Torque Drop Research Articles

Stabilizing control of two-wheeled wheelchair with movable payload using optimized interval type-2 fuzzy logic

The control schemes of a wheelchair having two wheels with movable payload utilizing the concept of a double-link inverted pendulum have been investigated in this article. The proposed wheelchair has been simulated using SimWise 4D software considering the most efficient parameters. These parameters are extracted using the spiral dynamic algorithm while being controlled with interval type-2 fuzzy logic controller (IT2FLC). The robustness and stability of the implemented controller are assessed under different situations including standing upright, forward motion and application of varying directions and magnitudes of outer disturbances to movable (up and down) system payload. It is shown that the two-wheeled wheelchair adopted by the newly introduced controller has achieved a 94% drop in torque for both Link1 and Link2 and more than 98% fall in distance travelled in comparison with fuzzy logic control type-1 (FLCT1) controller employed in an earlier design. The present study has further considered the increased nonlinearity and complexity of the additional moving payload. From the outcome of this study, it is obvious that the proposed IT2FLC-spiral dynamic algorithm demonstrates better performance than FLCT1 to manage the uncertainties and nonlinearities in case of a movable payload two-wheel wheelchair system.

Experimental Investigation of the Seamless Gearshift Mechanism Using an Electric Motor and a Planetary Gear-Set

Vehicle transmission which has discrete gear-stages inevitably produces torque drop during shifting gears. This torque drop should be minimized because it may lead to uncomfortable driving feeling and degradation of acceleration performance. In accordance with the spread of electric-powered vehicle technology, this study proposes novel transmission architecture to eliminate torque drop during shifting gears by using one electric motor and verifies its operating concept through experiments with a test-bench. The proposed transmission, called CGST (clutchless geared smart transmission) can synchronize the gear-shaft to be engaged for the next gear-stage with the output shaft by using a planetary gear-set and an electric motor. The CGST has a dual input gear-box with even and odd gear-stages on different input shafts, and the planetary gear-set and the electric motor control the speeds of each input shafts to smoothly engage the next gear-stage. This idea was verified by the simplified test-rig in this study. Three distinct scenarios for gear-shift including starting from engine idling, odd to even gear-shift, and even to odd gear-shift were conducted in the experiment. The shifting performance of the CGST was evaluated by comparing it with the results of the manual transmission (MT). As a result, the CGST shows only 24% of torque drop of the MT, and torque oscillation followed after gear-shifting is reduced by 26%. Although the developed test bench was of limited size, the possibility and expected performance of the CGST have been confirmed as the solution for seamless transmission.

Simulation Study on Dynamics of Hydraulic Turbines Used in Drilling Engineering

Hydroturbines have a very wide range of applications, which are commonly found in wind turbines, water turbines, aero engines, etc. This paper provided a detailed turbine design and a design method of turbine blade shape. Using the CFD (computational fluid dynamics) method, based on the realizable k-ɛ turbulence model and Euler multiphase flow model, the effects of different external loads, blade numbers, blade installation angles, and flow rates on the force condition of turbine and the influence of different solid contents, particle sizes, and densities on turbine performance were studied. The simulation results show that, under the action of fluid, when the starting torque of turbine is larger than the external load, the turbine starts to move, the angular velocity increases until it remains constant, the absolute value of impact force decreases, and the impact torque decreases until it is equal to the external load; while the starting torque of turbine is smaller than the external load, the turbine stays still. The increase of the particle size, content, and density of the solid phase will lead to an increase in the torque and pressure drop of the turbine and ultimately leads to the increase of turbine input, output power, and efficiency.

