Rotational Torque Research Articles

Optimal design and control of permanent magnet assisted dual rotor motor

As high-performance motors, permanent magnet motors are widely used in a wide range of applications. It has become a consensus to mine reluctance torque in permanent magnet motors. The combination of permanent magnet motors and reluctance motors to generate higher output torque is one of the hotspots in motor research. A dual-rotor motor can be formed by connecting a coaxial connector or a concentric end disk, which can make the motor generate higher torque. However, although the motor torque has been improved, the cogging torque still affects the output torque of the motor. This paper describes a method to reduce the cogging torque of the permanent magnet rotor of the permanent magnet-assisted double rotor motor. By analyzing the motor power equation, it is concluded that the pole arc coefficient, the thickness of the magnetic steel, the length of the air gap, and the slot width of the stator have four influences on the teeth. For the parameters of the slot torque, the upper and lower limits of the parameter value are obtained according to the size of the motor. A certain parameter is taken as a fixed value, and the remaining parameters are uniformly valued. Use parametric scanning to determine the optimal value range of the parameter, and use Maxwell for parameterization. Simulation and analysis show that the cogging torque of the motor is reduced by 90% and the torque ripple is reduced by 50%. In order to simplify the motor control system, this paper designs a fuzzy controller based on granular functions, and the fuzzy rules of the fuzzy controller are to perform feature sampling and fit the response function, eliminating fuzzification and defuzzification, improving the response speed of fuzzy control, and simplifying the control system.

Evaluation of microstructure, mechanical and magnetic properties of laser powder bed fused Fe-Si alloy for 3D magnetic flux motor application

Since their high power-to-volume property, electric machines with 3D magnetic flux (3D-flux) structure are of great current interest. In them, the flux path is typically achieved by utilizing a soft magnetic composite (SMC) material to minimize the eddy current losses. Here, laser powder bed fusion (LPBF) technique is employed to manufacture a soft magnetic core (Fe-3.5 wt%Si alloy) with the following advantages: i) the (001) texture of Fe-Si alloy is well aligned with the Z direction of the 3D-flux path, which is the easiest magnetization direction in the cubic system; ii) the strength and ductility of the annealed alloy are far superior to those of SMCs. The alternating-current ring method was employed to measure the magnetic properties and a simulation of the 3D-flux electric machine was conducted. The results illustrated that the rotary torque generated with the additively manufactured alloy is 19.1% higher than that of SMCs in the weak magnetic field excited by ferrite at the 50 Hz frequency. However, it is important to note that the additively manufactured alloy also exhibited higher total iron loss in strong magnetic field and high electric frequency, indicating a need for further research to optimize the microstructure and reduce losses for medium/high frequency applications.

Processing and Properties of Wood-Plastic Composite Containing Alkali-Treated Birch Wood Shavings and Bioadditive Obtained by Biorefinery of Birch Bark

In the last two decades, there has been increased interest in research focused on developing innovative polymer composite materials for food packaging, obtained by compounding polymers with organic fillers, intended for the manufacture of food storage containers. Woodplastic composites (WPCs), due to high content of lignocellulosic filler, are consideredbiocomposites and can be used for the fabrication of such types of containers. Their formulations include, along with the matrix and the filler, functional additives. One of the most important considerations while developing a food packaging material is to choose eco-friendly additives. The suberinic acids (SAs), extracted from birch outer bark by hydrolysis in KOH water solution, were examined as lubricants in the formulation of recycled polypropylene/polylactic acid (rPP/PLA) composite filled with the alkali-treated milled birch shaving microparticles and proceeded by extrusion and injection molding. The incorporation of Sas in a birch wood-rPP/PLA composite was performed by treaing the wood microparticles with the SAs water suspension at the defined concentration. Their presence at the optimal content in the composite improved its processing by reducing the extruder rotor torque and injection pressure, which increased the mechanical properties and decreased the wettability of the composite.

