Time-domain Error Research Articles

Time-domain output error system identification of iced aircraft aerodynamics

A \(\Delta\)-model approach to characterize changed aircraft dynamics due to icing is analytically derived and its parameters are estimated. The model extension is formulated as a separate module in the aircraft flight mechanics simulation and can be used in existing simulation models. The application of the output error method in time domain allows to satisfactorily match model outputs and measurements as well as calculated aerodynamic derivatives. Using available flight data of a light business jet with different ice accumulation cases provided by EMBRAER, model parameters of the \(\Delta\)-model are determined and interpreted pertaining to the aerodynamic degradation caused by icing. The results show good promise that the combination of modeling approach and estimation technique could be applicable to extend existing simulator models providing a basis for pilot training under icing conditions.

Orbital reference frame estimation with power spectral density constraints for drag-free satellites

The drag-free satellites are widely used in the field of fundamental science as they enable the high-precision measurement in pure gravity fields. This paper investigates the estimation of local orbital reference frame (LORF) for drag-free satellites. An approach, taking account of the combination of the minimum estimation error and power spectral density (PSD) constraint in frequency domain, is proposed. Firstly, the relationship between eigenvalues of estimator and transfer function is built to analyze the suppression and amplification effect on input signals and obtain the eigenvalue range. Secondly, an optimization model for state estimator design with minimum estimation error in time domain and PSD constraint in frequency domain is established. It is solved by the sequential quadratic programming (SQP) algorithm. Finally, the orbital reference frame estimation of low-earth-orbit satellite is taken as an example, and the estimator of minimum variance with PSD constraint is designed and analyzed using the method proposed in this paper.

Compression of ECG Signal Based on Improving the Signal Sparsity Adopting QRS-Complex Estimation and Spatial Domain Transforms

In this paper, an ECG signal compression technique based on improving the signal sparsity adopting QRS-complex estimation and spatial domain transforms is proposed. Compressive Sensing (CS) framework is utilized for this purpose; where the difference between the rate of change of a signal and the rate of change of its information contents is utilized. The proposed method starts with estimating the QRS-complex through the detection of the maximum amplitudes and the start and end points of the signal components. The error signal calculated as the difference between the estimated QRS-complex samples and original ECG samples is transformed using either DWT, DCT or FFT. QRS-complex estimation results in sparser timedomain error signal and the sparsity is increased by adopting the spatial-domain transforms. The proposed technique is assessed by calculating PRD and CR. Numerical results indicate that DWT gives a higher CR and lower PRD. The effect of increasing the signal sparsity, signal length, wavelet filters and wavelet decomposition levels have been studied. Comparison with recently published results [1] adopted only QRS-estimation and DWT indicate that the utilization of CS with both QRS-estimation and DWT yields to improved acceptable retrieved signal quality and higher CR. Moreover, comparison with other four CS-based algorithms [2]-[5] and other traditional ECG compression algorithm [6] indicates the superior performance of the proposed algorithm.

A solution of High-precision WLAN positioning based on TDOA and PTP

For indoor WLAN positioning it is difficult to achieve decimeter or centimeter-level precision questions, to IEEE1588v2 (PTP) precision network clock synchronization technology and the arrival time difference principle (TDOA), combined with non line of sight (NLOS) error mitigation techniques ranging research and design a set based on the existing WLAN (IEEE802.11x series of standards) device with high precision realtime location solutions. First, build a high-performance software-defined radio network communications platform, for accurate measurement of the radio signal arrival time and is calculated based on TDOA location. Secondly, the use of high-precision clock IEEE1588v2 standard equipment PTPGrand-2100 as a network clock source, through the integrated application of multi-hop latency compensation and asymmetric compensation algorithm to ensure nanosecond clock synchronization between the various WLAN access points (AP) accuracy(Experiments show that 1 nanosecond time synchronization error is equivalent to 10 to 30 cm of positioning error). Finally, based NLOS error becomes stability principle, filtered NLOS error and pre-positioned before the data, eliminate the influence of the greatest degree of NLOS error, the time domain error control in wireless ranging 5ns or less to achieve decimeter or more accurately estimate the position. The case can be widely used in mobile Internet, logistics management, mineral exploration, health and other needs of the precise location services (LBS) in other industry sectors.

