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  • 1.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hostettler, Roland
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An Improvement in the Observation Model for Monte Carlo Localization2014In: Proceedings of the 11th International Conference on Informatics in Control, Automation and Robotics: Vienna, Austria, 1-3, September, 2014, SciTePress, 2014, p. 498-505Chapter in book (Refereed)
    Abstract [en]

    Accurate and robust mobile robot localization is very important in many robot applications. Monte Carlo localization (MCL) is one of the robust probabilistic solutions to robot localization problems. The sensor model used in MCL directly influence the accuracy and robustness of the pose estimation process. The classical beam models assumes independent noise in each individual measurement beam at the same scan. In practice, the noise in adjacent beams maybe largely correlated. This will result in peaks in the likelihood measurement function. These peaks leads to incorrect particles distribution in the MCL. In this research, an adaptive sub-sampling of the measurements is proposed to reduce the peaks in the likelihood function. The sampling is based on the complete scan analysis. The specified measurement is accepted or not based on the relative distance to other points in the 2D point cloud. The proposed technique has been implemented in ROS and stage simulator. The result shows that selecting suitable value of distance between accepted scans can improve the localization error and reduce the required computations effectively.

  • 2.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An improvement in the observarion model for Monte Carlo localization2014Conference paper (Refereed)
  • 3.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Observation model for Monte Carlo Localization2014Conference paper (Other academic)
  • 4.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems. Department of Computer EngineeringUniversity of Baghdad.
    Pierobon, Giovanni
    Department of Information EngineeringUniversity of Padova.
    Varagnolo, Damiano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Modeling and Calibrating Triangulation Lidars for Indoor Applications2018In: Informatics in Control, Automation and Robotics: 13th International Conference, ICINCO 2016 Lisbon, Portugal, 29-31 July, 2016 / [ed] Kurosh Madani, Dimitri Peaucelle, Oleg Gusikhin, Cham: Springer Publishing Company, 2018, p. 342-366Conference paper (Refereed)
    Abstract [en]

    We present an improved statistical model of the measurement process of triangulation Light Detection and Rangings (Lidars) that takes into account bias and variance effects coming from two different sources of uncertainty:                                                                           {\$}{\$}(i) {\$}{\$}                 mechanical imperfections on the geometry and properties of their pinhole lens - CCD camera systems, and                                                                           {\$}{\$}(ii) {\$}{\$}                 inaccuracies in the measurement of the angular displacement of the sensor due to non ideal measurements from the internal encoder of the sensor. This model extends thus the one presented in [2] by adding this second source of errors. Besides proposing the statistical model, this chapter considers:                                                                           {\$}{\$}(i) {\$}{\$}                 specialized and dedicated model calibration algorithms that exploit Maximum Likelihood (ML)/Akaike Information Criterion (AIC) concepts and that use training datasets collected in a controlled setup, and                                                                           {\$}{\$}(ii) {\$}{\$}                 tailored statistical strategies that use the calibration results to statistically process the raw sensor measurements in non controlled but structured environments where there is a high chance for the sensor to be detecting objects with flat surfaces (e.g., walls). These newly proposed algorithms are thus specially designed and optimized for inferring precisely the angular orientation of the Lidar sensor with respect to the detected object, a feature that is beneficial especially for indoor navigation purposes.

  • 5.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Varagnolo, Damiano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Calibrating distance sensors for terrestrial applications without groundtruth information2017In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 17, no 12, p. 3698-3709, article id 7911206Article in journal (Refereed)
    Abstract [en]

    This paper describes a new calibration procedure for distance sensors that does not require independent sources of groundtruth information, i.e., that is not based on comparing the measurements from the uncalibrated sensor against measurements from a precise device assumed as the groundtruth. Alternatively, the procedure assumes that the uncalibrated distance sensor moves in space on a straight line in an environment with fixed targets, so that the intrinsic parameters of the statistical model of the sensor readings are calibrated without requiring tests in controlled environments, but rather in environments where the sensor follows linear movement and objects do not move. The proposed calibration procedure exploits an approximated expectation maximization scheme on top of two ingredients: an heteroscedastic statistical model describing the measurement process, and a simplified dynamical model describing the linear sensor movement. The procedure is designed to be capable of not just estimating the parameters of one generic distance sensor, but rather integrating the most common sensors in robotic applications, such as Lidars, odometers, and sonar rangers and learn the intrinsic parameters of all these sensors simultaneously. Tests in a controlled environment led to a reduction of the mean squared error of the measurements returned by a commercial triangulation Lidar by a factor between 3 and 6, comparable to the efficiency of other state-of-the art groundtruth-based calibration procedures. Adding odometric and ultrasonic information further improved the performance index of the overall distance estimation strategy by a factor of up to 1.2. Tests also show high robustness against violating the linear movements assumption.

