Fuzzy Active Control of Flexible Structures by Using Electromagnetic Actuators

Abstract

Numerical and experimental investigations are carried out to assess the possibility of controlling a flexible beam by using an electromagnetic actuator (EMA). The advantage of EMAs is that they do not require contact with the structure so they can be applied to light and small mechanisms. Nevertheless, their open-loop instability and nonlinear dynamic behavior relating to excitation frequency can limit their fields of application. The EMA is designed and dimensioned as a function of the structure to be controlled. The effect of the EMA is considered a restoring force; consequently, the structure is still linear, which enables the calculation of the modal matrices of the structure. Moreover, an inverse model of the EMA is proposed to implement a linear action block for the frequency range used. The gap distance is estimated by using a modal approximation of the displacements resulting from the measurements. The control strategy is a fuzzy controller with displacements and velocities as inputs. Fuzzy controllers are used for their effectiveness in the presence of nonlinearities and uncertainties. The system is modeled and the characteristics of the model are identified experimentally. Several control configurations are assessed by using numerical simulations, and then the controller is tested experimentally in the context of impact perturbations. The results show the effectiveness and robustness of the developed control.