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  • 1501.
    Zhong, Mengyu
    et al.
    Uppsala University, WoMHeR (Centre for Women’s Mental Health during the Reproductive Lifespan). Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division Vi3. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    van Zoest, Vera
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bilal, Ayesha Mae
    Uppsala University, WoMHeR (Centre for Women’s Mental Health during the Reproductive Lifespan). Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Psychiatry.
    Papadopoulos, Fotios C.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Psychiatry.
    Castellano, Ginevra
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division Vi3.
    Unimodal vs. Multimodal Prediction of Antenatal Depression from Smartphone-based Survey Data in a Longitudinal Study2022In: ICMI '22: Proceedings of the 2022 International Conference on Multimodal Interaction / [ed] Raj Tumuluri; Nicu Sebe; Gopal Pingali; Dinesh Babu Jayagopi; Abhinav Dhall; Richa Singh; Lisa Anthony; Albert Ali Salah, Association for Computing Machinery (ACM), 2022, p. 455-467Conference paper (Refereed)
    Abstract [en]

    Antenatal depression impacts 7-20% of women globally, and can have serious consequences for both the mother and the infant. Preventative interventions are effective, but are cost-efficient only among those at high risk. As such, being able to predict and identify those at risk is invaluable for reducing the burden of care and adverse consequences, as well as improving treatment outcomes. While several approaches have been proposed in the literature for the automatic prediction of depressive states, there is a scarcity of research on automatic prediction of perinatal depression. Moreover, while there exist some works on the automatic prediction of postpartum depression using data collected in clinical settings and applied the model to a smartphone application, to the best of our knowledge, no previous work has investigated the automatic prediction of late antenatal depression using data collected via a smartphone app in the first and second trimesters of pregnancy. This study utilizes data measuring various aspects of self-reported psychological, physiological and behavioral information, collected from 915 women in the first and second trimesters of pregnancy using a smartphone app designed for perinatal depression. By applying machine learning algorithms on these data, this paper explores the possibility of automatic early detection of antenatal depression (i.e., during week 36 to week 42 of pregnancy) in everyday life without the administration of healthcare professionals. We compare uni-modal and multi-modal models and identify predictive markers related to antenatal depression. With multi-modal approach the model reaches a BAC of 0.75, and an AUC of 0.82.

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  • 1502. Zhu, Xumin
    et al.
    Li, Jian
    Stoica, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Knowledge-aided adaptive beamforming2008In: IET Signal Processing, ISSN 1751-9675, E-ISSN 1751-9683, Vol. 2, no 4, p. 335-345Article in journal (Refereed)
  • 1503. Zhu, Xumin
    et al.
    Li, Jian
    Stoica, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Knowledge-aided space-time adaptive processing2011In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 47, no 2, p. 1325-1336Article in journal (Refereed)
  • 1504. Zhu, Xumin
    et al.
    Li, Jian
    Stoica, Peter
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Guerci, J
    Knowledge-aided space-time adaptive processing2007In: 41st ASILOMAR Conference on Signals, Systems and Computers., 2007Conference paper (Refereed)
  • 1505. Zhusubaliev, Zhanybai
    et al.
    Churilov, Alexander
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Complex Dynamic Phenomena in a Low-Order Model of Non-Basal Testosterone Regulation2011In: Proc. 50th Conference on Decision and Control, Piscataway, NJ: IEEE , 2011Conference paper (Refereed)
  • 1506.
    Zhusubaliyev, Zhanybai T.
    et al.
    Southwest State Univ, Dept Comp Sci, Dynam Nonsmooth Syst Int Sci Lab, 50 Years October Str 94, Kursk 305040, Russia..
    Avrutin, Viktor
    Univ Stuttgart, Inst Syst Theory & Automat Control, Pfaffenwaldring 9, D-70550 Stuttgart, Germany..
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control.
    Doubling of a closed invariant curve in an impulsive Goodwin's oscillator with delay2021In: Chaos, Solitons & Fractals, ISSN 0960-0779, E-ISSN 1873-2887, Vol. 153, article id 111571Article in journal (Refereed)
    Abstract [en]

    In the present paper, we focus on the doubling of closed invariant curves associated with quasiperiodic dynamics. We consider a 5D map derived from a hybrid model originating from systems biology and containing a continuous part with time delay and pulse-modulated feedback. Using numerical bifurcation analysis, we show that doubling bifurcation takes place on a closed 2D invariant manifold. We explain how such a configuration of the phase space can be created and highlight the role of delay.

