engleski

Nonreciprocal vibration transmission by the use of concurrent non-collocated feedback control loops

The challenge of inducing stable and robust non-reciprocal transmission of sound is seen as an important milestone down the pathway towards developing active acoustic metamaterials. Structures that can transmit sound or vibration in a non-reciprocal manner may be considered as an analogue of an electrical diode and could be useful in many applications. This paper focuses on conceptual development and experimental validation of an active metamaterial cell that does not obey the reciprocity principle. The structural cell considered, when activated, significantly attenuates vibration transmission through it in one direction and increases it in the opposite direction. The effect is present in a broad frequency band. The loss of reciprocity is induced by using two concurrent velocity feedback loops with non-collocated sensor-actuator pairs. Inertial accelerometers with time-integrated outputs are used in conjunction with miniature electrodynamic force actuators. The study is first carried out theoretically using an electromechanically fully coupled lumped parameter model of an otherwise flexible active structure. The derived model is used to conduct analysis of the control system stability and performance. Given that the non-collocated transducer arrangement is considered, special attention is paid to selection of parameters of the passive system which ensure satisfactory gain margins when the system is made active. In fact, criteria for unconditional stability are derived analytically, in terms of two simple inequalities for the system with idealised sensor-actuator pairs. For realistic transducers, however, the unconditional stability is not possible. Nevertheless, if the two inequalities are respected, useful gain margins of the active system can be expected. This is verified experimentally using a dedicated 3D-printed experimental setup. A substantial reduction of vibration transmission in the desired direction, accompanied by an increase in the opposite one is recorded experimentally.

active vibration control ; dynamic reciprocity ; active metamaterials ; stability of active control systems ; performance of active control systems

nije evidentirano