Low Torque Research Articles

Experimental Study on the Effect of Calcium Aluminate Cement Addition on the Drying and Physical Properties of Refractory Castables Containing Colloidal Silica.

Colloidal silica-bonded castables offer several advantages compared to traditional calcium aluminate cement (CAC)-bonded castables, including lower torque values during mixing, superior drying properties, and a lower CaO content. Nevertheless, information on the combination of CAC and colloidal silica is limited, and the effect of CAC additions on the drying properties of colloidal silica-bonded castables remains unknown. In this study, these drying properties were measured by rapidly heating 400 kg samples to 500 °C and assessing the resulting damage to each sample. Additionally, the physical and chemical properties of small-scale samples were analyzed to evaluate the impact of CAC addition. The analyzed properties included cold crushing strength (CCS), density, permanent linear change (PLC) and weight loss. The microstructure of the samples was investigated by FESEM and EDS. The results indicate that adding 1.5 wt.% increased the cold crushing strength at 20 °C, while lower CAC amounts had no noticeable effect. A mullite phase was observed in the sample without CAC, and correspondingly, anorthite was found in those with CAC additions. The samples exhibited significant differences in the drying tests, with the degrees of damage increasing with the CAC addition.

Further Application Of Automatic Control Based On Servo Motor In Smart Grid

The paper summarize the advantages and applications of servo motor. As a kind of equipment that can replace manual long-distance inspection, the intelligent inspection device for overhead transmission lines can significantly improve inspection efficiency and reduce labor intensity. The servo motor with high power density and low torque ripple can guarantee the high precision and stable operation of the intelligent inspection device in line inspection, which provides a certain practical intelligent application significance for transmission line inspection.

Proposal for Cane Tip Position to Achieve Both High Stability and Low Joint Torque Using Inverse Dynamics Analysis in T-Cane Gait

T-cane is a primary method used to prevent falls. Although canes effectively increase stability and reduce load, the specific position of the cane tip that maximizes these effects is not yet clear. Furthermore, the cane tip position that enhances effectiveness may also increase the burden on the user. In this study, we used the center of pressure (CoP) as an indicator of stability and shoulder joint adduction torque as an indicator of burden. In this study, we propose a cane tip position that increases the stability of the cane user, but does not increase the burden, through experiment. The experiment involved healthy young male participants. The results confirmed that the CoP increased with the cane tip position. The shoulder joint adduction torque increased with the cane tip position and then remained constant. The results suggest that the participants can walk with higher stability per load when the cane tip was positioned 30 cm in front of the right foot on the ground.

Modeling and Comparison of Design Features of Pendulum and Radial Micro-Hydropower Plants Considering the Influence of Variable Design Parameters

This article provides a comparative analysis of pendulum and radial micro-hydropower plants. The novelty of this study lies in the comparative analysis of units that are fundamentally different in design to achieve the most rational option for low-speed rivers. It has been established that a pendulum micro-hydropower plant has a high torque with relatively small dimensions but operates cyclically. At a diameter of 1 m and a blade area of 0.3 m2, the peak torque was 140 N·m. At the same time, the design is sensitive to the blade area and at 0.6 m2 and a lever length of 1.5 m, the torque reached 430 N·m. A radial micro-hydropower plant has lower torque but operates constantly. At an area of 1.23 m2 and a diameter of 1 m, the torque was 40.4 N·m. Accordingly, in terms of specific area with a diameter of 1 m, a pendulum micro-hydropower plant has up to 12 times more torque. It has been established that the pendulum hydropower plant best satisfies the requirements for converting a low river speed into high revolutions of a current generator.

Model Predictive Control of Aero-Mechanical Actuators with Consideration of Gear Backlash and Friction Compensation

To address the issues of low positional accuracy and significant torque pulsation caused by gear backlash and nonlinear friction in the mechanical transmission mechanism of aeronautical flap electromechanical actuators, we propose a model predictive control method for flap electromechanical actuator considering gear backlash and friction compensation. Firstly, we model the gear backlash in the electromechanical actuator’s mechanical transmission mechanism and design a corresponding torque current compensation method using a simplified dead zone model. Secondly, the LuGre compensation friction model is introduced, and a friction torque current compensation method is developed to address the nonlinear friction torque generated during system operation. Finally, the proposed current compensation strategies are employed to mitigate the adverse effects of gear backlash and nonlinear friction on system control performance. The simulation results demonstrate that the proposed method enhances position tracking accuracy, reduces torque pulsation, and significantly improves the overall control performance of the system.