The Effect Of Concentric Prime Movers Vs. Synergist Muscle Contraction On Coactivation Ratios

PURPOSE: The purpose of this study was to examine the coactivation ratio of agonist to antagonist muscle groups with varying pre-exhaustion protocols, and to see if postactivation potentiation is influenced by pre-exhaustion. METHODS: Eight college age males and females were recruited for the study. Each participant visited the Human Performance Laboratory four times over the duration of the study. Subjects were monitored via EMG and randomly performed 1 set of 50 repetitions maximal voluntary knee extension, knee flexion, and knee extension/flexion at 60°•s-1 using an isokinetic machine on the dominant leg. They performed 1 set of 10 repetitions of modified Peterson step-up testing at pre-exercise, immediately post-exercise, and seven (7) min following exercise. RESULTS: The 50 repetitions of isokinetic knee extension, flexion, extension/flexion at 60•s-1resulted in a significant drop in peak torque in all groups (P<0.01). Pre-exhausting the agonist muscle group prior to Pearson step-up improved agonist skeletal muscle motor unit recruitment (P<0.05). Pre-exhausting the antagonist muscle group with flexion and combination prior to Pearson step-up did not have any effect on agonist skeletal muscle motor unit recruitment. Pre-exhausting the agonist muscle group down-regulated antagonist muscle activity. Coactivation improved only by fatiguing the agonist muscle group. Postactivation potentiation was only affected by fatiguing the agonist muscle group (P<0.05). CONCLUSIONS: We conclude that pre-exhausting the agonist muscle group might be beneficial for improving muscle activity in functional rehabilitation exercises and during the period of recovery. Given the small number of subjects in this study, additional research using larger subject groups and different fatiguing and post-activation protocols is warranted to support the use of pre-exhaustion techniques to improve activity/recruitment of atrophied muscle in physical therapy settings.

GPU-accelerated numerical analysis of jet interference in a six-jet Pelton turbine using Finite Volume Particle Method

The Pelton turbine is an impulse turbine typically installed for high head hydroelectric power plants. For a site with a rated head H and discharge Q, a higher specific speed turbine results in a more compact generating unit with reduced manufacturing costs but requires a larger number of jets. However, by increasing the number of jets and specific speed, the water jets tend to interfere, creating a significant energy loss. In the present research, the interaction between two adjacent jets in a six-jet Pelton runner is simulated using a GPU-accelerated particle-based in-house solver based on the 3-D Finite Volume Particle Method (FVPM). The numerical simulations are performed at eight operating points ranging fromN/NBEP=0.89 to N/NBEP=1.31,where N is the runner rotational speed, and BEP is the Best Efficiency Point. The torque and efficiency trends, as well as the speed range in which the jets interfere, are well-captured, which provides confidence in the use of the numerical simulations for the design optimization of Pelton turbines. The simulations, in particular, evidence a significant torque and efficiency drop at high rotational speeds, due to jet interference. Furthermore, jet disturbance yields load fluctuations at rotational speeds both lower and higher than the NBEP, which is likely to amplify fatigue damage. Both phenomena are worth considering that in the design process of a Pelton machine.

Numerical methodology to predict and analyze cavitating flows in a Kaplan turbine

A computational methodology to predict the appearance and the evolution of the cavitation phenomena in a scale model of a 5–blades Kaplan turbine was developed. The cavitating flow was modeled by a homogeneous approach with a barotropic state law and the k − ω SST turbulence model. RANS simulations were performed, near the Best Efficiency Point, on two computational domains (D1 and D2) comprising one periodic interblades channel consisting of the guide vanes, the runner blade and the cone (domain D1) or taking into account the entire draft tube (domain D2). At first, non–cavitating simulations were carried out in domain D1 in order to match numerical conditions to the experimental ones (similar mass flow Q, head H and mainly the torque T) via an iterative procedure. From this reference operating point obtained in free–cavitation regime, cavitating simulations were performed on both computational domains by reducing the Thoma number, σ. Two different inlet boundary conditions were tested: the classical one, imposing the mass flow rate Q; the new one, fixing the total pressure and, consequently, keeping the machine head H constant during the cavitation drop, as in experiments. In all the performed calculations, the outlet boundary condition is given by a constant static pressure. Computed torque and efficiency drop curves were compared to available experimental data. The best results were obtained with the computational domain D2 applying a constant total pressure on the inlet. The torque and efficiency evolutions were well–predicted with the proposed calculation methodology, and the numerical cavitation structures agreed with experimental observations. Analyses of the blade loading during cavitation breakdown are also proposed in the article. Unsteady simulations are under investigation to improve the prediction and the analyses of more developed cavitating regimes.

