Search

This article discusses the construction of a dynamic model for controlling the position of the blades of a vertical-axis wind generator using an automatic approach; a method is presented that relates the rotation of the motor to the position of the blades, which allows the optimization of the operation of the control system. In the research process, an automatic approach is used, which makes it possible to carry out numerical calculations that predict the behavior of the system at various values of motor rotation. The model allows us to analyze the dependence of the position of the blades on the rotation of the motor and determine the optimal parameters of the mathematical control model. The main goal of our study is to develop a mathematical model of the mechanism for further adjustment of the wind turbine blade position control system depending on the wind speed.

Abstract The puncture of glass fibre reinforced polymer (GFRP) laminate is a primary damage pattern of wind turbine blades due to lightning strikes. A numerical simulation model of positive streamer propagation in a needle‐to‐plate air gap with a GFRP laminate is established to investigate the breakdown mechanism of GFRP laminate. The model not only considers the dynamics of charged particles in the air and the composite laminate, but also the current continuity at gas–solid interfaces. The simulated streamer discharge pattern and the surface streamer length are in good agreement with the observation results. The distributions and evolutions of the electron number density, electric field, and surface charge densities during streamer propagation are obtained. It is found that the enhancement of the electric field on the GFRP laminate is caused by the rapid deposition of positive and negative space charges on the GFRP laminate after a secondary streamer incepts on the lower surface of the GFRP laminate. The effects of the applied voltage, relative permittivity, and thickness of the GFRP laminate on the electric field on the GFRP laminate are investigated. The obtained results could assist in further understanding of the mechanism of GFRP wind blade breakdown due to lightning strikes.

ional Academy of Sciences of Belarus, Minsk, the Republic of Belarus The substantiation of the design and technological scheme of the machine for the mechanical collection of the Colorado potato beetle in the production of environmentally friendly potato is carried out. The parameters and modes of rotors with flexible-elastic blades and regulators of the amplitude of their oscillations, providing high-quality shaking and collection of Colorado potato beetle individuals from the tops with minimal damage, have been experimentally substantiated. A description of the laboratory installation, an experimental sample of a combined unit is presented, and a methodology for conducting experiments is described. Experimental studies were carried out in 2004-2008 in the experimental field of the Educational institution "Grodno State Agrarian University" (UO "GGAU") and in the fields of the Agricultural production cooperative (SEC) "Zanemansky" of the Mostovsky dis-trict of the Grodno region. It was found that in order to reduce the energy intensity of the process, the interaction of the rotor with the tops in its apical part, where the maximum con-centration of Colorado potato beetle individuals takes place, is expedient. The minimum amount of beetle on the tops and the absence of visible damage to it are achieved when the diameter of the nylon threads of the blade is 1.2-1.5 mm, and the rational position of the regulator from the rotor axis is 0.14-0.18 m according to the energy intensity condition. Under the condition of minimal energy consumption of the process and without visible damage to the leaves, the circumferential speed range of the rotor should be 3-4 m/s. A regression equation of the second degree is obtained, which determines the relationship of the residual number of beetle individuals on the tops after the passage of the machine with the circumferential speed of the rotor Voc, the position of the regulator on the radius of the rotor Rr and the cross section of the blade Sbl. The optimal values were determined by solving the equation: Voc = 3.7 m/s, Rr = 0.16 m, Sbl = 1800 mm2 .

Blade icing detection is critical to maintaining the health of wind turbines, especially in cold climates. Rapid and accurate icing detection allows proper control of wind turbines, including shutting down and clearing the ice, thus ensuring turbine safety. This article presents a wavelet-driven multiscale graph convolutional network (MWGCN), which is a supervised deep learning model for blade icing detection. The proposed model first uses wavelet decomposition to capture multivariate information in the time and frequency domains, and then employs a temporal graph convolutional network (GCN) to model the intervariable correlations of the decomposed multiscale wavelets and their temporal dynamics. In addition, this article introduces scale attention to the MWGCN for a further improvement of the model and proposes the method to address the class imbalance problem of the training data sets. Finally, the article conducts comprehensive experiments to evaluate the proposed model, and the results demonstrate the effectiveness of the model in blade icing detection and its better performance over eight state-of-the-art algorithms, with 17.2% and 11.3% higher F1 scores over the best state-of-the-art baseline on the labeled datasets. [ABSTRACT FROM AUTHOR]

Automation is a key technology for a sustainable and secure meat sector in the future, both in terms of productivity and work environment. New robotic technologies, such as the so-called “meat factory cell,” (MFC) aim to contribute to this goal, but they require new “smart” tools that provide sensor feedback, which enable robots to perform complex tasks. This article presents one such tool: the smart knife, which gives real-time feedback on its contact status with meat, as well as cutting depth. The tool and the system are described, and its operation evidenced via electromagnetic (EM) simulation using the Ansys High-Frequency Structure Simulator. Furthermore, the performance of the knife is validated using pork loin meat: in the worst case, knife is shown to have an error of 1.78% for contact detection, and a mean error of 7.66 mm (±1.45 mm) for depth detection. This article also presents brief discussion regarding eventual use of the knife as part of the MFC control system, in addition to future work to be performed. [ABSTRACT FROM AUTHOR]

