Section 9.1 The 2DOF Structure for Stable Plants Internal stability:Consider the typical 2DOF system.The input-output relationship is as follows: e(s) C2(s) r(s) 1+G(s)C1(S) y(s) 1 d(s) 1+G(s)C1(s) It can be seen that the internal stability of the closed-loop system is only determined by Ci(s).The analysis for the internal stability is similar to that in a 1DOF system Design:The design of a 2DOF system involves two steps: DDesign C1(s)for good disturbance response 2Design C2(s)for good tracking response 4口：4@4242定90C Zhang,W.D..CRC Press.2011 Version 1.0 7/95Section 9.1 The 2DOF Structure for Stable Plants Internal stability: Consider the typical 2DOF system. The input-output relationship is as follows: e(s) r(s) = C2(s) 1 + G(s)C1(s) y(s) d(s) = 1 1 + G(s)C1(s) It can be seen that the internal stability of the closed-loop system is only determined by C1(s). The analysis for the internal stability is similar to that in a 1DOF system Design: The design of a 2DOF system involves two steps: 1 Design C1(s) for good disturbance response 2 Design C2(s) for good tracking response Zhang, W.D., CRC Press, 2011 Version 1.0 7/95