Tolerance Band Research Articles

Tolerance bands for exponential family functional data

AbstractA tolerance band for a functional response provides a region that is expected to contain a given fraction of observations from the sampled population at each point in the domain. This band is a functional analogue of the tolerance interval for a univariate response. Although the problem of constructing functional tolerance bands has been considered for a Gaussian response, it has not been investigated for non‐Gaussian responses, which are common in biomedical applications. We describe a methodology for constructing tolerance bands for two non‐Gaussian members of the exponential family: binomial and Poisson. The approach is to first model the data using the framework of generalized functional principal components analysis. Then, a parameter is identified in which the marginal distribution of the response is stochastically monotone. We show that the tolerance limits can be readily obtained from confidence limits for this parameter, which in turn can be computed using large‐sample theory and bootstrapping. Our proposed methodology works for both dense and sparse functional data. We report the results of simulation studies designed to evaluate its performance and get recommendations for practical applications. We illustrate our proposed method using two actual biomedical studies, and also provide computer source code that implements our method.

Effect of Floating Support Parameters on the Load-Sharing Performance of EDPGS Based on Mathematical Statistical Methods

The encased differential planetary gear system (EDPGS) allows power to be distributed among multiple output paths, enhancing efficiency and reducing weight. Uniform load distribution ensures stable system operation and prolongs service life. However, stochastic manufacturing errors leading to uneven load distribution pose challenges in engineering practice. To investigate the impact of floating support parameters on the load-sharing performance within an acceptable tolerance band, a dynamic model of the EDPGS considering time-varying meshing stiffness and random errors is established using the Monte Carlo method. This study employs the orthogonal experimental design method to analyze the effects of floating support stiffness and clearance on the load-sharing characteristics. The findings indicate that a larger sample size leads to a probability distribution of load-sharing coefficients closer to the Gaussian distribution, with minimal influence on the expectation and variance. Furthermore, this study highlights the significant influence of floating structure parameters on load-sharing characteristics in the encased stage systems compared to the differential stage. Decreasing floating support stiffness or increasing floating clearance proves beneficial in enhancing the load-sharing performance of the system.

Inflation Targeting in India: A Further Assessment

We assess India’s inflation-targeting regime at the eight-year mark. The Reserve Bank of India continues to be a flexible inflation targeter: it responds to both the output gap and inflation when setting policy rates. It has become neither more hawkish nor more reactive with the transition to inflation-targeting. Evidence points to improved outcomes: inflation is lower and less volatile, inflation expectations are better anchored and the transmission of monetary policy is more effective. Given this record, radical changes such as broadening the RBI’s monetary mandate, abandoning the target in favour of a more discretionary regime, targeting core instead of headline inflation or altering the target and tolerance band would be risky and counterproductive. One obvious area for improvement entails updating the weight of food prices in the CPI basket. We estimate the correct weight of food at today’s per capita income to be closer to 40 per cent instead of the current 45.8 per cent. This would likely fall further to around 30 per cent in a decade from now due to the projected increase in per capita incomes. This correction should ameliorate concerns about the design and practice of the current inflation targeting regime. JEL Codes: E5, E52

Experimental investigation on creep behaviors and life prediction across phase-transformation of thermal aged 16MND5 steel

Reactor pressure vessel (RPV) is one of the key equipment for nuclear power plant, and long-term exposure to high temperature is an important factor causing its performance deterioration. Under core meltdown conditions, RPV steel experiences high temperature creep due to the In-Vessel Retention (IVR) mitigation measures. This paper aims to investigate high-temperature mechanical properties, especially for the creep behaviors of 16MND5 steel after thermal aging at 650 °C for 2000 h. The results showed that the yield stress and ultimate tensile strength of the 16MND5 steel are decreased, and the creep rupture time is rapidly shortened after thermal aging. The microstructure was analyzed by scanning and transmission electron microscopy (SEM, TEM). 16MND5 steel showed a typical bainitic phase before thermal aging. After 2000 h of thermal aging, the micro-grains were coarsened, and finally changed into a ferritic microstructure. Based on Larson-Miller (LM), Orr-Sherby-Dorn (OSD) parameters methods and Kachanov-Rabotnov (K–R) model to predict uniaxial creep life after thermal aging, the prediction results are satisfactory, and all within the double tolerance band. This work reveals the creep damage mechanism of 16MND5 steel after thermal aging, and provides basic data for the implementation of IVR strategy in nuclear power plants after long-term service.

