Small Moment Of Inertia Research Articles

Study of Self-Excited Pitch Oscillations of Conical-Spherical Body at Mach Number M = 1.75 and Two Moments of Inertia

Tests of a conical-spherical body in a supersonic wind tunnel were carried out on a free oscillation installation along the pitch angle at a Mach number M = 1.75 and two moments of inertia of the body relative to the axis of rotation. For a body with a large moment of inertia, self-oscillations with the amplitude of ca. 10 deg were obtained. For the first time, the phenomenon of degeneration of self-oscillations for a body with a smaller moment of inertia has been discovered. An attempt was made to model the phenomenon using an ordinary linear differential equation of the first order

Magnetic properties of a 3U CubeSat with electric propulsion

Nano-satellites, which are following the CubeSat standard are increasingly utilized for demanding industrial and astronomical applications with critical requirements on pointing and stability. Due to their small moment of inertia, even a small disturbance torque - caused by the residual magnetic moment - can result in a significant effect on the attitude. In order to study the magnetic moment of a 3 U CubeSat, an electrical model with a representative set of subsystems has been developed. A simulation tool was developed to calculate the magnetic field generated by the current flow inside the satellite. The simulation tool served to study the CubeSat mission so-called CLIMB, which employs a Field-emission electric propulsion electric propulsion system to rise its orbit by 500 km with a power consumption of 40 W at operation. In this context, the magnetic fields of this high energy density nano-satellite were measured for different operation modes inside the magnetic test facility of IABG. The data were correlated to the simulation results of the automatized model. It demonstrates, that the magnetic dipole moment is dominated by soft and hard magnetic materials like Li-ion batteries, especially at the discharging modes. This results in magnetic dipole moments of 14 mAm2 to 18 mAm2 for discharging and in between 4 mAm2 and 6 mAm2 for charging modes. The simulation tool was verified by a comparison with multi dipole models of the satellite and by modeling the impact of the solar panels only.

Simulation and modeling of manipulator for unmanned aerial vehicles

In order to improve the operation ability of unmanned aerial vehicles (UAV), this paper designs a lightweight manipulator for quadrotor UAV. First, according to the requirements of the task and the load of the UAV, an aerial manipulator with lightweight and small moment of inertia is designed, and the 3D model of the manipulator is established in the Creo software. The maximum deformation and stress under different load conditions were analyzed by Ansys Workbench software, and the dynamic analysis was carried out in ADAMS software to obtain the driving moment required by each joint of the manipulator under load conditions. Finally, the dynamic model of the aerial manipulator system is established according to the Newton-Euler method, and the maximum workspace of the manipulator in the hovering state is generated by the Monte Carlo method. The research results show that the deformation and stress level are small, and the workspace meets the operation requirements, which proves that the designed manipulator has certain engineering application value.

Design strategy and performance evaluation of novel miniature two-dimensional (2D) piston pump with a dual stacking mechanism

Since the traditional axial piston pumps have limitations to fulfill the development demands of hydraulic pumps under the electrification trend and maintain a high volumetric efficiency within various operating conditions, a new two-dimensional (2D) piston pump is proposed. In this study, the novel structure and working principle developed to raise the power density and achieve better performance were comprehensively introduced. As the motions of rotary and reciprocating are employed together, the new pump can achieve the purpose of compact structure, a small moment of inertia, and self-balancing of reciprocating inertial force. In addition, an accurate flow area during the oil discharge process was re-defined. A nonlinear mathematical model of the instantaneous flow rate of the new 2D pump for evaluating leakage performance and volumetric efficiency was established and studied in detail. Moreover, crucial features for further improvement of working performance were discussed. Then, a prototype pump was made to experimentally measure the output flow at various load pressures (from 1 MPa to 8 MPa) and rotational speeds (from 1000 r/min to 6000 r/min). The volumetric efficiency was in a range of 91.27% to 99.21%. The results of simulations and experiments well demonstrated the capabilities of the proposed novel 2D pump.

