An approach to guide a mobile robot from an initial position to a goal position avoiding any obstacle in its path, when navigating in a semi-structured environment, is proposed in this paper. Such an approach, hereinafter referred to as tangential escape, consists in changing the current robot orientation through a suitable combination of the values of the angular and linear velocities (the control actions) whenever an obstacle is detected close to it. Then, the robot starts navigating in parallel to the tangent to the obstacle, regarding the point of the obstacle boundary the robot sensing system identifies as the closest one. The stability of the control system designed according this approach is proven, showing that the robot reaches any reachable goal, with or without a prescribed final orientation. Such a control system is programmed onboard a mobile platform whose sensing system is a laser scanner which provides 181 range measurements, for experimental validation. The results obtained are presented and discussed, allowing concluding that the tangential escape approach is able to guide the robot along trajectories that result in a reduction of the traveling time, thus saving batteries and reducing the motor wearing

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Neste trabalho nós mostramos como determinar o potencial efetivo para uma teoria com quebra espontânea de simetria.

This paper addresses the human-robot cooperation problem on object transportation tasks, particularly when a human grasps one side of the object while the other extremity is carried by the robot. The robot is equipped with a pair of infrared sensors used to obtain the load's status and apply it as a feedback to accomplish a specific task. A nonlinear controller is proposed to allow the robot to perform coordinated movements and thus help a human to carry an object from an initial position to a final goal with a defined position and orientation. The controller is proved to be asymptotically stable at the equilibrium point, which guarantees the accomplishment of the task. In contrast to other methods, the approach presented in this paper does not use either force or visual information to estimate the status of the robot and the object. In order to validate the proposed method some experiments are shown.