In Car Audio

This chapter presents implementations of advanced in Car Audio Applications. The system is composed by three main different applications regarding the In Car listening and communication experience. Starting from a high level description of the algorithms, several implementations on different levels of hardware abstraction are presented, along with empirical results on both the design process undergone and the performance results achieved

System approach to robust acoustic echo cancellation through semi-blind source separation based on independent component analysis

We live in a dynamic world full of noises and interferences. The conventional acoustic echo cancellation (AEC) framework based on the least mean square (LMS) algorithm by itself lacks the ability to handle many secondary signals that interfere with the adaptive filtering process, e.g., local speech and background noise. In this dissertation, we build a foundation for what we refer to as the system approach to signal enhancement as we focus on the AEC problem. We first propose the residual echo enhancement (REE) technique that utilizes the error recovery nonlinearity (ERN) to "enhances" the filter estimation error prior to the filter adaptation. The single-channel AEC problem can be viewed as a special case of semi-blind source separation (SBSS) where one of the source signals is partially known, i.e., the far-end microphone signal that generates the near-end acoustic echo. SBSS optimized via independent component analysis (ICA) leads to the system combination of the LMS algorithm with the ERN that allows for continuous and stable adaptation even during double talk. Second, we extend the system perspective to the decorrelation problem for AEC, where we show that the REE procedure can be applied effectively in a multi-channel AEC (MCAEC) setting to indirectly assist the recovery of lost AEC performance due to inter-channel correlation, known generally as the "non-uniqueness" problem. We develop a novel, computationally efficient technique of frequency-domain resampling (FDR) that effectively alleviates the non-uniqueness problem directly while introducing minimal distortion to signal quality and statistics. We also apply the system approach to the multi-delay filter (MDF) that suffers from the inter-block correlation problem. Finally, we generalize the MCAEC problem in the SBSS framework and discuss many issues related to the implementation of an SBSS system. We propose a constrained batch-online implementation of SBSS that stabilizes the convergence behavior even in the worst case scenario of a single far-end talker along with the non-uniqueness condition on the far-end mixing system. The proposed techniques are developed from a pragmatic standpoint, motivated by real-world problems in acoustic and audio signal processing. Generalization of the orthogonality principle to the system level of an AEC problem allows us to relate AEC to source separation that seeks to maximize the independence, hence implicitly the orthogonality, not only between the error signal and the far-end signal, but rather, among all signals involved. The system approach, for which the REE paradigm is just one realization, enables the encompassing of many traditional signal enhancement techniques in analytically consistent yet practically effective manner for solving the enhancement problem in a very noisy and disruptive acoustic mixing environment.PhDCommittee Chair: Biing-Hwang Juang; Committee Member: Brani Vidakovic; Committee Member: David V. Anderson; Committee Member: Jeff S. Shamma; Committee Member: Xiaoli M

An investigation of the utility of monaural sound source separation via nonnegative matrix factorization applied to acoustic echo and reverberation mitigation for hands-free telephony

