| 1. |
- Andersson, Alina, et al.
(författare)
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Robustness of the Moore-Greitzer Compressor Model's Surge Subsystem with New Dynamic Output Feedback Controllers
- 2014. - 3
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Ingår i: 19th IFAC World Congress. - : Elsevier. - 2405-8963. - 9783902823625 ; 47, s. 3690-3695
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Konferensbidrag (refereegranskat)abstract
- This work presents an extension of a design procedure for dynamic output feedback design for systems with nonlinearities satisfying quadratic constraints. In this work we used an axial gas compressor model described by the 3-state Moore-Greitzer compressor model (MG) that has some challenges for output feedback control design (Planovsky and Nikolaev 1990), (Rubanova 2013). The more general constraints for the investigation of the robustness with respect to parametric uncertainties and measurement noise are shown.
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| 2. |
- Pchelkin, Stepan S., et al.
(författare)
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Algorithms for finding gaits of locomotive mechanisms : case studies for Gorilla robot brachiation
- 2016
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Ingår i: Autonomous Robots. - : Springer Science and Business Media LLC. - 0929-5593 .- 1573-7527. ; 40:5, s. 849-865
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Tidskriftsartikel (refereegranskat)abstract
- We consider a model of a 24-degree-of-freedom monkey robot that is supposed to perform a brachiation locomotion, i.e. to swing 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 procedure consisting on the following steps: (a) to introduce a parametrized family of coordination patterns to be enforced on the dynamics with respect to a path coordinate; (b) to formulate geometric equality constraints that are necessary to achieve a periodic locomotion; (c) to generate trajectories from integrable reduced dynamics associated with the passive hinge; (d) to 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 computation of an approximate gradient of the cost function into the search algorithm significantly improving the computational efficiency.
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| 3. |
- Pchelkin, Stepan S., et al.
(författare)
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On Orbital Stabilization for Industrial Manipulators : Case Study in Evaluating Performances of Modified PD plus and Inverse Dynamics Controllers
- 2017
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Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 25:1, s. 101-117
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Tidskriftsartikel (refereegranskat)abstract
- Orbital stabilization is one of the available alternatives to the classical asymptotic stabilization, known as the reference tracking control, which is typically considered and implemented for controlling motions of industrial robot manipulators. Since asymptotic orbital stability means convergence of solutions of a closed-loop system to an orbit of a reference trajectory, instead of tracking it as a function of time, new feedback designs can potentially improve performance with respect to several key criteria for industrial manipulators such as absolute path accuracy for tool's motions and robustness to uncertainties in the model. The main outcomes of this paper are a new class of controllers that achieve asymptotic orbital stabilization of motions and a novel analytical method for analysis and redesign of system's dynamics using an excessive set of easy-to-compute transverse coordinates. The contributions have been validated in a series of experimental studies performed on a standard industrial robot ABB IRB 140 with the IRC5-system extended with an open control interface. The outcomes of the tests show that the proposed redesign allows achieving significantly reduced deviations of the actual trajectories from the desired ones at different ranges of speeds and for several different paths, often outperforming the state-of-the-art commercial implementations. A comprehensive discussion of one of such experiments is given.
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| 4. |
- Andersson, Alina, et al.
(författare)
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Analytic Parameterization of Stabilizing Controllers for the Surge Subsystem of the Moore-Greitzer Compressor Model
- 2013
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Ingår i: Proc. 2013 American Control Conference (ACC2013). - 0743-1619. - 9781479901777 ; , s. 5257-5262
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 5. |
- Freidovich, Leonid B, et al.
(författare)
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Experimental implementation of stable oscillations of the Furuta pendulum around the upward equilibrium
- 2007
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Ingår i: IEEE/RSJ International conference on intelligent robots and systems, 2007. IROS 2007. - Piscataway, N.J : IEEE Operations Center. - 9781424409129 ; , s. 171-176
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 6. |
- Freidovich, Leonid B, et al.
(författare)
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Transverse linearization for mechanical systems with passive links, impulse effects, and friction forces
- 2009
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Ingår i: Proceedings of the 48th IEEE conference on decision and control, 2009, held jointly with the 2009 28th Chinese control conference (CDC/CCC 2009). - : IEEE conference proceedings. - 9781424438723 - 9781424438716 ; , s. 6490-6495
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Konferensbidrag (refereegranskat)abstract
- We consider a class of mechanical systems with an arbitrary number of passive (non-actuated) degrees of freedom. In addition to control forces, we take into account viscous and Coulomb friction forces and impacts with the environment modeled as impulsive updates of the states. We assume that a motion planning task is solved and a feasible forced periodic motion is described in terms of piece-wise smooth virtual holonomic constraints. The main contribution is an analytical method for computing coefficients of an impulsive linear control system, solutions of which approximate dynamics transversal to the preplanned trajectory. This linear system is shown to be useful for stability analysis and for design of feedback controllers orbitally stabilizing forced periodic motions in the hybrid mechanical system. As an illustration, we apply the obtained theoretical results providing a rigorous proof of orbital exponential stability of the periodic tumbling motion for a model of a descending strip of paper in a still air.
