Optimization of Actuator Placement

A consistent limitation of existing approaches to optimize the placement of actuators in flexible smart structures to control vibrations is that they require the derivation of a closed-form fitness function for optimization, thus reducing and limiting the complexity of problems that can be solved. In contrast, Professor Afagh and his coworkers have proposed an optimization approach that benefits from simplicity of the fitness function and the applicability of the technique to any configuration of actuators in a structure with any degree of topological complexity.

In this approach a finite element model of the structure is used to develop the fitness function from the frequency response function (FRF) for the first few selected vibration modes. The fitness function is based on the maximization of actuation authorities (represented by the generated accelerations or displacements) over these modes, either independently (for individual modal control), or over a combination of actuation authorities (for multi-modal control). This allows the actuation authority and efficiency of an actuator that is placed anywhere within a judiciously selected area of the structure to be determined. A genetic algorithm is then used to optimize the configuration of a selected number of actuators on the structure. In this way, the data acquisition is decoupled from the optimization process, eliminating the need for derivation of a closed-form solution. This is the main advantage of the proposed method in comparison to previous approaches. It can, therefore, be employed for complex topologies where closed-form analytical solutions cannot be obtained, or where derivation of such a solution would be prohibitively difficult.

Smart fin test bed

FEM model of the fin in experimental  configuration

1st (bending), 2nd (torsional) and 3rd(bending) modes of the fin