Neural Network-Based Muscle Torque Estimation Using Mechanomyography During Electrically-Evoked Knee Extension and Standing in Spinal Cord Injury.

This study sought to design and deploy a torque monitoring system using an artificial neural network (ANN) with mechanomyography (MMG) for situations where muscle torque cannot be independently quantified. The MMG signals from the quadriceps were used to derive knee torque during prolonged functional electrical stimulation (FES)-assisted isometric knee extensions and during standing in spinal cord injured (SCI) individuals. Three individuals with motor-complete SCI performed FES-evoked isometric quadriceps contractions on a Biodex dynamometer at 30° knee angle and at a fixed stimulation current, until the torque had declined to a minimum required for ANN model development. Two ANN models were developed based on different inputs; Root mean square (RMS) MMG and RMS-Zero crossing (ZC) which were derived from MMG. The performance of the ANN was evaluated by comparing model predicted torque against the actual torque derived from the dynamometer. MMG data from 5 other individuals with SCI who performed FES-evoked standing to fatigue-failure were used to validate the RMS and RMS-ZC ANN models. RMS and RMS-ZC of the MMG obtained from the FES standing experiments were then provided as inputs to the developed ANN models to calculate the predicted torque during the FES-evoked standing. The average correlation between the knee extension-predicted torque and the actual torque outputs were 0.87 ± 0.11 for RMS and 0.84 ± 0.13 for RMS-ZC. The average accuracy was 79 ± 14% for RMS and 86 ± 11% for RMS-ZC. The two models revealed significant trends in torque decrease, both suggesting a critical point around 50% torque drop where there were significant changes observed in RMS and RMS-ZC patterns. Based on these findings, both RMS and RMS-ZC ANN models performed similarly well in predicting FES-evoked knee extension torques in this population. However, interference was observed in the RMS-ZC values at a time around knee buckling. The developed ANN models could be used to estimate muscle torque in real-time, thereby providing safer automated FES control of standing in persons with motor-complete SCI.

The repeated bout effect can occur without mechanical and neuromuscular changes after a bout of eccentric exercise.

Changes in muscle fascicle mechanics have been postulated to underpin the repeated bout effect (RBE) observed following exercise-induced muscle damage (EIMD). However, in the medial gastrocnemius (MG), mixed evidence exists on whether fascicle stretch amplitude influences the level of EIMD, thus questioning whether changes in fascicle mechanics underpin the RBE. An alternative hypothesis is that neural adaptations contribute to the RBE in this muscle. The aim of this study was to investigate the neuromechanical adaptations during and after repeated bouts of a highly controlled muscle lengthening exercise that aimed to maximize EIMD in MG. In all, 20 subjects performed two bouts of 500 active lengthening contractions (70% of maximal activation) of the triceps surae, separated by 7days. Ultrasound constructed fascicle length-torque (L-T) curves of MG, surface electromyography (EMG), maximum torque production, and muscle soreness were assessed before, 2hours and 2days after each exercise bout. The drop in maximum torque (4%) and the increase in muscle soreness (24%) following the repeated bout were significantly less than following the initial bout (8% and 59%, respectively), indicating a RBE. However, neither shift in the L-T curve nor changes in EMG parameters were present. Furthermore, muscle properties during the exercise were not related to the EIMD or RBE. Our results show that there are no global changes in gastrocnemius mechanical behavior or neural activation that could explain the observed RBE in this muscle. We suggest that adaptations in the non-contractile elements of the muscle are likely to explain the RBE in the triceps surae.