  • 1507. Zhusubaliyev, Zhanybai T.
    et al.
    Churilov, Alexander N.
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Bifurcation phenomena in an impulsive model of non-basal testosterone regulation2012In: Chaos, ISSN 1054-1500, E-ISSN 1089-7682, Vol. 22, no 1, p. 013121-Article in journal (Refereed)
    Abstract [en]

    Complex nonlinear dynamics in a recent mathematical model of non-basal testosterone regulation are investigated. In agreement with biological evidence, the pulsatile (non-basal) secretion of testosterone is modeled by frequency and amplitude modulated feedback. It is shown that, in addition to already known periodic motions with one and two pulses in the least period of a closed-loop system solution, cycles of higher periodicity and chaos are present in the model in hand. The broad range of exhibited dynamic behaviors makes the model highly promising in model-based signal processing of hormone data. 

  • 1508. Zhusubaliyev, Zhanybai T.
    et al.
    Churilov, Alexander N.
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Time Delay Induced Multistability and Complex Dynamics in an Impulsive Model of Endocrine Regulation2014In: 2014 European Control Conference (ECC), 2014, p. 2304-2309Conference paper (Refereed)
    Abstract [en]

    The effects caused by the introduction of a time delay in the continuous part of an impulsive (hybrid) model of endocrine feedback regulation are studied by bifurcation analysis. It is concluded that larger (in some well-defined sense) values of the time delay give rise to a broad range of nonlinear dynamics phenomena that have not been observed for the smaller ones. Among such behaviors are e.g. border-collision bifurcations, bistability, and quasiperiodic solutions. The reason for the more complex dynamics exhibited by the model in this case is a discontinuity of the Jacobian of a discrete mapping describing the propagation of the model dynamics from one firing of the impulsive feedback to another.

  • 1509. Zhusubaliyev, Zhanybai T.
    et al.
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Martins da Silva, Margarida
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Bifurcation analysis for PID-controller tuning based on a minimal neuromuscular blockade model in closed-loop anesthesia2013In: Proc. 52nd Conference on Decision and Control, Piscataway, NJ: IEEE , 2013, p. 115-120Conference paper (Refereed)
  • 1510. Zhusubaliyev, Zhanybai T.
    et al.
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Martins da Silva, Margarida
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Bifurcation analysis of PID-controlled neuromuscular blockade in closed-loop anesthesia2015In: Journal of Process Control, ISSN 0959-1524, E-ISSN 1873-2771, Vol. 25, p. 152-163Article in journal (Refereed)
  • 1511.
    Zhusubaliyev, Zhanybai T.
    et al.
    Southwest State Univ, Dept Comp Sci, Dynam Nonsmooth Syst Int Sci Lab, 50 Years October Str 94, Kursk 305040, Russia..
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control.
    Proskurnikov, Anton, V
    Politecn Torino, Dept Elect & Telecommun, Turin, Italy.;Russian Acad Sci, Inst Problems Mech Engn, St Petersburg, Russia..
    Impulsive Goodwin's Oscillator Model of Endocrine Regulation: Local Feedback Leads to Multistability2021In: 2021 7TH INTERNATIONAL CONFERENCE ON EVENT BASED CONTROL, COMMUNICATION, AND SIGNAL PROCESSING (EBCCSP), IEEE, 2021Conference paper (Refereed)
    Abstract [en]

    The impulsive Goodwin's oscillator (IGO) is a hybrid model that captures complex dynamics arising in continuous systems controlled by pulse-modulated (event-based) feedback. Being conceived to describe pulsatile endocrine regulation, it has also found applications in e.g. pharmacokinetics. The original version of the IGO assumes the continuous part of the model to be a chain of first-order blocks. This paper explores the nonlinear phenomena arising due to the introduction of a local continuous feedback as suggested by the endocrine applications. The effects caused by a nonlinear feedback law parameterized by a Hill function are compared to those arising due to a simpler and previously treated case of affine feedback law. The hybrid dynamics of the IGO are reduced to a (discrete) Poincare map governing the propagation of the model's continuous states through the firing instants of the impulsive feedback. Bifurcation analysis of the map reveals in particular that both the local Hill function and affine feedback can lead to multistability, which phenomenon has not been observed in the usual IGO model.

