Section 9.1 The 2DOF Structure for Stable Plants Figure:Typical 2DOF system C1(s)-The controller of the disturbance loop C2(s)-The controller of the reference loop.C2(s)is always stable For convenience of presentation,the structure is named "Structure I".Structure I has many equivalents,as shown in Figures.It should be pointed out that the C(s)s in these Figures are not identical to each other 4口，404注4生定分QC Zhang.W.D..CRC Press.2011 Version 1.0 5/95Section 9.1 The 2DOF Structure for Stable Plants Figure: Typical 2DOF system C1(s)—The controller of the disturbance loop C2(s)—The controller of the reference loop. C2(s) is always stable For convenience of presentation, the structure is named “Structure I”. Structure I has many equivalents, as shown in Figures. It should be pointed out that the C1(s)s in these Figures are not identical to each other Zhang, W.D., CRC Press, 2011 Version 1.0 5/95