Twist Control Research Articles

Transient control strategy of doubly-fed fan based on zero dynamic and super twist control

Transient control strategy of doubly-fed fan based on zero dynamic and super twist control

Emergence of Interlayer Coherence in Twist-Controlled Graphene Double Layers

We report enhanced interlayer tunneling with reduced linewidth at zero interlayer bias in a twist-controlled double monolayer graphene heterostructure in the quantum Hall regime, when the top (ν_{T}) and bottom (ν_{B}) layer filling factors are near ν_{T}=±1/2,±3/2 and ν_{B}=±1/2,±3/2, and the total filling factor ν=±1 or ±3. The zero-bias interlayer conductance peaks are stable against variations of layer filling factor, and signal the emergence of interlayer phase coherence. Our results highlight twist control as a key attribute in revealing interlayer coherence using tunneling.

回転翼の効率向上のための引張−ねじりカップリング特性 を用いたねじり角の受動制御

回転翼の効率向上のための引張−ねじりカップリング特性 を用いたねじり角の受動制御

Impact of optimized variable rotor speed and active blade twist control on helicopter blade–vortex interaction noise and environmental impact

Combined variable rotor speed and active blade twist helicopter technologies have the potential to reduce the environmental and acoustic impact of modern rotorcraft. This paper explores the aeroacoustics, environmental and ground noise impact of combined variable rotor speed and active blade twist helicopter rotors, optimized for simultaneous mitigation of source noise and NOx emissions. An integrated approach is employed including free-wake aeroelastic rotor modeling and time-domain aeroacoustic formulations fundamentally based on Acoustic Analogy. The overall method is incorporated into a multi-disciplinary design space exploration and surrogate-model-assisted optimization algorithm. The developed framework is deployed towards devising optimal variable rotor speed and active blade twist control for a representative twin-engine light helicopter operating in a realistic descent trajectory. The obtained rotor control schedules achieve overall ground noise reductions of up to 7 dB with concurrent NOx reductions of 11%, relative to the conventional rotor. The proposed approach provides new insight into rotor wake behavior and blade–vortex interactions, as well as environmental impact and ground noise footprint of combined variable rotor speed and active blade twist helicopter concepts.

Optimal Segment Control of Active Twist Rotor for Power Reduction in Forward Flight

The segment control of active twist rotor is investigated to evaluate the effectiveness in rotor power reduction. A numerical model for predicting the isolated rotor power and loads in steady level flights is deployed and validated. A parametric sweep of the amplitude and phase angle for uniform single-harmonic active twist control is conducted to demonstrate the mechanism of active twist control in rotor power reduction. The optimal control schedules and segment layouts of the segment twist control for power reduction while considering saturation limits are obtained using an optimization framework based on genetic algorithm. Up to 5-seg configuration is considered. The results indicate that the segment twist control reduces the rotor power more than the uniform twist control by applying divergent control schedules to each segment. The load distribution of the rotor disk is harmonized in both circumferential and spanwise directions. The 2-seg and 3-seg control configurations are appropriate, while the configurations with more segments yield limited benefits and they may be penalized with an increase in system complexity.

Improved sine-trim2 model for the simultaneous elimination of aerodynamic lift, roll, and pitch moment vibrations of rigid rotor helicopters

An improved sine-trim method called sine-trim2 is proposed from the original sine-trim method, based on the phasor superposition principle, to simultaneously eliminate the aerodynamic lift, roll, and pitch moment vibrations of rigid rotor helicopters. The advancing blade concept rotor aerodynamic analysis model is modified and applied on the basis of the free-wake method associated with the inner-trim and outer-trim modules. A hybrid individual blade control system with the blade pitch and linear twist is applied to simultaneously adjust the blade lift and lift arm at each azimuth angle. In the sine-trim2 method, the number of rotor blades should be greater than or equal to four to successfully apply the phasor superposition principle for all kinds of aerodynamic vibration phasors of each blade. Two kinds of lift arm distributions (constant lift arm and sinusoidal lift arm) in one revolution that can both meet the requirements of vibration elimination are considered. Calculation results show that although the sine-trim2 method can eliminate the aerodynamic lift, roll, and pitch moment vibrations of the rigid rotor with either lift arm distribution. A proper sinusoidal lift arm as the control target will have lower control difficulty and efficiency loss than the constant lift arm. The optimal individual blade pitch and twist control distributions, which are both comprehensive superpositions of many higher harmonic inputs, are obtained in each azimuth in one rotation revolution.

