37 research outputs found

    On the Control of a One Degree-of-Freedom Juggling Robot

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    International audienceThis paper is devoted to the feedback control of a one degree-of-freedom (dof) juggling robot, considered as a subclass of mechanical systems subject to a unilateral constraint. The proposed approach takes into account the whole dynamics of the system, and focuses on the design of a force input. It consists of a family of hybrid feedback control laws, that allow to stabilize the object around some desired (periodic or not) trajectory. The closed-loop behavior in presence of various disturbances is studied. Despite good robustness properties, the importance of good knowledge of the system parameters, like the restitution coefficient, is highlighted. Besides its theoretical interest concerning the control of a class of mechanical systems subject to unilateral constraints, this study has potential applications in non-prehensile manipulation, extending pushing robotic tasks to striking-and-pushing tasks

    Speed-gradient adaptive high-gain observers for synchronization of chaotic systems

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    "We address the problem of output feedback synchronization of certain chaotic systems, under parameter uncertainty. That is, given a master system, the objective is to design a slave system that copies the dynamics of the master and reconstructs both the state and the values of the constant parameters of the master system. Hence, the synchronization problem that we address enters in the framework of Pecora and Carroll and relies on adaptive observer theory. In particular, the conditions that we impose take the form of persistency of excitation.

    Local-homogeneity-based global continuous control for mechanical systems with constrained inputs: finite-time and exponential stabilisation

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    "A global continuous control scheme for the finite-time or (local) exponential stabilisation of mechanical systems with constrained inputs is proposed. The approach is formally developed within the theoretical framework of local homogeneity. This has permitted to solve the formulated problem not only guaranteeing input saturation avoidance but also giving a wide range of design flexibility. The proposed scheme is characterised by a saturating-proportional-derivative type term with generalised saturating and locally homogeneous structure that permits multiple design choices on both aspects. The work includes a simulation implementation section where the veracity of the so-cited argument claiming that finite-time stabilisers are faster than asymptotical ones is studied. In particular, a way to carry out the design so as to, indeed, guarantee faster stabilisation through finite-time controllers (beyond their finite-time convergence) is shown.

    Adaptive tracking control of Euler-Lagrange systems with bounded controls

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    "We solve the simultaneous closed?loop identification and tracking?control problems for fully actuated Euler-Lagrange systems under input constraints. We use a nonlinear adaptive controller reminiscent of computed?torque?type controllers in which linear correction terms are saturated in order to comply with the imposed bounds on the control inputs. Adaptation, reminiscent of gradient methods, is used also with saturation. With respect to related literature, our contribution consists in establishing uniform global asymptotic stability. Therefore, our control scheme ensures robustness with respect to bounded perturbations and uniform convergence of the estimation errors for any initial conditions.

    Estudio analĂ­tico de la media logarĂ­tmica de diferencia de temperaturas

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    "La media logarítmica de diferencia de temperaturas (LMTD, por sus siglas en inglés) ha causado inconveniencias en diversas aplicaciones tales como ciertos programas de simulación de procesos. Su forma indeterminada es una de las principales causas de tales inconveniencias. Tal indeterminación es una consecuencia del procedimiento incompleto que generalmente se desarrolla para su obtención en los libros de texto. El análisis dinámico y el diseño de control de intercambiadores de calor a través de modelos de parámetros agrupados que usan la LMTD como fuerza conductora (de intercambio de calor, i.e. diferencia promedio de temperatura entre los fluidos) pueden también ser víctimas de tales inconsistencias. Este trabajo está dedicado a dar una solución a tales inconveniencias a través de un análisis matemático formal de la LMTD. Primero, un procedimiento completo para su obtención es desarrollado, dando como resultado una expresión completa bien definida. Posteriormente, diversas propiedades analíticas de la expresión resultante, tales como la continuidad y la diferenciabilidad en todo su dominio, son probadas. La utilidad de los resultados es comentada a lo largo del texto.""The logarithmic mean temperature difference (LMTD) has caused inconveniences in several applications like equationoriented flow sheeting programs. Such inconveniences have arisen from its indeterminate form. This is a consequence of the incomplete model derivation generally developed in the textbooks. Heat exchanger dynamic analysis and control synthesis through lumped-parameter models using the LMTD as driving force (fluid mean temperature difference) may suffer from such inconsistencies too. This paper is devoted to give a solution to such inconveniences by providing a formal mathematical treatment of the LMTD. First, a complete derivation is restated resulting in a complete well-defined expression. Then, several interesting analytical properties of the resulting expression, like continuous differentiability on its domain, are proved. The usefulness of the results is highlighted throughout the text.

