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Control of a DC motor using BS2 on a Professional Development Board supplied by Parallax Inc.is attempted. All the control modes like P, PD and PID are carried. The Pulse Width Modulated signal is used to drive the motor at desired speeds. This is a part of the Mechatronics course offered by Mechanical and Aerospace Engg. Dept. in Spring 2010.
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IMPLEMENTATION OF A
DC MOTOR SPEED CONTROL
MAE 576 [MECHATRONICS] LAB-3GROUP E
Chembrammel Elavunkal Srinivasan Vishwajeet
University at Buffalo, Mechatronics, Spring 2010
Problem Statement
Creation and calibration of digital sensors - Building and interfacing a digital encoder to quantize and measure angular motions with focus on angular velocity measurement
Interfacing actuators along with necessary drive electronics –specifically examining the interfacing a DC fan motor to the BS2.
Using different control laws to try to achieve desired performance criteria-specifically examining one or more of the following control schemes(on-off ,P, PI,PD,PID);
Quantitatively logging the resulting data to evaluate the actual performance –specifically examining creation of a real time logging interface using Stamp Plot.
Flow Chart
Plant layout
Circuit Diagram
Motor
System implementation
Calibration of optical switch
For white back ground
The binary value of the voltage switched states at 9mmThe range of operation is between 5mm and 9mm
For Black back ground
CALIBRATION OF OPTICAL SWITCH CONTD.
The encoder
Made out of QRB1114 The number of gradations on the
reflecting disc is 24 to get a count of 12 cycles per revolution Gives better RPM / count by the optical
sensor
Measurement Authenticity
PIN HighPWM (255 Duty)
MAX RPM = 6500 +/- 10%MAX VOLT = 10VRPM = 10/12 X 6500 = 5400
Motor drive
The motor is driven using PWM values changing the duty cycle
PWM
RPM
Range of operation
Calibration of PWM drive
PWM drive calibration result
The PWM cannot drive the motor below the 34% duty-cycle, which corresponds to 1.7 volts for the amplifier gain of 2. This corresponds to a cut-off voltage of 3.5V of the motor, and a motor speed of 1000 rpm.
The range of operation of the motor is 34% to 100% of maximum duty cycle of the input signal.
Tachometer testing
12V Input
Low noise
high noise
50 ms sampling time
100 ms sampling time
Tachometer calibration
On-OFF control
1000 ms
100 ms
50 ms
Differential Gap Control
Differential gap
P control
PI Control
PD Control
PID Control
Conclusion
Achieved Encoder Implementation
Familiarized Motor Drive Techniques
PWM with RC with OPAMP with BJT
Understood Open Loop Control methods
Achieved Closed Loop Control Using ON/OFF
ON/OFF with differential gap
PID family
Understood Limitations of Digital Systems
