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With the rapid growth of the helical piling industry for oil and gas projects and transmission lines, reliable installation torque estimates and measurements become crucial. This paper presents a theoretical model developed to estimate the torsional resistance of cohesionless soils to helical pile installation. The theoretical torque model was verified using installation records collected from different sites. The paper also highlights factors that affect helical pile installation, including soil properties, fluctuation in groundwater levels, shape of pile shaft, pile geometry, and method of helical pile installation. The proposed torsional resistance model was then used to establish the traditional torque factors to proportionally correlate the axial capacity of helical pile and the installation torque. The results of the study indicated that the torque factor is a function of the load path (i.e., tension or compression). Therefore, torque factors in compression and tension, [K.sub.c] and [K.sub.t], respectively, were formulated and presented in the paper. Key words: helical piles, screw piles, torque, capacity, cohesionless, sand, compression, tension. Etant donne le developpement rapide du secteur de production des pieux helicoidaux, utilises dans les projets petroliers et gaziers et dans l'installation de canalisations de transport, il devient essentiel de realiser des estimations et mesures fiables du couple d'installation de ces pieux. Le present article presente un modele theorique concu pour permettre d'estimer la resistance de torsion de sols non cohesifs a l'installation de pieux helicoidaux. Le modele theorique de couple a ete verifie a l'aide de donnees d'installation collectees sur differents site. L'article souligne egalement les facteurs qui influent sur l'installation de pieux helicoidaux, en particulier les proprietes du sol, les variations du niveau de la nappe phreatique, la forme du fut du pieu, la geometrie du pieu et la methode d'installation du pieu helicoidal. Le modele de resistance de torsion propose a ete ensuite utilise pour etablir les facteurs de couple traditionnels qui relient proportionnellement la capacite axiale du pieu helicoidal au couple d'installation. Les resultats de l'etude ont montre que le facteur de couple est fonction de la voie de contrainte (c.-a-d. de tension ou de compression). Ainsi, les facteurs de couple en compression et en tension, [K.sub.c] et [K.sub.t], respectivement, et leur equation sont presentes dans le present article. [Traduit par la Redaction] Mots-cles: pieux helicoidaux, pieux visses, couple, capacite, non cohesif, sable, compression, tension., Introduction The installation of an [alpha]-helical pile is typically accomplished in the field by applying torque to the pile shaft using a rotary motor connected to the pile head. A [...]

This technical note presents explicit formulas for calculating the response moments of stochastic systems by polynomial dimensional decomposition entailing independent random input with arbitrary probability measures. The numerical results indicate that the formulas provide accurate, convergent, and computationally efficient estimates of the second-moment properties. DOI: 10.1061/(ASCE)EM. 1943-7889.0000117 CE Database subject headings: Stochastic processes; Polynomials; Decomposition; Statistics. Author keywords: Stochastic mechanics; Orthogonal polynomials; Analysis of variance; High-dimensional model representation.

The paper investigates the design of continuous steel-concrete composite beams with compact cross section using the elastic analysis with limited redistribution. The permissible moment redistribution which satisfies the requirements of the ultimate limit state (collapse) and serviceability limit state (crack width in the concrete slab) was computed. An advanced finite element program accounting for all mechanical nonlinearities and time-dependent phenomena (creep and shrinkage of concrete) was used. An extensive parametric analysis aimed to determine the influence of several geometrical parameters on the permissible moment redistribution was carried out on propped cantilevers and fixed-end beams. The analyzed parameters include the shape of the steel profile, the ratio between the depths of concrete slab and steel beam, the steel to concrete area ratio, and the reinforcement percentage of the concrete slab. The analysis was limited to compact steel sections (AISC 360-05) or class 1 steel sections (Eurocode 3) and low ductility reinforcing steel (elongation at maximum load [[epsilon].sub.ru]=2.5%). The moment redistribution domain which satisfies the rotation compatibility in the critical sections, due to the attainment of the rupture of the reinforcement or the local buckling of the steel profile, and the control of cracking ( DOI: 10.1061/(ASCE)ST.1943-541X.0000098 CE Database subject headings: Composite beams; Concrete; Steel; Continuous beams; Bending; Nonlinear analysis; Finite element method; Moment distribution; Cross sections. Author keywords: Composite beams; Concrete; Steel; Continuous beams; Bending moments; Nonlinear analysis; Finite-element method.

Almost half a century ago, it was predicted that the confinement of quantum fluctuations could induce mechanical rotation -- the Casimir torque. This prediction has now been confirmed using liquid crystals. Experimental evidence for the Casimir torque., Author(s): Slobodan Zumer Author Affiliations: Elusive torque sensed by liquid crystals Quantum physics tells us that empty space is filled with fluctuating electromagnetic fields. If two metal plates are positioned [...]

