Torque Generation Research Articles

Design and Analysis of a Novel Electromagnetic-Propulsion Rotary Machine With External Blending-Shaped Tessellation Magnet Pattern

One major challenge for the design of rotary machine of electric propulsion aircraft is how to improve its torque output and power density. The objective of this paper is to propose a novel external blending-shaped tessellation (EBT) magnet pattern for electromagnetic rotary machine. It can offer several advantages. First, it helps to increase the magnetic flux density in the airgap, and thus the torque output of the rotary machine is increased. Second, it enhances the self-shielding effect greatly, and thus the back iron can be removed completely and replaced with low-density materials. As a result, the rotor mass can be reduced and the system dynamics could be improved. Third, the improved torque and the reduced mass may contribute to the high power density as well. The design concept and operating principle of the proposed external blending-shaped tessellation magnet pattern are presented. Following that, the magnetic field distribution is formulated analytically through Laplace's and Poisson's equations. Then the torque generation of the rotary machine is modeled mathematically. Subsequently, the numerical simulation is conducted to validate the analytical models of the magnetic field distribution and torque output. The magnetic flux density and torque output of the proposed magnet pattern are compared with those of conventional magnet arrays. A research prototype of the electric rotary machine with the EBT magnet pattern is developed, and an experimental test platform is constructed. Experiments are conducted on the magnetic flux density and torque output to verify the proposed design and analytical models. The experimental results validate the derived analytical model of magnetic field and the output torque, and the effectiveness of the magnet array in improving the output characteristic. It shows that the output torque generated by the proposed design is larger than that of conventional Halbach array by 27 percent.

Generation of time-independent torque by ultrasonic guided waves

The excitation of acoustic waves by a unidirectional transducer, integrated in a piezoelectric cylindrical tube or disk, can lead to a time-independent torque. This phenomenon, demonstrated earlier in experiments and analyzed with coupling-of mode theory, is explained in detail, starting on the level of lattice dynamics of a piezoelectric crystal. Expressions are derived for the stationary torque in the form of integrals over the volume or surface of the piezoelectric, involving the electric potential and displacement field associated with the acoustic waves generated by the transducer.Simulations have been carried out with the help of the finite element method for a tube made of PZT for two cases: A pre-defined potential on the surface of the tube and metal electrodes buried in the piezoelectric. The displacement field and electric potential of the high-frequency acoustic waves (between 200 and 300 kHz) were computed and used in the evaluation of the integrals. The attenuation due to various loss channels of the acoustic waves in the system has been analyzed in detail, as this plays a crucial role for the efficiency of torque generation. It is conjectured that time-reversal symmetry, present in the absence of attenuation, prohibits the generation of a static torque at least in the linear limit.A qualitative comparison is made between the simulations and earlier experiments. Discrepancies are attributed to lack of knowledge of the relevant material constants of the piezoelectric and to a simplified modeling of the electrode geometry in the cylindrical tube, which was necessary for reasons of numerical accuracy.

Thermal analysis and temperature evaluation on a magnetic‐geared dual‐rotor machine

AbstractThe thermal performance of the magnetic‐geared dual‐rotor machine (MGDRM) is investigated. Because the effective component in the outer airgap magnetic field harmonics is low, the torque production of MGDRM cannot match the regular permanent magnetic synchronous machine (PMSM). Although the analysis shows that the torque generation of the MGDRM is weak, this conclusion is limited in the electromagnetic field. The MGDRM outer rotor should also be considered from the thermal aspect, and the effect on the torque generation should be valued in particular. The outer rotor thermal buffer effect blocks the heating flow from the winding to the inner rotor magnets. Thus, the MGDRM can withstand a heavy electrical load in a short period, producing higher torque. With this understanding, the torque production ability of the MGDRM can extend to a higher level, even close to the regular PMSM. To validate the analysis, a MGDRM machine is prototyped, and the dual‐rotor temperature information acquisition is realised by a wireless data collection. The rotor temperature estimation technology on the dual‐rotor is then investigated as an auxiliary function. The estimation error can be limited around 5°C, which is good for warning the thermal risk. And thus the MGDRM overheating can be safely adopted to extend the torque generation.

