ACTUATOR FAULT-TOLERANT CONTROL IN A TWO D.O.F.
PLANAR MANIPULADOR
Claudio URREA Hassan NOURA Mustapha OULADSINE
Laboratoire des Sciences de l’Information et des Syst`emes
LSIS-UMR CNRS 6168
Domaine Scientifique de St J´erˆome
13397 Marseille Cedex 20.
Universit´e Paul C´ezanne, Aix-Marseille III. France.
claudio.urrea@lsis.org, hassan.noura@lsis.org
Abstract: The aim of this paper is to show the ability of a controlled system to
maintain control objectives, in spite of the occurrence of a fault. Fault-tolerance
is obtained through controller reconfiguration of an industrial robot. Faultaccommodation
is used to change controller structure to avoid the consequences
of a actuator failure. Simulations of a Planar Robot Model, when it is placed in
the same plane of the action of the gravity force are presented. The robot model
includes several parameters usually discarded in current models, such as driving,
non-linear friction, and gear trains, for an industrial-type robotic manipulator and
its actuators.
Keywords: Fault-tolerant control systems, actuator faults, robot modelling, robot
simulation.
1. INTRODUCTION
Many industrial robots are typically used to perform
tasks such as arc welding, spray painting, laser cutting
and debarring (Craig, 1986; Hu and Dawson, 1996).
Because of this, high-speed and accuracy manipulation is
one of the most important performance requirements of a
robot manipulator. Such goals will not be achieved if the
dynamic models are simplified (Arai and Tachi, 1994).
On the other hand, in industrial systems for manufacture,
faults have often lead to irregularities, accidents
and even casualties (Paredis and Khosla, 1994; Noura
et al., 2000a). Continued operation of these systems has
both economic and safety implications. Every industrial
system is vulnerable to faults that can lead to failure
of the complete system, unless mitigating strategies are
included at the design stage (Noura et al., 2000b). In
automated systems, the goal of the fault-tolerance is to
continue operation in spite of failures, if this is possible.
A general problem has been that fault conditions could
not be treated as an integrated part of system design.
Therefore, automated systems to provide uninterrupted
service, even in the presence of failures are required.
Current fault-tolerant manipulator designs require the
addition of redundant links i.e. redundant manipulators
with redundant actuators (Ting et al., 1994; Groom
et al., 1999). In this paper, we present results from
simulations of the state equation model developed for
an industrial-type robotic manipulator IBM 7535 B 04
and its actuators. The ability of a controlled system to
maintain control objectives, in spite of the occurrence of
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