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The article explains the development of a new longitudinal-torsional hybrid-type ultrasonic motor, which is shown to exhibit large torque and low revolution speed. The motor is shown to be small, light and noiseless with a hollow and short cylindrical structure.

The bacterial flagellar motor drives the rotation of flagellar filaments and enables many species of bacteria to swim. Torque is generated by interaction of stator units, anchored to the peptidoglycan cell wall, with the rotor. Recent experiments [Yuan J, Berg HC (2008) Proc Natl Acad Sci USA 105:1182-1185] show that at near-zero load the speed of the motor is independent of the number of stators. Here, we introduce a mathematical model of the motor dynamics that explains this behavior based on a general assumption that the stepping rate of a stator depends on the torque exerted by the stator on the rotor. We find that the motor dynamics can be characterized by two timescales: the moving-time interval for the mechanical rotation of the rotor and the waiting-time interval determined by the chemical transitions of the stators. We show that these two timescales depend differently on the load, and that their cross-over provides the microscopic explanation for the existence of two regimes in the torque-speed curves observed experimentally. We also analyze the speed fluctuation for a single motor by using our model. We show that the motion is smoothed by having more stator units. However, the mechanism for such fluctuation reduction is different depending on the load. We predict that the speed fluctuation is determined by the number of steps per revolution only at low load and is controlled by external noise for high load. Our model can be generalized to study other molecular motor systems with multiple power-generating units. torque-speed relationship | model | rotary | stepping statistics | speed fluctuation

A simple analytical method is developed for determining the optimal combination of stator pole and rotor pole numbers for a multi-tooth flux-switching permanent magnet (FSPM) machine, and the optimal design of the stator teeth for maximum torque. In addition, the rotor pole width and the split ratio are optimized by finite element analysis. The optimized multi-tooth FSPM machine exhibits a significantly higher torque capability and requires a significantly lower volume of magnet material than a conventional FSPM machine. The performance of the proposed multi-tooth FSPM machine is validated experimentally. Index Terms--Multi-tooth, permanent magnet, flux-switching, brushless, direct-drive.

We present an efficient tool for design analysis of a synchronous reluctance motor (SynRM). We use winding function analysis (WFA) instead of finite-element analysis (FEA). With WFA, parameter sensitivity can be analyzed and the effects of parameters on the machine design can be evaluated very rapidly (under linear condition). We investigated the effect of rotor skewing, stator winding chording, pole arc, and interpolar air-gap length on average torque and torque ripple. We compare the results obtained by WFA with those obtained by 2-D FEA. We show that the two methods give approximately the same results but WFA requires less computation time. Index Terms--Finite-element method, reluctance motor, torque ripple, winding function.

In this paper, we investigate the effects of space harmonics of single-phase fine start permanent-magnet (LSPM) motors on starting performance. We construct an equivalent electric circuit considering the harmonics for the analysis, in which the magnetostatic field computation is coupled with finite-element modeling. We analyze the starting characteristics by circuit simulation and show that the results compare well with those of time-step finite-element analysis and of experiments. Index Terms--Equivalent circuit, line-start permanent magnet motor, space harmonics, starting torque.

Switched reluctance machines have emerged as an important technology in industrial automation; they represent a real alternative to conventional variable speed drives in many applications. This paper reviews the technology status and trends in switched reluctance machines. It covers the various aspects of modeling, design, simulation, analysis, and control. Finally, it discusses the impact of switched reluctance machines technology on intelligent motion control. Index Terms--Acoustic noise, finite-element analysis, switched reluctance motor, torque ripple.

The conceptual design of homopolar superconductivity synchronous motors (HSSMs) that apply to low-speed and high torque for ship propulsion applications is described. Superconducting synchronous motors compared with conventional motors has reduced the motor size and has enhanced the efficiency.

