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The paper proposes a low-pass filter adaptive iterative learning control (LPF-AILC) strategy for unmatched, uncertain, time-varying, non-parameterized nonlinear systems (NPNL systems). To address the difficulty of nonlinear parameterization terms in system models, a new function approximator (FSE-RBFNN), which combines the radial basis function neural network (RBFNN) and Fourier series expansion (FSE), is introduced to model each time-varying nonlinear parameterized function. The adaptive backstepping method is used to design control laws and parameter adaptive laws. In the process of controller design, we may encounter the problem of too many derivatives, which can cause parameter explosions after derivatives. Therefore, we introduce a first-order low-pass filter to solve this problem and simplify the structure of the controller. As the number of iterations increases, the maximum tracking error gradually decreases until it converges to the nearby region, approaching zero within the entire given interval [0, T], according to the Lyapunov-like synthesis. To mitigate the impact of initial state errors, a dynamically changing boundary layer is introduced, along with a series to deal with the unknown error upper bounds. Finally, two simulation examples prove the correctness of the proposed control method. [ABSTRACT FROM AUTHOR]

On-policy deep reinforcement learning (DRL) has the inherent advantage of using multi-step interaction data for policy learning. However, on-policy DRL still faces challenges in improving the sample efficiency of policy evaluations. Therefore, we propose a multi-step on-policy DRL method assisted by off-policy policy evaluation (abbreviated as MSOAO), whichs integrates on-policy and off-policy policy evaluations and belongs to a new type of DRL method. We propose a low-pass filtering algorithm for state-values to perform off-policy policy evaluation and make it efficiently assist on-policy policy evaluation. The filtered state-values and the multi-step interaction data are used as the input of the V-trace algorithm. Then, the state-value function is learned by simultaneously approximating the target state-values obtained from the V-trace output and the action-values of the current policy. The action-value function is learned by using the one-step bootstrapping algorithm to approximate the target action-values obtained from the V-trace output. Extensive evaluation results indicate that MSOAO outperformed the performance of state-of-the-art on-policy DRL algorithms, and the simultaneous learning of the state-value function and the action-value function in MSOAO can promote each other, thus improving the learning capability of the algorithm. [ABSTRACT FROM AUTHOR]

This study used a watershed algorithm to detect canopy cover in dryland forests. The objective of this study was to determine the best parameters of the watershed segmentation algorithm to obtain information on crown closure from filtered and unfiltered high- and very-high-resolution images. The best performance of each parameter combination of the tolerance value (T), mean value (M), and variance value (V), which is written as C:[T]-[M]-[V], is determined based on the level of accuracy. This study used Pleiades-1B and SPOT-6 images as primary digital data. The results showed that the low-pass filtered Pleiades-1B image showed the best performance with a combination of parameters C6-MF:[10]-[0.7]- [0.3], with an overall accuracy (OA) of 91.0% and an accuracy Kappa (KA) of 83.2%. The low-pass filtered Spot-6 image shows a combination of parameters C7-MF:[10]-[0.8]-[0.2], which has an accuracy of 90.6% OA and 65.4% KA. This study concludes that the filtered image with a low-pass filter always yields more accurate results than the original data (without a filter) for both Pleiades-1B and SPOT-6 images. The very high spatial resolution provides better accuracy than the high spatial resolution. [ABSTRACT FROM AUTHOR]

A low-power clock and data recovery circuit with a quarter rate operating at 10 GHz is presented. This circuit consists of a phase lock loop and an input data retiming circuit. The phase-locked loop includes an LC oscillator, a quarter-rate detector, a charge pump, and a low-pass filter. The output of the oscillator is applied to a two-bit counter, so the clock frequency is reduced to 2.5 GHz with eight different phases which applied to the phase detector to sample the input data in different phases. Each sampling is done in 12.5 picoseconds. The innovative application of this two-bit counter eliminates the requirement of the multiphase oscillator, thus helps to reduce overall power dissipation. The power consumption of the voltage control oscillator is about 5.83 mW. In addition, reducing the clock frequency improves the performance of the phase detector circuit. The total power dissipation of the proposed CDR is evaluated to be 10.9 mW from a 1.8 V supply. [ABSTRACT FROM AUTHOR]

In the past decade, the proliferation of modern telecommunication technologies, including 5G, and the widespread adoption of the Internet-of-things (IoT) have led to an unprecedented surge in data generation and transmission. This surge has created an escalating demand for advanced signal processing capabilities. Microwave photonic (MWP) processors offer a promising solution to satisfy this unprecedented demand for data processing by capitalising on the high bandwidth and low latency achievable by optical systems. In this work, we introduce an integrated MWP processing unit for all-optical RF filtering using elemental antimony. We exploit the crystallisation dynamics of antimony to demonstrate a photonic leaky integrator, which is configured to operate as a first-order low-pass filter with a bandwidth of 300 kHz and ultra-compact footprint of 16 × 16 μm2. We experimentally demonstrate the implementation of such a filter as an envelope detector to demodulate an amplitude-modulated signal. Finally, a discussion on achieving bandwidth tunability is presented. [ABSTRACT FROM AUTHOR]

This paper presents a multiple-input fully differential operational transconductance amplifier (MI-FD OTA) with very low power consumption. To obtain a differential MOS pair with minimum supply voltage and minimum power consumption, the multiple-input bulk-driven MOS transistor operating in the subthreshold region is used. To show the advantage of the MI-FD OTA, a fifth-order Chebyshev filter was used to realize a low-pass filter capable of operating with a supply voltage of 0.5 V and consuming 60 nW at a nominal setup current of 3 nA. The proposed filter uses five MI-FD OTAs and five capacitors. The total harmonic distortion (THD) was 0.97% for a rail-to-rail sinusoidal input signal. The MI-FD OTA and the filter application were designed and simulated in the Cadence environment using a 0.18 µm CMOS process from TSMC. The robustness of the design was confirmed by Monte Carlo analysis and process, voltage, and temperature corner analysis. [ABSTRACT FROM AUTHOR]

Context. Microwave stub filters are widely used in radio engineering and telecommunication systems, as well as in technical information protection systems due to simplicity of design, possibility of realization in microstrip design and manufacturability in mass production. For synthesis of stub filters nowadays traditional methods based on transformation of low-frequency prototype filters on LC-elements into filtering structures on elements with distributed parameters are used. The transformations used are approximate and provide satisfactory results for narrowband stub filters. In this connection there is a necessity in development of direct synthesis methods for stub filters, excluding various approximations and providing obtaining of amplitude-frequency characteristics with optimal shape for any bandwidths. Objective. The purpose of the study is to develop a method for direct synthesis of stub band-pass filters and low-pass filters with Chebyshev amplitude-frequency response in the passband. Method. The procedure of direct synthesis includes the formulation of relations for filter functions of plume structures, selection of approximating functions of Chebyshev type for filter functions and formation of a system of nonlinear equations for calculation of parameters of filter elements. Results. A method for the direct synthesis of stub bandpass and lowpass filters with Chebyshev response is developed. Conclusions. Scientific novelty of the work consists in the development of a new method of direct synthesis of l stub filters. The method, in contrast to approximate traditional methods of synthesis of microwave filters, is exact, and the obtained solutions of synthesis problems are optimal. The experiments confirmed the performance of the proposed method and the optimality of the obtained solutions. Prospects for further research suggest adapting the method to the synthesis of filter structures with more complex resonators compared to stubs. [ABSTRACT FROM AUTHOR]

