1,720,960 research outputs found
A sampling-based tree planner for navigation among movable obstacles
No full textThis paper proposes a planner that solves Navigation Among Movable Obstacles problems giving robots the ability to reason about the environment and choose when manipulating obstacles. It finds a path from a robot start configuration S to a goal configuration G taking into consideration the possibility of moving objects if G cannot be reached or if moving objects may significantly shorten the path. The planner combines the A*-Search and the exploration strategy of the Kinodynamic Motion Planning by Interior-Exterior Cell Exploration algorithm. It is locally optimal and independent from the size of the map and from the number, shape, and position of obstacles. It assumes full world knowledge but it can be easily extended in order to explore unknown environments
Receding Horizon Task and Motion Planning in Changing Environments
Full text linkComplex manipulation tasks require careful integration of symbolic reasoning and motion planning. This problem, commonly referred to as Task and Motion Planning (TAMP), is even more challenging if the workspace is non-static, e.g. due to human interventions and perceived with noisy non-ideal sensors. This work proposes an online approximated TAMP method that combines a geometric reasoning module and a motion planner with a standard task planner in a receding horizon fashion. Our approach iteratively solves a reduced planning problem over a receding window of a limited number of future actions during the implementation of the actions. Thus, only the first action of the horizon is actually scheduled at each iteration, then the window is moved forward, and the problem is solved again. This procedure allows to naturally take into account potential changes in the scene while ensuring good runtime performance. We validate our approach within extensive experiments in a simulated environment. We showed that our approach is able to deal with unexpected changes in the environment while ensuring comparable performance with respect to other recent TAMP approaches in solving traditional static benchmarks. We release with this paper the open-source implementation of our method
A Control Framework Definition to Overcome Position/Interaction Dynamics Uncertainties in Force-Controlled Tasks
No full textWithin the Industry 4.0 context, industrial robots need to show increasing autonomy. The manipulator has to be able to react to uncertainties/changes in the working environment, displaying a robust behavior. In this paper, a control framework is proposed to perform industrial interaction tasks in uncertain working scenes. The proposed methodology relies on two components: i) a 6D pose estimation algorithm aiming to recognize large and featureless parts; ii) a variable damping impedance controller (inner loop) enhanced by an adaptive saturation PI (outer loop) for high accuracy force control (i.e., zero steady-state force error and force overshoots avoidance). The proposed methodology allows to be robust w.r.t. task uncertainties (i.e. , positioning errors and interaction dynamics). The proposed approach has been evaluated in an assembly task of a side-wall panel to be installed inside the aircraft cabin. As a test platform, the KUKA iiwa 14 R820 has been used together with the Microsoft Kinect 2.0 as RGB-D sensor. Experiments show the reliability in the 6D pose estimation and the high-performance in the force-tracking task, avoiding force overshoots while achieving the tracking of the reference force
Teaching Robot Programming for Industry 4.0
No full textThis paper presents a master course project on intelligent robotics offered by the University of Padova (Italy). The goal is that of training Master students for Industry 4.0 by offering a multidisciplinary laboratory experience in which two robots and a human must collaborate to fulfill an assembly task: one manipulator robot has to recognize some pieces on a table, manipulate them, and place them on the top of a mobile robot. The mobile robot has to carry these pieces within an arena until reaching an assembly station where the human operator will complete the assembly task. Through our constructivist approach, students learn how to face a rapidly evolving discipline requiring the integration and cooperation of multiple subsystems to create complex behaviors. They learn how to program autonomous robots by using the Robot Operating System. They learn how to exhaustively document their activity explaining design choices, the benefits and the limits of their approaches, as well as proposing new solutions to overcome these limitations. They learn how to properly implement and comment code as well as create step-by-step instructions to enable future users to reproduce their systems. The project is organized as a challenge to motivate students to propose innovative ideas: students are subdivided into teams, every team proposes its own solution, and different scores are assigned according to the proposed difficulty level and the required working time
Autonomous Learning of the Robot Kinematic Model
No full textRobotics systems are becoming more and more autonomous and reconfigurable. In this context, the design of algorithms capable of deriving kinematics and dynamics models directly from data could be particularly useful. In this article, we present an algorithm that learns a forward kinematics model of a robot starting from a time series of visual observations. Our strategy can be applied to any robot with serial kinematics composed of revolute and prismatics joints. First, the algorithm identifies the robot kinematic structure, i.e., a high-level description of the robot geometry that defines the connections between the rigid-bodies composing the robot. Then, the algorithm derives the forward kinematics relying on a Gaussian process (GP) model. More precisely, the GP model is based on a polynomial kernel, defined exploiting the kinematic structure previously identified. The effectiveness of the proposed solution has been tested via extensive Monte Carlo simulations, as well as via experiments on a real UR10 robot
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Using robotics to train students for Industry 4.0
Full text linkThis paper presents the master course on Autonomous Robotics that we offer at the School of Engineering of the University of Padova (Italy). Its novelty is the assignment of a lab project carefully designed to train students on autonomous and industrial robotics in the framework of Industry 4.0: the "Industry 4.0 Robotics Challenge". Students have to program both a manipulator and a mobile robot, together with a 3D vision system, in order to collaborate in the fulfillment of a pick-place-transport industrial task. We adopt a constructionist approach: project-based learning and team-based learning are applied to robotics and Industry 4.0. The project is organized as a challenge to motivate students to propose innovative ideas. A survey on students' satisfaction is reported at the end of the paper. We made the description of both the hardware and software setup, together with tutorials and wikis, publicly available to let other robotics instructors replicate our proposal and make it a point of reference for teaching robotics in the frame of Industry 4.0
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