Motion Curves Research Articles

Gradient of Segmental Dynamics in Stereoregular Poly(Methyl Methacrylate) Melts Confined between Pristine or Oxidized Graphene Sheets.

Segmental dynamics in unentangled isotactic, syndiotactic, and atactic poly(methyl methacrylate) (i-, a-, and s-PMMA) melts confined between pristine graphene, reduced graphene oxide, RGO, or graphene oxide, GO, sheets is studied at various temperatures, well above glass transition temperature, via atomistic molecular dynamics simulations. The model RGO and GO sheets have different degrees of oxidization. The segmental dynamics is studied through the analysis of backbone torsional motions. In the vicinity of the model nanosheets (distances less than ≈2 nm), the dynamics slows down; the effect becomes significantly stronger with increasing the concentration of the surface functional groups, and hence increasing polymer/surface specific interactions. Upon decreasing temperature, the ratios of the interfacial segmental relaxation times to the respective bulk relaxation times increase, revealing the stronger temperature dependence of the interfacial segmental dynamics relative to the bulk dynamics. This heterogeneity in temperature dependence leads to the shortcoming of the time-temperature superposition principle for describing the segmental dynamics of the model confined melts. The alteration of the segmental dynamics at different distances, d, from the surfaces is described by a temperature shift, (roughly speaking, shift of a characteristic temperature). Next, to a given nanosheet, i-PMMA has a larger value of than a-PMMA and s-PMMA. This trend correlates with the better interfacial packing and longer trains of i-PMMA chains. The backbone torsional autocorrelation functions are shown in the frequency domain and are qualitatively compared to the experimental dielectric loss spectra for the segmental -relaxation in polymer nanocomposites. The (analogous of dielectric loss, , for torsional motion) curves of the model confined melts are broader (toward lower frequencies) and have lower amplitudes relative to the corresponding bulk curves; however, the peak frequencies of the curves are only slightly affected.

Trajectory Planning and Control of Handling Robot Manipulator

In view of the lack of automation of the current material handling measures, based on a brief introduction to the structure of the handling robot, this article mainly studies the trajectory planning and control of the manipulator. First, the basic structure of the manipulator is simplified, the joint coordinate system of the robot arm is established by the Denavit-Hartenberg (D-H) method, and then the kinematics forward and inverse solution model is obtained by analysis. The fifth-order polynomial interpolation algorithm is used to plan the space trajectory of the rotating joint, and Matlab is applied to perform modeling and simulation to verify the rationality of the robot structure design and obtain the motion trajectory and each rotation of the mechanical claw end in the space rectangular coordinate system. Experiments on the motion curve, velocity curve and acceleration curve of the joint are implemented. Finally, the manipulator is controlled by the single-chip microcomputer, and the theoretical model data and trajectory are practiced. Practical results show that the control after trajectory planning reduces the loss of the manipulator and the overall accuracy and stability are higher.

A hybrid control strategy for grinding and polishing robot based on adaptive impedance control

In order to realize the active and compliant motion of the robot, it is necessary to eliminate the impact caused by processing contact. A hybrid control strategy for grinding and polishing robot is proposed based on adaptive impedance control. Firstly, an electrically driven linear end effector is designed for the robot system. The macro and micro motions control model of the robot is established, by using impedance control method, which based on the contact model of the robot system and the environment. Secondly, the active compliance method is adopted to establish adaptive force control and position tracking control strategies under impact conditions. Finally, the algorithm is verified by Simulink simulation and experiment. The simulation results are as follows: The position tracking error does not exceed 0.009 m, and the steady-state error of the force is less than 1 N. The experimental results show that the motion curve coincides with the surface morphology of the workpiece, and the contact force is stable at 10 ± 3 N. The algorithm can realize more accurate position tracking and force tracking, and provide a reference for the grinding and polishing robot to realize surface processing.

