Speeding up of calculation for μ-synthesis of low order H∞ controllers

In this paper, a numerical optimization problem for μ-synthesis with a reduced order controller is studied. A local solution is searched for starting from a reduced order controller, where μ-analysis and a local search method for a reduced order H_∞ controller are applied, alternatively. A main different point from the standard DK-iteration is that the procedure is all conducted for frequency response data and no representation by state equations is required. Therefore, not the plant order but the number of frequency gridding mainly affects computation time. In this paper, in order to develop a more efficient algorithm, a method of reducing the number of LMIs in the calculation of a descent direction is given. Numerical examples show that computation time can be reduced drastically compared with our previous algorithm.