This paper proposes a model-based observer for state estimation in nonlinear hysteretic structural systems. The observer combines a nonlinear model and response measurements to estimate the complete dynamic response of the structure of interest. The feedback gain of the observer is computed by an iterative algorithm that accounts for the nonlinearity of the system and minimizes the trace of the state

An academic model for passive vibration control of human arm suffering from essential tremors is proposed. The nonlinear uncontrolled system equations are linearised around arbitrary postural positions showing variations of linear natural frequencies as functions of postural positions. The coupled system, i.e. the model of the arm with the attached nonlinear absorber, is treated via a time multiple

This paper focuses on the experimental verification of a dynamical model describing percussive drilling. The design of the experimental apparatus is introduced firstly, and then the dynamic interactions between rock and indenter are studied experimentally by varying three control parameters, including frequency and amplitude of excitation, and pneumatic pressure applied on the indenter. Additionally

In recent years, many moving force identification (MFI) methods have been proposed to monitor moving forces indirectly from structural responses. However, the prior knowledge about moving forces has not been reasonably considered in the existing methods, so the identified moving forces are not accurate enough. To improve the accuracy of MFI results, a novel MFI method is proposed based on a semi-convex

In a structural health monitoring (SHM) system that uses digital cameras to monitor cracks of structural surfaces, techniques for reliable and effective data compression are essential to ensure a stable and energy-efficient crack images transmission in wireless devices, e.g., drones and robots with high definition cameras installed. Compressive sensing (CS) is a signal processing technique that allows

Limited condition monitoring data are recorded with label information in practice, which make the fault identification task more challenging. A semi-supervised learning (SSL) approach can be employed to increase the identification performance of the classifiers under such situation. In this study, a three-stage SSL approach using data augmentation (DA) and metric learning is proposed for an intelligent

Cable-supported structure is a common system widely used in engineering, with the rapid development of the infrastructure and transportation industry, its structural form has become more and more complicated. Multi-segment cable system, which consists of a suspension cable and several lateral supports, such as the cable-damper system, the main cable of a suspension bridge, etc., is one of the important

The double-beam system with several elastic supports is one of most significant mechanical models in engineering structures. Its dynamic characteristics are crucial for structural design, vibration control, health monitoring, and other dynamic issues. In the dynamic analysis of double-beam systems, since existing researches often need to make some assumptions or approximations to the displacement function

A non-resonant stepping type piezoelectric actuator with bolt-clamped configuration was developed and tested in this work. This actuator was operated under clamping and driving mechanism by using two longitudinal-bending transducers. The longitudinal and bending deformations of the transducer were used to clamp and drive the slider, respectively. Such principle is totally different from the existing

Performing non-destructive testing on metallic components with very complex geometries, such as turbine blades, is very challenging. To inspect such components, powerful and robust non-destructive inspection protocols must be defined. Process Compensated Resonance Testing (PCRT) is a relatively novel approach that records a broadband vibrational fingerprint for each component and employs vibrational

In this paper, a two-dimensional (2D) time domain spectral element method (SEM) is developed for concrete-filled steel tube (CFST) and piezoelectric lead zirconate titanate (PZT) patches coupling system, where the piezoelectric and inverse piezoelectric effect of PZT actuator and sensor and their coupling effect with CFST are considered. The local wave field and the response of the embedded PZT sensor

This article presents a method for evaluating the torque output of orbit type displacement machines. Orbit machines are commonly used as hydraulic motors, for applications involving low speed and high torque output. The evaluation of the actual shaft torque as well as the hydro-mechanical efficiency in positive displacement machines is a topic that still presents challenges related to the evaluation

In this paper, a disbond detection method for aeronautical honeycomb sandwich composites using Lamb waves is proposed. Due to the scale mismatching between the wavelength and the panel thickness, the honeycomb core cannot be homogenized to a single layer medium in wave propagating model with short wavelength. Waves can leak through the honeycomb core and be reflected back and forth between the top

Gear transmission error (TE) has become a promising diagnostic tool due to the fact that, compared with vibration responses, it is much less affected by the transfer path from the source to the measurement, and it can be measured conveniently using shaft encoders installed on the input and output of a gear stage. It is also the direct cause of vibration and noise in gears, and it is directly linked

