Torque Matching Research Articles

Reductions in Motor Unit Firing are Associated with Clinically Meaningful Leg Extensor Weakness in Older Adults.

Weakness, one of the key characteristics of sarcopenia, is a significant risk factor for functional limitations and disability in older adults. It has long been suspected that reductions in motor unit firing rates (MUFRs) are one of the mechanistic causes of age-related weakness. However, prior work has not investigated the extent to which MUFR is associated with clinically meaningful weakness in older adults. Forty-three community-dwelling older adults (mean: 75.4 ± 7.4years; 46.5% female) and 24 young adults (mean: 22.0 ± 1.8years; 58.3% female) performed torque matching tasks at varying submaximal intensities with their non-dominant leg extensors. Decomposed surface electromyographic recordings were used to quantify MUFRs from the vastus lateralis muscle. Computational modeling was subsequently used to independently predict how slowed MUFRs would negatively impact strength in older adults. Bivariate correlations between MUFRs and indices of lean mass, voluntary activation, and physical function/mobility were also assessed in older adults. Weak older adults (n = 14) exhibited an approximate 1.5 and 3Hz reduction in MUFR relative to non-weak older adults (n = 29) at 50% and 80% MVC, respectively. Older adults also exhibited an approximate 3Hz reduction in MUFR relative to young adults at 80% MVC only. Our model predicted that a 3Hz reduction in MUFR results in a strength decrement of 11-26%. Additionally, significant correlations were found between slower MUFRs and poorer neuromuscular quality, voluntary activation, chair rise time performance, and stair climb power (r's = 0.31 to 0.43). These findings provide evidence that slowed MUFRs are mechanistically linked with clinically meaningful leg extensor weakness in older adults.

Anisotropic molecular coarse-graining by force and torque matching with neural networks.

We develop a machine-learning method for coarse-graining condensed-phase molecular systems using anisotropic particles. The method extends currently available high-dimensional neural network potentials by addressing molecular anisotropy. We demonstrate the flexibility of the method by parametrizing single-site coarse-grained models of a rigid small molecule (benzene) and a semi-flexible organic semiconductor (sexithiophene), attaining structural accuracy close to the all-atom models for both molecules at a considerably lower computational expense. The machine-learning method of constructing the coarse-grained potential is shown to be straightforward and sufficiently robust to capture anisotropic interactions and many-body effects. The method is validated through its ability to reproduce the structural properties of the small molecule's liquid phase and the phase transitions of the semi-flexible molecule over a wide temperature range.

Perception of Torque is Impacted by a Subset of Features Related to the Motor Command.

Accurate perception of one's self-generated torques is integral to sensorimotor control. Here, we examined how features of the motor control task, specifically the variability, duration, muscle activation pattern, and magnitude of torque generation, relate to one's perception of torque. Nineteen participants generated and perceived 25% of their maximum voluntary torque (MVT) in elbow flexion while simultaneously abducting at their shoulder to 10%, 30%, or 50% of their MVT in shoulder abduction (MVT[Formula: see text]). Subsequently, participants matched the elbow torque without feedback and without activating their shoulder. The shoulder abduction magnitude affected the time to stabilize the elbow torque (p 0.001), but did not significantly impact the variability of generating the elbow torque (p = 0.120) or the co-contraction between the elbow flexor and extensor muscles (p = 0.265). The shoulder abduction magnitude influenced perception (p = 0.001) in that the error in matching the elbow torque increased with an increased shoulder abduction torque. However, the torque matching errors neither correlated with the time to stabilize and variability in generating the elbow torque, nor the co-contraction of the elbow muscles. These findings suggest that the total torque generated during a multi-joint task impacts the perception of a torque about a single joint; yet, effective and efficient generation of the torque about a single joint does not impact the torque percept.

Study on a flow-field-based meanline model of nozzled twin-entry mix-flow turbine

