Objects Of Arbitrary Shape Research Articles

РОЗРОБКА СИСТЕМИ РУЧНОГО РОБОТА-МАНІПУЛЯТОРА З ДИСТАНЦІЙНИМ УПРАВЛІННЯМ

The aim of this research work is to research and develop a system of a hand-like remote-controlled robotic arm. Devices of this design are currently in demand in many areas of human life, in particular during rescue operations. The described device must be able to hold an object of arbitrary shape using a gripper, has acceptable positioning and control accuracy. Such a device can be used to work in a harmful or hazardous environment, thereby minimizing the harmful effects on humans. The control system of such a device must provide a protocol for transferring data from the input device to the end handle of the manipulator to perform the corresponding movement. To start the development process, market analysis was conducted, in the process of which several similar products were identified and compared against each other and the system being developed. As a result of that analysis, comparison table was created listing the main features of the system being developed in comparison to existing solutions on the market, to check whether it will be competitive at the current market.In this article, such system is proposed and later developed with the analysis of modern technical components and taking into account the accompanying scientific and technical research. In the course of the work, the analysis of existing technical solutions was carried out, the principles of operation of individual components were considered, and the process of developing the final system was described. As a processor device, it was decided to use the Arduino Uno and Arduino Nano microprocessor boards, which provide convenient tools for working with ATmega microprocessors with high performance and energy efficiency.As a result of this work, functional, logical and electrical circuits were created and described, which were used to create a working prototype of the system, as well as a diagram of the model of the manipulator body, which was printed using a 3D printer. Using the created circuits, a working prototype of the described system was built, which was successfully tested, a demonstration of which is given in the work. The created one can be integrated as a subsystem into a larger-scale project.

Fitting Terrestrial Laser Scanner Point Clouds with T-Splines: Local Refinement Strategy for Rigid Body Motion

T-splines have recently been introduced to represent objects of arbitrary shapes using a smaller number of control points than the conventional non-uniform rational B-splines (NURBS) or B-spline representatizons in computer-aided design, computer graphics and reverse engineering. They are flexible in representing complex surface shapes and economic in terms of parameters as they enable local refinement. This property is a great advantage when dense, scattered and noisy point clouds are approximated using least squares fitting, such as those from a terrestrial laser scanner (TLS). Unfortunately, when it comes to assessing the goodness of fit of the surface approximation with a real dataset, only a noisy point cloud can be approximated: (i) a low root mean squared error (RMSE) can be linked with an overfitting, i.e., a fitting of the noise, and should be correspondingly avoided, and (ii) a high RMSE is synonymous with a lack of details. To address the challenge of judging the approximation, the reference surface should be entirely known: this can be solved by printing a mathematically defined T-splines reference surface in three dimensions (3D) and modeling the artefacts induced by the 3D printing. Once scanned under different configurations, it is possible to assess the goodness of fit of the approximation for a noisy and potentially gappy point cloud and compare it with the traditional but less flexible NURBS. The advantages of T-splines local refinement open the door for further applications within a geodetic context such as rigorous statistical testing of deformation. Two different scans from a slightly deformed object were approximated; we found that more than 40% of the computational time could be saved without affecting the goodness of fit of the surface approximation by using the same mesh for the two epochs.