  • 1512. Zhusubaliyev, Zhanybai T.
    et al.
    Mosekilde, Erik
    Churilov, Alexander N.
    Medvedev, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Multistability and hidden attractors in an impulsive Goodwin oscillator with time delay2015In: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 224, no 8, p. 1519-1539Article in journal (Refereed)
    Abstract [en]

    The release of luteinizing hormone (LH) is driven by intermittent bursts of activity in the hypothalamic nerve centers of the brain. Luteinizing hormone again stimulates release of the male sex hormone testosterone (Te) and, via the circulating concentration of Te, the hypothalamic nerve centers are subject to a negative feedback regulation that is capable of modifying the intermittent bursts into more regular pulse trains. Bifurcation analysis of a hybrid model that attempts to integrate the intermittent bursting activity with a continuous hormone secretion has recently demonstrated a number of interesting nonlinear dynamic phenomena, including bistability and deterministic chaos. The present paper focuses on the additional complexity that arises when the time delay in the continuous part of the model exceeds the typical bursting interval of the feedback. Under these conditions, the hybrid model is capable of displaying quasiperiodicity and border collisions as well as multistability and hidden attractors.

  • 1513.
    Åberg, Anna Cristina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Elmgren Frykberg, Gunilla
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Rehabilitation Medicine.
    Halvorsen, Kjartan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Medio-lateral stability of sit-to-walk performance in older individuals with and without fear of falling2010In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 31, no 4, p. 438-443Article in journal (Refereed)
  • 1514.
    Åberg, Anna Cristina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Halvorsen, Kjartan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    From, Ingrid
    Dalarna Univ, Sch Educ Hlth & Social Studies, SE-79188 Falun, Sweden.
    Bergman Bruhn, Åsa
    Dalarna Univ, Sch Educ Hlth & Social Studies, SE-79188 Falun, Sweden.
    Oestreicher, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Visual Information and Interaction. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Melander-Wikman, Anita
    Lulea Univ Technol, Div Hlth & Rehab, Dept Hlth Sci, SE-97187 Lulea, Sweden.
    A study protocol for applying user participation and co-learning: Lessons learned from the eBalance project2017In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 14, no 5, article id 512Article in journal (Refereed)
    Abstract [en]

    The eBalance project is based on the idea that serious exergames-i.e., computer gaming systems with an interface that requires physical exertion to play-that are well adapted to users, can become a substantial part of a solution to recognized problems of insufficient engagement in fall-prevention exercise and the high levels of fall-related injuries among older people. This project is carried out as a collaboration between eight older people who have an interest in balance training and met the inclusion criteria of independence in personal activities of daily living, access to and basic knowledge of a computer, four staff working with the rehabilitation of older adults, and an interdisciplinary group of six research coordinators covering the areas of geriatric care and rehabilitation, as well as information technology and computer science. This paper describes the study protocol of the project's initial phase which aims to develop a working partnership with potential users of fall-prevention exergames, including its conceptual underpinnings. The qualitative methodology was inspired by an ethnographical approach implying combining methods that allowed the design to evolve through the study based on the participants' reflections. A participatory and appreciative action and reflection (PAAR) approach, accompanied by inquiries inspired by the Normalization Process Theory (NPT) was used in interactive workshops, including exergame testing, and between workshop activities. Data were collected through audio recordings, photos, and different types of written documentation. The findings provide a description of the methodology thus developed and applied. They display a methodology that can be useful for the design and development of care service and innovations for older persons where user participation is in focus.

