Feedback control equivalent unity system

The analysis of feedback control systems can often be facilitated by conversion to an equivalent unity feedback system, i.e. a feedback loop in which the feedback path is represented by a steady-state gain of unity. There are two principal cases to consider. 

Fig. 7.86. Equivalent unity feedback block diagram of control system illustrated in Fig. 7.42 including non-linear element...

Fig. 7.38. Unity feedback system equivalent to the control loop shown in Fig. 7.37 when the dynamics of the feedback path are not significant...

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