Showing papers by "Gonzalo López-Nicolás published in 2011"

A Sliding-Mode-Control Law for Mobile Robots Based on Epipolar Visual Servoing From Three Views

Abstract: Driving mobile robots to precise locations is of recognized interest, and using vision sensors in this context supplies many advantages. We propose a novel control law based on sliding-mode theory in order to drive mobile robots to a target location, which is specified by a previously acquired reference image. The control scheme exploits the piecewise epipolar geometry of three views on the basis of image-based visual servoing, in such a way that no 3-D scene information is required. The contribution of the paper is a new control law that achieves convergence to the target with no auxiliary images and without changing to any approach other than epipolar-based control. Additionally, the use of sliding-mode control deals with singularities, thus allowing the robot to move directly toward the target as well as avoiding the need of a precise camera calibration. The effectiveness of our approach is tested with simulations and real-world experiments.

Adaptive Simmering Control for Domestic Induction Cookers

Abstract: The goal of this paper is twofold. First, we aim at investigating the potentials of reset observers (ReOs) applied to process control. Second, we aim to overcome the existing performance limitations of the temperature control in domestic cookers. To this end, we present an adaptive simmering control for induction cookers, whose parameters are updated online, depending on the estimates provided by a multiple-model ReO (MMReO). This new observer results in extending the idea of multiple models to the state observer framework. The MMReO consists of a reinitialized ReO and of multiple fixed identification models. The resultant control scheme satisfies the user requirements such as quick heating up, accurate temperature control, and fast disturbance rejection, outperforming previous results. Moreover, the proposed control scheme reduces energy consumption, and consequently, it can increase the efficiency of the whole cooking process. Additionally, a fixed robust quantitative feedback theory (QFT)-based controller is designed, and it is also used for comparison purposes. Several verification tests are carried out in real induction hobs to emphasize the effectiveness of our proposal compared with the QFT-based controller.

Vision-based exponential stabilization of mobile robots

Abstract: A new smooth closed loop time invariant control law is proposed for the exponential stabilization of mobile robots with nonholonomic motion constraints. The control scheme relies solely on visual information and includes an observer for the system state estimation by means of the essential matrix. The problem of model degeneracies due to short baseline is solved with the definition of a virtual target that provides a stable estimation of the essential matrix. The novelty of this paper lies in the new vision-based control scheme with state observer which is robust, ensuring convergence to the target location. The stability of the system under the proposed control law is demonstrated and experimental results show the goodness of the approach.

Scene structure recovery from a single omnidirectional image

Abstract: This work tackles the problem of recovering the structure of a scene from a single image. The goal is to interpret automatically the image to obtain the spatial layout of the scene. In essence, the method proposed classifies the environment as floor or walls and their relative positions. Instead of using standard cameras for solving this particular task, our work is novel in using omnidirectional vision, which is advantageous as it captures in a single image the whole surrounding structure. We also consider man-made indoor scenes, where geometric relationships like parallelism and orthogonality are common. Our contribution is a new method for recovering the scene layout by using extracted line segments from a single omnidirectional image. Collection of lines and geometric constraints provide sufficient information to generate a set of possible scene structures. We also create a map of orientations in the image to test these hypotheses and select the one with the best fitting as the resultant structure.

Homography-based multi-robot control with a flying camera

Abstract: This paper addresses the problem of visual control of a set of mobile robots In our framework, the perception system consists of a calibrated flying camera looking downward to the mobile robots The robots are assumed to undergo planar motion considering nonholonomic constraints The goal of the task is to control the multi-robot system to a desired configuration relying solely on visual information given by the flying camera The desired multi-robot configuration is defined with an image of the set of robots in that configuration Then, any arbitrary configuration can be easily defined by this image without any additional information As contribution, a new image-based control scheme is presented relying on the homography induced by the multi-robot system to lead the robots to the desired configuration The stability of the control law is analyzed and simulations are provided to illustrate the proposal