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  • 1515.
    Åberg, Anna Cristina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Thorstensson, Alf
    Tarassova, Olga
    Halvorsen, Kjartan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Calculations of mechanisms for balance control during narrow and single-leg standing in fit older adults: a reliability study2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 3, p. 352-357Article in journal (Refereed)
  • 1516.
    Åhgren, P
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control. AUTOMATIC CONTROL.
    Stoica, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    A simple method for estimating the impulse responses of loudspeakers2003In: IEEE Trans Consumer Electronics, Vol. 49, p. 889-893Article in journal (Refereed)
  • 1517.
    Åhgren, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    On System Identification and Acoustic Echo Cancellation2004Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The topic of acoustic echo cancellation has received a lot of interest over the years. Even though the topic is relatively old, the increasing demand for hands-free telephony has made it more important than ever before. Furthermore, in recent years new applications such as Internet Protocol (IP) telephony and stereophonic hands-free telephony have emerged that also require acoustic echo cancellation in order to function properly.

    This thesis is partly about acoustic echo cancellation which has the purpose to remove the acoustic echoes from the loudspeaker sound signals picked up by the microphones in hands-free telephony systems. If the attenuation of the echoes is small, as it is in a hands-free telephony setup, good acoustic echo cancellation is required for the setup to work well. Several methods are presented in this thesis, addressing various acoustic echo cancellation areas such as doubletalk detection, stereophonic acoustic echo cancellation and ordinary acoustic echo cancellation. While some of the results are basically extensions of existing acoustic echo cancellation algorithms, others are more innovative in the sense that they offer solutions to previously unsolved problems or outperform by far existing algorithms.

    The second part of this thesis is about system identification which is also a relatively old, but still very active topic. System identification deals with the problem of building mathematical models of dynamic systems and its applications are manifold. One particular area where system identification is needed is the aforementioned acoustic echo cancellation application, where models of the acoustic paths between the loudspeakers and the microphones need to be determined. This thesis presents some explanations and additions to two well-known system identification algorithms. Furthermore, it provides new solutions to two previously unsolved system identification problems.

  • 1518.
    Åhgren, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Teleconferencing, system identification and array processing2001Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The area of teleconferencing has long yielded great interest in the signal processing community. The main reasons for this are probably the huge interest from the industry and the challenging problems of the topic. The problems of teleconferencing are relevant for several different disciplines in signal processing. Three of these are Acoustic Echo Cancellation, System Identification and Sensor Array Signal Processing. In this thesis some problems related to these disciplines are studied. The thesis is divided into 6 parts, one for each paper included.

    In the first part a new adaptive algorithm is applied to the acoustic echo cancellation problem. It is shown to perform much better than the Normalized Least Mean Squares (NLMS) algorithm and while it performs worse than the standard Recursive Least Squares (RLS) algorithm it is shown to be computationally simpler than this.

    In the second part the hierarchical RLS algorithm is analyzed. The extraordinary results presented for this algorithm in previous papers are discussed and explained.

    In the third part a new initialization method for RLS is presented that yields the exact Least Squares estimates while not being computationally more demanding than RLS. This is an important contribution since the standard initialization of the RLS algorithm is somewhat arbitrary.

    In the fourth part a method is presented that deals with the problem of estimating the common factors out of an arbitrary number of polynomials. Two problems of array processing and system identification are stated as problems for common factor estimation and the presented method is applied to these. For these two problems the method is shown to perform better than existing methods.

    In the fifth part a method for beamforming using few sensors is presented. Data-dependent beamformers usually perform badly when there are few sensors in the array, particularly when the beamformer constraints are numerous. The method presented deals with this problem by approximately fulfilling the beamformer constraints and hence getting extra degrees of freedom for suppressing interferences.

    In the sixth part the previously unsolved problem of array processing of non-zero mean signals is solved for the colored noise case. Methods are presented both for the estimation problem and the detection problem and are shown to perform well in numerical examples.

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  • 1519.
    Åmand, Linda
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Ammonium Feedback Control in Wastewater Treatment Plants2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The aeration process is often the single largest consumer of electricity in a wastewater treatment plant. Aeration in biological reactors provides microorganisms with oxygen which is required to convert ammonium to nitrate. Ammonium is toxic for aqueous ecosystems and contributes to eutrophication. The importance of aeration for the treatment results in combination with the high costs motivates automatic control of the aeration process.

    This thesis is devoted to ammonium feedback control in municipal wastewater treatment plants. With ammonium feedback control, the aeration intensity is changed based on a measurement of the outlet ammonium concentration. The main focus of the thesis is design, implementation, evaluation and improvement of ammonium PI (proportional-integral) controllers.