Variable geometry twin-entry turbine has advantages in fuel economy, low-end torque, emission and turbo-engine matching of internal combustion engine. The reliability of performance prediction method for nozzled twin-entry turbine is heavily dependent on the understanding of flow mechanism of the turbine which is always confronted by time-dependent unequal admissions. This paper establishes a new meanline model of a nozzled twin-entry turbine based on the internal flow features. Firstly, flow mechanism of the twin-entry turbine with a vaned nozzle under different admissions is investigated via an experimentally validated CFD method. Results clearly demonstrate that the flow distortion in spanwise direction caused by unequal admissions notably influences the turbine efficiency discrepancy between symmetric unequal admissions, especially the two partial admissions. The evolution of flow distortion in the nozzle passage is the key to the performance discrepancy, which is impossible to be considered by a conventional performance model of a nozzled twin-entry turbine. Inspired by this, a newly-designed meanline model, named ‘parallel nozzle’ is proposed. Specifically, a nozzle passage is divided into two parallel sub-passages in spanwise direction to consider the flow distortion in nozzle passage. The model is validated against the detailed CFD results in terms of both overall performance and detailed flow parameters over different admissions. Results prove that turbine performance and flow parameters are well predicted by the model. Specifically, the influence of admissions on nozzled twin-entry turbine performance and flow parameters can be predicted by the method in satisfying accuracy.

A Novel Torque Matching Strategy for Dual Motor-Based All-Wheel-Driving Electric Vehicles

The market for electric vehicles is growing rapidly. Among them, the demand for a dual motor type 4 WD (Four -Wheel Driving) system is increasing. In this paper, we present the Torque Matching Strategy (TMS) method to select the optimal torque distribution ratio for dual motors. The TMS controller operates to set the optimal efficiency point by linearizing the drive efficiency combination of the two motors. Driving simulation and testing were performed through five drive cycles in the driver model interworking environment implemented in MATLAB and Carsim. The optimal distribution ratio was derived according to the front and rear gear ratios under the load condition, and the driving was verified by comparing it with the TMS control method. The efficiency was numerically verified by comparing the power loss of the driving motor. It reduced up to 34% in Urban Dynamometer Driving Schedule and up to 56.3% in Highway fuel efficiency test. The effectiveness of the TMS control method was demonstrated through the distribution rate trend based on the operation cycle and power loss.

Is subject-specific musculoskeletal modelling worth the extra effort or is generic modelling worth the shortcut?

The majority of musculoskeletal modelling studies investigating healthy populations use generic models linearly scaled to roughly match an individual’s anthropometry. Generic models disregard the considerable variation in musculoskeletal geometry and tissue properties between individuals. This study investigated the physiological implications of personalizing musculoskeletal model geometry (body segment mass, inertia, joint center, and maximum isometric muscle force). Nine healthy athletes performed ten repetitions of 15 meter sprints at 75–95% of their maximum sprinting speed and ten repetitions of unanticipated sidestep cut trials with a 4.5–5.5 m/s approach running speed. Structural magnetic resonance imaging was collected on the lower extremities, from which subject-specific musculoskeletal models were developed. A one-dimensional statistical parametric mapping paired t-test was used to compare generic and subject-specific musculoskeletal models for: lower-limb kinematics, kinetics, torque matching, as well as hamstrings, adductors, and quadriceps muscle activations and fiber dynamics. Percentage change of geometric parameters between generic and subject-specific models were determined. Compared to generic models, subject-specific models showed significantly lower ankle dorsi/plantar flexion angle during sprinting and several significantly different net joint moments during sprint and cut tasks. Additionally, subject-specific models demonstrated better torque matching, more physiologically plausible fiber lengths, higher fiber velocities, lower muscle forces, and lower simulated activations in a subset of investigated muscles and motor tasks. Furthermore, subject-specific models identified between-limb differences that were not identified with generic models. Use of subject-specific modeling, even in healthy populations, may result in more physiologically plausible muscle fiber mechanics. Implementing subject-specific models may be especially beneficial when investigating populations with substantial geometric between-limb differences, or unilateral musculoskeletal pathologies, as these are not captured by a generic model.

Multiphase PMSM With Asymmetric Windings for More Electric Aircraft

This article presents a multiphase permanent magnet synchronous motor (PMSM) for the more electric aircraft propulsion. The stator winding of the motor is composed of multiple sets of multiphase windings with different parameters. The purpose of the motor design is to modify the distribution of the high-efficiency area of the motor by reasonably matching the winding parameters of each set, thereby making the motor more suitable for the working condition of more electric aircraft and improving the working efficiency of the motor. This article analyzes the selection principle of slot-pole combination and the influence that asymmetric windings have on the motor magnetic field. Three basic matching modes are proposed: equal torque matching, equal power matching, and equal speed matching. The motor model is established, with the external characteristics, efficiency, and dynamic response of different matching modes being compared and analyzed. The results show that equal torque matching and equal speed matching can reduce the total loss of the motor in a complete flight working condition, whereas equal power matching is not suitable for more electric aircraft.