ПРО СТІЙКІСТЬ РІВНОМІРНОГО ОБЕРТАННЯ У СЕРЕДОВИЩІ З ОПОРОМ НЕСИМЕТРИЧНОГО ТВЕРДОГО ТІЛА ПІД ДІЄЮ ПОСТІЙНОГО МОМЕНТУ У ІНЕРЦІАЛЬНІЙ СИСТЕМІ ВІДЛІКУ

Assuming that the center of mass of a rigid asymmetric body is on the third main axis of inertia of a rigid body, the conditions for the asymptotic stability of uniform rotation of a dynamically asymmetric solid rigid body with a fixed point are obtained. These conditions are obtained in the form of a system of three inequalities based on the Lénard-Shipar test, written in innormal form. The rigid body is under the action of gravity, dissipative moment and constant moment in the inertial frame of reference. The rotation of a rigid asymmetric body around the center of mass is studied. Uniform rotation around the center of mass of a rigid asymmetric body will be unstable in the absence of a constant moment. Cases of absence of dynamic or dissipative asymmetry are considered. It is shown that the equilibrium position of a rigid body will be stable only under the action of the reducing moment. Dynamic asymmetry has a more significant effect on the stability of rotation of an asymmetric rigid body than dissipative asymmetry. Stability conditions have been studied for various limiting cases of small or large values of restoring, overturning, or constant moments. It is noted that for sufficiently large values of the modulus of the reducing moment, the rotation of the asymmetric solid will be asymptomatically stable. If the axial moment of inertia is the greatest or the smallest moment of inertia, then at sufficiently large values of angular velocity, both under the action of the overturning moment and under the action of the reducing moment, the rotation of the asymmetric solid will be asymptomatically stable. Analytical studies of the influence of dissipative, constant, overturning and restorative moments on the stability of uniform rotations of asymmetric and symmetric solids have been carried out. It is shown that in the absence of dynamic and dissipative symmetries, the obtained stability conditions coincide with the known ones.

A paratrooper model sensitivity analysis for personnel airdrop

Personnel airdrop operations are subject to the unsteady flow around aircraft and variations in the paratrooper's exit orientation, body, weight, and balance. This could lead to non-repeatable airdrop operations including the possibilities of the paratrooper colliding with the aircraft or, after parachute deployment, another paratrooper leaving the opposite side. An exit trajectory sensitivity analysis addressing variations in mass distributions, exit velocity, initial position, and initial orientation is, therefore, an essential tool to increase aircrew and soldier safety. The goal of this study is to conduct time accurate simulations of two high-fidelity paratrooper models with different weight and balance data exiting the left- and right-side troop/exit doors of a C-130 after an initial prescribed motion. The aircraft model has an open troop door with fully-opened air deflector and extended flaps flying at 1,000 ft and 130 kn, and without propeller blades. Upon completing an initial prescribed motion, the paratrooper model is permitted to respond to the influence of the aircraft flow field and gravity. Solutions are calculated using HPCMP CREATETM-AV Kestrel software. In these simulations, the initial exit motion, position, and orientation are fixed. Trajectory data are extracted and compared. A normalized parameter of distance to the paratrooper diameter is defined to measure the trajectory translation deviations from a baseline exit case. The results show that trajectory data are more sensitive to the weight and balance data than aerodynamic forces/moments, which are functions of body profiles. For all tested right exits, the maximum deviations measure about three paratrooper body reference diameters, and all follow similar trajectory paths. Cases with small moments of inertia around the z-axis and a small side-force can lead to a negative yaw turn at initial exit times and a possible contact of main canopy container with the aircraft. The results show that left and right exit trajectories are very different mainly due to the asymmetries of paratrooper models. The results of these simulations document and characterize the associated strong moments, and the final states of the trajectories will serve as initial conditions for the subsequent parachute deployment.