An important part of some packaging cartons is the crash-lock base. A recent investigation of the torque required for its erection has made some linearizing assumptions. It is here shown that these can be avoided as the relations connecting the angles between panels can be found. This also indicates that the final increase in the required torque is due to geometric effects rather than frictional ones. [DOI: l0.1115/1.3151800]

Flexibility is widely accepted as an important component of fitness, yet flexibility training can be detrimental to muscle performance particularly where a high number of stretch cycles are performed. The purpose of this study was to investigate whether chronic proprioceptive neuromuscular facilitation (PNF) stretch training could successfully improve the knee flexion range of motion without having a detrimental effect on the peak isokinetic torque of the quadriceps. The minimum knee angle in flexion and the peak isokinetic quadriceps torque were measured at 120 and 270[degrees] x [s.sup.-1]. Subjects then participated in a 4-week quadriceps flexibility training program consisting of 3 cycles of PNF stretching performed 3 times a week. The range of motion was recorded before and after the first stretching session of each week. At the end of the 4-week period, the peak isokinetic quadriceps torque and flexibility were again measured. The mean (SE) improvement in the knee flexion range of motion over the whole program was 9.2[degrees] (1.45[degrees]), and typical gains after a single stretching session were around 3[degrees]. Post hoc analysis showed that the pretraining session range of motion was significantly improved in week 4 compared with the pretraining session range of motion in weeks 1 and 2 (p < 0.05). There was no change (p = 0.9635) in the peak isokinetic torque produced at 120[degrees] x [s.sup.-1] (week 1: 121.9 (4.6) N x m; week 2: 121.9 (5.2) N x m) or at 270[degrees] x [s.sup.-1] (week 1: 88.1 (3.4) N x m; week 2: 88.6 (4.9) N x m). These findings suggest that it is possible to improve flexibility using 3 PNF stretch cycles performed 3 times a week without altering muscle isokinetic strength characteristics. KEY WORDS PNF, quadriceps, chronic

It is not well understood how posture (nonfocal joints) is stabilized during rapid joint movements. Interaction torque arising at the joints due to the movement of the adjacent joints will disturb the nonfocal joint unless it is compensated by muscle torque. The aim of this study was to clarify the mechanism underlying the incomplete stabilization of nonfocal posture during two types of fast single-joint flexion tasks, i.e., elbow flexion and shoulder flexion, with and without a hand-held weight. Participants were 5 men and 4 women (M age = 22.2 yr., SD = 4.8). The relationship between interaction torque and muscle torque and between angular displacement and torque components of the nonfocal joints were examined. The anticipatory muscle activity at the nonfocal joint produced compensatory muscle torque during the early phase of the rapid movement. However, nonfocal joints displayed a consistent displacement pattern, i.e., an initial extension followed by a flexion during the movement. The initial extension was in the direction of the interaction torque and its magnitude was related to the onset delay of the muscle torque against the interaction torque. The flexion movement of the nonfocal joints during the task was in the direction of the overcompensating muscle torque against interaction torque. This mechanism may have certain implications for anticipatory postural adjustment problems.

Assessment of multiple volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service rules, such as ASME, BS, and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple cracklike flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two differently sized nonaligned volumetric flaws such as local thin areas is clarified by applying the body force method. Unlike multiple cracklike flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction that indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) diagram, which is a simple assessment procedure for vessels with volumetric flaws. [DOI: 10.1115/1.3110036] Keywords: fitness for service (FFS) rule, plastic collapse, volumetric flaws, alignment rule, p-M (pressure-moment) diagram

A wireless drive and control method using rotational magnetic field on a capsule micro robot is proposed, and both outer and inner actuators are Nd-Fe-B magnet cylinders with multiple magnetic poles in tegular shape alternating with dissimilar radial magnetization, through magnetic coupling with rotational magnetic field generated by the rotating outer actuator, the capsule robot is rotated by an embedded inner actuator, and axial thrust is generated by fluid dynamic pressure distributing on outer surface of the robot with spiral blade, thus the screw motion of the micro robot in intestine is realized. Mathematical model on magnetic torque is established based on equivalent magnetic charge method, and the characteristics of magnetic torque with respect to structural parameters of actuators and swimming effect of the robot are studied theoretically and experimentally. Index Terms--Capsule micro robot, equivalent magnetic charge method, magnetic torque, spiral drive.

