Heuristic-Based Algorithm for Active Control

A simple effective control algorithm, free from the problem of time delay, is proposed. It is a closed-open loop control. The control force is applied to the structure at the current time to cancel the portion of the system velocity that is induced by the response and the external load at the preceding time step. This control concept is motivated by the fact that, for a single degree of freedom (SDOF) structure subjected to external loadings, the energy of the external load is imparted to the structure by changing the structural velocity. A simple, closed-form equation is used to compute the control force for SDOF systems, and for multiple degree-of-freedom (MDOF) systems, it is used in conjunction with the mode-superposition method. Numerical examples are used to demonstrate the effectiveness of the proposed control algorithm. A strategy for coping with the spillover effect is also proposed. The results of the examples show that the proposed control algorithm can reduce the maximum structural response by one order of magnitude and has the ability to reduce the peak that occurs during the first few cycles of the time history, an ability that linear control laws lack. Unlike most control algorithms that deal with the state space of the system that usually involves complex-valued eigenvalues and eigenvectors, the proposed control algorithm deals with the real-valued normal modes of the system.