We extend a recently developed class of uniaxial symmetric rate-independent models to simulate complex asymmetric mechanical hysteresis phenomena. The main features of the novel formulation, that allows for the evaluation of the generalized force by solving a scalar equation and employing only one history variable, are illustrated by developing two specific instances of the class, namely the Asymmetric

A technique to reconstruct the displacement field throughout the structure from pointwise measurements under different noise sources is proposed. The developed estimator is a Proportional Observer (PO) that exploits a linear, frequency independent, relation between the estimated state-space vector and the measurements. To improve its accuracy, the PO concept is then extended to the definition of a

The second order Cyclostationarity Analysis (CA) is gaining attention for detection and classification of marine vehicles driven by propellers in broadband passive sonar systems, in which the Detection of Envelope Modulation On Noise (DEMON) is a standard tool for the same purpose. In this paper both CA and DEMON are discussed in the form of discrete digital formulae. It is shown that the three cyclo-spectra

Plastic/viscoelastic pipes, such as polyvinyl chloride (PVC), polyethylene (PE) and high-density polyethylene (HDPE), have been increasingly used in water piping systems, which has stimulated the study of viscoelastic hydrodynamics in these pipe systems. An in-depth understanding of the pipe-wall viscoelasticity features is beneficial and necessary to the effective application and management of plastic

Hydraulic shock absorbers are the exclusive components to attenuate the transmitted vibration to the chassis and also to improve the ride quality accordingly. Simultaneously, the shock absorbers contribute to the enhancement of the handling dynamics during cornering maneuvers through constrained roll mode of motion. Energy recovery using shock absorbers is essential for energy management/energy efficiency

An approach based on the time-domain equivalent source method (TESM) is developed for the indoor prediction of the pass-by noise of a vehicle in a small-scale semi-anechoic chamber. In the approach, a vehicle drives on a chassis dynamometer, and a number of microphones are distributed around the vehicle to measure the pressure radiated by the vehicle in the near field. Based on the idea of TESM, the

This paper investigates a technique for broadband vibration suppression using a graded metamaterial beam. A series of local resonators with the same mass but different natural frequencies are attached to the beam. The difference between the natural frequencies of neighboring local resonators is defined as the frequency spacing. The spectral element method (SEM) is used to model the graded metamaterial

Rotary electromagnetic generators that have high power density, large power output, and large rotational inertia are increasingly used in vibration energy-harvesting systems. When applied to single-degree-of-freedom (SDOF) systems, it is found that the inertance reduces the system frequency bandwidth. Furthermore, the maximum power output of SDOF systems is limited by the mechanical damping and the

In engineering, plate structures are one type of the main load-bearing structures. However, most of the designed plate-like metamaterials/metasurfaces need to be heavily grooved or drilled on the original plate surface, which will inevitably cause some destruction to the strength and stiffness of the host plate structures. To overcome this weakness, we propose a new conceptual design of pillared elastic

In electro-hydraulic system (EHS), there exist typical lumped uncertainties due to the uncertain hydraulic parameters and unknown external load, which usually decline the output dynamic performance. To address this problem, this paper proposes a neural adaptive control for single-rod EHS to improve the dynamic tracking performance of the cylinder position under these lumped uncertainties. A Radial-Basis-Function

This paper addresses the methodology of the bridge-vehicle dynamic model definition based on the free response measurements of an existing train and existing bridge spans. In the case of the railway vehicle, the methodology uses the impulse excitations of a single car by means of the wedge method. In the case of the bridge spans, free responses are collected after the passages of trains. The global

Small helicopters attract substantial attention because they feature better loading capacity and flight efficiency than multirotor helicopters. The main objective of this work is to study the modeling and flight controller design of a small helicopter. Based on a non-simplified helicopter model, a robust control law combined with a newly developed trajectory tracking controller is proposed. The inner

A physically-based thermal error model of the servo axis was established, aiming at the time-varying nonlinear thermal error of the screw. However, the thermal characteristic parameters of the model may differ from the working state of the machine tool. In order to analyze the influence of the variation of the thermal characteristic parameters on the prediction results of the model, and considering