RDE Plus - A Road to Rig Development Methodology for Complete RDE Compliance: Road to Chassis Perspective

<div class="section abstract"><div class="htmlview paragraph">To aid Original Equipment Manufacturers (OEM) in meeting future Real Driving Emissions (RDE) regulation criteria [<span class="xref">1</span>] across extended environmental conditions, a Road to Rig (R2R) whole vehicle development, calibration and verification approach, currently known as RDE Plus (RDE+), has been developed at HORIBA.</div><div class="htmlview paragraph">In this paper, the methodologies required for replicating real RDE road tests on a chassis dynamometer are discussed in depth. These include application of robot driver for successful cycle replication and repeatability and use of HORIBA’s Multi-function Efficient Dynamic Altitude Simulation (MEDAS) system in conjunction with a temperature and humidity controlled test cell to replicate the engine, vehicle and environmental conditions.</div><div class="htmlview paragraph">For RDE replication using a robot driver, two methods are presented. The first, is a speed matching method whereby a robot driver maintains the recorded vehicle speed via its own closed-loop control whilst road load is implemented via a Road Load Reconstruction (RLR) technique. The second is a “Torque Matching” (TM) method whereby robot driver pedal inputs are controlled in an open-loop mode and vehicle speed is implemented using Automatic Speed Regulation (ASR) of the chassis dynamometer. The former focuses on how robot driver controller tuning is used to successfully replicate real world driving if accurate road load components are known. The latter is presented as an elegant way to achieve a 1:1 road load match of a previously driven RDE test, or any other arbitrary road drive, with minimal prior information.</div><div class="htmlview paragraph">Considerations relating to vehicle preparation, robot driver tuning, and the application of HORIBA MEDAS will also be covered, including potential minor modifications to vehicles in pursuit of successful replication outcomes.</div><div class="htmlview paragraph">The RLR method showed good agreement in work done and CO<sub>2</sub> emissions for the real-world drives presented (approx. 2-3% difference). However, the TM method was able to demonstrate much less than 1% difference in these parameters when matching a previously driven test at the same conditions. This improved precision would be beneficial for minimizing the amount of back to back testing required to characterize the effect of powertrain calibration changes. NOx and PN emissions are also shown correlating well with the real road test values (< 10% difference).</div><div class="htmlview paragraph">This paper is the third in a series of ongoing technical reports from HORIBA on vehicle and engine development and calibration methodologies for RDE compliance. It is twinned with a concurrent SAE paper by the same authors covering Engine-in-Loop (EiL) methodologies and follows SAE Technical Paper 2019-01-0756 presented at WCX2019 [<span class="xref">2</span>, <span class="xref">3</span>]. Additionally, there are patent applications arising from the techniques demonstrated [<span class="xref">4</span>].</div></div>

Force perception at the shoulder after a unilateral suprascapular nerve block.

There are two key sources of information that can be used to match forces-the centrally generated sense of effort and afferent signals from mechanical receptors located in peripheral tissues. There is currently no consensus on which source of information is more important for matching forces. The corollary discharge hypothesis argues that subjects match forces using the centrally generated sense of effort. The purpose of this study was to investigate force matching at the shoulder before and after a suprascapular nerve block. The nerve block creates a sensory and muscle force mismatch between sides when matching loads. The torque matching accuracy did not change after the nerve block was administered. Directionally, the torque error was in the direction proposed by the corollary discharge hypothesis. However, the mismatch between deltoid EMG was substantially greater compared to the changes in the torque matching error after the block. The results support that sensory information is used during force matching tasks. However, since the nerve block also created a sensory disruption between sides, it is not clear how sensory information is reweighted following the nerve block and a role for sense of effort is still implicated.

Residual force enhancement during submaximal and maximal effort contractions of the plantar flexors across knee angle

Following active muscle lengthening, steady-state isometric force is elevated compared with an isometric contraction without prior lengthening for the same muscle length and activation level. This property of muscle contraction is known as residual force enhancement (RFE). Here, we aimed to determine whether neural factors may mask some of the mechanical benefits of RFE on plantar flexion torque production. Inherent to lengthening contractions is an increase in cortical and spinal-mediated inhibition, while knee flexion places the medial gastrocnemius at a neuromechanical disadvantage. Neuromuscular properties of the plantar flexors were investigated with a Humac Norm dynamometer in 10 males (∼27 years) with a flexed (90°) and extended (180°) knee and with or without calcaneal tendon vibration (frequency range: 80–110 Hz). There was no effect for vibration (p > 0.05), but there was an effect for knee angle (p < 0.05) such that there was a 2 fold increase in RFE with the knee flexed compared with extended. During submaximal torque matching, following active lengthening there was an activation reduction (electromyography; EMG) of 7.2 and 4.7% with the knee flexed and extended, respectively for soleus as compared with the reference isometric contraction, but no difference for the medial gastrocnemius. Despite attempting to excite Ia input onto the plantar flexor motor neuron pool, vibration had no influence on RFE. Surprisingly, RFE was elevated more for the knee flexed than extended, which was possibly owing to the activation differences across the disparate muscles of the triceps surae during the plantar flexion task.

