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  • 1.
    Andersson, Kennet
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Manchester, Ian R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Malm, Jan
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Assessment of cerebrospinal fluid outflow conductance using an adaptive observer-experimental and clinical evaluation2007In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 28, no 11, p. 1355-1368Article in journal (Refereed)
    Abstract [en]

    Idiopathic normal pressure hydrocephalus (INPH) patients have a disturbance in the dynamics of the cerebrospinal fluid (CSF) system. The outflow conductance, C, of the CSF system has been suggested to be prognostic for positive outcome after treatment with a CSF shunt. All current methods for estimation of C have drawbacks; these include lack of information on the accuracy and relatively long investigation times. Thus, there is a need for improved methods. To accomplish this, the theoretical framework for a new adaptive observer (OBS) was developed which provides real-time estimation of C. The aim of this study was to evaluate the OBS method and to compare it with the constant pressure infusion (CPI) method. The OBS method was applied to data from infusion investigations performed with the CPI method. These consisted of repeated measurements on an experimental set-up and 30 patients with suspected INPH. There was no significant difference in C between the CPI and the OBS method for the experimental set-up. For the patients there was a significant difference, −0.84 ± 1.25 µl (s kPa)−1, mean ± SD (paired sample t-test, p < 0.05). However, such a difference is within clinically acceptable limits. This encourages further development of this new real-time approach for estimation of the outflow conductance.

  • 2.
    Freidovich, Leonid B.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Robertsson, Anders
    Department of Automatic Control, LTH, Lund University.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, Rolf
    Department of Automatic Control, LTH, Lund University.
    Shaping stable periodic motions of inertia wheel pendulum: theory and experiment2009In: Asian journal of control, ISSN 1561-8625, E-ISSN 1561-8625, Vol. 11, no 5, p. 549-556Article in journal (Refereed)
    Abstract [en]

    We consider an underactuated two-link robot called the inertia wheel pendulum. The system consists of a free planar rotational pendulum and a symmetric disk attached to its end, which is directly controlled by a DC-motor. The goal is to create stable oscillations of the pendulum, which is not directly actuated. We exploit a recently proposed feedback-control design strategy based on motion planning via virtual holonomic constraints. This strategy is shown to be useful for design of regulators for achieving orbitally exponentially stable oscillatory motions. The main contribution is a step-by-step procedure on how to achieve oscillations with pre-specified amplitude from a given range and an arbitrary independently chosen period. The theoretical results are verified via experiments with a real hardware setup.

  • 3.
    Freidovich, Leonid B
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Manchester, Ian R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Experimental implementation of stable oscillations of the Furuta pendulum around the upward equilibrium2007In: IEEE/RSJ International conference on intelligent robots and systems, 2007. IROS 2007, Piscataway, N.J: IEEE Operations Center , 2007, p. 171-176Conference paper (Refereed)
    Abstract [en]

    Recently, a new technique for generating periodic motions in mechanical systems which have less actuators than degrees of freedom has been proposed. A motivating example for studying such motions is a dynamically stabilized walking robot, where the target trajectory is periodic, and one of the joints - the ankle joint - is unactuated, or weakly actuated. In this paper, the technique is implemented on the Furuta pendulum, an experimental testbed that is simpler than a walking robot but retains many of the key challenges - it is underactuated, open-loop unstable, and practical problems such as friction and velocity estimation must be overcome. We present a detailed description of the practical implementation of the controller. The experiments show that the technique is sufficiently robust to be useful in practice.

  • 4.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Spong, Mark
    A passive 2DOF walker: finding gait cycles using virtual holonomic constraints2008In: Proceedings of the 47th IEEE Conference on Decision and Control, IEEE , 2008, p. 5214-5219Conference paper (Refereed)
    Abstract [en]

    A planar compass-like biped on a shallow slope is the simplest model of a passive walker. It is a two-degrees-of-freedom impulsive mechanical system known to possess periodic solutions reminiscent to human walking. Finding such solutions is a challenging task. We propose a new approach to obtain stable as well as unstable hybrid limit cycles without integrating the full set of differential equations. The procedure is based on exploring the idea of parameterizing a possible periodic solution via virtual holonomic constraints. We also show that a 2-dimensional manifold, defining the hybrid zero dynamics associated with a stable hybrid cycle, in general, is not invariant for the dynamics of the model of the compass-gait walker.

  • 5.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Spong, Mark
    Erik Jonsson School of Engineering and Computer Science, University of Texas, Dallas, USA.
    A passive 2-DOF walker: hunting for gaits using virtual holonomic constraints2009In: IEEE Transactions on Robotics, ISSN 1552-3098, Vol. 25, no 5, p. 1202-1208Article in journal (Refereed)
    Abstract [en]

    A planar compass-like biped on a shallow slope is one of the simplest models of a passive walker. It is a 2-degree-of-freedom (DOF) impulsive mechanical system that is known to possess periodic solutions reminiscent of human walking. Finding such solutions is a challenging computational task that has attracted many researchers who are motivated by various aspects of passive and active dynamic walking. We propose a new approach to find stable as well as unstable hybrid limit cycles without integrating the full set of differential equations and, at the same time, without approximating the dynamics. The procedure exploits a time-independent representation of a possible periodic solution via a virtual holonomic constraint. The description of the limit cycle obtained in this way is useful for the analysis and characterization of passive gaits as well as for design of regulators to achieve gaits with the smallest required control efforts. Some insights into the notion of hybrid zero dynamics, which are related to such a description, are presented as well.

  • 6.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Robertsson, Anders
    LTH, Lund University.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, Rolf
    Friction compensation based on LuGre model2006In:  45th IEEE Conference on Decision and Control, New York: IEEE , 2006, p. 3837-3842Conference paper (Refereed)
    Abstract [en]

    We consider a tracking problem for mechanical systems. It is assumed that feedback controller is designed neglecting some disturbances, which could be approximately modeled by a dynamic LuGre friction model. We are interested to derive an additive observer-based compensator to annihilate or reduce the influence of such a disturbance. We exploit a recently suggested approach for observer design for LuGre-friction-model-based compensation. In order to follow this technique, it is necessary to know the Lyapunov function for the unperturbed system, parameters of the dynamic friction model, and to have certain structural property satisfied. The case when this property is passivity with respect to the matching disturbance related to the given Lyapunov function is illustrated in the paper with an example of a DC-motor. The main contribution is some new insights into numerical real time implementation of friction compensators for various LuGre-type models. The other contribution, built upon the main one, is experimental verification of the suggested observer design procedure.

