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  • 251.
    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.
    On the design, development and motion control of a HUmanoid Robotic Leg via pneumatic artificial muscles2017Inngår i: 2016 IEEE International Conference on Robotics and Biomimetics, ROBIO 2016, Piscataway, NJ, 2017, s. 1637-1642, artikkel-id 7866562Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this article, the design and implementation of a HUmanoid Robotic Leg (HURL) is presented. The motion of the HURL is achieved via pneumatic muscle actuators, a pneumatic form of actuation possessing crucial attributes for the implementation of a biomimetic design that mimics the motion characteristics of a human ankle. The HURL's properties are described in detail, while its 2-DoF motion capabilities (dorsiflexion - plantar flexion, eversion - inversion) are experimentally evaluated via an advanced nonlinear PID-based control algorithm

  • 252.
    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.
    Arvanitakis, Ioannis
    Department of Electrical and Computer Engineering, University of Patras.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Multi-parametric constrained optimal control of a pneumatic artificial muscle2012Inngår i: 10th Portuguese Conference in Automatic Control: University of Madeira, July 16-18, 2012, s. 135-140Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Pneumatic Artificial Muscle (PAM) is a highly non-linear form of actuation that is characterized by a decrease in the actuating length when pressurized. Its non-linear nature and time-varying parameters cause difficulties in modelling their characteristics and designing controllers for high-performance positioning systems. In this article, the control problem of a PAM is considered. A constrained linear and PieceWise Affine (PWA) system model approximation is utilized and a controller composed of: a) a feedforward term regulating control input at specific setpoints, and b) a Constrained Finite Time Optimal Controller (CFTOC) handling any deviations from the system’s equilibrium points is synthesized. Simulation studies are used to investigate the efficacy of the suggested controller.

  • 253.
    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.
    Arvanitakis, Ioannis
    Electrical and Computer Engineering Department, University of Patras.
    Manesis, Stamatis
    Electrical and Computer Engineering Department, University of Patras.
    Switching model predictive control of a pneumatic artificial muscle2013Inngår i: International Journal of Control, Automation and Systems, ISSN 1598-6446, E-ISSN 2005-4092, Vol. 11, nr 6, s. 1223-1231Artikkel i tidsskrift (Fagfellevurdert)
    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 and improve 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 simulation studies indicate the overall scheme's efficiency.

  • 254.
    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.
    Arvanitakis, John
    Electrical and Computer Engineering Department, University of Patras.
    Manesis, Stamatis
    Electrical and Computer Engineering Department, University of Patras.
    Piecewise affine modeling and constrained optimal control for a pneumatic artificial muscle2013Inngår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, nr 2, s. 904-916Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this article, the modeling and control problem of a Pneumatic Artificial Muscle (PAM) is being considered. The PAM is an actuator characterized by a decrease in the actuating length when pressurized. Its non-linear nature and time-varying parameters cause difficulties in modeling their characteristics, as well as in designing controllers for high-performance positioning systems. A constrained linear and PieceWise Affine (PWA) system model approximation is formulated and a control scheme composed of: a) a feedforward term regulating control input at specific setpoints, and b) a Constrained Finite Time Optimal Controller (CFTOC) handling any deviations from the system’s equilibrium points is being synthesized. Extended experimental studies are utilized to prove the efficacy of the suggested controller.

  • 255.
    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.
    Kominiak, Dariusz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Unander-Scharin, Åsa
    Luleå tekniska universitet, Institutionen för konst, kommunikation och lärande, Musik och dans.
    Towards the Development of a Novel Upper-Body Pneumatic Humanoid: Design and Implementation2016Inngår i: 2016 European Control Conference, ECC 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 395-400, artikkel-id 7810317Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this article, the conceptual design of a 14 Degree-of-Freedom (DOF) upper-body pneumatic humanoid is presented. The movement capabilities of this novel robotic setup are achieved via Pneumatic Artificial Muscles (PAMs), a form of actuation possessing crucial attributes for the development of biologically-inspired robots. To evaluate the feasibility of the humanoid’s design properties, a 5-DOF robotic arm is developed and experimentally tested, while being studied from the scope of implementing a robotic structure capable of producing smooth and human-like motion responses, while maintaining the inherent compliance provided by the PAM technology.

