High Torque Conditions Research Articles

Surface electromyographic frequency characteristics of the quadriceps differ between continuous high- and low-torque isometric knee extension to momentary failure.

Surface EMG (sEMG) has been used to compare loading conditions during exercise. Studies often explore mean/median frequencies. This potentially misses more nuanced electrophysiological differences between exercise tasks. Therefore, wavelet-based analysis was used to evaluate electrophysiological characteristics in the sEMG signal of the quadriceps under both higher- and lower-torque (70% and 30% of MVC, respectively) isometric knee extension performed to momentary failure. Ten recreationally active adult males with previous resistance training experience were recruited. Using a within-session, repeated-measures, randomised crossover design, participants performed isometric knee extension whilst sEMG was collected from the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL). Mean signal frequency showed similar characteristics in each condition at momentary failure. However, individual wavelets revealed different frequency component changes between the conditions. All frequency components increased during the low-torque condition. But low-frequency components increased, and high-frequency components decreased, in intensity throughout the high-torque condition. This resulted in convergence of the low-torque and high-torque trial wavelet characteristics towards the end of the low-torque trial. Our results demonstrate a convergence of myoelectric signal properties between low- and high-torque efforts with fatigue via divergent signal adaptations. Further work should disentangle factors influencing frequency characteristics during exercise tasks.

Research on electro-hydraulic composite drive winch and energy recovery system for mobile crane

Owing to the high power consumption and limited control precision of traditional hydraulic drive winch systems, this study proposes hydraulic and electric-type energy recovery systems. The accumulator used in the hydraulic type has low energy density, which makes it difficult to store a large amount of energy. Meanwhile, the electric motor/generator used in the electric type cannot solve the secondary slip because of oil leakage, which leads to low controllability and high-power consumption under near-zero speed and high torque conditions. Thus, based on electric construction machinery with high-pressure, energy-dense electric energy storage units, this study proposes an electro-hydraulic composite drive winch and energy recovery system and control strategy for mobile cranes. Considering the good control characteristics of the electric motor/generator and the high-power density of the hydraulic accumulator, this hydroelectric composite drive and energy recovery system may solve the secondary sliding challenge and ensure large torque output at near-zero speed. A simulation model of the mobile crane is established to verify the feasibility of the proposed system and control strategy. The research results showed that the system is more efficient at recovering energy when the weight is lowered by a greater distance.

Measuring the through-plane and in-plane oxygen apparent diffusion coefficients in the gas diffusion layer

Accurately predicting oxygen mass transport resistance and current distribution in fuel cells requires significant knowledge of oxygen diffusion coefficients in both in-plane and through-plane directions. However, there are few methods for measuring in-plane oxygen diffusion coefficients, which are important parameters for simulating oxygen flux distribution in gas diffusion layers (GDLs). In this study, we establish measurement methods and calculations for both in-plane and through-plane oxygen diffusion coefficients. Using in-house designed cells, we measure the in-plane and through-plane oxygen apparent diffusion coefficients of a commercial carbon paper (AvCarb EP40) at various torques and gas flow rates. We also simulate oxygen flux distributions in the GDL under each torque and gas flow rate. Our results show that the channel part is the major contributor to total oxygen flux at high torque conditions and that an increase in torque leads to a decrease in the contribution from the land part. Simulation results also suggest that a higher gas flow rate and lower torque contribute to a more uniform distribution of oxygen flux in the GDL.

Experimental studies on premixed charge and reactivity-controlled compression ignition combustion modes using gasoline/diesel fuel combination

Homogeneous charge compression ignition (HCCI) is a promising technology to reduce NOx and soot emissions in compression ignition (CI) engines. However, this technology lacks combustion control to circumvent the knocking and misfire limitations. Premixed charge compression ignition (PCCI) and reactivity-controlled compression ignition (RCCI) are techniques that use partial homogeneous charge to reduce NOx and soot emissions. Here, combustion is regulated either by controlling the injection timing or fuel reactivity. PCCI uses a part of fuel as premixed to form a partially homogeneous charge and the rest as direct-injected. RCCI, on the other hand, uses a low reactive fuel (LRF) for port injection to form a partially homogeneous charge and a high reactive fuel (HRF) for direct injection. In this work, we studied PCCI and RCCI modes using commercially available fuels like diesel and gasoline, and we compared the results with diesel baseline operation. Adding 40% (by weight) heated diesel port injection to normal diesel operation in PCCI mode at different loads showed a minimum reduction in NOx and smoke emissions by 15% and 6%, respectively, when compared with diesel baseline. This mode was found to be equally efficient with diesel baseline operation at low torque conditions. Similarly, adding 40% (by weight) of gasoline port injection to normal diesel operation in RCCI mode at different loads showed a minimum reduction in NOx and smoke emissions by 20% and 14%, respectively, when compared with diesel baseline. This mode was found to be equally efficient with diesel baseline operation at high torque conditions.