The creation a non-contact rotary mechanism powered by close-range ultrasonic energy

This abstract presents the development and evaluation of a non-contact rotary mechanism powered by close-range ultrasonic energy, with a primary emphasis on its design and performance. The pursuit of efficient, contactless rotary motion has gained significant importance in various industrial and technological applications. This study describes the innovative design of a rotary mechanism utilizing ultrasonic energy as the driving force, obviating the need for physical contact with rotating components. The design of this novel rotary mechanism leverages ultrasonic transducers to generate high-frequency vibrations, which are then transformed into rotational motion through a precisely engineered mechanism. The research explores the intricate details of the design, including the choice of materials, transducer placement, and resonance tuning to optimize performance. The mechanism's construction ensures low friction and minimal wear, making it a promising candidate for applications where reduced mechanical wear and maintenance are critical. Performance assessment of the ultrasonic rotary mechanism encompasses a comprehensive examination of key parameters, such as rotational speed, torque, power consumption, and efficiency. Experimental results reveal the mechanism's capability to achieve a high rotational speed while maintaining low energy consumption, thus underscoring its energy-efficient nature.

Stick–Slip Characteristics of Drill Strings and the Related Drilling Parameters Optimization

To eliminate or reduce stick–slip vibration in torsional vibration of the drilling string and improve the rate of penetration (ROP), a stick–slip vibration model of the drilling string considering the ROP was established based on the multidimensional torsional vibration model of the drilling string. The model was verified by simulation analysis. The characteristics of the drilling string stick–slip vibration in the three stages of stationary, slip, and stick were analyzed. This paper investigated the influence of rotary torque, rotary speed, and weight on bit (WOB) on stick–slip vibrations in the drill string. Based on this, the relationship between the drilling parameters and ROP was established. Drilling parameter optimization was completed for soft, medium-hard, and hard formations. Results showed that appropriately increasing torque and decreasing WOB can reduce or even eliminate stick–slip vibrations in the drill string and increase the ROP. The parameter optimization increased the ROP by 11.5% for the soft formation, 13.7% for the medium-hard formation, and 14.3% for the hard formation. The established drill string stick–slip vibration model provides theoretical guidance for optimizing drilling parameters in different formations.

Fluid–Structure Interaction Analysis of a Wind Turbine Blade with Passive Control by Bend–Twist Coupling

The idea of improving the energy output for small wind turbines without compromising the remaining aspects of the technology, such as costs and structural integrity, is very appealing in the context of the growing concern for global warming and the goal of providing electricity to remote and isolated regions. This work aims to contribute to the development of distributed wind generation by exploring the effects of bend–twist coupling on the performance of a wind turbine with a focus on a small rotor based on the NREL Phase VI blade geometry. After defining a structure in composite materials exhibiting the coupling behavior along with a reference counterpart, a comparative numerical analysis is performed using a Fluid–Structure Interaction (FSI) analysis. The main numerical framework is based on commercial software and consists of a finite-volume solver for fluid physics, a finite-element solver for solid physics, and a coupling interface for the interaction problem. The results, complemented with the predictions from a one-way analysis based on the blade-element momentum theory are used to define the increments in rotor torque. The analysis of the annual energy yield shows a 3% increase due to the bend–twist coupling used as a passive pitch mechanism, considering a Rayleigh distribution with an 11 m/s average wind speed. Simultaneously, the coupling causes increments of 0.2% and 0.3% for the blade root flapwise moment and the rotor thrust force, respectively, when considering parked conditions and a simplified extreme wind model.

Reproducibility of subscapularis muscle thickness measurement using ultrasound imaging. -Relationship between subscapularis muscle thickness and internal rotation torque of the shoulder joint-

