Torque Reduction Research Articles

Multiday load carriage decreases ability to mitigate ground reaction force through reduction of ankle torque production

The aim of this study was to examine the impact of backpack load carriage on lower limb strength and loading rate change in a cohort that match military recruit profiles. Twenty-six participants walked on a treadmill either carrying a military load carriage system (32 kg) or unloaded for 2 h on two consecutive days. Participants ground reaction forces and strength measures were assessed using a force platform and dynamometry, respectively. Testing included assessments before and after treadmill walking on days one and two, and 24 h following day 2. When assessed by mixed methods ANOVA (alpha: 0.05) statistically significant interaction effects were observed for loading peak (p = 0.031), loading rate (p = 0.035) and plantarflexor torque dynamometry variables at 60°s−1 (p = 0.011) and 120°s−1 (p = 0.024). Repeated measures correlation highlighted associations between plantarflexor torque at 60°s−1 and loading rate (r = −0.901, p < 0.001). Load carriage reduced lower limb torque which did not recover between days. Plantarflexor torque reductions were associated with increases in loading rate. Practitioners should consider that load bearers are more likely to experience lower limb injury during multi-day load carriage. Future work should develop protocols to reduce plantarflexor torque loss in order to reduce ground reaction force change.

Cogging Torque Dynamic Reduction Based on Harmonic Torque Counteract

This article presents a method to reduce cogging torque in permanent magnet (PM) machines from dynamic control based on harmonic torque counteract (HTC). We find the possibility of dynamic cancellation of cogging torque and harmonic torque by studying their generation mechanism and period characteristics, and further study the current harmonic injection scheme for cogging torque reduction. Further, two case studies of an integer slot PM machine and a fractional slot PM machine based on finite element analysis well validate the proposed method. Among them, the cogging torque of a 6-slot/2-pole PM synchronous machine is weakened from 932.0 to 56.2 mN.m, with a weakening ratio of 94.0%, and the cogging torque of the other with 6-slot/4-pole is weakened from 1.23 N.m to 44.21 mN.m, with a weakening ratio of 96.4%. The theory of this article can be extended to PM machines with other different pole/slot combinations and topologies.

Investigation Cogging Torque of PMM with rotor and Stator optimization for renewable energy application

This paper proposes the cogging torque reduction by using the optimization of the slotting method on the stator and the cutting edge of the rotor side magnet of the Permanent Magnet Machiene (PMM), of the Synchrounous Generator (PMSG). Here, the effect on the cross-sectional area of the magnetic poles and the additional width of the slot opening will lead to an improvement in the reduction of cogging torque for the investigated of the machine. The proposed machine has 6 poles and 18 slots with a fixed slot opening widths on the stator and modified magnetic poles on the rotor. The software used to investigate and analyze the saturation of the induced cores in the stator and rotor of machine is the magnetic finite element method (FEMM 4.2). The most cost-effective method to minimize the presence of cogging torque of any PMSG is to conduct the modification of the rotor where the magnets are located and modify the stator structure despite the complexity and cost of manufacturing the stator. Here, the cutting of magnetic edge structure using a simple cutting method is implemented. This is a different method from that already widely implemented for cutting the edge of the magnet surface. The simulation results show that the PMSG cogging torque by cutting the magnetic edge and adding a dummy slot can significantly minimize the cogging torque. It is found that the cogging torque reduction is 99.47 percent. This condition as the low cogging torque and low PMG speed can be used for reference design and PMSG construction for renewable energy plants such as in geothermal power plants.

Method of Cogging Torque Reduction for Built-in Permanent Magnet Synchronous Motor

Cogging torque is one of the main factors that deteriorate the performance of permanent magnet motor. In order to reduce the cogging torque of built-in permanent magnet motor, a method of optimizing Rib and DminMag to reduce groove torque of built-in permanent magnet motor was proposed. Firstly, the relationship between Rib and DminMag and groove torque is analyzed through the expression of groove torque. Secondly, the optimal Rib and DminMag were found by finite element parametric calculation, and compared with the pre-optimization groove torque, the groove torque was significantly reduced. Finally, the main performance of motor before and after optimization is not significantly reduced.

Metformin Alters the Chemotaxis and Flagellar Motility of Escherichia coli.

