Mass Uncertainty Research Articles

Identification, mass, and age of primary red clump stars from spectral features derived with the LAMOST DR7

ABSTRACT Although red clump (RC) stars are easy to identify due to their stability of luminosity and colour, about 20–50 per cent are actually red giant branch (RGB) stars in the same location on the HR diagram. In this paper, a sample of 210 504 spectra for 184 318 primary RC (PRC) stars from the LAMOST DR7 is identified, which has a purity of higher than 90 per cent. The RC and the RGB stars are successfully distinguished through LAMOST spectra (R ∼ 1800 and signal-to-noise ratio >10) by adopting the XGBoost ensemble learning algorithm, and the secondary RC stars are also removed. The SHapley Additive exPlanations (SHAP) value is used to explain the top features that the XGBoost model selected. The features are around Fe5270, MgH & Mg Ib, Fe4957, Fe4207, Cr5208, and CN, which can successfully distinguish RGB and RC stars. The XGBoost is also used to estimate the ages and masses of PRC stars by training their spectra with Kepler labelled asteroseismic parameters. The uncertainties of mass and age are 13 and 31 per cent, respectively. Verifying the feature attribution model, we find that the age-sensitive element XGBoost is consistent with the literature. Distance of the PRC stars is derived by KS absolute magnitude calibrated by Gaia EDR3, which has an uncertainty of about 6 per cent and shows the stars mainly located at the Galactic disc. We also test the XGBoost with R ∼ 250, which is the resolution of the Chinese Space Station Telescope under construction; it is still capable of finding sensitive features to distinguish RC and RGB.

Design Method of Tuned Mass Damper by Linear-Matrix-Inequality-Based Robust Control Theory for Seismic Excitation

AbstractThis paper presents a new design method based on a robust-control strategy in the form of a linear matrix inequality (LMI) approach for a passive tuned mass damper (TMD), which is one of the common passive-control devices for structural vibration control. To apply the robust control theory, we first present an equivalent expression that describes a passive TMD as an active TMD. Then, some LMI-based condition is derived that not only guarantees robust stability but also allows us to adjust the robust H∞ performance. In particular, this paper considers the transfer function from a seismic-wave input to structural responses. Unlike other methods, this method formulates the problem to be a convex optimization problem that ensures a global optimal solution and considers uncertainties of mass, damping, and stiffness of a structure for designing a TMD. Numerical example uses both a single-degree-of-freedom (SDOF) and 10DOF models and seismic waves. The simulation results demonstrated that the TMD that is designed by the presented method has good control performance even if the structural model includes uncertainties, which are the modeling errors.

Statistical analysis of the human middle ear mechanical properties.

Many experimental data on the human middle ear (ME) mechanics and dynamics can be found in the literature. Nevertheless, discussions about the uncertainties of these data are scarce. The present study compiles experimental data on the mechanical properties of the human ME. The summary statistics of mean and standard deviation of the data were collected and the coefficients of variation were computed and pooled. Moreover, the linear correlation and distribution were assessed for the ossicles' mass. Results show that, generally, the uncertainties of the stiffness properties of the tympanic membrane, ligaments, and tendons are larger than the uncertainties of the ossicles' mass. In addition, the uncertainties of the ME response vary across frequency. The vibration measures, such as the stapes' velocity normalized by the sound pressure at the tympanic membrane, are more uncertain than ME input impedance and reflectance. It is expected that the results presented in this study will provide the basis for the development of probabilistic models of the human ME.

The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER). III. The Mass Function of Young Stellar Clusters in M33

Abstract We measure the star cluster mass function (CMF) for the Local Group galaxy M33. We use the catalog of stellar clusters selected from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region survey. We analyze 711 clusters in M33 with 7.0 < log ( Age / yr ) < 8.5 , and log(M/M ⊙) > 3.0 as determined from color–magnitude diagram fits to individual stars. The M33 CMF is best described by a Schechter function with power-law slope α = − 2.06 − 0.13 + 0.14 , and truncation mass log(M c /M ⊙) = 4.24 − 0.13 + 0.16 . The data show strong evidence for a high-mass truncation, thus strongly favoring a Schechter function fit over a pure power law. M33's truncation mass is consistent with the previously identified linear trend between M c , and star formation rate surface density, ΣSFR. We also explore the effect that individual cluster mass uncertainties have on derived mass function parameters, and find evidence to suggest that large cluster mass uncertainties have the potential to bias the truncation mass of fitted mass functions at the 1σ level.