Identification of Non-Transversal Motion Bifurcations of Linkages

Abstract The local analysis is an established approach to the study of singularities and mobility of linkages. The key result of such analyses is a local picture of the finite motion through a configuration. This reveals the finite mobility at that point and the tangents to smooth motion curves. It does, however, not immediately allow to distinguish between motion branches that do not intersect transversally (which is a rather uncommon situation that has only recently been discussed in the literature). The mathematical framework for such a local analysis is the kinematic tangent cone. It is shown in this paper that the constructive definition of the kinematic tangent cone already involves all information necessary to distinguish different motion branches. A computational method is derived by amending the algorithmic framework reported in previous publications.

Development and Performance Analysis of Pneumatic Soft-Bodied Bionic Actuator.

The design of a pneumatic soft-bodied bionic actuator derives from the structural characteristics and motion mechanism of biological muscles, combined with the nonlinear hyperelasticity of silica gel, which can improve the mobility and environmental adaptability of soft-bodied bionic robots. Based on Yeoh's second-order constitutive model of silica gel, the deformation analysis model of the actuator is established, and the rationality of the structure design and motion forms of the actuator and the accuracy of the deformation analysis model are verified by using the numerical simulation algorithm. According to the physical model of the pneumatic soft-bodied bionic actuator, the motion and dynamic characteristics of the actuator are tested and analyzed, the curves of motion and dynamic characteristics of the actuator are obtained, and the empirical formula of the bending angle and driving torque of the actuator is fitted out. The results show that the deformation analysis model and numerical simulation method are accurate, and the pneumatic soft-bodied bionic actuator is feasible and effective, which can provide a design method and reference basis for the research and implementation of soft-bodied bionic robot actuator.

Optimization of Central Pattern Generator based Quadruped Animation using Time Series with Genetic Algorithm

Generating believable quadruped motion is a challenging task for application like Games, Virtual Reality and Augmented Reality, where runtime user interaction is needed. In order to successfully generate the believable motion, the runtime or dynamic adjustment to motion gaits is essential. As the use of Central Pattern Generator (CPG) is vital in generating range of dynamic quadruped motions, the optimization is crucial for smooth motion curves. We use the Genetic Algorithm (GA) based tuning technique to optimize the motion curves generated through CPG. The quadruped motion generated through CPG is applied on Skeletal joints and then optimized through fitting the artificial motion parameters tuned using genetic algorithm. The results generated shows much smooth and stable quadruped motion with believable gait patterns.

Convergence of nonlocal geometric flows to anisotropic mean curvature motion

We consider nonlocal curvature functionals associated with positive interaction kernels, and we show that local anisotropic mean curvature functionals can be retrieved in a blow-up limit from them. As a consequence, we prove that the viscosity solutions to the rescaled nonlocal geometric flows locally uniformly converge to the viscosity solution to the anisotropic mean curvature motion. The result is achieved by combining a compactness argument and a set-theoretic approach related to the theory of De Giorgi's barriers for evolution equations.

KeyFrame extraction for human motion capture data via multiple binomial fitting

AbstractIn this paper, we make two contributions. The first is to propose a new keyframe extraction algorithm, which reduces the keyframe redundancy and reduces the motion sequence reconstruction error. Secondly, a new motion sequence reconstruction method is proposed, which further reduces the error of motion sequence reconstruction. Specifically, we treated the input motion sequence as curves, then the binomial fitting was extended to obtain the points where the slope changes dramatically in the vicinity. Then we took these points as inputs to obtain keyframes by density clustering. Finally, the motion curves were segmented by keyframes and the segmented curves were fitted by binomial formula again to obtain the binomial parameters for motion reconstruction. Experiments show that our methods outperform existing techniques, in terms of reconstruction error.

Dynamic analysis of main transmission mechanism of high-speed cold heading machine based on rigid-flexible coupling model

In the research of high speed cold heading machine, only single part is studied. The interaction between the components of the main drive mechanism is rarely studied. The motion of the main transmission mechanism of the cold heading machine was analysed. The interaction between the components of the main transmission mechanism was studied. This article adopts the theory of multi-body system dynamics. The rigid-flexible coupling model of the main transmission mechanism was established. The dynamics and kinematics simulation of the main transmission mechanism was carried out. The motion curve and stress of the rigid-flexible coupling model are obtained. Compared with the rigid model, the rationality of the rigid flexible coupling model was demonstrated. It provided a reference for further fatigue analysis and optimization of the main transmission mechanism.