Real-Time Implementation and Control of Multi-Source Electric Vehicle Traction Motor under Various Drive Conditions

The hybridization of multiple energy sources is crucial for electric vehicles to deliver the same performance as modern fossil fuel-based automobiles. This paper presents a torque and speed control strategy for an electric vehicle DC traction motor by regulating the power flow from two energy sources, namely battery and supercapacitor systems, to resist unpredictable disturbances. A control system with three control loops is applied to regulate the speed of the traction motor. The outer speed control loop is a nonlinear state feedback controller with a disturbance observer, which is capable of handling non-linear systems with unpredictable disturbances. The inner voltage and current control loop are precisely tuned PI controllers. Using an adaptive energy management method that varies depending on the state of charge of the source, the total reference current needed to support the load demand is split between two sources. A laboratory prototype system model is generated, and the performance is analyzed under motoring and regenerative braking conditions. For monitoring and controlling the system, the dSPACE DS1202 real-time simulator is employed. The performance of the proposed control system is evaluated and it is found that the settling time to settle within a tolerance band of 1% is 0.75 s.

Optimal Process Parameters of the Binder to Reduce Air Pollution and to Improve the Emission Effect from Composite Production

Today the prepreg technology for the manufacture of products from polymer composite materials is widely used in the global industry. This technology involves the use of prepregs obtained by preliminary impregnation of the reinforcing materials with binder solutions, which contain up to 50% environmentally sensitive and fire hazardous solvents. However, in many cases no systematic approach is used to solve the issues of choosing the optimal values of the solvent content in the binder solution to ensure its specified viscosity according, as well as the issues of safety of the industrial activity; instead, these issues are solved independently. It results in the unreasonable expense, loss of quality of the composite products and insufficient level of safety of production activity at the relevant workplaces. This study deals with the systematic prediction of the process parameters, taking into consideration the safety of operational procedures during the impregnation of prepregs and permissible range of deviations from their regulated value. The method and the relevant implementing technique for the prediction of optimal process parameters of the binder solutions for impregnation of prepregs in view of safety of the production activity have been developed. Dependences of the viscosity of the binder on its temperature and volume content of one-component, binary and three-component solvents have been obtained, with the tolerance band specified for the volume and weight contents of the solvent in the binder, which provides an acceptable deviation in the solution viscosity for the effective impregnation of prepreg. The paper proposes and substantiates the criterion of content of the binary solvent in the binder being optimal one in terms of process conditions. This criterion provides both the specified quality of impregnation of the reinforcing material and requirements for the safety of production activity. The actual hands-on examples are considered as related to the determination of optimal content of the binary solvent with the components for the specific binder and alcohol-acetone solvent. It is shown that the optimal weight concentration of acetone in the solvent is 0.085, with the solvent weight content in the mixture of 0.279. These parameters provide the maximum allowable concentration of solvent vapors, ensuring the safety of production activity. It should also be noted, that the solvent weight content differs by maximum 5% from the value required when using alcohol only, which provides high safety margin of the production activity.

Robust performance comparison of PMSM for flight control applications in more electric aircraft.

