Variable Inertia Research Articles

Maximum Integration Capacity Analysis of Distributed Generator in Distribution Power System

The integration of distributed generator (DG) will bring a series of influence in distribution power system. With the trend of a large number of DG penetration, researches on the maximum integration capacity of DG become a hot research topic. A multi-objective optimization model with objective functions of the maximum DG output, network losses and voltage stability index are formulated. Particle swarm optimization (PSO) algorithm is adopted with variable inertia weight to calculate the maximum DG output. IEEE 33-bus test system with DG units is taken as one example to compute the maximum integration capacity. The results show that the proposed method is reasonable and effective.

Nonlinear dynamic modeling for a diesel engine propeller shafting used in large marines

Longitudinal vibration, torsional vibration and their coupled vibration are the main vibration modes of the crankshaft-sliding bearing system. However, these vibrations of the propeller-crankshaft-sliding bearing system generated by the fluid exciting force on the propeller are much more complex. Currently, the torsional and longitudinal vibrations have been studied separately while the research on their coupled vibration is few, and the influence of the propeller structure to dynamic characteristics of a crankshaft has not been studied yet. In order to describe the dynamic properties of a crankshaft accurately, a nonlinear dynamic model is proposed taking the effect of torsional-longitudinal coupling and the variable inertia of propeller, connecting rod and piston into account. Numerical simulation cases are carried out to calculate the response data of the system in time and frequency domains under the working speed and over-speed, respectively. Results of vibration analysis of the propeller and crankshaft system coupled in torsional and longitudinal direction indicate that the system dynamic behaviors are relatively complicated especially in the components of the frequency response. For example, the 4 times of an exciting frequency acting on the propeller by fluid appears at 130 r/min, while not yield at 105 r/min. While the possible abnormal vibration at over-speed just needs to be vigilant. So when designing the propeller shafting used in marine diesel engines, strength calculation and vibration analysis based only on linear model may cause great errors and the proposed research provides some references to design diesel engine propeller shafting used in large marines.

Thermophysical property variations across Dione and Rhea

Maps of the variation in bolometric Bond albedo and thermal inertia across Rhea and Dione have been produced using various day and nighttime observations, taken by Cassini’s Composite Infrared Spectrometer (CIRS). The albedo maps show the same trend that has been previously observed on these satellites from reflected sunlight and thermal observations: a higher albedo on their leading hemispheres. The thermal inertia maps show two previously unknown anomalous high thermal inertia regions: low latitudes on Dione’s leading hemisphere and the bright ejecta blanket of Rhea’s Inktomi crater.The thermal inertia on Dione increases modestly from a background value of 8Jm−2K−1s−1/2 to 11Jm−2K−1s−1/2 in a region preferentially bombarded by high-energy electrons. We believe that this region on Dione is probably analogous to the thermally anomalous regions recently discovered at equivalent locations on Mimas and Tethys, dubbed Pac-Man features. The smaller magnitude of Dione’s thermal anomaly, compared to that of Mimas and Tethys, provides additional evidence that surface alteration by high-energy electrons produces these anomalies, as the high-energy electron flux decreases with increasing distance from Saturn. However, unlike on Mimas and Tethys, the thermally anomalous region on Dione does not display a spatially correlated decrease in the IR/UV (0.930μm/0.338μm) color ratio, implying that the minimum electron energy threshold of the IR/UV ice surface darkening mechanism is not met on Dione. The average of the mapped bolometric Bond albedos on the leading and trailing hemispheres of Dione are 0.49±0.11 and 0.44±0.13 respectively.On Rhea the thermal inertia increases from a background value of 10Jm−2K−1s−1/2 to 19Jm−2K−1s−1/2 on the ejecta blanket of Inktomi crater, probably due to a mixture of high and low thermal inertia material in this region, such as a fine- and large-grain ice mixture. This is the first time a thermal inertia anomaly has been associated with an impact crater on an icy saturnian satellite. On Rhea the average of the mapped bolometric Bond albedos on the leading and trailing hemispheres are 0.59±0.11 and 0.56±0.13 respectively.

