Torque Reduction Research Articles

P‐109: Stress‐Free Folding Hinge for Foldable OLED Display Device

The core technologies for the foldable display device are a flexible OLED panel, a flexible cover window and a folding hinge. Among them a hinge controls folding motion trajectory of an OLED panel. It is very important for an OLED panel not to apply any additional stress during folding motion. We developed the stress‐free folding (SFF) hinge with a virtual axis structure (VAS). Using SFF hinge we can achieved that the stress on OLED panel during folding is almost same as the free folding stress. As a result, there is no issue on an OLED panel in 200k folding reliability test with SFF hinge. Its torque reduction is less than 20% after 200k folding test.

A novel African buffalo optimization for the minimization of cogging torque in modified permanent magnet DC motor

Nowadays, various approaches have been presented to minimize the cogging torque in permanent magnet DC motors. However, tentatively entire approaches are rather incapable of reducing the cogging torque and this can cause a variety of problems. A large quantity of electric energy is formed in a PMDC motor concurrently, the majority of the energy exhausted because these motors are not operated at full load. Therefore, in this paper, a novel African Buffalo Optimization (ABO) based cogging torque reduction technique is proposed in modified PMDC motor. Moreover, this paper includes the mathematical-modeling design of the proposed approach to optimize the design of modified PMDC Motor. The proposed technique is implemented in Infolytica MotorSolve Software v4.1. Consequently, the Signal to Noise Ratio (SNR) of a modified PMDC motor can be improved by this proposed ABO technique. The simulation outcomes of the proposed technique are compared with dissimilar existing techniques in terms of cogging torque, flux density, armature speed, net magnetomotive force, and so on. Thus, the comparison shows that the proposed method is significantly improved the performance of a modified PMDC motor while compared with the other methods.

Emerging the dual string drilling and dual coil tubing drilling technology in a geothermal well applications

The challenges found in geothermal well drilling have forced the industry to develop new significant cost effective, time saver technologies to go for deeper geothermal resources beyond their traditional limits. To overcome these challenges, the new Dual String Drilling (DSD) technology which is based on penetration pathway of drilling fluid and rock cuttings during drilling a well. The principle of DSD employs drilling fluid flows through the annulus of inner and outer string pipe while cutting from the bottom of the well through inner pipe. The paper describes the novel Dual String Drilling (DSD) technology, predicting their occurrence and advantages on drilling of geothermal well. The outcome shows that with DSD approach a lot of time will be saved to circulate the kick out of the well. Additionally, the characteristic response of DSD enables to improve the hole cleaning capacity, to prevent pipe stuck, better well stability, reduction in torque and drag, to remove the dynamic equivalent circulating density gradient in geothermal wells. Moreover, the paper also depicts the system and method for dual coil tubing drilling of horizontal well which follows the same principle as DSD. The comparison of DSD with conventional drilling assesses that the DSD technology is affordable and appropriate for geothermal well drilling.

Analysis and reduction of cogging torque in direct‐drive external‐rotor permanent magnet synchronous motor for belt conveyor application

Permanent magnet synchronous motor (PMSM) shows the great potential for use in direct drive system because of its excellent low-speed direct-drive capability. However, it suffers from the adverse effect of the cogging torque in comparison with the asynchronous motor. Therefore, reducing the cogging torque, especially the external-rotor PMSM (ERPMSM) for belt conveyor application, is necessary for enhancing the stable operation and precise positioning performances of the belt conveyor.Herein, a novel tangential magnetization low-speed high-torque ERPMSM is proposed and analysed. Furthermore, the expression of the cogging torque of the proposed ERPMSM is derived by energy method. Based on the special structure of the ERPMSM, a new method for cogging torque reduction is introduced. The comparative FEA results for four ERPMSM models are presented to verify the accuracy and effectiveness of this method. The accuracy of the cogging torque FEA results is confirmed by a prototype. Finally, the influence of this method on ERPMSM performance is also analysed carefully in this paper.

The Effects of Cogging Torque Reduction in Axial Flux Machines.

