Microsoft Word - 10 jan final aftr acceptance

The present work deals with the problem of frequency weighted controller reduction using balanced singular perturbation approximation. The advanced controller design methods like LQG/LTR or based synthesis methods sometimes leads to an controller of order comparable to plant and sometimes unstable controller whereas lower order controller should be sought out to keep the closed-loop stability and system performance within acceptable limit. For unstable controller reduction a controller decomposition algorithm using real Schur transformation is developed. The algorithm discussed for computation of balancing transform is based on orthogonal transformation which extends the applicability of algorithm to non-minimal controllers. Resulting closed-loop system with reduced order controller is guaranteed to preserve the most of the time domain and frequency domain characteristics and it is shown that proposed algorithm gives better performance than other existing techniques. The algorithm is fully implementable in MATLAB and illustrated by an example.