Temperature- and frequency-dependent variations of the rotor ([R'.sub.r]) and stator ([R.sub.s]) resistances pose a challenge in the accurate estimation of flux and velocity in the sensorless control of induction motors (IMs) over a wide speed range. Solutions have been sought to the problem by signal injection and/or by the use of different algorithms for the different parameters and states of the same motor. In this paper, a novel Extended-Kalman-Filter (EKF)-based estimation technique is developed for the solution of the problem based on the consecutive operation of two EKF algorithms at every time step. The proposed 'braided' EKF technique is experimentally tested under challenging parameter and load variations in a wide speed range, including low speed. The results demonstrate a significantly increased accuracy in the estimation of [R.sub.s] and [R'.sub.r], as well as load torque, flux, and velocity in transient and steady state, when compared with single EKFs or other approaches taken to estimate these parameters and states in the sensorless control of IMs. The improved results also motivate the utilization of the new estimation approach in combination with a variety of control methods which depend on accurate knowledge of a high number of parameters and states. Index Terms--Braided Extended Kalman Filter (EKF), induction motors (IMs), load-torque estimation, rotor- and stator-resistance estimation, speed sensorless control.

This paper deals with the detection of mechanical load faults in induction motors during speed transients. The detection strategy is based on stator current analysis. Mechanical load faults generally lead to load torque oscillations at specific frequencies related to the mechanical rotor speed. The torque oscillations produce a characteristic sinusoidal phase modulation of the stator current. Speed transients result in time-varying supply frequencies that prevent the use of classical, Fourier transform-based spectral estimation. This paper proposes the use of a timefrequency distribution, the Wigner Distribution, for stator current analysis. Fault indicators are extracted from the distribution for on-line condition monitoring. The proposed methods are implemented on a low-cost digital signal processor. Experimental results in a steady-state and during transients with load torque oscillations and load imbalance are presented. Index Terms--Digital signal processors (DSPs), fault detection, induction motor, load unbalance, mechanical fault, motor current signature analysis, torque oscillation, Wigner Distribution (WD).

This study assessed the mechanical reliability and validity of the INRTEK iSAM 9000 isokinetic dynamometer, and compared the obtained torque values of the prototype device with those from a traditional device. Sixty volunteers (40 men and 20 women) were tested at 60[degrees] per second for shoulder, knee, and trunk flexion, and extension on both the Cybex 6000 and a new isokinetic dynamometer (iSAM 9000). Intraclass correlation coefficients (ICC) and standard errors of measurement (SEM) revealed a high level of reproducibility and precision in the device's torque measurements (ICC range = 0.94-0.98; SEM range = 5.2-29.7). Pearson r values revealed very high relationships between the two instruments (set 1: r = 0.84-0.93; set 2: r = 0.87-0.93; P < 0.05). Significantly higher peak torque for both sets of left and right knee flexion and extension, right shoulder extension and trunk extension was found for the iSAM 9000 compared to the Cybex 6000 (P < 0.05). The strong ICCs and small SEMs support the device's mechanical reliability and validity. The high correlation coefficients between the prototype dynamometer and the Cybex 6000 support the new device's validity in the measurement of isokinetic torque. The findings of this study will be used to refine the next generation of the INRTEK isokinetic device with respect to test protocols and the reliability of measuring human muscle performance. KEY WORDS muscular strength, peak torque, angular velocity, industry, Cybex

Although several studies have investigated the acute effect of static stretching exercises, the duration of exercises that negatively affects performance has not been ascertained. This study was conducted to determine the acute effect of different static stretching durations on quadriceps isometric and isokinetic peak torque production. The 50 participants were randomly allocated into five equivalent sized groups and were asked to perform a stretching exercise of different duration (no stretch, 10-second stretch, 20-second stretch, 30-second stretch, and 60-second stretch). The knee flexion range of motion and the isometric and concentric isokinetic peak torques of the quadriceps were measured before and after a static stretching exercise in the four experimental groups. The same parameters were examined in the control group (no stretch) without stretching, before and after a 5-minute passive rest. There were no significant differences among groups before the experimentation regarding their physical characteristics and performances (P > 0.05). These results reflect the different groups' homogeneity. Significant knee joint flexibility increases (P < 0.001) and significant isometric and isokinetic peak torque reductions (P < 0.05-0.001) have been shown to occur only after 30 and 60 seconds of quadriceps static stretching. Stretching reduced isometric peak torque by 8.5% and 16.0%, respectively. Concerning isokinetic peak torque after 30 and 60 seconds of stretching, it was reduced by 5.5% vs. 11.6% at 60[degrees]/s and by 5.8% vs. 10.0% at 180[degrees]/s. We suggest that torque decrements are related to changes of muscle neuromechanical properties. It is recommended that static stretching exercises of a muscle group for more than 30 seconds of duration be avoided before performances requiring maximal strength. KEY WORDS stretching duration, isometric contraction, isokinetics, knee extensors