Mitigation of Voltage Flicker at Smart Loads with Renewable Wind Energy in Distribution Systems

This activity handles displaying and furthermore control of astute tons for request reaction organization under improved invasion of reasonable power ages (RPGs) at desperate degree. The raised penetration of RPGs, particularly twist control at particular degree, is defined with harming impact on voltage impact. An irreversible magnet synchronous machine based volatile rate wind control transformation structure is planned with a breeze rate considering stochastic and furthermore routine effects. The recreated wind control directly into the flow structure produces stochastic and additionally consistent power fluctuations. For the tons require criticism organization, fullconnected self-commutated catches based converters are utilize to control sharp tons (SLs). These SLs are over seen for partaking in structure transports voltage strategy and in addition glints decrease. From disperate calculations, it is observed that SLs work in improving the voltage measurements of the examination feeder.

Adaptive pitch control of full-scale ship composite propeller using shape memory alloy to enhance propulsive efficiency in off-design conditions

In this study, we investigate the use of shape memory alloy for adaptive control of twist of the propeller blade for a full-scale marine composite propeller of actual blade geometry, to offset the reduction in its hydrodynamic efficiency in off-design conditions. A full-scale ship propeller of 4.2 m diameter, made of graphite–epoxy laminate integrated with Nitinol fibre–reinforced hybrid composite (shape memory alloy hybrid composite) patches, is considered. The shape memory alloy hybrid composite patches are placed such that the recovery stress induced on heating the pre-strained shape memory alloy fibres embedded in martensite phase to the austenite phase causes twisting deformation in the propeller blade. The open water performance is estimated from the flow solution obtained using the finite volume method considering viscous flow and fluid structure interaction, while the deformation analysis is performed using the finite element method based on the first-order shear deformation theory, considering the nonlinearity due to large deformation. It is shown for the first time for a ship propeller of actual size and shape that the heating of the shape memory alloy fibres generates sufficient twist in the propeller to cause appreciable improvement (up to 6.3%) in its hydrodynamic efficiency in off-design conditions with lower advance ratios, thereby enhancing its fuel efficiency.

Optimized Comparative Analysis of an Active Twist for Helicopter Rotor Blades with C- and D-Spar Designs

The application of macrofiber composite (MFC) actuators to an active twist control of helicopter rotor blades significantly reduces the vibration and noise without the use of complex mechanisms in the rotating systems. The applicability of two main spar designs and two variants of utilization of MFC actuators for an active twist of advanced helicopter rotor blades is examined in the present study. For this reason, 3D finite-element models and the corresponding piezoelectric, static torsional, and modal analyses are developed using the ANSYS code. Due to the great dimension of the numerical problem to be solved, an optimization methodology is developed employing the design of experiments and the response surface technique. The numerical results found are validated successfully by quasi-static tests on a demonstration blade, which confirm the high accuracy of the 3D finite-element models developed and the corresponding analyses performed.

Chirality Induction in Bioorganometallic Conjugates

Considerable attention has been given to the research field of bioorganometallic chemistry, which is a hybrid chemistry field between biology and organometallic chemistry. The introduction of biomolecules, which have hydrogen bonding sites and chiral centers, into organometallic compounds is a promising strategy to construct chirality-organized bioorganometallic conjugates. This feature paper sketches an outline of induction of helical chirality into bioorganometallic conjugates by the control of a torsional twist of the organometallic moiety. Topics covered included control of the helical chirality of 1,n′-disubstituted ferrocene moieties in ferrocene-dipeptide conjugates, and the chirality induction of the Au(I)–Au(I) axis in the dinuclear organogold(I)-uracil conjugates.

Influence of vagal control on sex-related differences in left ventricular mechanics and hemodynamics.

