Control Systems - Block Diagram Reduction - Tutorialspoint Note − Follow these steps in order to calculate the transfer function of the block diagram having multiple inputs. Step 1 − Find the transfer function of block diagram by considering one input at a time and make the remaining inputs as zero. Step 2 − Repeat step 1 for remaining inputs. Step 3 − Get the overall transfer function by adding all those transfer functions. The block diagram reduction process [PDF] Feedback Fundamentals - Caltech Computing The controller has two blocks the feedback block. C. and the feedforward block. F. There are two disturbances acting on the process, the load distur-bance. d. and the measurement noise. n. The load disturbance represents disturbances that drive the process away from its desired behavior. The process variable. x. is the real physical variable that we want to control.