This paper presents a 3-D optimal design, regarding both magnetic and thermal characteristics, for a three-phase induction motor used in a high-pressure scroll compressor. In the scroll compressor, the three-phase induction motor does play an important role of causing dynamic force, but generates high heat, which exerts negative influences on both lifetime and performance. Thus, it is necessary to design the scroll compressor considering two physical disciplines in order to improve the performance while protecting against overheating. A 3-D topology approach using a multiobjective function yields optimal design with higher torque and more efficient heat transfer. Index Terms--Induction motor, 3-D optimal design, topology approach.

This paper addresses the torque production and losses of concentrated winding permanent magnet motors. These synchronous motors having either semi-closed slots or open slots with two different rotor structures are studied. The rotors have either embedded magnets or surface magnets. Embedded magnet rotors are in some cases easier to manufacture than surface magnet rotors, and therefore, it was in the authors' interest to study and compare these two basic constructions. In open slot concentrated winding motors, it is possible to use prefabricated coils, which leads to low-cost and fast stator winding manufacturing. Hence, this stator type is the most interesting one to be studied. Different slot and pole combinations are considered based on the finite element analysis (Flux2D by Cedrat is employed in the computations). Index Terms--Concentrated winding, embedded magnets, open slots, permanent magnet motor, rotor surface magnets, semi-closed slots.

In this work, the classic theory of Timoshenko beams is revisited using screw theory. The theory of screws is familiar from robotics and the theory of mechanisms. A key feature of the screw theory is that translations and rotations are treated on an equal footing and here this means that bending, torsion, and extensions can all be considered together in a particularly simple manner. By combining forces and torques into a six-dimensional vector called a wrench, Hooke's law for the Timoshenko beam can be written in a very simple form. From here simple expressions can be found for the kinetic and potential energy densities of the beam. Hence equations of motion for small vibrations of the beam can be easily derived. The screw theory also leads to a new understanding of the boundary conditions for beams. It is demonstrated that simple boundary conditions are closely related to mechanical joints. In order to set up the boundary conditions for a beam attached to a joint, a system of wrenches dual to the screws representing the freedoms of the joint must be found. Finally, a screw version of the Rayleigh-Ritz numerical method is introduced. An example is investigated in which the boundary conditions on the beam lead to vibrational modes of the beam involving bending, torsion, and extension at the same time. [DOI: 10.1115/1.3063630]

We discuss the controversy about the demonstration of the law of the lever as given by Archimedes. One aspect of the discussion concentrates on the meaning of the postulates which he utilized. We analyze what consequences would arise if nature behaved in such a way that the lever followed a generalized power law. In particular, we consider the cases of a torque independent of the distances of the bodies to the fulcrum, proportional to these distances, and quadratic in the distances. [DOI: 10.1119/1.2978002]

Powered hand tools have the potential to produce reaction forces that may be associated with upper extremity musculoskeletal disorders. In this study, subjective ratings of discomfort and acceptability of reaction forces were collected in an attempt to identify their associations with factors such as work location, and response covariates such as grip force and tool handle displacement. Three work configurations using pistol grip and right angle pneumatic nutrunners on horizontal and vertical surfaces were set up in the laboratory. Twenty healthy right-handed male participants operated four tools at nine locations and the corresponding subjective responses were collected. The results indicate that normalized grip force during the torque buildup period was a significant factor for both subjective ratings. For the unacceptable torque reactions across the three tool configurations, the ratio of hand moment impulse over tool torque impulse was significantly greater than for the acceptable reactions. For pistol grip tools used on the vertical surface, as the working height increased 30 cm, the odds of an unacceptable rating over an acceptable rating increased 1.6 times. Prediction models for subjective ratings of discomfort and acceptability provide insight regarding either workstation design or exposure control. These models can further be used to establish exposure limits based on handle displacement and grip force. Keywords: Power tools; Exposure assessment; Predictive models

Optical traps have been used in a multitude of applications requiring the sensing and application of forces. However, optical traps also have the ability to accurately apply and sense torques. Birefringent particles experience a torque when trapped in elliptically polarized light. By measuring the frequency content of the exiting beam, the rotational rates can be set up in a feedback loop and actively controlled. Here we describe an optical trap with feedback torque control to maintain constant rotational rates despite the introduction of an increased drag on the particle. As a result, this research has the potential to advance the understanding of rotary motor proteins such as F1 ATPase. OCIS codes: 120.4640, 140.7010, 350.4855.