ТЕОРЕТИЧНІ ТА ПРАКТИЧНІ АСПЕКТИ ГЛОБАЛЬНОЇ ІНТЕРПОЛЯЦІЇ ТОЧКОВИМ ПОЛІНОМОМ ГЕОМЕТРИЧНОЇ КОМПОЗИЦІЇ З КРАТНИМИ ТОЧКАМИ

The article shows the sequence of parameterization, along the coordinate axis, of the original discretely presented line (DPL) and is presented in general form by a point polynomial. Possible options for the appearance of multiple points are considered and the values of the parameters for these options are presented. It is indicated that with the appearance of multiple points on the DPL in the constituent elements of a point polynomial, uncertainties arise. It is proved that all these uncertainties are revealed, the limits of which, at the nodal points, are zero or one. It is shown that the uncertainties that arise with the appearance of multiple points on the DPC are not an obstacle to global interpolation using a point polynomial. That is, for any composition of three points, the construction and recording structure of a point polynomial remains unchanged. However, there are no restrictions on creating a composition of three points. This fact is proved in this article. A composite numerical matrix is presented in accordance with which conditional interpolation occurs. The elements of this compositional matrix are the values of the characteristic functions of the interpolant at the nodal points. It is shown that the elements of the compositional interpolation matrix do not change in the presence of any geometric composition of three points. Only the status of these elements can be changed. In one case, their values are accurate, and in the other, they can be the limit to which the value of the characteristic function of a point polynomial follows. Geometric modeling of volumetric objects of arbitrary shape requires the construction of its surface. Usually, the construction of surfaces is done by drawing a mesh on it. If a mesh is applied on the surface of a geometric body of an arbitrary shape, has a constant number of lines in the direct and transverse directions, then cells of various sizes, both large and very small, will appear. On large cells, the surface reproduction error will increase, and on small cells, the consumption of modeling resources will increase, and the efficiency and quality of modeling will decrease. Keywords: multiple points, geometric composition, compositional matrix, disclosure of uncertainties, point polynomial.

Magnetic noise from metal objects near qubit arrays

All metal objects support fluctuating currents that are responsible for evanescent-wave Johnson noise in their vicinity due both to thermal and quantum effects. The noise fields can decohere qubits in their neighborhood. It is quantified by the average value of $B(x,t)B(x',t')$ and its time Fourier transform. We develop the formalism particularly for objects whose dimensions are small compared with the skin depth, which is the appropriate regime for nanoscale devices. This leads to a general and surprisingly simple formula for the noise correlation function of an object of arbitrary shape. This formula has a clear physical interpretation in terms of induced currents in the object. It can also be the basis for straightforward numerical evaluation. For a sphere, a solution is given in closed form in terms of a generalized multipole expansion. Plots of the solution illustrate the physical principles involved. We give examples of how the spatial pattern of noise can affect quantum information processing in nearby qubits. The theory implies that if the qubit system is miniaturized to a scale $D$, then decoherence rates of qubits scale as $1/D$.

An automated image analysis platform for the study of weakly -adhered cells

Details of the design and implementation of an open-source platform for studying the adhesion of cells attached to solid substrata are provided. The hardware is based on a laser-cut flow channel connected to a programmable syringe pump. The software automates all aspects of the flow rate profile, data acquisition and image analysis. An example of the pelagic diatom Thalassiosira rotula adhered to poly(dimethyl siloxane) surfaces is provided. The procedure described enables the shear rate to be converted to drag force for arbitrary-shaped objects, of utility to the study of many cell species, especially ones that are obviously non-spherical. It was determined that 90% of cells are removed with the application of drag forces < N, and that this value is relatively independent of the incubation time on the surface. This result is important to understand how marine species interact with polymer surfaces that are used in electrical insulator applications.

A hybrid ALE/implicit function method for simulating microwave heating with rotating objects of arbitrary shape

Moving objects are widely applied in microwave heating process for improving heating uniformity. In order to improve the heating effect, various moving objects with complex shapes will be used in microwave heating. However, for objects with irregular shapes, it is difficult to model the object movement due to the difficulty of characterizing the object's boundaries. In this paper, by using Arbitrary Lagrange Eulerian (ALE) method to track the object movement, the position of the object is expressed by a time-varying implicit function. The impact of the moving object on the electromagnetic field distribution is therefore represented by the change of the implicit parameter. Meanwhile, after the heat source is transformed back to the initial position by a coordinate transformation method, the calculation of the heating process of the moving object can be realized in a fixed mesh structure, thus re-meshing is avoided. A 2-D model and a 3-D model with rotating objects in irregular shapes are used to illustrate the proposed method. Experiments are conducted to testify the validity of the proposed method. Good agreements have been obtained. Moreover, the results show that, for dealing with the cases with moving objects in complex shapes, this method is much more accurate and efficient than the ALE-remeshing method.

Acoustic radiation torque on a compressible spheroid.

Starting with the theoretical framework for calculating the acoustic radiation force on a compressible spheroid [Jerome et al., J. Acoust. Soc. Am. 148, 2403-2415 (2020)], the present work develops a model for the corresponding acoustic radiation torque. A general result is obtained that may be applied to an object of arbitrary size, shape, and impedance in an arbitrary incident sound field. Like for the radiation force, the general result for the radiation torque is a summation of terms involving products of the coefficients in spherical wave expansions of the incident and scattered fields. For the compressible spheroid under consideration, spheroidal wave expansions are employed to satisfy the boundary conditions on the surface of the spheroid to obtain the scattering coefficients. Results are presented for the radiation torque exerted on a compressible spheroid by a progressive or standing incident plane wave. The results illustrate the dependence of the radiation torque on the size, aspect ratio, and impedance of the spheroid and on its orientation with respect to the incident wave field.