  • 6.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Varagnolo, Damiano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Joint Temperature-Lasing Mode Compensation for Time-of-Flight LiDAR Sensors2015In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 15, no 12, p. 31205-31223Article in journal (Refereed)
    Abstract [en]

    We propose an expectation maximization (EM) strategy for improving the precision of time of flight (ToF) light detection and ranging (LiDAR) scanners. The novel algorithm statistically accounts not only for the bias induced by temperature changes in the laser diode, but also for the multi-modality of the measurement noises that is induced by mode-hopping effects. Instrumental to the proposed EM algorithm, we also describe a general thermal dynamics model that can be learned either from just input-output data or from a combination of simple temperature experiments and information from the laser’s datasheet. We test the strategy on a SICK LMS 200 device and improve its average absolute error by a factor of three.

  • 7.
    Alhashimi, Anas W.
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Varagnolo, Damiano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Statistical modeling and calibration of triangulation Lidars2016In: ICINCO 2016: Proceedings of the 13th International Conference on Informatics in Control, Automation and Robotics / [ed] Peaucelle D.,Gusikhin O.,Madani K, SciTePress, 2016, p. 308-317Conference paper (Refereed)
    Abstract [en]

    We aim at developing statistical tools that improve the accuracy and precision of the measurements returned by triangulation Light Detection and Rangings (Lidars). To this aim we: i) propose and validate a novel model that describes the statistics of the measurements of these Lidars, and that is built starting from mechanical considerations on the geometry and properties of their pinhole lens - CCD camera systems; ii) build, starting from this novel statistical model, a Maximum Likelihood (ML) / Akaike Information Criterion (AIC) -based sensor calibration algorithm that exploits training information collected in a controlled environment; iii) develop ML and Least Squares (LS) strategies that use the calibration results to statistically process the raw sensor measurements in non controlled environments. The overall technique allowed us to obtain empirical improvements of the normalized Mean Squared Error (MSE) from 0.0789 to 0.0046

  • 8.
    Andersson, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Bortolin, Gianantonio
    Volvo CE.
    Backén, Staffan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Estimation of side-slip angles of a Volvo A25E articulated all-wheel drive hauler based on GPS/INS measurements2011In: Proceedings of SAE 2011 Commercial Vehicle Engineering Congress and Exhibition, Society of Automotive Engineers, Incorporated , 2011Conference paper (Refereed)
    Abstract [en]

    Traction control for off-road vehicles such as articulated all-wheel drive haulers is of great importance to improve the vehicle performance. A well-known method to reduce the slip and thereby improve the traction is to engage differential locks in the driveline of the vehicle. The drawbacks of differential locks engaged are for instance increased wear, increased fuel consumption but also reduced turnability of the vehicle. Therefore, the differentials should be locked only when necessary, ideally only when slip occurs or is about to occur. A number of methods to detect slip has been reported in the literature. Some of them utilize dynamical models of the vehicle where side-slip angles are important inputs. This paper describes an off-line estimator for the side-slip angles of an articulated vehicle based on measurements from Global Positioning System (GPS) and Inertial Navigation System (INS). The current implementation is a proof of concept and the intention is to develop a system that can be used as a reference for on-line estimators. By comparing measurements from two GPS/INS units, mounted on the front and rear part of the vehicle, it is possible to estimate the side-slip angles of both the front and rear part. The method has been tested on a Volvo A25E articulated all-wheel drive hauler equipped with two high precision GPS/INS units (NovAtel's SPAN-CPT). Tests have been performed when driving on asphalt, gravel and snow. The results from the tests are discussed.

