Publications

This paper describes the modelling, simulation and visual servo control of a robot-arm designed for supervision of complex task environments. This robot (mini-robot) has 2 degrees of freedom (hereafter d.o.f.) and it is attached at the end of another anthropomorphic robot with 7 d.o.f. (main robot). In order to achieve a suitable supervision, the mini-robot has to perform a given trajectory around the workspace where the task is developed. With the purpose of obtaining an accurate and fast supervision, this paper presents a novel tracking method carried out in the image space using direct visual servo control.

La presente investigacion docente engloba la generacion de recursos web y multimedia. Para ello, se ha puesto a disposicion de los alumnos en una web mediante el gestor de contenidos Joomla. Ademas, se han creado materiales, que estan disponibles en la web para los alumnos, que incluyen presentaciones y grabaciones en video de las clases. De esta manera, los alumnos pueden volver a ver una clase con el objetivo de reforzar los conocimientos adquiridos o seguir la docencia si, por algun motivo, no pudieron asistir. La plataforma propuesta se ha probado con las asignaturas Sistemas de Control Automatico y Robotica del Master Universitario en Automatica y Robotica.

This paper proposes several task space control approaches for complex on-orbit high degrees of freedom robots. These approaches include redundancy resolution and take the non-linear dynamic model of the on-orbit robotic systems into account. The suitability of the proposed task space control approaches is explored in several on-orbit servicing operations requiring visual servoing tasks of complex humanoid robots. A unified open-source framework for space-robotics simulations, called OnOrbitROS, is used to evaluate the proposed control systems and compare their behaviour with state-of-the-art existing ones. The adopted framework is based on ROS and includes and reproduces the principal environmental conditions that eventual space robots and manipulators could experience in an on-orbit servicing scenario. The architecture of the different software modules developed and their application on complex space robotic systems is presented. Efficient real-time implementations are achieved using the proposed OnOrbitROS framework. The proposed controllers are applied to perform the guidance of a humanoid robot. The robot dynamics are integrated into the definition of the controllers and an analysis of the results and practical properties are described in the results section.

La presente investigacion docente engloba la generacion de recursos web y multimedia. Para ello, se ha puesto a disposicion de los alumnos en una web mediante el gestor de contenidos Joomla. Ademas, se han creado materiales que estan a disponibles en la web para los alumnos, que incluyen presentaciones y grabaciones en video de las clases. De esta manera, los alumnos pueden volver a ver una clase con el objetivo de reforzar los conocimientos adquiridos o seguir la docencia si, por algun motivo, no pudieron asistir. La plataforma propuesta se ha probado con las asignaturas Sistemas de Control Automatico y Robotica del Master Universitario en Automatica y Robotica.

A direct visual-servoing algorithm for control of a space-based two-arm manipulator is proposed in this paper. The algorithm can be utilized in a two-arm manipulators configuration, where one of the arms performs the manipulation and the second arm is dedicated to the observation of the target zone of manipulation. The algorithm utilizes both visual features extracted from onboard cameras and force and torque measured at the manipulator's end-effector to control the movements of the manipulator during on-orbit servicing operations. The algorithm takes into account the relative dynamics of the bodies involved, it relies on images taken independently from de-localized cameras, e.g. at the end-effector of a second manipulator, and it integrates an impedance control for the compensation of eventual contact reactions when the end effector touches and operates the target body. The analytical derivations demonstrate the stability of the algorithm and incorporate an impedance compliance strategy into an optimal framework formulation. Simulations results in two different scenarios have been presented to show the adequate behavior of the presented approach in on-orbit-servicing operations.