Asynchronous distributed optimal power control for fatigue load minimization in wind farms

An asynchronous distributed optimal power control (OPC) scheme is proposed to minimize fatigue load in the wind farms (WFs) in this paper. To better satisfy the grid code, each wind turbine (WT) in the scheme is equipped with an energy storage system (ESS) at the DC link of the WT converter. Based on the WT topology, a WT-ESS control model is established, thus developing an OPC scheme to control the generator torque, pitch angle, and ESS output simultaneously for reducing fatigue load. By formulating the model predicted control (MPC)-based optimal problems, the virtual mechanical power control is proposed to regulate the ESSs output for clarifying the power interactions among WTs and ESSs. In order to achieve more effective control of the above three parameters among multiple WTs-ESSs, an asynchronous distributed alternating direction method of multipliers (AD-ADMM) is developed to simultaneously minimize the variations of thrust force, shaft torque, and flapping moment load of the WTs in a wider range. Considering the impact of communication delays, the proposed AD-ADMM algorithm has the higher time efficiency and system robustness. The convergence of the proposed AD-ADMM algorithm is analyzed, and several cases are used to validate the performance of the OPC scheme.© 2017 Elsevier Inc. All rights reserved.

A Review of the State of the Art of Torque Ripple Minimization Techniques for Permanent Magnet Synchronous Motors

Industrial applications such as automation, robots, and electric vehicles are widely employing permanent magnet synchronous motors (PMSM) due to inherent characteristics such as high torque to power ratio, low maintenance, high efficiency, and wide operating range. However, PMSM drives can suffer from unwanted torque ripples caused by periodic disturbances of the electromagnetic effect. First, this paper analyses the sources of torque ripple in PMSMs. Second, the torque measurement techniques of the PMSM including torque sensors, torque observers, and indirect measurement methods are discussed to highlight their shortcomings. Third, this paper categorizes and summarizes advanced control-based torque ripple minimization (CB-TRM) techniques for the PMSM by critically evaluating their impacts. These CB-TRM techniques actively control the current waveforms to ensure smooth torque generation and mitigate the effects of torque ripples. Finally, the paper concludes by discussing remaining research questions and opportunities for future research on TRM techniques for PMSMs.

Synthesis, dynamic modeling, prototyping and control of a handheld rotational inertia generator.

This paper explores the design and experimental validation of a three-degree-of-freedom variable inertia generator. An inertia generator is a handheld haptic device that renders a prescribed inertia. In the mechanism proposed in this paper, three-dimensional torque feedback is achieved by accelerating three pairs of flywheels mounted on orthogonal axes. While the primary objective of this work is to design an inertia generator, this study also includes developing other functionalities for the device that exploit its torque generation capabilities. These include the ability to generate a predefined torque profile and to simulate a viscous environment through damping, which are both utilized to assess the device's performance. The device proved to accurately render the necessary torques for every functionality while presenting some limitations for damping and rendering an inertia smaller than the device's inherent inertia.

A Novel Passive Occupational Shoulder Exoskeleton With Adjustable Peak Assistive Torque Angle For Overhead Tasks.

Overhead tasks are a primary inducement to work-related musculoskeletal disorders. Aiming to reduce shoulder physical loads, passive shoulder exoskeletons are increasingly prevalent in the industry due to their lightweight, affordability, and effectiveness. However, they can only handle specific tasks and struggle to balance compactness with a sufficient range of motion effectively. We proposed a novel passive occupational shoulder exoskeleton designed to handle various overhead tasks at different arm elevation angles, ensuring sufficient ROM while maintaining compactness. By formulating kinematic models and simulations, an ergonomic shoulder structure was developed. Then, we presented a torque generator equipped with an adjustable peak assistive torque angle to switch between low and high assistance phases through a passive clutch mechanism. Ten healthy participants were recruited to validate its functionality by performing the screwing task. Measured range of motion results demonstrated that the exoskeleton can ensure a sufficient ROM in both sagittal (164°) and horizontal (158°) flexion/extension movements. The experimental results of the screwing task showed that the exoskeleton could reduce muscle activation (up to 49.6%), perceived effort and frustration, and provide an improved user experience (scored 79.7 out of 100). These results indicate that the proposed exoskeleton can guarantee natural movements and provide efficient assistance during overhead work, and thus have the potential to reduce the risk of musculoskeletal disorders. The proposed exoskeleton provides insights into multi-task adaptability and efficient assistance, highlighting the potential for expanding the application of exoskeletons.