The efficient management of commercial orchards strongly requires accurate information on plant growing status for the implementation of necessary farming activities such as irrigation, fertilization, and pest control. Crown planar area and plant number are two very important parameters directly relating to fruit growth conditions and the final productivity of an orchard. In this study, in order to propose a novel and effective method to extract the crown planar area and number of mature and young papayas based on visible light images obtained from a DJ Phantom 4 RTK, we compared different vegetation indices (NGRDI, RGBVI, and VDVI), filter types (high- and low-pass filters), and filter convolution kernel sizes (3–51 pixels). Then, Otsu's method was used to segment the crown planar area of the papayas, and the mean–standard deviation threshold (MSDT) method was used to identify the number of plants. Finally, the extraction accuracy of the crown planar area and number of mature and young papayas was validated. The results show that VDVI had the highest capability to separate the papayas from other ground objects. The best filter convolution kernel size was 23 pixels for the low-pass filter extraction of crown planar areas in mature and young plants. As to the plant number identification, segmentation could be set to the threshold with the highest F-score, i.e., the deviation coefficient n = 0 for single young papaya plants, n = 1 for single mature ones, and n = 1.4 for crown-connecting mature ones. Verification indicated that the average accuracy of crown planar area extraction was 93.71% for both young and mature papaya orchards and 95.54% for extracting the number of papaya plants. This set of methods can provide a reference for information extraction regarding papaya and other fruit trees with a similar crown morphology. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for the removal of dual decaying DC offsets (DDCOs) to enhance discrete Fourier transform-based phasor estimation. The method proposed in this paper uses the sum of even samples and the sum of odd samples from the input signal to remove the AC components, thereby precisely estimating the primary and secondary DDCOs. The fluctuations induced by DCCOs present in the output of traditional DFT methods are eliminated by using the estimated DCCOs. The performance of the method was evaluated in terms of both mathematical-generated signals and fault current signals from a 154 kV Korean overhead transmission system. PSCAD/EMTDC was used to generate fault current signals at various fault distances and angles. The results show that the proposed method can estimate the phasor of the fundamental frequency component accurately regardless of the primary and secondary DCCOs. The paper concludes by describing the hardware implementation in a prototype unit that considers the real-world requirements of power system protection. [ABSTRACT FROM AUTHOR]

The frequent operation of the switching devices inside the converter valve (mainly composed of thyristors) and other equipment in the converter station of ultra-high voltage direct current (UHVDC) transmission system generates a large number of high harmonics and high-frequency interference, which is the main source of error of the DC electronic current transformers (ECT). In order to better understand the transfer characteristics of DC ECT, this paper considers the effects of temperature and frequency on the shunt and low-pass filter at the same time, and combines the field test at different temperatures with different current frequencies, the results are compared and fitted to obtain the broadband model of the transformer taking into account the temperature. Based on this model, the mechanism and degree of influence of different equipment parameters on the broadband transfer characteristics of the transformer are further analyzed by setting different analog circuit parameters and digital sampling frequencies. The results show that different temperatures, shunt radius, shunt residual inductance, low-pass filter cut-off frequency, sampling frequency of the combined unit affect the broadband transfer characteristics of the transformer, and when a certain threshold is reached, the accuracy of the transformer does not meet the current standard requirements, which should be taken into account during the analysis process, and the results have a reference value for the parameter selection of the transformer.

The Lunar Environment heliospheric X-ray Imager (LEXI) and Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) missions will image the Earth’s dayside magnetopause and cusps in soft X-rays after their respective launches in the near future, to specify global magnetic reconnection modes for varying solar wind conditions. To support the success of these scientific missions, it is critical to develop techniques that extract the magnetopause locations from the observed soft X-ray images. In this research, we introduce a new geometric equation that calculates the subsolar magnetopause position (\begin{document}$ {R}_{\mathrm{s}} $\end{document}) from a satellite position, the look direction of the instrument, and the angle at which the X-ray emission is maximized. Two assumptions are used in this method: (1) The look direction where soft X-ray emissions are maximized lies tangent to the magnetopause, and (2) the magnetopause surface near the subsolar point is almost spherical and thus \begin{document}$ {R}_{\mathrm{s}} $\end{document} is nearly equal to the radius of the magnetopause curvature. We create synthetic soft X-ray images by using the Open Geospace General Circulation Model (OpenGGCM) global magnetohydrodynamic model, the galactic background, the instrument point spread function, and Poisson noise. We then apply the fast Fourier transform and Gaussian low-pass filters to the synthetic images to remove noise and obtain accurate look angles for the soft X-ray peaks. From the filtered images, we calculate \begin{document}$ {R}_{\mathrm{s}} $\end{document} and its accuracy for different LEXI locations, look directions, and solar wind densities by using the OpenGGCM subsolar magnetopause location as ground truth. Our method estimates \begin{document}$ {R}_{\mathrm{s}} $\end{document} with an accuracy of \begin{document}$ {10\;\mathrm{c}\mathrm{m}}^{-3} $\end{document}. The accuracy improves for greater solar wind densities and during southward interplanetary magnetic fields. The method captures the magnetopause motion during southward interplanetary magnetic field turnings. Consequently, the technique will enable quantitative analysis of the magnetopause motion and help reveal the dayside reconnection modes for dynamic solar wind conditions. This technique will support the LEXI and SMILE missions in achieving their scientific objectives.

