Resonance Poles Research Articles

High-Bandwidth Tracking Control of Piezoactuated Nanopositioning Stages via Active Modal Control

Due to the lightly damped resonance and intrinsic nonlinearities, it is difficult for the piezoactuated nanopositioning stage to realize high-bandwidth and high-accuracy control. To handle these limitations, in this work, a dual-loop control scheme based on state-feedback-based modal method is designed to both actively damp and stiffen the resonant mode and to suppress the effects of nonlinearities of the piezoactuated nanopositioning stage. In this scheme, the state-feedback-based modal controller is first designed in the inner loop to enlarge both the damping ratio and natural frequency of the first resonant mode. Then, a proportional–integral (PI) controller is utilized in the outer loop for eliminating the tracking errors caused by other disturbances and nonlinearities including hysteresis and creep. To maximize the control bandwidth of system under the proposed dual-loop scheme, an optimization method is thus proposed for simultaneously tuning the parameters of the inner and the outer loop controllers. Finally, to validate the proposed dual-loop control scheme, comparative experiments are carried out on a piezoactuated nanopositioning stage. Results demonstrate that the proposed control scheme improves the bandwidth of the system from 497 Hz (with PI control) and 1543 Hz (with a commonly used positive acceleration, velocity, and position damping control and a PI controller) to 6546 Hz, which is 664 Hz larger than the first resonant frequency of the original system, validating the effectiveness of the proposed dual-loop scheme on high-bandwidth control. Note to Practitioners—The demand of high-bandwidth and high-accuracy piezoactuated nanopositioning stages increases rapidly. However, the lightly damped resonance of the mechanism and the intrinsic nonlinearities of the piezoelectric actuator limit the tracking performance of the stage. A dual-loop control structure is adopted in this work to improve the tracking performance of the nanopositioning stage. Different from most of the vibration control methods proposed in the literature which aimed only at improving the damping ratio, a state-feedback-based modal controller is designed in the inner-loop for improving both the damping ratio and the stiffness of the system. This task is realized by re-placing the resonant poles of the system to the optimized location. The outer-loop controller adopts the high-gain PI control for eliminating the tracking errors. More importantly, in order to realize the high-bandwidth and high-accuracy control, a numerical optimization method is proposed for simultaneously tuning the parameters of the controllers in inner and outer loops. The controller design is simple, and it can be applied to other systems with second or higher order in which the first resonant mode dominates the system dynamics.

Soft dipole resonance in neutron-rich 8He

Abstract In neutron-rich 8He, we study the soft dipole resonance, which is regarded as a dipole oscillation of four valence neutrons against the 4He core, and its effect on the low-energy electric dipole strength with a 4He+n+n+n+n five-body cluster model. This work is an extended study of an earlier letter [T. Myo and K. Katō, Phys. Rev. C 106, L021302 (2022)]. The five-body unbound 1− states of 8He are obtained with complex-energy eigenvalues by using the complex scaling method and the dipole strength is calculated in terms of the complex-scaled Green’s function. Two kinds of dominant excitation modes are confirmed in the dipole strength below 20 MeV of the excitation energy. The strengths below 10 MeV are exhausted by the 7He+n channel, which sequentially decays to 6He+n+n. Above 10 MeV, the strengths arise from the soft dipole mode of four neutrons (4n) oscillating against the 4He core. We further explore the possibility of the soft dipole resonance for this state by carefully searching for the resonance pole and finally predict the corresponding resonance with the excitation energy of 14 MeV and the decay width of 21 MeV. The soft dipole resonance exhausts about half of the dipole strength in the relative motion between the 4He core and 4n.

Pseudoscalar charmonium pair interactions via the Pomeron exchange mechanism

Following the observation of the fully-heavy tetraquark candidates $X(6900)$ and possible $X(6300)$ in the di-$J/\psi$ spectrum by the LHCb Collaboration, we investigate the near-threshold dynamics of the pseudoscalar quarkonium pairs in a coupled-channel approach in the di-$\eta_c$ channel. We show that the Pomeron exchange mechanism should be a general dynamics in the near-threshold heavy quarkonium pair interactions. In the di-$\eta_c$ channel, a coupled-channel system involving the di-$\eta_c$, $\eta_c$-$\eta_c(2S)$ and di-$\eta_c(2S)$ interactions can be established. Their $S$-wave interactions near threshold via the Pomeron exchange potential can produce near-threshold resonance poles similar to the di-$J/\psi$, $J/\psi$-$\psi(2S)$ and di-$\psi(2S)$ coupled channels. Interestingly, we find here that the pole positions are more shifted to the corresponding thresholds and turn out to be different from those seen in the di-$J/\psi$ spectrum. Taking into account the suppression of the heavy quark spin flips in the transitions between two vector and two pseudoscalar heavy quarkonium systems, the enhancements in the di-$\eta_c$ spectrum should be different from those seen in the di-$J/\psi$ channel. Experimental study of the di-$\eta_c$ channel should be useful for disentangling the nature of the fully-heavy tetraquark systems.

