Problem Of Motion Research Articles

A framework for 3D tracking of frontal dynamic objects in autonomous cars

Both recognition and 3D tracking of frontal dynamic objects are crucial problems in an autonomous vehicle, while depth estimation as an essential issue becomes a challenging problem using a monocular camera. Since both camera and objects are moving, the issue can be formed as a structure from motion (SFM) problem. In this paper, to elicit features from an image, the YOLOv3 approach is utilized beside an OpenCV tracker. Subsequently, to obtain the lateral and longitudinal distances, a nonlinear SFM model is considered alongside a state-dependent Riccati equation (SDRE) filter and a newly developed observation model. Additionally, a switching method in the form of switching estimation error covariance is proposed to enhance the robust performance of the SDRE filter. The stability analysis of the presented filter is conducted on a class of discrete nonlinear systems. Furthermore, the ultimate bound of estimation error caused by model uncertainties is analytically obtained to investigate the switching significance. Simulations are reported to validate the performance of the switched SDRE filter. Finally, real-time experiments are performed through a multi-thread framework implemented on a Jetson TX2 board, while radar data is used for the evaluation.

Kriging-based prediction of the Earth’s pole coordinates

Abstract Coordinates of the Earth’s pole represent two out of five Earth orientation parameters describing Earth’s rotation. They are necessary in transformation between celestial reference frame and terrestrial reference frame and what goes further in precise positioning and navigation, applications in astronomy, communication with outer space objects. Complexity of measuring techniques and data processing involved in the pole coordinates determination make it impossible to obtain them in real-time mode, hence a prediction problem of the polar motion emerges. In this study, geostatistical prediction methods, i. e., simple and ordinary kriging are applied. Millions of predictions have been performed to draw reasonable conclusions on prediction capabilities of applied kriging variants. The study is intended in ultra-short-term prediction (up to 15 days into the future) using the IERS EOP 14 C04 (IAU2000A) and IERS EOP 05 C04 (IAU2000A) series as a reference. Mean absolute prediction errors (for days 1–15) with respect to IERS 14 C04 are ranging 0.66–5.25 mas for PMx and 0.47–3.59 mas for PMy. On the other hand, for IERS 05 C04 the values are 0.60–4.95 mas and 0.44–3.29 mas for PMx and PMy; respectively. The results indicate competitiveness of the introduced methods with existing ones.

Parallel Structure from Motion for Sparse Point Cloud Generation in Large-Scale Scenes.

Scene reconstruction uses images or videos as input to reconstruct a 3D model of a real scene and has important applications in smart cities, surveying and mapping, military, and other fields. Structure from motion (SFM) is a key step in scene reconstruction, which recovers sparse point clouds from image sequences. However, large-scale scenes cannot be reconstructed using a single compute node. Image matching and geometric filtering take up a lot of time in the traditional SFM problem. In this paper, we propose a novel divide-and-conquer framework to solve the distributed SFM problem. First, we use the global navigation satellite system (GNSS) information from images to calculate the GNSS neighborhood. The number of images matched is greatly reduced by matching each image to only valid GNSS neighbors. This way, a robust matching relationship can be obtained. Second, the calculated matching relationship is used as the initial camera graph, which is divided into multiple subgraphs by the clustering algorithm. The local SFM is executed on several computing nodes to register the local cameras. Finally, all of the local camera poses are integrated and optimized to complete the global camera registration. Experiments show that our system can accurately and efficiently solve the structure from motion problem in large-scale scenes.

In-depth analysis reveals complex molecular aetiology in a cohort of idiopathic cerebral palsy.

