design is considered. Frequency domain performance specifications are considered, and a robust design versus plant parametric perturbations is carried out. A method is presented, based on an efficient interval algorithm, which allows the construction of convergent inner and outer approximations of the set of the robustly performing design parameters, called the robust Q set. The knowledge of the robust Q set gives interesting information for the controller design. In particular the knowledge of the specifications limiting the Q set allows a constraint relaxation approach for facing the presence of multiple performance specifications