응력 집중 저감을 위한 머드 모터 커넥팅 로드 설계 개선에 관한 연구

Ground drilling technology for drilling has an environment where the major parts are prone to damage due to high stress, torque, and harsh operating conditions that can occur in the rotary power transfer structure. Research for preventing this damage is very important, as it can be coupled with the nature of drilling operations that take a long time in operation, which can lead to enormous cost and time consumption. Previous work investigated the cause of damage by analyzing the working environment and breakage of drilling holes for connecting rods, and a power transfer component of directional mud motors used in ground drilling systems. The material properties by heat treatment conditions for applied materials were analyzed. Based on prior work, we evaluated whether the stress concentration part shown in the analysis results matched the actual damage occurring point by conducting a structural analysis of the connecting rod, a damaged part, using the finite element analysis. We also analyzed how to reduce the stress concentration phenomenon that occurs during the mud motor operation by conducting part shape and design changes between the connecting rod and key parts.

Experimental Investigation on Control of an Infinitely Variable Transmission System for Tidal Current Energy Converters

High operation performance of a tidal current energy converter (TCEC) requires a gear transmission with a continuously variable speed ratio for low-speed and high-torque conditions. A nonlinear closed-loop control combined with an integral time-delay feedback control is developed to adjust the speed ratio of an infinitely variable transmission (IVT) system for TCECs. A speed ratio control for the IVT system involves a forward speed controller and a crank length controller for different tidal current speed ranges. The time-delay control is designed to reduce speed fluctuations of the output speed of the IVT with an accurate speed ratio. Experimental investigation was carried out to test the validity of the proposed control strategy for the IVT system. An instrumented rotation speed measurement system is designed so that quantities needed for the time-delay control variable can be measured. Experimental results show that the speed ratio of the IVT with the proposed control strategy can achieve an excellent tracking response for the desired constant output speed and reduce speed fluctuations of the output speed of the IVT by the time-delay feedback control.

Road Load Based Model for Vehicle Repair and Maintenance Cost Estimation

A techno-economic model is developed based on road-load simulation results expressed in relation to slip energy (SE) at the tire–pavement interface and the repair and maintenance (R&M) cost obtained from published sources and data from state agencies. Tire SE allows for the consideration of aggressive acceleration and deceleration, high torque conditions (for instance, driving an upslope grade), and roadway curvature. Tire SE data used in this effort were generated using physics-based simulation models of different vehicle types for arrays of road conditions (e.g., grades, curvatures) and driving cycles (i.e., vehicle speed profiles). R&M costs were estimated for various vehicle categories and accumulated vehicle mileage. The approach is based on relating the probability density functions (PDFs) of SE and R&M costs. Asymptotic series expansion for an incomplete gamma function was used to approximate the gamma functions and to determine the gamma ratio function that is used as the coefficient to SE to estimate R&M costs. The average R&M cost per mile results from the model compared with the arithmetic mean R&M cost data from fleet operators and published data. The model can serve as a method for predicting R&M cost as a function of road load to vehicle fleet.

Alleviation Technique for Thermal Concentration on Power Devices Driving a PMSM under Zero-Speed and High-Torque Condition

Alleviation Technique for Thermal Concentration on Power Devices Driving a PMSM under Zero-Speed and High-Torque Condition