Inhibited swimming capacity of fish entrained in wake vortices behind a semi-cylinder

The loss of fish swimming capacity induced by those energetic vortical structures is detrimental, and limited research on the mechanism of fish entrainment in the vortex has been reported. The present study investigated the entrainment of a fish in vortices generated in wake of a semi-cylinder. The swimming fish was modeled using an undulatory NACA0012 airfoil behind semi-cylinders with a diameter D from 0.1 to 2.4 times the fish body length (L). It was found that the fish couldn't get higher propulsion from the low momentum flow for D > 0.8L. The wake of the fish was distorted by the shedding vortices and trailing-edge vortices (TEVs) arose at fishtail. The length- and time-scale of TEVs were positive correlated with these of oncoming co-directional vortices. The uncontrollable hydrodynamics induced by TEVs could elucidate the disruption of fish stability by surrounding vortices, manifested as a loss of propulsion, the generation of a unidirectional torque, and increased power consumption. The fish head gradually got energy from the turbulent flow of oncoming vortices, but fails to compensate adverse effects of the TEVs. The recovery of swimming capacity occurred only in the less disturbed flow between the wake vortices.

Motion-Based Control Strategy of Knee Actuated Exoskeletal Gait Orthosis for Hemiplegic Patients: A Feasibility Study

In this study, we developed a unilateral knee actuated exoskeletal gait orthosis (KAEGO) for hemiplegic patients to conduct gait training in real-world environments without spatial limitations. For this purpose, it is crucial that the controller interacts with the patient’s gait intentions. This study newly proposes a simple gait control strategy that detects the gait state and recognizes the patient’s gait intentions using only the motion information of the lower limbs obtained from an embedded inertial measurement units (IMU) sensor and a knee angle sensor without employing ground reaction force (GRF) sensors. In addition, a torque generation method based on negative damping was newly applied as a method to determine the appropriate amount of assistive torque to support flexion or extension movements of the knee joint. To validate the performance of the developed KAEGO and the effectiveness of our proposed gait control strategy, we conducted walking tests with a hemiplegic patient. These tests included verifying the accuracy of gait recognition and comparing the metabolic cost of transport (COT). The experimental results confirmed that our gait control approach effectively recognizes the patient’s gait intentions without GRF sensors and reduces the metabolic cost by approximately 8% compared to not wearing the device.

Analysis, simulation and experimental research on the mechanisms of lantern-shaped strand defects in the conductor construction of transmission line

This paper focuses on theoretical, numerical simulation, and experimental research on the lantern-shaped strand defect that arises in tension stringing constructions of large-section conductors. Starting from considerations for factors such as the construction environment and the characteristics of the conductor passing through blocks, this paper presents the causes of conductor torque generation and analyzes the distribution of axial forces on the outmost layer strands and the outmost adjacent layer strands of the conductor when subjected to bending and twisting. Taking into account the contact forces between strands in different layers, this paper thoroughly examines the mechanical causes that lead to the occurrence of the lantern-shaped strand defect in conductors. It concludes that the axial compression and the external contact force acting on the outermost adjacent layer strands are crucial in the formation of the lantern-shaped strand defect. To numerically simulate the lantern-shaped defect, a finite element model is developed to replicate the passage of a 1250 mm2 large-section conductor through the block system. Furthermore, considering actual working conditions, a test equipment is designed and constructed to replicate the lantern-shaped defect. The shape and size of the lantern-shaped defect obtained from the tests exhibited a substantial agreement with the simulation results, suggesting concordance between theoretical analysis and real situation. This research methodology can be used to analyze defects in conductors with varying sections, serving as a theoretical foundation for the prevention and control of construction defects in conductors.

Screw-in force, torque generation, and performance of glide-path files with three rotation kinetics.

