자동형 가변 동력전달장치를 이용한 로봇손의 개발

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2014. 8. 조규진.This paper presents a way to improve performance of a tendon driven robotic hand using Passive Variable Transmission. The concept of research was inspired by the human pulley mechanism which changes the moment arm of tendon by pulleys, which makes it possible for a human hand to rapidly and powerfully grasp an object. To mimic the pulley mechanism of the human hand, Passive Variable Transmission is applied, which changes the path of the tendon wire passively as the human hand pulleys do. This PVT Mechanism is a transmission for a tendon driven mechanism, which varies a moment arm of a tendon wire by changing the lengths of compliant material when the tension of the tendon wire is changing. If the tension of the tendon wire is small, the moment arm remains short. As the tension gets bigger, the moment arm increases. Thus, when the joint rotates without load, the moment arm is short and the joint rotates rapidly. On the other hand, if the joint is blocked by an obstacle, the tension increases, which increases the moment arm, and the joint generates a bigger moment. The goal of this research was to develop a suitable PVT design for a small finger structure. After trying a number of concept designs, the spring type PVT was chosen. This spring type PVT has been tested to certificate that this PVT can change the tendon wire moment arm passively. Before fabricating the robotic hand, the parametric study was conducted. Based on the results of the parametric study, parameters of the spring type PVT was decided, and a robotic hand was fabricated. By comparing with an existing tendon driven robotic hand, H2 hand from Meka, it was confirmed that the fabricated robotic hand used 20% rated output and showed 40% grasping performance. There has been a structural limitation on robotic hands in mimicking the grasping performance of human hands. This paper will show prospective view of using the Passive Variable Transmission Mechanism to improve the grasping performance of robotic hands.Abstract i Contents iii List of Tables v List of Figures vi Chapter 1 Introduction 1 Chapter 2 Passive Variable Transmission 3 2.1 Concept of PVT 3 2.2 PVT Concept Test 5 2.2.1 Rotation speed test 6 2.2.2 Fingertip force test 6 Chapter 3 Spring Type PVT 8 3.1 Concept Designs of PVT 8 3.2 Design Modifications for Performance 10 3.3 Spring Type PVT 12 3.3.1 Mechanism of the Spring Type PVT 12 3.3.2 Test for the spring type PVT 14 Chapter 4 Parametric Study 17 4.1 Design Parameters of Spring Type PVT 17 4.1.1 Design Parameters of the Spring Type PVT 17 4.1.2 Moment by Design Parameters 21 4.2 Kinematic Properties of PVT 24 4.2.1 Kinematic properties for a spring constant 24 4.2.2 Kinematic properties for initial deformation 26 4.2.3 Result of parametric study 27 Chapter 5 Robotic Hand 28 5.1 Finger Design of Robotic hand 28 5.2 Fabrication of Robotic hand 31 Chapter 6 Grasping performance 34 Chapter 7 Conclusion 35 Bibliography 37 국문 초록 41Maste

Design and analysis of a novel long-distance double tendon-sheath transmission device for breast intervention robots under MRI field

Cancer represents a major threat to human health. Magnetic resonance imaging (MRI) provides superior performance to other imaging-based examination methods in the detection of tumors and offers distinct advantages in biopsy and seed implantation. However, because of the MRI environment, the material requirements for actuating devices for the medical robots used in MRI are incredibly demanding. This paper describes a novel double tendon-sheath transmission device for use in MRI applications. LeBus grooves are used in the original transmission wheels, thus enabling the system to realize long-distance and large-stroke transmission with improved accuracy. The friction model of the transmission system and the transmission characteristics model of the novel tendon-sheath structure are then established. To address the problem that tension sensors cannot be installed in large-stroke transmission systems, a three-point force measurement method is used to measure and set an appropriate preload in the novel tendon-sheath transmission system. Additionally, experiments are conducted to verify the accuracy of the theoretical model and multiple groups of tests are performed to explore the transmission characteristics. Finally, the novel tendon-sheath transmission system is compensated to improve its accuracy and the experimental results acquired after compensation show that the system satisfies the design requirements

A finger mechanism for adaptive end effectors

This paper presents design and analysis of a rigid link finger, which may be suitable for a number of adaptive end effectors. The design has evolved from an industrial need for a tele-operated system to be used in nuclear environments. The end effector is designed to assist repair work in nuclear reactors during retrieval operation, particularly for the purpose of grasping objects of various shape, size and mass. The work is based on the University of Southampton's Whole Arm Manipulator, which has a special design consideration for safety and flexibility. The paper discusses kinematic issues associated with the finger design, and to the end of the paper specifies the limits of finger operating parameters for implementing control law

