Robust H∞ controller design by loop shaping approach

The paper describes the loop shaping design method on the basis of normalized coprime factorization H_∞ control theory. The loop shaping approach can gain physical insight in system dynamics, and is effective in tradeoff between performance robustness and stability robustness. The H_∞ control theory based upon normalized coprime factorization is concise in expression and high efficient without iteration. Furthermore, the loop shaping design strategy combined with the H_∞ control theory has an indicator to know whether the shaping functions are valid or not and point out how to improve the adjustment. The case study on a longitudinal flight control system shows the high efficiency and effectiveness of this methodology