Research on inflation and floating-up process of unmanned underwater vehicle based on collaborative simulation technology

For solving the problem of unmanned underwater vehicle (UUV) recovery, a multidisciplinary collaborative simulation method is proposed to simulate the inflatable deployment of an annular airbag and the motion of an UUV: a) a deployment dynamic model of the underwater airbag is established, the volume expansion rate curve of the airbag during the inflatable deployment process based on the control volume algorithm is obtained, and the accuracy of the model is verified by experiments; b) under the condition of a constant volume expansion rate of the airbag, a hydrodynamic model that couples the six-degree of freedom rigid body motion and the local deployment of the airbag is established, and calculations are performed using a custom program. The simulation method is used to study the effects of the ‘stop’ water depth on the motion characteristics of the vehicle, and the accuracy of the calculations is verified via the two-way fluid-structure interaction method. According to the calculation results for the effective deployment volume of the airbag and the motion curve of the centre of mass of the underwater vehicle, the ultimate floating depth of the vehicle can be predicted, which provides a reference for engineering implementation.

Eliminating the contact bounce of AC contactor based on speed feedback

SummaryContactor bounce has a serious impact on its electrical life and closed reliability in the process of closing the main circuit. Controlling the contact movement is one of the effective ways to reduce the bounce effect. In this paper, the contact movement characteristics are concerned directly. A big speed and small acceleration of contact are expected to complete the closure. The mathematical model of the circuit and the magnetic circuit are established, and the dynamic characteristics of the electromagnetic system are analyzed. The closed‐loop control system of contact motion characteristic based on speed feedback is constructed, and the speed tracking effect is improved effectively by fuzzy control. The experiment results showed that the control method proposed is correct, and the actual speed curve of the contact was consistent with the planned motion curve. The contact speed of the contact decreases obviously, which can achieve the goal of restraining the bounce of the contact.

Spectral Correlation Between the Non-uniform Input Ground Motion and the Dynamic Response of the Surrounding Rocks of a Long Tunnel

To generate several different time-history curves of ground motion, which have the ability to reflect local site effects, such as the traveling-wave effect and attenuation effect, for long circular tunnels, a random method for the synthesis of ground motion is employed. The dynamic response of the surrounding rocks of a long tunnel under the uniform and non-uniform input ground motions is analyzed using the vertical input method. Based on this, the spectral correlation between the input ground motion and the dynamic response of the surrounding rocks is investigated through the coherence function. Unlike the results under the uniform input ground motion, the transmission coefficient of the surrounding rock monitoring points of each section along the axial direction of the tunnel under the non-uniform input ground motion varies in the main frequency band. In addition, at the same frequency, the transmission coefficient of the monitoring points gradually increases along the tunnel’s axial direction, but the increasing magnitude is variable. The correlation function of each monitoring point along the tunnel axis under the non-uniform input ground motion generally decreases with frequency. Moreover, the further the distance from the tunnel entrance, the faster the attenuation of correlation. The maximum coherence coefficient and the axial distance of the tunnel are basically in conformity with the quadratic polynomial relationship. However, the maximum coherence coefficient of the non-uniform input ground motion is considerably greater than that of the uniform input ground motion. The gap increases with the distance, and the maximum gap is about 0.15.

Toward improved 3D carotid artery imaging with Adaptive CaRdiac cOne BEAm computed Tomography (ACROBEAT).

