Design and implementation of nonlinear control strategies

A number of active control systems have been developed, fabricated and installed in full-scale structures and they have been subjected to actual wind forces and ground motions. Based on the observed response of several of these systems, a number of improvements to the hardware and software design of these systems are desirable. One of which is concerned with the control algorithms used. For example, linear quadratic regulator (LQR) has been used extensively but full-scale structural applications have shown that it is difficult to employ LQR to produce a significant peak response reduction when the peak response occurs during the first few cycles of the time history. Thus, one of the tasks at hand is to improve upon LQR and other generally linear control laws in order to produce better peak response reduction under control resource constraints. The purpose of this paper is to introduce two types of control laws for improved peak response control of civil engineering structures based on nonlinearization strategies. Through a series of simulation studies and experimental verification in the laboratory using a model structure, it is shown that the proposed new control laws can significantly improve peak response reduction under the same constraints imposed on the control resources as in the linear quadratic regulator case.