Author: DANIELA JUANITA LOPEZ ARAUJO
DANIELA JUANITA LOPEZ ARAUJO (2008)
"Esta tesis se enfoca en la estabilización global de un avión planar de despegue y aterrizaje verticales (PVTOL, por sus siglas en inglés). Este sistema tiene una dinámica compleja que hace difícil el diseño de controladores orientados a resolver el problema de estabilización global. Esto se debe principalmente a su naturaleza subactuada. Adicionalmente, otras limitaciones son consideradas en este estudio: el carácter positivo (unidireccional) de la propulsión y la naturaleza acotada de las entradas. Un primer enfoque que resuelve el problema de estabilización global, tomando en cuenta las restricciones mencionadas, fue propuesto por A. Zavala-Río, I. Fantoni y R. Lozano en 2003; no obstante el parámetro de acoplamiento lateral " fue despreciado debido al pequeño valor que usualmente tiene en la práctica, simplificando así la dinámica del sistema. Sin embargo los resultados obtenidos en simulación para corroborar la eciencia del esquema propuesto, muestran que el objetivo de control es logrado aún tomando valores positivos de E. Por otro lado, algunos trabajos recientes han propuesto soluciones al problema de estabilización global considerando la dinámica completa del sistema, pero dependen del valor exacto de E". Así pues, en esta tesis se demuestra analíticamente que el esquema de control inicialmente propuesto por A. Zavala-Río, I. Fantoni y R. Lozano en 2003 bajo las restricciones de entrada arriba mencionadas, considerando E = 0, logra el objetivo de estabilización global aún cuando E > 0, para valores suficientemente pequeños de E pero sin la necesidad de conocer su valor exacto."
"This thesis focuses on the global stabilization of the Planar Vertical Take-O and Landing (PVTOL) aircraft. Such a system has a complex dynamics that renders di cult the design of controllers oriented to solve the global stabilization problem. This is mainly due to its under-actuated nature. In addition, other limitations are considered in this study: the positive (unidirectional) character of the thrust and the bounded nature of the inputs. A rst approach that solves the global stabilization problem, taking the mentioned restrictions into account, was proposed by A. Zavala-R o, I. Fantoni, and R. Lozano in 2003; however the lateral coupling parameter was neglected due to the small value that it usually has in practice, simplifying the system dynamics. Nevertheless the simulation results that were performed to corroborate the e ciency of the proposed scheme, show that the control objective is achieved even taking positive values of. On the other hand, recent works have proposed solutions to the global stabilization problem considering the whole system dynamics, but they depend on the exact knowledge of E. Thus, in this thesis, it is analytically proved that the control scheme initially proposed by A. Zavala-R o, I. Fantoni, and R. Lozano in 2003 under the above mentioned input restrictions, considering E = 0, achieves the global stabilization objective even when E > 0 , provided that is E small enough but without the need to know its exact value."
DANIELA JUANITA LOPEZ ARAUJO (2013)
"La tesis se enfoca en el diseño de leyes de control adaptables para robots manipuladores que consideran la naturaleza acotada de los actuadores. Se proponen esquemas generalizados para regulaci on y seguimiento globales por retroalimentacion de estados,cuyas estructuras permiten obtener versiones adaptables acotadas de algoritmos tipo PD previamente propuestos para el caso de conocimiento parametrico exacto.Tambien se diseño una ley de control tipo SP-SD por retroalimentacion de salida para la estabilizacion global de posicion. Con respecto a trabajos previos, los esquemas adaptables propuestos son los primeros que resuelven los problemas de control formulados: globalmente, sin involucrar discontinuidades, evitando saturacion de entrada y liberando las ganancias de control de restricciones para evitar el fenomeno de saturacion. Mas a un, ninguno de los esquemas propuestos esta restringido a usar una funcion de saturacion especta para lograr el acotamiento deseado sino que es posible escoger cualquiera dentro de un conjunto de funciones pasivas acotadas que incluye la tangente hiperbolica como caso particular. La escacia de los controladores propuestos es probada tanto en simulacion como experimentalmente."