BackgroundFew studies have reported on the morphometry of the subscapularis muscle using ultrasound imaging (USI); and their reproducibility has not been verified. ObjectivesThis study aimed to clarify the relative and absolute reproducibility of USI measurements of subscapularis muscle thickness at rest and during isometric contraction as well as the degree of change in muscle thickness caused by the amount of internal rotational torque in the shoulder joint. DesignTwo-group repeated-measures study. MethodsThe subjects were the inferior fibers of the subscapularis muscle of 40 healthy adult males. Muscle thickness was measured at rest and at 10%–30% of the maximum isometric internal rotation torque. Intraclass correlation coefficients (ICC) and Brand Altman analysis were used for reproducibility measurement. The degree of change in muscle thickness at each torque was also calculated. ResultsIntra- and inter-rater ICCs (ranged from 0.69 to 0.91) were good. A proportional error was observed in intra-rater measurements. Both minimal detectable change 95 (ranged from 2.33 to 6.47) were high. The subscapularis muscle thickness was significantly increased at 10% torque (25.49 ± 3.80 mm), 20% torque (26.07 ± 3.90 mm), and 30% torque (25.96 ± 3.82 mm) as compared to that in resting conditions (24.53 ± 4.46 mm) (p < 0.05). ConclusionThe reproducibility and error of the subscapularis muscle thickness measurement using USI used in this study were clarified when repeated measurements were made in the same limb position and under the same probe installation conditions, suggesting that the contraction of the subscapularis muscle can be estimated by muscle thickness measurement.

Machine learning algorithms for real-time coal recognition using monitor-while-drilling data

ABSTRACT Accurate coal seam identification is crucial in coal mining to prevent resource wastage and potential damage to coal seams from misplaced explosives. The current industry standard involves drilling past the seam and refilling the hole, a resource-intensive process. Manual seam detection is error-prone, and geophysical logging, performed for only a subset of drill holes, is costly and time-consuming. Monitor-While-Drilling (MWD) data captures drill response metrics like rotary speed and torque, influenced by local geology. These MWD measurements offer insights into geology, including hardness and rock type; They can be used for real-time rock recognition using advanced artificial intelligence techniques. This study focuses on developing tools for precise coal recognition and identification of the top of coal seams using MWD data. Several Machine Learning classifiers are employed, each providing unique data interpretations, and their results are integrated into a more reliable prediction. An artificial neural network is used for rock density regression, which is then used to correct depth offset between geophysical loggings and drill MWD data. The research demonstrates that MWD data can enable real-time coal seam identification, reducing the reliance on time-consuming and expensive geophysical logging. The integrated model accurately identifies the top of coal seams within a ± 20 cm margin.

Force-Controlled Biomechanical Simulation of Orthodontic Tooth Movement with Torque Archwires Using HOSEA (Hexapod for Orthodontic Simulation, Evaluation and Analysis).

This study aimed to investigate the dynamic behavior of different torque archwires for fixed orthodontic treatment using an automated, force-controlled biomechanical simulation system. A novel biomechanical simulation system (HOSEA) was used to simulate dynamic tooth movements and measure torque expression of four different archwire groups: 0.017″ x 0.025″ torque segmented archwires (TSA) with 30° torque bending, 0.018″ x 0.025″ TSA with 45° torque bending, 0.017″ x 0.025″ stainless steel (SS) archwires with 30° torque bending and 0.018″ x 0.025″ SS with 30° torque bending (n = 10/group) used with 0.022″ self-ligating brackets. The Kruskal-Wallis test was used for statistical analysis (p < 0.050). The 0.018″ x 0.025″ SS archwires produced the highest initial rotational torque moment (My) of -9.835 Nmm. The reduction in rotational moment per degree (My/Ry) was significantly lower for TSA compared to SS archwires (p < 0.001). TSA 0.018″ x 0.025″ was the only group in which all archwires induced a min. 10° rotation in the simulation. Collateral forces and moments, especially Fx, Fz and Mx, occurred during torque application. The measured forces and moments were within a suitable range for the application of palatal root torque to incisors for the 0.018″ x 0.025″ archwires. The 0.018″ x 0.025″ TSA reliably achieved at least 10° incisal rotation without reactivation.

