5.3. Response to Setpoint Changes
A simplified [assuming gm(s) = gv(s) = 1] feedback block diagram is shown in Figure 5-10. This simplification is equivalent to lumping the measurement and valve dynamics into the process transfer function. By convention, we denote the output of the controller block as u(s), which is also the manipulated input. Notice that we are focusing on setpoint changes only, so we have not included the disturbance block. In Section 5.7 we will focus on disturbances.
Figure 5-10. Simplified control block diagram. Disturbances are neglected and valve and measurement dynamics are lumped into the process transfer function.