Torque Excitation Research Articles

Impact of Mounting Blocks on Drivability

Precedent papers have shown that motor-block (i.e., electric motor and speed reducer) rolling motion onto its mounting blocks has an important effect on the drivability rating. The drivability aspect is crucial for an electric vehicle because of the high torque gradient at low speeds or between regenerative and motor modes. Within the context of the new European emission standard, automotive engineers have to focus their research on fuel-efficient vehicles. Therefore, many car manufacturers are directed toward zero-emission vehicles as a solution, hence the development of the electric vehicle. To lead this vehicle project from the very early design steps, it is very important to assess and optimize customer perception during vehicle use. We also need to assess the difference between the vehicle response to driver request and that expected from the driver himself. This aspect of vehicle customer perception is called drivability and is evaluated by numerous maneuvers such as tip-in and back out of the accelerator pedal (tip-out) or acceleration from a rest position (takeoff). During tip-in, the torque gradient causes oscillations of the driveline and a jerk of the vehicle. Moreover, precedent works have shown that torque excitation causes a roll motion of the motor block (i.e., the electric motor and speed reducer) onto its mounting blocks and therefore shocks on the vehicle acceleration.

Dynamic Torque Analysis of a Wind Turbine Drive Train Including a Direct-Driven Permanent-Magnet Generator

Mechanical interactions between a wind turbine and a direct-driven permanent-magnet synchronous generator (PMSG) are studied, and a model to analyze the system behavior is suggested. The proposed model can be applied to analyze the mechanical vibrations of direct-driven wind turbine installations both in steady state and in dynamic cases. The cogging torque and torque ripple of the PMSG are used as excitation sources in the mechanical model. Four different permanent-magnet rotor constructions are analyzed. It is shown that the maximum allowable value of the cogging torque of the direct-driven permanent-magnet wind generator in this case is 1.5%-2% of the rated torque even when the corresponding resonance frequency does not occur in the operational speed range of the wind turbine. Furthermore, it was noticed that the resonance caused by the excitation torque should occur at the lowest possible speed.

Structure Noise Prediction of Submarine by Propeller Excitation

When boundary element (BE) was coarse, the general Gauss quadrature of Helmholtz integral equation (HIE) on it was not accurate. A mesh-less refined integral algorithm (RIA) of BEM was used to overcome this problem. Then RIA coupled with FEM/CFD was applied to predict submarine propeller excited hull underwater noise. The thrust and torque excitations of propeller simulated via CFD were loaded on to submarine respectively to calculate the acoustic response, and the sound power and main peak frequencies were obtained. Results show that, thrust mainly excites submarine axial mode and high sound area appears at the two conical-type ends, and torque mainly excites circumferential mode and high sound area appears at the broadside of cylindrical section, but with rather smaller sound power and radiation efficiency than the former. So, main attention should be focused on thrust excitation when perform the sound radiation reduction of submarine that propeller excited. Keywords: Submarine, Propeller excitation, Refined integral algorithm, Vibro-acoustic, CFD/FEM.

RESPONS GETARAN TORSIONAL POROS MODEL TURBIN ARUS LAUT SUMBU VERTIKAL AKIBAT EKSITASI MOMEN PUNTIR

Shaft Torsional Vibration Response of Vertical Axis Ocean Current Turbine Model Due to Torque Excitation. The current research aimed to study the torsional vibration response of Vertical Axis Ocean Current Turbine due torandomly torque excitation pattern, owing to the variety of ocean current velocity. The turbine model is composed of 3 aluminum blades of NACA 0018 connected to steel shaft. Turbine dimensions are 10 cm of chord, 1.8 cm of chamber and 100 cm of span. The variation of ocean current velocity is 0.5 m/s, 1.0 m/s, 1.5 m/s, 2.0 m/s, 2.5 m/s and 3.0 m/s. The Model has 2 degree of freedom which is described into two 2nd order differential equations. The eigenvalue solution yields the model’s natural frequencies; 201,38 rad/s and 457.91 rad/s. Fourier series is used to define the equation of torsional excitation, whilst the vibration equation is solved using Laplace Transform. According to analysis, there is no resonance occur. That because of the system’s natural frequencies is diverse to the magnitude of excitation frequencies. Model will be statically twisted first before vibrated. The response will be transient first then constantly steady. Furthermore, the bigger torque excitation will cause the bigger angular displacement as well the amplitude.