Dichotomy in TCR V-domain dynamics binding the opposed inclined planes of pMHC-II and pMHC-I α-helices

Ligand recognition by the human α/β T-cell antigen receptor (TCR) heterodimer protein, unlike the surface immunoglobulin (sIg) B-cell receptor, is not governed by relative binding affinity. Its interaction with the peptide (p) plus major histocompatibility complex (MHC) protein (abbrev. pMHC) likely involves some different molecular mechanism linking pMHC binding to T-cell functions. Recent analytical geometry of TCR:pMHC-II solved crystallographic structures (n = 40) revealed that each variable (V)-domain is bound in similar, yet mathematically unique orientations to its target pMHC groove. The relative position of the central cysteine of each V-domain was examined by multivariable calculus in spherical coordinates, where a simple volume element (dV) was found to describe clonotypic geometry with pMHC-II. Here, the study was expanded to include TCR:pMHC-I structures, and to model a physical mechanism, specifically involving the two directionally opposed inclined planes (IP) manifest by the two major α-helices prominent in both MHC-I and MHC-II proteins. Calculations for rotational torque of each V-domain, together with acceleration up and down the slopes of both MHC α-helices were used to estimate the time a given V-domain spends sliding down its cognate MHC IP. This V-domain rotation/sliding mechanism appears to be quantitatively unique for each TCR:pMHC V-domain (n = 40). However, there is an apparent and common dichotomy between the mobility of each V-domain with respect to the two classes of MHC proteins. Evolutionary motifs in the MHC helices support that the V-domains negotiate the opposed inclined planes of pMHC ligands in clonotypic fashion. Thus, this model is useful in understanding how mechanical forces are linked to TCR function.

Computational Fluid Dynamics Turbulence Model and Experimental Study for a Fontan Cavopulmonary Assist Device.

Head-flow HQ curves for a Fontan cavopulmonary assist device (CPAD) were measured using a blood surrogate in a mock circulatory loop and simulated with various computational fluid dynamics (CFD) models. The tests benchmarked the CFD tools for further enhancement of the CPAD design. Recommended Reynolds-Averaged Navier-Stokes (RANS) CFD approaches for the development of conventional ventricular assist devices (VAD) were found to have shortcomings when applied to the Fontan CPAD, which is designed to neutralize off-condition obstruction risks that could contribute to a major adverse event. The no-obstruction condition is achieved with a von Karman pump, utilizing large clearances and small blade heights, which challenge conventional VAD RANS-based CFD hemodynamic simulations. High-fidelity large eddy simulation (LES) is always recommended; however, this may be cost-inhibitive for optimization studies in commercial settings, thus the reliance on RANS models. This study compares head and power predictions of various RANS turbulence models, employing experimental measurements and LES results as a basis for comparison. The models include standard k-ϵ, re-normalization group k-ϵ, realizable k-ϵ, shear stress transport (SST) k-ω, SST with transitional turbulence, and Generalized k-ω. For the pressure head predictions, it was observed that the standard k-ϵ model provided far better agreement with experiment. For the rotor torque, k-ϵ predictions were 30% lower than LES, while the SST and LES torque values were near identical. For the Fontan CPAD, the findings support using LES for the final design simulations, k-ϵ model for head and general flow simulation, and SST for power, shear stress, hemolysis, and thrombogenicity predictions.

CFD simulation of an axial discharge rotor-stator mixer: LES versus RANS predictions

The large eddy simulation (LES) technique is used to model the turbulent flow of water in a two-stage, axial discharge, in-line rotor-stator mixer. The WALE sub-grid scale model is employed, and the resulting filtered velocity field is ensemble averaged to predict the mean velocity, turbulent kinetic energy, energy dissipation rate, and energy production rate. The results of these 3-D sliding mesh simulations are compared to analogous RANS predictions on similar meshes using the realizable k-ε turbulence model. Stator slot flow rate and rotor torque/power draw are also monitored. RANS and LES predict similar mean velocity profiles, flow rate and rotor torque. LES predicts higher turbulent kinetic energy, but lower dissipation rate compared to RANS. Results from a coarse and refined computational mesh are compared to discuss the significance of resolving smaller scales for LES. The effect of operating conditions on throughput, power draw, and other quantities of practical utility are also discussed. It was found that prediction of macroscopic quantities such as flow rate and power draw can be done efficiently using either RANS or LES on a relatively course mesh while capturing turbulence quantities requires a well refined LES simulation.