Metformin is a biguanide molecule that is widely prescribed to treat type 2 diabetes and metabolic syndrome. Although it is known that metformin promotes the lifespan by altering intestinal microorganism metabolism, how metformin influences and alters the physiological behavior of microorganisms remains unclear. Here we studied the effect of metformin on the behavior alterations of the model organism Escherichia coli (E. coli), including changes in chemotaxis and flagellar motility that plays an important role in bacterial life. It was found that metformin was sensed as a repellent to E. coli by tsr chemoreceptors. Moreover, we investigated the chemotactic response of E. coli cultured with metformin to two typical attractants, glucose and α-methyl-DL-aspartate (MeAsp), finding that metformin prolonged the chemotactic recovery time to the attractants, followed by the recovery time increasing with the concentration of stimulus. Metformin also inhibited the flagellar motility of E. coli including the flagellar motor rotation and cell swimming. The inhibition was due to the reduction of torque generated by the flagellar motor. Our discovery that metformin alters the behavior of chemotaxis and flagellar motility of E. coli could provide potential implications for the effect of metformin on other microorganisms.

The Effect of Intake Valve Timing on Spark-Ignition Engine Performances Fueled by Natural Gas at Low Power

To reduce the greenhouse effect, it is important to reduce not only carbon dioxide but also methane emissions. Methane gas can be not only a fossil fuel (natural gas) but also a renewable energy source when it is extracted from biomass. After biogas has been purified, its properties become closer to those of natural gas or methane. Natural gas is an alternative energy source that can be used for spark-ignition engines, but its physicochemical properties are different from those of gasoline, and the spark-ignition engine control parameters need to be adjusted. This article presents the results of a study that considers a spark-ignition engine operating at different speeds (2000 rpm, 2500 rpm, and 3000 rpm) and the regulation of the timing of intake valve closure when the throttle is partially open (15%), allowing the engine to maintain the stoichiometric air–fuel mixture and constant spark timing. Studies have shown a reduction in engine break torque when petrol was replaced by natural gas, but break thermal efficiency has increased and specific emissions of pollutants (NOx, HC, CO2 (g/kWh)) have decreased. The analysis of the combustion process by the AVL BOOST program revealed different results when the engine ran on gasoline as opposed to when it ran on natural gas when the timing of intake valve closure changed. The volumetric efficiency of the engine and the speed of the combustion process, which are significant for engine performance due to the different properties of gasoline and natural gas fuels, can be partially offset by adjusting the spark timing and timing of intake valve closure. The effect of intake valve timing on engine fueled by natural gas more noticeable at lower engine speeds when the engine load is low.

Corticospinal excitability remains unchanged in the presence of residual force enhancement and does not contribute to increased torque production.

BackgroundFollowing stretch of an active muscle, muscle force is enhanced, which is known as residual force enhancement (rFE). As earlier studies found apparent corticospinal excitability modulations in the presence of rFE, this study aimed to test whether corticospinal excitability modulations contribute to rFE.MethodsFourteen participants performed submaximal plantar flexion stretch-hold and fixed-end contractions at 30% of their maximal voluntary soleus muscle activity in a dynamometer. During the steady state of the contractions, participants either received subthreshold or suprathreshold transcranial magnetic stimulation (TMS) of their motor cortex, while triceps surae muscle responses to stimulation were obtained via electromyography (EMG), and net ankle joint torque was recorded. B-mode ultrasound imaging was used to confirm muscle fascicle stretch during stretch-hold contractions in a subset of participants.ResultsFollowing stretch of the plantar flexors, an average rFE of 7% and 11% was observed for contractions with subthreshold and suprathreshold TMS, respectively. 41–46 ms following subthreshold TMS, triceps surae muscle activity was suppressed by 19–25%, but suppression was not significantly different between stretch-hold and fixed-end contractions. Similarly, the reduction in plantar flexion torque following subthreshold TMS was not significantly different between contraction conditions. Motor evoked potentials, silent periods and superimposed twitches following suprathreshold TMS were also not significantly different between contraction conditions.DiscussionAs TMS of the motor cortex did not result in any differences between stretch-hold and fixed-end contractions, we conclude that rFE is not linked to changes in corticospinal excitability.

