Damping Levels Research Articles

Rate-Sensing Performance of Imperfect Capacitive Ring-Based MEMS Coriolis Vibrating Gyroscopes at Large Drive Amplitudes.

This paper investigates the effect of electrostatic nonlinearity on the rate-sensing performance of imperfect ring-based Coriolis Vibrating Gyroscopes (CVGs) for devices having 8 and 16 evenly distributed electrodes. Mathematical models are developed for CVGs operating in (i) an open loop for a linear electrostatically trimmed device, (ii) a closed loop where a sense force balancing is applied to negate the sense quadrature response, and the effects of electrostatic nonlinearity are investigated for increasing drive amplitudes. The modeling indicates the nonlinear responses for 8- and 16-electrode arrangements are quite different, and this can be attributed to the nonlinear frequency imbalance, which depends on the drive and sense frequency softening as well as the presence of self-induced parametric excitation in the sense response. In open loop the 16-electrode arrangement exhibits much weaker levels of nonlinearity than the 8-electrode arrangement because the nonlinear frequency imbalance is less sensitive to drive amplitude. For devices operating in closed-loop with sense force balancing to ensure the drive and sense responses are in-phase/anti-phase, it is shown that ideal rate-sensing performance is achieved at large drive amplitudes for both 8- and 16-electrode arrangements. Using sense force balancing, rate sensing can be achieved using either the sense response or the required balancing voltage. For the latter, large nonlinear frequency imbalances and low damping levels enhance rate-sensing performance.

Model-free parameter tuning with continuous genetic algorithm: Application to virtual controlled object-based active vibration controller

Active vibration control is a powerful approach to provide higher damping effects over a broad range of frequencies. However, most of them generally involve a modeling process of a controlled structure, complicating the controller design. The main contribution of this study is to present a novel tuning scheme of a model-free active oscillation controller based on continuous genetic algorithm (CGA), which can simplify a controller design process by eliminating the need for plant modeling. The model-free controller is developed using a virtual controlled object (VCO) as its foundation. VCO makes it possible to construct an active damping controller without knowing any specifications of a real controlled structure. In the offline tuning of the design variables of the controller, we use a reference-controlled object (RCO) - a single-degree-of-freedom (SDOF) structure defined by the designer - to assess the damping level instead of the actual controlled structure model. This evaluation is feasible due to the robustness of the VCO-based design, which accommodates variations in the controlled object structures. The application of the CGA, which has the global search ability, enables automatically specifying the optimal parameter values without costly trial-and-error works. The effectiveness of the auto-optimized model-free damping controller is demonstrated through numerical examples across different mechanical systems, with comparisons made to a trial-and-error-tuned controller. The main finding is that the controller can reduce the vibration amplitudes even though plant modeling of the actual controlled objects is not accompanied at all. As the representative results, the resonance peaks of two different cantilever plates were suppressed by 14.38 and 27.13 dB in the low-frequency band. The detailed-specification-independent nature provided by the model-free design makes it possible to apply the resultant controller to various structures because the robustness is enforced.

Theoretical Model and Shaking Table Experiment of Eddy Current–Enhanced Friction Pendulum Tuned Mass Damper

ABSTRACTTraditional pendulum tuned mass dampers (PTMDs) necessitate substantial vertical space, and conventional friction pendulum systems (FPS‐TMDs) struggle to balance low activation thresholds with adequate damping levels due to their reliance on friction forces. This study presents an innovative eddy current–enhanced friction pendulum tuned mass damper (ECEFP‐TMD), which capitalizes on eddy current damping to lower the activation threshold effectively. Simultaneously, incidental friction damping provides a complementary dual–damping scheme. We developed a robust theoretical model, underpinned by shaking table experiments, to demonstrate the ECEFP‐TMD's superior vibration mitigation. Findings reveal that eddy current damping not only diminishes the activation threshold but also streamlines the adjustment of damping levels. The integrated dual–damping mechanism substantially augments energy dissipation, thus reducing the acceleration response of structures subjected to seismic activity. Particularly, for FPS‐TMDs with minimal friction coefficients, the inclusion of eddy current damping substantially elevates seismic resilience, mitigating stick–slip behavior typically induced by excessive friction damping.