Tidal Turbine Benchmarking Project: Stage I - Steady Flow Experiments

The tidal turbine benchmarking project, funded by the UK's EPSRC and the Supergen ORE Hub, has conducted a large laboratory scale experiment on a highly instrumented 1.6m diameter tidal rotor. The turbine is instrumented for the measurement of spanwise distributions of flapwise and edgewise bending moments using strain gauges and a fibre Bragg optical system, as well as overall rotor torque and thrust. The turbine was tested in well-defined flow conditions, including grid-generated freestream turbulence, and was towed through the 12.2m wide, 5.4m deep long towing tank at Qinetiq’s Haslar facility. The turbine scale was such that blade Reynolds numbers were Re=3x10^5 and therefore post-critical, whilst turbine blockage was kept low at 3.1. In order to achieve higher levels of freestream turbulence a 2.4m by 2.4m turbulence grid was towed 5m upstream of the turbine. Measurements to characterise the grid generated turbulence were made at the rotor plane using an Acoustic Doppler Velocimeter and a five-hole pressure probe. An elevated turbulence of 3.1% with homogeneous flow speed across the rotor plane was achieved using the upstream turbulence grid. The experimental tests are well defined and repeatable, and provide relevant data for validating models intended for use in the design and analysis of full-scale turbines. This paper reports on the first experimental stage of the tidal benchmarking programme, including the design of the rotor and comparisons of the experimental results to blade resolved numerical simulations.

Deadbeat-Direct Torque and Flux Control of a Brushless Axial-Flux Magnetic-Geared Double-Rotor Machine for Power-Splitting HEVs

A deadbeat-direct torque and flux control (DB-DTFC) for brushless axial-flux magnetic-geared double-rotor machines (AMGDRMs) is presented in this paper. The AMGDRM is employed as a power-splitting component in hybrid electric vehicles (HEVs) to enable speed decoupling between the internal combustion engine (ICE) and load. Since the rigid connection between the ICE and the drive train is replaced by the AMGDRM, fast torque control of the AMGDRM is required for the ICE speed regulation. Furthermore, the ICE torque contains abundant harmonics, inevitable sinusoidal components are introduced to the modulating rotor torque for torque balance, and further to the PM rotor torque owing to the magnetic-gear effect. Since both the PM rotor of the AMGDRM and the traction motor contribute to the hybrid electric system total torque output (i.e., torque coupling), the cascaded traction motor should compensate the PM rotor torque ripple actively to guarantee smooth total output torque. However, proportional-integral (PI) regulator suffers from limited bandwidth and thus could not realize accurate torque decoupling. Therefore, DB-DTFC, where torque and flux linkage are decoupled and respectively achieve their reference commands within two sampling periods, i.e., deadbeat responses, is proposed to enable a faster and more robust ICE speed control and accurate torque decoupling. The DB-DTFC law is derived and discrete-time close-loop current and flux linkage observers of the AMGDRM are developed. The proposed scheme and its superiorities are experimentally validated on an AMGDRM prototype test bench.

The Design of a Reaction Flywheel Speed Control System Based on ADRC

The reaction flywheel is a crucial operational component within a satellite’s attitude control system. Enhancing the performance of the reaction flywheel speed control system holds significant importance for satellite attitude control. In this paper, an active disturbance rejection control (ADRC) approach is introduced to mitigate the impact of uncertain disturbances on reaction flywheel speed control precision. The reaction flywheel speed control system is designed as an ADRC controller due to the current challenge of measuring unknown disturbances accurately in the reaction flywheel system. To derive the rotor’s speed observation value and the estimated total disturbances value, the sampled data of the reaction flywheel rotor position and torque control signal are fed into the extended state observer. The estimated total disturbances value is compensated on feedforward control, which could mitigate significantly the effects of various nonlinear disturbances. The paper initially establishes the rationale behind the reaction flywheel ADRC controller through theoretical analysis, followed by analysis of the differences of performance of reaction flywheel control by the ADRC controller and the PID controller in MATLAB/SIMULINK. Simulation results demonstrate the evident advantages of the ADRC controller over the PID controller in terms of speed command tracking capability and disturbances suppression ability. Subsequently, the ADRC controller program and the PID controller program are implemented on the reaction flywheel control circuit, and experiments are conducted to contrast speed command tracking and disturbance suppression. Importantly, the experimental outcomes align with the simulation results.