In this thesis we investigate the applicability and utility of Monaural Sound Source Separation (MSSS) via Nonnegative Matrix Factorization (NMF) for various problems related to audio for hands-free telephony. We first investigate MSSS via NMF as an alternative acoustic echo reduction approach to existing approaches such as Acoustic Echo Cancellation (AEC). To this end, we present the single-channel acoustic echo problem as an MSSS problem, in which the objective is to extract the users signal from a mixture also containing acoustic echo and noise. To perform separation, NMF is used to decompose the near-end microphone signal onto the union of two nonnegative bases in the magnitude Short Time Fourier Transform domain. One of these bases is for the spectral energy of the acoustic echo signal, and is formed from the in- coming far-end user’s speech, while the other basis is for the spectral energy of the near-end speaker, and is trained with speech data a priori. In comparison to AEC, the speaker extraction approach obviates Double-Talk Detection (DTD), and is demonstrated to attain its maximal echo mitigation performance immediately upon initiation and to maintain that performance during and after room changes for similar computational requirements. Speaker extraction is also shown to introduce distortion of the near-end speech signal during double-talk, which is quantified by means of a speech distortion measure and compared to that of AEC. Subsequently, we address Double-Talk Detection (DTD) for block-based AEC algorithms. We propose a novel block-based DTD algorithm that uses the available signals and the estimate of the echo signal that is produced by NMF-based speaker extraction to compute a suitably normalized correlation-based decision variable, which is compared to a fixed threshold to decide on doubletalk. Using a standard evaluation technique, the proposed algorithm is shown to have comparable detection performance to an existing conventional block-based DTD algorithm. It is also demonstrated to inherit the room change insensitivity of speaker extraction, with the proposed DTD algorithm generating minimal false doubletalk indications upon initiation and in response to room changes in comparison to the existing conventional DTD. We also show that this property allows its paired AEC to converge at a rate close to the optimum. Another focus of this thesis is the problem of inverting a single measurement of a non- minimum phase Room Impulse Response (RIR). We describe the process by which percep- tually detrimental all-pass phase distortion arises in reverberant speech filtered by the inverse of the minimum phase component of the RIR; in short, such distortion arises from inverting the magnitude response of the high-Q maximum phase zeros of the RIR. We then propose two novel partial inversion schemes that precisely mitigate this distortion. One of these schemes employs NMF-based MSSS to separate the all-pass phase distortion from the target speech in the magnitude STFT domain, while the other approach modifies the inverse minimum phase filter such that the magnitude response of the maximum phase zeros of the RIR is not fully compensated. Subjective listening tests reveal that the proposed schemes generally produce better quality output speech than a comparable inversion technique

An investigation of the utility of monaural sound source separation via nonnegative matrix factorization applied to acoustic echo and reverberation mitigation for hands-free telephony

In this thesis we investigate the applicability and utility of Monaural Sound Source Separation (MSSS) via Nonnegative Matrix Factorization (NMF) for various problems related to audio for hands-free telephony. We first investigate MSSS via NMF as an alternative acoustic echo reduction approach to existing approaches such as Acoustic Echo Cancellation (AEC). To this end, we present the single-channel acoustic echo problem as an MSSS problem, in which the objective is to extract the users signal from a mixture also containing acoustic echo and noise. To perform separation, NMF is used to decompose the near-end microphone signal onto the union of two nonnegative bases in the magnitude Short Time Fourier Transform domain. One of these bases is for the spectral energy of the acoustic echo signal, and is formed from the in- coming far-end user’s speech, while the other basis is for the spectral energy of the near-end speaker, and is trained with speech data a priori. In comparison to AEC, the speaker extraction approach obviates Double-Talk Detection (DTD), and is demonstrated to attain its maximal echo mitigation performance immediately upon initiation and to maintain that performance during and after room changes for similar computational requirements. Speaker extraction is also shown to introduce distortion of the near-end speech signal during double-talk, which is quantified by means of a speech distortion measure and compared to that of AEC. Subsequently, we address Double-Talk Detection (DTD) for block-based AEC algorithms. We propose a novel block-based DTD algorithm that uses the available signals and the estimate of the echo signal that is produced by NMF-based speaker extraction to compute a suitably normalized correlation-based decision variable, which is compared to a fixed threshold to decide on doubletalk. Using a standard evaluation technique, the proposed algorithm is shown to have comparable detection performance to an existing conventional block-based DTD algorithm. It is also demonstrated to inherit the room change insensitivity of speaker extraction, with the proposed DTD algorithm generating minimal false doubletalk indications upon initiation and in response to room changes in comparison to the existing conventional DTD. We also show that this property allows its paired AEC to converge at a rate close to the optimum. Another focus of this thesis is the problem of inverting a single measurement of a non- minimum phase Room Impulse Response (RIR). We describe the process by which percep- tually detrimental all-pass phase distortion arises in reverberant speech filtered by the inverse of the minimum phase component of the RIR; in short, such distortion arises from inverting the magnitude response of the high-Q maximum phase zeros of the RIR. We then propose two novel partial inversion schemes that precisely mitigate this distortion. One of these schemes employs NMF-based MSSS to separate the all-pass phase distortion from the target speech in the magnitude STFT domain, while the other approach modifies the inverse minimum phase filter such that the magnitude response of the maximum phase zeros of the RIR is not fully compensated. Subjective listening tests reveal that the proposed schemes generally produce better quality output speech than a comparable inversion technique

The manufacture and characterisation of microscale magnetic components.