The axial angular momentum (AAM) budget of zonal atmospheric annuli extending from the surface to a given height and over meridional belts is discussed within the framework of conventional and transformed Eulerian mean (TEM) theory. Conventionally, it is only fluxes of AAM through the boundaries and/or torques at the surface that are able to change the AAM of an annulus. TEM theory introduces new torques in the budget related to the vertically integrated Eliassen--Palm flux divergence and also new AAM fluxes of the residual difference circulation. Some of these torques are displayed for various annuli. In particular, the application of TEM theory generates a large positive torque at tropospheric upper boundaries in the global case. This torque is much larger than the global mountain and friction torques but is cancelled exactly by the new vertical AAM fluxes through the upper boundary. It is concluded that the TEM approach complicates the analysis of AAM budgets but does not provide additional insight. Isentropic pressure torques are believed to be similar to the TEM torques at the upper boundary of an annulus. The isentropic pressure torques are evaluated from data and found to differ in several respects from the TEM torques.

The growing interest in a thorough revision of the tenets of classical electrodynamics [1,2] compels us to reconsider the torque-production mechanism presently applied to homopolar machines founded--indistinctively--on Ampere or Grassmann's [...]

A novel structure for sensorless induction motor drive is proposed based on flux vector acceleration torque control. The proposed structure combines direct torque control with speed estimation based on slip frequency evaluation. A stable drive operation is enabled in a wide range of operating speeds, including at standstill. Index Terms--Direct torque control (DTC), induction motor (IM), sensorless drive, speed estimation.

Cogging torque is a source of vibration and noise in permanent-magnet (PM) machines. This torque is proportional to the PM flux and the reluctance variation, and is independent of the load current. In this paper, two methods for cogging torque reduction in an axial PM machine with field weakening capability are presented. The machine's rotor configuration considers two sections: one PM pole that provides the field excitation and one iron section in charge of providing low d-axis reluctance. Significant reduction of the cogging effects is achieved by adjusting stator geometry and rotor pole configuration. Three-dimensional finite-element analysis is used to demonstrate these improvements. Conclusions and design recommendations are presented for a 5-kW eight-pole PM machine prototype under construction. Index Terms--Axial flux permanent-magnet (AFPM) machine, cogging torque reduction, three-dimensional finite-element analysis (3D-FEA).

Bacteria swim by rotating long thin helical filaments, each driven at its base by a reversible rotary motor. When the motors of peritrichous cells turn counterclockwise (CCW), their filaments form bundles that drive the cells forward. We imaged fluorescently labeled cells of Escherichia coli with a high-speed charge-coupled-device camera (500 frames/s) and measured swimming speeds, rotation rates of cell bodies, and rotation rates of flagellar bundles. Using cells stuck to glass, we studied individual filaments, stopping their rotation by exposing the cells to high-intensity light. From these measurements we calculated approximate values for bundle torque and thrust and body torque and drag, and we estimated the filament stiffness. For both immobilized and swimming cells, the motor torque, as estimated using resistive force theory, was significantly lower than the motor torque reported previously. Also, a bundle of several flagella produced little more torque than a single flagellum produced. Motors driving individual filaments frequently changed directions of rotation. Usually, but not always, this led to a change in the handedness of the filament, which went through a sequence of polymorphic transformations, from normal to semicoiled to curly 1 and then, when the motor again spun CCW, back to normal. Motor reversals were necessary, although not always sufficient, to cause changes in filament chirality. Polymorphic transformations among helices having the same handedness occurred without changes in the sign of the applied torque.

We investigated the uniaxial magnetic anisotropy of perpendicular magnetic film formed on various intermediate layers (IMLs) using torque magnetometry. We carefully analyzed the shapes of the torque curves so that we could separate the magnitudes of the quadratic ([K.sub.u1]) and quartic ([K.sub.u2]) anisotropy energy terms. However, it turned out that the [K.sub.u] values contained inevitable errors caused by the dispersion of magnetic anisotropy when they were estimated at a finite measurement magnetic field ([H.sub.ext]), and that the true [K.sub.u2] terms were close to zero among all of our samples. Then, we utilized the [H.sub.ext] dependence of the apparent [K.sub.u] values for the analysis of magnetic anisotropy dispersion of perpendicular media. Through a systematic study on various IMLs, it was directly proven that the magnetic dispersion of the CoCrPt-Si[O.sub.2] storage layer arose not only from the addition of oxide into the storage layer but also from the crystal growth on ill-suited IMLs. We further demonstrated that a Pt-Cr/Ru-laminated IML successfully avoided magnetic dispersion, which led to excellent recording performance with less total spacing between the storage layer and the soft-magnetic underlayer. Index Terms--CoCrPt alloy, magnetic anisotropy, magnetic dispersion, perpendicular recording, torque magnetometry.

