ABSTRACT
As discussed in Chapter 5, for an active, semi-active or hybrid control system, its controller system will utilise and analyse the measured signals from the sensory system, compute the necessary control forces or other quantities based on a given control algorithm, and command the control devices to make corresponding reactions, so that the structure can adapt itself to structural changes and to varying usage patterns and loading conditions. An active, semi-active or hybrid control system will not lead to the desired control performance if the control algorithm is not appropriately designed. The structural control theory is therefore developed to find appropriate control algorithms for active, semi-active or hybrid control systems. There are a number of excellent books introducing various structural control theories (Soong 1990; Ou 2003; Preumont 2011). 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. The basic concepts to be introduced in this chapter include stability, controllability and observability of a control system. The commonly used control algorithms include pole assignment, linear optimal control, independent modal space control (IMSC), sliding mode control (SMC), H2 and H∞ control, adaptive control, artificial intelligent control and semi-active control. The application of the control algorithms for vibration control of civil structures will be presented in Chapter 13. Because the performance of the control system also depends on the placement of the control devices and sensors used in the system, the optimal control device placement and the collective placement of sensors and control devices will be discussed in Chapters 10 and 11, respectively.
