ABSTRACT
System modeling always can only describe the engineering plant approximately (e.g. there exists the error between them), so there have been great deals of literatures which show interesting in the study of system robust control problems which subject to system and external uncertainty [1, 2]. But such robust controller which tackles the uncertainty of controlled plant is assumed to be implemented exactly. This demand seems validity, but actually, as the inevitable uncertainty in advanced controller operation and engineering implementation, such as environment temperature variation, the digital device’s word capacity, and data transform error, etc. controller implementation exactly is impossible in the actual engineering, e.g. the closed system is fragile to the uncertainty in controllers itself.