Angle measurement technology based on magnetization vector for narrow space applications

With the wide application of laser in the field of skin plastic surgery, micro laser galvanometer scanner has made great progress in this field with its portability. However, the measurement method used to measure the deflection angle of laser galvanometer in the narrow space of scanner with high precision remains to be studied. In this paper, an angle measurement method based on magnetic field is proposed, and the effect of the shapes of permanent magnets (PMs) on the measurement is studied by theoretical and experimental study under the condition that the maximum available space for the PMs is a 10 mm side cube. An angle measuring experimental device is set up, and the contrast experiment is carried out with different PMs which are the same as simulation. The experimental results show that cylindrical PM is more suitable than other PMs, which is consistent with the simulation results, and the maximum nonlinearity error is 0.562%. This method has the advantages of small volume, non-contact measurement, small moment of inertia, good dynamic response and no external excitation for the PMs, so it has a broad application prospect in micro laser galvanometer scanner.

Comparison of sheep and human middle-ear ossicles: anatomy and inertial properties

The sheep middle ear has been used in training to prepare physicians to perform surgeries and to test new ways of surgical access. This study aimed to (1) collect anatomical data and inertial properties of the sheep middle-ear ossicles and (2) explore effects of these features on sound transmission, in comparison to those of the human. Characteristic dimensions and inertial properties of the middle-ear ossicles of White-Alpine sheep (n = 11) were measured from high-resolution micro-CT data, and were assessed in comparison with the corresponding values of the human middle ear. The sheep middle-ear ossicles differed from those of human in several ways: anteroinferior orientation of the malleus handle, relatively small size of the incus with a relatively short distance to the lenticular process, a large area of the articular surfaces at the incudostapedial joint, and a relatively small moment of inertia along the anterior–posterior axis. Analysis in this study suggests that structure and orientation of the middle-ear ossicles in the sheep are conducive to an increase in the hinge-like ossicular-lever-action around the anterior–posterior axis. Considering the substantial anatomical differences, outcomes of middle-ear surgeries would presumably be difficult to assess from experiments using the sheep middle ear.

Stability Analysis and Fault Changes on Wind Turbine Effect in Multi Machine Power System

This study presents stability analysis using a new approach to model the disturbances that occur in multi-machine systems connected with wind turbines. Consideration of stability and operability of conventional electric power systems planning and developing facing problems with the integration of installations in wind power plants (WPP) is needed because the current system is connected with renewable energy. This study highlighting the effects of WPP connected to a multi-engine 9 bus system from the effect of changes in disturbances occurring on several buses when operating. Disruption in multi-machine systems connected with wind turbines can affect system stability. The noise changes from bus to bus in the voltage drop effect on the system bus. The effect of wind turbine when a fault has a small moment of inertia can make the system unstable on the bus. The results of simulations carried out using ETAP to observe system stability have been carried out. The simulation results show that a system disruption that occurs in a multi engine system connected to the wind turbine does not result in a decrease in the bus near the fault then the stability decreases.

Design and Experimental Evaluation of a 12 kW Large Synchronous Reluctance Motor and Control System for Elevator Traction

Recently, a new type of motor, synchronous reluctance motor (SRM), has attracted wide attention from academia and industry because of its potential applications in fans, pumps, and elevator traction systems. Compared with traditional motors, these motors have lower eddy-current loss, less torque ripple, reduced noise, smaller moment of inertia, and faster dynamic response, and they provide a greater operating efficiency and safety and are simpler and easier to maintain. However, the ontology design and operation control of SRMs continue to be significant hurdles that must be overcome prior to practical implementation. In order to facilitate the practical application of SRMs in industry, at the invitation of an elevator company, we designed a large SRM for elevator traction. Herein, we describe the design of the proposed system and present a theoretical analysis of the system. Furthermore, we fabricate a real prototype and the corresponding control system and perform an experimental test under the rated operating conditions and $1.5\times $ overload conditions in order to verify the SRM’s performance. The results of the experimental testing were satisfactory and consistent with the theoretical calculations. At present, we have entered the stage of small-batch trial production and we expect to ultimately implement this novel design. Further, the approach to ontology design and operation control in this study can be used to inform the future development of novel SRMs.