A NOVEL ANALYTICAL EXPRESSIONS MODEL FOR CORONA CURRENTS BASED ON CURVE FITTING METHOD USING ARTIFICIAL NEURAL NETWORK

The analytical expressions for corona discharge currents are usually represented by the mathematic models based on curve fitting method. For the complex mechanisms, none of these currently models can describe a measured corona current with arbitrary waveforms. A novel curve fitting method using BP neural network (BPNN) technique is applied to describe the mathematic model of the corona currents in time domain. The analytical expressions for the currents can be established via extracting the weights and thresholds parameters of the trained BPNN. The expressions all have the same structure which has only four types of parameters, and the structure is independent of the corona current waveforms. The curve fitting for the measured corona currents with arbitrary waveforms by different models was carried out, and the results were analyzed, which indicate that the BPNN method performs best. Compared with the current expressions fitted by the double exponential function and Gaussian function, the expressions by BPNN can fit the current waveforms with the lowest mean square error (MSE) in time domain and the highest accuracy to spectra of the currents in frequency domain. The proposed method is suitable for establishing a unified analytical expressions model for corona currents with arbitrary shapes.

Multiple-degree-of-freedom sinusoidal vibration generation based on a hexapod platform

This article presents an active control strategy for generating multiple-degree-of-freedom sine and swept-sine vibration by using a hexapod platform as a shaker. In contrast to the typical frequency domain control approach of shaker controllers, the presented strategy is implemented in time domain, which brings an advantage of avoiding iteration, reducing the time required to adjust control signal. The novel strategy is combined by two parts: first, 36 finite impulse response filters are designed based on system identification, which compensate the multiple-input multiple-output system; then adaptive disturbance cancellation method is used, acquiring high-precision sine vibration. Swept-sine vibration generation is implemented by expanding the designed compensating filters. Experiments were carried out to evaluate the validity of this control strategy. The result showed that the time domain error is less than 1 mg, essentially being kept in the level of environment noise.

Linearization of Coupled Pointing and Tracking Dynamical Equations

Cooperative pointing and tracking is one important characteristic of deep space inter-satellite laser communication, so that the dynamic mathematical model is complicated nonlinearity and coupling. The contribution of this paper is to substitute the time-domain error transfer function of state equations and to linearize the state space for the sake of physical realization easily in terms of previous authors’ work. The method applied is state feedback and coordinate transformation in nonlinear field, the calculated result is demonstrated that differential equations modeled can be transferred into canonical controllable form and realized physically.

Stability analysis of multimachine thermal power systems using the nature-inspired modified cuckoo search algorithm

The stability of modern interconnected thermal power systems is greatly affected by the presence of low-frequency inertial oscillations in the system, due to various forms of disturbances experienced. This paper provides an efficient damping solution to these oscillations based on nature-inspired modified cuckoo search algorithm-based controller design. The proposed controller design is formulated as a parameter optimization problem based on damping ratio and time-domain error deviations. The effectiveness of the proposed damping controller design is illustrated by performing the nonlinear time domain simulations of the test multimachine power systems under various operating conditions and disturbances. Moreover, an exhaustive comparative stability analysis is performed based on the damping performance of the modified cuckoo search controller design over the genetic algorithm-based and cuckoo search algorithm-based controller designs.

A time-domain noise-coupling technique for continuous-time sigma-delta modulators

In this paper, a time-domain noise-coupling technique based on the pulse width modulation is proposed. The time-domain quantization error is digitally extracted and shaped by an asynchronous digital filter. This digitally filtered quantization error is applied to the quantizer input to increase the modulator's noise-shaping order. By using this technique in continuous-time sigma-delta modulators, the modulator's shaping property is significantly enhanced. Comparative analytical calculations and simulation results are presented to estimate the performance of modulators employing the proposed quantizer. System-level simulation results reveal a (L + 2)th order noise-shaping capability of the proposed modulator while it employs only L analog integrators. The effects of main circuit non-idealities in the modulator's performance are analytically investigated and confirmed by the simulation results.

Investigation on the Optimization Criteria for the Design of Variable Fractional Delay Filters

In recent research on the optimization of variable fractional delay (VFD) filters, group delay errors have been paid additional attention besides the conventional criterion of frequency response errors. While group delay physically measures the delay of the magnitude envelop of a signal, an important application of the VFD filters is to estimate the instantaneous delayed samples, such as in the applications of interpolation. In view of this, the impact of the group delay error on the estimation of instantaneous samples is investigated in this brief. Analysis and simulation results show that in such applications, the traditional criterion of frequency response errors reflects the time-domain errors and group delay errors do not show a slight impact on the time-domain errors.

