James O. Ramsay
Ramsay offers an introduction to the basic concepts involved in the design of feedback loops for controlling the performance of a process that converts one or more inputs into one or more outputs. The exposition is geared toward behavioral scientific scenarios, but is broadly applicable. The idea of using a differential equation to describe the dynamic characteristics of a system is explained, and then three types of control strategies are illustrated. These are proportional control, integrative control and derivative control, corresponding to using information from the current state of the output, using past information, and using the current rate of change, respectively. The advantages and disadvantages of these three types of control are sketched. Methods for estimating differential equations from repeated observations of the process are outlined.