An axial flux permanent magnet single-rotor generator has good potential in various applications that require high efficiency, prolonged service life, as well as low mass and dimensions. However, the effect of cogging torque diminishes generator efficiency and flexibility of functionality. The effect of cogging torque arises because of a small air gap between the stator teeth and the rotor. In this article, we suggest that shifting the opposite teeth of the stator to the optimal angle can reduce the effect of cogging torque. A special axial flux permanent magnet generator is developed to choose the optimal disposition of the permanent magnet and stator teeth in the frame. The impact of the optimal angle on the cogging torque, output power, and generator efficiency is investigated. This analytical study with experimental testing proves that the optimal angle between opposite teeth can significantly decrease cogging torque and improve output power and efficiency. The results show that cogging torque decreases significantly (4–5 times) at an optimal angle of 7.5° as compared with that of other angles, although magnetic flux and output power decline slightly but efficiency increases.

An exploration of frictional and vibrational behaviors of textured deep groove ball bearing in the vicinity of requisite minimum load

In case of lightly loaded radial ball bearings, failure mechanisms other than fatigue such as smearing of raceways due to increased frictional torque and vibrations often prevail. Hence, attempts have been made herein for reducing the frictional torque and minimizing the vibrations of a radial deep groove ball bearing employing surface textures at the inner race. Nanosecond pulsed laser was used to create texture (involving micro-dimples having different dimple area density) on the inner race of test bearings. Using an in-house developed test rig, frictional torque and vibrational parameters were measured at different speeds and light loads (i.e. in vicinity of 0.01C, where C is dynamic load capacity of radial ball bearing). Significant reduction in frictional torque and overall vibrations were found in the presence of micro-dimples on inner race at light loads irrespective of operating speeds. Even without satisfying the minimum load needed criteria for the satisfactory operation, substantial reduction in smearing marks was found on the races of textured ball bearings in comparison to conventional cases.

Novel Bio-Inspired Algorithm for Speed Control and Torque Ripple Reduction of Switched Reluctance Motor in Aerospace Application

Switched Reluctance Motor (SRM) is an electrical motor which operates by a reluctance torque that has stator and rotor salient poles. It also has a simple configuration and reasonable power electronics necessity for both AC and DC machines within adjustable-speed drives. The problem working on it is, SRM with doubly salient poles introduce a torque ripple in its output which leads to deteriorated performance on speed control. In this proposed work, torque ripple reduction and speed control of SRM is implemented, utilizing an asymmetrical converter with PI-PWM controller with the aid of Bio-inspired algorithms. By utilizing the best value of flux, torque ripple and integral square error of speed and settling times, controller design is performed. The proposed research work compares three optimization algorithms namely Crow Search Algorithm, an Improved Ant Lion Optimization Algorithm and Modified Chaotic Starling Particle Swarm technique to control the speed and torque reduction of SRM in aerospace applications. To obtain the optimal parameter values, optimization techniques are introduced and the optimized controller results are compared with other conventional controller results. In normal operation, the engine operates with two phases simultaneously, but it is modelled to meet the load specification, which is single and double phase faulty. Detection of fault gives a great outcome in control of an electrical drive system. Reduction of faulty operation time leads to better motor lifetime that is obtained by early detection of a fault. This paper presents how the five-phase switched reluctance motor is designed to meet the needs of flap actuators in mid-sized aircraft. Electrical systems are modelled to provide the right functionality at the right time in advanced aircraft. However, requirement of power for the landing gear and secondary flight control only a short duration. The system is powered on and off as required, thus preserving power. Control performance and fault analysis were verified by the results of the MATLAB simulation. Experiments have been carried out more effectively to compare the results obtained with those of simulations.

Ripple torque lessening in space vector pulse width modulation based direct torque control of permanent magnet synchronous motor drive

In this work, the ripple reduction in torque using space vector pulse width modulation based direct torque control of permanent magnet synchronous motor by employing the predictive current to estimate the flux magnitude is discovered. To lessen the ripple in current, a model-based predictive current is used to estimate the magnitude of current applied for flux estimation. Two control plans are applied to show the viability of the framework. MATLAB/Simulink is used to develop a model of PMSM and simulate the system considering different control algorithm. Simulation is performed for both simple current control and SVPWM-DTC control scheme. The result of the simulation indicates that the torque and current ripple is less for SVPWM-DTC with considerable initial overshoot.