This paper proposes an active filter (AF) topology to reduce the torque ripple and harmonic noises in a permanent-magnet synchronous motor. The topology consists of an insulated-gate bipolar transistor AF and two resistance-inductance-capacitance high-pass electromagnetic interference (EMI) noise filters, i.e., one in the primary and the other in the secondary circuit of the coupling 1 : 1 transformer. The AF is characterized by detecting the harmonics in the motor phase voltages by comparing the measured phase values with the reference voltages generated as a function of the motor parameters and control setting values under field-oriented control. The AF uses the hysteresis voltage control method, while the motor main circuit uses the hysteresis current control method; thus, the two control methods independently work together to provide an almost sinusoidal voltage to the motor windings. The simulation results show total harmonic distortion drops of greater than 13% with EMI noise damping down to ~ -10 dB as well as considerable reduction in torque ripple. Index Terms--Active power filter, electromagnetic interference (EMI), permanent-magnet synchronous motor (PMSM), rotor reference frame, torque ripple, voltage harmonic.

In this paper, we present a novel mechanism for recording at a head field significantly below the medium coereivity in a perpendicular recording geometry. By applying a localized ac field at adequate frequency to the perpendicular recording medium, saturation recording can be achieved with recording field amplitudes significantly below the medium coercivity, or the medium perpendicular anisotropy field. A scheme utilizing spin torque to generate a localized ac field at high frequency (tens of gigahertz) with kilo-oersted field amplitude in the medium is proposed along with a systematic modeling analysis. Recording simulations at high linear densities are presented. Index Terms--Microwave, perpendicular recording, spin momentum transfer, spin torque.

Current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) heads with a current screen layer were fabricated, and the recording performance was measured. An output voltage of 1.9 mV and head-amp signal-to-noise ratio (SNR) of about 30 dB were obtained from a 50-nm-wide head with an operating voltage of 120 mV. The MR ratio was 4%-5%, shield gap was 36 nm and resistance was 72 [ohm] With using the thermal fly-height control (TFC), the fabricated head showed a potential to yield a 382 Gb/[in.sup.2] recording (1252 kBPI x 305 kTPI). The current screen structure reduced the spin torque noise since just a low sensing current of 1-2 mA was required for obtaining a high output. Newly developed CPP-GMR films with a current screen layer showed the MR ratio of 18%-19% with the RA product of 0.2-0.3 [ohm] x [m.sup.2][micro]. Calculation showed that this film allows us to achieve 30 dB or more in the head-amp SNR when the sensor width was 40 nm or larger. The current screen CPP-GMR head is thus an attractive candidate that has a high potential suitable for an areal density of 500 Gb/[in.sup.2] or more. Below 40 nm, an all metal CPP-GMR head with the MR ratio of 10% or more would be the best candidate. Index Terms--CPP-GMR, magnetic head, magnetic recording, noise, spin torque.

