scholarly journals An innovative method to calibrate a spinner anemometer without the use of yaw position sensor

2016 ◽  
Vol 1 (2) ◽  
pp. 143-152 ◽  
Author(s):  
Giorgio Demurtas ◽  
Nick Gerardus Cornelis Janssen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Calibration Method ◽  
Mean Value ◽  
Position Sensor ◽  
Flow Angle ◽  
Angle Measurements ◽  
Innovative Method ◽  
Calibration Methods ◽  
The Mean

Abstract. A spinner anemometer can be used to measure the yaw misalignment and flow inclination experienced by a wind turbine. Previous calibration methods used to calibrate a spinner anemometer for flow angle measurements were based on measurements of a spinner anemometer with default settings (arbitrary values, generally k1,d  =  1 and k2,d  =  1) and a reference yaw misalignment signal measured with a yaw position sensor. The yaw position sensor is normally present in wind turbines for control purposes; however, such a signal is not always available for a spinner anemometer calibration. Therefore, an additional yaw position sensor was installed prior to the spinner anemometer calibration. An innovative method to calibrate the spinner anemometer without a yaw positions sensor was then developed. It was noted that a non-calibrated spinner anemometer that overestimates (underestimates) the inflow angle will also overestimate (underestimate) the wind speed when there is a yaw misalignment. The new method leverages the non-linearity of the spinner anemometer algorithm to find the calibration factor Fα by an optimization process that minimizes the dependency of the wind speed on the yaw misalignment. The new calibration method was found to be rather robust, with Fα values within ±2.7 % of the mean value for four successive tests at the same rotor position.

scholarly journals An innovative method to calibrate a spinner anemometer without use of yaw position sensor

2016 ◽  
Author(s):  
Giorgio Demurtas ◽  
Nick Gerardus Cornelis Janssen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Calibration Method ◽  
Mean Value ◽  
Position Sensor ◽  
Flow Angle ◽  
Angle Measurements ◽  
Innovative Method ◽  
Calibration Methods ◽  
The Mean

Abstract. A spinner anemometer can be used to measure the yaw misalignment and flow inclination experienced by a wind turbine. Previous calibration methods used to calibrate a spinner anemometer for flow angle measurements were based on measurements of a spinner anemometer with default settings and a reference yaw misalignment signal measured measured with a yaw position sensor. The yaw position sensor is normally present in wind turbines for control purposes, however, such a signal is not always available for a spinner anemometer calibration. Therefore, an additional yaw position sensor has been installed prior to the spinner anemometer calibration. An innovative method to calibrate the spinner anemometer without a yaw positions sensor was then developed. It was noted that a non calibrated spinner anemometer that overestimate (underestimate) the inflow angle will also overestimate (underestimate) the wind speed when there is a yaw misalignment. The new method leverage on the non linearity of the spinner anemometer algorithm to find the calibration factor Fα by an optimization process that minimizes the dependency of the wind speed to the yaw misalignment. The new calibration method was found to be rather robust with Fα values within ±2.7 % of the mean value for four successive tests at the same rotor position.

Interannual Wind Speed Variations and Estimated Wind Turbine Generator Energy Output at Selected Sites in the Pacific Northwest

1985 ◽  
Vol 107 (3) ◽  
pp. 237-239
Author(s):  
R. W. Baker
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Pacific Northwest ◽  
Power Measurement ◽  
Energy Output ◽  
Turbine Generator ◽  
Wind Turbine Generator ◽  
Speed Variation ◽  
Percent Increase ◽  
The Mean

The hourly wind speed data collected over a six-year period at four wind power measurement locations are used to estimate the annual energy output of a large wind turbine generator. The interannual energy and wind speed variations are discussed. The estimated interannual energy output at each location is related to the mean annual wind speed variation. The data indicate that at three of the four locations the estimated interannual energy variation varied as the square of the mean annual wind speed variation. That is, a 10 percent increase in the mean annual wind speed resulted in a 20 percent increase in the annual energy output. At the fourth location there was an approximate linear relationship.

scholarly journals Quantitative diffusion tensor MRI-based fiber tracking of human skeletal muscle

