scholarly journals On Relationship Between Time-Domain and Frequency-Domain Disturbance Observers and Its Applications

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Jinya Su ◽  
Wen-Hua Chen ◽  
Jun Yang
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Disturbance Observer ◽  
Matching Condition ◽  
Existence Condition ◽  
Design Guideline ◽  
Pass Filter ◽  
Functional Disturbance ◽  
Low Pass Filter ◽  
Unity Gain

This paper provides a generic analysis of the relationship between time- and frequency-domain disturbance observer (DOB) design methodology. It is discovered that the traditional frequency-domain DOBs using a low-pass filter with unity gain can only handle disturbances satisfying matching condition, while the traditional time-domain DOBs always generate an observer with a high-order. A functional disturbance observer (FDOB) is proposed to improve the existing results together with its design guideline, frequency analysis, and existence condition. Compared with the existing frequency-domain DOBs, the proposed FDOB can handle more classes of disturbances, while compared with the existing time-domain DOBs, the proposed FDOB can generate an observer with a lower-order. Numerical examples are presented to illustrate the main findings of this paper including a rotary mechanical system of nonminimum phase.

Disturbance-observer based control of voltage-source-converter under unbalanced voltage conditions

2017 ◽  
Vol 14 (6) ◽  
pp. 522-531 ◽  
Author(s):  
Akhtar Rasool ◽  
Esref Emre Ozsoy ◽  
Fiaz Ahmad ◽  
Asif Sabanoviç ◽  
Sanjeevikumar Padmanaban
Keyword(s):  
Disturbance Observer ◽  
Operating Conditions ◽  
Voltage Source ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Content Type ◽  
Negative Sequence ◽  
First Order ◽  
Unbalanced Voltage ◽  
Low Pass

Purpose This paper aims to propose a novel grid current control strategy for grid-connected voltage source converters (VSCs) under unbalanced grid voltage conditions. Design/methodology/approach A grid voltage dynamic model is represented in symmetrical positive and negative sequence reference frames. A proportional controller structure with a first-order low-pass filter disturbance observer (DOB) is designed for power control in unbalanced voltage conditions. This controller is capable of meeting the positive sequence power requirements, and it also eliminates negative sequence power components which cause double-frequency oscillations on power. The symmetrical components are calculated by using the second-order generalized integrator-based observer, which accurately estimates the symmetrical components. Findings Proportional current controllers are sufficient in this study in a wide range of operating conditions, as DOB accurately estimates and feed-forwards nonlinear terms which may be deteriorated by physical and operating conditions. This is the first reported scheme which estimates the VSC disturbances in terms of symmetrical component decomposition and the DOB concept. Originality/value The proposed method does not require any grid parameter to be known, as it estimates nonlinear terms with a first-order low-pass filter DOB. The proposed control system is implemented on a dSPACE ds1103 digital controller by using a three-phase, three-wire VSC.

Filtering of Electronic Speckle Correlation Fringes

2012 ◽  
Vol 198-199 ◽  
pp. 1202-1207
Author(s):  
Fei Guo ◽  
Mei Zhao ◽  
Xiu Ying Fan ◽  
Jin He Bao ◽  
Wen Bang Sun
Keyword(s):  
Frequency Domain ◽  
Speckle Noise ◽  
Filter Medium ◽  
Space Domain ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Speckle Correlation ◽  
Low Pass ◽  
Mean Filter

Speckle correlation fringes include a large quantity of speckle noise. It is first to consider how to reduce speckle noise before using phase formula to calculate. Filter is usually used to reduce speckle noise. From two aspects of frequency domain and space domain, we adopted mean filter, medium filter, Butterworth low-pass filter and homomorphism filter to process the speckle correlation fringes obtained by experiment. It is shown that the speckle correlation fringes are clearer and more easily interpreted and automatic processed after being filtered.

scholarly journals Design of Reconfigurable Bandwidth Filtering Antenna and Its Applications in IR/UWB System

