Low Torque Research Articles

The Fabrication of High-Hardness and Transparent PMMA-Based Composites by an Interface Engineering Strategy.

The high-hardness and transparent PMMA-based composites play a significant role in modern optical devices. However, a well-known paradox is that conventional PMMA-based composites with high loadings of nanoparticles usually possess high surface hardness at the cost of poor transparency and toughness due to the aggregation of nanoparticles. In this work, ideal optical materials (SiO2/PMMA composites) with high transparency and high surface hardness are successfully fabricated through the introduction of the flow modifier Si-DPF by conventional melt blending. Si-DPF with low surface energy and high transparency, which is located at the SiO2/PMMA interface, and nano-SiO2 particles are homogeneously dispersed in the PMMA matrix. As an example, the sample SiO2/PMMA/Si-DPF (30/65/5) shows outstanding transparency (>87.2% transmittance), high surface hardness (462.2 MPa), and notched impact strength (1.18 kJ/m2). Moreover, SiO2/PMMA/Si-DPF (30/65/5) also presents a low torque value of composite melt (21.7 N⋅m). This work paves a new possibility for the industrial preparation of polymer-based composites with excellent transparency, surface hardness, processability, and toughness.

ALGORITHM FOR DETERMINING THE TORQUE OF ELECTRIC MOTORS USING INDIRECT MEASUREMENT METHODS

Indirect torque measurement methods can be performed in a variety of ways, depending on the specific situation and available tools. One such way is to measure the displacement, or speed of rotation of the shaft and use this information to calculate the moment using the moment of inertia equation. For this, it is necessary to know the moment of inertia and the angular acceleration, which can be measured using a gyroscope or accelerometer. Another way is to measure the voltage and current in the electrical circuit connecting the motor and the power source by determining the power of the electric motor. However, indirect methods of measuring torques of electric motors are based on the measurement of other physical parameters that correlate with torque, such as current, voltage, rotation frequency, etc. These methods are often used because of their cost-effectiveness and ease of implementation, but they have some drawbacks. In particular: indirect methods are usually less accurate than direct methods because they depend on mathematical models and correlations between different parameters, which may be imprecise or incomplete; parameters that are measured by indirect methods may be influenced by external factors, which may affect the accuracy of measurements; calibration of devices is usually carried out in laboratory conditions, so the results may not reflect real operating conditions; the mathematical models used to determine the torque may be non-linear. This can lead to errors in measurements, especially at high or low torque values; indirect methods do not provide direct feedback about the real torque, which can lead to delays in process regulation and control. This can be critical for some applications where fast and accurate torque control is essential; indirect methods may be less efficient or unsuitable for some types of electric motors or applications. For example, when using high-frequency or multiphase motors, indirect methods may not provide sufficient accuracy or stability of measurements. The article examines algorithms for determining the rotational parameters of electric motors using indirect measurement methods. An analysis of the characteristics of electric motors according to their energy data was carried out. The measurement possibilities are determined based on the functional dependence of the torque on the power of the electric motor and the speed of rotation of its shaft. The characteristics of the power components are studied and the results of their simulation are given. An analysis of the methods of determining the angular velocity and angular acceleration of the electric motor shaft was carried out, and the role of these parameters in the determination of the torque was investigated. A two-channel network-type information and measurement system is proposed, which allows data collection and their visualization, where one channel is used to measure power, the other to measure shaft rotation speed.

Real-World Pipe-Out Emissions from Gasoline Direct Injection Passenger Cars

The analysis of real-world emissions is necessary to reduce the emissions of vehicles during on-road driving. In this paper, the matrix of gasoline direct injection passenger cars is applied to analyze the real-world emissions. The results show that high acceleration and high speed conditions are major conditions for the particulate number emissions, and the particulate number emissions are positively correlated with torque and throttle opening. The catalyst temperature and saturation are important factors that affect nitrogen oxide emission. The nitrogen oxide emissions of low speed and low torque conditions cannot be ignored in real-world driving. The carbon dioxide emissions are positively correlated with acceleration, torque and throttle opening. Once the vehicles are in the acceleration condition, the carbon dioxide emissions increase rapidly. The vehicles with higher average emission factors are more susceptible to driving behaviors, and the differences in the emission factors are more obvious, leading to an increase in the difficulty of emission control.