Determination of Multisine Coefficients for Power Amplifier Testing

This paper proposes a setup for a best multisine design method that uses a time-domain optimization. The method is based on minimization of the time-domain error, so its resulting multisine has a very accurate ACLR estimation. This is because its probability distribution and sample-to-sample correlation are close to those of the original signal, which are crucial for the testing of nonlinear power amplifiers. In addition, a hyperbolic-tangent function is introduced to control the ripple of tone magnitudes within signal bandwidth. For the verification, multisines were generated and compared for many aspects such as normalized error, in-band ripple, and ACLR estimation. Test results with different numbers of tones provide supporting evidence that the suggested multisine design has better ripple suppression, by up to 7 dB, and better accuracy, by up to 0.2 dB, when compared to the conventional method. The accuracy of the ACLR was improved by about 5 dB when the number of tones was 4. The suggested method improves the ACLR estimation performance of multisine testing due to its closer resemblance to the target modulation signal.

A Wavelet-Collocation-Based Trajectory Piecewise-Linear Algorithm for Time-Domain Model-Order Reduction of Nonlinear Circuits

Trajectory piecewise-linearization-based reduced- order macromodeling methods have been proposed to characterize the time-domain behaviors of large strongly nonlinear systems. However, all these methods rely on frequency-domain model-order-reduction (MOR) methods for linear systems. Therefore, the accuracy of the reduced-order models in time domain cannot always be guaranteed and controlled. In this paper, a wavelet-collocation-based trajectory piecewise-linear approach is proposed for time-domain MOR of strongly nonlinear circuits. The proposed MOR method is performed in time domain and is based on a wavelet-collocation method. Compared with nonlinear MOR methods in frequency domain, the proposed method in time domain maintains higher accuracy for modeling transient characteristics of nonlinear circuits, which are very important in macromodeling and transient analysis for nonlinear circuits. Furthermore, a nonlinear wavelet companding technique is developed to control the modeling error in time domain, which is useful for balancing the overall modeling error over the whole time region and improving the simulation efficiency at higher level. The numerical results show that the proposed method has high macromodeling accuracy in time domain, and the modeling-error distribution in time domain can be efficiently controlled by the wavelet companding technique.

An analytical derivation of the optimum source patterns for the pseudospectral time-domain method

In the computational electromagnetics and acoustics, spatially smoothed sources are often utilized to alleviate the aliasing errors in the pseudospectral time-domain (PSTD) algorithms. In our work, an analytical derivation of the optimum source patterns is presented according to the accurately derived expressions of the dominant source-introduced aliasing errors according to the circular discrete convolution and Tailor series expansion method. We quantitatively demonstrate, for the first time in literature, that the aliasing errors can be optimally suppressed and rapidly reduced to the negligible levels by these optimum patterns and with the increment of source cells. We also provide the different implementation schemes of the optimal patterns both for the soft and hard source cases. The numerical calculation and 1D PSTD transient simulations are conducted to verify the excellent performance of these optimum sources.

Robust tracking control design for uncertain robotic systems with persistent bounded disturbances

AbstractIn this study, a robust nonlinear L∞‐gain tracking control design for uncertain robotic systems is proposed under persistent bounded disturbances. The design objective is that the peak of the tracking error in time domain must be as small as possible under persistent bounded disturbances. Since the nonlinear L∞ ‐gain optimal tracking control cannot be solved directly, the nonlinear L∞ ‐gain optimal tracking problem is transformed into a nonlinear L∞ ‐gain tracking problem by given a prescribed disturbance attenuation level for the L∞ ‐gain tracking performance. To guarantee that the L∞ ‐gain tracking performance can be achieved for the uncertain robotic systems, a sliding‐mode scheme is introduced to eliminate the effect of the parameter uncertainties. By virtue of the skew‐symmetric property of the robotic systems, sufficient conditions are developed for solving the robust L∞ ‐gain tracking control problems in terms of an algebraic equation instead of a differential equation. The proposed method is simple and the algebraic equation can be solved analytically. Therefore, the proposed robust L∞ ‐gain tracking control scheme is suitable for practical control design of uncertain robotic systems. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Novel Error Separation Method for Straightness Measurement

novel time-domain error separation method which can reconstruct straightness profile of workpiece exactly for on-machine measurement has successfully been developed. The proposed method is based on difference measurement and can use two or three displacement probes. It possesses following characteristics: (i) adapting to long or short workpiece, (ii) assuming no prior knowledge, (iii) employing large shears, (iv) needing no accurate zero-adjustment of probes, and (v) reconstructing various surfaces including smooth, non-smooth, periodic and non-periodic profiles with no theoretical error. The shortest length which can be reconstructed exactly has been calculated in time-domain method. The theoretical analysis justifies the effectiveness of this method.