"This thesis focuses on the design of adaptive control schemes for robot manipulators under the consideration of the bounded nature of actuators. Generalized state-feedback controllers are proposed for global regulation and trajectory tracking, whose structures allow to obtain adaptive versions of bounded PD-type algorithms previously developed under the consideration of the exact knowledge of the system parameters. A globally stabilizing SP-SD-type output-feedback adaptive regulation scheme is also developed. With respect to previous works, the proposed adaptive controllers are the first to solve the formulated control problems: globally, free of discontinuities throughout the scheme, avoiding input saturation, and liberating the control gains from the satisfaction of saturation avoidance inequalities. Moreover, the developed controllers are not restricted to use a specic saturation function to achieve the required boundedness, but may involve any one within a set of bounded passive functions that include the hyperbolic tangent as a particular case. The efficiency of the proposed methodology was proven both through simulation and experimental implementations."
"This work is devoted to prove that the nonlinear control scheme previously proposed by Zavala-Río, Fantoni and Lozano for the global stabilisation of the planar vertical take-off and landing (PVTOL) aircraft with bounded inputs neglecting the lateral force coupling is robust with respect to the parameter characterising such a lateral force coupling, ϵ, as long as such a parameter takes small enough values. In other words, global stabilisation is achieved even if ϵ > 0, provided that such a parameter be sufficiently small. As far as the authors are aware, such a property has not been proved in other existing control schemes when the value of ϵ is not known. The presented methodology is based on the use of embedded saturation functions. Furthermore, experimental results of the control algorithm implemented on a real prototype are presented."
"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"
"An observer-less output-feedback global continuous control scheme for the finite-time or (local) exponential stabilization of mechanical systems with constrained inputs is proposed. The approach is formally developed within the theoretical framework of local homogeneity. The closed-loop analysis incorporates a complementary insight on the control-induced motion dissipation through an ad hoc feedback-system passivity theorem. The work includes a simulation implementation section where the performance difference of the proposed scheme with previous observer-based and differentiation algorithms is brought to the fore."
"In this work, a generalized adaptive scheme for the global motion control of robot manipulators with constrained inputs is proposed. It gives rise to various families of bounded adaptive controllers defined through a general class of saturation functions. Compared with adaptive tracking control algorithms previously developed in a bounded input context, the proposed adaptive approach guarantees the motion control objective for any initial condition, avoiding discontinuities throughout the scheme, preventing the inputs to reach their natural saturation bounds, and permitting innovation on the saturating structure through its generalized form, giving a wide range of possibilities for performance improvement. Experimental results corroborate the efficiency of the proposed scheme"
"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."
Further advancements on the output-feedback global continuous control for the finite-time and exponential stabilisation of bounded-input mechanical systems: desired conservative-force compensation and experiments
"Global Saturating-Proportional Saturating-Derivative (SP-SD) type continuous control for the finite-time or (local) exponential stabilisation of mechanical systems with bounded inputs is achieved avoiding velocity variables in the feedback, and further simplified through desired conservative-force compensation. The proposed output-feedback controller is not a simple extension of the on-linecompensation case but it rather proves to entail a closed-loop analysis with considerably higher degree of complexity that gives rise to more involved requirements. Interestingly, the proposal even shows that actuators with higher power-supply capabilities than in the on-line compensation case are required. Other important analytical limitations are further overcome through the developed algorithm. Experimental tests on a multi-degree-of-freedom robot corroborate the efficiency of the proposed approach."
"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."
"A Saturating-Proportional Saturating-Derivative type global continuous control scheme with desired gravity compensation for the finite-time or (local) exponential stabilization of robotic systems with constrained inputs, avoiding velocity variables in the feedback, is presented. The proposed output-feedback controller proves to need a closed-loop analysis with considerably higher degree of complexity, and entail more involved consequent requirements, than in the on-line compensation case. Other analytical limitations are further overcome through the developed algorithm. Simulation tests corroborate the efficiency of the proposed approach."