Angle specific analysis of hamstrings and quadriceps isokinetic torque identify residual deficits in soccer players following ACL reconstruction: a longitudinal investigation

ABSTRACT Analysing the isokinetic curve is important following ACL reconstruction as there may be deficits in torque production at specific points throughout the range of motion. We examined isokinetic (60°.s-1) torque-angle characteristics in 27 male soccer players (24.5 ± 3.9 years) at 3 time-points (17 ± 5; 25 ± 6; and 34 ± 7 weeks post-surgery). Extracted data included knee flexor and extensor peak torque, conventional hamstrings: quadriceps (H/Q) ratio, and angle-specific torque using Statistical Parametric Mapping (SPM). There were significant involved limb increases in extension peak torque at each assessment (p<0.001); however, asymmetry favouring the un-involved limb was observed (p<0.01). Flexion peak torque was greater on the un-involved limb at assessments 1 and 2 only (p<0.05). The angle of peak torque was not significantly different at individual time-points or within-limbs across the 3 assessments. SPM revealed involved limb angle-specific reductions in extension torque across the full range of motion at time-points 1 and 2 (p<0.001) but only in angles [51-80°] at assessment 3 (p<0.05). Between limb H/Q angle differences [33-45°] were shown at assessments 2 and 3. The ratio ranged from 1.60-0.74 depending on the angle tested. Angle-specific moment curves are useful for monitoring patterns of strength development during rehabilitation.

Binary AGNs simulations with radiation pressure reveal a new duty cycle, and a reduction of gravitational torque, through ‘minitori’ structures

ABSTRACT We produce the first set of radiation hydrodynamics simulations of binary active galactic nuclei (AGNs) at parsec-scale separation in scale-model simulations. We use SPH for hydrodynamics, and raytracing to calculate optical depths and radiation pressure from the two AGNs. We confirm that, without radiation pressure, the sign of gravitational torque is sensitive to the binary parameters, although in one of our two orbital configurations the binary should coalesce in a time-scale of &amp;lt;109 yr. However, radiation pressure quickly destroys the ‘minitori’ around each supermassive black hole (SMBH), drastically reducing gravitational torques and accretion, and greatly increasing the coalescence time-scale. Our simulations suggest a new ‘minitorus’ duty cycle with a time-scale of ∼10 binary periods (∼106 yr when scaling our models to a total binary mass of 2 × 107 M⊙). The growth and blow-out phases of the ‘minitori’ are of similar time-scales, and thus we expect about half of observed binary SMBHs to be active, in at least one component. The ‘minitorus’ structure provides asymmetries that could be observed by infrared interferometry.

Dynamic Analysis of Surface-Mounted Permanent Magnet Type Coaxial Magnetic Gear With Damper Bar Considering Magnetic Field Modulation Effect

Coaxial Magnetic Gear (CMG) has unstable dynamic characteristics by hunting or pull-out action of the output rotor when the load or speed are changed, unlike traditional mechanical gears. These dynamic characteristics need to be improved in order to secure the reliability of mechanical power transmission system by fast and accurate response. In this paper, the damper bar used in synchronous machines is considered as a method to improve the dynamic characteristics of CMG. The Surface-mounted Permanent Magnet (SPM) type CMG is selected as the analysis model. The space harmonics of the magnetic flux density of stationary and rotary members of CMG namely, modulating pieces, inner and outer rotor, are analyzed and characterized the influence of them on the improvement of dynamic characteristics as well as torque reduction. Also, the magnetic flux density characteristics and the damping effect are compared according to the position of the damper bars on two rotors and the modulating pieces. In conclusion, the considerations about the perspective for design and application are presented when using the damper bar for SPM type CMG.

Data-Driven Adaptive Torque Oscillation Compensation for Multi-Motor Drive Systems

Multi-motor drive systems (MMDS) combine several drives that work together to fulfill one task. Compared to conventional single-motor drive systems modular product concepts can be realized with MMDS thanks to additional degrees of freedom. Because of their mechanical structure consisting of several shafts, clutches, and gear pairings, complex deflection shapes arise which lead to unintended torque oscillations.To compensate for these torque oscillations a data-driven adaptive multiple-input single-output scheme based on two cascaded recursive least squares estimators is proposed. Here, weights (manipulable amplitudes) for each order (multiple of a fundamental frequency) to be compensated are multiplied with unit amplitude harmonic signals of a reference oscillator and added as reference torques to the torque controllers of the MMDS’s drives. These weights are continually adapted by an online identification of transfer paths and disturbances. Furthermore, the torque contribution of the individual drives concerning the compensation task can be changed at runtime utilizing a weighting matrix as tuning parameter by analytically solving a quadratic program with a linear equality constraint. Hence, the proposed algorithm is suitable for automatic self-commissioning requiring only marginal expert intervention. Experimental investigations prove the compensation capability of the approach whereby a reduction of the output torque’s total harmonic distortion (THD) of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$80\%$</tex-math></inline-formula> from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$26.8\%$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5.4\%$</tex-math></inline-formula> for a representative operation point is achieved.

