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  • 1.
    Adaldo, Antonio
    et al.
    Department of Automatic Control, School of Electrical Engineering, KTH Royal Institute of Technology.
    Mansouri, Sina Sharif
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Kanellakis, Christoforos
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Dimarogonas, Dimos V.
    Department of Automatic Control, School of Electrical Engineering, KTH Royal Institute of Technology.
    Johansson, Karl H.
    Department of Automatic Control, School of Electrical Engineering, KTH Royal Institute of Technology.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Cooperative coverage for surveillance of 3D structures2017In: IEEE International Conference on Intelligent Robots and Systems, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1838-1845, article id 8205999Conference paper (Refereed)
    Abstract [en]

    In this article, we propose a planning algorithm for coverage of complex structures with a network of robotic sensing agents, with multi-robot surveillance missions as our main motivating application. The sensors are deployed to monitor the external surface of a 3D structure. The algorithm controls the motion of each sensor so that a measure of the collective coverage attained by the network is nondecreasing, while the sensors converge to an equilibrium configuration. A modified version of the algorithm is also provided to introduce collision avoidance properties. The effectiveness of the algorithm is demonstrated in a simulation and validated experimentally by executing the planned paths on an aerial robot.

    The full text will be freely available from 2019-12-14 11:35
  • 2.
    Alexhs, Kostas
    et al.
    University of Patras, Department of Electrical and Computer Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tzes, Anthony
    University of Patras, Department of Electrical and Computer Engineering.
    Autonomous quadrotor position and attitude PID/PIDD control in GPS-denied environments2011In: International Review of Automatic Control, ISSN 1974-6059, E-ISSN 1974-6067, Vol. 4, no 3Article in journal (Refereed)
    Abstract [en]

    This article addresses the control problem of an unmanned quadrotor in the absence of absolute position measurement data (e.g. GPS, external cameras). Based on an attached Inertia Measurement Unit, a sonar and an optic flow sensor, the quadrotor’s translational and rotational motion-vector is estimated using sensor fusion algorithms. A control scheme consisted of three Proportional-Integral-Derivative (PID) controllers for the translational motions, combined with three Proportional-Integral-Derivative-second Derivative (PIDD) controllers for the attitude dynamics is utilized in order to achieve accurate position hold and attitude tracking. The controller is implemented on a quadrotor prototype in indoor position hold experiments and aggressive attitude regulation maneuvers.

  • 3.
    Alexis, Kostas
    et al.
    Swiss Federal Institute of Technology.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tzes, Anthony
    University of Patras.
    Experimental Constrained Optimal Attitude Control of a Quadrotor subject to Wind Disturbances2014In: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 12, no 6, p. 1289-1302Article in journal (Refereed)
    Abstract [en]

    The design and experimental verification of a Constrained Finite Time Optimal Controller (CFTOC) for attitude maneuvers of an Unmanned Quadrotor operating under severe wind conditions is the subject of this article. The quadrotor’s nonlinear dynamics are linearized in various operating points resulting in a set of piecewise affine models. The CFTO–controller is designed for set-point maneuvers taking into account the switching between the linear models and the state and actuation constraints. The control scheme is applied on experimental studies on a prototype quadrotor operating both in absence and under presence of forcible atmospheric disturbances. Extended experimental results indicate that the proposed control approach attenuates the effects of induced wind–gusts while performing accurate attitude set–point maneuvers.

  • 4.
    Alexis, Kostas
    et al.
    Electrical and Computer Science Department, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tzes, Anthony
    Electrical and Computer Science Department, University of Patras.
    Model predictive quadrotor control: attitude, altitude, and position experimental studies2012In: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 6, no 12, p. 1812-1827Article in journal (Refereed)
    Abstract [en]

    This article addresses the control problem of an unmanned quadrotor in an indoor environment where there is lack of absolute localization data. Based on an attached Inertia Measurement Unit, a sonar and an optic flow sensor, the state vector is estimated using sensor fusion algorithms. A novel Switching Model Predictive Controller is designed in order to achieve precise trajectory control, under the presence of forcible wind–gusts. The quadrotor’s attitude, altitude and horizontal linearized dynamics result in a set of Piecewise Affine models, enabling the controller to account for a larger part of the quadrotor’s flight envelope while modeling the effects of atmospheric disturbances as additive–affine terms in the system. The proposed controller algorithm accounts for the state and actuation constraints of the system. The controller is implemented on a quadrotor prototype in indoor position tracking, hovering and attitude maneuvers experiments. The experimental results indicate the overall system’s efficiency in position/altitude/attitude set–point maneuvers.