A new universal active filter configuration is presented in this paper which is capable of realizing all three first-order filter responses namely all pass (AP), low pass (LP) and high pass (HP) using a single second generation voltage conveyor (VCII+), a virtually grounded capacitor and two resistors. The proposed circuit offers tunability of the cut-off frequency, gain (for HP filter) and simultaneous availability of two filter outputs, one at a low impedance node (HP/AP), the other output, namely the LPF will require a voltage buffer to avoid loading. The nonideal analysis of filter responses based on the nonideal model of VCII+ is carried out by considering all the parasitic immittances and nonideal gains and found that they have no significant effect on the performance of the proposed filter structure. Sensitivity analysis with respect to active and passive components has also been carried out. The functionality of the presented circuit has been validated through simulations and experimental results, where the VCII+ was implemented using the macro model of the commercially available CFOA IC AD844. Additionally, the proposed circuit has been tested using a CMOS VCII+ implemented with 0.18 μ m TSMC technology parameters. The tests include advanced evaluations based on Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

A fractional low-pass filter operating in a low-frequency range is necessary for the filtering of biomedical signals. Thus, we propose a fractional low-pass filter of order (1 + α) which is implemented using a current follower transconductance amplifier (CFTA). The presented structure is compact. It comprises of five CFTAs along with three grounded capacitors and two resistors. Additionally, this filter structure can be electronically tuned for its order and frequency variation, and these tunings are independent of each other. This electronic tuning is established through the bias current of the active component used. The layout of the proposed filter was designed in Cadence Virtuoso, covering 7920 μ m2 of chip area. It is operating at ±900 mV with a power consumption of 6.8 mW. In the simulation results, both pre-layout and post-layout results are included, which indicates that the design is appropriate for fabrication. To check robustness, PVT analysis, Monte-Carlo analysis and THD are also performed. The proposed circuit has also been tested through experiment and its results are also presented. The proposed filter is used to implement a Leaky-Integrate-and-Fire neuron model. [ABSTRACT FROM AUTHOR]

This article describes a low-voltage, low-power fractional-order low-pass filter (FO-LPF) of order 1 + α, which is implemented using a voltage differencing differential difference amplifier (VDDDA). The VDDDA structure is implemented using the bulk-driven metal oxide semiconductor transistor technique. The transistors operate in the subthreshold region to maintain low-supply voltage and low-power consumption. The FO-LPF structure implemented using this VDDDA structure is compact. It includes three VDDDAs and three grounded capacitors along with two active resistors implemented using MOS transistors. In addition, this filter structure provides electronic tuning of its order and cut-off frequency through the bias current of the active component used. The effects of tracking error and parasitics on the functionality of the proposed FO-LPF were investigated. The VDDDA and filter operate at ±300 mV and dissipate only 207 nW and 663 nW of power, respectively. Thus, the VDDDA structure and filter are suitable for low-voltage and low-power operation. Layouts of the proposed VDDDA as well as the FO-LPF were designed in the Cadence Virtuoso environment. Post-layout simulation results of the designed circuits imply that they are suitable for fabrication. Noise, total harmonic distortion, Monte-Carlo, and PVT analyses were also performed. [ABSTRACT FROM AUTHOR]

This research presents a new method to improve the ability of small-scale microgrids to maintain stability during temporary disturbances. This is achieved by combining a simplified Unified Power Flow Controller (UPFC) configuration with a low-pass filter (LCL) in the Distributed Generation (DG) unit. The DG unit consists of a Photovoltaic (PV) system that is linked to the grid via a dc-dc buck converter and inverter. The dc-dc converter ensures a consistent output voltage that is linked to the inverter, which produces the necessary ac voltage to power the grid. The downsized Unified Power Flow Controller (UPFC) with a Low Capacitance-Inductance (LCL) filter utilizes the Direct Current (DC) connection of the Distributed Generation (DG) unit to generate an appropriate series voltage. This voltage is then injected into the power line to enhance transient stability. In order to get the highest level of system stability while minimizing expenses, a nonlinear discrete-time Hamilton- Jacobi-Bellman (HJB) optimal control approach is used. The control strategy is specifically developed to optimize the functioning of the microgrid, with the primary goal of decreasing the total cost associated with stability improvement. The cost function is estimated by using a Neural Network that utilizes the weighted residual approach. The simulation results confirm the efficacy of the suggested model and control method. The integration of the DG unit, LCL, and UPFC architecture exhibits exceptional efficacy in attenuating oscillations within the system. This study adds to the progress in comprehending and using decreased UPFC structures in microgrid setups, presenting a feasible approach to achieve improved stability and dependability in distributed power systems. [ABSTRACT FROM AUTHOR]

The object of study is the audio file transcription system. The article presents a study on the impact of using high-pass, low-pass, and bandpass filters on the process of transcribing audio files. The aim of the work is to speed up the transcription of groups of audio files. The study identifies several types of audio data for which pre-filtering is applied. The research is part of solving the problem of transcribing audio files using neural network-based systems. The article provides an overview of works on pre-processing of voice files, analyzes the advantages and disadvantages of the described approaches. The use of complex preprocessing algorithms improves the recognition quality but significantly slows down its speed or requires additional computing power. Therefore, pre-filtering is used to improve speech recognition quality without reducing the speed of the system as a whole. The article includes experimental studies on the effect of filtering frequencies on the speed of voice transcription. The obtained research results allow us to conclude that the use of a bandpass filter with a lower passband frequency in the range of 150-200 Hz and an upper passband frequency in the range of 3500-7000 Hz allows for an increase in transcription speed not only through the use of video cards but also through the use of central processors and pre-filtering. It is also proposed to remove empty segments by energy of the signal and speed up the voice, which affects the time of its transcription, using the aforementioned filters. Ref. 5, pic. 2, tabl. 7

The aim of the research is to identify the optimal method for smoothing the surface of a hybrid digital bathymetric model (HDBM). The initiation of this research is justified by the fact that a model created from diverse types of data may have different surface textures and outliers. This diversity may cause problems in subsequent data processing stages, such as generating depth contours. As part of the adopted research methodology, fifteen filters were analysed. Filtering techniques were examined for filter type, the number of iterations, weights, and window size. The result is the adopted research methodology, which enabled the selection of the optimal filtering method. The research undertaken in this work is an extension of the methodology for developing an HDBM. An important aspect of the research is the approach to elaborating on such kinds of models in shallow and ultra-shallow waters adjacent to the land, as well as the use of data obtained by modern measurement platforms, such as unmanned surface vehicles (USV) and unmanned aerial vehicles (UAV). The studies fit into the general context of works related to the development of this type of model and undoubtedly provide a solid reference for further development or improvement of similar methods. [ABSTRACT FROM AUTHOR]

An ultra-compact low-pass spoof surface plasmon polariton (SSPP) filter based on an interdigital structure (IS) is designed. Simulated dispersion curves show that adding the interdigital structure in an SSPP unit effectively reduces its asymptotic frequency compared with traditional and T-shaped SSPP geometries, and the unit dimensions can be conversely reduced. Based on that, three IS-based SSPP units are, respectively, designed with different maximum intrinsic frequencies and similar asymptotic frequencies to constitute the matching and waveguide sections of the proposed filter, and the unit number in the waveguide section is adjusted to improve the out-of-band suppression. Simulation results illustrate the efficient transmission in the 0~5.66 GHz passband, excellent out-of-band suppression (over 24 dB) in the 5.95~12 GHz stopband and ultra-shape roll-off at 5.74 GHz of the proposed filter. Measurement results on a fabricated prototype validate the design, with a measured cut-off frequency of 5.53 GHz and an ultra-compact geometry of 0.5 × 0.16 λ02. [ABSTRACT FROM AUTHOR]

This paper presents a multiple-input fully differential operational transconductance amplifier (MI-FD OTA) with very low power consumption. To obtain a differential MOS pair with minimum supply voltage and minimum power consumption, the multiple-input bulk-driven MOS transistor operating in the subthreshold region is used. To show the advantage of the MI-FD OTA, a fifth-order Chebyshev filter was used to realize a low-pass filter capable of operating with a supply voltage of 0.5 V and consuming 60 nW at a nominal setup current of 3 nA. The proposed filter uses five MI-FD OTAs and five capacitors. The total harmonic distortion (THD) was 0.97% for a rail-to-rail sinusoidal input signal. The MI-FD OTA and the filter application were designed and simulated in the Cadence environment using a 0.18 µm CMOS process from TSMC. The robustness of the design was confirmed by Monte Carlo analysis and process, voltage, and temperature corner analysis.

