Periodic Error Research Articles

Recognition of Air Passengers' Willingness to Pay for Seat Selection for Imbalanced Data Based on Improved XGBoost

Passenger-paid seat selection is one of the important sources of ancillary revenue for airlines, and machine learning-based willingness-to-pay identification is of great practicality for airlines to accurately tap potential willing passengers. However, affected by periodic statistical errors, air passenger order data often has some problems such as high noise, high latitude, and unbalanced category. In view of this, this paper proposes a method for identifying air passengers' willingness to pay for seat selection based on improved XGBoost, which is improved and integrated from three stages: data, feature, and algorithm. The feasibility of the proposed multi-stage improved integration method is verified by real airline passenger dataset, and the experimental results show that the proposed improved method has better classification effect when compared with the classical six imbalance classification models, which provides a basis for accurate marketing of airline paid seat selection programs.

Impact of tropical convective conditions on solar irradiance forecasting based on cloud motion vectors

Intra-day forecasts of global horizontal solar irradiance (GHI) are widely produced by displacing existing clouds on a geo-stationary satellite image to their future locations with cloud motion vectors (CMVs) derived from preceding images. The CMV estimation methods assume rigid cloud bodies with advective motion, which performs reasonably well in mid-latitudes but can be strained for tropical and sub-tropical climatic zones during prolonged periods of seasonal convection. We study the impact of the South Asian monsoon time convection on the accuracy of CMV based forecasts by analysing 2 years of forecasts from three commonly used CMV methods—Block-match, Farnebäck (Optical flow) and TV-L1 (Optical flow). Forecasted cloud index (CI) maps of the entire image section are validated against analysis CI maps for the period 2018–2019 for forecast lead times from 0 to 5.5 h. Site-level GHI forecasts are validated against ground measured data from two Baseline Surface Radiation Network stations—Gurgaon (GUR) and Tiruvallur (TIR), located in hot semi-arid and tropical savanna climatic zones respectively. The inter-seasonal variation of forecast accuracy is prominent and a clear link is found between the increase in convection, represented by a decrease in outgoing longwave radiation (OLR), and the decrease in forecast accuracy. The GUR site shows the highest forecast error in the southwest monsoon period and exhibits a steep rise of forecast error with the increase in convection. The highest forecast error occurs in the northeast monsoon period of December in TIR. The impact of convection on the number of erroneous time blocks of predicted photovoltaic production is also studied. Our results provide insights into the contribution of convection to errors in CMV based forecasts and shows that OLR can be used as a feature in future forecasting methods to consider the impact of convection on forecast accuracy.

Fiber-based two-wavelength heterodyne laser interferometer.

Displacement measuring interferometry is a crucial component in metrology applications. In this paper, we propose a fiber-based two-wavelength heterodyne interferometer as a compact and highly sensitive displacement sensor that can be used in inertial sensing applications. In the proposed design, two individual heterodyne interferometers are constructed using two different wavelengths, 1064 nm and 1055 nm; one of which measures the target displacement and the other monitors the common-mode noise in the fiber system. A narrow-bandwidth spectral filter separates the beam paths of the two interferometers, which are highly common and provide a high rejection ratio to the environmental noise. The preliminary test shows a sensitivity floor of 7.5pm/Hz at 1 Hz when tested in an enclosed chamber. We also investigated the effects of periodic errors due to imperfect spectral separation on the displacement measurement and propose algorithms to mitigate these effects.

AUDIT OF FINANCIAL RESULTS: ORGANIZATIONAL AND METHODOLOGICAL PRINCIPLES OF CONDUCT

The purpose of the article is research and generalization of organizational and methodical approaches to the audit of financial results and development of directions for their improvement. The purpose and tasks of the audit of financial results are revealed in the article. The levels of the legal framework used during the audit are defined: the first - codes and laws of Ukraine, the second - accounting and auditing standards, the third - branch regulations, the fourth - regulatory documents at the enterprise level. The sources of the audit are highlighted, which are grouped into basic documents that regulate the accounting of financial results. These include primary documents, accounting registers, financial reporting, tax reporting, and non-financial reporting. Approaches to the audit of financial results based on the results of research by domestic scientists are analyzed. The stages of the audit are defined (organizational, preparatory, main (technological), final). The sequence of planning the audit of financial results is proposed, which includes the collection of information about the financial and economic activity of the enterprise, the analysis of the main economic indicators, the verification of the mutual consistency of the indicators of the financial reporting forms, the determination of the level of materiality and the assessment of the audit risk, the assessment of the state of the internal control system, the drawing up of the plan and the verification program. Approaches to the development of an audit program (accounting, legal, industry) have been determined. Possible errors detected by the auditors during the inspection were analyzed (violations in determining the cost of works and services, display of interest received from the bank, write-off of general production costs, display of errors of past periods in financial statements). An algorithm for checking the comparability of the Balance Sheet and the Statement of Financial Results is presented. A format for summarizing the results of the audit of financial results is proposed, which will ensure the visibility of the work performed by the auditors and the control of detected errors, violations and remarks.

