Parallel Damping Research Articles

Non-linear torsional Alfv\'en waves evolving in stratified viscous plasmas: Coronal hole plumes

We model solar atmospheric structures characterised by parallel structuring. We focus on Alfv\'en waves in the weakly non-linear regime to highlight the efficiency of non-linear wave steepening when dissipative effects are prominent. We also consider the local and equilibrium conditions involved in shock formation and the shock's contributions to coronal seismology. Coronal plumes were modelled analytically by implementing the magnetohydrodynamic (MHD) theory in cylindrical geometry. Here, the stratification and viscosity are present internal to the plume, whilst effects of the external medium, together with equilibrium conditions, are implied where the magnetic fields are parallel to the plume axis. We implemented a second-order thin flux tube approximation to obtain a wave equation that points to effects tied to non-linear, dissipative, and stratification terms, as well as terms representing atmospheric conditions. The impact of shear viscosity on non-linear Alfv\'en waves extracted by the Cohen-Kulsrud-Burgers-type equation proves more efficient when propagated to higher altitudes. The dissipative effects linked to the dimensionless viscosity indicate that the dissipative effects are not linear. Meanwhile, the delay in shock formation enables energy conversions at higher altitudes, thereby maintaining coronal heating at higher levels. The efficiency of parallel structuring and viscous damping is enhanced by such transverse structuring, as it is directly proportional to the external plasma-beta . It is observed that Alfv\'en pulses may undergo a backward shock, either in the lower levels of coronal plasma or as they propagate toward higher regions, implying a conversion of energy occurring at various altitudes. A peak was observed, indicating that the interplay reverses at heights around $1.5$ solar radii. Such effects are shown to play a key role in the context of coronal seismology.

Including the parallel mass flow in calculating the steady-state solutions and stability of the momentum balance equations for a quasisymmetric stellarator

The Helically Symmetric Experiment (HSX) is a quasisymmetric stellarator with minimal parallel viscous damping in a helical direction. The parallel flow (Vǁ) along the magnetic field is similarly weakly damped by viscosity. In this paper, the self-consistent steady-state parallel and poloidal momentum balance equations are used to show that a large Vǁ on the order of the ion thermal velocity can increase the ion resonant radial electric field (Er) beyond the value calculated using the typical approximation that Vǁ is zero. By altering the damping of Vǁ, either by degrading the quasisymmetry or varying the neutral density, the ion resonant Er can shift in a controllable fashion. It is shown explicitly that there exist stable and unstable steady-state solutions in the two-dimensional space of Vǁ and Er. A stability analysis of each solution is performed by calculating the eigenvalues and eigenvectors of the Jacobian. The unstable solution corresponds to a saddle point in which the eigenvalues have opposite signs. The analysis leads to the conclusion that unstable solutions occur when the derivative of the total poloidal damping with respect to Er is positive. A hysteresis in Er and Vǁ is observed when the radial current density is linearly increased to a maximum and then decreased back to zero. Jumps in the radial electric field and the parallel flow are observed as the radial current density drives the evolution from one stable point to the next. This result is similar to experimental data observed on several devices.

A physiologically enhanced muscle spindle model: using a Hill-type model for extrafusal fibers as template for intrafusal fibers

The muscle spindle is an essential proprioceptor, significantly involved in sensing limb position and movement. Although biological spindle models exist for years, the gold-standard for motor control in biomechanics are still sensors built of homogenized spindle output models due to their simpler combination with neuro-musculoskeletal models. Aiming to improve biomechanical simulations, this work establishes a more physiological model of the muscle spindle, aligned to the advantage of easy integration into large-scale musculoskeletal models. We implemented four variations of a spindle model in Matlab/Simulink®: the Mileusnic et al. (2006) model, Mileusnic model without mass, our enhanced Hill-type model, and our enhanced Hill-type model with parallel damping element (PDE). Different stretches in the intrafusal fibers were simulated in all model variations following the spindle afferent recorded in previous experiments in feline soleus muscle. Additionally, the enhanced Hill-type models had their parameters extensively optimized to match the experimental conditions, and the resulting model was validated against data from rats’ triceps surae muscle. As result, the Mileusnic models present a better overall performance generating the afferent firings compared to the common data evaluated. However, the enhanced Hill-type model with PDE exhibits a more stable performance than the original Mileusnic model, at the same time that presents a well-tuned Hill-type model as muscle spindle fibers, and also accounts for real sarcomere force-length and force-velocity aspects. Finally, our activation dynamics is similar to the one applied to Hill-type model for extrafusal fibers, making our proposed model more easily integrated in multi-body simulations.

