Conference Paper

A Two-Fingered Anthropomorphic Robotic Hand with Contact-Aided Cross Four-Bar Mechanisms as Finger Joints

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Abstract

This paper presents an anthropomorphic design of a robotic finger with contact-aided cross four-bar (CFB) linkages. Anatomical study shows that finger joints have a complex structure formed by non-symmetric surfaces and usually produce complex movement than a simple revolute motion. The articular system of human hand is firstly investigated. Kinematics of a CFB mechanism is then analyzed and computer aided design of fixed and moving centrodes of CFB mechanism is presented. Gripping analysis of human hand shows two easily ignored components of a finger, fingernail and soft fingertip. Based on the range of motion of the joints of the most flexible thumb finger, a two-joint anthropomorphic finger is developed by using contact-aided CFB linkages which can also be used for joint design of prosthetic knee. Prototype of a two-fingered hand is manufactured by using 3D printing technology and gripping of a wide range of objects is tested.

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... A CFB linkage is used for passive adjustment due to the complicated contacting surfaces. References [18] and [19] propose a method to exactly duplicate the kinematic characteristics of a rigid-link four-bar mechanism by using the centrodes of the four-bar linkage. A mechanism that is overconstrained may be the best choice in problems of machine design when larger and variable loads must be sustained by means of mass and compliance, especially when the maintenance of mechanical accuracy is important [20]. ...
Article
(This is an open access publication which can be accessed from http://mechanismsrobotics.asmedigitalcollection.asme.org/article.aspx?articleid=2599272 ) In recent years, applications in industrial assemblies within a size range from 0.5 mm to 100 mm are increasing due to the large demands for new products, especially those associated with digital multimedia. Research on grippers or robotic hands within the mesoscopic scale of this range has not been explored in any great detail. This paper outlines the development of a gripper to bridge the gap between microgrippers and macrogrippers by extending the gripping range to the mesoscopic scale, particularly without the need to switch grippers during industrial assembly. The mesoscopic scale gripper (meso-gripper) researched in this work has two modes of operation: passive adjusting mode and angled gripping mode, adapting its configuration to the shape of object automatically. This form of gripping and the associated mechanism are both novel in their implementation and operation. First, the concept of mesoscopic scale in robotic gripping is presented and contextualized around the background of inefficient hand switching processes and applications for assembly. The passive adjusting and angled gripping modes are then analyzed and a dual functional mechanism design proposed. A geometric constraint method is then demonstrated which facilitates task-based dimensional synthesis after which the kinematics of synthesized mechanism is investigated. The modified synthesized mechanism gripper is then investigated according to stiffness and layout. Finally, a 3D printed prototype is successfully tested, and the two integrated gripping modes for universal gripping verified.
... tactile system such as [16] describing the design and higher performance of a biomimetic fingertip (fingerprint) compared with a smooth fingertip, [17] presenting the anthropomorphic design and gripping performance of a robotic finger and [18] introducing the design and performance of a multi-element sensory array based on the mammalian whisker sensory system. ...
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... A CFB linkage is used for passive adjustment due to the complicated contacting surfaces. References [18] and [19] propose a method to exactly duplicate the kinematic characteristics of a rigid-link four-bar mechanism by using the centrodes of the four-bar linkage. A mechanism that is overconstrained may be the best choice in problems of machine design when larger and variable loads must be sustained by means of mass and compliance, especially when the maintenance of mechanical accuracy is important [20]. ...
... A CFB linkage is used for passive adjustment due to the complicated contacting surfaces. References [18] and [19] propose a method to exactly duplicate the kinematic characteristics of a rigid-link four-bar mechanism by using the centrodes of the four-bar linkage. A mechanism that is overconstrained may be the best choice in problems of machine design when larger and variable loads must be sustained by means of mass and compliance, especially when the maintenance of mechanical accuracy is important [20]. ...
Article
Full-text available
(This is an open access publication which can be accessed from http://mechanismsrobotics.asmedigitalcollection.asme.org/article.aspx?articleid=2599272 ) In recent years, applications in industrial assemblies within a size range from 0.5mm to 100mm are increasing due to the large demands for new products, especially those associated with digital multimedia. Research on grippers or robotic hands within the mesoscopic scale of this range has not been explored in any great detail. This paper outlines the development of a gripper to bridge the gap between micro-grippers and macro-grippers by extending the gripping range to the mesoscopic scale, particularly without the need to switch grippers during industrial assembly. The mesoscopic scale gripper (meso-gripper) researched in this work has two modes of operation: passive adjusting and an angled gripping, adapting the shape of object automatically to an appropriate configuration. This form of gripping and the associated mechanism are both novel in their implementation and operation. Firstly, the concept of mesoscopic scale in robotic gripping is presented and contextualized around the background of inefficient hand switching processes and applications for assembly. The passive adjusting and angled gripping modes are then analyzed and a dual functional mechanism design proposed. A geometric constraint method is then demonstrated which facilitates task-based dimensional synthesis after which the kinematics of synthesized mechanism is investigated. The modified synthesized mechanism gripper is then investigated according to stiffness and layout. Finally, a 3D printed prototype is successfully tested and the two integrated gripping modes for universal gripping verified.
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The purpose of this work is to develop a 3D inverse dynamic model of the human finger for estimating the muscular forces involved during free finger movements. A review of the existing 3D models of the fingers is presented, and an alternative one is proposed. The validity of the model has been proved by means of two simulations: free flexion-extension motion of all joints, and free metacarpophalangeal (MCP) adduction motion. The simulation shows the need for a dynamic model including inertial effects when studying fast movements and the relevance of modelling passive forces generated by the structures studying free movements, such as the force exerted by the muscles when they are stretched and the passive action of the ligaments over the MCP joint in order to reproduce the muscular force pattern during the simulation of the free MCP abduction-adduction movements.
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The Center for Engineering Design at the University of Utah, and the Artificial Intelligence Laboratory at the Massachusetts Institute of Technology have developed a robotic end effector intended to function as a general purpose research tool for the study of machine dexterity. The high performance, multifingered hand will provide two important capabilities. First, it will permit the experimental investigation of basic concepts in manipulation theory, control system design and tactile sensing. Second, it will expand understanding required for the future design of physical machinery and will serve as a "test bed" for the development of tactile sensing systems. The paper includes: 1) a discussion of issues important to the development of manipulation machines; 2) general comments regarding design of the Utah/M.I.T. Dextrous Hand; and, 3) a detailed discussion of specific subsystems of the hand.
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