Ändra sökning
Avgränsa sökresultatet
1234567 51 - 100 av 736
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51.
    Andrikopoulos, Georgios
    et al.
    University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    University of Patras.
    An experimental study on thermodynamic properties of pneumatic artificial muscles2012Ingår i: 2012 20th Mediterranean Conference on Control & Automation: Barcelona, Spain, July 3-6, 2012, Piscataway, NJ: IEEE Communications Society, 2012, s. 1334-1340Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the past fifty years, several attempts have been made to model the characteristics of Pneumatic Artificial Muscles (PAMs). PAM models based on their geometrical properties are the most commonly found ones in the scientific literature. In the process of deriving those models a lot of assumptions and simplifications are made due to the fact that PAM is a highly non-linear form of actuation. The purpose of this study is to propose additional considerations for future model improvements that will augment the overall model accuracy, and will best describe the relationship between force, displacement and non-linear thermal properties of PAM actuators through extensive observation and analysis of its thermodynamic characteristics during long-run operation experiments. In this article multiple experimental results will be presented that prove the relation between the thermodynamic properties of the PAMs, especially in iterative operations, and the accuracy on the muscle's force-prolongation relationship.

  • 52.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Design and Development of an Exoskeletal Wrist Prototype via Pneumatic Artificial Muscles2015Ingår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 50, nr 11, s. 2709-2730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Full or partial loss of function in the shoulder, elbow or wrist is an increasingly common ailment caused by various medical conditions like stroke, occupational and sport injuries, as well as a number of neurological conditions, which increases the need for the development and improvement of upper limb rehabilitation devices. In this article, the design and implementation of the EXOskeletal WRIST (EXOWRIST) prototype is presented. This novel robotic appliance’s motion is achieved via pneumatic artificial muscles, a pneumatic form of actuation possessing crucial attributes for the development of an exoskeleton that is safe, reliable, portable and low-cost. Furthermore, the EXOWRIST’s properties are presented in detail and compared to the recent wrist exoskeleton technology, while its two degrees-of-freedom movement capabilities (extension-flexion, ulnar-radial deviation) are experimentally evaluated via a PID- based control algorithm. Experimental results involving initial testing of the proposed exoskeleton on a healthy human volunteer for the preliminary evaluation of the EXOWRIST’s attributes are also presented.

  • 53.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Electrical and Computer Engineering Department, University of Patras.
    Development and control of a hybrid controlled vertical climbing robot based on pneumatic muscle actuators2011Ingår i: Journal of Control Engineering and Technology (JCET), ISSN 2223-2036, Vol. 1, nr 2, s. 53-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article presents the development and control of a novel hybrid controlled vertical climbing robot based on Pneumatic Muscle Actuators (PMAs). PMAs are highly non–linear pneumatic actuators where their elongation is proportional to the internal pressure. The vertical sliding of the robot is based on four PMAs and through the combined and sequential contraction–extension of the pneumatic muscles and cylinders, upward and downward movements are executed. For controlling the movement of the robot and to cope with the high non–linearities of the system, a simplified and highly functional hybrid control scheme, based on PID and On/Off control, has been adopted. The efficacy of the proposed scheme is presented through multiple experimental results where it is shown that the utilized controller is able to provide fast (on/off) and accurate (PID) translations to the robot.

  • 54.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Incorporation of Thermal Expansion in Static Force Modeling of Pneumatic Artificial2015Ingår i: IEEE Mediterranean Conference on Control and Automation, Torremolinos, Spain, June, 16-19, 2015 / [ed] V. Munoz, Piscataway, NJ: IEEE Communications Society, 2015, s. 414-420, artikel-id 7158784Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the thermal expansion effect is considered as the main cause of the gradual shift in the force- displacement relationship, which describes the operation of Pneumatic Artificial Muscles (PAMs). A modified static force modeling approach is proposed, based on fundamental PAM modeling techniques, while incorporating the geometrical properties that are being affected by the thermal build-up occurring during PAM’s continuous operation. The effects of thermal expansion are documented via experimental studies and the acquired data are utilized for the validation of the proposed modeling method. Further evaluation is performed via comparison of modeling accuracy between the proposed modeling approach and the fundamental static force modeling techniques.

  • 55.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Motion control of a novel robotic wrist exoskeleton via pneumatic muscle actuators2015Ingår i: Proceedings of 2015 IEEE 20th International Conference on Emerging Technologies & Factory Automation (ETFA 2015): Luxembourg, 8-11 Sept. 2015, Piscataway, NJ: IEEE Communications Society, 2015, artikel-id 7301464Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the motion control problem of a robotic EXOskeletal WRIST (EXOWRIST) prototype is considered. This novel robotic appliance’s motion is achieved via pneumatic muscle actuators, a pneumatic form of actuation possessing crucial attributes for the development of an exoskeleton that is safe, reliable, portable and low-cost. The EXOWRIST’s properties are presented in detail and compared to the recent wrist exoskeleton technology, while its two degrees- of-freedom movement capabilities (extension-flexion, ulnar- radial deviation) are experimentally evaluated on a healthy human volunteer via an advanced nonlinear PID-based control algorithm.

  • 56.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Non-linear control of pneumatic artificial muscles2013Ingår i: 21st IEEE Mediterranean Conference on Control and Automation, June 25-28, Platanias, Chania, Crete, Greece, 2013, 2013, s. 729-734, artikel-id 6608804Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the control problem of Pneumatic Artificial Muscles is being considered. A non-linear PID structure is being synthesized, providing ameliorated compensation of the PAMs’ non-linear hysteretic phenomena and advanced robustness. Experimental studies are being utilized to prove the overall efficiency of the proposed control scheme regarding: a) set-point tracking performance for the position control of a single PAM and torsion angle control of an antagonistic PAM setup, as well as b) disturbance rejection in both single and antagonistic control scenarios.