Dynamical modeling and attitude analysis for the spacecraft with lateral solar arrays

• The dynamical model of the spacecraft with two groups of lateral solar arrays is established. • Global modes of the model are obtained and used to discrete the PDEs of the system. • Comparisons of the natural characteristics are performed with finite element model. • Dynamic responses of attitude motion and flexible vibration are performed by simulation examples. The dynamics and attitude motion of the three-axis stabilized spacecraft installed with lateral solar arrays is investigated in terms of the rigid-flexible coupled global modes of the system. The spacecraft consists of a rigid platform with small moment of inertia and two groups of flexible solar arrays with relatively large moment of inertia installed on the rigid rotation shafts. The rigid-flexible coupled dynamic model of the spacecraft is established by using the Hamiltonian Principle. The global mode method is employed to work out the natural frequency and global modal shapes of the rigid-flexible coupled dynamic model combined with corresponding boundary conditions. To validate the effectiveness of the analytical results obtained by global mode method, the natural frequencies and mode shapes obtained from finite element model using MSC.Patran software are used as a reference. A numerical example is given to show that the results obtained from both methods are matched very well (the relative errors of the corresponding frequencies are small enough) and the rigid motion of the platform is coupled with the vibration mode of the flexible solar arrays. This implies that the global analytical modes can be used to accurately describe the rigid-flexible coupled motion of the spacecraft. By comparing with the finite element model, the reduced dynamical model derived in terms of the global modes of the system has a lower dimension. Numerical simulations for the system with variations of parameters and dynamic responses analysis for different applied forces are performed to illustrate that, the characteristics of the model are affected by inner and external factors.

Frequency-Distinct Control of Wind Energy Conversion System Featuring Smooth and Productive Power Output

Improving maximum power point tracking ability (MPPTA) and smoothing electric power fluctuation (EPF) are two important goals for optimizing wind power generation. Sufficient works have been done on both goals separately, but the multi-objective optimization of wind energy conversion system (WECS) is lack of theoretical analysis. In this paper, the small signal analysis method is applied to get a frequency-domain declaration for both MPPTA and EPF. The analysis results show when applying traditional optimal torque control (OTC), a larger moment of inertia of WECS is preferred for smoothing EPF, while a smaller moment of inertia is preferred for improving MPPTA, i.e., the two optimization goals contradict with each other. Furthermore, the existing control strategies for improving MPPTA are summarized as virtual-inertia embedded OTC, which turns out to have adverse impacts on EPF. To simultaneously optimize these two contradictory goals, a novel frequency-distinct optimal torque control approach is proposed, and a novel criterion for evaluating MPPTA is presented to facilitate controller parameter design. The analysis results and the proposed control strategy are fully verified by refined co-simulation platform based on GH Bladed and real time digital simulator.

Higher-order symmetry energy and neutron star core-crust transition with Gogny forces

We study the symmetry energy and the core-crust transition in neutron stars using the finite-range Gogny nuclear interaction and examine the deduced crustal thickness and crustal moment of inertia. We start by analyzing the second-, fourth- and sixth-order coefficients of the Taylor expansion of the energy per particle in powers of the isospin asymmetry for Gogny forces. These coefficients provide information about the departure of the symmetry energy from the widely used parabolic law. The neutron star core-crust transition is evaluated by looking at the onset of thermodynamical instability of the liquid core. The calculation is performed with the exact (i.e., without Taylor expansion) Gogny EoS for the core, and also with its Taylor expansion in order to assess the influence of isospin expansions on locating the inner edge of neutron star crusts. It is found that the properties of the core-crust transition derived from the exact EoS differ from the predictions of the Taylor expansion even when the expansion is carried through sixth order in the isospin asymmetry. Gogny forces, using the exact EoS, predict the ranges $0.094 \text{ fm}^{-3} \lesssim \rho_t \lesssim 0.118\text{ fm}^{-3}$ for the transition density and $0.339 \text{ MeV fm}^{-3} \lesssim P_t \lesssim 0.665 \text{ MeV fm}^{-3}$ for the transition pressure. The transition densities show an anticorrelation with the slope parameter $L$ of the symmetry energy. The transition pressures are not found to correlate with $L$. Neutron stars obtained with Gogny forces have maximum masses below $1.74M_\odot$ and relatively small moments of inertia. The crustal mass and moment of inertia are evaluated and comparisons are made with the constraints from observed glitches in pulsars.