    The benefits of ammonium feedback control are established through long-term experiments at three large wastewater treatment plants in Stockholm, Sweden. With ammonium feedback control, energy savings up to around 10 % were achieved compared to keeping the dissolved oxygen concentration constant. The experiments generated several lessons learned with regard to implementation and evaluation of controllers in full-scale operation.

    The thesis has established guidelines on how to design ammonium feedback controllers for situations when cost-effective operation is the overall aim. Simulations have demonstrated the importance to limit the dissolved oxygen concentration in the process and under what conditions the energy saving with ammonium feedback control is large.

    The final part of the thesis treats improvements of ammonium PI control through minor modifications to the control structure or controller. Three strategies were studied: gain scheduling control, repetitive control, and a strategy reacting to oxygen peaks in the last aerobic zone. The strategies all had their benefits but the ammonium feedback controller was the key factor to improved aeration control.

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  • 1520.
    Åmand, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    A regional Swedish consortium for research and education: Demand-driven research within wastewater and sludge management2010In: Proc. 2nd IWA Water and Energy Conference, International Water Association , 2010, p. 100-101Conference paper (Refereed)
  • 1521.
    Åmand, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Energy efficient ammonium feedback control2012In: New Developments in IT & Water, 2012Conference paper (Refereed)
    Abstract [en]

    Ammonium feedback control is increasingly used to determine the dissolved oxygen set-point in aerated activated sludge processes. This study compare ammonium feedback control with different controller settings to constant dissolved oxygen control and a dissolved oxygen profile created by minimising the air flow rate. All simulated scenarios are set to reach the same treatment level of ammonium, based on a daily flow proportional average concentration. The influent included daily variations only, and comparisons are performed at different plant loads. The results suggest that ammonium feedback control can achieve close to optimal performance if a near proportional controller based on the in-situ ammonium concentration is used. Compared to constant oxygen concentration the best performing ammonium controller can achieve a 2.5 – 3.5 % savings in the air flow rate, while the optimal solution can achieve a 3 – 4 % saving.

  • 1522.
    Åmand, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Learning control applied to continuous wastewater treatment systems: an initial study2010In: Proc. 2nd IWA Water and Energy Conference, International Water Association , 2010, p. 98-99Conference paper (Refereed)
  • 1523.
    Åmand, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Optimal aeration control in a nitrifying activated sludge process2012In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 46, no 7, p. 2101-2110Article in journal (Refereed)
  • 1524. Åmand, Linda
    et al.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    The optimal dissolved oxygen profile in a nitrifying activated sludge process: comparisons with ammonium feedback control2013In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 68, no 3, p. 641-649Article in journal (Refereed)
    Abstract [en]

    Ammonium feedback control is increasingly used to determine the dissolved oxygen (DO) set-point in aerated activated sludge processes for nitrogen removal. This study compares proportional-integral (PI) ammonium feedback control with a DO profile created from a mathematical minimisation of the daily air flow rate. All simulated scenarios are set to reach the same treatment level of ammonium, based on a daily average concentration. The influent includes daily variations only and the model has three aerated zones. Comparisons are made at different plant loads and DO concentrations, and the placement of the ammonium sensor is investigated. The results show that ammonium PI control can achieve the best performance if the DO set-point is limited at a maximum value and with little integral action in the controller. Compared with constant DO control the best-performing ammonium controller can achieve 1-3.5% savings in the air flow rate, while the optimal solution can achieve a 3-7% saving. Energy savings are larger when operating at higher DO concentrations.

  • 1525.
    Åmand, Linda
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Laurell, C.
    Stark-Fujii, K.
    Thunberg, A.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Lessons learnt from evaluating full-scale ammonium feedback control in three large wastewater treatment plants2014In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 69, no 7, p. 1573-1580Article in journal (Refereed)
    Abstract [en]

    Three large wastewater treatment plants in Sweden participate in a project evaluating different types of ammonium feedback controllers in full-scale operation. The goal is to improve process monitoring, maintain effluent water quality and save energy. The paper presents the outcome of the long-term evaluation of controllers. Based on the experiences gained from the full-scale implementations, a discussion is provided about energy assessment for the purpose of comparing control strategies. The most important conclusions are the importance of long-term experiments and the difficulty of comparing energy consumption based on air flow rate measurements.