The efficient management of commercial orchards strongly requires accurate information on plant growing status for the implementation of necessary farming activities such as irrigation, fertilization, and pest control. Crown planar area and plant number are two very important parameters directly relating to fruit growth conditions and the final productivity of an orchard. In this study, in order to propose a novel and effective method to extract the crown planar area and number of mature and young papayas based on visible light images obtained from a DJ Phantom 4 RTK, we compared different vegetation indices (NGRDI, RGBVI, and VDVI), filter types (high- and low-pass filters), and filter convolution kernel sizes (3–51 pixels). Then, Otsu’s method was used to segment the crown planar area of the papayas, and the mean–standard deviation threshold (MSDT) method was used to identify the number of plants. Finally, the extraction accuracy of the crown planar area and number of mature and young papayas was validated. The results show that VDVI had the highest capability to separate the papayas from other ground objects. The best filter convolution kernel size was 23 pixels for the low-pass filter extraction of crown planar areas in mature and young plants. As to the plant number identification, segmentation could be set to the threshold with the highest F-score, i.e., the deviation coefficient n = 0 for single young papaya plants, n = 1 for single mature ones, and n = 1.4 for crown-connecting mature ones. Verification indicated that the average accuracy of crown planar area extraction was 93.71% for both young and mature papaya orchards and 95.54% for extracting the number of papaya plants. This set of methods can provide a reference for information extraction regarding papaya and other fruit trees with a similar crown morphology.

This paper presents a novel method for the removal of dual decaying DC offsets (DDCOs) to enhance discrete Fourier transform-based phasor estimation. The method proposed in this paper uses the sum of even samples and the sum of odd samples from the input signal to remove the AC components, thereby precisely estimating the primary and secondary DDCOs. The fluctuations induced by DCCOs present in the output of traditional DFT methods are eliminated by using the estimated DCCOs. The performance of the method was evaluated in terms of both mathematical-generated signals and fault current signals from a 154 kV Korean overhead transmission system. PSCAD/EMTDC was used to generate fault current signals at various fault distances and angles. The results show that the proposed method can estimate the phasor of the fundamental frequency component accurately regardless of the primary and secondary DCCOs. The paper concludes by describing the hardware implementation in a prototype unit that considers the real-world requirements of power system protection.

The problem of non-ideal inertia of the photovoltaic energy storage system (PVESS) may occur due to unreasonable voltage control parameters. In response to this issue, this paper establishes an equivalent reduced-order model (EROM) for PVESS. This EROM considers the current control loop, voltage control loop and the virtual inertia control loop based on low-pass filter. This low-pass filter can effectively enhance the system’s virtual inertia. Since the output impedance of this EROM can visually reflect the external characteristics of the virtual inertia control loop, it is suitable for inertia analysis of PVESS. Furthermore, the impact of voltage control parameters and low-pass filter bandwidth on the system’s inertia is discussed from the perspective of the frequency response of the output impedance. Finally, the switch model of the PVESS is built on the RT-BOX hardware-in-the-loop experimental platform. The validity of the EROM and theoretical analysis is verified by several sets of experimental results.

Nowadays, energy decarbonization due to integrating renewable energy sources presents important challenges to overcome. The intermittent nature of photovoltaic systems reduces power quality by producing voltage variations and frequency deviations in electrical system networks, especially in weak and isolated distribution systems in developing countries. This paper presents a power smoothing method for improving the low-pass filter and moving average for grid-connected photovoltaic systems. This novel method includes state-of-charge monitoring control of the supercapacitor's energy storage system to reduce the fluctuations of photovoltaic power at the point of common coupling. A case study for a microgrid in a high-altitude city in Ecuador is presented with exhaustive laboratory tests using real data. This research aims to improve energy power quality in electrical distribution systems to cope with the growth of renewable penetration. The results demonstrate significant power quality and stability improvements achieved through the proposed method. For instance, the power smoothing method effectively reduced power fluctuations by 16.7% with the low-pass filter, 14.05% with the ramp-rate filter, and 9.7% with the moving average filter. [ABSTRACT FROM AUTHOR]

Bridge influence lines can reflect the performance status of bridge structures and are an important tool to evaluate high-speed railway bridges. Because a high-speed train can cause large dynamic response on a bridge, it is difficult to identify the static influence line of the bridge. To extract the static bridge influence lines for bridge evaluation, this paper proposes a low-pass filter design method for static influence line identification. By maximizing the difference in bridge static and dynamic energy, the relationship between the frequency domain characteristics of the bridge dynamic response and the filter parameters is established. Based on this relationship, reasonable values of the low-pass filter parameters can be determined. After filtering the dynamic response, the quasi-static response can be effectively obtained, and the bridge static influence line can be identified through the least square regularization method. Finally, a numerical example of the vehicle–bridge interaction model is used to verify the effectiveness of the proposed method. The results show that the low-pass filter designed through the proposed principle can accurately remove the dynamic effects, and its stability and robustness are good. The research results provide a reliable method for the static influence line identification of high-speed railway bridges. [ABSTRACT FROM AUTHOR]

This paper introduces a novel algorithm for designing a low-pass filter (LPF) and a microstrip Wilkinson power divider (WPD) using a neural network surrogate model. The proposed algorithm is applicable to various microwave devices, enhancing their performance and frequency response. Desirable output parameters can be achieved for the designed LPF and WPD by using the proposed algorithm. The proposed artificial neural network (ANN) surrogate model is employed to calculate the dimensions of the LPF and WPD, resulting in their efficient design. The LPF and WPD designs incorporate open stubs, stepped impedances, triangular-shaped resonators, and meandered lines to achieve optimal performance. The compact LPF occupies a size of only 0.15 λg × 0.081 λg, and exhibits a sharp response within the transmission band, with a sharpness parameter of approximately 185 dB/GHz. The designed WPD, operating at 1.5 GHz, exhibits outstanding harmonics suppression from 2 GHz to 20 GHz, with attenuation levels exceeding 20 dB. The WPD successfully suppresses 12 unwanted harmonics (2nd to 13th). The obtained results demonstrate that the proposed design algorithm effectively accomplishes the LPF and WPD designs, exhibiting desirable parameters such as operating frequency and high-frequency harmonics suppression. The WPD demonstrates a low insertion loss of 0.1 dB (S21 = 0.1 dB), input and output return losses exceeding 30 dB (S11 = −35 dB, S22 = −30 dB), and an output ports isolation of more than 32 dB (S23 = −32 dB), making it suitable for integration into modern communication systems. [ABSTRACT FROM AUTHOR]

