Incipient fault detection and diagnosis provide a firm grounding for machine health monitoring. Nevertheless, fault signatures at the time of an incipient fault are extremely weak and easily submerged by interference. Currently, signal processing based approaches and machine learning based approaches have been studied for incipient fault detection and diagnosis. However, the former requires relevant

We are experiencing a period of renewed interest in human activities in outer space and, in particular, the return of humans to the Moon. Multiple lunar missions, including the NASA led Artemis project and the China and Russia International Lunar Research Station propose a sustained human presence on the Moon which will require in-situ resource extraction and usage. This article explores the likely

An upgraded airframe/engine integrated design approach for a full-waverider vehicle considering thrust chamber design is proposed. Compared with the existing design approach of the full-waverider vehicle, the isolator, the combustor, and the nozzle are designed complementally. First, the airframe and inlet are generated using the full-waverider theory, the isolator with the centroid offset variable

The morphing wing aircraft, with good performances of flexibility and motility, has been paid more and more attention by researchers in recent years. During the unfolding process, the flow direction above the thin-walled plate structures embedded in the swept wing changes due to the relative movement of the plate with the outside airflow. The plate on the swept wing and the outside flow comprise a

A nonlinear analysis is presented for low-velocity impact behavior of a graphene platelets-reinforced metal foams (GPLRMF) cylindrical shell with spinning motion in thermal environment, in which the initial geometric imperfection is incorporated. Taking three different graphene platelets (GPLs) distribution patterns into account, the GPLs reinforcement is either uniformly-distributed or functionally-graded

In the current pretension design of mesh reflector antennas based on the equilibrium matrix method (EMM), the truss and hinge deformation cannot be accurately captured, which will deteriorate the shape accuracy of the antenna. To solve this problem, this paper proposes a new EMM-based pretension design method. In this method, the rod of the truss is modeled as Euler-Bernoulli beam, and the joint of

Vibration isolators with quasi-zero stiffness (QZS) property is an ideal solution for suppressing undesirable vibrations in engineering systems. Previous QZS isolators were mainly designed based on single-degree-of-freedom QZS structures without the capability for multi-directional vibration isolation. In this work, a Kresling-origami-inspired isolator (KOI) with QZS property in axial, torsional and

Journal of Guidance, Control, and Dynamics, Ahead of Print.

As the weakest point of the pipeline, the weld seam is prone to various internal defects and has great safety risks, so it is necessary to conduct a weld seam inspection. In addition, accurately detecting small-sized defects from high-resolution and low-contrast X-ray images is still a challenging task. Therefore, this paper proposes a defect detection method for high-resolution weld images, including

Carbon fiber reinforced polymers (CFRPs) with large thickness (≥20 mm) are being extensively used for aerospace structures, and are prone to the manufacturing and in-service defects due to the complexity and difficulty of manufacturing. This study addresses an intensive interrogation of multi-parameter optimization towards a high-quality ultrasonic total focusing method (TFM) imaging for diverse and

All objects are subject to deformations of their shapes that correspond to their natural vibration modes. The analysis of these modes is extremely useful for structural design and structural health monitoring. Traditionally, expensive measurement equipment and many vibration sensors have been required to analyze vibration modes. Recently, a method that measures displacement from images (digital image

Operational modal analysis (OMA) of long-span road bridges from vibration measurements is a topic of interest due to its potential applications within structural health monitoring. Algorithms for the automation of OMA (AOMA) have been proposed since around 2005, relying on machine learning to automate previously manual tasks. The fundamental principles of AOMA are explained in the theory of this work

We assessed the integrated safety, health, and performance risk to crews on long-duration missions, specifically to Mars. Using a systems approach rather than one focused on individual countermeasures, we examined the trade space around several such risks to identify high-potential risk mitigation strategies and characterize aspects of Mars mission architectures that could lower aggregated risk. Current

Hollow cathodes are widely used in electric thrusters due to their high emission electron density and low maintained voltage. The hollow cathode performance may significantly change under different keeper working conditions. In this study, a series of ground experiments were carried out to study the effects of the keeper current and the distance between keeper and cathode top on the emission characteristics

The flow characteristics of injectors with oscillations play a significant role in the mechanism of combustion instability. And combustion instability reduces engine reliability. Therefore, an efficient VOF-to-DPM model-based method is proposed to evaluate the effect of inlet mass flow rate oscillation on the injectors in liquid rocket engines. In this method, the VOF-to-DPM model, which can portray

The problem of relative drift elimination between the satellites in the swarm is considered in the paper. The proposed decentralized control takes into account a communication constraint such as limited size of communication area. Only the satellites within the communication area can be identified by relative motion determination system. The control aim is to eliminate the mean relative drift between

It is known that boundary layer transition and turbulent separation flow after transition can be influenced significantly by surface roughness. Since the traditional hybrid RANS/LES method cannot predict the boundary layer transition, and the RANS-based transition model cannot accurately simulate the massively separated flow, the present study sought to build an effective modeling strategy for the

