| The Robot with a "Wedgie"! | 1997-99 |
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Wedgie got his name back when he was designed as a demonstration sumo wrestling robot for the 1996/97 Mechatronics course at the University of Utah when I was doing my MS studies. When I first designed Wedgie, he had a "wedge" shaped pushing mechanism for sumo wrestling, that's why he's called Wedgie. Wedgie was a popular robot, even after I redesigned him for a soccer event by removing the wedge mechanism and replacing it with a gripper.
Wedgie's brain is a MIT Handy Board microcontroller. The MIT Handy Board is a popular controller at the University of Utah, Department of Mechanical Engineering. The students of Mechatronics use the Handy Board for their autonomous robot projects. Since Wedgie was a demonstration robot for the class, using the Handy Board seemed appropriate. The Handy Board has 7 analog input channels, 4 DC motor driver ports, 9 digital input channels, and an LCD display, etc. The Handy Board is user friendly and can easily be programmed by Interactive C. Interactive C is similar to C with built-in functions to control motor ports, I/O ports, LCD screen, buzzer, etc. on the Handy Board. There's a lot of documentation available over the internet relating to the Handy Board! The Handy Board is very robust and was able to stand the abuse of college engineering students year-after-year.
Wedgie is packed with sensors. The robot has six IR light detectors located above his brain. A custom machined sensor mount was made for all six IR detectors. Wedgie has a wide field of view when it comes to finding and tracking an IR light source. For object detection and avoidance, Wedgie is equipped with a Polaroid sonar module. The sonar transducer is mounted directly in front of his body. For orientation, Wedgie uses a Vector 2X digital compass. That way, he'll never get lost going to Granny's house. Optional sensors such as IR trip sensors are used when his gripper mechanism is attached (see figure below). Wedgie also has a few tilt sensors to detect inclination.
Wedgie uses a differential drive system for locomotion. Two Tamiya Hobby's DC motor gearbox sets make up his drive system. A caster wheel supports his rear end. The gearbox sets can be purchased from Edmund Scientifics or Mondotronics. Tamiya Hobby offers a wide variety of motor gearbox sets for toys and robotics. For Wedgie, I chose the High Power Gearbox with a gear ratio of 64.8-to-1. The ratio provided enough torque to propel him around at a moderate speed. Too fast of a speed would have caused Wedgie to become unstable; hence uncontrollable. The Handy Board's DC motor output ports were only capable of delivering 600 mAmps of current. However, the DC motors on Wedgie required at least 1.5 to 2 Amps of current. A separate motor driver circuit was used to provide the required power. A schematic of the motor driver circuit including notes can be found on the MIT Handy Board web site. The motor driver circuit has been used by Mechatronics students for over a year now and has proven to be robust.
Wedgie's body is made of aluminum and plastic. The main platform was machined from an 1/8" sheet of aluminum. The battery holder, sensor mounts, and Handy Board carriage was machined from acrylic and HDPE. Wheels were machined from aluminum with rubber tires from a local hobby store. An optional gripper mechanism can be attached to the front of Wedgie for tasks such as picking up trash or playing ball. The gripper mechanism is controlled by two hobby servos giving Wedgie a two degrees-of-freedom hand. All of the vital components such as his brain and sensors are encased in protective enclosures. Wedgie was designed to survive a drop from a building and any abuse Mechatronics students can dish out!
Wedgie has been known to play soccer, sumo wrestle, follow light, avoid objects, pick up trash, chase little kids around during elementary school demonstrations, etc. He's tough, smart and fun to watch.