    Bounded positive adaptive control for counterflow heat exchangers

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    "In this work, we propose an outlet temperature control scheme for counterflow heat exchangers, that takes into account and actually exploits the analytical-stability features inherent to the open-loop dynamics. As a result, outlet temperature regulation is achieved through a simple adaptive controller which does not need to feedback the whole state vector and does not depend on the exact value of the system parameters. Furthermore, positivity and boundedness (nonsaturation) of the input flow rate are additionally guaranteed through the proposed approach, without entailing complex control algorithms or stability proofs. The analytical developments are corroborated through experimental results.

    Output-feedback proportional-integral-derivative-type control with multiple saturating structure for the global stabilization of robot manipulators with bounded inputs

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    "An output-feedback proportional integral derivative-type control scheme for the global regulation of robot manipulators with constrained inputs is proposed. It guarantees the global stabilization objective-avoiding input saturation-releasing the feedback not only from the exact knowledge of the system structure and parameter values but also from velocity measurements. With respect to previous approaches of the kind, the proposed controller is expressed in a generalized form whence multiple saturating structures may be adopted, thus enlarging the degree of design flexibility. Furthermore, experimental tests on a two-degree-of-freedom direct-drive manipulator corroborate the efficiency of the proposed scheme.

    A generalized scheme for the global adaptive regulation of robot manipulators with bounded inputs

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    "In this work, a generalized adaptive control scheme for the global position stabilization of robot manipulators with bounded inputs is proposed. It gives rise to various families of bounded controllers with adaptive gravity compensation. Compared with the adaptive approaches previously developed in a bounded-input context, the proposed scheme guarantees the adaptive regulation objective: globally, avoiding discontinuities in the control expression as well as in the adaptation auxiliary dynamics, preventing the inputs to reach their natural saturation bounds, and imposing no saturation-avoidance restriction on the control gains. Experimental results corroborate the efficiency of the proposed adaptive scheme.

    Output-feedback adaptive control for the global regulation of robot manipulators with bounded inputs

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    "In this paper, an output-feedback adaptive scheme for the global position stabilization of robot manipulators with bounded inputs is proposed. Compared to the previous output-feedback adaptive approaches developed in a bounded-input context, the proposed free-of-velocity feedback controller guarantees the adaptive regulation objective: globally, avoiding discontinuities throughout the scheme, preventing the inputs to reach their natural saturation bounds, and imposing no saturation-avoidance restriction on the control gains. Moreover, the developed scheme is not restricted to the use of a specific saturation function to achieve the required boundedness, but may involve any one within a set of smooth and non-smooth (Lipschitz-continuous) bounded passive functions that include the hyperbolic tangent and the conventional saturation as particular cases. Experimental results corroborate the efficiency of the proposed scheme.

    Output-feedback adaptive SP-SD-Type control with an extended continuous adaptation algorithm for the global regulation of robot manipulators with bounded inputs

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    "In this work, an output-feedback adaptive SP-SD-type control scheme for the global position stabilization of robot manipulators with bounded inputs is proposed. Compared with the output-feedback adaptive approaches previously developed in a bounded-input context, the proposed velocity-free feedback controller guarantees the adaptive regulation objective globally (i.e. for any initial condition), avoiding discontinuities throughout the scheme, preventing the inputs from reaching their natural saturation bounds and imposing no saturation-avoidance restrictions on the choice of the P and D control gains. Moreover, through its extended structure, the adaptation algorithm may be configured to evolve either in parallel (independently) or interconnected to the velocity estimation (motion dissipation) auxiliary dynamics, giving an additional degree of design flexibility. Furthermore, the proposed scheme is not restricted to the use of a specific saturation function to achieve the required boundedness, but may involve any one within a set of smooth and non-smooth (Lipschitz-continuous) bounded passive functions that include the hyperbolic tangent and the conventional saturation as particular cases. Experimental results on a 3-degree-of-freedom manipulator corroborate the efficiency of the proposed scheme
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