| 1. |
- Burdakov, S. F., et al.
(author)
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Robust control of nonlinear mechanical systems using linear feedback
- 1999
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In: Automation and remote control. - NEW YORK, NY, USA. - 0005-1179 .- 1608-3032. ; 60:11, s. 1577-1586
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Journal article (peer-reviewed)abstract
- A linear law of control of a mechanical system through drives nonrigidly connected to the system is suggested. The law involves measurement of the positions of links and angular velocities of drives and features a nonminimal-phase character of the transfer function. Stability conditions that remain valid with an increase in the gain are set zip. Results of the numerical modeling in solving problems of positioning anal tracking for robots (manipulators) are described.
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| 2. |
- Castillo, Ismael, et al.
(author)
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Barrier sliding mode control and on-line trajectory generation for the automation of a mobile hydraulic crane
- 2018
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In: 15th International Workshop on Variable Structure Systems (VSS). - : IEEE. - 9781538664391 ; , s. 162-167
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Conference paper (peer-reviewed)abstract
- In this paper we propose an implementation scheme of independent joint control for a four-degree-of-freedom heavy-duty hydraulic actuated crane. First, on-line generation of feasible trajectories, following a driver's lead and satisfying the actuator constrains for the redundant kinematic chain, is performed. Second, an implementation of two new Sliding Mode algorithms with variable barrier function gains, which allow robust tracking of the generated trajectory with alleviation of high frequency oscillations, is presented. Experimental results are presented to show the effectiveness of the proposed semi-automation scheme, exploiting the forestry application motivated low accuracy requirement.
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| 3. |
- Freidovich, Leonid B., Docent, 1973-, et al.
(author)
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Analysis of limit-cycle walking for a compass-like biped robot
- 2010
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In: 8th IFAC Symposium on Nonlinear Control Systems. - : Elsevier. - 9783902661807 ; , s. 1181-1186
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Conference paper (peer-reviewed)abstract
- We consider an impulsive mechanical system modeling dynamics of a planar two-link walker commonly known as a compass-gait biped. It is assumed that there is actuation in the hip but that the desired periodic trajectory describes an unstable passive walking gait. We recall and apply a recently developed technique for design of orbitally stabilizing feedback controllers. After that, we illustrate how to assess various properties of the closed-loop system. In particular, sensitivity to perturbations of the slope of the walking surface is analyzed and an estimate for possible deviations from the nominal trajectory is computed analytically.
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| 4. |
- Freidovich, Leonid B., Docent, 1973-, et al.
(author)
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On generating pre-defined periodic motions in underactuated mechanical systems : The cart-pendulum example
- 2011
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In: 18th IFAC World Congress. - : Elsevier. - 9783902661937 ; , s. 4588-4593
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Conference paper (peer-reviewed)abstract
- We study the problem of generating oscillations in underactuated mechanical systems with a chosen time-evolution of some of the generalized coordinates. We consider a classical planar pendulum on a cart example and find conditions of existence of a solution. These conditions are expressed in terms of functions defining synchronization between the actuated and underactuated variables known as virtual holonomic constraints. Explicit expressions for these functions are computed for the cart-pendulum system where the pendulum angle is set to follow a trajectory like a pure sinusoidal waveform around the upright equilibrium. Once the valid virtual constraint has been found with the proposed method, the earlier developed techniques can be applied in order to design an orbitally stabilizing feedback control law. © 2011 IFAC.
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| 5. |
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| 6. |
- Freidovich, Leonid B., 1973-, et al.
(author)
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Shaping stable periodic motions of inertia wheel pendulum : theory and experiment
- 2009
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In: Asian Journal of Control. - : Wiley. - 1561-8625 .- 1934-6093. ; 11:5, s. 549-556
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Journal article (peer-reviewed)abstract
- 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.
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| 7. |
- Freidovich, Leonid B., Docent, 1973-, et al.
(author)
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Transverse linearization for underactuated nonholonomic mechanical systems with application to orbital stabilization
- 2012. - 1
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In: Distributed decision making and control. - London : Springer. - 9781447122647 - 9781447122654 ; , s. 245-258
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Book chapter (peer-reviewed)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, Sergei V., et al.
(author)
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LMI approach for solving periodic matrix Riccati equation
- 2007
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In: 3<sup>rd</sup> IFAC workshop on Periodic Control Systems (PSYCO). - : Elsevier. - 9783902661302 ; , s. 254-256
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Conference paper (peer-reviewed)abstract
- The paper presents a new method for numerical solution of matrix Riccati equation with periodic coefficients. The method is based on approximation of stabilizing solution of the Riccati equation by trigonometric polynomials.
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| 9. |
- La Hera, Pedro M., 1981-, et al.
(author)
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Gait synthesis for a three-link planar biped walker with one actuator
- 2010
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In: IEEE International Conference on Robotics and Automation (ICRA), 2010. - 9781424450381 ; , s. 1715-1720
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Conference paper (peer-reviewed)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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| 10. |
- La Hera, Pedro M., 1981-, et al.
(author)
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Orbital stabilization of a pre-planned periodic motion to swing up the Furuta pendulum : theory and experiments
- 2009
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In: ICRA. ; , s. 3562-3567
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Conference paper (peer-reviewed)abstract
- 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.
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