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Project Presentation Team 8

Project Presentation Team 8 . Michael Mui Sanjay Krishnan. Hardware – Mechanical . Wooden Platform Dimensions: 600 mm x 100mm platform, 80 mm from the bottom of the chassis. Single piece of wood spans the car and forms the sensor boom and the PCB mounting platform Sensor boom

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Project Presentation Team 8

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  1. Project Presentation Team 8 Michael Mui Sanjay Krishnan

  2. Hardware – Mechanical • Wooden Platform • Dimensions: 600 mm x 100mm platform, 80 mm from the bottom of the chassis. • Single piece of wood spans the car and forms the sensor boom and the PCB mounting platform • Sensor boom • Extension of the wooden platform • Sensors dimensions: 190mm lead front wheels, 50 mm from the ground, 3 Sensors @ 100 mm apart • Wheels • 52 mm rims, rubber, treaded

  3. Hardware - Electronic • Safety • Plastic connectors to disconnect the motor drive circuitry • Diodes tied to VCC on ADC circuit • Emergency stop switch with a heavy wooden extension that trips on impact • Modular design • Separate power supply board and sensor/motor drive board • Custom power supply unit, regulated boost converter with various output voltages • Molex twisted pair sensor wiring for noise and extensibility considerations • Extended from 2 sensors to 3 with ease • Also allowed for easily extending power to various components from the PSU

  4. Hardware - Sensors Lateral Position in cm Estimated Lateral Position in cm

  5. Hardware – Sensors Actual ADC readings before estimate • Circuitry • Un-biased, Un-buffered, 68k,680k inverting amplifier with diode rectifier • Issues • Right sensor had significantly more noise than the other sensors

  6. Software - Overview Sensor Reading Steering Planning Velocity Planning Calibration while(true) Saturation Servo steering_control Global Variables Motor Drive motor_control RTOS IRQ @ 50 kHZ

  7. Software - Details • Lookup table for decision making • Software determines control strategy based on sensor readings • All integer arithmetic • Efficient memory usage • 4 sec auto-calibration mode • Mode locks down a reference input for the feedback loop

  8. Control – Overview • Lookup table • Lookup table based on the 3 sensor readings to determine the state of the car , 10 cases • Proportional Control • Various forms of proportional control based on the lookup table • Issues with derivative/integral control • Calibration steady state error • Velocity Planning • Slowing down on crossings , steps and oscillations • Lost track slow down

  9. Control – Lookup table if center_value < 1cm of reference: continue current action else if between left and right sensors: proportional control to the center value with constant kp if reasonably straight: start acceleration timer accelerate else hold constant speed else if step consider even small values of sensor readings valid rail left or right, trimming down to the center with contstantkp/2 lower constant speed else if crossing slow drasitically, continue current action else if lost shutoff motor velocity = function_of_turn_angle(steering_input)//subject to constraints set above

  10. Gain Constants • Determined largely through trial and error Steering proportional constant kp: 4.9015 radians/meter Steering proportional constant step kp: 2.4507 radians/meter Sensor noise mean: .12 cm Determining a crossing: All sensors read closer than 6cm at the same time Determining a step: L/R read a value greater than the noise mean and the other two read values roughly 2 stdevs under the mean.

  11. Step response Each tick .02 s

  12. Contributions • Michael: mechanical design, software, velocity control • Sanjay: sensor circuitry, lookup table, motor drive • Yashraj: Power Supply Circuit

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