  • 5.
    Alexis, Kostas
    et al.
    Department of Electrical and Computer Engineering, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tzes, Anthony
    Department of Electrical and Computer Engineering, University of Patras.
    On trajectory tracking model predictive control of an unmanned quadrotor helicopter subject to aerodynamic disturbances2014In: Asian journal of control, ISSN 1561-8625, E-ISSN 1561-8625, Vol. 16, no 1, p. 209-224Article in journal (Refereed)
    Abstract [en]

    In this article a Model Predictive Control (MPC) strategy for the trajectory tracking of an unmanned quadrotor helicopter is presented. The quadrotor’s dynamics are modeled by a set of Piecewise Affine (PWA) systems around different operating points of the translational and rotational motions. The proposed control scheme is dual and is consisted by an integral MPC for the translational motions, followed by a MPC–scheme for the quadrotor’sattitude motions’ tracking. By the utilization of PWA representations, the controller is computed for a larger part of the quadrotor’s flight envelope. Theproposed dual control scheme is able to calculate optimal control actions with robustness against atmospheric disturbances (e.g. wind gusts) and physical constraints of the quadrotor (e.g. maximum lifting forces or fixed thrust limitations in order to extend flight endurance). Extended simulation studies prove the efficiency of the MPC–scheme, both in trajectory tracking and aerodynamic disturbances attenuation.

  • 6.
    Alexis, Kostas
    et al.
    Department of Electrical and Computer Engineering, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tzes, Anthony
    Department of Electrical and Computer Engineering, University of Patras.
    Switching model predictive attitude control for a quadrotor helicopter subject to atmospheric disturbances2011In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 19, no 10, p. 1195-1207Article in journal (Refereed)
    Abstract [en]

    In this article a Switching Model Predictive Attitude Controller for an Unmanned quadrotor Helicopter subject to atmospheric disturbances is presented. The proposed control scheme is computed based on a Piecewise Affine (PWA) model of the quadrotor’s attitude dynamics, where the effects of the atmospheric turbulence are taken into consideration as additive disturbances. The switchings among the PWA models are ruled by the rate of the rotation angles and for each PWA system a corresponding model predictive controller is computed. The suggested algorithm is verified in experimental studies in the execution of sudden maneuvers subject to forcible wind disturbances. The quadrotor rejects the induced wind–disturbances while performing accurate attitude tracking.

  • 7.
    Alexis, Kostas
    et al.
    Department of Electrical and Computer Engineering, University of Patras.
    Papachristos, Christos
    Department of Electrical and Computer Engineering, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Tzes, Anthony
    Department of Electrical and Computer Engineering, University of Patras.
    Model predictive quadrotor indoor position control2011In: 19th Mediterranean Conference on Control & Automation (MED 2011): [Aquis Corfu Holiday Palace], Corfu, Greece, 20 - 23 June 2011, Piscataway, NJ: IEEE Communications Society, 2011Conference paper (Refereed)
    Abstract [en]

    This article addresses the control problem of quadrotors in environments where absolute-localization data (GPS, positioning from external cameras) is inadequate. Based on an attached IMU and an optical flow sensor the quadrotor’s translational velocity is estimated using an Extended Kalman Filter. Subject to the velocity measurements, the roll, pitch and yaw (RPY) angles, the angular rates and the translational accelerations a switching Model Predictive Controller is designed. The quadrotor dynamics is linearized at various operating points according to the angular rates and the RP angles. The switching is inferred according to the various linearized models of the quadrotor. The controller is applied on a quadrotor prototype in low-altitude position hold maneuvers at very constrained environments. The experimental results indicate the overall system’s efficiency in position/altitude set–point maneuvers.

  • 8.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    An improvement in the observarion model for Monte Carlo localization2014Conference paper (Refereed)
  • 9.
    Alhashimi, Anas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Observation model for Monte Carlo Localization2014Conference paper (Other academic)
  • 10.
    Andrikopoulos, George
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    HUmanoid Robotic Leg via pneumatic muscle actuators: implementation and control2018In: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 53, no 1-2, p. 465-480Article in journal (Refereed)
    Abstract [en]

    In this article, a HUmanoid Robotic Leg (HURL) via the utilization of pneumatic muscle actuators (PMAs) is presented. PMAs are a pneumatic form of actuation possessing crucial attributes for the implementation of a design that mimics the motion characteristics of a human ankle. HURL acts as a feasibility study in the conceptual goal of developing a 10 degree-of-freedom (DoF) lower-limb humanoid for compliance and postural control, while serving as a knowledge basis for its future alternative use in prosthetic robotics. HURL’s design 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.