2007 ◽  
Vol 103 (2) ◽  
pp. 673-681 ◽  
Author(s):  
Drew A. Lansdown ◽  
Zhaohua Ding ◽  
Megan Wadington ◽  
Jennifer L. Hornberger ◽  
Bruce M. Damon
Keyword(s):  
Muscle Fiber ◽  
Diffusion Tensor ◽  
Fiber Tracking ◽  
Laboratory Frame ◽  
Mean Value ◽  
Pennation Angle ◽  
Frame Of Reference ◽  
Fiber Tracts ◽  
Angle Measurements ◽  
The Mean

Diffusion-tensor magnetic resonance imaging (DT-MRI) offers great potential for understanding structure-function relationships in human skeletal muscles. The purposes of this study were to demonstrate the feasibility of using in vivo human DT-MRI fiber tracking data for making pennation angle measurements and to test the hypothesis that heterogeneity in the orientation of the tibialis anterior (TA) muscle's aponeurosis would lead to heterogeneity in pennation angle. Eight healthy subjects (5 male) were studied. T1-weighted anatomical MRI and DT-MRI data were acquired of the TA muscle. Fibers were tracked from the TA's aponeurosis by following the principal eigenvector. The orientations of the aponeurosis and muscle fiber tracts in the laboratory frame of reference and the orientation of the fiber tracts with respect to the aponeurosis [i.e., the pennation angle (θ)] were determined. The muscle fiber orientations, when expressed relative to the laboratory frame of reference, did not change as functions of superior-to-inferior position. The sagittal and coronal orientations of the aponeurosis did not change in practically significant manners either, but the aponeurosis′ axial orientation changed by ∼40°. As a result, the mean value for θ decreased from 16.3 (SD 6.9) to 11.4° (SD 5.0) along the muscle's superior-to-inferior direction. The mean value of θ was greater in the deep than in the superficial compartment. We conclude that pennation angle measurements of human muscle made using DT-MRI muscle fiber tracking are feasible and reveal that in the foot-head direction, there is heterogeneity in the pennation properties of the human TA muscle.

scholarly journals A Truncated Matrix Completion Algorithm Using Prior Information for Wind Turbine Clutter Suppression

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Minghe Mao ◽  
Tianhe Li ◽  
Mingwei Shen ◽  
Ning Cao ◽  
Rui Shi ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Prior Information ◽  
Matrix Completion ◽  
Diagonal Element ◽  
Mean Value ◽  
Singular Value ◽  
Clutter Suppression ◽  
Shrinking Process ◽  
The Mean ◽  
Recovery Result

The conventional matrix completion (MC) regularizes each singular value equally, and thus the rank cannot be well approximated, which greatly limits the flexibility and accuracy of MC usage. In this paper, a truncated MC algorithm using prior information to determine the threshold while generating the target rank is proposed for the wind turbine clutter suppression of weather radar. During the singular value shrinking process, an appropriate threshold is selected to obtain the optimal approximation of the sampling matrix. Specifically, the mean value of the diagonal element in the recovered weather matrix is calculated to improve the robustness of the recovery result effectively. Simulation results demonstrate that the proposed algorithm reduces the computational complexity as well as further improves the MC accuracy and realizes the effective suppression of the wind turbine clutter.

Objective cyclodeviation measurement in normal subjects by means of Cyclocheck® application

2020 ◽  
pp. 112067212090531
Author(s):  
Justyna Simiera ◽  
Agata Joanna Ordon ◽  
Piotr Loba
Keyword(s):  
Normal Subjects ◽  
Mean Value ◽  
Angle Measurements ◽  
Corrected Visual Acuity ◽  
Normal Individuals ◽  
Muscle Balance ◽  
Study Population ◽  
The Mean ◽  
Fundus Photographs ◽  
The Right

Purpose: To evaluate the range of cyclodeviation in normal individuals by means of Cyclocheck® application recently designed by the authors and freely available at www.cyclocheck.com . Methods: Healthy subjects with normal muscle balance, best-corrected visual acuity of ⩾0.8, and stereopsis on Randot charts of ⩽100 s of arc were included in the study. Two separate digital fundus photographs were taken of each eye of every patient. The disk-foveal angle was calculated using the Cyclocheck® application. The average result of the disk-foveal angle measurements were considered for data analysis. Results: A total of 131 patients met inclusion criteria for the study population. The mean value of the disk-foveal angle in the whole study group (both right and left eye) was 6.39° ± 2.72° with 5.26° ± 2.56° (range from −0.4° to 12.55°) in the right eye and 7.52° ± 2.39° (range from 1.25° to 12.76°) in the left eye. The mean value of the disk-foveal angle of the left eye was greater by 2.26° than that of the right eye. Conclusion: Cyclocheck® software allows easy assessment of cyclodeviation. Normal individuals present with a positive value of the disk-foveal angle with a certain spread of the results. The analysis of obtained measurements revealed a significant asymmetry between both eyes with the left eye being more excyclodeviated in an otherwise orthotropic population, which remains a subject for further investigations.