Enstrümantasyon sırasında seçilen farklı tork ayarlarının endodontik tedavi görmüş dişlerin kırılma dayanımına etkisi

Background: The study evaluated the effect of root canal instrumentation at low and high torque settings on the fracture strength of endodontically treated teeth. 
 Methods: Ninety extracted single-rooted human mandibular incisors were randomly divided into one control (CG) and two experimental groups (n=30): no instrumentation or filling (CG), instrumentation with ProTaper Universal files at low torque settings, and instrumentation with ProTaper Universal files at high torque settings. Root canal filling was performed with an epoxy resin-based sealer and gutta-percha using a single-cone technique in the experimental groups. Each specimen was tested for fracture strength. The analysis of variance and Tukey test were used to analyze the obtained data. The significance level was set at 0.05. 
 Results: Statistically significant differences were observed between the groups (p = 0.001). While the difference between the CG and low torque groups was not significant (p > 0.05), the difference between the CG and high torque, low and high torque groups was significant (p < 0.05). 
 Conclusion: According to this study results, since the lowest fracture strength value was observed in the high torque group, clinicians may be advised to choose the lowest torque settings recommended by the manufacturers for rotary systems.

Comparison of Drivetrain Topologies for an Ankle Gait Cycle

Powered prosthesis actuation is a field where energy efficiency and mass are important characteristics. The motion requirements of high torque at low speed and low torque at high speed are difficult to effectively combine in a single electric motor. A possibility is to use an oversized direct–drive motor that can deliver the peak torque. However, this results in a heavy actuation system and low overall efficiency. A common practice is combining a smaller electric motor with a gear reduction system. In the literature, novel redundant electric actuation systems have been presented with or without locking mechanisms to mitigate this problem. In this work, we provide a comparison of multiple electrical actuation systems composed of electric motors, gear reduction systems and locking mechanisms. This is done using the gait cycle of a human ankle as a case study. An electric motor with a double stator and a single rotor combined with a gearbox shows the most promising overall results when taking energy loss, total mass and complexity of the system into account.

A New Dual Stator Permanent Magnet Machine Based on Field Modulation Theory

Increasing industrial development puts forward high requirements for the performances of stator permanent magnet (PM) machines, such as torque density and efficiency. The paper proposes a new dual stator PM machine based on field modulation theory (DSPMM), which employs the intermediate rotor participating in the electromechanical energy conversion of the internal and external machine. The proposed machine has the advantages of high torque density and high efficiency and solves the problem of insufficient space utilization of a single stator machine. The evolution process and working principle of the proposed DSPMM are studied. The flux-switching-type PM (FSPM) and the flux-reversal-type PM (FRPM) are employed in the proposed DSPMM, which forms four representative machines. For a fair comparison, the proposed machines employ identical key parameters, i.e., PM volume, the outer radius of the outer stator, and active airgap length. Based on finite element analysis (FEA), the electromagnetic performances of the four representative DSPMM under no-load and rated load, and different copper consumption conditions are analyzed and compared. The calculated results show that the proposed DSPMM with inner FSPM stator and outer FRPM stator can provide high output torque, low torque ripple, high power factor, and high efficiency.

Characterization of the file-specific heat-treated ProTaper Ultimate rotary system.