Commercial Vehicle Intake System Flow Field Mechanism Analysis

The numerical simulation and fluid dynamics simulation of the internal flow field and its influence mechanism of a commercial vehicle intake system were carried out aim at studying the flow field characteristics of the intake system. The internal and surface pressure, velocity, and turbulent kinetic energy distribution of intake systems under the rated operating conditions and three high torque conditions of the engine were analyzed. The simulation results showed that with the increase of the mass flow of the intake air, the pressure distribution on the surface of the intake system increased, and the pressure drop of the inlet and outlet increased rapidly. With the increase of the mass flow, the scale and number of vortexes in the intake system increased sharply. The distribution of turbulent kinetic energy is more related to the velocity field distribution. However the internal turbulent energy distribution of the intake system is concentrated under one condition. As the intake air mass flow rate drops from 1,500 kg/h to 764 kg/h, the pressure drop of the intake system drops from 2,858,566 Pa to 721,411 Pa; the average turbulent energy decreases from 5.41 m2/s2; to 0.896 m2/s2. In this paper, the research on the flow field of the engine intake system aims to provide research directions for the early stage of the structural design of the intake system of large agricultural vehicles.

Experimental investigations on performance, emission and combustion characteristics of Diesel-Hydrogen and Diesel-HHO gas in a Dual fuel CI engine

Stringent emission norms being followed throughout the world increases the demand for clean and green fuels. Gaseous fuels like compressed natural gas (CNG), liquefied petroleum gas (LPG) and hydrogen are promising alternatives to conventional diesel and gasoline. The use of hydrogen in the IC engine has gained interest among the researchers as it can be easily produced from water through electrolysis. Electrolysis of water produces stoichiometric mixture of hydrogen and oxygen in the ratio of 2:1. This study investigates the performance and emission characters of introducing hydrogen and HHO gas in the inlet manifold of a compression ignition engine in dual fuel mode. Experiments were conducted at 5 different torque conditions where hydrogen and HHO gases are supplied at the flow rate of 6, 12, 18, 24, 30 and 36 LPM along with air in the inlet manifold. The HHO gas was synthesized using stored hydrogen and oxygen in the ratio of 2:1. The performance and emission characteristics were noted for all the conditions. The introduction of hydrogen and HHO gas has reduced the diesel energy share ratio by 86% and 70% respectively at no torque condition.HC emission was found to be decreased at high torque condition when compared to neat diesel operation. Significant increase in NOx emission was noted with increase in gases substitution and torque. CO2 and smoke emissions showed positively decreasing trend as the gas percentage increases, due to reduction in carbon content of the fuel mixture. The cylinder pressure reduced with increase in the flow rate of gases. Combustion duration increases with increase in flow rate as well as increase in torque. It was noted that Brake Thermal Efficiency (BTE) reduced for all operating conditions except at 6 LPM of HHO gas addition in the combustion chamber.

A Performance Evaluation System of an HTS Pole for Large-Scale HTS Wind Power Generators

Currently, the bottleneck in the development of large-scale high temperature superconducting (HTS) wind power generators is that high torque causes problems in HTS coils. Therefore, it is necessary to confirm the applicability to full generators by evaluating the performances of HTS coils in high torque condition. This paper deals with a performance evaluation system (PES) design for a 10-MW HTS wind power generator and a comparative analysis of the PES with the full generator. The magnetic field distribution and output power of the full generator were presented. The rated output torque and the force of the 10-MW HTS generator were calculated, and the PES for the full generator consisted of three HTS poles and the 1/20 times stator of the full generator. The modeling verification process of the PES for the generator was defined. The stator winding and circuit diagram of the PES were illustrated. Finally, the torque and force of the full generator and PES were analyzed and compared. As a result, the electromagnetic forces of one HTS pole were calculated considering the stator interaction, and the performance of the HTS pole using the PES was proven similar to the HTS pole in the full generator. The PES was confirmed suitable for testing HTS coils for large-scale HTS generators.

First principles and integrated modelling achievements towards trustful fusion power predictions for JET and ITER

Predictability of burning plasmas is a key issue for designing and building credible future fusion devices. In this context, an important effort of physics understanding and guidance is being carried out in parallel to JET experimental campaigns in H and D by performing analyses and modelling towards an improvement of the understanding of DT physics for the optimization of the JET-DT neutron yield and fusion born alpha particle physics. Extrapolations to JET-DT from recent experiments using the maximum power available have been performed including some of the most sophisticated codes and a broad selection of models. There is a general agreement that 11–15 MW of fusion power can be expected in DT for the hybrid and baseline scenarios. On the other hand, in high beta, torque and fast ion fraction conditions, isotope effects could be favourable leading to higher fusion yield. It is shown that alpha particles related physics, such as TAE destabilization or fusion power electron heating, could be studied in ITER relevant JET-DT plasmas.