  • 1526. Åmand, Linda
    et al.
    Nygren, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Applications of repetitive control in activated sludge processes2011Conference paper (Other academic)
  • 1527. Åmand, Linda
    et al.
    Olsson, Gustaf
    Carlsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Aeration control: a review2013In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 67, no 11, p. 2374-2398Article, review/survey (Refereed)
    Abstract [en]

    This review covers automatic control of continuous aeration systems in municipal wastewater treatment plants. The review focuses on published research in the 21st century and describes research into various methods to decide and control the dissolved oxygen (DO) concentration and to control the aerobic volume with special focus on plants with nitrogen removal. Important aspects of control system implementation and success are discussed, together with a critical review of published research on the topic. With respect to DO control and determination, the strategies used for control span from modifications and developments of conventional control methods which have been explored since the 1970s, to advanced control such as model-based predictive and optimal controllers. The review is supplemented with a summary of comparisons between control strategies evaluated in full-scale, pilot-scale and in simulations.

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  • 1528.
    Önell, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control. AUTOMATIC CONTROL.
    Söderström, T
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control. AUTOMATIC CONTROL.
    Halvorsen, K
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control. AUTOMATIC CONTROL.
    Lanshammar, H
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Automatic control. AUTOMATIC CONTROL.
    Identifiering av människokroppens balanssystem2000In: Reglermöte 2000 (National Conference on Control), 2000Conference paper (Refereed)
  • 1529.
    Önell, Annica
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Quantifying human balance: Analysis of force plate data1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is a lack of reliable methods for assessment of balance suited for routine use in clinical settings. The thesis focuses on analysis of force plate data for evaluation of balance during normal, unperturbed standing and sitting. Some commonly used force plate based methods during unperturbed standing are presented.

    Traditional measures, which have been used to quantify the postural sway during standing, were applied to seated children with and without spina bifida. Fundamental differences, that can not be observed visually, were found between the groups. However, the reliability on an individual level was limited since the method could not be used to distinguish between subjects from the two groups.

    It is not only of interest to measure how much the subject sways, but also what movement strategy the subject uses, that is, how he or she sways. A method for analysis of the movement strategy in the sagittal plane during standing is presented and tested. The subject's movements are compared to the movements of an inverted pendulum model. For movement analysis a kinematic measurement system is usually required, while the inverted pendulum method only needs force plate data for the analysis.

    To investigate the relationship between different force plate measures the measures were a) compared to each other and b) compared to a clinical balance test. Results on stroke patients showed that many of the measures quantify different aspects of standing. The standard deviation of the vertical ground reaction force was the only measure that was significantly correlated to the clinical balance test. Measurements on healthy adults and three groups of subjects with reduced or not fully developed balance were analysed to investigate the vertical force further. The healthy adults damped the vertical bodyoscillations caused by the heartbeats more efficiently than the other three groups.

    Finally, it was investigated under what conditions system identification can be used to model the balance system. In contrast to previous studies the model parameters were successfully estimated without any external perturbations and without a kinematic measurement system.

  • 1530.
    Özkan, Emre
    et al.
    Middle East Tech Univ, Dept Elect & Elect Engn, Ankara, Turkey.
    Wahlström, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Godsill, Simon J.
    Univ Cambridge, Dept Engn, Cambridge CB2 1TN, England.
    Rao-Blackwellised Particle Filter for Star-ConvexExtended Target Tracking Models2016In: 2016 19th International Conference on Information Fusion, 2016, p. 1193-1199Conference paper (Refereed)
    Abstract [en]

    In this paper, we explore the potential gains in using Sequential Monte Carlo (SMC) methods for extended target tracking (ETT) models based on Gaussian processes (GP). The existing random hypersurface based ETT models use Extended/Unscented Kalman filter for inference, which may lead to poor performance under high uncertainty. Particle filters (PFs) are known to provide robust performance in the cases where the non-linear Kalman filtering solutions fail. We design a Rao-Blackwellised particle filter (RBPF) where we exploit the conditional linear Gaussian structure of the GP parameters. We illustrate the gain in the performance with simulations.

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