Modal Frequency and Damping Identification of the FAST Cabin-Cable System

The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) faces challenges in establishing high-precision rigid connections between the receiver and the reflective surface due to its vast spatial span. Innovatively, FAST suspends the feed cabin in mid-air using six supporting cables. The precise positioning of the feed focal point is achieved through the coordinated control of cable extension and retraction, along with the A-B axis and the Stewart platform within the cabin. The cables and the feed cabin form a large parallel mechanism. Since the cables are flexible, and the feed cabin remains at a high altitude during observations, it is inevitably subject to internal and external disturbances. To quickly dissipate these disturbances, the system requires a certain level of damping, which directly affects the pointing and tracking accuracy of FAST. During the 2022–2023 operational period, there were multiple instances where the pulleys of the curtain mechanism on the supporting cables became stuck and were carried to the top of the towers by the cables. This also led to the phenomenon where the pulleys, after being stuck, would rapidly slide down the cables due to accumulation. At such moments, the cabin-cable system would experience instantaneous excitation, causing vibrations. This study uses the intrinsic time-scale decomposition (ITD) method to analyze the inertial navigation data installed in the cabin during these events, identifying modal frequencies and damping ratios. The analysis results show that the lowest primary vibration frequency of the FAST cabin-cable suspension system ranges from approximately 0.12 to 0.2 Hz, with a damping ratio of no less than 0.004. These data indicate that the current structure of FAST has a strong energy dissipation capability, providing important reference points for improving the control accuracy of FAST and for the upgrade of the feed support system.

Abstract 4143940: Circulating Mitochondrial DNA: Biomarker and Inflammation Mediator in Cardiac Ischemia/Reperfusion Injury

Introduction: Ischemia/reperfusion (I/R) injury occurs after coronary revascularization, contributing to infarct size. Circulating mitochondrial DNA (mtDNA) levels are elevated in acute myocardial infarction (MI) patients, and act as Damage Associated Molecular Patterns (mtDNA DAMP), which are recognized by the Toll-like receptor 9 (TLR9), initiating pro-inflammatory responses. Prior studies have shown that loss of TLR9 prevents I/R injury in isolated mouse hearts. However, mtDNA DAMP levels have not been measured in ST-elevation MI (STEMI) patients, and whether blocking TLR9 in mice can reduce I/R injury remains unknown. Hypothesis: MtDNA DAMP levels serve as markers of STEMI related cardiac injury. Blocking the activation of TLR9 will decrease cardiac I/R injury. Methods: MtDNA DAMP levels in serum were measured pre- and 24 hours post- PCI in 55 STEMI patients and 37 healthy controls by qPCR. To evaluate the role of TLR9 on I/R injury, ODN2088 was used to block TLR9 receptor, wild type and TLR9 germline KO mice were subjected to close-chest I/R surgery with minimal systemic inflammation. The cardiac systolic function and infarct size were assessed. Immune cells were isolated from the injured left ventricle and spleens and detected by flow cytometry. Results: Pre- PCI mtDNA DAMP levels were increased ~200 folds in STEMI patients compared to healthy controls. After PCI, the elevated mtDNA DAMP levels reduced significantly, while the troponin T levels increased, suggesting mtDNA is an early marker of MI. Compared with negative ODN, ODN2088 treatment at reperfusion reduced infarct size and total leukocytes, myeloid cells, neutrophils and TNF-α+ cells, and a trend of reduced IL-1β+ cells, and there was no difference in IL-6+ cells, total macrophages and residential macrophages. Loss of TLR9 in male and female mice significantly reduced infarct size by ~40% and preserved the systolic function. Meanwhile, there is no difference between genders. Conclusions: Circulating mtDNA DAMP level is an early marker of STEMI and may predict the success of PCI. Blocking the mtDNA DAMP-TLR9 signaling pathway during reperfusion significantly reduces I/R injury, indicating it is a viable therapy to mitigate cardiac I/R injury after prompt coronary revascularization.