Toward Trustworthy and Comfortable Lane Keeping Assistance System: An Empirical Study of the Level of Haptic Authority

ABSTRACT A shared control system has received steady attention as it can mitigate or avoid potential weaknesses of autonomous driving. According to the preliminary study, the drivers’ experience was found to change significantly depending on the system’s intervention strategy. In particular, driver satisfaction was found to decrease significantly due to the feeling of disturbance or interference. In this study, a strategy was suggested to adjust the haptic authority according to human torque to minimize the feeling of disturbance. Twelve control strategies were designed as a prototype to investigate their effects on the driver’s experience. As a result, a positive effect on the driving experience was observed by providing adequate torque reduction. Based on the regression model of satisfaction, optimal design parameters were derived. The results of this study are expected to contribute to designing more favorable control strategy of a shared steering control system.

Pengaruh Kombinasi Pemangkasan Ujung Magnet Permanen dan Axial Channel pada inti rotor terhadap Torka Cogging pada Generator Tipe Fractional Slot Number

This paper is about to discuss the effect of combining a magnetic shaping technique with an axial channel in the rotor core to reduce the cogging torque of a permanent magnet synchronous generator. Computation process is performed by using the optimization response surface method. In this case, this research is done by employing two types of axial channel systems, namely circular and hexagonal. The axial channel area at the core of the engine rotor is 0.000279683 m2. Determination of magnetic shaping was carried out with an angle of 10 and a surface angle of 530. The effect of the combination of the cogging torque reduction technique with magnetic shaping and axal channel was analyzed by numerical method based on the finite element method (FEMM). Based on the analysis, it is found that the combination shows a decrease in cogging torque by 98% when compared with the cogging torque in the initial design (initial structure). Another advantage of the combination of the two cogging torque reduction techniques is that there is no significant increase in the magnetic flux density of the engine core. It can be said that the combination of the cogging torque reduction technique and the axial channel at the core of the engine rotor can significantly reduce the cogging torque.

Cogging torque reduction based on segmented skewing magnetic poles with different combinations of pole‐arc coefficients in surface‐mounted permanent magnet synchronous motors

The calculation and reduction of cogging torque are fundamental to the evaluation and optimisation of motor performance. Considering that the accuracy of the cogging torque calculated by analytical method (AM) is low, an accurate calculation model of the effective air-gap length considering the actual stator slot structure and suitable for any motor is proposed, the cogging torque of 6p36s surface-mounted permanent magnet synchronous motor (SPMSM) are calculated accurately and verified by finite element method (FEM). Furthermore, the segmented skewing magnetic poles with different combinations of pole-arc coefficients are designed to weaken cogging torque, and the optimal combination of pole-arc coefficients and tilting angle of the adjacent magnetic poles are summarised by AM and particle swarm optimisation (PSO) algorithm. Finally, the cogging torques of six SPMSMs with different slot-pole combinations including 6p36s, 4p36s, 6p9s, 8p9s, 8p12s and 10p12s are analysed, and the results indicate that the cogging torque can be greatly weakened based on segmented skewing magnetic poles with different combinations of pole-arc coefficients, and other performances of the motors are basically not affected.

Central fatigue aetiology in prolonged trail running races.

What is the central question of this study? Are spinal and/or supraspinal perturbations implicated in central fatigue induced in the plantar flexor muscles following prolonged trail running races? What is the main finding and its importance? The study confirmed the presence of central fatigue following various trail running distances from 40 to 170km. The reduction in the V-wave in conjunction with the lack of change in the H-reflex suggests that a major component of this central fatigue may arise from supraspinal mechanisms in the plantar flexor muscles. Trail running races are known to induce considerable impairments in neuromuscular function of which central mechanisms are a substantial component. However, the loci of this central fatigue (i.e. supraspinal and/or spinal) is not well identified. The aim of this study was to better understand central fatigue aetiology induced in the plantar flexor muscles by various trail running distances from 40 to 170km. Eighteen runners participated in the study and neuromuscular function of their plantar flexors was tested before (PRE) and after (POST) various races during the Ultra-Trail du Mont Blanc. Neuromuscular function was evaluated with voluntary and evoked contractions using electrical tibial nerve stimulation. H-reflex and V-wave responses were also measured during submaximal and maximal voluntary contraction, respectively. Reductions in maximal voluntary contraction torque (-29%; P<0.001) and voluntary activation level (-12%; P<0.001) were observed after trail running races. The V-wave was reduced in soleus (-35%; P=0.003) and gastrocnemius medialis (-28%; P=0.031), with no changes for the H-reflex in soleus (P=0.577). The present study confirmed the presence of central fatigue following trail running exercise. The reduction in the V-wave in conjunction with the lack of change in the H-reflex suggests that a major component of this central fatigue may arise from supraspinal mechanisms.

