Adaptive Obstacle Avoidance for a Class of Collaborative Robots

In a human–robot collaboration scenario, operator safety is the main problem and must be guaranteed under all conditions. Collision avoidance control techniques are essential to improve operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or with objects inadvertently left within the operational workspace. On this basis, collision avoidance algorithms for moving obstacles are presented in this paper: inspired by algorithms already developed by the authors for planar manipulators, algorithms are adapted for the 6-DOF collaborative manipulators by Universal Robots, and some new contributions are introduced. First, in this work, the safety region wrapping each link of the manipulator assumes a cylindrical shape whose radius varies according to the speed of the colliding obstacle, so that dynamical obstacles are avoided with increased safety regions in order to reduce the risk, whereas fixed obstacles allow us to use smaller safety regions, facilitating the motion of the robot. In addition, three different modalities for the collision avoidance control law are proposed, which differ in the type of motion admitted for the perturbation of the end-effector: the general mode allows for a 6-DOF perturbation, but restrictions can be imposed on the orientation part of the avoidance motion using 4-DOF or 3-DOF modes. In order to demonstrate the effectiveness of the control strategy, simulations with dynamic and fixed obstacles are presented and discussed. Simulations are also used to estimate the required computational effort in order to verify the transferability to a real system

Position Control of a 3-CPU Spherical Parallel Manipulator

The paper presents the first experimental results on the control of a prototypal robot designed for the orientation of parts or tools. The innovative machine is a spherical parallel manipulator actuated by 3 linear motors; several position control schemes have been tested and compared with the final aim of designing an interaction controller. The relative simplicity of machine kinematics allowed to test algorithms requiring the closed-loop evaluation of both inverse and direct kinematics; the compensation of gravitational terms has been experimented as well

Design of a miniaturized work-cell for micro-manipulation

The paper describes the design and development of a miniaturised workcell devoted to the robotized micro manipulation and assembly of extremely small components, jointly carried out by the University of Brescia, University of Bergamo, University of Ancona and the Institute of Industrial Technologies and Automation of the Italian National Research Council in the framework of the project PRIN2009 MM&A, funded by MIUR. Besides analyzing theoretical and practical aspects related to the design of the work cell components (positioning and orienting devices, grippers, vision and control systems), an automated test bed for the assembly of micro pieces whose typical dimension belongs to the submillimeter scale range has been implemented. The perspective is to contribute to the realization of general automatic production systems at the moment absent for objects of these dimensions

Design of a miniaturized work-cell for micro-manipulation

The paper describes the design and development of a miniaturised workcell devoted to the robotized micro manipulation and assembly of extremely small components, jointly carried out by the University of Brescia, University of Bergamo, University of Ancona and the Institute of Industrial Technologies and Automation of the Italian National Research Council in the framework of the project PRIN2009 MM&A, funded by MIUR. Besides analyzing theoretical and practical aspects related to the design of the work cell components (positioning and orienting devices, grippers, vision and control systems), an automated test bed for the assembly of micro pieces whose typical dimension belongs to the submillimeter scale range has been implemented. The perspective is to contribute to the realization of general automatic production systems at the moment absent for objects of these dimensions

Static performance improvement of an industrial robot by means of a cable-driven redundantly actuated system

Every industrial robot has a specific kinematics, which often results in anisotropic performance within its workspace in terms of force and velocity. A cable-driven system can be used to improve the force manipulability of a robot by introducing an actuation redundancy. Such system acts directly on the robot end-effector increasing its flexibility of use in applications where a higher and more uniform force performance is required. This work is focused on high-thrust operations, for example robotic friction stir welding or incremental forming, realized by means of a highly anisotropic industrial robot

A Flexible Framework for Robotic Post-Processing of 3D Printed Components

Three-dimensional (3D) printing has revolutionized the production of mechanical components by enabling the creation of objects of complex geometry, but at the same time it has introduced new issues related to post-processing operations. Similarly, robotics has seen an evolution with the emergence of collaborative robots, which can support the operator in human-centric applications. This work aims to bring these two technologies together by presenting a flexible framework for processing raw products obtained through 3D printing technology with the support of collaborative robotics. This framework lays the foundation for the subsequent development of a human-robot cooperation protocol with the aim of simplifying post-processing and particularly finishing operations of metal-printed 3D objects. In this paper, an initial integrated solution is proposed that can address the post-processing needs of objects from 3D printing, providing guidance on the software and hardware tools to be used and the process to be followed to achieve a quality product in compliance with the relevant standards. Verifications in a simulation environment and through algorithms based on the kinematics and statics of a Fanuc collaborative robot implemented in a numerical environment allow verification of the feasibility of several operations. The result is a comprehensive framework that starts from the feasibility study and reaches the completion of the 3D printed component through finishing and post-processing operations

Visual based control system of a 3-CPU translational parallel manipulator

Recent advances in vision devices and image processing has allowed to integrate vision sensors into the control architecture of robot systems to include information regarding robot’s environment: in this case the feedback loop handles operational space variables based on a real time estimation of the end-effector pose obtained by means of an elaboration of visual measurements. The paper presents an application of visual servoing on a 3-CPU translational parallel manipulator with a camera mounted directly on the moving platform, in the so-called eye-in-hand configuration. After an introductory description of the robot and of the control and vision hardware, the calibration process of the camera is explained and a PD controller with gravity compensation is presented

Visual based control system of a 3-CPU translational parallel manipulator

none2PALPACELLI M.; PALMIERI G.Palpacelli, MATTEO CLAUDIO; Palmieri, Giacom

A lockable spherical joint for robotic applications

The paper proposes the mechanical design of a lockable spherical joint, which is designed to be manually or automatically configured in different kinematic solutions. In fact it can be used as a conventional spherical joint or converted in a universal joint or still downgraded to a revolute joint. Therefore different configurations can be chosen according to user needs. In particular, two of the three axes of revolution, arranged in the typical roll-pitch-roll sequence of robot spherical wrists, can be locked alternatively in order to provide two differently arranged U-joints. It can be demonstrated that such behavior allows to activate different mobilities of two classes of reconfigurable parallel kinematics manipulators. The transition between such mobilities occurs exploiting the concept of over-constrained kinematics, which is realized by the lockable joint during the switching phase in order to avoid an instantaneous mobility of the robot