  • 7.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Robertsson, Anders
    LTH, Lund University.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, Rolf
    LTH, Lund University.
    LuGre-model-based friction compensation2010In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 18, no 1, p. 194-200Article in journal (Refereed)
    Abstract [en]

    A tracking problem for a mechanical system is considered. We start with a feedback controller that is designed without attention to disturbances, which are assumed to be adequately described by a dynamic LuGre friction model. We are interested in deriving a superimposed observer-based compensator to annihilate or reduce the influence of such a disturbance. We exploit a recently suggested approach for observer design for LuGre-friction-model-based compensation. In order to apply this technique, it is necessary to know the Lyapunov function for the unperturbed system, as well as the parameters of the dynamic friction model, and to verify that a certain structural property satisfied. The case when the system is passive with respect to the matching disturbance related to the given Lyapunov function is illustrated in this brief with a DC-motor example. The main contribution is some new insights into the numerical real-time implementation of a compensator for disturbances describable by one of various LuGre-type models. The other contribution, which is built upon the main one, is experimental verification of the suggested model-based observer design procedure.

  • 8.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Robertsson, Anders
    LTH, Lund University.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, Rolf
    LTH, Lund University.
    Periodic motions of the Pendubot via virtual holonomic constraints: theory and experiments2008In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 44, no 3, p. 785-798Article in journal (Refereed)
    Abstract [en]

    This paper presents a new control strategy for an underactuated two-link robot, called the Pendubot. The goal is to create stable oscillations of the outer link of the Pendubot, which is not directly actuated. We exploit a recently proposed feedback control design strategy, based on motion planning via virtual holonomic constraints. This strategy is shown to be useful for design of regulators for achieving: stable oscillatory motions, a closed-loop-design-based swing-up, and propeller motions. The theoretical results are verified via successful experimental implementation.

  • 9.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Gordillo, F.
    Gomez-Estern, F.
    Aracil, J.
    Partial-energy-shaping control for orbital stabilization of high frequency oscillations of the Furuta pendulum2007In: PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-14, 2007, p. 1432-1437Conference paper (Refereed)
    Abstract [en]

    We consider the problem of creating oscillations of the Furuta pendulum around the open-loop unstable equilibrium. Following a recently proposed technique, we start with shaping the energy of the unactuated link. An dissipativity-based controller is designed to create oscillations, neglecting possibility of unbounded motion of the directly actuated link. After that, an auxiliary linear feedback action is added to the control law, stabilizing a desired level of the reshaped energy. Parameters of the controller are tuned to approximately keep the originally created oscillations but ensuring bounded motion of both links. The analysis is valid only for oscillations of sufficiently high frequency and is based on higher order averaging technique. Performance of the designed controller is verified using numerical simulations and experiments.

  • 10.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gordillo, F
    Departamento de Ingenieria de Sistemas y Automática, Universidad de Sevilla.
    Gómez-Estern, F
    Departamento de Ingenieria de Sistemas y Automática, Universidad de Sevilla.
    Aracil, J
    Departamento de Ingenieria de Sistemas y Automática, Universidad de Sevilla.
    Partial-energy-shaping control for orbital stabilization of high-frequency oscillations of the furuta pendulum2009In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 17, no 4, p. 853-858Article in journal (Refereed)
    Abstract [en]

    We consider the problem of creating oscillations of the Furuta pendulum around the open-loop unstable equilibrium. We start with a control transformation shaping the energy of the passive link. Then, a dissipativity-based controller is designed to create oscillations, neglecting the possibility of unbounded motion of the directly actuated link. After that, an auxiliary linear feedback action is added to the control law stabilizing a desired level of the reshaped energy. Parameters of the controller are tuned to approximately keep the originally created oscillations but ensuring bounded motion of both links. The analysis is valid only for oscillations of sufficiently high frequency and is based on higher order averaging technique. The performance of the designed controller is verified using numerical simulations as well as experimentally.

  • 11.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gómez-Estern, F
    Departamento de Ingenieria de Sistemas y Automática, Universidad de Sevilla.
    Gordillo, F
    Departamento de Ingenieria de Sistemas y Automática, Universidad de Sevilla.
    Aracil, J
    Departamento de Ingenieria de Sistemas y Automática, Universidad de Sevilla.
    Modification via averaging of partial-energy-shaping control for creating oscillations: cart-pendulum example2009In: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 82, no 9, p. 1582-1590Article in journal (Refereed)
    Abstract [en]

    We consider the challenging problem of creating oscillations in underactuated mechanical systems. Target oscillatory motions of the indirectly actuated degree of freedom of a mechanical system can often be achieved via a straightforward to design feedback transformation. Moreover, the corresponding part of the dynamics can be forced to match a desired second-order system possessing the target periodic solution (Aracil, J., Gordillo, F., and Acosta, J.A. (2002), 'Stabilization of Oscillations in the Inverted Pendulum', in Proceedings of the 15th IFAC World Congress, Barcelona, Spain; Canudas-de-Wit, C., Espiau, B., and Urrea, C. (2002), 'Orbital Stabilisation of Underactuated Mechanical Systems', in Proceedings of the 15th IFAC World Congress, Barcelona, Spain). Sometimes, it is possible to establish the presence of periodic or bounded motions for the remaining degrees of freedom in the transformed system. However, typically this motion planning procedure leads to an open-loop unstable orbit and by necessity should be followed by a feedback control design. We propose a new approach for synthesis of a (practically) stabilising feedback controller, which ensures convergence of the solutions of the closed-loop system into a narrow tube around the preplanned orbit. The method is illustrated in detail by shaping oscillations in the inverted pendulum on a cart around its upright equilibrium. The complete analysis is based on application of a non-standard higher-order averaging technique assuming sufficiently high frequency of oscillations and is presented for this particular example.

  • 12.
    Freidovich, Leonid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Manchester, Ian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Stability analysis and control design for an underactuated walking robot via computation of a transverse linearization2008In: Proceedings of the 17th IFAC World Congress, 2008, p. 10166-10171Conference paper (Refereed)
    Abstract [en]

    The problem is to create a hybrid periodic motion, reminiscent of walking, for amodel of an underactuated biped robot. We show how to construct a transverse linearization analytically and how to use it for stability analysis and for design of an exponentially orbitally stabilizing controller. In doing so, we extend a technique recently developed for continuous-time controlled mechanical systems with degree of underactuation one. All derivations are shown on an example of a three-link walking robot, modeled as a system with impulse effects.

