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  • 301.
    Blom, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Method and System for Quality-Based Power Control in Cellular Communications Systems2002Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    A method and system for quality-based transmission power control in a cellular communications system (100) are disclosed, whereby a network operator can specify the transmission quality requirements using a measurement that better reflects the actual quality perceived by the users. All transmitter power levels in the network can be controlled by identical power regulators (200), each of which can adapt to individual traffic situations in order to achieve the specified quality. For example, in a GSM frequency-hopping network, the FER together with the parameters estimated from the current traffic situation (54), are mapped onto a target C/I (56), which in turn, the power control algorithm strives (16) to achieve (58, 60). Consequently, the power regulators can adapt to the traffic situation experienced by each receiver.

  • 302.
    Blom, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Pole Placement Design of Power Control Algorithms1999Inngår i: Proceedings of the 49th IEEE Vehicular Technology Conference, 1999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Time delays reduces the performance of any controlled system. If neglected in the design phase, the system may even become unstable when using the designed controller. Several power control strategies have been proposed in order to improve the capacity of cellular radio systems, but time delays are usually neglected. Here, it is shown that the problems can be handled by considering the time delays in the design phase in order to choose the appropriate parameter values. Most popular algorithms can be seen as special cases of an integrating controller. This structure is extended first to a proportional integrating (PI)-controller and then further on to a general linear controller of higher orders. Corresponding design procedures are outlined based on techniques, such as pole placement, from the field of automatic control. The PI-controller is a very appealing choice of structure, with better performance compared to an I-controller and less complex than a higher order controller. The benefits are further illuminated by network simulations.

  • 303.
    Blomberg, Magnus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    High Bandwidth Control of a Small Aerial Vehicle2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Small aerial vehicles such as quad-rotors have been widely used commercially, for research and for hobby for the last decade with use still growing. The high interest is mainly due to the vehicles being small, simple, cheap and versatile.

    Among rigid body dynamics fast dynamics exist cohering to motors and other fast actuators. A linear quadratic control design technique is here investigated. The design technique suggests that the linear quadratic controller can be designed with penalties on the slow states only. The fast dynamics are modeled but the states are not penalised in the linear quadratic design. The design technique is here applied and evaluated. The results show that this in several cases is a suitable design technique for linear quadratic control design.

    MATLAB and Simulink have been widely used for design and implementation of control systems. With additional toolboxes these control systems can be compiled to and run on remote computers. Small, lightweight computers with high computational capacity are now easily accessible. In this thesis an avionics solution based on a small, powerful computer is presented. Simulink models can be compiled and transferred to the computer from the Simulink environment. The result is a user friendly way of rapid prototyping and evaluation of control systems.

    Fulltekst (pdf)
    High Bandwidth Control of a Small Aerial Vehicle
  • 304.
    Bochkov, Alexander
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Frequency Domain Properties of Regression Dynamical Models and Optimal Input Design for Estimation of Frequency Functions1984Rapport (Annet vitenskapelig)
  • 305.
    Bodesund, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Pose estimation of a VTOL UAV using IMU, Camera and GPS2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    When an autonomous vehicle has a mission to perform, it is of high importance that the robot has good knowledge about its position. Without good knowledge of the position, it will not be able to navigate properly and the data that it gathers, which could be of importance for the mission, might not be usable. A helicopter could for example be used to collect laser data from the terrain beneath it, which could be used to produce a 3D map of the terrain. If the knowledge about the position and orientation of the helicopter is poor then the collected laser data will be useless since it is unknown what the laser actually measures.

    A successful solution to position and orientation (pose) estimation of an autonomous helicopter, using an inertial measurement unit (IMU), a camera and a GPS, is proposed in this thesis. The problem is to estimate the unknown pose using sensors that measure different physical attributes and give readings containing noise.

    An extended Kalman filter solution to the simultaneous localisation and mapping (SLAM) is used to fuse data from the different sensors and estimate the pose of the robot.

    The scale invariant feature transform (SIFT) is used for feature extraction and the unified inverse depth parametrisation (UIDP) model is used to parametrise the landmarks. The orientation of the robot is described by quaternions.

    To be able to evaluate the performance of the filter an ABB industrial robot has been used as reference. The pose of the end tool of the robot is known with high accuracy and gives a good ground truth so that the estimations can be evaluated. The results shows that the algorithm performs well and that the pose is estimated with good accuracy.

    Fulltekst (pdf)
    FULLTEXT02
  • 306.
    Bodin, Camilla
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Automatic Flight Maneuver Identification Using Machine Learning Methods2020Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis proposes a general approach to solve the offline flight-maneuver identification problem using machine learning methods. The purpose of the study was to provide means for the aircraft professionals at the flight test and verification department of Saab Aeronautics to automate the procedure of analyzing flight test data.

    The suggested approach succeeded in generating binary classifiers and multiclass classifiers that identified six flight maneuvers of different complexity from real flight test data. The binary classifiers solved the problem of identifying one maneuver from flight test data at a time, while the multiclass classifiers solved the problem of identifying several maneuvers from flight test data simultaneously.

    To achieve these results, the difficulties that this time series classification problem entailed were simplified by using different strategies. One strategy was to develop a maneuver extraction algorithm that used handcrafted rules. Another strategy was to represent the time series data by statistical measures. There was also an issue of an imbalanced dataset, where one class far outweighed others in number of samples. This was solved by using a modified oversampling method on the dataset that was used for training.

    Logistic Regression, Support Vector Machines with both linear and nonlinear kernels, and Artifical Neural Networks were explored, where the hyperparameters for each machine learning algorithm were chosen during model estimation by 4-fold cross-validation and solving an optimization problem based on important performance metrics. A feature selection algorithm was also used during model estimation to evaluate how the performance changes depending on how many features were used. The machine learning models were then evaluated on test data consisting of 24 flight tests. The results given by the test data set showed that the simplifications done were reasonable, but the maneuver extraction algorithm could sometimes fail. Some maneuvers were easier to identify than others and the linear machine learning models resulted in a poor fit to the more complex classes.

    In conclusion, both binary classifiers and multiclass classifiers could be used to solve the flight maneuver identification problem, and solving a hyperparameter optimization problem boosted the performance of the finalized models. Nonlinear classifiers performed the best on average across all explored maneuvers.

    Fulltekst (pdf)
    fulltext
  • 307.
    Bodin, Erik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Davidsson, Henric
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Model-Based Design of a Fork Control System in Very Narrow Aisle Forklifts2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis explains the model-based design of a fork control system in a turret head operated Very Narrow Aisle forklift in order to evaluate and push the limits of the current hardware architecture. The turret head movement consists of two separate motions, traversing and rotation, which both are hydraulically actuated.

    The plant is thoroughly modeled in the Mathworks softwares Simulink/Simscape to assist in the design of the control system. The control system is designed in Simulink/Stateflow and code-generated to be evaluated in the actual forklift.

    Optimal control theory is used to generate a minimum-jerk trajectory for auto-rotation, that is simultaneous traversing and rotation with the load kept in centre.

    The new control system is able to control the system within the positioning requirements of +/- 10 mm and +/- 9 mrad for traversing and rotation, respectively. It also shows good overall performance in terms of robustness since it has been tested and validated with different loads and on different versions of the forklift. However, the study also shows that the non-linearities of the system, especially in the hydraulic proportional valves, causes problems in a closed-loop control system.

    The work serves as a proof of concept for model-based development at the company since the development time of the new control system was significantly lower than for the original control system.

    Fulltekst (pdf)
    fulltext
  • 308.
    Boers, Yvo
    et al.
    THALES, The Netherlands.
    Driessen, Hans
    THALES, The Netherlands.
    Karlsson, Rickard
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Torstensson, Johan
    Linköpings universitet.
    Trieb, Mikael
    Linköpings universitet.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Track Before Detect Algorithm for Tracking Extended Targets2006Inngår i: IEE Proceedings - Radar Sonar and Navigation, ISSN 1350-2395, E-ISSN 1359-7086, Vol. 153, nr 4, s. 345-351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For certain types of sensor-target configurations, a point target model or approach is not suitable and the physical extent of the target is accounted for during processing. An extended target track-before-detect (TBD) algorithm is presented and the performance is compared to an algorithm based on the point target assumption. Simulations illustrate the gain in performance obtained by using the extended target model where a particle filter is used for the TBD implementation.