Mitigating the bilateral deficit: reducing neural deficits through residual force enhancement and activation reduction.

The bilateral deficit (BLD) is characterized by a reduction in maximal voluntary torque during a bilateral contraction relative to the sum of left and right unilateral contractions. The BLD has been attributed to interhemispheric inhibition as a result of unilateral torque differences between limbs. If the BLD is the result of interhemispheric inhibition, lowering activation for a torque matching task, as shown in residual force enhancement (RFE), may help overcome the decrease in neural drive during bilateral contractions. Therefore, the purpose of the present study was to determine whether RFE could reduce the BLD. Participants (n = 12) performed both isometric and RFE MVCs of the elbow flexors under three conditions: (1) unilateral-left; (2) unilateral-right; and (3) bilateral. To directly address the purpose of the study, a sub-group of participants that displayed both RFE and a BLD ("Responders", n = 6) were selected from the participant pool. "Responders" displayed RFE (7.1 ± 5.3%) and an isometric BLD (BI: - 9.9 ± 3.2%). In the RFE state, the BLD was no longer significant (- 5.8 ± 7.9%), accompanied by the elimination of differences in biceps brachii EMG between arms (left: - 11.7 ± 10.3%; right: - 11.5 ± 13.2%), as seen during isometric contractions (left: - 12.0 ± 23.2%; right: - 21.1 ± 16.6%). Residual force enhancement appears to mitigate the BLD, alleviating the effects of a decrease in neural drive by allowing more force for a given level of muscle activation when compared to a purely isometric contraction.

EMG-Torque Dynamics Change With Contraction Bandwidth.

An accurate model for ElectroMyoGram (EMG)-torque dynamics has many uses. One of its applications which has gained high attention among researchers is its use, in estimating the muscle contraction level for the efficient control of prosthesis. In this paper, the dynamic relationship between the surface EMG and torque during isometric contractions at the human ankle was studied using system identification techniques. Subjects voluntarily modulated their ankle torque in dorsiflexion direction, by activating their tibialis anterior muscle, while tracking a pseudo-random binary sequence in a torque matching task. The effects of contraction bandwidth, described by torque spectrum, on EMG-torque dynamics were evaluated by varying the visual command switching time. Nonparametric impulse response functions (IRF) were estimated between the processed surface EMG and torque. It was demonstrated that: 1) at low contraction bandwidths, the identified IRFs had unphysiological anticipatory (i.e., non-causal) components, whose amplitude decreased as the contraction bandwidth increased. We hypothesized that this non-causal behavior arose, because the EMG input contained a component due to feedback from the output torque, i.e., it was recorded from within a closed-loop. Vision was not the feedback source since the non-causal behavior persisted when visual feedback was removed. Repeating the identification using a nonparametric closed-loop identification algorithm yielded causal IRFs at all bandwidths, supporting this hypothesis. 2) EMG-torque dynamics became faster and the bandwidth of system increased as contraction modulation rate increased. Thus, accurate prediction of torque from EMG signals must take into account the contraction bandwidth sensitivity of this system.

Contralesional Hemisphere Regulation of Transcranial Magnetic Stimulation-Induced Kinetic Coupling in the Poststroke Lower Limb.