Abstract unavailable please refer to PD

Aeroelastic effects of mistuning and coupling in turbomachinery bladings

A numerical method has been developed to study the effects of structural mistuning on the aeroelastic behaviour of turbomachinery cascades. The specific objectives of the work presented here were the following: A method was to be developed that can assess the major effects of structural mistuning in a cascade in sub- and transonic flow situations. The influence of mechanical and aerodynamic coupling between the blades as well as coupling between multiple modes for each blade was to be included. Accurate representations of the aerodynamic forces, taken from a modern three-dimensional unsteady aerodynamic solver were to be used. The method should be applicable for design use, meaning that it has to supply results quickly for a large number of configurations. The applicability and accuracy of the method was to be demonstrated by comparison of numerical results to available data from recent experiments. The influence of major parameters on the aeroelastic stability and on the resonant amplitude of representative test cases should be assessed. The approach used to achieve these goals is the combination of a linearised Euler method for the aerodynamic calculations with a modal reduction technique, where the structural properties of each blade are represented by only a few eigenmodes. The method is validated and applied to two test cases, comprising of a transonic compressor rotor and a high pressure turbine rotor. Both are representative of modern turbomachinery designs. The final conclusions of this work are: The newly developed method is capable to assess the dominant effects of structural mistuning in turbomachinery cascades, including the mechanical and aerodynamic coupling of adjacent blades and the aerodynamic coupling of multiple modes with arbitrarily complex modeshapes. In this method, the aerodynamic characteristics of the cascade are accurately represented using the generalised unsteady aerodynamic coefficients derived from a modern three-dimensional flow solver, applicable to and validated for both sub- and transonic configurations. The simplifications employed significantly contribute to the computational efficiency of the method, making it applicable for design purposes as well as for the assessment of large parametric variations or for statistical studies of stochastically mistuned configurations. The current method is successfully validated by a comparison of numerical to experimental data. The applicability and accuracy is demonstrated by the favourable agreement between measured and computed results. Based on these validations, the method is applied to study the influence of major parameters on the aeroelastic behaviour of the selected test cases. The results show a wide range of phenomena, dependent on the type and strength of mistuning, frequency, modeshape and interblade phase angle. The results highlight the close inter-dependence of the aeroelastic stability derived from the eigenvalue analysis and the resonant amplitudes derived from the forced response analysis

Parameterized Modeling and Scheduling of Dataflow Graphs

There is no abstract available. (Also cross-referenced as UMIACS-TR-99-73

Näyttöön perustuva näkökulma CP kuntoutukseen : katsauksia fysioterapiasta, fysioterapiaan liittyvistä motorisista menetelmistä sekä ortooseista