Characterization of diffractive relief structures over large areas by stitching interference microscopic topography

The development of diffractive optical elements (DOEs)enables fascinatingly compact design and chromatic aberration correction. Fabrication errors of DOEs include periodic pattern error, relief profile error and roughness which affect imaging quality and diffraction efficiency. Characterization of the DOE requires thus multi-scale measurement of the surface topography over the full aperture of 10 mm scale. This paper presents a method based on the white light interferometry in combination of subaperture stitching. Firstly, the principle of measurement and subaperture layout design is introduced. The measuring system is easily set up by integrating a scanning platform with the interference microscope. Subaperture stitching algorithm is developed based on the surface height change related to the scanning motion error. The slope of the relief profile is used to model the deviations of overlapping point pairs induced by lateral shift and rotation. Finally, the topography and fabrication error of a Fresnel lens surface are experimentally obtained and characterized over the full aperture through stitching of totally 67 subapertures.

Motion-Induced Phase Error Compensation Using Three-Stream Neural Networks

Phase-shifting profilometry (PSP) has been widely used in the measurement of dynamic scenes. However, the object motion will cause a periodical motion-induced error in the phase map, and there is still a challenge to eliminate it. In this paper, we propose a method based on three-stream neural networks to reduce the motion-induced error, while a general dataset establishment method for dynamic scenes is presented to complete three-dimensional (3D) shape measurement in a virtual fringe projection system. The numerous automatically generated data with various motion types is employed to optimize models. Three-step phase-shift fringe patterns captured along a time axis are divided into three groups and processed by trained three-stream neural networks to produce an accurate phase map. The actual experiment’s results demonstrate that the proposed method can significantly perform motion-induced error compensation and achieve about 90% improvement compared with the traditional three-step phase-shifting algorithm. Benefiting from the robust learning-based technique and convenient digital simulation, our method does not require empirical parameters or complex data collection, which are promising for high-speed 3D measurement.

Prediction Errors Analysis and Correction on FCS-MPC for the Cascaded H-Bridge Multilevel Inverter

Predictive errors restrict high performance of finite control set model predictive control (FCS-MPC) in the cascaded H-bridge multilevel inverter.In order to solve this problem, the influence mechanisms of parameter mismatch, model discretization, and sampling error on voltage and current prediction errors are analyzed in this article. A hierarchical multifactorial error correction method is proposed. The known voltage prediction errors of the previous adjacent prediction periods are first fed back to calculate the voltage predictive error factors and self-correct the next voltage prediction errors. And then the current prediction errors are calibrated by the corrected voltage and the calculated current predictive error factor. This proposed method involves a simple structure and a good inhibitory ability on multifactorial prediction errors. Finally, experimental results in a three-phase five-level cascaded H-bridge multilevel inverter support the theoretical analysis and the proposed method.

Research on a Measurement Method for the Ocean Wave Field Based on Stereo Vision

The wave parameter is an important environmental input condition. Traditional contact wave measurement methods are unable to meet the requirements of high precision, non-contact, and ship wave field assessment. Alternatively, stereo vision technology can realize a non-contact and mobile form of measurement. However, this technology suffers from poor timeliness and adaptability. This paper proposes a comprehensive wave measurement method that is based on stereo vision, wherein the gridding of siftGPU is used to achieve the fast matching of large images. The whole algorithm can be run within 6 s and it guarantees more than 20,000 feature-matching logarithms. Furthermore, by utilizing the least squares method and sea surface wave surface theory, the sea surface base level can be calculated without control points, along with the inversion of the sea wave parameters (wave height, period, and wave direction) and error point fitting. The rationality and superiority of the algorithm were verified through multiple comparison experiments. Compared with the Richard Brancker Research (RBR) wave height meter, the measurement error of the wave height is less than 10%, the period error is less than 0.5 s, and the wave direction error is less than 10° with the proposed method.

Ultra-Precision Cutting and Characterization of Reflective Convex Spherical Blazed Grating Elements.