  • 57.
    Andrikopoulos, Georgios
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras , Electrical and Computer Engineering Department, University of Patras.
    Novel Considerations on Static Force Modeling of Pneumatic Muscle Actuators2016Ingår i: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, Vol. 21, nr 6, s. 2647-2659, artikel-id 7501612Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, an overview of the most significant static force modeling approaches of Pneumatic Muscle Actuators (PMAs) is presented, while a modified static force modeling approach, which is based on fundamental PMA modeling techniques, is proposed. In addition, the thermal expansion effect is considered as the main cause of the gradual shift in the PMA’s force-displacement relationship and the geometric properties, which are being affected by the thermal build-up occurring during PMA’s continuous operation, are incorporated into the static force models. The effects of thermal expansion are documented via experimental studies and the acquired force-displacement data are utilized for the validation of the proposed modeling method in PMAs of different nominal dimensions and at constant test pressures. Finally, an additional evaluation is performed via the comparison of the accuracy between the proposed model and the existing geometric static modeling approaches.

  • 58.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Pneumatic artificial muscles: a switching model predictive control approach2013Ingår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 21, nr 12, s. 1653-1664Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, a switching Model Predictive Controller (sMPC) for a Pneumatic Artificial Muscle (PAM) is presented. The control scheme is based on a switching PieceWise Affine (PWA) system model approximation that is able to capture the high nonlinearities of the PAM, while improving the overall model accuracy, and is composed of: a) a feed-forward term regulating control input at specific reference set-points, and b) a switching Model Predictive Controller handling any deviations from the system’s equilibrium points. Extended experimental studies are being presented that prove the overall scheme’s efficiency.

  • 59.
    Antonino-Daviu, José Alfonso
    et al.
    Institute for Energy Engineering, Universitat Politecnica de Valencia.
    Climente-Alarcón, Vicente
    Institute for Energy Engineering, Universitat Politecnica de Valencia, Aalto University.
    Tsoumas, Ioannis P.
    Siemens Industry Sector, Automation and Drives.
    Georgoulas, Georgios
    Department of Informatics and Communications, Technology TEI of Epirus.
    Pérez, Rafaël B.
    Department of Nuclear Engineering, University of Tennessee, Knoxville.
    Multi-harmonic tracking for diagnosis of rotor asymmetries in wound rotor induction motors2013Ingår i: IECON Proceedings (Industrial Electronics Conference), Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2013, s. 5555-5560, artikel-id 6700043Konferensbidrag (Refereegranskat)
    Abstract [en]

    Most of the research work hitherto carried out in the induction motors fault diagnosis area has been focused on squirrel-cage motors in spite of the fact that wound-rotor motors are typically less robust, having a more delicate maintenance. Over recent years, wound-rotor machines have drawn an increasing attention in the fault diagnosis community due to the advent of wind power technologies for electricity generation and the widely spread use of its generator variant, the Doubly-Fed Induction Generators (DFIGs) in that specific context. Nonetheless, there is still a lack of reliable techniques suited and properly validated in wound-rotor industrial induction motors. This paper proposes an integral methodology to diagnose rotor asymmetries in wound-rotor motors with high reliability. It is based on a twofold approach; the Empirical Mode Decomposition (EMD) method is employed to track the low-frequency fault-related components, while the Wigner-Ville Distribution (WVD) is used for detecting the high-frequency failure harmonics during a startup. Experimental results with real wound-rotor motors demonstrate that the combination of both perspectives enables to correctly diagnose the failure with higher reliability than alternative techniques relying on a unique informational source

  • 60.
    Arranz, Miguel Castano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Robust methods for control structure selection in paper making processes2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Process industries have to operate in a very competitive and globalized environment, requiring efficient and sustainable production processes. As a result, production targets need to be translated into control objectives which are usually formulated as performance specifications of the process, i.e. tracking of references or rejection of process disturbances. This is often a hard and difficult task which involves assumptions and simplications because of the process complexity. Complexity arises often due to the large scale character of a process, i.e. a pulp and paper can host thousands of control loops. A critical step in the design of these loops is the choice of the structure of the control, which means that controllers need to be placed between sensors and actuators.Current methods for control structure selection include the Interaction Measures (IMs). The IMs help the designer to select a subset of the most significant input-output channels, which will form a reduced model on which the control design will be based. The IMs are traditionally evaluated using a nominal model of the process. However, all process models are affected by uncertainties as simplifications and approximations are unavoidable during modeling. Thus, the validity of the control structure suggested by the IMs cannot be assessed by only analyzing the nominal model. The first part of this thesis focuses in analyzing the sensitivity of the IMs to model uncertainties in order to determine a robust control structure which is feasible for all the uncertainty set.It also becomes clear that, control structure selection requires extensive knowledge about how the multiple process variables are interconnected. The second part of this thesis focuses on creating IMs which can help the control designers to understand the propagation of effects in the process, and express this propagation in directed graphs for an intuitive understanding of the process which will help to design a feasible control structure. These methods have been inspired by coherence analysis used in brain connectivity.Neurons and neural populations interact with each other in different brain processes related to events as perception, or cognition. Electroencephalography (EEG) is a measure of electrical activity in the brain which is acquired from sensors positioned on the surface of the head, each of the electrodes collects the aggregated voltage of a neuron population. Analyzing the flow of information between populations of neurons allows to understand the communication between different parts of the brain in different brain processes. In a very similar way, analyzing the flow of information between variables in an industrial process will provide designers with the required information to understand the behavior of the plant.