  • 309.
    Boers, Yvo
    et al.
    THALES, The Netherlands.
    Driessen, Hans
    THALES, The Netherlands.
    Torstensson, Johan
    Linköpings universitet.
    Trieb, Mikael
    Linköpings universitet.
    Karlsson, Rickard
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Track Before Detect Algorithm for Tracking Extended Targets2005Rapport (Annet vitenskapelig)
    Abstract [en]

    For certain types of sensor-target configurations, a point target model or approach is not suitable and the physical extent of the target is accounted for during processing. An extended target track-before-detect (TBD) algorithm is presented and the performance is compared to an algorithm based on the point target assumption. Simulations illustrate the gain in performance obtained by using the extended target model where a particle filter is used for the TBD implementation.

    Fulltekst (pdf)
    FULLTEXT01
  • 310.
    Borg, Markus
    et al.
    RISE SICS AB, Sweden.
    Olsson, Thomas
    RISE SICS AB, Sweden.
    Svensson, John
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Piggybacking on an Autonomous Hauler: Business Models Enabling a System-of-Systems Approach to Mapping an Underground Mine2017Inngår i: 2017 IEEE 25TH INTERNATIONAL REQUIREMENTS ENGINEERING CONFERENCE (RE), IEEE , 2017, s. 372-381Konferansepaper (Fagfellevurdert)
    Abstract [en]

    With ever-increasing productivity targets in mining operations, there is a growing interest in mining automation. In future mines, remote controlled and autonomous haulers will operate underground guided by LiDAR (Light Detection And Ranging) sensors. We envision reusing LiDAR measurements to maintain accurate mine maps that would contribute to both safety and productivity. Extrapolating from a pilot project on reliable wireless communication in Bolidens Kankberg mine, we propose establishing a System-of-Systems (SoS) with LiDAR-equipped haulers and existing mapping solutions as constituent systems. SoS requirements engineering inevitably adds a political layer, as independent actors are stakeholders both on the system and SoS levels. We present four SoS scenarios representing different business models, discussing how development and operations could be distributed among Boliden and external stakeholders, e.g., the vehicle suppliers, the hauling company, and the developers of the mapping software. Based on eight key variation points, we compare the four scenarios from both technical and business perspectives. Finally, we validate our findings in a seminar with participants from the relevant stakeholders. We conclude that to determine which scenario is the most promising for Boliden, trade-offs regarding control, costs, risks, and innovation must be carefully evaluated.

  • 311. Bestill onlineKjøp publikasjonen >>
    Boström-Rost, Per
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    On Informative Path Planning for Tracking and Surveillance2019Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis studies a class of sensor management problems called informative path planning (IPP). Sensor management refers to the problem of optimizing control inputs for sensor systems in dynamic environments in order to achieve operational objectives. The problems are commonly formulated as stochastic optimal control problems, where to objective is to maximize the information gained from future measurements. In IPP, the control inputs affect the movement of the sensor platforms, and the goal is to compute trajectories from where the sensors can obtain measurements that maximize the estimation performance. The core challenge lies in making decisions based on the predicted utility of future measurements.

    In linear Gaussian settings, the estimation performance is independent of the actual measurements. This means that IPP becomes a deterministic optimal control problem, for which standard numerical optimization techniques can be applied. This is exploited in the first part of this thesis. A surveillance application is considered, where a mobile sensor is gathering information about features of interest while avoiding being tracked by an adversarial observer. The problem is formulated as an optimization problem that allows for a trade-off between informativeness and stealth. We formulate a theorem that makes it possible to reformulate a class of nonconvex optimization problems with matrix-valued variables as convex optimization problems. This theorem is then used to prove that the seemingly intractable IPP problem can be solved to global optimality using off-the-shelf optimization tools.

    The second part of this thesis considers tracking of a maneuvering target using a mobile sensor with limited field of view. The problem is formulated as an IPP problem, where the goal is to generate a sensor trajectory that maximizes the expected tracking performance, captured by a measure of the covariance matrix of the target state estimate. When the measurements are nonlinear functions of the target state, the tracking performance depends on the actual measurements, which depend on the target’s trajectory. Since these are unavailable in the planning stage, the problem becomes a stochastic optimal control problem. An approximation of the problem based on deterministic sampling of the distribution of the predicted target trajectory is proposed. It is demonstrated in a simulation study that the proposed method significantly increases the tracking performance compared to a conventional approach that neglects the uncertainty in the future target trajectory.

    Fulltekst (pdf)
    fulltext
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    presentationsbild
  • 312.
    Boström-Rost, Per
    et al.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Axehill, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Hendeby, Gustaf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Informative Path Planning for Active Tracking of Agile Targets2019Inngår i: 2019 IEEE Aerospace Conference, Institute of Electrical and Electronics Engineers (IEEE), 2019, s. 1-11, artikkel-id 06.0701Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper proposes a method to generate informative trajectories for a mobile sensor that tracks agile targets.The goal is to generate a sensor trajectory that maximizes the tracking performance, captured by a measure of the covariance matrix of the target state estimate. The considered problem is acombination of estimation and control, and is often referred to as informative path planning (IPP). When using nonlinear sensors, the tracking performance depends on the actual measurements, which are naturally unavailable in the planning stage.The planning problem hence becomes a stochastic optimization problem, where the expected tracking performance is used inthe objective function. The main contribution of this work is anapproximation of the problem based on deterministic sampling of the predicted target distribution. This is in contrast to prior work, where only the most likely target trajectory is considered.It is shown that the proposed method greatly improves the ability to track agile targets, compared to a baseline approach.   

  • 313.
    Boström-Rost, Per
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Axehill, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Hendeby, Gustaf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Informative Path Planning in the Presence of Adversarial Observers2019Inngår i: 2019 22nd International Conference on Information Fusion (FUSION), 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers the problem of gathering information about features of interest in adversarial environments using mobile robots equipped with sensors. The problem is formulated as an informative path planning problem where the objective is to maximize the gathered information while minimizing the tracking performance of the adversarial observer. The optimization problem, that at first glance seems intractable to solve to global optimality, is shown to be equivalent to a mixed-integer semidefinite program that can be solved to global optimality using off-the-shelf optimization tools.

  • 314.
    Boström-Rost, Per
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Axehill, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Hendeby, Gustaf
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    On Global Optimization for Informative Path Planning2018Inngår i: IEEE Control Systems Letters, ISSN 2475-1456, Vol. 2, nr 4, s. 833-838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The problem of path planning for mobilesensors with the task of target monitoring is considered. A receding horizon optimal control approach based on the information filter is presented, where the limited field of view of the sensor can be modeled by introducing binary variables. The resulting nonlinear mixed integer problem to be solved in each sample, with no apparent tractable solution, is shown to be equivalent to a problem that robustly can be solved to global optimality using off-the-shelf optimization tools.

    Fulltekst (pdf)
    fulltext
  • 315.
    Braga, Andre R.
    et al.
    University of Federal Ceara, Brazil.
    Fritsche, Carsten
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Bruno, Marcelo G. S.
    Aeronaut Institute Technology, Brazil.
    Gradient-Based Recursive Maximum Likelihood Identification of Jump Markov Non-Linear Systems2017Inngår i: 2017 20TH INTERNATIONAL CONFERENCE ON INFORMATION FUSION (FUSION), IEEE , 2017, s. 228-234Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with state inference and parameter identification in Jump Markov Non-Linear System. The state inference problem is solved efficiently using a recently proposed Rao-Blackwellized Particle Filter, where the discrete state is integrated out analytically. Within the RBPF framework, Recursive Maximum Likelihood parameter identification is performed using gradient ascent algorithms. The proposed learning method has the advantage over (online) Expectation Maximization methods, that it can be easily applied to cases where the probability density functions defining the Jump Markov Non-Linear System are not members of the exponential family. Two benchmark problems illustrate the parameter identification performance.

