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- System with electronic relay
- Adjustable hysterisis and dead
zone
- Display phase plane diagram on
CRO
- Stability study by describing
function method
Introduction
Most physical systems are
nonlinear to some extent, however, for purpose of analysis
and design these are taken as nearly linear. In a few systems
nonlinear elements are deliberately introduced to get some
specific advantage. One such system is a relay control system,
often referred to as bang-bang or ON-OFF system. The controller
in such a system is replaced by a power relay resulting in
a substantial cost reduction. In the present unit a simulated
second order system is controlled by an electronic relay.
Apart from a study of the relay characteristics the experiment
introduces the concept of Describing Function. Finally the
phase plane method of analysis is covered in detail where
the switching trajectories can be displayed on an X-Y oscilloscope.
Figures below give the block diagram of the feedback system
and the characteristics of the simulated relay.
The accompanying literature covers a brief
treatment of the nonlinear system analysis through Describing
Function and Phase Plane methods. Steps for conducting various
experiments are described along with sample test results.
Experiments
- Study of the relay characteristics
and display of the same on CRO for different values
of hysteresis and dead zones. Hysteresis and dead
zone of the built-in 3-position electronic relay are
adjustable in the range 0-600mV and 0-500mV respectively.
The transfer characteristics and output of the relay
under various settings provide insight into the relay
performance
- Study of the effect of hysteresis
on system stability. Sustained oscillations may occur
in the system under various conditions, especially
where hysteresis is present. The amplitude and frequency
of such oscillations are predicted from a graphical
analysis and then verified experimentally on the unit
- Phase plane analysis of relay
control system for various values of Hysterisis and
Dead Zones. The nature of the singular point in the
phase plane diagram has importance in the stability
studies of nonlinear systems. Here the phase trajectory
is viewed on the CRO and the effect of changing hysteresis
and dead zone observed
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Relay
with deadzone
Linear system
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Features & Specifications
- Simulated electronic relay using high
speed IC’s
- Simulated 2nd order linear plant. Facility
for displaying x and x(dot) signals
- Dead zone variable from 0-600mV (approx.)
- Hysteresis variable from 0-500mV (approx.)
- Built-in signal sources – sine
and square Amplitude: 0-1V (min.) variable
- Frequency: 10, 20, 40, 80, 100, 200,
400, 800 and 1000Hz
- IC regulated internal power supplies
- 110V±10%, 50Hz mains operation
- Literature and patch cords included
- Essential accessory - a dual beam
CRO
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