This paper describes a robust performance comparison of flight control actuation controllers based on a permanent magnet synchronous motor (PMSM) in more electric aircraft (MEA). Recently, the PMSM has become a favorite for the flight control applications of more electric aircraft (MEA) due to their improved efficiency, higher torque, less noise, and higher reliability as compared to their counterparts. Thus, advanced nonlinear control techniques offer even better performance for the control of PMSM as noticed in this research. In this paper, three nonlinear approaches i.e. Feedback Linearization Control (FBL) through the cancellation of the non-linearity of the system, the stabilization of the system via Backstepping Control (BSC) using the Lyapunov candidate function as well as the robust performance with chattering minimization by applying the continuous approximation based Sliding Mode Control (SMC) are compared with generalized Field-Oriented Controller (FOC). The comparison of FOC, FBL, BSC and SMC shows that the nonlinear controllers perform well under varying aerodynamic loads during flight. However, the performance of the sliding mode control is found superior as compared to the other three controllers in terms of better performance characteristics e.g. response time, steady-state error etc. as well as the control robustness in the presence of the uncertain parameters of the PMSM model and variable load torque acting as a disturbance. In essence, the peak of the tolerance band is less than 20% for all nonlinear and FOC controller, while it is less than 5% for SMC. Steady state error for the SMC is least (0.01%) as compared to other three controllers. Moreover, the SMC controller is able to withstand 50% parameter variation and loading torque of 10 N.m without significant changes in performance. Six simulation scenarios are used to analyze the performance and robustness which depict that the sliding mode controller performs well in terms of the desired performance for MEA application.

Compressor fouling detection by image analysis

Gas turbine fouling is commonly known as responsible for performance degradation in terms of compression ratio and efficiency. The adhesion of micro-sized particles (soil, soot, salt, etc.) caused the modification of the blade shapes and the surface roughness. Both of these two effects determine the modification of the compressor performance over the unit operation. Due to the lack of capability to forecast the fouling intensity, it could be useful to estimate the fouling intensity during the machine overhaul, collecting strategical data by which a specific characterization of a given machine in a given operating site can be done. The present paper proposes and validates a helpful methodology for estimating the deposit intensity by an image analysis procedure. An image-detection technique has been carried out before and after the contamination process, and, using a subtraction process, a quantitative analysis of the fouled regions can be developed. The results show that, with a careful light and camera setup, the intensity of the deposits can be estimated with an acceptable tolerance band, which allows the possibility of collecting quantitative data on compressor deposits during overhaul operations. This generates a valuable starting point for predicting the overtime degradation of the unit and/or estimating the filtration section efficiency.

Inflation tolerance ranges in the New Keynesian model

A number of central banks in advanced countries use ranges, or bands, around their inflation target to formulate their monetary policy strategy. The adoption of such ranges has been proposed by some policymakers in the context of the Fed and the ECB reviews of their strategies. Using a standard New Keynesian macroeconomic model, we analyze the consequences of tolerance range policies, characterized by a stronger reaction of the central bank to inflation when inflation lies outside the range, than when it is close to the target, i.e. the central value of the band. We show that (i) a tolerance band should not be a zone of inaction: the lack of reaction may trigger substantial unwarranted volatility and lead to multiple equilibria; (ii) the trade-off between the reaction needed outside the range versus inside appears unfavorable: a very strong reaction, when inflation is far from the target, is required to compensate for a moderately lower reaction within tolerance band; (iii) these results, obtained within the framework of a stylized model, are robust to many alterations, in particular allowing for the zero lower bound.

Wind turbine bearing fault diagnosis by maximum generalised Gaussian cyclostationarity blind deconvolution

This study aims to assess the performance of IGGCS/GGS as a criterion for blind deconvolution in the detection of wind turbine bearing faults. The challenges associated with diagnosing wind turbine bearing faults include two primary issues: (1) the theoretical fault frequencies or orders may not align with the actual fault frequencies or orders, and (2) the vibration signal deviates from a Gaussian distribution. Consequently, the application of the blind deconvolution criterion ICS2, as utilized in CYCBD, may encounter difficulties due to the aforementioned reasons. To address this, the criterion is modified from ICS2 to IGGCS/GGS, and a tolerance band is introduced during the generation of the weighting matrix. These modifications aim to mitigate the impact of the aforementioned challenges. The effectiveness of the modified blind deconvolution approach, referred to as CYCBDβ, is evaluated in this study by comparing its performance against that of CYCBD using two distinct datasets from 2.0 MW wind turbines.