In this work, based on the diffraction principle of reflective blazed grating, the structure size of the convex spherical blazed grating unit is determined, the machining accuracy of the convex spherical blazed grating is formulated, the effects of tool nose radius and Poisson burr on the diffraction efficiency of the convex spherical blazed grating are analyzed, and the performances of cutting convex gratings with microcrystalline aluminum RSA6061 and RSA6061+ chemically plated NiP for two workpiece materials are compared. A convex spherical blazed grating with a radius of curvature R = 41.104 mm, substrate diameter 14 mm, grating density 53.97 line/mm, and blaze angle of roughly 3.8° is turned by a four-axis ultra-precision machining system by adjustment of the cutting tool, workpiece material, and cutting parameters, as well as modification of the layouts of the blazed grating on the convex sphere. The results of the testing of convex spherical blazed grating elements in both layouts show that the size error of the grating period is close for both layouts, the size error of grating height is smaller in the equal-along-arc layout, the blaze angle error in the equal-along-projection layout is only 0.74%, and the average roughness of the blazed surface is less than 5 nm to meet the processing quality requirements of the reflective convex spherical blazed grating. The greater the blaze angle accuracy of the blazed grating, the higher its diffraction efficiency, so the grating element with an equal-along-projection layout has a higher diffraction efficiency than the grating element with an equal-along-arc layout. RSA6061+ chemically plated NiP material is superior to RSA6061 material in Poisson burr height and blazed surface roughness, which is more suitable for Offner-type imaging spectrometers in the spectral range 0.95–2.5 μm (SWIR).

Choices of the Critical Frequency for φ in TL-φ Algorithms When Applied to Multi-Degree of Freedom Systems

TL-φ algorithms are newly developed explicit structure-dependent integration algorithms utilized for solving the temporally discretized equations of motion. In contrast to the existing algorithms, the most significant improvement of TL-φ algorithms is in diminishing the amount of period errors by introducing a precorrection coefficient φ into the integration parameters of TL-φ algorithms, which is related to the critical frequency of a system. In the previous work, the fundamental frequency of the system is deemed to be the critical frequency, so that φ is a constant scaling corresponding to the fundamental frequency for both single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems. However, for a MDOF system, the first mode may not contribute to the total response more than other ones under a given external excitation, calculating φ only by the fundamental frequency will underestimate the contribution of the higher-frequency modes to structural dynamics. In this paper, choices of the critical frequency for φ when applying TL-φ algorithms to MDOF systems are investigated thoroughly. By considering the initial structural properties of the system and the frequency characteristics of the external excitation simultaneously, a calculation criterion of φ for MDOF systems under specific external excitations is proposed. Four numerical examples with different initial structure properties and loading conditions are designed, and the results demonstrate that the proposed criterion can be potentially used to solve structural dynamic problems of MDOF systems with a more desirable numerical dispersion performance.

Point-Wise Phase Estimation Method in Fringe Projection Profilometry under Non-Sinusoidal Distortion.

In fringe projection profilometry, high-order harmonics information of distorted fringe will lead to errors in the phase estimation. In order to solve this problem, a point-wise phase estimation method based on a neural network (PWPE-NN) is proposed in this paper. The complex nonlinear mapping relationship between the gray values and the phase under non-sinusoidal distortion is constructed by using the simple neural network model. It establishes a novel implicit expression for phase solution without complicated measurement operations. Compared with the previous method of combining local image information, it can accurately calculate each phase value by point. The comparison results show that the traditional method is with periodic phase errors, while the proposed method can effectively eliminate phase errors caused by non-sinusoidal phase shifting.

A dual-explicit model-based integration algorithm with higher-order accuracy for structural dynamics

Several model-based or structure-dependent integration algorithms with explicit displacement formulation and unconditional stability are recently developed. According to the difference equations, these algorithms can be divided into dual-explicit and semi-explicit, where the first category algorithms are explicit for both displacement and velocity, while the second category are only explicit for displacement. The well-known Chen-Ricles (CR) and Chang algorithms are two representatives of dual-explicit and semi-explicit model-based algorithms, respectively. The model-based integration algorithms are promising with excellent computing efficiency, but most of them are second-order accurate. In this paper, a new dual-explicit (NDE) algorithm with higher-order accuracy is developed. The integration parameters of the NDE algorithm are obtained by using the pole mapping and second-order Pade approximation. Numerous important numerical characteristics including the consistency and local truncation error, stability, numerical dispersion and energy dissipation and overshoot are systematically analyzed for the new algorithm. It is found that the NDE algorithm is fourth-order accurate for free vibration without damping. As for forced vibration with/without damping and free vibration with damping, the NDE algorithm is no longer fourth-order accurate, but it is still more accurate than the CR and Chang algorithms. In addition, the period error of the algorithm is extremely small. Three representative numerical examples are finally provided to demonstrate the high accuracy of the NDE algorithm. Several classical and latest model-based integration algorithms and three fourth-order accurate algorithms are also adopted for comparisons. It has been proved that the NDE algorithm has much better performance than other selected model-based algorithms.