An alternative approach for chaos: A plane pendulum with oscillating torque

The shooting method is applied to obtain chaotic motions for a pendulum with a oscillatory torque excitation on its support. It shows that if the pendulum is placed at certain spots, the corresponding motion will become chaotic. It proves the coexistence of uncountably many non-periodic motions and countably many periodic motions of the pendulum.

Thermal effects on magnetization switching under radio frequency excitations

Magnetization thermal switching dynamics under radio frequency (rf) excitations are studied based upon optimal reversal path and logarithmic susceptibility concepts. We characterize thermal magnetization switching under both rf magnetic field and spin torque excitations. For rf magnetic field induced thermal switching, magnetization thermal stability barrier dependence upon rf frequency is compared to zero temperature magnetization dynamic coercivity dependence upon rf frequency. The maximum thermal reversal barrier reduction happens near linearized small angle magnetization resonant frequency, quite different from zero temperature coercivity frequency response. For magnetic elements excited by rf spin torque current, we study adiabatic and nonadiabatic spin torque effects on thermal stability barrier frequency dependence. For cylindrical symmetric case, nonadiabatic term does not affect thermal reversal barrier reduction to leading order. For thin film element without cylindrical symmetry, nonadiabatic term affects frequency response of normalized logarithmic susceptibility significantly only when its magnitude is comparable to that of the adiabatic spin torque term.

Three dimensional vibration generators with a single rotational input

This paper presents a novel device capable of generating three-dimensional vibrations with a single-axis of rotation. The device resembles a vibration motor with an eccentric weight, but the weight is allowed to move up and down in parallel to the axis of rotations. While spinning of the eccentric weight causes lateral vibrations, vertical vibrations are excited by superposing a periodic torque on the rotary shaft. The frequency and magnitude of vertical oscillations can be independently regulated. Since the vertical natural frequency is sensitive to rotational speeds, maximum vertical oscillations can be achieved by properly adjusting the rotational speed according to the excitation frequency. Relations between the excitation torque and the vertical shaking force are examined using the frequency response for the linearized system. Numerical simulations on the original nonlinear system are conducted to verify the performance of vertical oscillations.

Damping Torsional Interharmonic Effects of Large Drives

Current source thyristor converters are the most widespread technology for large drives, and today still a suitable choice for supplying high-power variable speed drives because of excellent reliability records. The integer and noninteger harmonics generated by line-commutated converters cause pulsating torque harmonics on the motor and on the grid side of the converter. Intersections of harmonic excitation frequencies with torsional natural frequencies of mechanical drive trains (motor-driven load or generator train) cannot always be avoided in the operating-speed range of the motor. Continuously generated harmonic torque excitations could have a critical impact on the torsional behavior of the entire train. It is therefore mandatory to perform torsional analyses during the design stage of large drives, as specified in API 617 [1] to avoid torsional interaction issues. In multiunit plants, more sophisticated analyses have to be performed, considering the fully coupled electrical and mechanical system. The risk for operational problems increases with increasing percentage of converter loads (converter power relative to the short circuit level of the grid). Some oil and gas production sites, e.g., offshore platforms, are based on island or island-like power systems. To mitigate the risk of torsional issues with increasing percentage of converter loads in weak power systems, new devices for damping torsional resonance modes have been developed and successfully tested. The effect of torsional mode damping will be explained by coupled electromechanical simulations and by measurement results from applying an integrated torsional mode damper (TMD) to a 30 MW gas compression train. The TMD does not require changes to the mechanical or electrical system design and can be designed as a retrofit control system extension for variable speed drives from different manufacturers.

