Team F: MissingNo

Read more about us at our website!

Getting a robot to perform even a simple task is a monumental achievement because so many little things have to all work flawlessly. We emphasize simplicity and robustness in our design, a Connect Four playing robot with few moving parts and closed loop control. The resulting machine was consistent and precise, giving it a winning edge over the competition. The robot can be broken down into three main subsystems: a hopper and magazine, a rack and pinion, and a chip dispenser.

CAD Render of the Entire System

Before the game begins, twenty one Connect Four game pieces are poured into the hopper. A metal rotor inside the hopper agitates the chips until they align with a hole in its base. The aligned chips fall through this hole and stack on top of each other in a vertical tube that serves as the robot’s magazine. The rotor periodically changes direction to prevent jamming. When the magazine is full, the chips block the light from an IR LED. After an infrared sensor in the magazine detects this the robot stops the rotor and signals that it is ready to play.

The Hopper Subsystem

The robot’s chip dispenser is mounted on a set of parallel case hardened steel rods that allow it to move left and right. This motion is controlled using a stepper motor that drives a gear rack and pinion. When it isn’t the robot’s turn, the robot moves its chip dispenser out of the neutral zone surrounding the game board. When it is the robot’s turn, the robot uses the rack and pinion to align the chip dispenser with the column on the game board it chooses to play in. Satisfactory position control may be achieved by counting the stepper motor’s steps, but we close the loop by using an OMRON IR gate sensor. The IR gate is usually blocked by a piece of black acrylic, but narrow slits have been cut out to mark key positions such as the center of game board columns and the base of the hopper. A limit switch at the far left of the gear rack is used as an additional safeguard; it trips to prevent damage if the stepper motor tries to drive past the gear rack’s mechanical limit.

The Rack and Pinion Subsystem

Once the robot is aligned with the column it wishes to play in, the chip dispenser drops a chip into the board. The key to the chip dispenser is a large circular cam at the base of the magazine. This cam is driven by a ¼ scale servo motor, can rotate 180 degrees, and has cutouts on opposite sides that allow it to grasp the bottom chip in the magazine and pull it out. Once the cam has pulled the bottom chip out of the magazine, it deposits the chip in a chute that reorients it and drops it into the game board. The chip dispenser has several sets of IR sensors that follow the chip’s progress. If the cam has failed to remove a game piece from the magazine the IR sensors will detect this and the robot will attempt to retrieve a chip from the magazine again. If the chip becomes stuck in the chute or hung up on the rim of the game board, the robot will shake the chip dispenser with the rack and pinion until the chip is jarred loose.

The Chip Dispenser Subsystem

Our robot is framed with MK T-slotted aluminum. In addition to being stiff and sturdy, T-slotted aluminum is modular. This modularity allows us to easily change the robot’s alignment, or quickly disassemble it for repairs. The non-structural pieces of the robot are made from acrylic because it can be laser cut, allowing us to quickly and easily create complex parts with tight tolerances. Acrylic is brittle and can shatter if too much force is applied, so we manufactured spares of all acrylic components so we could make repairs on short notice.

The Completed Robot

This robot has two processors. The sensors are read and the motors are driven by an Arduino, and a Gumsitx module handles game state and move selection. This configuration allows us to look eight moves ahead during the early game and up to ten moves ahead during the mid and late game. The farther our robot looks ahead, the better our chances of outfoxing our opponent and scoring a win!

Additionally, our robot is Bluetooth capable. Anyone with an Android cell phone and our mobile application can play as or play against our robot.
Our Mobile Phone App

Here's a video of our finished system in action:

Team Members and Roles:
Volkan Erin, ECE ’11:Electrical design, programming, Bluetooth communication, Andriod application
Kaiwen Gu, ECE ‘11: Electrical design, programming, motor control, error correction and detection
Ethan Minogue, ECE ‘11: Mechanical design, fabrication of frame and rack and pinion, website and video
Gary Verma, MechE ’11: Mechanical design, fabrication of chip dispenser and hopper

1 comment:

  1. Was one of your contributors Kaiwen Gu of Seattle, WA? If so, could you put me in contact with him, for a job offer?