11 research outputs found
An application of a constrained adaptive lattice-structure allpass-based notch filter for advanced control of surface-mounted permanent-magnet synchronous drives
No full textA constrained adaptive lattice-structure allpass-based notch filter provides minimal phase delay and complete attenuation of the notch frequency. The allpass sections of the filter are realized as structurally lossless bounded real functions, with a minimum number of delay elements and multipliers. The filter structure admits orthogonal tuning of the notch frequency and notch bandwidth. An improved control scheme for surface-mounted permanent-magnet synchronous (SMPMS) drives ensures stable high-performance operation in the Bur weakening region, utilizing the over-modulation and six-step modes of the space vector modulation (SVM). An automatic transition into the flux weakening region is achieved by controlling the reference voltage magnitude. The fifth and seventh stator current harmonics of the fundamental frequency, generated in the over-modulation and six-step modes, propagate through the current control loops, resulting in the sixth harmonic in the reference voltage for the flux weakening loop and deteriorating drive performance. To properly filter the sixth harmonic over the extended speed range of the drive, the constrained adaptive lattice-structure allpass-based notch filter is employed
Inductorless bandpass filter design using allpass elements
No full textBibliography: p. 69-71.This title is not available online. Access options are:
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The Complex Order Fractional Derivatives and Systems are Non Hermitian
No full textPublisher Copyright:
© 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.This paper discusses the concept of fractional derivative with complex order from the application point of view. It is shown that a fractional derivative is hermitian, if and only if the order is real. The hermitian part of complex order derivatives behave like allpass filters with almost logarithmic phase.authorsversionpublishe
Robust flux weakening scheme for surface-mounted permanent-magnet synchronous drives employing an adaptive lattice-structure filter
No full textAn advanced control structure for surface-mounted permanent-magnet synchronous (SMPMS) drives provides a stable, high performance operation in the flux weakening region, utilizing the over-modulation and six-step modes of the space vector modulation (SVM). An automatic transition into flux weakening is achieved by controlling the reference voltage magnitude. The fifth and seventh stator current harmonics of the fundamental frequency, generated in the over-modulation and six-step modes, propagate through the current control loops, resulting in the sixth harmonic in the reference voltage and deteriorating drive performance. To filter the sixth harmonic, an adaptive lattice-structure allpass-based notch filter is employed, providing minimal phase delay and complete attenuation of the sixth harmonic
Multi-wavelength arbitrary waveform generation through spectro-temporal unitary transformations
No full textTemporal waveform manipulation is a fundamental functionality in optics and crucial for applications like optical communications, microwave photonics and quantum optics. Traditional IQ- or phase-amplitude modulators shape light by carving energy from the input lightwave and are thus fundamentally lossy, and cannot apply independent modulation to multiple input wavelengths simultaneously. Taking inspiration from the space-time duality, we produce arbitrary unitary spectro-temporal transformations on multiple temporal input vectors with a modulation structure comprising of only lossless phase modulation and dispersive allpass filtering. The bandwidth of the output waveforms is not restricted by the driving electronics and independent transformations can be performed simultaneously on multiple orthogonal inputs such as spectrally separated frequency tones. This overcomes the main limitations of traditional electro-optic modulators and offers fundamental new insight into temporal wave manipulation
Four decades of water recycling in Atlantis (Western Cape, South Africa): Past, present and future
No full textThe primary aquifer at Atlantis (Western Cape, South Africa) is ideally suited for water supply and the indirect recycling of urban stormwater runoff and treated domestic wastewater for potable purposes. The relatively thin, sloping aquifer requires careful management of the artificial recharge and abstraction for balancing water levels. Water quality management is a further key issue at Atlantis for ensuring the highest quality potable water. Groundwater quality varies from point to point in the aquifer, while urban runoff and wastewater qualities vary greatly. The layout of the town allows for the separation of stormwater from the residential and industrial areas as well as separate treatment of domestic and industrial wastewater. This permits safe artificial recharge of the various water quality portions at different points in the aquifer, either for recycling or for preventing seawater intrusion. All of the management actions are dependent on detailed data collection and this paper describes the various parts of the system, describes the data collection activities, and provides results of the monitoring and aquifer responses over the past four decades. Challenges related to iron fouling of production boreholes are also described. The presence of emerging contaminants was studied in 2008 but requires follow-up research for establishing the extent of any possible threat to water recycling. In order to address the shortcomings of the system a risk management plan based on the Hazard Analysis and Critical Control Points approach was developed. Lessons learnt from the Atlantis experience can be transferred to other potential sites for establishment of similar systems in arid and semi-arid areas of South Africa and the African continent.Keywords: Atlantis, managed aquifer recharge, water recycling, groundwater, stormwater, wastewater, monitorin
Development and Analysis of Non-Delay-Line Constant-Fraction Discriminator Timing Circuits, Including a Fully-Monolithic CMOS Implementation
No full textA constant-fraction discriminator (CFD) is a time pick-off circuit providing time derivation that is insensitive to input-signal amplitude and, in some cases, input-signal rise time. CFD time pick-off circuits are useful in Positron Emission Tomography (PET) systems where Bismuth Germanate (BGO)/photomultiplier scintillation detectors detect coincident, 511-keV annihilation gamma rays.