This thesis utilises an evidence-based approach to critically evaluate and summarize effectiveness research on physiotherapy, physiotherapy-related motor-based interventions and orthotic devices in children and adolescents with cerebral palsy (CP). It aims to assess the methodological challenges of the systematic reviews and trials, to evaluate the effectiveness of interventions in current use, and to make suggestions for future trials Methods: Systematic reviews were searched from computerized bibliographic databases up to August 2007 for physiotherapy and physiotherapy-related interventions, and up to May 2003 for orthotic devices. Two reviewers independently identified, selected, and assessed the quality of the reviews using the Overview Quality Assessment Questionnaire complemented with decision rules. From a sample of 14 randomized controlled trials (RCT) published between January 1990 and June 2003 we analysed the methods of sampling, recruitment, and comparability of groups; defined the components of a complex intervention; identified outcome measures based on the International Classification of Functioning, Disability and Health (ICF); analysed the clinical interpretation of score changes; and analysed trial reporting using a modified 33-item CONSORT (Consolidated Standards of Reporting Trials) checklist. The effectiveness of physiotherapy and physiotherapy-related interventions in children with diagnosed CP was evaluated in a systematic review of randomised controlled trials that were searched from computerized databases from January 1990 up to February 2007. Two reviewers independently assessed the methodological quality, extracted the data, classified the outcomes using the ICF, and considered the level of evidence according to van Tulder et al. (2003). Results: We identified 21 reviews on physiotherapy and physiotherapy-related interventions and five on orthotic devices. These reviews summarized 23 or 5 randomised controlled trials and 104 or 27 observational studies, respectively. Only six reviews were of high quality. These found some evidence supporting strength training, constraint-induced movement therapy or hippotherapy, and insufficient evidence on comprehensive interventions. Based on the original studies included in the reviews on orthotic devices we found some short-term effects of lower limb casting on passive range of movement, and of ankle-foot orthoses on equinus walk. Long term effects of lower limb orthoses have not been studied. Evidence of upper limb casting or orthoses is conflicting. In the sample of 14 RCTs, most trials used simple randomisation, complemented with matching or stratification, but only three specified the concealed allocation. Numerous studies provided sufficient details on the components of a complex intervention, but the overlap of outcome measures across studies was poor and the clinical interpretation of observed score changes was mostly missing. Almost half (48%) of the applicable CONSORT-based items (range 28 32) were reported adequately. Most reporting inadequacies were in outcome measures, sample size determination, details of the sequence generation, allocation concealment and implementation of the randomization, success of assessor blinding, recruitment and follow-up dates, intention-to-treat analysis, precision of the effect size, co-interventions, and adverse events. The systematic review identified 22 trials on eight intervention categories. Four trials were of high quality. Moderate evidence of effectiveness was established for upper extremity treatments on attained goals, active supination and developmental status, and of constraint-induced therapy on the amount and quality of hand use and new emerging behaviours. Moderate evidence of ineffectiveness was found for strength training's effect on walking speed and stride length. Conflicting evidence was found for strength training's effect on gross motor function. For the other intervention categories the evidence was limited due to the low methodological quality and the statistically insignificant results of the studies. Conclusions: The high-quality reviews provide both supportive and insufficient evidence on some physiotherapy interventions. The poor quality of most reviews calls for caution, although most reviews drew no conclusions on effectiveness due to the poor quality of the primary studies. A considerable number of RCTs of good to fair methodological and reporting quality indicate that informative and well-reported RCTs on complex interventions in children and adolescents with CP are feasible. Nevertheless, methodological improvement is needed in certain areas of the trial design and performance, and the trial authors are encouraged to follow the CONSORT criteria. Based on RCTs we established moderate evidence for some effectiveness of upper extremity training. Due to limitations in methodological quality and variations in population, interventions and outcomes, mostly limited evidence on the effectiveness of most physiotherapy interventions is available to guide clinical practice. Well-designed trials are needed, especially for focused physiotherapy interventions.Tässä väitöskirjassa arvioidaan kriittisesti tutkimuksia CP-lasten ja -nuorten kuntoutuksessa käytetystä fysioterapiasta ja muista liikkumisen