Effect of moisture on the electric field and breakdown voltage of XLPE cable interconnectors

Dampness in the joint is a common defect of power cables, and the influence of moisture on the performance of the intermediate joint is very important. The electric field distribution of the joint is analyzed by simulation, and the XLPE sample is used as an experimental object to test the breakdown voltage under different damp levels. Simulation results show that in the composite interface outside the main insulation, the electric field at the water film is only 20%–60% of normal. However, the electric field around the water film generally increases, and as the degree of moisture increases, the electric field distortion becomes more serious, which is prone to inducing breakdown accidents. The electric field around the water film outside the conductor has no obvious distortion and will not directly induce accidents. Through the breakdown voltage experiment of the damp XLPE sample, it is found that the average breakdown voltage is 85%–94% of normal, and it decreases with the increase of moisture. The experimental results are consistent with the simulation results. The results can be used to guide the cause analysis of cable intermediate joint accidents.

Collisional damping in debris discs: Only significant if collision velocities are low

Context. Dusty debris discs around main sequence stars are observed to vary widely in terms of their vertical thickness. Their vertical structure may be affected by damping in inelastic collisions. Although kinetic models have often been used to study the collisional evolution of debris discs, these models have not yet been used to study the evolution of their vertical structure. Aims. We extend an existing implementation of a kinetic model of collisional evolution to include the evolution of orbital inclinations and we use this model to study the effects of collisional damping in pre-stirred discs. Methods. We evolved the number of particles of different masses, eccentricities, and inclinations using the kinetic model and used Monte Carlo simulations to calculate collision rates between particles in the disc. We considered all relevant collisional outcomes including fragmentation, cratering, and growth. Results. Collisional damping is inefficient if particles can be destroyed by projectiles that are of much lower mass. If that is the case, catastrophic disruptions shape the distributions of eccentricities and inclinations, and their average values evolve slowly and at the same rate for all particle sizes. Conclusions. The critical projectile-to-target mass ratio (Yc) and the collisional timescale jointly determine the level of collisional damping in debris discs. If Yc is much smaller than unity, a debris disc retains the inclination distribution that it is born with for much longer than the collisional timescale of the largest bodies in the disc. Such a disc should exhibit a vertical thickness that is independent of wavelength even in the absence of other physical processes. Collisional damping is efficient if Yc is of order unity or larger. For millimetre-sized dust grains and common material strength assumptions, this requires collision velocities of lower than ~40 m s−1. We discuss the implications of our findings for exo-Kuiper belts, discs around white dwarfs, and planetary rings.

Effects of Wall and Freespace Damping Levels on Virtual Wall Stiffness Classification.

Virtual damping is often employed to improve stability in virtual environments, but it has previously been found to bias perception of stiffness, with its effects differing when it is introduced locally within a wall/object or globally in both the wall and in freespace. Since many potential applications of haptic rendering involve not only comparisons between two environments, but also the ability to recognize rendered environments as belonging to different categories, it is important to understand the perceptual impacts of freespace and wall damping on stiffness classification ability. This study explores the effects of varying levels of freespace and wall damping on users' ability to classify virtual walls by their stiffness. Results indicate that freespace damping improves wall classification if the walls are damped, but will impair classification of undamped walls. These findings suggest that, in situations where users are expected to recognize and classify various stiffnesses, freespace damping can be a factor in narrowing or widening gaps in extended rate-hardness between softer and stiffer walls.

Unveiling nonlinear phi-bit dynamics in elastic systems: Advancing quantum-inspired computing

Phi-bits, the classical mechanical analogs of qubits, play a pivotal role in the development of quantum-analog computing systems. Understanding the nonlinear processes governing control and interconnectivity among phi-bits is imperative for their advancement. These phi-bits, existing as acoustic waves within arrays of interconnected waveguides, exhibit a remarkable ability to maintain coherent superpositions of two states under external nonlinear driving forces. Manipulating the frequency, amplitude, and phase of external drivers allows precise control over phi-bit states. To analyze and predict the nonlinear response of phi-bits to external stimuli, we have developed a discrete element model. This model comprehensively captures various types, strengths, and orders of nonlinearities stemming from intrinsic medium coupling between waveguides and external factors like signal generators, transducers, and ultrasonic couplant assemblies. Our study unveils significant insight, highlighting how nonlinearity type, strength, order, and damping impact the complex amplitudes' modulus and phases in the coherent superposition of phi-bit states, with a notable impact on their predictability and stability, particularly at high damping levels. This investigation explores the controlled creation of phi-bits to observe the superposition of states, essential for advancing phi-bit-based quantum analogue information processing platforms.

