Linear Force Research Articles

Direct electromagnetic force control of linear induction motor with end effects using fuzzy controller

In this article is a present dynamic model of a linen induction motor with end effects, occurs when the electromagnetic system of the motor is open. Instead of the angular speed and electromagnetic torque as a rotation motor, in the linear induction motor we have linear speed and linear electromagnetic force, which are sufficiently influenced by the open electromagnetic system of the primary and secondary elements of the linear motor. The choice of an appropriate control system for a linear induction motor is of particular importance considering the use of this type of motor in manufacturing. There are different types of control schemes for standard rotary motors that have their own advantages and disadvantages. When choosing a motor control scheme, we strive to achieve the following parameters, such as smoothness of regulation, ability to regulate in all four quadrants, accuracy of regulation, range of regulation and last but not least, simplicity of regulation. One such method that meets these criteria for rotary motors is the direct torque control method with space vector modulation. The control system of the linear induction motor proposed in this paper is based on this method, taking into account the open electromagnetic system and the occurrence of the end effects of the linear induction motor. Instead of the angular reference velocity as a rotary motor, in this case we have a linear reference velocity to the input, which is compared to the current linear velocity of the motor. The present paper also uses the vector modulation method by analogy with direct torque control with space vector modulation of the rotary motor. For the conversion of a linear velocity to a linear electromagnetic force, instead of a standard PI controller, it is using a fuzzy controller to convert a linear velocity to a reference electromagnetic force.

A Two Degree-of-Freedom Rotary-Linear Machine With Transverse-Flux Structure

This paper proposes a two-degree-of-freedom rotary-linear machine with transverse-flux structure. In the proposed machine, the rotary flux and linear flux are naturally decoupled, hence its linear force and rotary torque can be controlled independently. Unlike the conventional rotary-linear machines with 3D-flux pattern, the proposed machine with transverse-flux structure can employ circumferentially laminated steel sheets to provide outstanding electromagnetic performance. The topology and operation principle of the proposed machine are introduced, while the naturally decoupled-flux feature is explained by analytical modelling and 3D finite-element method. A parametric study of pole-pair numbers combination is conducted to obtain the optimal pole-pair numbers in both axial and circumferential directions. The optimal electromagnetic performances are quantitatively compared with other two conventional rotary-linear machines, while an experimental prototype is manufactured to verify the proposed concepts.

Solar cycle as a distinct line of evidence constraining Earth’s transient climate response

Severity of warming predicted by climate models depends on their Transient Climate Response (TCR). Inter-model spread of TCR has persisted at ~ 100% of its mean for decades. Existing observational constraints of TCR are based on observed historical warming response to historical forcing and their uncertainty spread is just as wide, mainly due to forcing uncertainty, and especially that of aerosols. Contrary, no aerosols are involved in solar-cycle forcing, providing an independent, tighter, constraint. Here, we define a climate sensitivity metric: time-dependent response regressed against time-dependent forcing, allowing phenomena with dissimilar time variations, such as the solar cycle with 11-year cyclic forcing, to be used to constrain TCR, which has a linear time-dependent forcing. We find a theoretical linear relationship between the two. The latest coupled atmosphere-ocean climate models obey the same linear relationship statistically. The proposed observational constraint on TCR is about 1/3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{1}}/{{3}}$$\\end{document} as narrow as existing constraints. The central estimate, 2.2 oC, is at the midpoint of the spread of the latest generation of climate models, which are more sensitive than those of the previous generations.