harjoitteista sekä ortooseista näyttöön perustuvasta näkökulmasta. Tutkimuskysymyksinä on, millaisia menetelmällisiä haasteita liittyy tämän aihealueen järjestelmällisiin katsauksiin ja satunnaistettuihin tutkimuksiin, ja mikä on erilaisten nykyisin käytössä olevien fysioterapiamenetelmien vaikuttavuus. Menetelmät: Sähköisistä tietokannoista haettiin järjestelmällisiä katsauksia erilaisista fysioterapian menetelmistä (elokuuhun 2007) ja ortooseista (toukokuuhun 2003). Kaksi arvioijaa valitsi, keräsi tiedon ja arvioi katsausten laadun "Overview Quality Assessment Questionnaire" -kriteereillä, joihin oli lisätty valmiit vastausvaihtoehdot. Neljästätoista satunnaistetusta vertailututkimuksesta, jotka oli julkaistu tammikuun 1990 ja kesäkuun 2003 välillä, analysoitiin niissä käytettyjä menetelmiä: otanta, rekrytointi ja ryhmien välinen vertailtavuus; monimuotoisen intervention määritellyt osatekijät; tulosmittarit toimintakyvyn, toimintarajoitteiden ja terveyden kansainvälisen luokituksen (ICF) mukaan; muutoksen kliinisen merkittävyyden tulkinta; ja raportoinnin laatu 33-osioisen CONSORT:iin (Consolidated Standards of Reporting Trials) perustuvan tarkistuslistan avulla. Fysioterapiamenetelmien vaikuttavuusselvitystä varten haettiin satunnaistettuja vertailututkimuksia sähköisistä tietokannoista vuodesta 1990 helmikuuhun 2007 asti. Kaksi arvioijaa arvioit itsenäisesti tutkimusten laadun, keräsi tiedot tutkimuksista, luokitteli tulokset ICF:n mukaan ja arvioi näytön asteen van Tulder ym. (2003) mukaan. Tulokset: Hauissa löytyi 21 katsausta erilaisista fysioterapiamenetelmistä ja 5 katsausta ortooseista. Fysioterapiakatsauksissa oli arvioitu yhteensä 23 satunnaistettua vertailututkimusta ja 104 havainnoivaa tutkimusta CP-lapsilla ja -nuorilla. Ortoosikatsauksissa tutkimuksia oli vastaavasti 5 ja 27. Kuusi fysioterapiakatsausta oli laadultaan hyviä. Niissä todettiin, että on jotain näyttöä voimaharjoittelun, pakotetun yläraajan käytön ja ratsastusterapian hyödyistä, ja että tieteellinen näyttö on riittämätöntä kokonaisvaltaisista fysioterapia- tai toimintaterapiainterventioista. Ortoosikatsauksissa olevien tutkimusten mukaan löytyi lyhyen ajan näyttöä siitä, että kipsaus voi lisätä passiivista liikelaajuutta, ja että plantaarifeksiota rajoittavilla ortooseilla voi olla suotuisa vaikutus varvaskävelyyn. Alaraajaortoosien pitkäaikaisvaikutuksia ei ollut tutkittu. Näyttö yläraajan kipsien tai -lastojen vaikuttavuudesta on ristiriitaista. Neljäntoista satunnaistetun tutkimuksen otoksessa useimmissa tutkimuksissa oli käytetty yksinkertaista satunnaistamista täydennettynä matching- ja stratifikaatio-tekniikoilla, mutta vain kolmessa tutkimuksessa ryhmäjaon salaus varmistettiin. Monet tutkimukset määrittelivät selkeästi monimuotoisen intervention eri osia. Eri tutkimusten mittarit olivat harvoin samoja, eikä niissä tapahtuneiden muutosten kliinistä merkitystä tulkittu. Puolet soveltuvista CONSORT:iin pohjautuvista kysymyksistä (vaihteluväli 28 32) oli raportoitu riittävän hyvin. Puutteita oli tulosmittareiden, ryhmäkoon määrittämisen, satunnaistamismenetelmän, ryhmäjaon salaamisen ja satunnaistamisen, mittaajien sokkouttamisen, tutkimuksen tekemisen ajankohtien, ryhmäkohtaisen analyysin (intention-to-treat), tuloksen luottamusvälien, muiden samanaikaisten interventioiden ja mahdollisten haittojen raportoinnissa. Järjestelmälliseen katsaukseen hyväksyttiin 22 satunnaistettua tutkimusta, jotka luokiteltiin kahdeksaan terapialuokkaan. Neljä tutkimusta oli laadultaan hyviä. Kohtalaista näyttöä löytyi kahdesta terapialuokasta: 1) yläraajojen terapia lisäsi tavoitteiden saavuttamista, käsivarren aktiivista ulkokiertoa ja vaikutti lapsen kehitystasoon, sekä 2) pakotettu käden käyttö lisäsi käden käytön määrää ja laatua. Voimaharjoittelun vaikuttamattomuudesta kävelynopeuteen ja askelpituuteen löytyi kohtalaista näyttöä ja karkeamotoriikkaan ristiriitaista näyttöä. Muissa terapialuokissa tutkimusnäyttö oli heikkoa, ja huolimatta tutkimusten heikosta laadusta tutkittujen ryhmien välillä ei ollut eroja. Johtopäätökset: Parhaiden katsausten johtopäätökset näytöstä joidenkin fysioterapiamenetelmien sekä vaikuttavuudesta että näytön riittämättömyydestä ovat luotettavia. Menetelmällisesti heikkojen katsausten tuloksia kannattaa tulkita varoen. Kaikkiaan katsausten mukaan tieteellinen näyttö useimmista fysioterapiamenetelmistä ja ortooseista oli riittämätöntä heikkojen alkuperäistutkimusten takia. CP-lasten ja -nuorten satunnaistetuista tutkimuksista huomattava määrä oli sekä menetelmiltään että raportoinniltaan hyviä tai melko hyviä. Tämä osoittaa, että hyvin toteutettu ja raportoitu satunnaistettu tutkimus monimuotoisissa interventioissa voidaan toteuttaa heterogeenisessä potilasryhmässä. Tutkimusmenetelmissä ja toteuttamisessa on silti parannettavaa tietyin kohdin, ja tutkijoiden kannattaa noudattaa raportoidessaan CONSORT -suosituksia. Järjestelmällisessä katsauksessa yläraaja-harjoittelun vaikuttavuudesta löytyi kohtalaista tutkimusnäyttöä. Muiden tutkimusten heikkouksista ja tutkittujen potilasryhmien, interventioiden ja käytettyjen tulosmittareiden erilaisuudesta johtuen useista fysioterapian menetelmistä on saatavilla vain rajoitetusti käytäntöön soveltuvaa tietoa. Uusia tutkimuksia tarvitaan erityisesti kohdennetuista interventioista

