Robotics Challenge: Obstacle Course

This repository contains the codebase and documentation for Team 404 (Group 9) in the UCL Robotics and AI Year 1 Challenge. The team members are Morgan, Ian, Xavier, and Helitha.

Our robot, PAXTON, is designed to autonomously traverse a complex obstacle course using a combination of advanced mobility, sensors, and preprogrammed logic. Paxton features:

• Passively transforming wheels to assist in climbing over uneven terrain while being smooth on even surfaces.
• Ackermann steering and differential drive, allowing both agile turning and stable movement.
• A servo-actuated gripper mechanism to hook onto elevated structures such as the lava pit and zipline for obstacle traversal.

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Repository Structure

• Trial run: Component-level test scripts used during early development

• wall following versions: Iterative prototypes of the wall-following algorithm

• control versions: Full control scripts including line following, crossroad handling, and obstacle interaction

• Final_control.ino: The final version of the code deployed to the Arduino for the obstacle course challenge

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How to Operate Paxton

1. Start/Stop:

   • Press the onboard button to start the robot.
   • Press again to stop.
   • Alternatively, a "stop" command received over WiFi will halt the robot.

   These inputs are handled by the button_check() and wifi_check() functions.

2. Navigation Modes:
   The robot operates in four distinct modes, each represented by an integer:

   • MODE_DEAD: Robot is stopped (kill switch activated).
   • MODE_LINE_FOLLOWING: Follows the black line using reflectance sensors.
   • MODE_CROSSROAD_TAKING: Executes a predefined direction at a detected crossroad.
   • MODE_WALL_FOLLOWING: Follows walls using IR distance sensors.

3. Line Following and Crossroads:

   • Crossroads must be preprogrammed in the crossroadDirections[] array (e.g., {LEFT, STRAIGHT, RIGHT}).
   • Functions involved:
     • auto_tracking(): Main PID-based line following.
     • check_crossroad(): Detects forks and crossroads.
     • take_crossroad(): Executes the programmed direction.

4. Wall Following:

   • The wall_following() function uses data from IR sensors to navigate parallel to walls.
   • If the robot encounters a frontal obstacle, turn_right() is invoked to change direction.

5. Obstacle Handling (Lava Pit & Zipline):

   • The robot uses the lifting() function to raise its gripper mechanism and latch onto elevated supports.
   • Once hooked, the robot drives forward to cross the obstacle.

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Core Sensor Functions

• Reflectance_Sensor_Reading():
  Populates sensorValuesFull[] with raw discharge times from each reflectance sensor.
  Applies a threshold to produce binary readings in sensorValuesBinary[]. Both arrays are stored in the same order and direction as the actual robot.

• IR_Sensor_Reading():
  Reads analog values from IR distance sensors and estimates distances (in cm), stored in distanceIR[].

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Motor Control Functions

• go_Advance_4_wheel(int leftFrontSpeed, int rightFrontSpeed, int leftBackSpeed, int rightBackSpeed):
  Controls all four motors individually.

• go_Advance_2_wheel(int leftSpeed, int rightSpeed):
  Controls the left and right side motors together for simpler movement.

• stop_Stop():
  Stops all motors immediately, alternatively either of the previous two functions can be called with speed 0 for all motors.

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Notes

• The PID controller for line following is tuned using:

  • Kp = 30
  • Ki = 0
  • Kd = 0

• Reflectance sensor data is processed in real-time to determine lateral error, which is corrected by PID output.