Electronics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 163
Author(s):  
Zhuohang Zhang ◽  
Zhongming Pan
Keyword(s):  
System Design ◽  
Time Domain ◽  
Low Cost ◽  
Impulse Radio ◽  
Dynamic Adjustment ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Compact Size ◽  
Low Pass ◽  
Communication Frequency

A reconfigurable bandwidth antenna for an impulse radio-UWB (IR/UWB) system design is illustrated in this paper. By adopting a continuously tunable low-pass filter by varactor at the feed of the antenna, the proposed antenna obtains a continuous tunable bandwidth from 1.02 GHz to 2.42 GHz. To ensure the identifiability of transmitted pulses in (IR-UWB) system, the antenna is analyzed in both frequency domain and time domain. The proposed antenna is valid with a system fidelity factor (SFF) above 0.8 while the bandwidth is tuning. The compact size, low cost, and tunable bandwidth with the identifiability of the transmitted pulse makes it suitable for UWB impulse radars to improve the utility ratio of frequency, and dynamic adjustment avoids interference of the IR-UWB in other communication frequency bands.

FFT Thermoelastic Solutions for Moving Heat Sources

1997 ◽  
Vol 119 (1) ◽  
pp. 156-162 ◽  
Author(s):  
Y. Ju ◽  
T. N. Farris
Keyword(s):  
Heat Source ◽  
Frequency Domain ◽  
Hot Spot ◽  
Surface Displacement ◽  
Elastic Half Space ◽  
Heat Sources ◽  
Moving Heat Source ◽  
Line Heat Source ◽  
Pass Filter ◽  
Low Pass Filter

An analytical frequency domain solution is obtained using the spatial Fourier transform for thermal and thermoelastic fields due to an arbitrary heat source or thermal distribution moving at constant speed over the surface of an insulated, traction free elastic half space. Conversions between the space and frequency domains for the input and output are performed efficiently and robustly using FFT techniques. The method is validated by comparison to the analytical result for the moving line heat source in which it is shown that numerical evaluation of the analytical solution is problematic for large speeds or distances from the heat source. The utility of the method is illustrated on the constant patch moving heat source and discretely distributed multiple heat sources known as the “hot spot” problem. It is shown, through several examples, that the effect of hot spots on surface displacement and tangential stress is small. Finally, this conclusion is generalized by quantifying the frequency domain solution for the moving heat source problem as a low pass filter.

scholarly journals Generalized Chebyshev-like Approximation for Low-pass Filter

2011 ◽  
Vol 7 (1) ◽  
pp. 5-8
Author(s):  
Hisham Swady
Keyword(s):  
Time Domain ◽  
Analog Circuits ◽  
Analog Filters ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Novel Approach ◽  
Odd Order ◽  
Low Pass ◽  
Time Domain Response ◽  
Chebyshev Filter

Analog filters constitute indispensible component of analog circuits and still playing an important part in interface with analog real world. realizing filters with odd order is preferred because of its time response . Therefore, this paper is conducted to introduce a new generalized Chebyshev – like approximation for analog filters. The analyses presented to realize the filters with odd order. This proposed novel approach offer good results in terms of flat delay and time domain response. Also, the achieved results are validated by comparison to normal Chebyshev filter via investigation several examples.

Q-phase compensation of seismic records in the frequency domain

1996 ◽  
Vol 86 (4) ◽  
pp. 1179-1186
Author(s):  
Maksim Bano
Keyword(s):  
Wave Field ◽  
Frequency Domain ◽  
Real Data ◽  
Processing Technique ◽  
Signal Spectrum ◽  
Variable Model ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Seismic Wavelet ◽  
Inverse Q Filtering