  • 11.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Arvanitakis, John
    Department of Electrical and Computer Engineering, University of Patras.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A switched system modeling approach for a pneumatic muscle actuator2012In: 2012 IEEE International Conference on Industrial Technology, ICIT 2012, Piscataway, NJ: IEEE Communications Society, 2012, p. 833-839Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to present a switched system approach for the dynamic modeling of Pneumatic Muscle Actuators (PMAs). PMAs are highly non-linear pneumatic actuators where their elongation is proportional to the interval pressure. During the last two decades, various modeling approaches have been presented that describe the behavior of PMAs. While most mathematical models are characterized by simplicity and accuracy in describing the attributes of PMAs, they are limited to static performance analysis. Static models are proven to be insufficient for real time control applications, thus creating the need for the development of dynamic PMA models. A collection of experimental and simulation results are being presented that prove the efficiency of the proposed approach.

  • 12.
    Andrikopoulos, Georgios
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Design, development and control of a human-inspired two-arm robot via Pneumatic Artificial Muscles2017In: 2017 25th Mediterranean Conference on Control and Automation, MED 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 241-246, article id 7984125Conference paper (Refereed)
    Abstract [en]

    In this article, the design and implementation of a 10 Degree-of-Freedom (DoF) human-inspired two-arm robot is presented. Multiple Pneumatic Artificial Muscles (PAMs) in antagonistic formations are incorporated for undertaking the two arms' movements, while the design goal is the replication of human-like motion patterns, described by smoothness, inherent compliance and accuracy. To evaluate the feasibility of the proposed concept, the 10-DoF robot is developed and experimentally tested in open and closed-loop control scenarios via the use of a multiple Advanced Nonlinear PID (ANPID) based scheme.

  • 13.
    Andrikopoulos, Georgios
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On the design, development and motion control of a HUmanoid Robotic Leg via pneumatic artificial muscles2017In: 2016 IEEE International Conference on Robotics and Biomimetics, ROBIO 2016, Piscataway, NJ, 2017, p. 1637-1642, article id 7866562Conference paper (Refereed)
    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

  • 14.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 muscle2012In: 10th Portuguese Conference in Automatic Control: University of Madeira, July 16-18, 2012, p. 135-140Conference paper (Refereed)
    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.

  • 15.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 muscle2013In: International Journal of Control, Automation and Systems, ISSN 1598-6446, E-ISSN 2005-4092, Vol. 11, no 6, p. 1223-1231Article in journal (Refereed)
    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.

  • 16.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 muscle2013In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, no 2, p. 904-916Article in journal (Refereed)
    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.

  • 17.
    Andrikopoulos, Georgios
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Kominiak, Dariusz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Unander-Scharin, Åsa
    Luleå University of Technology, Department of Arts, Communication and Education, Music and dance.
    Towards the Development of a Novel Upper-Body Pneumatic Humanoid: Design and Implementation2016In: 2016 European Control Conference, ECC 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 395-400, article id 7810317Conference paper (Refereed)
    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.

  • 18.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    A Survey on applications of pneumatic artificial muscles2011In: 19th Mediterranean Conference on Control and Automation, MED 2011, Piscataway, NJ: IEEE Communications Society, 2011, p. 1439-1446Conference paper (Refereed)
    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

  • 19.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Adaptive internal model control scheme for a pneumatic artificial muscle2013In: European Control Conference (ECC), July 17-19, Zurich, Switzerland 2013, 2013, p. 772-777Conference paper (Refereed)
    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.

  • 20.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Advanced nonlinear PID-based antagonistic control for pneumatic muscle actuators2014In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, no 12, p. 6926-6937, article id 6786031Article in journal (Refereed)
    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.

  • 21.
    Andrikopoulos, Georgios
    et al.
    University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    University of Patras.
    An experimental study on thermodynamic properties of pneumatic artificial muscles2012In: 2012 20th Mediterranean Conference on Control & Automation: Barcelona, Spain, July 3-6, 2012, Piscataway, NJ: IEEE Communications Society, 2012, p. 1334-1340Conference paper (Refereed)
    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.

  • 22.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Design and Development of an Exoskeletal Wrist Prototype via Pneumatic Artificial Muscles2015In: Meccanica (Milano. Print), ISSN 0025-6455, E-ISSN 1572-9648, Vol. 50, no 11, p. 2709-2730Article in journal (Refereed)
    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.

