I am not sure of the difference between normal single input and the 2 DOF PID controller in simulink. I noticed that the 2 DOF PID block accepts the reference (r) and the measurement(y) separately but under the hood it computes the error=r-y which is what the normal PID accepts as a single input. They both seem to be doing the same thing. I have a control problem where the reference point changes as well as the measurement signal. How will the 2 DOF PID controller make a difference to my control problem compared to the normal single input PID block? Or what problem does the 2 DOF PID controller solve compared with the normal single input?