    Fulltekst (pdf)
    fulltext
  • 316.
    Braga, André R.
    et al.
    Aeronautics Institute of Technology, Brazil.
    Bruno, Marcelo G.S.
    Aeronautics Institute of Technology, Brazil.
    Özkan, Emre
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Fritsche, Carsten
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Cooperative Terrain Based Navigation and Coverage Identification Using Consensus2015Inngår i: 18th International Conference on Information Fusion (Fusion), 2015: Proceedings, IEEE , 2015, s. 1190-1197Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a distributed online method for joint state and parameter estimation in a Jump Markov NonLinear System based on a distributed recursive Expectation Maximization algorithm. State inference is enabled via the use of Rao-Blackwellized Particle Filter and, for the parameter estimation, the E-step is performed independently at each sensor with the calculation of local sufficient statistics. An average consensus algorithm is used to diffuse local sufficient statistics to neighbors and approximate the global sufficient statistics throughout the network. The evaluation of the proposed algorithm is carried out on a Terrain Based Navigation problem where the unknown parameters of the observation noise model contain relevant information about the terrain properties.

    Fulltekst (pdf)
    fulltext
  • 317.
    Braga, André R.
    et al.
    Federal University of Ceara, Quixada, Brazil.
    Fritsche, Carsten
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Bruno, Marcelo G. S.
    Aeronautics Institute of Technology, Sao Jose dos Campos, Brazil.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Rapid System Identification for Jump Markov Non-Linear Systems2017Inngår i: Proc. 2017 IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP), IEEE, 2017, s. 714-718Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work evaluates a previously introduced algorithm called Particle-Based Rapid Incremental Smoother within the framework of state inference and parameter identification in Jump Markov Non-Linear System. It is applied to the recursive form of two well-known Maximum Likelihood based algorithms who face the common challenge of online computation of smoothed additive functionals in order to accomplish the task of model parameter estimation. This work extends our previous contributions on identification of Markovian switching systems with the goal to reduce the computational complexity. A benchmark problem is used to illustrate the results.

    Fulltekst (pdf)
    fulltext
  • 318.
    Braga, André Ribeiro
    et al.
    Division of Electronics Engineering, Aeronautics Institute of Technology, São José dos Campos, Brazil.
    Fritsche, Carsten
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Bruno, Marcelo G. S.
    Division of Electronics Engineering, Aeronautics Institute of Technology, São José dos Campos, Brazil.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Cooperative Navigation and Coverage Identification with Random Gossip and Sensor Fusion2016Inngår i: Proc. IEEE 9th Sensor Array and Multichannel Signal Processing Workshop (SAM), Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 1-5Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper is concerned with cooperative Terrain Aided Navigation of a network of aircraft using fusion of Radar Altimeter and inter-node range measurements. State inference is performed using a Rao-Blackwellized Particle Filter with online measurement noise statistics estimation. For terrain coverage measurement noise parameter identification, an online Expectation Maximization algorithm is proposed, where local sufficient statistics at each node are calculated in the E-step, which are then distributed to neighboring nodes using a random gossip algorithm to perform the M-step at each node. Simulation results show that improvement on positioning and calibration performance can be achieved compared to a non-cooperative approach.

    Fulltekst (pdf)
    fulltext
  • 319.
    Brannmark, Cecilia
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Cellbiologi. Linköpings universitet, Hälsouniversitetet.
    Palmer, Robert
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Cellbiologi. Linköpings universitet, Hälsouniversitetet.
    Glad, Torkel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Cedersund, Gunnar
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Cellbiologi. Linköpings universitet, Hälsouniversitetet.
    Strålfors, Peter
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Cellbiologi. Linköpings universitet, Hälsouniversitetet.
    Mass and Information Feedbacks through Receptor Endocytosis Govern Insulin Signaling as Revealed Using a Parameter-free Modeling Framework2010Inngår i: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 285, nr 26, s. 20171-20179Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Insulin and other hormones control target cells through a network of signal-mediating molecules. Such networks are extremely complex due to multiple feedback loops in combination with redundancy, shared signal mediators, and cross-talk between signal pathways. We present a novel framework that integrates experimental work and mathematical modeling to quantitatively characterize the role and relation between coexisting submechanisms in complex signaling networks. The approach is independent of knowing or uniquely estimating model parameters because it only relies on (i) rejections and (ii) core predictions (uniquely identified properties in unidentifiable models). The power of our approach is demonstrated through numerous iterations between experiments, model-based data analyses, and theoretical predictions to characterize the relative role of co-existing feedbacks governing insulin signaling. We examined phosphorylation of the insulin receptor and insulin receptor substrate-1 and endocytosis of the receptor in response to various different experimental perturbations in primary human adipocytes. The analysis revealed that receptor endocytosis is necessary for two identified feedback mechanisms involving mass and information transfer, respectively. Experimental findings indicate that interfering with the feedback may substantially increase overall signaling strength, suggesting novel therapeutic targets for insulin resistance and type 2 diabetes. Because the central observations are present in other signaling networks, our results may indicate a general mechanism in hormonal control.

    Fulltekst (pdf)
    FULLTEXT01
  • 320.
    Braun, M. W.
    et al.
    Arizona State University, AZ, USA.
    McNamara, B. A.
    Arizona State University, AZ, USA.
    Rivera, Daniel E.
    Arizona State University, AZ, USA.
    Stenman, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Model-on-Demand Identification for Control: An Experimental Study and Feasibility Analysis for MOD-based Predictive Control2000Rapport (Annet vitenskapelig)
    Abstract [en]

    An experimental study of "Model-on-Demand" (MoD) identification is made on a pilot-scale brine-water mixing tank. MoD estimation is compared against semi-physical modeling techniques using identification data generated from a systematically designed m-level Pseudo Random Sequence (PRS) input. The estimated models are the basis for evaluating the usefulness of MoD-based Model Predictive Control (MPC). For this application, MoD-MPC is shown to provide better performance at high bandwidths compared to a linear MPC controller.

    Fulltekst (pdf)
    Model-on-Demand Identification for Control: An Experimental Study and Feasibility Analysis for MOD-based Predictive Control
    Fulltekst (ps)
    FULLTEXT01
  • 321.
    Braun, Martin W.
    et al.
    Arizona State University, USA.
    Rivera, Daniel E.
    Arizona State University, USA.
    Stenman, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A 'Model-on-Demand' Identification Methodology for Nonlinear Process Systems2001Inngår i: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 74, nr 18, s. 1708-1717Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An identification methodology based on multi-level pseudo-random sequence (multi-level PRS) input signals and 'Model-on-Demand' (MoD) estimation is presented for single-input, single-output non-linear process applications. 'Model-on-Demand' estimation allows for accurate prediction of non-linear systems while requiring few user choices and without solving a non-convex optimization problem, as is usually the case with global modelling techniques. By allowing the user to incorporate a priori information into the specification of design variables for multi-level PRS input signals, a sufficiently informative input-output dataset for MoD estimation is generated in a 'plant-friendly' manner. The usefulness of the methodology is demonstrated in case studies involving the identification of a simulated rapid thermal processing (RTP) reactor and a pilot-scale brine-water mixing tank. On the resulting datasets, MoD estimation displays performance comparable to that achieved via semi-physical modelling and semi-physical modelling combined with neural networks. The MoD estimator, however, achieves this level of performance with substantially lower engineering effort.