  • 23.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Electrical and Computer Engineering Department, University of Patras.
    Development and control of a hybrid controlled vertical climbing robot based on pneumatic muscle actuators2011In: Journal of Control Engineering and Technology (JCET), ISSN 2223-2036, Vol. 1, no 2, p. 53-58Article in journal (Refereed)
    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.

  • 24.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Incorporation of Thermal Expansion in Static Force Modeling of Pneumatic Artificial2015In: IEEE Mediterranean Conference on Control and Automation, Torremolinos, Spain, June, 16-19, 2015 / [ed] V. Munoz, Piscataway, NJ: IEEE Communications Society, 2015, p. 414-420, article id 7158784Conference paper (Refereed)
    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.

  • 25.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Motion control of a novel robotic wrist exoskeleton via pneumatic muscle actuators2015In: 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, article id 7301464Conference paper (Refereed)
    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.

  • 26.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Non-linear control of pneumatic artificial muscles2013In: 21st IEEE Mediterranean Conference on Control and Automation, June 25-28, Platanias, Chania, Crete, Greece, 2013, 2013, p. 729-734, article id 6608804Conference paper (Refereed)
    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.

  • 27.
    Andrikopoulos, Georgios
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 Actuators2016In: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, Vol. 21, no 6, p. 2647-2659, article id 7501612Article in journal (Refereed)
    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.

  • 28.
    Andrikopoulos, Georgios
    et al.
    Department of Electrical and Computer Science, University of Patras.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Manesis, Stamatis
    Department of Electrical and Computer Engineering, University of Patras.
    Pneumatic artificial muscles: a switching model predictive control approach2013In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 21, no 12, p. 1653-1664Article in journal (Refereed)
    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.

  • 29.
    Arvanitakis, John
    et al.
    University of Patras, Department of Electrical and Computer Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 robots2011In: 2011 IEEE Conference on Emerging Technologies & Factory Automation (ETFA 2011): Toulouse; 5 September - 9 September 2011, Piscataway, NJ: IEEE Communications Society, 2011, article id 6059092Conference paper (Refereed)
    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.

  • 30.
    Brusell, Angelica
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Andrikopoulos, Georgios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A survey on Pneumatic Wall-Climbing Robots for Inspection2016In: 24th Mediterranean Conference on Control and Automation MED: June 21-24, Athens, Greece, 2016, Piscataway. NJ: IEEE Communications Society, 2016, p. 220-225, article id 7535885Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to present a survey on inspection applications of Pneumatic Wall-Climbing Robots (PWCR). In general, a PWCR utilizes negative pressure as its adhesion method, through mainly suction cups or negative pressure thrust-based mechanisms. Their main advantage being their ability to climb non-ferromagnetic surfaces, such as glass and composite materials, in comparison with climbing robots based on magnetic adhesion methods. A growing application area is the utilization of PWCRs for inspection purposes for accelerating the otherwise time consuming procedures of manual inspection, while offering the important advantage of protecting human workers from hazardous and/or unreachable environments. This article will summarize the key enabling inspection applications of PWCRs in the following areas: a) Construction, b) Industrial Infrastructures, as well as c) Aircraft applications.

  • 31.
    Brusell, Angelica
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Andrikopoulos, Georgios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Novel considerations on the negative pressure adhesion of electric ducted fans: An experimental study2017In: 2017 25th Mediterranean Conference on Control and Automation, MED 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1404-1409, article id 7984315Conference paper (Refereed)
    Abstract [en]

    In this article, the potential of utilizing an Electric Ducted Fan (EDF) as an adhesion actuator is investigated in detail, where an experimental setup is implemented for evaluating the EDF's ability to adhere to a test surface through negative pressure generation. Different design variables and modifications to the original EDF structure are tested, while their impact on the adhesion efficiency is experimentally evaluated. The presented investigation acts as a preliminary study to the goal of incorporating the resulting optimized negative pressure-based actuation method in a wall-climbing robot for inspection of aircraft fuselages

  • 32.
    Carholt, Cristoffer
    et al.
    Luleå University of Technology.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Fresk, Emil
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Andrikopoulos, Georgios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Design, Modelling and Control of a Single Rotor UAV2016In: 24th Mediterranean Conference on Control and Automation,: June 21-24, Athens, Greece, 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 840-845, article id 7536015Conference paper (Refereed)
    Abstract [en]

    In this article, a novel Vertical Take-Off and Landing (VTOL) Single Rotor Unmanned Aerial Vehicle (SR- UAV) will be presented. The SRUAV’s design properties will be analysed in detail, with respect to technical novelties outlining the merits of such a conceptual approach. The system’s model will be mathematically formulated, while a cascaded P-PI and PID-based control structure will be utilized in extensive simulation trials for the preliminary evaluation of the SR-UAV’s attitude and translational performance.

