Proposed Error Model Research Articles

인공위성 자세결정 시스템을 위한 등가 오차모델

We introduce the error models for an attitude determination system(ADS) with gyroscopes and stellar sensor. The ADS error models are derived according to the definition of the reference frame and of the attitude error. The equivalent error models applicable to the attitude determination system with large attitude errors are presented. The simulation results show that the proposed error models improve performance of the attitude determination system.

Analysis of Phase Evaluation Algorithms in an Interferometric Method for Static Deformation Measurement

This article describes and analyses an interferometric method for measuring displacements and deformation. The method can be used for a very accurate evaluation of the change in the surface shape of structures used in industry. The paper proposes several multistep phase calculation algorithms and describes an automatic evaluation process using the measurement technique. A complex analysis is also performed of various factors that can have a negative effect on the practical measurement and evaluation process. An analysis is made of the proposed multistep phase calculation algorithms using the proposed error model. It is shown that the resulting phase measurement errors can be effectively reduced by using suitable phase calculation algorithms. The analysis can be applied for a complex comparison of the accuracy and stability of such algorithms.

Switched-Current bandpass Sigma–Delta modulators for AM digital radio receivers

This paper discusses the use of switched-current (SI) circuits to design Band-Pass ΣΔ Modulators (BP-ΣΔMs) suitable for AM digital radio receivers. First of all, the paper briefly outlines the concept and principles of BP-ΣΔMs, and introduces two modulator architectures which are obtained by applying a lowpass-to-bandpass transformation (i.e. z−1→−z−2) to a first-order and a second-order Low-Pass ΣΔ Modulator (LP-ΣΔM), respectively. The resulting BP-ΣΔMs, respectively of second-order and of fourth-order, are then used as case studies for SI circuit implementation. Systematic analysis of the errors associated to SI circuits is carried out and models are presented to evaluate their incidence on the performance of BP-ΣΔMs; the significance of the different errors is illustrated via the two selected case studies. Fully-differential regulated-folded cascode SI memory cells are chosen to attenuate these errors. Based on the proposed error models, optimization is carried out to fulfill AM radio requirements in practical modulator implementations. Two IC prototypes have been fabricated in a CMOS 0.8μm technology, and measured, to validate the presented design methodology. One of these prototypes uses the fourth-order architecture to digitize AM signals, and features 10.5-bit resolution with 60mW power consumption from a 5V supply voltage. The other uses the second-order architecture and features 8-bit with 42mW in the commercial AM band, from 540 to 1600kHz. Experimental results show correct noise-shaping for sampling frequencies up to 16MHz, which means a significant operation frequency enhancement as compared to previously reported SI ΣΔ Modulators.

Comparison of SDINS in-flight alignment using equivalent error models

The psi-angle model and the equivalent tilt (ET) model have been widely used for in-flight alignment (IFA) to align and to calibrate a strapdown inertial navigation system (SDINS) on a moving base. However, these models are not effective for a system with large attitude errors because the neglected error terms in the models degrade the performance of a designed filter. In this paper, with an odometer as an external aid, a velocity-aided SDINS is designed for IFA. Equivalent error models applicable to IFA with large attitude errors are derived in terms of rotation vector error and additive and multiplicative quaternion errors. It is found that error models in terms of additive quaternion error (AQE) become linear. Thus the proposed error models reduce unmodeled error terms for a linear filter. From a number of van tests, it is shown that the proposed error models effectively improve the performance of IFA.

Computer-aided error modeling approach to improve the accuracy of turning processes

In this paper, a computer-aided error modeling approach for enhancing the accuracy and the effectiveness of the turning process is discussed. Rigid body kinematics is used to derive error models that correlate the resultant errors in the machine tool workspace to the imperfection and misalignment of positioning elements and workpieces. Using the proposed error modeling technique, the machine tool is capable of fulfilling the major aim of any machining process to produce workpieces within the imposed tolerances of form, dimension, surface finish and quality. The effectiveness of the proposed error modeling approach has been further increased by a computer-aided searching algorithm to identify the robust measuring points with respect to the designated tolerance. For arbitrarily shaped manufacturing parts, the identified measuring points are least sensitive to the potential measuring errors in parameter estimation. The effectiveness of the proposed error modeling approach is demonstrated by simulation results.

The role of the error model in the determination of the relaxation time spectrum

The determination of the relaxation time spectrum from noisy experimental data is an ill-posed problem. Methods suitable for the treatment of such problems are regularization methods and maximum entropy methods. The solutions obtained thereby depend on the assumed errors of the given data. In order to obtain reliable results it is therefore necessary to test the correctness of the assumed error model. With the help of the well-known extension of the Shapiro and Wilk’s W test the proposed error model could be tested. The application of this test to synthetic data and experimental data from rheological measurements is investigated.

Performance of signature registers in the presence of correlated errors

In signature analysis, aliasing is usually examined under the independent or the q-ary symmetric error model. In contrast to the independent error model, the q-ary error model assumes space correlation among outputs. However, both independent and q-ary error models assume that the errors resulting from consecutive test vectors are independent over time. This assumption is reasonable for combinational circuits but certainly unrealistic for sequential logic circuits as the outputs of a sequential circuit depend on the previous state as well as the current input vector. For this reason a new error model, called the generalised time dependent q-ary (GTDQ) error model, is proposed. This error model extends the q-ary error model to consider both space and time correlation. A second parameter c is used to model the time correlation. By modelling the signature analyser as a Markov process the authors obtain a closed form expression for exact aliasing probability for arbitrary test length for a class of multiple-input linear automata signature registers (MILASRs). An easily verifiable criterion is given to determine whether a MILASR falls into this category. Finally, experimental results are provided for some real sequential circuits to validate the proposed error models.

An Estimator of Examinee-Level Measurement Error Variance That Considers Test Form Difficulty Adjustments

A model and estimator for examinee-level measure ment error variance are developed. Although the bi nomial distribution is basic to the modeling, the pro posed error model provides some insights into problems associated with simple binomial error, and yields estimates of error that are quite distinct from bi nomial error. By taking into consideration test form difficulty adjustments often used in standardized tests, the model is linked also to indices designed for identi fying unusual item response patterns. In addition, av erage error variance under the model is approximately that which would be obtained through a KR-20 estimate of reliability, thus providing a unique justification for this popular index. Empirical results using odd-even and alternate-forms measures of error variance tend to favor the proposed model over the binomial.