  • 61.
    Arranz, Miguel Castaño
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Practical tools for the configuration of control structures2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Process industries have to operate in a very competitive and globalized environment, requiring efficient and sustainable production processes. Production targets need to be translated into control objectives and are usually formulated as performance specifications of the process. The controller design is a difficult task which involves assumptions and simplifications because of the process complexity. Complexity arises often due to the large scale character of a process, i.e. a pulp and paper mill which can be composed by thousands of control loops. A critical step is the choice of the control configuration, which involves choosing a set of measurements to be used to calculate the control action for each actuator.Current methods for Control Configuration Selection (CCS) include Interaction Measures (IMs). The probably most widely used IM dates back to 1966 when the Relative Gain Array (RGA) was introduced by Bristol. However, these methods rarely become applied in industry, where control structures are often designed based on previous experience or common sense in interpreting process knowledge, but without the support of theoretical and systematic tools.The work in this thesis is oriented towards the development of these tools for industry application. Several topics on CCS are addressed to deal with this lack of practical use, including the robustness to model uncertainty, the need of parametric process models of the complex process, the lack of tools which present the information in connection to the process layout, and the delay from research to education and finally industry application.The main contribution of this thesis is on the consideration of model uncertainty in the CCS problem. Since uncertainty is an intrinsic property of all process models, the validity of the control configuration suggested by the IMs cannot be assessed by only analyzing the nominal model. This thesis introduces methods for the computation of the uncertainty bounds of two gramian-based IMs, which can be used to design robust control configurations.The requirement of process models is an important limitation for the use of the IMs, and the complexity of modeling increases with the number of process variables. This thesis presents novel results in the estimation of IMs, which aim to remove the need of parametric process models for the design of control configurations.CCS using IMs is a heuristic approach, being interpretation needed to select the process interconnections on which control will be based. The traditional IMs present information as an array of real numbers which is disjoint from the process layout. This thesis describes new methods for the interaction analysis of complex processes using weighted graphs, allowing integrating the analysis with process visualization for an increased process understanding.As final contribution, this thesis describes the development of the software tool ProMoVis (Process Modeling and Visualization), which is a platform in which state-of-the-art research in CCS is implemented for facilitating its use in industry applications.

  • 62.
    Arvanitakis, John
    et al.
    University of Patras, Department of Electrical and Computer Engineering.
    Nikolakopoulos, George
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Zermas, Demetris
    University of Patras, Department of Electrical and Computer Engineering.
    Tzes, Anthony
    University of Patras, Department of Electrical and Computer Engineering.
    On the adaptive performance improvement of a trajectory tracking controller for non-holonomic mobile robots2011Ingår i: 2011 IEEE Conference on Emerging Technologies & Factory Automation (ETFA 2011): Toulouse; 5 September - 9 September 2011, Piscataway, NJ: IEEE Communications Society, 2011, artikel-id 6059092Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article a novel performance improvement scheme is being presented for the problem of designing a trajectory tracking controller for non–holonomic mobile robots with differential drive. Based on the robot kinematic equations, an error dynamics controller is being utilized for allowing the robot to follow an a priori defined reference path, with a desired velocity profile. The main novelty of this article stems from the utilization of a gradient based adaptive scheme that is able to adapt the controller’s gain ruling the rising and settling time of the robot and up to now has been ad–hoc selected. The proposed adaptation scheme is based on the robot’s path tracking errors and is able to provide an on–line adjustment for the performance improvement, independently of the selected path type. Multiple experimental test cases, including the movement of the robot on various path profiles, prove the efficacy of the proposed scheme.

  • 63.
    Asheghan, Mohammad Mostafa
    et al.
    Universidad Carlos III de Madrid.
    Sayyaddelshad, Saleh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Beheshti, Mohammad Taghi Hamidi
    Control and Communication Networks Lab, Electrical Engineering Department, Tarbiat Modares University.
    Tavazoeid, Mohammad Saleh
    Electrical Engineering Department, Sharif University of Technology, Tehran.
    Non-fragile control and synchronization of a new fractional order chaotic system2013Ingår i: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 222, s. 712-721Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we address global non-fragile control and synchronization of a new fractional order chaotic system. First we inspect the chaotic behavior of the fractional order system under study and also find the lowest order (2.49) for the introduced dynamics to remain chaotic. Then, a necessary and sufficient condition which can be easily extended to other fractional-order systems is proposed in terms of Linear Matrix Inequality (LMI) to check whether the candidate state feedback controller with parameter uncertainty can guarantee zero convergence of error or not. In addition, the proposed method provides a global zero attraction of error that guarantees stability around all existing equilibrium points. Finally, numerical simulation are employed to verify the validity of the proposed algorithm.

  • 64.
    Asplund, Gunnar
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Datorstyrd rotationsdämpning vid containerhantering med gantrykran1988Rapport (Övrigt vetenskapligt)
  • 65.
    Atta, Khalid
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Extremum Seeking Control: Stability, Accuracy, and Applications2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In many applications, there is a variable that indicates the overall performance and that must be maximized, such as the output of a hydro power turbine or a mineral processing plant, or that must be minimized, such as CO2 emissions or the consumption of resources. Extremization of this variable (maximization or minimization) through adjusting the influencing manipulated variables is occasionally required without prior knowledge of the optimal values of the manipulated variables or of the optimized variable. Extremum seeking control (ESC), which is an on-line concept for the optimization of dynamic systems, can achieve this task.Many types of ESC have been proposed in the literature, and the majority of these approaches are based on the gradient descent optimization method. The most common type of ESC is the classic ESC, which is based on adding a sinusoidal perturbation to the manipulated variables followed by the use of a band pass filter (BPF) to find an estimate of the gradient of the output with respect to the input. The plant is then extremized by adjusting the manipulated variables to make this estimate approach zero.In this work, an alternative approach called phasor ESC is proposed, which is based on estimating the phasor of the plant output at the perturbation frequency rather than the gradient. Stability analysis of the phasor ESC is presented, including local and semi-global practical asymptotic stability for general non-linear dynamic plants. As an improvement of the existing stability analysis of the classic ESC, a less constrained semi-global practical asymptotic stability condition is also presented. In perturbation-based ESC, the output will continuously oscillate due to the input perturbation. As noted in the literature, the averaged system may not converge to the optimum point, and an average offset from the optimal value will emerge. This offset is negligible in the case of a small perturbation signal but will increase as the perturbation amplitude increases. In this work, a modification for the classic ESC and phasor ESC is proposed that improves the accuracy by reducing this offset. Two applications of ESC are considered: cone crushers and hydro power plants. Cone crushers are used for reducing the size of minerals and are considered to be a key component of many mineral processing plants. On-line optimization of the throughput is proposed based on the concept of ESC. A novel model of cone crushers is presented that can predict the flow and the size distribution of the output as a function of the primary manipulated variables, and simulations of ESC control on this model are presented.For hydro power plants, which are considered to be the most important source of renewable energy, phasor ESC is proposed for constructing and correcting the combinator, which ensures the optimal and efficient operation of the Kaplan turbine. Moreover, phasor ESC is proposed as a tool for maximum power point tracking in micro hydro plants by manipulating the turbine speed, and a test rig is used to conduct an experiment to validate this approach.