Effect of TiO2 inoculants on the wear conduct of the aluminium AA 6061/red mud high performance hybrid composite

The current work focuses on the manufacturing of aluminium AA 6061 composites and its tribological characterization. This is achieved by reinforcing the matrix with red mud. However, the uniform dispersion of red mud requires ultrasonic assisted stir casting and the use of optimum wt.% of TiO2 inoculants. In this regard, the composition of red mud is fixed at 2 wt.%, since the addition of red mud beyond 2 wt.% results in the agglomeration, while the wt.% of TiO2 inoculants is varied from 2 wt.% to 6 wt.%. The wear tests are conducted as per the L9- Orthogonal Array (OA) for a load range of 10 N to 30 N, sliding distance of 500 m to 2500 m, disk rotation speed of 200 RPM to 600 RPM. The regression coefficients are more than 0.9 and close to unity and the error between the experimental outcomes and statistical values are within the tolerance band. The SWR and COF is minimized for 2 wt.% of red mud, 4 wt.% of TiO2, beyond which there is a slight increase in the wear of the composites attributed to the agglomeration of the reinforcments in certain localized regions and the presence of voids in other regions.

Command-Filtered Robust Adaptive NN Control With the Prescribed Performance for the 3-D Trajectory Tracking of Underactuated AUVs.

A novel robust adaptive neural network (NN) control scheme with prescribed performance is developed for the 3-D trajectory tracking of underactuated autonomous underwater vehicles (AUVs) with uncertain dynamics and unknown disturbances using new prescribed performance functions, an additional term, the radial basis function (RBF) NN, and the command-filtered backstepping approach. Different from the traditional prescribed performance functions, the new prescribed performance functions are innovatively proposed such that the time desired for the trajectory tracking errors of AUVs to reach and stay within the prescribed error tolerance band can be preset exactly and flexibly. The additional term with the Nussbaum function is designed to deal with the underactuation problem of AUVs. By means of RBF NN, the uncertain item lumped by the uncertain dynamics of AUVs and unknown disturbances is eventually transformed into a linearly parametric form with only a single unknown parameter. The developed control scheme ensures that all signals in the AUV 3-D trajectory tracking closed-loop control system are bounded. Simulation results with comparisons show the validity and the superiority of our developed control scheme.

Flexible Inflation Targeting: Concepts and application in India


 The paper analyses issues important in adapting flexible inflation targeting (FIT) to emerging markets. This sets the context in which the evolution of FIT in India and its performance record are analysed. The dominance of supply shocks implies flexibility and fiscal-monetary coordination are necessary. Coordination can reduce the output sacrifice of disinflation, even as it aids fiscal consolidation. Communication has a major role in guiding expectations towards the inflation target. Strict implementation of inflation targeting imposed a large output sacrifice in the early years, but reversal to flexible implementation, in line with the original agreement, succeeded in keeping inflation largely within announced tolerance bands with a good growth recovery. Forecasting has improved and errors in both directions indicate the absence of bias. While there were supportive events in the initial years, such as the 2014 crash in oil prices and softening of food price inflation, the regime has also survived adverse periods of pandemic related supply-chain snarls and rising oil prices. A long period of disinflation and output sacrifice need not be necessary to anchor inflation expectations when there is complementary supply-side action. Since policy has to respond if inflation persistently exceeds the tolerance band, this also contributes to anchoring inflation expectations.

