Francesco Pescarmona

A new methodology for the determination of the workspace of six-DOF redundant parallel structures actuated by nine wires

The WiRo-6.3 is a six-degrees of freedom (six-DOF) robotic parallel structure actuated by nine wires, whose characteristics have been thoroughly analyzed in previous papers in reference. It is thought to be a master device for teleoperation; thus, it is moved by an operator through a handle and can convey a force reflection on the operators hand. A completely new method for studying the workspace of this device, and of virtually any nine-wire parallel structure actuated by wire is presented and discussed, and its results are given in a graphical form.

Spacesuits and EVA Gloves Evolution and Future Trends of Extravehicular Activity Gloves

The total time of Extravehicular Activity (EVA) performed by astronauts has increased significantly during the past few years. On the other hand, the bulk and stiffness of the suit itself and in particular of the gloves generate some difficulties for the astronauts to perform their tasks in space. Therefore, it is necessary to improve the EVA glove technology for future needs. Since a lack of categorized information for those who want to improve EVA gloves is evident, in this work a survey on related literature has been carried out and fundamental data has been categorized. The paper starts with an overview on the historical and chronological progress of EVA suits and EVA gloves followed by a review of the previously demonstrated EVA gloves including American and Russian ones. The remaining part of the paper is dedicated to the characteristics of current EVA gloves and to present and future trends in research for further improvements.

Human Hand: Kinematics, Statics and Dynamics

The human hand is an extremely complex system due to its large number of degrees of freedom (DoF) within a significantly reduced space. Moreover, it is required for most of the tasks performed by humans. That is why it is necessary to understand deeply all the characteristics of the human hand in order to develop devices interacting with it: to support it, to substitute injured parts, to help the recovery from injuries, or to enhance the performances while preserving its natural level of dexterity. The aim of this paper is to provide a complete and exhaustive summary of the kinematic, static and dynamic characteristics of the human hand as a preliminary step towards the development of hand devices such as prosthetic/robotic hands and exoskeletons. Both fields provide promising opportunities in research and space applications; the former through humanoid robotic helpers (e.g., Eurobot, Robonaut), the latter through the rising necessity to help the astronauts during Extravehicular Activity (EVA). In literature, several papers can be found analyzing kinematics, workspace, constraints and forces of the human hand 2,4 . However this information is scattered among several papers, regarding in particular the exerted forces and the dependencies of joint forces and velocities from the angular values of the same joint or the adjacent one. Direct and inverse kinematics are presented for all the fingers and the data related to maximum forces, velocities, acceleration for each joint of each finger has been collected and is presented in this work.

Constraint Study for a Hand Exoskeleton: Human Hand Kinematics and Dynamics

In the last few years, the number of projects studying the human hand from the robotic point of view has increased rapidly, due to the growing interest in academic and industrial applications. Nevertheless, the complexity of the human hand given its large number of degrees of freedom (DoF) within a significantly reduced space requires an exhaustive analysis, before proposing any applications. The aim of this paper is to provide a complete summary of the kinematic and dynamic characteristics of the human hand as a preliminary step towards the development of hand devices such as prosthetic/robotic hands and exoskeletons imitating the human hand shape and functionality. A collection of data and constraints relevant to hand movements is presented, and the direct and inverse kinematics are solved for all the fingers as well as the dynamics; anthropometric data and dynamics equations allow performing simulations to understand the behavior of the finger.

Effects of EVA Glove on Hand Performance

The human hand is a very particular limb: it has a wide range of degrees of freedom, permitting to achieve a great variety of movements, and is also one of the most sensorized parts of the human body. These characteristics make it the most important tool for astronauts to perform extravehicular activity (EVA). However, mandatory EVA equipment strongly reduces hand performances, in particular as regards dexterity, tactile perception, mobility and fatigue. Several studies have been conducted to determine the influence of the EVA glove on manual capabilities, both in the past and more recently. This study presents experimental data regarding the performance decay which occurs in forces, fatigue and capability to execute tasks when wearing a non pressurized EVA glove, in comparison with bare-handed potential. Moreover, mechanical resistance of the glove has been measured and imposed pressure maps are presented. Results yield a deeper knowledge on how EVA gloves hinder human hand performance and how this is related to their stiffness.