Role of spectrally varying mount properties in influencing coupling between powertrain motions under torque excitation

The influence of spectrally varying mount properties (including stiffness and damping) on the dynamics of powertrain motions is analytically examined. To overcome the deficiency of the direct inversion method (limited to only the frequency domain analysis), two methods are developed that describe the mount elements via a transfer function (in Laplace domain) or analogous mechanical model. New analytical formulations are verified by comparing the frequency responses with numerical results obtained by the direct inversion method (based on Voigt type mount model). Eigensolutions and transient responses of a spectrally varying mounting system are also predicted from new models. Based on complex eigenstructure, new coupling indices, including modal kinetic energy fractions, are defined for each method. Complex eigenvalue problem formulation with spectrally varying properties provides a closer match with measured natural frequencies than the real eigensolution with frequency-independent mounts. Given spectral variance in the mount properties, a simple roll mode decoupling scheme is suggested for the powertrain isolation system. Finally, an axiom for torque roll axis decoupling is provided by employing direct and adjoint eigenvalue problems.

Dynamic analysis of gear pairs with a gross motion effect using the dynamic stiffness matrix method

A continuum approach using the dynamic stiffness matrix (DSM) method (DSMM) is presented for the dynamic analyses of spur gear pairs incorporating the gross motion effect. A continuum dynamic model of spur gears was formulated based on the dynamic stiffness using the non-uniform Timoshenko beam theory. A systematic DSM for a gear pair was assembled including the elemental DSMs of two mating gears and non-linear Hertzian contact stiffness. The DSMs were updated at each computing step to reflect the time-varying property due to the moving mesh points. A bisection procedure was used to calculate the natural frequencies as the systematic DSM of the gear pair became singular. The mass and stiffness matrices were calculated by taking a numerical derivative of the systematic DSM. Finally, the gear dynamic responses caused by the external torque and gross motion excitation resulted. The effect of gross motion is also discussed.

Current-driven, electrically detected ferromagnetic resonance in electrodeposited spin valves

We investigate the ferromagnetic resonance of Co/Cu/Co trilayers by use of AC-spin-transfer torque excitations. Magnetic structures are grown in a 6-μm-thick commercial nanoporous polycarbonate membranes by use of electrodeposition in a cobalt/copper single bath. We show that microwave magnetic excitations corresponding to the uniform mode of the two cobalt layers are electrically detected as a change of the DC voltage of the system.

Intermittent behaviour of a cracked rotor in the resonance region

Vibrations of the Jeffcott rotor are modelled by a three degree of freedom system including coupling between lateral and torsional modes. The crack in a rotating shaft of the rotor is introduced via time dependent stiffness with off-diagonal couplings. Applying the external torque to the system allows to observe the effect of crack “breathing” and gain insight into the system. It is manifested in the complex dynamic behaviour of the rotor in the region of internal resonance, showing a quasi-periodic motion or even non-periodic behaviour. In the present paper report, we show the system response to the external torque excitation using nonlinear analysis tools such as bifurcation diagram, phase portraits, Poincaré maps and wavelet power spectrum. In the region of resonance, we study intermittent motions based on laminar phases interrupted by a series nonlinear beats.

Four-quadrant instantaneous torque control of switched reluctance machine at low speed based on co-energy control

An instantaneous torque control scheme of switched reluctance machines for four-quadrant operation at low speed based on co-energy considerations is presented. The co-energy is estimated online with a co-energy estimator, which only requires easily obtainable parameters such as the machine terminal quantities and the machine characteristics at low current. By regulating the co-energy while tracking a one-dimensional co-energy profile, the torque contribution of each phase of the switched reluctance machine can be controlled and optimised. Thus, the requirement of pre-measured data is reduced when compared to current-profiling methods. The closed-loop control system is analysed and then designed based on internal model control. The excitation sequence and torque sharing function for four-quadrant operation to produce smooth torque output are also presented. The operation limits of the scheme are examined. Computer simulation and experimental results confirm that the proposed scheme can be exploited to reduce the high-frequency torque ripples significantly.

