Consider Figs. 16.3 and 16.4 illustrating cascade control. 

(a) Suppose you were to apply feedforward control, instead of cascade control, to handle disturbances D₁ and D₂. Where do you expect feedforward control to be more benefcial: for D₁, or D₂? Explain why.
(b) Draw a block diagram that is a modifcation of Fig. 16.4 that uses feedforward control for the D₁ disturbance.
(c) What additional sensors would be required for feedforward control of D₁?

Reactor Feed in temperature set point (master) TT)- TC Water surge tank i Jacket temperature | set point V (slave) LC -- LT Reactor - TC TT Cooling water out XD- Product Cooling water makeup Circulation pump Figure 16.3 Cascade control of an exothermic chemical reactor. D1 D2 Gal Gd2 Secondary controller Primary controller Y sp2 Y1 Y2 Gp1 E1 Ge1 E2 Gc2 Gp2 Ysp1 G, sp1 sp Kml Ym2 Gm2 ml Gm1 Figure 16.4 Block diagram of the cascade control system.