Search

It has been demonstrated in previous literature that a tapered dashpot is a physical embodiment of the mem-dashpot, while a displacement-dependent fluid inerter device can be modeled as a mem-inerter. In this paper, a displacement-dependent diamond-shaped structure spring device is found to be a physical realization of a mem-spring via both theoretical and experimental research. A quarter-car model of the suspension system equipped with the mem-spring is established by the Lagrangian method, and it is exhibited in simulation that the mem-spring has load adaptivity and the ability to improve suspension performance. An investigation reveals the mechanism behind load adaptivity from the perspective of energy storage, namely, a mem-spring with different initial displacement values can be equivalent to a semi-active spring performing an initial-position-dependent stiffness control strategy. Finally, the load adaptivity and performance benefits are verified through the bench test of the suspension system equipped with the mem-spring prototype. Thanks to such load adaptivity, the suspension system with the mem-spring can provide smoother and more constant ride comfort as well as better road holding performance than the one with a linear spring. [ABSTRACT FROM AUTHOR]

To reveal the effect of cubic nonlinear stiffness on the longitudinal vibration responses of the rod system, the model of longitudinal vibration response analysis is established in this study for the double-rod system coupled through a nonlinear element, exhibiting the characteristic of cubic nonlinear stiffness. Then, the governing equations of the double-rod system are obtained through the Hamilton principle combined with the variational procedure, and solved by the Galerkin truncation method. The longitudinal dynamic behavior is validated to explore the impact of nonlinear element on the longitudinal vibration responses of the double-rod system. According to the numerical results, the nonlinear element has a significant impact on the longitudinal vibration responses of the double-rod system. On the one hand, the nonlinear element induces the longitudinal complex dynamic behavior, including magnitude-jumping, the area of multiple continuous amplitudes, quasi-periodic state, and others. On the other hand, the nonlinear element could change the characteristics of the longitudinal vibration responses from the double-rod system. The reasonable parameters of the nonlinear element play a role in reducing the vibration of the double-rod system. [ABSTRACT FROM AUTHOR]

In recent years, wave-based analog computing has been at the center of attention for providing ultra-fast and power-efficient signal processing enabled by wave propagation through artificially engineered structures. Building on these structures, various proposals have been put forward for performing computations with waves. Most of these proposals have been aimed at linear operations, such as vector-matrix multiplications. The weak and hardly controllable nonlinear response of electromagnetic materials imposes challenges in the design of wave-based structures for performing nonlinear operations. In the present work, first, by using the method of inverse design we propose a three-port device, which consists of a combination of linear and Kerr nonlinear materials, exhibiting the desired power-dependent transmission properties. Then, combining a proper arrangement of such devices with a collection of Mach–Zehnder interferometers (MZIs), we propose a reconfigurable nonlinear optical architecture capable of implementing a variety of nonlinear functions of the input signal. The proposed device may pave the way for wave-based reconfigurable nonlinear signal processing that can be combined with linear networks for full-fledged wave-based analog computing.

Frequency multipliers are used in electronic devices to generate spectrally pure sinusoidal signals in the frequency range from a few to tens of GHz. The multipliers are used to multiply the frequency of highly stable but more low-frequency devices with the subsequent extraction of the necessary harmonics from the frequency spectrum of the received microwave range. The frequencies selected after multiplication (set) have significantly higher energy, spectral and range characteristics, which allows them to be used as local oscillators and synthesizers in receiving and transmitting systems. The authors of this paper theoretically substantiate and practically demonstrate the possibility of an unconventional implementation of a microstrip multiplier of the microwave range based on a directional traveling wave filter. The proposed implementation does not require the use of active semiconductor elements. The well-known circuit and technological principles for the creation of microstrip microwave multipliers are considered in the paper. The features, problems and shortcomings arising from their implementation are analyzed. The effectiveness of using the balanced circuit for frequency multiplication is confirmed. A list of mandatory requirements and conditions necessary for the implementation of the microwave multipliers is given. It is demonstrated that the features of the microstrip travelling-wave filter are identical to the conditions and requirements for the implementation of balanced multipliers. It is shown and substantiated how an unconventional implementation of a passive microwave multiplier is possible due to the electromagnetic interaction of the input and output nodes of such a filter with an annular travelling-wave resonator. Using the example of modifying a block diagram of a directional filter into a multiplier circuit, the possibility of creating a microwave doubler is confirmed by separating a given frequency from the frequency spectrum of a traveling-wave ring resonator.