138 可変速電動機駆動回転機械のねじり振動の計測とシミュレーション

This paper introduces phenomena causing damaging torsional vibration of rotating machinery driven by Variable Speed Drive (VSD) Motor. Inter-harmonic frequencies contained in excitation torque generated by motor, because of its distinctive pattern, may coincide with natural frequencies of rotating machinery during operation even though the machinery was designed so that fundamental frequency and its harmonics can avoid coincidence with natural frequencies in the operating speed range. Torque of rotor shaft and output current of VSD were measured during product test. Quantitative guidelines for torque associated with sideband frequencies of VSD output current and modal damping ratio for VSD driven rotating machinery are proposed. Integrated mechanical (rotating machinery) and electrical (motor with VSD system) simulation was also conducted and its results were compared with measured data.

A mathematical model for lateral rotor dynamic analysis of soft mounted asynchronous machines

AbstractThis paper shows a mathematical model for lateral rotor dynamic analysis of soft mounted asynchronous machines with sleeve bearings, due to harmonic and transient excitation. The simplified analytical model combines the electromagnetic, the rotor dynamic, and the specific characteristic of sleeve bearings, considering foundation stiffness and damping. Based on the shown mathematical description, it is possible to calculate the complex eigenvalues and eigenvectors, which describe the natural vibrations, the limit of stability, the relative shaft displacements, the bearing house vibrations and the dynamic foundation forces, due to rotor excitations and air gap torque excitations. Based on the simplified plane analytical model a three‐dimensional finite element model is also derived. The aim of this paper is not to replace a finite element calculation, but to show the mathematical coherences between rotor dynamic, electromagnetic and sleeve bearing characteristic for soft mounted asynchronous machines, considering foundation stiffness and damping, based on a simplified mathematical model.

Effect of non-proportional damping on the torque roll axis decoupling of an engine mounting system

Several mounting system design concepts are conceptually used to decouple the engine roll mode though limited success has been observed in practice. One shortcoming of the existing theories or design methods is that they ignore non-proportional viscous damping in their formulations. It seems that the rigid-body vibrations are coupled whenever non-proportional damping is introduced to the mounting system even though the torque roll axis decoupling is still theoretically possible with proportional damping assumption. To overcome this deficiency, we re-formulate the problem for a non-proportionally damped linear system while recognizing that significant damping may be possible with passive (such as hydraulic) or adaptive mounts. The complex mode method is employed in our work and the torque roll axis decoupling paradigm is re-examined given mount rate ratios, mount locations and orientation angles as key design parameters. We derive a necessary axiom for a mode in the torque roll axis direction provided two eigenvalue problems, in terms of stiffness and damping matrices, are concurrently satisfied. Two numerical examples are chosen to examine both steady-state and transient responses and the extent of coupling or decoupling is quantified. Results show that the torque roll axis for a mounting system with non-proportional damping (under oscillating torque excitation) is indeed decoupled when one of the damped modes lies in the torque roll axis direction. Finally, eigensolutions are validated by using experimental data.

Quantification of clearance-induced impulsive sources in a torsional system

The impulse response problem in a multi-degree-of-freedom torsional system with multiple clearances is examined with focus on the quantification of the source. This system is related to a vehicle driveline and a map of external transient torque excitations is defined within the operating range of an internal combustion engine. Nonlinear transient solutions are found numerically for the entire excitation map. Proposed metrics include a global metric that indicates the number and nature of impacts, metrics measured just before impact, the relative kinetic energy and relative acceleration of impacting bodies and metrics measured just after impact, initial torque rise, initial velocity rise, peak to peak acceleration and time-windowed mean-square acceleration. Phase plane analysis is applied to explain the differences between the magnitudes of impulses for impact types, illustrating that the relative acceleration between impacting bodies and the relative kinetic energy determine the impact severity. Analysis shows that the metrics measured after impact correlate well. Nonetheless, using numerical or experimental data sets for systems with multiple clearances, it is demonstrated that the windowed mean-square acceleration metric permits an ‘energy’ calculation with multiple impact events that could be either isolated or combined. Chief contributions of this research include better quantification and an understanding of impulsive sources that arise during rapid changes in external torque excitations.

