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  • Presentation: 2018-08-31 13:15 Ada Lovelace, B-huset, Linköping
    Lindfors, Martin
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Frequency Tracking for Speed Estimation2018Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Estimating the frequency of a periodic signal, or tracking the time-varying frequency of an almost periodic signal, is an important problem that is well studied in literature. This thesis focuses on two subproblems where contributions can be made to the existing theory: frequency tracking methods and measurements containing outliers.

    Maximum-likelihood-based frequency estimation methods are studied, focusing on methods which can handle outliers in the measurements. Katkovnik’s frequency estimation method is generalized to real and harmonic signals, and a new method based on expectation-maximization is proposed. The methods are compared in a simulation study in which the measurements contain outliers. The proposed methods are compared with the standard periodogram method.

    Recursive Bayesian methods for frequency tracking are studied, focusing on the Rao-Blackwellized point mass filter (RBPMF). Two reformulations of the RBPMF aiming to reduce computational costs are proposed. Furthermore, the technique of variational approximate Rao-Blackwellization is proposed, which allows usage of a Student’s t distributed measurement noise model. This enables recursive frequency tracking methods to handle outliers using heavy-tailed noise models in Rao-Blackwellized filters such as the RBPMF. A simulation study illustrates the performance of the methods when outliers occur in the measurement noise.

    The framework above is applied to and studied in detail in two applications. The first application is on frequency tracking of engine sound. Microphone measurements are used to track the frequency of Doppler-shifted variants of the engine sound of a vehicle moving through an area. These estimates can be used to compute the speed of the vehicle. Periodogram-based methods and the RBPMF are evaluated on simulated and experimental data. The results indicate that the RBPMF has lower rmse than periodogram-based methods when tracking fast changes in the frequency.

    The second application relates to frequency tracking of wheel vibrations, where a car has been equipped with an accelerometer. The accelerometer measurements are used to track the frequency of the wheel axle vibrations, which relates to the wheel rotational speed. The velocity of the vehicle can then be estimated without any other sensors and without requiring integration of the accelerometer measurements. In situations with high signal-to-noise ratio (SNR), the methods perform well. To remedy situations when the methods perform poorly, an accelerometer input is introduced to the formulation. This input is used to predict changes in the frequency for short time intervals.  

  • Presentation: 2018-09-05 09:30 K3, Kåkenhus, Norrköping
    Sernheim, Åsa-Sara
    Linköping University, Department of Social and Welfare Studies, Division of Occupational Therapy.
    Time for Activities for Girls and Women with Rett Syndrome2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Irrespective of the great individual variation, people diagnosed with RTT largely rely on support from others to be able to do and participate in activities throughout their lives. This thesis focuses on which activities are done and liked/disliked by girls and women with RTT in Sweden. The overall aim was to describe the everyday lives of female individuals with Rett syndrome.

    Two studies are included in this thesis. The first is a descriptive study, using secondary data from three earlier questionnaires, encompassing data from 175 participants (girls/women) described by 365 informants (parents/staff). Content analysis was used to analyse the openended questions. In the second study a Time-geographic diary method and the software VISUAL-TimePAcTs computer program, DAILY LIFE 2011 were used. Ten participants (teenagers/young female adults) with RTT and their 63 informants participated in the diary study.

    The main findings in the first study (I) were that the girls and women with RTT enjoyed activities that included aspects of ‘contact’, ‘sensory impression’ and ‘motion’. The activities most enjoyed over the years were bathing/swimming, listening to music or being outdoors/walking. The parents and staff also liked to do the same activities that the girls or women enjoyed doing, described as sharing their joy. Of the few activities that were reported as being unenjoyable, most were daily care activities.

    The diary study (II) showed that the most frequently reported activities were hygiene/toilet, moving around indoors, eating and getting dressed. Most time was spent in sleeping, daily care, medical and health care activities and also for travel/transportation. Little time remained for other kinds of activities especially for the young adults. Most time was spent with staff, thereafter with families, and the least time was spent with friends. The participant response that was reported most often during activities was ‘interested’, while ‘opposed’ was the least reported. Responses of ‘opposition’ were primarily seen during caring activities such as toileting, using the breathing mask, stretching, brushing teeth, being woken up, dressing and putting on orthoses. Responses of ‘engagement’ were noted in contexts of socialising, playing and communicating activities with friends or staff. Engagement responses were also reported during activities of ‘motion’ such as changing body position, moving in the water or gymnastics, eating food and snacks, and even when watching/listening to films, books or music.

    Thus, increased knowledge concerning the importance of activities for girls and women with RTT is essential for their well-being, participation and continued development. Increased knowledge could facilitate the choice of activities and a more varied use of activities. Regardless of age, severity of symptoms or developed skills, it is important that not only basic needs such as sleep, daily care and medical health care activities are fulfilled for individuals with Rett syndrome. It is also essential for them to spend time with friends, family and staff doing enjoyable activities both at home and in other places. 

    List of papers
    1. Activities that girls and women with Rett syndrome liked or did ot like to do
    Open this publication in new window or tab >>Activities that girls and women with Rett syndrome liked or did ot like to do
    2018 (English)In: Scandinavian Journal of Occupational Therapy, ISSN 1103-8128, E-ISSN 1651-2014, Vol. 25, no 4, p. 267-277Article in journal (Refereed) Published
    Abstract [en]

    Objective: Activities occur in all people’s lives. This study investigated over a period of time, 15 years, what activities were enjoyed or not enjoyed and what activities parents and staff liked to do with girls/women with Rett syndrome.

    Method: A descriptive study was conducted using secondary data from three earlier questionnaires at the Swedish National Rett Center. The first questionnaire provided data on 123 girls/women with Rett syndrome, the second on 52 and the third questionnaire, on 39. Informants were parents and/or staff, in total 365. Open-ended questions were analysed using a content analysis approach.

    Results: Three categories appeared: Being in motion, receiving impressions and having contact. Bathing/swimming, listening to music and being outdoors/walking were the most enjoyed activities over the years. Of the few activities that were reported as being unenjoyable, most were daily care activities. The activities that the parents/staff enjoyed doing with the girls/women were similar to those the girls/women themselves liked to do.

    Conclusion: A preliminary overview for both liked and disliked activities of girls/women with Rett syndrome was presented. This knowledge could facilitate the choice and use of activities.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2018
    Activities of daily living, human activities, human development, neurodevelopmental disorders, qualitative research
    National Category
    Health Sciences
    urn:nbn:se:liu:diva-136247 (URN)10.1080/11038128.2016.1250812 (DOI)000436878200005 ()27817243 (PubMedID)2-s2.0-84994304785 (Scopus ID)
    Available from: 2017-04-03 Created: 2017-04-03 Last updated: 2018-07-26Bibliographically approved