We present an analytical method for the calculation of cogging torque in surface permanent-magnet (PM) motors. The cogging torque is calculated by integrating the Maxwell stress tensor inside the air gap. The principle of complex relative air-gap permeance derived from conformal transformation of the slot geometry is used to take into account the effect of slotting and to calculate the radial and tangential components of the air-gap flux density required for integration of the tangential component of the Maxwell stress tensor. We implemented the proposed analytical solution on a 7-kW four-pole surface PM motor and compared the results with finite-element solutions. We present an example of finding the optimal magnet angular span to yield minimum cogging torque as an example of the effectiveness of the method. Index Terms--Air-gap permeance, cogging torque, magnetic fields, permanent-magnet motors.

Gait modification is a nonsurgical approach for reducing the external knee adduction torque in patients with knee osteoarthritis (OA). The magnitude of the first adduction torque peak in particular is strongly associated with knee OA progression. While toeing out has been shown to reduce the second peak, no clinically realistic gait modifications have been identified that effectively reduce both peaks simultaneously. This study predicts novel patient-specific gait modifications that achieve this goal without changing the foot path. The modified gait motion was designed for a single patient with knee OA using dynamic optimization of a patient-specific, full-body gait model. The cost function minimized the knee adduction torque subject to constraints limiting how much the new gait motion could deviate from the patient's normal gait motion. The optimizations predicted a 'medial-thrust' gait pattern that reduced the first adduction torque peak between 32% and 54% and the second peak between 34% and 56%. The new motion involved three synergistic kinematic changes: slightly decreased pelvis obliquity, slightly increased leg flexion, and slightly increased pelvis axial rotation. After gait retraining, the patient achieved adduction torque reductions of 39% to 50% in the first peak and 37% to 55% in the second one. These reductions are comparable to those reported after high tibial osteotomy surgery. The associated kinematic changes were consistent with the predictions except for pelvis obliquity, which showed little change. This study demonstrates that it is feasible to design novel patient-specific gait modifications with potential clinical benefit using dynamic optimization of patient-specific, full-body gait models. Further investigation is needed to assess the extent to which similar gait modifications may be effective for other patients with knee OA. Index Terms--Dynamic optimization, knee adduction moment, movement prediction, osteoarthritis (OA).

An important factor in the performance of brush seals for a wide range of gas turbine applications is the rate of wear at the seal to shaft interface, which is dependant on the contact pressure that exists between the bristles and rubbing surface. This is dependent on a variety of effects. Principally, these are the aerodynamic forces bending the bristles onto the rubbing surface, frictional effects within the bristle pack and at the backing ring that arise with the application of pressure differential, geometrical changes due to centrifugal and thermal growths, and transient differential movements of the rotor that develop in flight manoeuvres. In order to investigate the effect of these phenomena on contact pressure, a test facility has been devised in which the torque exerted by a brush seal on a rotating shaft is used as an indirect measurement of contact pressure. This has necessitated the design of a test facility in which all system torques can be fully calibrated. Consequently, a pressure balanced design has been adopted in which applied seal differential and pressure levels have a minimal effect on axial loads at the rotor bearing assembly. The primary method of torque measurement is the instantaneous deceleration of the rotor. Thus, measurements over a wide speed range are acquired with high frequency instrumentation. The means whereby small parasitic torques are evaluated and corrected is given. Results demonstrating the dependence of contact pressure on seal differential and pressure levels are presented.

A method of actively maintaining voltage margin in field-oriented induction machine controllers is proposed. A voltage-margin controller is developed that rejects dc.link and load disturbances, such that current regulation and field orientation is maintained. In addition, the voltage-margin controller coupled with rotor-flux-oriented control is shown to provide maximum torque capability equivalent to stator-flux-oriented control. Index Terms - DC-link, field-oriented control (FOC), field-weakening, overmodulation, rotor-flux-oriented (RFO), stator-flux-oriented (SFO), torque capability, voltage margin.

A zero net tidal torque is experienced by a satellite on an eccentric orbit in the absence of significant permanent asymmetry. Theoretical calculations show that this period for satellite Titan is 15.82 to 15.93 days, and the value depends on the tidal dissipation model. Radar observations also yield the same results. Radar data and asymmetry constraints show a large highland plateau of water-ice with a diameter of about 18 kilometers. The plateau is surrounded by hydrocarbon ocean.

