Gabriele Vassura

Development of UB Hand 3: Early Results

The first part of this paper describes the development of a humanoid robot hand based on an endoskeleton made of rigid links connected with elastic hinges, actuated by sheath routed tendons and covered by continuous compliant pulps. The project is called UB Hand 3 (University of Bologna Hand, 3rd version) and aims to reduce the mechanical complexity of robotic end effectors yet maintaining full anthropomorphic aspect and a good level of dexterity. In the second part this paper focuses on the early experiences of the UB Hand 3 in performing manipulation tasks.

A novel approach to mechanical design of articulated fingers for robotic hands

The paper first discusses the reasons why simplified solutions for the mechanical structure of fingers in robotic hands should be considered a worthy design goal. After a brief discussion about the mechanical solutions proposed so far for robotic fingers, a different design approach is proposed. It considers finger structures made of rigid links connected by flexural hinges, with joint actuation obtained by means of flexures that can be guided inside each finger according to different patterns. A simplified model of one of these structures is then presented, together with preliminary results of simulation, in order to evaluate the feasibility of the concept. Examples of technological implementation are finally presented and the perspective and problems of application are briefly discussed.

UBH 3: an anthropomorphic hand with simplified endo-skeletal structure and soft continuous fingerpads

The paper describes work in progress at the University of Bologna concerning the design of a new anthropomorphic robot hand. The hand is based on the modular assembly of articulated fingers that adopt an original configuration of their structure, made with rigid links connected by elastic hinges that are coaxially crossed by flexible tendons. This innovative design is suitable to host distributed sensory equipment and continuous compliant cover, allowing a high level of anthropomorphism together with great structural simplification, reliability enhancement and cost reduction. Furthermore, the proposed solution is very flexible, as it can be adapted to many different hand configurations and is not dependent on a particular type of actuation, being compatible with future availability of any kind of artificial muscles.

The DEXMART hand: Mechatronic design and experimental evaluation of synergy-based control for human-like grasping

This paper summarizes recent activities carried out for the development of an innovative anthropomorphic robotic hand called the DEXMART Hand. The main goal of this research is to face the problems that affect current robotic hands by introducing suitable design solutions aimed at achieving simplification and cost reduction while possibly enhancing robustness and performance. While certain aspects of the DEXMART Hand development have been presented in previous papers, this paper is the first to give a comprehensive description of the final hand version and its use to replicate human-like grasping. In this paper, particular emphasis is placed on the kinematics of the fingers and of the thumb, the wrist architecture, the dimensioning of the actuation system, and the final implementation of the position, force and tactile sensors. The paper focuses also on how these solutions have been integrated into the mechanical structure of this innovative robotic hand to enable precise force and displacement control of the whole system. Another important aspect is the lack of suitable control tools that severely limits the development of robotic hand applications. To address this issue, a new method for the observation of human hand behavior during interaction with common day-to-day objects by means of a 3D computer vision system is presented in this work together with a strategy for mapping human hand postures to the robotic hand. A simple control strategy based on postural synergies has been used to reduce the complexity of the grasp planning problem. As a preliminary evaluation of the DEXMART Hand’s capabilities, this approach has been adopted in this paper to simplify and speed up the transfer of human actions to the robotic hand, showing its effectiveness in reproducing human-like grasping.

Mechanical And Control Features Of The University Of Bologna Hand Version 2

In this paper, the main design features of the University of Bologna robotic hand version II (UB Hand 11), currently at the set-up phase, are pre- sented. In particular, a detailed description is given of the adopted solutions with respect to hand-arm me- chanical integration, sensorial equipment, and control architecture and algorithms.

Integrated Mechatronic Design for a New Generation of Robotic Hands

Abstract In this paper, an overall description of the design of a robotic hand is discussed, with particular attention to the required sensory subsystem, its integration within the mechanical structure of the hand and the required control architecture. Different solutions for the joint configuration and the structure of the tendon network adopted for the transmission system are present together with three types of sensors applied on the finger and on the actuators. The integrated design of the hand finger and the sensors is reported and the motivations leading to this particular implementation are thoroughly addressed, taking into account both the mechanical constraints and the control requirements.

Design of a Single-Acting Constant-Force Actuator Based on Dielectric Elastomers

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator, which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator.

Development of the UB Hand IV: Overview of Design Solutions and Enabling Technologies

The replication of the human hands functionality and appearance is one of the main reasons for the development of robot hands. Despite 40 years of research in the field [1], the reproduction of human capabilities, in terms of dexterous manipulation, still seems unachievable by the state-of-the-art technologies. From a design perspective, even defining the optimal functionalities of a robotic end-effector is quite a challenging task since possible applications of these devices span industrial robotics, humanoid robotics, rehabilitation medicines, and prosthetics, to name a few. Therefore, it is reasonable to think that the design solutions, which are well suited to a single domain, might not be readily taken as general guidelines. For example, industrial manipulators are often equipped with basic grippers, which are conceived so as to increase the throughput and the reliability, and are assumed to operate in structured environments. In this case, the enhanced manipulation skills and the subsequent cost increases must be carefully motivated by the application requirements.

WireMan: a portable wire manipulator for touch-rendering of bas-relief virtual surfaces

An haptic interface actuated by parallel wires is under development. Differently from other known wire-based haptic devices, the proposed system explicitly addresses the capability to be tailored on a human body in order to obtain a portable interface, that should be used for achieving haptic perception by visually impaired people. The device is based on a system of three concurrent wires connected to the operators finger, obtaining 3D mobility capabilities. The paper shows in particular how this device can be efficiently used in the exploration of bas-relief virtual surfaces in spite of its intrinsic manipulability limits. This capability has been fully confirmed by preliminary 2D tests, whose results are presented and discussed.

Differentiated layer design to modify the compliance of soft pads for robotic limbs

Most of robotic soft pads studied so far were made with a thick layer of homogeneous material shaped around a rigid core; their behavior has been widely investigated in the literature, mainly under compressive contact load, showing typical non-linear relationship between contact deformation and applied load (the so called power law). This paper proposes differentiated layer design, that is the adoption of a single elastic material, dividing the overall thickness of the pad into layers with different structural design (e.g. a continuous skin layer coupled with an internal layer with voids). The purpose is to modify the actual pad compliance and the resulting power law; in particular, given the material and the allowable pad thickness, to increase the compliance with respect to a non structured pad. Some possible internal layer structures are described, compatible with rapid prototyping manufacturing. Their compressive behaviors are tested and comparatively evaluated showing that the concept can work and be exploited for useful application.