It is desired to control liquid level h₂ in the storage tank system shown in Fig by manipulating flow rate q₃ Disturbance variable q₁ can be measured. Use the information available to do the following:

(a) Draw a block diagram for a feedforward feedback control system.

(b) Derive an ideal feedforward controller based on a steady-state analysis.

(c) Suppose that the flow-head relation for the hand valve is q₂ = C?h₁ ? h₂. Does the ideal feedforward controller of part (b) change?

Available Information

(i) The two tanks have uniform cross-sectional areas, A₁ and A₂, respectively.

(ii) The valve on the exit line of Tank 1 acts as a linear resistance with a flow-head relation, q_{2 =?}(h₁ ? h₂)/R.

(iii) The transmitters and control valve are pneumatic instruments that have negligible dynamics.

(iv) The pump operates so that flow rate q₃ is independent of h₂ when the control valve stem position is maintained constant.

42 43 Tank 1 Tank 2