Abstract The attenuation process acts as a low-pass filter that attenuates the high frequencies (absorption) of the signal spectrum and also changes the phase of the seismic wavelet (dispersion). Seismic frequency losses are usually recovered according to an appropriate processing technique (such as deterministic or statistical deconvolution methods), while phase distortions are generally disregarded. Therefore, accurate processing of seismic data requires a careful investigation of the relationship between absorption and phase. In this article, a procedure is presented to accomplish this goal. To account for anelastic losses, a complex power function of frequency for the phase velocity is introduced into the one-way wave-field equation in 1D. The compensation, for both effects (absorption and dispersion) described here, is analyzed in the context of wave-field extrapolation in one dimension 1D, equivalent to that in the f-k domain as phase-shift and/or Stolt migration. The phase-only inverse Q filtering works in the frequency domain. It provides for dispersion according to a constant-Q (frequency-independent) model and is valid for any positive value of Q. The extension of this algorithm for a Q depth-variable model is also shown. The amplitude compensation is accomplished through the use of a standard statistical approach. Synthetic and real data are shown to illustrate both amplitude and phase inverse Q filtering of seismic reflection records.

On Fractional Order Disturbance Observer

2003 ◽  
Author(s):  
YangQuan Chen ◽  
Blas M. Vinagre ◽  
Igor Podlubny
Keyword(s):  
Fractional Order ◽  
Disturbance Observer ◽  
Vibration Suppression ◽  
Patent Application ◽  
Cutoff Frequency ◽  
Relative Degree ◽  
Phase Margin ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass

In this paper, for the first time, the fractional order disturbance observer (FO-DOB) is proposed for vibration suppression applications such as hard disk drive servo control. It has been discovered in a recently published US patent application (US20010036026) (Chen et al., 2001) that there is a tradeoff between the the phase margin loss and the strength of the low frequency vibration suppression. Given the required cutoff frequency of the low pass filter, also known as the Q-filter, it turns out that the relative degree of the Q-filter is the major tuning knob for this tradeoff. As a motivation for the fractional order Q-filter, a solution based on integer order Q-filter with a variable relative degree is introduced which is the key contribution of US20010036026. Then, a fractional order disturbance observer based on the fractional order Q-filter is proposed. The implementation issue is also discussed. The nice point of this paper is that the traditional DOB is extended to fractional order DOB with the advantage that the FO-DOB design is now no longer conservative or aggressive, i.e., given the cutoff frequency and the desired phase margin, we can uniquely determine the fractional order of the low pass filter.

scholarly journals Parameter Selection Guidelines for a Parabolic Sliding Mode Filter Based on Frequency and Time Domain Characteristics

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Shanhai Jin ◽  
Ryo Kikuuwe ◽  
Motoji Yamamoto
Keyword(s):  
Time Domain ◽  
Sliding Mode ◽  
Robot Manipulator ◽  
Parameter Selection ◽  
Phase Lag ◽  
Transient Time ◽  
Pass Filter ◽  
Low Pass Filter ◽  
The Time Domain ◽  
Two Parameters

This paper presents the results of quantitative performance evaluation of an authors’ new parabolic sliding mode filter, which is for removing noise from signals in robotics and mechatronics applications, based on the frequency and time domain characteristics. Based on the evaluation results, the paper presents selection guidelines of two parameters of the filter. The evaluation results show that, in the frequency domain, the noise removing capability of the filter is almost the same as that of the second-order Butterworth low-pass filter (2-LPF), but its phase lag is smaller (maximum 150 degree) than that of 2-LPF (maximum 180 degree). Moreover, the filter produces smaller phase lag than a conventional parabolic sliding mode filter with appropriate selection of the parameters. In the time domain, the filter produces smaller overshoot than 2-LPF and the conventional one, while maintaining short transient time, by using an appropriately selected parameter. The presented parameter selection guidelines state that the values of the parameters should be chosen according to some estimated characteristics of the input and some desired characteristics of the output. The effectiveness of the filter and the presented guidelines is validated through numerical examples and their application to a closed-loop, force control of a robot manipulator.

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