To compare design, metallurgy and mechanical performance of the ProTaper (PT) Ultimate system with instruments of similar dimensions from the ProGlider, PT Gold and PT Universal systems. New PT Ultimate instruments (n=248) were compared with instruments of similar dimensions from ProGlider (n=31), PT Gold (n=155) and PT Universal (n=155) systems regarding their number of spirals, helical angle, blade symmetry, tip geometry, surface finishing, nickel/titanium ratio, phase transformation temperatures and mechanical performance. One-way anova and nonparametric Mood's median tests were used for statistical comparison (α=5%). All instruments had symmetrical blades without radial lands or flat sides, similar surface finishing and an almost equiatomic nickel/titanium ratio, whilst the number of spirals, helical angles and the tip geometry were different. PT Ultimate instruments showed 3 distinct heat treatments that matched with the colour of their metal wire. Slider and ProGlider instruments had similar R-phase start (Rs) and R-phase finish (Rf) temperatures. SX, F1, F2, F3 and Shaper instruments showed equivalent heat treatments (Rs ~45.6°C and Rf ~28.3°C) that were similar to their PT Gold counterparts (Rs ~47.9°C and Rf ~28.2°C), but completely distinct to the PT Universal ones (Rs ~16.2°C and Rf ~-18.2°C). Amongst the PT Ultimate instruments, the lowest maximum torques were observed in the SX (0.44 N cm), Slider (0.45 N cm) and Shaper (0.60 N cm) instruments, whilst the highest was noted in the FXL (4.90 N cm). PT Ultimate Slider and ProGlider had similar torsional (~0.40 N cm) and bending loads (~145.0 gf) (p=1.000), whilst the other PT Ultimate instruments showed statistically significantly lower maximum torque, higher angle of rotation and lower bending load (higher flexibility) than their counterparts of the PT Universal and PT Gold systems. The PT Ultimate system comprises instruments with 3 distinct heat treatments that showed similar phase transformation temperatures to their heat-treated analogues. PT Ultimate instruments presented lower torsional strength and superior flexibility than their counterparts, whilst maximum torque, angle of rotation and bending loads progressively increased with their sizes.

A Comprehensive Performance Comparison between Segmental and Conventional Switched Reluctance Machines with Boost and Standard Converters

This paper presents the comparisons between two types of switched reluctance machines (SRMs) and SRM converters. An SRM with a segmental rotor is compared with a conventional SRM (CSRM), and an SRM converter containing a passive boost circuit is compared with a conventional asymmetric half-bridge (AHB) converter. The segmental SRM has an asymmetric rotor with a segmented structure. The four rotor segments are made of steel laminations. Two segments are misaligned with the other two by 15 degrees. The torque ripple of the SRM with this structure is decreased, and the static torque is increased compared to a conventional SRM. The boost converter comprises a front-end circuit and a conventional AHB converter. The front-end circuit boosts the voltage level. The boosted voltage accelerates the rising and falling progress of the phase current. In this way, the SRM can obtain a greater speed and a smaller torque ripple. The comparison is conducted in simulation and validated through the experimental results. The experiment results have demonstrated that the segmental SRM obtains a maximum 7% torque ripple reduction at a low-speed range, compared to the CSRM. With the boost converter, both the CSRM and the segmental SRM can achieve a lower torque ripple and a higher maximum speed.

Design and analysis of consequent pole permanent magnet synchronous motor with low torque ripple

AbstractPermanent magnet (PM) motor with consequent pole (CP) rotor can improve the PM utilisation ratio. However, one group of PMs with the same polarity is replaced by iron core, which deteriorates the electromagnetic performances of the motor, including asymmetric air‐gap magnetic field and larger torque ripple. To solve this problem, this study analyses the relationship between the torque ripple and the stator‐rotor magnetomotive force (MMF) harmonics, determines the harmonic orders causing the torque ripple of the CP PM (CPPM) motor, and proposes an unequal‐turn four‐layer winding structure which can eliminate the determining harmonics in the stator MMF. Furthermore, the electromagnetic performances of the CPPM motors with the proposed winding structure and traditional CPPM motors are investigated by the finite‐element analysis. It is verified that the CPPM motor with the proposed structure has better motor performances.

Numerical Investigations on Operation Modes and Transients of IPM Machines with Dual Windings