Research on auxiliary resonant commutated pole inverter for driving brushless DC motor

The brushless DC motor is generally used in small satellite flywheel systems due to its good control performance and structure robustness. However, its driving inverter still suffers from hard-switching that leads to higher loss and larger heatsink requirement. The resulting low power density and EMI problems have been a great challenge for the space satellite applications. This paper describes a novel auxiliary resonant commutated pole inverter (ARCPI) for driving the brushless DC motor. An inserted inductor is controlled to resonant with the buffer capacitor of the inverter’s lower arm switches; a resonant capacitor is paralleled with the inductor branch as well. Zero-current switching and zero-voltage switching conditions are therefore realized for the switches of the entire circuit. The reverse recovery problem of diodes are also avoided by zero current turning-off. The working states of the proposed novel ARCPI inverter are analyzed and the mathematical model for every state is established. Furthermore, the parameter design is discussed to provide soft-switching conditions. Finally, the proposed ARCPI inverter is applied for driving a brushless DC motor. A voltage/current double closed control loop is designed for the motor controller and the system simulation setup is built. The simulation results prove that soft-switching operation is realized for all of the switches; the proposed inverter is effective for driving brushless DC motors. Besides, the motor current fluctuation decreases by 45.7%. The motor torque and the motor speed present with good control performance as well.

Mitigation of Motor Overvoltage in SiC-Based Drives Using Soft-Switching Voltage Slew-Rate ($dv/dt$) Profiling

In silicon carbide (SiC) device based motor drives, the high-voltage slew-rate ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> ) associated with the fast-switching transitions results in excessive motor overvoltage, due to the reflected wave phenomenon, which increases the motor winding insulation stress and causes premature failure while raising electromagnetic interference (EMI) problems. This article proposes a soft-switching voltage slew-rate profiling approach to mitigate the motor overvoltage in SiC-based cable-fed drives. The proposed approach optimizes the rise/fall time of the output voltage according to the cable length, without altering the switching speed of the SiC devices. Since increasing the switching rise/fall time using conventional approaches, such as increasing the gate resistance, results in an increased switching power loss, the proposed profiling approach is implemented using a soft-switching inverter. The optimum rise/fall time that can significantly mitigate the overvoltage is derived using frequency- and time-domain analysis. The auxiliary resonant commutated pole inverter (ARCPI) is adopted as an example of the soft-switching inverter to experimentally verify the proposed slew-rate profiling approach for the overvoltage mitigation. The analysis and experimental results show that the motor overvoltage is fully mitigated when the output voltage rise/fall time is set as the cable antiresonance period, i.e., four times of the wave transmission time along the cable. Furthermore, the slew-rate profiling approach along with the ARCPI reduces the switching loss and improves the EMI performance at the high-frequency region, compared with the conventional hard-switching converter. Specifically, the maximum efficiency of the ARCPI is about 99%.

Autoionization decay and radiative decay for doubly excited 1Po resonance states in H− and Ps− ions

The autoionization decay (AD) and radiative decay (RD) for doubly excited 1Po resonance states in H− and Ps− are studied using correlated exponential wavefunctions based on the variational methods. To trace the resonance poles from Ps− to H−, the nuclear mass is varied from one unit to infinitely heavy. Resonance positions, widths related to AD rates, oscillator strengths, the ratios of oscillator strengths between the Feshbach and shape resonances (FSR), RD rates for the lowest two FSR in the 1Po spectrum, are reported. Few results are new, and others are comparable with the available theoretical and experimental data.

