Mass Center Coordinates Research Articles

Design and dynamics calculations of shallot seed feeding mechanism

Research on shallot planting feeding technology is an integral part of the shallot planter associations in which determines the suitable drop of shallot seeds to the planting mechanism. The shape of shallot seed will affect the process of selecting the feeding mechanism and feeding funnel shape. The dynamics study of shallot seeds in the feeding funnel and their movement (that is dependent on the profile and mass property of seeds) is important for manufacturing and running a good mechanism. The shallots will then be transferred by the feeding mechanism to the planting mechanism with a suitable falling trajectory. In this research, design and calculation of dynamics of the feeding mechanism of the shallot seeds is investigated using dynamics equations and also Autodesk Inventor Professional and Matlab Simulink codes. The suitable ranges of feeding mechanism parameters are obtained for the analyzed shallot seeds in terms of the specific shape, weight and mass center coordinates of the seeds.

System of metrological assurance of traceability of measurements of mass geometry characteristics

A system of metrological support is proposed that allows testing for type approval, verification and calibration of stands for measuring mass, coordinates of mass center and moments of inertia. The mathematical model of a special standard has been developed. It is based on the analytical principles for the determination of the mass center coordinates and inertia moments of homogeneous bodies with a regular geometric shape. The standard consists of a set of modules and fasteners of a special shape. Each module is a reference measure of both mass, center of mass coordinates, and moments of inertia, and can be used either separately or in a set with other modules. A scheme for transferring units of values from state primary standards of mass and length to stands using special standards has been developed. A method for calibration of special standards has been developed. It includes indirect measurements of the coordinates of the center of mass and moments of inertia based on the results of direct measurements of the mass and geometric dimensions of the standard modules’ elements, as well as measurements of the form deviations and deviations of position of the standard modules’ surfaces and static balancing of the standard. Technical requirements for special standards have been developed to minimize methodological measurement uncertainties when reproducing units of values by the standard. A line of special standards was created, their certification and approval in Rosstandart was carried out. Stand verification methods using special standards have been developed and approved. The type approval of two stands was carried out using special standards. The decision to grant a patent for the invention “Method for determining the error of the stand for measuring the characteristics of the mass geometry of products and a device for its implementation” was received.

Low-Cost Experimental System for Center of Mass and Center of Pressure Measurement (June 2018)

Falls happen when the center of mass of body is outside of its base of support and the recovery of the center of mass back to the base of support failed. Balance ability is an essential ability needed for humans’ daily routine activities. Improving balance ability should result in a better and more convenient way of living. There are various factors influence on balance ability. The focus of this paper is to investigate which factors have the greatest effect on balance. Balance ability is measured by deviations of center of pressure in both $x$ -direction (side-to-side) and $y$ -direction (front-to-back) with the age, height, body mass index, and location of body center of mass. Coordinates of subject’s joints were tracked and recorded by a motion capture system with three cameras and then were used to calculate the coordinates of segment’s mass center. The coordinates of whole body mass center were determined using the weighted segmental method. The trajectories of the center of pressure were tracked and recorded by a Wii balance board under five standing postures and slow sway movement along $x$ -direction (side-to-side) situations. The information obtained from the center of mass and the center of pressure data analysis may assist with fall prediction and prevention. With a basic training on system operation, laypersons may use this affordable low cost system at home as an exercise tool to improve balance capability and reduce fall risk factors.

Molecular dynamics for ion-tuned wettability in oil/brine/rock systems

The dependence of wettability on brine ionic composition in oil/brine/rock systems, which is denoted as ion-tuned wettability, has important applications in geoscience. Due to the involvement of non-continuum effects, molecular dynamics (MD) simulation is necessary to improve understanding of its mechanism. This work establishes a reliable molecular dynamics (MD) framework to study ion-tuned wettability. We prove that our model system can well represent the wettability of the real oil/brine/rock system, and that the wettability alteration from the MD results is qualitatively consistent with the EDL repulsion theory when ion-binding does not exist. In the process to establish the MD framework, our work suggests that adding counter ions to balance interface charges is good for studying concentration effect on wettability, and the contact angle defined from mass center coordinates is effective to measure the wettability of the nano-scale MD system. This work provides the basis for on-going studies using MD simulation to reveal the mechanism of ion-tuned wettability.