Direct Multivariable Control for Modular Multilevel Converters

Modular multilevel converters (MMCs) have enabled new and demanding applications for power electronics in the high voltage/high power range. In these applications, very fast and tight control of all variables of the MMC is of prime importance. This article presents a new multivariable control (MVC) concept, which enables independent and extremely fast control of all essential variables. For each variable, a tolerance band can be specified, which is strictly met even under unexpected severe transients and disturbances. The minimized dead times achieved by the control are more than one order of magnitude smaller than the state of the art. The MVC has been implemented based on FPGA-hardware and digital signal processing of the measured values. Experimental results of the control performance and the robustness against parameter variation are presented, using a down scaled MMC with 96 submodules. These results include the analysis of steady-state operation, dynamic performance, and fault scenarios.

The relationship between the short-term and long-term Phillips curve for the Czech Republic

Inflation in Czech Republic in 2021 significantly deviated from the tolerance band. Although the economic results are lagging behind expectations, inflationary pressures, mainly from abroad, are still intensifying. At the same time, the rapid rise in consumer prices affects not only households and consumers, but also business and companies. As is known, a very important tool for understanding inflation is the Phillips curve, which shows the relationship between two variables, the first one is inflation and the second one is unemployment. The aim of this paper is to research the relationship between the short-term Philips curves and long-term Phillips curves for the Czech Republic. For this purpose, data on the inflation rate and unemployment rate between 1993 and 2018 were contrasted based on data published by the Czech Statistical Office. The short-term Phillips curve was assumed under adaptive expectation conditions, whereby a regression analysis was undertaken using SPSS statistical software to determine suitable values for the corresponding parameters. In addition, and in accordance with the trend figure and data description figure for both the unemployment rate variable and inflation rate variable, the basis for the development of the long-term Phillips curve is described. Subsequently, it is concluded that a mutually substitutive relationship exists with regards to the short-term and that the long-term is an irregular circular curve that moves in a clockwise direction.

Does Inflation Targeting Policy Matter for Inflation Performance?

Purpose – Inflation targeting (IT) is a practice that central banks around the world began to adopt as early as 1990. Due to the high accountability and high transparency of central banks under IT policy, the practice expected that inflation targets would have better inflation performance. In this study, it is explored whether inflation targeting policy has positive effects on inflation performance, focusing on inflation persistence. Also, it is explored whether the behavior of inflation rates overshooting or undershooting a target range (or a tolerance band around a target level) is asymmetric. Design/Methodology/Approach – An autoregressive (AR) model is adapted with a self-exciting threshold autoregressive (TAR) model to study inflation persistence before and after inflation targeting was adopted, respectively. To address issues that events unrelated to inflation targeting policy could explain the findings, counterfactual exercises for non- inflation target are conducted. Findings – It was found that inflation target, particularly developed inflation target, have experienced a decrease in inflation persistence after implanting inflation targeting. Also, there is limited evidence on the asymmetrical behavior of inflation rates between overshooting and undershooting an inflation target range, or tolerance band, around a target level. Research Implications – The findings in this study support the positive effect of IT policy on inflation performance. In particular, it is stronger for developed inflation target than less developed inflation target. In addition, the findings support that most central banks do not show asymmetrical responses to inflation rates between overshooting and undershooting a target range or tolerance band around a target level.

Blade Envelopes Part I: Concept and Methodology

Abstract Blades manufactured through flank and point milling will likely exhibit geometric variability. Gauging the aerodynamic repercussions of such variability, prior to manufacturing a component, is challenging enough, let alone trying to predict what the amplified impact of any in-service degradation will be. While rules of thumb that govern the tolerance band can be devised based on expected boundary layer characteristics at known regions and levels of degradation, it remains a challenge to translate these insights into quantitative bounds for manufacturing. In this work, we tackle this challenge by leveraging ideas from dimension reduction to construct low-dimensional representations of aerodynamic performance metrics. These low-dimensional models can identify a subspace which contains designs that are invariant in performance—the inactive subspace. By sampling within this subspace, we design techniques for drafting manufacturing tolerances and for quantifying whether a scanned component should be used or scrapped. We introduce the blade envelope as a computational manufacturing guide for a blade that is also amenable to qualitative visualizations. In this paper, the first of two parts, we discuss its underlying concept and detail its computational methodology, assuming one is interested only in the single objective of ensuring that the loss of all manufactured blades remains constant. To demonstrate the utility of our ideas, we devise a series of computational experiments with the Von Karman Institute’s LS89 turbine blade.

