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TRAINER KITS

SL
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Description:

Fault Switches

These enable a fault to be introduced
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Error Amplifier
This is used to combine potentiometer signals to provide the error
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Power Amplifier
This drives the motor in opposite directions for a given input
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Motor
This motor is in the mechanical unit and drives the motor in opposite directions for a
given input
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1 belt reduction
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Potentiometer P3
This can be linked to any input to provide an adjustable input the error amplifier
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Result
Thus familiarized with the analogue servo fundamentals trainer
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Apparatus Required:
Sl no
1
2
3

Apparatus
Feed back system
Operational amplifier
Analogue unit

Qty
1
1
1

Range

Theory:
Inverter
If R0=R1 then the scaling factor becomes -1 and we have a sign reverse or inverter
used to change the sign reverse or inverter used to change the sign of a voltage
...
Note two levels of simplification of the
circuit diagram which are commonly applied
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An inverter may be simply shown as an amplifier symbol with -1 written inside it
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This is a very important and useful property of
operational amplifier circuits
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a) Connect the circuit as per the diagram
b) Set the potentiometers P1 and P3 to zero and make the connections as per the
figure
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d) If P1 and P3 are adjusted separately in the individual waveforms will be
displayed
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f) Slightly increase P1 and P3 and note that the waveform peaks limit as the
amplifier is being momentarily over-loaded
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Result:
Thus familiarized with the operational amplifier characteristics
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Apparatus Required:
Sl no
1
2
3

Apparatus
Feedback system
Operational Amplifier
Analogue unit

Qty
1
1
1

Range

Theory:
Steady State Characteristics:
The over all characteristics of motor may be considered from aspects
a) Steady state which are concerned with constant very slowly changing operating
condition
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The motor is operated in a range of steady state conditions
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Initially the motor speed increases
substantially linearly with voltage to the amplifier
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Result:
Thus familiarized with the characteristics of motor, tacho-generator and brake
characteristics
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Apparatus Required:
Sl no
1
2
3
4

Apparatus
Electromechanical unit
Brake unit
Tacho unit
Connecting wire

Qty
1
1
1

Range

Theory:
Control system in which the output has an effect upon the quality in such manner
has to maintain the desired output value is called automatic control system
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If the error signal rotates the motor to increase the error, this is positive feed back
and this system is useless
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d) Reserve the supply polarity to the potentiometer to make output shaft follow in
same direction as input motion by considering the voltages
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EX NO: 5
INFLUENCE OF GAIN
Aim:

To study the effect of variation of gain in a closed loop system
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E= X-Y
The process of comparison is represented by a conventional symbol as in the
diagram, where the input and output may not necessary be electrical system
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The design and performance characteristics of systems are often considered in
terms of the response to step or rump input
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Procedure:
a) The analogue unit and mechanical unit should be connected together by the 34 way ribbon scale
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c) Arrange the system with the solid connections with error amplifier feedback
100kohm giving
...
1 Hz and adjust P3 to provide a square wave
input of 5v
e) Set P1 to zero and arrange an X-Y display
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g) When the gain is further increased, its useful to examine the error amplifier output
which is 6v
h) Set the amplifier feedback resistor to 330 kilo Ohm giving G = 3
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Result:
Thus studied the effects of variation of gain in a closed loop system
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All practical motors have a constant friction called Coulomb friction
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There is a minimum input below which the system will not respond
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Procedure:
a)
b)
c)
d)
e)
f)

Connect the system as per system arrangement
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1 Hz
Turn P1 to 100 and a slightly oscillatory response should be obtained
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Increase the feedback resistor s to 330k, g=3
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Result:
Hence studied the effect of velocity feedback on system stability
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Equipment Required:
Analogue unit
Mechanical unit
Power supply
Oscilloscope
Description:
The step response of a system is an important general indication of system
performance
...
This is sometimes
termed the ramp response and is represented, where all signals are assumed to be
available as voltages
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Ve = Vi - Vo
Procedure:
a)
b)
c)
d)
e)
f)

Connect the system as per diagram
Include X-Y display and the triangle input
Add the solid connection and set P2 to zero
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1Hz
Apply an input of 5v at 0
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and 5
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EX NO: 8
UNSTABLE SYSTEM
Aim:

To make a study about an unstable system
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An additional separate delay in system can because more marked able to move
further before the drive is reserved
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Characteristics may be obtained by the op-amp circuit where there is a capacitor in
parallel with o/p resistor
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b) Set the error feedback resistor to 100kohm, apply a square 15v at 0
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Result:
Hence the unstable system is studied
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Ve = Vr – Vs
Procedure:
Connect the circuit as per the diagram and set P2 to zero
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Set P2 to zero
Make an x-y display with the tacho-generator output to show the step response
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1mf capacitor
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EX NO: 10
INTRODUCTION TO 3 TERM CONTROL
Aim:

To have an introduction to the 3 term control
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Three Term controller:
A general controller combines integral and derivative actions, with the direct error as
in circuit
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b) Arrange the circuit, where the upper amplifier is connected as a limited
differentiator
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d) Set the test frequency to about 1Hz
e) Since the capacitor is 1mf , a voltage rate of change of 1V/s would gives I=40mA

Result:
Hence the introduction of 3 term control is studied
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Apparatus Required:
Analog unit
Mechanical unit
Power supply
Single amplifier
Theory:
The 3 term controller is a standard and versatile controller much used in
position process temperature and similar control system
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It is important to not that the controller has two amplifier in each path to the pa input
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Use the power amplifier zero to set the output index away from 0
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Turn up p4 and it should be possible to obtain dead beat operation
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EX NO: 12
TRANSIENT VELOCITY FEEDBACK AND DERIVATIVE FEED-FORWARD
Aim:
To study the transient velocity feedback and derivative feed-forward
Apparatus Required:
Analog unit
Mechanical unit
Power supply
Oscilloscope
Theory:
Velocity feedback has a powerful effect in improving transient response but also has
the effect of increasing following error
...

If a capacitor is placed in the velocity feedback line which may in practice be an
operational amplifier the steady component is blocked preventing increased error but
varying component is transmitted velocity feedback
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2 Hz and examine

Result:
Thus the transient velocity and derivative feed forward are studied

EX NO: 13
TRANSFER FUNCTIONS AND CLOSED LOOP FREQUENCY RESPONSE
Aim:

To study the transfer functions and closed loop frequency response principle
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In general the output will differ in magnitude from the input and there will be a phase
difference in the illustration
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Procedure:
A suitable circuit can be plugged up using the amplifier in the control of the analog
board
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Check the relative phase and magnitude are approximately is increased the output will
decreases in magnitude
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8Hz applied
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A more convenient display for phase angle examination is to use the triangular wave
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EX NO: 14
APPLICATION OF FREQUENCY RESPONSE METHOD
Aim:

To study the application of frequency response method
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The error increases due to the steady
component of the feedback
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Set P1 to 100
Adjust P3 to about -/+90 degrees
Open switch 2
Note down the readings

Result:
Thus the application of frequency response method is studied
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Apparatus Required:
1
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Description:
The digital servo fundamental trainer combines hardware and software based
learning environment
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It contains;
A power supply
33-100 Mechanical Units
33-100 Digital Units
USB Interface Unit
Connecting cable
USB Interface unit:
The digital fundamental trainer has a single USB interface unit which is supplied as
part of 81-120 digital units
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Digital unit:
This unit provides a digital interface so that 33-100 mechanical units may be used
to each of the concept of digital control
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The various other servo funds and their concept and usage ate given,
A/D and D/A conversion concept
Motor control
Analogue shaft position sensing
Digital shaft position sensing
Position control loops
Speed control loops
PID control
A/D and D/A Conversion Concept:
A simple A/D system
A
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Motor Controls:
The D/A output and computers used to control the motor voltage
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For investigating the motor response at different drive
Analogue Shaft Position Sensing:
Using the A/D and the input potentiometer using the A/D input shaft potentiometer
with the motor rotating
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Using an incremental encoder with a two phase track
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Position Control Loops:
A positional servo using proportional control and an analogue sensor, positional
servo using proportional control and digital sensor
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Proportional control:
Proportional control with derivative action proportional control with derivative and
integral action,
Result:
Hence familiarized with the digital servo trainer and the fundamentals

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