This article presents a utilization of viscoelastic damping to reduce control system complexity for strain-actuated solar
array (SASA) based spacecraft attitude control systems (ACSs). SASA utilizes intelligent structures for attitude control,
and is a promising next-generation spacecraft ACS technology with the potential to achieve unprecedented levels of
pointing accuracy and jitter reduction during key scientific observation periods. The current state-of-the-art SASA
implementation utilizes piecewise modeling of distributed piezoelectric (PZT) actuators, resulting in a monolithic
structure with the potential for enhanced ACS reliability. PZT actuators can operate at high frequencies, which enables
active vibration damping to achieve ultra-quiet operation for sensitive instruments. Relying on active damping alone,
however, requires significant control system complexity, which has so far limited adoption of intelligent structures in
spacecraft control systems. Here we seek to understand how to modify passive system design in strategic ways to reduce
control system complexity while maintaining high performance. An integrated physical and control system design (codesign) optimization strategy is employed to ensure system-optimal performance, and to help understand design coupling
between passive physical aspects of design and active control system design. In this study, we present the possibility of
utilizing viscoelastic material distributed throughout the SASA substructure to provide tailored passive damping,
intending to reduce control system complexity. At this early phase of study, the effect of temperature variation on material
behavior is not considered; the study focuses instead on the design coupling between distributed material and control
systems. The spatially-distributed design of both elastic and viscoelastic material in the SASA substructure is considered
in an integrated manner. An approximate model is used that balances predictive accuracy and computational efficiency.
This model approximates the distributed compliant SASA structure using a series of rigid links connected by generalized
torsional springs and dampers. This multi-link pseudo-rigid-body dynamic model (PRBDM) with lumped viscoelastic
damping models is derived, and is used in numerical co-design studies to quantify the tradeoffs and benefits of using
distributed passive damping to reduce the complexity of SASA control systems.
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A Plate-Like Sensor for the Identification of Sample Viscoelastic Properties Using Contact Resonance Atomic Force Microscopy
Abstract In this article, we present a new contact resonance atomic force microscopy-based method utilizing a square, plate-like microsensor to accurately estimate viscoelastic sample properties. A theoretical derivation, based on Rayleigh–Ritz method and on an “unconventional” generalized eigenvalue problem, is presented and a numerical experiment is devised to verify the method. We present an updated sensitivity criterion that allows users, given a set of measured in-contact eigenfrequencies and modal damping ratios, to select the best eigenfrequency for accurate data estimation. The verification results are then presented and discussed. Results show that the proposed method performs extremely well in the identification of viscoelastic properties over broad ranges of nondimensional sample stiffness and damping values.
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- PAR ID:
- 10211411
- Date Published:
- Journal Name:
- ASME Letters in Dynamic Systems and Control
- Volume:
- 1
- Issue:
- 3
- ISSN:
- 2689-6117
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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SUMMARY Full-waveform inversion (FWI) methods rely on accurate numerical simulation of wave propagation in the analysed medium. Acoustic or elastic wave equations are often used to model seismic wave propagation. These types of simulations do not account for intrinsic attenuation effects due to material anelasticity, and thus correction techniques have been utilized in practice to partially compensate the anelasticity. These techniques often only consider the waveform amplitude correction based on averaging of overall amplitude response over the entire data set, and ignore the phase correction. Viscoelastic wave equations account for the anelastic response in both waveform amplitude and phase, and are therefore a more suitable alternative. In this study, we present a novel 3-D Gauss–Newton viscoelastic FWI (3-D GN-VFWI) method. To address the main challenge of the Gauss–Newton optimization, we develop formulas to compute the Jacobian efficiently by the convolution of virtual sources and backward wavefields. The virtual sources are obtained by directly differentiating the viscoelastic wave equations with respect to model parameters. In order to resolve complex 3-D structures with reasonable computational effort, a homogeneous attenuation (Q factor) is used throughout the analysis to model the anelastic effects. Synthetic and field experiments are performed to demonstrate the utility of the method. The synthetic results clearly demonstrate the ability of the method in characterizing a challenging velocity profile, including voids and reverse velocity layers. The field experimental results show that method successfully characterizes the complex substructure with two voids and undulating limestone bedrock, which are confirmed by invasive tests. Compared to 3-D elastic FWI results, the presented viscoelastic method produces more accurate results regarding depths of the voids and bedrock. This study suggests that the improvement of imaging accuracy would warrant the widespread use of viscoelastic wave equations in FWI problems. To our best knowledge, this is the first reported study on 3-D GN-VFWI at any scale. This study provides the new theory and formulation for the use of Gauss–Newton optimization on the 3-D viscoelastic problem.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1115/1.4049538