Thermal management integrated with three-dimensional heat pipes for air-cooled permanent magnet synchronous motor

Permanent magnet synchronous motors (PMSMs) are widely used in pure or hybrid electric vehicles for transportation applications. The cooling strategy for PMSMs is still a challenge in the field of thermal engineering. This study presents a novel thermal management method/design based on phase-change heat pipes for PMSMs. Two thermal management modules (TMMs) with different heat-pipe layouts are prepared, including the straightly embedded module in an enclosure (SEME) and three-dimensional rounding module (RM). The impacts of different ambient temperature and various working condition on the cooling effectiveness of the two modules are analyzed experimentally and numerically. Experimental results show that by replacing the convectional motor stator with this heat-pipe-based enclosure component, the effective time to control the temperature of a PMSM can be prolonged by 28.6 and 21.4% when the motor operates continuously under high-speed and high-torque conditions, respectively. The peak temperature of the PMSM under rated conditions can be significantly reduced by 22.3%, which helps increase the power density of PMSMs. Besides, both experimental and simulation results show that the use of a SEME promotes higher heat dissipation ability than RM.

The Programmable Permanent Magnet Actuator: A Paradigm Shift in Efficiency for Low-Speed Torque-Holding Robotic Applications

In this letter, we propose a new type of electromagnetic actuator called the “programmable permanent magnet” (PPM) actuator. The PPM actuator is designed to tackle low-speed high-torque applications where classic electromagnetic actuators are highly inefficient. The PPM actuator is based on the application of pulsed current to magnetize a hard ferromagnetic stator that is made of individual SmCo (custom grade) magnets placed in a Halbach array configuration. The motor creates a springlike torque function that generates up to 0.2 N·m. Unlike electromagnetic actuators, by design, the PPM actuator does not draw current while exerting torque. Instead, the motor's power consumption depends on its rotational speed or torque variations. The PPM actuator is, by consequence, most efficient, whereas classical electromagnetic motors are most inefficient, and is a new alternative to actuators for robotic applications, which tend to operate in low-speed, high-torque conditions. The prototyped PPM actuator measures 47 mm in diameter, with a height of 35 mm and weight of 200 g, and has been successfully integrated in a commercially available 2-finger gripper from Robotiq, Inc.

Experimental and Numerical Investigation on Windage Power Losses in High Speed Gears

Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. An evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Mechanical power losses are usually distinguished into two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid dynamics of the environment, which surrounds the gears. The relative magnitude of these phenomena is dependent on the operative conditions of the transmission: load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. A new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry (PIV) measurements for investigating the flow field surrounding the rotating gear. The experiment has been computationally replicated, performing Reynolds-averaged Navier–Stokes (RANS) simulations in the context of conventional eddy viscosity models, achieving good agreement for all of the speed of rotations.

Characterization and performance analysis of a new type of a high water-based hydraulic motor with a self-balanced distribution valve mode

High water-based hydraulic motors (HWBHMs) with advantages including higher specific power and shorter acceleration and braking time can be used to directly drive loads. In particular, low speed and high torque high water-based hydraulic motors work well in limited space and for special applications (open flame areas). However, traditional structure and flow distribution mechanisms cause serious leakage and lower work efficiency for low speed and high torque high water-based hydraulic motors. Thus, a new structure and flow distribution mechanism with self-balanced distribution valve groups for a high water-based hydraulic motor need to be developed to work in high pressure, low speed, and high torque conditions. In this paper, a high water-based hydraulic motor was theoretically analyzed and the working principle behind a high water-based hydraulic motor was briefly introduced. Numerical simulations were performed to examine the effects of the distribution valve parameters on the distribution performance. An orthogonal test method was used to determine the optimized structure parameters. A simulation model of a high water-based hydraulic motor was established using the AMESim simulation method to validate the feasibility of the optimized structure parameters. This research has laid a foundation for the further development of a high water-based hydraulic motor with low speed and high torque.

Direction-Specific Impairments in Cervical Range of Motion in Women with Chronic Neck Pain: Influence of Head Posture and Gravitationally Induced Torque.