The effect of shaft twisting on the reduction of the electromagnetic torque of adownhole motor

The effect of shaft twisting on the reduction of the electromagnetic torque of adownhole motor

Influence of superimposed low frequency oscillations on single-pass honing of long-chipping steel

Single-pass honing is used as a finishing process to meet high demands regarding form and dimensional accuracy of drilled bores. The disadvantages of single-pass honing compared to the conventional long-stroke honing are high process forces and torques as well as an increased risk of chip space clogging of the abrasive stones. A significant reduction in process forces and torques can be achieved by superimposing the axial movement with oscillations. In this work the kinematic basics of different oscillation parameters and their effects on single-pass honing of long-chipping steel are analyzed. It can be concluded that by superimposing low frequency oscillations in single-pass honing, the process forces and torques as well as the specific energy consumption can be reduced significantly without a decline in surface quality and form accuracy.

Development of a Gait Rehabilitation Robot Using an Exoskeleton and Functional Electrical Stimulation: Validation in a Pseudo-paraplegic Model.

ABSTRACTObjective:We have developed a robot for gait rehabilitation of paraplegics for use in combination with functional electrical stimulation (FES). The purpose of this study was to verify whether the robot-derived torque can be reduced by using FES in a healthy-person pseudo-paraplegic model.Methods:Nine healthy participants (22–36 years old) participated in this study. The robot exoskeleton was designed based on the hip–knee–ankle–foot orthosis for paraplegia. Participants walked on a treadmill using a rehabilitation lift to support their weight. The bilateral quadriceps femoris and hamstrings were stimulated using FES. The participants walked both with and without FES, and two walking speeds, 0.8 and 1.2 km/h, were used. Participants walked for 1 min in each of the four conditions: (a) 0.8 km/h without FES, (b) 0.8 km/h with FES, (c) 1.2 km/h without FES, and (d) 1.2 km/h with FES. The required robot torques in these conditions were compared for each hip and knee joint. The maximum torque was compared using one-way analysis of variance to determine whether there was a difference in the amount of assist torque for each gait cycle.Results:Walking with the exoskeleton robot in combination with FES significantly reduced the torque in hip and knee joints, except for the right hip during extension.Conclusions:In the healthy-participant pseudo-paraplegic model, walking with FES showed a reduction in the robot-derived torque at both the hip and knee joints. Our rehabilitation robot combined with FES has the potential to assist paraplegics with various degrees of muscle weakness and thereby provide effective rehabilitation.

Evaluation of Drag Reduction Effect and Torque Generated at the Base of Riblet with Direct Numerical Simulation in Turbulent Channel Flow

Reducing fluid drag and the energy required for fluid transport is an important issue. Riblet is used as a method to reduce frictional drag. Direct numerical simulation (DNS) was used to research the drag reduction effect of the riblet and the torque generated at the base of the riblet. The riblet is a three-dimensional riblet whose height and span vary with respect to the flow direction. The riblet is represented by a superposition of two sine waves, with amplitude and phase determined randomly. The torque and drag reduction effects were investigated for 1108 cases of riblets with different geometries. The friction Reynolds number, defined by the friction velocity uτ [m/s] and the kinematic viscosity ν [m2/s], is 110. The results show that torque is a shape parameter and is most dependent on pressure of the riblet surface. A Paretooptimal solutions that minimizes both the torque and the drag increase ratio was investigated. As a result, four Pareto solutions were found. The drag force generated on each face of the riblet was also analyzed and compared to the Pareto solution in all cases. The results show that the Pareto optimal solution group has a smaller fraction of drag due to pressure than all cases.