DETECTION OF THE ANGLE CHANGE BETWEEN CAMERA AND STAR TRACKER BASED ON STAR OBSERVATION

Abstract. Satellites in orbit are affected by changes in thermal environment and other factors, and the angle of optical axis between the camera and star tracker (Cam-ST) changes. As a result, the attitude measurement error of the orbital period appears, leading to a decrease in the accuracy of the geometric positioning of the image. This paper proposes a star observation mode, using the stars as the control point, so as to detect the angle change between the Cam-ST throughout the orbital period. This paper is based on 20 sets of star observation data from the Jilin-1 video satellite. Through methods such as star point extraction and pre-recognition, the camera's pointing in the inertial space is obtained. Then the angle with the optical axis of star tracker (ST) is calculated, and the error law of the angle between the Cam-ST is obtained. The experimental results show that the Cam-ST optical axis angle will produce a regular error change during the satellite orbit period. After fitting, the error of the angle between the camera and the star tracker (Cam-ST) is reduced from 47.86" to 5.63". Through the method of star observation, the errors between Cam-ST angle can be effectively improved. The high accuracy of the camera's pointing measurement within the orbit period range is of great significance for satellite global mapping without ground control points (GCPs).

Correction of Field Orientation Inaccuracy Caused by Resolver Periodic Error and Rotor Time Constant Variation for Indirect Field-Oriented Control Induction Motor Drives

This article proposes an algorithm correcting the field orientation inaccuracy caused by resolver periodic error and rotor time constant variation. It is found that the periodic error brings harmonic current vectors and torque ripples while the rotor time constant variation makes <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> currents deviate from the reference values. The cross-product of fundamental and harmonic current vectors contains the information of resolver periodic error. The gradient descent method with a variable step is introduced to compensate the periodic error. During the process, the cross-product is minimized. A new form of cross-product calculation is derived to reduce the computation time. The rotor time constant is identified by the reactive-power based model reference adaptive system (MRAS). Voltages and currents in the stationary reference frame are used in the reference model to avoid the influence of resolver periodic error. Appropriate parameters of the MRAS are selected to guarantee the stability. The algorithm is integrated with an induction motor drive which is based on indirect field-oriented control. The feasibility of the proposed algorithm is verified by simulation results and experiments.

An Unscented Kalman Filter–based iterative learning controller for multibody rotating scan optical spacecraft

In this paper, to address the periodic control problem facing high-precision observation for multibody rotating scan optical spacecraft connected with active magnetic bearing (AMB), the Unscented Kalman Filter (UKF)–based iterative learning controller (UILC) is proposed. In the UILC, an adaptive backstepping controller (ABC) is deployed in the main loop to make the system state converge, and an UKF module is substituted for the memory module to use feedback information in real time and eliminate error propagation between adjacent periods. In the paper, the 9 degrees of freedom (DOF) error discrete dynamics are first derived to facilitate the convergence proved in the discrete domain. Then, the convergence analysis of the closed-loop system is investigated, and the state error supremum of closed-loop system in the mean square is indicated. Finally, for a comparison with the classical iterative learning controller (ILC), a series of numerical simulations are performed. As indicated by the simulation results, the UILC is capable of eliminating periodic deviation and error propagation during the adjacent periods.

Preview control for discrete-time periodic systems with state delay

State feedback and output feedback control strategies are developed for discrete-time periodic systems with state delay via periodic preview control (PPC) technique in this article. To utilize future reference information for the controller design, a periodic augmented error system (PAES) with delay is constructed using the state augmentation technique and difference operator approach. Then, the PPC problem is converted into a stabilization problem. Furthermore, the state feedback and static output preview controllers are designed and sufficient conditions that guarantee the closed-loop stability of PAES are derived via the linear matrix inequality (LMI) approach. Finally, two examples are presented to illustrate the effectiveness of the proposed method.

An Adaptive Angle Error Compensator for IPMSMs With Periodic Loads in the Flux Weakening Region

When the load of a motor changes periodically with the mechanical angle, the speed also changes. There are obvious amplitude attenuation and phase shift in the high-frequency band of the phase-locked loop, resulting in the periodic angle error between the estimated angle and the real angle when the motor is in the high-speed flux weakening region. The periodic angle error easily leads to the deterioration of the flux weakening control performance, and causes greater speed and current fluctuations. In this article, an adaptive angle error compensator (AAEC) is proposed to reduce the angle error caused by the periodic load and improve the performance of the flux weakening control. In order to avoid the influence of the angle error direct-current drift in the speed dynamic process on the AAEC iteration, the switch mode AAEC (SMAAEC) is proposed to replace the AAEC. The experimental results show that in the flux weakening region, the SMAAEC can greatly reduce the fluctuations of the speed, angle error, and currents, and improve the steady-state performance of the controller.