Purpose The purpose of this paper has been to present new solutions to the nonlinear control problem of the degrees of freedom (6-DOF) attitude dynamics of reentry space vehicles. Among eligible control methods for the spacecraft’s attitude dynamics one can distinguish some sliding-mode control schemes. Besides there are several backstepping control approaches. In addition, one can find results on model predictive control concepts and optimal control-type concepts. Furthermore, one can distinguish methods which perform disturbance estimation and disturbance compensation thus improving the robustness of the reentry space vehicles’ control loop. Besides, this control problem is often treated with use of methods which rely on state-space model transformations and on changes of state variables. The aim of the present paper has been to achieve control and stabilization for the attitude dynamics of reentry space vehicles without forth and back state-space model transformations, changes of state variables (diffeomorphisms), and without the associated singularity issues. To this end, two new nonlinear control methods have been proposed: (i) nonlinear optimal control and (ii) flatness-based control in successive loops. Design/methodology/approach In this paper, the control problem for the multivariable and nonlinear 6-DOF dynamics of the attitude of autonomous reentry space vehicles is solved with the use of (i) a nonlinear optimal control method and (ii) a flatness-based control approach which is implemented in successive loops. To apply method (i) that is nonlinear optimal control, the dynamic model of the reentry space vehicle undergoes approximate linearization at each sampling instant with the use of first-order Taylor series expansion and through the computation of the associated Jacobian matrix. The linearization point is defined by the present value of the system’s state vector and by the last sampled value of the control inputs vector. To compute the feedback gains of the optimal controller an algebraic Riccati equation is repetitively solved at each time-step of the control algorithm. The global stability properties of the nonlinear optimal control method are proven through Lyapunov analysis. To implement control method (ii), that is flatness-based control in successive loops, the state-space model of the 6-DOF attitude dynamics of the autonomous reentry space vehicles is separated into two subsystems, which are connected between them in cascading loops. Each one of these subsystems can be viewed independently as a differentially flat system and control about it can be performed with inversion of its dynamics as in the case of input-output linearized flat systems. The state variables of the second subsystem become virtual control inputs for the first subsystem. In turn, exogenous control inputs are applied to the second subsystem. The whole control method is implemented in two successive loops and its global stability properties are also proven through Lyapunov stability analysis. The proposed method achieves stabilization of the attitude dynamics of the space vehicle without the need of diffeomorphisms and complicated state-space model transformations. Findings In the first control method that the article proposes, the dynamic model of the attitude of the reentry space vehicle undergoes approximate linearization around a temporary operating point which is updated at each sampling period. For the approximately linearized state-space description of the system, an H-infinity feedback controller is designed. To select the controller’s gains, an algebraic Riccati equation is repetitively solved at each time-step of the control method. The global stability properties of the control scheme are proven through Lyapunov analysis. In the second control method of the paper, the dynamic model of the reentry space vehicle is decomposed into a series of subsystems which are connected in chained form. It is proven that these subsystems if viewed independently, are differentially flat. In the chained subsystems, the state vector of the subsequent subsystem becomes virtual control input to the preceding subsystem. From the last subsystem, the real control inputs vector is found. The global stability properties of the flatness-based control method are also proven through Lyapunov analysis. Research limitations/implications There are no research limitations about the proposed control methods for the attitude dynamics of reentry space vehicles. On the contrary, a benefit from using either the nonlinear optimal control approach or the flatness-based control in successive loops for the attitude dynamics of the reentry space vehicle is that a solution of the control and stabilization problem for this nonlinear system can be reached without state-space model transformations and complicated changes of state variables. Practical implications A significant part of the research on nonlinear control for aerospace systems has been on the application of state-space model transformations which allow for writing these systems’ dynamics into an equivalent representation where the solution of the control and state estimation problems can be significantly simplified. In this regard, Lie algebra-based control methods and flatness-based control with transformation into canonical forms pursue the application of diffeomorphisms which allow for writing the initial nonlinear state-space model into an equivalent input-output linearized state-space form. These transformations often precede also the application of sliding-mode control, because it is only for systems in the input-output linearized form that one can follow a systematic procedure for selecting sliding surfaces. The nonlinear optimal and the flatness-based control method in successive loops, which are proposed in this paper, achieve solution for the control and stabilization problem of the attitude dynamics of reentry space vehicles without needing to apply any transformations for these spacecrafts’ state-space model and without imposing any changes of state variables. Social implications Control for autonomous reentry space vehicles has been a nontrivial research topic in the area of aerospace science and technology. Obviously, there is significant benefit from solving the attitude control problem for reentry space vehicles These aerospace systems become more reliable and the success of the associated missions is ensured. Space exploration and exploitation with the use of reentry space vehicles is carried out for civilian or defense purposes and affects the quality of living, prosperity, peace and international cooperation at a worldwide scale. Originality/value The results of this study are genuine and novel. The first method that the paper proposes for the 6-DOF attitude dynamics of reentry space vehicles is a nonlinear optimal (H-infinity) control scheme. The second method that the paper proposes for the attitude dynamics of reentry space vehicles is flatness-based control implemented in successive loops. The proposed methods achieve stabilization of the attitude dynamics of the space vehicle without the need of diffeomorphisms and complicated state-space model transformations.

En el presente articulo se describe la investigacion docente desarrollada con el objetivo de llevar a cabo el seguimiento y aplicacion, del sistema interno de garantia de calidad de la Escuela Politecnica Superior de la Universidad de Alicante, al Master Universitario en Automatica y Robotica. Esta investigacion es fruto de una red docente en la que han participado todos los profesores con docencia en el Master, y en la que han trabajado coordinadamente con el objetivo de recoger los principales indicadores de calidad del Master atendiendo a distintos criterios. Estos indicadores han servido, por un lado, para comprobar la existencia o no de deficiencias en la implantacion e imparticion del Titulo. Por otro lado, estos indicadores han servido como base para la elaboracion de la documentacion requerida para la reacreditacion del Master ante la ANECA. En este articulo se describe la coordinacion llevada a cabo, las principales consideraciones a tener en cuenta para la implantacion del sistema de garantia de calidad, asi como las conclusiones extraidas de la red.

Este articulo presenta el enfoque docente utilizado en la ensenanza de la asignatura “Robots y Sistemas Sensoriales” impartida por el area de Ingenieria de Sistemas y Automatica en las titulaciones de Informatica en la Universidad de Alicante. Se va a describir el contexto en el que se encuentra dicha asignatura dentro de la Universidad, ademas se presenta el temario que se imparte asi como una descripcion de las practicas que deben realizar los alumnos; explicando previamente las herramientas disponibles para la realizacion de las mismas.