How much do model errors influence the closed loop performance? This question is investigated for the control problem of designing active damping of vibrations in a viscoelastic cantilever beam. The beam is physically modeled using Fourier transformed Euler-Bernoulli beam equations. For control design the standard LQG technique is employed, and two different finite order models are used. One is...

The experimental evaluation of damping performance in a granular-material-filled box beam is presented. The study determined that granular-fill provided significant damping for a high impact excited free-free box beam. A large modal loss factor, exceeding 0.15, was obtained for the few lowest bending modes of the beam. The damping was effective over the frequency range 40 300 Hz. A variety of d...

In this paper, the detection and the localization of a local perturbation are assessed by analysing the frequency changes only (fundamental mode and overtones). After describing the method used herein applied to the bending beam and based on the perturbation theory, experimental application to a 1D plexiglas beam is shown using frequency and modal analysis technique. The damage is considered as...

In this paper we consider the Gaussian beam mode analysis of imaging arrays on submillimetre-wave radio telescopes. We show how it is possible to describe any of the off-axis beams generated by the array in terms of the same on-axis beam mode set. The mapping process can be easily analysed using a modal approach.

Initial commissioning results from the PEP-II transverse coupled-bunch feedback systems are discussed. In particular, the performance of key hardware and coupled-bunch damping results are described in some detail. Beam dynamics related measurements presented include beam transfer functions and selected modal growth and damping rates.

In this study, an improved GA-based damage detection algorithm using a set of combined modal features that include natural frequency, mode shape, and modal strain energy is proposed. In order to achieve the objective, the following approaches are implemented. Firstly, a new GA-based damage detection algorithm is formulated for beam-type structures. A schematic of the GA-based damage detection a...

The average polarization properties of conal single and double profiles directly reflect the polarization-modal structure of the emission beams which produce them. Conal component pairs exhibit large fractional linear polarization on their inside edges and virtually complete depolarization on their outside edges; whereas profiles resulting from sightline encounters with the outer conal edge are...

Measurement of dynamic responses plays an important role in structural health monitoring, damage detection and other fields of research. However, in aerospace engineering, the physical sensors are limited in the operational conditions of spacecraft, due to the severe environment in outer space. This paper proposes a virtual sensor model with partial vibration measurements using a convolutional ...

We have developed an alternative FRD empirical model for the parallel laser beam technique which can accommodate contributions from both scattering and modal diffusion. It is consistent with scattering inducing a Lorentzian contribution and modal diffusion inducing a Gaussian contribution. The convolution of these two functions produces a Voigt function which is shown to better simulate the obs...