Backgorund: Nowadays, everybody's life is dominated by COVID-19, which might have been the source of severe acute respiratory syndrome coronavirus 2. This virus disrupts the lungs first of all. Recently, it has been found that coronavirus may affect the brain. Because all body actions rely on the brain, hence investigating its healthy is an essential item in coronavirus effects. Method: Brain image segmentation can be helpful in the detection of the regions damaged by the effects of coronavirus. Since every image given by photography devices may have noises, therefore, first of all, the brain magnetic resonance angiography (MRA) images must be denoised for best investigation. In the present paper, we have presented the construction of multishearlets based on multiwavelets for the first time and have used them for the purpose of denoising. Multiwavelets have some advantages to wavelets. Therefore, we have used them in the shearlet system to expand the properties of multiwavelets in all directions. After denoising, we have proposed a scheme for the automatic characterization of the initial curve in the active contour model for segmentation. Detecting the initial curve is a challenging task in active contour-based segmentation because detecting an initial curve far from the desired region can lead to unfavorable results. Results: The results show the performance of using multishearlets in detecting affected regions by COVID-19. Using multishearlets has led to the high value of peak signal-to-noise ratio and Structural similarity index measure in comparison with original shearlets. Original shearlets are constructed from wavelets whereas we have constructed multishearlets from multiwavelets. Conclusion: The results show that multishearlets can neutralize the effect of noise in MRA images in a good way rather than shearlets. Moreover, the proposed scheme for segmentation can lead to 0.99 accuracy. [ABSTRACT FROM AUTHOR]

Interior Permanent Magnet Synchronous Motor (IPMSM) motion-sensorless speed control necessitates precise knowledge of rotor flux, speed, and position. Due to numerous non-ideal aspects, such as converter nonlinearities, detection errors, integral initial value, and parameter mismatches, the conventional first-order integrator's estimated rotor flux experiences a DC offset (Doff). Low-pass filters (LPF) with a constant cut-off frequency yield accurate estimates only in the medium- and high-speed range; however, at the low-speed area, both magnitude and phase estimates are inaccurate. The presented technique resolves the aforementioned issue for a broad speed range. In order to achieve precise flux estimation, this article presents an improved technique of flux estimator with two distinct drift mitigation strategies for the motion-sensorless field-oriented control (FOC) system of IPMSM. Using the orthogonality of the α - and β -axes, the proposed drift elimination system can estimate drift in different situations while maintaining a high level of dynamic performance. The stator flux linkage (SFL) computation in the synchronous coordinate is established from the estimation of the rotating shaft's permanent magnetic flux linkage orientation and the statistical equations model of the SFL. By comparing the calculated SFL vector to the SFL vector derived from the stator winding voltage and currents integral model with a drift PI compensation loop, a feedback loop is formed to neutralize integral drift, and the rotational speed and position of an IPMSM is estimated utilizing the vector product of the two flux linkages in a phase-locked loop. Theoretical interpretation is presented, and Matlab Simulink simulations, as well as experimental outcomes, consistently demonstrate that the suggested estimation techniques can eliminate the phenomenon of flux drift. [ABSTRACT FROM AUTHOR]

A new structure of microstrip-based low-pass filter with wide stopband and sharp roll-off is introduced, in this paper. In the proposed topology, resonators with T and modified L Shapes have been used. To improve the suppression factor and relative stopband bandwidth, the second resonator has been added to the first resonator. The designed filter has been fabricated on a 20 mm thickness RO4003 substrate, which has a loss tangent of 0.0021 and a relative dielectric constant equal to 3.38. All parameters including roll of rate, stopband, bandwidth, return loss, insertion loss, and figure of merit have significant coefficients. Simulation has been ran using advanced design system software. The 3dB cutoff frequency is appropriate. The value of the insertion loss parameter is <0.1 dB and the S11 parameter is -22 dB at this point. The stopband is extended from 2.42 up to 24 GHz, which shows an ultra-stopband. The results of the simulation and experiment are almost similar, which indicates a proper performance of the designed structure. [ABSTRACT FROM AUTHOR]

This work studies the behavior of the Lorenz system by exploiting the similarities between that chaotic system and a low-pass filter. Simulations and physical tests performed using highly precise electric circuits validate the proposed model. The study allowed us to conclude that it is possible to have a degree of control over the cutoff frequency of the filter, which in turn preserves chaotic oscillation. The bifurcation diagram and Lyapunov exponent are employed to confirm that the controllable parameters are in fact responsible for the desired effects and that changes on the cutoff frequency have no effect on the position of the equilibrium points of the system. • The Lorenz system can be seen as a filter. • σ corresponds to the cutoff frequency of the RC low-pass filter. • A bifurcation diagram is used to adjust the cutoff frequency. [ABSTRACT FROM AUTHOR]

This paper proposes a nonlinear flux linkage observer for the PMSM speed controls without motion sensors, introducing the deviation among the real stator flux linkage and an estimated stator flux linkage to suppress feedback and integral flux drift. In the position detection of an interior PMSM without a speed sensor, the traditional back EMF integration method uses a pure integrator, or LPF, to estimate the stator flux. Its inherent defects inevitably lead to inaccurate flux estimation, which directly affects the estimation of the motor mover position, resulting in the decline in motor control operation and the distortion of phase current. This paper uses an improved integrator with adaptive compensation. The projected value of the stator flux linkage has been derived from the estimated value of the rotor permanent magnetic flux linkage position angle and the algebraic model (m-model) of the stator flux linkage, along with a synchronous coordinate system. The IPMSM stator coil flux linkage obtained from the stator coil current and integral voltage models in the static coordinate system is compared to form a feedback closed-loop to suppress the integral drift, and using the cross-product approach of the actual and estimated flux linkage yields the projected value of the IPMSM rotor speed and position through a PLL. Compared with the existing motion-sensorless observers, the methodology proposed in this article is simple and exhibits better dynamic and static estimation performance. Extensive and comprehensive MATLAB computer simulation and experimental findings validate the proposed motion-sensorless control mechanism. [ABSTRACT FROM AUTHOR]

In this paper, a groove gap waveguide (GGW) low-pass filter is proposed for the first time. Gap waveguide technology represents an interesting alternative as a low-loss, cost-effective, high-performance transmission line and packaging solution for microwave and millimeter-wave systems. This technology may exhibit a frequency behavior similar to rectangular waveguide but with some advantages such as the no need of electrical contact between the upper and lower plates of the GGW, making it an attractive alternative in the design of satellite devices at high frequencies. However, all the previous literature focused on band-pass filters, while design methods for GGW low-pass filters have not been reported. Furthermore, in this paper a new manufacturing approach is proposed and its performance has been compared with traditional methods such as Computer Numerical Control (CNC) milling. The new approach relies on the Selective Laser Melting (SLM)-3D printing of the filter followed by a post-processing step, in which it is partially mechanized using CNC milling to improve the surface finish. Measurements of the manufactured prototypes are also included to compare both techniques at millimeter-waves, showing the advantages of the new fabrication method and the excellent agreement with the simulations.

