ABSTRACT
This chapter provides a concise introduction to some basic concepts of structural control theory and to some commonly used control algorithms in structural vibration control. It introduces the basic concepts that include stability, controllability and observability of a control system. Civil structures are normally stable structures designed to serve people. Stability is a basic requirement for all civil structures equipped with control devices. Stability can be understood more directly with the aid of Laplace transform and the characteristic equation. The concepts of controllability and observability, introduced by R. E. Kalman, play a significant role in control theory: they appear as necessary and sometimes as sufficient conditions for the existence of a solution to most control problem. The structural responses of a civil structure are dominated by a few mode components, such as the first few modes of vibration.