Interventional treatments of aneurysms in the carotid artery are increasingly being supplemented with three-dimensional (3D) x-ray imaging. The 3D imaging provides additional information on device sizing and stent malapposition during the procedure. Standard 3D x-ray image acquisition is a one-size fits all model, exposing patients to additional radiation and results in images that may have cardiac-induced motion blur around the artery. Here, we investigate the potential of a novel dynamic imaging technique Adaptive CaRdiac cOne BEAm computed Tomography (ACROBEAT) to personalize image acquisition by adapting the gantry velocity and projection rate in real-time to changes in the patient's electrocardiogram (ECG) trace. We compared the total number of projections acquired, estimated carotid artery widths and image quality between ACROBEAT and conventional (single rotation fixed gantry velocity and acquisition rate, no ECG-gating) scans in a simulation study and a proof-of-concept physical phantom experimental study. The simulation study dataset consisted of an XCAT digital software phantom programmed with five patient-measured ECG traces and artery motion curves. The ECG traces had average heart rates of 56, 64, 76, 86, and 100bpm. To validate the concept experimentally, we designed and manufactured the physical phantom from an 8-mm diameter silicon rubber tubing cast into Phytagel. An artery motion curve and the ECG trace with an average heart rate of 56bpm was passed through the phantom. To implement ACROBEAT on the Siemens ARTIS pheno angiography system for the proof-of-concept experimental study, the Siemens Test Automation Control System was used. The total number of projections acquired and estimated carotid artery widths were compared between the ACROBEAT and conventional scans. As the ground truth was available for the simulation studies, the image quality metrics of Root Mean Square Error (RMSE) and Structural Similarity Index (SSIM) were also utilized to assess image quality. In the simulation study, on average, ACROBEAT reduced the number of projections acquired by 63%, reduced carotid width estimation error by 65%, reduced RMSE by 11% and improved SSIM by 27% compared to conventional scans. In the proof-of-concept experimental study, ACROBEAT enabled a 60% reduction in the number of projections acquired and reduced carotid width estimation error by 69% compared to a conventional scan. A simulation and proof-of-concept experimental study was completed applying a novel dynamic imaging protocol, ACROBEAT, to imaging the carotid artery. The ACROBEAT results showed significantly improved image quality with fewer projections, offering potential applications to intracranial interventional procedures negatively affected by cardiac motion.

Analytical solutions and computational nomograms for maximum pressure angle for cam mechanisms for full and half cycloidal and harmonic motion curves

High pressure angles in cams with roller followers still pose as a problem in cam projects. The main objective of this work is to deduce the maximum pressure angle equations for full and half cycloidal and harmonic motion curves for translating roller followers in radial cams and create nomograms that can calculate this parameter by simply connecting two points by a straight line in a chart. The nomograms were made for the mentioned curves via an open source software and it is discussed the limitations of the given charts and the advantages of using the current method. Additionally, the paper reinforces the need for authors to make it clear that another well known and frequently used nomogram cannot be used as is for half curves. Although use of nomograms has fallen into disuse, it still has applications in textbooks and quick preliminary analysis in real life projects.

Evaluation of Seismic Performance of Ancient Timber Structure Based on Incremental Dynamic Analysis

In order to study the seismic performance of ancient timber structures under different earthquake intensities, this paper uses the finite element software ABAQUS to establish a finite element model. Through the incremental dynamic analysis (IDA) of the model under the action of two-way horizontal earthquake, IDA curves of multiple ground motion records are obtained, and the IDA curves of 16%, 50%, and 84% ratio are calculated. Combined with the earthquake vulnerability theory, the earthquake vulnerability matrix is established to evaluate the seismic resistance of the ancient timber structures. It provides a reference for the future anti-seismic research of ancient buildings, and also provides an effective way for timber structure anti-seismic safety evaluation.

Comparison of the Vibration Response of a Rotary Dobby with Cam-Link and Cam-Slider Modulators

Abstract This article presents the kinematic modeling and analysis of cam profiles of two different types of modulator: a cam-link and a cam-slider modulators. Kinematic and dynamic models of the two different modulators were established based on the motion curves of the main shaft of the rotary dobby. Simulations were carried out in Simulink to analyze the vibration responses under different rotary speeds, and vibration responses of the two mechanisms were compared. The results show that the cam-link modulator vibrates smoothly at speeds of <700 rpm, and theoretically, the speed should not exceed 1,400 rpm. The cam-slider modulator vibrates smoothly at speeds of <500 rpm, and theoretically, the speed should not exceed 1,000 rpm. The cam-slider modulator is more suitable for use at low speeds, whereas the cam-link modulator is more appropriate for high speeds. When both the cam-slider and cam-link modulators operate at high speeds, vibration distortion occurs, leading to bifurcation and chaotic vibration. Further knowledge of the complex behaviors associated with detachment of the follower from the cam can support the design of more sophisticated controllers aimed at avoiding follower detachment.