The neural constraints underlying hemiparetic gait dysfunction are associated with abnormal kinetic outflow and altered muscle synergy structure. Recent evidence from our lab implicates the lesioned hemisphere in mediating the expression of abnormally coupled hip adduction and knee extension synergy, suggesting a role of cortical networks in the regulation of lower limb motor outflow poststroke. The potential contribution of contralesional hemisphere (CON-H) in regulating paretic leg kinetics is unknown. The purpose of this study is to characterize the effect of CON-H activation on aberrant across-joint kinetic coupling of the ipsilateral lower-extremity muscles poststroke. Amplitude-matched adductor longus motor-evoked potentials were elicited using single pulse transcranial magnetic stimulation (TMS) of the lesioned (L-H) and CON-Hs during an isometric adductor torque matching task from 11 stroke participants. For 10 control participants, TMS of the contralateral and ipsilateral hemisphere were given during the same task. TMS-induced torques were characterized at the hip and knee joints to determine the differential regulation of abnormal kinetic synergies by each motor cortices. The TMS-induced ratio of knee extension/hip adduction torques was quantified during 40 and 20% of maximum adduction torque. For both the 40 and 20% target adduction tasks, we find that contralesional stimulation significantly reduced but did not eliminate the TMS-induced ratio of knee extension/hip adduction torques for the stroke group (p = 0.0468, p = 0.0396). In contrast, the controls did not present a significantly different TMS-evoked torque following stimulation (p = 0.923) of the hemisphere ipsilateral to the test leg. The reduced expression of abnormal across-joint kinetic coupling suggests that the CON-H may contribute an adaptive role in lower limb control poststroke. Future study of neuromodulation paradigms that leverage adaptive CON-H activation may yield clinically relevant gains in lower limb motor function poststroke.

Selection and design of drive modules for robot joint based on dynamic load characteristics

This paper presents the selection and design process of joint motors and gears for robot systems. The velocity, acceleration, and torque profiles of each joint that satisfy a given task are calculated using dynamic and kinematic analysis, and the required motor torque to drive the joint is calculated with respect to the combination of module inertia and gear ratios. Considering energy efficiency, motor parameters, and switching characteristics of the inverter, the correlation between the module inertia and gear ratio for driving joints is investigated, and the final combination is determined by referring to commercial gear data sheets. From the determined motor inertia, various motor designs are possible. To compare the performance and determine the optimal model, performance metrics of drive motors, torque matching, coil temperature, and the motor constant, are proposed and the significance of these figures are discussed.

Methodology for system-level analysis of a fan–motor design for a vacuum cleaner

In the present study, a methodology for conducting a system-level analysis of a fan–motor assembly in a vacuum cleaner is presented. This system consisted of three components, a fan, motor, and the flow resistance of the motor, or of the vacuum cleaner. The combined characteristics of the fan and the motor were obtained from torque matching at a constant throttling condition, and a pressure drop was implemented under a constant flow rate to account for the flow resistance. By combining these two steps, the performance characteristics of the fan–motor assembly and the vacuum cleaner system could be predicted over the whole range of operation, based on the characteristics of each component. The predicted performance for power, flow rate, pressure, and efficiency using the present method agreed well with the experimental results obtained for an equivalent system, within 2% difference at best efficiency point. Three models of the fan–motor assembly (S1, S2, and S3) were analyzed at the component level, and the decrease in efficiency produced by flow resistance was estimated to be 1% (S1 and S3 models) or 4.7% (S2 model) using the present method. The characteristics of the fan, extracted from those of the fan–motor assembly, were used for validating the computational fluid dynamics. The computational fluid dynamics results of this study predicted higher efficiency due to simplification of the geometry, but an accurate prediction of best efficiency point location was obtained. The proposed method is also applicable for detecting system leakage and identifying system resistance without direct measurement.

Downregulating Aberrant Motor Evoked Potential Synergies of the Lower Extremity Post Stroke During TMS of the Contralesional Hemisphere.

Growing evidence demonstrates unique synergistic signatures in the lower limb (LL) post-stroke, with specific across-plane and across-joint representations. While the inhibitory role of the ipsilateral hemisphere in the upper limb (UL) has been widely reported, examination of the contralesional hemisphere (CON-H) in modulating LL expressions of synergies following stroke is lacking. We hypothesize that stimulation of lesioned and contralesional motor cortices will differentially regulate paretic LL motor outflow. We propose a novel TMS paradigm to identify synergistic motor evoked potential (MEP) patterns across multiple muscles. Amplitude and background activation matched adductor MEPs were elicited using single pulse TMS of L-H and CON-H (control ipsilateral) during an adductor torque matching task from 11 stroke and 10 control participants. Associated MEPs of key synergistic muscles were simultaneously observed. By quantifying CON-H/L-H MEP ratios, we characterized a significant targeted inhibition of aberrant MEP coupling between ADD and VM (p = 0.0078) and VL (p = 0.047) exclusive to the stroke group (p = 0.028) that was muscle dependent (p = 0.039). We find TA inhibition in both groups following ipsilateral hemisphere stimulation (p = 0.0014; p = 0.015). We argue that ipsilaterally mediated attenuation of abnormal synergistic activations post stroke may reflect an adaptive intracortical inhibition. The predominance of sub 3ms interhemispheric MEP latency differences implicates LL ipsilateral corticomotor projections. These findings provide insight into the association between CON-H reorganization and post-stroke LL recovery. While a prevailing view of driving L-H disinhibition for UL recovery seems expedient, presuming analogous LL neuromodulation may require further examination for rehabilitation. This study provides a step toward this goal.