Torque dynamic performance enhancement of five‐phase permanent magnet synchronous motor with open‐circuit fault

AbstractMultiphase permanent magnet synchronous motors (PMSMs) have attracted much more attention for their high efficiency, low torque ripple and good fault tolerance. However, open‐circuit fault results in asymmetrical motor behaviour, and deteriorates torque performance, especially dynamic response. This paper proposes a novel fault‐tolerant direct torque and flux control (DTFC) strategy to restrain fluctuating torque and enhance torque dynamic performance of a five‐phase PMSM with open‐circuit fault. The novelty of the proposed strategy is the development of DTFC based on stator flux orientation under the open‐circuit fault condition and the third harmonic current suppression with carrier‐based pulse width modulation technology. Consequently, the decoupling control of torque and stator flux can be achieved under the open‐circuit fault condition, and the third harmonic current can be restrained without additional control. Combined with deadbeat control, the heavy computation burden can be reduced. Thus, the proposed strategy not only can enhance torque dynamic performance under open‐circuit fault operation, but also keep smooth torque with circular stator flux trajectory before and after open‐circuit fault. The effectiveness of the proposed strategy is verified by the simulation and experimental results.

Dynamic overmodulation strategy based on torque and flux optimal tracking for DTC‐SVM of surface‐mounted PMSM drives

AbstractDirect torque control with space vector modulation has been increasingly attracting emphasis for permanent‐magnet synchronous machine control, benefiting from a high dynamic response and low torque ripple. However, the rapid tracking performance of torque and stator flux linkage is gradually deteriorating as the machine enters the overmodulation region because of the output‐voltage limitation of the inverter. Therefore, to enhance the system tracking performance in the overmodulation region, an innovative overmodulation method based on torque and flux optimal tracking is proposed. In contrast to the conventional overmodulation method where only one of the torque and stator flux linkage tracking is considered, the proposed strategy first constructs the weightless cost function to achieve a trade‐off control between the torque and stator flux linkage. Then, by using an equivalent geometric path to intuitively express the weightless cost function, the minimum cost function can be easily solved and the optimal output voltage vector can be determined correspondingly, to achieve the fast‐tracking of both the torque and stator flux linkage. Additionally, the voltage utilization of different overmodulation schemes is also analysed. Finally, the experimental results demonstrate the efficiency and practicality of the proposed strategy.

Females demonstrate lower levels of activity, psychological readiness and strength symmetry after anterior cruciate ligament reconstruction than males, and also recovery of quadriceps strength and hop symmetry is delayed in females undergoing reconstruction with a quadriceps tendon autograft.

To investigate sex-based recovery differences in patients undergoing anterior cruciate ligament reconstruction (ACLR) with a hamstring (HT) or quadriceps (QT) tendon autograft. This study included 97 patients, including 50 females (HT = 25, QT = 25) and 47 males (HT = 24, QT = 23), assessed presurgery and at 12- and 24-month postoperatively via surveys, laxity, isokinetic knee extensor and flexor torque and a 6-hop performance battery. Limb symmetry indices (LSIs) were calculated. Outcomes were compared between males and females, as well as within each graft type. Males reported significantly higher Tegner scores at 12 (p = 0.029) and 24 (p = 0.031) months, Anterior Cruciate Ligament Return to Sport after Injury scores at 12 (p = 0.009) and 24 (p = 0.010) months, and a significantly higher lateral hop LSI at 12 (p = 0.045) months, knee extensor torque LSI at 12 (p = 0.020) months, and knee flexor torque LSI at 12 (p = 0.001) and 24 (p = 0.039) months. Females undergoing ACLR with a QT (vs. HT) graft demonstrated a lower knee extensor torque LSI at 12 (p = 0.006) months, a lower lateral hop LSI at 12 (p = 0.038) months, and a lower medial hop LSI at 12 (p = 0.042) months. Females reported less activity and psychological readiness, as well as strength symmetry. Furthermore, the recovery of quadriceps strength and hop symmetry was delayed in females (vs. males) undergoing ACLR with a QT graft. A better understanding of these differences will assist in counselling on expectations, determining the most appropriate graft construct and permitting more targeted rehabilitation. Level IV.