Calibration of sampling oscilloscopes with high-speed photodiodes

We calibrate the magnitude and phase response of equivalent-time sampling oscilloscopes to 110 GHz. We use a photodiode that has been calibrated with our electrooptic sampling system as a reference input pulse source to the sampling oscilloscope. We account for the impedance of the oscilloscope and the reference photodiode and correct for electrical reflections and distortions due to impedance mismatch. We also correct for time-base imperfections such as drift, time-base distortion, and jitter. We have performed a rigorous uncertainty analysis, which includes a Monte Carlo simulation of time-domain error sources combined with error sources from the deconvolution of the photodiode pulse, from the mismatch correction, and from the jitter correction

Adaptive control of tunable dispersion compensator that minimizes time-domain waveform error by steepest descent method

We propose a novel technique to compensate dispersion adaptively. First, an error is calculated from the waveform of output signal in the time domain. Then a tunable dispersion compensator is controlled toward minimizing the error value by means of steepest-descent method. Transmission experiments and simulations show that the proposed technique can compensate the dispersion quickly for a wide dispersion range

Prediction error method-based second-order structural identification algorithm in stochastic state space formulation

This paper presents a time-domain prediction error method (PEM)-based system identification method for the identification of second-order structural parameters of linear structural systems. The state space model of a linear structure is first expanded into linear AutoRegressive Moving Average with eXogenous excitation (ARMAX) or AutoRegressive Moving Average (ARMA) models by matrix fraction description. Second-order structural parameters are then estimated directly from measured time series data by applying the PEM to ARMAX and ARMA models. The proposed structural identification method can incorporate as much as possible structural information known a priori into the structural identification process to improve the identification accuracy. To avoid the practical difficulty often associated with input measurement, a two-stage structural health monitoring procedure is proposed. Once the mass matrix is identified from the first stage, data collected from ambient vibration survey can be used to identify other structural parameters in the second stage. The effectiveness of the proposed structural identification method as well as the corresponding structural health monitoring method is evaluated through numerical simulation in the context of the ASCE benchmark problem on structural health monitoring. The numerical results show that the proposed method is capable of locating and quantifying damages reasonably well in the presence of 10% measurement noise and limited sensor information. Copyright © 2006 John Wiley & Sons, Ltd.

On time-domain and frequency-domain MMSE-based TEQ design for DMT transmission

We reconsider the minimum mean square error (MMSE) time-domain equalizer (TEQ), bitrate maximizing TEQ (BM-TEQ), and per-tone equalizer design (PTEQ) for discrete multitone (DMT) transmission and cast them in a common least-squares (LS) based framework. The MMSE-TEQ design criterion can be formulated as a constrained linear least-squares (CLLS) criterion that minimizes a time-domain (TD) error energy. From this CLLS-based TD-MMSE-TEQ criterion, we derive two new least-squares (LS) based frequency-domain (FD) MMSE-TEQ design criteria: a CLLS-based FD-MMSE-TEQ criterion and a so-called separable nonlinear LS (SNLLS) based FD-MMSE-TEQ design. Finally, the original BM-TEQ design is shown to be equivalent to a so-called iteratively-reweighted (IR) version of the SNLLS-based FD-MMSE-TEQ design. This LS-based framework then results in the following contributions. The new, IR-SNLLS-based BM-TEQ design criterion gives rise to an elegant, iterative, fast converging, Gauss-Newton-based design algorithm that exploits the separability property. The intermediate FD-MMSE-TEQ designs establish a link between the TD-MMSE-TEQ on one hand and the BM-TEQ and the PTEQ on the other hand. Moreover, the considered LS-based equalizer designs-although at first sight very different in nature-exhibit remarkable correspondence when turned into equivalent generalized eigenvalue problems.

Adaptive Fuzzy Tuned PID Controller for Combustion of Utility Boiler

This article deals with the proposed design of adaptive fuzzy tuned PID controller for combustion process in utility boiler. Advanced PID controllers are designed separately for fuel and air to regulate the inputs to the utility boiler in proper ratio and maintain the desired steam pressure at the turbine inlet, irrespective of the change in steam demand. Online adaptive error factor for tuning the PID controller for fuel is presented as per the boiler dynamics, considering turbine first-stage pressure and throttle pressure. Online adaptive error factor to tune the PID controller for air is presented by measuring oxygen in the flue gas path at the outlet of the boiler economizer. The gains of the PID controllers are adjusted online in accordance with the adaptive fuel and air error factor using fuzzy logic tuning scheme. The real-time studies were carried out on the lab scale experimental set-up using conventional PID and adaptive fuzzy tuned PID control strategies. The robustness of the adaptive fuzzy tuned PID control scheme is demonstrated for both positive and negative changes in the set point as well as in the load perturbation. The performances of all the control schemes are compared quantitatively using both time domain specifications and error integral criteria. The implementation of an adaptive fuzzy tuned PID control scheme for air and fuel flow for combustion in utility boiler gave better results than conventional PID scheme.