  • 256.
    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.
    A Survey on applications of pneumatic artificial muscles2011Inngår i: 19th Mediterranean Conference on Control and Automation, MED 2011, Piscataway, NJ: IEEE Communications Society, 2011, s. 1439-1446Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aim of this article is to present a survey on applications of Pneumatic Artificial Muscles (PAMs). PAMs are highly non–linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last decade, there has been a significant increase in the industrial and scientific utilization of PAMs due to their advantages such as high strength and small weight, while various types of PAMs with different technical characteristics have been appeared in the relative scientific literature. This article will summarize the key enabling applications in PAMs that are focusing in the following areas: a) Biorobotic, b) Medical, c) Industrial, and d) Aerospace applications

  • 257.
    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.
    Adaptive internal model control scheme for a pneumatic artificial muscle2013Inngår i: European Control Conference (ECC), July 17-19, Zurich, Switzerland 2013, 2013, s. 772-777Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Pneumatic Artificial Muscle (PAM) is a highly non-linear form of actuation that is characterized by a decrease in the actuating length when pressurized. Its nonlinear nature and time-varying parameters cause difficulties in modeling their characteristics and designing controllers for high-performance positioning systems. In this article, the model identification and control problem of a PAM is being considered. The identification of the PAM’s model parameters is being carried out by a Recursive Least Square (RLS) based algorithm, while an Internal Model Control (IMC) structure is being synthesized. Experimental studies are being utilized to prove the overall efficiency of the suggested control scheme, regarding: a) set-point tracking performance through selected positioning scenarios, b) robustness through disturbance cancellation, and c) adaptability through hysteresis shift compensation.

  • 258.
    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.
    Advanced nonlinear PID-based antagonistic control for pneumatic muscle actuators2014Inngår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, nr 12, s. 6926-6937, artikkel-id 6786031Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, the positioning control problem of pneumatic muscle actuators (PMAs) is being considered. A two-degree-of-freedom nonlinear proportional-integral-derivative structure is being synthesized, providing ameliorated compensation of the PMAs' nonlinear hysteretic phenomena and advanced robustness through disturbance cancellation. Experimental studies are being utilized to prove the overall efficiency of the proposed control scheme with regard to set-point tracking performance for the position control of a single PMA, torsion angle control of a nonsymmetrical antagonistic PMA setup, and disturbance rejection in both single and antagonistic control scenarios.

  • 259.
    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 muscles2012Inngår i: 2012 20th Mediterranean Conference on Control & Automation: Barcelona, Spain, July 3-6, 2012, Piscataway, NJ: IEEE Communications Society, 2012, s. 1334-1340Konferansepaper (Fagfellevurdert)
    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.

  • 260.
    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 Muscles2015Inngår i: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 50, nr 11, s. 2709-2730Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 261.
    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 actuators2011Inngår i: Journal of Control Engineering and Technology (JCET), ISSN 2223-2036, Vol. 1, nr 2, s. 53-58Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 262.
    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 Artificial2015Inngår 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, artikkel-id 7158784Konferansepaper (Fagfellevurdert)
    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.

  • 263.
    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 actuators2015Inngår 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, artikkel-id 7301464Konferansepaper (Fagfellevurdert)
    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.

  • 264.
    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 muscles2013Inngår i: 21st IEEE Mediterranean Conference on Control and Automation, June 25-28, Platanias, Chania, Crete, Greece, 2013, 2013, s. 729-734, artikkel-id 6608804Konferansepaper (Fagfellevurdert)
    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.

  • 265.
    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 Actuators2016Inngår i: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, Vol. 21, nr 6, s. 2647-2659, artikkel-id 7501612Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 266.
    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 approach2013Inngår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 21, nr 12, s. 1653-1664Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 267.
    André, Simon
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Design and Optimization of Controllers for an Electro-Hydraulic System2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Electro-Hydraulic (EH) systems are commonly used in the industry for applications that require high power-weight ratios and large driving forces. The EH system studied in this master thesis have recently been upgraded with new hardware components and as a part of this upgrade a new controller was requested. The system consists of a controller that computes a control signal for an electric motor. The motor drives a gear pump that generates a flow of hydraulic fluid. The flow is then directed to a cylinder. The movements of a piston in the cylinder is affected by the flow and the piston position can be measured. The measured piston position is then fed back to the controller and the control loop is complete. The system was previously controlled using a Proportional-Integral-Derivative (PID) controller and the purpose of this thesis is to compare the old controller with alternative control strategies suitable for this application. The evaluation of the controllers is based on both software and hardware simulations and results in a recommendation for final implementation of the best suited controller. The control strategies chosen for investigation are: a retuned PID controller, a PID controller with feed forward from reference, a PID based cascade controller, a Linear Quadratic (LQ) controller, and a Model Predictive Controller (MPC). To synthesize the controllers an approximate model of the system is formed and implemented in the software environment Matlab Simulink. The model is tuned to fit recorded data and provides a decent estimation of the actual system. The proposed control strategies are then simulated and evaluated in Simulink with the model posing as the real system. These simulations resulted in the elimination of the cascade controller as a possible candidate since it proved unstable for large steps in the reference signal. The remaining four controllers were all selected for simulation on the real hardware system. Unfortunately the MPC was never successfully implemented on the hardware due to some unknown compatibility error and hence eliminated as a possible candidate. The three remaining control strategies, PID, PID with feed forward from reference and the LQ controller, were all successfully implemented and simulated on hardware. The results from the hardware simulations compared to simulations made with the old controller, as well as the results from the software simulations, were then evaluated. Depending on the purpose one of two control strategies is recommended for this application. The LQ controller achieved the best overall performance and is presented as the control strategy best suited for this application.