  • 13.
    Gusev, Sergei
    et al.
    Department of Mathematics and Mechanics, St. Petersburg State University, St. Petersburg, Russia.
    Johansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Varga, Andras
    Institute of Robotics and Mechatronics, German Aerospace Center, DLR, Germany.
    A numerical evaluation of solvers for the periodic riccati differential equation2010In: BIT Numerical Mathematics, ISSN 0006-3835, E-ISSN 1572-9125, Vol. 50, no 2, p. 301-329Article in journal (Refereed)
    Abstract [en]

    Efficient and accurate structure exploiting numerical methods for solvingthe periodic Riccati differential equation (PRDE) are addressed. Such methods areessential, for example, to design periodic feedback controllers for periodic controlsystems. Three recently proposed methods for solving the PRDE are presented andevaluated on challenging periodic linear artificial systems with known solutions and applied to the stabilization of periodic motions of mechanical systems. The first twomethods are of the type multiple shooting and rely on computing the stable invariantsubspace of an associated Hamiltonian system. The stable subspace is determinedusing either algorithms for computing an ordered periodic real Schur form of a cyclicmatrix sequence, or a recently proposed method which implicitly constructs a stabledeflating subspace from an associated lifted pencil. The third method reformulatesthe PRDE as a convex optimization problem where the stabilizing solution is approximatedby its truncated Fourier series. As known, this reformulation leads to a semidefiniteprogramming problem with linear matrix inequality constraints admitting aneffective numerical realization. The numerical evaluation of the PRDE methods, withfocus on the number of states (n) and the length of the period (T ) of the periodicsystems considered, includes both quantitative and qualitative results.

  • 14.
    Gusev, Sergei
    et al.
    Department of Mathematics and Mechanics, St. Petersburg State University, St. Petersburg, Russia.
    Johansson, Stefan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Varga, Andras
    Institute of Robotics and Mechatronics, German Aerospace Center, DLR, Oberpfaffenhofen, Germany.
    A Numerical Evaluation of Solvers for the Periodic Riccati Differential Equation2009Report (Other academic)
    Abstract [en]

    Efficient and robust numerical methods for solving the periodic Riccati differential equation (PRDE) are addressed. Such methods are essential, for example, when deriving feedback controllers for orbital stabilization of underactuated mechanical systems. Two recently proposed methods for solving the PRDE are presented and evaluated on artificial systems and on two stabilization problems originating from mechanical systems with unstable dynamics. The first method is of the type multiple shooting and relies on computing the stable invariant subspace of an associated Hamiltonian system. The stable subspace is determined using algorithms for computing a reordered periodic real Schur form of a cyclic matrix sequence, and a recently proposed method which implicitly constructs a stable subspace from an associated lifted pencil. The second method reformulates the PRDE as a maximization problem where the stabilizing solution is approximated with finite dimensional trigonometric base functions. By doing this reformulation the problem turns into a semidefinite programming problem with linear matrix inequality constraints.

  • 15.
    Johansson, Stefan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North).
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Varga, Andras
    Institute of Robotics and Mechatronics, German Aerospace Center, DLR, Oberpfaffenhofen, Germany.
    Comparing One-shot and Multi-shot Methods for Solving Periodic Riccati Differential Equations2007In: Proceedings of the third IFAC Workshop on Periodic Control Systems (PSYCO’07), International Federation of Automatic Control , 2007, p. 1-6Conference paper (Refereed)
    Abstract [en]

    One-shot methods and recently proposed multi-shot methods for computing stabilizing solutions of continuous-time periodic Riccati differential equations are examined and evaluated on two test problems: (i) a stabilization problem for an artificially constructed time-varying linear system for which the exact solution is known; (ii) a nonlinear stabilization problem for a devil stick juggling model along a periodic trajectory. The numerical comparisons are performed using both general purpose and symplectic integration methods for solving the associated Hamiltonian differential systems. In the multi-shot method a stable subspace is determined using recent algorithms for computing a reordered periodic real Schur form. The results show the increased accuracy achievable by combining multi-shot methods with structure preserving (symplectic) integration techniques.

  • 16.
    La Hera, Pedro
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    New approach for swinging up the Furuta pendulum: theory and experiments2009In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 19, no 8, p. 1240-1250Article in journal (Refereed)
    Abstract [en]

    The problem of swinging up inverted pendulums has often been solved by stabilizing a particular class of homoclinic structures present in the dynamics of a physical pendulum. Here, new arguments are suggested to show how other homoclinic curves can be preplanned for dynamics of the passive-link of the robot. This is done by reparameterizing the motions according to geometrical relations among the generalized coordinates, which are known as virtual holonomic constraints. After that, conditions that guarantee the existence of periodic solutions surrounding the planned homoclinic orbits are derived. The corresponding trajectories, in contrast to homoclinic curves, admit efficient design of feedback control laws ensuring exponential orbital stabilization. The method is illustrated by simulations and supported by experimental studies on the Furuta pendulum. The implementation issues are discussed in detail.

  • 17.
    La Hera, Pedro M.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gait synthesis for a three-link planar biped walker with one actuator2010In: IEEE International Conference on Robotics and Automation (ICRA), 2010, 2010, p. 1715-1720Conference paper (Refereed)
    Abstract [en]

    We consider a 3-link planar walker with two legs and an upper body. An actuator is introduced between the legs, and the torso is kept upright by torsional springs. The model is a 3-DOF impulsive mechanical system, and the aim is to induce stable limit-cycle walking in level ground. To solve the problem, the ideas of the virtual holonomic constraints approach are explored, used and extended. The contribution is a novel systematic motion planning procedure for solving the problem of gait synthesis, which is challenging for non-feedback linearizable mechanical systems with two or more passive degrees of freedom. For a preplanned gait we compute an impulsive linear system that approximates dynamics transversal to the periodic solution. This linear system is used for the design of a stabilizing feedback controller. Results of numerical simulations are presented to illustrate the performance of the closed loop system.