  • 66.
    Atta, Khalid
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Modeling and on-line optimization of cone crushers2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This licentiate thesis deals with the Modeling, Control, and On-line optimization of Cone Crushers. Cone crushers are used for size reduction of minerals and are considered as a central element in many mineral processing plants. It consists of a cone rotating eccentrically inside a larger bowl and the particles are crushed in the cavity between these. In spite of its simple construction, the cone crusher represents a complex system from a modeling point of view, as its operation comprises many physical actions that are combined together to give the overall behavior.The main purpose of the work is to have a dynamic model that can predict the ow and the size distribution of the crusher as a function of the main manipulated variables so that realistic simulation of closed loop control strategies can be achieved. The model is based on rst principles and includes many factors that are known to aect the operation of the crusher, e.g operation of the crusher with two dierent materials. For the control of the crusher, a number of dierent approaches were considered. First, a simple PI controller of the percentage of large material in the output produced was simulated. It is known and also predicted by the model that the cone crusher's total throughput depends on the Eccentric Speed, and exhibits a quasi-concave response with respect to this variable.On-line optimization of the throughput is suggested to be based on the concept of Extremum Seeking Control (ESC).Two dierent methods of ESC were applied. The classic Band Pass Filters based approach, and the Extended Kalman Filter Based approach. Both methods were modied in order to achieve improved performance. These modications can be applied on other plants as well. Simulations of the closed loop for the two methods have demonstrated the applicability of ESC for optimizing the crusher on-line. The optimum operating point was reached in all cases, leading to improvement of the performance of the crusher.

  • 67.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Utilization of Generic Consumer Modeling in Planning and Optimization of District Heating and Cooling Systems2018Ingår i: Proceedings of the 21st Nordic Process Control Workshop / [ed] Kurt-Erik Häggblom, 2018Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    District heating and cooling (DHC) networks are large scale complex systems which aregenerally difficult to operate and optimize. The large thermal inertia in the systems leadsto long reaction times on changes at the consumer side, which means that forecasting ofconsumer behaviour is a needed tool for efficient operation. Within the European Unionmany major research project target the energy reduction on the consumption side and peakload management while maintaining customer satisfaction.The optimal operation of a DHC network can therefore be considered as an interestingarea of investigation due to a number of aspects, like (i) the vast amount of the energy that is distributed by these networks, (ii) the demand to provide a better quality of services by the operators of these networks, and (iii) compliance with new environmental regulations. In this presentation, we discuss a possible conceptual method that utilizes a simpliedstatic model of different types of consumers in the network to design a decision supportsystem that will guide the operators of the DHC network to optimally operate the networkwith different operational scenarios that include but not limited to: (i) energy consumptionminimization, (ii) economic operation, (iii) peak load reduction/shifting, and (iv) environmentally friendly operation. In its current form, the operator will be informed, while in thefuture these actions could be fully automated in a closed loop context.The DHC network in Luleå, Sweden will be used as a test case which represents a typicalmedium size network. The case has a number of properties which motivate its study likee.g. the distributed generation possibilities, the geographical distribution of the consumers,and the different types of consumers in the area. The presentation will be concluded with anoutlook on future tracks of research and development

  • 68.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Guay, Martin
    Department of Chemical Engineering, Queens University, Kingston, ON K7L 3N6, Canada.
    Adaptive amplitude fast proportional integral phasor extremum seeking control for a class of nonlinear system2019Ingår i: Journal of Process Control, ISSN 0959-1524, E-ISSN 1873-2771, Vol. 83, s. 147-154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a modification of the fast phasor extremum-seeking control for the fast optimization of a class of Wiener-Hammerstein nonlinear dynamical systems. The proposed technique provides a significant improvement of the closed-loop system's performance. This study introduces a new adaptive amplitude technique that is used to adaptively adjust the perturbation amplitude to a small predetermined value in a neighbourhood of the system's unknown optimal equilibrium. An analysis of the system demonstrates that semi-global practical stability analysis of the overall system to the unknown optimum is achieved. The effectiveness of the proposed approach is illustrated using numerical examples. The approach is also implemented for the optimal operation of a lean burn combustion system.

  • 69.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Guay, Martin
    Department of Chemical Engineering, Queen’s University, Kingston, ON, Canada.
    Comment on “On stability and application of extremum seeking control without steady-state oscillation” [Automatica 68 (2016) 18–26]2019Ingår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 103, s. 580-581Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This correspondence revisits the results reported in a recent Automatica paper (Wang et al., 2016). We show that the claim of exponential stability of the extremum-seeking control system presented in Theorem 1 is not correct. An alternative stability analysis using the Lyapunov–Malkin theorem is considered. A counterexample is also presented.

  • 70.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Guay, Martin
    Department of Chemical Engineering, Queens University, Kingston, ON.
    Fast proportional integral phasor extremum seeking control for a class of nonlinear system2017Ingår i: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, nr 1, s. 5724-5730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a modification of the phasor extremum-seeking control for the fast optimization of a class of Wiener-Hammerstein nonlinear dynamical systems with a general strict unimodal nonlinearity. Based on the prior knowledge of the system’s relative order and number of non-minimum phase zeros, the proposed approach uses a high frequency perturbation signal and the phasor of the plant output to enable fast convergence of the overall system without the need for filters of the plant’s input and output. The extremum-seeking controller has two modes. In addition to the integral term, a proportional term is used to enable the application to very slow and integrating systems. Semi-global practical asymptotic stability analysis of the overall system to the unknown optimum is achieved. The effectiveness of the proposed approach is illustrated using numerical examples for different types of Wiener-Hammerstein systems.