This paper investigates the flux-weakening characteristics and transient response of a dual winding interior permanent magnet (DWIPM) machine designed using the 2010 Toyota Prius IPM Machine specifications. In order to thoroughly adjust the main flux, dual windings are fed by separate identical inverters. Thus, significantly high-torque for high-speed requirements can be simply achieved by making one of the inverters open-circuited. Transient response of the DWIPM machine, including torque and current pulsations, occurring during normal drive or deactivation of one of the inverters has also been investigated for different operation modes. The flux-weakening performance characteristics of the proposed DWIPM machine have been compared with those of its single-fed counterpart in order to highlight the benefits and drawbacks of the dual-winding topology. The steady-state performance characteristics, torque/speed and power/speed curves, efficiency maps, machine transient response, different machine design options with various numbers of turns per phase and current amplitudes, and the importance of the electromagnetic coupling between dual windings have all been addressed. For transient and steady-state analyses, 2D, nonlinear, time-stepping finite element method (FEM) has been employed. It has been revealed that the proposed DWIPM machine exhibit significantly improved flux-weakening characteristics, particularly high-power at constant power region and high efficiency at constant torque region, and quite low current and torque pulsations occurring during operation mode change.

Muscle strength, rate of torque development and neuromuscular activation of the upper arm muscles in children and adolescents with spina bifida

BackgroundThe use of locomotive devices requires sufficient levels of upper limb strength. Therefore, it is important to evaluate the maximal isometric torque, rate of torque development and neuromuscular activation in youth with spina bifida. The objective was to investigate these parameters in the elbow muscles of youth with spina bifida versus healthy age-matched peers. MethodsForty-eight participants (8–17 years) were recruited: Spina Bifida (n = 23) and non-affected Controls (n = 25). Maximal isometric elbow flexor/extensor contractions were performed to assess maximal muscle strength (peak torque) and rate of torque development, along with synchronized electromyography recording in the biceps and triceps brachii muscles. FindingsDuring elbow flexor contractions, Spina Bifida showed reduced rate of torque development in the early contraction phase (0–50 ms) along with lowered relative rate of torque development in the later rate of torque development phase (0–100/200/300 ms) compared to controls. Spina Bifida showed reduced rate of torque development for the elbow extensors in the later phase of rising muscle force (0–200/300 ms) compared to controls. Lower isometric peak torque and smaller triceps brachii electromyography amplitudes (0–200/300 ms) were observed during elbow extensor contractions in Ambulatory spina bifida participants vs. controls. InterpretationAlthough a majority of peak torque and rate of torque development parameters did not differ, significant impairments in maximal and rapid elbow muscle force characteristics were noted in Spina Bifida compared to non-affected Controls. Ambulatory and Non-ambulatory spina bifida participants demonstrated similar rate of torque development in their upper arm muscles.

Regulation of the central safety factor and normalized beta under low NBI torque in DIII-D

An algorithm has been designed to simultaneously control the central safety factor (q0) and normalized beta (βN) while ensuring near-zero torque from neutral beam injection in DIII-D. Feedback control of q0 and βN in tokamaks can be beneficial due to the close relationship that these variables have with plasma performance and magneto-hydrodynamic stability. In addition, low neutral-beam-torque conditions are of special interest in present devices because future burning-plasma tokamaks such as ITER will most likely operate at very low plasma rotation. The control synthesis of the algorithm presented in this work is based on a linearized, one-dimensional (1D) model of the current-profile dynamics coupled with a zero-dimensional (0D) plasma-energy balance. The actuators considered are neutral beam injection and electron-cyclotron heating and current drive, and discrete logic determines the neutral-beam injection powers that deliver near-zero torque. The algorithm has been tested in nonlinear, 1D simulations using COTSIM (Control-Oriented Transport SIMulator) and in DIII-D experiments, demonstrating satisfactory performance.

Effect of Groove Size on Aerodynamic Performance of a Low Reynolds Number UAV Propeller (Part II)

Following on from the author's previous work on grooved propellers, numerical investigations are carried out on Applied Precision Composites Slow Flyer 10×7 propeller. Computational Fluid Dynamics is used to analyze the novel design. The grooved sections considered have a rectangular geometry measuring 0.1×0.3mm, 0.2×0.1mm, 0.2×0.2mm and 0.2×0.3mm which are placed at 0.09c, 0.17c, 0.32c and 0.42c from the leading edge. The results of the study showed that the presence of grooves modified the flow characteristics having only a negative impact on the thrust performance. However, the grooves improved the power performance due to torque reduction. The analysis of the KP results showed, in most models, the low torque relative to the baseline in the operational range of the low to medium advance ratio range. However, the improvement in torque did not improve the efficiency in all models.

