Transcript Motor Control of an Oscillating Pendulum

Motor Control of an Oscillating
Pendulum
Nick Myers and Chirag Patel
March 9, 2004
Advised by: Dr. James Irwin and Mr. Jose Sanchez
Bradley University Department of Electrical Engineering
and Technology
Presentation Overview
•Project Objectives
•System Block Diagrams
•Original Schedule of Tasks to be completed
•Work Completed (Nick)
•Work to be Completed (Nick)
•Work Completed (Chirag)
•Work to be Completed (Chirag)
•Revised Schedule of Tasks to be completed
•Summary of Progress
•Questions
Objectives
To initialize the oscillation of a weighted
pendulum using microprocessor
controlled motor bursts.
To oscillate the pendulum to a
predefined angle and, using optical
sensor outputs, maintain the angle of
oscillation.
System Level Block Diagram
User Input: Start/Stop
EMAC Motor Control and Sensor
Reading
Pendulum Oscillation
Angle
Subsystem Level Block Diagram
User Input
8051 MicroController
Board
EMAC to Hardware
Interface
DC Motor
Pendulum Arm
Pendulum Swing
Angle
Motor Power Supply
Feedback
Optical Sensors
Schedule of Tasks
WEEK
SCHEDULED TASKS
1
Code to start/stop oscillation, output motor bursts (PWM), read the sensors
Design and build pendulum structure, start H-Bridge
2
Code to use sensor FB to change duty cycle to change for increasing speed.
Design and build H-Bridge
3
Code to use sensor FB to change duty cycle to change for increasing speed.
Design and build power supply circuit.
4
Code to use sensor FB to change duty cycle to change for increasing speed.
Design and build power supply circuit.
5
Code to use sensor FB to change duty cycle to change for increasing speed.
Design and build power supply circuit.
6
Code to use sensor FB to change duty cycle to change for increasing speed.
Design and build power supply circuit, release the charge in sync with EMAC
7
Code to read the predefined height sensor and keep oscillation steady.
Design and build power supply circuit, release the charge in sync with EMAC
8 | 9 Troubleshooting
10 | 11 Project Modifications: Addition of Multiple Sensors
12 | 13 Prepare for student expo and project presentation
Goals Accomplished to Date




Motor control switch to allow user to switch
motor on/off
H-bridge hardware to allow motor to turn in
both directions
H-bridge microprocessor code to switch Hbridge automatically based on pendulum
location and direction
Construction of our pendulum unit
H-bridge Hardware
A
1
0
B
0
1
C
0
1
D
1
0
Motor Direction
Forward
Backward
H-bridge Hardware




The H-bridge uses (4) N-Channel Power
Transistors
The H-bridge operates on a supply voltage of
+15V DC
The H-bridge ideally accepts input voltages of
0V or +15V DC
Finding the appropriate transistors to power
our motor was difficult
H-bridge Microprocessor Code



The H-bridge will switch motor burst direction
every time the pendulum passes equilibrium.
Once the direction is switched, a burst will
immediately be sent.
The H-bridge code will be called by the
sensor input interrupt.
H-bridge Microprocessor Code
Initialization of H-bridge by
setting 31H to 1
Yes
Output P1.4
Set 31H to 0
31H=1?
No
Output P1.5
Set 31H to 1
Constructed Pendulum
Goals to be Accomplished




Complete hardware interface for EMAC to Hbridge
Calculate timing for motor burst lengths to be
called by H-bridge code
Create timing code that will burst the motor
with increasing lengths as pendulum period
increases
Compile H-bridge code with all other project
codes
Goals Accomplished to Date

Optical Sensor with desired switching times and code
to read the sensors through EMAC.

PWM Signal Code to initiate oscillation.

Pulse Width Measurement Code to control speed of
oscillation

Design of Pendulum Structure
Optical Sensor

Two sensors to be used
– One at equilibrium
– Another at desired swing of
oscillation

RF = 200 to limit current to 20 mA
– Enough current to transmit infrared
signal
– Not enough current to damage
Optical Sensor

R1 = 4700 to account for desired
on/off switching times
– ON Switching Time
• 8us * 1.7 = 14.4 us
– OFF Switching Time
• 50us * 1.6 = 80us
PWM Signal

Current PWM signal = 1khz
@ 33% Duty cycle.
– Actual frequency will be
much smaller.

PWM signal will be used to
initiate the oscillation of the
pendulum.
– Once pendulum is beyond
the equilibrium sensor,
timed pulse signals will be
used to oscillate the
pendulum.
Pulse Width Measurement

Pulse Width Measurement
code used to measure length
of time sensor is obstructed
by pendulum.
– This time will be used to
control the length of the
pulse sent to motor to
control oscillation of
pendulum.
• Faster oscillation =
Smaller pulses
• Slower oscillation =
Larger pulses
Goals to be Accomplished

Construct code for the timed pulses of constant length in order to
sustain oscillation beyond the equilibrium sensor.

Construct code to adjust the length of the timed pulses which will
be dependent upon the pulse width measurement.

Construct code to maintain oscillation once the predefined height
sensor is reached.
Software Flowchart
PWM SIGNAL TO
INIT. OSCILLATION
OUT
OF
EQ.?
SENSO
R
NO
PULSE WIDTH
MEASUREMENT
TIMED PULSES OF LENGTH
TO BE DETERMINED UPON
PULSE WIDTH
PRESE
T
SENSO
R??
MAINTAIN
OSCILLATION
NO
Revised Schedule of Tasks
WEEK
SCHEDULED TASKS
7
Code to output pulses of constant length.
Complete interfacing of EMAC and H-Bridge
8
Code to adjust the length of the pulses, dependent upon speed of oscillation.
Design and build power supply circuit to hold/release charge.
9
Code to adjust the length of the pulses, dependent upon speed of oscillation.
Design and build power supply circuit to hold/release charge.
10
Code to maintain speed of oscillation once predefined sensor is reached
Keypad/LCD/Initialization Code
11
Code to maintain speed of oscillation once predefined sensor is reached.
Compile all code and Troubleshoot.
12
Troubleshoot/Prepare for student expo
Troubleshoot/Prepare for student expo
13
Prepare for student expo and project presentation
Prepare for student expo and project presentation
Progress to Date

Completed motor on/off
switch

Completed Optical sensor
timing values and code

Completed H-bridge
hardware

Completed PWM signal code

Completed pulse width
measurement code

Completed pendulum
construction


Completed H-bridge
software
Partially completed EMAC to
H-bridge interfacing
Questions?