Wire-Driven Pneumatic Actuation of a New 6-DOF Haptic Master

The paper presents the results of a work carried out by the Department of Mechanics of Politecnico di Torino, concerning the study and development of a six degrees of freedom force reflecting master structure for teleoperation (haptic device) to be controlled by an operator. The latter imposes the six-dimensional linear and angular displacement of a handle, controlling a remote slave robot or interacting with virtual reality. On the other hand, the operator receives a force feedback related to the environment in which the slave robot or virtual device operates. Since the actuators must be force controlled in order to generate a resultant corresponding to the desired wrench, pneumatic actuation has been chosen because it is particularly suitable to the application and quite economical.Copyright

A Novel Continuous Alternate Motion Mechanism With Two Input Wheels

This paper presents the design of a mechanism with the following specifications: continuous alternate motion, wide motion phases with constant angular velocity, parallel input and output shafts, and great strokes. Those specifications derive from a possible application in the textile field. The mechanism is composed of two star wheels properly coupled together: there are two counter-rotating input wheels, alternately coupling with slots first, then teeth at each side of the output wheel. As usual for star wheels, pins and slots handle the acceleration and deceleration phases, while the constant velocity phase is performed by coupling sectors of toothed gears. A proper design of pins and slots is performed, so that at the same time when a pin from one input wheel is releasing a slot, a pin from the other input wheel engages a slot on the other side of the output wheel, forcing the latter to an opposite motion. In this way the output wheel has a continuous and smooth alternate motion. By annihilating the arrest phases typical of star wheels, the proposed system eliminates the discontinuities in the acceleration diagram. The paper develops a complete parametrical analysis of the device, underlining the effect of the constraints on the shape of the motion laws with particular emphasis on the acceleration and deceleration phases. In this way the output wheel has a continuous and smooth alternate motion. With respect to an analogous mechanism realizing the same laws of motion, e.g., cams, this device is very compact and economical, also presenting parallel input and output shafts, and significantly reduces sliding and wear

A force-feedback six-degrees-of freedom wire-actuated master for teleoperation: the WiRo 6.3

Purpose – This paper aims to present an innovative example of a master for teleoperation capable of moving in six degrees of freedom and of providing a force and torque feedback on the operators hand.Design/methodology/approach – After a brief overview of what the state of the art in teleoperation has to offer, the paper outlines the choice of an innovative structure in terms of both geometry and components, pointing out its main characteristics compared with traditional interfaces.Findings – The master for teleoperation WiRo‐6.3 has been designed and constructed and is fully operative, thanks to the following theoretical analyses: positional and orientation workspace(s), forward and inverse kinematics, statics, overall control strategies. The mechanical details are also presented.Research limitations/implications – The WiRo‐6.3 is suitable to those applications in which human command is necessary but potentially harmful, and where a force‐feedback interface is preferred to obtain better control over the...

Development of a Haptic Device with Wire-Driven Parallel Structure

This study focuses on the specific problems that may arise in the development of a parallel, cable-driven device designed for teleoperations systems utilizing force-reflection feedback. A redundant six degrees-of-freedom structure, actuated by nine wires, is described as a convenient layout for a haptic master for telemanipulation. A methodology for the kinematic and static analysis and the evaluation of the device workspace is described. The condition of force closure is used to find all available poses of the end-effector, thereby defining the workspace, whose characteristics are assessed by opportunely conceived indexes. Typical characteristics of cable and implementations thereof in the device are considered. Regarding the realization of the device, relevant attention is given to the definition of the control logic, which can be complex for parallel devices. The selection of the actuators, crucial in realizing force feedback, is discussed. In particular, pneumatic actuation is considered, verified as the most appropriate method for implementation and force control of the cylinders.

Calibration of a Robotized Bending System

The paper describes a method to identify the mechanical inaccuracies which may be present in the swinging unit of a robotized bending system. The method allows calculating the corrections that must be provided to the control system to compensate the mechanical inaccuracies. Finally, the procedure has been applied to a real bending system and the results are presented.