Novel integrated coupled inductor boost with RL parallel damping network for improving dynamic response

Novel integrated coupled inductor boost with RL parallel damping network for improving dynamic response

Design and Application of Led Driver Based on Isolated DC-DC Cuk Converter by Comparing Power Led Models

Design and application of led driver with isolated cuk converter for 10W is realized in this paper especially for automotive purposes. The advantage of isolated cuk topology than conventional Cuk topology is to have electrical isolation with supply and load and providing same polarity output. Besides, power led model including constant voltage and exponential models is obtained and employed in simulation study for comparison. Furthermore, maximum current limitation of power led is provided via dsPIC30f4011 microcontroller. Also, power switch is operated by 100 kHz switching frequency, and connection of the power led driver to the source provided by LC with parallel damping filter, whose noise reduction shown by application as well. With experimental set up, proving the desired results achieved by the converter, led current-voltage, input voltage-current are measured. Simulation results also verifies application. Moreover, exponential power led model provides more accurate results than constant voltage model.

A Parallel Scheme of Friction Dampers and Viscous Dampers for Girder-End Longitudinal Displacement Control of a Long-Span Suspension Bridge under Operational and Seismic Conditions

Benefitting from economic development and technological progress, long-span suspension bridges, with their superior span capacity and good economy, have been built in large numbers in recent decades. However, the excessive cumulative longitudinal displacement at the girder ends in the process of bridge operation leads to the degradation of, and fatigue damage to, the connecting components. This study aims to solve the problem with an effective parallel damping scheme of friction dampers and viscous dampers. Firstly, the phenomenon that quasi-static longitudinal displacement accounts for the majority of cumulative displacement is confirmed by the decomposition of measured displacement data at the girder end, which is caused by the asymmetric geometric deformation of the main cable induced by the moving vertical loads of a long-span suspension bridge. An efficient control performance analysis method is proposed based on the formation mechanism of the quasi-static longitudinal displacement. Secondly, the friction damper with a continuous damping model is employed to achieve an effective control performance with respect to the quasi-static longitudinal displacement. Thirdly, in order to realize the target of operational and seismic dual control, a parallel scheme of friction dampers and viscous dampers is proposed, aiming to reduce the cumulative value in the operational state, and maximum value in the seismic state, for longitudinal displacement at the girder ends of a long-span suspension bridge.

Transmission Line Effects of Long Gate-to-Gate Interconnections in Adiabatic Quantum-Flux-Parametron Logic Circuits

Adiabatic quantum-flux-parametron (AQFP) logic is an energy-efficient superconductor logic family that utilizes adiabatic switching of logic gates. At present, a pure inductance is used to model a gate-to-gate interconnection in AQFP logic circuits. However, it is necessary to consider the transmission line effects when the interconnection length becomes long to take into account the propagation delay. This study investigated the transmission line effects of a long gate-to-gate interconnection in AQFP logic circuits. We observed reflection effects in a long transmission line between AQFP gates. These effects induced errors when the interconnection length exceeded several hundred micrometers. We adopted a damping resistance to stabilize the reflection effect to realize an error-free long gate-to-gate interconnection. The circuit simulations confirmed that a damping resistance connected in parallel to the transmission line effectively stabilizes the reflection effect, enabling an interconnection length that is longer than 1 mm. We fabricated AQFP buffer chains that included a long transmission line with and without a parallel damping resistance, and measured their bit error rates. The results showed that the parallel damping resistance effectively improves the bit error rate at high frequencies.

Finite element human body models with active reflexive muscles suitable for sex based whiplash injury prediction.

