Block Diagram Quick Reference
From ControlTheoryPro.com

1 Quick Reference
where
 is the system output,
 is the reference input or desired output,
 is the filtered reference input,
 is the error between and ,
 is the plant,
 is the feedback sensor,
 is the prefilter used shape the reference input, and
 is the controller.
where
 is the open loop transfer function
Note that is not part of the OL but is part of the tranfer fuction from to . See below.
where
 is the closed loop transfer function
where
 is the disturbance rejection transfer function
Note that the is from to .
2 All Transfer Functions
Below is an equation relating every input to the output
The transfer function from r to y is
The transfer function from d_i to y is
The transfer function from d_o to y is
The transfer function from n to y is
For the system to be stable all transfer functions must be stable.