In this paper, distribution of required forces and moments to the supporting legs of a six-legged robot is handled as a torque-distribution problem. This approach is comparatively contrasted to the conventional approach of tip-point force distribution. The formulation of dynamics is performed by using the joint torques as the primary variables. The sum of the squares of the joint torques on the supporting legs is considered to be proportional to the dissipated power. The objective function is constructed as this sum, and the problem is formulated as to minimize this quadratic objective function with respect to linear equality and inequality constraints. It is demonstrated that the torque-distribution scheme results in a much more efficient distribution compared with the conventional scheme of force distribution. In contrast to the force distribution, the torque-distribution scheme makes good use of interaction forces and friction in order to minimize the required joint torques. Index Terms--Force distribution, legged locomotion, robot dynamics, six

This paper presents a novel low-speed and high-torque motor, self-commutating low-speed reluctance motor (SCLRM), for direct-drive applications. With six diodes connected to the stator windings, it is capable of self-commutating when working on normal three-phase ac source for constant-speed operation. It provides an uncomplicated and low-cost method to increase the torque capability of the traditional vernier-type motors without the requirement of permanent magnets and inverter drive. In this paper, the basic theory of SCLRM is presented, including the operation principle and the mathematical models from which the calculation equations of the inductance parameters as well as the electromagnetic torque are deduced. Besides, the simulation and implemental results are shown, and the reasons of the improvement of the torque capability are analyzed. Moreover, an inverter drive system for SCLRM whose topology is different from that of the standard three-phase inverter is proposed for variable-speed applications. Index Terms--Direct drive, high torque, low speed, reluctance motor, self-commutating.

High torque pulsation is a major disadvantage of most interior permanent-magnet (IPM) motor configurations. Choosing the proper number of stator slots and winding distribution as well as increasing number of phases are among the possible solutions for reducing torque pulsation. In this paper, five-phase IPM motor with fractional-slot stator is studied. It is shown that despite other IPM motors, the new five-phase IPM motor with fractional slot has a very low torque pulsation. For comparison purposes, a five-phase IPM motor with common configuration is also considered. It is shown that the torque pulsation of the proposed fractional-slot five-phase IPM motor is much lower than the conventional five-phase IPM motor. Nonlinear finite-element method is used to analyze different machine configurations. A prototype four-pole five-phase IPM motor with 15 stator slots has been built and is used for experimental verification. Index Terms--Cogging torque, finite-element analysis, five-phase interior permanent-magnet (IPM) motor, torque pulsation.

This paper proposes a strategy to minimize the losses of an induction motor propelling an electric vehicle (EV). The proposed control strategy, which is based on a direct flux and torque control scheme, utilizes the stator flux as a control variable, and the flux level is selected in accordance with the torque demand of the EV to achieve the efficiency-optimized drive performance. Moreover, among EV's motor electric propulsion features, the energy efficiency is a basic characteristic that is influenced by vehicle dynamics and system architecture. For this reason, the EV dynamics are taken into account. Simulation tests have been carried out on a 1.1-kW EV induction motor drive to evaluate the consistency and the performance of the proposed control approach. Index Terms--Direct torque control (DTC), electric vehicle (EV), induction motor, loss minimization.

Optimal time trajectories, based on the Pontryagin's maximum principle, are deduced for a squirrel-cage induction motor with constant load torque. These trajectories are valid for acceleration and deceleration with or without the load torque and for a loaded or unloaded motor, and ensure the minimal time transients with the stator current limited to the previously fixed value. Moreover, the optimal trajectories place the motor at the end of the transient at the minimum current point, which is close to the one of maximum efficiency, thus combining the brevity of the transients with the saving of energy. An optimal-time control system that implements these trajectories is designed. The results of the simulation of the proposed control system and the results of the experiments on a real drive are presented. Index Terms--Constant load torque, energy saving, maximum principle, optimal control, squirrel-cage motors.

The purpose of the present study was to clarify the effect of static stretching on muscular performance during concentric isotonic (dynamic constant external resistance [DCER]) muscle actions under various loads. Concentric DCER leg extension power outputs were assessed in 12 healthy male subjects after 2 types of pretreatment. The pretreatments included (a) static stretching treatment performing 6 types of static stretching on leg extensors (4 sets of 30 seconds each with 20-second rest periods; total duration 20 minutes) and (b) nonstretching treatment by resting for 20 minutes in a sitting position. Loads during assessment of the power output were set to 5, 30, and 60% of the maximum voluntary contractile (MVC) torque with isometric leg extension in each subject. The peak power output following the static stretching treatment was significantly (p < 0.05) lower than that following the nonstretching treatment under each load (5% MVC, 418.0 [+ or -] 82.2 W vs. 466.2 [+ or -] 89.5 W; 30% MVC, 506.4 [+ or -] 82.8 W vs. 536.4 [+ or -] 97.0 W; 60% MVC, 478.6 [+ or -] 77.5 W vs. 523.8 [+ or -] 97.8 W). The present study demonstrated that relatively extensive static stretching significantly reduces power output with concentric DCER muscle actions under various loads. Common power activities are carried out by DCER muscle actions under various loads. Therefore, the result of the present study suggests that relatively extensive static stretching decreases power performance. KEY WORDS. stretch, warm-up, performance, torque, velocity, rate of torque development

