Motor%20Control%20of%20an%20Oscillating%20Pendulum

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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

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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

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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.

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System Level Block Diagram
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Subsystem Level Block Diagram
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Schedule of Tasks
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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 H-bridge
  automatically based on pendulum location and
  direction
• Construction of our pendulum unit

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H-bridge Hardware
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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

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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.

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H-bridge Microprocessor Code
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Constructed Pendulum
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Goals to be Accomplished

• Complete hardware interface for EMAC to H-bridge
• 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

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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

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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

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PWM Signal

• Current PWM signal 1khz _at_ 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.

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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

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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.

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Software Flowchart
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Revised Schedule of Tasks
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Progress to Date

• Completed motor on/off switch
• Completed H-bridge hardware
• Completed H-bridge software
• Partially completed EMAC to H-bridge interfacing

• Completed Optical sensor timing values and code
• Completed PWM signal code
• Completed pulse width measurement code
• Completed pendulum construction

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Questions?