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LINK LENGTH CONTROL USING DYNAMICS FOR PARALLEL
MECHANISM WITH ADJUSTABLE LINK PARAMETERS

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W. Tanaka , T. Arai , K. Inoue , T. Takubo , Y. Mae and Y. Koseki 3
'Department of System Innovation, Division of System Science and Applied Informatics,
Graduate School of Engineering Science, Osaka University
1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
"Department of Human and Artificial Intelligence Systems,
Faculty of Engineering, University of Fukui
3
National Institute of Advanced Industrial Science and Technology

ABSTRACT
There has always been a workspace problem with parallel mechanisms. Previously we have proposed
a parallel mechanism with linear passive joints to adjust link length. This parallel mechanism can
achieve different workspaces by adjusting the link length. We have tried to control the link lengths of
the parallel mechanism not active but passive using dynamics. This paper proposes the control
algorithm of these passive linear joints, to adjust the link lengths using dynamics in the case of a 2-
DOF planer prototype.

KEYWORD

Parallel mechanism, Dynamics, Adjustable mechanical parameter, Passive joint control.

INTRODUCTION
Parallel mechanisms have some good advantages compared with conventional articulated arms. The
only drawback is its small workspace due to its in-parallel configuration.
Whole of the large workspace may not always be required in one task, and the workspace may be
divided into smaller sub-workspaces corresponding to individual tasks as shown in Figure 1. This is
our basic idea in the paper [1]. If each sub-workspace can be covered by a corresponding parallel
mechanism that is not individuality different but a single mechanism with differently adjusted
mechanical parameters, the whole workspace can be achieved by just one machine. Our idea is to
cover each sub-workspace by a machine that has adjustable mechanical parameters.
There are some mechanical parameters which can be adjusted, such as base plate parameters, end-
effector parameters and link parameters. This paper discussed the parallel mechanism with adjustable