Rezia Molfino

Critical review of current trends in shape memory alloy actuators for intelligent robots

Purpose – The purpose of this paper is to review the current application areas of shape memory alloy (SMA) actuators in intelligent robotic systems and devices.Design/methodology/approach – This paper analyses how actuation and sensing functions of the SMA actuator have been exploited and incorporated in micro and macro robotic devices, developed for medical and non‐medical applications. The speed of response of SMA actuator mostly depends upon its shape and size, addition and removal of heat and the bias force applied. All these factors have impact on the overall size of the robotic device and the degree of freedom (dof) obtained and hence, a comprehensive survey is made highlighting these aspects. Also described are the mechatronic aspects like the software and hardware used in an industrial environment for the control of such nonlinear actuator and the type of sensory feedback devices incorporated for obtaining better control, positioning accuracy and fast response.Findings – SMA actuators find wide ap...

Constraint Singularities of Force Transmission in Nonredundant Parallel Robots With Less Than Six Degrees of Freedom

The analysis of the workspace singularities is one of the fundamental aspects in the design of parallel robots. The architecture singularities are generally studied analysing the local properties of the Jacobian matrix. Nevertheless, for limited-DOF parallel robots, there is a category of singularities (constraint or constructive singularities), relating to the constraint force transmission, which are not described by this matrix. This paper deals with a general approach to the analysis of these singularities, used in the synthesis of a Linear Delta robot to suitably modify its geometry, remarkably improving the structural behavior. Details and numerical results are provided.@DOI: 10.1115/1.1588343#

Kinematics Analysis of the Exechon Tripod

The Exechon 5-Axis Parallel Kinematic Machine (PKM) is a successful design created in Sweden and adopted by many producers of machine tools around the world. A new version of the manipulator is being developed as a component of a mobile self-reconfigurable fixture system within an inter-European project. The basic Exechon architecture consists of a 3-degree-of-freedom (dof) parallel mechanism (PM) connected in series with a two- or three-dof spherical wrist. The PM has two UPR (4-dof) legs, constrained to move in a common rotating plane, and an SPR (5-dof) leg. The paper presents the kinematic analysis of both the PM and the hybrid parallel-serial architecture. We describe the complex three-dimensional motion pattern of the PM platform, derive the kinematic equations and provide explicit solutions for the inverse kinematics.Copyright

Roboclimber the 3 ton spider

Purpose – The aim of the research is to design, build and test a robot able to autonomously execute slope consolidation tasks.Design/methodology/approach – A multidisciplinary approach has been adopted to solve the problem: mechanical and control architecture have been conceived simultaneously. Modularity and lifecycle are considered. The robot can climb by means of four legs and two ropes. The drilling system is hosted onboard. Drilling process is fully automated, motion can be controlled in tele‐operation.Findings – The performance of the first prototype has satisfied the end‐user; new on‐site tests and improvements are planned.Research limitations/implications – Roboclimber is cumbersome; both robot transport and on‐site positioning are complex operations. Coordination between legs motion and ropes tensioning is a difficult task.Practical implications – The system reduces operating costs and working time, while avoiding the human presence in unsafe and harsh environments.Originality/value – Roboclimber...

SwarmItFIX: a multi‐robot‐based reconfigurable fixture

Purpose – The use of thin sheets with 3D geometries is growing in quantity, due to current progress towards life‐cycle design and sustainable production, and growing in geometrical complexity, due to aesthetic and quality concerns. The growth in manufacturing equipment flexibility has not kept pace with these trends. The purpose of this paper is to propose a new reconfigurable fixture to shorten this gap.Design/methodology/approach – The design implements a novel concept of fixturing. Without interrupting the machining process, a swarm of adaptable mobile agents periodically reposition and reconfigure to support the thin‐sheet workpiece near the tool‐point. The technology has been developed by adopting a multi‐disciplinary, life‐cycle approach. Modularity and eco‐sustainability paradigms have informed the design.Findings – The performance of the physical prototype in an industrial scenario is highly satisfactory. Experiments demonstrate the ability of the system to reconfigure while maintaining machining ...

