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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

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Motor Control of an Oscillating Pendulum

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  1. 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

  2. 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

  3. 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.

  4. System Level Block Diagram

  5. Subsystem Level Block Diagram

  6. Schedule of Tasks

  7. 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

  8. H-bridge Hardware

  9. 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

  10. 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.

  11. H-bridge Microprocessor Code

  12. Constructed Pendulum

  13. 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

  14. 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

  15. 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 Optical Sensor

  16. 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.

  17. 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 Pulse Width Measurement

  18. 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.

  19. PWM SIGNAL TO INIT. OSCILLATION OUT OF EQ.? SENSOR NO PULSE WIDTH MEASUREMENT TIMED PULSES OF LENGTH TO BE DETERMINED UPON PULSE WIDTH PRESET SENSOR?? NO MAINTAIN OSCILLATION Software Flowchart

  20. Revised Schedule of Tasks

  21. 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 Progress to Date

  22. Questions?

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