lab1
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UNIVERSITI KUALA LUMPUR
Malaysia France Institute
FAB 40803
CONTROL SYSTEM 2LAB REPORT 1 : Speed and Position Control of DC Motor
JAMALUDDIN BIN HASAN
5021321006
MOHD RAFFAR BIN RAMLI
50213210014
Group : M102D1
Course: MECHATRONICS
Lecturer Name: YUSOF BIN MOHD EKHSAN
1. Introduction:
For this experiment, we have observed and analyzed the characteristics of Speed and Position
Control of DC Motor. In this experiment, we have observed the output voltage for actual output
and the input voltage of the desired input for a given situation. Besides that, we also had an
observation on the loads that affect the output voltage.
Figure 1 shows a typical DC motor feedback control system. The input represents the voltage
that will act as a reference signal to the controller. The summing element subtracts the feedback
from the reference signal to form an error signal. The error signal is scaled by a controller and
fed to the motor. Generally, there are two types of DC motor controls.
Speed Control
The speed of the DC motor is used as feedback signal. A typical example is shown in Figure 2.
An optical encoder is attached to the shaft of motor. Its frequency is proportional to the speed of
motor. A frequency-to-voltage converter is employed to convert the speed information into
voltage, ranging from 0 to 5V. This signal is then fed into the controller as feedback signal. By
comparing with the reference voltage, the controller will drive the motor to the desired speed.
Position control
The (rotational) position of the DC motor is used feedback signal. As shown in Figure 3, the DC
motor is coupled with a gearbox to reduce the speed. The encoder is formed by a potentiometer
that varies proportional to the shaft position of the motor. This signal is then fed into the
controller as feedback signal. By comparing with the reference voltage, the controller will drive
the motor to the desired position. Typically, the position varies from 0 to 180o.
2. Objectives:
The main objectives of this experiment / practical are :
i. To study the feedback control using an electronic controller
ii. To implement speed control of DC motor with optical encoder feedback
iii. To implement position control of DC motor with potentiometer feedback
3. Hardware Requirements:
i. Speed/Position Motor Plant Module* (Plant)
ii. PID Controller Module (Controller)
iii. Dual-channel power supply (+12Vdc and –12Vdc)
iv. Oscilloscope
v. Accessories: BNC cables, T-connectors and power connectors
PID Controller Module
Speed/Position Motor Plant Module
Experiment 1-1:
Open Loop Speed Control of a DC Motor
Operation procedure :
1. First of all, all the cables and wires must be disconnected from the hardware module.
2. Then, the power supply is being turn on at the voltage rating to +12Vdc for channel-1,
and –12Vdc for channel-2. The hardware module is being connected to the power supply.
3. The output 1 of the motor plant is being connected to the channel-2 of the oscilloscope.
4. The Input-1 (speed control) of the plant and channel-1 of the oscilloscope is being
connected to the Adjust of the Motor Plant using T-connector. This is the case without
feedback control. The motor should be spinning up as expected.
5. The potentiometer is being adjusted to vary the speed of the motor. Below are the
encoder’s output voltage that has been recorded in this experiment.
Input Voltage (Desired) Output Voltage (Actual)
0V 0V
0.5V 0.1V
1.0V 0.4V
1.5V 0.6V
2.0V 0.9V
2.5V 1.2V
3.0V 1.4V
6. The graph is being plotted for the of output voltage (actual) vs. input voltage (desired).
(The graph is on the next page)
0 0.5 1 1.5 2 2.5 30
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
OUTPUT VOLTAGE VS INPUT VOLTAGE
7. While the motor is running, we have tried to hold the motor shaft and observed the
change in the output voltage.
8. The Input 1 is being disconnected by turning off the motor.
Next, a feedback controller will be inserted into the plant.
DISCUSSION
From the graph that being observed, the encoder output voltage is proportionally increasing to
the input voltage given. This is because the frequency of optical encoder is proportional to the
speed of the motor. On the other hands, we have tried to hold the motor shaft while its running.
Through this observation, we could see that the output voltage is decreasing and the motor shaft
is slowly stopped. This is because the speed of the motor is used as the feedback signal to speed
control DC motor system. This will effect its torque when a load is being added into the system.
Experiment 1-2:
Close Loop Speed Control of a DC Motor with Optical Encoder Feedback
Operation procedure :
1. Firstly, the power supply is being connected to the PID controller.
2. The potentiometer Rp2 is being set to minimum (counter-clockwise), Rd to minimum
(counterclockwise), and Ri to maximum (clockwise).
3. The Adjust of the plant is been connected to the Input of the PID controller.
4. The Output-1 of the plant is being connected to Feedback of the controller.
5. Next, the output of the controller is connected to Input-1 of the plant. The motor should
be spinning up as expected.
6. The potentiometer (VAR) of motor plant is being adjusted to approximately 1.5V.
7. First, select P-controller by setting the PROP of the controller (dip switch = 1) to“ON”.
Other switches should be set “OFF”.
8. The value of potentiometer Rp2 (varying Kp) is being adjusted to get an optimum
response.
9. The speed of the motor is being varied by adjusting the potentiometer VAR and the
changes in output is being observed.
10. Next, the PID controller is being selected by setting the PROP, DIFF and INTG of the
controller to “ON”.
11. Slowly the respective potentiometers Rp2, Rd, and Ri is being varie to get an optimum
output response (minimum steady-state error and less oscillation).