Wind turbines (WTs) can beseriously damaged by lightning strikes and they can be struck by a significant number of flashes. This should be taken into account when the WT lightning protection system is designed. Moreover, WTs represent a path for the lightning current that can modify the well-known effects of the lightning discharge in terms of radiated electromagnetic fields, which are a source of damage and interference for nearby structures and systems. In this paper, a WT struck by a lightning discharge is analyzed with a full-wave modelling approach, taking into account the details of the WT and its interactions with the lightning channel. The effects of first and subsequent return strokes are analyzed as well as that of the rotation angle of the struck blade. Results show that the lightning current along the WT is mainly affected by the ground reflection and by the reflection between the struck blade and the channel. The computed electromagnetic fields show that, for subsequent return strokes, the presence of a WT almost doubles their magnitude with respect to a lightning striking the ground. Such enhancement is emphasized when the inclined struck blade is considered. [ABSTRACT FROM AUTHOR]

Robotic 3-D measurement for evaluating the final shape of blades can improve product quality and reduce fabrication costs. However, large or complex objects require multiple scans from different viewpoints to capture the entire object. They must then be registered to a common frame. Errors in registration artificially introduce defects and surface discontinuities in the reconstructed object model. To address the sources of inaccurate registration for methods relying on pairwise associated points, this manuscript describes an inlier selection approach based on the geometric properties of rigid registration, called RiGID. It readily applies to registration strategies that use 3-D interest points and descriptors to associate data across overlapping point clouds. RiGID converts geometric constraint violations into distributions over geometric error values. Analysis of the distributions provides a deterministic and data adaptive way to identify inlier sets. Given the inlier set, standard registration approaches may be applied. RiGID is an efficient preprocessor to rigid registration. It reduces the amount of input data and improves the inlier ratio, which translates to more efficient and accurate registration. Evaluation of the method shows a higher inlier rate and lower registration error compared to baseline outlier rejection methods. The approach is well suited to surfaces with smooth regions and a high percentage of outliers (up to 90%), which engine and turbine blades exhibit. [ABSTRACT FROM AUTHOR]

Tandem rotor, as a concept, promises a higher diffusion capacity than a single rotor. However, it is reported to have a lower operating range than the conventional rotor. Inflow distortion can lead to significant changes in the flow dynamics of the axial-flow compressor. Further, a highly loaded tandem blade is likely to be severely affected due to the inflow distortions. In this study, circumferential distortion is imposed at the inlet of a tandem stage and its response is studied, using steady and unsteady probes. The performance characteristics and other aerodynamics parameters under the circumferential distortion are compared with the clean inflow case. As expected, the tandem stage experiences a significant drop in the total pressure rise and operating range under circumferential distortion. A large deficit in the total pressure, efficiency, and axial velocity is observed in the distorted region. The casing pressure traces, Morlet wavelet analysis, and Fast Fourier Transform techniques are used to analyze the unsteady data. The stall is incepted in the form of a low-intensity spike, which later evolved into a fully grown stall within 2.5 rotor revolutions. Further, the amplitude of the stall cell under the circumferential distortion is found to be higher than the clean flow. [ABSTRACT FROM AUTHOR]

Additional guide vane (GV) to the Savonius rotor is used to overcome the low rotor efficiency. This study is experimentally carried out to know the influence of guide vane in improving two blades Savonius rotor performance. There were four designs of guide vane which are 4, 5, 6 blades and installed at different tilt angles, which were 0°, 20°, 40°, and 60°. The experiment was done under wind speed of 5.9 m/s, 7.0 m/s, 8.1 m/s, 9.3 m/s and 10.4 m/s. The results show that the 6 blades of GV at a 60° tilt angle attained the best Cp, which was 0.0279 at the tip speed ratio of 0.53. The Cp increased up to 40% with six blades of GV. Wind direction identified significantly affected the rotor performance. The rotor performed best on the wind direction of 0° attained Cp of 0.079, but when the wind direction was modified on 30°, the rotor with 6 GV attained Cp of 0.0153 did not perform better than without GV that produced Cp of 0.0166. The guide vanes improve the Savonius rotor performance compared to the rotor without a guide vane. However, the wind direction also needs to be considered no less important factor affecting the Savonius rotor performance.

Currently, renewable energies, including wind energy, have been experiencing significant growth. Wind energy is transformed into electric energy through the use of wind turbines (WTs), which are located outdoors, making them susceptible to harsh weather conditions. These conditions can cause different types of damage to WTs, degrading their lifetime and efficiency, and, consequently, raising their operating costs. Therefore, condition monitoring and the detection of early damages are crucial. One of the failures that can occur in WTs is the occurrence of cracks in their blades. These cracks can lead to the further deterioration of the blade if they are not detected in time, resulting in increased repair costs. To effectively schedule maintenance, it is necessary not only to detect the presence of a crack, but also to assess its level of severity. This work studies the vibration signals caused by cracks in a WT blade, for which four conditions (healthy, light, intermediate, and severe cracks) are analyzed under three wind velocities. In general, as the proposed method is based on machine learning, the vibration signal analysis consists of three stages. Firstly, for feature extraction, statistical and harmonic indices are obtained; then, the one-way analysis of variance (ANOVA) is used for the feature selection stage; and, finally, the k-nearest neighbors algorithm is used for automatic classification. Neural networks, decision trees, and support vector machines are also used for comparison purposes. Promising results are obtained with an accuracy higher than 99.5%.

