文档介绍：Available online at hanism
and
Machine Theory
Mechanism and Machine Theory 43 (2008) 565–575
ate/mechmt
Improvement of balancing accuracy of robotic systems:
Application to leg orthosis for rehabilitation devices
V. Arakelian *, S. Ghazaryan
De´partement de Ge´nie Me´canique et Automatique, LGCGM EA 3913, Institut National des Sciences Applique´es (.) de Rennes,
20 avenue des Buttes de Coe¨smes – CS 14315, F-35043 Rennes, France
Received 21 January 2007; received in revised form 7 May 2007; accepted 8 May 2007
Available online 2 July 2007
Abstract
The balancing of robotic systems is an important issue because it allows significant reduction of torques. However the
literature review shows that the gravity balancing of robotic systems is carried out by weightless springs. For many bal-
ancing schemes it is the source of errors.
This paper deals with an analytically tractable solution for the gravity balancing considering the spring mass. For this
purpose, the relationship between the stiffness coefficient of the spring and its mass is provided. Then this relationship is
introduced into the balancing equation and spring elastic force is determined taking into account its mass. For zero length
springs, the stiffness coefficient of the springs is determined from a quadratic equation and for non-zero length springs from
a cubic equation. In this way, an exact balancing of gravitational forces is achieved, which allows improving the balancing
accuracy of robotic systems.
The efficiency of the suggested approach is illustrated by numerical examples. An application to the balancing of the leg
orthosis for robotic rehabilitation is also presented.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Gravity balancing; Spring balancer; Robotic system; Rehabilitation devise
1. Introduction
Balancing of mechanisms is a well-known research field, which finds practical applications in high-speed
machines, machine-tool industry, robotics and in