11-04-2013, 03:28 PM
Design of a low-cost five-finger anthropomorphic robotic arm with
nine degrees of freedom
Design of a low-cost.pdf (Size: 273.64 KB / Downloads: 39)
Abstract
The aim of this work was to design and demonstrate a dexterous
anthropomorphic mobile robotic arm with nine degrees of freedom using readily
available low-cost components to perform different object- picking tasks for
immobile patients in developing nations. The robotic arm consists of a shoulder,
elbow, and wrist and five-finger gripper. It can perform different gripping actions,
such as lateral, spherical, cylindrical and tip-holding gripping actions using a fivefinger
gripper; each finger has three movable links. The actuator used for the
robotic arm is a high torque dc motor coupled with a gear assembly for torque
amplification, and the five-finger gripper consists of five cables placed like
tendons in the human arm. The robotic arm utilizes a controller at every link to
trace the desired trajectory with high accuracy and precision. Digital
implementation of the control algorithm is done on an Atmel Atmega-16
microcontroller using trapezoidal approximation and Newton’s backward
difference methods. The arm can be programmed or controlled manually to
perform a variety of object-picking tasks. A prototype of the robotic arm was
constructed, and test results on a variety of object-picking tasks are presented.
Introduction
In this work, the design and implementation of a novel low-cost
anthropomorphic robotic arm to assist immobile patients in developing countries
with object-picking tasks are presented. The design of the gripper determines the
ability of the arm to pick up objects of different shapes and sizes; therefore, the
arm is constructed to imitate the movements and design of the most skilled
gripper known: the human hand. The project utilizes flexible roller chains to form
the fingers of the gripper. These roller chains are robust, low cost and serve as the
linkage mechanism. To obtain the push and pull action of tendons present in the human hand, the chains are pulled using a cable attached to every finger and are
restored to their original position by the elastic force of springs attached to every
link of the fingers. In the past, various attempts have been made to mimic the
human hand; however, these designs involve complex and costly approaches for
the grasping mechanism. Lotti et al. used springs to connect parts of the fingers,
which limits its load-lifting capacity because weak links made of springs cannot lift
heavy objects. In addition, the control system used is also complex. The Jacobsen
and Iversen four-finger gripper with 4 degrees of freedom for each finger was a
revolutionary device. Its actuation requires 32 independent polymeric tendons
and pneumatic actuators, which make the control and maintenance of the device
costly. Fukaya et al. used the concept of an interconnected linkage mechanism
and cables to pull each finger. In developing countries such as India, cost
constraints prevent the widespread use of assistive robotic arms. Thus, the design
and demonstration of a low-cost versatile assistive robotic arm are of interest. In
this paper, the authors propose an approach to develop a less complex robotic
arm with low manufacturing costs and high gripper strength.
Conclusion
This paper presents a dexterous anthropomorphic robotic arm with 9
degrees of freedom that is useful for performing different object-picking task for
immobile patients. The robotic arm can be constructed using readily available,
low-cost components. The inverse kinematics model was used to determine the
trajectory of the mobile platform, the robotic arm and the five-finger gripper. A
prototype of the designed robotic arm was constructed, and its functionality was
verified with a variety of object-picking tasks. In the next model of this robotic
arm, shape memory alloys will be used as actuators instead of dc motors, and
tactile sensors will be employed in the gripper to perform closed-loop control in
the five- finger gripper. It is envisioned that the design of low-cost assistive
robotic arms will lead to their wider adoption and deployment in developing
nations to assist immobile individuals