Effects of an 11-Week Detraining, Imposed by the COVID-19 Confinement, on Handball Players' Shoulder Rotator Isokinetic Profile, Shoulder Range of Motion, and Ball Release Velocity.

Background and Objectives: The COVID-19 confinement significantly impacted the physical condition of athletes. However, the detraining impacts of this period on the shoulder rotator and range of motion in handball players have not been studied. Thus, the main aim of this study was to investigate the effect of this 11-week detraining period, imposed by the COVID-19 pandemic confinement, on the shoulder rotator isokinetic profile (peak torque, ratio, fatigue index), shoulder rotator and flexion range of motion, and ball release velocity in handball players. Materials and Methods: A total of 16 handball players, with a mean age of 22.38 (5.28) years, participated in this study. The isokinetic strength was assessed using two protocols (three repetitions at an angular velocity of 60°/s and 20 repetitions at an angular velocity of 180°/s). In addition, the range of motion and ball release (at jump and standing shots) were measured. All these measurements were assessed before and after the COVID-19 confinement. Results: The results showed a significant reduction in the peak torque of the external rotation of their dominant and non-dominant shoulders. In addition, confinement significantly increased the fatigue index of external rotation and internal rotation and reduced the range of motion of internal rotation. Additionally, the ball release velocity during standing and jump shots was significantly reduced. Conclusions: These results suggested that strengthening external and internal rotation as well as recovering the internal rotation range of motion may be necessary after a detraining period in order to prevent shoulder injuries.

Toward Reducing Undesired Rotation Torque in Maglev Permanent Magnet Synchronous Linear Motor

The dq current transformation method can be used to achieve the drive control of the maglev permanent magnet synchronous linear motor (MPMSLM). Specifically, the control of the suspension force Fz can be achieved by controlling the d-axis current, and the control of the thrust force Fx can be achieved by controlling the q-axis current. However, the direct use of the dq current transformation method on traditional MPMSLM structures produces an additional rotation torque around the y-axis. In order to reduce this additional torque, a new MPMSLM structure is proposed in this work. First, the characteristics of additional torque through finite element analysis are analyzed. Second, the Halbach permanent magnet array and coil size are optimized, and the topology of the MPMSLM coil is designed to reduce the additional torque. The decoupling performance and current of the proposed MPMSLM are experimentally verified through open-loop experiments using finite element simulation software. Finally, the decoupling algorithm of the generalized inverse matrix is used to achieve the decoupling between forces Fx and Fz and torque Ty and the d-axis and q-axis currents in each drive unit. Based on this, a three-degree-of-freedom closed-loop control system of the MPMSLM is designed. The LabVIEW 2018 software is used for the simulation analysis of the three-degree-of-freedom MPMSLM motion control system, and the results show that the proposed motor structure has superior closed-loop control performance.

To flat or not to flat? Exploring the impact of flat-side design on rotary instruments using a comprehensive multimethod investigation.

