The article proposes a nonlinear H-infinity (optimal) control approach to the problem of control of closed-chain robotic mechanisms. The dynamic model of the closed-chain robotic mechanism undergoes approximate linearization, round a local operating point. This local equilibrium is re-calculated at each iteration of the control program and consists of the present value of the state vector of the robotic mechanism and of the last value of the control input that was exerted on it. The linearization is based on Taylor series expansion and the computation of the associated Jacobian matrices. The modelling error due to truncation of higher order terms from this expansion is compensated by the robustness of the control scheme. Next, an H-infinity feedback controller is designed. The feedback gain is computed after solving an algebraic Riccati equation at each iteration of the control algorithm. The control scheme provides solution to a mini-max differential game in which the disturbances and modelling errors try to maximize a quadratic cost functional, while the control input tries to minimize it. Through Lyapunov stability analysis it is proven that the control loop satisfies an H-infinity tracking performance criterion, which signifies elevated robustness to model uncertainty and external perturbations. Moreover, under moderate conditions the global asymptotic stability of the control loop is proven.
En este articulo se describen las principales aportaciones e innovaciones educativas llevadas a cabo en el Master Universitario en Automatica y Robotica de la Universidad de Alicante desde su implantacion en el curso 2010/2011 hasta la actualidad. Se describira, por un lado, la metodologia docente y los principales indicadores de calidad del titulo y, por otro lado, los laboratorios virtuales remotos desarrollados. Estos laboratorios conforman una de las principales innovaciones educativas desarrolladas, ya que permiten a todo el alumnado tener un acceso seguro a recursos costosos y limitados como son robots y sistemas de automatizacion. El presente trabajo muestra las principales caracteristicas de los mismos, asi como su uso por parte del alumnado para su autoevaluacion. Asimismo, se destaca su impacto en la docencia a traves de los resultados obtenidos, asi como el grado de satisfaccion del alumnado con este tipo herramientas. Finaliza el articulo indicando las principales conclusiones que pueden extraerse de los resultados, asi como las innovaciones didacticas en desarrollo en el Master.
The depth perception in the objects of a scene can be useful for tracking or applying visual servoing in mobile systems. 3D time-of-flight (ToF) cameras provide range images which give measurements in real time to improve these types of tasks. However, the distance computed from these range images is very changing with the integration time parameter. This paper presents an analysis for the online adaptation of integration time of ToF cameras. This online adaptation is necessary in order to capture the images in the best condition irrespective of the changes of distance (between camera and objects) caused by its movement when the camera is mounted on a robotic arm.
La Escuela Politecnica Superior de la Universidad de Alicante, oferta un variado programa de formacion de postgrado que se materializa en trece titulaciones de masteres (todas ellas relacionadas con la ingenieria y la arquitectura), que permiten al alumnado que finaliza sus estudios de Grado, completar su formacion universitaria. En la actualidad, las titulaciones universitarias tienen que someterse a un exigente Sistema de Garantia de Calidad que es controlado y revisado de forma periodica para conseguir una mejora continuada en dichas titulaciones. Por este motivo, es necesaria la realizacion de diversos informes de seguimiento (que seran posteriormente evaluados) y en los cuales se analizan diversas �evidencias� para determinar los niveles de calidad de la titulacion. Una de dichas �evidencias� es la Tasa de abandono en la titulacion. Para obtener unos buenos resultados, se persigue disponer de informacion y herramientas que contribuyan a disminuir significativamente las tasas de abandono en los estudios de masteres, hecho que repercutira positivamente en la renovacion de la acreditacion del estudio de master correspondiente. El objetivo, por tanto consistira en realizar un diagnostico de la situacion e identificar las causas del abandono para la posterior realizacion de propuestas de mejora. Palabras clave: Master, calidad, tasa de abandono, re-acreditacion, ANECA. - 2466
In this article, we describe a new approach for the tracking of trajectories with occlusions, using image-based control, referred to here as movement flow-based visual servoing. This approach allows the tracking of trajectories specified in the image space and shows a correct behaviour in the 3-D Cartesian space. One of the main contributions of this method is a tracking that is not dependent on time, which affords a better tracking as the system is not subject to time restrictions. To make the tracking of trajectories with occlusions possible, we describe the inclusion of information from the movement flow into an estimator based on the Kalman filter. To verify the correct behaviour of this approach, an eye-in-hand camera system is employed.
In this paper, a cooperative robot-robot approach to construct metallic structures is presented. In order to deve lop this task, a visual-force control system is proposed. The visual information is composed of an eye-in-hand camera, and a time of flight 3D camera. Both robots are equipped by a force sensor at the end-effector. In order to allow a human cooperate with both robots, an inertial motion capture system and an indoor localization system are em ployed. This multisensorial approach allows the robots to cooperatively construct the metallic structure in a flexible way and sharing the workspace with a human operator. -
<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> A nonlinear H-infinity (optimal) control approach is developed for the problem of the control of the spherical rolling robot. The solution of such a control problem is a nontrivial case due to underactuation and strong nonlinearities in the system's state-space description. The dynamic model of the robot undergoes approximate linearization around a temporary operating point which is recomputed at each timestep of the control method. The linearization relies on Taylor series expansion and on the computation of the system's Jacobian matrices. For the linearized dynamics of the spherical robot an H-infinity controller is designed. To compute the controller's feedback gains an algebraic Riccati equation in solved at each iteration of the control algorithm. The global asymptotic stability properties of the control method are proven through Lyapunov analysis. Finally, for the implementation of sensorless control for the spherical rolling robot, the H-infinity Kalman Filter is used as a robust state estimator.
In this paper, we described our experience in teaching robotics and sensorial systems in computer science degrees at the University of Alicante. The work presented in this paper has been done during the last three academic courses, with about 150 students being registered annually. VISUAL and ROBOLAB tools are jointly used for teaching this subject because they allow students to evaluate their developed algorithms and use them in practical experiences in robotics environments. The system does an automatic evaluation of the students' results, verifying whether the trajectories chosen are optimal for the problems solved