  • 33.
    Castaño Arranz, Miguel
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Birk, Wolfgang
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Survey on Control Configuration Selection and New Challenges in Relation to Wireless Sensor and Actuator Networks2017In: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, no 1, p. 8810-8825Article in journal (Refereed)
    Abstract [en]

    This survey on Control Configuration Selection (CCS) includes methods based on relative gains, gramian-based interaction measures, methods based on optimization schemes, plantwide control, and methods for the reconfiguration of control systems. The CCS problem is discussed, and a set of desirable properties of a CCS method are defined. Open questions and research tracks are discussed, with the focus on new challenges in relation to the emerging area of Wireless Sensors and Actuator Networks.

  • 34.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Identification of building damage using armax model: A parametric study2016In: Diagnostyka, ISSN 1641-6414, Vol. 17, no 3, p. 3-14Article in journal (Refereed)
    Abstract [en]

    The Structural Identification approach is used to identify and localize the existence of damage for a steel frame. The black box linear parametric model called Auto-Regressive Moving Average with eXternal input (ARMAX) was utilized for the construction of the Frequency Response Functions, based on simulation results. The Singular Value Decomposition method was adopted to identify how many significant eigenvalues exist and plot the Complex Mode Indicator Function for the complete frame. Three damage indices were adopted to evaluate the state of damage in the frame. The results indicated that the ARMAX is a robust scheme for structural damage detection.

  • 35.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Posicast Control of Structures Using MR Dampers2016In: Structural Control and Health Monitoring: The Bulletin of ACS, ISSN 1545-2255, E-ISSN 1545-2263, Vol. 23, no 8, p. 1121-1134Article in journal (Refereed)
    Abstract [en]

    In this article, a novel application of a semi active Posicast control scheme for structures with Magneto- Rheological (MR) dampers is presented. MR dampers are considered to be highly promising of semi-active control systems, which are becoming increasingly popular for alleviating the effects of dynamic loads on civil engineering structures because they combine the merits of both passive and active control systems. The main contribution of this article relates to the design, application, tuning and performance evaluation of the novel Posicast control scheme for structural control. The efficiency of the suggested control strategy was evaluated by performing numerical simulations of a benchmark three-story building with an MR damper, rigidly attached between the first floor and the ground. The damper’s behaviour was simulated using the Bouc-Wen model. Seven evaluation criteria were used to assess the performance of the proposed posicast control scheme in reducing the excited structure’s responses to dynamic loading. The simulation’s results indicated that the Posicast control scheme had significant advantages over conventional alternatives in terms of performance and efficiency.

  • 36.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. College of Engineering, Department of Civil Engineering, University of Mosul, Mosul, Iraq.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Dritsas, Leonidas
    University of Patras, Department of Electrical Engineering.
    Semi-active control of flexible structures using closed-loop input shaping techniques2017In: Structural Control and Health Monitoring: The Bulletin of ACS, ISSN 1545-2255, E-ISSN 1545-2263, Vol. 24, no 5, article id e1913Article in journal (Refereed)
    Abstract [en]

    In this research effort, a novel approach on the control of structures with magnetorheological (MR) dampers is presented, based on an appropriately adapted closed-loop version of the generic input shaping control theory. The MR damper is a very promising kind of semi-active control system (actuator), mixing the advantages of the active and passive structural control systems, hence their increasing use as attenuators that reject the effects of dynamic loads on civil engineering structures. The main contribution of this article is the application and performance evaluation of the novel ‘Linear Matrix Inequality-based’ feedback version of the input shaping control theory for the first time in the area of structural control. The need for the use of a feedback version of input shaping control stems from the design trade-off between robustness and speed of response requirements. A simulation of a benchmark three-story building with one MR damper is employed to verify the efficiency of the proposed control approach. The nonlinear behaviour of the MR damper, rigidly connected between the first floor of the structure and the ground, is captured by the well-known Bouc–Wen model. The superiority and effectiveness of the proposed scheme in reducing the responses of the structure were proved using seven quantifiable evaluation criteria and by comparing these results with those achieved by classical and well-established alternative control schemes.