  • 9.
    Andersson, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Broström, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tyre parameter estimation based on control of individual wheel drives2014In: International Journal of Vehicle Autonomous Systems, ISSN 1471-0226, E-ISSN 1741-5306, Vol. 12, no 3, p. 247-265Article in journal (Refereed)
    Abstract [en]

    This paper describes a method to estimate tyre parameters for traction control applications based on control of individual wheel drives. The tyre parameters that are estimated are the rolling radius in driven mode (i.e. the rolling radius when the input torque to the wheel is zero) and the tyre longitudinal elasticity factor. The rolling radius in driven mode and the tyre longitudinal elasticity factor depend on several factors, among them the normal load. An important property of the method is that no transfer of load occurs during the estimation phase since the actual velocity of the vehicle is kept constant. Results from tests with ArtiTRAX, a 240 kg electric vehicle that carries 80 kg extra weight in three different front axle and rear axle distributions, are presented.

  • 10.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Cervantes, Michel J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Maximum power point tracking for micro hydro power plants using extremum seeking control2015In: 2015 IEEE International Conference on Control Applications (CCA 2015): Sydney, Australia, September 21-23 2015, Piscataway, NJ: IEEE Communications Society, 2015, p. 1874-1879, article id 7320883Conference paper (Refereed)
    Abstract [en]

    In this work, we propose using extremum seeking control (ESC) as a tool for maximum power point tracking in micro hydro power plants. The phasor ESC, which is based on estimating the phasor of the plant output at the perturbation frequency, was modified by stimating the phasors of multiple harmonics of this frequency. This modification will improve the performance of ESC by reducing the luctuations in control variables that may appear in noisy environments as a result of high-amplitude perturbation signals. A test rig was used to experimentally verify the proposed approach and to demonstrate the usability of ESC in hydro power plants.

  • 11.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Cervantes, Michel J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Phasor Extremum Seeking and its Application in Kaplan Turbine Control2014In: 2014 IEEE International Conference on Control Applications (CCA 2014): Juan Les Antibes, France, 8 -10 October 2014, Piscataway, NJ: IEEE Communications Society, 2014, p. 298-303Conference paper (Refereed)
    Abstract [en]

    The Combinator is an important part in Kaplan turbine control. It ensures that the turbine will operate in an optimum way, in terms of maximum efficiency of the plant. This work suggests a new sinusoidal perturbation based extremum seeking algorithm based on the phasor of the output. We propose to use this algorithm for generating the required data to build and correct the combinator. Simulations are presented showing the applicability of the proposed methods.

  • 12.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Accuracy Improvement of Extremum Seeking Control2017In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 62, no 4, p. 1952-1958, article id 7498657Article in journal (Refereed)
    Abstract [en]

    In this work, we present a modification for theclassic and phasor extremum seeking control algorithms in orderto improve the accuracy by removing or reducing the convergenceerror. The modulation signals were replaced by a sum of sinusoidsin order to remove the equilibrium shift in the controlled variableof the averaged system. The convergence error is calculated as afunction of the number of sinusoids used in the modulation signal.A simulation example is presented to illustrate the improvement.

  • 13.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Control oriented modeling of flow and size distribution in cone crushers2014In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 56, p. 81-90Article in journal (Refereed)
    Abstract [en]

    This work presents a dynamic model for prediction of flow and output size distribution of cone crushers. The main purpose of the model is for simulation of closed-loop control using the Closed Side Setting (CSS) and the eccentric speed (ω) as manipulated variables. The idea of modeling crushers as cascaded zones is adopted throughout this work. The capacity, the length, the stroke, and the compression ratio of each zone are taken into consideration. Simulation results are presented in the form of the Crusher Performance Map (CPM) and the dynamic response for production of different size classes to steps input in ω and CSS. The simulations also include operation with recycling of oversize output, as well as the input of mixed materials. As an example, closed-loop control of the ratio of the large-size output to the total size output was simulated.

  • 14.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Extremum seeking control based on phasor estimation2015In: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 85, p. 37-45Article in journal (Refereed)
    Abstract [en]

    We present an extremum seeking control algorithm based on the estimation of the phasor of the perturbation frequency in the output of the plant. The phasor estimator is based on a continuous time Kalman filter, which is reduced into a variable gain observer by explicitly solving the special case of the Riccati equation. Local stability of the proposed al- gorithm for general non-linear dynamic systems using averaging and singular perturbations is presented for the single input case. The advantage of the presented algorithm is that it can be used on plants with large and even variable phase lag.