  • 71.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Guay, Martin
    Queen's University.
    Lucchese, Riccardo
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A geometric phasor extremum seeking control approach with measured constraints2019Konferensbidrag (Refereegranskat)
  • 72.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Maximum power point tracking for micro hydro power plants using extremum seeking control2015Ingår i: 2015 IEEE International Conference on Control Applications (CCA 2015): Sydney, Australia, September 21-23 2015, Piscataway, NJ: IEEE Communications Society, 2015, s. 1874-1879, artikel-id 7320883Konferensbidrag (Refereegranskat)
    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.

  • 73.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Cervantes, Michel J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Phasor Extremum Seeking and its Application in Kaplan Turbine Control2014Ingår i: 2014 IEEE International Conference on Control Applications (CCA 2014): Juan Les Antibes, France, 8 -10 October 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 298-303Konferensbidrag (Refereegranskat)
    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.

  • 74.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Guay, Martin
    Department of Chemical Engineering, Queens University, Kingston, ON.
    On the Generalization and Stability Analysis of Pareto Seeking Control2018Ingår i: IEEE Control Systems Letters, E-ISSN 2475-1456, Vol. 2, nr 1, s. 145-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this letter, we address a multi-objective on-line optimization problem for unknown dynamical systems by providing a generalization of the Pareto seeking controller (PSC). The idea of the PSC is to drive the system to the Pareto front in the absence of knowledge of the values of the objectives or the input values to achieve Pareto optimality. Two special cases are presented, for two objectives and three objectives. A stability analysis is presented for the case of two objectives and two inputs, which shows that the controller practically drives the system into the neighborhood of the Pareto front, for any initial condition. Two simulation examples for the special cases are also presented

  • 75.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Accuracy Improvement of Extremum Seeking Control2017Ingår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 62, nr 4, s. 1952-1958, artikel-id 7498657Artikel i tidskrift (Refereegranskat)
    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.

  • 76.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Control oriented modeling of flow and size distribution in cone crushers2014Ingår i: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 56, s. 81-90Artikel i tidskrift (Refereegranskat)
    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.

  • 77.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Extremum seeking control based on phasor estimation2015Ingår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 85, s. 37-45Artikel i tidskrift (Refereegranskat)
    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.

  • 78.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    On the stability analysis of phasor and classic extremum seeking control2016Ingår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 91, s. 55-62Artikel i tidskrift (Refereegranskat)
    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.

  • 79.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    On-Line Optimization of Cone Crushers using Extremum-Seeking Control2013Ingår i: 2013 IEEE Multi-conference on Systems and Control (Conference on Control Applications), Hyderabad, India, August 28-30, 2013, 2013, s. 1054-1060Konferensbidrag (Refereegranskat)
    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.

  • 80.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pareto Seeking Control: On-line multi-objective optimization of dynami systems2014Konferensbidrag (Övrigt vetenskapligt)
  • 81.
    Atta, Khalid
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Gustafsson, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pareto Seeking Control: On-line multi-objective optimization of dynami systems2014Konferensbidrag (Refereegranskat)
  • 82.
    Avdelidis, Nicolas P.
    et al.
    University of Thessaly, Center of Research and Evaluation of Human Performance, Department of Physical Education and Sports Science, Karyes, Trikala.
    Kappatos, Vassilios
    Department of Technology and Innovation (ITI), University of Southern Denmark (SDU).
    Georgoulas, Georgios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Kravelis, Petros S.
    Laboratory of Knowledge and Intelligent Computing, Department of Computer Engineering, Technological Educational Institute of Epirus, Arta.
    Deli, Chariklia K.
    University of Thessaly, Center of Research and Evaluation of Human Performance, Department of Physical Education and Sports Science, Karyes, Trikala.
    Theodorakeas, Panagiotis
    National Technical University of Athens, NDT Lab, Materials Science and Engineering Department, School of Chemical Engineering, Zografou Campus, Athens.
    Giakas, Giannis
    University of Thessaly, Center of Research and Evaluation of Human Performance, Department of Physical Education and Sports Science, Karyes, Trikala.
    Tsiokanos, Athanasios L.
    University of Thessaly, Center of Research and Evaluation of Human Performance, Department of Physical Education and Sports Science, Karyes, Trikala.
    Koui, Maria
    National Technical University of Athens, NDT Lab, Materials Science and Engineering Department, School of Chemical Engineering, Zografou Campus, Athens.
    Jamurtas, Athanasios
    University of Thessaly, Center of Research and Evaluation of Human Performance, Department of Physical Education and Sports Science, Karyes, Trikala.
    Detection and characterization of exercise induced muscle damage (EIMD) via thermography and image processing2017Ingår i: Smart Materials and Nondestructive Evaluation for Energy Systems 2017: Portland, United States,  27-28 March 2017 / [ed] Norbert G. Meyendorf, SPIE - International Society for Optical Engineering, 2017, artikel-id 101710RKonferensbidrag (Refereegranskat)
    Abstract [en]

    Exercise induced muscle damage (EIMD), is usually experienced in i) humans who have been physically inactive for prolonged periods of time and then begin with sudden training trials and ii) athletes who train over their normal limits. EIMD is not so easy to be detected and quantified, by means of commonly measurement tools and methods. Thermography has been used successfully as a research detection tool in medicine for the last 6 decades but very limited work has been reported on EIMD area. The main purpose of this research is to assess and characterize EIMD, using thermography and image processing techniques. The first step towards that goal is to develop a reliable segmentation technique to isolate the region of interest (ROI). A semi-automatic image processing software was designed and regions of the left and right leg based on superpixels were segmented. The image is segmented into a number of regions and the user is able to intervene providing the regions which belong to each of the two legs. In order to validate the image processing software, an extensive experimental investigation was carried out, acquiring thermographic images of the rectus femoris muscle before, immediately post and 24, 48 and 72 hours after an acute bout of eccentric exercise (5 sets of 15 maximum repetitions), on males and females (20-30 year-old). Results indicate that the semi-automated approach provides an excellent bench-mark that can be used as a clinical reliable tool