Bayesian continuous wavelet transform for time-varying damping identification of cables using full-field measurement

Bayesian continuous wavelet transform for time-varying damping identification of cables using full-field measurement

Wind-induced collapse mode and mechanism of super-large hyperbolic steel reticulated shell cooling tower with stiffening rings

Wind-induced collapse mode and mechanism of super-large hyperbolic steel reticulated shell cooling tower with stiffening rings

An innovative method for improving rainfall prediction in Gujarat state through a fusion model DWT, 1DCNN and LSTM

In countries like India where agriculture is a major industry, accurate prediction of rainfall is crucial. The ability to forecast rainfall helps in planning crop cultivation and has a positive impact on both local and national economies. Nevertheless, conventional statistical techniques prove inadequate for forecasting precipitation over extended periods of time owing to the erratic characteristics inherent in climate phenomena. To address this issue, various ML models such as Decision Tree (DT), Support Vector Machine (SVM), Random Forest (RF), and Discrete Wavelet Transform, have been explored for precipitation prediction. Large-scale data analysis and overcoming intricate challenges have become achievable through the utilization of deep learning, which has proven to be a potent approach. It combines the advantages of multiple methodologies and algorithms in order to develop accurate precipitation forecasting models. In this study, researchers treated rainfall time series as signals and used the Discrete Wavelet Transform method along with Convolutional Neural Network (CNN) and Long Short-Term Memory (LSTM) network methods to analyze and reconstruct these signals. The research employed a dataset acquired from the Indian Meteorological Department and NASA, covering the years 1901 to 2022. This extensive collection comprised diverse meteorological parameters such as relative humidity, wet bulb temperature, Surface Pressure, soil dampness levels, relative humidity, temperatures (min and max), wind speed data in addition to rainfall records. The fusion of these three methods - DWT-CNN-LSTM deep model - consistently demonstrated excellent performance in key evaluation metrics such as MAE and RMSE. This approach achieved remarkable results in accurately predicting precipitation patterns for Gujarat State over the specified time period.

Xác định cản nhớt của kết cấu sử dụng phương pháp dải tần số cực trị

The classical half-power bandwidth (HPB) method is known as a simple and widely used method to identify damping in experimental research on structural vibrations. However, this method is only effective in systems with small damping and separate natural frequencies. This paper presents the extreme frequency bandwidth (EFB) method and proposes a formula to estimate the viscous damping ratio from the extreme points of the real part of the frequency response function (FRF) in the displacement spectrum analysis of structures. The displacement FRF is obtained by Fourier transform of the simulated load and response signals of the system. The results show that the EFB method can identify the viscous damping in structures that have one or more degrees of freedom with different damping levels.

Semi-active control implementation in aircraft landing gear systems using hardware-in-the-loop test bench

In small-sized aircraft landing gear systems, magnetorheological (MR) dampers offer an innovative approach to adjusting damping levels under wide range of operating situations in order to achieve competing control objectives such as ride comfort, suspension travel, and energy consumption. Also, MR dampers have nonlinear dynamics and exhibit hysteresis. In this context, this paper aims to present a Hardware-In-the-Loop (HIL) technique for the implementation of backstepping control and linear quadratic regulator (LQR) control. Experimental results highlight that, compared to passive suspension (Passive Off), backstepping control and LQR control approaches reduce the fuselage vertical acceleration by 29.13% and 24.95%, respectively. Moreover, the ISO 2631 standard was adopted to evaluate ride comfort. LQR control can able to minimize the fuselage roll acceleration under a random road profile. Also, LQR control provides the highest performance in terms of fuselage roll acceleration, achieving a 6.2% improvement with lower energy consumption. By utilizing HIL, semi-active control methods can be tested and developed without the need for the aircraft, while keeping the characteristics that the physical aircraft would bring.

Analysis of adaptive parameter tuning control strategy of VSG

Abstract The traditional virtual synchronous inverter employs constant inertia and damping control, resulting in poor reliability when the system faces disturbances. Consequently, this paper proposes a synchronous virtual machine network control strategy based on adaptive technology. Firstly, the traditional principle is analyzed, followed by an examination of the effects of varying inertia and damping levels on the power grid. Leveraging the power angle characteristic and frequency oscillation characteristic of synchronous generators, an inertia and damping adaptive control strategy is devised. Subsequently, the effectiveness of the strategy is validated through simulation curves generated by a Simlink model.

