| 1. |
- Freidovich, Leonid B., 1973-, et al.
(författare)
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Shaping stable periodic motions of inertia wheel pendulum : theory and experiment
- 2009
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Ingår i: Asian Journal of Control. - : Wiley. - 1561-8625 .- 1934-6093. ; 11:5, s. 549-556
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Gusev, Sergei V., et al.
(författare)
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LMI approach for solving periodic matrix Riccati equation
- 2007
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Ingår i: 3<sup>rd</sup> IFAC workshop on Periodic Control Systems (PSYCO). - : Elsevier. - 9783902661302 ; , s. 254-256
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Konferensbidrag (refereegranskat)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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| 3. |
- La Hera, Pedro M., 1981-, et al.
(författare)
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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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Ingår i: ICRA. ; , s. 3562-3567
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Konferensbidrag (refereegranskat)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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| 4. |
- Mettin, Uwe, et al.
(författare)
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Generating human-like motions for an underactuated three-link robot based on the virtual constraints approach
- 2007
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Ingår i: Proceedings of the 46th IEEE conference on decision and control. - 9781424414970 ; , s. 5138-5143
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 5. |
- Mettin, Uwe, 1979-, et al.
(författare)
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Parallel elastic actuators as a control tool for preplanned trajectories of underactuated mechanical systems
- 2009
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Ingår i: The international journal of robotics research. - : Sage journals online. - 0278-3649 .- 1741-3176. ; 29:9, s. 1186-1198
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Shiriaev, Anton, et al.
(författare)
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Can we make a robot ballerina perform a pirouette? : orbital stabilization of periodic motions of underactuated mechanical systems.
- 2008
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Ingår i: Annual Reviews in Control. - : Elsevier BV. - 1367-5788 .- 1872-9088. ; 32:2, s. 200-211
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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