Consider the PCM furnace module of Appendix H. Assume that oxygen exit concentration c_O2 is the CV, air flow rate AF is the MV, and fuel gas purity FG is the DV.

1. Using the transfer functions given below, design a feedforward control system.
2. Design a PID controller based on the IMC tuning relations and a reasonable choice for τ_c.
3. Simulate the combined FF-FB controllers for a sudden change in d at t = 10 min, from 1 to 0.9. Which controller is superior? Justify your answer.