Cogging Torque Reduction of Axial-flux Magnetic Gear with Integer Gear Ratio by Unequal-width Pole-pieces

Cogging Torque Reduction of Axial-flux Magnetic Gear with Integer Gear Ratio by Unequal-width Pole-pieces

Modification of Pole Pitch and Pole Arc in Rotor Magnets for Cogging Torque Reduction in BLDC Motor

Cogging torque is an unfavorable hindrance in Permanent Magnet Brushless DC (PMBLDC) motor. In medium-low power PMBLDC motors, the surplus oscillations and intolerable noise happen because of the harmonic magnetic forces created by cogging torque. This paper introduces a new approach for the diminution of cogging torque. This method is based on placement irregularities in rotor magnets, and for this a new combination of pole arc and pole pitch was considered. The reference model has a pole pitch of 90° and pole arc of 63°. The new pole pitch is attained by the application of shifting technique on the permanent magnet and for the new pole arc it was resized. An analytical expression using the Virtual Work Method (VWM) Method was derived for locating the pole pitch and pole arc with nominal cogging torque in the PMBLDC motor. The technique is explored using 3D Finite Element Analysis (FEA). The comparison of the simulation and analytical results of cogging torque is accomplished. It is figured out that the cogging torque minimization in the analytical results exhibited acceptable agreement with FEA analysis.

Wearable Multifunctional Additive Hand System for Enhancing the Workspace and Grasping Capability of the Human Hand

In this study, a wearable multifunctional additive hand (MAH) system is proposed for enhancing the workspace and grasping capability of the human hand. The MAH system consists of a main body and three fingers, and each finger has two joints. To optimize the performance, the following five parameters are considered: finger length, number of fingers, number of joints, base frame size, and joint angle range. The MAH system is designed to assist the human hand in the inward and outward modes. In the inward mode, the finger joints of the proposed system rotate in the same direction as the finger flexion of the human hand, whereas in the outward mode, the robotic fingers of the MAH system rotate in opposite directions. The proposed system provides assistive torque and expands the workspace of the human hand in the inward mode. When the additive finger joints rotate outward, they grasp an object as a third hand. The validity of the proposed system is verified analytically by changing the design parameters, considering the workspace expansion and joint torque reduction. An alpha shape is introduced to calculate the expanded workspace volume using the proposed system. The joint torque was estimated by utilizing kinematics and the force equilibrium equation, assuming that the human hand with the MAH system holds a postulated object.

Lubrication of saliva layer on oral and throat mucosa and its friction reduction effect of swallowing

Swallowing disorder has been becoming a serious issue with increasing in elderly people. Disorder sometimes appears with a decrease in saliva, because saliva has an important role in lubrication over the oral cavity and throat. Though the structure of biological mucosa has been studied physiologically, there are only few studies that examined the influence of its oral and throat mucosa on fluid lubrication. Therefore, we investigated the friction reduction effect on the oral cavity and pharynx. There is a thin liquid phase with a thickness of about 0.1 mm called saliva layer on oral and throat mucosa. It is necessary to evaluate the rheological properties of mucus with low viscosity and high spinnability like saliva layer using a PEO solution, because of the viscosity characteristics different from the shear viscosity. The PEO solution concentration was determined from the measurement of the viscous characteristic by the rotational viscometer to set the same viscosity as that of saliva. Therefore, we investigated the rheological characteristics by measuring the extensional viscosity to make a mucus using a PVA coating. We measured friction torque on the artificial mucosa lubricated by PEO solution. The effect of torque reduction of friction by high-viscosity liquids (100% glycerin solution) on the artificial mucosa was clarified in this study. We considered apparent slip occurs in the saliva layer. However, there was no effect of friction reduction on the low viscosity (40% glycerin aqueous solution). Even if apparent slip occurs in the artificial mucosa, the viscosity on the artificial mucosa is the same as that of the liquids.

Robustness of Backstepping Multiphase Induction Machine Control in Presence of Open Phases Fault

When increasing the power, Multiphase Induction Machine (MPIM) offer, compared to the three-phase induction machine, an interesting alternative reduction of the current switched by inverter and at the windings, allow a torque reduction ripples. In addition, the number of phases more than three offers increased reliability by allowing the machine to continue to operate even if one or more phases fail, which favors its use in applications requiring more reliability such as electric cars. Most previous works have focused on the speed/flux regulation of multiphase machine, ignoring the open phases fault. This paper present the robustness of backstepping technique for multiphase induction machine control taking account of open phases faults. The proposed robustness study involves a multi-loop nonlinear controller designed to meet the two main control objectives, i.e. tight speed regulation for a wide range speed-reference variation and rotor flux regulation. The feedback control convergence is formally analyzed using Lyapunov technique and its performances are illustrated by simulation.