Design of a new fractional-order QFT controller based on automatic loop shaping

This paper presents a new robust fractional order controller tuned based on Quantitative Feedback Theory (QFT). The new fractional-order controller structure is a general fractional-order zero-pole model. Firstly the virtue and the flexibility of the controller are analyzed in detail. The parameters of the controller are tuned based on Quantitative Feedback Theory (QFT). The PSO technique has been employed to tune the controller automatically that can greatly reduce the computational effort compared to manual graphical techniques. A fractional-order compensator with the proposed structure and a minimum number of parameters, introduced into the QFT design, can more approach to the optimal QFT controller and make the open loop transfer function closer to the QFT bounds in Nichols chart.