Abstract
This paper is concerned with the exact description of the structured uncertainty for robust control. So far, the structured uncertainty of the plant was often expressed as affine perturbations of the coefficient matrices in the state-space or the descriptor form representation. However, this type of expression is sometimes very conservative for the uncertainty due to physical parameter perturbations. Therefore, in this paper, a systematic method to describe the physical parameter perturbations in an exact way is given based on the LFT and the descriptor form representation. It is shown that the proposed uncertainty description combined with the mixed μ analysis gives a sharp robust performance bound compared to the conventional uncertainty expressions via numerical examples.