The ability to accurately predict the aerodynamic torque and lift and drag forces on a 2-D model of a 0.18 aspect ratio biconvex circular-arc disk operating in a compressible flow using computational fluid dynamics (CFD) was investigated. Fluent 6.0 was the CFD package utilized to perform these calculations. Grid-convergence and time-convergence/stability were analyzed first, followed by a qualitative study of the Spalart-Allmaras, k-[epsilon], and k-[omega] turbulence models with their enhancement features and model variants. Fluent was used to predict the pressure profile on the disk surface for disk positions 30, 45, and 60 deg (where 0 deg is the fully closed position) and over a range of pressure ratios. The pressure ratios were selected to determine the capability of CFD to accurately predict the flow field and resulting torque in flows ranging from nearly incompressible to highly compressible. Fluent predictions for the pressure profiles on the disk were compared to test data so that the lift and drag forces and aerodynamic torque could be determined responsibly. Acceptable comparisons were noted. [DOI: 10. l 115/1.2236129] Keywords: butterfly valve, compressible flow, aerodynamic torque, bearing force, CFD

This paper describes an integrated starter generator (ISG) for automobile applications with 42-V powernet. This system is based on an induction machine which is directly mounted on the engine crankshaft and controlled using the technique of direct torque control (DTC). The suitability of the technique for ISG application is explained. The control structure of DTC for ISG application is described. Detailed experimental results from a 1.4-1 diesel engine are presented demonstrating the performance of the system during cranking as well as generation. The ISG also incorporates the feature of 'on the fly start' during generation mode. Details of a low voltage high current power converter developed for this application are also given. Index Terms--Crankshaft mounted integrated starter generator (ISG), direct torque control (DTC) technique, induction machine, 'on the fly start' (OTFS) mode, 42-V PowerNet.

Permanent magnet-assisted reluctance synchronous machine (PM--RSM) starter alternator systems are credited with good performance for wide speed range in hybrid electric vehicles. This paper proposes a motion-sensorless motor/generator control of PM--RSM from zero speed up to maximum speed, using direct torque and flux control with space vector modulation. A quasioptimal stator flux reference with a flux versus torque functional is proposed. A stator flux observer in wide speed range uses combined voltage-current models for low speeds, and only the voltage model for medium to high speeds, both in proportional-integral closed loop. A novel rotor speed and position observer with a fusion strategy employs signal injection and only one D-module vector filter in stator reference--for low speed, combined with a speed observer from the stator flux vector estimation--for medium-high speed. The proposed system is introduced piece by piece and then implemented on a dSpace 1103 control board with a 350-A metal-oxide-semiconductor field-effect transistor-pulse-width modulation converter connected to a 42-Vdc, 55-Ah battery, and a 140-Nm peak torque PM-RSM. Extensive experimental results from very low speed to high speed, regarding observers and drive responses, including artificial loading (motoring and generating), seem very encouraging for future starter-alternator systems. Index Terms--Direct torque and flux control (DTFC), hybrid electric vehicles (HEV), integrated starter-alternators (ISA), permanent magnet-assisted reluctance synchronous motor (PM-RSM), sensorless control.

For the reduction of the cogging torque of permanent-magnet synchronous machines several approaches are known. But cogging torque predictions for arbitrary types of machines using the same approach are still troublesome and imprecise. Therefore, a fast optimization process is developed and presented in this paper. Here, the combination of both numerical and analytical simulation results in such a fast method. Index Terms--Cogging torque, notches in teeth, optimization, permanent-magnet synchronous-machine, two-dimensional (2-D) finite elemenet method (FEM).

This work analyzes the use of conforming and nonconforming movement techniques for torque calculation with high-order hierarchic interpolation in electrical machines thin air gaps. For the nonconforming movement formulation, the Lagrange multipliers are used. The moving band is used for the conforming case. The behavior of torque results as a function of interpolation order and air-gap thickness is discussed. In order to compare formulations, results for two thin air-gap machines are shown. Index Terms--Hierarchic elements, Lagrange multipliers, movement, torque.