  • 37.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Investigation of changes in modal characteristics before and after damage of a railway bridge: A case study2015In: The IES Journal Part A: Civil & Structural Engineering, ISSN 1937-3260, E-ISSN 1937-3279, Vol. 8, no 2, p. 131-144Article in journal (Refereed)
    Abstract [en]

    The linear, time-invariant transfer function Txy has been utilized for the construction of FRF, based on the ambient vibration measurements. The results presented here indicated the possibility to identify and localize damages in steel railway bridges from the variations in the modal characteristics of the structure. The comparison between the modal characteristics for the healthy and collapsed bridge confirmed that damage had been existed. The abnormal percentage of change in modal damping, between the healthy and any other condition for a structure, can be regarded as a serious indicator for early stages of damage, while the high percentage of change in modal damping can clearly indicate the existence of damage in that structure. The average ratio of change in the damping ratio from the healthy to the collapsed bridge was about 206 % and this ration could be regarded as an index for the existence of a serious damage in steel bridges, which needs further evaluation in other test cases.

  • 38.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    A comparative study on the identification of building natural frequencies based on parametric models2014In: Proceedings of the 33rd IASTED International Conference on Modelling, Identification and Control: February 17 – 19, 2014, Innsbruck, Austria, 2014Conference paper (Refereed)
    Abstract [en]

    The analysis and design of civil engineering structures is a complex problem, which is based on many assumptions to simplify these operations. This in turn, leads to a difference in the structural behaviour between calculations based models and real structures. Structural identification was proposed by many researchers as a tool to reduce this difference between models and actual structures. Moreover, Parametric models and non-parametric models were used intensively for system identification by many researchers. In this research effort, the system identification concept is utilized to identify the natural frequencies for a steel building’s frames. Different black box linear parametric models such as Transfer Function model (TF), Auto-Regressive model with eXternal input model (ARX), Auto-Regressive Moving Average with eXternal input (ARMAX) model, Output Error model structure (OE), and Box-Jenkins model (BJ) were examined for identifying the first 10th natural frequencies for the building’s frames, based on simulation results. Abaqus 6.12 finite-element software was utilized to perform the time history analysis for the examples and the obtained responses at one point of the roofs (assumed as a sensor) were further processed by the parametric models to obtain the building’s natural frequencies based on the Abaqus time history analysis results (assumed as a measurements). After that, Abaqus 6.12 was utlized again to perform another analysis, which is called frequency analysis to obtain the building’s natural frequencies and mode shapes based on the stiffness and mass (not the measurements) of the buildings. The results showed that the linear parametric models TF, ARX, ARMAX, OE, and BJ are robust to identify the natural frequencies of building and they are recommend for future work.

  • 39.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Comfort Level Identification for Irregular Multi-storey Building Subjected to Vibrations2015In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 50, p. 40-49Article in journal (Refereed)
    Abstract [en]

    In this article, the System Identification approach is being used to identify the vertical frequencies of the top storey in a multi-storey building prefabricated from reinforced concrete in Stockholm. Before building construction, detailed investigation indicated that the building will not be affected by train vibrations from the nearby railway yard. After building completion, disturbing vibrations were observed in the building. Three measurement types namely: ambient vibration test, forced vibration test on the rails, and forced vibration test have been performed in order to specify the probable reasons for these vibrations. Five methods of structural identification approach, specifically: ARX, ARMAX, BJ, OEand State Space Models have been implemented for the identification process in this study usingthe tests' results. All the test types and model structures utilized have identified a concentration inthe floor only, which is close to the frequencies of human body parts. Furthermore, the article concludes that the ARMAX model and the Output Error model have indicated an excellent performance to predict the mathematical models of vibration's propagation in the building, when compared with other models used from the three types of tests. In addition, the results of the aforementioned system identification methods, implemented for this study, have indicated that there are no other reasons for the disturbing vibrations still observed in the building. Furthermore, the results confirmed the correctness of the previous theoretical and experimental results obtained by different specialists, who stated that the values of floor acceleration are within the acceptable limits, and the probable reason for any disturbance is the resonance between the generated low frequencies and the human body parts’ frequencies.

  • 40.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Semi-active structural control strategies2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 31-34Article in journal (Refereed)
    Abstract [en]

    The utilization of structural control systems to alleviate the responses of civil engineering structures, under the effects of dynamics loadings, has become a standard technology, while still there are numerous of current research approaches for advancing the effectiveness of these methodologies. It is important for successful application of smart structure to provide an effective control algorithm to compute the control forces to be applied on the building in order to reduce the external disturbances. The aim of this article is to provide a review of the control strategies to control the performance of semi-active systems utilized in civil engineering structures.