Left ventricular (LV) twist mechanics differ between men and women during acute physiological stress, which may be partly mediated by sex differences in autonomic control. While men appear to have greater adrenergic control of LV twist, the potential contribution of vagal modulation to sex differences in LV twist remains unknown. Therefore, the present study examined the role of vagal control on sex differences in LV twist during graded lower body negative pressure (LBNP) and supine cycling. On two separate visits, LV mechanics were assessed using two-dimensional speckle-tracking echocardiography in 18 men (22 ± 2 yr) and 17 women (21 ± 4 yr) during -40- and -60-mmHg LBNP and 25% and 50% of peak supine cycling workload with and without glycopyrrolate (vagal blockade). LV twist was not different at baseline but was greater in women during -60 mmHg in both control (women: 16.0 ± 3.4° and men: 12.9 ± 2.3°, P = 0.004) and glycopyrrolate trials (women: 17.7 ± 5.9° and men: 13.9 ± 3.3°, P < 0.001) due to greater apical rotation during control (women: 11.9 ± 3.6° and men: 7.8 ± 1.5°, P < 0.001) and glycopyrrolate (women: 11.6 ± 4.9° and men: 7.1 ± 3.6°, P = 0.009). These sex differences in LV twist consistently coincided with a greater LV sphericity index (i.e., ellipsoid geometry) in women compared with men. In contrast, LV twist did not differ between the sexes during exercise with or without glycopyrrolate. In conclusion, women have augmented LV twist compared with men during large reductions to preload, even during vagal blockade. As such, differences in vagal control do not appear to contribute to sex differences in the LV twist responses to physiological stress, but they may be related to differences in ventricular geometry. NEW & NOTEWORTHY This is the first study to specifically examine the role of vagal autonomic control on sex-related differences in left ventricular (LV) mechanics. Contrary to our hypothesis, vagal control does not appear to primarily determine sex differences in LV mechanical or hemodynamic responses to acute physiological stress. Instead, differences in LV geometry may be a more important contributor to sex differences in LV mechanics.

Blade tip vortex measurements on actively twisted rotor blades

Active rotor control concepts, such as active twist actuation, have the potential to effectively reduce the noise and vibrations of helicopter rotors. The present study focuses on the experimental investigation of active twist for the reduction of blade–vortex interaction (BVI) effects on a model rotor. Results of a large-scale smart-twisting active rotor test under hover conditions are described. This test investigated the effects of individual blade twist control on the blade tip vortices. The rotor blades were actuated with peak torsion amplitudes of up to $$2^\circ$$ and harmonic frequencies of 1–5/rev with different phase angles. Time-resolved stereoscopic particle image velocimetry was carried out to study the effects of active twist on the strength and trajectories of the tip vortices between $$\psi _\text {v}= 3.6^\circ$$ and $$45.7^\circ$$ of vortex age. The analysis of the vortex trajectories revealed that the 1/rev active twist actuation mainly caused a vertical deflection of the blade tip and the corresponding vortex trajectories of up to $$1.3\%$$ of the rotor radius R above and $$-1\%R$$ below the unactuated condition. An actuation with frequencies of 2 and 3/rev significantly affected the shapes of the vortex trajectories and caused negative vertical displacements of the vortices relative to the unactuated case of up to $$2\%R$$ within the first $$35^\circ$$ of wake age. The 2 and 3/rev actuation also had the most significant effects on the vortex strength and altered the initial peak swirl velocity by up to $$-34$$ and $$+31\%$$ relative to the unactuated value. The present aerodynamic investigation reveals a high control authority of the active twist actuation on the strength and trajectories of the trailing blade tip vortices. The magnitude of the evoked changes indicates that the active twist actuation constitutes an effective measure for the mitigation of BVI-induced noise on helicopters.

Performance based multidisciplinary design optimization of morphing aircraft

The aeronautical industry is currently facing contradictory aircraft design requirements. There is a need to increase speed and capacity while minimizing the environmental impact. Novel configurations and morphing solutions are being proposed to address these requirements. In order to achieve the optimal aircraft configuration or the best morphing solution for a given mission, it is necessary to explore Multidisciplinary Design Optimization (MDO) solutions during the conceptual design phase. To this end, a MDO framework is proposed for conceptual design and analysis of new aircraft configurations, including the capability to analyze and quantify the effect of morphing wing solutions on aircraft performance. To illustrate the versatility and capabilities of the MDO tool, the design of a morphing wingtip on a conventional aircraft for two different flight conditions is assessed based on a reference model transport aircraft. Also, the performance of a morphing bending and twist control applied to a reference joined-wing configuration to improve lateral-directional stability is quantified. The results obtained show a significant reduction in fuel consumption when introducing a wingtip, although an incremental and negligible reduction was verified when enabling the wingtip with morphing capabilities. A considerable increase in yaw authority was achieved for the joined-wing model with the bending-twist morphing wingtip, however this morphing concept was not able to reach the same roll authority as conventional ailerons.