Uncertainties associated with the backward integration of dwarf satellites using simple parametric potentials

ABSTRACT In order to backward integrate the orbits of Milky Way (MW) dwarf galaxies, much effort has been invested in recent years to constrain their initial phase-space coordinates. Yet equally important are the assumptions on the potential that the dwarf galaxies experience over time, especially given the fact that the MW is currently accreting the Large Magellanic Cloud (LMC). In this work, using a dark-matter-only zoom-in simulation, we test whether the use of common parametric forms of the potential is adequate to successfully backward integrate the orbits of the subhaloes from their present-day positions. We parametrize the recovered orbits and compare them with those from the simulations. We find that simple symmetric parametric forms of the potential fail to capture the complexities and the inhomogeneities of the true potential experienced by the subhaloes. More specifically, modelling a recent massive accretion like that of the LMC as a sum of two spherical parametric potentials leads to substantial errors in the recovered parameters of the orbits. These errors rival those caused due to (a) a 30 per cent uncertainty in the virial mass of the MW and (b) not modelling the potential of the recently accreted massive satellite. Our work suggests that (i) the uncertainties in the parameters of the recovered orbits of some MW dwarfs may be underestimated and that (ii) researchers should characterize the uncertainties inherent to their choice of integration techniques and assumptions of the potential against cosmological zoom-in simulations of the MW, which include a recently accreted LMC.

An Adaptive Nonsingular Fast Terminal Sliding Mode Controller for Dynamic Walking of a 5-Link Planar Biped Robot in Both Single and Double Support Phases

This paper aims to design an improved adaptive nonsingular fast terminal sliding mode controller for a fully actuated planar biped robot with five degrees of freedom in the single support (SSP) and double support (DSP) phases in the presence of external perturbation and uncertainties. A new sliding surface was proposed to avoid singularities and the chattering phenomenon. The proposed controller guarantees fast convergence of error signals in finite time. Unlike similar studies, the presented method considers a whole cycle of one step of walking, including SSP, double impact, and DSP phases. Also, the proposed approach does not require a predefined upper limit to estimate uncertainty using an adaptive law. Notably, dynamic walking was preferred over static walking to achieve more similarity to human walking. The designed trajectories were determined according to the position of the waist and swinging legs ankle, which could then be converted into the position of joints using inverse kinematics equations. The simulation results were used to approve the proposed controller's fast and robust tracking performance in the presence of external disturbances, mass, and inertia uncertainties without predefined knowledge of their upper bounds.

비선형 자기부상시스템의 저차 외란관측기 제어기 설계에 대한 연구

In this paper, we study on a reduced-order disturbance observer (DOB) controller for nonlinear Electro-magnetic suspension (EMS) systems with mass uncertainty. Since it is rather complicated to design a nonlinear DOB controller for nonlinear systems, this paper aims to design a linear DOB controller for nonlinear systems. Since noise suppression of reduced-order DOB controller is superior to that of standard DOB controller, this paper focuses on the reduced-order DOB controller. Using the case study of nonlinear EMS systems, it is found that the followings should be carefully chosen for the design of reduced-order DOB controller: high-frequency gain of the nominal model, pole and zero location of the nominal model, selection of Q-filter, and the choice of primary controller.

Particle configurations in the NNK̅ system

Three-body AAB model for the NNK(snn = 0) kaonic cluster is considered based on the configuration space Faddeev equations. Within a singlechannel approach, the difference between masses of nucleons and kaons and the charge independence breaking of nucleon-nucleon interaction are taken into consideration. We definite the particle configurations in the system according to the particle masses and pair potentials. There are two sets of the particle configurations, ppK, npK and nnK°, npK, charged and neutral. The three-body calculations are performed by applying NN and NK phenomenological isospin-dependent potentials. The mass and energy spectra related to the particle configurations are presented. We evaluate the mass and energy uncertainties for the NNK model. An analogy to NNN model for the H and He nuclei is proposed.

