10-12 September 2014
Title: THE DEVELOPMENT OF A FAST PICK-AND-PLACE ROBOT WITH AN INNOVATIVE CYLINDRICAL DRIVE
Professor at McGill University
The food-processing industry is calling for ever faster means to package poultry and other edibles, which has motivated the development of fast pick-and-place robots. The tasks at hand usually comprise motions involving the subgroup of Schönflies displacements.These are characterized by three independent translations and one rotation about an axis of fixed orientation.Commercial robots of this kind are available, e.g., Adept's Quattro and ABB's Flexpicker.
The architecture of these robots stems from that of the Delta, designed to produce three independent translations of its moving plate within a parallel architecture. The challenge these systems face is the need to provide a 180° turn of their moving platform, which is impeded by their parallel architecture. Both the Quattro and the Flexpicker are supplied with ingenious mechanisms to produce this rotation, but the mechanism adds a substantial complexity to the overall system.
As an alternative, a family of simple, isostatic architectures was proposed recently by two Taiwanese researchers.These architectures include two limbs, each carrying a cylindrical shoulder, which is actuated, and ending by screw nuts coupled to each forearm by means of a universal joint. A rod that carries two screws (ballscrews) of distinct pitches in series plus the gripper at one end, plays the role of the moving platform of parallel robots.The rod is moved with four degrees of freedom in a similar fashion to the long pepper mill seen in Italian restaurants, with the two screw nuts playing the role of the waiter's hands.
Moreover, each shoulder is driven by one collar that undergoes cylindrical motion (rotation about an axis and translation along a direction parallel to the axis), the challenge here being the design of the drive that can provide the two degrees of freedom of a cylindrical motion. Such a drive, dubbed the C-drive and developed at McGill University, is actuated by two identical motors that are fixed to the base, and carries a closed kinematic chain that was synthesized by means of an application of the theory of displacement subgroups. One instance of the Taiwanese architecture is currently being developed at McGill University, with oneC-drive per arm.
The principles of operation of the robot and its main components are highlighted in this presentation.
Title: APPLICATION OF FRACTIONAL CONTROL TO FLEXIBLE ROBOTS AND VIBRATION SUPPRESSION
Prof. Vicente Feliu Batlle
Escuela Técnica Superior de Ingenieros Industriales
University of Castilla-La Mancha
Avda Camilo José Cela s/n
New robotic applications have appeared in the last decades which require the use of manipulators much lighter and/or larger than industrial robots. In both cases these manipulators exhibit mechanical vibrations when they perform motion tasks. Their controllers must therefore be more sophisticated than the controllers of industrial robots since they must combine quick and precise motions with vibration suppression. The purpose of this talk is twofold: give an overview of the control systems of flexible robots and to explore the use of fractional order controllers in this context.
This talk starts with an introduction to flexible robots and their applications. Then some of their dynamical issues are described. After, a review on the control of these robots is provided, which includes both free motion control (pick and place tasks) and constrained motion control (robot in contact with an object, force control). Often these control systems include two nested loops: the inner loop implements a servomotor in charge of performing the robot movement and the outer loop is a controller in charge of suppressing the mechanical vibrations. Subsequently, methods to design robust fractional-order controllers are developed at the two levels: for the motion control inner loop and for the vibration cancellation outer loop. A general methodology is proposed to design fractional-order controllers at these two levels. It yields quite different controllers with different tuning rules for the inner and outer loops. Finally, some application examples are developed for both free and constrained motion control of these robots.