1,720,998 research outputs found
A new mechanism for soft landing in robotic space exploration
Full text linkLanding safely is the key to successful exploration of the solar system; the mitigation of the connected effects of collision in mechanical systems relies on the conversion of kinetic energy into heat or potential energy. An effective landing-system design should minimize the acceleration acting on the payload. In this paper, we focus on the application of a special class of nonlinear preloaded mechanisms, which take advantage of a variable radius drum (VRD) to produce a constant reactive force during deceleration. Static and dynamic models of the mechanism are presented. Numerical results show that the system allows for very efficient kinetic energy accumulation during impact, approaching the theoretical limit
3D-printed poly(oxymethylene): Improving printability via PMMA sacrificial substrates and characterization of the mechanical and thermal properties
No full textThe fabrication of poly(oxymethylene) by means of additive manufacturing is still a problematic procedure due to the low adhesion with standard printing plates and extended warping. The use of polymers as alternative substrates is an effective way, especially if their glass-transition temperature is below the processing temperatures. Using poly(methyl methacrylate) sheets as sacrificial substrate, standard samples of poly(oxymethylene) are successfully printed, a result achieved in the past only by means of expensive and complex equipment. Furthermore, the mechanical and thermal properties of poly(oxymethylene) upon UV aging up to 500 h are investigated. Our results demonstrate that aging of 3D-printed poly(oxymethylene) causes chain scission and weakening of intermolecular bonds, crystallization of part of the amorphous areas, and results in the embrittlement of the material. The intermolecular structure of poly(oxymethylene) has been investigated by means of Fourier transform infrared spectroscopy
Human–robot interaction through eye tracking for artistic drawing
Full text linkIn this paper, authors present a novel architecture for controlling an industrial robot via an eye tracking interface for artistic purposes. Humans and robots interact thanks to an acquisition system based on an eye tracker device that allows the user to control the motion of a robotic manipulator with his gaze. The feasibility of the robotic system is evaluated with experimental tests in which the robot is teleoperated to draw artistic images. The tool can be used by artists to investigate novel forms of art and by amputees or people with movement disorders or muscular paralysis, as an assistive technology for artistic drawing and painting, since, in these cases, eye motion is usually preserved
Computer-assisted design defines a novel actuation principle based on liquid structures
No full text.We present a framework for new structural metamaterials we refer to as liquid structures: a topology of bistable mechanisms made up of a high number of cells that are sub-mechanisms composed of pseudo-rigid links and joints. The name liquid structures comes from the similarities they present with the kinematics of the constant flow of incompressible fluids they are inspired to in a limited domain. Computational Fluid Dynamics (CFD) is employed to define the layout of the cells through a two-step process where: (i) the node displacements are computed by the CFD tool itself; (ii) the kinematic synthesis of each cell is subsequently performed. We report an illustrative case and an example of application (a brake system) where star- and diamond-type cells are employed. Our proposal opens a new avenue of computer-assisted design of mechanical actuator
Robotic Sponge and Watercolor Painting Based on Image-Processing and Contour-Filling Algorithms
No full textIn this paper, the implementation of a robotic painting system using a sponge and the watercolor painting technique is presented. A collection of tools for calibration and sponge support operations was designed and built. A contour-filling algorithm was developed, which defines the sponge positions and orientations in order to color the contour of a generic image. Finally, the proposed robotic system was employed to realize a painting combining etching and watercolor techniques. To the best of our knowledge, this is the first example of robotic painting that uses the watercolor technique and a sponge as the painting media
Liquid structures: A novel Computational Fluid Dynamics (CFD) inspired metamaterial
Full text linkWe present a theoretical framework for new structural metamaterials we refer to as liquid structures: a topology of bistable mechanisms made up of a high number of cells that are sub-mechanisms composed of pseudo-rigid links and joints. The name liquid structures comes from the similarities they present with the kinematics of the constant flow of incompressible fluids they are inspired by in a limited domain. The layout of the cells are obtained through a two-step process where: (i) the node displacements are computed by means of a Computational Fluid Dynamics tool feeding and (ii) the kinematic synthesis of each cell that is subsequently performed. We report two illustrative examples where star- and diamond-type cells are employed. The paper concludes with a detailed discussion about future theoretical and manufacturing challenges arising from this new metamaterial paradigm
Crowded Environment Navigation with NEAT: Impact of Perception Resolution on Controller Optimization
Full text linkCrowd navigation with autonomous systems is a topic which has seen a rapid increase in interest recently. While it appears natural to humans, being able to reach a target can prove difficult or impossible to a mobile robot because of the safety issues related to collisions with people. In this work we propose an approach to control a robot in a crowded environment; the method employs an Artificial Neural Network (ANN) that is trained with the NeuroEvolution of Augmented Topologies (NEAT) method. Models for the kinematics, perception, and cognition of the robot are presented. In particular, perception is based on a raycasting model which is tailored on the ANN. An in-depth analysis of a number of parameters of the environment and the robot is performed and a comparative analysis is presented; finally, results of the performance of the controller trained with NEAT are compared to those of a human driver who takes over the controller itself. Results show that the intelligent controller is able to perform on par with the human, within the simulated environment
Performance evaluation of a robotic architecture for drawing with eyes
Full text linkEye tracking is a sensing technology that allows a computer to monitor eye movements and determine where a subject is looking. In this paper, we evaluate the performance of a robotic architecture that enables to control a robot arm through eye tracking and to draw using the motion of the eyes only. The usability of the system is assessed by a drawing experiment where 10 naïve subjects learned to operate the robot manipulator with eyes. Results suggest that the gaze-based human-robot interface may be considered an intuitive and efficient technology to perform a drawing task, and could be beneficial beyond amputees and patients with various forms of movement impairments
The Archimede Rover: A Comparison between Simulations and Experiments
No full textIn this paper, we propose an in-depth evaluation of the performance of the Archimede rover while traversing rough terrain with loose soil. In order to better analyze this, the reality gap is evaluated when simulating the behavior with an open-source simulator. To this extent, we implement a full model of the rover in the open-source dynamics simulator Gazebo, along with several types of terrains that replicate the experimental conditions. The rover control system is equipped with a kinematics model that allows for driving in different modes. We implement an odometric system aboard the rover, as well as an external optical absolute tracking system as reference. We estimate the drift occurring during driving in different configurations, two types of soil with corresponding wheel geometries. The results show good adherence of the odometry when the rover drives on planar ground; conversely, as expected, a marked influence of slope is seen on wheel drift. The reality gap between simulations and experimental results is kept comparatively small provided that slopes are not present
Peg-in-hole operation with a cobot without using external sensors
No full textCollaborative robots, or cobots, are designed to interact with humans and to be easy to use, drastically reducing the integration costs. In this paper, we present the results of a peg-in-hole operation, performed by an UR5 cobot equipped with a standard gripper, without the use of external force or torque sensors. The operation consists of the insertion of a 48-tooth involute spline shaft in a corresponding hub. A two-phase helicoidal descent is performed by the robot. During the first phase, the value of the force vector at the tool center point is used to detect if the shaft is centered. During the second phase, the variation of the torque at shoulder joint is used to detect the insertion. Over 1000 peg-in-hole operations, the successful rate was 96.7%. Among these shafts, only the 10% needed a second trial. The overall mean time for an operation is 5.5 seconds
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