1. The problem statement, all variables and given/known data PI Design The transfer functions represent the dynamics of a typical commercial turbofan engine between fuel flow rate [tex]\Delta[/tex]WF in pps and fan speed increment [tex]\Delta[/tex]N1 in rpm and between fuel flow rate and high-pressure turbine outlet temperature increment [tex]\Delta[/tex]T in degrees Rankine. "Since zero steady-state error is desired, an integral control approach will be used. To simplify the process, append a free integrator to Eqs. 1 and 2 and regard the resulting transfer functions as design plants. Keep in mind that the integrator has already been included when designing your controllers." 2. Relevant equations (1) [tex]\Delta[/tex]N1(s) / ([tex]\Delta[/tex]WF(s)) = 247.37(s+8.906) / ((s+2.855)(s+5.421)) (2) [tex]\Delta[/tex]T(s) / ([tex]\Delta[/tex]WF(s)) = 167.995(s+4.79)(s+2.075) / ((s+2.855)(s+5.421)) 3. The attempt at a solution At this point i really don't even know what a "free integrator" is, and searching my prof's notes and the internet hasn't really given me anything to work with. I'm hoping this is something of a brain fart, because this is only the first part of a very long assignment. Any help would be appreciated.