Adaptive cable-driven parallel robots can adjust the position of one or more pulley blocks to optimize performance within a given workspace. Because of their augmented kinematic redundancy, adaptive systems have several advantages over their traditional counterparts featuring the same numbers of cables. In this paper, we explore the application of adaptive cable-driven robots to cable-suspended camera systems. Performance of the traditional and of the adaptive designs are analyzed, using dexterity and stiffness as performance metrics. Results show superior performance of the adaptive design compared to the traditional system. An illustrative design problem for adaptive cable-suspended camera systems is also presented and solved.

Sophia-3 (string-operated planar haptic interface for arm rehabilitation) is a planar cable-driven device with a tilting working plane. It represents the first application of the adaptive cable-driven design paradigm recently introduced by the authors, featuring a moving pulley-block that allows the robot to achieve excellent force capabilities, despite the low number of cables. This study presents the design, kinematics, and control of the device and results of experimental validation on healthy subjects.

Flexible automatic assembly is an emerging need in several industries in the developed countries, owing to the growing market request of small batch productions. This paper introduces a new class of flexible assembly systems, that we define as fully-flexible assembly systems (F-FAS), and addresses the problem of comparing their direct production costs to that of a generic flexible robotized work cell, whose reconfiguration for batch change requires time. Conversely, the F-FAS is a fully-flexible system, able to handle a highly mixed production order in which the size of the batch may be as small as one piece. Convenience analysis revealed that the F-FAS becomes more convenient in certain conditions, especially with complex assemblies and small batch sizes. First experimental data are presented to demonstrate the viability of the fully-flexible system.

This paper introduces the design and experimental validation of a flexible robotized work cell for automated assembly of bends on top of a heat exchanger coil. This automatic system is based on the use of a specifically designed end-effector, able to store several bends together and to singularize and insert them in the tubes. In this way the pick-and-place operations that are typical in automated assembly are eliminated, thus dramatically reducing cycle time. Automatic bowl-feeders are used to serialize bends in the tool crib, where the end-effectors are refilled in hidden time after each tool change. A machine vision system identifies tube positions and detects defects on tube tops, to avoid insertion in damaged tubes. The insertion scheme is derived by comparing tube positions to those stored in a database, so the work cell can produce a highly variable product mix.

This work deals with the kinematic and dynamic modeling of a 3-DOF, under-actuated, pendulum-like manipulator and its control system. The cable-based device is capable of completing point-to-point planar motions, driving the end-effector from a starting pose to a goal pose, by means of two actuators only. The device relies on parametric excitation to control the oscillations of the variable-length pendulum. Unlike a previous work, the dynamic model introduced here is consistent with the assumption of cable-based device. Several control strategies are compared through numerical simulations.

A dynamic model is presented for omnidirectional wheeled mobile robots, including wheel/motion surface slip. We derive the dynamics model, experimentally measure friction coefficients, and measure the force to cause slip (to validate our friction model). Dynamic simulation examples are presented to demonstrate omnidirectional motion with slip. After developing an improved friction model, compared to our initial model, the simulation results agree well with experimentally-measured trajectory data with slip. Initially, we thought that only high robot velocity and acceleration governed the resulting slipping motion. However, we learned that the rigid material existing in the discontinuities between omnidirectional wheel rollers plays an equally important role in determining omnidirectional mobile robot dynamic slip motion, even at low rates and accelerations.