Damping Levels Research Articles

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.

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

With advancement of dry-air cooling technology, it has become feasible to use steel reticulated shell structures in design and construction of industrial cooling towers. Steel reticulated shell cooling towers (SRSCTs) with light weight, high strength, and rapid construction have development potential. Wind-induced collapse accidents in cooling towers frequently occur, characterized by pronounced nonlinear behavior involving significant deformation and material failure. Nevertheless, current stability and collapse analyses of cooling towers based on linear theory and elastic deformation are inadequate and unsafe. Thus, the wind-resistant stability of SRSCTs must be evaluated considering their inherent high flexibility and low damping levels. Considering a 220 m high hyperbolic SRSCT as a case study, a wind-induced collapse FEM simulation and analysis were performed. The average and fluctuating wind loads were measured in a reduced-scale model during wind tunnel tests and used as the time-variant wind pressure in a structural finite-element model. The dynamic performance and buckling collapse analyses of the cooling tower were conducted considering geometric and material nonlinearities. The entire wind-induced failure process of the SRSCT in extreme winds was systematically investigated. The weaknesses in the structural stiffness and the failure process were quantified, with five failure stages and four failure modes. The failure stages included linear elasticity, local member failure, local regional failure, overall structural failure, and collapse. The failure modes included circumferential plastic buckling zone failure, windward buckling failure of the shell, crosswind failure of the stiffening ring (hinged curved-beam mechanism), and windward failure of the stiffening ring (triangular arch-like mechanism). This study confirms that development of plastic buckling zones and formation of plastic hinges, considering geometric and material nonlinearity, are the dominant factor in wind-induced failure and collapse of SRSCTs.

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.

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.

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.

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.

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

Space elevators are a promising technology for future space transportation. The primary component of a space elevator is a tether deployed from a geostationary orbit towards the Earth and into deep space. Payloads can be transported using a climber moving along the tether. However, obtaining a deeper comprehension of the precise dynamics of a space elevator is challenging. The tether could have various deformations such as elongation, bending, and torsion owing to its flexible nature and the low level of vibration damping in space. Therefore, understanding those effects on the tether is essential for the design concept of a space elevator. Reproducing the behavior of space tether systems on the ground is challenging, which is primarily due to the scale of the system and the difficulty of accurately replicating a space environment. Thus, high-fidelity numerical analysis methods are required to analyze the dynamic response of space elevators precisely. Previously proposed analysis models of space tether systems with climbers have focused on elongation, bending, and rigid body motion of the tether, and the effect of torsional deformation has been neglected. However, a tether can be twisted easily owing to its low torsional stiffness. This study established high-fidelity numerical simulation models for space elevators considering large deformations including the torsion of a tether. This study developed a flexible multibody model with a moving climber using the absolute nodal coordinate formulation with 14 degrees of freedom. Further, the gravitational perturbation caused by the non-sphericity of the Earth was considered. Using the constructed model, the motion and deformation of nonequatorial space elevators caused by the climber motion and the disturbance in the space environment were investigated. The obtained results indicate that gravitational perturbation can induce torsional deformation, particularly at higher anchor latitudes.

Development and characterization of self-centering friction dampers with confined shape memory alloy bars

This study proposes a new self-centering, shape memory alloy bar-based device to address the tension-compression asymmetry and limited energy dissipation capacity of similar SMA bar-based devices. The proposed device, named the Confined Superelastic Friction Damper (CSFD), employs buckling-restrained SMA bars to maintain symmetry in force-displacement responses and enhance effectiveness in both tension and compression. The device also integrates a frictional damping mechanism, contributing to increased energy dissipation capacity. First, an optimal annealing condition is investigated for as-received SMA bars to achieve a satisfactory superelastic response. Then, the working and design principles of the CSFD are outlined. The experimental characterization of CSFD devices in various configurations is conducted under an increasing amplitude loading protocol. The devices are tested with different levels of frictional damping to assess the effects of the added frictional forces on device characteristics. Analysis of test results considers parameters such as hysteresis curves, maximum force, equivalent viscous damping, and self-centering efficiency to provide a comprehensive performance evaluation of each device. Findings reveal that while a single buckling-restrained SMA bar device exhibits up to 90 % higher forces in compression than in tension, a CSFD device with two such bars nearly eliminates this asymmetry. Compared to tension-only SMA devices, capable of symmetric response, the proposed CSFD device demonstrates a 2.6 times higher force-resisting capacity. For all devices, the addition of some frictional damping improves the energy dissipation and equivalent viscous damping capacity, while leading to some reduction in self-centering efficiency.

Soft Sensory-Motor System Based on Ionic Solution for Robotic Applications.

