Abstract
The existence of unstable zeros makes it difficult to construct inverse system and model matching system, etc. It is well known that a system with unequal number of inputs and outputs almost always has no zeros. The two-delay output control system proposed by Mita et al attracts attention because it can avoid zeros. Two-delay output control system is a digital system which augments number of outputs by observing outputs twice in a sampling period.
In this paper, the condition to avoid zeros is obtained for the systems in which geometric multiplicity of zeros of basic discrete-time system is greater than one. By using the state-space representation, the necessary and sufficient conditions are obtained that two-delay control system achieves strong stabilization. Furthermore, it is shown that the necessary and sufficient conditions to construct a stable inverse system are the same as the conditions for strong stabilization.
