Robust controller design of multivariable perturbed systems with QFT

We present a robust controller design method for perturbed MIMO systems by combining pseudo-diagonalization technique and the quantitative feedback theory (QFT). The pseudo-diagonalization method can be used to synthesize a pre-compensator with pre-assigned form, such as PI, PID type controllers, to achieve maximal degree of diagonal dominance. Once the dominance is reached, the well-known SISO QFT technique is then employed to design a robust diagonal controller for the compensated plant such that the required robust stability and tracking performance are satisfied. A numerical example is given to illustrate the feasibility of the method presented for designing a robust controller for perturbed MIMO systems.