Numerical Regge pole analysis of resonance structures in state-to-state reactive differential cross sections

This is the third (and the last) code in a collection of three programs [Sokolovski et al. (2011), Akhmatskaya et al. (2014)] dedicated to the analysis of numerical data, obtained in an accurate simulation of an atom-diatom chemical reaction. Our purpose is to provide a detailed description of a FORTRAN code for complex angular momentum (CAM) analysis of the resonance effects in reactive angular scattering [for CAM analysis of integral reactive cross sections see [Akhmatskaya et al. (2014)]. The code evaluates the contributions of a Regge trajectory (or trajectories) to a differential cross section in a specified range of energies. The contribution is computed with the help of the methods described in [Dobbyn et al. (1999), Sokolovski and Msezane (2004), Sokolovski et al. (2007)]. Regge pole positions and residues are obtained by analytically continuing S-matrix element, calculated numerically for the physical integer values of the total angular momentum, into the complex angular momentum plane using the PADE_II program [Sokolovski et al. (2011)]. The code represents a reactive scattering amplitude as a sum of the components corresponding to a rapid “direct” exchange of the atom, and the various scenarios in which the reactants form long-lived intermediate complexes, able to complete several rotations before breaking up into products. The package has been successfully tested on the representative models, as well as the F + H2→ HF+H benchmark reaction. Several detailed examples are given in the text. Program summaryProgram title:DCS_ReggeCPC Library link to program files:https://doi.org/10.17632/gf4gm82n6m.1Licensing provisions: GPLv3Programming language:FORTRAN 90Supplementary material:PADE_II, MPFUN and QUADPACK packages, validation suites, script files, input files, readme files, Installation and User GuideNature of problem: The package extracts the positions and residues of resonance poles from numerical scattering data supplied by the user. This information is then used for the analysis of resonance structures observed in reactive differential cross sections.Solution method: The S-matrix element is analytically continued in the complex plane of either energy or angular momentum with the help of Padé approximation of type II. Resonance Regge trajectories are identified and their contributions to a differential cross section are evaluated at different angles and energies.Additional comments including restrictions and unusual features: Use of multiple precision MPFUN package.

A Synchronous Auxiliary Resonant Commutated Pole Soft-Switching Inverter With Improved Load Adaptability

To realize a soft-switching inverter with small volume and high efficiency, a synchronous auxiliary resonant commutated pole (SARCP) soft-switching inverter with improved load adaptability is proposed, which only contains two auxiliary inductors. In one switching cycle, all commutation processes can be synchronously assisted by an auxiliary inductor. Soft switching is achievable for all switches of the SARCP inverter. Compared with the auxiliary resonant commutated pole (ARCP) inverter, the SARCP inverter has improved load adaptability, especially in the light load current condition, which is beneficial to reduce the total power loss and the dc-link capacitance. The equivalent circuits of the SARCP inverter are given under different operation modes. The operation principle, soft-switching implementation conditions, parameter optimization design methods, and the characteristics of the SARCP inverter are analyzed. Finally, simulation and experimental results verify the effectiveness of the SARCP inverter.

An Efficient Three-Phase Resonant Pole Inverter With Low Conduction Loss of Switching Devices

A novel three-phase resonant pole inverter is put forward in the interest of high-efficiency. When the auxiliary circuit is in the working condition, soft-switching can be realized to reduce switching loss, bringing about the efficiency improvement. In particular, the current flowing through switches of the novel inverter is no more than the load current, which is a distinct advantage over other three-phase resonant pole inverters. In addition, the distinct advantage is in favor of low conduction loss of switches, enhancing the efficiency of the inverter. Modes of operation in a switching cycle are discussed in the brief. The experimental results imply that switches realize soft-switching. Besides, the efficiency of the novel inverter reaches 98.5% at rated output power of 3kW. Hence, the novel soft-switching inverter has efficiency advantage in comparison with other similar inverters.

An Efficient Resonant Pole Inverter With the Synchronous Switch Mode Control

A novel resonant pole inverter is proposed for the sake of the efficient operation of the three-phase inverter. When the auxiliary unit works, the main switches can accomplish zero-current turn-on and zero-voltage turn-off. Meanwhile, the auxiliary switches can accomplish zero-current turn-on and zero-current turn-off. In particular, the main switches and the auxiliary switches can accomplish the synchronous switching in each switching cycle, which can simplify the control method of the inverter. This brief discusses the operating stages of the inverter in one switching cycle and selection rules of parameters. The experiment confirms that the switching devices accomplish soft-switching. The efficiency at rated output power 3kW reaches 98.3%, which implies the efficiency advantage over the hard-switching inverter. It can be concluded that the presented inverter in this brief has important reference to the research of the high-performance inverter.