  • 268.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Papadakis, Stefanos
    FORTH.
    Traganitis, Apostolos
    FORTH & UoC.
    Vasilios, Siris
    AUEB.
    Adjacent Channel Interference in 802.11a Is Harmful: Testbed Validation of a Simple Quantification Model2011Inngår i: IEEE COMMUNICATIONS MAGAZINE, ISSN 0163-6804, Vol. 49, nr 3, s. 160-166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wireless LAN radio interfaces based on the IEEE 802.11a standard have lately found widespread use in many wireless applications. A key reason for this was that although the predecessor, IEEE 802.11b/ g, had a poor channelization scheme, which resulted in strangling adjacent channel interference (ACI), 802.11a was widely believed to be ACI-free due to a better channelization combined with OFDM transmission. We show that this is not the case. ACI does exist in 802.11a, and we can quantify its magnitude and predict its results. For this, we present minor modifications of a simple model originally introduced by [1] that allow us to calculate bounding values of the 802.11a ACI, which can be used in link budget calculations. Using a laboratory testbed, we verify the estimations of the model, performing experiments designed to isolate the affected 802.11 mechanisms. This isolation was enabled by not using the wireless medium, and emulating it over cables and attenuators. Our results show clear throughput degradation because of ACI in 802.11a, the magnitude of which depends on the interfering data rates, packet sizes, and utilization of the medium.

  • 269.
    Anistratov, Pavel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Lane-Deviation Penalty for Autonomous Avoidance Maneuvers2018Inngår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control, Beijing, July 16-20, 2018, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A formulation of an offline motion-planning method for avoidance maneuvers based on a lane-deviation penalty function is proposed,which aims to decrease the risk of a collision by minimizing the time when a vehicle is outside of its own driving lane in the case ofavoidance maneuvers. The penalty function is based on a logistic function. The method is illustrated by computing optimal maneuversfor a double lane-change scenario. The results are compared with minimum-time maneuvers and squared-error norm maneuvers. Thecomparison shows that the use of the considered penalty function requires fewer constraints and that the vehicle stays less time in theopposing lane. The similarity between the obtained trajectories for different problem configurations was noticed. This property couldbe used in the future for predicting an intermediate trajectory online from a sparse data set of maneuvers.

  • 270.
    Anistratov, Pavel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Olofsson, Björn
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Segmentation and Merging of Autonomous At-the-Limit Maneuversfor Ground Vehicles2018Inngår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control, Beijing, July 16-20, 2018, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To decrease the complexity of motion-planning optimizations, a segmentation and merging strategy for maneuvers is proposed. Maneuvers that are at-the-limit of friction are of special interest since they appear in many critical situations. The segmentation pointsare used to set constraints for several smaller optimizations for parts of the full maneuver, which later are merged and compared withoptimizations of the full maneuver. The technique is illustrated for a double lane-change maneuver.

  • 271.
    Ankelhed, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    An Efficient Implementation of Gradient and Hessian Calculations of the Coefficients of the Characteristic Polynomial of I-XY2011Rapport (Annet vitenskapelig)
    Abstract [en]

    This is a report about a project in robust multivariable control. In the project we investigated how to decrease the computational complexity of calculating the gradient and Hessian of coefficients of the characteristic polynomial of the matrix I-XY that often appear in H-infinity controller synthesis. Compared to a straight-forward implementation, our new implementation managed to decrease the number of operations required to calculated the gradient and Hessian by several orders of magnitude by utilizing the structure of the problem.

  • 272.
    Ankelhed, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On design of low order H-infinity controllers2011Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    When designing controllers with robust performance and stabilization requirements, H-infinity synthesis is a common tool to use. These controllers are often obtained by solving mathematical optimization problems. The controllers that result from these algorithms are typically of very high order, which complicates implementation. Low order controllers are usually desired, since they are considered more reliable than high order controllers. However, if a constraint on the maximum order of the controller is set that is lower than the order of the so-called augmented system, the optimization problem becomes nonconvex and it is relatively difficult to solve. This is true even when the order of the augmented system is low.

    In this thesis, optimization methods for solving these problems are considered. In contrast to other methods in the literature, the approach used in this thesis is based on formulating the constraint on the maximum order of the controller as a rational function in an equality constraint. Three methods are then suggested for solving this smooth nonconvex optimization problem.

    The first two methods use the fact that the rational function is nonnegative. The problem is then reformulated as an optimization problem where the rational function is to be minimized over a convex set defined by linear matrix inequalities (LMIs). This problem is then solved using two different interior point methods.

    In the third method the problem is solved by using a partially augmented Lagrangian formulation where the equality constraint is relaxed and incorporated into the objective function, but where the LMIs are kept as constraints. Again, the feasible set is convex and the objective function is nonconvex.

    The proposed methods are evaluated and compared with two well-known methods from the literature. The results indicate that the first two suggested methods perform well especially when the number of states in the augmented system is less than 10 and 20, respectively. The third method has comparable performance with two methods from literature when the number of states in the augmented system is less than 25.