Time walk and noise-induced timing jitter in time pick-off circuits are discussed along with optimal and sub-optimal timing filters designed to minimize timing jitter. Additionally, the effects of scintillation-detector statistics on timing performance are discussed, and Monte Carlo analysis is developed to provide estimated timing and energy spectra for selected detector and time pick-off circuit configurations. The traditional delay-line CFD is then described with a discussion of deterministic (non statistical) performance and statistical Monte Carlo timing performance. A new class of non-delay-line CFD circuits utilizing lowpass- and/or allpass-filter delay-line approximations is then presented. The timing performance of these non-delay-line CFD circuits is shown to be comparable to traditional delay-line CFD circuits.
Following the development and analysis of non-delay-line CFD circuits, a fully-monolithic, non-delay-line CFD circuit is presented which was fabricated in a standard digital, 2-μ, double-meta], double-poly, n-well CMOS process. The CMOS circuits developed include a low time walk comparator having a time walk of approximately 175 ps for input signals with amplitudes between 10-mV to 2000-mV and a rise time (10 - 90%) of 10 ns. Additionally, a fifth-order, continuous-time filter having a bandwidth of over 100 MHz was developed to provide CFD signal shaping without a delay line. The measured timing resolution (3.26 ns FWITh1, 6.50 ns FWTM) of the fully-monolithic, CMOS CFD is comparable to measured resolution (3.30 ns FWHM, 6.40 ns FWTM) of a commercial, discrete, bipolar CFD containing an external delay line. Each CFD was tested with a PET EGO/photomultiplier scintillation detector and a preamplifier having a 10-ns (10 - 90%) rise-time. The development of a fully-monolithic, CMOS CFD circuit, believed to be the first such reported development, is significant for PET and other systems that employ many front-end CFD time pick-off circuits
Using fractional delay to control the magnitudes and phases of integrators and differentiators
No full textThe use of fractional delay to control the magnitudes and phases of integrators and differentiators has been addressed. Integrators and differentiators are the basic building blocks of many systems. Often applications in controls, wave-shaping, oscillators and communications require a constant 90° phase for differentiators and -90° phase for integrators. When the design neglects the phase, a phase equaliser is often needed to compensate for the phase error or a phase lock loop should be added. Applications to the first-order, Al-Alaoui integrator and differentiator are presented. A fractional delay is added to the integrator leading to an almost constant phase response of -90°. Doubling the sampling rate improves the magnitude response. Combining the two actions improves both the magnitude and phase responses. The same approach is applied to the differentiator, with a fractional sample advance leading to an almost constant phase response of 90°. The advance is, in fact, realised as the ratio of two delays. Filters approximating the fractional delay, the finite impulse response (FIR) Lagrange interpolator filters and the Thiran allpass infinite impulse response (IIR) filters are employed. Additionally, a new hybrid filter, a combination of the FIR Lagrange interpolator filter and the Thiran allpass IIR filter, is proposed. Methods to reduce the approximation error are discussed. © The Institution of Engineering and Technology 2007.AL-ALAOUI M. A., 2006, FACTA U SER ELEC ENE, V19, P143; AlAlaoui MA, 1997, INT J ELEC ENG EDUC, V34, P331; ALALAOUI MA, 1994, IEEE T CIRCUITS-I, V41, P186, DOI 10.1109-81.269060; ALALAOUI MA, 1992, ELECTRON LETT, V28, P1376, DOI 10.1049-el:19920875; ALALAOUI MA, 1993, ELECTRON LETT, V29, P376, DOI 10.1049-el:19930253; Al-Alaoui MA, 2001, IEEE T CIRCUITS-I, V48, P1326, DOI 10.1109-81.964421; ALALAOUI MA, 1993, ELECTRON LETT, V29, P934, DOI 10.1049-el:19930623; ALALAOUI MA, 1995, IEEE T CIRCUITS-I, V42, P220, DOI 10.1109-81.382477; Chen YQ, 2002, IEEE T CIRCUITS-I, V49, P363; Crochiere R. E., 1983, MULTIRATE DIGITAL SI; Fliege N.J., 1994, MULTIRATE DIGITAL SI; Laakso TI, 1996, IEEE SIGNAL PROC MAG, V13, P30, DOI 10.1109-79.482137; Luengo