  • 18.
    La Hera, Pedro M.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Orbital stabilization of a pre-planned periodic motion to swing up the Furuta pendulum: theory and experiments2009In: ICRA: 2009 IEEE International conference in robotics an automation, 7 vol., 2009, p. 3562-3567Conference paper (Refereed)
    Abstract [en]

    The problem of swinging up inverted pendulums has often been solved by stabilization of a particular class of homoclinic structures present in the dynamics of the standard pendulum. In this article new arguments are suggested to show how different homoclinic curves can be preplanned for dynamics of the passive-link of the robot. This is done by reparameterizing the motion according to geometrical relations among the generalized coordinates. It is also shown that under certain conditions there exist periodic solutions surrounding such homoclinic orbits. These trajectories admit designing feedback controllers to ensure exponential orbital stabilization. The method is illustrated by simulations and supported by experimental studies.

  • 19.
    La Hera, Pedro
    et al.
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Manchester, Ian
    Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge MA, 02139, USA.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Identification and control of a hydraulic forestry crane2008In: Proceedings of the 17th IFAC World Congress: COEX, South Korea, Elsevier , 2008, p. 2306-2311Conference paper (Refereed)
    Abstract [en]

    This article presents the identification and control of an electro-hydraulic crane. The crane is of the type used on forestry vehicles known as forwarders, which travel off-road collecting logs cut by the harvesters. The dynamics identified include significant frictional forces, dead zones, and structural and hydraulic vibrations. The control algorithm proposed, comprised of a linear controller and a compensator for nonlinearities, is able to accurately track a reference trajectory for the end effector, despite uncertainties in the arm mechanics and hydraulic system dynamics. A further control design is presented which uses an inner loop to compensate for vibrations in the hydraulic system, and its performance is experimentally verified.

  • 20.
    La Hera, Pedro
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. SLU, Dept Forestry Technol, Umeå, Sweden and Swedish Cluster Forest Technol, Vindeln, Sweden.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Norwegian Univ Sci & Technol, Dept Engn Cybernet, Trondheim, Norway.
    Freidovich, Leonid B
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Gusev, Sergey V.
    Stable walking gaits for a three-link planar biped robot with one actuator2013In: IEEE Transactions on robotics, ISSN 1552-3098, E-ISSN 1941-0468, IEEE transactions on robotics, Vol. 29, no 3, p. 589-601Article in journal (Refereed)
    Abstract [en]

    We consider a benchmark example of a three-link planar biped walker with torso, which is actuated in between the legs. The torso is thought to be kept upright by two identical torsional springs. The mathematical model reflects a three-degree-of-freedom mechanical system with impulse effects, which describe the impacts of the swing leg with the ground, and the aim is to induce stable limit-cycle walking on level ground. The main contribution is a novel systematic trajectory planning procedure for solving the problem of gait synthesis. The key idea is to find a system of ordinary differential equations for the functions describing a synchronization pattern for the time evolution of the generalized coordinates along a periodic motion. These functions, which are known as virtual holonomic constraints, are also used to compute an impulsive linear system that approximates the time evolution of the subset of coordinates that are transverse to the orbit of the continuous part of the periodic solution. This auxiliary system, which is known as transverse linearization, is used to design a nonlinear exponentially orbitally stabilizing feedback controller. The performance of the closed-loop system and its robustness with respect to various perturbations and uncertainties are illustrated via numerical simulations.

  • 21.
    Manchester, Ian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, K
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Shiriaev, Anton S
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Experimental Testing of a Method for On-Line Identification of the Cerebrospinal Fluid System2007In: 29th IEEE Annual International Conference on Engineering in Medicine and Biology, Lion, France, 2007, 2007, p. 2843-2846Conference paper (Refereed)
    Abstract
  • 22.
    Manchester, Ian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Kennet
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Andersson, Nina
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Shiriaev, Anton S
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    A nonlinear obsever for on-line estimation of the cerebrospinal fluid outflow restistance.2008In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 44, no 5, p. 1426-1430Article in journal (Refereed)
    Abstract [en]

    Accurate estimates of the outflow resistance of the human cerebrospinal fluid system are important for the diagnosis of a medical condition known as hydrocephalus. In this paper we design a nonlinear observer which provides on-line estimates of the outflow resistance, to the best of our knowledge the first method to do so. The output of the observer is proven to globally converge to an unbiased estimate. Its performance is experimentally verified using the same apparatus used to perform actual patient diagnoses and a specially-designed physical model of the human cerebrospinal fluid system.

  • 23.
    Manchester, Ian R
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Kennet
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Andersson, Nina
    Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
    Shiriaev, Anton S
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Eklund, Anders
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    A nonlinear observer for on-line estimation of the cerebrospinal fluid outflow resistance2008In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 44, p. 1426-1430Article in journal (Refereed)
  • 24.
    Manchester, Ian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Savkin, A V
    On Motion Planning for an Underactuated Ship: Fundamental Limitations and a Bearings-Only Navigation Strategy2007In:  IEEE Conference on Decision and Control, 2007, p. 2411-2416Conference paper (Refereed)
  • 25.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, P X
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Planning human-like motions for an underactuated humanoid robot based on the virtual constraints approach.2007In: 13th International Conference on Advanced Robotics (ICAR 2007), Jeju Island, South Korea, 2007, 2007, p. 585-590Conference paper (Refereed)
  • 26.
    Mettin, Uwe
    et al.
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    La Hera, Pedro
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    How Springs Can Help to Stabilize Motions of Underactuated Systems with Weak Actuators2008Conference paper (Refereed)
    Abstract [en]

    In the field of robotics the energy spent for actuation is always an issue. It is often the case that some desired motions cannot be achieved by the robot due to limitations in actuation power. We suggest a simple solution to the problem: complement the actuators by some configuration of mechanical springs which delivers a torque profile that is well-tuned for the desired robot motion. As a result, the control effort for the original actuator will be reduced. In this case study we consider an underactuated planar two-link robot for experimental demonstration of the concept. The virtual holonomic constraints approach serves as analytical tool to parameterize, plan, and stabilize desired periodic motions.

  • 27.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Generating human-like motions for an underactuated three-link robot based on the virtual constraints approach2007In: Proceedings of the 46th IEEE conference on decision and control, 2007, p. 5138-5143Conference paper (Refereed)
    Abstract [en]

    In the field of robotics there is a great interest in developing strategies and algorithms to reproduce human-like behavior. In this paper, we consider motion planning and generation for humanoid robots based on the concept of virtual holonomic constraints. For this purpose, recorded kinematic data from a particular human motion are analyzed in order to extract geometric relations among various joint angles defining the instantaneous postures. The analysis of a simplified human body representation leads to dynamics of a corresponding underactuated mechanical system with parameters based on anthropometric data of an average person. The motion planning is realized by considering solutions of reduced system dynamics assuming the virtual holonomic constraints are kept invariant The relevance of such a mathematical model in accordance to the real human motion under study is shown. An appropriate controller design procedure is presented together with simulation results of a feedback-controlled robot.