Моделювання коливальних процесів віброударних систем

In order to improve the efficiency of methods and means of mathematical modeling of vibro-impact systems, a generalized function of the periodic mode of movement of the executive body has been developed. It is presented in the form of the dependence of the shock impulse on the ratio of the angular velocities of the linear conservative system and its own. When obtaining this function, the Heaviside integral jump function and the periodic Green's function were used. The function of the dependence of the oscillation frequency on the impact impulse is determined from the impact conditions for the function of the system's response to a periodic sequence of impulses. The design model of a vibroimpact system is considered, both with one impact element and a motion limiter, and with a double-sided impact pair with alternate impact interactions with the limiters. In the intervals between impacts, there is a linear force interaction. When developing the mathematical model, a stereomechanical impact model was used, which is characterized by the velocity recovery coefficient after the impact. The analysis of the dependence function of the oscillation frequency on the shock impulse made it possible to obtain skeletal diagrams of resonant and quasi-resonant oscillations of vibro-impact systems with one and many degrees of freedom. Based on the obtained phase diagrams of the state of vibro-impact systems, it was determined: in a system with a gap, an increase in the impact speed increases the oscillation frequency, and the vibro-impact nonlinearity is «hard»; in a system with tension, with an increase in the value of the shock impulse, the oscillation frequency decreases (nonlinearity is «soft»). In the absence of a gap, the system is isochronous. Depending on the initial energy reserve and the location of the limiters in an asymmetric oscillatory system, with one degree of freedom, there can be vibro-impact modes with both one (closer located) and both limiters. In a linear conservative system with several degrees of freedom, a single-impact T-periodic regime is realized. If the dissipation during motion and impact is very small, then a regime close to resonant can exist in the system. In this case, periodic oscillations are supported by a weak external periodic force. The developed mathematical model makes it possible to fully describe the process of changing the relative coordinate of the movement of the working body, both in transient and in the established modes of movement of the system.

An active hybrid Reynolds-averaged Navier–Stokes/large eddy simulation approach for gray area mitigation

During the transition from the RANS (Reynolds-Averaged Navier–Stokes) mode to the LES (Large Eddy Simulation) mode, i.e., in the so-called gray area, continuous hybrid RANS/LES approaches suffer from the well-known problem of excessively slow generation of resolved structures. Indeed, when the mesh is refined in the direction of the flow, the model is designed to reduce the modeled energy, but there is no mechanism to transfer the equivalent amount of energy into the resolved motion. Hence, the total turbulent energy and turbulent stresses are underestimated, which strongly affects the prediction of the mean flow. This also constitutes a violation of the conservation of mechanical energy, which can only be corrected by an active approach, i.e., an approach that allows the injection of resolved energy. The aim of this work is to develop such an active approach based on the introduction of a fluctuating volume force into the resolved momentum equation, similar to the anisotropic linear forcing (ALF) method proposed previously. The major difference with ALF is that the new method does not require target statistics obtained by a RANS computation but is based on a simple analysis of the rate of energy transfer related to variations in resolution, enabling the forcing to be extended to continuous hybrid RANS/LES. The application of the new method to the cases of a channel with or without periodic constriction shows a drastic improvement over the case without forcing. Although the method is applied herein to a particular hybrid RANS/LES approach (HTLES, hybrid temporal LES), it can easily be extended to any other approach, as long as a parameter identifies variations in resolution, and thus offers vast application prospects.

An accurate theoretical formula for linear momentum, force and kinetic energy

The paper demonstrates that the existing mathematical formulas of linear momentum, force and kinetic energy in physics are incomplete, since such formulas have been formulated without incorporation of mass-energy equivalence relation E = mc2. Therefore, new reformulations of the main equations of linear momentum, force and kinetic energy in the realm of special relativity are proposed. The proposed formulas provide same mathematical outcomes as the old formulas, displaying same behavior of the system when velocity approaches to speed of light, but, most importantly, comprise only velocity of the light and mass of object to provide well-defined expressions. [Formulae available with the full text]. These formulas vividly reveal that every physical variable depends solely on relativistic mass. Therefore, it modifies Newton’s second law of motion and states that the force depends on rate of change of relativistic mass of object rather than its velocity. In this highly interesting topic, primary purpose here has been to present a succinct and the carefully reasoned account of a new aspect of the Newton’s second law of motion which properly allows to derive the new mathematical formulas of linear momentum, force and kinetic energy.

