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.