Impact of Geometry Parameters of a Sliding Surface of a Bearing on Tribological Characteristics of Sliding Bearings

One of the characteristic parameters which is important for functioning of a journal bearing is relative clearance which has a direct impact on the bearing performance during an initial run-in period and standard operation. An equally important aspect is the proper selection of journal and bearing materials, as it ensures their proper cooperation, i.e., possibly low coefficient of friction, low resistance to motion and minimal wear. Another important issue is the geometry of the working surface of the bearing, i.e., giving it a proper shape by the use of lubricating microgrooves (micro-channels) which support the formation of an oil film. Forming a sliding surface in such a manner contributes to a better cooperation between the journal and the bearing. The paper presents the results of tribological tests, specifically the impact of the use of two types of lubricating microgrooves, made on the internal surface of the bearing on tribological characteristics. The tests were conducted for journal bearings composed of the bearing coated with casted SnSb12Cu6Pb alloy and the steel journal. During the tests, the friction torque, bearing temperature and voltage drop on the internal resistance of oil film were registered. As a result of the investigation, it was noticed that the use of rounded lubricating microgrooves has a positive effect on the tribological characteristics and can contribute to increasing the load-bearing capacity and durability of the journal bearings.

Reduction of On-Load Terminal Voltage Distortion in Fractional Slot Interior Permanent Magnet Machines

On-load terminal voltage distortion can significantly reduce the flux weakening operation region of electrical machines. This paper investigates the effectiveness of several harmonics reduction methods, e.g., rotor skewing, rotor pole shaping, and stator tooth-tip shaping, on the terminal voltage distortion reduction in fractional slot interior permanent magnet machines. It is found that skewing can only reduce the peak terminal voltages, but not total harmonic distortion, while the average torque is also notably lower. However, on-load terminal voltage distortions can be greatly reduced by rotor pole or stator tooth-tip shaping with only a slight average torque drop. It is found that the local magnetic saturation is largely alleviated based on the magnetic permeance and flux path modification. Finally, these analyses are experimentally validated based on the measured torque speed curves of two prototype machines having the same stator, but different rotors with or without rotor pole shaping.

Analysis and Design of a Hybrid Rare-Earth-Free Permanent Magnet Reluctance Machine by Frozen Permeability Method

Hybrid-type switched reluctance machine (SRM) by adding permanent magnets (PMs) in the stator of the SRM is gaining significant attention in order to solve the rare-earth PM problems, such as price instability and environmental problems. However, the addition of PMs in an SRM leads to positive and negative effects on torque production at the same time, because PMs in the stator assist the flux linkage of phase windings but aggravate total reluctance due to a slot for each PM. This paper is to propose a hybrid PM reluctance machine (PMRM) (hereinafter referred to as a hybrid PMRM) having a rare-earth-free PM in the stator, and the machine is analyzed and designed in terms of PM thickness by torque separation during freezing permeability in steel. The level of excitation current is not important in the variation of reluctance torque and mutual torque, but the thickness of PM has a major effect on both reluctance torque and mutual torque. Although bigger thickness in PM causes negative effect on reluctance torque production, total torque in the hybrid PMRM has been improved by a distinct margin, since mutual torque enhancement is much larger than reluctance torque drop. As a result, the proposed PMRM has an increase of 10.1% in efficiency compared with the same design without PM.

Comparative Study of Drag Reducers for Light Hydrocarbon Flow

The study of drag reduction is very important for the transport of hydrocarbons through long pipelines. The reduction in pressure drop along the pipeline leads to larger volumes transported for the same pumping energy, or lower power pumps can be used to carry the same flow rate. In this study, two drag reducer agents were tested on commercial diesel. The experiments were run in rheometer and pipe in order to compare their relative capability to reduce torque and pressure drop, respectively. Despite the different flow mode and turbulence level in both methods, a qualitative correlation between their results could be established. The experiments conducted in a rheometer allow quickly selecting the best drag reducer agent with small sample volume and good accuracy. The limitations of this technique are also highlighted by comparison of the drag reduction measured using the two techniques.

Does a Mental Training Session Induce Neuromuscular Fatigue?

