Real-Time Tip Position Control of a Flexible Link Robot


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ABSTRACT

Lightweight flexible robots are widely used in space applications due to their fast
response and operation at high speed compared to conventional industrial rigid link
robots. But the modeling and control of a flexible robot is more complex and difficult due
to distributed structural flexibility. Further, a number of control complexities are
encountered in case of flexible page link robots such as non-minimum phase and under
actuated behavior, non linear time varying and distributed parameter systems.

Introduction

Robots are widely used in many areas such as in industries, microsurgery, defense, space
vehicles etc. in order to make the life of people more comfortable, safety and
sophisticated. Initially these are massive in structure and their application was limited to
only industrial purposes. Day by day due to advancement of modern technology, robots
have become integral part of the development and progress of nation. Now they are used
in the areas of specific interest starting from industry, biotech, research & development,
defense, entertainment are name to few.

What is a flexible robot?

When the rigid links are replaced by lightweight links it is their inherent property
that they undergo some damped vibration before it comes to the steady state. In contrast
to this when rigid page link robots are actuated they go to their final destination as a page link the
whole. However, if we move flexible page link very slowly to its final position in case of a
regulation problem or tracking to a very low frequency signal would result almost no or
zero deflection. Therefore, it can be said that speed of operation which actually determine
the tip vibration; higher the speed more seriously excited vibration and vice versa.

Why flexible robot?

Always fast response and weight are the requirements in the design and analysis
in any system of interest. So these requirements necessitate the robot must have
lightweight links which will enable them to be used in any area. In earlier days robots
were primarily used in industrial automation sectors and their application in all other
fields were limited. The application of robots especially in space were mainly constrained
by their massive structures, bulky so flexible robot was an option for it and since then
research on flexible structures control and modeling increased rapidly.

Motivation

Many researchers have addressed on in the both modeling and control aspects of
flexible page link robot. The primary goal is to control the tip vibration as fast as possible. In
addition to that many authors have reported the most crucial problems associated with
flexible page link robot are that non-minimum phase characteristic, non-collocated system and
under actuated system [14] [18]. Design and analysis of controller for such systems is of
very interest because the controller can be applicable to a wide class of system.

Conclusions

In this the chapter we discuss many advantages and disadvantages associated with the
controller even some of the future challenges and scope for further development. The
dynamics of the flexible page link robot is discussed in chapter 3 where AMM and FEM
models are obtained. The basic difference in both of these models are deflection in AMM
is obtained in terms of number of modes while in FEM the cumulative deflections at
nodes of elements give the deflection of tip of the robot.