Diseño de un controlador por convergencia de estado para un sistema teleoperado no lineal con retardo de comunicación

En este artículo se presenta el modelado y análisis de un sistema de teloperación bilateral no lineal de n grados de libertad controlado por convergencia de estado. Se considera que el operador humano aplica una fuerza constante sobre el manipulador local mientras realiza la tarea. Además, la interacción entre el manipulador remoto y el entorno se considera pasiva. La comunicación entre el sitio local y remoto se realiza mediante un canal de comunicación con retardo de tiempo. El análisis presentado en este artículo considerada que éste es variable. En este artículo también se demuestra la estabilidad del sistema utilizando la teoría de Lyapunov-Krasovskii demostrándose que el esquema de control por convergencia de estado para el caso con retardo de tiempo variable asegura la estabilidad del sistema de teleoperación no lineal. También se muestra experimentalmente que, para el caso de protocolos de comunicación fiables, el esquema propuesto garantiza que se logra la coordinación posición local-remoto.

State Convergence Theory Applied to a Delayed Teleoperation System

State convergence is a control strategy that was proposed in the early 2000s to ensure stability and transparency in a teleoperation system under specific control gains values. This control strategy has been implemented for a linear system with or without time delay. This paper represents the first attempt at demonstrating, theoretically and experimentantally, that this control strategy can also be applied to a nonlinear teleoperation system with n degrees of freedom and delay in the communication channel. It is assumed that the human operator applies a constant force on the local manipulator during the teleoperation. In addition, the interaction between the remote manipulator and the environment is considered passive. Communication between the local and remote sites is made by means of a communication channel with variable time delay. In this article the theory of Lyapunov-Krasovskii was used to demonstrate that the local-remote teleoperation system is asymptotically stable.

Real-time bilateral control of a nonlinear teleoperation system

In this work, we study the bilateral control of a nonlinear teleoperator system with constant delay, proposes a control strategy by state convergence, which directly connect the local and remote manipulator through feedback signals of position and speed. The control signal allows the remote manipulator follow the local manipulator through the state convergence even if it has a delay in the communication channel. The bilateral control of the teleoperator system considers the case when the human operator applies a constant force on the local manipulator and when the interaction of the remote manipulator with the environment is considered passive. The stability analysis is performed using functional of Lyapunov-Krasovskii, it showed that using a control algorithm by state convergence for the case with constant delay, the nonlinear local and remote teleoperation system is asymptotically stable, also speeds converge to zero and position tracking is achieved.

Control of a Nonlinear Teleoperation System by State Convergence

In this work, we proposes a control strategy that allows the remote manipulator follow the local manipulator through the state convergence even if it has a delay in the communication channel. The bilateral control of the teleoperator system considers the case were the human operator applies a constant force on the local manipulator and when the interaction of the remote manipulator with the environment is considered passive. The stability analysis was performed using Lyapunov- Krasovskii functional, it showed for the case with constant delay, that using a proposed control algorithm by state convergence resulted in asymptotically stable, local and remote the nonlinear teleoperation system.

Advances in Control of Teleoperation System by State Convergence

In this work, we proposes a control strategy by state convergence applied to bilateral control of a nonlinear teleoperator system with constant delay. The bilateral control of the teleoperator system considers the case when the human operator applies a constant force on the local manipulator and when the interaction of the remote manipulator with the environment is considered passive. The stability analysis is performed using Lyapunov-Krasovskii functional, it showed that using an control algorithm by state convergence for the case with constant delay, the nonlinear local and remote teleoperation system is asymptotically stable, also speeds converge to zero and position tracking is achieved. This work also presents the implementation of an experimental platform. The mechanical structure of the arm that is located in the remote side has been built and the electric servomechanism has been mounted to control their movement.

Control of a Teleoperation System by State Convergence with Variable Time Delay

In this paper, we propose a novel control scheme for bilateral teleoperation of n degree-of-freedom (DOF) nonlinear robotic systems with time-varying communication delay. We consider that the human operator contains a constant force on the local manipulator. The local and remote manipulators are coupled using state convergence control scheme. By choosing a Lyapunov-Krasovskii functional, we show that the local-remote teleoperation system is asymptotically stable. It is also shown that, in the case of reliable communication protocols, the proposed scheme guarantees that the remote manipulator tracks the delayed trajectory of the local manipulator. The time delay of communication channel is assumed to be unknown and randomly time varying, but the upper bounds of the delay interval and the derivative of the delay are assumed to be known.