The flat-type vibration motor has an axial-gap structure. Analyzing axial-gap motors with the two-dimensional (2-D) finite-element method is very difficult because we have to define the analysis surface as a cylindrical surface. In order to simulate the flat-type vibration motor, we have developed new equations of calculation for the torque of the motor, which is uses a 2-D grid model. We have measured the load torque of the vibration motor which is used for the motion transient analysis. The simulated vibration characteristic is compared with experimental value. Index Terms--Axial gap, finite-element method (FEM), grid, mobile phone, motion transient, vibration motor.

Introduction During the intervening 15 years since the first publication of this paper, (1) a great many things have changed in the space business. Of the original introduction that follows, […]

Inexpensive experimental techniques now exist for indirectly measuring forces within the moving human body. These techniques involve nontrivial applications of basic physical principles, have practical uses, and are appropriate for undergraduate experimentation. A two-dimensional video motion analysis is used to find the accelerations of various parts of the body, and anatomical geometry is used to determine specific biomechanical forces and torques. The simple movement of a dancer landing from a vertical jump is analyzed through the use of a theoretical model of the leg to find the forces in the tendons attached to the knee. It is shown that these forces can be sufficiently large to lead to injury if jumps are performed repetitively. [DOI: 10.1119/1.2149868]

A direct torque control (DTC) strategy for dual three-phase induction motor drives is discussed in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The DTC strategy is based on a predictive algorithm and is implemented in a synchronous reference frame aligned with the machine stator flux vector. The advantages of the discussed control strategy are constant inverter switching frequency, good transient and steady-state performance, and low distortion of machine currents with respect to direct self-control (DSC) and other DTC schemes with variable switching frequency. Experimental results are presented for a 10-kW DTC dual three-phase induction motor drive prototype. Index Terms--Deadbeat algorithm, digital control, direct torque control, dual three-phase induction machine, multiphase drives.

A Reynolds-averaged Navier-Stokes computational model of homogeneous multiphase flow is presented. Cavitation driven thrust and torque breakdown over a wide range of advance ratios is modeled for an open propeller. Computational results are presented as a form of validation against water tunnel measured thrust and torque breakdown for the propeller. Successful validation of the computational model is achieved. Additional observations are made with regards to cavity size and shape as well as cavitation breakdown behavior. [DOI: 10.1115/1.1988343]

In this paper, direct torque control (DTC) algorithms for a split-phase induction machine (SPIM) are established. An SPIM has two sets of three-phase stator windings, with a shift of thirty electrical degrees between them. The significant contributions of this paper are: 1) two new methods of DTC technique for an SPIM are developed, called Resultant Flux Control Method and Individual Flux Control Method and 2) advantages and disadvantages of both methods are discussed. High torque ripple is a disadvantage for three-phase DTC. It is found that torque ripple in an SPIM can be significantly reduced without increasing the switching frequency. Index Terms--Direct torque control (DTC), individual flux control method, resultant flux control method, split-phase induction machine (SPIM).

This paper presents the development of a four-quadrant switched reluctance machine (SRM) drive for high dynamic applications. Comprehensive fundamentals and analysis for operating switched reluctance machines in four quadrants are presented. The drive is designed based on a high dynamic control strategy called Direct Instantaneous Torque Control (DITC). The functionality of DITC is discussed in detail for both motoring and generating operation. A methodology to generate switching functions directly by the hysteresis torque controllers for SRMs is proposed. The proposed controller was prototyped and tested on a digital signal processor/field-programmable gate array development platform. High dynamic operation in both motoring and generating mode and the transition between these modes are validated by experimental results presented at the end of this paper. Index Terms--Four quadrant, switched reluctance machine (SRM), torque controller.

For the calculation of torque in brushless (BL) alternating current motors a local method is proposed, based on the Maxwell stress theory and the filtered contributions due to the harmonics of the magnetic vector potential in the motor air gap. By considering the space fundamental field only, the method can efficiently estimate the average synchronous torque for a variety or motor topologies, including concentrated winding designs. For BL direct current motor analysis a global method is introduced, based on the virtual work principle expressed in terms of energy components in various motor regions. The method leads to simplifications in the average torque calculation and enables the direct identification of the cogging and ripple components. The mathematical procedures have been validated against experiments and other numerical techniques. Index Terms--Brushless (BL) permanent-magnet (PM) motor, cogging torque, electric machine simulation, finite-element analysis (FEA), ripple torque, synchronous machine.