Neuro-fuzzy adaptive control of a revolute stewart platform carrying payloads of unknown inertia

SUMMARYIn this research, a Stewart parallel platform with rotary actuators is simulated and a prototype is tested under different operative conditions. The purpose is to make the robot robust against inertia variations considering the fact that different payloads of unknown size may be transported. Due to the complexity issued by expressing the equations of motion with independent variables, the governing equations are derived by Lagrange's method using Lagrange multipliers for imposing the kinematic constraints imposed on this parallel robot. Eliminating Lagrange multipliers by projecting the equations onto the orthogonal complement of the space of constraints, the equations of motion are transformed to a reduced form suitable for the purpose of controller design. The control approach considered here is based on a neuro-fuzzy interference method. As a first step, each revolute arm link are individually trained under different loadings and diverse maneuvers. It is purposed that once employed together, the links will have learned how to collaborate with each others for performing a common task. Training data are divided to several clusters by using a subtractive clustering algorithm. For every cluster, a fuzzy rule is derived so that the output follows the desired trajectory. In the last stage, these rules are employed by utilizing back propagation algorithms and the effectiveness of the neuro-fuzzy system becomes approved by performing multiple maneuvers and its robustness is checked under various inertia loads. The controller has ultimately been implemented on a prototype of the Stewart mechanism in order to analyze the reliability and feasibility of the method.

Sliding mode attitude control using thrusters and pulse modulation for the ASTER mission

ASTER, the first Brazilian mission to the deep space, targets the exploration of the triple asteroid system known as 2001 SN263. The mission requires an attitude controller robust and capable of coping with the non-linearities and the uncertainties present during the exploration phase. For such requirements, this paper studies the applicability of two controllers, designed based on the sliding mode control (SMC) technique, one of the controllers include an adaptive law used to compensate for the spacecraft’s inertia variation. One application is performed where gain scheduling is used for controlling two different phases: exit from tumbling and track a dynamic reference. The actuators of the attitude control loops are impulsive thrusters. They are activated by pulse width modulation (PWM) or pulse width pulse frequency modulation (PWPFM). Simulation studies, performed in realistic scenarios, show that the SMC can maintain stability and performance when these modulation techniques are used to approximate the continuous commands. It is also shown that PWM can provide better performance, but at a higher control cost. In this sense, PWPFM is more appropriate with respect to the fuel consumption and activation times.

Thermal infrared observations and thermophysical characterization of OSIRIS-REx target asteroid (101955) Bennu

Near-Earth Asteroids (NEAs) have garnered ever increasing attention over the past few years due to the insights they offer into Solar System formation and evolution, the potential hazard they pose, and their accessibility for both robotic and human spaceflight missions. Among the NEAs, carbonaceous asteroids hold particular interest because they may contain clues to how the Earth got its supplies of water and organic materials, and because none has yet been studied in detail by spacecraft. (101955) Bennu is special among NEAs in that it will not only be visited by a spacecraft, but the OSIRIS-REx mission will also return a sample of Bennu’s regolith to Earth for detailed laboratory study. This paper presents analysis of thermal infrared photometry and spectroscopy that test the hypotheses that Bennu is carbonaceous and that its surface is covered in fine-grained (sub-cm) regolith. The Spitzer Space Telescope observed Bennu in 2007, using the Infrared Spectrograph (IRS) to obtain spectra over the wavelength range 5.2–38μm and images at 16 and 22μm at 10 different longitudes, as well as the Infrared Array Camera (IRAC) to image Bennu at 3.6, 4.5, 5.8, and 8.0μm, also at 10 different longitudes. Thermophysical analysis, assuming a spherical body with the known rotation period and spin-pole orientation, returns an effective diameter of 484±10m, in agreement with the effective diameter calculated from the radar shape model at the orientation of the Spitzer observations (492±20m, Nolan, M.C., Magri, C., Howell, E.S., Benner, L.A.M., Giorgini, J.D., Hergenrother, C.W., Hudson, R.S., Lauretta, D.S., Margo, J.-L., Ostro, S.J., Scheeres, D.J. [2013]. Icarus 226, 629–640) and a visible geometric albedo of 0.046±0.005 (using Hv=20.51, Hergenrother, C.W. et al. [2013]. Icarus 226, 663–670). Including the radar shape model in the thermal analysis, and taking surface roughness into account, yields a disk-averaged thermal inertia of 310±70Jm−2K−1s−1/2, which is significantly lower than several other NEAs of comparable size. There may be a small variation of thermal inertia with rotational phase (±60Jm−2K−1s−1/2). The spectral analysis is inconclusive in terms of surface mineralogy; the emissivity spectra have a relatively low signal-to-noise ratio and no spectral features are detected. The thermal inertia indicates average regolith grain size on the scale of several millimeters to about a centimeter. This moderate grain size is also consistent with low spectral contrast in the 7.5–20μm spectral range. If real, the rotational variation in thermal inertia would be consistent with a change in average grain size of only about a millimeter. The thermophysical properties of Bennu’s surface appear to be fairly homogeneous longitudinally. A search for a dust coma failed to detect any extended emission, putting an upper limit of about 106g of dust within 4750km of Bennu. Three common methodologies for thermal modeling are compared, and some issues to be aware of when interpreting the results of such models are discussed. We predict that the OSIRIS-REx spacecraft will find a low albedo surface with abundant sub-cm sized grains, fairly evenly distributed in longitude.

