Paper: Adaptive multirobot formation planning to enclose and track a target with motion and visibility constraints

Title: Adaptive multirobot formation planning to enclose and track a target with motion and visibility constraints
Author: G. López-Nicolás, M. Aranda and Y. Mezouar
Journal: IEEE Transactions on Robotics, vol. 36, no. 1, pp. 142-156, Feb. 2020.
Abstract: Addressing the problem of enclosing and tracking a target requires multiple agents with adequate motion strategies. We consider a team of unicycle robots with a standard camera on board. The robots must maintain the desired enclosing formation while dealing with their nonholonomic motion constraints. The reference formation trajectories must also guarantee permanent visibility of the target by overcoming the limited field of view of the cameras. In this article, we present a novel approach to characterize the conditions on the robots’ trajectories taking into account the motion and visual constraints. We also propose online and offline motion planning strategies to address the constraints involved in the task of enclosing and tracking the target. These strategies are based on maintaining the formation shape with variable size or, alternatively, on maintaining the size of the formation with flexible shape.
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Paper: Multi-camera architecture for perception strategies

Title: Multi-camera architecture for perception strategies
Authors: Enrique Hernández, Gonzalo López-Nicolás and Rosario Aragüés.
Conference: IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2019), September 10-13, 2019, Zaragoza, Spain.
Abstract: Building the 3D model of an object is a complex problem that involves aspects such as modeling, control, perception or planning. Performing this task requires a set of different views to cover the entire surface of the object. Since a single camera takes too long to travel through all these positions, we consider a multi-camera scenario. Due to the camera constraints such as the limited field of view or self-occlusions, it is essential to use an effective configuration strategy to select the appropriate views that provide more information of the model. In this paper, we develop a multi-camera architecture built on the Robot Operating System. The advantages of the proposed architecture are illustrated with a formation-based algorithm to compute the view that satisfies these constraints for each robot of the formation to obtain the volumetric reconstruction of the target object.

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Paper: Survey on multi-robot manipulation of deformable objects

Title: Survey on multi-robot manipulation of deformable objects
Authors: Rafael Herguedas, Gonzalo López-Nicolás, Rosario Aragüés and Carlos Sagüés.
Conference: IEEE International Conference on Emerging Technologies and Factory Automation (ETFA 2019), September 10-13, 2019, Zaragoza, Spain.
Abstract: Autonomous manipulation of deformable objects is a research topic of increasing interest due to the variety of current processes and applications that include this type of tasks. It is a complex problem that involves aspects such as modeling, control, perception, planning, rasping, estimation, etc. A single robot may be unable to perform the manipulation when the deformable object is too big, too heavy or difficult to grasp. Then, using multiple robots working together naturally arises as a solution to perform coordinately the manipulation task. In this paper, we contribute a survey of relevant state of-the-art approaches concerning manipulation of deformable objects by multiple robots, which includes a specific classification with different criteria and a subsequent analysis of the leading methods, the main challenges and the future research directions.

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Paper: Multi-camera coverage of deformable contour shapes

Title: Multi-camera coverage of deformable contour shapes
Authors: Rafael Herguedas , Gonzalo López-Nicolás and Carlos Sagüés.
Conference: IEEE International Conference on Automation Science and Engineering (CASE 2019), August 22-26, 2019, Vancouver, BC, Canada.
Abstract: Perception of deformation is a key problem when dealing with autonomous manipulation of deformable objects. Particularly, this work is motivated by tasks where the manipulated object follows a prescribed known deformation with the goal of performing a desired coverage of the object’s contour along its deformation. The main contribution is a simple yet effective novel perception system in which a team of robots equipped with limited field-of-view cameras covers the object’s contour according to a prescribed visibility objective. In order to define a feasible visibility objective, we propose a new method for obtaining the maximum achievable visibility of a contour from a circumference around its centroid. Then, we define a constrained optimization problem and we solve it iteratively to compute the minimum number of cameras and their near optimal positions around the object that guarantee the visibility objective, over the entire deformation process.