Robustness Analysis for Adaptive Model Predictive and Sliding Mode Controllers Regulating Longitudinal Tire Slip Ratio

This study aims to evaluate the robustness of Adaptive Model Prediction Controllers (AMPC) and First Order Sliding Mode Controllers (FOSMC) facing modelling uncertainties or external disturbances when used to track longitudinal tire slip ratio. Changing road conditions create uncertainties in the friction coefficient of the tire-road interface, and the uncertainty of mass is caused by over/under loads on the nominal mass of the vehicle. the external perturbations are generally linked to the angle of inclination of the road. The efficiency of the controllers, in terms of ensuring the minimum braking time in the face of uncertainties and perturbations, is evaluated by numerical simulation and detailed comparison.

Robust Adaptive Control Allocation Schemes for Overactuated Underwater Vehicles under Actuator Faults

In this paper, we investigate the fault-tolerant path following control problem for an overactuated underwater vehicle subject to input saturation and rate of change constraints, actuator faults and parametric (mass and inertia) uncertainty. A robust adaptive control allocation strategy is proposed capable to reconfigure the distribution of the control effort among the remaining healthy actuators in the case some of them failed. The online estimation of actuators' effectiveness and bias fault parameters is integrated with the control allocation and reconfiguration unit. The robustness and performance of the scheme are shown by evaluating the results of simulations and pool experiments of different path-following control problems using overactuated underwater vehicles.

An adaptive sliding mode fault-tolerant control for semi-active suspensions with magnetorheological dampers based on T-S fuzzy vehicle models

This paper investigates an improved adaptive sliding mode fault-tolerant control strategy for a magnetorheological semi-active suspension system with parametric uncertainties and actuator faults. Using the experimental data collected by a quarter-vehicle test rig, an adaptive-network-based fuzzy inference system is employed to establish a learning-based magnetorheological damper model firstly. The Takagi-Sugeno fuzzy approach is introduced to deal with the uncertainties of sprung mass and pitch rotary inertia and then the corresponding Takagi-Sugeno faulty semi-active suspension system is constructed. An adaptive sliding mode fault-tolerant controller is proposed, in which the magnetorheological damper fault gain is observed by the designed estimation law, and the asymptotical stability of the system is further analyzed. Finally, numerical simulation tests are conducted to demonstrate the effectiveness of the designed control scheme.

Cooperative Locomotion Via Supervisory Predictive Control and Distributed Nonlinear Controllers

Abstract This paper presents a hierarchical nonlinear control algorithm for the real-time planning and control of cooperative locomotion of legged robots that collaboratively carry objects. An innovative network of reduced-order models subject to holonomic constraints, referred to as interconnected linear inverted pendulum (LIP) dynamics, is presented to study cooperative locomotion. The higher level of the proposed algorithm employs a supervisory controller, based on event-based model predictive control (MPC), to effectively compute the optimal reduced-order trajectories for the interconnected LIP dynamics. The lower level of the proposed algorithm employs distributed nonlinear controllers to reduce the gap between reduced- and full-order complex models of cooperative locomotion. In particular, the distributed controllers are developed based on quadratic programing (QP) and virtual constraints to impose the full-order dynamical models of each agent to asymptotically track the reduced-order trajectories while having feasible contact forces at the leg ends. The paper numerically investigates the effectiveness of the proposed control algorithm via full-order simulations of a team of collaborative quadrupedal robots, each with a total of 22 degrees-of-freedom. The paper finally investigates the robustness of the proposed control algorithm against uncertainties in the payload mass and changes in the ground height profile. Numerical studies show that the cooperative agents can transport unknown payloads whose masses are up to 57%, 97%, and 137% of a single agent's mass with a team of two, three, and four legged robots.