Solar sail appears to be promising and effective spacecraft in interplanetary missions; however, performance degradation is inevitable during its long-term voyage, caused by materials wastage and accidents. This study designed a solar sail with numerous discrete elements (SSNDE) and an intelligent attitude control strategy (IACS) to prevent performance degradation and decrease its harmful effect. Structural analysis of SSNDE revealed improvement in reduction of system errors caused by irregular blade deformation and mechanical abrasion via employing numerous discrete elements with rigid boundaries. Furthermore, IACS enables SSNDE to maintain control ability despite the invalidation of a quarter of blades, which can be verified by simulation results. The SSNDE design and its IACS endow an effective solution to decrease performance degradation against material wastage and unpredictable accidents in interplanetary missions. Moreover, they reveal the potential of intelligent strategy in the future aerospace industry. [ABSTRACT FROM AUTHOR]

A stability control device (SCD) is a passive inlet cover treatment that can be applied to high suction performance inducers. Significant improvements in stability have been observed when an inducer operates with an SCD, including suppression of backflow at the leading edge of the inducer at low off-design flow coefficients. This is possible because of a local increase in mass flow at the leading edge of the pump, which allows an inducer to operate with an incidence near the design point value over a wide range of flow coefficients. In this paper, the suction performance of several inducers was explored with several different SCD geometries and at different flow coefficients. Specifically, five different SCD geometries were considered to explore the influence that SCD bleed slot width and resistance to flow through the SCD channel have on inducer performance. Further, removal of tangential velocity of the energized fluid transporting through the SCD channel was considered for some scenarios to highlight the impact of swirl on inducer performance. The results reveal that for all inducers and SCD combinations considered, the most important factor affecting the mass flow through the SCD, and subsequent mass flow gain, is the inlet diffusion of the inducer. This holds for both single-phase and multiphase scenarios. Further, the cavitation number where cavitation first starts to develop in the blade throat passage of the inducer is primarily dependent on the inlet blade angle and not the SCD geometry. Consequently, the shape of the cavitation breakdown curve is largely determined by the inducer blade angle. [ABSTRACT FROM AUTHOR]

The power produced by a wind turbine depends on environmental conditions, working parameters, and interactions with nearby turbines. However, these aspects are often neglected in the design of data-driven models for wind farms’ performance analysis. In this article, we propose to predict the active power and to provide reliable prediction intervals via ensembles of multivariate polynomial regression models that exploit a higher number of inputs (compared to most approaches in the literature), including operational and thermal variables. We present two main strategies: the former considers the environmental measurements collected at the other wind turbines in the farm as additional modeling information for the turbine under analysis; the latter combines multiple models relative to different operative conditions. We validate our approach on real data from the SCADA system of a wind farm in Italy and obtain a MAE of the order of 1.0% of the rated power of the turbine. Moreover, due to the structure of our approach, we can gain quantitative insights on the covariates most frequently selected depending on the working region of the wind turbines. [ABSTRACT FROM AUTHOR]

Magnifying lenses based on acoustic metamaterials (MMs) play an important role in many practical applications requiring acoustic focusing and amplification detection. However, the current 3D meta-lenses are still plagued by low flexibility, huge volumes, and high manufacture costs. We report a 3D meta-lens composed of discretely distributed meta-helicoid element that can solve the above problems. We improve the traditional helical MMs by reducing the number of blades to increase the distance between blades, achieving higher transmission efficiency and avoiding blade adhesion during manufacture. In order to eliminate the uneven phase and pressure of single-helicoid MMs at the outlet, pipe extension method is used to unify the phase and pressure. Via adjusting the spiral pitch, the meta-helicoid can generate 0- $2 \boldsymbol {\pi }$ phase delay with a fixed outline size while maintaining transmittance greater than 90%. Based on the small single-helicoid meta-element, we design and manufacture a low-cost 3D magnify meta-lens with compact size. We demonstrate, both theoretically and experimentally, the acoustic meta-lens can make the normally incident signals focus on the prescribed point, enhances pressure amplitude about three times, and can flexibly manipulate focus point. Moreover, the bandwidth of the meta-lens is as wide as about 5.6 kHz. Our new strategy may offer an alternate route to the design of novel meta-lens and devices for acoustic focusing and amplification detection. [ABSTRACT FROM AUTHOR]

This article proposes a generalized neural continual learning-based cybertwin (GNC) modeling framework to realize developing one wind turbine (WT) cybertwin serving multiple modeling tasks in the wind farm operations and maintenance (O&M). A generalized WT cybertwin modeling problem, which considers modeling one cybertwin for multiple tasks without additional computational burden, is studied for the first time. Fully connected neural networks are adopted as the backbone for developing the GNC model. The online elastic weight consolidation method is incorporated to mitigate the catastrophic forgetting phenomenon among different modeling tasks. Computational experiments are conducted to validate the effectiveness of the proposed GNC framework based on the supervisory control and data acquisition data. Modeling tasks in three important problems of the wind farm O&M, the WT gearbox failure detection, WT blade breakage detection, and wind power prediction, are considered in the experiment. Compared with other benchmarking models, such as the multiple neural cybertwins, neural cybertwin, and regularized neural cybertwin, the proposed GNC can achieve high accuracies on both new tasks and existing tasks, which further verifies the WT cybertwin generalization via the proposed GNC. [ABSTRACT FROM AUTHOR]

In this paper the fabrication and characterization of a novel wireless pressure sensor system that can monitor and report real-time changes in pressure on the rotor blade of a low speed axial compressor is demonstrated. The pressure sensor was positioned on the second-stage rotor at approximately the mid-span location on the pressure surface of the blade near the leading edge and hard wired to a circuit box located on the center line of the compressor drum. The output of the pressure sensor is converted from a voltage to a frequency and transmitted wirelessly via circularly polarized antenna to a stationary antenna that was approximately 1 meter away, mounted at the centerline location on the inlet cart. The output signal was recorded on a spectrum analyzer with a LabVIEW program for data acquisition. Compressor rotation was ramped from 0 RPM up to its design speed of 1000 RPM and the airflow was decreased by closure of downstream throttle valve until the compressor stalled. The measurements from the wireless pressure system show increasing pressure as compressor flow rate is decreased, until a precipitous drop in pressure occurs which signals that the compressor has stalled. [ABSTRACT FROM AUTHOR]