Mental training, as physical training, enhances muscle strength. Whereas the repetition of maximal voluntary contractions (MVC) induces neuromuscular fatigue, the effect of maximal imagined contractions (MIC) on neuromuscular fatigue remains unknown. Here, we investigated neuromuscular alterations after a mental training session including MIC, a physical training session including MVC, and a combined training session including both MIC and MVC of the elbow flexor muscles. Ten participants performed 80 MIC (duty cycle, 5-s MIC and 10-s rest), 80 MVC (identical duty cycle), or 80 MVC and 80 MIC (5-s MVC, 2-s rest, 5-s MIC, and 3-s rest) in three separate sessions. MVC torque was assessed five times over the course of the training and 10 min after the end of the training in the three protocols. Central activation ratio (CARc), reflecting central fatigue, and corticospinal excitability, at rest and during MIC, were estimated using transcranial magnetic stimulation. Both the physical training and the combined training induced an approximately 40% drop of MVC torque, accompanied with an approximately 10% decrease of CARc without significant difference between the two sessions. On the contrary, the repetition of MIC did not reduce maximal force production capacity and did not alter CARc. Corticospinal excitability was always facilitated during MIC compared with that during rest, ensuring that the participants imagined the desired movement. These results suggested that one session of mental training alone or combined with physical training do not induce (additional) neuromuscular fatigue despite the repetitive activation of the corticospinal track. Motor imagery may be added to physical practice to increase the total workload without exacerbating neuromuscular fatigue.

Role of the cytoskeleton in muscle transcriptional responses to altered use

In this work, the interaction between the loss of a primary component of the skeletal muscle cytoskeleton, desmin, and two common physiological stressors, acute mechanical injury and aging, were investigated at the transcriptional, protein, and whole muscle levels. The transcriptional response of desmin knockout (des(-/-)) plantarflexors to a bout of 50 eccentric contractions (ECCs) showed substantial overlap with the response in wild-type (wt) muscle. However, changes in the expression of genes involved in muscle response to injury were blunted in adult des(-/-) muscle compared with wt (fold change with ECC in des(-/-) and wt, respectively: Mybph, 1.4 and 2.9; Xirp1, 2.2 and 5.7; Csrp3, 1.8 and 4.3), similar to the observed blunted mechanical response (torque drop: des(-/-) 30.3% and wt 55.5%). Interestingly, in the absence of stressors, des(-/-) muscle exhibited elevated expression of many these genes compared with wt. The largest transcriptional changes were observed in the interaction between aging and the absence of desmin, including many genes related to slow fiber pathway (Myh7, Myl3, Atp2a2, and Casq2) and insulin sensitivity (Tlr4, Trib3, Pdk3, and Pdk4). Consistent with these transcriptional changes, adult des(-/-) muscle exhibited a significant fiber type shift from fast to slow isoforms of myosin heavy chain (wt, 5.3% IIa and 71.7% IIb; des(-/-), 8.4% IIa and 61.4% IIb) and a decreased insulin-stimulated glucose uptake (wt, 0.188 μmol/g muscle/20 min; des(-/-), 0.085 μmol/g muscle/20 min). This work points to novel areas of influence of this cytoskeletal protein and directs future work to elucidate its function.

Co-Surge Detection and Control for Bi-Turbo Engines with Experimental Evaluation

A V-type engine with a bi-turbocharger configuration utilizes the exhaust energy well which gives a fast torque response. An unwanted instability, called co-surge, can occur in such engines where the two interconnected compressors alternately go into flow reversals. If co-surge occurs, the control system must quell the oscillations with as little disturbance in engine torque as possible. A model of a bi-turbocharged engine is presented, combining a mean value engine model and a Moore-Greizer compressor model for surge. The model is validated against measurements on a vehicle dynamometer, showing that it captures the frequency and amplitude of the co-surge oscillation. The model is used to develop detection and control strategies for co-surge that rapidly returns the turbo to a stable operating point. Both simulations and experimental evaluation on the vehicle show that the developed strategies are successful in rapidly detecting and quelling co-surge. The selection of actuators is also studied. With no or small pressure drops over the throttle, it is necessary to use the bypass valves. However, for operating conditions with moderate and high pressure drops over the throttle, it is shown that it is sufficient to only open the throttle. This has the advantage, compared to opening the bypass valves, that it reduces the drop in boost pressure and thus reduces the drop in engine torque.