  • 15.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On the stability analysis of phasor and classic extremum seeking control2016In: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 91, p. 55-62Article in journal (Refereed)
    Abstract [en]

    In this work we present a semi-global practical asymptotic stability analysis for phasor extremum seeking control with a general non-linear dynamic system. With the same technique applied to the classic band pass filter algorithm, we present a more relaxed (less constrained) semi-global practical asymptotic stability condition compared to earlier work. The results are based on a non approximated averaging for both control techniques.

  • 16.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On-Line Optimization of Cone Crushers using Extremum-Seeking Control2013In: 2013 IEEE Multi-conference on Systems and Control (Conference on Control Applications), Hyderabad, India, August 28-30, 2013, 2013, p. 1054-1060Conference paper (Refereed)
    Abstract [en]

    This article demonstrates the ability of on-lineoptimization of cone crushers, specifically maximization of thetotal throughput of the crusher by adjusting the eccentric speed(ω). The on-line optimization was based on the Extremum-Seeking Control (ESC) approach, which is advantageous whenoptimizing systems with unknown time varying characteristics.Two types of gradient based approaches are tested in simulation,the traditional Band-pass filters method and a methodutilizing the Extended Kalman Filter (EKF). Both methodsperform satisfactory, demonstrating the good potential of ESCfor online-optimization of cone crushers. To deal with unwantedbehavior of the EKF based approach for situations when thegradient is not correctly estimated, a modification is suggestedbased on detecting this condition and accommodating for it.

  • 17.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Pareto Seeking Control: On-line multi-objective optimization of dynami systems2014Conference paper (Other academic)
  • 18.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Pareto Seeking Control: On-line multi-objective optimization of dynami systems2014Conference paper (Refereed)
  • 19. Björkman, Eric
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Method for controlling drying of wood2015Patent (Other (popular science, discussion, etc.))
  • 20. Björkman, Eric
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Björkman, Peder
    Method for determining an action2015Patent (Other (popular science, discussion, etc.))
  • 21.
    Broström, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Andersson, Ulf
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Scale-Model Articulated Vehicle with Individual Wheel Drives for Traction Control Studies2014Conference paper (Other academic)
  • 22.
    Broström, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Andersson, Ulf
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Scale-Model Articulated Vehicle with Individual Wheel Drives for Traction Control Studies2015In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 10, no 3, p. 305-319Article in journal (Refereed)
    Abstract [en]

    Small scale model vehicles have been successfully used in multiple projects for research and for evaluation of models. ArtiTRAX, an experimental platform designed at Luleå University of Technology, is introduced to study the behaviour of articulated vehicles with individually driven wheels. Three case studies are presented: energy efficiency due to load transfer, online tyre parameter estimation and articulation angle control. The platform was shown to be a valuable asset for research in this area. It gives insight into the problem of controlling overactuated systems and the design hazard of using multiple integrators. ArtiTRAX is shown to be controllable through a kinematic model by only using actuation of the wheel drives. The difference of energy consumption as a function of longitudinal torque distribution indicates that the effectiveness of the motors should be considered when controlling the motor currents. The lateral distribution of motor current as a function of the articulation angle has to be considered in order to minimise the energy consumption of an articulated vehicle. Further research is necessary for understanding the mechanisms and relations between the energy consumption and the controlled motor currents

  • 23.
    Broström, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Optimization of a Quarter Vehicle Model2016In: 24th Mediterranean Conference on Control and Automation (MED), Piscataway, NJ: IEEE Communications Society, 2016, p. 485-489, article id 7535963Conference paper (Refereed)
    Abstract [en]

    This paper presents a quarter vehicle model that is currently being used in optimization for energy-efficient control. The model uses the contact-point tyre model approach together with the mapped behaviour of the powertrain to generate an approximate behaviour of the target vehicle. The model is used to optimize two driving cases. The model shows promising results and is believed to enable future research in optimal control of articulated vehicles.

