- 1 - 2006 Florida Conference on Recent Advances in Robotics, FCRAR 2006 Miami, Florida, May 25-26, 2006 Design of an Anthropomorphic Underactuated Hand Prosthesis with Passive-Adaptive Grasping Capabilities Salim Nasser Florida International University 10555 W. Flagler St. Miami, Florida 33174 (305) 348-2569 snass001@fiu.edu Diana Rincon Florida International University 10555 W. Flagler St. Miami, Florida 33174 (305) 348-2569 rincond@fiu.edu Manuel Rodriguez Florida International University 10555 W. Flagler St. Miami, Florida 33174 (305) 348-2569 rodriguezmj@gmail.com ABSTRACT This paper presents the design and mechanical features of a functional self-adaptive, multi fingered prosthetic hand that improves upon current prosthetic hands. Commercially available hand prostheses, though functional, have limitations such as weight, as result of vast numbers of parts, intricate mechanisms requiring constant maintenance as well as the extremely high cost to the user. The hands design discussed is based on an underactuated 15 degree-of-freedom, 1-degree-of-actuation configuration, fully capable of performing activities of daily living. Each finger is fully independent from each other and is designed to adapt to objects of any geometry while possessing the ability of pick up smaller objects through pinching, by means of a position adjustable thumb. The system provides safe and reliable grasping without the need for feed back sensors, multiple servos, or any type of data processing. The design is focused towards providing upper limb amputees with the option of a prosthetic hand that is cosmetically appealing, functionally comparable with other prosthesis of its type, while decreases cost and weight issues by using an approach that eliminates the need for complex electrical systems, circuitry, and multiple servomotors while decreasing the number of parts and cost of manufacturing. Keywords Hand Prosthesis, Underactuated, Self-adaptive, upper-limb amputees 1. INTRODUCTION For the past decade or so, there has been an increased interest in the design of functionally and cosmetically anthropomorphic robotic end-effectors. The technology and expertise has crossed over into, and benefited the area of prosthetic hand design [6]. Unfortunately, this type of technology is expensive and generally inaccessible to those without insurance or monetary means in developed countries and almost completely inaccessible to most in developing countries. At the most general level, upper-limb prostheses are actuated by means of body or external power, with a hook or hand-shaped end-effectors. In the United States, approximately 70 percent of upper-limb prosthesis users wear hooks [7]. In most other parts of the world, especially in developing countries, human hand-like prostheses are the most commonly preferred. Compared to hooks, prosthetic hands generally offer less function and durability at greater weight and cost [9]. Nonetheless, many individuals still choose hands over hooks, primarily for cosmetic reasons. The design being put forth by this paper describes a highly functional prosthesis that decreases overall weight and costs through the use of a simplified system consisting of a signal motor controlling all five fingers, with each finger being passively adaptive [9]. 2. PROSTHETICS BACKGROUND There are a wide variety of prosthetic devices available for upper- limb amputees ranging from those that are mostly cosmetic on one end, to those with functionality in mind on the other end. In general, most prostheses are designed with both extremes in mind [1]. Though cosmetic prostheses offer a more natural look and feel, they sacrifice functionality and versatility while also being relatively expensive. Active prostheses can be divided into two general categories: body-powered prosthesis, and myo-electric prosthesis. 2.1 BODY POWERED PROSTHESIS Body-powered prostheses are powered and controlled by gross movements of the shoulder, upper arm, or chest and are captured by a harness system which is attached to a cable that is connected to a terminal device (hook or hand) [1]. They tend to be of moderate cost and weight while being very durable at the sacrifice of esthetics. Figure 1. Body-Powered Prosthesis 2.2 ELECTRIC POWERED PROSTHESIS These types of prostheses use small electrical motors found in the terminal device (hand or hook), wrist, and elbow [1]. Electrical activity transmitted from the residual limb to the surface electrodes on the prosthetic fitting control the different motors by means of a microprocessor unit. For the most part, these are pinched type devices consisting of a pair of rigid fingers in opposition to a rigid thumb which are limited to a single degree of freedom; that is an open or close. These types of prosthesis are sometimes covered by a hand like glove providing greater proximal function and increased cosmetic appeal (often at the