Backgorund: Nowadays, everybody's life is dominated by COVID-19, which might have been the source of severe acute respiratory syndrome coronavirus 2. This virus disrupts the lungs first of all. Recently, it has been found that coronavirus may affect the brain. Because all body actions rely on the brain, hence investigating its healthy is an essential item in coronavirus effects. Method: Brain image segmentation can be helpful in the detection of the regions damaged by the effects of coronavirus. Since every image given by photography devices may have noises, therefore, first of all, the brain magnetic resonance angiography (MRA) images must be denoised for best investigation. In the present paper, we have presented the construction of multishearlets based on multiwavelets for the first time and have used them for the purpose of denoising. Multiwavelets have some advantages to wavelets. Therefore, we have used them in the shearlet system to expand the properties of multiwavelets in all directions. After denoising, we have proposed a scheme for the automatic characterization of the initial curve in the active contour model for segmentation. Detecting the initial curve is a challenging task in active contour-based segmentation because detecting an initial curve far from the desired region can lead to unfavorable results. Results: The results show the performance of using multishearlets in detecting affected regions by COVID-19. Using multishearlets has led to the high value of peak signal-to-noise ratio and Structural similarity index measure in comparison with original shearlets. Original shearlets are constructed from wavelets whereas we have constructed multishearlets from multiwavelets. Conclusion: The results show that multishearlets can neutralize the effect of noise in MRA images in a good way rather than shearlets. Moreover, the proposed scheme for segmentation can lead to 0.99 accuracy.

DC microgrid systems have been increasingly employed in recent years to address the need for reducing fossil fuel use in electricity generation. Distributed generations (DGs), primarily DC sources, play a crucial role in efficient microgrid energy management. Energy storage systems (ESSs), though vital for enhancing microgrid stability and reliability, currently lack cost-effectiveness. Each ESS technology serves a specific purpose, suggesting that hybridizing these technologies can improve microgrid stability and reliability while extending the ESS’s lifespan. This paper proposes an optimization of the capacity and cost of a hybrid ESS, comprising a battery and a supercapacitor, in a standalone DC microgrid. This optimization is achieved by calculating the cut-off frequency of a low-pass filter (LPF). The supercapacitor supplies the high fluctuation component of renewable power generation and load demand, while the battery caters to the low fluctuation component. To minimize the designed objective function, including the total net present value (NPV) and replacement cost of the hybrid ESS, a meta-heuristic strategy called the Whale optimization algorithm (WOA) is employed within a MATLAB environment. The optimization takes into account real PV power, wind turbine power and load demand. The results show that reducing power fluctuation for the battery can lower the cost of the hybrid ESS. Compared to a battery-only microgrid system with an $NPV_{total}$ of $\$ $ 6,153,059, the hybrid ESS has an $NPV_{total}$ of $\$ $ 5,413,846. Thus, the hybrid ESS can reduce the total cost of the entire project by 12.01% compared to the system with only a battery. Consequently, the hybrid ESS’s total system life-cycle cost is lower than that of a system using only a battery.

In surface roughness measurements, the presence of spikes in the primary profile can disable a normal filter from extracting the shape and waviness components. The robust spline filter (RSF) has been proposed to solve this problem. However, because ISO 16610-32, an RSF standard, has a significant deficiency, it was withdrawn in the Technical Specifications stage. The other proposed RSFs only show the method and a few examples with normal roughness and spike. Therefore, because the characteristics of each RSF have not been clarified, which RSF should be used for which primary profiles is not clear. This is one of the reasons for the delay in establishing ISO. In addition, the measurement sites need the establishment of robust spline filter selection guidelines. Therefore, in this paper, the characteristics of RSFs are clarified. Additionally, the points to be considered in using RSFs are summarized. Finally, the filter that should be selected for the specific application is identified. These results are expected to contribute to the widespread use of RSFs in the industrial world, avoid confusion at the measurement site, and help establish a new RSF standard. [ABSTRACT FROM AUTHOR]

A control for the rotation of an eccentric wheel that asymptotically stabilizes the equilibrium state of the Translational Oscillator with Rotating Actuator (TORA) is proposed. The nonlinear dependence of the force arising from the deformation of the elastic elements of the model on the displacement is taken into account since neglecting this nonlinearity can lead to the loss of model accuracy. It is shown that such a control is robust, and a method for assessing the domain of robustness in the parameter space of the mechanical system is proposed. The obtained results are illustrated using a real model as an example. [ABSTRACT FROM AUTHOR]

Compared with current source converters, voltage source converters (grid-forming converters) have better frequency support capabilities, voltage support capabilities, and regulation performance, thus they have broad application prospects. However, the grid-forming (GFM) converter has insufficient current control ability, and it easily causes problems such as overcurrent issues when a fault occurs. Thus, this insufficiency is one of the most important challenges the GFM converter is faced with. Aiming to solve the problems mentioned above, this paper proposes a control method of a GFM converter achieved with a low-pass filter structure and an additional current loop. The additional current loop controls the dq-axis current components by acting on the outer loop to generate appropriate phase and voltage amplitude reference. The low-pass filter structure is used to solve the system frequency stability problem caused by the inclusion of the additional current loop. On the premise of ensuring that the system frequency meets the grid-connection requirements, the proposed strategy rapidly limits the output current within the allowable range and guarantees expected voltage source characteristics of the converter during the fault period. Finally, the effectiveness and superiority of the proposed control strategy are verified by MATLAB/Simulink simulations. [ABSTRACT FROM AUTHOR]

A new structure of microstrip-based low-pass filter with wide stopband and sharp roll-off is introduced, in this paper. In the proposed topology, resonators with T and modified L Shapes have been used. To improve the suppression factor and relative stopband bandwidth, the second resonator has been added to the first resonator. The designed filter has been fabricated on a 20 mm thickness RO4003 substrate, which has a loss tangent of 0.0021 and a relative dielectric constant equal to 3.38. All parameters including roll of rate, stopband, bandwidth, return loss, insertion loss, and figure of merit have significant coefficients. Simulation has been ran using advanced design system software. The 3dB cutoff frequency is appropriate. The value of the insertion loss parameter is

Abstract This paper describes the design of a compact microstrip microwave diplexer based on bandpass filters and a stepped impedance resonator for 4G applications. The diplexer is composed of two band-pass filters (BPF) that operate at 1.8 and 2.5 GHz. Both bandpass filters for the receiver at 1.705-1.895 GHZ and the transmitter at 2.41-2.6 GHZ have a -3dB fractional bandwidth of 10.5 % and 7.6 % respectively. These BPF, suitable for 4G telecommunications, are examined, evaluated, developed, and simulated, yielding theoretically consistent results. With a dielectric permittivity of 4.4 and a thickness of 1.6 mm, FR-4 is employed as a substrate material. The theoretical design and simulation are used to calculate the size and position of the SIR and feed lines. The diplexer has a low insertion loss and a high isolation, and its efficiency is quantitatively analyzed using the HFSS software. This application allows us to swiftly and simply create electrodynamic structures. A diplexer prototype was developed using a typical method of fabricating PCBs, with a structural area of (47.4020x247.063=11711.28 mm2). The obtained simulation results of the proposed circuit are in good agreement with the measurements.