Auxiliary resonant commutated pole soft-switching inverter with simple topology

Auxiliary resonant commutated pole soft-switching inverter with simple topology

Identifying Resonant Poles by Visual Inspection of Pole-Zero Plots

We derive the s- and z-plane pole regions for continuous-time and discrete-time LTI systems to yield resonance. In this way, resonance can be identified by visual inspection of the pole-zero plot, without the need for calculations.

Emergence of ghost in once-subtracted on-shell unitarization in glueball-glueball scattering

We investigate the scattering of two scalar glueballs in pure YM theory, using the well known dilaton potential. We perform the calculations considering a glueball mass of about mG ≈ 1.7 GeV, as predicted by lattice QCD. We begin with the tree-level theory, but the question about the presence of a bound state needs a deeper study to be answered. Thus we unitarize the theory through a self energy loop function consisting of a single subtraction at the single glueball resonance pole. We show that this choice is inconsistent as it leads to the emergence of a ghost-like state with negative norm. This problem is related with the sign of the coefficient in the first order term of the expansion of the reverse unitarized amplitude. We briefly discuss the solution which consists of an additional subtraction in the loop function, as presented in Eur.Phys.J.C 82 (2022) 5, 487.

Enabling Resonant Commutated Pole in Parallel Power FET Bridge Legs

To meet the requirements of higher current ratings and lower thermal impedances, paralleling power field-effect transistor (FET) discretes or modules is often a cost-effective or even an unavoidable solution. While paralleling FETs allows for a significant reduction in conduction loss, the switching loss is increased in hard-switching applications. This article proposes a generic soft-switching modulation scheme for parallel power FET bridge legs. Part of the paralleled FET legs is chosen as an auxiliary leg that is turned on prior to the remaining main legs. A resonant commutated pole (RCP) mode is then created, which enables the high-side FET of the auxiliary leg to achieve zero-current switching (ZCS) or quasi-ZCS and the remaining FETs to achieve zero-voltage switching. Thus, we can significantly reduce the switching loss that normally dominates the total power loss of high-frequency hard-switching converters particularly at partial and light loads. Experimental results from three parallel GaN high-electron-mobility transistor legs validate the effectiveness of this RCP-enabled solution in reducing switching losses and improving power conversion efficiencies. This article is accompanied by supplementary JIF and PDF files demonstrating the operational details of the RCP mode.

Robust Active Damping Strategy for DFIG Wind Turbines

Doubly fed induction generators (DFIGs) with an LCL filter are widely used for wind power generation. In these energy conversion systems, there is an interaction between the grid-side converter (GSC) and the rotor-side converter (RSC) control loops, the generator and the LCL filter that must be properly modeled. Such interaction between the GSC and the RSC proves to have a significant influence on the stability. Several active damping (AD) methods for grid-connected converters with an LCL filter have been proposed, nevertheless, the application of these techniques to a DFIG wind turbine is not straightforward, as revealed in this article. To achieve a robust damping irrespective of the grid inductance, this article proposes an AD strategy based on the capacitor current feedback and the adjustment of the control delays to emulate a virtual impedance, in parallel with the filter capacitor, with a dominant resistive component in the range of possible resonance frequencies. This work also proves that, by applying the AD strategy in both converters simultaneously, the damping of the system resonant poles is maximized when a specific value of the grid inductance is considered. Experimental results show the interaction between the GSC and the RSC and validate the proposed AD strategy.

An Ignored Culprit of Harmonic Oscillation in LCL-Type Grid-Connected Inverter: Resonant Pole Cancelation

Resonant pole cancelation is usually adopted in the current control or active damping to tackle the filter resonance in the LCL-type grid-connected inverter. However, its potential impact on the system stability has not been adequately assessed. This article provides a comprehensive investigation on three typical control schemes that utilize resonant pole cancelation. An important finding is drawn that the resonant pole cancelation violates the so-called internal stability, which can give rise to the undesired harmonic oscillation in grid current. From the physical insights, it is revealed that the resonant pole cancelation does not essentially eliminate the LCL resonance but merely “hide” it in the system, which can still be triggered and, thereby, turns into the culprit of the harmonic oscillation. The theoretical expectation is validated by the simulation and experimental results.