Previous research has not produced a satisfactory resource to study reflexive muscle activity for investigating potentially injurious whiplash motions. Various experimental and computational studies are available, but none provided a comprehensive biomechanical representation of human response during rear impacts. Three objectives were addressed in the current study to develop female and male finite element human body models with active reflexive neck muscles: 1) eliminate the buckling in the lower cervical spine of the model observed in earlier active muscle controller implementations, 2) evaluate and quantify the influence of the individual features of muscle activity, and 3) evaluate and select the best model configuration that can be used for whiplash injury predictions. The current study used an open-source finite element model of the human body for injury assessment representing an average 50th percentile female anthropometry, together with the derivative 50th percentile male morphed model. Based on the head-neck kinematics and CORelation and Analyis (CORA) tool for evaluation, models with active muscle controller and parallel damping elements showed improved head-neck kinematics agreement with the volunteers over the passive models. It was concluded that this model configuration would be the most suitable for gender-based whiplash injury prediction when different impact severities are to be studied.

Series and parallel resonance active damping of three‐phase buck‐type dynamic capacitor for reactive compensation and harmonic suppression

Series and parallel resonance tend to occur and cause harmonic distortion when the distribution system contains a shunt power capacitor to compensate inductive load and dynamic capacitor (D-CAP) to suppress harmonics. This study focuses on the series and parallel resonance active damping of three-phase buck-type D-CAP, so as to achieve better power quality control. Two virtual resistor damping methods for series resonance, D-CAP power capacitor voltage or D-CAP front-end buffer inductor current feedback, are introduced and compared. Then, parallel resonance is damped by generating certain harmonic currents in the phase with the selective harmonic voltage at the point of common coupling (PCC), equivalent to controlling the D-CAP as a virtual harmonic resistor. In addition, the power balance of D-CAP is interpreted to ensure no additional energy control loop is needed for the active damping. To further improve the parallel resonance damping, the self-adjusted damping gain is proposed by the closed-loop regulation of harmonics in PCC voltage. Finally, coordinated control between reactive and multiple harmonic currents is introduced for the whole combined control to avoid over-modulation. A wide variety of experimental results from a 33 kVar/220 V laboratory prototype are provided to demonstrate the validity of the combined control.

A Multi-Priority Control of Asymmetric Coordination for Redundant Dual-Arm Robot

The paper develops a multi-priority control method of asymmetric coordination for a redundant dual-arm robot. A novel dual-arm coordination impedance is introduced to the multi-priority control, and then the performance of the object tracking and the redundant joints is improved by the regulation of the relative Cartesian errors between two arms. The control of asymmetric coordination is divided into the main task and the secondary task. The control of the main task can regulate the two end-effectors’ errors and the relative errors by building the model of spatial parallel spring and damping (SPSDM), which establishes the dual-arm coordination impedance relation in Cartesian space. The control of the secondary task optimizes the performance of the redundant joint impedance and joint limit avoidance in null space. Finally, a typical asymmetric coordination experiment of peg-in-hole is carried out to verify the validity and feasibility of the proposed method. The results indicate that the proposed dual-arm coordination impedance can regulate the relative tracking errors between two objects directly, and in the context of the external impact force applied to the two end-effectors, the peg-in-hole dual-arm task can be achieved successfully.

Parallel propagation and damping of electromagnetic waves in a partially ionized plasma with multiple species

We study the propagation of electromagnetic waves (or incompressible waves with negligible thermal pressure) along the magnetic field in a partially ionized plasma with multiple species. Because of differences in mass and density, each species responds to and hence affects the perturbations of electromagnetic fields differently. Collisions among all the species further complicate the process. With a linear analysis, the dispersion relation of parallel propagation covering a large range of frequencies, from magnetohydrodynamics (MHD) waves to light waves, with an arbitrary combination of multiple positively charged species, negatively charged species, and neutral species is derived based on a multi-fluid treatment, in combination with Faraday's law and Ampere's law including the displacement current. In a collisional plasma, when the collision frequency is lower than the gyrofrequencies of charged species, the resonances are at the gyrofrequencies of each charged species and the cutoff frequencies are related to the densities of the charged species. Stopbands in which waves propagate with extremely high phase velocity but are strongly damped form between some of these characteristic frequencies. In the MHD wave frequency range, the coupling with neutral species slows the propagation speed compared with the Alfvén speed. The collisions between plasma and neutrons efficiently contribute to the wave damping, which is significantly reduced when the neutral species are completely driven with plasma by collisions. When the collisions become stronger, the resonances and cutoffs become weaker and may disappear. The species could couple tightly and act as a single fluid if the collisions among them are strong enough.