A new Gaussian Process based model for non-linear wave loading on vertical cylinders

We aim to establish a fast and accurate model for fast prediction of nonlinear loading on vertical cylinders such as are typically used for fixed offshore wind turbines. We follow a ‘Stokes-type’ force model and approximate the amplitude of the higher harmonics of force by relating these to the linear force time series raised to appropriate power through amplitude and phase coefficients. We reanalyse previous experimental data and perform new experiments to expand the parameter space and establish a force coefficients database for engineering applications. A machine learning model is used to interpolate the database and make predictions on the higher order force coefficients. The machine learning model also provides a cross-validated confidence interval to indicate the prediction uncertainty and reflect model reliability. We further extend the prediction capability to unidirectional random waves with a novel force segmentation method, which localised wave groups from the random background. The new Stokes-Gaussian Process (Stokes-GP) model developed can provide engineering predictions of nonlinear wave loading on a cylinder for individual wave groups and random seas, which are straightforward to apply and fast to compute and the important higher-order loading components are considered. This will significantly improve the accuracy of the loading prediction and the ease of application for force predictions.

A modified approach for a scaled boundary shell formulation in structural isogeometric analysis

In this contribution, an efficient modification of the scaled boundary finite element method for shells is presented to compute accurate results for h-refinement. While previous works on the scaled boundary shell formulation showed inaccurate and unstable results for fine meshes, this modification overcomes such problems by the assumption of a linear force distribution over the thickness. Furthermore, the shell formulation is derived in the framework of isogeometric analysis by discretizing the bottom surface of the shell as a reference surface. This leads to a solution for in-plane directions in a weak sense, while the scaling direction is solved analytically by a modified Padé expansion. Therefore, the normal vector on the reference surface is constructed and the shell is scaled along that leading to an extensible shell formulation incorporating a three-dimensional linear elastic constitutive relation. Since the isogeometric analysis is utilized, an exact derivation of the normal vector and its gradient is possible. Initial curvature locking and Poisson’s thickness locking are eliminated inherently while shear locking and volumetric locking are alleviated by mesh refinement. The power of the modified approach is presented by standard benchmark problems and compared to the results of the unmodified approach and standard shell formulations.

Newton’s Second Law on Positive Real Line R_+

In this work, a classical particle that moves on will be investigated by using the affine commutator relation which corresponds to the Poisson bracket in classical mechanics where the equation of motions and the Newton’s second law will be modified. Two example of physical systems will be studied further using the modified Newton’s second law namely free particle and harmonic oscillator. The result concludes that for a free particle, the force on is no longer zero and a linear force due positive real line and fixed momentum. While, classical dynamics on for simple harmonic oscillator system is a qubic force.

High-Order Boussinesq Equations for Water Wave Propagation in Porous Media

To accurately capture wave dynamics in porous media, the higher-order Boussinesq-type equations for wave propagation in deep water are derived in this paper. Starting with the Laplace equations combined with the linear and nonlinear resistance force of the dynamic conditions on the free surface, the governing equations were formulated using various independent velocity variables, such as the depth-averaged velocity and the velocity at the still water level and at an arbitrary vertical position in the water column. The derived equations were then improved, and theoretical analyses were carried out to investigate the linear performances with respect to phase celerity and damping rate. It is shown that Boussinesq-type models with Padé [4, 4] dispersion can be applied in deep water. A numerical implementation for one-dimensional equations expressed with free surface elevation and depth-averaged velocity is presented. Solitary wave propagation in porous media was simulated, and the computed results were found to be generally in good agreement with the measurements.