  • 28.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Helbo, Jan
    Aalborg university, Denmark.
    Motion planning for humanoid robots based on virtual constraints extracted from recorded human movements2008In: Intelligent Service Robotics, ISSN 1861-2776, Vol. 1, no 4, p. 289-301Article in journal (Refereed)
    Abstract [en]

    In the field of robotics there is a great interest in developing strategies and algorithms to reproduce human-like behavior. In this paper, we consider motion planning for humanoid robots based on the concept of virtual holonomic constraints. At first, recorded kinematic data of particular human motions are analyzed in order to extract consistent geometric relations among various joint angles defining the instantaneous postures. Second, a simplified human body representation leads to dynamics of an underactuated mechanical system with parameters based on anthropometric data. Motion planning for humanoid robots of similar structure can be carried out by considering solutions of reduced dynamics obtained by imposing the virtual holonomic constraints that are found in human movements. The relevance of such a reduced mathematical model in accordance with the real human motions under study is shown. Since the virtual constraints must be imposed on the robot dynamics by feedback control, the design procedure for a suitable controller is briefly discussed.

  • 29.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Reducing control efforts for preplanned motions by parallel elastic actuators2010In: The international journal of robotics research, ISSN 0278-3649, E-ISSN 1741-3176, Vol. 29, no 9, p. 1186-1198Article in journal (Refereed)
    Abstract [en]

    A lack of sufficient actuation power as well as the presence of passive degrees of freedom are often serious constraints for feasible motions of a robot. Installing passive elastic mechanisms in parallel with the original actuators is one of a few alternatives that allows for large modifications of the range of external forces or torques that can be applied to the mechanical system. If some motions are planned that require a nominal control input above the actuator limitations, then we can search for auxiliary spring-like mechanisms complementing the control scheme in order to overcome the constraints. The intuitive idea of parallel elastic actuation is that spring-like elements generate most of the nominal torque required along a desired trajectory, so the control efforts of the original actuators can be mainly spent in stabilizing the motion. Such attractive arguments are, however, challenging for robots with non-feedback linearizable non-minimum phase dynamics that have one or several passive degrees of freedom. We suggest an approach to resolve the apparent difficulties and illustrate the method with an example of an underactuated planar double pendulum. The results are tested both in simulations and through experimental studies.

  • 30.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Parallel elastic actuators as a control tool for preplanned trajectories of underactuated mechanical systems2009In: The international journal of robotics research, ISSN 0278-3649, E-ISSN 1741-3176, Vol. 29, no 9, p. 1186-1198Article in journal (Refereed)
    Abstract [en]

    A lack of sufficient actuation power as well as the presence of passive degrees of freedom are often serious constraints for feasible motions of a robot. Installing passive elastic mechanisms in parallel with the original actuators is one of a few alternatives that allows for large modifications of the range of external forces or torques that can be applied to the mechanical system. If some motions are planned that require a nominal control input above the actuator limitations, then we can search for auxiliary spring-like mechanisms complementing the control scheme in order to overcome the constraints. The intuitive idea of parallel elastic actuation is that spring-like elements generate most of the nominal torque required along a desired trajectory, so the control efforts of the original actuators can be mainly spent in stabilizing the motion. Such attractive arguments are, however, challenging for robots with non-feedback linearizable non-minimum phase dynamics that have one or several passive degrees of freedom. We suggest an approach to resolve the apparent difficulties and illustrate the method with an example of an underactuated planar double pendulum. The results are tested both in simulations and through experimental studies.

  • 31.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ortiz Morales, Daniel
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Trajectory planning and time-independent motion control for a kinematically redundant hydraulic manipulator2009In: Advanced Robotics, 2009. ICAR 2009. International Conference on, IEEE conference proceedings, 2009, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this paper we consider the problem of motion planning and control of a kinematically redundant manipulator, which is used on forestry machines for logging. Once a desired path is specified in the 3D world frame, a trajectory can be planned and executed such that all joints are synchronized and constrained to the Cartesian path. We introduce an optimization procedure that takes advantage of the kinematic redundancy so that time-efficient joint and velocity profiles along the path can be obtained. Differential constraints imposed by the manipulator dynamics are accounted for by employing a phase-plane technique for admissible path timings. In hydraulic manipulators, such as considered here, the velocity constraints of the individual joints are particularly restrictive. We suggest a time-independent control scheme for the planned trajectory which is built upon the standard reference tracking controllers. Experimental tests underline the benefits and efficiency of the model-based trajectory planning and show success of the proposed control strategy.

  • 32.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bätz, Georg
    Institute of Automatic Control Engineering, Technical University of Munich.
    Wollherr, Dirk
    Institute of Automatic Control Engineering, Technical University of Munich.
    Ball dribbling with an underactuated continuous-time control phase2010In: 2010 IEEE International Conference on Robotics and Automation (ICRA), 2010, p. 4669-4674Conference paper (Refereed)
    Abstract [en]

    Ball dribbling is a central element of basketball. One main challenge for realizing basketball robots is to stabilize periodic motions of the ball. This task is nontrivial due to the hybrid (discrete-continuous) nature of the corresponding dynamics. The ball can be only controlled during ball-manipulator contact and moves freely otherwise. We propose a manipulator equipped with a spring that gets compressed when the ball bounces against it. Hence, we can have continuous-time control over this underactuated Ball-Spring-Manipulator system until the spring releases its accumulated energy back to the ball. This paper illustrates the motion-planning procedure for a ball-dribbling cycle with such an underactutated continuous-time control phase. An orbital stabilizing controller is designed based on a transverse linearization along a desired periodic motion. Numerical simulations show the performance of the control system in preparation to experimental studies.