An improved finite set model predictive control of SRM drive based on a voltage vectors strategy for low torque ripple

The robust rotor structure and fault-tolerance characteristics of the Switched Reluctance Motors (SRMs) are the best choice for next-generation Electric Vehicle (EV) applications. This machine has few restraints like high torque and flux ripples. However, the existing Model Predictive Control (MPC) using multiple control objectives and maximum sectors in the switching table results in high torque ripples due to the improper sector partition, Voltage Vectors (VVs) and weight factor (K1) selection. This paper proposes a Finite Set-Model Predictive Control (FS-MPC) for an analytical model of a non-linearity SRM machine to analyze the torque ripple performance. The proposed VVs are derived using sector partition based on the rotor position. The control is designed as a single cost function with the weighting factor contributing to smooth torque by selecting optimal control signals. Simulation studies and experiments with a four-phase 8/6 SRM drive verifies the enhanced FS-MPC for real-time implementation. The dynamic speed and ripple values of SRM Drives are measured using a mixed signal oscilloscope and the sensor probes. The laboratory outcomes calculate the analytical equations to validate the findings. The calculated value of torque ripple is 9 % through this FS-MPC. The study reveals that the proposed method is well suited for torque ripple reduction than flux ripples.

The root cause of disruptive NTMs and paths to stable operation in DIII-D ITER baseline scenario plasmas

Abstract Analyses of the DIII-D ITER Baseline Scenario database support that the disruptive m,n=2,1 magnetic islands are pressure gradient driven, non-linear instabilities seeded in a sequence of stochastic transient magnetic perturbations, and that the current profile relaxation does not affect the m,n=2,1 island onset rate. At low torque, these Neoclassical Tearing Modes are most commonly seeded by non-linear 3-wave coupling when the differential rotation between the q=1 & q=2 rational surfaces approaches zero. Lack of statistically significant difference between the current profiles of stable and unstable states, as well as lack of correlation between the tearing mode onset rate and the current profile relaxation both reject causality between the current profile evolution and the 2,1 magnetic island onsets in these plasmas. These support that preserving the differential rotation between the q=1 and q=2 rational surfaces is key to long pulse stable operation in the plasma scenario planned for ITER, while optimization of the current profile within the explored parameter space may lead to much weaker improvements than sustaining the differential rotation.

Design and Implementation of A Low-Cost Parachute Landing System for Fixed-Wing Mini Unmanned Aerial Vehicles

Fixed-wing mini-UAVs (Unmanned Aerial Vehicles) face difficulties due to the need for runways during take-off and landing. While fixed-wing UAVs are capable of using catapults during take-off, various landing systems are required for landing. Therefore, in this study, a parachute system design and production were carried out for the safe landing of fixed-wing mini-UAVs. The produced parachute utilized ultra-lightweight ripstop nylon fabric and suspension lines, while a carbon fiber tube was chosen for the launching system for its lightweight and strength. The parachute deployment system was triggered by a servo motor with low power consumption and high torque. During tests, the parachute was activated at a height of 47 meters during flight. The parachute deployment was completed in 1.42 seconds, and the descent with the parachute lasted 11 seconds. The vertical descent speed of the parachute during landing was measured at 4.27 m/s. The produced parachute landing system was manufactured at 71% lower cost compared to existing parachute landing systems in the literature and on the market. Additionally, the ultra-light ripstop parachute weighed 56 grams, making it 12% lighter than similar systems. Considering the advantages in terms of cost and weight, it is anticipated that parachute landing systems will be increasingly used for fixed-wing UAVs in the future.

Guaranteed real-time cooperative collision avoidance for n-DOF manipulators

Abstract This paper presents a decentralized, cooperative, real-time avoidance control strategy for robotic manipulators. The proposed avoidance control law builds on the concepts of artificial potential field functions and provides tighter bounds on the minimum safe distance when compared to traditional potential-based controllers. Moreover, the proposed avoidance control law is given in analytical, continuous closed form, avoiding the use of optimization techniques and discrete algorithms, and is rigorously proven to guarantee collision avoidance at all times. Examples of planar and 3D manipulators with cylindrical links under the proposed avoidance control are given and compared with the traditional approach of modeling links and obstacles with multiple spheres. The results show that the proposed avoidance control law can achieve, in general, faster convergence, smaller tracking errors, and lower control torques than the traditional approach. Furthermore, we provide extensions of the avoidance control to robotic manipulators with bounded control torques.