We aimed to evaluate the screw-in force, torque generation, and performance of three nickel-titanium (NiTi) glide-path files with different rotational kinetics. ProTaper Ultimate Slider (PULS) and HyFlex EDM Glide-path (HEDG) files were used for canal shaping with constant rotation (CON) or the alternative rotation technique (ART). In the ART mode, the NiTi file was periodically rotated at a speed of 1.5 times faster than that in the CON mode. WaveOne Gold Glider was used with reciprocating motion (WOGG_RCP). Sixty J-shaped resin blocks were assigned to five groups: PULS_CON, PULS_ART, HEDG_CON, HEDG_ART, and WOGG_RCP (n = 12). Glide-path preparation was performed using an automated pecking device. During glide-path preparation, the screw-in force and clockwise and counterclockwise torques were recorded and the number of pecking motions required to reach the working length was determined. The centering ratio was calculated after glide-path preparation using stereomicroscopic images. Data were analyzed using one-way analysis of variance with the Games-Howell post hoc test and the Kruskal-Wallis test with Bonferroni correction. PULS_ART generated a lower maximum screw-in force than PULS_CON. The average number of pecking motions required to reach the working length by HEDG_ART was lower than that by HEDG_CON. The mean centering ratios of PULS_CON and HEDG_CON were -0.04 and -0.06, respectively, while those of PULS_ART, HEDG_ART, and WOGG_RCP were 0.09, 0.01, and 0.08, respectively. The ART mode reduced the screw-in force of PULS and enabled faster glide-path preparation with the HEDG file.

Conceptual design and experimental study of a flexible oscillating hydrokinetic turbine

Harnessing the energy of deep ocean currents to power deep-sea observation equipment has emerged as a significant focus in recent years. Given the extremely low flow speeds in the deep sea, hydrokinetic turbines need to demonstrate reliable self-starting ability. A novel flexible oscillating hydrokinetic turbine is proposed in the present study to address this challenge. The advantage of the flexible oscillating hydrokinetic turbine lies in the ability to adjust the posture of the flexible blades to create optimal attack angles at different positions. Particle Image Velocimetry measurements are employed to reveal the internal flow field. The results indicate that the incoming flow through the turbine cavity induces two substantial deflections in the inflow and outflow regions, contributing to the generation of significant positive torque. The flexible blades can achieve suitable attack angles at various positions as per the expectations. Especially in the downstream region, the blades adopt a diversion state, thereby avoiding the generation of excessive negative torque. The parametric study was conducted through a water flume and a dynamic testing platform. The results indicate that when the number of blades is six and the installation angle of the blade frame is 20°, the power coefficient of the flexible oscillating hydrokinetic turbine reaches its maximum, exceeding 0.18. A full-process interdisciplinary simulation platform test showed that a flexible oscillating hydrokinetic turbine with a radius of 1 m can self-start in conditions as low as 0.1 m/s. At a flow speed of 0.5 m/s, the turbine can generate over 900 Wh of power per day, enough to power sensors or support an Autonomous Underwater Vehicle’s monthly cruise.

Electrokinetic Torque Generation by DNA Nanorobotic Arms Studied via Single-Molecule Fluctuation Analysis.

DNA nanotechnology has enabled the creation of supramolecular machines, whose shape and function are inspired from traditional mechanical engineering as well as from biological examples. As DNA inherently is a highly charged biopolymer, the external application of electric fields provides a versatile, computer-programmable way to control the movement of DNA-based machines. However, the details of the electrohydrodynamic interactions underlying the electrical manipulation of these machines are complex, as the influence of their intrinsic charge, the surrounding cloud of counterions, and the effect of electrokinetic fluid flow have to be taken into account. In this work, we identify the relevant effects involved in this actuation mechanism by determining the electric response of an established DNA-based nanorobotic arm to varying design and operation parameters. Borrowing an approach from single-molecule biophysics, we determined the electrical torque exerted on the nanorobotic arms by analyzing their thermal fluctuations when oriented in an electric field. We analyze the influence of various experimental and design parameters on the "actuatability" of the nanostructures and optimize the generated torque according to these parameters. Our findings give insight into the physical processes involved in the actuation mechanism and provide general guidelines that aid in designing and efficiently operating electrically driven nanorobotic devices made from DNA.