Development of a method for distributed detection of microcracks on structural elements with very small crack opening displacements is described in this study. Robust principal component analysis (RPCA) and support vector machine (SVM) techniques were employed for denoising and classification of the signals. The objective was to detect microcracks in structural elements less than 30 µm in size. The

Diagnosis and prognostics of rolling element bearings have been widely studied in recent years, but very few researches were dealing with high-speed train wheel set bearings (HSTWSB). Most prognostics and health management (PHM) models are generally based on obtaining the remaining useful life (RUL) of concerned bearings. Since it is difficult to quantify and to monitor bearing status from vibration

The real-time monitoring of railway vehicles is becoming a key factor for safety and the optimization of the maintenance costs. In this context, the secondary anti-yaw suspension system represents a key element, subjected to degradation phenomenon. This paper presents a model-based real time monitoring technique of the anti-yaw damping. The approach is based on a constrained nonlinear estimation procedure

The control performance of linear motor (LM) is deteriorated by payload variations, friction, and external disturbances. In this paper, a robust recursive sliding mode controller combined with an adaptive disturbance observer (RSM-ADO) is proposed for the high-speed and high-precision control of an LM positioner. The benefits of the proposed ADO lie in that it can be designed without the need for the

The modes of linear time invariant mechanical systems can be estimated from output-only vibration measurements under ambient excitation conditions with subspace-based system identification methods. In the presence of additional unmeasured periodic excitation, for example due to rotating machinery, the measurements can be described by a state-space model where the periodic input dynamics appear as a

Sliding cables are widespread in engineering applications. The friction between the cable and the sliding components results in the existence of diversified motion states of the contact points, which leads to many difficult problems for traditional analysis methods. This paper proposes an effective and robust nonlinear complementarity function based framework for static and dynamic analyses of sliding

Fault diagnosis is crucial for the printing quality assurance of a 3D printer. This paper presents a pre-classified reservoir computing (PCRC) method to diagnose the health condition of a 3D printer using the data collected by a low-cost attitude sensor. As the data from the low-cost attitude sensor often contain a large amount of interference information, it is difficult to accurately diagnose the

In the open literature, many authors have used the fractional calculus in conjunction with the finite element method to model certain viscoelastic systems. The so-named fractional derivative model may be a better option for transient analyses of systems containing viscoelastic materials due to its causal behavior and its capability to fit accurately the viscoelastic damping properties and to represent

A new sensitivity enhancement scheme, mainly comprised of a harmonic oscillator and a set of magnetic material, is proposed for desirable applications in cantilever-based resonant sensors. The basic idea is to magnetically apply a pre-stress on the harmonic oscillator to achieve a larger frequency offset. The applied axial pre-stress, which varies the equivalent stiffness of the harmonic oscillator

Pneumatic artificial muscle (PAM) actuators are a kind of biomimetic actuators, which are being widely used in the applications of biomimetic robots and medical auxiliary devices. However, PAM systems usually have high nonlinearities, uncertainties, and time-varying characteristics, which bring challenges for accurate dynamic modeling and controller design. To deal with the above issues, in this paper

This paper presents some new results relating to nonstationary signal analysis, particularly relating to the ADF test statistic. The first main result is a simple interpretation of the ADF statistic motivated by dimensional analysis. It is argued that the ADF statistic essentially counts the number of cycles of the dominant frequency component in a sample. The analysis also points to a critical frequency

The internal resonance of electrostatically coupled cubic nonlinear low-frequency micro-resonator and linear high-frequency micro-resonator is investigated experimentally. A phenomenon of frequency locking is observed at 1:3 frequency ratio of two resonators for the first time when the coupling strength exceeds a certain value. Then the theoretical study is made to explain the frequency locking phenomenon

During whole-body vibration (WBV), dynamic forces measured at the excitation-subject interface in directions other than the excitation axis, i.e. cross-axis response, are analysed using the principal component analysis (PCA) and virtual coherence techniques. The study applied these operations to the inline and cross-axis forces measured with twelve semi-supine human subjects exposed to longitudinal

In this paper, a novel two-stage observer strategy for improving the measurement of tool forces is presented. The mass-spring-damper system which inevitably occurs when a tool and a (compliant) force sensor are combined is studied and its adverse influence on the measurement signal is analyzed. The proposed observer consists of two stages. The first stage captures the input-output characteristics from