Stability analysis of disturbance observer based controllers for two-wheel wheelchair systems

Previously, two-wheel wheelchair systems have been receiving attention since they have high mobility better than conventional four-wheel wheelchair systems. However, in two-wheel wheelchair systems, pitch angle must be stabilized by actuated wheels since two-wheel wheelchair systems are underactuated systems. Furthermore, stabilization control needs to be achieved under parameter variation or disturbances considering safety of human. In this paper, two kinds of disturbance observer (DOB) based controllers are compared in terms of stability of inertia variation. One is Lyapunov controller based on pitch angle disturbance observer with DOB. The other is Lyapunov controller based on synthesized pitch angle disturbance observer. Root locus is conducted to analyze stability of inertia variation of these systems. Simulation and experimental results verify the accuracy of this analysis.

Hybrid recurrent wavelet neural network control of PMSM servo-drive system for electric scooter

Due to nonlinear uncertainties of the electric scooter such as nonlinear friction force of the transmission belt and clutch, these will lead to degenerate tracking responses in command current and speed of the permanent magnet synchronous motor (PMSM) servo-driven electric scooter. In this study a novel hybrid recurrent wavelet neural network (HRWNN) control system is proposed to raise robustness of the PMSM servo-driven electric scooter under the occurrence of the variation of rotor inertia and load torque disturbance. First, the field-oriented mechanism is applied to formulate the dynamic equation of the PMSM servo drive. Then, a novel HRWNN control system is proposed to control motion for a PMSM servo-driven electric scooter. The HRWNN control system composed of a supervisor control, a RWNN and a compensated control with adaptive law. The online parameter training methodology with adaptive law in the RWNN is derived based on the Lyapunov stability theorem. Then adaptive law of the parameter in the RWNN can be updated by using the gradient descent method and the backpropagation algorithm. Finally, the effectiveness of the proposed control scheme is verified by experimental results.

Optimal Lumped Mass Matrices by Minimization of Modal Errors for Beam Elements

This paper clarifies the reason why error occurs in the mass lumping procedure and presents a new approach to construct lumped mass matrices for Euler–Bernoulli beam elements, which contain both translational and rotational degrees of freedom. Lumped mass matrices provide the proper translational inertia but change the rotational inertia compared with the continuous mass representation. Therefore, the optimal lumped mass matrices are expressed through the adoption of a variable rotational inertia parameter to counterbalance the decreased or increased rotational inertia. The goal of this study is to propose lumped mass matrices to minimize the modal error for beam elements. The accuracy of the new mass matrices is validated by a number of numerical tests.

Evaluation of Tension Force Using Vibration Technique Related to String and Beam Theory to Ratio of Moment of Inertia to Span

Evaluation of strength of cable using vibration method is widely applied on the bridge health monitoring. The vibration method is based on the natural frequency recorded from cable that used to estimate the strength of cable on cable stayed and suspension bridges. Many practical formulae to estimate cable tension using natural frequency have been proposed. The cables applied on the bridge have the variation of moment inertia to length. The calculation of strength of cable based on the flat taut string theory ignores the sag-extensibility and bending stiffness of the cable. On the other hand, the beam theory includes the parameter of bending stiffness to compute the natural frequency of beam. The specimen used in the laboratory experiment is the strep steel. The section properties of the specimen were 2mm of thickness, 38.5mm of wide and 1000mm of length respectively. The ratio of the moment of inertia to length of the specimen is 9.15. The investigation shows that the experiment result is closed to the analytical solution by using string theory. In addition, the results of the beam-string, stoke, and irvine theories are closed to each other, but quite different from the experiment result. Adopting the flat taut string theory and the beam theory, this paper shows the compatibility cable behaviour that is close to the beam or string based on the moment of inertia to length ratio.