Transient mass and heat transport modeling in a multi-tray packed bed solid desiccant dehumidifier: A parametric analysis

Using desiccant dehumidification technology, it is possible to dry the air before it reaches a climate-controlled area. Additionally, the development of theoretical models is crucial to understanding the intrinsic processes of this technology due to the interdependent physics involved in transport, adsorption, and heating dynamics. This study develops a computer model to better explain transient mass and heat transport in a multi-tray packed bed solid desiccant dehumidifier (MPBDD). A two-dimensional (2D) model that considers the conservation of mass, momentum, and heat is built. A Linear Driving Force (LDF) model is used in the study to theoretically characterize the moisture adsorption properties of the solid desiccant (Silica gel). Also, Saha, Boelman and Kashiwagi (S-B-K) equation has been applied to calculate the equilibrium water concentration. The model's validity is evaluated by contrasting theoretical predictions with experimental findings also testing with a different published article. To explore how the dehumidification system behaves under various operating situations and parameter variations, a parametric analysis was conducted. The system inlet temperature, inlet relative humidity, and bed length are among the analyzed variables. It was discovered that the highest performance was achieved with an input velocity of 0.4 m.sec−1, relative humidity of 54 %, and bed length of 0.15 m.

Water vapor mass transfer in alginate–graphite bio-based hydrogel for atmospheric water harvesting

This study presents experimental and theoretical investigations on water vapor mass transfer of a novel hydrogel compound based on alginate and graphite. This hydrogel enables rapid, reproducible, and thermally driven cycles for the adsorption and desorption of water vapor from ambient air for atmospheric water harvesting applications. We study the impacts of hydrogel composition on sorption capacity and kinetics using sorption/regeneration experiments under various environmental conditions. Theoretical models based on Fick's law of diffusion and Linear Driving Force are developed and validated with experiments to optimize thermal cycling conditions within the temperature range of 20–100 °C. The bio-based hydrogel exhibited remarkable water uptake, ranging from 0.5 to 0.9 g/g, with RH below 30 and 50 %, respectively. This low-humidity setting enables a water production rate of 1.6–2.9 L/kg of sorbent per day with a low-grade thermal regeneration (60–100 °C). Natural graphite microparticles improve water vapor release kinetics during regeneration, with an effective diffusivity coefficient of around 10−11 m²/s.

Chemo-mechanical forces modulate the topology dynamics of mesoscale DNA assemblies

The intrinsic complexity of many mesoscale (10–100 nm) cellular machineries makes it challenging to elucidate their topological arrangement and transition dynamics. Here, we exploit DNA origami nanospring as a model system to demonstrate that tens of piconewton linear force can modulate higher-order conformation dynamics of mesoscale molecular assemblies. By switching between two chemical structures (i.e., duplex and tetraplex DNA) in the junctions of adjacent origami modules, the corresponding stretching or compressing chemo-mechanical stress reversibly flips the backbone orientations of the DNA nanosprings. Both coarse-grained molecular dynamics simulations and atomic force microscopy measurements reveal that such a backbone conformational switch does not alter the right-handed chirality of the nanospring helix. This result suggests that mesoscale helical handedness may be governed by the torque, rather than the achiral orientation, of nanospring backbones. It offers a topology-based caging/uncaging concept to present chemicals in response to environmental cues in solution.

Homogenization of the Navier–Stokes equations in perforated domains in the inviscid limit

We study the solution u ɛ to the Navier–Stokes equations in perforated by small particles centered at with no-slip boundary conditions at the particles. We study the behavior of u ɛ for small ɛ, depending on the diameter ɛ α , α > 1, of the particles and the viscosity ɛ γ , γ > 0, of the fluid. We prove quantitative convergence results for u ɛ in all regimes when the local Reynolds number at the particles is negligible. Then, the particles approximately exert a linear friction force on the fluid. The obtained effective macroscopic equations depend on the order of magnitude of the collective friction. We obtain (a) the Euler–Brinkman equations in the critical regime, (b) the Euler equations in the subcritical regime and (c) Darcy’s law in the supercritical regime.