Influence of end-effect and end-winding on the electromagnetic losses and efficiency in high speed permanent magnet machines

<span>Permanent-magnet excitation machines (SPMMs) having mounted magnet on the outer surface of their rotor are preferred for high speed applications such as turbochargers, mechanical turbo-compounding systems, racing engines and fuel pumps, over other types of machines including induction and switched-reluctance machines, since the SPMMs integrate the features of high torque density, compact rotor structure, high reliability and simple structure. However, in the SPMMs, due to the need for a retaining sleeve for the rotor, a large magnetic airgap results and consequently a large magnet thickness is required, hence the magnetic end-effect is relatively high. On the other hand, the use of an overlapping distributed winding leads to a significantly large end-winding length. Hence, the end-effect and the end-winding influences on the performances of a high-speed SPMM is considered in this paper. With a view to get the impact of the end-effect, a comparison between three-dimensional (3D-FEA) results and counterparts two-dimensional finite element analyses (2D-FEA) have been conducted. Results show that, higher efficiency at low torque and low speed due to the low electromagnetic losses and at high speeds due to the high flux-weakening capability are seen when the influences of end-effect as well as end-winding are taken into account.</span>

Electromagnetic-thermal Coupled Analyses and Joint Optimisation of Electrically-excited Flux-switching Linear Machines

Electrically-excited flux-switching machines are advantageous in simple and reliable structure, good speed control performance, low cost, etc., so they have arouse wide concerns from new energy field. However, they have much lower torque density/thrust density compared with the same type PM machines. To overcome this challenge, electromagnetic-thermal coupled analysis is carried out with respect to water-cooled electrically-excited flux-switching linear machines (EEFSLM). The simulation results indicate that the conventional fixed copper loss method (FCLM) is no longer suitable for high thrust density design, since it is unable to consider the strong coupling between the electromagnetic and thermal performance. Hence, a multi-step electromagnetic-thermal joint optimisation method is proposed, which first ensures the consistency between the electromagnetic and thermal modelling and then considers the effect of different field/armature coil sizes. By using the proposed joint optimisation method, it is found that the combination of relatively large size of field coil and relatively low field copper loss is favourable for achieving high thrust force for the current EEFSLM design. Moreover, the thrust force is raised by 13-15% compared with using the FCLM. The electromagnetic and thermal performance of the EEFSLM is validated by the prototype test.

Design and Analysis of Dual Stator PMSM With Separately Controlled Dual Three-Phase Winding for eVTOL Propulsion

The propulsion system of the electric-powered vertical take-off and landing aircraft requires a high level of performances, including power density, efficiency, noise vibration and harshness, and fault tolerance. Among many types of conventional electric motor, the outer rotor surface-mounted permanent magnet synchronous motor (SPMSM) is widely used for its high power density and low torque pulsation. However, these advantages are degraded when the multiphase winding is applied to secure the fault-tolerance characteristics. To overcome the limit of conventional motor topology, the dual stator permanent magnet synchronous motor with separately controlled dual three-phase winding is proposed. The advantages of the proposed topology are resulted from the feature of mechanical, electrical, and magnetic isolation. To maximize the distinctive feature, a design process considering separated current vector control (SCVC) method is established. A design example is presented to demonstrate the impacts of the proposed design process considering SCVC on the power density maximization, torque harmonic reduction, and efficiency improvement. Finally, the experimental verification is presented to validate the proposed design and control techniques.

Low-Ripple Continuous Control Set Model Predictive Torque Control for Switched Reluctance Machines Based on Equivalent Linear SRM Model

In this article, a low-ripple continuous control set (CCS) model predictive torque control (MPTC) method for switched reluctance machines (SRMs) is proposed. The inherent high nonlinearity of the SRMs makes it difficult to solve the optimization problem in the CCS MPTC algorithm analytically. To address this issue, an equivalent linear SRM model is adopted, and the cost function is also properly modified. Then, with the torque boundary values provided by executing the voltage vectors of an improved switching table, the optimization problem in the CCS MPTC method becomes simple and analytically solvable. The Lagrange multiplier method is employed to solve this optimization problem analytically and generate the optimum torque reference values for the active phases. Based on the estimated torque variation rates, the duty cycles for each phase are calculated. Extensive simulation and experimental tests are carried out in a four-phase 8/6 SRM setup. These testing results reveal that the proposed CCS MPTC method shows much lower torque ripples and current ripples in a wide speed range with a low computational burden than the existing finite control set MPTC methods.