Soft robots claim the architecture of actuators, sensors, and computation demands with their soft bodies by obtaining fast responses and adapting to the environment. Sensory-motor coordination is one of the main design principles utilized for soft robots because it allows the capability to sense and actuate mutually in the environment, thereby achieving rapid response performance. This work intends to study the response for a system that presents coupled actuation and sensing functions simultaneously and is integrated in an arbitrary elastic structure with ionic conduction elements, called as soft sensory-motor system based on ionic solution (SSMS-IS). This study provides a comparative analysis of the performance of SSMS-IS prototypes with three diverse designs: toroidal, semi-toroidal, and rectangular geometries, based on a series of performance experiments, such as sensitivity, drift, and durability. The design with the best performance was the rectangular SSMS-IS using silicon rubber RPRO20 for both internal and external pressures applied in the system. Moreover, this work explores the performance of a bioinspired soft robot using rectangular SSMS-IS elements integrated in its body. Further, it investigated the feasibility of the robot to adapt its morphology online for environment variability, responding to external stimuli from the environment with different levels of stiffness and damping.

Optimized MMC passive impedance shaping method for high frequency oscillation suppression

Recent years, there have been several high-frequency oscillation events in modular multilevel converter (MMC) based DC current projects. Considering the wideband oscillation characteristics of this issue, passive MMC impedance shaping methods are superior solutions for their advantages over the active methods in enhancing the broadband damping level. However, the optimization of parallel passive devices mainly focused on reactive power compensation and the suppression of characteristic harmonics generated by low-level inverters, which is not applicable to MMC systems. To address the optimization design problem of passive damping devices, this paper proposes an optimized design method for passive filters by analyzing the relationship between the passive damping device and the impedance shaping effect of the inverter. The proposed method reduces the capacity of the passive damping device while ensuring system stability margin. Finally, the effectiveness of the proposed passive impedance shaping strategy is verified through time-domain simulations considering changes in AC side operating conditions and power reduction operation of the MMC.

Impact of Sources of Damping On the Fragility Estimates of Wind Turbine Towers

Abstract Fragility estimates in wind turbine towers have been investigated but the the effect of damping on fragility has not been studied. While damping can often be small, it can come from different sources for a wind turbine. This paper demonstrates that even for small levels of equivalent viscous damping, a combination of sources can have a significant impact on the estimate of the fragility of a wind turbine in operational conditions. The widely studied 5MW reference wind turbine is considered for this study. The fragility analysis is performed considering the tower fore-aft displacement and acceleration responses. The impact of different sources of damping on fragility is estimated and ranked to qualitatively understand the impact of damping on the lifetime performance of the tower and develop approximate estimates of their quantitative changes.

Design and control of a compliant robotic actuator with parallel spring-damping transmission

AbstractPhysically compliant actuator brings significant benefits to robots in terms of environmental adaptability, human–robot interaction, and energy efficiency as the introduction of the inherent compliance. However, this inherent compliance also limits the force and position control performance of the actuator system due to the induced oscillations and decreased mechanical bandwidth. To solve this problem, we first investigate the dynamic effects of implementing variable physical damping into a compliant actuator. Following this, we propose a structural scheme that integrates a variable damping element in parallel to a conventional series elastic actuator. A damping regulation algorithm is then developed for the parallel spring-damping actuator (PSDA) to tune the dynamic performance of the system while remaining sufficient compliance. Experimental results show that the PSDA offers better stability and dynamic capability in the force and position control by generating appropriate damping levels.

PENGARUH TINGKAT PARTISIPASI ANGKATAN KERJA, KUALITAS PENDUDUK, DAN TINGKAT PENGANGGURAN TERBUKA TERHADAP PERTUMBUHAN EKONOMI DI PROVINSI SUMATERA UTARA

This study aims to analyze the influence of the Labor Force Participation Rate, population quality, and the level of open response to economic growth in North Sumatra Province. This research uses secondary data from 2017-2021. The model used is the panel data regression model with three types of estimation, namely the commond effect model, the fixed effect model and the random effect model. To determine which model is best for use in the test through three tests Chow test, Hausmant test and LM test. Based on the test results that have been carried out, the selected model is the fixed effect model. The partial results show that the Variable Labor Force Participation Rate has a positive and significant effect on economic growth in North Sumatra, while the quality of the population and the level of open response have a negative and significant effect on economic growth in North Sumatra and together (simultaneously) the labor force participation rate. population quality, and the level of open damping have a positive effect on economic growth in North Sumatra Province. As well as the test results for the coefficient of determination obtained by the R Square value showing a value of 0.351 or 35.1% indicating that the ability of the independent variable to explain the effect on the dependent variable and the remaining 64.9% can be explained by other variables outside the research variables. Recommendations for the election of the government of North Sumatra can provide training to job seekers so that they have skills, and the government has achievements in opening jobs so that it will reduce action and can increase economic growth.