Coupling mechanism and data-driven approaches for high power wet clutch torque modeling and analysis

We propose a hybrid model that integrates conventional mechanism methods with state-of-the-art data-driven techniques to study torque characteristics during the high power clutch engagement process. Experimental validations using clutch bench tests demonstrate that our hybrid model has an error of 7.0%, outperforming conventional mechanistic models and reducing the average error in predicting clutch torque by 12%. With this developed hybrid model, we systematically investigated the impact of oil pressure, oil temperature, and disc size on torque characteristics under various working conditions. Our findings reveal that pressure has the most significant impact on clutch torque. While the influence of the other two factors on overall clutch torque is relatively diminished, temperature can significantly change the viscous torque and disc size can markedly change torque generation time.

Asymmetric flapping of a multi-segmented elastic structure

Motivated by the propulsion of animals using articulated bodies, this study experimentally investigates the deformation and torque generation of a multi-segmented structure undergoing flapping motion. The segmented structure consists of multiple rigid segments connected in a line through elastic sheets functioning as elastic hinges. To enhance the asymmetry in the deflection of the segmented structure between the power and recovery strokes, the elastic hinges are designed to bend only one way from their original position. To characterize the deflection profile of the segmented structure, new definitions are proposed for the effective bending stiffness of the entire structure and the dimensionless speed representing the relative magnitude of the fluid force acting on the structure to its internal bending force. These two quantities are used to determine the tip deflection adjusted by the discrete profile. Two typical deflection responses during the recovery stroke are identified, namely, an in-phase response and a delayed response. The difference in these deflection responses causes substantial changes in torque and thrust generation, particularly during the early stage of the subsequent power stroke. An evaluation of the torque and thrust generation performance, in terms of the net cyclic value and the degree of asymmetry between the two strokes, reveals the optimal model design and operation conditions of the segmented structure.

Development of a Novel Radial-Flux Machine With Enhanced Torque Profile Employing Quasi-Cylindrical PM Pattern

This article presents a novel radial-flux surface-mounted PM (SPM) machine with quasi-cylindrical pole pattern (QCPP). With the proposed configuration, the cogging torque and torque ripple of surface-mounted machines could be greatly decreased due to the adoption of large eccentric distance and the reduction of high-order airgap flux density harmonics. Moreover, the increase of fundamental flux component helps to improve torque generation well. Additionally, the magnet poles are semi-embedded into the rotor, and thus the sleeve in conventional SPM machines is no longer necessary, which helps to reduce the airgap size and improve the torque output further. Besides, the quasi-cylindrical magnet could offer lower rotor eddy loss and higher anti-demagnetization capability than conventional radial and eccentric pole patterns. Studies have been conducted on the novel structure to validate its advantages. Firstly, the topological structure and working principle of the QCPP machine are presented. Then, the influence of the QCPP structural parameters on the torque performance is investigated. Next, an electrical machine with quasi-cylindrical pole pattern is designed. Subsequently, the electromagnetic characteristics, such as flux density distribution, back EMF, average torque, cogging torque, torque ripple, eddy loss in sleeve, rotor stress and anti-demagnetization capability, of the proposed machine are analyzed and compared with those of conventional SPM machine with eccentric magnetic poles and skewing slots. Finally, one research prototype is developed, and experiments are carried out to evaluate the design concept and performance of the proposed QCPP machine.

Modeling and Hover Flight Control of a Micromechanical Flapping-Wing Aircraft Inspired by Wing–Tail Interaction

This article intends to give a comprehensive model to a brand new micromechanical flapping-wing aircraft inspired by wing–tail interaction. In this aircraft, the flapping-wing induced flow contributes to the tail control torque generation. However, this also makes the wing–tail interaction nonnegligible, and this flow would be disturbed by the relative flow produced by the body motion. The dominant unsteady aerodynamic effects of the flapping wing are considered. The flapping-wing induced flow over the tail is included when analyzing the tail aerodynamics. Especially, the aerodynamic–dynamic coupling effect of both the wing and the tail is considered to account for the force due to the body motion. A nonlinear and time-periodic simulation model of the aircraft is, thus, established. The model is averaged and linearized around hover status. Because of the combination of the wing–tail interaction with the aerodynamic–dynamic coupling, the state and control matrixes, including both the induced flow effect and the body motion effect, can be obtained. The pitch dynamics are analyzed, and it is found that the tail can push the two unstable oscillatory poles closer to the imaginary axis. The role of the tail is fully demonstrated by considering the induced flow. Cascade controllers are also designed according to the root-locus plot based on the built model. Due to the inclusion of the wing–tail interaction and the aerodynamic–dynamic coupling, the controllers are proved to be efficient in the attitude stabilization during statistic hover, descent, and ascent flights. Our proposed model can be easily applied to the modeling of other flapping-wing aircraft with similar structures, and it makes the controller design process more efficient and targeted.