When using robots to carry out grinding and polishing processing of industrial blades, due to factors such as non-zero approach speed and discontinuous dynamic characteristics, the robot grinding and polishing processing has contact force impact and oscillation problems during the contact transition process, which seriously affects the quality of the blade surface processing, contour accuracy, and control system stability. In order to solve the problem of large impact of contact force in robot grinding and polishing, this paper proposes an optimization method for impact suppression in the transition state of robot grinding and polishing. Taking the robot abrasive belt grinding and polishing as the research object, the adaptive weighted particle swarm algorithm is used to optimize the input shaper and realize the parameter self-tuning of the input shaping technology. The experimental results show that the stabilization time is shortened by about 86.5%, and the maximum overshoot of contact force is reduced by about 88.5% during contact transition. The method proposed in this paper can realize the smooth transition of the blade grinding and polishing process, does not need system modeling, effectively shorten the system stabilization time, reduce the maximum overshoot, and accelerate the system response speed, and it has strong stability and flexibility. [ABSTRACT FROM AUTHOR]

Accordingto recent grid codes, large-scale wind turbines (WTs) are required to provide fast frequency response (FFR). The existing stepwise inertial control methods suggest immediate incremental power injection by WTs, followed by the abrupt over-production termination to avoid over-deceleration of the rotor speed. These methods have a drawback that they impose severe secondary frequency drops (SFD), or they consider an unrealistic constant wind speed during their inertial control support. This paper proposes a novel Gaussian distribution-based inertial control (GDBIC) scheme that can improve the frequency nadir without rotor speed over-deceleration. Upon detecting a power imbalance, WT increases the output power with an incremental power and declines it following Gaussian distribution trajectory controlled by a standard deviation parameter, ensuring by this convergence of the rotor speed to a stable equilibrium. The proposed scheme is also capable of responding to a second cascade event. The performance of the GDBIC is tested on the wind-integrated IEEE 9-bus system and the IEEE 39-bus system in DIgSILENT PowerFactory. It is also compared with other methods reported in literature. Furthermore, experimental tests are used to verify the performance of the proposed scheme, using two different hardware-in-the-loop testing facilities. The blade fatigue is studied using Fatigue, Aerodynamics, Structures, and Turbulence (FAST) Code. The simulation and experimental results showed that the release of the kinetic energy in rotors using the proposed GDBIC scheme allows significant improvement of the frequency nadir, with no SFD, as well as contribute to reliable operation during abrupt wind changes. [ABSTRACT FROM AUTHOR]

Wind turbine blade erosion is typically assessed in situ using visual inspection, which is a rudimentary qualitative assessment of the condition of the blade coating system. On coated test specimens in laboratory test conditions, mass loss can provide a better understanding of the stage of erosion, but cannot be extended to real world applications. In this work, by using analysis of photographs, microscopy images, mass data, and gloss data together, it was found that gloss measurements can effectively quantify changes in coating microstructure as a result of rain erosion. This was achieved by correlating and comparing mass loss measurements over time with surface gloss and verifying the erosion stages with photographs and microscopy images. As such, gloss was shown to represent the erosion stages with greater accuracy than the current industry methods. This novel technique has been shown to identify the incubation period, that is the onset of erosion damage, by detecting microstructure changes which are not visible to the naked eye, nor is determinable by mass loss. The quantitative output from the gloss methodology thus allows wind turbine owners and operators to assess, manage, and plan more efficiently for costly erosion repairs and future inspections. The system is presently being used in a laboratory setting, though it has the potential to be combined with drones or climber robots to be remotely used within the wind farm. [ABSTRACT FROM AUTHOR]

Helicopter main rotor blade flashes in radar measurements are an often-used feature for target classification. While focus is often placed on being able to detect them, little attention has been given to what is required to ensure that they are reliably and persistently intercepted. Using mathematical analysis and simulation, this article explores the probability of helicopter blade flash interception in search radar. The effects of radar antenna azimuth beamwidth, scan rate, and waveform on the average probability of intercept for two-bladed helicopter blade flashes (a worst-case scenario) are examined. The results presented provide an upper bound on achievable flash detection performance and can be used to understand and optimize the performance of helicopter classification modes. [ABSTRACT FROM AUTHOR]

A dual-polarized radar system is utilized for non-contact sensing applications involving rotational motion. Polarization-centric methods are employed to sense and characterize responses from an electric motor with various bearing faults and to sense responses from a high-velocity fan. Conventional characterizations, such as power spectral densities and micro-Doppler responses, are compared with polarization-based statistical approaches such as polarization entropy and a newly proposed micro-Entropy approach inspired by the micro-Doppler approach. [ABSTRACT FROM AUTHOR]

Reliability analysis and performance evaluation are complementary methods to quantify nonfunctional aspects of a system. However, a range of factors such as concurrency and heterogeneity quickly exacerbate the state-space explosion problem when attempting detailed system-level modeling and simulation of high-performance computing (HPC) systems. To overcome these impediments to modeling and analysis, this article develops a hierarchical model of an application that implements checkpointing running in an HPC environment subject to application, network, and system-wide outages. The modeling approach ensures that the number of states is linear in the number of checkpoints and possesses a low constant factor for the number of recovery states most relevant to the external influences contributing to degraded application performance. We illustrate the types of analysis enabled by the model through a series of examples with parameters determined empirically from data logs of the Blue Waters supercomputer located at the University of Illinois at Urbana–Champaign. A comprehensive comparative analysis of the model parameters indicates that lowering the failure rate of network nodes would most significantly reduce application downtime. We also discuss how the modeling approach can be used to objectively assess both current and hypothetical future systems to identify competitive designs and enhancements. [ABSTRACT FROM AUTHOR]