Study of torque matching of revolving vane compressor and expander

An investigation was carried out to find the most optimum configuration, particularly the torque matching characteristics, of an integrated Revolving Vane compressor- expander. To carry out the study, a mathematical model of the integrated compressor-expander was developed. An open cycle air refrigeration system was adopted. The controlled parameter was the angle shift between the compressor and the expander. The observed parameters were the peak torque requirement and the bearing load. The results show that when properly matched, the peak torque can be reduced by more than 65% while the bearing loads can be reduced by up to 25%, depending on operating conditions. Unfortunately, the optimum angle shifts for peak torque do not always coincide with those for bearing load. When the pressure and inertial components of the torques are comparable or when the inertial component is dominant, the optimum angle shifts for peak torque and bearing load are around 180° and 330°, respectively. When the pressure component is dominant, the optimum angle shift for peak torque is equal to the angle difference between the pressure peak torques of the compressor and the expander while for bearing load is around 150°.

Effect of 14 days of bed rest in older adults on parameters of the body sway and on the local ankle function

This study explored the effects of a 14-day horizontal bed rest (BR) without countermeasures on postural sway, maximal voluntary torque and precision of voluntary torque matching. Sixteen subjects were tested before, immediately after and two weeks after BR. The increase in frequency and amplitude after BR was comparable for both sway subcomponents (rambling and trembling) in medial-lateral direction. But in anterior–posterior direction, rambling increased more in frequency (−7% vs. +31%, p<0.05) while trembling increased more in amplitude (+35% vs. +84%, p<0.05). The drop in maximal voluntary torque after BR was present for plantar flexion (p<0.05) but not for dorsal flexion. After the BR, the subjects were less precise in the dorsal flexion torque matching task (p<0.05). All the observed parameters, except the dorsal flexion torque matching error, returned back to the pre-BR values after the two weeks of re-conditioning. Results of this study indicate that body sway subcomponents responded differently to BR. Based on these findings, it was not possible to draw clear assumptions on the effects of neural and structural changes on body sway.

A torque matched aerodynamic performance analysis method for the horizontal axis wind turbines

AbstractAn analysis method is developed to test the operational performance of a horizontal axis wind turbines. The rotor is constrained to the torque–speed characteristic of the coupled generator. Therefore, the operational conditions are realized by matching the torque generated by the turbine over a selected range of incoming wind velocity to that needed to rotate the generator. The backbone of the analysis method is a combination of Schmitz' and blade element momentum (BEM) theories. The torque matching is achieved by gradient‐based optimization method, which finds correct wind speed at a given rotational speed of the rotor. The combination of Schmitz and BEM serves to exclude the BEM iterations for the calculation of interference factors. Instead, the relative angle is found iteratively along the span. The profile and tip losses, which are empirical, are included in the analysis. Hence, the torque at a given wind speed and rotational speed can be calculated by integrating semi‐analytical equations along the blade span. The torque calculation method is computationally cheap and therefore allows many iterations needed during torque matching. The developed analysis method is verified experimentally by testing the output power and rotational speed of an existing wind turbine model in the wind tunnel. The generator's torque rotational speed characteristic is found by a separate experimental set‐up. Comparison of experiments with the results of the analysis method shows a good agreement. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Computational Procedure to Replace a Bulky Flywheel for a Process Machine by a Combination of Appropriately Controlled VVVf Drive for Motor and a Smaller Flywheel

Process machines with tougher duty cycles are subjected to wide fluctuations in load torque. These often need a bulky flywheel for torque equalization with disadvantages of torsional oscillations. This results into fatigue of mechanical power transmission elements leading subsequently to equipment failure causing prolonged and frequent down time which results into financial losses. A simpler acceptable alternative is proposed in this article. Suitably monitored VVVf drives and low moment of inertia offer a much better alternative, for improving the system behavior drastically. Controlling the power input to the main electric drive with VVVf technique can generate almost matching demand torque characteristics. A much smaller flywheel is able to improve the accuracy to have better torque matching. This paper deals with estimation of necessary moment of inertia of flywheel in view of minimizing the difference in the required demand torque characteristics and the generated supply torque characteristics.