Cascade Connection Research Articles

Scalable Nonlinear Sequence Generation using Composite Mersenne Product Registers

We introduce a novel composition method that combines linear feedback registers into larger nonlinear structures and generalizes earlier methods such as cascade connections. We prove a Chaining Period Theorem which provides the cycle structure of these register constructions. We then use this Chaining Period Theorem and a new construction we call a Product Register (PR) to introduce a flexible and scalable register family with desirable properties, which we term Composite Mersenne Product Registers (CMPRs). We provide an algorithm to estimate the linear complexity of a chosen CMPR and investigate the statistical properties and security of a CMPR-based pseudorandom generator. Finally, we propose a family of CMPR-based stream ciphers and provide comparisons with the TRIVIUM stream cipher in terms of hardware area and security.

Artificial Visual System for Stereo-Orientation Recognition Based on Hubel-Wiesel Model.

Stereo-orientation selectivity is a fundamental neural mechanism in the brain that plays a crucial role in perception. However, due to the recognition process of high-dimensional spatial information commonly occurring in high-order cortex, we still know little about the mechanisms underlying stereo-orientation selectivity and lack a modeling strategy. A classical explanation for the mechanism of two-dimensional orientation selectivity within the primary visual cortex is based on the Hubel-Wiesel model, a cascading neural connection structure. The local-to-global information aggregation thought within the Hubel-Wiesel model not only contributed to neurophysiology but also inspired the development of computer vision fields. In this paper, we provide a clear and efficient conceptual understanding of stereo-orientation selectivity and propose a quantitative explanation for its generation based on the thought of local-to-global information aggregation within the Hubel-Wiesel model and develop an artificial visual system (AVS) for stereo-orientation recognition. Our approach involves modeling depth selective cells to receive depth information, simple stereo-orientation selective cells for combining distinct depth information inputs to generate various local stereo-orientation selectivity, and complex stereo-orientation selective cells responsible for integrating the same local information to generate global stereo-orientation selectivity. Simulation results demonstrate that our AVS is effective in stereo-orientation recognition and robust against spatial noise jitters. AVS achieved an overall over 90% accuracy on noise data in orientation recognition tasks, significantly outperforming deep models. In addition, the AVS contributes to enhancing deep models' performance, robustness, and stability in 3D object recognition tasks. Notably, AVS enhanced the TransNeXt model in improving its overall performance from 73.1% to 97.2% on the 3D-MNIST dataset and from 56.1% to 86.4% on the 3D-Fashion-MNIST dataset. Our explanation for the generation of stereo-orientation selectivity offers a reliable, explainable, and robust approach for extracting spatial features and provides a straightforward modeling method for neural computation research.

Tunable Absorptive Dual Notch Filters Using A Stub-Loaded Coupled Line with An Inductor

This paper presents tunable absorptive dual-notch filters using a stub-loaded coupled line with an inductor. The two-pole Butterworth filter function is modified to attain absorptive responses at a notch frequency. In addition, a stub-loaded coupled line with an inductor is employed to obtain dual-band bandstop responses, the required coupling coefficients, and quality factors based on the modified Butterworth function at two notch frequencies. In the proposed filter, tunable absorptive dual-notch responses are accomplished without using auxiliary circuits, such as an impedance matching network. The two resonant frequencies and the quality factors of the resonators are independently controlled by adjusting the three loading capacitances of the resonator. Three types of filters are designed and then built on a substrate with <i>ε<sub>r</sub></i> = 3.42 and <i>h</i> = 30 mils. The first filter (Filter A) attained a return loss of 11.2–17.1 dB/10.5–24.4 dB at 0.76–0.98 GHz/1.05–1.28 GHz. The measured return loss of the second filter (Filter B) was 12.5–14.8 dB/10.2–12.3 dB at 0.84–1.08 GHz/1.35–1.59 GHz. For Filter C, equipped with a 4-pole response achieved through the cascade connection of two 2-pole filters (Filter B), a return loss of 11.2–15.1 dB/14.2–27.3 dB was obtained at 0.9–1.1 GHz/1.38–1.63 GHz. The application areas of the proposed filters include cognitive radios and carrier aggregation systems requiring two transmit frequencies.

Linear-acoustic effects of asymmetrical undercutting of toneholes of woodwind instruments.