To solve theproblems of an insufficient braking moment for the eddy current retarder at high speed, a small braking moment and slow response of the hydraulic retarder at low speed, and a low power density of the existing electromagnetic hydraulic retarder(EHR), a novel radially distributed electromagnetic-hydraulic retarder(R-EHR) was proposed. The R-EHR fully absorbs the advantages of the braking characteristics of hydraulic retarders and eddy current retarders. The cooling fluid is used to realize the braking of the hydraulic part. At the same time, it acts on the heating surfaces to improve the torque of the electromagnetic part. In this paper, finite element models of the flow field and electromagnetic field are established to predict braking performance. The braking performance of the R-EHR is obtained by bench test, the error between the simulation and experimental data is compared, and the experimental data are analyzed. The results show that the proportion of electromagnetic braking torque in the novel R-EHR is more reasonable. The braking torque increased by 26% and the power density increased by 37.5% at 2000 RPM compared to that of the EHR. The R-EHR can control the braking torque only by adjusting the current, thus simplifying the control system. [ABSTRACT FROM AUTHOR]

The asymmetric loads on wind turbines are becoming a fatal constraint factor with the increase of wind turbine size. In order to tackle this challenge, individual pitch control mechanism is introduced into the wind turbines. However, the application scopeof the traditional individual pitch control (IPC) is limited due to the complex dynamic coupling among wind turbine components, the strong nonlinearity of the pitch system and the inevitable unmodeled dynamics. Therefore, a multivariable model-free adaptive control (MIMO-DE-MFAC) strategy with differential characteristic is first proposed in this paper. Then, the proposed method is applied to the individual pitch control of the 5MW wind turbine. The simulation results from FAST demonstrate that the MIMO-DE-MFAC achieves a notable performance improvement on blade root compared with the PI. Furthermore, compared with other existing model-free adaptive control (MFAC) strategies, the proposed method not only achieves the optimal control results, but also has stronger robustness in speed-varying wind fields. Finally, the hardware-in-the-loop (HIL) experiment further verifies the reliability of the above simulation results, which provides a useful reference value for the field test. [ABSTRACT FROM AUTHOR]

Wind farms are usually located in high-latitude areas, which bring a high risk of icing. Traditional methods of anti-blade-icing are limited by extra costs and potential damages to the original mechanical structure. Model-based methods are heavily dependent on mathematical models of the blade icing, which are prone to produce erroneous estimation. As data-driven models are better able to achieve competitive performances for the blade icing estimation, this article proposes a temporal attention-based convolutional neural network (TACNN). This novel data-driven model introduces a temporal attention module into a convolutional neural network, with the goal of determining the importance of sensors and timesteps and automatically identifying discriminative features from raw sensor data. Benchmark experiments on ten public datasets of multivariate time-series classification show competitive performance against the state-of-the-art methods. Compared with ten baseline networks and three widely used attention mechanisms, the TACNN shows significant advantages applying to three real-world datasets. These datasets are logged by the supervisory control and data acquisition system and contain operational and environmental measurements such as power and temperature. The ablation study and sensitivity study demonstrate the effectiveness of the key components of the TACNN. The practicability of the TACNN is further verified through online estimation testing. [ABSTRACT FROM AUTHOR]

Innovations in material properties of goaltender skates have improved the protective characteristics of the boot, leading to redesign of the blade holder to resemble players' holders. The redesigned blade holder introduces the ability to customize blade alignment, which may grant a performance advantage. We investigated the effect of blade alignment on kinematics and plantar pressure during the execution of two different goaltender-specific movement patterns: (1) the butterfly drop to recovery and (2) the lateral butterfly slide to recovery. The main objective of this study was to investigate the effect of three blade alignment conditions. The secondary objective was to compare two neutral alignment conditions, which was facilitated by studying the effects of two different holders on kinematics and plantar pressure during two goaltender-specific techniques. A male goaltender with professional experience completed an A–B–A design, executing five trials of A, B, and A for both movements with each blade alignment condition (n = 30 per collection, n = 90 overall) on synthetic ice in a controlled lab environment. Blade alignment conditions were defined by the alignment of the blade holder on the boot and the type of blade holder. Kinematic and plantar pressure data were collected simultaneously using 3D motion capture and in-skate pressure insoles, respectively. Increased butterfly drop velocity (2.07 ± 0.09 m/s) and peak plantar pressure (77.19 ± 2.67 psi) were revealed when executing the butterfly drop with medial alignment. This work suggests medial blade alignment may enable the goaltender to drop into the butterfly position faster, potentially increasing the likelihood of making a save. [ABSTRACT FROM AUTHOR]