Control strategy of twist springback for aluminium alloy hybrid thin-walled tube under mandrel-rotary draw bending

The focus of this work is to investigate the control strategy of twist springback of an industrial aluminium alloy extruded tube after mandrel-rotary draw bending, which is a complex nonlinear physical process with coupling multi-factor interactive effects. A particularly pronounced twist springback characteristic of an AA6060-T4 hybrid thin-walled bent tube was observed. It leads to difficulty at the assembly stage due to the inaccurate geometry of product. For an accurate modelling of material behaviours, a non-quadratic anisotropic yield criterion integrated with combined isotropic and kinematic hardening model was adopted to describe the strain-stress behaviours including anisotropy, Bauschinger effects and permanent softening. The corresponding mechanical tests, e.g., enhanced forward-reverse simple shear tests, were performed to identify the material parameters. By using the improved and validated finite element model, two process control strategies related to the mandrel nose placement and the axial push assistant loading are proposed for the assessment of the control efficiency. The simulation results indicate that the mandrel nose placement mainly affects the longitudinal angular springback but not twist deformation in the circumferential sections. The angular springback angle firstly increases and then decreases after several tests of forward mandrel nose placement. The other control strategy, additional axial push assistant loading with high boost, is able to reduce twist deformation, but the compensation of angular springback is not attained and even a slight increase is observed. It also leads to the rise of the of wrinkle tendency in the intrados sidewall. Finally, the wipe die rake is put forward to reduce the wrinkle tendency due to the high boost applied for twist control.

Optimum active twist input scenario for performance improvement and vibration reduction of a helicopter rotor

In this paper, the best actuation scenario is sought using a multitude of active twist control inputs taking advantage of a global search algorithm to improve performance and reduce vibration of a helicopter rotor. The active twist schemes include a single harmonic, multiple harmonic, and three different segmented non-harmonic actuation cases. An advanced particle swarm assisted genetic algorithm (PSGA) is employed for the optimizer. In addition, a comprehensive rotorcraft analysis code CAMRAD II is used to reach the trim and to predict the rotor power and hub vibratory loads. A scale-down BO-105 model is used for the reference rotor while assuming the actuator material embedded in the blade structure. Among the active twist control inputs, the non-harmonic cases show the best performance gains in reducing the hub vibrations and power consumptions. The hub vibration is reduced by up to 87% while the rotor power required is decreased by 3.3% as compared to the baseline uncontrolled rotor in low speed descending flight condition when using the non-harmonic active twist schedules. The resulting optimized actuation profiles are found for each of the active twist control cases and the physical mechanism leading to less vibration and power consumption is discussed. The Pareto optimum is also examined to illustrate the simultaneous reduction in the power required and the hub vibration of the rotor.

TWIST1 Integrates Endothelial Responses to Flow in Vascular Dysfunction and Atherosclerosis.

Blood flow-induced shear stress controls endothelial cell (EC) physiology during atherosclerosis via transcriptional mechanisms that are incompletely understood. The mechanosensitive transcription factor TWIST is expressed during embryogenesis, but its role in EC responses to shear stress and focal atherosclerosis is unknown. To investigate whether TWIST regulates endothelial responses to shear stress during vascular dysfunction and atherosclerosis and compare TWIST function in vascular development and disease. The expression and function of TWIST1 was studied in EC in both developing vasculature and during the initiation of atherosclerosis. In zebrafish, twist was expressed in early embryonic vasculature where it promoted angiogenesis by inducing EC proliferation and migration. In adult porcine and murine arteries, TWIST1 was expressed preferentially at low shear stress regions as evidenced by quantitative polymerase chain reaction and en face staining. Moreover, studies of experimental murine carotid arteries and cultured EC revealed that TWIST1 was induced by low shear stress via a GATA4-dependent transcriptional mechanism. Gene silencing in cultured EC and EC-specific genetic deletion in mice demonstrated that TWIST1 promoted atherosclerosis by inducing inflammation and enhancing EC proliferation associated with vascular leakiness. TWIST expression promotes developmental angiogenesis by inducing EC proliferation and migration. In addition to its role in development, TWIST is expressed preferentially at low shear stress regions of adult arteries where it promotes atherosclerosis by inducing EC proliferation and inflammation. Thus, pleiotropic functions of TWIST control vascular disease and development.