In a propulsion system of cryogenic liquid rockets, low frequency pressure oscillation is an important topic on the oxygen jet condensation. It is a challenge to capture the numerical characteristic of pressure oscillation precisely, especially the frequency and amplitude. Aiming at the mechanism and excitation process of pressure oscillation, an oxygen jet condensation simulation is conducted by a

The inverse method of characteristics (iMoC) is often employed to simulate the axisymmetric flow behind a predefined shock wave shape. Firstly, two marching schemes of iMoC were compared in this work: the intersection of the left- and right-running Mach lines and the intersection of the left-running Mach line and streamline. The intersection of the left-running Mach line and streamline is discovered

The inlet distortion problem exists in a boundary layer ingesting propulsion system, and the distortion position is almost stable, which seriously affects the fan performance and stability margin (SM). To effectively improve the distortion resistance of the fan, three non-axisymmetric stator (NAS) schemes are designed according to the parameter distribution law of the distorted flow field in front

The panel vibration of air intake system that excitated by fluid-structural interaction, engine thrust variation and noise has decisive influences on the performance of an air-breathing hypersonic vehicle. The design of such type of intake system should contain the determination of configurational parameters and physical dimensions by considering both flow and structural vibrations, and a clear design

Journal of Guidance, Control, and Dynamics, Ahead of Print.

High-order wheel polygonal wear is a significant concern on China’s high-speed trains; thus far, no satisfactory solution to prevent polygonal wear has been provided. In this study, a simplified vehicle-track coupling dynamic model was established, and the frequency response functions (FRF) of the wheel-rail force were obtained under multiple wheelsets conditions. After integrating a wheel-rail wear

In this paper, a new procedure is developed to decouple the governing equations of non-classically damped structures with frequency dependent properties. To start, a modal state formulation is used to eliminate the off-diagonal elements that damping might otherwise create in the transfer matrix. From there on, the transfer matrix is expanded in series and decoupling is achieved through an iterative

This paper presents a technique based on Wiener path integrals (WPI) for computing the survival probability of nonlinear oscillators under combined nonstationary stochastic and periodic excitation. Specifically, the equation of motion is equivalently decomposed into a correlated combination of a nonlinear stochastic differential equation (SDE) and a nonlinear deterministic differential equation. The

In this study, the effect of a velocity-pulsating stoichiometric hydrogen-oxygen mixture entering an expanding combustion chamber on the detonation wave is investigated. The hybrid sixth-order weighted essentially non-oscillatory centered difference scheme was used to solve the Navier–Stokes equations with a one-step two species chemistry model. The results verify that the induction zone is extended

Autonomy is an increasingly essential component of future space missions, and new technologies are necessary to accommodate off-nominal occurrences onboard that may pose risks to mission success. Identifying a suitable maneuver plan for onboard, low-thrust mission applications in cislunar space remains challenging, particularly in the case of unanticipated events. This investigation addresses this

The purpose of this paper is to study the development of space-age aesthetics culture and arts in seven decades since 1950s. The first known use of “space-age” was in 1946, and was defined as “of, relating to, or befitting the age of space exploration.” A more popular definition for the “space age” is “The space age is the time period in human history related to the space race, space exploration, and

The NewSpace approach of utilizing CubeSats and smaller satellites for complex LEO missions that once were reserved only for bigger platform, paired with the requirement of enduring reliability and quality assurance on batches of tens of satellites, is paving the way for the use of commercial-off-the-shelf (COTS) components in micro-satellite missions. The recent global supply chain issues and extended

The phenomenon of mean-motion resonance overlapping, which generates heteroclinic connections between unstable resonant orbits, is known to be crucial for the generation of large-scale chaos and global instability in celestial systems. This instability in turn can be profitably leveraged for the purposes of low-energy space mission trajectory design. In most prior work leveraging such phenomena, though

High order numerical simulations of underexpanded supersonic cold jets issuing from a circular sonic nozzle are conducted to investigate the effective source location of axisymmetric mode screech tones. The frequency and sound pressure level of screech tone agree well with the experimental results in literature. The detailed generation processes of axisymmetric screech modes in a complete cycle are

For acoustic source localisation in a fluid, sound pressure is traditionally measured using a microphone array, and acoustic beamforming is then applied to the pressure signals to localise the source. However, in some engineering applications, it is not feasible to place the microphone/hydrophone array in the fluid to localise an acoustic source. Hence, this work proposes a vibroacoustic beamforming

Any measurement in condition monitoring applications is associated with disturbing noise. Till now, most of the diagnostic procedures have assumed the Gaussian distribution for the noise. This paper shares a novel perspective to the problem of local damage detection. The acquired vector of observations is considered as an additive mixture of signal of interest (SOI) and noise with strongly non-Gaussian

Aerodynamic collision avoidance manoeuvres provide an opportunity for satellites in Low Earth Orbits to reduce the risk during close encounters. With rising numbers of satellites and objects in orbit, satellites experience close encounters more frequently. Especially those satellites without thrusting capabilities face the problem of not being able to perform impulsive evasive manoeuvres. For satellites