  • 322.
    Braun, Martin W.
    et al.
    Arizona State University, AZ, USA.
    Rivera, Daniel E.
    Arizona State University, AZ, USA.
    Stenman, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Foslien, W
    Honeywell Technology Center, MN, USA.
    Comparison of Global Nonlinear Models and "Model-on-Demand" Estimation Applied to Identification of a RTP Wafer Reactor1999Rapport (Annet vitenskapelig)
    Abstract [en]

    "Model on Demand" (MoD) simulation of the temperature dynamics in a simulated Rapid Thermal Process-ing (RTP) reactor is compared against various types of global models (ARX, semiphysical, combined semiphysical with neural net). The identication data is generated from a m-level pseudo-random sequence input whose parameters are specied systematically using a priori information readily available to the engineer. The MoD estimator outperforms the ARX model and two semi-physical models, while matching the performance of a combined semi-physical with neural net model. This makes MoD estimation an appealing alternative to global methods because of its reduced engineering eort and simplified a priori knowledge regarding model structure.

    Fulltekst (pdf)
    FULLTEXT01
  • 323.
    Braun, M.W.
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Rivera, D.E.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Stenman, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Foslien, W.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hrenya, C.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Multi-Level Pseudo-Random Signal Design and 'Model-on-Demand' Estimation Applied to Nonlinear Identification of a RTP Wafer Reactor1999Rapport (Annet vitenskapelig)
    Abstract [en]

    Guidelines are presented for specifying the design parameters of multi-level pseudo-random sequences in a manner useful for “plant-friendly” nonlinear system identification. These multi-level signals are introduced into a rapid thermal processing wafer reactor simulation and compared against a well-designed pseudo-random binary sequence (PRBS). The resulting data serves as a database for a “model on demand” (MoD) predictor. MoD estimation is attractive because it requires less engineering effort to model a nonlinear plant, compared to global nonlinear models such as neural networks. The improved fit of multi-level signals over the PRBS signal, as well as the usefulness of the MoD estimator, is demonstrated on validation data.

    Fulltekst (pdf)
    FULLTEXT01
  • 324.
    Braunisch, Jan
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Language Independent Speech Visualization2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A speech visualization system is proposed thatcould be used by a deaf person for understanding speech.Several novel techniques are proposed, including: (1) Minimizing spectral leakage in the Fourier transform by using avariable-length window. (2) Making use of the fact that there is no spectral leakage in order to calculate how much of the energy of the speech signal is due to its periodic component vs. its nonperiodic component. (3) Modelling the mouth and lips as a band-pass filter and estimating the central frequency and bandwidth of this filter in order to assign colours tounvoiced speech sounds.

    Fulltekst (pdf)
    speechvisualization
  • 325.
    Bshara, M.
    et al.
    Higher Institute for Applied Sciences and Technology, Damascus, Syrian Arab Republic.
    Orguner, Umut
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    L. Van, Biesen
    Universiteit Brussel, Brussels, Belgium.
    GPS positioning and groung-truth reference points generation2011Inngår i: Joint IMEKO TC11-TC19-TC20 Int. Symp. Metrological Infrastructure, Environmental and Energy Measurement and Int. Symp. of Energy Agencies of Mediterranean Countries, IMEKO-MI 2011, Curran Associates, Incorporated, 2011 , 2011, s. 111-116Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The global positioning system (GPS) is a Global Navigation Satellite System (GNSS) uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, which enable GPS receivers to determine their current location, the time, and their velocity [1]. Initially, the GPS was developed for military applications, but very quickly became the most used technology in positioning even for end-user applications run by individuals with no technical skills. GPS reading are used also as reference points for many positioning techniques such as the techniques that depend on the transmitted electromagnetic signal to determine the position of the transmitter or the receiver, due to their superior accuracy comparing to such techniques. But how accurate are those readings, and how to obtain accurate reference points starting from raw GPS observations even when they are corrupted with errors. In this paper, a practical study about GPS positioning is provided. Generating the ground-truth reference points depending on GPS observations is also provided and discussed in details.

  • 326.
    Bshara, Mussa
    et al.
    Vrije University Brussels, Belgium.
    Orguner, Umut
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Van Biesen, Leo
    Vrije University Brussels, Belgium.
    Fingerprinting Localization in Wireless Networks Based on Received-Signal-Strength Measurements: A Case Study on WiMAX Networks2010Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 59, nr 1, s. 283-294Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers the problem of fingerprinting localization in wireless networks based on received-signal-strength (RSS) observations. First, the performance of static localization using power maps (PMs) is improved with a new approach called the base-station-strict (BS-strict) methodology, which emphasizes the effect of BS identities in the classical fingerprinting. Second, dynamic motion models with and without road network information are used to further improve the accuracy via particle filters. The likelihood-calculation mechanism proposed for the particle filters is interpreted as a soft version (called BS-soft) of the BS-strict approach applied in the static case. The results of the proposed approaches are illustrated and compared with an example whose data were collected from a WiMAX network in a challenging urban area in the capitol city of Brussels, Belgium.

    Fulltekst (pdf)
    FULLTEXT01
  • 327.
    Bshara, Mussa
    et al.
    Vrije Universiteit Brussel, Belgium.
    Orguner, Umut
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Van Biesen, Leo
    Vrije Universiteit Brussel, Belgium.
    Robust Tracking in Cellular Networks Using HMM Filters and Cell-ID Measurements2011Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, nr 3, s. 1016-1024Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A localization algorithm based on cell identification (Cell-ID) information is proposed. Instead of building the localization decisions only on the serving base station, all the detected Cell-IDs (serving or nonserving) by the mobile station are utilized. The statistical modeling of user motion and the measurements are done via a hidden Markov model (HMM), and the localization decisions are made with maximum a posteriori estimation criterion using the posterior probabilities from an HMM filter. The results are observed and compared with standard alternatives on an example whose data were collected from a worldwide interoperability for microwave access network in a challenging urban area in the Brussels capitol city.

    Fulltekst (pdf)
    FULLTEXT01
  • 328.
    Bshara, Mussa
    et al.
    Vrije Universiteit Brussel, Belgium.
    Orguner, Umut
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Van Biesen, Leo
    Vrije Universiteit Brussel, Belgium.
    Tracking in WiMAX Networks Depending on SCORE Measurements2009Inngår i: Proceedings of the 6th Workshop on Positioning, Navigation and Communication, 2009, s. 229-234Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Tracking in WiMax networks is gaining a lot of interest; especially after the mobile WiMax became one of the emerging technologies that promote low-cost deployment and evolving to provide IP-based services of high mobility including providing location-based services (LBS). Therefore, locating users in a cheap way thatdepend on the available network resources is becoming more and more interesting and an active topic for researchers. In this paper we consider the problem of tracking in WiMAX networks depending on SCOREobservations. The provided examples show that with efficient measurement data processing and with the help of already available data (street maps), plausible results can be achieved.

  • 329.
    Burak Guldogan, Mehmet
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Orguner, Umut
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gaussian mixture PHD filter for multi-target tracking using passive doppler-only measurements2012Inngår i: IET Conference Publications: vol 2012, issue 595 CP, IEEE conference proceedings, 2012, Vol. 2012, nr 595 CP, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we analyze the performance of the Gaussian mixture probability hypothesis density (GM-PHD) filter in tracking multiple non-cooperative targets using a passive sensor network. Non-cooperative transmissions from illuminators of opportunity like GSM base stations, FM radio transmitters or digital broadcasters are exploited by non-directional separately located Doppler measuring sensors. Clutter, missed detections and multi-static Doppler variances are incorporated into a realistic multi-target scenario. Simulation results show that the GM-PHD filter successfully tracks multiple targets using only Doppler shift measurements in a passive multi-static scenario.

  • 330.
    Burden, Sam
    et al.
    University of California at Berkeley, USA.
    Ohlsson, Henrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Sastry, Shankar
    University of California at Berkeley, USA.
    Parameter Identification Near Periodic Orbits of Hybrid Dynamical Systems2012Inngår i: Proceedings of the 16th IFAC Symposium on System Identification, 2012, s. 1197-1202Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a novel identification framework that enables the use of first-order methods when estimating model parameters near a periodic orbit of a hybrid dynamical system. The proposed method reduces the space of initial conditions to a smooth manifold that contains the hybrid dynamics near the periodic orbit while maintaining the parametric dependence of the original hybrid model. First-order methods apply on this subsystem to minimize average prediction error, thus identifying parameters for the original hybrid system. We implement the technique and provide simulation results for a hybrid model relevant to terrestrial locomotion.

