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Cumulative Design Review Team 22: Driver Assist

Cumulative Design Review Team 22: Driver Assist. Primary Solution. Our solution is to create a joystick that mechanically controls the steering wheel, brakes, and throttle The joystick will pivot horizontally allowing the driver to turn left and right. Block Diagram. CDR Deliverables.

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Cumulative Design Review Team 22: Driver Assist

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  1. Cumulative Design ReviewTeam 22:Driver Assist

  2. Primary Solution • Our solution is to create a joystick that mechanically controls the steering wheel, brakes, and throttle • The joystick will pivot horizontally allowing the driver to turn left and right.

  3. Block Diagram

  4. CDR Deliverables Steve Cook: • 3D print top half of the joystick • Install hand brake and throttle Sam Burke: • Implementation of gear train • Mount gear train to drive steering wheel • 3-D printed gears Andrew Klinkowski: • Full control over DC motor at required spec of 1.5rps • Aid in the 3D design of joystick Qingchuan Wu: • Charger optimization increased to 85% • Power supply rails well regulated

  5. Old Joystick Design • Heavy • Loose tension on brake and throttle • Throttle felt small and uneasy to use

  6. New Joystick Design

  7. Brake Prototype • The brake stops the car and control reverse in the video game. • Includes: potentiometer, wire, and hand brake • Potentiometer sends a voltage reference between 0.58V to 4.5V depending on depression of hand brake • Higher voltage corresponds to harder braking • 10k Potentiometer is used to reduce power and maximize voltage reference swing.

  8. Throttle Voltage Mapping • The video game controller maps 0 acceleration at 3.92V and increase until it hits max acceleration at 0V. • The throttle used maps 0.886V before acceleration and 4.33V for max acceleration. • A circuit was designed to mapped the throttles .886V to the games input of 3.92V. • And to take the throttles max acceleration voltage 4.33V and map it to 0V.

  9. Voltage Mapping Schematic

  10. Motor Driver • The driver amplifies the ATmega32’s outputs to be used by the motor

  11. Basic Motor Phase control U/V phase excitation A’ = 0 B’= 1 A = 0 B = 1 Flow of current

  12. Power – Battery Charger Requirement • Charge external 12V NiMH battery from the cigarette port. 11- 14V input • Limit Charging current below 4A • Limit Charging voltage below 16V

  13. Battery Charger • Used to charge external battery pack from 12V car battery

  14. Battery Charger Features • Thermal Feedback Shutdown • Input Overload Protection • Input Reverse Polarity Protection • Output short circuit <20s • Charging Completion Indication • Adjustable output

  15. Power – Battery Charger Result

  16. Battery charger result • 80% efficiency at 14V and 2A • Peak output current 6.4A at 8V • Requires heat sink to optimize • Feedback control needs adjustment

  17. Power Supply

  18. Power – Power Supply • Requirement • Provide regulated supply voltage 7.5V for controller • Provide 2 isolated voltages 12V for driving Mosfet • Implementations • Forward converter • PI control on 5V output • Transformer and mutual inductors for cross regulation.

  19. Power – Power Supply • Requirement • Provide regulated supply voltage 7.5V for controller • Provide 2 isolated voltages 12V for driving Mosfet • Implementations • Flyback converter • PI control on 7.5V output • Mutual inductance regulation on 12V outputs • Current transformer sensing

  20. Power – Power Supply Result • Green: 100 ohm Red 20 ohm Blue 24 ohm

  21. Motor Selection Current Motor Specifications • Speed: 66.666rps • Torque: .125Nm • Brushless DC Requirements to Control Steering Wheel • Speed: ~1.5rps • Torque: 6Nm

  22. Gearing • A gearing ratio of 54 will allow us to have the outputted torque required, while staying close to the required rps. • .125Nm * 54 = 6.75Nm • Speed = (4000rpm/60)/54 = 1.23457 rps

  23. Gear Train Design • To design a gear train with a 54:1 ratio 4 stages where used. • Stages 1-3 had a 3:1 ratio and stage 4 included a 2:1 ratio • Stages 1-3 were created using a gears with 60 and 20 teeth • Stage 4 was created with gears having 130 and 60 teeth

  24. Gear Train Design

  25. Gear Train Implementation

  26. FDR Deliverables Steve Cook: • 3D print bottom half of joystick • Install top and bottom half together • Joystick will have full control over gas/brake and steering wheel Sam Burke: • Mount motor to gear train • Design base for user to sit in • Stabilize gear train Andrew Klinkowski: • Full control over DC motor at required spec of 1.5rps • Process Hall Effect Sensor Data • Drive Motor from PIC controller to PWM stall current Qingchuan Wu: • Charger optimization increased to 85% • Power supply rails well regulated • Complete power system

  27. Motor Phase control- Buck (CDR) U/V phase excitation A’ = PWM B’= 1 A = 0 B = 1 Flow of current Normal PWM on PWM off

  28. Motor Phase control- Boost (CDR) U/V phase excitation A’ = 0 B’= 1 A = PWM B = 1 Flow of current Normal PWM on PWM off

  29. Power – Battery Charger Result

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