Dynamics and adaptive backstepping control of rotor-hybrid foil-magnetic bearings system

The hybrid foil-magnetic bearing (HFMB) is a contactless-type bearing composed of a foil bearing (FB) in the inner side and an active magnetic bearing (AMB) in the outer side. It has the advantages of low drag torque, high DN value (bearing inner diameter times rotating speed), and high supporting efficiency. However, significant subsynchronous vibration will degrade the stability of the rotor-HFMBs system, which is an obstacle to the industrial implementation of HFMBs. To control the rotor vibration, this paper presents a dynamic model of the rotor-HFMBs system with unknown parameters and the design of an adaptive backstepping controller (ABC) for it. The stability of the closed-loop system is established. Simulation results of the rotor-HFMBs system controlled by ABC are compared with the proportional-integral-derivative controller (PID), illustrating that the ABC is capable of eliminating rotor vibration, and it is more effective than the PID.

Design and Validation of a Modular, Backdrivable Ankle Exoskeleton.

Partial-assist ankle exoskeletons have been limited by inherent trade-offs between favorable characteristics including high torque capacity, high control bandwidth, back-drivability, compliance, and low mass. Emerging quasi-direct drive actuators have a rigid transmission with a low gear ratio, enabling inherent backdrivability and compliance with accurate torque and position control. Our existing modular, backdrivable exoskeleton system (M-BLUE) uses quasi-direct drive actuators at the hip and/or knee to deliver high assistive torques alongside low dynamic backdrive torques, enabling natural interaction with users with remnant voluntary motion. This paper extends our modular system with the design and validation of a back-drivable ankle exoskeleton module to assist both plantarflexion and dorsiflexion. The bi-directional torque capabilities enable the study of control methods and gait outcomes for able-bodied users and users with gait impairments. Benchtop tests of the actuator performance and control bandwidth indicate that the position, voltage, and current control modes can provide assistance to the ankle joint across activities of daily living (ADLs). We also implement an optimal task-agnostic energy shaping controller for an experiment with a single human subject to validate the ability of the ankle exoskeleton to provide biomimetic torque assistance across a circuit of ADLs.

Rotor design and optimization of synchronous reluctance machine with low torque ripple

Rotor design and optimization of synchronous reluctance machine with low torque ripple

Performance Evaluation of Biomimetic-Designed Rotary Blades for Straw Incorporation in an Intensive Tillage System

A rotary tiller is a common tillage tool for straw incorporation in an intensive tillage system. However, rotary tillage for seedbed preparation in dense-straw mulching conditions experiences high torque and poor performance of straw incorporation. Nowadays, a great deal of studies have been focused on mimicking the morphological features of low-resistance animals to improve the performance of soil-engaging tools. Accordingly, the present study investigated the performance of three C-type rotary blades (i.e., conventional, serrated, and biomimetic) under three straw lengths (50, 100, and 150 mm) for incorporation of straw into the field using an in situ field tillage testing bench. Compared to the conventional and serrated blades, the biomimetic blade had lower straw displacement (decreased by an average of 50 mm and 7 mm, respectively), higher straw burying rate (increased by an average of 5.2% and 7.8%, respectively), better straw distribution (decreased by an average of 9.1% and 10.4% on the coefficient of variation, respectively), as well as lower torque and power (decreased by an average of 3.3 N·m and 4.4 N·m, respectively) under all straw lengths. The improved performance of the biomimetic blade could be attributed to the fact that its typical teeth configuration was designed by mimicking the smooth arc of the mole-rat’s claw. These results demonstrated that the biomimetic-designed blade could be a better option for incorporating dense straw into the field conditions.

Machinability of Basalt/PBS sustainable composites: a comprehensive experimental analysis

ABSTRACT Basalt fiber reinforced polybutylene succinate (BFPBS) composite offer competitive solutions for medium load applications but face significant drilling challenges. Present study seeks to perform an exhaustive machinability analysis and optimize pivotal drilling variables, to mitigate delamination and enhance machining efficacy in BFPBS laminates. Experimental exploration involved three distinct drill geometries: an 8 mm twist drill and two modified step drills, facilitating scrutiny of pilot diameter’s impact on drilling behavior. Mapping force signals, morphological analysis, chip formation investigation, and specific cutting energy calculation were conducted to deepen comprehension of BFPBS machinability. Modified step drill showed superior performance with lower thrust force and torque. Feed rate primarily affected thrust force, whereas tool geometry notably influenced exit delamination. Multiple linear regression models enabled Genetic Algorithm optimization, revealing Pareto optimal sets balancing thrust, torque, and delamination. Step drills show potential for reduced energy use and improved efficiency in BFPBS composite machining, benefiting various industries.