Cerebral palsy is the most prevalent physical disability in children; however, its inherent molecular mechanisms remain unclear. In the present study, we performed in-depth clinical and molecular analysis on 120 idiopathic cerebral palsy families, and identified underlying detrimental genetic variants in 45% of these patients. In addition to germline variants, we found disease-related postzygotic mutations in ∼6.7% of cerebral palsy patients. We found that patients with more severe motor impairments or a comorbidity of intellectual disability had a significantly higher chance of harbouring disease-related variants. By a compilation of 114 known cerebral-palsy-related genes, we identified characteristic features in terms of inheritance and function, from which we proposed a dichotomous classification system according to the expression patterns of these genes and associated cognitive impairments. In two patients with both cerebral palsy and intellectual disability, we revealed that the defective TYW1, a tRNA hypermodification enzyme, caused primary microcephaly and problems in motion and cognition by hindering neuronal proliferation and migration. Furthermore, we developed an algorithm and demonstrated in mouse brains that this malfunctioning hypermodification specifically perturbed the translation of a subset of proteins involved in cell cycling. This finding provided a novel and interesting mechanism for congenital microcephaly. In another cerebral palsy patient with normal intelligence, we identified a mitochondrial enzyme GPAM, the hypomorphic form of which led to hypomyelination of the corticospinal tract in both human and mouse models. In addition, we confirmed that the aberrant Gpam in mice perturbed the lipid metabolism in astrocytes, resulting in suppressed astrocytic proliferation and a shortage of lipid contents supplied for oligodendrocytic myelination. Taken together, our findings elucidate novel aspects of the aetiology of cerebral palsy and provide insights for future therapeutic strategies.

Improved Estimates of the Vertical Structures of Rain Using Single Frequency Doppler Radars

It is important to understand the statistical–physical structure of the rain in the vertical so that observations aloft can be translated meaningfully into what will occur at the surface. In order to achieve this understanding, it is necessary to gather high temporal and spatial resolution observations of rain in the vertical. This can be achieved by translating radar Doppler spectra into drop size distributions. A long-standing difficulty in using such measurements, however, is the problem of vertical air motion, which can shift the Doppler spectra and therefore significantly alter the deduced drop size distributions and integrated variables. In this work, we overcome this difficulty by requiring that the measured radar reflectivity and the calculated rainfall rates satisfy fundamental physical theory. As a consequence, the mean vertical airspeed can be estimated and removed. Application of this new approach is demonstrated using vertically pointing Doppler radar observations in weak convection. It is shown that the new approach produces what appear to be better estimates of the rainfall rates as well as estimates of the temporal and spatial regionally coherent updraft and downdrafts occurring in the precipitation. The technique is readily applicable to other radars, especially those operating at non-attenuating frequencies.

Chimney Sweeping Robot Based on a Pneumatic Actuator

The need of improving the quality of professions led to the idea of simplification of processes during chimney sweeping. These processes have been essentially the same for tens of years. The goal of this paper is to bring an automation element into the chimney sweeping process, making the job easier for the chimney sweeper. In this paper, an essentially in-pipe robot is presented, which uses brushes to move while simultaneously cleaning the chimney or pipeline. The problem of the robot motion was reduced using an in-pipe robot due to the environments and obstacles that the robot has to face. An approach of using a pneumatic actuator for motion is presented along with the mechanical design. The next part of this paper is focused on the mathematical model of the robot motion, as well as its simulation and testing in the experimental pipeline. The simulations were compared with the experimental measurements and a few analyses were conducted describing the simulation model and its differences with the real robot, as well as considering certain parameters and their impact on the performance of the robot. The results are discussed at the end of the paper.

Pure low-frequency and pure high-frequency ship motion equations in regular waves