D, 2000, IEEE T CIRCUITS-II, V47, P482, DOI 10.1109-82.842118; MINOCHA S, 1993, INT J CIRC THEOR APP, V21, P265, DOI 10.1002-cta.4490210306; Mitra S. K., 2006, DIGITAL SIGNAL PROCE, DOI India; NAGAHARA M, 2003, P 42 IEEE C DEC CONT, P6539; Oppenheim A., 1997, SIGNALS SYSTEMS; Pei SC, 2004, IEEE SIGNAL PROC LET, V11, P788, DOI 10.1109-LSP.2004.835473; Pei SC, 2001, IEEE T CIRCUITS-I, V48, P389; RABINER LR, 1970, IEEE T ACOUST SPEECH, VAU18, P204, DOI 10.1109-TAU.1970.1162090; TASSART S, 1997, P IEEE INT C AC SPEE, V1, P455; THIRAN JP, 1971, IEEE T CIRCUITS SYST, VCT18, P659, DOI 10.1109-TCT.1971.1083363; Tseng CC, 2006, IEE P-VIS IMAGE SIGN, V153, P79, DOI 10.1049-ip-vis:20045208; VAIDYANATHAN PP, 1993, MULTI RATE SYSTEMS F; Valimaki V., 2000, INT ACOUSTICS SPEECH, V6, P387013121
The Design of Digital Fractional-order Differentiators and Integrators
No full text本文介紹一些常見的數位微積分器及分數階微積分器。第二到四章介紹三種積分的數值方：Newton-Cotes quadrature rule, Gauss-Legendre quadrature rule 和 Clenshaw-Curtis quadrature rule。伴隨這些數值方而來的小數週期元件就利用一些已熟知的小數週期延遲濾波器，例如: FIR Lagrange 和IIR allpass fractional delay filters來做IIR數位積分器的設計。我們用圖形比較以上設計的優缺點並提出一個合併的設計。第五章我們用一系列的方法來設計分數階微積分器。先是比較一些連續輸入數位化， 轉換的方法；其次利用二項展開或連分數展開，使得分數階可以化成整數階。利用最小平方誤差的方法來降低錯誤率。我們比較不同方法的頻率響應上的錯誤率以及在相位上的表現。並且，我們討論這些濾波器的特性。最後第六章，我們做一些整理和建議未來可以繼續研究的方向。In this thesis, we introduce a few designs of digital integrator, and a few designs of fractional-order differintegrator. We apply some numerical integration rules and fractional delay filters to obtain the closed form design of IIR digital integrators. There are three types of numerical integration rules to be investigated: Newton-Cotes quadrature rule, Gauss-Legendre quadrature rule and Clenshaw-Curtis quadrature rule. The fractional delay involved in the design will be implemented by FIR Lagrange and IIR allpass fractional delay filters. Also, a combined version is proposed. Several digital filter design examples are illustrated to demonstrate the effectiveness. Chapter 5 is to show the designs of the fractional-order differintegrator. We find a suitable generating function to fit the ideal fractional-order differintegrator. Then discretize the fractional-order with a power series expansion or continued fraction expansion. Last, we discuss the different methods to decrease the absolute magnitude error. Moreover, the filter properties will also be presented at the end of the chapter. Finally, we make a conclusion of this thesis and suggest the future work in chapter 6.Chapter 1 Introduction 1
Chapter 2 Digital Integrator Design Using Newton-Cotes Quadrature Rules 5
2.1 Introduction 5
2.2 Newton-Cotes quadrature rules 6
2.3 Design using Newton-Cotes quadrature rules 7
2.3.1 Use Newton-Cotes quadrature rules to design IIR filters based on the same sampling period T 8
2.3.2 Use Newton-Cotes quadrature rules to design IIR filters based fixed end points 9
2.4 Implementation 12
2.4.1 FIR Lagrange filter approximation 12
2.4.2 IIR allpass filter approximation 14
2.4.3 Combined approximation 17
2.5 Conclusion 20
Chapter 3 Digital Integrator Design Using Gauss-Legendre Quadrature Rules 21
3.1 Introduction 21
3.2 Gauss-Legendre quadrature rules 22
3.3 Design using Gauss-Legendre quadrature rules 23
3.4 Implementation 28
3.5 Conclusion 30
Chapter 4 Digital Integrator Design Using Clenshaw-Curtis Quadrature rules 31
4.1 Introduction 31
4.2 Design using Clenshaw-Curtis quadrature rules 32
4.3 Implementation 35
4.4 Conclusion and Comparison 37
Chapter 5 Fractional-order Differintegrator Design 39
5.1 Introduction 39
5.2 Design of FIR approximation to fractional differintegrators using power series expansion 40
5.3 Design of FIR approximation to fractional differintegrators using fractional delay filter 45
5.4 Design IIR fractional-order differintegrator using continued fraction expansion 48
5.5 Design of IIR approximations to fractional differintegrators using least square error 53
5.5.1 Some approximation schemes 54
A. Padé approximation 54
B. Prony’s method 55
C. Shanks’ method 56
5.5.2 Experimental result 57
5.6 Conclusion 60
Chapter 6 Conclusion and Future Work 63
Reference 6
Fysikaaliseen mallinnukseen pohjautuva epäharmonisten pianon äänten parametrinen synteesi
