Abstract
In this paper, the physical structure of the H∞ controllers (especially, the central controller) for the so-called four block and one block standard problems, which have been derived by the Conjugation method, is investigated based on the differential game theory. As the results of that, it makes clear that H∞ controller has not only the mechanism of full state observer, but also that of reasonable disturbance estimator. The former is well-known fact, but the latter is an important structure to understand H∞ controllers. The disturbance estimated in the controller is used to diminish the effect of exogenous input on the controlled output. Furthermore, from the view of this feedforward structure, the essential difference between four block and one block problem also makes clear.