The problem of ship motions in waves can be seen as a coupled problem of manoeuvring and seakeeping. The former is a low-frequency motion problem in terms of time scale of ship motion, whereas the latter is relatively a high-frequency motion problem. They can be separately predicted by solving a group of low-frequency ship motion equations and a group of high-frequency ship motion equations. However, the theoretical basis behind both usual groups of motion equations may be questionable. In our previous study, a time-averaged method was introduced to derive the pure low-frequency ship motion equations in regular waves. The new equations have a few additional terms which are the mean inertial forces and moments due to wave-induced high-frequency motions, compared with the usual equations. The low-frequency ship motion equations were then solved to predict ship manoeuvring in waves by means of a modelling approach. It has been demonstrated that these additional terms are non-negligible for manoeuvring prediction, if amplitudes of high-frequency motions are large enough, e.g. in the condition of long wave length and large wave amplitude. In this study, we will give out the more complete pure low-frequency ship motion equations in regular waves and some new explanations. The pure high-frequency ship motion equations are also derived by subtracting the pure low-frequency ship motion equations from transient ship motion equations. On the aspect of manoeuvring prediction, there are two improvements, as compared with before. One is that the mean inertial forces and moments due to second-order high-frequency motions are retained in the pure low-frequency motion equations. The other is that the effect of longitudinal ship speed is taken into account in the modelling approach. As will be shown, the prediction accuracy is improved.

Aerial Infrared Object Tracking via an improved Long-term Correlation Filter with optical flow estimation and SURF matching

At present, there are many excellent algorithms in the field of visual object tracking. The correlation filter algorithms are more suitable for infrared object tracking, for the tracking performance is the best. Especially, the long-term correlation tracking has received much attention, owing to its ability to handle the problems of universal tracking (e.g., slight deformation, small-displacement motion, partial occlusion and out of view). However, there are three imperfections such that it fails to solve the problem of rapid motion, it cannot cope with the problem of boundary effect perfectly, and it has poor tracking effect in the case of severe occlusion and severe deformation. Aiming at the problem of rapid motion, the FlowNet 2.0 is introduced to accomplish optical flow estimation, offering motion information and predicting trajectory change process. Aiming to address the concern of boundary effect perfectly, the adjustable Gaussian window is effective to separate the object and the background, improving classifier discrimination. Aiming at the issue of poor tracking effect in the case of severe occlusion and severe deformation, the SURF feature-based matching method is effective to accurately track object and improve the infrared object tracking performance. In addition, the ratio between average peak-to-correlation energy (APCE) and its historical average, as a further complement of maximum response, is introduced to achieve the online updating mechanism, jointly determining whether the tracker needs to be updated, the SURF matching needs to be carried out or the tracker needs to be initialized by re-detector. Our algorithm is validated on synthetic infrared aerial object image sequences, real infrared thermal aerial object image sequences and a public database named AMCOM FLIR respectively. The extensive experimental testify that our improved approach achieves an optimal effect for aerial infrared object tracking in terms of precision plot, success plot and speed.

CNN-Based LCD Transcription of Blood Pressure From a Mobile Phone Camera.

Routine blood pressure (BP) measurement in pregnancy is commonly performed using automated oscillometric devices. Since no wireless oscillometric BP device has been validated in preeclamptic populations, a simple approach for capturing readings from such devices is needed, especially in low-resource settings where transmission of BP data from the field to central locations is an important mechanism for triage. To this end, a total of 8192 BP readings were captured from the Liquid Crystal Display (LCD) screen of a standard Omron M7 self-inflating BP cuff using a cellphone camera. A cohort of 49 lay midwives captured these data from 1697 pregnant women carrying singletons between 6 weeks and 40 weeks gestational age in rural Guatemala during routine screening. Images exhibited a wide variability in their appearance due to variations in orientation and parallax; environmental factors such as lighting, shadows; and image acquisition factors such as motion blur and problems with focus. Images were independently labeled for readability and quality by three annotators (BP range: 34–203 mm Hg) and disagreements were resolved. Methods to preprocess and automatically segment the LCD images into diastolic BP, systolic BP and heart rate using a contour-based technique were developed. A deep convolutional neural network was then trained to convert the LCD images into numerical values using a multi-digit recognition approach. On readable low- and high-quality images, this proposed approach achieved a 91% classification accuracy and mean absolute error of 3.19 mm Hg for systolic BP and 91% accuracy and mean absolute error of 0.94 mm Hg for diastolic BP. These error values are within the FDA guidelines for BP monitoring when poor quality images are excluded. The performance of the proposed approach was shown to be greatly superior to state-of-the-art open-source tools (Tesseract and the Google Vision API). The algorithm was developed such that it could be deployed on a phone and work without connectivity to a network.

