Control-relevant identification for two degrees of freedom control

The prefilter-based control-relevant identification scheme for single-input single-output (SISO) systems proposed earlier is useful for a one degree of freedom (DOF) control design. In this paper, we propose a control-relevant identification scheme for the synthesis of control-relevant, model-based, two-DOF controller. We propose a systematic method for the design of the two prefilters required for the estimation of the two distinct control relevant models. While one of the prefilters is based on the nature of disturbance characteristics and disturbance regulation specification, the second is based on the nature of set point signal and the specification for the set point tracking. The closed loop performance achieved with control relevant models and direct estimated model, using the internal model control (IMC)-based two-DOF controller, is analysed. The results obtained validate the significance of proposed control-relevant model-based two-DOF control, when the nature of set point/disturbance signals and the respective specifications for tracking and regulation are different.