In the article by means of the combined use of the mathematical apparatus of the Laplace transform and its discrete analogue (D – transform) on the basis of the method of harmonic linearization, we obtain the equations that describe spontaneous periodic processes occurring in nonlinear continuous discrete systems (CDS) of automatic control. The obtained equations of periodic processes take into account the specifics of the dynamic properties of nonlinear CDS and take a different form depending on the features of the structural scheme of the system under study (from the type of nonlinear element, the quantity and location of the pulsed elements relative to the nonlinear element). They allow us to investigate the simplest spontaneous periodic processes, as well as periodic processes specific to the CDS, the frequency of which is not related to the integral relation with the frequency of the switching of the pulse element of the system. This makes it possible to more fully take into account the kind of possible periodic modes in the system and improve the accuracy of their parameters.

Reviewed features of harmonic linearization of nonlinear element in control systems with the digital computer onboard (DCO) in the circuit of control. Difficulties of this task solution become more complicated because of the system of automatic control with DCO in the circuit of control naturally is continuous-discrete system (CDS). The main characteristic of CDS is signal interruption in one or many points of the system with saving uninterrupted outgoing system signal. It was proved that depending on mutual arrangement of nonlinear and impulse elements in the structure of CDS it is necessary to use different coefficients of harmonic linearization of nonlinear element. This will allow more closely take in account of possible system periodical modes and increase the precision of its parameters determination.

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Anyone who ever gave attention to advances in circuit elements will be familiar with the three elementary two-terminal passive elements: resistor, inductor, capacitor and their memory counterparts: memristor, meminductor and memcapacitor, respectively. Similarly, it is reported that the mem-dashpot and the mem-spring were viewed as the memory counterparts of the damper and the spring in the field of mechanical engineering. However, what is the memory counterpart of the inerter as a new two-terminal element? In 2018, Zhang predicted the existence of such a mechanical element, which he called a mem-inerter. Although he postulated this element, until now no one offered either a useful physical realization or an example of a mem-inerter. Here, a displacement-dependent fluid inerter device is found to be a physical realization of a mem-inerter, though with a parasitic element called the extended mem-dashpot, which is viewed as the mechanical counterpart of an extended memristor. Experimental results confirm this finding and the existence of the mem-inerter and the extended mem-dashpot in the real world. This work is very helpful in finding and designing mem-inerter and extended mem-dashpot devices, and modeling some important nonlinear hysteretic devices and systems, which is a fundamental branch of research in nonlinear dynamics. [ABSTRACT FROM AUTHOR]