  • 41.
    Edrees, Tarek
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Skanska Sverige AB Technology, Bridge and Civil Engineering.
    A state-of-the-art review of Structural Control Systems2015In: Journal of Vibration and Control, ISSN 1077-5463, E-ISSN 1741-2986, Vol. 21, no 5, p. 919-937Article in journal (Refereed)
    Abstract [en]

    Nowadays the utilization of structural control systems for alleviating the responses of civil engineering structures, under the effects of different kinds of dynamics loadings, has become a standard technology, while still there are numerous of current research approaches for advancing the effectiveness of these methodologies. The aim of this article is to review the state of the art technologies in structural control systems by introducing a general literature review for all the types of vibrations control systems that have been appeared till now. These systems can be classified into four main groups: a) passive, b) semi active, c) active, and d) hybrid based on their operational mechanism. A brief description of each of these main groups and their subgroups, with their corresponding advantages and disadvantages will be also extendedly reported in this review. This article will conclude by providing an overview of some innovative practical implementations of devices, which are able to demonstrate their potentials and future directions of structural control systems in civil engineering.

  • 42.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Mansouri, Sina Sharif
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Kanellakis, Christoforos
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Halén, Erik
    Luleå tekniska universitet.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Reduced complexity calibration of MEMS IMUs2017In: 2017 25th Mediterranean Conference on Control and Automation, MED 2017, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1316-1320, article id 7984300Conference paper (Refereed)
    Abstract [en]

    In this article a reduced complexity calibration method for Micro-Electro-Mechanical Systems (MEMS) Inertial Measurement Units (IMUs) will be presented, which does not need the rotating reference tables, commonly used in the gyroscope calibration. As it will be presented, in the proposed novel scheme fixed angle rotations have been utilized to observe the integral of the gyroscope signals to find the corresponding sensitivity, axis misalignment and acceleration sensitivity matrices. This appraoch has the significant merit of high norm accuracy, easiness of use, low cost and simplicity in construction, thus allowing anyone with a basic electronics knowledge to calibrate an IMU.

    The full text will be freely available from 2019-07-20 09:02
  • 43.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A generalized Frame Adaptive MPC for the low-level control of UAVs2018Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to establish an adaptiveModel Predictive Control (MPC) scheme for the angular rate and thrust control of a multirotor Unmanned Aerial Vehicle (UAV). The proposed model adaptiveness comes from estimating the movement of the Center of Gravity (CoG) combined withthe thrust constant of the motors, making the system robust to disturbances and fast to adapt to changing parameters, while also taking under consideration the control signal bounds in order to guarantee for no motor stalls, while flying. The linear requirements of the MPC are adhered to by transforming the estimation and control problem into a control signal squared domain, making the system linear. The efficacy of the proposed estimation and control scheme is presented in simulations where worst case scenarios have been considered.

  • 44.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Experimental Evaluation of a Full Quaternion Based Attitude Quadrotor Controller2015In: 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, article id 7301555Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to present a novel quater- nion based control scheme for the attitude control problem of a quadrotor and experimentally evaluate its performance. A quaternion is a hyper complex number of rank 4 that can be utilized to avoid the inherent geometrical singularity when representing rigid body dynamics with Euler angles or the complexity of having coupled differential equations with the Direction Cosine Matrix (DCM). In the presented approach the novel contributions consist of: a) the quadrotor’s attitude model and b) the proposed non–linear Proportional squared (P^2) control algorithm, which have been proposed and experimentally evaluated fully in the quaternion space, without any transformations nor calculations in the Euler angle nor the DCM spaces. The established control scheme is combined with a quaternion based Madwick Complementary filter for estimating the attitude quadrotor’s responses. Multiple experi- mental results, including the case where external disturbances are acting on the quadrotor, are being presented for proving the efficiency and the robustness of the proposed novel quaternion based controller.