Simulating Boundary Fields of Arbitrary-shaped Objects in a Reverberation Chamber

In a reverberation chamber, analytical solutions exist in very limited scenarios for the distribution of the boundary fields. For arbitrary-shaped objects, analytical solutions may not exist. To solve this problem, a general numerical method is proposed to obtain the mean field distribution near arbitrary-shaped objects in a random diffused-wave environment. The proposed method combines the full-wave method and the Monte-Carlo method; the numerical results are validated and compared with that from analytical equations. The proposed method can be applied to arbitrary-shaped objects with general material properties.

Method of optimization synthesis of parameters of actuating system of anthropomorphic gripper with adaptive control

Gripper is a basic component of any robot. Its functionality is determined by realized number of degrees of freedom and control system. Anthropomorphic robots (AR) possess the biggest number of mobilities. Usage of group drive with adaptive control of mobile links is developing way of AR construction. This method allows to grasp and hold arbitrary shape objects when the motors number is less than mobilities number. Method of parametric synthesis of actuating system (AS) of AG made by two subsystems: the main kinematic chain (MKC) and motion transmission system (MTS) is represented in the article. MKC including two output links connected with each other and gripper base by rotational pairs with parallel axes is considered. MTS is parallel leverage mechanism. Subsystems are connected with each other by additional functional connection. The connection provides moving torque in MKC kinematic pairs. The presented approach is based on choosing MTS parameters that provide producing maximum torque in MKC kinematic pairs of its links end positions. The obtained equations of connection reflect the specificity of AS construction. The optimality criterion is defined and formalized by revealed equations of connection. The presented method allows to choose MTS parameters providing rational functioning of anthropomorphic gripper AS.

Acoustic radiation force on a compressible spheroid

The acoustic radiation force on a compressible spheroid is calculated using expansions of the scattered field in terms of both spherical and spheroidal wave functions. There is no restriction on the size or acoustic impedance of the spheroid, the structure of the incident field, or the orientation of the spheroid with respect to the incident field. The solution is the same as that developed previously for the radiation force on an elastic sphere, which is expressed as a summation of terms involving products of the coefficients in spherical wave expansions of the incident and scattered fields [Ilinskii etal., J. Acoust. Soc. Am. 144, 568–576 (2018)]. Spheroidal wave expansions are used to satisfy the boundary conditions on the compressible spheroid, and far-field asymptotes are used to relate the spheroidal and spherical wave scattering coefficients analytically. Explicit expressions for the scattering coefficients are available for spheroids with rigid or free surfaces. Results are compared with available analytical solutions for various limiting cases. The theoretical framework may be employed for objects of arbitrary shape provided the spherical wave expansion of the scattered field is known. [T.S.J. is supported by the Applied Research Laboratories Chester M. McKinney Graduate Fellowship in Acoustics.] a)Deceased.

Acoustic radiation force on a compressible spheroid.

The acoustic radiation force on a compressible spheroid is calculated using expansions of the scattered field in terms of both spherical and spheroidal wave functions that are matched analytically in the far field. There is no restriction on the size or impedance of the spheroid, the structure of the incident field, or the orientation of the spheroid with respect to the incident field. The form of the solution is the same as that developed previously for the radiation force on an elastic sphere, which is a summation of terms involving products of the coefficients in spherical wave expansions of the incident and scattered fields. Spheroidal wave expansions are employed to satisfy the boundary conditions and obtain the scattering coefficients. While the scattering coefficients must be obtained numerically for compressible spheroids, explicit expressions in terms of radial wave functions are available for spheroids with rigid or free surfaces. Results are compared with available analytical expressions for various limiting cases. The theoretical framework may be extended to objects of arbitrary shape.

Casimir effect with machine learning

Vacuum fluctuations of quantum fields between physical objects depend on the shapes, positions, and internal composition of the latter. For objects of arbitrary shapes, even made from idealized materials, the calculation of the associated zero-point (Casimir) energy is an analytically intractable challenge. We propose a new numerical approach to this problem based on machine-learning techniques and illustrate the effectiveness of the method in a (2+1) dimensional scalar field theory. The Casimir energy is first calculated numerically using a Monte-Carlo algorithm for a set of the Dirichlet boundaries of various shapes. Then, a neural network is trained to compute this energy given the Dirichlet domain, treating the latter as black-and-white pixelated images. We show that after the learning phase, the neural network is able to quickly predict the Casimir energy for new boundaries of general shapes with reasonable accuracy.