Three-dimensional printing by material extrusion enables the production of fully functional dynamic piezoelectric sensors in a single process. Because the complete product is finished without additional processes or assembly steps, single-process manufacturing opens up new possibilities in the field of smart dynamic structures. However, due to material limitations, the 3D-printed piezoelectric sensors contain electrodes with significantly higher electrical resistance than classical piezoelectric sensors. The continuous distribution of the capacitance of the piezoelectric layer and the resistance of the electrodes results in low-pass filtering of the collected charge. Consequently, the usable frequency range of 3D-printed piezoelectric sensors is limited not only by the structural properties but also by the electrical properties. This research introduces an analytical model for determining the usable frequency range of a 3D-printed piezoelectric sensor with resistive electrodes. The model was used to determine the low-pass cutoff frequency and thus the usable frequency range of the 3D-printed piezoelectric sensor. The low-pass electrical cutoff frequency of the 3D-printed piezoelectric sensor was also experimentally investigated and good agreement was found with the analytical model. Based on this research, it is possible to design the electrical and dynamic characteristics of 3D-printed piezoelectric sensors. This research opens new possibilities for the design of future intelligent dynamic systems 3D printed in a single process. [ABSTRACT FROM AUTHOR]

The object of the study is a three-phase shunt active power filter, which consists of a two-level voltage inverter, a capacitive storage device and a damping RL-link. Decomposition of the object of study according to the rate of motion of a dynamic system makes it possible to divide this system into two subsystems, interconnected by control. The influence of the dynamic characteristics of the low-pass filter, which acts as a subsystem of communication between the voltage stabilization circuit on the capacitor of the three-phase shunt active power filter and the circuits of compensating current, on the stability of the system is considered. The formation of the compensation current is carried out by forcing the introduction of sliding modes of the first order. The mathematical model of the voltage stabilization subsystem on the capacitor using the vector of the equivalent control under the assumption of the existence of a sliding mode in the formation of the compensation current was built. The analysis of the stability of the voltage stabilization system using a low-pass filter of the second order on the first approximation was performed. To do this, the characteristic equation of a closed system for which an interval characteristic polynomial was constructed, the Kharitonov theorem, and the Rauss-Hurwitz method for a family of these polynomials was used. To confirm the theoretical assumptions, a simulation model was built and the results of digital modeling were analyzed. [ABSTRACT FROM AUTHOR]

In the framework of current off-policy actor–critic methods, the state–action pairs in an experience replay buffer (called historical behaviors) cannot be used to improve the policy, and the target network and the clipped double Q-learning techniques need to be used to evaluate the policy. The framework limits the policy learning capability in complex environments, and needs to maintain four critic networks. As a result, we propose an efficient and lightweight off-policy actor–critic (EL-AC) framework. In the policy improvement, an efficient off-policy likelihood ratio policy gradient algorithm with historical behaviors reusing (PG-HBR) is proposed, which promotes the agent to learn an approximately optimal policy by using the historical behaviors. Moreover, a theoretically interpretable universal critic network is designed. It can approximate the action-value and the state-value functions simultaneously, so as to obtain the advantage function in PG-HBR. In the policy evaluation, we develop the algorithms of low-pass filtering for target state-values and adaptive controlling algorithm for overestimation bias, which can evaluate the policy efficiently and accurately using only one universal critic network. Extensive evaluation results indicate that EL-AC outperforms the state-of-the-art off-policy actor–critic methods in terms of approximately optimal policy learning and neural network storage space occupation, and it is more suitable for policy learning in complex environments. • An off-policy likelihood ratio policy gradient algorithm with historical behaviors reusing (PG-HBR) under the maximum entropy RL is proposed to learn an approximately optimal policy efficiently. • A universal critic network is introduced to approximate the action-value and state-value functions simultaneously. • An algorithm of low-pass filtering for target state-values is designed to effectively limit the correlation of the online action-value and the target value. • An algorithm of adaptive controlling for overestimation bias of action-values can detect whether the action-value is overestimated and discard the overestimated action-value autonomously. • Experiments on a series of continuous control benchmarks in OpenAIgym and PyBullet indicate that the proposed EL-AC framework outperforms some state-of-the-art reinforcement learning algorithms (SAC, TD3 and DDPG). [ABSTRACT FROM AUTHOR]

The aim of the research is to identify the optimal method for smoothing the surface of a hybrid digital bathymetric model (HDBM). The initiation of this research is justified by the fact that a model created from diverse types of data may have different surface textures and outliers. This diversity may cause problems in subsequent data processing stages, such as generating depth contours. As part of the adopted research methodology, fifteen filters were analysed. Filtering techniques were examined for filter type, the number of iterations, weights, and window size. The result is the adopted research methodology, which enabled the selection of the optimal filtering method. The research undertaken in this work is an extension of the methodology for developing an HDBM. An important aspect of the research is the approach to elaborating on such kinds of models in shallow and ultra-shallow waters adjacent to the land, as well as the use of data obtained by modern measurement platforms, such as unmanned surface vehicles (USV) and unmanned aerial vehicles (UAV). The studies fit into the general context of works related to the development of this type of model and undoubtedly provide a solid reference for further development or improvement of similar methods.

An ultra-compact low-pass spoof surface plasmon polariton (SSPP) filter based on an interdigital structure (IS) is designed. Simulated dispersion curves show that adding the interdigital structure in an SSPP unit effectively reduces its asymptotic frequency compared with traditional and T-shaped SSPP geometries, and the unit dimensions can be conversely reduced. Based on that, three IS-based SSPP units are, respectively, designed with different maximum intrinsic frequencies and similar asymptotic frequencies to constitute the matching and waveguide sections of the proposed filter, and the unit number in the waveguide section is adjusted to improve the out-of-band suppression. Simulation results illustrate the efficient transmission in the 0~5.66 GHz passband, excellent out-of-band suppression (over 24 dB) in the 5.95~12 GHz stopband and ultra-shape roll-off at 5.74 GHz of the proposed filter. Measurement results on a fabricated prototype validate the design, with a measured cut-off frequency of 5.53 GHz and an ultra-compact geometry of 0.5 × 0.16 λ02.