Effective liquid fuel atomization is an ultimate aim for the prefilming airblast atomizer in aero-engines, and the liquid fuel breakup behavior is the key indicator of atomization quality. Whereas, the prefilmer lip structure is unnoticed but of great influence on this breakup process. In this paper, the rectangular block structured prefilmer lip and the triangular prism structured prefilmer lip are

Accurately and rapidly predicting the multi-conditions characteristics of turbines is fundamental for realizing efficient energy conversion and optimal layout schemes. Based on supervised graph learning approaches, this work is dedicated to establishing a fast multidisciplinary prediction model for gas turbines. The research target is a gas turbine blade with complex cooling channels. An Aerodynamic

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Full-field imaging of guided ultrasonic waves is an emerging Nondestructive Testing (NDT) technique for the inspection of thin-walled structures. One of the most effective full-field processing techniques is the Local Wavenumber Estimation (LWE) which can be applied to detect various types of damage in both homogeneous and multilayer specimens. In this paper, we discuss the possibilities for optimizing

In this paper, different compressible correction strategies for k-ω turbulence model are proposed. The dilatation dissipation term, which is significant in compressible flow, is taken into account and modeled in the Favre-averaged k-equation and ω-equation. We propose correction model for the dilation dissipation term based on the gradient Mach number in this paper, the coefficients of which are calibrated

Abstract not available

The consistent probability distribution between training & testing data is one of the prerequisites for valid intelligent diagnosis models. Nevertheless, the ineluctable distribution discrepancies produced by variable working conditions cause intense conflicts with the above. Besides, many existing models fail to explicitly characterize the correlation between data, which makes them difficult to mine

Efficient energy harvesting from low and broadband frequency has always been a challenging problem. This paper proposes a solution in the form of an electromagnetic bi-stable vibration energy harvester (BVEH) with asymmetric potential barriers, in which the vibrator is attracted to the top magnet and repelled from the bottom magnet. By combining a magnetic spring and a mechanical spring, the BVEH achieves

When using Lamb wave for damage detection in plate-like structures, factors such as unknown material properties, anisotropy and iterative operation for solving nonlinear equations make it difficult to accurately localize damages. This problem becomes even more difficult when multiple damages exist in the plate. To overcome these difficulties, a rapid technique for localizing multiple damages in plate-like

Novel aerospace technology research has been driven by increased interest in governmental and privatized space travel efforts. One such technology is friction stir welding (FSW), often promoted as a capable in-space manufacturing process. FSW literature currently has gaps regarding its operation in lunar conditions. As an initial approximation, this study simulated lunar cooling heat fluxes via a controlled

To prevent the degradation of control performance resulting from the use of the clipped approach, this paper presents a novel control strategy for CDC (continuous damping control) semi-active suspensions using the Takagi-Sugeno (T-S) fuzzy method based on a piecewise affine (PWA) vertical dynamics model. First, to account for the significant tension-compression asymmetry and dissipative constraint

This study first summarized a piezoelectric excitation source arrangement guideline for sandwich annular traveling wave transducers, which can excite ideal traveling waves for driving while ensuring consistent circumferential stiffness of the annular transducer. Consequently, a general structural design method was proposed for annular sandwich traveling wave piezoelectric transducers operating with

Vibrations and drifting motions of a post-capture spacecraft may lead to its instability and safety risk, which therefore need to be absorbed or isolated. However, it is expected that the vibrational energy is not wasted but harvested to power the wireless sensors. Motivated by this concept and inspired by the movement of a bird, a quadrilateral shape isolation system with an energy harvester is proposed

The studies of earth observation satellite (EOS) scheduling for stationary targets have been increasing rapidly in recent years. However, these studies ignore EOS scheduling for moving targets (EOSSMT), which is urgently needed in many situations. EOSSMT is more complicated due to two factors, 1) location prediction of the moving targets and 2) algorithm design of EOSSMT optimization model for highly-nonlinear

The windmilling imbalance condition occurs after engine shut-down due to fan blade loss, but the engine continues to rotate under aerodynamic forces. This condition can induce undesirable structural excitation throughout the engine and airframe. Especially in the progression of larger high-bypass-ratio fans with fewer blades with larger chords, the excitation is considerably greater and is directly

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Journal of Guidance, Control, and Dynamics, Ahead of Print.

Journal of Guidance, Control, and Dynamics, Ahead of Print.

In order to design a drag-based predictor-corrector entry guidance in the future, new analytical formulae, expressed as finite-term Chebyshev series, are developed for fast predicting a three-dimensional (3D) Hypersonic Gliding Trajectory (HGT) by proposing a Newton-like method to solve a highly nonlinear entry dynamics model. Specifically, first, a new reduced-order dynamics model is developed by

Abstract not available

Condition-based monitoring for critical assets is reliant on the quality of the indicators used for condition inference. These indicators must be sensitive to the development of faults under constant and non-stationary operating conditions. Latent variable models in the time-preserving framework offer a powerful learning-based technique for the monitoring of critical assets as they only require healthy