  • 331.
    Busk, Tomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Blind Channel Equalization for Shortwave Digital Radio Communications2020Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis the concept of Blind Channel Equalization has been examined and algorithms suitable to blindly equalize the channel are presented and evaluated on simulated data. The concept of blind equalization is to equalize a communica- tions channel without relying on a training sequence or pilot tone, which may be either unknown to the receiver or not exist at all. In total, seven blind equaliza- tion algorithms have been implemented, these are the: lms-cma (Constant Modu- lus Algorithm), rls-cma, mma (Multi Modulus Algorithm), rca (Reduced Constel- lation Algorithm), cna-6 (Constant Norm Algorithm), lms-dfe (Decision Feedback Equalization) and rls-dfe. The equalizers are designed as adaptive fir-filters that are recursively updated by either an lms- or rls-algorithm, according to a cost function specified by the chosen algorithm with the aim to appoximate the inverse h−1 of the communications channel h. Thanks to the recursive update the algorithms can easily be implemented either in offline or online systems.

    The results show that the rls-algorithms offer shorter convergence times and over all better performance than its lms counterparts. If the signal constellation is known by the receiver in advance the rls-dfe offers the best channel tracking ability, resulting in the lowest symbol error rate.The rls-cma offers the roughly the same mseR -performance (mean square error from the equalizer output to the closest radius of the constellation points) but it lacks the ability to handle the doppler shift as well as the rls-dfe does. The results also show that the mma, cna-6 and rca-algorithms do not offer any better performance than the more commonly used and studied lms-cma algorithm.

    When the receiver incorrectly assumes the signal constellation, it can identify the correct constellation. Test results show that the rls-cma is especially good at amplitde recovery, while the rls-dfe is suitable to recover the phase of the signal. Lastly the rca is useful to recover psk-4 modulated signals as its cost function match the psk-4 constellation.

    Fulltekst (pdf)
    fulltext
  • 332.
    Byström, Kim
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Mobility Analysis of Zoo Visitors2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In a collaboration between Kolmården Zoo and Linköping University, supported by the Norrköping municipality’s fund for research and innovation, mobility measurements have been performed inside the zoo. These measurements have been done by six WiFi sniffers collecting anonymised MAC addresses from the visitors smartphones. The aim of this thesis is to analyse these data to understand visitor flows in the park and other statistics using a model based mobility analysis. The work implies that one can make a rather good prediction of the geographical visitor distribution using this equipment and statistical models.

    Fulltekst (pdf)
    Mobility analysis of zoo visitors
  • 333.
    Bäck, Marcus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Grey-Box Modelling of a Quadrotor Using Closed-Loop Data2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis a quadrotor is studied and a linear model is derived using grey-box estimation, a discipline in system identification where a model structure based on physical relations is used and the parameters are estimated using input-output measurements. From IMU measurements and measured PWM signals to the four motors, a direct approach using the prediction-error method is applied. To investigate the impact of the unknown controller the two-stage method, a closed-loop approach in system identification,  is applied as well. The direct approach was enough for estimating the model parameters. The resulting model manages to simulate the major dynamics for the vertical acceleration and the angular rates well enough  for future control design. 

    Fulltekst (pdf)
    fulltext
  • 334.
    Bäckman, Henrik
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Brändström, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Modelling and Control of an Electro-Hydraulic Forklift2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    To meet the increasing demand on control precision in industrial forklifts, physical modelling of the lifting system has been combined with parameter estimations from data. A number of different controllers have been evaluated in terms of their ability to achieve a load independent lifting speed. The model and controller performance as well as stability properties were evaluated in simulations, and the most promising controller was implemented on the real system. Especially the electric motor turned out to be difficult to model, and therefore experimental data was used to approximate some parts of it. This, along with some friction parameters that had to be estimated caused a slight loss in model generality. An observer (Extended Kalman filter) was used to estimate the unknown states, including the velocity of the forks. The simulated performance of the MPC controller was slightly better than the PID controller, except for a bigger overshoot when starting from a turned off motor. The PID controller also handles model errors better, because of its integral action. Due to the simplicity in relation to performance, only the PID controller was implemented on the forklift. The model turned out to perform well, but not well enough to estimate the lifting height accurately. The PID controller worked as intended and it could therefore be concluded that a more advanced control algorithm, such as an MPC controller, is not necessary for this system.

    Fulltekst (pdf)
    fulltext
  • 335.
    Bäckström, Christer
    et al.
    Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi. Linköpings universitet, Tekniska högskolan.
    Klein, Inger
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Parallel Non-binary Planning in Polynomial Time: The SAS-PUS Class1991Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper formally presents a class of planning problems, the SAS-PUS class, which allows non-binary state variables and parallel execution of actions. The class is proven to be tractable, and we provide a sound and complete, polynomial time algorithm for planning within this class. Since the SAS-PUS class is an extension of the previously presented SAS-PUBS class, this result means that we are getting closer to tackling realistic planning problems in sequential control. In such problems, a restricted problem representation is often sufficient but the size of the problems make tractability an important issue.

  • 336.
    Bäckström, Christer
    et al.
    Linköpings universitet, Institutionen för datavetenskap, TCSLAB - Laboratoriet för teoretisk datalogi. Linköpings universitet, Tekniska högskolan.
    Klein, Inger
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Planning in Polynomial Time: The SAS-PUBS Class1990Rapport (Annet vitenskapelig)
    Abstract [en]

    This article describes a polynomial-time, O(n3), planning algorithm for a limited class of planning problems. Compared to previous work on complexity of algorithms for knowledge-based or logic-based planning, our algorithm achieves computational tractability, but at the expense of only applying to a significantly more limited class of problems. Our algorithm is proven correct, and it always returns a parallel minimal plan if there is a plan at all.

  • 337.
    Bärlund, Alexander
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Nonlinear MPC for Motion Control and Thruster Allocation of Ships2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Critical automated maneuvers for ships typically require a redundant set of thrusters. The motion control system hierarchy is commonly separated into several layers using a high-level motion controller and a thruster allocation (TA) algorithm. This allows for a modular design of the software where the high-level controller can be designed without comprehensive information on the thrusters, while detailed issues such as input saturation and rate limits are handled by the TA. However, for a certain set of thruster configurations this decoupling may result in poor control performance due to the limited knowledge in the high-level controller about the physical limitations of the ship and the behavior of the TA.

    This thesis investigates different approaches of improving the control performance, using nonlinear Model Predictive Control (MPC) as a foundation for the developed motion controllers due to its optimized solution and capability of satisfying constraints. First, a decoupled system is implemented and results are provided for two simple motion tasks showing problems related to the decoupling. Thereafter, two different approaches are taken to remedy the observed drawbacks. A nonlinear MPC controller is developed combining the motion controller and thruster allocation resulting in a more robust control system. Then, in order to keep the control system modularized, an investigation of possible ways to augment the decoupled system so as to achieve similar performance as the combined system is carried out. One proposed solution is a nonlinear MPC controller with time-varying constraints accounting for the current limitations of the thruster system. However, this did not always improve the control performance since the behavior of the TA still is unknown to the MPC controller.

    Fulltekst (pdf)
    fulltext
  • 338.
    Caines, Peter E.
    et al.
    Harvard University, MA, USA.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Prediction Error Estimators: Asymptotic Normality and Accuracy1976Inngår i: Proceedings of the 1976 IEEE Conference on Decision and Control including the 15th Symposium on Adaptive Processes, 1976, s. 652-658Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper the asymptotic normality of a large class of prediction error estimators is established. (Prediction error identification methods were introduced in [1] and further developed in [2] and [3].) The observed processes in this paper are assumed to be stationary and ergodic and the parameterized process models are taken to be non-linear regression models. In the gaussian case the results presented in this paper constitute substantial generalizations of previous results concerning the asymptotic normality of maximum likelihood estimators for (i) processes of independent random variables [9,4] and (ii) Markov processes [5]; these results also generalize previous results on the asymptotic normality of least squares estimators for autoregressive moving average processes [6,7]. The asymptotic normality theorem gives formulae for the covariances of the asymptotic distributions of the parameter estimation errors arising from the specified class of prediction error identification methods. Employing these formulae it is demonstrated that the prediction error method using the determinant of the residual error covariance matrix as loss function is asymptotically efficient with respect to the specified class of prediction error estimators regardless of the distribution of the observed processes.