BackgroundCervical range of motion (ROM) is commonly assessed in clinical practice and research. In a previous study we decomposed active cervical sagittal ROM into contributions from lower and upper levels of the cervical spine and found level- and direction-specific impairments in women with chronic non-specific neck pain. The present study aimed to validate these results and investigate if the specific impairments can be explained by the neutral posture (defining zero flexion/extension) or a movement strategy to avoid large gravitationally induced torques on the cervical spine.MethodsKinematics of the head and thorax was assessed in sitting during maximal sagittal cervical flexion/extension (high torque condition) and maximal protraction (low torque condition) in 120 women with chronic non-specific neck pain and 40 controls. We derived the lower and upper cervical angles, and the head centre of mass (HCM), from a 3-segment kinematic model. Neutral head posture was assessed using a standardized procedure.FindingsPrevious findings of level- and direction-specific impairments in neck pain were confirmed. Neutral head posture was equal between groups and did not explain the direction-specific impairments. The relative magnitude of group difference in HCM migration did not differ between high and low torques conditions, lending no support for our hypothesis that impairments in sagittal ROM are due to torque avoidance behaviour.InterpretationThe direction- and level-specific impairments in cervical sagittal ROM can be generalised to the population of women with non-specific neck pain. Further research is necessary to clarify if torque avoidance behaviour can explain the impairments.

Experimental studies on simultaneous injection of ethanol–gasoline and n-butanol–gasoline in the intake port of a four stroke SI engine

Two separate injectors were used to simultaneously inject ethanol and gasoline in the intake port of a single cylinder SI engine. The relative amounts of the two fuels on mass basis and the spark timing were changed using a real time controller. Neat gasoline could be used till 35% throttle beyond which higher thermal efficiency and torque could be obtained by switching to 30% ethanol. This system can be used to provide sufficient margin for knock free operation. Efficiency and torque were better at a mass ratio of 1:1 (50% of ethanol and 50% of gasoline) due to faster combustion as a result of better mixture preparation as compared to conventional pre-blended injection of gasoline and ethanol. However, NO and HC were slightly elevated. This dual injection system can allow the use of ethanol only when needed while permitting stoichiometric operation even under high torque conditions by adjusting the proportion of ethanol. Ethanol–gasoline and n-butanol–gasoline were compared in terms of performance and emission with dual injection strategy. The amount of n-butanol has to be increased with increase in torque conditions for better performance and low emission. The benefit of using ethanol with gasoline is significant at high torque conditions.

An Investigation of Hydraulic Motor Efficiency and Tribological Surface Properties

Hydraulic motor efficiency does not depend upon viscosity alone. Under low-speed, high-torque conditions, hydraulic motors operate in the boundary regime and, therefore, surface interactions of lubricant additives can affect friction and efficiency. This article presents an investigation of boundary film formation, friction, and surface topography in benchtop tribometers and hydraulic motors. Fluids investigated included those with varied antiwear packages (zinc dialkyldithiophosphate [ZDDP], ashless) and friction modifiers (with and without) and base oil (Group I, Group III). The mechanical efficiencies of geroler, axial piston, bent-axis, and radial piston motors were measured under low-speed, high-torque conditions. The addition of a friction modifier to an ashless hydraulic fluid increased the efficiency of the motors at low speed. Energy-dispersive X-ray spectroscopy (EDX) analysis of motor surfaces after testing revealed the presence of tribochemical films from the hydraulic fluid additives. In benchtop tribometer testing, the friction modifier reduced friction significantly but also increased wear. This could be related to surface competition of the friction modifier and antiwear chemistries, as evidenced by the reduced concentration of phosphorus on the surface. These findings are significant because they provide insights toward the development of fluids that can enhance motor efficiency but also demonstrates the need for a well-balanced additive package so that improved motor efficiency can be achieved without affecting other important properties of the fluid.

PMSM Control Simulation Based on Pumping Unit

To study direct drive pumping unit of operating state, permanent magnet synchronous motor open-loop control system was used to model and simulate based on Matlab/Simulink software, and analyzed the waveforms change with different torque. The results indicate that permanent magnet synchronous motor can operate smoothly under low speed and high torque condition, and can meet work requirement of direct drive pumping unit with acceleration. The proposed Simulink simulation system can achieve stable control in actual operation, and its effectiveness was confirmed experimentally. Results of simulation analysis have some certain practical value for pumping unit driven by permanent magnet synchronous motor. DOI : http://dx.doi.org/10.11591/telkomnika.v12i4.4836