  • 24.
    Delshad, Saleh Sayyad
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nonlinear observer design for a class of Lipschitz time-delay systems with unknown inputs: LMI approach2011In: Proceedings of the XXIII International Symposium on Information, Communication and Automation Technologies. (ICAT-2011), Piscataway, NJ: IEEE Communications Society, 2011Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider a method to design a full-order nonlinear observer for a class of nonlinear time-delay systems with unknown inputs. Based on Lyapunov-Krasovskii functional, we derive a sufficient condition for existence of the designed observer which requires solving a set of nonlinear matrix inequalities. Then, the achieved condition is formulated in terms of two linear matrix inequalities (LMIs). Finally, the proposed observer is illustrated with an example.

  • 25. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Control of a delay system using robust finite-dimensional controller2001In: CSEE '2001: Conference Proceedings, Luleå tekniska universitet, 2001Conference paper (Other academic)
  • 26. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Dynamic modeling of flotation circuits2000In: Future Trends in Automation in Mineral and Metal Processing: a proceedings volume from the IFAC workshop / MM 2000, Finland, 22-24 August 2000 / [ed] Sirkka-Liisa Jämsä-Jounela, Kidlington: Pergamon Press, 2000, p. 197-202Conference paper (Refereed)
  • 27. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Dynamic modeling of flotation circuits2000In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, p. 197-202Article in journal (Refereed)
    Abstract [en]

    The modeling of flotation is a difficult task due to the influences of mineralogical features of ores, floatability of various minerals governed by pulp environments, flotation kinetics and hydrodynamic variables. In the paper the dynamic modeling of flotation is studied. Based on the first order flotation rate equation, the dynamic description of a continuous flotation process is obtained both for a single continuous flotation cell and n cells arranged in series. A dynamic model for the multi-component case of continuous flotation is also discussed. The models obtained give the dynamic behaviors when the flotation parameters are changed due to the variation of the chemical and physical environment

  • 28. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Modelling and control of a flotation process1999In: Control and optimization in minerals, metals and materials processing: proceedings of the International Symposium on Control and Optimization in Minerals, Metals and Materials Processing ; [part of the] 38th Annual Conference of Metallurgist of CIM, 38e Conférence Annuelle des Métallurgistes de l'ICM - [theme:] gateway to the 21st century - Aux portes du 21e siècle, August 22 - 26 Août, 1999, Québec City, Québec, Canada / [ed] D. Hodouin; C. Bazin; A. Desbiens, Montreal: MetSoc , 1999, p. 285-298Conference paper (Refereed)
    Abstract [en]

    A general description of a flotation process is given. The dynamic model of a MIMO nonlinear subprocess in flotation, i.e. the pulp levels in five compartments in series is developed and the model is verified with real data from a production plant. In order to reject constant disturbances five extra states are introduced and the model is modified. An exact linearization has been made for the non-linear model and a linear quadratic Gaussian controller is proposed based on the linearized model. The simulation result shows an improved performance of the pulp level control when the set points are changed or a disturbance occur. In future the controller will be tested in production

  • 29. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Robustness of a pulp level control system2000In: Reglermöte: preprints, Uppsala, 2000Conference paper (Other academic)
  • 30. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Model identification of a nonlinear subprocess in a continuous paper pulp digester2006In: Measurement and control - applications for the operator: Control Systems 2006, June 6-8, 2006, Tampere Finland / [ed] Risto Ritala, Finnish Society of Automation , 2006Conference paper (Refereed)
  • 31. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Model parameter estimation of simplified linear models for a continuous paper pulp digester2007In: Journal of Process Control, ISSN 0959-1524, E-ISSN 1873-2771, Vol. 17, no 2, p. 115-127Article in journal (Refereed)
    Abstract [en]

    A physical model of a continuous paper pulp digester is simplified and two subprocesses selected from the digester are modelled by coupled linear partial differential equations. This study focuses on the parameter identification of the simplified linear models. Finite-dimensional approximation of the model is made and a software package developed for identification of distributed parameter processes is applied. This identification system is developed for flexibility to allow identification for different choices of subprocesses and process variables. Unknown parameters of the subprocess models are estimated and the results are illustrated by process simulation and model validation.

  • 32. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Physical model parameter estimation of a nonlinear process2007In: Proceedings of the 2006 IEEE International Conference on Control Applications Applications: Munich, Germany, 4 - 6 October 2006, Piscataway, NJ: IEEE Communications Society, 2007, p. 2933-2938Conference paper (Refereed)
    Abstract [en]

    A physical model of a nonlinear subprocess in a continuous paper pulp digester is discussed and simplified. Model approximation is carried out in order to produce a simple linear model to be used for unknown parameter estimation of the physical model. The Taylor series expansion and the orthogonal collocation method are applied for the model linearization and model lumping, respectively. The reduced model is expressed as a standard state space form. The model parameters are estimated in the least squares sense, and the parameters retain their own physical meanings. The results of the parameter estimation are discussed and the model is verified using validation data.