  • 33.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sampei, Mitsuji
    Tokyo Institute of Technology, Department of Mechanical and Control Engineering.
    Optimal ball pitching with an underactuated model of a human arm2010Conference paper (Refereed)
    Abstract [en]

    A new approach for solving an optimal motion planning problem for a simplified 2-degrees-of-freedom model of a human arm is proposed. The motion of interest resembles ball pitching. The model of a planar two-link robot is used with actuation only at the shoulder joint and a passive spring at the elbow joint representing the stiffness of the arm. The goal is formulated as finding a trajectory and the associated torque of the active joint that maximizes the velocity of the end effector in horizontal direction at the moment of crossing a vertical ball-release line. The basic idea is to search for an optimal motion parametrized by the horizontal displacement of the end-effector from the start point to the release point. The suggested procedure leads to analytical expressions for the coefficients of a nonlinear differential equation that governs the geometric relation between the links along an optimal motion. The motion planning task is reformulated to a finite-dimensional search for the corresponding initial conditions.

  • 34.
    Mettin, Uwe
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Analysis of human-operated motions and trajectory replanning for kinematically redundant manipulators2009In: 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems: St.Louis, USA, 2009, p. 795-800Conference paper (Refereed)
    Abstract [en]

    We consider trajectory planning for kinematically redundant manipulators used on forestry machines. The analysis of recorded data from human operation reveals that the driver does not use the full potential of the machine due to the complexity of the manipulation task. We suggest an optimization procedure that takes advantage of the kinematic redundancy so that time-efficient joint and velocity profiles along the path can be obtained. Differential constraints imposed by the manipulator dynamics are accounted for by employing a phase-plane technique for admissible path timings. Velocity constraints of the individual joints are particularly restrictive in hydraulic manipulators. Our study aims for semi-autonomous schemes that can provide assistance to the operator for executing global motions.

  • 35.
    Meza-Sanchez, Iliana M
    et al.
    CICESE, Mexico .
    Aguilar, Luis T
    Instituto Politecnico Nacional, Mexico .
    Shiriaev, Anton
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Orlov, Yury
    CICESE, Mexico .
    Periodic motion planning and nonlinear H-infinity tracking control of a 3-DOF underactuated helicopter2011In: International Journal of Systems Science, ISSN 0020-7721, E-ISSN 1464-5319, Vol. 42, no 5, p. 829-838Article in journal (Refereed)
    Abstract [en]

    Nonlinear H-infinity synthesis is developed to solve the tracking control problem into a 3-DOF helicopter prototype. Planning of periodic motions under a virtual constraints approach is considered prior the controller design in order to achieve our goal. A local H-infinity controller is derived by means of a certain perturbation of the differential Riccati equations that appear while solving the corresponding H-infinity control problem for the linearised system. Stabilisability and detectability properties of the control system are thus ensured by the existence of the proper solutions of the unperturbed differential Riccati equations, and hence the proposed synthesis procedure obviates an extra verification work of these properties. Due to the nature of the approach, the resulting controller additionally yields the desired robustness properties against unknown but bounded external disturbances. Convergence and robustness of the proposed design are supported by simulation results.

  • 36.
    Ortiz Morales, Daniel
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Steps in trajectory planning and controller design for a hydraulically driven crane with limited sensing2010In: IEEE International Conference on Intelligent Robots and Systems, IEEE conference proceedings, 2010, p. 3836-3841Conference paper (Refereed)
    Abstract [en]

    In the forest industry, trees are logged and harvested by human-operated hydraulic manipulators. Eventually, these tasks are expected to be automated with optimal performance. However, with todays technology the main problem is implementation. While prototypes may have rich sensing information, real cranes lack certain sensing devices, such as encoders for position sensing. Automating these machines requires unconventional solutions. In this paper, we consider the motion planning problem, which involves a redesign of optimal trajectories, so that open loop control strategies can be applied using feed-forward control signals whenever sensing information is not available.

  • 37.
    Ortiz Morales, Daniel
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro
    Sveriges lantbruksuniversitet .
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Norwegian University of Science and Technology.
    Path-constrained motion analysis: an algorithm to understand human performance on hydraulic manipulators2015In: IEEE Transactions on Human-Machine Systems, ISSN 2168-2291, Vol. 45, no 2, p. 187-199Article in journal (Refereed)
    Abstract [en]

    We propose a novel method to analyze how human operators use hydraulic manipulators of heavy-duty equipment. The approach is novel in the sense that it applies knowledge of motion planning and optimization techniques used in robotics. As an example, we consider the case of operating a forestry crane. To that end, we use motion data that has been recorded during standard operation with the help of sensors and a data acquisition unit. The data backs up the notion that operators work by performing repeatable patterns observed in the trajectories of the manipulator's joints. We show how this nominal behavior is computed, and consequently this allow us to present the following: 1) an analytical procedure to analyze motions, 2) how to represent the "performance" of the operator in a 2D plot, 3) an example of how to use this information to suggest customized control settings, and 4) some complementary ideas needed for improving efficiency through automation.

  • 38.
    Ortiz Morales, Daniel
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro
    Sveriges lantbruksuniversitet .
    Mettin, Uwe
    Department of Transmission and Hybrid Systems, IAV Automotive Engineering, Berlin, Germany.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton
    Norwegian University of Science and Technology.
    Increasing the level of automation in the forestry logging process with crane trajectory planning and control2014In: Journal of Field Robotics, ISSN 1556-4959, E-ISSN 1556-4967, Vol. 31, no 3, p. 343-363Article in journal (Refereed)
    Abstract [en]

    Working with forestry machines requires great amount of training to be sufficiently skilledto operate forestry cranes. In view of this, introducing automated motions, as those seenin robotic arms, is ambitioned by this industry for shortening the amount of training timeand make the work of the operator easier. Motivated by this fact, we have developedtwo experimental platforms for testing control systems and motion planning algorithms inreal-time. They correspond to a laboratory setup and a commercial version of a hydraulicmanipulator used in forwarder machines. The aim of this article is to present the results ofthis development by providing an overview of our trajectory planning algorithm and motioncontrol method, with a subsequent view of the experimental results. For motion control,we design feedback controllers that are able to track reference trajectories based on sensormeasurements. Likewise, we provide arguments to design controllers in open-loop for thecase of machines lacking of sensing devices. Relying on the tracking efficiency of thesecontrollers, we design time efficient reference trajectories of motions that correspond tologging tasks. To demonstrate performance, we provide an overview of an extensive testingdone on these machines.