Performance Enhancement of Tilt-Body Micro Air Vehicle by Use of Orthotropic Laminated Proprotors

A passive twist control is considered as an adaptive way to maximize the overall efficiency of a proprotor developed for convertible Micro Air Vehicles (MAV). In this paper, adaptation of the proprotor geometry in accordance to flight configurations is achieved by induced twist generated by the inherent structural coupling effect in anisotropic composite material and centrifugal force emanating from the tip load. Beam Finite Element Model based on Rotating Timoshenko Theory is used to predict structural loads, while Blade Element Momentum Theory is employed to predict the aerodynamic performance of adaptive proprotor as applied on Micro Air Vehicles (MAV). The iterative process of combination of aerodynamic model and structural model is used to compute the steady-state deformation of the flexible laminated proprotor blade due aerodynamic loads. Finally, the optimal design of lamina blade material is carried out to investigate the potential of flexible blade in the proprotorperformance enhancement.

Cosine apodization of dual-resonance all-fiber acousto-optic tunable filters.

We experimentally demonstrate a novel cosine apodization technique for dual-resonance all-fiber acoustic-optic tunable filter. The technique is based on a hybrid control of input acoustic polarization state and circumferential fiber twist. We will show that intrinsic sidelobe spectra occurring between dual filtering bands are successfully suppressed through our approach, which will be also theoretically confirmed via our analytical and numerical studies. The results illustrate that the spectral positions of each resonance are tuned linearly and continuously by the fiber twist, and that overall sidelobe spectra between two resonances are suppressed regardless of fiber twist angle. The proposed scheme is useful to minimize cross talk between adjacent wavelength channels in optical sensor systems. We highlight that our approach is directly applicable to low-noise matched filtering.

Performance improvement of small-scale rotors by passive blade twist control

A passive twist control is proposed as an adaptive way to maximize the overall efficiency of the small-scale rotor blade for multifunctional aircrafts. Incorporated into a database of airfoil characteristics, Blade Element Momentum Theory is implemented to obtain the blade optimum twist rates for hover and forward flight. In order to realize the required torsion of blade between hover and forward flight, glass/epoxy laminate blade is proposed based on Centrifugal Force Induced Twist concept. Tip mass is used to improve the nose-down torsion and the stabilization of rotating flexible blade. The laminate blades are tested in hover and forward flight modes, with deformations measured by Laser Displacement Sensor. Two Laser Displacement Sensors are driven by the tracking systems to scan the rotating blade from root to tip. The distance from blade surface to a reference plane can be recorded section by section. Then, a polynomial surface fitting is applied to reconstruct the shape of rotating blade, including the analysis of measurement precision based on the Kline–McClintock method. The results from deformation testings show that nose-down torsion is generated in each flight mode. The data from a Fluid Structure Interaction model agrees well with experimental results at an acceptable level in terms of the trend predictions.

The control of twisting somersaults

In the takeoff and early flight phase of a twisting somersault, joint coordination is based on feed-forward control whereas in the late stages of the flight phase configuration adjustments are made using feedback control to ensure accurate completion of the movement and appropriate landing orientation. The aim of this study was to use a computer simulation model of aerial movement to investigate the extent to which arm and hip movements can control twist and somersault rotation in the flight phase of a twisting somersault. Two mechanisms were considered for the control of twist in simulated target trampoline movements with flight times of 1.4s. In the first case a single symmetrical arm adduction correction was made using delayed feedback control based on the difference between the twist rate in a perturbed simulation and the twist rate in a target movement comprising a forward somersault with 1½ twists. Final corrections were made using symmetrical arm abduction and hip flexion to adjust the twist and somersault angles. In the second case continual asymmetrical arm adduction/abduction adjustments were used to remove the tilt from a perturbed full twisting backward somersault using delayed feedback control based on twist angle and angular velocity. The first method was able to cope with perturbations to a forward somersault with 1½ twists providing the feedback time delay was less than 200ms. The second method was able to correct a perturbed full twisting backward somersault providing the feedback time delay was less than 125ms.