  • 33. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Su, F
    Luleå tekniska universitet.
    Fuzzy logic control of flotation process1998In: Reglermöte '98: preprints, Lund: Reglerteknik, Lunds tekniska högskola , 1998Conference paper (Other academic)
  • 34. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Su, Fenwei
    Luleå tekniska universitet.
    Application of fuzzy control to a flotation process1999In: Proceedings of the 14th World Congress: International Federation of Automatic Control : Beijing, P.R. China, 5 - 9 July 1999 / [ed] Han-Fu Chen, Kildington: Publ. for the International Federation of Automatic Control by Pergamon, , 1999, p. 391-396Conference paper (Refereed)
    Abstract [en]

    The application of fuzzy logic in the control of flotation is studied in this paper. A general description of apatite flotation process is given and a dynamic model is developed. A fuzzy logic controller is proposed for a nonlinear isolated continuous flotation process. The knowledge base of the controller is constructed on the basis of the semi-batch results from the apatite flotation experiments and available knowledge sources. The design of the controller does not need an exact process model. The simulation result shows that the fuzzy logic controller can reduce collector dosage consumption of the apatite flotation process while maintaining the phosphorous content in magnetite concentrate within an acceptable limits less than 0.025% P. Stability of the fuzzy control system is discussed

  • 35. Ding, Limei
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Su, Fenwei
    Luleå tekniska universitet.
    Application of fuzzy control to a flotation process1999In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 32, no 2, p. 6998-7003Article in journal (Refereed)
    Abstract [en]

    The application of fuzzy logic in the control of flotation is studied in this paper. A general description of apatite flotation process is given and a dynamic model is developed. A fuzzy logic controller is proposed for a nonlinear isolated continuous flotation process. The knowledge base of the controller is constructed on the basis of the semi-batch results from the apatite flotation experiments and available knowledge sources. The design of the controller does not need an exact process model. The simulation result shows that the fuzzy logic controller can reduce collector dosage consumption of the apatite flotation process while maintaining the phosphorous content in magnetite concentrate within an acceptable limits less than 0.025% P. Stability of the fuzzy control system is discussed

  • 36. Ding, Limei
    et al.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Application of reduced models for robust control and state estimation of a distributed parameter system2009In: Journal of Process Control, ISSN 0959-1524, E-ISSN 1873-2771, Vol. 19, no 3, p. 539-549Article in journal (Refereed)
    Abstract [en]

    This paper studies the application of reduced models of a distributed parameter system for robust process control and state estimation. We take the approach of integrating model reduction, parameter identification, and model uncertainty analysis, in purpose to find an appropriate trade-off between complexity and robust performance. The application example is the temperature system in a continuous paper pulp digester. Physical modeling of this process results in coupled linearized partial differential equations which are then reduced into low-order nominal process models using an orthogonal collocation approximation method.Two different approaches to obtaining a model uncertainty description are adapted for use on a distributed parameter system with low-order nominal model and shown to produce similar results when tested with measurement data. It is also demonstrated how this uncertainty description, in combination with the reduced model, may be used for robust control design and verification of the control performance on the distributed parameter system.Finally, the possibility of estimating the distributed process state using a state observer for the reduced process is demonstrated. Measurements of the process state in a certain position is available and is shown to agree with the estimated state at the same position.