12. The speed of the motor is being varied and the changes in output is been observed.
13. With the optimum response, the encoder’s output voltage for input voltage of [0V, 0.5V,
1.0V, 1.5V, 2.0V, 2.5V, 3.0V] is being recorded.
14. The graph is being plotted for the of output voltage (actual) vs. input voltage (desired).
0 0.5 1 1.5 2 2.5 30
0.5
1
1.5
2
2.5
3
3.5
Close Loop Speed Control of DC Motor with Optical Encoder Feedback
Channel 1, Volt
Channel 2, Volt
Channel 1(Input) Channel 2(Output)
0 V 0.8V
0.5 V 1.2V
1.0 V 1.6V
1.5 V 2.0V
2.0 V 2.4V
2.5 V 2.8V
3.0 V 3.0V
15. While the motor is running, we have tried to hold the motor shaft and observed the
change in the output voltage.
16. The experimental results for open loop and close loop speed controls is being compared.
DISCUSSION
From the graph that being observed, the close loop speed control of DC motor by using the optical
encoder feedback is constant and proportionally increase for both channel 1 and channel 2. Speed
Control of DC Motor with Optical Encoder Feedback can be maintained constant by adjusting
the motor terminal voltage as the load torque changes. For example, load torque increases, speed
decreases, speed error end increases, results in control signal Vc. A closed loop controller can be
an analog circuit, a digital circuit made of logic gates, or a microcontroller. In a closed loop
system, a microcontroller will have two main tasks.
a) Constantly adjust the average power delivered to the motor to reach the required velocity.
b) Precisely calculate the position/angle of the motor’s output shaft.
Experiment 1-3:
Open Loop Position Control of a DC Motor
Operation procedure :
1. First of all, all the cables/wires is being disconnected from the hardware module.
2. Then, the power supply is being turn on at the voltage rating to +12Vdc for channel-1,
and –12Vdc for channel-2. The hardware module is being connected to the power supply.
3. Output-1 of the motor plant is been connected to channel-2 of the oscilloscope.
4. The Adjust of the Motor Plant is being connected to the Input-2 (position control) of the
plant and channel-1 of the oscilloscope using T-connector. This is the case without
feedback control.
5. The potentiometer (VAR) is being adjusted to vary the position of the motor.
6. Turn off the motor.
Next, a feedback controller will be inserted into the plant.
Result:
Servo motor rotates to the left Output waveform of Servo motor when it rotates to the
left
Servo motor rotates to the Right Output waveform of Servo motor when it rotates to the
right.
Observation:
From the experiment that have been done, we should able to see that the DC motor rotate from 0 to
180 degree once the potentiometer is varied. We found that that if the value of potentiometer is
increased, the motor rotates anticlockwise for 180 degrees, while if the potentiometer is
decreased, the motor rotates clockwise for 180 degrees.
Conclusion:
Unfortunately, in our experiment, we found that sometimes, when then potentiometer is varied
they were no difference in motor speed. Therefore, we assumed that the module has a problems
and within a few minutes the plant module has explode. This causes a major problem to us
because we could not continue further on this experiment.
Experiment 1-4:
Close Loop Position Control of a DC Motor with Potentiometer Feedback
Operation procedure :
1. Firstly, the power supply is being connected to the PID controller.
2. The potentiometer Rp2 is being set to minimum (counter-clockwise), Rd to minimum
(counterclockwise), and Ri to maximum (clockwise).
3. Next the Adjust of the plant is connected to Input of the PID controller.
4. Output-2 of the plant is being connected to Feedback of the controller.
5. The Output of the controller is connected to Input-2 of the plant.
6. The potentiometer (VAR) of motor plant is being adjusted to approximately 1.5V.
7. First, the P-controller is being selected by setting the PROP of the controller (dip switch
= 1) to “ON”. Other switches should be set “OFF”.
8. The value of potentiometer Rp2 (varying Kp) is being adjusted to get an optimum
response.
9. The position of the motor is being vary by adjusting the potentiometer VAR and the
changes in output is being observed. Repeat step 8 if necessary.
10. Next, the PID controller is being selected by setting the PROP, DIFF and INTG of the
controller to “ON”.
11. Slowly the respective potentiometers Rp2, Rd, and Ri is being vary to get an optimum
output response (minimum steady-state error and less oscillation).
12. The position of the motor is being vary and the changes in output is being observed.
Repeat step 11 if necessary.
13. With the optimum response, the encoder’s output voltage for input voltage of [0V, 0.5V,
1.0V, 1.5V, 2.0V, 2.5V, 3.0V] is being recorded.
14. Compare the experimental results for open loop and close loop speed controls.
Unfortunately, for this experiment, we cannot proceed and observed its response because of the
hardware problem that has been occur in previous experiment. This have effect the result for this
experiment and we cannot measure its output.
4. CONCLUSION
As the conclusion for this experiment, we could able see the different results that have been
produced using the open loop and close loop system of the speed and position control of the DC
motor. By using the open loop speed control, we can see that the encoder output voltage is
proportionally increasing to the input voltage given. Meanwhile, for the close loop speed control of a DC
motor using the optical encoder feedback, the output is constant and proportionally increased for both
channel 1 and channel 2. The applications of PID controller benefit the system, whereby the
system can be reduced in terms of steady state error, overshoot and transient response.
Unfortunately, for the experiments 1.3 and 1.4 we couldn’t able to see the result because of the
malfunction of plant module and it cause a major problem for us. Initially, the motor speed was
just increase due to the potentiometer variation.
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