Vibration Suppression Control based on Final State Control Considering Convergence Time and Inertia Variation for Industrial Robot

Vibration Suppression Control based on Final State Control Considering Convergence Time and Inertia Variation for Industrial Robot

Finding the buckling load of non-uniform columns using the iteration perturbation method

The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory system is used to calculate the critical load of the trigonometrically varied inertia column. In doing so, the equilibrium equation of the column is theoretically studied using the perturbation method. Accuracy of the calculated results is evaluated by comparing the solution with numerical results. Effect of improving the initial guess on the solution accuracy is investigated. Effects of varying parameters of the trigonometrically varied inertia and the uniformly tapered columns on their stability behavior are studied. Finally, using the so-called “perfectibility” parameter, two design goals, i.e., being lightweight and being strong, are studied for the discussed columns.

Hybrid P-PI sliding mode position and speed controller for variable inertia drive

Control system for a variable inertia drive based on a hybrid P-PI sliding mode controller and reference trajectory generator is described in this paper. Sliding mode block with boundary layer (active for large error values) and the P-PI block (active for small error values) are combined in one controller. Simulation results show that this control approach can decrease tracking error, enhance system robustness and attenuate high frequency chattering in the control signal. The results of simulation are confirmed by experimental studies. Streszczenie. W artykule przedstawiono uklad sterowania dla napedu o zmiennej bezwladności. W ukladzie tym zaproponowano generator trajektorii wzorcowej oraz hybrydowy regulator polozenia i predkości. W regulatorze polączono blok regulatora ślizgowego z warstwą graniczną (aktywny dla duzych wartości uchybu) z blokiem P-PI (aktywnym dla malych wartości uchybu). Badania symulacyjne wykazaly, ze takie podejście zmniejsza bledy śledzenia, poprawia odpornośc i eliminuje szybkie oscylacje sygnalu sterującego. Badania eksperymentalne potwierdzily wyniki. (Hybrydowy P-PI - ślizgowy regulator polozenia i predkości dla napedu o zmiennej bezwladności)

Dynamics and Balance Control of the Reaction Mass Pendulum: A Three-Dimensional Multibody Pendulum With Variable Body Inertia

Pendulum models have been studied as benchmark problems for development of nonlinear control schemes, as well as reduced-order models for the dynamics analysis of gait, balance and fall for humanoid robots. We have earlier introduced the reaction mass pendulum (RMP), an extension of the traditional inverted pendulum models, which explicitly captures the variable rotational inertia and angular momentum of a human or humanoid. The RMP consists of an extensible “leg”, and a “body” with moving proof masses that gives rise to the variable rotational inertia. In this paper, we present a thorough analysis of the RMP, which is treated as a three-dimensional (3D) multibody system in its own right. We derive the complete kinematics and dynamics equations of the RMP system and obtain its equilibrium conditions. We show that the equilibria of this system consist of an unstable equilibrium manifold and a stable equilibrium manifold. Next, we present a nonlinear control scheme for the RMP, which is an underactuated system with three unactuated degrees of freedom (DOFs). This scheme asymptotically stabilizes this underactuated system at its unstable equilibrium manifold, with a vertically upright configuration for the “leg” of the RMP. The domain of convergence of this stabilization scheme is shown to be almost global in the state space of the RMP. Numerical simulation results verify this stability property of the control scheme and demonstrate its effectiveness in stabilizing the unstable equilibrium manifold.

Vibration of a thin rectangular plate subjected to series of moving inertial loads

In this article, the resonance of a rectangular plate due to multiple traveling masses is studied. Two series of moving inertial loads traversing the plate surface along parallel rectilinear trajectories with opposite directions are considered. This investigation is of significance in engineering mechanics dealing with the vibration of two-lane slab-type bridges under the moving vehicles. The peak values of DAF (dynamic amplification factor) are determined with respect to the variation of loads velocity and inertia as well as their spacing.