Design and implementation of shape‐adaptive and multifunctional robotic gripper

AbstractThis paper presents a multifunctional underactuated two fingered adaptive grippers for grasping a wide range of objects in different working scenarios. Two layered‐based novel multifunctional gripper design is proposed by stacking a multijointed closed‐chain mechanism over a multijointed double parallelogram mechanism to achieve a maximum number of grasping techniques. The multijointed closed‐chain mechanism is employed to perform power, shape‐adaptive grasping, and a multijointed double parallelogram mechanism is used to perform scooping, parallel, and pinch grasping. For stable shape‐adaptive/power grasping, the proposed design allows more contact points between the object and the contact surface of fingers as compared to previous gripper mechanisms. Moreover, a complete mathematical model relating the contact forces at the links of each finger to the linear actuation force and spring torque is developed to conduct stability analysis of the proposed gripper design. Finally, simulations and several experiments are performed using real objects in a reconfigurable environment to demonstrate and validate the stable grasping capabilities of the proposed gripper.

Enhanced MIMO-DCT-OFDM system using cosine domain equaliser

ABSTRACT The Discrete Cosine Transform (DCT) can be used instead of the conventional Discrete Fourier Transform (DFT) for the Orthogonal Frequency Division Multiplexing (OFDM) construction, which offers many advantages. In this paper, the Multiple-Input-Multiple-Output (MIMO) DCT-OFDM is enhanced using a proposed Cosine Domain Equaliser (CDE) instead of a Frequency Domain Equaliser (FDE). The results are evaluated through the Rayleigh fading channel with Co-Carrier Frequency Offset (Co-CFO) of different MIMO configurations. The average bit error probability and the simulated time of the proposed scheme and the conventional one are compared, which indicates the importance of the proposed scheme. Also, a closed formula for the number of arithmetic operations of the proposed equaliser is developed. The proposed equaliser gives a simulation time reduction of about 81.21%, 83.74% compared to that of the conventional Linear Zero Forcing (LZF)-FDE and Linear Minimum Mean Square Error (LMMSE)-FDE, respectively, for the case of a 4 × 4 configuration.

Nonlinear Equalization for Performance Enhancement of FBMC Systems Using Walsh Transform

The Filter Bank Multi-Carrier (FBMC) is an interesting recent technology for next-generation wireless radio communication systems. Equalization is a fundamental technique for enhancing Bit Error Rate (BER) performance. The traditional Linear Zero Forcing (LZF) and Linear Minimum Mean Square Error (LMMSE) equalizers have large noise amplification and high complexity, respectively. As the estimated error of the Signal-to-Noise Ratio (SNR) grows, the BER performance of the LMMSE equalizer degrades. In this paper, we present a Joint Low Complexity Optimized ZF-Successive Interference Cancellation (JLCOZF-SIC) equalizer for FBMC communication systems that are based on the Walsh–Hadamard Transform (WHT) rather than the Fast Fourier Transform (FFT). As in the MMSE-Successive Interference Cancellation (MMSE-SIC) equalizer, the proposed equalizer avoids the estimating error induced by average power per symbol estimation. The simulation results show that the proposed algorithm improves the system performance more than the existing algorithms. Furthermore, the proposed equalization provides stability in the BER performance at high levels of the co-Carrier Frequency Offset (co-CFO). In terms of computational complexity, the proposed scheme has a lower computational complexity than traditional schemes.