  • 273.
    Ankelhed, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On low order controller synthesis using rational constraints2009Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    In order to design robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the plant, the problem is no longer convex and it is then relatively hard to solve. These problems become very complex, even when the order of the system to be controlled is low.

    The approach used in the thesis is based on formulating the constraint on the maximum order of the plant as a polynomial equation. By using the fact that the polynomial is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex polynomial function is to be minimized over a convex set defined by linear matrix inequalities.

    To solve this optimization problem, two methods have been proposed. The first method is a barrier method and the second one is a method based on a primal-dual framework. These methods have been evaluated on several problems and compared with a well-known method found in the literature. To motivate this choice of method, we have made a brief survey of available methods available for solving the same or related problems.

    The proposed methods emerged as the best methods among the three for finding lower order controllers with the same or similar performance as the full order controller. When the aim is to find the lowest order controller with no worse than +50% increase in the closed loop H-infinity norm, then the three compared methods perform equally well.

  • 274.
    Ankelhed, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Utvärdering av DC-labben2006Rapport (Annet vitenskapelig)
    Abstract [en]

    I denna rapport jämförs två olika metoder för att ta fram en modell för att kunna reglera en DC-motor med lead-lagreglering. I den ena metoden identifieras två parametrar i en given modell av andra ordningen, medan i den andra metoden skattas ett antal punkter i ett bodediagram direkt med hjälp av frekvensanalys. Resultaten indikerar att de två metoderna är ungefär likvärdiga för den process som studerats.

  • 275.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Partially Augmented Lagrangian Method for Low Order H-Infinity Controller Synthesis Using Rational Constraints2011Rapport (Annet vitenskapelig)
    Abstract [en]

    When designing robust controllers, H-infinity synthesis is a common tool touse. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex, even when the order of the system is low.

    The approach used in this work is based on formulating the constraint onthe maximum order of the controller as a polynomial (or rational) equation.This equality constraint is added to the optimization problem of minimizingan upper bound on the H-innity norm of the closed loop system subjectto linear matrix inequality (LMI) constraints. The problem is then solvedby reformulating it as a partially augmented Lagrangian problem where theequality constraint is put into the objective function, but where the LMIsare kept as constraints.

    The proposed method is evaluated together with two well-known methodsfrom the literature. The results indicate that the proposed method hascomparable performance in most cases, especially if the synthesized con-troller has many parameters, which is the case if the system to be controlledhas many input and output signals.

  • 276.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Partially Augmented Lagrangian Method for Low Order H-Infinity Controller Synthesis Using Rational Constraints2012Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 57, nr 11, s. 2901-2905Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This technical note proposes a method for low order H-infinity synthesis where the constraint on the order of the controller is formulated as a rational equation. The resulting nonconvex optimization problem is then solved by applying a partially augmented Lagrangian method. The proposed method is evaluated together with two well-known methods from the literature. The results indicate that the proposed method has comparable performance and speed.

  • 277.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Primal-Dual Method for Low Order H-Infinity Controller Synthesis2010Inngår i: Proceedings of Reglermöte 2010, Lund, 2010Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    When designing robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex, even when the order of the system is low.

    The approach used in this work is based on formulating the constraint on the maximum order of the controller as a polynomial (or rational) equation. By using the fact that the polynomial (or rational) is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex function is to be minimized over a convex set defined by linear matrix inequalities.

    The proposed method is evaluated together with a well-known method from the literature. The results indicate that the proposed method performs slightly better.

  • 278.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Primal-Dual Method for Low Order H-Infinity Controller Synthesis2010Rapport (Annet vitenskapelig)
    Abstract [en]

    When designing robust controllers, H-infinity synthesis is a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex, even when the order of the system is low.

    The approach used in this work is based on formulating the constraint on the maximum order of the controller as a polynomial (or rational) equation. By using the fact that the polynomial (or rational) is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex function is to be minimized over a convex set defined by linear matrix inequalities.

    The proposed method is evaluated together with a well-known method from the literature. The results indicate that the proposed method performs slightly better.

  • 279.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Primal-Dual Method for Low Order H-Infinity Controller Synthesis2009Inngår i: Proceedings of the 48th IEEE Conference on Decision and Control held jointly with the 28th Chinese Control Conference, IEEE , 2009, s. 6674-6679Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When designing robust controllers, H-infinity synthesisis a common tool to use. The controllers that result from these algorithms are typically of very high order, which complicates implementation. However, if a constraint on the maximum order of the controller is set, that is lower than the order of the (augmented) system, the problem becomes nonconvex and it is relatively hard to solve. These problems become very complex,even when the order of the system is low.

    The approach used in this work is based on formulating the constraint on the maximum order of the controller as a polynomial (or rational) equation. By using the fact that the polynomial (or rational) is non-negative on the feasible set, the problem is reformulated as an optimization problem where the nonconvex function is to be minimized over a convex set defined by linear matrix inequalities.

