Quidditch Robot

Building and coding a robot to track and retrieve balls in a game of "quidditch" (Video).

Authors

• Carter Barnett
• Jonathan Cochran
• Bryson Jaipean
• Cameron Retzlaff

Background

• Timeline of 5 weeks to build, wire, program, and successfully test a “quidditch” robot
• "Quidditch" is defined as:
  • Rotate the IR Beacon to assign the robot to Team 1 or Team 2
  • If the robot bumps into an obstruction it must recover to keep playing
  • Actively track and catch balls then deposit them on the respective side
  • If a yellow ball, or “snitch,” enters the field, the robot must prioritize catching that ball
  • Must not intentionally damage other robots

Directory

• Algorithm
  • Tracking
  • Retrieval
• PID Control
• Robot Design

Algorithm

Tracking

• Radio transmits position of robot, balls, and other robots on the field
• Designed state machine algorithm to automatically focus robot on the closest ball
• Filters balls that are already retrieved
• Developed algorithm to prioritize capturing a ball within the “golden snitch” hue range
  • Capturing this ball "wins" the game

Tracking Diagram

Retrieval

• Oriented robot and balls in same reference frame with global and robot (local) reference frames
• Determined angle between the robot and ball in the robot’s reference frame
• Developed algorithm to reorient robot's approach angle as it neared a ball
• Detected if ball within capture zone with IR distance sensors
• Closed gate and retrieved ball to home side if ball in capture zone

Retrieval Diagram

PID Control

• Required to rotate a DC motor to a precise angle
• Tuned with Ziegler-Nichols method
• Selected PD controller due to fastest rise time and no overshoot
• Resulted in reaching desired angle quickly

PI

PD

PID

"No Overshoot" PID

Robot Design

• Aluminum body frame, two driving wheels, and an unpowered rear drifting wheel
• Capture balls with gate created from 3D printed parts and popsicle sticks
  • Powered by a standard servo motor
• Detect if a ball is within the gate with IR distance sensors
• Impact with obstacles detected by limit switches attached to front and back bumpers
• Detect IR beacon with an IR frequency sensor, rotated with a DC motor
  • Fixed on the front of the robot
• Detect robot with camera above playing field via a unique marker atop the robot
• Broadcast position on playing field via radio to local radio chip on the robot's Arduino board

Robot Front View

Robot Side View

Arduino Wiring

3ft x 3ft Playing Field