By operation of the distillation columns you are often interested to maintain output despite fluctuations in the composition, ex. feed composition and feed flow. One possible actuator-variable is here reflux (determined by the reflux ratio) or distillation stream. Modeling of distillation columns dynamic behavior is extensive, but often engineers trying to make simple models for columns dynamics, with parameters determined based on operational data (both static data and step responses).  Column Dynamic expected approximately be described by the following transfer functions:

Y(s/D(s) = 2*exp(-20s)/95s+1

Y(s/F(s) = 1*exp(-30s)/2* 60s +1

1. Determine a static feedforward controller

2. Determine a dynamic feedforward controller

3. Determine a PI controller on the use of Direct Synthesis Method (use tau_c = 30)

4. Simulate the closed feedforward controller from 1 and 2nd

5. Repeat (4) using the combined feedforward and feedback loops

6  Which controller gives the best result?