Enhanced Sliding Mode Control for a Nonlinear Active Suspension Full Car Model

This paper delivers findings on optimal robust control studies of nonlinear full car models. A nonlinear active suspension full car model is used, which considers the dynamic of a hydraulic actuator. The investigation on the benefit of using Sliding Mode Control (SMC) structure for the effective trade-off between road handling. The design of SMC in the chassis/internal subsystem is enhanced by modifying a sliding surface based on Proportional-Integral-Derivatives (PID) with the utilization of particle swarm optimization (PSO) algorithm in obtaining the best optimum value of control parameters. The switching control is designed through the Lyapunov function, which includes the boundedness of uncertainties in sprung masses that can guarantee the stability of the control design. The responses of the proposed controller have improved the disturbance rejection up to 60% as compared to the conventional SMC controller design and shown the high robustness to resist the effect of varying the parameter with minimal output deviations. The study proved that the proposed SMC scheme offers an overall effective performance in full car active suspension control to perform a better ride comfort as well as the road handling ability while maintaining a restriction of suspension travel. An intensive computer simulation (MATLAB Simulink) has been carried out to evaluate the effectiveness of the proposed control algorithm under various road surface conditions.

Mass measurements of Ga60–63 reduce x-ray burst model uncertainties and extend the evaluated T=1 isobaric multiplet mass equation

We report precision mass measurements of neutron-deficient gallium isotopes approaching the proton drip line. The measurements of Ga60–63 performed with the TITAN multiple-reflection time-of-flight mass spectrometer provide a more than threefold improvement over the current literature mass uncertainty of Ga61 and mark the first direct mass measurement of Ga60. The improved precision of the Ga61 mass has important implications for the astrophysical rp process, as it constrains essential reaction Q values near the Zn60 waiting point. Based on calculations with a one-zone model, we demonstrate the impact of the improved mass data on prediction uncertainties of x-ray burst models. The first-time measurement of the Ga60 ground-state mass establishes the proton-bound nature of this nuclide, thus constraining the location of the proton drip line along this isotopic chain. Including the measured mass of Ga60 further enables us to extend the evaluated T=1 isobaric multiplet mass equation up to A=60.Received 14 August 2021Revised 22 October 2021Accepted 16 November 2021DOI:https://doi.org/10.1103/PhysRevC.104.065803©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBinding energy & massesCoulomb energies & analogue statesModels based on symmetriesNuclear astrophysicsNuclear physics of explosive environmentsNuclear reactionsNucleosynthesis in explosive environmentsShell modelProperties59 ≤ A ≤ 89MassTechniquesMass spectrometryTime-of-flight mass spectrometryNuclear Physics

Stabilization of electrostatic MEMS resonators using a stochastic optimal control

Noise-induced motions are a significant source of uncertainty in the response of electrostatic MEMS where electrical and mechanical sources contribute to noise and can result in sudden and dramatic loss of stability. In this manuscript, we present an analysis for the stabilization of an electrostatically actuated MEMS resonator in the presence of noise processes using a stochastic optimal control scheme. A stochastic lumped-mass model that accounts for the uncertainty in mass, mechanical restoring force, bias voltage, and AC voltage amplitude of the resonator is presented. The Ito^ equations, describing the averaged modulations of the resonator's total energy and phase difference, are obtained via the stochastic averaging of energy envelope. The stochastic optimal control law aiming at minimization the pull-in probability of the resonator is determined via the stochastic dynamic programming equations associated with the Ito^ equations. We show that the resulting stochastic optimal feedback control, with a careful selection of its control gain, can be used to suppress the noise-activated pull-in instability of the disturbed resonator. The impact of the time delay inherent in the feedback control input on the control effectiveness is investigated. In addition, the control scheme also shows superior performance in counteracting the deterministic pull-in instability of the resonator operating in the dynamic pull-in frequency band. Good agreement between the theoretical results and numerical simulation is demonstrated.

Robust Cooperative Control of Networked Train Platoons: A Negative-Imaginary Systems’ Perspective

By virtue of the wide implementation of communication-based train control (CBTC) systems and moving-block signaling systems, cooperative control for trains shows great potential in improving line utilization, passenger comfort, and operation flexibility. However, the operation of train platoons faces great challenges induced by model uncertainties, unpredictable resistances, and time-varying disturbances. To address these problems, consensus-based robust cooperative control schemes are presented in this article for both homogeneous and heterogeneous train platoons. Taking the physical connection between carriages into consideration, each train in the platoon is modeled as a negative-imaginary (NI) system, and the NI property is rigorously proved in this article. In the foundation of cooperative control theories of NI systems, robust strictly NI controllers considering the network topology are utilized to track a predefined motion reference. The proposed controllers are robust to both mass uncertainties and external disturbances. Moreover, the line utilization for the railway system and the ride comfort for the passengers are improved using the proposed control schemes. Numerical simulations are given to showcase the effectiveness and robustness of the proposed controllers.

