New Algorithm for Active Structural Control

Abstract

A simple effective algorithm for active structural control is proposed. It applies the control force at every time step, minimizing the system energy that is carried over from one time step to the next. The control force needed for the next time step is computed by a simple closed form solution at the current time utilizing the available information. Therefore, the proposed control algorithm is free from time delay problems. The control algorithm is derived from the theory of single-degree-of-freedom (SDF) systems and is extended to multiple-degree-of-freedom (MDF) systems by making use of the modal synthesis. Numerical examples are used to demonstrate the effectiveness of the proposed control law. Practical problems in active control, such as the spillover effect, the actuator's capacity limit, and the problems associated with the limited number of sensors are discussed. Various strategies to cope with these problems, in particular, an artificial neural network as the state estimator, are proposed in the paper. The results of the examples show that the proposed control algorithm can reduce the 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.