The article proposes maglev wind yaw system for wind turbine to yaw for wind. Two degrees-of-freedom (2-DOF) suspension model is constructed with the suspension current dynamics. A dual-loop cooperative suspension control including inverse system compensation, pseudo suspension control, and hybrid decoupling control is proposed to ensure nacelle stable suspension without pitching. The inverse system compensation gives the nominal current reference; and then the pseudo suspension control is designed from sliding mode controller with the nonlinear function to acquire two pseudo control input, and then 2-DOF disturbance observers based on two sliding mode surfaces and their sign function are proposed to get high-frequency interference, and cooperate with the linear relationship to decouple and give two sides current reference. The closed-loop stability of nacelle suspension has proved by the Lyapunov function, air gap asymptotic tracking can be reached in finite time. The state feedback controller with adaptive compensation is designed to enhance the current dynamic response. Finally, the simulation and experimental results show that the proposed strategy has faster suspension dynamic response, smaller steady-state error, and synchronization error. [ABSTRACT FROM AUTHOR]

The blades of contemporary turboprop engines have a complex spatial configuration. They can be classified as shells. Methods for the shells calculation are well known. A number of computer programs have been created on their basis. However, these programs do not take into account the peculiarities associated with the mutual influence of deformations of the blade and the aerodynamic and inertial loads acting on it. The aim of this work is to develop a method of finite element calculation of aircraft propeller blades taking into account aeroelastic effects and to create a computer program on its basis that is available to a wide range of designers and engineers. The finite element method is used in a geometrically nonlinear formulation. As the initial one, the equilibrium equation is used, which includes a complete nonlinear stiffness matrix and takes into account both conservative and non-conservative loads. The blade of one of the serial propellers was calculated. The effect of deformations on the magnitude of the aerodynamic load and, as a result, on the stresses in the design sections was found and analyzed. The proposed technique and the program compiled on its basis can be used in the design of aircraft propeller blades.

Abstract There exists periodic modulation problem in radar echoes due to the main rotor blades periodic blockage in helicopter‐borne fire‐control radar which is mounted atop the main rotor mast of the helicopter. Such modulation echo induces a set of ghosts in synthetic aperture radar (SAR) image, further resulting in a poor performance of subsequent tracking and striking. To address this problem, this article proposes a method on rotor blades blockage modulation suppression for helicopter‐borne SAR. By decomposing the blocked echo into the form of Fourier series in the azimuth direction, a reference function could be constructed to suppress the modulation directly by adopting an iterative approximation strategy. This method effectively avoids the complex blocked data recovery methods, and thus can be used to suppress various kinds of periodic modulation components without requiring certain distribution models. Both simulated and real‐measured data are processed to demonstrate the effectiveness of the proposed algorithm.

Abstract The micro‐Doppler (m‐D) effect depends on the rotation of rotor blades in addition to the translation of the platform. Thus it is a characteristic for identifying small unmanned aerial vehicles (UAVs). However, compared with the Doppler signal induced by the translation of the platform, the m‐D signal is weak. In this article, a highly localised data‐association method, intrinsic synchrosqueezing analysis (ISA), is proposed for estimating m‐D characteristics from the returned signal of small UAVs with a dual‐channel radar. Employing synchrosqueezing transform on intrinsic mode functions derived from noise‐assisted multivariate empirical mode decomposition, the proposed ISA method separates the Doppler signal and enables denoising and sharpening time‐frequency representation of the m‐D signal. Simulation results confirm the theoretical analysis, showing the feasibility of estimating m‐D features in a noisy environment. Applications on field data illustrate brighter prospects for identifying small UAVs.

Direct grid coupling of permanent magnet synchronous generators (PMSG) for wind energy conversion systems provides certain advantages with the penalties of maximum power point tracking (MPPT) and reactive power control. This article proposes a novel PMSG design philosophy such that optimizing PMSG design at the initial stage would compensate for the drawbacks arising from the lack of an MPPT algorithm. Also, the ability to maintain a high PF across a wide range of operating power levels is investigated by considering reactive power in the design process. In this article, optimization of slot/pole combination is described for direct grid coupled PMSGs to extract as much energy as possible according to wind data. A new benchmark, adequacy factor, is presented to determine the slot/pole combination. Variation of the reactive power is theoretically analyzed. A relationship is established between induced electromotive force, synchronous inductance values of machines, and the PF. Fixed and variable speed operations of PMSGs are compared in terms of annual energy yield. Finally, theoretical analyses are validated through laboratory testing of prototype generators. [ABSTRACT FROM AUTHOR]

Alterations in the structure of a magnetron, e.g., the A6 relativistic magnetron, are proposed, which considerably increase the device’s build-up speed. We cover the magnetron vane surfaces with semiconductor layers of nonzero electric conductivity, with an exact geometrical design. Semiconductor layers with considerable mechanical strength also provide excellent shielding for the vanes against the high-energy relativistic electrons’ bombardment. The novel structure introduces several new free parameters to the magnetron design procedure and considerably increases the design flexibility. A multistage exact optimization procedure, performed by extensive computer simulations, shows that applying silicon carbide layers with proper geometrical design doubles the build-up speed. In a general trend, we also indicate that adding semiconductor layers with nonzero electric conductivity to the magnetron vanes’ surfaces typically fastens the system by reducing the build-up transient time. It is verified that the insertion of conductivity to the vanes’ bodies with the proper design of shape and depth can increase the mode frequencies, build-up speed, and strength against electrons bombardment, saving the output amplitude. Finally, as shown by the simulation results data, the system behavior is analyzed theoretically. [ABSTRACT FROM AUTHOR]

