Performance evaluation of an input/output selection criterion via normalized LQG closed-loop comparison

One essential task in control system design is the optimal selection of inputs and outputs (I/O). In this paper a new concept for solving the I/O selection problem is proposed. It is based on normalized comparison of LQG closed loops, which are designed for each potential actuator/sensor separately. The LQG controller is iteratively tuned to obtain a prescribed and fixed value of a suitable system norm quantity. The proposed placement criterion is applied to flexible structures and demonstrated for an academic example and for a large-scale blended-wing-body (BWB) passenger aircraft pre-design model. Comparison to a state-of-the-art open-loop I/O selection method from literature verifies the proposed approach, but also shows that the closed-loop approach provides additional system insight and highly flexible applicability.