Eccentric contractions induce rapid isometric torque drop in dystrophin‐deficient dogs

We tested the hypothesis that eccentric contractions (ECCs) rapidly induce greater-than-normal isometric torque drop in dystrophin-deficient golden retriever muscular dystrophy (GRMD) muscles. ECCs were imposed by forcibly stretching activated muscles. The results indicate that isometric torque drop was greater in GRMD versus controls (P < 0.0001). Our findings support the hypothesis that ECCs induce greater-than-normal isometric torque drop in GRMD muscles. The magnitude of ECC-induced isometric torque loss may be an ideal clinical endpoint in the GRMD model.

Eccentric contractions induce rapid isometric torque drop in dystrophin-deficient dogs

Eccentric contractions induce rapid isometric torque drop in dystrophin-deficient dogs

Modeling Torque Versus Speed, Shot Noise, and Rotational Diffusion of the Bacterial Flagellar Motor

We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E. coli motor at various pH and temperature conditions. In particular, the dramatic drop of torque at high rotation speeds (the "knee") is shown to arise from saturation of the proton flux. Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads. This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions.

Measurements of Leakage and Power Loss in a Hybrid Brush Seal

Simplicity, low cost, and easy replacement make labyrinth seals the primary seal type in gas turbines. However, excessive leakage and potential for rotordynamic instability are well known issues. Brush seals effectively control leakage in air breathing engines, albeit only applied for relatively low pressure differentials. Hybrid brush seals (HBSs) are an alternative to resolve poor reliability resulting from bristle tip wear while also allowing for reverse rotation operation. The novel configuration incorporates pads contacting the shaft, which under rotor spinning lifts off due to the generation of a hydrodynamic pressure. The ensuing gas film prevents intermittent contact, thus lowering the operating temperature and thermal distortions and even eliminating bristle wear. The hybrid brush seal improves sealing, is more durable and reliable than conventional brush seals, and allows reverse shaft rotation without seal damage. This paper presents measurements of power loss and leakage in a HBS for increasing pressure differentials over a range of rotor speeds. The test HBS, Haynes-25 bristle pack (∼850 bristles∕cm) and 45 deg lay angle, is 166.4 mm in diameter and integrates 20-arcuate pads connected with thin electrical-discharge machined webs (EDM-webs) to the seal casing. The webs are designed with low radial stiffness to allow for rotor excursions and high axial stiffness to avoid pad pitching motions resulting from high pressure differentials across the seal. Measured drag power at low rotor speeds (&lt;11 m∕s at 1300 rpm) decreases as the pressure differential across the seal increases. At a fixed rotor speed, a significant drop in drag torque (and drag power) ensues as the supply pressure increases, thus demonstrating that a gas film separates the rotor from the seal pads. Additionally, the operating temperature measured at the rotor/seal interface remains approximately constant (∼24°C) during tests with shaft rotation (power loss and drag torque measurements) under pressurized conditions, indicating that the rotor and seal pads are not in contact. Flow rate measurements at room temperature (25°C) show an improved sealing ability with a leakage reduction of about 36% when compared with a first generation shoed-brush seal. The HBS calculated effective clearance (∼50 μm) is approximately 70% smaller than the radial clearance (∼180 μm) of an ideal noncontacting seal with similar rotor diameter. Improved brush seal technology will increase the efficiency of gas turbines while also aiding to improve the engine stability and to reduce vibrations.

Experimental study of heating fluid between two concentric cylinders with cavities

In this paper, we are concerned with the heating fluid in the annular space between two concentric cylinders where the inner cylinder with cavities is rotated and the outer cylinder is at rest. The effects of cavities of the inner cylinder on the heating fluid and the cavitation behavior are examined. We measured the flow rate, rotating speed of rotor, friction torque, temperature rise and pressure drop between inlet and outlet of this device. The flow rate of water ranged from 0.42×10−4 to 4.59×10−4 m3/s at the inlet. The friction torque and the quantity of heat of the inner cylinder with cavities were larger than the case of no cavities, and they increased as the rotating speed of inner cylinder increased. The efficiency was close to about 1 as the rotating speed of inner cylinder increased. The behavior of cavitation in the cavity on the surface of inner cylinder was discussed.