  • 339.
    Caines, Peter
    et al.
    Harvard University, MA, USA.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Asymptotic Normality and Accuracy of Prediction Error Estimation1976Inngår i: Proceedings of JACC 1976, 1976Konferansepaper (Fagfellevurdert)
  • 340. Bestill onlineKjøp publikasjonen >>
    Callmer, Jonas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Autonomous Localization in Unknown Environments2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Over the last 20 years, navigation has almost become synonymous with satellite positioning, e.g. the Global Positioning System (GPS). On land, sea or in the air, on the road or in a city, knowing ones position is a question of getting a clear line of sight to enough satellites. Unfortunately, since the signals are extremely weak there are environments the GPS signals cannot reach but where positioning is still highly sought after, such as indoors and underwater. Also, because the signals are so weak, GPS is vulnerable to jamming. This thesis is about alternative means of positioning for three scenarios where gps cannot be used.

    Indoors, there is a desire to accurately position first responders, police officers and soldiers. This could make their work both safer and more efficient. In this thesis an inertial navigation system using a foot mounted inertial magnetic mea- surement unit is studied. For such systems, zero velocity updates can be used to significantly reduce the drift in distance travelled. Unfortunately, the estimated direction one is moving in is also subject to drift, causing large positioning errors. We have therefore chosen to throughly study the key problem of robustly estimating heading indoors.

    To measure heading, magnetic field measurements can be used as a compass. Unfortunately, they are often disturbed indoors making them unreliable. For estimation support, the turn rate of the sensor can be measured by a gyro but such sensors often have bias problems. In this work, we present two different approaches to estimate heading despite these shortcomings. Our first system uses a Kalman filter bank that recursively estimates if the magnetic readings are disturbed or undisturbed. Our second approach estimates the entire history of headings at once, by matching integrated gyro measurements to a vector of magnetic heading measurements. Large scale experiments are used to evaluate both methods. When the heading estimation is incorporated into our positioning system, experiments show that positioning errors are reduced significantly. We also present a probabilistic stand still detection framework based on accelerometer and gyro measurements.

    The second and third problems studied are both maritime. Naval navigation systems are today heavily dependent on GPS. Since GPS is easily jammed, the vessels are vulnerable in critical situations. In this work we describe a radar based backup positioning system to be used in case of GPS failure. radar scans are matched using visual features to detect how the surroundings have changed, thereby describing how the vessel has moved. Finally, we study the problem of underwater positioning, an environment gps signals cannot reach. A sensor network can track vessels using acoustics and the magnetic disturbances they induce. But in order to do so, the sensors themselves first have to be accurately positioned. We present a system that positions the sensors using a friendly vessel with a known magnetic signature and trajectory. Simulations show that by studying the magnetic disturbances that the vessel produces, the location of each sensor can be accurately estimated.

    Delarbeid
    1. Robust Heading Estimation Indoors
    Åpne denne publikasjonen i ny fane eller vindu >>Robust Heading Estimation Indoors
    2013 (engelsk)Rapport (Annet vitenskapelig)
    Abstract [en]

    Indoor positioning in unknown environments is crucial for rescue personnel and future infotainment systems. Dead-reckoning inertial sensor data gives accurate estimate of distance, for instance using zero velocity updates, while the heading estimation problem is inherently more difficult due to the large degree of magnetic disturbances indoors. We propose a Kalman filter bank approach based on supporting a magnetic compass with gyroscope turn rate information, where a hidden Markov model is used to model the presence of magnetic disturbances. In parallel, we suggest to run a robust heading estimation system based on data from a sliding window. The robust estimate is used to detect filter divergence, and to restart the filter when needed. The underlying assumptions and the heading estimation performance are supported in field trials using more than 500 data sets from more than 50 venues in 5 continents.

    sted, utgiver, år, opplag, sider
    Linköping: Linköping University Electronic Press, 2013. s. 13
    Serie
    LiTH-ISY-R, ISSN 1400-3902 ; 3061
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-91393 (URN)
    Forskningsfinansiär
    eLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsLinnaeus research environment CADICS
    Tilgjengelig fra: 2013-04-23 Laget: 2013-04-23 Sist oppdatert: 2013-05-08
    2. Robust Heading Estimation Indoors using Convex Optimization
    Åpne denne publikasjonen i ny fane eller vindu >>Robust Heading Estimation Indoors using Convex Optimization
    2013 (engelsk)Rapport (Annet vitenskapelig)
    Abstract [en]

    The problem of estimating heading is central in the indoor positioning problem based on mea- surements from inertial measurement and magnetic units. Integrating rate of turn angular rate gives the heading with unknown initial condition and a linear drift over time, while the magnetometer gives absolute heading, but where long segments of data are useless in prac- tice because of magnetic disturbances. A basic Kalman filter approach with outlier rejection has turned out to be difficult to use with high integrity. Here, we propose an approach based on convex optimization, where segments of good magnetometer data are separated from disturbed data and jointly fused with the yaw rate measurements. The optimization framework is flexible with many degrees of freedom in the modeling phase, and we outline one design. A recursive solution to the optimization is derived, which has a computational complexity comparable to the simplest possible Kalman filter. The performance is evaluated using data from a handheld smartphone for a large amount of indoor trajectories, and the result demonstrates that the method effectively resolves the magnetic disturbances.

    sted, utgiver, år, opplag, sider
    Linköping: Linköping University Electronic Press, 2013. s. 9
    Serie
    LiTH-ISY-R, ISSN 1400-3902 ; 3060
    Emneord
    Heading estimation, magnetometer, gyro, disturbances, optimization
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-91392 (URN)LiTH-ISY-R-3060 (ISRN)
    Forskningsfinansiär
    eLLIIT - The Linköping‐Lund Initiative on IT and Mobile CommunicationsLinnaeus research environment CADICS
    Tilgjengelig fra: 2013-04-23 Laget: 2013-04-23 Sist oppdatert: 2014-06-16bibliografisk kontrollert
    3. An Inertial Navigation Framework for Indoor Positioning with Robust Heading
    Åpne denne publikasjonen i ny fane eller vindu >>An Inertial Navigation Framework for Indoor Positioning with Robust Heading
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Indoor localization in unknown environments is considered, using inertial measurements from accelerometers, gyroscopes and magnetometers. Foot-mounted inertial sensors allow for stand-still detection triggering zero velocity updates that reduces the inertial navigation system (ins) drift in distance traveled from cubical to linear in time. We present a statistical framework, based on an navigation model. The standard stand-still mode is complemented with binary modes of magnetic disturbances. Test statistics for these two mode estimation problems are derived. Instead of making hard decisions, a hidden Markov model filter is used to compute the mode probabilities, leading to soft measurement updates in the Kalman filter.