  • 39.
    Ortíz Morales, Daniel
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    La Hera, Pedro X.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. The Department of Engineering Cybernetics, Norwegian University of Science and Technology, Trondheim, Norway.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. The Department of Engineering Cybernetics, Norwegian University of Science and Technology, Trondheim, Norway.
    Open-loop control experiments on driver assistance for crane forestry machines2011In: 2011 IEEE International Conference on Robotics and Automation (ICRA), IEEE conference proceedings, 2011, p. 1797-1802Conference paper (Refereed)
    Abstract [en]

    A short term goal in the forest industry is semi-automation of existing machines for the tasks of logging and harvesting. One way to assist drivers is to provide a set of predefined trajectories that can be used repeatedly in the process. In recent years much effort has been directed to the design of control strategies and task planning as part of this solution. However, commercialization of such automatic schemes requires the installation of various sensing devices, computers and most of all a redesign of the machine itself, which is currently undesired by manufacturers. Here we present an approach of implementing predefined trajectories in an open-loop fashion, which avoids the complexity of sensor and computer integration. The experimental results are carried out on a commercial hydraulic crane to demonstrate that this solution is feasible in practice.

  • 40.
    Park, Yeonchool
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Westerberg, Simon
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lee, Sukhan
    ISRC, Sungkyunkwan University, Suwon, Korea.
    3D Log Recognition and Pose Estimation for Robotic Forestry Machine2011In: 2011 IEEE International Conference on Robotics and Automation (ICRA), 2011, p. 5323-5328Conference paper (Refereed)
    Abstract [en]

    Successful recognition and pose estimation of logs and trees as well as workspace modeling in the forest environment is essential for extensive automation of the harvesting and logging tasks of forestry machines. However, the free-form features of logs, few reliable textural features, large edge extraction errors, and segmentation faults caused by the barks on the surface of the logs present clear challenges for recognition and classification. To solve these problems, robust algorithms able to recognize and estimate poses of a variety of objects even under poor and partial inputs need to be developed.In this paper we focus on the most relevant task of recognizingand estimating postures of a bunch of logs located on the groundwith varying orientation and distance. Experiments carried outwith the help of a structured light camera demonstrate the feasibility of the proposed algorithm.

  • 41.
    Pchelkin, Stepan S.
    et al.
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Shiriaev, Anton
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Mettin, Uwe
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Aoyama, Tadayoshi
    Lu, Zhiguo
    Fukuda, Toshio
    Shaping Energetically Efficient Brachiation Motion for a 24-DOF Gorilla Robot2011Conference paper (Refereed)
    Abstract [en]

    We consider a 24-degrees-of-freedom monkey robot that is supposed to perform brachiation locomotion, i.e. swinging from one row of a horizontal ladder to the next one using the arms. The robot hand is constructed as a planar hook so that the contact point about which the robot swings is a passive hinge. We identify the 10 most relevant degrees of freedom for this underactuated mechanical system and formulate a tractable search: (a) introduce a family of coordination patterns to be enforced on the dynamics with respect to a path coordinate; (b) formulate geometric equality constraints that are necessary for periodic locomotion; (c) generate trajectories from integrable reduced dynamics associated with the passive hinge; (d) evaluate the energetic cost of transport. Moreover, we observe that a linear approximation of the reduced dynamics can be used for trajectory generation which allows us to incorporate the gradient of the cost function into the search algorithm.

  • 42.
    Pchelkin, Stepan S.
    et al.
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Shiriaev, Anton
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Robertsson, Anders
    Department of Automatic Control, LTH, Lund University.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Integrated Time-Optimal Trajectory Planning and Control Design for Industrial Robot Manipulator2013In: 2013 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS), Tokyo, JAPAN, 2013, p. 2521-2526Conference paper (Refereed)
    Abstract [en]

    We consider planning and implementation of fast motions for industrial manipulators constrained to a given geometric path. With such a problem formulation, which is quite reasonable for many standard operation scenarios, it is intuitively clear that a feedback controller should be designed to achieve orbital stabilization of a time-optimal trajectory instead asymptotic. We propose an algorithm to convert an asymptotically stabilizing controller into an orbitally stabilizing one and check achievable performance in simulations and, more importantly, in experiments performed on a standard industrial robot ABB IRB 140 with the IRC5-system extended with an open control interface. It is verified that the proposed re-design allows significantly reduced deviations of the actual trajectories from the desired one at high speeds not only for a chosen base feedback design but also outperforming the state-of-the-art commercial implementation offered by ABB Robotics.

  • 43.
    Pchelkin, Stepan
    et al.
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Shiriaev, Anton
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Department of Engineering Cybernetics, Norwegian University of Science and Technology.
    Gusev, Sergei
    Department of General Mathematics and Informatics, St. Petersburg State University.
    Kwon, Woong
    Mechatronics & Manufacturing Technology Center, Samsung Electronics Co..
    Natural sit-down and chair-rise motions for a humanoid robot2010Conference paper (Refereed)
    Abstract [en]

    We discuss a constructive procedure for planning human-like motions of humanoid robots on finite-time intervals. Besides complying with various constraints present in the robot dynamics, it allows us to reflect certain features of recorded and analyzed motions of a test person, even though the dimensions, the mass distribution, and the actuation of the robot are different. So, the steps in motion planning are complemented by a novel algorithm for control design to ensure contraction of the orbits of various perturbed closed-loop motions to the orbit of the prescribed target trajectory.

  • 44. Pchelkin, Stepan
    et al.
    Shiriaev, Anton S.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Mettin, Uwe
    Gusev, Sergei V.
    Kwon, Woong
    Paramonov, Leonid
    A dynamic human motion: coordination analysis2015In: Biological Cybernetics, ISSN 0340-1200, E-ISSN 1432-0770, Vol. 109, no 1, p. 47-62Article in journal (Refereed)
    Abstract [en]

    This article is concerned with the generic structure of the motion coordination system resulting from the application of the method of virtual holonomic constraints (VHCs) to the problem of the generation and robust execution of a dynamic humanlike motion by a humanoid robot. The motion coordination developed using VHCs is based on a motion generator equation, which is a scalar nonlinear differential equation of second order. It can be considered equivalent in function to a central pattern generator in living organisms. The relative time evolution of the degrees of freedom of a humanoid robot during a typical motion are specified by a set of coordination functions that uniquely define the overall pattern of the motion. This is comparable to a hypothesis on the existence of motion patterns in biomechanics. A robust control is derived based on a transverse linearization along the configuration manifold defined by the coordination functions. It is shown that the derived coordination and control architecture possesses excellent robustness properties. The analysis is performed on an example of a real human motion recorded in test experiments.