Torsional Vibration Analysis for Large-Scale Reciprocating Compressor Crankshaft

This paper presents a new method which combined multi-body dynamics theory and finite element technology to calculate transient stress of the crankshaft of the large-scale reciprocating compressor. On the basis of multi-body dynamics theory, the kinematical simulation of the crankshaft, the connecting rod, the piston and other components were performed, and thus to get the vibration modal of the crankshaft. So we can judge whether the crankshafts torsional resonance will happen, as well as get the real loads on the crankshaft when it worked. Then the transient stress of the crankshaft can be calculated using finite element technology. Comparing to traditional stress calculating methods, this new method not only considers the variable inertia which caused by reciprocating masss movement, but also can calculate the integrated vibration stress of crankshaft in three directions, including torsion, lateral and axial. Therefore, this method can describe dynamic characteristics of the crankshaft more accurately and more entirely.

Nuclear inertia and the decay modes of superheavy nuclei

Superheavy nuclei produced up to now decay mainly by α emission and spontaneous fission. For atomic numbers larger than 121 cluster decay has a good chance to compete. While calculated α decay half-lives are in agreement with experimental data within one order of magnitude and cluster decay experiments are also very well accounted for, the discrepancy between theory and experiment can be as high as ten orders of magnitude for spontaneous fission. We analyze some ways of improving the accuracy: using a semiempirical formula for α decay and changing the parameters of analytical superasymmetric fission and of the universal curve for cluster decay. For spontaneous fission we act on nuclear dynamics based on potential barriers computed by the macroscopic–microscopic method and employing various nuclear inertia variation laws. Applications are illustrated for 284Cn and Z = 118–124 even–even parent nuclei.Communicated by Steffen Bass

PID Control of Hybrid Injection Molding Machine Temperature

This article analyzing the importance of PID in the design of the temperature process controller for hybrid injection mould machine. The injection mould machine is a basic requirement of plastic. Its process to mould the items through adjustment of proper temperatures realized desired shapes. And it is very indispensable to maintain these desired temperatures. PID controller is used as an industrial process controller. It may not get satisfying results when used as a temperature process controller. The temperature process has the characteristics of non-linearity, large inertia and time variations. To solve these problems, this article put forward an effective controller design by introducing PID in the designing of temperature process controller. The paper drafted the performance analysis of PID controller versus based controller designs.

CHARACTERIZATION OF BACKBENDING IN EVEN–EVEN ISOTOPES OF 164–174Hf AND 154–164Dy NUCLEI BY A MODIFIED PHENOMENOLOGICAL MODEL

A modified phenomenological model is used to calculate nuclear energy levels and describe successfully the backbending of the moment of inertia for the ground state bands in even–even isotopes of Hf and Dy nuclei. The model is a combination of the Myers and Swiatecki model with variable moment inertia (VMI) model. Since the Myers and Swiatecki model has a deviation from experimental energies in which it takes into account pairing effect with constant moment of inertia, in the rotation of nuclei, the Coriolis force acts to de-pair the nucleons pair and align their angular momentum with nuclei total angular momentum, thus Coriolis force increasing and decrease the rotational energy. So, the moment of inertia varies with the angular momentum. Therefore, we modified this model by adding a term to make the moment of inertia vary with angular momentum in the same manner of the VMI model which has a term added to the rotational energy equation. The modified model fits remarkably with the experimental observation and other models in many cases with the use of few parameters especially in rotational nuclei regions similar to Hf and Dy nuclei.

Tapered Beam Fundamental Natural Frequency Based on Rayleigh Quotient

Different continuous variations in the inertia are considered in achieving cantilever tapered beams to match functional design and resistance requirements. In this investigation, the expressions of linear and cubic variations in the inertia are associated to a linear mass distribution. An exact solution of the fourth order differential equation, with none constant coefficients governing the studied tapered beam element equilibrium, is obtained for each case. These displacements functions are normalized and introduced in the well known Rayleigh quotient formula for calculating the fundamental natural frequency. The accuracy of the approach over the use of the above approximation has been validated by beam references results, produced quite interesting results in numerical comparisons. Also, two curves corresponding to fixed-free and free-fixed boundary conditions, for a graphical evaluation of the natural frequency are given. They consider various degrees of taper corresponding to the two inertia variations.