FRF estimation using multiple kernel-based regularisation

Nonparametric kernel-based modelling of dynamical systems offers important advantages over other nonparametric techniques; the estimate is a continuous function, the model complexity is continuously tuneable, and stability, causality and smoothness are imposed on the impulse response estimate. However, for lightly damped systems, most of the existing kernel-based approaches for estimating the impulse- or frequency response function fail because classical kernels are not appropriate for describing lowly damped resonances. Smoothness is imposed on the entire frequency axis with the diagonal correlated or stable spline kernel, with as a result that resonances cannot be captured well. By introducing the superposition of different kernels, carrying prior knowledge about the resonant poles of the system, we make the kernel-based modelling of lightly-damped systems possible with high-accuracy. We use a frequency domain local rational modelling technique as preprocessing step to determine the most dominant poles, and include these as prior knowledge in the kernels. The performance of the new kernel is demonstrated on a highly resonating simulated system and compared to the state of the art nonparametric frequency domain approaches.

Nature of X(6900) and its production mechanism at LHCb

We show that the Pomeron exchanges play a unique role in vector charmonium scatterings. Such a mechanism can provide a natural explanation for the nontrivial structures in the di-J/ψ spectrum observed by the LHCb Collaboration. The narrow structure X(6900), as a dynamically generated resonance pole, can arise from the Pomeron exchanges and coupled-channel effects between the J/ψ-J/ψ, J/ψ-ψ(2S) scatterings. A pole structure near the di-J/ψ threshold is also found. Meanwhile, we predict that X(6900) can produce significant threshold enhancement in the J/ψ-ψ(2S) energy spectrum which can be searched for at LHCb.

Self-consistent O(4) model spectral functions from analytically continued functional renormalization group flows

In this paper we explore practicable ways for self-consistent calculations of spectral functions from analytically continued functional renormalization group (aFRG) flow equations. As a particularly straightforward one we propose to include parametrizations of self-energies based on explicit analytic one-loop expressions. To exemplify this scheme we calculate the spectral functions of pion and sigma meson of the $O(4)$ model at vanishing temperature in the broken phase. Comparing the results with those from previous aFRG calculations, we explicitly demonstrate how self-consistency at all momenta fixes the tight relation between particle masses and decay thresholds. In addition, the two-point functions from our new semianalytic FRG scheme have the desired domain of holomorphy built in and can readily be studied in the entire cut-complex frequency plane, on physical as well as other Riemann sheets. This is very illustrative and allows, for example, to trace the flow of the resonance pole of the sigma meson across an unphysical sheet. In order to assess the limitations due to the underlying one-loop structure, we also introduce a fully self-consistent numerical scheme based on spectral representations with scale-dependent spectral functions. The most notable improvement of this numerically involved calculation is that it describes the three-particle resonance decay of an off-shell pion, ${\ensuremath{\pi}}^{*}\ensuremath{\rightarrow}\ensuremath{\sigma}\ensuremath{\pi}\ensuremath{\rightarrow}3\ensuremath{\pi}$. Apart from this further conceptual improvement, overall agreement with the results from the considerably simpler semianalytic one-loop scheme is very encouraging, however. The latter can therefore provide a sound and practicable basis for self-consistent calculations of spectral functions in more realistic effective theories for warm and dense matter.

Robust L Approximation of an LCL Filter Type Grid-Connected Inverter Using Active Disturbance Rejection Control under Grid Impedance Uncertainty

High-order filters, such as LCL, are more commonly employed in grid-connected inverters (GcIs) as an interference element for the better attenuation of switching harmonics. However, LCL filters may have resonance poles and antiresonance zeros in the frequency response with inverter side current. This may affect the stability of the system and limit the control bandwidth with the simple single-loop PI control. This becomes severe with the introduction of grid impedance due to the large distance between renewable energy sources and the power grid. To mitigate this effect, active damping and sensorless damping is preferred with pre-information about grid impedance. In this paper, linear active disturbance rejection control (ADRC) is introduced, first to L filter type GcI and later extended to LCL filter type GcIs with minimum modification. From the frequency analysis, it is shown that the characteristics of the proposed control scheme remain the same even with a change in filter order and grid impedance. The resonance poles and antiresonance zeros in the LCL filter are compensated via the pole–zero cancelation technique. In addition to this, the preserve bandwidth, simple control design, and decoupled current control are also achieved with the proposed method. The robustness of the proposed method is compared with the single-loop PI control under different filter types and grid impedance uncertainty through MATLAB simulation and experimental outcomes.