The reliability assessment method for sealing structure of subsea horizontal clamp connector based on sealing and strength

The reliability assessment of the Subsea Horizontal Clamp Connector (SHCC) sealing performance faces a challenge due to the lack of characteristic dimension evaluation methods. Hence, this paper develops the Comprehensive Sealing Reliability Evaluation (CSRE) method. This approach allows for the simultaneous analysis of failure in two dimensions: structural sealing and structural strength, incorporating the uncertainty of fuzzy stress in the evaluation. The CSRE method is based on Bayesian networks, using contact stress as a critical parameter to establish structural sealing failure nodes with gasket coefficients combined with the API standards for acceptance. Simultaneously, it establishes structural strength failure nodes using an improved stress interference model. When applying the CSRE method, this paper, through Monte Carlo simulations combined with torque transmission mechanics and finite element contact models, analyzes the reliability variations of the developed SHCC under different torque levels. The results indicate that the sealing reliability of SHCC is related to sealing pressure and structural strength, with excessively high or low torque affecting its sealing reliability. At an input torque of 2400 N·m, its reliability reaches the maximum value, which is 0.9912. The presented CSRE approach, validated through experimentation and method comparison, demonstrates greater alignment with engineering practicality.

DIII-D research to provide solutions for ITER and fusion energy

The DIII-D tokamak has elucidated crucial physics and developed projectable solutions for ITER and fusion power plants in the key areas of core performance, boundary heat and particle transport, and integrated scenario operation, with closing the core-edge integration knowledge gap being the overarching mission. New experimental validation of high-fidelity, multi-channel, non-linear gyrokinetic turbulent transport models for ITER provides strong confidence it will achieve Q ⩾ 10 operation. Experiments identify options for easing H-mode access in hydrogen, and give new insight into the isotopic dependence of transport and confinement. Analysis of 2,1 islands in unoptimized low-torque IBS demonstration discharges suggests their onset time occurs randomly in the constant β phase, most often triggered by non-linear 3-wave coupling, thus identifying an NTM seeding mechanism to avoid. Pure deuterium SPI for disruption mitigation is shown to provide favorable slow cooling, but poor core assimilation, suggesting paths for improved SPI on ITER. At the boundary, measured neutral density and ionization source fluxes are strongly poloidally asymmetric, implying a 2D treatment is needed to model pedestal fuelling. Detailed measurements of pedestal and SOL quantities and impurity charge state radiation in detached divertors has validated edge fluid modelling and new self-consistent ‘pedestal-to-divertor’ integrated modeling that can be used to optimize reactors. New feedback adaptive ELM control minimizes confinement reduction, and RMP ELM suppression with sustained high core performance was obtained for the first time with the outer strike point in a W-coated, compact and unpumped small-angle slot divertor. Advances have been made in integrated operational scenarios for ITER and power plants. Wide pedestal intrinsically ELM-free QH-modes are produced with more reactor-relevant conditions, Low torque IBS with W-equivalent radiators can exhibit predator-prey oscillations in T e and radiation which need control. High-β P scenarios with q min > 2, q 95–7.9, β N > 4, β T–3.3% and H 98y2 > 1.5 are sustained with high density ( n¯ = 7E19 m−3, f G–1) for 6 τ E, improving confidence in steady-state tokamak reactors. Diverted NT plasmas achieve high core performance with a non-ELMing edge, offering a possible highly attractive core-edge integration solution for reactors.

Experimental analysis of failure modes depending on different loading conditions applied on cylindrical polyamide 66 gears

Abstract Engineering plastics are increasingly used for gearing systems, such as in the automotive sector, e-mobility sector, and household appliances. The basic task of the gearing system is to efficiently transfer power from the source to the application user. The use of engineering plastics for gearing applications is conditioned by the lack of tribological characteristics of material pairs which influence on fatigue and wear behaviour of the whole gearing system. The paper presents testing of the steel/Polyamide 66-gear by determining fatigue life in an infinite area, considering high precision optical measurements in the range of micro-meter accuracy of abrasion flank wear together with surface temperature in contact, providing an important database for engineers about material suitability for appropriate mechanical systems. Observing the results, gear flank wear of PA66 HT is directly proportional to the meshing temperature and torque. Thermal melting is a characteristic failure mode of the polymer gears which are exposed to higher load levels. In the middle torques, the dominant failure mode is flank fracture known as pitch point fracture. The greater impact of the gear wear mechanism occurs at lower torques where initial crack propagation starts at the pitch point and ends in the tooth root area.