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| 7. |
- Freidovich, Leonid B., Docent, 1973-, et al.
(författare)
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Transverse linearization for underactuated nonholonomic mechanical systems with application to orbital stabilization
- 2012. - 1
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Ingår i: Distributed decision making and control. - London : Springer. - 9781447122647 - 9781447122654 ; , s. 245-258
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Bokkapitel (refereegranskat)abstract
- We consider a class of mechanical systems with an arbitrary number of passive (nonactuated) degrees of freedom, which are subject to a set of nonholonomic constraints. We assume that the challenging problem of motion planning is solved giving rise to a feasible desired periodic trajectory. Our goal is either to analyze orbital stability of this trajectory with a given time-independent feedback control law or to design a stabilizing controller. We extend our previous work done for mechanical systems without nonholonomic constraints. The main contribution is an analytical method for computing coefficients of a linear reduced-order control system, solutions of which approximate dynamics that is transversal to the preplanned trajectory. This linear system is shown to be useful for stability analysis and for design of feedback controllers orbitally, exponentially stabilizing forced periodic motions in nonholonomic mechanical systems.We illustrate our approach on a standard benchmark example.
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| 8. |
- Gusev, Sergey, et al.
(författare)
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Modification of a PD+ controller for the orbital stabilization of the motions of an all-wheel drive mechanical system
- 2016
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Ingår i: Journal of Applied Mathematics and Mechanics. - : Elsevier BV. - 0021-8928. ; 79:6, s. 546-555
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Tidskriftsartikel (refereegranskat)abstract
- The problem of the orbital stabilization of the forced periodic motions of a non-linear all-wheel drive mechanical system is considered within the framework of a model that is widely used in problems of the planning of the motions and feedback design for industrial robotic manipulators. The basic result is the explicit indication of one of the possible redundant sets of coordinates tranverse to the nominal motion and the derivation of the linearization of their behaviour in an explicit form. The latter enabledus to validate the original approach in the controller design problem and to analyse the behaviour of the closed system in the neighbourhood of the nominal motion. The analytical results are illustrated by solving the problem of stabilizing the motion of the working tool of an industrial ABB IRB140 robotic manipulator that is suboptimal with respect to its high-speed response taking account of the known constraints imposed on the limiting values of the angular velocities of the individual robot components.
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| 9. |
- Gusev, Sergei V., et al.
(författare)
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SDP-based approximation of stabilising solutions for periodic matrix Riccati differential equations
- 2016
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Ingår i: International Journal of Control. - : Informa UK Limited. - 0020-7179 .- 1366-5820. ; 89:7, s. 1396-1405
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Tidskriftsartikel (refereegranskat)abstract
- Numerically finding stabilising feedback control laws for linear systems of periodic differential equations is a nontrivial task with no known reliable solutions. The most successful method requires solving matrix differential Riccati equations with periodic coefficients. All previously proposed techniques for solving such equations involve numerical integration of unstable differential equations and consequently fail whenever the period is too large or the coefficients vary too much. Here, a new method for numerical computation of stabilising solutions for matrix differential Riccati equations with periodic coefficients is proposed. Our approach does not involve numerical solution of any differential equations. The approximation for a stabilising solution is found in the form of a trigonometric polynomial, matrix coefficients of which are found solving a specially constructed finite-dimensional semidefinite programming (SDP) problem. This problem is obtained using maximality property of the stabilising solution of the Riccati equation for the associated Riccati inequality and sampling technique. Our previously published numerical comparisons with other methods shows that for a class of problems only this technique provides a working solution. Asymptotic convergence of the computed approximations to the stabilising solution is proved below under the assumption that certain combinations of the key parameters are sufficiently large. Although the rate of convergence is not analysed, it appeared to be exponential in our numerical studies.
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| 10. |
- La Hera, Pedro M., 1981-, et al.
(författare)
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Gait synthesis for a three-link planar biped walker with one actuator
- 2010
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Ingår i: IEEE International Conference on Robotics and Automation (ICRA), 2010. - 9781424450381 ; , s. 1715-1720
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Konferensbidrag (refereegranskat)abstract
- 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.
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