Beyond Human Hand: Shape-Adaptive and Reversible Magnetorheological Elastomer-Based Robot Gripper Skin.

Developing a simple and universal solution for gripping fragile, multiscaled, and arbitrary-shaped objects using a robot gripper is challenging. Herein, we propose a universal, shape-adaptive/-retaining and reversible, hardness-variable gripper skin that serves as a resourceful solution for grasping such objects without damaging them. The proposed universal gripper skin based on a magnetorheological elastomer is attached to a robot gripper. The proposed skin takes the shape of a target object as soon as the gripper grasps the object. At this time, we solidify the gripper skin by applying a magnetic field, thereby allowing the gripper to grasp the target object easily. After releasing the objects, the magnetic field is removed and the deformed proposed gripper skin rapidly restores its original shape. The proposed adaptive gripper skin is made to grasp various target objects, such as cylinders, cuboids, and triangular prisms, based on which its grasping performance is evaluated.

Fabrication of 3D Temperature Sensor Using Magnetostrictive Inkjet Printhead

Abstract Recently, the three-dimensional (3D) printing technique has attracted much attention for creating objects of arbitrary shape and manufacturing. For the first time, in this work, we present the fabrication of an inkjet printed low-cost 3D temperature sensor on a 3D-shaped thermoplastic substrate suitable for packaging, flexible electronics, and other printed applications. The design, fabrication, and testing of a 3D printed temperature sensor are presented. The sensor pattern is designed using a computer-aided design program and fabricated by drop-on-demand inkjet printing using a magnetostrictive inkjet printhead at room temperature. The sensor pattern is printed using commercially available conductive silver nanoparticle ink. A moving speed of 90 mm/min is chosen to print the sensor pattern. The inkjet printed temperature sensor is demonstrated, and it is characterized by good electrical properties, exhibiting good sensitivity and linearity. The results indicate that 3D inkjet printing technology may have great potential for applications in sensor fabrication.

An Efficient Recursive Approach for Electromagnetic Scattering by Arbitrary-Shaped Multilayer Cylinders

We present a recursive version of the previously proposed fast algorithm for computation of the field scattered from arbitrary-shaped multilayer objects. As in the original version, the field at each layer is represented by a series of cylindrical functions with unknown coefficients. In order to determine these coefficients, a linear system of equations is obtained through a procedure based on the boundary conditions between the layers. Instead of solving this large system by applying conventional linear solvers as done in the original version, through an approach based on Thomas algorithm, we derive recursive expressions to compute the scattered field. While the accuracy of the results for both versions are almost the same, the recursive version has lower time and memory complexity. Hence, it supersedes the original version.

Translational and rotational resonance frequencies of a disk in a single-axis acoustic levitator

In this study, we investigate the acoustic levitation of a disk in a single-axis acoustic levitator operating at 21.53 kHz. First, two acoustic models based on the finite element method are employed for calculating the acoustic radiation force and torque on a levitating disk. The models are also used for calculating the vertical, horizontal, and torsional trapping stiffness and its corresponding natural frequencies. Furthermore, translational and angular oscillations of the disk are captured by a high-speed camera, and a tracking algorithm is employed for extracting the natural frequencies of the oscillations. The experimental natural frequencies present good agreement with those predicted by the models. Although the numerical model was employed for simulating the forces and torques on a disk, the presented method is general and it can be employed for simulating the acoustic levitation of objects of arbitrary shapes and sizes.

Capabilities of ADDA code for nanophotonics

The open-source code ADDA is based on the discrete dipole approximation (DDA) – a numerically exact method derived from the frequency-domain volume-integral Maxwell equation. It can simulate interaction of electromagnetic fields (scattering and absorption) with finite 3D objects of arbitrary shape and composition. Besides standard sequential execution on CPU or GPU, ADDA can run on a multiprocessor distributed-memory system, parallelizing a single DDA calculation. This together with almost linear scaling of computational complexity with number of dipoles (discretization voxels) allows large system sizes and/or fine discretization levels. ADDA is written in C99 and is highly portable. It provides full control over the scattering geometry (particle morphology and orientation, incident beam) and allows one to calculate a wide variety of integral and angle-resolved quantities, including those related to point-dipole excitation. Moreover, ADDA can rigorously and efficiently account for plane homogeneous substrate near the particle, and employ rectangular-cuboid voxels. It also incorporates a range of state-of-the-art DDA improvements, increasing both the accuracy and computational speed of the method. At the conference we will describe the main features of current version of ADDA with special emphasis on nanoparticles and present several simulation examples.