Stability Analysis of Teleoperation System by State Convergence with Variable Time Delay

We propose a novel control scheme for bilateral teleoperation of n degree-of-freedom (DOF) nonlinear robotic systems with time-varying communication delay. A major contribution from this work lies in the demonstration that the structure of a state convergence algorithm can be also applied to nth-order nonlinear teleoperation systems. By choosing a Lyapunov Krasovskii functional, we show that the local-remote teleoperation system is asymptotically stable. The time delay of communication channel is assumed to be unknown and randomly time varying, but the upper bounds of the delay interval and the derivative of the delay are assumed to be known.

Metodología de Diseño y Análisis de Sistemas Teleoperados Considerando Dinámica No Lineal

Cuando la separación física entre el sistema local y remoto es relativamente corta, el retardo no es perceptible; sin embargo, cuando el manipulador local y el manipulador remoto se encuentran a una distancia lejana uno del otro, el retardo de tiempo ya no es insignificante e influye negativamente en la realización de la tarea. El retardo de tiempo en un sistema de control introduce un atraso de fase que a su vez degrada el rendimiento del sistema y puede causar inestabilidad. Los sistemas de teleoperación pueden sacar provecho de la posibilidad de estar presente en dos lugares simultáneamente, sin embargo, el uso de Internet y otras redes de conmutación de paquetes, tales como Internet2, impone retardos de tiempo variables, haciendo que los esquemas de control ya establecidos elaboren soluciones para hacer frente a inestabilidades causadas por estos retardos de tiempo variables. En este trabajo de tesis se presenta el modelado y análisis de un sistema de teloperación bilateral no lineal de n grados de libertad controlado por convergencia de estado. La comunicación entre el sitio local y remoto se realiza mediante un canal de comunicación con retardo de tiempo. El análisis presentado en este trabajo considera que el retardo puede ser constante o variable. Los principales objetivos de este trabajo son; 1) Desarrollar una arquitectura de control no lineal garantizando la estabilidad del sistema teleoperado, 2) Evaluar la estabilidad del sistema considerando el retardo en la comunicación, y 3) Implementación de los algoritmos desarrollados para probar el desempeño de los mismos en un sistema experimental de 3 grados de libertad. A través de la teoría de Estabilidad de Lyapunov y el funcional Lyapunov-Krasovskii, se demuestra que el sistema de lazo cerrado es asintóticamente estable. Estas conclusiones de estabilidad se han obtenido mediante la integración de la función de Lyapunov y aplicando el Lema de Barbalat. Se demuestra también que se logra sincronizar las posiciones del manipulador local y remoto cuando el operador humano no mueve el manipulador local y el manipulador remoto se mueve libremente. El esquema de control propuesto se ha validado mediante simulación y en forma experimental empleando un sistema de teleoperación real desarrollado en esta tesis doctoral y que consta de un un manipulador serie planar de tres grados de libertad, un manipulador local, PHANTOM Omni, el cual es un dispositivo haptico fabricado que consta de 3 grados de libertad (en fuerza) y que proporciona realimentación de fuerza en los ejes x,y,z. El control en tiempo real se ha diseñado usando el Sistema Operativo en Tiempo Real QuaRC de QUARC en el lado local y el Simulink Real-Time Windows TargetTM en el lado remoto. Para finalizar el resumen se destaca el impacto de esta tesis en el mundo científico a través de los resultados publicados: 2 artículos en revistas con índice de impacto , 1 artículo en una revista indexada en Sistemas, Cibernética e Informática, 7 artículos en congresos y ha obtenido un premio en la 9a. Conferencia Iberoamericana en Sistemas, Cibernética e Informática, 2010. ABSTRACT When the physical separation between the local and remote system is relatively short, the delay is not noticeable; however, when the local manipulator and the remote manipulator are at a far distance from each other, the time delay is no longer negligible and negatively influences the performance of the task. The time delay in a control system introduces a phase delay which in turn degrades the system performance and cause instability. Teleoperation systems can benefit from the ability to be in two places simultaneously, however, the use of Internet and other packet switched networks, such as Internet2, imposes varying time delays, making established control schemes to develop solutions to address these instabilities caused by different time delays. In this thesis work we present a modeling and analysis of a nonlinear bilateral teloperation system of n degrees of freedom controlled by state convergence strategy. Communication between the local and remote site is via a communication channel with time delay. The analysis presented in this work considers that the time-delay can be constant or variable. The main objectives of this work are; 1) Develop a nonlinear control schemes to ensure the stability of the teleoperated system, 2) Evaluate the system stability considering the delay in communication, and 3) Implementation of algorithms developed to test the performance of the teleoperation system in an experimental system of 3 degrees of freedom. Through the Theory of Stability of Lyapunov and the functional Lyapunov-Krasovskii, one demonstrates that the closed loop system is asymptotically stable.. The conclusions about stability were obtained by integration of the Lyapunov function and applying Barbalat Lemma. It further shows that the positions of the local and remote manipulator are synchronize when the human operator stops applying a constant force and the remote manipulator does not interact with the environment. The proposed control scheme has been validated by means of simulation and in experimental form using a developed system of real teleoperation in this doctoral thesis, which consists of a series planar manipulator of three degrees of freedom, a local manipulator, PHANTOM Omni, which is an haptic device that consists of 3 degrees of freedom (in force) and that provide feeback force in x-axis, and, z. The control in real time has been designed using the Operating system in Real time QuaRC of Quanser in the local side and the Simulink Real-Time Windows Target in the remote side. In order to finalize the summary, the highlights impact of this thesis in the scientific world are shows through the published results: 2 articles in Journals with impact factor, one article in a indexed Journal on Systemics, Cybernetics and Informatics, 7 articles in Conferences and has won an award in 9a. Conferencia Iberoamericana en Sistemas, Cibernética e Informática, 2010.