Rotational dissociation of impulsively aligned van der Waals complexes.

The nonadiabatic alignment dynamics of weakly bound molecule-atom complexes, induced by a moderately intense 300 fs nonresonant laser pulse, is calculated by direct numerical solution of the time-dependent Schrödinger equation. Our method propagates the wave function according to the coupled channel equations for the complex, which can be done in a very efficient and stable manner out to large times. We present results for two van der Waal complexes, CS2-He and HCCH-He, as respective examples of linear molecules with large and small moments of inertia. Our main result is that at intensities typical of nonadiabatic alignment experiments, these complexes rapidly dissociate. In the case of the CS2-He complex, the ensuing rotational dynamics resembles that of isolated molecules, whereas for the HCCH-He complex, the detachment of the He atom severely perturbs and essentially quenches the subsequent rotational motion. At intensities of the laser pulse ≲2.0 × 1012 W/cm2, it is shown that the molecule-He complex can rotate and align without breaking apart. We discuss the implications of our findings for recent experiments on iodine molecules solvated in helium nanodroplets.

VARIABLE LOAD, CONSTANT SPEED, AND ESTIMATED CAPACITANCE RELUCTANCE GENERATOR

Switched reluctance machine has various desirable features, which comes from its simple construction. They are the wide speed range, high temperature operation and small moment of inertia, constant frequency irrespective of load or capacitance variations with good efficiency and improved voltage regulation. It is possible to use it as a wind driven alternator which may be connected to the common network. The steady-state analysis of the reluctance generator based on d-q axes transformation is carried out, with the saturation effect as an essential element. The required capacitance in the different operating conditions is determined to satisfy the main requirements of constant voltage for a loaded reluctance generator. This system proposed feasibility and validity are simulated on MATLAB/SIMULINK.

Theoretical and Experimental Proof of Alkali-Metal Atom as Polar Atom

In addition to polar molecules, there is no polar atom in the natural world, which is a deep-rooted traditional concept that has lasted for more than a century. However, our research showed that alkali-metal atoms form an exception. In theory, we proved that alkali atom may be polar atom doesn't conflict with quantum mechanics, which is a great breakthrough in measurement theory of quantum mechanics. Variation of the capacitance with temperature and density offers a means of separating polar and nonpolar atom, but no one has done these experiments so far. If alkali atom is nonpolar atom, its capacitance should be independent of temperature and density, because atomic nucleus located at the center of the electron cloud. Our experiments showed that Na, K, Rb and Cs atoms are polar atoms, because their capacitance is not only related to temperature, but also to density. Unlike alkali atoms, the capacitance of Hg gas is independent of temperature and density, so mercury is nonpolar atom. Therefore atoms can be divided into two categories: polar and nonpolar atom, this discovery will lead to an exciting revolution in Bose- Einstein condensation (BEC) research and condensed matter physics. BEC experiments have been carried out for decades, but the number of condensed atoms is still very small (<107) because scientists has never applied an electric field. Our innovation lies in the application of an electric field, we don't need magnetic field and lasers. When V=390 volts, condensates contained up to 2.51 × 1017 sodium atoms; when V=350 volts, condensates contained up to 1.93 × 1017 cesium atoms, large-scale BEC at T=343 K or 353 K has been observed. Now scientists generally assume that polar molecules may be used as candidate materials for quantum computers. In the future, polar atoms will replace polar molecules as candidate materials for quantum computers, because of its very small moment of inertia.