  • 37. Fakharian, Ahmad
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An iterative-LMI based H2 control of singular perturbation systems2011In: 2011 IEEE International Conference on Control Applications (CCA): 28 - 30 Sept. 2011, Denver, Colorado, USA ; part of 2011 5th IEEE Multi-Conference on Systems and Control (MSC) / [ed] Jagannathan Sarangapani, Piscataway, NJ: IEEE Communications Society, 2011, p. 1505-1509Conference paper (Refereed)
    Abstract [en]

    In this paper an iterative LMI based approach for solving the H2 control problem using static state feedback for singular perturbation systems is proposed. The proposed controller is given in terms of the solution of a set of matrix inequalities independent of singular parameter . These inequalities are not in the form of linear matrix inequalities (LMI). By introducing a new iterative algorithm, these inequalities are solved through iterative LMI formulation. To show the effectiveness of the proposed algorithm comparing to other standard time-scale decomposition methods, an illustrative example is also provided

  • 38. Fakharian, Ahmad
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    H2 static state feedback control or linear singular perturbation systems: a new approach2011In: 2011 Canadian Conference on Electrical and Computer Engineering, CCECE 2011: May 8-11 2011, Niagara Falls, Ontario, Canada, Piscataway, NJ: IEEE Communications Society, 2011, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this paper a new approach for solving the H2 control problem using static state-feedback for LTI singular perturbation systems is proposed which achieves a minimum bound on the H2 performance level of closed-loop system. The proposed controller is given in terms of the solution of a set of matrix inequalities independent of singular parameter . These inequalities are not in the form of linear matrix inequalities (LMI). By introducing a new algorithm, these inequalities are solved through LMI formulation. To show the effectiveness of the proposed algorithm comparing to other standard time-scale decomposition methods, an illustrative example is also provided.

  • 39.
    Fakharian, Ahmad
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Khanian, M. Yousefi Azar
    Islamic Azad University.
    A new approach on H-infinity control of linear singular pertubation systems2011In: 2011 9th IEEE International Conference on Control and Automation (ICCA 2011): Santiago, Chile, 19 - 21 December 2011, Piscataway, NJ: IEEE Communications Society, 2011, p. 969-973Conference paper (Refereed)
    Abstract [en]

    In this paper a new approach for solving the H∞ control problem using static state-feedback for LTI singular perturbation systems is proposed. The proposed controller is given in terms of the solution of a set of matrix inequalities independent of singular parameter . These inequalities are not in the form of linear matrix inequalities (LMI). By introducing a new algorithm, these inequalities are solved through LMI formulation. To show the effectiveness of the proposed algorithm comparing to other methods, an illustrative example is also provided.

  • 40. Fakharian, Ahmad
    et al.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Mehrfam, Mohsen
    Department of Electrical and Computer Engineering, Islamic Azad University.
    Adaptive Kalman filtering based navigation: an IMU/GPS integration approach2011In: Proceedings of the 8th IEEE International Conference on Networking, Sensing and Control: Delft, The Netherlands, 11-13 April, 2011, Piscataway, NJ: IEEE Communications Society, 2011, p. 181-185Conference paper (Refereed)
    Abstract [en]

    This paper investigates on the development and implementation of a high integrity navigation system based on the combined use of the Global Positioning System (GPS) and an inertial measurement unit (IMU) for land vehicle applications. The complementary properties of the GPS and the INS have motivated several works dealing with their fusion by using a Kalman Filter. The conventional kalman filter has a fix error covariance matrix in all times of processing. Multi-sensor based navigation system that is implemented in this paper is called data synchronization. Also, multi-rate operations that are compared with conventional Kalman filtering has fix error covariance matrix. Therefore, when GPS outage occurred we have improper treat by kalman filter. In this paper we present an Adaptive method instead of conventional methods. It is shown that proposed method has a better performance rather than conventional method. Experimental results show the effectiveness of the GPS/INS integrated system.

  • 41.
    Fakharian, Ahmad
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hosseini, Saman
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hybrid object detection using improved Gaussian mixture model2011In: 11 International Conference on Control, Automation and Systems (ICCAS2011): 26-29 October 2011, Kintex, Korea, Piscataway, NJ: IEEE Communications Society, 2011, p. 1475-1479Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a novel approach to detect moving objects in a complex background. The Gaussian mixture model (GMM) is an effective way to extract moving objects from a video sequence. However, the conventional mixture Gaussian method suffers from false motion detection in complex backgrounds and slow convergence. This work, in order to achieve robust and accurate extraction of the shapes of moving objects, applies a hybrid method to remove noise from images. The proposed model consists of two stages. The first stage consists of a fourth order PDE and the second stage is a relaxed median Experimental results show that the proposed model performs well even in the presence of higher levels of noise.