In this article, a novel time-domain frequency estimation approach is proposed based on the well-known subspace identification method. Differing from the fast Fourier transformation method, the nonlinear identification for frequency estimation is reformulated into the eigenvalue identification problem, which avoids the spectrum peak search. The recursive frequency estimation approach is proposed based on the updating/downdating of the Cholesky decomposition, where the extended observability matrix can be identified from a small matrix with lower computation cost. In addition, a gap metric-oriented performance indicator is proposed as a test statistic for fault detection as well as the evaluation of fault severity. The effectiveness of the proposed methods is verified for frequency estimation and fault diagnosis performance through numerical simulations and the experimental measurements from a laboratory unmanned aerial vehicle rig with partial blade damage. [ABSTRACT FROM AUTHOR]

The objective of this paper is to experimentally and numerically investigate the transient cavitation flow during the startup process of mixed flow pump with emphasis on studying the influence of blade numbers. The transient cavitation simulation was studied based on the improved SST k-ωk turbulence model and the Zwart cavitation model. Firstly, in order to obtain the relationship between transient flow rate and the variation of rotational speed at startup, a theoretical analysis based on the fast transients of centrifugal pump was first applied to mixed flow pump and was verified by the current experiment study. Subsequently, the influence of blade number on the cavitation flow in the startup was studied. It is found that the transient cavitation could be classified into four stages regardless of the number of blades: no cavitation stage, the cavitation growth stage, the cavitation reduction stage and the cavitation stabilization stage. However, the blade number does have an impact on the spatial-temporal evolution of cavitation. More specifically, when the blade number increases, the initial cavitation appeared lately, the coverage area of the triangular cavitation cloud and sheet cavitation both decreased, and the increase in blade number has a better inhibitory effect on the sheet cavitation at the cavitation growth stage, and can make sheet cavitation disappear more quickly at the cavitation reduction stage. [ABSTRACT FROM AUTHOR]

In this paper, the risk of cavitation erosion is assessed in a commercial water-jet pump using a recently developed numerical erosion assessment method by Arabnejad et al. (2021, "Numerical Assessment of Cavitation Erosion Risk Using Incompressible Simulation of Cavitating Flows," Wear, 464-465, p. 203529). This assessment is performed for two flow conditions with different cavitation erosion risk according to the experimental paint tests and the high erosion risk areas identified by the method are compared with the experimental results. This comparison shows that the applied method is capable of both identifying the regions of high erosion risk and also capturing the difference between the cavitation erosion risk in the two studied conditions. The latter capability of the numerical assessment method, which has not been reported in the literature for other published methods, is one step forward toward the application of the method in the design process of hydraulic machines. Furthermore, the numerical results are analyzed to explain the reasons for different erosion risk in the two conditions. This analysis reveals that this difference is mostly related to the stronger flow nonuniformities entering the rotor in the most erosive condition. Using the numerical results, one reason behind these stronger nonuniformities is identified to be the stronger bursting of vortices shed from the shaft in the most erosive condition. [ABSTRACT FROM AUTHOR]

A single top-hat antenna using blade modulation is presented for direction finding (DF). Unlike conventional DF techniques requiring an antenna array with multiple elements, the fixed single antenna is utilized to receive incoming signals. To enhance radiation pattern diversity and perform direction of arrival estimation, four rotating blades are placed around four corners of the antenna. The antenna is designed to operate at the frequency where the incoming wave is in resonance with the metallic blades. The incoming signals are recorded as blades rotating with an angle from 0 $^\circ $ to 180 $^\circ $. To validate the radiation pattern diversity at the resonant frequency and out of the operational frequency band, correlation coefficients of amplitude and phase of complex radiation patterns between the antennas with different blade rotation angles are investigated. DF accuracy in azimuth directions of the proposed single antenna with blade modulation is demonstrated by Cramer–Rao bound using the complex radiation patterns at different frequencies. [ABSTRACT FROM AUTHOR]

Large scale aerial deployment of miniature sensors in tough environmental conditions requires a deployment device that is lightweight, robust, and steerable. We present a novel samara-inspired autorotating craft that is capable of two flight modes (autorotating mode and diving mode) with an average glide angle of 28.9 $^{\circ }$ (1.81 m lateral distance per 1 m loss of altitude) in the former mode. The bidirectional transition between the two modes and directional control is achieved by using only a single actuator. Also, in order to minimize its glide angle, a design optimization methodology is presented for our prototype, diving samara autorotating wing, along with a new cyclic control strategy for directional control of autorotating descent. The dynamic model, simulated in a six degrees-of-freedom environment using the blade element theory, is integrated with genetic algorithm to derive parameters for the wing geometry, flap angle for autorotation, and the proposed cyclic control. The physical prototype autorotates at a descent velocity of 1.43 m/s and rotation speed 4.17 Hz, and is able to transit to diving mode in an average duration of 272 ms to increase its descent velocity by at least 17.6 times. At any point during the dive, it is able to transit back into autorotation in an average duration of 327 ms. Semioutdoor experiments were used to investigate the bidirectional transitions and verify the glide angle (28.9 $^{\circ }$), which is much improved from the previous prototype (SAW+, 58.4 $^{\circ }$). Lastly, as a demonstration of a real-life deployment scenario and environmental conditions, the prototypes were dropped from a fixed-wing unmanned aerial vehicle at a suburban test site. [ABSTRACT FROM AUTHOR]