  • 83. Bask, Michael
    Dynamic threshold generators for robust fault detection2005Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Detection of faults, such as clogged valves, broken bearings or biased sensors, has been brought more and more into focus during the last few decades. There are two main reasons why faults are important to detect at an early stage. Firstly, faults in safety critical applications, such as aircraft, nuclear reactors, cars and trains, may create risks of personal injuries. Secondly, faults in the manufacturing or process industry, e.g. flotation processes and steel plants, may cause decrease in quality or interruptions of production. A fault detection algorithm consists of two parts, the residual generator, which generates a residual, and the residual evaluator, which compares the residual, or a function of it, with a threshold to determine if a fault is present. The residual generation contains a process model and the residual can be described as a filtered difference between the measured and estimated process outputs. When no fault is present, the residual will be nonzero due to residual disturbances, i.e. measurement disturbances, process disturbances and model uncertainties. Therefore, the residual evaluation must be robust against these disturbances to avoid false alarms. Due to the model uncertainties, the residual is affected by the known input signals, which are, in general, time varying. To achieve a threshold that is as tight to the residual as possible, the threshold should also depend on the known input signals. To make this possible, parametric uncertainty in the process model is considered in this thesis. The dynamic threshold generator is introduced, a dynamic system whose output is the threshold and the inputs are the known process inputs. A dynamic threshold generator is developed for full-state measurement systems, assuming that the residual disturbances are constant and unknown but bounded. This dynamic threshold generator is then generalized to non-full state measurement systems with time-varying but bounded residual disturbances. Both generators depend on the unknown upper bounds of the residual disturbances. These upper bounds are replaced by design parameters, which are determined by minimizing the threshold for a set of fault free data. A nonlinear optimization solution is discussed. It is also shown that the residual generator state vector can always be parameterized such that the designing of the parameters can be done by linear optimization. A part of the generalized dynamic threshold generator is a system whose impulse response is an upper bound to another impulse response. Automatic methods to find realizable upper bounds are derived. To validate the methods in this thesis, two applications have been considered, detection of clogging in the valves of a flotation process and detection of faults in the compressor inlet temperature sensor of a jet engine.

  • 84. Bask, Michael
    On external model controller of vibrations2001Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A promising way to increase the suppression of vibration in mechanical systems is to apply active damping instead of passive damping, which is most widespread today. An active damper system consists of an actuator, a controller and at least one sensor, usually an accelerometer. The sensor measures the vibration and sends the measurements further to the controller in order to calculate the necessary damping force to be fed back to the mechanical system. A number of questions arises regarding active damper design, namely how to construct the active damper, what kind of sensors to use and where to place them, how to model the vibration and the mechanical system itself, and, last but not least, how to design the controller. This licentiate thesis deals with the controller design issue. The most widely used controller in active vibration control is the Filtered-X Least Mean Square Controller and it is briefly reviewed in this thesis. The main focus of the thesis is however on another structure, the External Model Controller (EMC). The EMC has much more degrees of freedom than the Filtered-X Controller but lacks performance and robust stability analysis as well reliable design methods. The four papers included in the thesis contribute to bridging this gap.

  • 85. Bask, Michael
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Linear optimization of parameters in dynamic threshold generators2005Ingår i: Proceedings of 16th IFAC World Congress: Prague, Czech Republic, July 3 - 8, 2005, Oxford: Elsevier, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    A model-based fault detection algorithm for linear systems with uncertain parameters is treated. An error system, bilinear in the uncertainties, generates the residual. The residual is compared to a threshold, which is generated by a linear system with the unknown uncertainty upper bounds as parameters. These unknown uncertainty upper bounds can be substituted by design parameters and this article suggests an algorithm to choose design parameter values such that the threshold is larger than the residual when no fault is present. This parameter design algorithm is applied to a sensor fault detection algorithm for a jet engine.

  • 86. Bask, Michael
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Model-based supervision of valves in a flotation process2003Ingår i: 42nd IEEE International Conference on Decision and Control, Piscataway, NJ: IEEE Communications Society, 2003, s. 744-749Konferensbidrag (Refereegranskat)
    Abstract [en]

    An observer based approach for detecting clogging in valves in flotation processes is investigated. Integral action and linear feedback applied to a nonlinear process model constitutes the observer for which local stability is shown. The integral terms give estimates of the clogging in the valves of the process and this estimate is compared to a constant threshold. Experiments on real data from Boliden's flotation series at the Boliden Area Concentrator, Sweden, show no false alarm during any of the two working conditions, PI control and LQ control. It is also shown that cloggings, simulated by manipulating measurement data, are promptly detected. The observer based fault detection algorithm is compared to an algorithm based on parameter estimation and advantages of the two approaches are highlighted.

  • 87. Bask, Michael
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Realizable upper bounds for the modulus of impulse responses2005Ingår i: SICE 2005 proceedings: SICE annual conference in Okayama : August 8-10, 2005 Okayama University, Japan, Tokyo: Society of Instrument and Control Engineers , 2005, s. 2045-2050Konferensbidrag (Refereegranskat)
    Abstract [en]

    This article treats the problem of finding a linear system whose impulse response is an upper bound for the modulus of the impulse response of another given system. These upper bounds are required for a newly developed fault detection algorithm1). Three different methods to calculate a realizable upper bound for an impulse response, which contains multiple real poles and distinct complex poles, are presented. The triangular inequality and linear optimization are used in the first and second method, respectively. In the third method, the original impulse response is used combined with time-delays. The upper bounds are calculated for a fictitious impulse response and compared with its modulus.

  • 88. Bask, Michael
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Robust time-varying thresholds for supervision of valves in a flotation process2004Ingår i: 2004 43rd IEEE Conference on Decision and Control: Nassau, Bahamas, 14 - 17 December 2004, Piscataway, NJ: IEEE Communications Society, 2004, s. 4305-4310Konferensbidrag (Refereegranskat)
    Abstract [en]

    Robust thresholds for observer-based residuals are developed for the purpose of detecting clogging in the valves of a flotation process. The observer in the residual generator is a linear model of the flotation process extended with integrators and corrected with a linear feedback term. The integral states in the observer constitute the residual. Contribution to the residual comes not only from the faults but also from uncertainties in measurements, estimates and working point To avoid false alarms generated by these uncertainties, robust time-varying thresholds depending on the uncertainties are derived. Experiments on a froth flotation process with four cascade coupled tanks are carried out successfully. The data was provided by Boliden Area Concentrator in Boliden, Sweden.