    The proposed method is evaluated together with a wellknown method from the literature. The results indicate that the proposed method performs slightly better.

  • 280.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Quasi-Newton Interior Point Method for Low Order H-Infinity Controller Synthesis2011Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 56, nr 6, s. 1462-1467Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This technical note proposes a method for low order H-infinity synthesis where the constraint on the order of the controller is formulated as a rational equation. The resulting nonconvex optimization problem is then solved by applying a quasi-Newton primal-dual interior point method. The proposed method is evaluated together with a well-known method from the literature. The results indicate that the proposed method has comparable performance and speed.

  • 281.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Additional Numerical Results for the Quasi-Newton Interior Point Method for Low Order H-Infinity Controller Synthesis2010Rapport (Annet vitenskapelig)
    Abstract [en]

    Here we present numerical results and timings obtained using our quasi-Newton interior point method on a set of 44 systems. We were not able to include these results in the article due to limited amount of space. Also results from our evaluation of HIFOO on the same systems are included.

  • 282.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Suboptimal Model Reduction using LMIs with Convex Constraints2006Rapport (Annet vitenskapelig)
    Abstract [en]

    An approach to model reduction of LTI systems using Linear Matrix Inequalities (LMIs) in an H-infinity framework is presented, where non-convex constraints are replaced with stricter convex constraints thus making it suboptimal. The presented algorithms are compared with the Optimal Hankel reduction algorithm, and are shown to achieve better results (i.elower H-infinity errors) in cases where some of the Hankel singular values are close, but not equal to each other.

  • 283.
    Ankelhed, Daniel
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Stenlind, Lars
    Linköpings universitet, Institutionen för systemteknik.
    Tillståndsskattning i robotmodell med accelerometrar2005Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this report is to evaluate different methods for identifying states in robot models. Both linear and non-linear filters exist among these methods and are compared to each other. Advantages, disadvantages and problems that can occur during tuning and running are presented. Additional measurements from accelerometers are added and their use with above mentioned methods for state estimation is evaluated. The evaluation of methods in this report is mainly based on simulations in Matlab, even though some experiments have been performed on laboratory equipment.

    The conclusion indicates that simple non-linear models with few states can be more accurately estimated with a Kalman filter than with an extended Kalman filter, as long as only linear measurements are used. When non-linear measurements are used an extended Kalman filteris more accurate than a Kalman filter. Non-linear measurements are introduced through accelerometers with non-linear measurement equations. Using accelerometers generally leads to better state estimation when the measure equations have a simple relation to the model.

  • 284.
    Annergren, Mariette
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Application-Oriented Input Design and Optimization Methods Involving ADMM2016Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis is divided into two main parts. The first part considers application-oriented input design, specifically for model predictive control (MPC). The second part considers alternating direction method of multipliers (ADMM) for ℓ1 regularized optimization problems and primal-dual interior-point methods.

    The theory of system identification provides methods for estimating models of dynamical systems from experimental data. This thesis is focused on identifying models used for control, with special attention to MPC. The objective is to minimize the cost of the identification experiment while guaranteeing, with high probability, that the obtained model gives an acceptable control performance. We use application-oriented input design to find such a model. We present a general procedure of implementing application-oriented input design to unknown, possibly nonlinear, systems controlled using MPC. The practical aspects of application-oriented input design are addressed and the method is tested in an experimental study.

    In addition, a MATLAB-based toolbox for solving application-oriented input design problems is presented. The purpose of the toolbox is threefold: it is used in research; it facilitates communication of research results; it helps an engineer to use application-oriented input design.

    Several important problems in science can be formulated as convex optimization problems. As such, there exist very efficient algorithms for finding the solutions. We are interested in methods that can handle optimization problems with a very large number of variables. ADMM is a method capable of handling such problems. We derive a scalable and efficient algorithm based on ADMM for two ℓ1 regularized optimization problems: ℓ1 mean and covariance filtering, and ℓ1 regularized MPC. The former occurs in signal processing and the latter is a specific type of model based control.

    We are also interested in optimization problems with certain structural limitations. These limitations inhibit the use of a central computational unit to solve the problems. We derive a distributed method for solving them instead. The method is a primal-dual interior-point method that uses ADMM to distribute all the calculations necessary to solve the optimization problem at hand.

  • 285.
    Annergren, Mariette
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Optimal Input Signal Design and MPC of Nonlinear Dynamical Systems2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main topics of this master’s project are control theory, system identification and convex optimization. The objective is to develop, implement and test methods for optimal input signal design and for control of a nonlinear dynamical system using MPC. The thesis begins with a theoretical part, in which some known results in these fields are summarized. In the applied part of the thesis, methods are developed and exemplified in MATLAB.

    Optimal input signal design is performed on specific FIR, ARX and DCmotor systems which are all controlled by an MPC. The implementation works very well for the FIR and ARX systems. The estimates of the true parameters fulfill the pre-specified requirements when using the optimal input signal constructed. An unexpected behavior is obtained of the estimates for the DC-motor system. Some additional approximations which were made in the design of the optimal input signal are thought to be the cause. Although, the source of the odd behavior were never confirmed. To be able to have a user-friendly environment for optimal input signal design, further work is necessary to overcome numerical problems in the implementation.