  • 42. Fakharian, Ahmad
    et al.
    Hosseini, Saman
    Islamic Azad University.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Precise hybrid motion detection and tracking in dynamic background2011In: The 19th Mediterranean Conference on Control and Automation (MED2011): June 20-23, 2011, Corfu, Greece, Piscataway, NJ: IEEE Communications Society, 2011, p. 1398-1402Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel and robust algorithm, for multiple motion detection and tracking in dynamic and complex scenes. The algorithm consists of two steps: at first, we use a robust algorithm for human detection. Then, Gaussian mixture model (GMM), Neighborhood-based difference and Overlapping-based classification are applied to improve human detection performance .The conventional mixture Gaussian method suffers from false motion detection in complex backgrounds and slow convergence. We combine three above mentioned methods to obtain detection. The second step of the proposed algorithm is object tracking framework based on Kalman filtering which works well in dynamic scenes. Experimental results show the high performance of the proposed method for multiple object tracking in complex and noisy backgrounds.

  • 43.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Generalized Reduced-Complexity Inertial Navigation System for Unmanned Aerial Vehicles2017In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 25, no 1, p. 192-207Article in journal (Refereed)
    Abstract [en]

    In this paper, a generic approach to attitude and position estimation, suited for any type of unmanned aerial vehicle, is presented. This will be achieved by establishing a generic framework, which can be extended using adaptive methods to determine the thrust properties of the engines and the mass of the aircraft, while keeping the overall computational complexity of the system low. Furthermore, the effect of magnetic disturbances will be reduced in a novel way by confining the magnetic errors to affect only heading, without compromising the pitch and roll estimation of the system with error-based estimation. The efficacy of the proposed framework will be evaluated through extended simulations and experimental validations on a multirotor. Finally, guidelines will be provided toward: 1) an implementation with a reduced computational complexity and 2) the utilization of the square-root formulations of the extended Kalman filter for extending the dynamic range of the filter.  

    The full text will be freely available from 2019-01-01 08:56
  • 44.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A survey of crane automation projects2001Other (Other academic)
  • 45.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Activity: Institute of Instrumentation Control and Automation2001Conference paper (Other (popular science, discussion, etc.))
  • 46.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Adaptiv reglering av klimatanläggningar1984Report (Other academic)
  • 47.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Automatisering av kranar1991In: Proceedings, Robotikdagar. Robotteknik och verkstadsteknisk automation: mot ökad autonomi, 1991Conference paper (Refereed)
  • 48.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Introduction to Modelica: An object-oriented language for modelling complex physical systems2011Conference paper (Other academic)
    Abstract [en]

    Modelica is an object-oriented language that is developed with the goal to be a convenient tool for modelling the dynamical behaviour of complex technical systems consisting of of components from different domains such as mechanical, optical, electrical, thermal, hydraulic, pneumatic, fluid, control and others. The object-oriented properties of the modelling language facilitates the writing of general model libraries that can easily be expanded and modied. The language is equation-based and it is easy to mix differential, algebraic and discrete equations with algorithms. The paper presents an overview of Modelica and demonstrates the usage of Modelica for simulation and optimisation.

  • 49.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Modelling and control of a rotary crane1995In: Proceedings of the Third European Control Conference: ECC 95, 1995, Vol. pt. 4, vol.4, p. 3805-3810Conference paper (Refereed)
    Abstract [en]

    This paper deals with the feedback control of a rotary crane. The goal is to design a control system that assists the operator to move the cargo without oscillations and correctly align the cargo at the final position. This is accomplished by a weakly coupled pair of state feedback controllers with a nonlinear compensator.

  • 50.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Modelling and control of rotary crane systems1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is devoted to the modelling and control of rotary crane systems. The goal is to design a control system that assists the operator to move a cargo without oscillations and to correctly align the cargo at the final position. The control system is divided into two independent parts, one dealing with the alignment of the load with the aid of a power swivel or a cargo rotating device, and a second that deals with the elimination of load oscillations. Both design and implementation of the control algorithms on a full scale crane are considered. In the cargo alignment system a linear cascade controller is considered that is shown to have near time-optimal performance for a system with saturation in both the angle and the angular rate of the power swivel. In the second part a weakly coupled pair of state feedback controllers with a nonlinear compensator is used to eliminate the load oscillations in two dimensions. In the third part of the thesis a software tool for simulation and real time control is presented. The development of the program started as a spin-off to the crane projects.

123 1 - 50 of 128
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