Identification of real translational and rotational displacements of six-axial shakers with only six measured linear accelerations

Abstract

Qualification tests on the vibrations of on-board equipment depend on the ability of the shaker used to reproduce as precisely as possible the excitation profiles stipulated by standards, given that real operational conditions are generally multiaxial. Using a set of six measured linear accelerations the original method proposed permits determining real six-axial shaker displacements combining three translations and three rotations. Thus, this method, named REDEAT (REal Displacement from Experimental Acceleration with inverse Technique), is useful for introducing these real displacements in the numerical simulation in view of experimentally validating the dynamic behavior model of on-board equipment. Moreover, the REDEAT method evaluates the deviation between real and intended forced displacements. Its principle resides in solving a system of nonlinear time-differential equations expressed, by resorting to numerical integration combining Newmark and Newton–Raphson schemes. In order to overcome the classical divergence issue inherent to the use of numerical integration, data processing tools are employed, consisting of the application of successive high pass filters and window functions. The REDEAT method is applied to a hydraulic 6-DOF shaker equipped with accelerometers and gyroscopes, through a combination of two harmonic rotations and a full 6-DOF random motion. In addition, the influence of the method’s parameters and of the six input accelerograms chosen from twelve is investigated.