An alternative numerical solution of 900/00/900 cross-ply laminated composite plate using displacement potential approach

ABSTRACTConventional loading with a composite plate has a very small moment of inertia due to its low height, and it was solved by shear deformation and other approaches. In the present study, a thin cross-ply 900/00/900 laminated composite plate is erected to increase its height, which increases its moment of inertia with load; increased moments of inertia of the plate increase its load-carrying capacity in a real structure. Finite difference solutions of a cross-ply 900/00/900 laminated plate made of T-300 carbon/epoxy are obtained using displacement potential approach. The plate behaves like a cantilever beam; one end of the plate is rigidly fixed and a uniformly distributed load is applied on its top span. The displacement potential approach is extended using the lamination theory of composite materials and plane stress concept. The different equivalent displacement, strain, and stress components at different sections of the plate with its deformed shape are discussed. Using the concept of the classical theory of laminations, different stress components along the lamina and inter-laminar regions are obtained. Besides to verify the reliability and soundness of the present numerical approach, the solutions of the present problem are compared with those of the finite element method.

Loosening up the Skyrme model

We consider the Skyrme model with the addition of extra scalar potentials that decrease the classical binding energies of the Skyrmions to about the 3% level -- without altering the pion mass -- if we insist on keeping platonic symmetries that are usually possessed by Skyrmions. A side effect of the potentials under consideration is the smaller size of the 1-Skyrmion resulting in a smaller moment of inertia and in turn a larger spin contribution to the energy upon semi-classical quantization. After taking into account the quantum contributions we find total binding energies at the 6% level.

Wobbling geometry in a simple triaxial rotor**Supported by President's Undergraduate Research Fellowship (PURF), Peking University, Major State 973 Program of China (2013CB834400), National Natural Science Foundation of China (11175002, 11335002, 11375015, 11345004, 11461141002), National Fund for Fostering Talents of Basic Science (NFFTBS) (J1103206) and Research Fund for the Doctoral Program of Higher Education (20110001110087)

The spectroscopic properties and angular momentum geometry of the wobbling motion of a simple triaxial rotor are investigated within the triaxial rotor model. The obtained exact solutions of energy spectra and reduced quadrupole transition probabilities are compared to the approximate analytic solutions from the harmonic approximation formula and Holstein-Primakoff formula. It is found that the low lying wobbling bands can be well described by the analytic formulae. The evolution of the angular momentum geometry as well as the K-distribution with respect to the rotation and the wobbling phonon excitation are studied in detail. It is demonstrated that with the increase of the wobbling phonon number, the triaxial rotor changes its wobbling motions along the axis with the largest moment of inertia to the axis with the smallest moment of inertia. In this process, a specific evolutionary track that can be used to depict the motion of a triaxial rotating nucleus is proposed.

Variable Angle of SRG for Wind Energy Control Application

Switched reluctance machine has various desirable features, which comes from its simple construction. They are the wide speed range, high temperature operation and small moment of inertia. There are many control variables, such as: firing angles, reference current, speed and voltage. This paper presents a nonlinear model of 6/4 Switched Reluctance Generator (SRG) with two converter (one with generator side and other with grid side) based on wind Energy system. This system provides a new approach to maximize the amount of power generated. Closed loop control with based PI current Control model is used. A Power converter in SRG can be produced maximum power efficiency and minimize the ripple contents in the output of SRG depend on the converter angles. A second power converter namely PI based controlled PWM inverter is used to interface the machine to the Grid. This system proposed feasibility and validity are simulated on MATLAB/SIMULINK. Keywords—Wind Energy, SRG, SHB, and VSC. was performed based on control of two separate converters. The control of the converter connected to SRG regulates the extraction of electrical power to be generated and the control of the converter connected to the grid is responsible for regulate the transmission of the generated energy to the grid. Fig. 1, shows 6/4 SRG. The winding A-A' in Fig. 1 is one of the machine phases. Fig. 2 shows the idealized inductance profile of a SRG. If saturation is neglected then the inductance varies linearly with respect to the overlap between the stator and rotor poles. The inductance is maximum when the rotor and stator poles are fully aligned and minimum when the poles are completely unaligned. For generation, the machine phases are excited during the negative slope of the inductance profile, (2). Fig. 3 shows the block diagram of the system. It is consist of wind turbine, SRG, asymmetric H-Bridge (AHB), and PWM inverter with control system