scholarly journals Flow angle measurement of a yawed turbine and comparison to models

2017 ◽  
Author(s):  
Tyler Gallant ◽  
David A. Johnson
Keyword(s):  
Wind Turbine ◽  
Flow Direction ◽  
Angle Of Attack ◽  
Experimental Results ◽  
Pressure Probe ◽  
Flow Profile ◽  
Local Flow ◽  
Flow Angle ◽  
Angle Measurements ◽  
Probe Measurements

Abstract. The torque generated by a wind turbine blade is dependent on several parameters, one of which is the angle of attack. Several models for predicting the angle of attack in yawed conditions have been proposed in the literature, but there is a lack of experimental data to use for direct validation. To address this problem, experiments were conducted under controlled conditions at the University of Waterloo Wind Generation Research Facility using a 3.4 m diameter test turbine. A five-hole pressure probe was installed in a modular 3D printed blade and was used to measure the angle of attack, α, as a function of several parameters. Local flow angle measurements for all azimuthal angles were obtained at radial positions of r / R = 0.55 and 0.72 at tip speed ratios (λ) of 5.0, 3.6, and 3.1. The yaw offset of the turbine was varied from −15° to +15°. Span-wise flow angle measurements are presented for the r / R = 0.55 cases, and show the variation in radial flow direction throughout yawed rotation. Experimental results were compared directly to angle of attack values calculated using a model proposed by Morote in 2015. Modeled values were found to be in close agreement with the experimental results. The angle of attack was shown to vary cyclically in the yawed case while remaining mostly constant when aligned with the flow, as expected. These five-hole probe measurements were also used to characterise the upstream flow profile. Wind speeds determined using the five-hole probe measurements are presented and are in agreement with measurements obtained in the wind facility during testing. The quality of results indicates the potential of the developed instrument for wind turbine measurements.

scholarly journals Horizontal and vertical distribution of wind speed in a vegetation canopy.

1991 ◽  
Vol 39 (3) ◽  
pp. 165-178
Author(s):  
A.F.G. Jacobs ◽  
J.H. van Boxel
Keyword(s):  
Standard Deviation ◽  
Wind Speed ◽  
Mean Value ◽  
Night Time ◽  
Scaling Parameter ◽  
Atmospheric Stratification ◽  
Scaling Parameters ◽  
Mean Wind Speed ◽  
Applied Meteorology ◽  
The Mean

Wind speed measurements within a maize row canopy were carried out to investigate the horizontal and vertical variability of the mean wind speed and its standard deviation. Attention was given to finding adequate scaling parameters of the within-canopy wind speed profiles under various atmospheric stratification states. A validation of existing model simulations was also carried out. The horizontal mean wind speed and its standard deviation can vary about 20% from its spatial mean value. During day time and night time the friction velocity appears to be a good scaling parameter. Clear nights, however, are exceptions, when the wind speed above the crop drops to a very low value. Then the free convection velocity appears to be an appropriate scaling parameter for the within-canopy processes. The canopy models of Wilson & Shaw [Journal of Applied Meteorology (1977) 16, 1197-1205] and Li et al. [Boundary-Layer Meteorology (1985) 33, 77-84] were found to simulate the spatially averaged mean wind profile within the range of the horizontal variability. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Documenting Wind Speed and Power Deficits behind a Utility-Scale Wind Turbine

2013 ◽  
Vol 52 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Brian D. Hirth ◽  
John L. Schroeder
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Farm ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Large Variability ◽  
Cost Of Energy ◽  
The Mean ◽  
Utility Scale ◽  
Turbine Wake

