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.
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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
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.
Goals Accomplished to Date n Motor control switch to allow user to switch motor on/off n H-bridge hardware to allow motor to turn in both directions n H-bridge microprocessor code to switch H- bridge automatically based on pendulum location and direction n Construction of our pendulum unit
n The H-bridge uses (4) N-Channel Power Transistors n The H-bridge operates on a supply voltage of +15V DC n The H-bridge ideally accepts input voltages of 0V or +15V DC n Finding the appropriate transistors to power our motor was difficult
H-bridge Microprocessor Code n The H-bridge will switch motor burst direction every time the pendulum passes equilibrium. n Once the direction is switched, a burst will immediately be sent. n The H-bridge code will be called by the sensor input interrupt.
Goals to be Accomplished n Complete hardware interface for EMAC to H- bridge n Calculate timing for motor burst lengths to be called by H-bridge code n Create timing code that will burst the motor with increasing lengths as pendulum period increases n Compile H-bridge code with all other project codes
Goals Accomplished to Date n Optical Sensor with desired switching times and code to read the sensors through EMAC. n PWM Signal Code to initiate oscillation. n Pulse Width Measurement Code to control speed of oscillation n Design of Pendulum Structure
Optical Sensor n Two sensors to be used –One at equilibrium –Another at desired swing of oscillation n RF = 200 to limit current to 20 mA –Enough current to transmit infrared signal –Not enough current to damage Optical Sensor n 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 n Current PWM signal = 1khz @ 33% Duty cycle. –Actual frequency will be much smaller. n 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 n 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 n Construct code for the timed pulses of constant length in order to sustain oscillation beyond the equilibrium sensor. n Construct code to adjust the length of the timed pulses which will be dependent upon the pulse width measurement. n Construct code to maintain oscillation once the predefined height sensor is reached.
Software Flowchart PWM SIGNAL TO INIT. OSCILLATION PULSE WIDTH MEASUREMENT TIMED PULSES OF LENGTH TO BE DETERMINED UPON PULSE WIDTH OUT OF EQ.? SENSO R PRESE T SENSO R?? MAINTAIN OSCILLATION NO
Progress to Date n Completed motor on/off switch n Completed H-bridge hardware n Completed H-bridge software n Partially completed EMAC to H-bridge interfacing n Completed Optical sensor timing values and code n Completed PWM signal code n Completed pulse width measurement code n Completed pendulum construction