Control Theory Applications for Dynamic Production Systems

4 Fundamental Dynamic Characteristics and Time Response

Fundamental dynamic characteristics of production systems and components can be obtained directly from the transfer functions that describe their behavior. These characteristics are important and fundamental because, like transfer functions, they do not depend on particular inputs; rather, they describe how quickly the outputs of a system or component tend to respond to inputs in general; for example, whether responses tend to be oscillatory and whether the system or component is stable or not stable. If stable, outputs tend to decay to a steady state with time; if not stable, outputs tend to continue to grow with time and not reach a steady state. Important fundamental dynamic characteristics are defined in this chapter, and their influence on time response is illustrated. This is useful because production engineers are familiar with time response and are comfortable with models and simulations that predict how production systems and their components respond to various inputs. In subsequent chapters, it will be shown how fundamental dynamic characteristics influence frequency response and how they can be used to design decision making for production systems.

Time constants, damping ratios, natural frequencies and stability are fundamental characteristics of dynamic behavior. These characteristics are defined in this chapter for continuous-time and discrete-time models of production systems and components, and they are ...