Bio-inspired Tensegrity Soft Modular Robots

In this paper, we introduce a design principle to develop novel soft modular robots based on tensegrity structures and inspired by the cytoskeleton of living cells. We describe a novel strategy to realize tensegrity structures using planar manufacturing techniques, such as 3D printing. We use this strategy to develop icosahedron tensegrity structures with programmable variable stiffness that can deform in a three-dimensional space. We also describe a tendon-driven contraction mechanism to actively control the deformation of the tensegrity mod-ules. Finally, we validate the approach in a modular locomotory worm as a proof of concept.Comment: 12 pages, 7 figures, submitted to Living Machine conference 201

A novel design process of low cost 3D printed ambidextrous finger designed for an ambidextrous robotic hand

This paper presents the novel mechanical design of an ambidextrous finger specifically designed for an ambidextrous anthropomorphic robotic hand actuated by pneumatic artificial muscles. The ambidextrous nature of design allows fingers to perform both left and right hand movements. The aim of our design is to reduce the number of actuators, increase the range of movements with best possible range ideally greater than a common human finger. Four prototypes are discussed in this paper; first prototype is focused on the choice of material and to consider the possible ways to reduce friction. Second prototype is designed to investigate the tendons routing configurations. Aim of third and fourth prototype is to improve the overall performance and to maximize the grasping force. Finally, a unified design (Final design) is presented in great detail. Comparison of all prototypes is done from different angles to evaluate the best design. The kinematic features of intermediate mode have been analysed to optimize both the flexibility and the robustness of the system, as well as to minimize the number of pneumatic muscles. The final design of an ambidextrous finger has developed, tested and 3D printed

Compliance Analysis of an Under-Actuated Robotic Finger

Under-actuated robotic hands have multiple applications fields, like prosthetics and service robots. They are interesting for their versatility, simple control and minimal component usage. However, when external forces are applied on the finger-tip, the mechanical structure of the finger might not be able to resist them. In particular, only a subset of disturbance forces will meet finite compliance, while forces in other directions impose null-space motions (infinite compliance). Motivated by the observation that infinite compliance (i.e. zero stiffness) can occur due to under-actuation, this paper presents a geometric analysis of the finger-tip compliance of an under-actuated robotic finger. The analysis also provides an evaluation of the finger design, which determines the set of disturbances that is resisted by finite compliance. The analysis relies on the definition of proper metrics for the joint-configuration space. Trivially, without damping, the mass matrix is used as a metric. However, in the case of damping (power losses), the physical meaningful metric to be used is found to be the damping matrix. Simulation experiments confirm the theoretical results

ReHand - a portable assistive rehabilitation hand exoskeleton

This dissertation presents a synthesis of a novel underactuated exoskeleton (namely ReHand2) thought and designed for a task-oriented rehabilitation and/or for empower the human hand. The first part of this dissertation shows the current context about the robotic rehabilitation with a focus on hand pathologies, which influence the hand capability. The chapter is concluded with the presentation of ReHand2. The second chapter describes the human hand biomechanics. Starting from the definition of human hand anatomy, passing through anthropometric data, to taxonomy on hand grasps and finger constraints, both from static and dynamic point of view. In addition, some information about the hand capability are given. The third chapter analyze the current state of the art in hand exoskeleton for rehabilitation and empower tasks. In particular, the chapter presents exoskeleton technologies, from mechanisms to sensors, passing though transmission and actuators. Finally, the current state of the art in terms of prototype and commercial products is presented. The fourth chapter introduces the concepts of underactuation with the basic explanation and the classical notation used typically in the prosthetic field. In addition, the chapter describe also the most used differential elements in the prosthetic, follow by a statical analysis. Moreover typical transmission tree at inter-finger level as well as the intra- finger underactuation are explained . The fifth chapter presents the prototype called ReHand summarizing the device description and explanation of the working principle. It describes also the kinetostatic analysis for both, inter- and the intra-finger modules. in the last section preliminary results obtained with the exoskeleton are shown and discussed, attention is pointed out on prototype’s problems that have carry out at the second version of the device. The sixth chapter describes the evolution of ReHand, describing the kinematics and dynamics behaviors. In particular, for the mathematical description is introduced the notation used in order to analyze and optimize the geometry of the entire device. The introduced model is also implemented in Matlab Simulink environment. Finally, the chapter presents the new features. The seventh chapter describes the test bench and the methodologies used to evaluate the device statical, and dynamical performances. The chapter presents and discuss the experimental results and compare them with simulated one. Finally in the last chapter the conclusion about the ReHand project are proposed as well as the future development. In particular, the idea to test de device in relevant environments. In addition some preliminary considerations about the thumb and the wrist are introduced, exploiting the possibility to modify the entire layout of the device, for instance changing the actuator location