Effects of process parameters on cutting forces, material removal rate, and specific energy in trochoidal milling

Trochoidal milling has been developed to enhance tool life during slot machining. It is characterized by reduced cutting forces, cutting temperature, and tool wear as compared to conventional milling processes. It is effective in machining difficult-to-cut materials, high-speed machining, and groove corners. However, this process has not been deeply investigated enough to discover its advantages and optimize its parameters. A full factorial design of 144 experiments has been applied in this paper to investigate extensively the effects of axial depth of cut, feed rate, and trochoidal step on material removal rate, cutting forces, and specific energy in trochoidal milling. Trochoidal step and axial depth of cut almost have the same contributions on cutting forces by 32% and 31% respectively, followed by feed rate by 25%. Feed rate, trochoidal step, and axial depth of cut influence the material removal rate by 37%, 30%, and by 19% respectively. The contributions of feed rate, trochoidal step, and axial depth of cut on relative specific energy are 57%, 24%, and 8% respectively. The increase of axial depth of cut increases the maximum resultant force till a threshold value, then it stabilizes. This behavior occurred due to the increase of the maximum engagement angle to a certain limit, then it does not increase any more. Both feed rate and trochoidal step linear affect maximum resultant force and material removal rate, while the relationships are non-linear for specific energy. It is recommended to machine slots in full depth with the highest possible trochoidal step and feed rate, considering the increase of tool wear and surface roughness. It is preferred to use a cutting tool of a large helix angle and small diameter to reduce the threshold axial depth of cut. Overall, this study is significant in characterizing, designing, and optimizing of trochoidal milling through experimental work.

An assessment method to ensure applicability of concrete capacity method for design of anchorages: Linear force distribution approach

AbstractThe concrete capacity design (CCD) method for the design of anchorages comes with a pre‐requisite that the base plate connecting the anchors of a group should be “sufficiently stiff.” This article addresses a frequently and vastly discussed topic in fastening technology, namely “What a sufficiently stiff base plate actually means?” The qualitative definition used by the codes requires that the deformation of the base plate should be small compared to the anchor displacements, in addition to the requirement that the base plate should remain linear elastic. This requirement indirectly ensures that the forces among the anchors of the group are distributed in a linear manner, which is the primary requirement to apply the CCD method for design of anchorages. Such a qualitative definition has raised more questions than answers and haunts the fastening technology community. Perhaps the possible solution to this problem requires asking the question differently, that addresses the problem directly: How can it be ensured that the tension forces among the anchors of a group are distributed in a linear manner? This paper first discusses the problem in detail highlighting several issues in the current approach and later provides an overview of an assessment method in form of a set of criteria that can be used to evaluate whether the tension force distribution is linear for an anchorage with a given anchor pattern, baseplate, attachment, and load case. The principle of the approach is based on a combination of simple mathematical formulations and the evaluation of finite element calculations performed on anchorages modeled with base plate, attachment, and anchors. The proposed formulations are described, and it is explained why they are adequate to find practical and safe general solutions to the problems. The application of the set of criteria allows the calculation of an optimum base plate thickness, sufficient to distribute the forces linearly among the anchors, without being overly conservative.

HEMA-based macro and microporous materials for CO2 capture

New polymeric macroporous materials based on poly 2-hydroxyethyl methacrylate (pHEMA) were synthesized and tested to adsorb CO2. To this purpose, bio and affordable amine-based molecules such as lysine (LYS) and histidine (HIS) were selected as CO2 active sites and used to functionalize HEMA monomer before its crosslinking polymerization. The as-prepared monomers and polymers were characterized by using Nuclear Magnetic Resonance (NMR), Fourier Infrared Spectroscopy (FT-IR), Thermal gravimetric analysis (TGA), and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray (EDX). Compared to materials reported in the recent literature, all produced ones provide exceptional adsorption capacity in the 162–193 ppm range. In particular, H-HEMA-LYS exhibits the best adsorption grade, well-fitting the Linear Driving Force (LFD) model. H-HEMA-LYS reusability was also tested for up to 5 cycles without significant loss in capture performance. Finally, to get insight into the role of morphology in CO2 adsorption, two diverse macroporous structures were synthesized (hydrogels and cryogels) for both HIS and LYS-based materials. As it turns out, hydrogel formulations of an average area ranging from 15.5 to 230 μm2 adsorb 12% more than cryogels with higher values (266–605 μm2).