Design of adaptive two-degree-of-freedom controller for inversion based reference input tracking of non-minimum phase system

This paper presents a novel technique towards inversion based reference input tracking control problem of non-minimum phase system which has unstable dynamics. Exact set point tracking can be possible by using inversion based system, but it is restricted to minimum phase systems only; whereas in case of non-minimum phase (NMP) system the concept of inversion technique gives unstable output response. To overcome this problem, a two-degrees-of-freedom (2DOF) control technique has been applied here for inversion based reference input tracking control problem of NMP system. It is shown that the combination of Model Reference Adaptive Control structure (MRAC) using MIT rule and state feedback control methodology in 2DOF framework can track the reference input trajectory of NMP system employing the inversion based technique with a small steady state error. Initial undershoot is an undesirable characteristic of NMP system which has also been minimized. The effectiveness of the proposed method has been established in simulation studies.