  • 45. Rubanova, A.
    et al.
    Robertsson, A.
    Shiriaev, Anton S.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Department of Engineering Cybernetics, Norwegian University of Science and Technology, Norway.
    Freidovich, Leonid B
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, R.
    Analytic parameterization of stabilizing controllers for the surge subsystem of the Moore-Greitzer compressor model2013In: American Control Conference (ACC), 2013, 2013, p. 5257-5262Conference paper (Refereed)
    Abstract [en]

    This paper is based on a new procedure for dynamic output feedback design for systems with nonlinearities satisfying quadratic constraints. The new procedure is motivated by the challenges of output feedback control design for the 3-state Moore-Greitzer compressor model. First, we use conditions for stability of a transformed system and the associated matching conditions to find the data of the stabilizing controllers for the surge subsystem. Second, using the set of stabilizing controllers satisfying the given constraints for the closed-loop system with the dynamic output feedback controller we made optimization over the parameter set. We present the data of the stabilizing controllers and the new constraints for the corresponding parameters. The contributions in this paper are simplified conditions for the synthesis and optimization over the control parameter set.

  • 46.
    Shiriaev, Anton
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Transverse linearization for hybrid controlled mechanical systems with one passive link2009In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 54, no 12, p. 2282-2888Article in journal (Refereed)
    Abstract [en]

    A general method for planning and orbitally stabilizing periodic motions for impulsive mechanical systems with underactuation one is proposed. For each such trajectory, we suggest a constructive procedure for defining a sufficient number of nontrivial quantities that vanish on the orbit. After that, we prove that these quantities constitute a possible set of transverse coordinates. Finally, we present analytical steps for computing linearization of dynamics of these coordinates along the motion. As a result, for each such planned periodic trajectory, a hybrid transverse linearization for dynamics of the system is computed in closed form. The derived impulsive linear system can be used for stability analysis and for design of exponentially orbitally stabilizing feedback controllers. A geometrical interpretation of the method is given in terms of a novel concept of a moving Poincare section. The technique is illustrated on a devil stick example.

  • 47.
    Shiriaev, Anton
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Manchester, Ian
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Can we make a robot ballerina perform a pirouette?: orbital stabilization of periodic motions of underactuated mechanical systems.2008In: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 32, no 2, p. 200-211Article in journal (Refereed)
    Abstract [en]

    This paper provides an introduction to several problems and techniques related to controlling periodic motions of dynamical systems. In particular, we consider planning periodic motions and designing feedback controllers for orbital stabilization. We review classical and recent design methods based on the Poincaré first-return map and the transverse linearization. We begin with general nonlinear systems and then specialize to a class of underactuated mechanical systems for which a particularly rich structure allows many of the problems to be solved analytically.

  • 48.
    Shiriaev, Anton
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gusev, Sergey
    St. Petersburg University.
    Computing a transverse linearization for mechanical systems with two and more passive degrees of freedom2010In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 55, no 4, p. 893-906Article in journal (Refereed)
    Abstract [en]

    This study examines the mechanical systems with an arbitrary number of passive (non-actuated) degrees of freedom and proposes an analytical method for computing coefficients of a linear controlled system, solutions of which approximate dynamics transverse to a feasible motion. This constructive procedure is based on a particular choice of coordinates and allows explicit introduction of a moving Poincaré section associated with a nontrivial finite-time or periodic motion. In these coordinates, transverse dynamics admits analytical linearization before any control design. If the forced motion of an underactuated mechanical system is periodic, then this linearization is an indispensable and constructive tool for stabilizing the cycle and for analyzing its orbital (in)stability. The technique is illustrated with two challenging examples. The first one is stabilization of a circular motion of a spherical pendulum on a puck around its upright equilibrium. The other one is creating stable synchronous oscillations of an arbitrary number of planar pendulums on carts around their unstable equilibria.

  • 49.
    Shiriaev, Anton
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gusev, Sergey
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Transverse linearization for controlled mechanical systems with several passive degrees of freedom2010In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 55, no 4, p. 893-906Article in journal (Refereed)
    Abstract [en]

    This study examines the mechanical systems with an arbitrary number of passive (non-actuated) degrees of freedom and proposes an analytical method for computing coefficients of a linear controlled system, solutions of which approximate dynamics transverse to a feasible motion. This constructive procedure is based on a particular choice of coordinates and allows explicit introduction of a moving Poincaré section associated with a nontrivial finite-time or periodic motion. In these coordinates, transverse dynamics admits analytical linearization before any control design. If the forced motion of an underactuated mechanical system is periodic, then this linearization is an indispensable and constructive tool for stabilizing the cycle and for analyzing its orbital (in)stability. The technique is illustrated with two challenging examples. The first one is stabilization of a circular motions of a spherical pendulum on a puck around its upright equilibrium. The other one is creating stable synchronous oscillations of an arbitrary number of planar pendula on carts around their unstable equilibria.

  • 50.
    Shiriaev, Anton
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Freidovich, Leonid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Johansson, Rolf
    Department of Automatic Control, LTH, Lund University.
    Robertsson, Anders
    Department of Automatic Control, LTH, Lund University.
    Global stabilization for a class of coupled nonlinear systems with application to active surge control2010In: Dynamics of continuous, discrete and impulsive systems, ISSN 1201-3390, E-ISSN 1918-2538, Vol. 17, no 6, p. 875-908Article in journal (Refereed)
    Abstract [en]

    We propose here a new procedure for output feedback design for systems with nonlinearities satisfying quadratic constraints. It provides an alternative for the classical observer-based design and relies on transformation of the closed-loop system with a dynamic controller of particular structure into a special block form. We present two sets of sufficient conditions for stability of the transformed block system and derive matching conditions allowing such a representation for a particular challenging example. The two new tests for global stability proposed for a class of nonlinear systems extend the famous Circle criterion applied for infinite sector quadratic constraints. The study is motivated and illustrated by the problem of output feedback control design for the well-known finite dimensional nonlinear model qualitatively describing surge instabilities in compressors. Assuming that the only available measurement is the pressure rise, we suggest a constructive procedure for synthesis of a family of robustly globally stabilizing feedback controllers. The solution relies on structural properties of the nonlinearity of the model describing a compressor characteristic, which includes earlier known static quadratic constraints and a newly found integral quadratic constraint. Performance of the closed-loop system is discussed and illustrated by simulations.

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