Dynamical equations of multibody systems on Lie groups

The Euler–Poinaré principle is a reduced Hamilton’s principle under Lie group framework. In this article, it is applied to derive a hybrid set of dynamical equations of rigid multibody systems, which include four parts: the classical Euler–Lagrange equations of rigid bodies in their translational coordinates of mass center; Euler–Poinaré equations via orientation matrices and their related angular velocities; the constraint equations due to different joints in Cartesian coordinates and Lie groups; and the reconstruction equations between special orthogonal groups and their Lie algebras. The generalized mass matrices of dynamical equations are constant, which is computationally efficient. All the equations can be constructed systematically and can be solved easily. The construction equations can be used to design Lie group integrators of multibody system dynamics. The procedure presented in this article can be extended easily to flexible multibody systems, systems with non-holonomic constraints, and so on.

Propellant Sloshing Parameter Extraction from Computational-Fluid-Dynamics Analysis

Propellant slosh is a potential source of disturbance critical to the stability of space vehicles. The sloshing dynamics are typically represented by a mechanical model of a spring–mass–damper system. This mechanical model is then included in the equation of motion of the entire vehicle for guidance, navigation and control analysis. The typical parameters required by the mechanical model include the natural frequency of the sloshing, sloshing mass, sloshing mass center coordinates, and critical damping coefficient. During the 1960s in the U.S. space program, these parameters were computed either from analytical solutions for simple geometries or by experimental testing for the subscale configurations. The purpose of this work is to demonstrate the soundness of a computational-fluid-dynamics approach in modeling the detailed fluid dynamics of tank sloshing and the excellent accuracy in extracting mechanical properties for different tank configurations and at different fill levels. As the first attempt, the work focuses mainly on the identification of the natural frequency and the equivalent slosh mass from the simulations. The paper presents verification against the analytical solution of natural frequency for two- and three-dimensional straight cylinders, and validation against experimental results for subscale Centaur Liquid Oxygen and Liquid Hydrogen tanks with and without baffles. The results show that computational-fluid-dynamics technology can provide accurate mechanical parameters for any tank configuration, and is especially valuable to the future design of propellant tanks.

Three-Dimensional Digital Representation of Granular Material Microstructure from X-Ray Tomography Imaging

This paper presents the use of x-ray tomography imaging to reconstruct a three-dimensional (3D) digital representation of individual particles in a granular system. The granular system is represented by the mass center coordinates and the morphology representation of each particle. An automated procedure using pattern recognition to identify related particle cross sections in adjacent serial images was developed. Procedures to calculate quantities needed for subsequent simulation of particle behavior including the volume and the momentum of inertia of each particle are also presented. The developments described in the paper enable modeling and simulation of the behavior, and experimental observations of the particle kinematics of real microstructures of granular materials in a true 3D platform.

Generalized formulas for the inertial characteristics of bodies of complex shape

1. With the aid of characteristic relations for the formation of body shapes we obtain generalized analytical formulas for calculating volumes, surfaces, mass center coordinates, and moments of inertia of the basic elements of a body of revolution and a body of translation with generators which are of arbitrary form. 2. The basic elements of the bodies studied include, in the form of special cases, entire groups of simpler bodies, computational formulas for which may be obtained from the generalized formulas by a substitution of the particular values of the geometrical parameters. 3. The generalized formulas and analytical expressions of the parametric coefficients make it possible to carry out laborious calculations of the mass geometrical characteristics of machines and mechanisms already designed on an electronic digital computer with great accuracy.