To assess the influence of a flat-side design on the geometry, metallurgy, mechanical performance and shaping ability of a novel nickel-titanium rotary instrument. Sixty-five new 25-mm flat-side rotary instruments (size 25, taper 0.04) and their nonflat-side prototypes (n = 65) were assessed for major deformations and examined regarding macroscopic and microscopic design, determination of nickel and titanium elements ratio, measurement of phase transformation temperature and evaluation of mechanical performance parameters including time/cycles to fracture, maximum torque, angle of rotation, maximum bending and buckling strengths and cutting ability. Additionally, unprepared canal areas, volume of hard tissue debris and percentage reduction of dentine thickness were calculated for each tested instrument after preparing mesial canals of mandibular molars (n = 12), using micro-CT imaging. Statistical analyses were performed using the U-Mann-Whitney test and independent Student t-test (α = 5%). The number of spirals (n = 8) and blade direction (clockwise) were similar between both flat and nonflat instruments, whilst the helical angles were equivalent (⁓25°). Flat-instruments showed inconsistencies in the homogeneity of the gold colour on the flat-side surface, blade discontinuity, and incomplete and variable S-shaped cross-sections. The titanium-to-nickel ratios were equivalent, but significant differences in the R-phase finish and austenitic start phase transformation temperatures were observed between the flat and nonflat-side instruments. The flat-side instruments demonstrated superior cutting ability compared to the nonflat instruments, as well as, significantly lower values for time to fracture, rotation to fracture and maximum torque to fracture (p < .001). No statistical difference was observed between tested instruments regarding angle of rotation (p = .437), maximum bending (p = .152) and buckling load (p = .411). Preparation protocols using flat and nonflat instruments did not show any statistically significant differences (p > .05). All flat-side instruments exhibited deformation after shaping procedures. The flat-side instrument showcased enhanced cutting ability compared to its nonflat counterpart. However, it exhibited inferior performance in terms of time, rotation and maximum torque to fracture, along with distinct phase transformation temperatures. No differences were observed in the titanium-to-nickel ratios, angle of rotation, maximum bending, buckling load, preparation time, percentage of untouched canal walls, volume of hard tissue debris and percentage reduction of dentine thickness.

The coupling of tower-shadow effect and surge motion intensifies aerodynamic load variability in downwind floating offshore wind turbines

As the deployment of large-scale wind turbines expands into deeper waters, the downwind floating offshore wind turbine (FOWT) becomes an increasingly attractive prospect. Yet, the aerodynamic performance of these turbines, which is significantly impacted by both the tower-shadow effect and the complex six degrees of freedom (6 DOFs) platform motions, exhibits a complexity that surpasses that of traditional upwind floating or downwind fixed wind turbines. To thoroughly explore this complexity, this study employs computational fluid dynamics (CFD) using the unsteady, non-compressible Reynolds-averaged Navier-Stokes (RANS) method on a full-scale model of a downwind FOWT. Our investigation primarily focuses on the intertwining impacts of the tower-shadow effect and the platform's surge motion on the aerodynamic behavior of downwind FOWTs. The study reveals several key findings: the downwind FOWT exhibits comparable, if not superior, power-generation capabilities to prevailing upwind FOWTs; the surge motion significantly dictates both the fluctuation periods and amplitudes of rotor thrust and torque; the tower-shadow effect induces sudden reductions in rotor thrust and torque at a frequency three times that of the rotor rotation; and intriguingly, the magnitude of these sudden drops can be amplified or diminished by the surge motion. The maximum drop amplitude of torque reaches 120–150% the magnitude of the minimum drop amplitude during selected surge motions. This demonstrates that the coupling effects of the tower-shadow effect and surge motion add another layer of variability to the turbine's performance. In conclusion, downwind FOWTs present heightened variability in aerodynamic loads, underscoring the need to consider the potential consequences on power fluctuation and structural fatigue in turbine design and operation.

Design and Realization of a Controlled Electromagnetic Breaking System

Industrial machines with sharp moving blades are extremely dangerous to workers. These machines often rotate for some time (called the run-down time) before completely stopping due to little or no brakes. In the case where brakes are used, they are mechanical in nature and are associated with problems of wear out and frequent maintenance among others. In this paper, we proposed a mathematical model and implementation of an electromagnet and design and construction of a mechanical support frame and a controller for the electromagnetic braking system. The electromagnetic braking system works on the principle of electromagnetism. To realize the semicircular electromagnets, we coil the gauge wires several times around a ferromagnetic core material. The electromagnet was connected to a 12 V 7 Ah battery and was used to lift a load whose mass and corresponding weight were predetermined using a scale balance. The magnetic force generated was equal to the amount of maximum load it could lift. The mechanical frame, on which the electromagnets, motor, battery, switches, and chain drive system were mounted, was designed using SolidWorks and constructed by measuring, cutting, and joining of iron materials. A microcontroller and a power MOSFET were used in the control circuit to drive the electromagnet. Major results such as the realized electromagnets and the magnitude of the electromagnetic force (1.43 N) produced by the electromagnets are presented. The mechanical frame and the control circuit are also presented. The braking force was greater than the rotation torque of the disc, and hence braking was achieved.