State Estimation for Distributed and Hybrid Systems

This thesis deals with two aspects of recursive state estimation: distributed estimation and estimation for hybrid systems. In the first part, an approximate distributed Kalman filter is developed. Nodes update their state estimates by linearly combining local measurements and estimates from their neighbors. This scheme allows nodes to save energy, thus prolonging their lifetime, compared to centralized information processing. The algorithm is evaluated experimentally as part of an ultrasound based positioning system. The first part also contains an example of a sensor-actuator network, where a mobile robot navigates using both local sensors and information from a sensor network. This system was implemented using a component-based framework. The second part develops, a recursive joint maximum a posteriori state estimation scheme for Markov jump linear systems. The estimation problem is reformulated as dynamic programming and then approximated using so called relaxed dynamic programming. This allows the otherwise exponential complexity to be kept at manageable levels. Approximate dynamic programming is also used to develop a sensor scheduling algorithm for linear systems. The algorithm produces an offline schedule that when used together with a Kalman filter minimizes the estimation error covariance

Automatic Gain Control in High speed WCDMA Terminals

In this study, it is investigated how different parameters influence 16QAM modulation. The focus is on how different parameters in the Automatic Gain Control algorithm influence raw bit error rates, but other parameters such as frequency error and misplaced decision levels are also investigated. The goal is not to develop optimal parameter configurations, but to gain some understanding on what parameters that are of great importance. The simulations are made with several types of fading multi path channels as well as Additive White Gaussian Noise (AWGN) channels. The investigations are carried out through simulations in a simulation environment implemented in Matlab. From the simulations the conclusion is drawn that 16QAM is more sensitive to frequency errors than QPSK and that an important parameter in the AGC is the DC blocker bandwidths. The optimal AGC design with repsect to bit error rate depends on the type of channel model used, but it seems that a slower AGC design is preferred when compared to a faster one. The step resonse simulations indicate that there is no problem with using a fast AGC. The AGC seems to be more important at high signal to noise ratios because the fading become more visible in that case

Sub-optimal sensor scheduling with error bounds

Abstract: In this paper the problem of sub-optimal sensor scheduling with a guaranteed distance to optimality is considered. Optimal in the sense that the sequence that minimizes the estimation error covariance matrix for a given time horizon is found. The search is done using relaxed dynamic programming. The algorithm is then applied to one simple second order system and one sixth order model of a fixed mounted model lab helicopter. Copyright c○2005 IFA

Optimal On-Line Scheduling of Multiple Control Tasks: A Case Study

We study the problem of dynamically scheduling a set of state-feedback control tasks controlling a set of linear plants. We consider an on-line non-preemptive scheduling policy that is optimal in the sense that it minimizes a quadratic performance criterion for the overall system. The optimal scheduling decision at each point in time is a function of the states of the controlled plants. To be able to solve the scheduling problem for realistic examples, we use the technique of relaxed dynamic programming to compute suboptimal solutions with error bounds. The approach is compared to earlier approaches in a case study involving simultaneous control of one ball-and-beam process and two DC-servo processes. We also show how the scheduling policy can be modified to allow for background tasks to execute when the need for control is small. 1

Model Based Information Fusion in Sensor Networks

In this paper, a model based sensor fusion algorithm for sensor networks is presented. The algorithm, referred to as distributed Kalman filtering is based on a previously presented algorithm with the same name. The weight selection process has been improved yielding performance improvements of several times for the examples studied. Also, solutions to both optimization problems involved in the iterative off-line weight selection process are given as closed form expressions. The algorithm is also demonstrated on a typical signal tracking application

Distributed Kalman Filtering Using Weighted Averaging

This paper addresses the problem of distributed Kalman filtering, with focus on limiting the required communication bandwidth. By distributed we refer to a scenario when all nodes in the network desire an estimate of the full state of the observed system and there is no centralized computation center. Communication only takes place between neighbors and only a fixed number of times each sample. To reduce bandwidth requirements of individual nodes, estimates instead of measurements are communicated. A new estimate is then formed as a weighted average of the neighbouring estimates. The weights are optimized to yield a small estimation error covariance in stationarity. The minimization can be done off line thus allowing only estimates to be communicated. The advantage of communicating estimates instead of measurements becomes more evident when the number of nodes exceeds the size of the state vector to be estimated. The algorithm is applied to one simple second order system and temperature sensing network

Automatic Gain Control In WCDMA Terminals

This article gives a presentation of the Automatic Gain Control algorithm used in WCDMA (3rd generation mobile networks). The focus is on how the controller bandwidth influences settling times and modulation distortion. This will be investigated through simulation for two different channel cases

Hästen, den bästa terapeuten? En kvalitativ studie om hästens betydelse för socialt arbete

The aim of this study was to examine businesses which use horses in various kinds of social work, and the opinions and experiences of the professional practitioners of these operations. I used semistructured interview to answer my questions, and I ended up interviewing eight people from seven different operations. Everyone was working in some kind of business which used horses as either an aid for the social work, or as a leisure activity for their clients. The clients had difficulties such as mental illness or some kind of disability. I found that my interviewees had experienced various forms of positive effects when their clients spent time with the animal. The professional practioners could see that their clients's motivation, trust and awareness had approved after spending time with the horse, and clients with psysical disabilties also gained from horsebackridning. But I also found that it is a theme which need more research and structure, and it needs people that's willing to fight for the cause

Prevalence and treatment of hip displacement in children with cerebral palsy in Finland

Purpose: The aim was to study the prevalence of hip displacements, dislocations, and the hip surgeries performed in a Finnish cohort of children with cerebral palsy not followed up in a hip surveillance program and to compare these with previous studies performed in Northern European countries before and after the implementation of hip surveillance programs. Methods: A cross-sectional study. A cohort including 480 children with cerebral palsy, born during the period 2000-2018, not enrolled in a hip surveillance program. Migration percentages were recorded from hip radiographs, age at first hip surgery and type of surgery was extracted from medical records. In a separate analysis, the inclusion criteria were adapted to fit two studies analyzing hip dislocation and hip surgery in Sweden, Norway, and Scotland before and after the implementation of a hip surveillance program. Chi-square tests were used to assess differences in proportions between the groups. Results: In total, 286 children (60%) have had at least one hip radiograph. Of these, 10 (3.5%) developed hip dislocation, which is more than in children of countries with hip surveillance programs (Sweden 0.7%, Scotland 1.3%, p < 0.001). Initial surgery to prevent hip dislocation was performed at an older age (p < 0.001). Conclusion: Children with cerebral palsy in Finland not participating in a surveillance hip program were more likely to undergo hip surgery at an older age and to develop hip displacements and dislocations. The results support the effectiveness of surveillance programs to prevent hip dislocation in children with cerebral palsy.Peer reviewe

Ökad tillämpning av ledningssystem i projekt

Att skapa en förståelse för hur företags ledningssystem kan tillämpas i verksamheten. Studien ska även finna en lösning för hur ledningssystem kan presenteras i ett webbaserat projektstyrningsverktyg för att skapa mervärde för användarna