Wide Speed Range Noise and Vibration Mitigation in Switched Reluctance Machines With Stator Pole Bridges

Noise, vibration, and harshness (NVH) issue in switched reluctance machines (SRMs), originating from their doubly salient structure and unique principle of operation, is addressed in this work by proposing a structural design modification in the stator, which increases stiffness to mass ratio of the structure. A 24-slot 16-pole (24s/16p) SRM designed with the aim of automotive application is studied here for the NVH optimization, at different target operating points, using stator pole bridges. Stator pole bridges link consecutive stator teeth to provide additional stiffness to the stator structure. Average torque reduction due to flux shorting in stator pole bridges is tackled by proposing a low-permeability material, with considerable stiffness, which has not yet seen its' application in SRM NVH domain. Multiphysics aspects of stator pole bridge design encompassing electromagnetic radial force, mechanical stress, steady-state temperature distribution, and acoustic noise analyses are presented in this article. Possible manufacturing issues are considered during the design phase and appropriate measures are implemented to facilitate easier construction of two 100-kW prototypes. The final design with stator pole bridges and a baseline design without any stator pole bridges are prototyped, after rigorous multiphysics optimization, for extensive testing. Experimental results verify simulation outputs and report a maximum noise reduction of 12.52 dBA in the stator pole bridge model compared to the baseline SRM.

RoboWalk: augmented human-robot mathematical modelling for design optimization

ABSTRACT Utilizing exoskeleton devices to help elderly or empower workers is a growing field of research in robotics. The structure of an exoskeleton can vary depending on user’s physical dimensions, joints or muscles targeted for assistance, and maximum achievable actuator torque. In this research, a Human-Model-In-the-Loop (HMIL) constrained optimization technique is proposed to design the RoboWalk lower-limb exoskeleton. RoboWalk is an under-actuated non-anthropomorphic assistive robot, that besides applying the desired assistive force, exerts an undesirable disturbing force leading to the user’s fall. The HMIL method uses the augmented human-robot 2D model to take RoboWalk and human body’s joint torques into account during optimization. The superiority of HMIL method is proven by comparing the results with other strategies in the literature. Obtained results reveal elimination of the disturbing forces, 2 N.m. reduction in average human knee-joint torque, and significant decrease in the actuator required torque.

Gelatinized and nongelatinized starch/pp blends: effect of starch source and carboxylic and incorporation

Due to the environmental impact caused by incorrect disposal and the non-biodegradability of synthetic polymers, the packaging sector seeks renewable raw materials. An alternative is the utilization of natural renewable polymer, such as thermoplastic starch (TPS), mixed with synthetics. However, the chemical incompatibility between these two materials leads to the use of a compatibilizer agent. Even though the compatibilizer effect of carboxylic acid on TPS blends have been studied, the correlation between the carboxylic acid and the starch source has not been investigated yet. Thus, this study focuses on the effects of added carboxylic acids (myristic (C14) and stearic (C18) acid) and the starch sources (corn, cassava, and potato) on the properties and microstructure of blends with TPS/PP (70/30). The results suggested that the compatibilizer effect of acids depends on the starch source and the length of the acid chain, where cassava blends with C14 showed better results. Acid insertion increased tensile strength and deformation at break, but reduced the elastic modulus, indicating a plasticizer effect. This behavior was related to the formation of amylose and lipid complexes (endogenous or added) during heating. Torque reduction and Tg displacement were also observed for acid blends. The SEM images showed two different morphological dispersions and a non-gelatinization effect due to the acid insertion. Results suggested that acids act differently according to the starch source.