    Based on this, a robust smoothed heading estimate is computed in a second stage using the magnetometer. The final position estimate is then obtained by fusing the ins output with the robust heading in a standard dead-reckoning filter. Experiments demonstrate that the robust heading decreases the relative error in position from 10% to less than 1%, despite large magnetic disturbances.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-92131 (URN)
    Tilgjengelig fra: 2013-05-08 Laget: 2013-05-08 Sist oppdatert: 2013-05-08
    4. RADAR SLAM using Visual Features
    Åpne denne publikasjonen i ny fane eller vindu >>RADAR SLAM using Visual Features
    Vise andre…
    2011 (engelsk)Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2011, nr 71Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A vessel navigating in a critical environment such as an archipelago, requires very accurate movement estimates. Intentional or unintentional jamming makes gps unreliable as the only source of information and an additional independent navigation system should be used. In this paper we suggest estimating the vessel movements using a sequence of radar images from the preexisting body-fixed radar. Island landmarks in the radar scans are tracked between multiple scans using visual features. This provides information not only about the position of the vessel but also of its course and velocity. We present here a complete navigation framework that requires no additional hardware than the already existing naval radar sensor. Experiments show that visual radar features can be used to accurately estimate the vessel trajectory over an extensive data set.

    sted, utgiver, år, opplag, sider
    Springer, 2011
    Emneord
    GPS, Navigation system, Radar, Sensor
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-72583 (URN)10.1186/1687-6180-2011-71 (DOI)000300999900001 ()
    Forskningsfinansiär
    Swedish Foundation for Strategic Research Swedish Research Council
    Merknad

    funding agencies|Strategic Research Center MOVIII||Swedish Foundation for Strategic Research||SSF||CADICS||Swedish Research Council||

    Tilgjengelig fra: 2011-11-29 Laget: 2011-11-29 Sist oppdatert: 2017-12-08bibliografisk kontrollert
    5. Silent Localization of Underwater Sensors Using Magnetometers
    Åpne denne publikasjonen i ny fane eller vindu >>Silent Localization of Underwater Sensors Using Magnetometers
    2010 (engelsk)Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2010, nr 1Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Sensor localization is a central problem for sensor networks. If the sensor positions are uncertain, the target tracking ability of the sensor network is reduced. Sensor localization in underwater environments is traditionally addressed using acoustic range measurements involving known anchor or surface nodes. We explore the usage of triaxial magnetometers and a friendly vessel with known magnetic dipole to silently localize the sensors. The ferromagnetic field created by the dipole is measured by the magnetometers and is used to localize the sensors. The trajectory of the vessel and the sensor positions are estimated simultaneously using an Extended Kalman Filter (EKF). Simulations show that the sensors can be accurately positioned using magnetometers.

    sted, utgiver, år, opplag, sider
    Hindawi Publishing Corporation, 2010
    Emneord
    Underwater sensor localization, Sensor network, Magnetometers, SLAM
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-53589 (URN)10.1155/2010/709318 (DOI)000274966500001 ()
    Prosjekter
    MOVIIICADICSLINK-SIC
    Tilgjengelig fra: 2010-01-25 Laget: 2010-01-25 Sist oppdatert: 2017-12-12bibliografisk kontrollert
    Fulltekst (pdf)
    Autonomous Localization in Unknown Environments
    Download (pdf)
    omslag
  • 341. Bestill onlineKjøp publikasjonen >>
    Callmer, Jonas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Topics in Localization and Mapping2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The need to determine ones position is common and emerges in many different situations. Tracking soldiers or a robot moving in a building or aiding a tourist exploring a new city, all share the questions ”where is the unit?“ and ”where is the unit going?“. This is known as the localization problem.Particularly, the problem of determining ones position in a map while building the map at the same time, commonly known as the simultaneous localization and mapping problem (slam), has been widely studied. It has been performed in cities using different land bound vehicles, in rural environments using au- tonomous aerial vehicles and underwater for coral reef exploration. In this thesis it is studied how radar signals can be used to both position a naval surface ves- sel but also to simultaneously construct a map of the surrounding archipelago. The experimental data used was collected using a high speed naval patrol boat and covers roughly 32 km. A very accurate map was created using nothing but consecutive radar images.A second contribution covers an entirely different problem but it has a solution that is very similar to the first one. Underwater sensors sensitive to magnetic field disturbances can be used to track ships. In this thesis, the sensor positions them- selves are considered unknown and are estimated by tracking a friendly surface vessel with a known magnetic signature. Since each sensor can track the vessel, the sensor positions can be determined by relating them to the vessel trajectory. Simulations show that if the vessel is equipped with a global navigation satellite system, the sensor positions can be determined accurately.There is a desire to localize firefighters while they are searching through a burn- ing building. Knowing where they are would make their work more efficient and significantly safer. In this thesis a positioning system based on foot mounted in- ertial measurement units has been studied. When such a sensor is foot mounted, the available information increases dramatically since the foot stances can be de- tected and incorporated in the position estimate. The focus in this work has therefore been on the problem of stand still detection and a probabilistic frame- work for this has been developed. This system has been extensively investigated to determine its applicability during different movements and boot types. All in all, the stand still detection system works well but problems emerge when a very rigid boot is used or when the subject is crawling. The stand still detection frame- work was then included in a positioning framework that uses the detected stand stills to introduce zero velocity updates. The system was evaluated using local- ization experiments for which there was very accurate ground truth. It showed that the system provides good position estimates but that the estimated heading can be wrong, especially after quick sharp turns.

    Delarbeid
    1. RADAR SLAM using Visual Features
    Åpne denne publikasjonen i ny fane eller vindu >>RADAR SLAM using Visual Features
    Vise andre…
    2011 (engelsk)Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2011, nr 71Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A vessel navigating in a critical environment such as an archipelago, requires very accurate movement estimates. Intentional or unintentional jamming makes gps unreliable as the only source of information and an additional independent navigation system should be used. In this paper we suggest estimating the vessel movements using a sequence of radar images from the preexisting body-fixed radar. Island landmarks in the radar scans are tracked between multiple scans using visual features. This provides information not only about the position of the vessel but also of its course and velocity. We present here a complete navigation framework that requires no additional hardware than the already existing naval radar sensor. Experiments show that visual radar features can be used to accurately estimate the vessel trajectory over an extensive data set.

    sted, utgiver, år, opplag, sider
    Springer, 2011
    Emneord
    GPS, Navigation system, Radar, Sensor
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-72583 (URN)10.1186/1687-6180-2011-71 (DOI)000300999900001 ()
    Forskningsfinansiär
    Swedish Foundation for Strategic Research Swedish Research Council
    Merknad

    funding agencies|Strategic Research Center MOVIII||Swedish Foundation for Strategic Research||SSF||CADICS||Swedish Research Council||

    Tilgjengelig fra: 2011-11-29 Laget: 2011-11-29 Sist oppdatert: 2017-12-08bibliografisk kontrollert
    2. Silent Localization of Underwater Sensors Using Magnetometers
    Åpne denne publikasjonen i ny fane eller vindu >>Silent Localization of Underwater Sensors Using Magnetometers
    2010 (engelsk)Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2010, nr 1Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Sensor localization is a central problem for sensor networks. If the sensor positions are uncertain, the target tracking ability of the sensor network is reduced. Sensor localization in underwater environments is traditionally addressed using acoustic range measurements involving known anchor or surface nodes. We explore the usage of triaxial magnetometers and a friendly vessel with known magnetic dipole to silently localize the sensors. The ferromagnetic field created by the dipole is measured by the magnetometers and is used to localize the sensors. The trajectory of the vessel and the sensor positions are estimated simultaneously using an Extended Kalman Filter (EKF). Simulations show that the sensors can be accurately positioned using magnetometers.

    sted, utgiver, år, opplag, sider
    Hindawi Publishing Corporation, 2010
    Emneord
    Underwater sensor localization, Sensor network, Magnetometers, SLAM
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-53589 (URN)10.1155/2010/709318 (DOI)000274966500001 ()
    Prosjekter
    MOVIIICADICSLINK-SIC
    Tilgjengelig fra: 2010-01-25 Laget: 2010-01-25 Sist oppdatert: 2017-12-12bibliografisk kontrollert
    Fulltekst (pdf)
    Topics in Localization and Mapping
    Download (pdf)
    omslag
  • 342.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Granström, Karl
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Nieto, Juan
    University of Sydney, Australia.
    Ramos, Fabio
    University of Sydney, Australia.
    Tree of Words for Visual Loop Closure Detection in Urban SLAM2008Inngår i: Proceedings of the '08 Australasian Conference on Robotics and Automation, 2008, s. 102-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper introduces vision based loop closure detection in Simultaneous Localisation And Mapping (SLAM) using Tree of Words. The loop closure performance in a complex urban environment is examined and an additional feature is suggested for safer matching. A SLAM ground experiment in an urban area is performed using Tree of Words, a delayed state information filter and planar laser scans for relative pose estimation. Results show that a good map estimation using our vision based loop closure detection can be obtained in near real, yet constant, time. It is shown that an odometry supported recall rate of almost 70% can be obtained with a false detection rate of about 0.01%.