Improved Constraints on the Initial-to-final Mass Relation of White Dwarfs Using Wide Binaries

Abstract We present observational constraints for the initial-to-final mass relation (IFMR) derived from 11 white dwarfs (WDs) in wide binaries (WBs) that contain a turnoff/subgiant primary. Because the components of WBs are coeval to a good approximation, the age of the WD progenitor can be determined from the study of its wide companion. However, previous works that used WBs to constrain the IFMR suffered from large uncertainties in the initial masses because their main-sequence primaries are difficult to age-date with good precision. Our selection of WBs with slightly evolved primaries avoids this problem by restricting to a region of parameter space where isochrone ages are significantly easier to determine with precision. The WDs of two of our originally selected binaries were found to be close double degenerates and are not used in the IFMR analysis. We obtained more precise constraints than existing ones in the mass range 1–2 M ⊙, corresponding to a previously poorly constrained region of the IFMR. Having introduced the use of turnoff/subgiant–WD binaries, the study of the IFMR is not limited anymore by the precision in initial mass, but now the pressure is on final mass, i.e., the mass of the WD today. Looking at the full data set, our results would suggest a relatively large dispersion in the IFMR at low initial masses. More precise determinations of the mass of the WD components of our targets are necessary for settling this question.

Testing parton distribution functions with t -channel single-top-quark production

The production of single top-quarks in the t-channel at hadron colliders imposes strong analytic constraints on parton distribution functions (PDFs) through its double deeply inelastic scattering (DDIS) form. We exploit this to provide novel consistency checks between LO, NLO and NNLO PDF fits and propose to include it as a constraint in future PDF fits. Furthermore, while it is well-known that the b-quark PDF is highly sensitive to the b-quark mass, we show that the treatment of this systematic uncertainty is still incomplete, fragmented or outright missing at the moment. Consequently, we conclude that the b-quark mass uncertainty is the dominant but so far broadly neglected theory uncertainty for this process.

Time‐varying robustness analysis of launch vehicles under thrust perturbations

AbstractThis article presents a robustness analysis for launch vehicles during atmospheric ascent. It is based on recent advances in the worst‐case analysis of uncertain, finite horizon linear time‐varying (LTV) systems. Integral quadratic constraints are used to represent the uncertainties leading to a worst‐case gain condition based on a parameterized Riccati differential equation (RDE). This framework readily covers certain parametric uncertainties, for example, aerodynamic uncertainties. However, the effects of thrust perturbations are inherently harder to address. They directly result in mass and balance uncertainties, and a deviation from the planned trajectory. The latter amounts to a shift from the nominal/reference trajectory that has to be accounted for. Since thrust is proportional to the mass change of the launch vehicle, the thrust uncertainty is modeled as an external disturbance acting on the system. In order to cover the deviation from the reference trajectory, a dynamic uncertainty model is added in the analysis. A worst‐case aerodynamic loads and lateral drift analysis under wind disturbances is performed. The LTV results are validated against Monte Carlo simulations of the space launcher's nonlinear model.

Backstepping Sliding Mode Control for Inverted Pendulum System with Disturbance and Parameter Uncertainty

The inverted pendulum system is highly popular in control system applications and has the characteristics of unstable, nonlinear, and fast dynamics. A nonlinear controller is needed to control a system with these characteristics. In addition, there are disturbances and parameter uncertainty issues to be solved in the inverted pendulum system. Therefore, this study uses a nonlinear controller, which is the backstepping sliding mode control. The controller is robust to parameter uncertainty and disturbances so that it is suitable for controlling an inverted pendulum system. Based on testing with step and sine reference signals without interference, the controller can stabilize the system well and has a fast response. In testing with disturbances and mass uncertainty, the backstepping sliding mode controller is robust against these changes and able to make the system reach the reference value. Compared with sliding mode control, backstepping sliding mode control has a better and more robust response to disturbances and parameter uncertainty.