    A general method of implementing MPC of nonlinear dynamical systems is constructed. It is problematic to use MPC to control a nonlinear system. The reason for this is that a nonlinear system in general corresponds to a non-convex optimization problem in the MPC algorithm. Our method is based on making the problem convex through a linearization of the nonlinear system dynamics. The method is tested on simulations of a reaction wheel pendulum and a two link robot arm. It works very well and the systems fulfill the control objectives. Each optimization problem takes about 0.3-1 second to solve when using cvx. This is in some situations too slow to be able to control a system in reality. Further work is recommended on implementing our method with another solver so that it can be tested on an actual system which requires new updates every milli- or microsecond.

  • 286.
    Annergren, Mariette
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Hansson, A.
    Wahlberg, Bo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    An ADMM Algorithm for Solving l(1) Regularized MPC2012Inngår i: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE , 2012, s. 4486-4491Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present an Alternating Direction Method of Multipliers (ADMM) algorithm for solving optimization problems with an ℓ1 regularized least-squares cost function subject to recursive equality constraints. The considered optimization problem has applications in control, for example in ℓ1 regularized MPC. The ADMM algorithm is easy to implement, converges fast to a solution of moderate accuracy, and enables separation of the optimization problem into sub-problems that may be solved in parallel. We show that the most costly step of the proposed ADMM algorithm is equivalent to solving an LQ regulator problem with an extra linear term in the cost function, a problem that can be solved efficiently using a Riccati recursion. We apply the ADMM algorithm to an example of ℓ1 regularized MPC. The numerical examples confirm fast convergence to sufficient accuracy and a linear complexity in the MPC prediction horizon.

  • 287.
    Annergren, Mariette
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kauven, D.
    Larsson, Christian A.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Potters, M. G.
    Tran, Q.
    Özkan, L.
    On the way to autonomous model predictive control: A distillation column simulation study2013Inngår i: 10th IFAC Symposium on Dynamics and Control of Process Systems, DYCOPS 2013, IFAC Secretariat , 2013, nr PART 1, s. 713-720Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Model Predictive Control (MPC) is a powerful tool in the control of large scale chemical processes and has become the standard method for constrained multivariable control problems. Hence, the number of MPC applications is increasing steadily and it is being used in application domains other than petrochemical industries. A common observation by the industrial practitioners is that success of any MPC application requires not only efficient initial deployment but also maintenance of initial effectiveness. To this end, we propose a novel high level automated support strategy for MPC systems. Such a strategy consists of components such as performance monitoring, performance diagnosis, least costly closed loop experiment design, re-identification and autotuning. This work presents the novel technological developments in each component and demonstrates them on a distillation column case study. We show that automated support strategy restores nominal performance after a performance drop is detected and takes the right course of action depending on its cause.

  • 288.
    Annergren, Mariette
    et al.
    KTH Royal Institute of Technology.
    Khoshfetrat Pakazad, Sina
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Wahlberg, Bo
    KTH Royal Institute of Technology.
    A Distributed Primal-dual Interior-point Method for Loosely Coupled Problems Using ADMMManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In this paper we propose an efficient distributed algorithm for solving loosely coupled convex optimization problems. The algorithm is based on a primal-dual interior-point method in which we use the alternating direction method of multipliers (ADMM) to compute the primal-dual directions at each iteration of the method. This enables us to join the exceptional convergence properties of primal-dual interior-point methods with the remarkable parallelizability of ADMM. The resulting algorithm has superior computational properties with respect to ADMM directly applied to our problem. The amount of computations that needs to be conducted by each computing agent is far less. In particular, the updates for all variables can be expressed in closed form, irrespective of the type of optimization problem. The most expensive computational burden of the algorithm occur in the updates of the primal variables and can be precomputed in each iteration of the interior-point method. We verify and compare our method to ADMM in numerical experiments.

  • 289.
    Annergren, Mariette
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Larsson, Christian A.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    MOOSE: A model based optimal input design toolbox2012Inngår i: 16th IFAC Symposium on System Identification, IFAC , 2012, nr PART 1, s. 1535-1540Konferansepaper (Fagfellevurdert)
    Abstract [en]

    MOOSE is a model based optimal input design toolbox developed for Matlab. The objective of the toolbox is to simplify the implementation of some optimal input design problems encountered in system identification. MOOSE provides an extra layer between the user and a convex optimization environment.