Side Effects of Damping Element Insertion in LCL Filter for DC/AC Inverter

The negative impacts or side effects of a damper circuit insertion in an LCL passive filter utilized to filter DC/AC inverters output voltage is presented in this paper. For comparative study, this paper discusses two damping configurations, namely series and parallel damping, as well as the LCL filter without damping element. Four criteria are used to explore the impacts of the damper circuits, i.e. their total harmonic distortions (THDs), the output voltage amplitude, the output power and the power efficiency. Theoretically and emphirically shown by previous studies, the damper can indeed reduce the peak resonance frequency of the filter in its frequency response curve. However, in any circumstance, it can potentially reduce the inverters power and efficiency, voltage output amplitude, and cannot improve its THD reduction. The analysis results have shown that the side effects depends also on the load conditions, which are different for each damping circuit configuration.

Design and Analysis of Second Order Passive Filters for Grid Connected Inverter with Series and Parallel Damping Resistors

Background/Objectives: Grid connected inverters are widely used to integrate renewable sources into the grid. The suitable power quality is required which can be either achieved using active or passive filters. This paper focuses on second order passive filters such as inductor capacitor (LC) and LC inductor (LCL) which can be used to attenuate harmonics for grid connect inverters. Methods/Statistical Analysis: To overcome the resonance of LCL filters passive damping 6-8 or active damping can be used. Active power filters are more expensive because of sensors and control systems additional cost. Passive damping strategies due to simple circuit and low cost are more favored. A LCL filter equipped with series or parallel resistor with a capacitor forms a LCL filter with damped resistor Addition of resistor to filter circuit will cause an increase in power losses. The peak resonance of LCL filter depends upon the value of resistor so select a value of resistor which decline peak resonance of filter. Findings: At resonance frequency they have some issues related to stability. LCL filter can be equipped with damping resistor but there are some power loss and introduction of voltage, current harmonic. Mathematical characteristics of passive filters such as LC, LCL, LCL with series resistor and LCL with parallel resistors are discussed in terms of effectiveness and stability in this paper. Application/Improvements: It is very useful for industrial application and power electronic converter.

Impact of relative phase shift on inward turbulent spreading

The relative cross-phase between density, temperature, and potential perturbations plays a major role in turbulent spreading and transport. Nonlinear Landau-Fluid simulations show that the electron wave-particle resonances provide a relatively strong parallel damping effect on the electron temperature perturbation and can induce a relative cross-phase shift of smaller than π∕2 angle between E × B velocity and the electron temperature perturbation for large electron temperature gradient, which yields a large spreading for electron. The relative phase for ions is about π∕2 and has no turbulent spreading effect on it. The inward turbulent spreading stops at the position where the radial turbulent correlation length is shorter than the magnetic surface spacing. The temperature pedestal height determines the energy loss due to the turbulent spreading.

Design and modelling of a fluid inerter

Mechanical spring-damper network performance can often be improved by the inclusion of a third passive component called the inerter. This ideally has the characteristic that the force at the terminals is directly proportional to the relative acceleration between them. The fluid inerter presented here has advantages over mechanical ball screw devices in terms of simplicity of design. Furthermore, it can be readily adapted to implement various passive network layouts. Variable orifices and valves can be included to provide series or parallel damping. Test data from prototypes with helical tubes have been compared with models to investigate parasitic damping effects of the fluid.

Modeling and Analysis of Radiated Emissions and Signal Integrity of Capacitively Loaded Printed Circuit Board Interconnections

This paper proposes methods for the modeling and analysis of signal integrity (SI) and radiated emission (RE) of capacitively loaded printed circuit board interconnections. Two techniques are considered for achieving a high level of SI, namely, source series damping and destination parallel damping. Low-order models are developed for the two methods, which enable a comparison of their SI performance and the identification of the key parameters that affect SI. Under certain conditions, the two methods are shown to have approximately the same SI performance. However, the two techniques can exhibit different characteristics in other respects, such as power dissipation, peak current, and RE. One particular characteristic that is studied in this paper is the performance with respect to far-field REs. A key objective of this paper is to develop a quantitative analysis and a qualitative understanding of the interplay between electromagnetic compatibility-electromagnetic interference and SI for the two damping techniques.