AbstractHigh-spatial-and-temporal-resolution radial velocity measurements surrounding a single utility-scale wind turbine were collected using the Texas Tech University Ka-band mobile research radars. The measurements were synthesized to construct the first known dual-Doppler analyses of the mean structure and variability of a single turbine wake. The observations revealed a wake length that subjectively exceeded 20 rotor diameters, which far exceeds the typically employed turbine spacing of 7–10 rotor diameters. The mean horizontal wind speed deficits found within the turbine wake region relative to the free streamflow were related to potential reductions in the available power for a downwind turbine. Mean wind speed reductions of 17.4% (14.8%) were found at 7 (10) rotor diameters downwind, corresponding to a potential power output reduction of 43.6% (38.2%). The wind speed deficits found within the wake also exhibit large variability over short time intervals; this variability would have an appreciable impact on the inflow of a downstream turbine. The full understanding and application of these newly collected data have the potential to alter current wind-farm design and layout practices and to affect the cost of energy.

Real-Time Estimation and Calibration of GLONASS Inter-Frequency Phase and Code Bias

2019 ◽  
Vol 73 (3) ◽  
pp. 746-762 ◽  
Author(s):  
Zhixin Yang ◽  
Hui Liu ◽  
Yidong Lou ◽  
Bao Shu ◽  
Longwei Xu ◽  
...  
Keyword(s):  
Real Time ◽  
Elevation Angle ◽  
Vertical Direction ◽  
Time Estimation ◽  
Calibration Method ◽  
Mean Value ◽  
Time Calibration ◽  
Calibration Methods ◽  
Code Bias ◽  
Frequency Phase

The frequency division multiple access (FDMA) strategy used in GLONASS causes inter-frequency phase bias (IFPB) and inter-frequency code bias (IFCB) between receivers from different manufacturers. The existence of IFPB and IFCB significantly increases the difficulties of fixing GLONASS ambiguity and limits the accuracy and reliability of GLONASS positioning. Moreover, the initial value of IFPB and IFCB may be unavailable or unreliable with the increasing number of receivers from different manufacturers in recent years. In this study, a real-time and reliable calibration algorithm of IFPB and IFCB based on multi-GNSS assistance is proposed by providing a fixed solution. Real-time IFPB rate and IFCB can be obtained using this algorithm without the initial IFPB and IFCB. The IFPB rate for all GLONASS satellites and IFCB for each GLONASS satellite are estimated due to different characteristics of IFPB and IFCB. IFPB calibration can be divided into constant and real-time IFPB calibrations to meet the different positioning requirements. Results show that constant IFPB rate has only 2 mm difference from the mean value of real-time IFPB rate. The IFPB rate and IFCB estimated by this algorithm have excellent stability, and the change in reference satellite cannot affect the results of IFPB rate and the stability of IFCB. The centimetre-level positioning results can be obtained using two calibration methods, and the positioning results with real-time calibration method are 10%–20% better than those with the constant calibration method. Under satellite-deprived environments, the improvements of multi-GNSS positioning accuracy with constant inter-frequency bias calibration gradually increase as the satellite cut-off elevation angle increases compared with GPS/BDS, which can reach up to 0·9 cm in the vertical direction.

Robust Design Optimization of Gear Parameters for a Wind Turbine Using Interval Analysis

2010 ◽  
Vol 224 (10) ◽  
pp. 2235-2245 ◽  
Author(s):  
R Dong ◽  
W Sun ◽  
H Xu
Keyword(s):  
Wind Turbine ◽  
Design Optimization ◽  
Robust Design ◽  
Optimization Method ◽  
Mean Value ◽  
Robust Design Optimization ◽  
Upper And Lower Bounds ◽  
Interval Numbers ◽  
Minimum Sensitivity ◽  
The Mean

A robust design optimization method is suggested to optimize the system parameters of a gear transmission for a wind turbine with minimum sensitivity of fatigue strength to variations in uncertain application factor, dynamic load coefficient, material property parameters, and other coefficients representing unknown working condition. Interval numbers are employed to model the uncertainties by which only the upper and lower bounds are needed. Based on interval mathematics, the original real-valued objective and constraint functions are replaced by the interval-valued functions, which directly represent the variation bounds of the new functions under uncertainty. The single-objective function is converted into two-objective functions for minimizing the mean value and the variation, and the constraint functions are reformulated with the acceptable robustness level, resulting in a bi-level mathematical model. The optimization results of gear parameter demonstrate the validity and feasibility of the presented method.

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