Real-time multi-physical system identification and virtual sensing for a lab-scale chemical stirred tank using parallel estimators

In the initial stages of developing a new chemical process, chemists usually use a lab-scale stirred tank to analyze the yield amount and study the mass balance. However, understanding the energy balance is challenging. Monitoring the energy balance requires separating device and process-related effects, which is time-consuming and requires insight into the dynamics of the device and process. As a result, most lab-scale studies often overlook it. A real-time multi-physical virtual sensing and system identification approach is proposed in this study to address this issue by estimating desired unknown electro-thermo-mechanical parameters, states, and disturbances. The estimated unknowns include heat transfer coefficients, motor temperature, stirring torque, and heat generation rate. For this aim, a multi-physical lumped model is developed, which covers the electro-thermal and electro-mechanical responses of the device, as well as the process-related thermo-mechanical effects. The model is decoupled, and three parallel extended Kalman filters are employed. The developed model, estimation procedure, and measurement system are implemented in two experimental examples, including a hydrogenation reaction and the reductive catalytic fractionation of biomass. Both cases use a low-cost data acquisition system designed and manufactured to perform the measurements in this research. Comparing the logged measurements with the estimated values indicates considerable agreement in both cases. Based on the results, decoupling the model and using parallel estimators make the tuning easier, improve observability, and reduce the estimation time.

Performance improvement of horizontal axis wind turbines using curved gurney flap: 3D numerical investigation

The impact of curved Gurney flaps on the performance of a 660 kW V47 horizontal axis wind turbine (HAWT) is analyzed in this study. The trailing edge of the turbine blades is passively modified by curved flaps. The continuity and momentum equations are solved using a Reynolds-averaged Navier-Stokes solver and Shear-Stress-Transport turbulent model. The effect of the direction and radius of curved flaps on the aerodynamic performance of the wind turbine (torque and power generation, flow separation, and thrust loads) is examined. The study examines how the curved flap’s performance on HAWT is affected by the blade pitch angle ([Formula: see text]) and wind speed ([Formula: see text]). According to the results, curve flaps have a positive impact on the output torque at lower pitch angles ([Formula: see text]). The average torque increase for [Formula: see text] and [Formula: see text] is 3.7% for curve flaps, while it is only 2.9% for flat flaps. This conclusion is not valid for higher pitch angles ([Formula: see text]) where the flap disrupts the aerodynamic performance. Further, the use of curve flaps with the radius of [Formula: see text] (inward-type) can improve the torque produced (up to [Formula: see text]) compared to other curved flaps and even flat flaps, especially around the nominal operating point. This conclusion is valid for [Formula: see text], while for higher pitch angles, the flat Gurney flap has better performance generally.

Experimental investigation of advanced turbine control strategies and load-mitigation measures with a model-scale floating offshore wind turbine system

To advance the control co-design of offshore wind energy systems, the authors perform basin-scale experiments with a fully instrumented and actuated floating offshore wind turbine model. The model consists of a 1:70 scale performance-matched model of the International Energy Agency Wind Technology Collaboration Programme 15-MW reference turbine atop the VolturnUS-S semisubmersible platform. The Reference OpenSource Controller provides real-time blade pitch and generator torque control. We aim to develop an open data set for the validation of numerical models in predicting the influence of turbine control and load-mitigation measures. For this purpose, we measure the effects of advanced turbine control features, including peak shaving and floating feedback as well as hull-based control using tuned mass dampers on the system. Overall, the results demonstrate measurable and consistent influences from the control and load-mitigation measures, thus confirming the usefulness as a validation data set. Peak shaving attenuates the response to wind turbulence at near-rated wind speed. Floating feedback reduces the load and platform pitch motion associated with the negative damping induced by blade pitch control. The tuned mass dampers also attenuate the system response near the targeted frequencies under suitable conditions. We also identify detrimental side effects of each load-mitigation measure.