  • 45.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Experimental Model Derivation and Control of a Variable Pitch Propeller Quadrotor2014In: 2014 IEEE International Conference on Control Applications (CCA 2014): Juan Les Antibes, France, 8 -10 October 2014, Piscataway, NJ: IEEE Communications Society, 2014, p. 723-729Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to present a novel quaternion based control scheme for the attitude control problem of a quadrotor equipped with variable pitch propellers. A variable pitch propeller is a type of propeller system utilizes a mechanical mechanism to change the pitch of the rotor blades, while when applied to quadrotors it results in an over-actuated control system. The novelty of the article stems from: a) the proposal of an experimental model for variable pitch propellers and b) the novel proposed thrust and power consumption optimisations for the over-actuated quadrotor. Throughout the article, the merits of the proposed novel approach are being analyzed and discussed, while the efficiency of the variable pitch propellers are being evaluated by extended simulation and experimental results.

  • 46.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Frame Induced Vibration Estimation and Attenuation Scheme on a Multirotor helicopter2015In: Decision and Control (CDC): Los Angeles, CA, 15-17 Dec. 2014, Piscataway, NJ: IEEE Communications Society, 2015, p. 5698-5703, article id 7040281Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to establish an induced frame vibration and attenuation scheme, specifically targeting the area of multi-rotor Unmanned Aerial Vehicles (UAVs), such as quadrotors. These types of unmanned small scale helicopters are characterised by small and light frames, which are vulnerable to vibrations induced by the operation of the motors or external environmental factors. The existence of such vibrations effecting the frame can significantly deteriorate the performance of the overall closed system and even drive it to instabilities. In this article spectral estimation schemes based on: a) Autoregressive (AR) modelling and b) Multiple Signal Classification (MUSIC) are being established and evaluated towards their ability to detect the induced vibration frequencies on the UAV, while an extended discussion is being presented on selecting the correct number of the identified induced vibrating frequencies. In a sequential stage, a vibration attenuation approach based on notch filtering is being presented, being able to correctly attenuate the induced vibrating frequencies in the measurements. The efficiency of the overall suggested scheme is being evaluated by experimental results that indicate the significant improvement in the measurements achieved bythe direct application of the proposed scheme.

  • 47.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Full quaternion based attitude control for a quadrotor2013In: European Control Conference (ECC), July 17-19, 2013, Zurich, Switzerland, 2013, p. 3864-3869, article id 6669617Conference paper (Refereed)
    Abstract [en]

    The aim of this article is to present a novel quaternion based control scheme for the attitude control problem of a quadrotor. A quaternion is a hyper complex number of rank 4 that can be utilized to avoid the inherent geometrical singularity when representing rigid body dynamics with Euler angles or the complexity of having coupled differential equations with the Direction Cosine Matrix (DCM). In the presented approach both the quadrotor's attitude model and the proposed non-linear Proportional squared (P^2) control algorithm have been implemented in the quaternion space, without any transformations and calculations in the Euler's angle space or DCM. Throughout the article, the merits of the proposed novel approach are being analyzed and discussed, while the efficacy of the suggested novel quaternion based controller are being evaluated by extended simulation results.

  • 48.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Generalized Reduced-Complexity Inertial Navigation System for Unmanned Aerial Vehicles2017In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 25, no 1, p. 192-207Article in journal (Refereed)
    Abstract [en]

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

    The full text will be freely available from 2019-01-01 08:56
  • 49.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Wuthier, David
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Generalized center of gravity compensation for multirotors with application to aerial manipulation2017In: IEEE International Conference on Intelligent Robots and Systems, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 4424-4429, article id 8206307Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to establish a generalized parameter estimation scheme to online estimate the Center of Gravity (COG) for multirotors, while using a geometric controller to perform position tracking for applications in aerial manipulation. The proposed scheme is developed so the controller uses the estimated COG to compensate and remove constant offset in the position tracking. The efficiency and validity of the proposed parameter estimation and compensation scheme is proved through two experimental evaluations, one when step changes to the COG are applied and one tracking experiment where a compact aerial manipulator is attached to the multirotor and performs sweeping motions.

    The full text will be freely available from 2019-12-14 09:08
  • 50.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ödmark, Kristoffer
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ultra WideBand enabled Inertial Odometry for Generic Localization2017In: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, no 1, p. 11465-11472Article in journal (Refereed)
    Abstract [en]

    In this paper we will present a inertial odometry localization system, utilizing Ultra WideBand distance measurements for corrections, as a generic localization solution. The proposed scheme is evaluated in two different measurement schemes, one cyclic and one based on stochastic events, which has the strong merit of minimizing the sampling rate, while adhering to covariance constraints on the state, allowing the system to conform with RF regulations. The efficacy of the proposed scheme is evaluated in extended experimental evaluation on an hexacopter Unmanned Aerial Vehicle

123 1 - 50 of 130
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