Fuzzy Proportional-Derivative Based Robot Arm Control for Object Transfer

With the development of robot technology, humanoid robot and human-robot interaction are gradually playing a more and more important role in our society. At present, the arm control of humanoid intelligent robot has become one of the hot research issues in the field of robot. This paper proposes a fuzzy based NAO robot hand control method to reduce the vibration and increase position accuracy during object transferring between NAO robot and human. The 5-DOF kinematics model of NAO robot right arm is first established. Motion path of the NAO robot arm during human-robot interaction is planned and conducted in Matlab and reality. The impact of control period, joint speed and trajectory error on vibration is observed and discussed. Based on the discussion, the fuzzy-PD control method is proposed. Experiments result indicates that the proposed Fuzzy-PD control method can reduce vibration and trajectory error, which can benefit the smooth motion control process of the NAO robot arm receiving objects in the process of human-robot interaction.

Prediction of Final Displacement of Tunnels in Time-Dependent Rock Mass Based on the Nonequidistant Grey Verhulst Model

Time-dependent deformations of rock are important factors for the design and construction of tunnels in the rock masses with time-dependent strength and deformation properties. Therefore, determination displacement and stable time of tunnel are an indispensable task in geotechnical engineering, especially during the design and construction of underground structures. However, in some types of rock masses, the tunnel displacement may increase for months or years after the excavation owing to the rheological behavior of the surrounding rock masses, which greatly influences the selection of the initial tunnel support system, the excavation layout, and the determination of its load-carrying capacity. In this paper, we present a method to quickly predict the final displacement and stable time of tunnels in time-dependent rock mass using the improved nonequidistant grey Verhulst model (INGVM) with Fourier series, which is used to reduce the periodic residual error. The proposed method is validated fairly via a test for a newly excavated roadway of −600 m level in a coal mine, Democratic People’s Republic of Korea. These results are useful references for similar projects in the future.

Оцінка клінічної ефективності індивідуалізованих протоколів корекції ергономічних параметрів роботи лікарів-стоматологів під час ендодонтичного лікування

The purpose of the study is to evaluate the clinical effectiveness of individualized protocols for the correction of ergonomic parameters of dentists’ work during endodontic treatment. Materials and methods: target research methods Rapid Upper Limb Assessment (for the upper extremities) and Rapid Entire Body Assessment (for the whole body of the dentist), StatPlus Pro software, X-ray examination. Results and discussion. The results of the retrospective analysis of scientific and evidence-based sources to verify the principles of ergonomics during the work performed using the Rapid Upper Limb Assessment and Rapid Entire Body Assessment criteria show that, сhanging the design of ergonomic work systems automatically improves the posture of workers, reduces the risk of diseases of the musculoskeletal system, and prevents negative consequences for overall health. During the evaluation of the clinical effectiveness of individualized protocols for the correction of ergonomic parameters of dentists' work, specific differences are observed when comparing the results of the Rapid Upper Limb Assessment and Rapid Entire Body Assessment criteria among dentists of the research group and the control group. As a result of the analysis it was established that in the research group, which ensured the implementation of the protocol for correcting ergonomic parameters of dentists during endodontic interventions according to a clearly defined algorithm, there was a specific trend to reduce the absolute number of registered errors in the 12-month monitoring period: 129 cases (32.25%) at the time of 3-month control, 100 cases (25.0%) at the time of 6-month control, 86 cases (21.50%) at the time of 12-month control. When comparing the data of the research group and the control group, it was found that the introduction of individualized protocols for the correction of ergonomic components in endodontic treatment reduces the incidence of errors and complications in the treatment of incisors by 3.0% (p&gt;0.05) 4.0% (p&gt;0.05), premolars – by 8.25% (p &lt;0.05), molars – by 20.25% (p &lt;0.05). Conclusion. The increase of clinical efficiency, quality of the conducted treatment, and its predictability at the use of individualized protocols of correction of ergonomic parameters of work of dentists during endodontic treatment are established. The proposed approach to the optimization of endodontic treatment in terms of compliance with relevant ergonomic criteria is individual-specific, and the systematization of general characteristics, which were registered among the entire sample, will help expand the integrated system of improving the quality and efficiency of dental care in its structure