Damage-aware structural control based on reinforcement learning

This contribution presents a semi-active control technique intended for mitigation of structural vibrations. The control law is derived in a repeated trial-and-error interaction between the control agent and a simulated environment. The experience-based training approach is used which is the defining feature of the machine learning techniques of reinforcement learning (RL). In particular, a specific modification of the Deep Q Learning (DQN) approach is applied. The involved artificial neural network not only approximates the expected reward of the control (which defines the control action and quantifies its performance), but additionally keeps track of structural damages. This requires a specific architecture, which allows the network to be damage-aware, and a specific training procedure, where the memory pool preserved for the RL stage of experience replay is populated with not only the observations, control actions, and rewards, but also with the momentary status of structural damage. Such an approach explicitly promotes the damage-awareness of the control agent. The proposed technique is tested and verified in a numerical example of a shear-type building model subjected to a seismic excitation. A tuned mass damper (TMD) with a controllable level of viscous damping is used to implement the semi-active actuation, and the optimally tuned classical TMD provides the reference response.

Interaction energy flow paths analysis of PMSG-based wind power integrated systems during LVRT and its parameter adjustment strategy

To solve the problem of oscillation instability in permanent magnetic synchronous generator (PMSG)-based wind power connected systems during low-voltage ride through (LVRT) process, a parameter adjustment strategy based on interaction energy path optimization is proposed in this paper. Firstly, a modular state-space model of PMSG under fault transient conditions is constructed, and the system is divided into five subsystems. Then, the dynamic energy function of subsystems reflecting the oscillation stability of the system is derived. Based on that, the dynamic energy flow path is described considering the introduction of LVRT control. On this basis, the interaction energy between LVRT control links and subsystems is analyzed, and the coupling mechanism of voltage support and damping characteristics in the LVRT process is explained. Further, aiming at the optimal change rate of the total interaction energy in the LVRT process, the adjustment strategy of LVRT control parameters is constructed to meet voltage and damping requirements. Finally, a PMSG-connected system model is built on the MATLAB/Simulink platform to verify the effectiveness of the adjustment strategy. The results show that the proposed method can effectively improve the damping level under the fault transient condition, as well as supporting system voltage.

How to Improve Robust Control of a Linear Time-Varying System by Using Experimental Data

This paper demonstrates that robust control based on only a priori information about the object’s uncertainty can be significantly improved through the additional use of experimental data. Generalized H∞-optimal controllers are designed for an unknown linear time-varying system on a finite horizon. These controllers optimize the damping level of exogenous and/or initial disturbances as well as the maximum deviation of the terminal state of the system. The design method does not require the persistent excitation condition or the rank condition, which ensure the identifiability of the system. As a result, the amount of experimental data can be significantly reduced.

Mapping for stable bilateral teleoperation of manipulators considering time delays

Teleoperation of manipulators has allowed extending the human skills to several areas, where the commands generated by a human operator on the leader robot are followed by a remote robot. For this purpose, position-position tracking requires a mapping given the mismatch between robot workspaces. This paper compares a pair of functions for mapping the haptic device commands to handle a remote robot, considering non-identical workspaces and a classic P+d control scheme. As part of the theoretical analysis, a Lyapunov-Krasovskii-based stability analysis is developed in steps, allowing us for determining the boundedness of velocities and coordination errors. Subsequently, the performance of the teleoperation system is compared using two mapping functions. To achieve a fair comparison of results, a test protocol is developed, where different levels of haptic device damping, time delays, and workspace scales are used to evaluate the time to complete the task and the average coordination errors. Based on the results, the mapping function influences the calculation of force feedback, stability of the system, and performance metrics. During a pick-and-place task, a reduction in coordination error is observed when the linear function is chosen, while the time to complete the task is lower when a non-linear function is considered.

High-fidelity flexible multibody model considering torsional deformation for nonequatorial space elevator

High-fidelity flexible multibody model considering torsional deformation for nonequatorial space elevator