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Paper: Tactile-driven grasp stability and slip prediction

Title: Tactile-driven grasp stability and slip prediction

Author: B. S Zapata-Impata, P. Gil, F. Torres
Journal: Robotics 2019, 8, 85.
Abstract: One of the challenges in robotic grasping tasks is the problem of detecting whether a grip is stable or not. The lack of stability during a manipulation operation usually causes the slippage of the grasped object due to poor contact forces. Frequently, an unstable grip can be caused by an inadequate pose of the robotic hand or by insufficient contact pressure, or both. The use of tactile data is essential to check such conditions and, therefore, predict the stability of a grasp. In this work, we present and compare different methodologies based on deep learning in order to represent and process tactile data for both stability and slip prediction.
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Paper: TactileGCN: A graph convolutional network for predicting grasp stability with tactile sensors

Title: TactileGCN: A graph convolutional network for predicting grasp stability with tactile sensors
Author: A. Garcia-Garcia, B.S. Zapata-Impata, S. Orts-Escolano, P. Gil, J. García
Conference: International Joint Conference on Neural Netwoks (IJCNN), 14-19 July 2019
Abstract: Tactile sensors provide useful contact data during the interaction with an object which can be used to accurately learn to determine the stability of a grasp. Most of the works in the literature represented tactile readings as plain feature vectors or matrix-like tactile images, using them to train machine learning models. In this work, we explore an alternative way of exploiting tactile information to predict grasp stability by leveraging graph-like representations of tactile data, which preserve the actual spatial arrangement of the sensor’s taxels and their locality. In experimentation, we trained a Graph Neural Network to binary classify grasps as stable or slippery ones. To train such network and prove its predictive capabilities for the problem at hand, we captured a novel dataset of ~ 5000 three-fingered grasps across 41 objects for training and 1000 grasps with 10 unknown objects for testing. Our experiments prove that this novel approach can be effectively used to predict grasp stability.
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Paper: Vision2tactile: feeling touch by sight

Title: Vision2tactile: feeling touch by sight
Author: B.S. Zapata-Impata, P. Gil, F. Torres
Conference: Robotics Science and Systems (RSS): Workshop on Closing the Reality Gap in Sim2real Transfer for Robotic Manipulation, June 23, 2019
Abstract: Latest trends in robotic grasping combine vision and touch for improving the performance of systems at tasks like stability prediction. However, tactile data are only available during the grasp, limiting the set of scenarios in which multimodal solutions can be applied. Could we obtain it prior to grasping? We explore the use of visual perception as a stimulus for generating tactile data so the robotic system can ‘feel’ the response of the tactile perception just by looking at the object.
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Papers at “Jornada de Jóvenes Investigadores del I3A”

Published in “Jornada de Jóvenes Investigadores del I3A”, vol. 7 (Proceedings of the VIII Jornada de Jóvenes Investigadores del I3A – June 6, 2019).

  • R. Herguedas, G. López-Nicolás, C. Sagüés. Minimal multi-camera system for perception of deformable shapes. (Link)
  • J. Martínez-Cesteros, G. López-Nicolás. Automatic image dataset generation for footwear detection. (Link)
  • E. Hernández-Murillo, R. Aragüés, G. López-Nicolás. Volumetric object reconstruction in multi-camera scenarios. (Link)

Paper: Deformation-Based Shape Control with a Multirobot System

Title: Deformation-based shape control with a multirobot system
Authors: Miguel Aranda, Juan Antonio Corrales and Youcef Mezouar
Conference: IEEE International Conference on Robotics and Automation, May 20-24, 2019 Montreal, Canada.
Abstract: We present a novel method to control the relative positions of the members of a robotic team. The application scenario we consider is the cooperative manipulation of a deformable object in 2D space. A typical goal in this kind of scenario is to minimize the deformation of the object with respect to a desired state. Our contribution, then, is to use a global measure of deformation directly in the feedback loop. In particular, the robot motions are based on the descent along the gradient of a metric that expresses the difference between the team’s current configuration and its desired shape. Crucially, the resulting multirobot controller has a simple expression and is inexpensive to compute, and the approach lends itself to analysis of both the transient and asymptotic dynamics of the system. This analysis reveals a number of properties that are interesting for a manipulation task: fundamental geometric parameters of the team (size, orientation, centroid, and distances between robots) can be suitably steered or bounded. We describe different policies within the proposed deformation-based control framework that produce useful team behaviors. We illustrate the methodology with computer simulations.
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