On the motion of rigid bodies in a perfect fluid

We consider the problem of motion of several rigid bodies immersed in a perfect compressible fluid. Using the method of convex integration we establish the existence of infinitely many weak solutions with a priori prescribed motion of rigid bodies. In particular, the dynamics is completely time–reversible at the motion of rigid bodies although the solutions comply with the standard entropy admissibility criterion.

Synchronization control for networked mobile robot systems based on Udwadia–Kalaba approach

This paper addresses the problem of synchronization control for networked multi-mobile robot systems from the perspective of analytical mechanics. By reformulating the task requirement as a constrained motion problem, a unified synchronization algorithm for networked multi-mobile robot systems with or without leaders is proposed in combination with algebraic graph theory and the Udwadia–Kalaba approach. With the proposed algorithm, the networked mobile robot system can achieve synchronization from arbitrary initial conditions for the leaderless case and realize accurate trajectory tracking with explicitly given reference trajectories for the leader-following case. Numerical simulations of a networked wheeled mobile robot system are performed under different network structures and various trajectory requirements to show the performance of the proposed control algorithm.

Mathematical modeling and analysis of conditions for the robot’s uniformly accelerated motion along a straight rail track, taking into account the delay intervals

The problem of the straight-line motion of a robot along a rectilinear rail track with the constant acceleration with delay intervals is considered. The aim of the paper is to determine and analyse the conditions describing the straight-line uniformly accelerated motion of the robot, taking into account the delay intervals. The law of speed change of the robot is simulated, using linear piecewise continuous functions of the time of motion. The necessary conditions for the uniformly accelerated motion of the robot in the acceleration and deceleration sections are formulated. Additionally, the criteria for uniformly variable acceleration and deceleration in the straight-line motion of the robot without delay intervals are recorded. It should be noted that the conditions and patterns presented in this paper have many practical applications. For example, they can be used in the development of traffic routes or in the operation of railway trains.

Interaction of ocean wave with a harbor covered by an ice sheet

A domain decomposition method is developed to solve the problem of wave motion inside a harbor with its surface covered by an ice sheet. The shape of the horizontal plane of the harbor can be arbitrary while the sidewall is vertical. The entrance of the harbor is open to the sea with a free surface. The linearized velocity potential theory is adopted for fluid flow, and the thin elastic plate model is applied for the ice sheet. The domain is divided into two subdomains. Inside the harbor, the velocity potential is expanded into a series of eigenfunctions in the vertical direction. The orthogonal inner product is adopted to impose the impermeable condition on the harbor wall, together with the edge conditions on the intersection of the harbor wall and the ice sheet. In the open sea outside of the harbor, through the modified Green function, the velocity potential is written in terms of an integral equation over the surface of the harbor entrance, or the interface between the two subdomains. On the interface, the orthogonal inner product is also applied to impose the continuity conditions of velocity and pressure as well as the free ice edge conditions. Computations are first carried out for a rectangular harbor without the ice sheet to verify the methodology, and then extensive results and discussions are provided for a harbor of a more general shape covered by an ice sheet with different thicknesses and under different incident wave angles.

A mean counting function for Dirichlet series and compact composition operators

We introduce a mean counting function for Dirichlet series, which plays the same role in the function theory of Hardy spaces of Dirichlet series as the Nevanlinna counting function does in the classical theory. The existence of the mean counting function is related to Jessen and Tornehave's resolution of the Lagrange mean motion problem. We use the mean counting function to describe all compact composition operators with Dirichlet series symbols on the Hardy–Hilbert space of Dirichlet series, thus resolving a problem which has been open since the bounded composition operators were described by Gordon and Hedenmalm. The main result is that such a composition operator is compact if and only if the mean counting function of its symbol satisfies a decay condition at the boundary of a half-plane.

