Nonlinear repetitive control of the metal cutting machine feed module with saturated input

The article discusses the methodology for constructing an automatic control system for the feed module of the cutting tool for lathes in the presence of input saturation. The presence of the saturation function is due to restrict unwanted movements of the feed module actuator. The generator for periodic signals, the hyperstability criterion, L-dissipativity conditions and an implicit reference model are used as the solution methods for structural synthesis of the control system. At the stage of simulation, the functioning quality of the developed control system is illustrated.

Effect of Static Bifurcation on Logical Stochastic Resonance in a Symmetric Bistable System

In previous research works, logical stochastic resonance (LSR) was reported to frequently occur in an asymmetric bistable system, where the bias parameter is the key factor to make the LSR appear. In this work, we investigate the effect of different anharmonic periodic signals on the pitchfork and saddle-node bifurcations in a symmetric bistable system. We focus on the relationship between the static bifurcation and LSR. We use both numerical and circuit simulations to analyze some interesting phenomena. Like the bias parameter, some anharmonic periodic signals also break the symmetry of the symmetric bistable system and lead to the saddle-node bifurcation. The anharmonic periodic signal with a constant term in its expanded Fourier series induces a reliable LSR in the symmetric bistable system. The key factor of LSR is the saddle-node bifurcation which implies the asymmetry of the system. Here, we replace the bias parameter by choosing an anharmonic periodic signal and make the LSR occur in a different way.

What causes the absence of pulsations in Central Compact Objects in supernova remnants?

Most young neutron stars belonging to the class of Central Compact Objects (CCOs) in supernova remnants do not have known periodicities. We investigated seven such CCOs to understand the common reasons for the absence of detected pulsations. Making use of XMM-Newton, Chandra, and NICER observations, we perform a systematic timing and spectral analysis to derive updated sensitivity limits for both periodic signals and multi-temperature spectral components that could be associated with radiation from hotspots on the neutron star surface. Based on these limits, we then investigated for each target the allowed viewing geometry that could explain the lack of pulsations. We find that it is unlikely (< 10−6) to attribute that we do not see pulsations to an unfavorable viewing geometry for five considered sources. Alternatively, the carbon atmosphere model, which assumes homogeneous temperature distribution on the surface, describes the spectra equally well and provides a reasonable interpretation for the absence of detected periodicities within current limits. The unusual properties of CCOs with respect to other young neutron stars could suggest a different evolutionary path, as that proposed for sources experiencing episodes of significant fallback accretion after the supernova event.

A Uniform Search for Nearby Planetary Companions to Hot Jupiters in TESS Data Reveals Hot Jupiters Are Still Lonely

We present the results of a uniform search for additional planets around all stars with confirmed hot Jupiters observed by the Transiting Exoplanet Survey Satellite (TESS) in its Cycle 1 survey of the southern ecliptic hemisphere. Our search comprises 184 total planetary systems with confirmed hot Jupiters with R p > 8 R ⊕ and orbital period <10 days. The Transit Least Squares algorithm was utilized to search for periodic signals that may have been missed by other planet search pipelines. While we recovered 169 of these confirmed hot Jupiters, our search yielded no new statistically validated planetary candidates in the parameter space searched (P < 14 days). A lack of planet candidates nearby hot Jupiters in the TESS data supports results from previous transit searches of each individual system, now down to the photometric precision of TESS. This is consistent with expectations from a high-eccentricity migration formation scenario, but additional formation indicators are needed for definitive confirmation. We injected transit signals into the light curves of the hot Jupiter sample to probe the pipeline’s sensitivity to the target parameter space, finding a dependence proportional to R p 2.32 P − 0.88 for planets within 0.3 ≤ R p ≤ 4 R ⊕ and 1 ≤ P ≤ 14 days. A statistical analysis accounting for this sensitivity provides a median and 90% confidence interval of 7.3 − 7.3 + 15.2 % for the rate of hot Jupiters with nearby companions in this target parameter space. This study demonstrates how TESS uniquely enables comprehensive searches for nearby planetary companions to nearly all the known hot Jupiters.

Mathematical modeling of signals, linear links and responses of telecommunications and radioelectronics systems in time domain

A single mathematical model of time characteristics of signals, links and responses of telecommunications and radioelectronics systems is suggested. It embodies Dirac- and Heaviside responses of all types of linear links, as well as their responses to the input in the form of periodic signals, no periodic finite and no periodic eternal signals. On the basis of the suggested model the algorithm for calculation of time characteristics was developed, which allows creation of effective automated simulations procedure of signals, links and responses in time-domain. The comparative quantitative analysis of accuracy of the suggested algorithm and discrete Fourier transformation (DFT) algorithm was carried out.

Modeling of Memristors under Periodic Signals of Different Parameters

In this paper, the problem of modeling memristors is studied. Two types of memristors with carbon and tungsten doping fabricated by the Knowm Inc. are tested. The memristors have been examined with either sinusoidal or triangle voltage wave periodic excitation. Some different frequencies, amplitudes and signal shapes have been applied. The collected data have been averaged and subjected to high frequency filtering. The quality of measurement data has also been discussed. The averaged measurement has been modeled using three popular memristor models: Strukov, Biolek and VTEAM. Some additional feathers to the considered models have been proposed and tested. Memristor is usually modeled by a set of algebraic-differential equations which link both electrical values (i.e., voltage and current) and the internal variable(s) responsible for the element dynamics. The interior-point with box constrains optimization method has been used to obtain the optimal parameters of the memristor model that fit best to the collected data. The results of the optimization process have been discussed and compared. The sensitivity to the different frequency range has been also examined and reviewed. Some conclusions and future work ideas have been postulated.

APPLICATION OF CYCLOSTATIONARY PROPERTIES OF PERIODIC SIGNALS FOR POWER ANALYSIS IN ELECTRIC CIRCUITS

Предложен циклостационарный подход к анализу мощности электрических цепей, возбуждаемых источниками периодических токов и напряжений. Получены теоретические выражения для характеристик мгновенной мощности на основе взаимной спектральной ковариационной функции и показана их связь со средней и полной мощностью. Проведен анализ гармонического распределения мощности в линейной цепи при периодическом воздействии. На примере численного расчета резонансной цепи продемонстрированы этапы циклостационарного анализа и получены основные характеристики мощности. The paper proposes a cyclostationary approach to the power analysis for electric circuits excited by sources of periodic currentsorvoltages.Theformalexpressions forcharacteristics of instantaneous power are obtained on the basis of cross spectral covariance function and their relation to the average and apparent power is established. The analysis of the harmonic distribution of the power in a linear circuit under periodic excitation is carried out. The main stages of the method are illustrated with a numerical simulation example.