Control Lab experiment EEP301, 5th sem electrical engineering @ IIT Delhi

1. EEL301LAB REPORT
DC MODULAR SYSTEM
11/5/2010
Group-3
AKSHAY GUPTA
AASTHA DUA
INDRA BHUSHAN
KUMAR SAURAV
MEHUL MITTAL
UMANG GUPTA
VIVEK MANGAL

2. DC MODULAR SERVO MOTOR
Assignment 6
Aim: We study the working of the pre-amplifier, PA150C and find out its characteristics.
Theory: This Pre-amplifier has two signal inputs and two outputs. If there is a positive voltage
on either of its inputs then one of its outputs becomes positive. Also if one of the output
becomes negative then the other output becomes positive.
Observation Table
Fig1. Graph Of V0(3) v/s Vi.
0
2
4
6
8
10
12
-1500 -1000 -500 0 500 1000 1500
Series1

3. Fig2. Graph of V0(4) vs Vi.
Fig3. Graph of V0(4-3) vs Vi.
0
2
4
6
8
10
12
-1500 -1000 -500 0 500 1000 1500
Series1
-15
-10
-5
0
5
10
15
-1500 -1000 -500 0 500 1000 1500
Series1

4. Calculations
From Fig3 we find the gain of the pre-amplifier by finding out the slope of the straight part of
the curve.
Slope 1= 1000*(0.59+0.621)/-(59+58.5)= 10.306
Slope 2=1000*(1.706+1.626)/-(166+155.3)=10.6713
Gain= 10.488
Assignment 6.2
Aim: To utilize the error signal output of the operational amplifier to drive the output
potentiometer via the pre-amplifier and motor.
Theory: When we rotate the input potentiometer then the output potentiometer cursor should
rotate to an angle nearly equal to that. If the output cursor stops before arriving at the set
position then the system is tolerant to an error and the motor will not respond till the error
exceeds a value.
Observations
Input Output Misalignment
0 5 5
45 42.5 2.5
90 77.5 12.5
135 117.5 17.5
180 220 40
270 260 30
330 313.75 16.25
360 347 13

5. Fig 4. Graph of Misalignment v/s input.
Assignment 7
Aim: To show that the improvement that results from closing the loop using feedback instead
of using an open loop.
Theory: When we use a feedback loop, we compare the actual speed with the required speed.
This produces an error signal to actuate the servo amplifier output so that the motor maintains
a more constant speed.
In this experiment, we simply feed back a signal proportional to the speed, using the
tachogenerator. We then compare it with a reference signal of opposite polarity, so that the
sum will produce an input signal of the required value.
Observations
Ref. Voltage(Volts) Tacho Voltage(Volts) Error Voltage(Volts) Speed (r/min)
-0.619 0.370 0.122 130
-2.434 1.83 0.478 660
-4.03 3.09 0.844 1120
-5.88 4.51 1.275 1640
-7.41 5.69 1.632 2060
-8.85 6.80 1.962 2470
0
5
10
15
20
25
30
35
40
45
0 50 100 150 200 250 300 350 400
Series1

6. Fig 5. Graph of Error Voltage v/s Speed.
Now to find out the effects of loading on speed we use the magnetic break as a load.
Brake Position Speed Error
0 2080 1.626
1 2080 1.626
2 2080 1.644
3 2040 1.738
5 1830 2.316
6 1640 2.82
7 1490 3.233
8 1330 3.73
9 1100 4.31
10 860 5.00
0
0.5
1
1.5
2
2.5
0 500 1000 1500 2000 2500 3000
Series1

7. Fig 6. Graph of Error voltage v/s Brake Position.
Fig 7. Graph of Speed v/s Breal Position.
Now we find the values for a different gain.
Brake Position Ref. Volts Error Volts Tacho-generator
Volts
Speed (r/min)
0 -3.606 0.728 2.75 1000
3 -3.606 0.793 2.69 970
4 -3.606 0.861 2.62 950
0
1
2
3
4
5
6
0 2 4 6 8 10 12
Series1
0
500
1000
1500
2000
2500
0 2 4 6 8 10 12
Series1

8. 6 -3.606 0.971 2.61 910
8 -3.606 1.060 2.42 880
9 -3.606 1.146 2.33 840
10 -3.606 1.243 2.24 810
Fig 8. Error volts v/s Brake
Fig 9. Speed v/s Brake
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 2 4 6 8 10 12
Series1
0
200
400
600
800
1000
1200
0 2 4 6 8 10 12
Series1

9. Now,
We have to find the reference Voltage at which the motor just stops.
We find this value by slowly tuning the knob and observing the motor.
Vref=-320.1 mV
N=1010 rpm.
Assignment 7.3
Aim: To assemble a simple reversible speed control system.
Theory: Because of its importance in speed control, the tacho-generator has become an
integral part of the motor.
Observations
Forward
Brake Position Tacho generator
Volts
Ref. Volts Error Volts Speed (r/min)
0 2.76 -3.145 0.95 1000
5 2.74 -3.153 0.95 990
8 2.72 -3.147 0.95 980
10 2.35 -3.147 0.95 850
Backward
Brake Position Tacho generator
Volts
Ref. Volts Error Volts Speed (r/min)
0 -2.78 2.542 1.697 1000
5 -2.75 2.546 1.697 990
8 -2.73 2.548 1.697 990
10 -2.31 2.548 1.697 840

10. Assignment 8
Aim: To familiarize ourselves with the term deadband and to investigate the effect of gain on
deadband and step response.
Theory: The deadband is the minimum input signal required to get a system response. So
knowing the error factor we can relate the signal input to the degree of misalignment that can
occur before there is a corrective response.
Observations
Gain Rotation Clockwise Rotation Anti-
clockwise
Total deadband
1 -55 80 135
2 -95 120 215
3 -70 100 170
4 -65 95 160
5 -60 85 145
Fig 10. Total deadband v/s Gain
0
50
100
150
200
250
0 1 2 3 4 5 6
Series1