Mixed H_2 and H∞ control

Mixed H_2 and H∞ norm analysis and synthesis problems are considered in this paper. It is shown that the mixed norm analysis combined with structured uncertainty can be used to give bounds on robust H_2 and H∞ performance. It is also shown that the mixed norm controller shares a separation property similar to those of pure H_2 or H∞ controllers. The obvious advantage for a mixed norm is that it gives a natural trade-off between H_2 performance and H∞ performance, and provides a potential framework for extending the μ-synthesis framework to address robust H_2 performance. A simple example is used to motivate the possible advantages such a framework might have over a pure H∞ theory