No full textThis dissertation studies methods for developing a parametric piano synthesis model using the physics-based approach. The goal is to develop a model that can be controlled with physically meaningful parameters. Moreover, the model is required to be computationally efficient for real-time implementation. The basis of this work is to use the digital waveguide technique for implementing a piano string model. The excitation signal, simulation of dispersion, the beating effect, and simulation of sympathetic resonances are considered. Novel and improved simulation methods are developed for each of these aspects by applying signal processing techniques and knowledge of the human auditory system. The new simulation methods include a novel excitation model with parametric control and the first closed-form design method for dispersion filter design. In addition, two new beating effect simulation methods suitable for parametric real-time synthesis are created. One of the developed methods can be also used for modifying the partial envelopes in recorded tones. Furthermore, an efficient and improved method for simulation of sympathetic resonances has been suggested. Additionally, a novel analysis method for estimating inharmonicity coefficient values from recorded tones, which is needed for high-quality synthesis, is developed giving good results. Finally, a real-time piano synthesis model without any sampled sounds is implemented using the developed simulation methods in collaboration with the Sibelius Academy. The model can be controlled in real-time using physical parameters, such as the fundamental frequency and the inharmonicity coefficient value. The implementation suggests that the goals set for this thesis work are met. The results can be applied to physics-based piano synthesis. The methods can be used to implement a synthesis model for restricted environments, and they can be used to produce test tones for evaluating properties of the human auditory system and testing signal analysis algorithms.Tämä väitöskirja käsittelee menetelmiä, joiden avulla voidaan luoda parametrinen pianosynteesimalli käyttäen fysikaaliseen mallinnukseen pohjautuvaa lähestymistapaa. Työn tavoitteena on tuottaa malli, jota voidaan ohjata fysikaalisesti tärkeillä muuttujilla. Lisäksi mallin on oltava tarpeeksi kevyt laskennallisesti, jotta se voidaan toteuttaa reaaliajassa. Työn lähtökohtana on aaltojohtotekniikalla toteutettu pianon kielimalli. Pianomallin eri piirteistä tarkastellaan erityisesti herätettä, dispersiota, huojuntaa sekä sympaattista värähtelyä, joiden simulointiin kehitetään uusia ja paranneltuja menetelmiä hyödyntämällä sekä signaalinkäsittelytekniikoita että tietoa ihmisen kuulojärjestelmän piirteistä. Herätteen tuottamiseen on kehitetty uusi menetelmä, jossa herätesignaalia voidaan kontrolloida parametreillä. Dispersioilmiötä simuloivan suotimen suunnitteluun on luotu uusi menetelmä, jolla suodin voidaan ensimmäistä kertaa suunnitella suljetun muodon kaavalla. Huojunnan simulointiin on vastaavasti kehitetty kaksi menetelmää, joita voidaan molempia käyttää reaaliaikaisissa ja parametrisissä malleissa. Toista menetelmää voidaan käyttää myös äänitettyjen äänten harmonisten vaimenemiskäyrien muokkaamiseen. Sympaattisten värähtelyiden simulointiin on puolestaan keksitty uusi, tehokas menetelmä. Lisäksi työssä on kehitetty uusi analyysimenetelmä dispersiosta aiheutuvan epäharmonisuuden mittaamiseen äänitetyistä signaaleista. Tulokset osoittavat että analyysimenetelmä tuottaa hyviä tuloksia. Lopuksi työssä on toteutettu yhteistyössä Sibelius-Akatemian kanssa reaaliaikainen pianosynteesiohjelma, jossa ei käytetä äänitettyjä ääniä. Synteesimallia voidaan ohjata reaaliajassa fysikaalisilla parametreillä, kuten perustaajuudella ja epäharmonisuuden määrällä. Toteutuksella, jossa käytetään tässä työssä kehitettyjä menetelmiä, osoitetaan että työlle asetetut tavoitteet ovat täyttyneet. Työn tuloksia voidaan hyödyntää fysikaaliseen mallinnukseen pohjautuvassa pianosynteesissä. Lisäksi synteesimallista on mahdollista kehittää kevyempi versio ympäristöihin, joissa käytettävissä oleva muistin määrä sekä prosessoriteho ovat rajalliset. Työssä esiteltyjä menetelmiä voidaan käyttää myös tuottamaan testiääniä ihmisen kuulojärjestelmän piirteiden analysointiin ja signaalianalyysimenetelmien testaamiseen.reviewe