Heat transfer enhancement and torque reduction by traveling wave-like blowing and suction in turbulent Taylor-Couette flow

Heat transfer enhancement and torque reduction by traveling wave-like blowing and suction in turbulent Taylor-Couette flow

The Effect of Magnet Structure on the Cogging Torque Reduction in a Permanent Magnet Generator

The cogging torque would still be a constant part of permanent magnet-electric machines. This happens because of the construction in which permanent magnets are attached to the rotor, and a slot is present at the core of the stator. The contact between the two, related to the distance between the magnetic surface and the stator slot, makes it challenging to eliminate the cogging torque. This study aims to maximize cogging torque by reducing it with a new method. The proposed method is a mixture of two techniques that indicate significant promise. This invention mixes two techniques to improve the final results. The first process is called magnetic edge shaping, and the second technique is called a dummy slot on the stator. A fractional slot number (FSN) type with 24 slots and 18 poles is the permanent magnet machine used for this investigation. This work is assisted by software version 4.2 of the Finite Element Magnetic Method (FEMM), which will simulate the original and the proposed design. The proposed method proved to be effective in minimizing the peak value of the cogging torque, as shown by the simulation results of 98% of the initial design. Combining the two techniques may reduce the tangential value of the flux so that the flux leading to the slot is lower than the initial design.

Minimizing Cogging Torque in Permanent Magnet Synchronous Generators for Small Wind Turbine Applications

Permanent magnet synchronous generators have a wide usage among electric machines, especially in small wind turbine systems. However permanent magnet synchronous generators suffer from cogging torque due to the magnetic interaction between the poles of the rotor’s permanent magnets and the steel laminations of the stator’s teeth. The cogging torque drawback is a major problem in this kind of generators that affects its functionality negatively. In this study the effectiveness of different cogging torque reduction techniques is compared with each other through finite element simulation using JMAG simulation software. Among the different cogging torque reduction techniques, in this study we consider changing the radial shoe depth, shifting permanent magnets, continuous skewing of the rotor or stator, step skewing of the rotor or stator, changing the slot opening width and also having dummy slots. We find that among the considered different approaches, continuous skewing reduces the cogging torque the most. We also find that step skewing of the rotor or stator, changing the slot opening width and having dummy slots can reduce the cogging torque in more or less the same amounts in magnitude. Our results indicate that changing the radial shoe depth has almost no effect in reducing the cogging torque.

補極付き磁極構造による3自由度球面アクチュエータのコギングトルクの低減

補極付き磁極構造による3自由度球面アクチュエータのコギングトルクの低減

Effects of branched-chain amino acid supplement on knee peak torque and indicators of muscle damage following isokinetic exercise-induced delayed onset muscle soreness

[Purpose] This study aimed to investigate the effects of branched-chain amino acid (BCAA) supplement on delayed onset muscle soreness (DOMS) by analyzing the maximum muscle strength and indicators of muscle damage.[Methods] Twelve men with majors in physical education were assigned to the BCAA group and placebo group in a double-blinded design, and repeated measurements were conducted. DOMS was induced with an isokinetic exercise. Following BCAA administration, the changes in the knee extension peak torque, flexion peak torque, aspartate aminotransferase (AST), creatine kinase (CK), and lactate dehydrogenase (LDH) concentrations were analyzed. The maximum knee muscle strength was measured at the baseline (pre-D0) following BCAA administration for 5 days before exercise (-D5, -4D, -3D, -2D, -1D). In contrast, the post-treatment measurements (D3) were recorded after BCAA administration for 3 days (post-D0, D1, D2). Blood samples were obtained before (pre-D0), immediately after (post-D0), 24 h (D1), 48 h (D2), and 72 h (D3) after the exercise to analyze the indicators of muscle strength. BCAA was administered twice daily for 8 days (5 days and 3 days before inducing DOMS and during the experimental period, respectively).[Results] There was no difference in the flexion peak torque between the groups. However, the BCAA group showed a significantly higher extension peak torque at D3 (second isokinetic exercise), compared to the placebo group (p<.05). There was no difference in AST changes between the groups. Nonetheless, the CK and LDH were significantly reduced in the BCAA group, compared to the placebo group. There was no correlation between the extension peak torque and flexion peak torque. However, the CK and LDH increased proportionately in DOMS. Moreover, their concentrations significantly increased with a decreasing peak torque (p<.01).[Conclusion] An exercise-induced DOMS results in a decrease in the peak torque and a proportional increase in the CK and LDH concentrations. Moreover, the administration of BCAA inhibits the reduction of the extension peak torque and elevation of CK and LDH concentrations. Therefore, BCAA might be administered as a supplement to maintain the muscle strength and prevent muscle damage during vigorous exercises that may induce DOMS in sports settings.