A method for revealing phase space structures of general time dependent dynamical systems

In this paper we develop new techniques for revealing geometrical structures in phase space that are valid for aperiodically time dependent dynamical systems, which we refer to as Lagrangian descriptors. These quantities are based on the integration, for a finite time, along trajectories of an intrinsic bounded, positive geometrical and/or physical property of the trajectory itself. We discuss a general methodology for constructing Lagrangian descriptors, and we discuss a “heuristic argument” that explains why this method is successful for revealing geometrical structures in the phase space of a dynamical system. We support this argument by explicit calculations on a benchmark problem having a hyperbolic fixed point with stable and unstable manifolds that are known analytically. Several other benchmark examples are considered that allow us the assess the performance of Lagrangian descriptors in revealing invariant tori and regions of shear. Throughout the paper “side-by-side” comparisons of the performance of Lagrangian descriptors with both finite time Lyapunov exponents (FTLEs) and finite time averages of certain components of the vector field (“time averages”) are carried out and discussed. In all cases Lagrangian descriptors are shown to be both more accurate and computationally efficient than these methods. We also perform computations for an explicitly three dimensional, aperiodically time-dependent vector field and an aperiodically time dependent vector field defined as a data set. Comparisons with FTLEs and time averages for these examples are also carried out, with similar conclusions as for the benchmark examples.

Lagrangian descriptors: a method for revealing phase space structures of general time dependent dynamical systems

Lagrangian descriptors are a recent technique which reveals geometrical structures in phase space and which are valid for aperiodically time dependent dynamical systems. We discuss a general methodology for constructing them and we discuss a "heuristic argument" that explains why this method is successful. We support this argument by explicit calculations on a benchmark problem. Several other benchmark examples are considered that allow us to assess the performance of Lagrangian descriptors with both finite time Lyapunov exponents (FTLEs) and finite time averages of certain components of the vector field ("time averages"). In all cases Lagrangian descriptors are shown to be both more accurate and computationally efficient than these methods.

Un algoritmo de replanificación en tiempo real basado en un índice de estabilidad de Lyapunov para líneas de metro

(SPA) En este trabajo, se propone un nuevo índice basado en el método directo de Lyapunov para el diseño de un algoritmo de reprogramación en tiempo real para líneas de metro. En este estudio se utiliza una versión modificada de un modelo de espacio de estados en tiempo real discreto, que considera los efectos de saturación en la línea de metro. Una vez que el modelo de espacio de estados se ha obtenido, el método directo de Lyapunov se aplica con el fin de analizar la estabilidad del sistema de la línea de metro. Como resultado de este análisis no sólo se propone un nuevo índice de estabilidad, sino también la creación de tres zonas de estabilidad para indicar el estado actual del sistema. Finalmente, se presenta un nuevo algoritmo que permite la reprogramación del calendario de los trenes en tiempo real en presencia de perturbaciones medianas. (ENG) A new Lyapunov-based index for designing a rescheduling algorithm in real time for metro lines has been proposed in this paper. A modified real time discrete space state model which considers saturation effects in the metro line has been utilized in this study. Once the space state model has been obtained, the direct method of Lyapunov is applied in order to analyze the stability of the metro line system. As a result of this analysis not only a new stability index is proposed, but also the establishment of three stability zones to indicate the current state of the system. Finally, a new algorithm which allows the rescheduling of the timetable in the real time of the trains under presence of medium disturbances has been presented.