Dynamic Control of Discharge Energy During WEDM for the Purpose of Eliminating Vibrations of the Wire Tool Electrode

Abstract Production in all industry fields is currently affected by new scientific and technical knowledge and the requirements for its rapid deployment. In many cases, the most modern and highly sophisticated technical systems are applied. Simultaneously, fully automated production systems are rather successfully used and progressive production technologies are implemented. In most cases, there is an integral part of a management system that operates the challenging technological processes. These processes would not be executable without the system’s precise control, which provides a suitable precondition for ensuring the high quality of manufactured products. However, the customer’s demanding requirements are not always met. These involve increased requests for the quality of the final product due to the reduction of the tolerance band and application of high-strength materials. This paper aims to describe one of the solutions by which it is possible to achieve a higher quality of the machined surface after wire electrical discharge machining (WEDM). The solution proposes that through dynamic management, the WEDM process eliminates the vibrations of the wire tool electrode and thereby achieves a substantial increase in the quality of the eroded area in terms of its geometric accuracy. With the support of an extensive database of information with precise exchange of information, the proposed system will allow to control the electro discharge process with regard to the optimal way of operation of the electro discharge machine on the basis of individually selected conditions.

Wear-out failure analysis of modular multilevel converter-based STATCOM: The role of the modulation strategy and IGBT blocking voltage

The modular multilevel converter (MMC) is an attractive option for medium- and high-voltage static synchronous compensator (STATCOM) application. For this application, three aspects are relevant. Firstly, reliability and efficiency are directly related to the operation costs of this converter. Secondly, either high IGBT blocking voltage capability, featuring few number of submodules (SMs), or low-voltage IGBT modules, with a larger number of SMs, can be employed in an MMC-STATCOM. Lastly, either modulation strategies with fixed or variable switching frequency can be employed. Nevertheless, the literature does not present works evaluating these three aspects of an MMC-STATCOM at the same time. Therefore, this paper analyzes the impact of modulation strategies and number of SMs on wear-out failure and efficiency of an MMC-STATCOM. The effect of all SM components is considered. Two distinct modulation strategies are selected: phase-shifted pulse-width modulation (PS-PWM), with fixed switching frequency, and nearest-level control with cell tolerance band algorithm (NLC-CTB), with variable switching frequency. Four commercially available semiconductor blocking voltages are considered to evaluate the converter with different number of SMs. The results demonstrate that the number of SMs and the modulation strategy affect the MMC-STATCOM performance. Indeed, the converter presents different reliability at system-level and energy losses per year, depending on the IGBT blocking voltage and modulation strategy. The design with higher IGBT blocking voltage is the most affected.

Experimental Verification of a New Oscillation-based Test Algorithm for Analog Circuits

Oscillation-based test algorithm has been proposed and verified experimentally as an alternative to the specification--based test of analog circuits. Active filters are transformed to oscillators using nonlinear feedback, realized with a Schmitt trigger. Faults are detected based on the deviation of the oscillation frequency outside the tolerance band due to the variation of different circuit components under test. This proposed technique ensures high test precision due to the processing of the oscillation frequency with the help of a purely digital circuit. Undetectable ranges of parametric faults of circuit components have been identified by simulation with Cadence virtuoso using the 0.18 µm CMOS technology. Then, practical circuits of second order Butterworth Low Pass Filter and Sallen-Key Band Pass Filter have been tested experimentally. Experimental results ensure high fault coverage of the proposed test strategy.