Abstract Type3-PLLs are widely used for carrier synchronization in tracking telemetry and command (TT&C) systems. A major challenge with the traditional Type3-PLL is how to further improve their acquisition and tracking speed without compromising the noise suppression ability and stability. In this article, drawn lessons from the nonlinear control theory, a new structural Type3-PLL is presented. The idea of the proposed Type3-PLL, which can be denoted by N-Type3-PLL, is to couple with a designed nonlinear element in the traditional Type3-PLL. The loop noise bandwidth is adaptively adjusted by the designed nonlinear element on the basis of the loop filter output, which is determined by the frequency-phase error. The output noise of the nonlinear element is then suppressed by the consequent low-pass filter. The influence of the nonlinear element parameters on the N-Type3-PLL is quantitatively analyzed and discussed. Simulation results indicate that the N-Type3-PLLs under various parameters can achieve locking faster than the traditional Type3-PLL in response to a step change in frequency. The nonlinear element parameters constraint the comprehensive performance of the N-Type3-PLL. The optimal parameters of the nonlinear element are solved via a suggested iterative feedback method. Compared with the traditional Type3-PLL, the output frequency of the N-Type3-PLL under the optimal parameters jitters much less and the standard deviation of frequency-phase error is reduced from 0.6198 (rad/s) 2 to 0.2264 (rad/s) 2 when the input SNR equals −15 dB. The lock time after the step is extended from 0.22 s to 0.24 s, which is within an acceptable range. The loss threshold of the proposed N-Type3-PLL is reduced from −20 dB to −23 dB. Highlights • A new structural Type3-PLL coupled with a designed nonlinear element is proposed. • The loop noise bandwidth of the proposed Type3-PLL can be adaptively adjusted. • Optimal parameters of the N-Type3-PLL are solved via a iterative feedback method. • The loss threshold of the proposed N-Type3-PLL is reduced from −20 dB to −23 dB. [ABSTRACT FROM AUTHOR]

Operational amplifiers (opamps) are often designed in stages. Distortion analysis of multistage opamps is challenging due to multiple non-linearity sources. Therefore, one effective analysis method is to consider a multistage opamp model as a cascade of condensed stages, with each stage modelled by one weakly non-linear element. Then, in order to obtain a satisfactory distortion model, accurate characterisation of the non-linearity of each stage is necessary. In this Letter, the authors propose an analytical calculation method for modelling the weak non-linearity of an amplifier stage consisting of several interconnected transistors. A stage circuit model created by this method can be used to produce analytical harmonic distortion characterisation of closed-loop circuits with peripheral elements. Numerical accuracy of the analytical method has been validated by transistor-level simulation. [ABSTRACT FROM AUTHOR]

We perform the comparative analysis of two methods aimed at the determination of complex transfer coefficients of nonlinear elements in the heterodyne frequency conversion. On the basis of the analysis of the available methods, we consider the specific features of the design of devices aimed at measuring the parameters of the units with frequency conversion. We describe the main sources of errors, such as the error caused by the reciprocity of the reference mixer and the amplitude-phase error. [ABSTRACT FROM AUTHOR]

Chua's concept of nonlinear higher-order elements is generalized with the aim of extending the procedures of predictive modeling of complex electrical systems to various nonelectrical domains. Special attention is paid to nanodevices with ambiguous hysteretic characteristics and their predictive modeling via unambiguous constitutive relations. It is shown on an example of spin-torque nano-oscillator how its Newton-like equation of motion can be used for constructing the predictive model of this device, and how this model can be useful for identifying the mechanisms of the oscillator dynamics. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electromagnetic transient (EMT) simulation of nonlinear elements in power systems is a particular challenge due to the requirements of an accurate representation and an efficient solution. The existing real-time simulators utilize a piecewise linear representation along with a fixed time step for the solution of nonlinear elements. This paper proposes the detailed methodologies for applying variable time stepping to real-time EMT simulation to improve the simulation accuracy and efficiency. The challenges, the feasible solutions, and corresponding restrictions of applying various variable time-stepping schemes along with nonlinear element solution methods in real time are discussed. The offline simulation and the real-time hardware emulation of two case studies, a full-bridge diode circuit and a power transmission system, are presented. The case studies were implemented on the field-programmable gate array device (Xilinx Virtex-7 XC7VX485T) in real time using high-level synthesis tool to achieve a parallelized and pipelined hardware design with minimum coding effort. The real-time emulation results captured by an oscilloscope are validated against the offline simulation on Saber and PSCAD/EMTDC software tools. [ABSTRACT FROM PUBLISHER]

Copyright of Technical Electrodynamics / Tekhnichna Elektrodynamika is the property of National Academy of Sciences of Ukraine, Institute of Electrodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)