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Epitaxy of Wide-Bandgap Semiconductors
Just a normal Smart carHsiang (Jeff) Hsu, Anthony Pope1 December 2016A car that monitors its location and avoids obstacles to get to any given (x,y) point
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ObjectiveGiven a set destination, the car will be able to detect obstacles, maneuver around them, and reach the desired location within 5 cm.
Tasks : Record position of car using IMU sensor and encoderUse ultrasonic sensor to sense obstaclesManeuver around obstaclesUse control loop to drive car to goal
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Design - Steering AssemblyServo Powered ControlServo Horn Connector2 connecting Linkages2 pivoting LinkagesLinkage Caps3
Design - Rear Axle Assembly2 3D-Printed bearings3D-Printed Motor MountMicro DC motor (1:150)2 gears for increased torque (1:2)
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Design - HousingLaser Cut from poplar wood5
Design - Electronics MSP432 MPU 9250 IMU unit Servo motor HC-SR04 Ultrasonic Sensor 6V DC micro motor w/ Encoder 9V battery for DC motor Power 5V DC MyCharge rechargeable battery
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Design - Circuitry7
Servo
PWM
Encoder Power
Sensor Power
Sensor Output Voltage Divider
Common Ground
Breadboard A - Motor Driver from Lab Breadboard B - Servo, Encoder, and Sensor
Design Final Prototype8
Block Diagram9MSP 432Ultrasonic SensorDC MotorEncoderServo MotorRising/Falling edge (digital input) triggers Interrupt and updates positionPWM signal (servo angle)PWM signal through H-BridgeDigital pulse generated and sent to sensor transmitterDigital pulse received and sent to MCUControl Loop is run on timer - updates servo angle based on positionPosition is updated within encoder interrupt based on mathematical modelIMU MagnetometerArduinoSerial Communication
Original Mathematical ModelingEncoder to distance Servo angle to radius of curvatureStraight line position update equationTurning position update equation10
New Mathematical Modeling11
given by IMU magnetometerD given by encoder reading
Control Algorithm Run control loop Move forward until an object is < 60cm Turn until the object is no longer visible Continue turning for x sec Run control on angle to get to Set position
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Control Algorithm
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Results
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Result Back Up Slide15
Future WorksImprove the real-world position mapping accuracyImprove control algorithm tuning (PD, PID)Implement more true Ackermann steering geometryAdd differential gear, or 2 separate motors to eliminate rear wheel slipperageImplement speed control and reverse direction
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Questions?17