This paper presents a solution to obtain torque smoothness of a brushless dc drive within a wide speed range. The voltage between the neutral point N(sub 0) of the inverter and the neutral point N of the machine (V(sub NN)(sub 0) voltage) is not always zero. This voltage disturbs the phase currents during commutation. Since, in the case of real EMF's, the limited loop bandwidth of the current controller does not allow the currents to follow the adapted reference, a compensative and a predictive term have been added to the controller output. Furthermore, the robustness of the concept in the case of parameter variations is studied.

An optimized rotor pole shape is proposed that has effectively reduced the partial demagnetization effect and cogging torque. The finite element method is used for showing that the optimized rotor pole shape has reduced the effect of the partial demagnetization and cogging torque.

Two-dimensional finite element based results are described for various methods of torque ripple reduction in flux-reversal motors. The effects of variation in magnet and rotor pole heights, rotor pole skewing and multiple teeth per rotor pole on the cogging torque and choice of teeth per rotor pole with the teeth depth resulting in torque ripple reduction are described.

The novel flux barrier is proposed by using the modified Taguchi method to reduce the cogging torque. The optimal novel flux barrier has reduced the cogging torque and torque ripple and it is verified by the results.

A new torque ripple minimization approach, the harmonic current injection method, is described and implemented in the new class of flux-controllable stator-permanent-magnet brushless (FC-SPMBL) motor. The injection of proper harmonic current components into the fundamental current has kept the variation of instantaneous power to the minimum, thus suppressing the torque ripple.

A novel practicable self-control scheme is described to suppress chaos in a spin-torque nano-oscillator in the presence of spin-polarized dc and ac. A complete chaos control diagram is obtained, which has shown that the employment of the self-control scheme over a broad frequency range of the ac can reduce the degree of chaoticity in the oscillator.

The electromagnetic performance of two permanent magnet brushless motors, such as flux-switching magnet (FSPM) and surface-mounted motor, is examined by the finite element analysis. The results have shown that both motors have displayed sinusoidal back-emf waveform and the FSPM motor has displayed not only larger airgap flux density, higher torque per copper loss, but also higher torque ripple due to cogging torque.

The impact of winding inductance variation on the performance of a three-phase three-stack claw pole permanent magnet motor with soft magnetic composite (SMC) stator is examined by using an improved phase variable model. The simulation results have shown that the phase current and the electromagnetic torque are affected by the variation of winding inductance.

The characteristics of the magnetic force and the torque in the conventional rotatory two-phase transverse flux machine (TFM) are examined by using the three-dimensional finite element method. The studies have shown that the unbalance magnetic force of a TEM is eliminated without sacrificing torque or power by introducing symmetric multipair cores.

The advance development and progress in the field of optical tweezers that are used in the increasing number of studies related to biochemical and biophysical processes are reviewed. The optical tweezers in conjunction with single-molecule manipulation and detection techniques could have significant implications in biochemical research.

A study examines the effects of screwdriver handle shape, surface material and workpiece orientation on torque performance, finger force distribution and muscle activity in a maximum screwdriving torque task. Screwdriver handles with combinations of circular or hexagonal cross-sectional shapes with double frustum and cone lateral shapes are found to be optimal.

This paper describes an investigation of DTC for permanent magnet synchronous motor (PMSM) drives. The analysis of PMSMs shows that the increase of electromagnetic torque is proportional to the increase of the angle between the stator and rotor flux linkages and therefore fast torque response can be obtained by increasing the rotating speed of the stator flux linkage as fast as possible. The implementation of DTC in PMSM drives is discussed and the switching table specific for an interior PMSMs is derived. The proposed control is implemented on a prototype PMSM, which has a standard induction motor stator, and the experimental results show that the torque response is extremely fast. It is also demonstrated that the position sensor is not essential for the inner torque control loop of PMSM drives with DTC. Key-words: Direct Torque Control, Permanent Magnet Motors, Stator Flux Linkage, Position Sensor, Inverter.