An impedance‐controlled parallel robot for high‐speed assembly of white goods

Purpose – Aims to discuss how impedance‐controlled parallel robots can effectively perform industrial assembly tasks.Design/methodology/approach – A new purely translational parallel robot has been designed to fulfil the requirements of industrial assembly tasks. The kinematic and dynamic models of the robot have been obtained in analytic form. A full‐scale prototype has been realized within the Italian research programme PRIDE (Parallel Robots Interacting with Dynamic Environments). An impedance control algorithm based on the kinematic and dynamic models has been implemented on the control unit of the PRIDE prototype. The effectiveness of the impedance‐controlled PKM has been evaluated performing the assembly of white goods components.Findings – The test results show that the combined use of impedance control and dynamic compensation applied to parallel kinematics machines allows to reduce remarkably the operational time compared to the currently used position‐controlled industrial robots.Research limita...

Integrated management of concurrent shopfloor operations

Abstract The problem of combining efficiency with flexibility is the basic challenge faced by the factories of the future. In this paper, the solution is investigated through expert governors that can manage the concurrency of manufacturing processes enabling efficient decentralized control for standard running conditions. Flexible adaptive control is possible when recovery intervention is requested as a result of unsteady occurrences. The presentation is carried out by programming facilities developed by the Industrial Robot Design Research Group of the University of Genova, Italy.

A Compliant Miniature Parallel Manipulator with Shape Memory Alloy Actuators

Light weight parallel manipulators are most desirable for aerospace, medical applications etc., where flexibility, low inertia, simplicity in operation, low stowed volume are important parameters. This paper presents the design and simulation of a flexible parallel manipulator with central elastic column that is made of superelastic nitinol. The actuators are shape memory SMA wires of 300 mum diameter. Unlike conventional rigid link parallel manipulators, the proposed manipulator does not have any joints, which is the major advantage. The proposed manipulator is investigated for its degree of freedom with virtual rigid segment concept and its large deflection is analyzed based on elastica approach. Its control aspect is briefly described and numerical simulation results are presented.

Design of a Microrobotic Wrist for Needle Laparoscopic Surgery

This paper addresses the design of a microwrist for needle laparoscopic surgery (needlescopy) using microelectromechanical system technology and an original three degree of freedom, 3D architecture. Advancement in needlescopy drives the development of multi-DOF microtools 1-2 mm in diameter with 3D mobility but standard available fabrication techniques are for 2.5D structures. Thus paper discusses the development steps and design solutions for the realization of the 3D wrist with available technology. A compliant mechanism is used, which is derived from a reference parallel kinematics mechanism architecture with three legs. A singular configuration of increased instantaneous mobility is exploited to achieve the desired 3D mobility. Alternative leg architectures are investigated to obtain satisfactory performance. The legs are fabricated as monolithic compliant structures and assembled to wrist base and end-effector. The definition of the leg geometry revealed a complex task. The steps to obtain the final design satisfying task requirements are detailed.

Armilleye : Flexible platform for underwater stereo vision

The paper describes ArmillEye, a 3-degree of freedom (DOF) flexible hybrid platform designed for agile underwater stereoptic vision. Effective telecontrol systems of remote operated vehicles require active and dexterous camera support in order to allow the operator to easily and promptly change the point of view, also improving the virtual reconstruction of the environment in difficult operative conditions (dirtiness, turbulence, and partial occlusion). The same concepts hold for visual servoing of autonomous underwater vehicles. ArmillEye was designed for this specific application; it is based on the concept of using a parallel-hybrid mechanism architecture that, in principle, allows us to minimize the ad hoc waterproof boxes (generally only for cameras) while the actuators, fixed to the base of the mechanism, can be placed into the main body of the underwater vehicle. This concept was revealed effective and was previously proposed for underwater arms. The synthesis of ArmillEye followed the specific aims of visual telecontrol and servoing, specifying vision workspace, dexterity, and dynamics parameters. Two versions of ArmillEye are proposed: the first one with two cameras to obtain a steroptic vision by using two viewpoints (two rotational freedoms with a fixed tilt or pan axis and vergence); the second one with one camera operated to obtain a stereoptic vision by using one viewpoint (two rotational freedoms with a fixed tilt or pan axis and extrusion).