Optimal placement of actuators in actively controlled structures

The paper deals with the influence of actuator/sensor locations and feedback gains on the optimum design of actively controlled structures. Two related problems are addressed. The first is a parametric study dealing with the effect of number and location of actuators on the minimum weight structural design, while satisfying constraints on the closed loop eigenvalues and damping ratios. The second problem addresses the optimal placement of actuators with the damping augmentation provided by the control action being used as the performance criterion. A solution methodology which allows for an integrated determination of feedback gains and actuator/sensor locations while maximizing the energy dissipated by the controller is presented. Since the actuator locations are spatially discrete whereas the feedback gains are continuous, the resulting optimization problem has mixed discrete-continuous design variables. This problem is solved using a hybrid optimization method which is a synergistic blend of artificial genetic search and gradient-based search techniques. The effectiveness of the proposed approach is illustrated via an application to an ACOSS-FOUR structure. The optimum results obtained using the hybrid optimization method are shown to outperform the optimum results obtained using gradient-based optimization techniques by factors ranging from 2.5 to 7.2.