TESTING THE CRITICAL VELOCITY OF A MAGNETIC FLUID SEAL WORKING IN A WATER ENVIRONMENT

Magnetic fluid seals are used in many applications, primarily in gas and vacuum environments. The unique properties of this type of seal are very low torque friction, high tightness, and almost unlimited durability. These parameters are also expected for seals that operate in a water environment. This article presents the results of a magnetic fluid seal's maximum (critical) velocity operating in a water environment. The scope of the investigation included an analysis of parameters such as the pressure of the sealed water and the properties of the magnetic fluid. Two independent parameters, such as the pressure change and the torque change of the seal, were used to determine the leakage. The results showed that the best performance was obtained for the fluid with the lowest dynamic viscosity. In addition, the water pressure had a significant effect. Furthermore, pressure change has been shown to be a better indicator of leakage occurrence at high speeds than measuring torque. The results indicate a different leakage mechanism at low and high pressures.

Characteristics Evaluation of a Segmental Rotor Type Switched Reluctance Motor with Concentrated Winding for Torque Density and Efficiency Improvement

With the rapid development of power electronic techniques and the increasing cost of permanent magnets (PMs) materials, switched reluctance motors (SRMs) have recently gained more attention. However, traditional SRMs have a relatively low torque density. For the sake of increasing the motor torque density, this paper proposes a novel segmental rotor type SRM. The proposed motor adopts hybrid stator poles and concentrated windings in the stator side and a segmental rotor structure in the rotor side, which is completely different from the structures of the traditional SRM. The special structure of the motor shortens the magnetic flux paths of the motor, separates the parts of the magnetic flux paths from one another, and eradicates the magnetic flux reversal in the motor stator in order to improve the electric utilization and output torque density of the motor. Meanwhile, the requirement of the magneto-motive force and the core loss of the motor is also decreased, thereby improving the efficiency of the motor. For the purpose of proving the proposed structure, the characteristics of the motor are analyzed using the finite element method and are compared to those of the traditional 12/8 SRM, which is designed for the same application. Moreover, the prototypes of the traditional 12/8 and proposed SRMs are manufactured, and experiments based on the prototypes are performed. Finally, the effectiveness of the structure of the proposed motor is further proven by the experimental results.

Fast and efficient simulation of the dynamical response of coaxial magnetic gears through direct analytical torque modelling

Coaxial magnetic gears have been of great interest amongst researchers and the industry since their introduction two decades ago. Although magnetic gears suffer from slippage at high torques and in general have lower torque density compared to their mechanical counterparts, they surpass their performance in terms of attained speeds, versatility, vibration attenuation, backdrivability and efficiency. Increasing the torque density is a major issue in magnetic drivetrains that has been extensively discussed in the literature. However, the calculation of the torque is typically performed through FEA and/or numerical methods, thus increasing the computational cost especially in dynamical simulations where the applied torques at the two rotors have to be calculated at each time step. The objective of this work is to introduce an analytical 2D model for fast and efficient calculation of the applied torques for every rotation angle, geometry configuration and constitutive parameters of the magnets using the Maxwell Stress Tensor. The results obtained from the model were compared against those obtained from FEA. The calculated torques at the inner and outer rotor were in perfect agreement with FEA, however the analytical model was more than two orders of magnitude faster. In addition, an analytical calculation of the torque ripple in coaxial magnetic gear drives is made possible using the proposed model. An investigation of the influence of the modulator ring on stall torque was performed illustrating that there is an optimum length value for the ferromagnetic segment to maximize torque density. Furthermore, the motion equations of the coaxial magnetic gear drive were formulated and a model was developed to simulate the dynamical response of the system without the requirement of torque calculation at each time step that significantly decreases computational cost. The slip effect was investigated and the resulting transmission error was determined.