This paper presents a new low-voltage CMOS structure for operational transconductance amplifier (OTA) exploiting the bulk-driven, the self-cascode and the multiple-input transistor techniques (MI). The multiple-input OTA (MIOTA) circuit operates in subthreshold region using 0.5V supply voltage and offers enhanced linearity. The MIOTA is developed for biopotential signal as well as electrocardiogram (ECG) signal processing circuit and it is exploited to design a 5th-order Chebyshev low-pass and 3rd-order band-pass filters with a dynamic range (DR) of 57.6 dB and 60.4 dB, and nanopower consumption of 50 nW and 60 nW, respectively. Due to the electronic tuning of cut-off frequency, the low-pass and band-pass filters are suitable for random noise and motion artifact noise reductions in biopotential signals. The circuits were designed in Cadence environment using the standard N-well $0.18~\mu \text{m}$ TSMC CMOS technology. Intensive post-layout simulation results along with the process, voltage, temperature analysis (PVT) and Monte Carlo (MC) prove the robustness of the design. The chip area of the proposed MIOTA is 0.00725 mm2 ( $118~\mu \text{m}\,\,\times 61.5\,\,\mu \text{m}$ ). Compared with standard OTA the MIOTA offers simplification of filter topology and reduced number of active elements. In order to demonstrate these advantages, the MIOTA-based filter was also build using commercially available OTA LT1228. The experimental results of OTA LT1228 confirm both the filter functionality and the advantages of the proposed MIOTA.

Abstract Design procedure of a novel transmission line low‐pass filter is presented. The filter has a flexible rejection response for a prescribed cut‐off frequency and an in‐band ripple factor. It is compact by using a Z‐shaped coupled‐line section, which is loaded with open‐circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in‐band specifications. The simulated results show that the circuit can generate low‐pass responses with third‐, fifth‐, and seventh‐order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut‐off frequency of 0.5/0.3 GHz are fabricated using a three‐/five‐layer PCB process, which generate seventh‐order low‐pass filtering responses with good selectivity. The experimental results agree well with the predictions.

This article deals with the modernization of an existing loading system for the analysis of elastic–plastic properties of sheet metals in plane stress. The identification of the beginning of plastic deformation of sheet metal in plane strain is important in the cold pressing of sheet metal and in the assessment of the load capacity of thin-walled structures in the automotive and aerospace industry. The design of the control structure of the hydraulic part of the loading system for cross testing was carried out to automatize the whole process of experimental evaluation. For this purpose, proportional pressure-reducing valves together with control electronics were designed. Thus, the loading system is a control system for which a control algorithm has been designed and implemented on a PC. A computer simulation was performed to verify the functionality of the load system. An FEM simulation was performed to verify the correctness of the proposed numerical models and to confirm the experimental results. A numerical nonlinear model of the selected material was applied for the specification of plastic deformations. From the results, it is possible to state the appropriateness of the used models as well as the appropriateness of using modernized equipment for subsequent analysis of the plastic deformation of cruciform specimens. [ABSTRACT FROM AUTHOR]

An improved class AB version of the super source follower is used to implement a compact and power-efficient second order analog low-pass filter. The proposed circuit achieves a 41% power reduction as well as an improvement in linearity and pass band gain with respect to its class A counterpart. Measurement results of a test chip prototype fabricated in a 180 nm CMOS technology show a power consumption ranging from 50.3 $\mu \text{W}$ to 85.27 $\mu \text{W}$ for cutoff frequencies from 600 kHz to 890 kHz, with a supply voltage of ±0.75 V. A third order intermodulation distortion of −35.34 dB (for an input signal of 0.4 mVpp and 350 kHz) and a THD of −69.7 dB (for an input signal of 0.4 mVpp and 100 kHz) are measured, which results in an improvement with respect to the conventional class A version of 13.98 dB and 43.6 dB, respectively. The silicon area is 0.0592 mm2 (using external capacitors). [ABSTRACT FROM AUTHOR]

Due to the reliance on model knowledge and the lack of compensation mechanism, Nonlinear Dynamic Inversion (NDI) control does not provide the essential robustness in the face of disturbances such as the Center of Gravity (CG) sudden change. To overcome this deficiency, a novel adaptive NDI control approach based on the L1 adaptive structure, called L1 Adaptive Nonlinear Dynamic Inversion (L1-ANDI), is presented, which can guarantee the desired dynamic performance while overcoming the influence of disturbances and uncertainties. In particular, the introduction of a low-pass filter makes the L1-ANDI control realize the decoupling of fast adaptation and robustness. Furthermore, the effect of CG variations on the aircraft is analyzed from the aerodynamic perspective, and the L1-ANDI-based flight controller is designed to eliminate the influence of the CG variations. A series of simulation results demonstrate that the designed flight controller can achieve satisfactory performance and is robust to the disturbance of CG sudden variations. [ABSTRACT FROM AUTHOR]

This study designed a wide-beamwidth pixelated dielectric resonator antenna (DRA) combined with a low-pass filter (LPF) to suppress harmonics. The DRA was designed to create a wide-beam pattern with a pixelated structure. The pixelated DRA was optimized by a genetic-learning particle swarm optimization algorithm. To prevent significant higher-mode radiation and harmonics from occurring in the DRA, an LPF was included in its feeding line. The filter had a seventh-order Chebyshev design, and a hybrid step-impedance filter was proposed by modifying the step-impedance filter for use in narrow spaces behind the ground. [ABSTRACT FROM AUTHOR]

Interior Permanent Magnet Synchronous Motor (IPMSM) motion-sensorless speed control necessitates precise knowledge of rotor flux, speed, and position. Due to numerous non-ideal aspects, such as converter nonlinearities, detection errors, integral initial value, and parameter mismatches, the conventional first-order integrator’s estimated rotor flux experiences a DC offset (Doff). Low-pass filters (LPF) with a constant cut-off frequency yield accurate estimates only in the medium- and high-speed range; however, at the low-speed area, both magnitude and phase estimates are inaccurate. The presented technique resolves the aforementioned issue for a broad speed range. In order to achieve precise flux estimation, this article presents an improved technique of flux estimator with two distinct drift mitigation strategies for the motion-sensorless field-oriented control (FOC) system of IPMSM. Using the orthogonality of the α- and β-axes, the proposed drift elimination system can estimate drift in different situations while maintaining a high level of dynamic performance. The stator flux linkage (SFL) computation in the synchronous coordinate is established from the estimation of the rotating shaft’s permanent magnetic flux linkage orientation and the statistical equations model of the SFL. By comparing the calculated SFL vector to the SFL vector derived from the stator winding voltage and currents integral model with a drift PI compensation loop, a feedback loop is formed to neutralize integral drift, and the rotational speed and position of an IPMSM is estimated utilizing the vector product of the two flux linkages in a phase-locked loop. Theoretical interpretation is presented, and Matlab Simulink simulations, as well as experimental outcomes, consistently demonstrate that the suggested estimation techniques can eliminate the phenomenon of flux drift.