1,720,999 research outputs found
Sensorless robotized cable contour following and connector detection
No full textThis paper focuses on the identification of the connector of a semi-deformable object (SDLO) (i.e. a deformable element as a cable featuring rigid parts as connectors) to perform insertion and disconnection tasks. We propose a cable tracing skill that allows a robotic arm to follow the unknown contour of a cable held for a small portion by a fixture, and to identify its connector that can be grasped and inserted or disconnected. No prior knowledge of the SDLO's length and shape is required. To slide along the cable, the last joint of the manipulator is made compliant to adapt to the SDLO shape and a recursive least squares algorithm with forgetting factor is exploited to estimate the future local shape of the cable and to speed up the contour following procedure. The detection of the connector is based on the estimated contact force acting on the robot's end-effector while sliding along the SDLO. Remarkably, the method does not require vision, tactile and/or force sensors, it makes use just of a parallel gripper equipped with simple fingertips, and it can be implemented directly in a generic robot programming language. The effectiveness of our strategy is assessed via experimental tests on two different SDLOs in several configurations with connected and unconnected ends. Finally, the skill is also exploited in the robotized assembly of a motorbike braking system
A systematic strategy for the architecture design of collaborative and reconfigurable assembly lines
No full textCurrent manufacturing environments have to face a competitive and evolving framework characterised by high-mix and low-volume demands. To properly deal with new requests coming from the market, Reconfigurable Assembly Systems (RASs) have to be designed. In this paper, we propose a methodology for the design of the architecture of a RAS, featuring both human and mobile robotic agents, and dealing with multi-product assembly of medium-light-weight products, originally assembled manually. In particular, a systematic methodology is proposed to define the number of workstations, specifying which set of operations must be performed in each one, and to design the system layout guaranteeing reconfigurability. To this end, the concepts of operation, datasheet of an operation, assembly tree, and macro-operation are introduced and formalised. Guidelines to automatise the required operations in a flexible way are also proposed. The method is applied to a use case where we define the proper number of workstations of a RAS to assemble several types of motorbike brakes, showing the reconfigurability of the system
Ahlfors regular spaces have regular subspaces of any dimension
Full text linkWe characterize Q-dimensional Ahlfors regular spaces among trees' boundaries and show how to construct, for each 0 < alpha < Q, an alpha-regular subspace. As an application, we give an alternative simple proof of the existence of alpha-regular subspaces of a Q-dimensional complete Ahlfors regular metric space (X, rho), which was proved in [8]
Vision-Based State and Pose Estimation for Robotic Bin Picking of Cables
No full textThis paper deals with the challenging task of picking semi-deformable linear objects (SDLOs) from a bin. SDLOs are deformable elements, such as cables, joined to a rigid part as a connector. We propose a vision-based strategy to detect, classify and estimate the pose and the state (free or occluded) of connectors belonging to an unspecified number of SDLOs, arranged in an unknown configuration in the bin. The connectors can then be grasped and manipulated by a dual-arm robot through a set of manipulation primitives. In this way, a single SDLO can be extracted from the bin and laid on the worktable. A subsequent association between the connectors and the extracted SDLOs is performed, allowing to firmly grasp a SDLO at its ends to further manipulate it. The procedure is tested in bin picking operations with several kinds of SDLOs and is applied to a use case involving a collaborative wire harnesses assembly task
Workflow modelling for human–robot collaborative assembly operations
No full textWith the advent of Industry 4.0, industries are requested to provide customisation of the products, with a high number of tailored features, which a pure robotic assembly line cannot provide. This suggests using a collaborative and flexible scenario together with the need for workflow modelling architectures. These can handle the communication and interaction among the actors of the workcell to improve the collaboration, making it more fluent, reliable, and able to correct workers’ oversights. Within this scenario, the main contribution of this paper is the introduction of a general library of atomic Predicates that can be combined with a first-order logic allowing to model general industrial assembly processes in human–robot collaboration. Such logics and Predicates allow to model and supervise the workflow, remaining hidden to the operator through an interface that intervenes only when errors have to be notified. The methodology has been validated on a complex collaborative assembly use case, requiring different tools and characterized by components of several sizes and shapes. Predicates have been mainly exploited to recognize human activities, allowing modelling and supervising the workflow
Potential Field-Based Online Path Planning for Robust Cable Routing
No full textThis paper tackles the complex task of routing elastic deformable linear objects (DLOs) characterized by considerable stiffness, such as cables or hoses, which are already constrained at both ends. Specifically, a single arm robot is controlled to slide along the unknown contour of the cable, performing collision-free contour following, and to insert specific DLO segments into intermediate known clips. The contour following motion is executed avoiding both collisions with static obstacles and excessive deformation of the manipulated DLO. In particular, the path is defined considering an artificial potential field that is updated after each sliding motion along the DLO. This field accounts for static obstacles, the local cable shape (reconstructed using tactile sensors on the gripper fingertips) and the estimation of the global DLO shape obtained from a dynamic model of the DLO, accounting for the constraints imposed by the clips and the gripper. The proposed method is experimentally validated on an industrial robot executing cable routing in several DLO configurations
Force-based semantic representation and estimation of feature points for robotic cable manipulation with environmental contacts
No full textThis work demonstrates the utility of dual-arm robots with dual-wrist force-torque sensors in manipulating a Deformable Linear Object (DLO) within an unknown environment that imposes constraints on the DLO's movement through contacts and fixtures. We propose a strategy to estimate the pose of unknown environmental contacts encountered during the manipulation of a DLO, classifying the induced constraints as unilateral, bilateral and fully constrained, exploiting the redundancy of force sensors. A semantic approach to define environmental constraints is introduced and incorporated into a graph-based model of the DLO. This model remains accurate as long as the DLO is under tension and is dynamically updated throughout the manipulation process, built by sequencing a set of primitives. The estimation strategy is validated through simulations and real-world experiments, demonstrating its potential in handling DLOs under various, possibly uncertain, constraints
Tactile based robotic skills for cable routing operations
No full textThis paper proposes a set of tactile based skills to perform robotic cable routing operations for deformable linear objects (DLOs) characterized by considerable stiffness and constrained at both ends. In particular, tactile data are exploited to reconstruct the shape of the grasped portion of the DLO and to estimate the future local one. This information is exploited to obtain a grasping configuration aligned to the local shape of the DLO, starting from a rough initial grasping pose, and to follow the DLO's contour in the three-dimensional space. Taking into account the distance travelled along the arc length of the DLO, the robot can detect the cable segments that must be firmly grasped and inserted in intermediate clips, continuing then to slide along the contour until the next DLO's portion, that has to be clipped, is reached. The proposed skills are experimentally validated with an industrial robot on different DLOs in several configurations and on a cable routing use case
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
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