This study proposes an innovative method to wirelessly measure the ultra-high temperatures of rotational parts in aero-engines/turbines. The upper measurement limit of this proposed sensor is $1100 ^\circ \text{C}$. Based on the thick film integration process, the inductor and capacitor are integrated in-situ on the ceramic turntable and ceramic blade. The inductor and capacitor operate in the high temperature and ultra-high temperature areas, respectively, and the temperature signal is transmitted through the electromagnetic coupling between the inductor coil and the antenna. The design of the structure separating the capacitor and inductors is important and can improve the sensor’s high temperature signal reading performance. The designed sensor is tested in the temperature range of 25– $1100 ^\circ \text{C}$ and the rotational speed range of 0–400 rpm. The results show that the minimum sensitivity of the sensor at different rotational speeds is 7.66 kHz/ $^\circ \text{C}$ , and the minimum sensitivity of the sensor at different rotational speeds is 7.83 kHz/ $^\circ \text{C}$. The maximum standard deviation and repeatability of the sensor measured across different temperatures and rotational speeds are 0.11(400 rpm, 900 °C)and 0.389%(400 rpm, 900 °C), respectively. The interference of the rotational speed on the temperature test of the sensor is negligible. The experimental results show that the sensor has strong signal strength in ultra-high temperature rotational environments and is suitable for ultra-high temperature testing. [ABSTRACT FROM AUTHOR]

PbTiO3 was used as a dopant and PbTiO3/titanium dioxide (TiO2) nanofibers (NFs) were used as a scattering layer in the photoanode of dye-sensitized solar cell (DSSC). Their effects on the characteristics of the photoanode of DSSC were studied. The DSSC with the modified photoanode by PbTiO3 and PbTiO3/TiO2 NFs was characterized by X-ray diffractometer (XRD), electrochemical impedance spectroscopy (EIS), ${J}$ – ${V}$ characterization, and incident photon current efficiency (IPCE) measurement. The results show that PbTiO3 and PbTiO3/TiO2 NFs can improve the photovoltaic characteristics of DSSC photoanode. The DSSC with modified photoanode by PbTiO3/TiO2 NFs shows better photoelectric conversion efficiency ($\eta $). Compared with the DSSC without modification (TiO2 photoanode), the photovoltaic conversion efficiency ($\eta $) of the DSSC with modified photoanode by PbTiO3/TiO2 NFs has increased by 19%. Based on this research, it can be considered that PbTiO3/TiO2 NFs can be used as one of the candidate materials to improve the photovoltaic performance of DSSCs. [ABSTRACT FROM AUTHOR]

Piercing connectors are among the most used equipment in electric circuit. With the continuous development of the electricity industry, higher requirements for the reliability and heat resistance of the piercing connectors are needed. Aiming at the problems of poor current carrying capacity and heat dissipation status, a multifield coupling model of the piercing connector is created to analyze the structural stress and deformation distribution under the action of preload from the bolt and simulate the temperature distribution under different current intensities and surface roughness. Meanwhile, the measured experiments of contact resistance and highest temperature are performed to explore the relationship between contact resistance and the highest temperature. Results show that the maximum stress of the piercing connector is in the contact region between the piercing blade and the wire, which may be the origin of strength failure. The greater the current intensity and surface roughness, the more obvious the temperature rise. The effect of the different specification combinations of power wire and branch wire on contact resistance is small. Moreover, a critical installation torque exists in the influence range. The experimentally measured temperature verifies that the simulation has high precision. In this article, the numerically calculated and experimentally measured results provide a theoretical basis for optimizing the manufacturing and service performance of the piercing connectors. [ABSTRACT FROM AUTHOR]

Heat flux is key parameter for evaluating the heat dissipation of turbine blade. The accurate measurement of heat flux is vital for the optimizing cooling system and fabrication of turbine blade. The thin film heat flux gauge is usually fabricated on insulated substrate and located away from the measured area of turbine blade. As a result, the changes of heat flux on the surface of turbine blade cannot be reflected quickly and accurately. This paper innovatively designs membrane structure of thin film heat flux gauge on nickel alloys. The sensor is fabricated on the surface of the nickel alloys by thin-film depositing technology to realize in-situ surface heat flux measurement, and ITO/In2O3 thermopile is used to replace precious thermopile to improve sensitivity. The results show that the sensitivity and response frequency of the sensor respectively are measured to be $61.93~\mu \text{V}$ /(kW/m2) and over 14400Hz respectively, which can measure heat flux of 236.4kW/m2 at $888^\circ \text{C}$. Besides, the thin film heat flux gauge is fabricated on the surface of turbine blade to verify functional feasibility with same preparation process of that on nickel alloys, and can obtain reproducible results. This work suggest that the thin film sensor based on ITO/In2O3 thermopile has great potential in applications used as optimizing cooling system of components in aeronautics and astronautics. [ABSTRACT FROM AUTHOR]

Model predictive control (MPC) is a control method that involves determining the input to a dynamical system as the solution to an optimization problem that is solved online. In the wind turbine research literature, MPC has received considerable attention for its ability to handle both actuator constraints and preview disturbance information about the oncoming wind, which can be provided by a lidar scanner. However, while many studies simulate the wind turbine response under MPC, very few physical tests have been carried out, likely due in part to the difficulties associated with solving the MPC problem in real time. In this work, we implement MPC on an experimental, scaled wind turbine operating in a wind tunnel testbed, using an active grid to create reproducible wind sequences and a hot-wire anemometer to generate upstream wind measurements. To our knowledge, this work presents the first physical test of MPC for blade pitch control of a scaled wind turbine. We compare two MPC strategies: one including preview disturbance information and one without. Our results provide further evidence that feedforward control can improve wind turbine performance in transition and above-rated conditions without increasing actuation requirements, which we hope will encourage industry experimentation and uptake of feedforward control methods. We also provide a high-level analysis and interpretation of the computational performance of the chosen approach. This work builds upon the results of an earlier study, which considered unconstrained optimal blade pitch control. [ABSTRACT FROM AUTHOR]