The methods of vibration fatigue stress simulation and strength evaluation under stationary state are quite complete, but the research on vibration fatigue under non-stationary state is insufficient. Based on the theory of structural dynamics and the principle of modal superposition method, the formula for calculating the dynamic stress of vibration fatigue under non-stationary state is deduced in

The cranes are usually controlled by a variety of actions including handling, lifting, carrying, then lowering and gripping the load. An intelligent control system could provide the operator with important advantages when performing all these operations. As the load cycle times are reduced, the operations are then performed more efficiently, and hence saving time, costs and increasing the overall productivity

Although the identification and analysis of structures with a localized nonlinearity, either weak or strong, is within reach, identification of multiple nonlinearities coexisting at different locations is still a challenge, especially if these nonlinearities are strong. In such cases, identifying each nonlinearity separately requires a tedious work or may not be possible at all in some cases. In this

The microvibration of the satellite moment wheel assembly (MWA) is an essential input for integrated simulation analysis of spacecraft microvibration, which forms the basis for spacecraft vibration suppression. Therefore, it is important to guarantee high-precision data from ground measurements of vibration sources for research into the stabilization accuracy of large space telescopes. In general,

Advances in energy harvesting techniques, along with low-power electronic devices open up the possibility of developing self-powered engineering systems. Most existing energy harvesters are constructed with beams such as cantilevers, fully-clamped beams and buckled beams. Here we present an attempt to add a new design dimension to the piezoelectric energy harvesters (PEHs) by exploiting a curved-beam

Structural health monitoring for plate structures is important since they are essential structural components in many applications. One interesting topic for structural health monitoring methods is to achieve accurate damage detection with a small number of sensors and without the requirement of a high-fidelity finite element model. Traditional damage detection techniques for plates need many sensors

Vibration and noise of gear meshing come from the dynamic working conditions, therefore, combining gear modification and dynamic characteristic analysis may offer reliable basis for the modification. Compared with profile modification and axial modification, 3-D modification is more comprehensive. The existing problems in current gear modification includes: (1) The ideal force under static or quasi-static

In this paper, broad-band phase-based motion magnification (BPMM) is used to improve the modal parameter estimation from high-speed video of a structure undergoing low amplitude vibration. The authors use a novel application of the phase-based motion magnification technique to obtain improved results in the presence of image noise. A numerical simulation is performed to demonstrate and quantify the

Prior to failure, most systems exhibit signs of changed characteristics. The early detection of this change is important to remaining useful life estimation. To have the ability to detect the inflection point or “elbow point” of an asset, i.e. the point of the degradation curve that marks the transition from nominal to faulty condition, can enable more sophisticated prognostics because this divide

This study considers the wave analysis and control of mono-coupled periodic mechanical systems, focusing on the properties of the secondary constants (propagation constants and characteristic impedances) as analytic functions of the Laplace transform variable s. In a general wave analysis process, we derive the secondary constants from the system dynamics, and evaluate the steady-state response for

Hybrid Simulation is a dynamic response simulation paradigm that merges physical experiments and computational models into a hybrid model. In earthquake engineering, it is used to investigate the response of structures to earthquake excitation. In the context of response to extreme loads, the structure, its boundary conditions, damping, and the ground motion excitation itself are all subjected to large

A resonant piezoelectric micro-jet (RPMJ) using a longitudinal transducer (LT) is proposed for achieving high-speed jetting of high-viscosity liquid. The continuous droplets are realized by the pressure change of micro-jet element (MJE) which can be generated by the high frequency vibration of the LT. The RPMJ is designed and its driving principle is simulated to reveal the pressure change and the

Correlated random variables are common in industry field. In reliability analysis community, Nataf transformation is considered as a powerful tool for handling correlated random variables, since it only requires the marginal probability distribution functions of input random variables. However, when accurate marginal probability distributions are unavailable, Nataf transformation cannot be used. This

Modally reduced order models are commonly adopted in system inversion. Their observability requires specific attention, since these models only accurately describe the dynamic behavior of the underlying system in a limited frequency range. This paper elaborates a methodology to investigate the observability of modally reduced order models with unknown parameters. The focus is on a particular type of