Three-Dimensional Unified Motion Control of a Robotic Standing Wheelchair for Rehabilitation Purposes.

Technological advances in recent years have shown interest in the development of robots in the medical field. The integration of robotic systems in areas of assistance and rehabilitation improves the user’s quality of life. In this context, this article presents a proposal for the unified control of a robotic standing wheelchair. Considering primary and secondary tasks as control objectives, the system performs tasks autonomously and the change of position and orientation can be performed at any time. The development of the control scheme was divided in two parts: (i) kinematic controller to solve the desired motion problem; and (ii) dynamic compensation of the standing wheelchair–human system. The design of the two controllers considers the theory of linear algebra, proposing a low computational cost and an asymptotically stable algorithm, without disturbances. The stability and robustness analysis of the system is performed by analyzing the evolution of the control errors in each sampling period. Finally, real experiments of the performance of the developed controller are performed using a built and instrumented standing wheelchair.

LAWS OF MOTION IN THE FRAME THEORIES OF GRAVITY

One of the most striking features of the general relativity (GR) is the fact that the matter that generates gravitational field cannot move arbitrarily, but must obey certain equations that follow from equations of the gravitational field as a condition of their compatibility. This fact was first noted in the fundamental Hilbert's work, in which equations of GR saw the world for the first time as variational Lagrange equations. Hilbert showed that in the case when fulfilling equations of the gravitational field which were born by an electromagnetic field, four linear combinations of equations of the electromagnetic field and their derivatives are zero due to the general covariance of the theory. It is known that this is what stimulated E. Noether to invent her famous theorem.
 As for "solid matter", for the compatibility of equations of the gravitational field, it is necessary that particles of dust matter move along geodesics of Riemannian space, which describes the gravitational field. This fact was pointed out in the work of A. Einstein and J. Grommer and according to V. Fock it is one of the main justifications of GR (although even before the creation of GR it was known that the motion along geodesics is a consequence of the condition of covariant conservation of energy-momentum of matter). This remarkable feature of GR all his life inspired Einstein to search on the basis of GR such theory from which it would be possible to derive all fundamental physics, including quantum mechanics.
 Interest in this problem (following Einstein, we name it the problem of motion) has resumed in our time in connection with the registration of gravitational waves and analysis of the conditions of their radiation, i.e. the need for its direct application in gravitational-wave astronomy.
 In this article we consider the problem to what extent the motion of matter that generates the gravitational field can be arbitrary. Considered problem is analyzed from the point of view symmetry of the theory with respect to the generalized gauge deformed groups without specification of Lagrangians.
 In particular it is shown, that the motion of particles along geodesics of Riemannian space is inherent in an extremely wide range of theories of gravity and is a consequence of the gauge translational invariance of these theories under the condition of fulfilling equations of gravitational field. In addition, we found relationships of equations for some fields that follow from the assumption about fulfilling of equations for other fields, for example, relationships of equations of the gravitational field which follow from the assumption about fulfilling of equations of matter fields.

Magnetic vortex near the extended linear magnetic inhomogeneity

In this paper, the problem of a magnetic vortex motion in a field of extended linear inhomogeneity is solved theoretically. The motion parameters are calculated by the method of collective variables (Thiel’s equation) with the vortex effective mass and the third-order gyrovector. On the basis of the equation of motion, the influence of the core mass and the third-order gyrovector on the character of the vortex motion as a quasiparticle is analyzed. Using the method of magnetostatic charges, analytical expressions are obtained for the effective potentials where the vortex core is located: (a) near the edge of the magnet or at the boundary of different magnetic phases, (b) near the linear inhomogeneity of local anisotropy (bidirectional and unidirectional). The solution of the equation of motion made it possible to obtain the trajectories of the core in various physical situations. In addition, the paper discusses the features of the Hall effect for vortices/skyrmions, which are provided by the inertial properties and a third-order gyrovector. It is shown that when the core of a linear inhomogeneity crosses a unidirectional anisotropy or the boundary of magnetic phases, a curvature of the trajectory is observed, which is similar to the refraction of light at the boundary of optically dissimilar environment. It is important to note that the introduction of the mass and gyroscopic effect of the third order in the equation of motion showed that the motion of the vortex, even in a homogeneous potential, is not translational. In this case, the trajectory is an overlay of cycloids of different rotation frequencies (analytical expressions are obtained for the frequencies). It is shown that, the introduction of the mass and the gyroscopic term of the third order, the motion of the vortex core cannot be considered translational at least during the time of the transition mode until the stationary mode of motion takes place.