FEATURES OF VIBRATION DAMPERS APPLICATION IN THE DESIGN OF VIBRATION-RESISTANT METAL CUTTING TOOLS

Dry and viscous friction is used as a damper of oscillation energy in the construction of metal-cutting tools. A mathematical model of a two-mass oscillatory scheme of the insert of an assembled milling cutter was developed and studied, one of the masses of which models the clamped part of the insert - a press connection with dry friction, and the other - the cantilever part, which is subject to self-oscillations that are possible in the process of metal cutting. The influence of dry friction in the press joint of the insert on the amplitude of resonant oscillations of the cutter and the part was analyzed. The possibility of reducing the magnitude of the cutter's self-oscillations is demonstrated by selecting the most suitable parameters for the press connection of inserts with the body of the assembled milling cutter. The influence of internal viscous friction in materials with a high level of energy damping on the amplitude of self-oscillations of the cutter was evaluated and the possibility of their use in the design of a vibration-resistant metal-cutting tool was considered.

Turn Compensation Control Development and Analysis for a Self-Propelled Sprayer Chassis Suspension System

Highlights An Experimental sprayer chassis suspension control system was developed and evaluated in headland turns. Turning evaluation performance metrics and methods were conceptualized in the context of sprayers. The Experimental chassis suspension system showed stability and comfort increases during aggressive turns. Boom stability improved significantly after completion of the turn for the Experimental suspension system. Abstract. A challenging economic, environmental, and regulatory landscape causes the need for efficient agricultural machinery. The performance of self-propelled sprayers depends on their ability to deposit chemicals accurately and efficiently, and increased machine sizes and faster driving speeds require consideration for sprayer chassis stability. One method of improving this stability is using variable damping elements in the sprayer chassis suspension system. In this work, an Experimental sprayer chassis suspension system that implemented turning event detection and variable damping control was developed for headland turning events. The Experimental chassis suspension system was tested for a constant speed headland turn maneuver at 10 to 25 m turn radii. The performance of the Experimental system was quantified in terms of operator comfort and operator health, chassis roll and roll rate amplitudes, and boom height sensor standard deviation, and this performance was compared to a Baseline sprayer suspension configuration. From the data collected, the Experimental suspension system improved chassis roll and roll rate stability by 30% to 40% for the entry portion of the turning event regardless of turn radius while also showing a 5% increase in ride quality. The need for tuning the damping level to the chassis yaw rate was identified from decreased comfort performance metrics at larger turn radii. Boom height stability improved significantly for Experimental suspension configurations, particularly after the turning event, showing an 8% to 21% improvement in boom height standard deviation. Further exploration of control parameters and their effects outside turning events should be conducted to ensure optimal control law settings based on machine configurations. Keywords: Chassis suspension, Control, Performance, Self-propelled sprayer, Stability, Turn event, Variable damping.

ANALISIS TINGKAT REDAM BUNYI DARI BEBERAPA JENIS BAHAN AKUSTIK KAIN PERCA

Research was carried out on the analysis of the sound absorption level of several types of patchwork acoustic materials which aims to find out whether patchwork can be used as a sound dampening material, to determine the sound absorption level of several types of patchwork acoustic materials and to determine the best attenuation level of several types of patchwork acoustic materials. the type of patchwork acoustic material. The background of this research is due to the acoustic quality of the room which has received less attention for the comfort of listeners when they are in a room. The study used variations of sound absorbing materials, namely cotton and denim patchwork. Measurement of the sound absorption coefficient of patchwork is done by making a sample chamber with a length of 13.5 cm, a width of 13.5 cm and a height of 8.5 cm. Sound Level Meter is a tool used to measure the level of sound pressure. Variations in the thickness of the patchwork used were 3, 5, and 10 mm. In measuring the entire inner wall surface of the sample room will be covered with patchwork, then the speaker is placed in the sample room. The sound source comes from speakers with a frequency of 90 dB which is arranged in a frequency range of 125, 250, 500, 1000, 2000 and 4000 Hz. The best damping level of the three materials is a mixture of cotton and denim with a thickness of 10 mm, because the thicker the patchwork layer, the α value obtained is 0.629.

Novel formula for determining bridge damping ratio from two wheels of a scanning vehicle by wavelet transform

A novel formula is derived for determining the bridge damping ratio from the correlation of the front and rear wheels of a test vehicle using the modal components extracted by the wavelet transform (WT). Firstly, closed-form solutions are derived for the dynamic responses of the bridge under a moving two-axle vehicle. Next, to remove the masking effect by vehicle’s frequencies, the wheel-bridge contact responses back-calculated from the vehicle responses are used in analysis. Then, the WT is employed to obtain the instantaneous amplitudes of the component responses of the two contact points. Finally, using the correlation between the two contact points, a novel formula is derived for the bridge damping ratio. The above derivations are validated by numerical simulations. Through the theoretical analysis and numerical simulations, the following conclusions are made: (1) the spatial correlation of the front and rear contact points is utilized to derive the bridge damping formula using the WT; (2) for multi-span bridges, the RANdom SAmple Consensus (RANSAC) can beneficially downplay the data points with large deviations near the internal supports in fitting the bridge damping ratio; (3) the first span can be reliably used to calculate the damping ratio of multi-span bridges, especially in the presence of pavement roughness; and (4) the formula has been attested to be robust against various levels of vehicle and bridge damping.