ANALYTICAL DESCRIPTION OF THE CONDITIONS OF NON-INTERSECTION OF GEOMETRIC OBJECTS IN THE PROBLEMS OF MODELING THE MOVEMENT OF PEOPLE FLOW

Optimal placement problems are part of the theory of operations research and computational geometry. This class relates to geometric design problems and has a wide range of applications.Despite the presence of various models and methods for solving problems of geometric design, they, as before, are relevant in those areas whose formalization is insufficient for the application of existing models and methods related to the need to take into account the characteristics of a particular subject area.One of the problems today is the organization of controlled evacuation of people from buildings of the necessary time, which calculated on the basis of their space-planning decisions. At present, there are no models of individual-stream movement of people that are adequate to the real flow. The interest in the model is motivated both by the need to pay attention to the movement of people with limited mobile capabilities in a mixed stream in a fairly wide range of public buildings of various classes of functional fire hazard, and by the impossibility of constructing adequate mathematical models, which based on an analytical description of relationships between people (for example, non-intersections), which have different dimensions, age, functionality, etc. It should be noted that the task of modeling the movement of people in each particular discrete time moment is a configuration of the placement of objects according to given constraints, the main of which are the conditions for their non-intersection.Therefore, an urgent problem for solving placement problems is the further development of the mathematical apparatus for describing the conditions for the non-intersection of objects of arbitrary spatial shapes, taking into account their continuous translations and rotations.In the work, quasi-phi functions are modified for the analytical description of non-intersection conditions for a rectangle and an ellipse, for an object composed of a rectangle and an ellipse, with a rectangle, for an object composed of a rectangle and an ellipse, with an ellipse. The use of a quasi-phi function allowed us to formalize the relations of objects (touch, non-intersection, intersection) for a wider class of spatial forms.The mathematical apparatus for the interaction of geometric objects is the basis of methods for modeling placement according to given constraints, modeling the movement of a stream of people.

A fast T-spline fitting method based on efficient region segmentation

T-spline has been recently developed to represent objects of arbitrary shapes in computer-aided design, computer graphics, and reverse engineering. In fact, fitting a T-spline over a point cloud is usually ineffective by using traditional iterative fit-and-refine paradigm. In traditional T-spline least-square fitting method, all control points are recomputed in each iteration, which costs large amount of calculations. In this paper, we propose a fast T-spline fitting method based on T-mesh segmentation. The segmentation technology is introduced to identify the inactive and active region of T-mesh. Computational costs can be largely reduced since only the control points in the active part need to be recalculated in the upcoming process, while those in inactive part are kept invariant once the fitting accuracy is achieved. Classical datasets are used to validate the proposed fast fitting method, and the experimental results yield that a total running time is reduced to $$34\%$$ of the traditional T-spline fitting method. We argue this method is particularly useful in the reconstruction of scanned scatter data of which the parameter distribution is not uniform.

A 3D Unstructured Mesh FDTD Scheme for EM Modelling

The Yee finite difference time domain (FDTD) algorithm is widely used in computational electromagnetics because of its simplicity, low computational costs and divergence free nature. The standard method uses a pair of staggered orthogonal cartesian meshes. However, accuracy losses result when it is used for modelling electromagnetic interactions with objects of arbitrary shape, because of the staircased representation of curved interfaces. For the solution of such problems, we generalise the approach and adopt an unstructured mesh FDTD method. This co-volume method is based upon the use of a Delaunay primal mesh and its high quality Voronoi dual. Computational efficiency is improved by employing a hybrid primal mesh, consisting of tetrahedral elements in the vicinity of curved interfaces and hexahedral elements elsewhere. Difficulties associated with ensuring the necessary quality of the generated meshes will be discussed. The power of the proposed solution approach is demonstrated by considering a range of scattering and/or transmission problems involving perfect electric conductors and isotropic lossy, anisotropic lossy and isotropic frequency dependent chiral materials.