  • 343.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Skoglund, Martin
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Silent Localization of Underwater Sensors Using Magnetometers2010Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2010, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sensor localization is a central problem for sensor networks. If the sensor positions are uncertain, the target tracking ability of the sensor network is reduced. Sensor localization in underwater environments is traditionally addressed using acoustic range measurements involving known anchor or surface nodes. We explore the usage of triaxial magnetometers and a friendly vessel with known magnetic dipole to silently localize the sensors. The ferromagnetic field created by the dipole is measured by the magnetometers and is used to localize the sensors. The trajectory of the vessel and the sensor positions are estimated simultaneously using an Extended Kalman Filter (EKF). Simulations show that the sensors can be accurately positioned using magnetometers.

    Fulltekst (pdf)
    FULLTEXT02
  • 344.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    An Inertial Navigation Framework for Indoor Positioning with Robust HeadingManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Indoor localization in unknown environments is considered, using inertial measurements from accelerometers, gyroscopes and magnetometers. Foot-mounted inertial sensors allow for stand-still detection triggering zero velocity updates that reduces the inertial navigation system (ins) drift in distance traveled from cubical to linear in time. We present a statistical framework, based on an navigation model. The standard stand-still mode is complemented with binary modes of magnetic disturbances. Test statistics for these two mode estimation problems are derived. Instead of making hard decisions, a hidden Markov model filter is used to compute the mode probabilities, leading to soft measurement updates in the Kalman filter.

    Based on this, a robust smoothed heading estimate is computed in a second stage using the magnetometer. The final position estimate is then obtained by fusing the ins output with the robust heading in a standard dead-reckoning filter. Experiments demonstrate that the robust heading decreases the relative error in position from 10% to less than 1%, despite large magnetic disturbances.

  • 345.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Probabilistic Stand Still Detection using Foot Mounted IMU2010Inngår i: Proceedings of the 13th International Conference on Information Fusion, 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider stand still detection for indoor localization based on observations from a foot-mounted inertial measurement unit (IMU). The main contribution is a statistical framework for stand-still detection, which is a fundamental step in zero velocity update (ZUPT) to reduce the drift from cubic to linear in time. First, the observations are transformed to a test statistic having non-central chi-square distribution during zero velocity. Second, a hidden Markov model is used to describe the mode switching between stand still, walking, running, crawling and other possible movements. The resulting algorithm computes the probability of being in each mode, and it is easily extendable to a dynamic navigation framework where map information can be included. Results of first mode probability estimation, second map matching without ZUPT and third step length estimation with ZUPT are provided.

    Fulltekst (pdf)
    FULLTEXT01
  • 346.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Robust Heading Estimation Indoors2013Rapport (Annet vitenskapelig)
    Abstract [en]

    Indoor positioning in unknown environments is crucial for rescue personnel and future infotainment systems. Dead-reckoning inertial sensor data gives accurate estimate of distance, for instance using zero velocity updates, while the heading estimation problem is inherently more difficult due to the large degree of magnetic disturbances indoors. We propose a Kalman filter bank approach based on supporting a magnetic compass with gyroscope turn rate information, where a hidden Markov model is used to model the presence of magnetic disturbances. In parallel, we suggest to run a robust heading estimation system based on data from a sliding window. The robust estimate is used to detect filter divergence, and to restart the filter when needed. The underlying assumptions and the heading estimation performance are supported in field trials using more than 500 data sets from more than 50 venues in 5 continents.

  • 347.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Robust Heading Estimation Indoors using Convex Optimization2013Inngår i: 2013 16TH INTERNATIONAL CONFERENCE ON INFORMATION FUSION (FUSION), IEEE , 2013, s. 1173-1179Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of estimating heading is central in the indoor positioning problem based on measurements from inertial measurement and magnetic units, Integrating rate of turn angular rate gives the heading with unknown initial condition and a linear drift over time, while the magnetometer gives absolute heading, but m here long segments of data are useless in practice because of magnetic disturbances. A basic Kalman filter approach with outlier rejection has turned out to be difficult to use with high integrity. Here, we propose an approach based on convex optimization, where segments of good magnetometer data are separated from disturbed data and jointly fused with the yaw rate measurements. The optimization framework is flexible with many degrees of freedom in the modeling phase, and we outline one design. A recursive solution to the optimization is derived, which has a computational complexity comparable to the simplest possible Kalman filter. The performance is evaluated using data from a handheld smartphone for a large amount of indoor trajectories, and the result demonstrates that the method effectively resolves the magnetic disturbances.

  • 348.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Robust Heading Estimation Indoors using Convex Optimization2013Rapport (Annet vitenskapelig)
    Abstract [en]

    The problem of estimating heading is central in the indoor positioning problem based on mea- surements from inertial measurement and magnetic units. Integrating rate of turn angular rate gives the heading with unknown initial condition and a linear drift over time, while the magnetometer gives absolute heading, but where long segments of data are useless in prac- tice because of magnetic disturbances. A basic Kalman filter approach with outlier rejection has turned out to be difficult to use with high integrity. Here, we propose an approach based on convex optimization, where segments of good magnetometer data are separated from disturbed data and jointly fused with the yaw rate measurements. The optimization framework is flexible with many degrees of freedom in the modeling phase, and we outline one design. A recursive solution to the optimization is derived, which has a computational complexity comparable to the simplest possible Kalman filter. The performance is evaluated using data from a handheld smartphone for a large amount of indoor trajectories, and the result demonstrates that the method effectively resolves the magnetic disturbances.

    Fulltekst (pdf)
    fulltext
  • 349.
    Callmer, Jonas
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Törnqvist, David
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Svensson, Henrik
    Nira Dynamics, Sweden.
    Carlbom, Pelle
    Saab Dynamics AB, Sweden.
    RADAR SLAM using Visual Features2011Inngår i: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 2011, nr 71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A vessel navigating in a critical environment such as an archipelago, requires very accurate movement estimates. Intentional or unintentional jamming makes gps unreliable as the only source of information and an additional independent navigation system should be used. In this paper we suggest estimating the vessel movements using a sequence of radar images from the preexisting body-fixed radar. Island landmarks in the radar scans are tracked between multiple scans using visual features. This provides information not only about the position of the vessel but also of its course and velocity. We present here a complete navigation framework that requires no additional hardware than the already existing naval radar sensor. Experiments show that visual radar features can be used to accurately estimate the vessel trajectory over an extensive data set.

    Fulltekst (pdf)
    fulltext
  • 350.
    Carlborg, Hampus
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Iredahl, Henrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Modeling and Temperature Control of an Industrial Furnace2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A linear model of an annealing furnace is developed using a black-box system identification approach, and used when testing three different control strategies to improve temperature control. The purpose of the investigation was to see if it was possible to improve the temperature control while at the same time  decrease the switching frequency of the  burners. This will lead to a more efficient process as well as less maintenance, which has both economic and environmental benefits.

    The estimated model has been used to simulate the furnace with both the existing controller and possible new controllers such as a split range controller and a model predictive controller (MPC). A split range controller is a control strategy which can be used when more than one control signal affect the output signal, and the control signals have different range. The main advantage with MPC is that it can take limitations and constraints into account for the controlled process, and with the use of integer programming, explicitly account for the discrete switching behavior of the burners.

    In simulation both new controllers succeed in decreasing the switching and the MPC also improved the temperature control. This suggest that the control of the furnace can be improved by implementing one of the evaluated controllers.

    Fulltekst (pdf)
    fulltext
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