Single chip solution for stabilization control & monocular visual servoing of small-scale quadrotor helicopter

This thesis documents the research undertaken to develop a high-performing design of a small-scale quadrotor (four-rotor) helicopter capable of delivering the speed and robustness required for agile motion while also featuring an autonomous visual servoing capability within the size, weight, and power (SWaP) constraint package. The state of the art research was reviewed, and the areas in the existing design methodologies that can potentially be improved were identified, which included development of a comprehensive dynamics model of quadrotor, design and construction of a performance optimized prototype vehicle, high-performance actuator design, design of a robust attitude stabilization controller, and a single chip solution for autonomous vision based position control. The gaps in the current art of designing each component were addressed individually. The outcomes of the corresponding development activities include a high-fidelity dynamics and control model of the vehicle. The model was developed using multi-body bond graph modeling approach to incorporate the dynamic interactions between the frame body and propulsion system. Using an algorithmic size, payload capacity, and flight endurance optimization approach, a quadrotor prototype was designed and constructed. In order to conform to the optimized geometric and performance parameters, the frame of the prototype was constructed using printed circuit board (PCB) technology and processing power was integrated using a single chip field programmable gate array (FPGA) technology. Furthermore, to actuate the quadrotor at a high update rate while also improving the power efficiency of the actuation system, a ground up FPGA based brushless direct current (BLDC) motor driver was designed using a low-loss commutation scheme and hall effect sensors. A proportional-integral-derivative (PID) technology based closed loop motor speed controller was also implemented in the same FPGA hardware for precise speed control of the motors. In addition, a novel control law was formulated for robust attitude stabilization by adopting a cascaded architecture of active disturbance rejection control (ADRC) technology and PID control technology. Using the same single FPGA chip to drive an on-board downward looking camera, a monocular visual servoing solution was developed to integrate an autonomous position control feature with the quadrotor. Accordingly, a numerically simple relative position estimation technique was implemented in FPGA hardware that relies on a passive landmark/target for 3-D position estimation. The functionality and effectiveness of the synthesized design were evaluated by performance benchmarking experiments conducted on each individual component as well as on the complete system constructed from these components. It was observed that the proposed small-scale quadrotor, even though just 43 cm in diameter, can lift 434 gm of payload while operating for 18 min. Among the ground up designed components, the FPGA based motor driver demonstrated a maximum of 4% improvement in the power consumption and at the same time can handle a command update at a rate of 16 kHz. The cascaded attitude stabilization controller can asymptotically stabilize the vehicle within 426 ms of the command update. Robust control performance under stochastic wind gusts is also observed from the stabilization controller. Finally, the single chip FPGA based monocular visual servoing solution can estimate pose information at the camera rate of 37 fps and accordingly the quadrotor can autonomously climb/descend and/or hover over a passive target