Analog Control System Design

This chapter deals with the analog control system design. It begins with a review of a classical control design and then explains the design of analog controllers in the s-domain. Analog controllers can be implemented using analog components or approximated with digital controllers using standard analog-to-digital transformations. In addition, direct digital control system design in the z-domain is very similar to the s-domain design of analog systems. Following this, the chapter obtains root locus plots for analog systems. The root locus method provides a quick means of predicting the closed-loop behavior of a system based on its open-loop poles and zeros. It characterizes a system's step response based on its root locus plot and discusses design proportional (P), proportional-derivative (PD), proportional-integral (PI), and proportional-integral-derivative (PID) controllers in the s-domain. The objective of control system design is to construct a system that has a desirable response to standard inputs. A desirable transient response is one that is sufficiently fast without excessive oscillations. A desirable steady-state response is one that follows the desired output with sufficient accuracy. Finally, the chapter describes the process of empirical tuning PID controllers using the Ziegler-Nichols approach.