Steady-state and time-dependent modelling of parallel transport in the scrape-off layer

The one-dimensional fluid code SOLF1D has been used for modelling of plasma transport in the scrape-off layer (SOL) along magnetic field lines, both in steady state and under transient conditions that arise due to plasma turbulence. The presented work summarizes results of SOLF1D with attention given to transient parallel transport which reveals two distinct time scales due to the transport mechanisms of convection and diffusion. Time-dependent modelling combined with the effect of ballooning shows propagation of particles along the magnetic field line with Mach number up to M ≈ 1 and supersonic transport when plasma–neutral interactions are not present. Asymmetric heat and particle fluxes are analysed for a case with poloidally asymmetric radial outflow (ballooning) and for a radial outflow with parallel momentum (rotation). In addition, parallel damping of the density and electron temperature calculated in SOLF1D is compared with the approximative model used in the turbulence code ESEL both for steady-state and turbulent SOL. Dynamics of the parallel transport are investigated for a simple transient event simulating the propagation of particles and energy to the targets from a blob passing across the flux tube at the outboard midplane and for more complex time-dependent data provided by ESEL.

Modeling and simulation of direct output current control for LCL-interfaced grid-connected inverters with parallel passive damping

Conventional grid-connected inverters with a single inductor filter have the disadvantages of the large volume, high cost and system dynamic restriction. One of attractive solutions is to replace the first-order L filters with the third-order LCL filters. However, Instability phenomenon often appears in practical applications of the direct output current control for the LCL-interfaced grid-connected inverters. In order to clarify the point, the system control model is developed and the characteristic equation is deduced. Based on the Routh-Hurwitz stability criterion, a significant conclusion is reached that instability is inevitable in the direct output current control for the LCL-interfaced inverters without damping whatever P, PI or PID control is used. Conventional solutions are putting resistances in series with the LCL filter so as to improve the system stability margin, which is well known as the series passive damping. Nevertheless, the feasibilities of the parallel passive damping are rarely discussed. This paper reveals, for the first time, the precise-quantified relationship between the parallel resistances, control parameters and stability margins so as to provide a general design criterion for the direct output current control for the LCL-interfaced grid-connected inverters. And then the influence of nonlinear factors such as the switching and over modulation saturation on the validity of conclusions is discussed. In agreement with the theoretical analysis, the simulation results demonstrate that the parallel passive damping can effectively enhance the system stability of the direct output current control for the LCL-interfaced grid-connected inverters with the ultra-low extra losses.

Measurements of Inertial Limit Alfvén Wave Dispersion for Finite Perpendicular Wave Number

Measurements of the dispersion relation for shear Alfvén waves as a function of perpendicular wave number are reported for the inertial regime for which V{A}>V{Te}. The parallel phase velocity and damping are determined as k{ perpendicular} varies and the measurements are compared to theoretical predictions. The comparison shows that the best agreement between theory and experiment is achieved for a fully complex plasma dispersion relation which includes the effects of electron collisions.

A macroscopic ansatz to deduce the Hill relation

In this study, we derive the hyperbolic force–velocity relation of concentric muscular contraction, first formulated empirically by A.V. Hill in 1938, from three essential model assumptions: (1) the structural assembly of three well-known elements – i.e. active, parallel damping, and serial – fulfilling a force equilibrium, (2) the parallel damping coefficient explicitly depending on muscle force output and three parameters, and (3) the kinematic gearing ratio between active and serial element being assigned to a parameter. The energy source within the muscle represented by the force of the active element is an additional fifth parameter. As a result we find the Hill “constants” A and B as functions of our five model parameters. Using A and B values from literature on experimental data, we predict heat power release of our model. By calculating enthalpy rate and mechanical efficiency, we compare the model heat power to predictions from another Hill-type model, to Hill's original findings, and to findings from modern muscle heat measurements. We reconsider why the biggest share of heat rate during isometric contractions (maintenance heat) and the velocity-dependent heat rate during concentric contractions in addition to maintenance heat rate (shortening heat rate) may be traced back to the same mechanism represented by the kinematic gearing ratio. Namely, we suggest that the serial element transfers attachment–detachment fluctuations of actin–myosin crossbridges within one sarcomere to others in the same sarcomere and to those in parallel and in series. Numerically, in case of negligible passive muscular damping, we find the ratio between A and isometric force (relative A) to depend exclusively on the kinematic gearing ratio, whereas the maintenance heat rate scales with the square of relative A. Moreover, this mechanical coupling internal to the muscle fibres may also be behind the macroscopic force dependency of the overall parallel damping coefficient.