Impulsive response of an automatic transmission system with multiple clearances: Formulation, simulation and experiment

Impulsive responses in geared systems with multiple clearances are studied when the mean torque excitation and system load change abruptly, with application to a vehicle driveline with an automatic transmission. First, torsional lumped-mass models of the planetary and differential gear sets are formulated using matrix elements. The model is then reduced to address tractable nonlinear problems while successfully retaining the main modes of interest. Second, numerical simulations for the nonlinear model are performed for transient conditions and a typical driving situation that induces an impulsive behaviour simulated. However, initial conditions and excitation and load profiles have to be carefully defined before the model can be numerically solved. It is shown that the impacts within the planetary or differential gears may occur under combinations of engine, braking and vehicle load transients. Our analysis shows that the shaping of the engine transient by the torque converter before reaching the clearance locations is more critical. Third, a free vibration experiment is developed for an analogous driveline with multiple clearances and three experiments that excite different response regimes have been carried out. Good correlations validate the proposed methodology.

Effect of Eccentricity on a Clutch System Under a Harmonically Varying Normal Load

This paper describes a clutch model having eleven degrees of freedom and three types of nonlinearity introduced by dry friction, double-stage stiffness, and spline clearances. The Coulomb friction formulations and spline clearance functions are smoothed before they are applied to the nonlinear system. The calculation of the dynamic response of the clutch is done by the Runge Kutta method. The dynamic behavior of both a healthy clutch system and clutch system containing an eccentricity defect is compared in the time and frequency domains. The effects of a harmonically varying load on the dynamic response of the defective clutch system with nonlinear dry friction and under sinusoidal torque excitation are also reported.

Excitation of Knee Extensor Muscles During Maximal Isometric Contraction at Different Hip and Knee Angles

The quadriceps consists of monoarticular and biarticular muscles. Since changes in hip angle only influence the length of biarticular muscles, it can be expected that monoarticular muscle excitation is not influenced by hip angles. PURPOSE: To compare excitation of the monoarticular (vastus lateralis VL and vastus medialis VM) and biarticular (rectus femoris RF) knee extensor muscles during maximal isometric contraction at different hip and knee angles. METHODS: Nine subjects (4 male; 5 female; mean ± SD: age 23 ± 2.29 yrs, mass 64.2 ± 11.7 kg, height 1.69 ± 0.10 m) gave informed consent to participate in this study. Each subject performed a 3-s maximal isometric knee extension at 6 knee angles (90°, 100°, 110°, 120°, 130° and 140°, full knee extension = 180°) on an isovelocity dynamometer with a 1-min rest period between trials. The test was repeated at three hip positions: sitting (H1), inclined (H2) and lying (H3). Hip angles were measured using a goniometer during isometric contractions. Torque data were corrected for gravity effects and normalized to the peak value recorded in H1 (any knee angle). A surface electromyography (EMG) system was used to measure muscle excitation of the RF, VL and VM. Raw EMG data were full-wave rectified and then root mean squared (RMS) with a 0.5-s window. The highest RMS value averaged over a 1-s window was used for analysis. All EMG data were normalized to the RMS value at 90° knee angle in H1. Repeated measures ANOVA (hip × knee) was used to determine the effect of hip and knee angles on peak isometric torque and muscle excitation. RESULTS: The three hip angles were 109.6 ± 3.16° (H1), 138.6 ± 3.5° (H2) and 163.6 ± 3.28° (H3). Peak torques were higher in H2 than in H1 and H3 (P = 0.044). A quadratic torque-angle relationship was observed as knee angle changed (P < 0.0005) at all hip angles. Hip angle influenced VL excitation (P = 0.029, H1 > H2 > H3) but not RF or VM excitation. All knee extensor EMG decreased as knee angle increased (RF: P < 0.0005, VL: P = 0.001, VM: P = 0.002) and there were no differences in the pattern of response at different hip angles. CONCLUSION: Knee extensor EMG-angle relationship does not correspond well with the torque-angle relationship. The fact that changes in hip angle do not affect biarticular but monoarticular muscles excitation urges further research on neuromuscular control mechanism.