Consider the storage tank with sight glass in Figure. The parameter values are R1 = 05 min/ft2, R2 = 2min/ft2, A1 = 10 ft2, Kv = 2.5cfm/mA, A2 = 0.8ft2, Km = 1.5mA/ft, and ?m = 0.5 min.(a) Suppose that R2 is decreased to 0.5 min/ft2. Compare the old and new values of the ultimate gain and the critical frequency. Would you expect the control system performance to become better or worse, justify your answer.(b) If PI controller settings arc calculated using the Ziegler-Nichols rules, what are the gain and phase margins? Assume R2 = 2 mm/ft.

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