PDE Evolutions for M-Smoothers in One, Two, and Three Dimensions

Local M-smoothers are interesting and important signal and image processing techniques with many connections to other methods. In our paper, we derive a family of partial differential equations (PDEs) that result in one, two, and three dimensions as limiting processes from M-smoothers which are based on local order-p means within a ball the radius of which tends to zero. The order p may take any nonzero value $$>-1$$ , allowing also negative values. In contrast to results from the literature, we show in the space-continuous case that mode filtering does not arise for $$p \rightarrow 0$$ , but for $$p \rightarrow -1$$ . Extending our filter class to p-values smaller than $$-1$$ allows to include, e.g. the classical image sharpening flow of Gabor. The PDEs we derive in 1D, 2D, and 3D show large structural similarities. Since our PDE class is highly anisotropic and may contain backward parabolic operators, designing adequate numerical methods is difficult. We present an $$L^\infty $$ -stable explicit finite difference scheme that satisfies a discrete maximum–minimum principle, offers excellent rotation invariance, and employs a splitting into four fractional steps to allow larger time step sizes. Although it approximates parabolic PDEs, it consequently benefits from stabilisation concepts from the numerics of hyperbolic PDEs. Our 2D experiments show that the PDEs for $$p<1$$ are of specific interest: Their backward parabolic term creates favourable sharpening properties, while they appear to maintain the strong shape simplification properties of mean curvature motion.

First apsidal motion and light curve analysis of 162 eccentric eclipsing binaries from LMC

We present an extensive study of 162 early-type binary systems located in the LMC galaxy that show apsidal motion and have never been studied before. For the ample systems, we performed light curve and apsidal motion modelling for the first time. These systems have a median orbital period of 2.2 days and typical periods of the apsidal motion were derived to be of the order of decades. We identified two record-breaking systems. The first, OGLE LMC-ECL-22613, shows the shortest known apsidal motion period among systems with main sequence components (6.6 years); it contains a third component with an orbital period of 23 years. The second, OGLE LMC-ECL-17226, is an eccentric system with the shortest known orbital period (0.9879 days) and with quite fast apsidal motion period (11 years). Among the studied systems, 36 new triple-star candidates were identified based on the additional period variations. This represents more than 20% of all studied systems, which is in agreement with the statistics of multiples in our Galaxy. However, the fraction should only be considered as a lower limit of these early-type stars in the LMC because of our method of detection, data coverage, and limited precision of individual times of eclipses.

Adaptive neuro-fuzzy modeling of a soft finger-like actuator for cyber-physical industrial systems

Soft robotics is a trending area of research that can revolutionize the use of robotics in industry 4.0 and cyber-physical systems including intelligent industrial systems and their interactions with the human. These robots have notable adaptability to objects and can facilitate many tasks in everyday life. One potential use of these robots is in medical applications. Due to the soft body of these robots, they are a suitable replacement for applications like rehabilitation and exoskeletons. In this paper, we present the neuro-fuzzy modeling of a soft pneumatic finger-like actuator. This actuator is a fiber-reinforced soft robot with the shape and dimensions of a real finger and moves in planar motion. A bending sensor is used as a feedback for curvature motion of this actuator. In order to model this actuator, an adaptive neuro-fuzzy inference system is utilized to overcome the hardship in the modeling of the nonlinear performance of the soft materials. An experimental setup is designed to obtain suitable input–output data needed for modeling. The results show the applicability of the utilized method in the modeling of the soft actuator.

Confusion threshold study of the Duffing oscillator with a nonlinear fractional damping term

In this study, the critical conditions for generating chaos in a Duffing oscillator with nonlinear damping and fractional derivative are investigated. The Melnikov function of the Duffing oscillator is established based on Melnikov theory. The necessary analytical conditions and critical value curves of chaotic motion in the sense of Smale horseshoe are obtained. The numerical solutions of chaotic motion, including time history diagram, frequency spectrum diagram, phase diagram, and Poincare map, are studied. The correctness of the analytical solution is verified through a comparison of numerical and analytical calculations. The effects of linear and nonlinear parameters on chaotic motion are also analyzed. These results are relevant to the study of system dynamics.