الفهرس 
INTRODUCTION AND SURVEYOnly 14 pages are availabe for public view
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Abstract
The design of high precision mechanisms can be achieved
by manufacturing high precise control components and
synthesis
of systems
intelligent
capable
for
compensating the errors and tolerances existing in the
utilized components.
Increasing the precision of the
servomechanisms
via preciseincorporating highly
components into the system usually does not lead to the
accuracy constraints and specifications imposed on such
systems. This fact is due to the manufacturing accuracy
limitations and the inherent dynamics which represent
one of their persistent nature. The only way to get such
precise is improve the servo-systemto
~ervos
performance to be able to compensate f or’ the different
kinds of errors specially those which are generated from
the non-linear effects of the system components.
Designing precise servos on the basis of the linear
theory of system analysis does not match with the
unavoidably existing non-linear effects apearing in the
pneumatic servo-systems. The natural way to reach the
required
accuracy
limits is to design non-linear
compensators adaptable to the inherent nonlinear effects
of the servo-system components.The present work deals with the problem of analysis and
modelling the Pneumatic Servo-Positioner together with
the design of a Non-Linear Compensator based on the
concept of Self-Oscillatory Contours.
First.
two types of models describing the pneumatic
cylinder and its control valves have been presented.
The two types are :
(a) A non-linear model in the form of an algorithm.
suitable for simulation on the digital computer, taking
into account all types of nonlinearities in the system.
It computes the system output directly in the time
domain. The model is valid even when the spool valve is
operated in the ON/OFF mode.
(b) A linearized model giving the transfer function of
the positioner in the Laplace domain without taking into
account any nonlinear e£fects. Both models are tested by
simulation on the digital computer to show the validity,
merits and limitaitons of each one.
Having the linearized and non-linear cheracteristics of
the pneumatic cylinder with its control valve, the
concept of self oscillatory contours is introduced as an
internal dither signal compensator.
A candidate dither loop is chosen and the mathematical
conditions necessary to have self sustained oscillations
have been derived, and the practical considerations of
realizing such loops are discussed. The chosen dither
loop is designed and tested both by simulation and
experimentation. The cheracteristics of the proposed
deSign are determined The designed dither
is used as a compensator for the
Pneumatic Servo-Positioner. The closed loop system is
tested by simulation on the digital computer and by
experimentation on a real system designed specially for
that purpose.
The main results of the research may be summerized in
the following points :
1. A practical procedure for designing non-linear
compensators for the Pneumatic Servo-Systems has been
formulated and experimentally checked.
2. The proposed non-linear compensator (the dither loop)
showed great superiority over the conventional linear
compensators. This fact has been easily verified by both
the modelling and the real tests which revealed the
better system response.
3. The obtained system responses showed a progressive
feature concerning the effective attenuation of the
higher harmonics by the control valve-pneumatic cylinder
combination.
4. The non-linear compensator was fully studied for
in the time domain or in theperformance
either
frequency domain for further development.