Input torque balancing through addition of an auxiliary, input torque balancing mechanism, is a well-known way for reducing drive speed fluctuations in high-speed camfollower mechanisms. This paper develops a methodology to design and optimize the so-called inverted cam mechanism (ICM), a simple, cam-based input torque balancing mechanism. It was already introduced in the 1950s, but the design methodologies proposed by Meyer zur Capellen (1964) and Michelin (1979) are, respectively, erroneous or too rough an approximation, and are corrected here. The describing equation that governs the ICM cam design, is shown to be a second-order, nonlinear, ordinary differential equation. It is solved by parameterizing its solution as a finite Fourier series, the coefficients of which are determined through a nonlinear least-squares problem. Based on this methodology, an ICM is designed for input torque balancing a high-speed, industrial cam-follower mechanism. The ICM's design parameters result from a design optimization, which aims at obtaining a compact and technologically feasible mechanism. The optimization problem is solved using a design chart, which is efficiently created based on a nondimensionalized analysis. [DOI: 10.1115/1.1876452]

High power density applications require special treatment in design optimization. Among the critical questions is how the working torque angle will change through an optimization analysis. We present a new method for computing and using the synchronous reactance that accounts for the torque angle in the midst of complex parameter changes. The challenge is to tally this effect along with the load power factor into a variable metric optimization. Our new technique both computes this reactance under heavy saturation and integrates it into the machine design. The technique also covers appropriate stator current excitation densities in transient and steady-state excitation. Index Terms--Deterministic, optimization, reactance, superconducting, synchronous.

This paper presents a novel current regulation algorithm for permanent-magnet ac (PMAC) machines that provides maximum torque-per-ampere capability in the entire field-weakened region. The algorithm provides robust current regulation with maximum efficiency and torque capability for PMAC machines despite significant changes in the voltage source and machine parameters. The algorithm identifies when the current regulator starts to saturate and determines the optimum d-axis current command for the machine. The q-axis current command is determined from the torque command and d-axis current feedback. When the voltage angle reaches the maximum angle, the current magnitude is decreased to provide maximum torque per ampere. Experimental results from a machine prototype show that the algorithm provides good overall dynamic response and smooth transitions into the field-weakened region with maximum torque-per-ampere capability in all four quadrants of operation. Index Terms--Field-weakened operation, permanent-magnet ac (PMAC) machine control, vector control.

The sixth-order torque ripple harmonic in induction motors under field-oriented control with voltage space phasor modulation is investigated by means of a simulation model. It is shown that the main reason for its appearance lies in the pulsewidth modulation. Measurements on a 220-kW asynchronous drive confirm the simulation results. A compensation strategy is proposed. Index Terms--Field-oriented control, induction motor, pulsewidth-modulation (PWM) converter, sixth harmonic, space phasor modulation, torque ripple.

Several high-performance motor drive applications require the motor drive to produce smooth torque with very stringent torque-ripple requirement. This paper is focused on various machine design considerations that can be used in reducing the torque ripple of a sinusoidally excited permanent-magnet brushless dc motor. The paper quantifies the various sources of torque ripple, which may be minimized by appropriate design considerations. The paper discusses the factors influencing the harmonic content of the induced voltage, effect of slot/pole combination, winding distribution, and magnetic saturation. Design optimization is directed to minimize cogging torque and the harmonic contents in the back electromotive force, thus reducing the overall torque ripple. Comprehensive finite-element (FE) analysis along with experimental data are provided to validate the theory. The research demonstrates that saturation in the magnetic circuit is another major contributor to the torque ripple and torque nonlinearity as the current increases. A model is developed to study the saturation effect on torque linearity and is verified by FE simulation. Design techniques have been provided to minimize the overall torque ripple and increase the torque linearity. Index Terms--Machine design, permanent-magnet machines, torque linearity, torque ripple.

Traction-drive speed reducers offer certain advantages over geared speed reducers. In particular, they generally run quieter than geared units and provide an opportunity for higher efficiency by eliminating sliding motion between contacting elements. In order to generate a sufficiently high output torque, some means must be provided to create a normal force between the rolling elements. This normal force, along with the friction coefficient, enables the device to transmit torque from one rolling member to the next. The speed reducer proposed here is designed so that the configuration of the rolling elements creates the needed normal force in response to the torque exerted back on the system by the downstream loading. Thus the device is self-actuating. Since the normal force is only present when needed, the rolling elements of the device can readily be disengaged, thus eliminating the need for a separate clutch in the drive system. This feature can be exploited to design a transmission with several distinct speed ratios that can be engaged and disengaged in response to changing speed requirements. [DOI: 10.1115/I. 1897410]