Dynamically isotropic 3-DoF active absorber mechanism with dissipation nonlinearities compensation and delayed feedback

Abstract

For the purpose of vibration absorption of light robotic structures, an active 3-DoF planar vibration absorber is proposed, analyzed and experimentally validated. To achieve a complete suppression of the vibration mode of a primary structure in more directions, a multibody system of the attached absorber must be dynamically isotropic, i.e. all its eigenfrequencies need be unified. Designing a physical 3-DoF vibration absorber with such properties is then determined by several kinematic and dynamic constraints. Besides, its complexity leads to the presence of kinematic joints with nonlinear passive resistance, which has a deteriorating effect on the active absorber performance. To compensate these nonlinearities and achieving dynamic isotropy, a symmetric planar active vibration absorber is designed and optimized with three supporting legs actuated by voice-coils. The two-level active control of each of the legs compensates the nonlinearities, mainly the Coulomb friction, and, subsequently, adjusts their properties by a Delayed Resonator feedback to gain the dynamically isotropic feature of the absorber. The actively enhanced absorber is structurally optimized, mechanically designed and assembled. Attention is paid to the mechatronic design of the legs including their seating to fine bearings. Finally, unique results of experimental validation are presented demonstrating an efficient multidirectional vibration absorption by the proposed and built dynamically isotropic vibration absorber demonstrator.