  • 290.
    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 motors2013Inngår i: IECON Proceedings (Industrial Electronics Conference), Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2013, s. 5555-5560, artikkel-id 6700043Konferansepaper (Fagfellevurdert)
    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

  • 291.
    António, Gonga
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Landsiedel, O.
    Soldati, Pablo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Johansson, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Multi-channel communication vs. adaptive routing for reliable communication in WSNs2012Inngår i: IPSN'12 - Proceedings of the 11th International Conference on Information Processing in Sensor Networks, Association for Computing Machinery (ACM), 2012, s. 125-126Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Interference and link dynamics constitute great concerns for stability and performance of protocols in WSNs. In this paper we evaluate the impact of channel hopping and adaptive routing on delay and reliability focusing on delay critical applications.

  • 292.
    Anveden Hertzberg, Naomi
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Coordinated Control for Multiple Autonomous Underwater Vehicles2014Student paper other, 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis discusses self- and event-triggered control for collective motion of

    autonomous underwater vehicles, for which rules are derived and analysed. The

    purpose is to enable coordinated underwater motion for agents that can not

    update their knowledge of the states of the group while submerged. A selftriggered

    control strategy is studied in which a designated leader agent broadcasts

    the upcoming waypoints for all agents, based on their desired position

    relative the leader. A Lyapunov based event-triggered approach is also studied

    using a potential based control strategy. Stability and convergence problems

    are discussed as well as the suitability of the control strategies based on feasible

    inter-surfacing times for the agents. Simulations illustrate the characteristics of

    the control strategies.

  • 293.
    Appelblad, André
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Development of a Temperature Controlled Cell for Surface Enhanced Raman Spectroscopy for in situ Detection of Gases2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This work describes a master’s thesis in engineering physics at Umeå University carried out during the spring semester of 2014. In the thesis the student has constructed and tested a temperature controlled cell for cooling/heating of surface-enhanced-Raman-spectroscopy (SERS) substrates for rapid detection of volatile substances. The thesis was carried out at the Swedish Defence Research Agency (FOI) in Umeå, Sweden. A Linkam Scientific Instruments TS1500 cell was equipped with a Peltier element for cooling/heating and a thermistor temperature sensor. A control system was constructed, based on an Arduino Uno microcontroller board and a pulse-width-modulated (PWM) H-bridge motor driver to control the Peltier element using a proportional-integral (PI) control algorithm. The temperature controlled cell was able to regulate the temperature of a SERS substrate within -15 to +110 °C and maintain the temperature over prolonged periods at ±0.22 °C of the set point temperature. Gas phase of 2-chloro-2-(difluoromethoxy)-1,1,1-trifluoro-ethane (isoflurane) was flowed through the cell and SERS spectra were collected at different temperatures and concentrations. This test showed that the signal is increased when the substrate is cooled and reversibly decreased when the substrate was heated.

    Keywords: temperature control, Raman scattering, surface enhanced Raman spectroscopy SERS, SERS substrate, volatile substances, Peltier module, thermistor, PWM, H-bridge, PI(D) control.

  • 294.
    Appelblom, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Modelling of Complex Dynamics in Fixed Bed Reactors2005Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Chemical reactors are a part of modern industry and the catalytic tubular fixed bed reactor examined in this work is an important reactor for chemicals production.

    In this work two different types of models for the reactor are studied; a pseudohomogeneous model and a heterogeneous model. The goal is to find differences in behaviour between these two types of reactor models and explain these.

    In a real reactor there exists two phases, a solid catalyst and a fluid reactant. Both these phases are in the pseudohomogeneous model treated as a single phase, a pseudofluid. In the heterogeneous model the two phases are treated separately.

    When comparing these types of models a few structural differences exist, void fraction, heat exchange between two phases, and heat dispersion in the phases, and all of these will affect the behaviour of the models differently.

    The models are studied using bifurcation analysis and linear analysis. Bifurcation theory is used to find and track different solutions depending on a certain parameter and to get a good overall picture of a system’s solutions and their type, steady state or sustained oscillation.

    Linear analysis is used to study linearization around a specific solution and to determine stability and frequency dependency.

    It is found that the concept of void fraction in the reactor model affects the behaviour only as a time scaling, while the concept of interfacial heat exchange affects the stability. The distribution of heat dispersion between phases has a significant impact on the reaction behaviour. Feedback is determined as the main cause for instabilities and oscillative solutions.

  • 295. Aragues, R.
    et al.
    Shi, Guodong
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Sagues, C.
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Distributed algebraic connectivity estimation for adaptive event-triggered consensus2012Inngår i: American Control Conference (ACC), 2012, IEEE , 2012, s. 32-37Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In several multi agent control problems, the convergence properties and speed of the system depend on the algebraic connectivity of the graph. We discuss a particular event-triggered consensus scenario, and show that the availability of an estimate of the algebraic connectivity could be used for adapting the behavior of the average consensus algorithm. We present a novel distributed algorithm for estimating the algebraic connectivity, that relies on the distributed computation of the powers of matrices. We provide proofs of convergence, convergence rate, and upper and lower bounds at each iteration of the estimated algebraic connectivity.