Sawi transformation for system of ordinary differential equations with application

The problem of motion of coupled harmonic oscillators can be modeled in the terms of system of ordinary differential equations (SODEs). In the present paper, authors used Sawi transformation for finding the solution of SODEs with application to determine the concentration of chemical reactants of chemical reaction in series. Authors have considered four numerical problems and determined their solutions step by step for explaining the complete method. After it, authors have taken a problem of physical chemistry for determining the concentration of chemical reactants (substances) of chemical reaction in series. Authors have obtained the solution of this problem by developing its mathematical model in terms of SODEs and then applying Sawi transformation on it. Results of this problem are visualized using tables and graphs. Results of the present paper show that the Sawi transformation provides us the exact solution of SODEs without large computational work.

The problem of motion in gauge theories of gravity

In this article we consider the problem to what extent the motion of gauge-charged matter that generates the gravitational field can be arbitrary, as well as what equations are superimposed on the gauge field due to conditions of compatibility of gravitational field equations. Considered problem is analyzed from the point of view symmetry of the theory with respect to the generalized gauge deformed groups without specification of Lagrangians. In particular it is shown, that the motion of uncharged particles along geodesics of Riemannian space is inherent in an extremely wide range of theories of gravity and is a consequence of the gauge translational invariance of these theories under the condition of fulfilling equations of gravitational field. In the cause of gauge-charged particles, the Lorentz force, generalized for gauge-charged matter, appears in equations of motion as a consequence of the gauge symmetry of the theory under the condition of fulfilling equations of gravitational and gauge fields. In addition, we found relationships of equations for some fields that follow from the assumption about fulfilling of equations for other fields. At the end of the article there is an Appendix, which briefly describes the main provisions and facts from the theory of generalized gauge deformed groups and presents the main ideas of a single group-theoretical interpretation of gauge fields of both external (space-time) and internal symmetry, which is an alternative to their geometric interpretation.

Attenuation of motion artifacts in fMRI using discrete reconstruction of irregular fMRI trajectories (DRIFT).

Numerous studies report motion as the most detrimental source of noise and artifacts in fMRI. Current motion correction methods fail to completely address the motion problem. Retrospective techniques such as spatial realignment can correct for between-volume misalignment but fail to address within volume contamination and spin-history artifacts. Prospective motion correction can prevent spin-history artifacts but currently cannot update the gradients fast enough to remove k-space filling artifacts, calling for a hybrid approach to fully address these problems. Motion can be mathematically formulated into the MR signal equation to describe the motion artifacts at their origin in k-space. From these equations, it is demonstrated that different motions have different effects on the signal. A novel motion correction algorithm is designed from these equations to remove motion-induced artifacts directly in k-space, discrete reconstruction of irregular fMRI trajectory (DRIFT). This method is evaluated rigorously using fMRI simulations and data from a rotating phantom inside the scanner. The results indicate that although some motion types have negligible effects on the MR signal, others produce catastrophic and lasting artifacts even after motion cessation. In simulation, DRIFT is able to remove motion artifacts in the absence of spin history. In a phantom scan, DRIFT significantly attenuates the motion artifacts in the fMRI data. Neither prospective nor retrospective motion correction methods could completely remove the motion artifacts from the fMRI data. However, DRIFT, as a retrospective technique, when combined with prospective motion correction, can eliminate a significant portion of motion artifacts.