Dissipativity and performance analysis of semiactive systems with smart dampers

This research investigates the dissipativity and performance of semiactive systems with smart dampers. It is known that the dissipative nature of smart dampers has an important effect on the performance of semiactive systems; yet, frequently applied semiactive control strategies do not consider dissipativity in the design. To exploit the effects of dissipativity on the semiactive performance, dissipative behavior is quantified using dissipativity indices; these indices are, then, used in the analysis and control design of structures with smart dampers. Two representative cases are considered: simple two-degree-of-freedom (2-DOF) systems and more complex, realistic structures that can be encountered in a practical structural control problem.; In the case of 2-DOF structures, a dissipativity index is utilized to modify a standard linear quadratic regulator (LQR) controller using linear matrix inequality (LMI) techniques to achieve better semiactive performance. Two numerical examples are considered. The first example is a shear building, where an ideal damper is attached in the first story. It is shown that the proposed control theory can be used not only to identify controllers that are suitable for a smart damper but also to improve the control force dissipativity and, thereby, the performance of the semiactive structure. In the second example, a highway bridge with a realistic magnetorheological (MR) damper model is analyzed; it is shown that smart dampers may further reduce the dissipativity of the controllers that originally have low dissipativity levels, often resulting in poor semiactive performance.; A recently-introduced three-dimensional base isolated benchmark building is used to investigate the benefits of a dissipativity analysis for a real-life problem. First, dissipativity performance-relations for the benchmark structure with a linear isolation layer are revealed. It is shown that a dissipativity analysis provides useful information about which controllers are more suitable for semiactive application. In another example, an equivalent linearization technique is applied to implement a linear control strategy for the nonlinear structure, and a dissipativity analysis is shown to be an essential tool for faster solutions to this sophisticated problem, where a conventional semiactive design may be very impractical, time consuming and computationally intensive.