  • 296. Aragues, Rosario
    et al.
    Shi, Guodong
    Dimarogonas, Dimos V.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Saguees, Carlos
    Johansson, Karl Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Mezouar, Youcef
    Distributed algebraic connectivity estimation for undirected graphs with upper and lower bounds2014Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 50, nr 12, s. 3253-3259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The algebraic connectivity of the graph Laplacian plays an essential role in various multi-agent control systems. In many cases a lower bound of this algebraic connectivity is necessary in order to achieve a certain performance. Lately, several methods based on distributed Power Iteration have been proposed for computing the algebraic connectivity of a symmetric Laplacian matrix. However, these methods cannot give any lower bound of the algebraic connectivity and their convergence rates are often unclear. In this paper, we present a distributed algorithm for estimating the algebraic connectivity for undirected graphs with symmetric Laplacian matrices. Our method relies on the distributed computation of the powers of the adjacency matrix and its main interest is that, at each iteration, agents obtain both upper and lower bounds for the true algebraic connectivity. Both bounds successively approach the true algebraic connectivity with the convergence speed no slower than O(1/k).

  • 297.
    Arain, Muhammad Asif
    et al.
    University of Genova , Genova, Italy; Warsaw University of Technology, Warshaw, Poland.
    Hultmann Ayala, Helon Vicente
    University of Genova , Genova, Italy; Warsaw University of Technology, Warshaw, Poland.
    Ansari, Muhammad Adil
    Science & Technology , Quaid-e-Awam University of Engineering, Sindh, Pakistan.
    Nonlinear System Identification Using Neural Network2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Magneto-rheological damper is a nonlinear system. In this case study, system has been identified using Neural Network tool. Optimization between number of neurons in the hidden layer and number of epochs has been achieved and discussed by using multilayer perceptron Neural Network.

  • 298.
    Aranovskiy, Stanislav
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. The Department of Control Systems and Informatics, National Research University of Information Technologies, Mechanics and Optics, Saint-Petersburg, Russia.
    Freidovich, Leonid
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Adaptive compensation of disturbances formed as sums of sinusoidal signals with application to an active vibration control benchmark2013Inngår i: European Journal of Control, ISSN 0947-3580, E-ISSN 1435-5671, Vol. 19, nr 4, s. 253-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An intuitive solution for the problem of adaptive attenuation of a disturbance formed as a finite sum of unknown sinusoidal signals is proposed for an internally stable discrete-time plant. The compensator is formed as a weighted sum of stable filters. An identification-based procedure for adaptive tuning of the coefficients is proposed for the case of unknown disturbance. We also propose a time-invariant compensator that provides perfect attenuation of a disturbance for the case when a model identification error is sufficiently small and disturbance frequencies are known. The technique is applied to a case study on a challenging benchmark example in the field of active vibration control. Attenuation of a disturbance formed as a sum of up to three sinusoidal signals with unknown/time-varying frequencies is demonstrated via simulation and experimental studies. (C) 2013 European Control Association. Published by Elsevier Ltd. All rights reserved.

  • 299.
    Aranovskiy, Stanislav
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Department of Control Systems and Informatics, ITMO University.
    Freidovich, Leonid
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nikiforova, LV
    Department of Control Systems and Informatics, ITMO University.
    Losenkov, AA
    Department of Control Systems and Informatics, ITMO University.
    МОДЕЛИРОВАНИЕ И ИДЕНТИФИКАЦИЯДИНАМИКИ ЗОЛОТНИКОВОГО ГИДРОРАСПРЕДЕЛИТЕЛЯ: ЧАСТЬ I. МОДЕЛИРОВАНИЕ / ЧАСТЬ II. ИДЕНТИФИКАЦИЯ2013Inngår i: Scientific and Technical Journal «Priborostroenie», ISSN 0021-3454, Vol. 56, nr 4, s. 253-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [ru]

    ЧАСТЬ I. МОДЕЛИРОВАНИЕ:

    Проанализированы подходы к моделированию гидрораспределителя. Предложена модель динамики золотника в гидрораспределителе, состоящая из двухподсистем — линейной и статически нелинейной.

    ЧАСТЬ II. ИДЕНТИФИКАЦИЯ:

    Предложен метод идентификации параметров модели, использующий датчикидавления и не требующий измерения положения штока золотника. Приведенырезультаты экспериментов.

  • 300.
    Aranovskiy, Stanislav
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Department of Control Systems and Informatics, ITMO University, Saint-Petersburg, Russia.
    Losenkov, Andrei
    Department of Control Systems and Informatics, ITMO University, Saint-Petersburg, Russia.
    Vazquez, Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Position control of an industrial hydraulic system with a pressure compensator2014Inngår i: Proceedings of the 2014 22nd Mediterranean Conference of Control and Automation (MED 2014), Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 1329-1334Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A problem of position control of a forestry crane is studied. Several features of industrial hydraulic systems are pointed out, namely a nonlinearity of a valve and a pressure compensator. A novel model of a hydraulic system with the pressure compensator is presented and analyzed, a static nonlinearity inversion and a velocity feedforward control term are introduced. Real-time experiments with controllers which use only position measurements illustrate utility of these terms.

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