Abstract
A major factor that limits the performance of dynamic-positioning machines, such as PKM's, is their propensity to vibrations, which will impose limitations on size of the working space, settling time and/or positioning accuracy. The objective of this research is to develop an Active 3DOF Stiffness Element (A3DSE) that can be installed at appropriate locations of a machine, which could dynamically compensate for the vibrations of the mechanical structure, by actuating in three degrees of freedom: one axial and two bending. The design idea is based on the incorporation of three piezoelectric displacement actuators, each equipped with a collocated, piezoelectric force sensor, in an axisymmetrical configuration within a mechanical holding structure, using suitable mechanical and electronic interfaces. Firstly, the mechanical design requirements and the design procedure for each of its components are discussed. Secondly, a dynamic identification and modeling of the A3DSE element is presented. Finally, the effectiveness of this element for active control is experimentally illustrated.