A Robust Internal Model-Based Fractional Order Controller for Fractional Order Plus Time Delay Processes

This letter proposes a fractional order internal model controller (FO-IMC) for a fractional order plus time delay (FrOPTD) process model to satisfy desired gain margin (A
_m
) and phase margin (φ
_m
) specifications. A method is proposed to solve four equations arising from the Am and φm specifications, which also generates solution of the system gain-cross-over frequency (ω
_g
) and phasecross-over frequency (ω
_p
) as intermediate variables. The designed FO-IMC is implemented on laboratory DC servosystem and compared with other integer order controller and fractional order controller.