Recall the artificial pancreas control problem from Section 23.2. In order to regulate blood glucose BG, you have two possible manipulated variables to choose from: pumping insulin F_Iand pumping glucagon F_G. As you already learned, insulin can be a life-saving drug, but an overdose of insulin can send the body into a coma. Glucagon operates by converting glycogen in the liver to glucose. Their corresponding transfer functions are given below (time is in minutes):

In addition, you have the following information relating the BG to a meal (disturbance) D:

(a) Using principles you have learned about processes in general, which manipulated variable would you select (insulin pump or glucagon pump) for the design of a feedback control device? Be very specific.
(b) For the insulin pump, design an appropriate PID controller for the system, using IMC tuning rules (assuming Ï„_c = 20 min). 

(c) Derive the theoretically optimal feed forward controller for this device, assuming you use insulin as the MV. Is this controller realizable? (explain why or why not) If not, what might you do to implement an appropriate controller?
(d) For the insulin pump controller you designed above, you are now asked to design a control system for the pump subsystem only. Of particular concern is the situation where the pump is not delivering insulin because of an occluded tube. Draw a block diagram for the loop consisting of the pump and a flow controller. Include a type 4 alarm system for safety.

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-1.5e-30s (20s + 1)(25s +1) BG(s) F,(s) BG(s) FG(s) Gp1(8) = 3.4e-15s 15s + 1 G,2(8) = 5e-10s 30s +1 BG(s) G,(s) = D(s)