  • 89. Bask, Michael
    et al.
    Medvedev, Alexander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Analysis of least-squares state estimators for a harmonic oscillator2000Ingår i: Proceedings of the 39th IEEE Conference on Decision and Control: December 12 - 15, 2000, Sydney Convention and Exhibition Centre, Sydney, Australia, Piscataway, NJ: IEEE Communications Society, 2000, Vol. 4, s. 3819-3824Konferensbidrag (Refereegranskat)
    Abstract [en]

    The concept of least-squares observer is revisited. Robustness properties of this class of observers with respect to norm-bounded measurement noise are investigated and shown to be very much dependent on the operator chosen for the observer implementation. For the case of a harmonic oscillator, an explicit observer parameterization in terms of the implementation operator and the oscillator frequency is obtained, and observer's existence conditions are proven and analyzed

  • 90. Bask, Michael
    et al.
    Medvedev, Alexander
    External model controller for active vibration isolation1998Konferensbidrag (Refereegranskat)
  • 91. Bask, Michael
    et al.
    Medvedev, Alexander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    External model repetitive controller for active vibration isolation1999Ingår i: Proceedings of Active 99: International Symposium on Active Control of Sound and Vibration : an international INCE symposium, Fort Lauderdale, Florida, USA, 1999 December 02-04 / [ed] Scott Douglas, Washington, DC: Institute of noise control engineering , 1999, s. 177-188Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper deals with the External Model Repetitive Controller, a structure that combines the classical repetitive disturbance model (in the form of a time delay with a unit feedback) with a feedback of a disturbance estimate. The latter is often termed the External Model Controller and has a broad spectrum of technical applications, e.g., active vibration control. By analyzing the controller performance under the assumption of a disturbance period modeling error, it is shown that an unacceptable performance degradation might occur even for very small values of the modeling error

  • 92.
    Berndtsson, Magnus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fault detection in lambda-tuned control loops2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Poorly operating control loops cause loss in productivity in almost every industry worldwide. Therefore performance monitoring has been an active area of research for the past decades. In this work, a newly developed fault detection method is applied to the monitoring of lambda-tuned control loops. The lambda-tuning method has, due to its simple use, become very popular in the pulp and paper industry and is now spreading to other industries. A model-based fault detection algorithm assuming uncertain process parameters is used for detecting changes in the process. The algorithm consists of two parts, a residual and a time-varying threshold. The a priori information obtained from lambda-tuning is used to create an observer, which is used as residual generator. Known process inputs are used together with upper bounds for the uncertainties and upper bounds for disturbances when calculating the detection threshold. The observer may have integral action in order to make the threshold tight to the residual. Upper bounds for the uncertainties in the process parameters and upper bounds for disturbances are tuning parameters in the algorithm. Two different methods for finding those parameter values are proposed. The first is an approach based on allowed loss in phase margin and the second consists of solving a nonlinear optimization problem to minimize the difference between the residual and the threshold. The algorithm is tested in a simple water tank system. The threshold handles step changes in reference value without giving any false alarms. A fault is introduced by widening of the output in the water tank which simulates a change in the process parameters. The residual then gets larger than the threshold and the fault is detected.

  • 93. Berndtsson, Magnus
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Design of a dynamic threshold generator for λ-tuned control loops2008Ingår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 16, nr 5, s. 623-631Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dynamic threshold generator is employed for detecting faults in λ-tuned control loops. To this end, an optimizationalgorithm for dynamic threshold generators is proposed. The a priori-information from λ-tuning is used in designing astate estimator with integral action. A dynamic threshold generator for the residual of this state estimator is derived and the optimization algorithm is applied. Simulations with measurement data from an experimental water tank setup show that the method is capable of detecting a small fault without generating false alarms.

  • 94. Berndtsson, Magnus
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fault detection in lambda-tuned control loops using an observer with integral action2006Ingår i: 45th IEEE Conference on Decision and Control, 2006 : 13 - 15 Dec. 2006, [San Diego, CA, USA] / [ed] Pradeep Misra, Piscataway, NJ: IEEE Communications Society, 2006, s. 538-543Konferensbidrag (Refereegranskat)
    Abstract [en]

    A model-based fault detection algorithm assuming uncertain process parameters is used for detecting poorly operating lambda-tuned control loops. The a priori information obtained from lambda-tuning is used to create an observer as residual generator. The observer has integral action which makes it possible to obtain a tight fault detection threshold. A linear optimization approach is used for finding the parameters in the threshold.

  • 95.
    Bhattacharya, Shaondip
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Multi-agent System Distributed Sensor Fusion Algorithms2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The concept of consensus filters for sensor fusion is not an entirely new proposition but one with an internally implemented Bayesian fusion is. This work documents a novel state update algorithm for sensor fusion which works using the principle of Bayesian fusion of data with variance implemented on a single integrator consensus algorithm. Comparative demonstrations of how consensus over a pinning network is reached are presented along with a weighted Bayesian Luenberger type observer and a ’Consensus on estimates’ algorithm. This type of a filter is something that is novel and has not been encountered in previous literature related to this topic to the best of our knowledge. In this work, we also extend the proof for a distributed Luenberger type observer design to include the case where the network being considered is a strongly connected digraph.