The influence of the presence and magnitude of asymmetrical undercutting of the toneholes of woodwind instruments on the change in their effective radius and the corresponding shift of the eigenfrequencies of the air duct is considered. Within the framework of the electro-acoustic analogy, a tonehole with an asymmetrical undercutting along the axis of the main bore is presented as a cascade connection of two holes with different radii (undercutting and not undercutting parts of the hole), and with a sideway undercutting-in the form of a parallel connection. Formulas for numerical calculations are given that make it possible to determine the effective radius of such holes for the open state in the low-frequency approximation. Based on the obtained dependencies, using the transmission-matrix method, the eigenfrequencies of an air duct with one hole were calculated and compared with the results of computer modeling in the COMSOL Multiphysics 5.6 program. It is shown that increasing the degree and angle of undercutting leads to an increase in the effective radius, a displacement of the "center of gravity" of the sound hole along the main bore axis, and has effect on the shift of resonant frequency.

Active Filters for Standard-Compliant Power Quality in Electrical Networks

The article is devoted to the analysis of three circuits of modular multilevel converters (MMCS) with cascade connection of single-phase bridge and half-bridge voltage converters, each of which operates in pulse width modulation (PWM) mode. The main feature of active filters based on MMS is the possibility of selective high-speed harmonic filtering in on–line mode: AF allows the suppression of any given set of harmonics, including the negative harmonic of the fundamental frequency (reverse sequence), with a given degree of suppression - to zero or a normalized value - by an appropriate task in the control program. For the practical implementation of MMS in solving problems of normalization of electricity quality indicators, the so-called DSB control algorithm of MMS was developed, based on the traditional "classical" theory of automatic control and the theory of three-phase circuits. A comparative assessment of the use of various MMC schemes for symmetry and reactive power compensation has been carried out. It is shown that the problem of voltage symmetry using MMS is a special one, requiring the use of special algorithms to solve it, ensuring the reactive nature of branches of MMS circuits.

CC-CBTA-Based Floating Inductance Simulator with CM/VM PID Controllers

This work describes voltage-mode (VM), current-mode (CM) PID controllers and an electrically controllable floating inductance (FI) simulator circuit. Only a single current-controlled current backward transconductance amplifier (CC-CBTA) and a grounded capacitor are used in the proposed FI simulator circuit. One CBTA, one CC-CBTA, two capacitors and one resistor are used in the proposed PID controllers. All of the proposed circuits have appropriate input and output impedance values, allowing them to be utilized in cascade connections without requiring a buffer circuit. There is also no matching constraint between the active and passive values of the proposed circuit. The SPICE software environment and experimental results were used to validate theoretical derivations and associated outcomes. The layout of the CC-CBTA has been built, and the post-layout simulations are carried out using the netlist extracted from the layout. Comparisons were made with similar circuits found in the professional literature.

Development of constant switching frequency model predictive control for DFIG-based wind energy conversion system in standalone and grid connected operation

This paper presents a constant switching frequency (CSF) model predictive control (MPC) for a doubly-fed induction generator (DFIG)-based wind energy conversion system (WECS) in standalone and grid-connected operations. The system comprises a cascade connection of a rotor side converter (RSC) and a grid side converter (GSC) with a common DC-link. A battery energy storage system (BESS) is also connected to the common DC-link via a bi-directional dc–dc converter (BDDC). The RSC is controlled through CSF-model predictive current control (CSF-MPCC) scheme in both standalone mode (SAM) and grid-connected mode (GCM) of operations. The GSC control employs the CSF-MPCC scheme in grid-connected operation, whereas CSF-model predictive voltage control (CSF-MPVC) scheme is implemented in standalone operation. Moreover, the power balance is achieved by controlling the BDDC using MPCC to discharge or charge the BESS in response to surplus or deficient power generation. The effectiveness of the proposed control approach for DFIG-based WECS in both SAM and GCM is verified through MATLAB-based simulation and experimental results under different dynamic conditions like variable wind velocity changing from 12 m/s to 8 m/s, different grid demands from 3 kW to 1.5 kW and load change of 4 kW to 6.5 kW. Moreover, the robustness of the proposed control is corroborated by parametric sensitivity, time delay, and grid unbalance, along with its low-voltage ride-through (LVRT) capability during an LLLG fault.

Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard

Feedback shift registers (FSRs) are used as a fundamental component in electronics and confidential communication. A FSR f is said to be reducible if all the output sequences of another FSR g can also be generated by f and the FSR g costs less memory than f. A FSR is said to be decomposable if it has the same set of output sequences as a cascade connection of two FSRs. Two polynomial-time computable transformations from Boolean circuits to FSRs are proposed such that the output FSR of the first (resp. second) transformation is irreducible (resp. indecomposable) if and only if the input Boolean circuit is satisfiable. Through the two transformations, it is proved that deciding irreducibility (indecomposability) of FSRs is NP-hard. Additionally, FSRs are constructed to show that there exist infinitely many irreducible (resp. indecomposable) FSRs which are decomposable (resp. reducible).

Exact Sinusoidal Signal Tracking on a Modified Topology of Boost and Buck-Boost Converters

This contribution presents new DC–DC Boost and Buck-Boost converter topologies to track sinusoidal signals in an exact form, that is, with zero error tracking. The proposed topology considers two DC–DC converters connected to the same load, which means that the converters are not in a cascade connection. To track the exact sinusoidal reference, the control algorithm is based on the indirect control algorithm and the harmonic balance method. The main contribution is to consider two control inputs that facilitate and permit canceling out the second harmonic generated by the nonlinearity of the model, and as a result there is a single frequency in the output. The result is such that the converters can track sinusoidal signals with exactly zero error. With this, there is a reduction in the potential negative effects on systems and equipment; some numerical results are presented to corroborate the proposal.

Synthesis of electronically tunable multifunction biquad filter using voltage differencing differential input buffered amplifiers

AbstractBiquad filters are commonly used in analog circuits for various purposes in signal processing and communication applications. We synthesize an analog active biquad filter with five types of voltage‐mode filtering functions. The filter is synthesized using a parallel passive resistor‐inductor‐capacitor (RLC) network and unity‐gain voltage differencing amplifier. A voltage differencing differential input buffered amplifier (VD‐DIBA) is the main active component, and the biquad filter has a three‐input single‐output (TISO) topology. By replacing the passive inductor and resistor with VD‐DIBA‐based inductance and resistance simulators with a subtractor, the TISO voltage‐mode versatile filter is obtained from two VD‐DIBAs, one resistor, and two capacitors connected to the ground. The proposed filter can provide five types of voltage‐mode filtering functions: inverting bandpass and lowpass responses as well as noninverting band‐stop, high‐pass, and all‐pass responses. The all‐pass filter requires no additional active components. The three input voltage nodes have high impedance, and a low‐impedance output voltage node facilitates cascade connections without using additional voltage buffers. In addition, the natural frequency and quality factor can be electronically tuned. The quality factor is controlled without disturbing the passband gain and natural frequency. The proposed filter is simulated and verified experimentally in the Personal Simulation Program with Integrated Circuit Emphasis (PSPICE) and through laboratory tests employing VD‐DIBAs implemented using commercially available components.

Reservoir Computing With Dynamic Reservoir using Cascaded DNA Memristors.

This article proposes molecular and DNA memristors where the state is defined by a single output variable. In past molecular and DNA memristors, the state of the memristor was defined based on two output variables. These memristors cannot be cascaded because their input and output sizes are different. We introduce a different definition of state for the molecular and DNA memristors. This change allows cascading of memristors. The proposed memristors are used to build reservoir computing (RC) models that can process temporal inputs. An RC system consists of two parts: reservoir and readout layer. The first part projects the information from the input space into a high-dimensional feature space. We also study the input-state characteristics of the cascaded memristors and show that the cascaded memristors retain the memristive behavior. The cascade connections in a reservoir can change dynamically; this allows the synthesis of a dynamic reservoir as opposed to a static one in the prior work. This reduces the number of memristors significantly compared to a static reservoir. The inputs to the readout layer correspond to one molecule per state instead of two; this significantly reduces the number of molecular and DSD reactions for the readout layer. A DNA RC system consisting of DNA memristors and a DNA readout layer is used to detect seizures from intra-cranial electroencephalogram (iEEG). We also demonstrate that a DNA RC system consisting of three cascaded DNA memristors and a DNA readout layer can be used to solve the time-series prediction task. The proposed approach can reduce the number of DNA strand displacement (DSD) reactions by three to five times compared to prior approaches.

Current-mode PID controllers employing commercially available active components

This work describes two current-mode (CM) PID controllers using only two commercially active components, namely, current feedback operational amplifier (CFOA), and four passive components, i.e. two capacitors and two resistors. They have appropriate output and input impedance values, allowing them to be utilized in cascade connections without requiring a buffer circuit. Since all capacitors are grounded, it is suitable for integrated circuit (IC) technology. Moreover, the controllers can be easily modified to operate in voltage-mode (VM), transimpedance-mode (TIM), and transadmittance-mode (TAM) PID controllers. Using 0.18 µm CMOS parameters and the PSPICE program, the proposed circuits are simulated to verify the theoretical behavior. To demonstrate the viability of the circuits, experimental tests using commercially available AD844 integrated circuits are performed. The suggested PID circuits are alsoexperimental tested in a closed-loop system as an example.

Synthesis of two-mass electromechanical systems with cascade connection of fractional-order controllers

The research focused on two-mass electromechanical systems widely utilized in industry. The challenge addressed in this work was to improve the synthesis of controllers for such systems to simplify it and enhance the quality of transition processes. Traditionally, the synthesis of control system loops for these systems was carried out using integer controllers and standard forms. However, this approach led to the synthesis of complex integer controllers that are difficult to implement. To overcome this issue, an original approach to the synthesis of control system loops based on the fractional characteristic polynomial is proposed. The fractional characteristic polynomial ensures the desired quality of the transition process given the implementation of a specified structure of the fractional controller. A new method of structural-parametric synthesis of fractional-order controllers is developed for the case of their cascade connection in multi-loop two-mass electromechanical systems. Additionally, an algorithm for synthesizing fractional-order controllers for the corresponding control loops is presented. This enabled the structural-parametric synthesis of fractional-order controllers for a two-mass electromechanical system with the cascade connection of controllers. Such an approach provides better quality of transition processes compared to classical integer controllers, simplifies the synthesis, and thereby enhances the quality of the synthesized systems. The impact of the synthesized fractional-order controllers using the proposed approach on the dynamic properties of the two-mass «thyristor converter – motor» system was investigated. The research results demonstrated the practical applicability of fractional controllers designed using the proposed method for the synthesis of automatic control systems of two-mass electromechanical systems in the industry.

New Approach of deriving Third-Order Quadrature Sinusoidal Oscillators

Numerous approaches/methods have been employed in the past to derive various third-order sinusoidal oscillators (TOSOs). In this communication, a new simple approach for realizing TOQSO is presented, utilizing a second order inverse high-pass active filter with a cascade connection of traditional lossless integrator. The proposed approach can provide quadrature voltage outputs by leveraging the availability of lossless integrator. It is demonstrated that the proposed approach has the potential to generate various TOQSOs, as exemplified by the voltage-mode TOQSO based on current feedback operational amplifiers (CFOAs). The oscillation condition (CO) and frequency (FO) of the derived oscillator can be independently controlled. Experimental results utilizing AD844 CFOA ICs have been included to validate the theoretical propositions.

Single-input multiple-output inverse filters designs with cascade capability

Enhancing a topology of the literature, single-input multiple-output first-order inverse filter topologies are presented in this work. They offer the features of minimized circuit complexity, grounded capacitors requirement and, the most important, the capability of cascade connection with other stages without extra buffers needed. This is achieved thanks to the properties of the Current Feedback Operational Amplifier terminals. The behavior of the structures with regards to the effect of parasitics is evaluated for establishing the suitable frequency range of their operation. The performance of the filters is evaluated using the OrCAD PSpice suite, as well as through experimental results.

Load Torque Observer for BLDC Motors Based on a HOSM Differentiator

An observer is proposed for a trapezoidal brushless DC motor composed of a cascade connection of a reduced-order Luenberger observer and a high-order sliding mode (HOSM) differentiator. This configuration can estimate the angular velocity and reconstruct the load torque, key elements for the control of this type of motor, under the mild assumption that the variable load torque and its k-th time derivatives are bounded. The proposed observer was tested on an experimental test bench based on Texas Instruments (TI) High Voltage Digital Motor Control (HVMTR Kit) using a Delfino F28379D micro controller. The results show that the velocity and load torque can be properly estimated, despite the presence of noise in the current measurements.

The Modeling of GaN-FET Power Devices in SPICE

This paper focuses on the problem of the modeling of FET power transistors made of gallium nitride offered by GaN Systems, Transphorm, and Nexperia. The considered devices have been available on the market since 2014. GaN-FETs are built as a cascade connection of a normally on gallium nitride HEMT and a normally off MOSFET made of silicon. On the manufacturer’s sites, one can find models of these devices for like-SPICE tools in the text form. The main goal of this paper is to evaluate the model’s accuracy by comparing calculation results obtained by the use of the considered models with the authors’ measurement results and datasheet. It has been demonstrated that the GaN Systems model built on controlled sources described by a set of arbitrarily selected mathematical functions more accurately reproduces the basic characteristics of a transistor. On the other hand, the models from Transphorm and Nexperia, which are constructed based on built-in semiconductor device models, more precisely calculate the values of selected functional transistor parameters.

Quadratic Programming for Continuous Control of Safety-Critical Multiagent Systems Under Uncertainty

This paper studies the control problem for safety-critical multi-agent systems based on quadratic programming (QP). Each controlled agent is modeled as a cascade connection of an integrator and an uncertain nonlinear actuation system. In particular, the integrator represents the position-velocity relation, and the actuation system describes the dynamic response of the actual velocity to the velocity reference signal. The notion of input-to-output stability (IOS) is employed to characterize the essential velocity-tracking capability of the actuation system. The standard QP algorithms for collision avoidance may be infeasible due to uncertain actuator dynamics. Even if feasible, the solutions may be non-Lipschitz because of possible violation of the full rank condition of the active constraints. Also, the interaction between the controlled integrator and the uncertain actuator dynamics may lead to significant robustness issues. Based on the current development of nonlinear control theory and numerical optimization methods, this paper first contributes a new feasible-set reshaping technique and a refined QP algorithm for feasibility, robustness, and local Lipschitz continuity. Then, we present a nonlinear small-gain analysis to handle the inherent interaction for guaranteed safety of the closed-loop multi-agent system. The proposed method is illustrated by numerical simulation and a physical experiment.

Cascade multi-resonant disturbance observer design. Application to a distillation column

In this work, we present a novel approach for input disturbance estimation design and implementation for dynamical processes under the influence of unknown disturbances that present a clear periodical behaviour of a known frequency. Both the design and the implementation are focused on simplicity. The observer consists of a set of transfer functions fed by the process manipulated variable and the sensor measurement that are implemented through a mixture of cascade and series connections. For the synthesis of the disturbance observer, we just need an input–output model of the process and one tuning parameter in each of the transfer functions. We present simple rules for the design considering the trade-off between the transient time needed to estimate changes in the behaviour of the disturbance and the robustness against measurement noise effects. We show the benefits in using this disturbance estimation as a feed-forward signal in both open loop and closed loop control applications, and we quantify the robustness modification when used together with a closed loop controller. The transfer functions of the observer include both a low pass filter and a set of resonant terms. We quantify the effect of the different terms and their parameter tuning. Our implementation method uses standard tools available in industrial control systems and we have applied it to a real distillation column under ambient temperature disturbances. The main contribution of this work is the simplicity of the design and implementation of the disturbance observer, making it suitable for the process industry and to be managed by non-experts in control systems. Another contribution is the a priori design based in intuitive engineering performance indices.

Methods of synthesis of overlapped subarrays with flat-topped radiation patterns in planar phased array antennas

One of the approaches to the design of phased array antennas (PAA) for beam scanning in a limited region of space is associated with formation of overlapped subarrays with flat-topped radiation patterns of width equal to the width of the scan region. Unlike linear subarrays, for which there exist many technical solutions, planar overlapped subarrays can be formed by two ways. One of them is based on cascade connection of linear subarrays arranged perpendicularly to each other. Another way is based on use of beamforming networks. Since the problems concerning synthesis of overlapped subarrays with flat-topped patterns in planar PAA is not yet sufficiently considered in the literature, the indicated problem remains of interest. The work considers two methods of synthesis of planar overlapped subarrays with flat-topped radiation patterns. One method is a conventional method based on Fourier transform of the required radiation pattern. Another method introduced in the paper is new one. It allows determination of amplitude distribution over subarray aperture with providing maximum level of the subarray factor in the broadside direction and with taking into account power balance distributed over the subarray radiating elements. The proposed method is compared with the conventional method based on the Fourier transform, and advantages of the former method over the latter one are shown. The paper contains results obtained for amplitude distributions for a few cases of subarray excitation and appropriate subarray factors characterizing the capabilities of the new method. The method proposed in the paper can be applied in the further studies concerning development of networks for feeding overlapped subarrays in planar limited-scan PAA of modular construction.