  • 96.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    D​IGITAL ​T​WIN​ – C​OMPUTATIONAL​ ​METHODS​ ​ZUR​ A​NALYSE​ ​UND O​PTIMIERUNG​ ​VON​ C​YBER​-P​HYSICAL​ S​YSTEMS2020Ingår i: 16. Symposium Energieinnovation, 12.-14.02.2020, Graz/Austria: ENERGY FOR FUTURE – Wege zur Klimaneutralität, Graz, Austria, 2020Konferensbidrag (Övrigt vetenskapligt)
    Abstract [de]

    Digital Twins und Cyber-Physikalische Systeme spielen eine wichtige Rolle in zukünftigen intelligenten Systemen wie Industrie 4.0 oder Energiesystemen. Sowohl bei Digital Twins als auch bei Cyber-Physikalischen Systemen sind Modellierung und Simulation zentrale Werkzeuge. Ein Trend in der modellbasierten Analyse und Optimierung ist die zunehmende Komplexität der betrachteten Systeme, wodurch etablierte Methoden an ihre Grenzen stoßen. Des weiteren erfordern viele Anwendungen die Kombination von datengetriebene Techniken mit First-Principle-Modellen. Aktuelle Studien haben gezeigt, dass die Co-Simulation ein vielversprechender Ansatz für die Modellierung und Simulation komplexer Systeme ist. In diesem Paper wird ein physikalisches Modell einer industriellen Energieversorgung und ein datengetriebenes Modell einer Photovoltaikanlage co-simuliert.

  • 97.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Industry applications of multivariable control2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the face of environmental regulations, optimization of industrial processes becomes necessary. This doctoral thesis summarizes the results of three application-driven projects in automatic control that were aimed at process optimization in the steel industry. The objective of the projects was to apply advanced control strategies to two important processes in steel making, namely pulverized coal injection (PCI) in blast furnaces and LD converters. Firstly, an LQ multivariable controller with gas leakage detection system for PCI vessels is designed and analyzed. Secondly, a foam level control system for the LD converter process using an audio signal for measurement is designed. Thirdly, it is attempted to create a single line flow control system for PCI using a video camera. In the latter two cases the conservative approach of inferring unmeasurable physical quantities from the audio and video sources is used. Moreover, all the designs are tested through implementation or experiments at the industrial plant. The control and gas leakage detection system ended up as a full-scale industrial implementation, whereas the projects comprising audio and video information is still at an experimental stage. Work with implementation and experiments pays off in experiences and further insights in the application of control theory, and reveals weaknesses and gaps in the existing theory. Thus, application-driven projects lead to practical solutions and at the same time pose new theoretical challenges. Consequently, this chain of events is favorable to both practitioners and theoreticians, and in turn stimulates the collaboration of industry and academia. Unfortunately, in many research projects this sequence is reversed which complicates technology transfer into industry. As a spin-off effect from the multivariable control project of the PCI process two topics are addressed anew. In the problem of measurement/actuator pairs assignment for decentralized control, the geometrical background of Gramian-based interaction measures is clarified. It is shown that weighted Gramian-based interaction measures can be effectively used for control structure design. In control structure improvement of multivariable control systems, it is shown that improvement potentials can be deduced from coarse models of the closed-loop system. Finally, in the projects comprising audio and video signals in control applications, it is concluded that the theory is rather undeveloped and that these sources should be treated as a multivariable system.

  • 98.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Intelligent industrial Processes: Automatic Control Perspective2014Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Intelligent Industrial Processes is an area of excellence in research and innovation at Luleå University of Technology (LTU), which was formed to promote multi-disciplinary research and innovation relating to Process Industrial Automation, also referred to as ProcessIT. LTU has a strong track record of research in close collaboration with process industries, where research results have often found their way into products and services strengthening the industries position on the global market.For this area of excellence a road mapping study with respect to Automatic Control research was conducted and is summarized in this white paper. The study shows that current research activities in Automatic Control are very relevant to Intelligent Industrial Processes, dealing with techniques for process understanding (modeling), design and implementation of control systems, and process monitoring, only to mention some.It is concluded that the design and establishment of an Open Research and Innovation Platform is essential for collaborative and multi-disciplinary research in the area. Such a software platform will enable industry partners to more efficiently work with their industrial processes and that in close collaboration with researchers and engineering businesses. At the same time researchers and innovators will have the opportunity to test and validate their results and innovations on real-life cases, enabling a swift exploitation of results. Some key principles for this software platform are the open source, open data and open innovation principles that need to be captured in the platform.The results of that study suggest initial automatic control research activities and a time line for stepping stones towards a full scale implementation of an Open Research and Innovation Platform by 2030.

  • 99.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Method for Controlling Vehicle Steering and Vehicle Behaviour: patent pendingPatent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    A steering system (100) and a control algorithm for vehicle servo-steering which acts so that a steering-wheel torque applied by the driver is transformed to a vehicle behaviour. The steering system (100) consists of a steering rack (124), and tie rods (125) connected to the steered wheels of the vehicle (127). The vehicle's steering wheel (120) is connected to the rack (124) via a steering column (121). The steering column (121) contains a torsion bar (128) with a torque sensor in order to measure the steering torque applied by the driver. An assistance torque is given by an actuator (115) which is controlled by a control system (110). The control system (110) contains a control algorithm which translates the steering torque applied by the driver to a reference value in the form of a yaw and/or lateral vehicle state. The servo-system is controlled so that this reference value is attained

  • 100.
    Birk, Wolfgang
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Multivariable control of a pneumatic conveying system1999Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This licentiate thesis deals with a multivariable controller of a pneumatic conveying system. The industrial process used to illustrate design, analysis and implementation of a multivariable controller is the injection of fine coal into a blast furnace. In the blast furnace process, coke is replaced by fine coal because of economical and environmental reasons. The coal mass flow to the blast furnace becomes a crucial parameter for its operation and hence a control system should be in place to maintain a constant flow. An optimal multivariable linear-quadratic controller has been designed in order to replace the conventional PI-controllers, which were not able to reach the desired control objectives. The design is analyzed by deriving the sensitivity functions of the closed loop system to noise, disturbances and uncertainties. The multivariable controller is then validated through experiments and test operation at the coal injection plant at SSAB Tunnplåt AB in Luleå, Sweden. The reached performance improvements compared with the conventional PI-controllers account for up to 80%. Finally, the controller is combined with a gas-leakage detection system to the commercially available product SafePCI, which is now installed and in operation at SSAB Tunnplåt AB in Luleå, Sweden.

1234567 51 - 100 av 736
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf