Midget Black
Lightweight Sumo Robot
2000/04

Purpose: Entrant for OCAD 2000 Sumo Robot Challenge Midget Black
Controller: Remote control via switches and buttons
Sensors: None
Locomotion: 2 x generic gearbox
2 x 1.5" R/C car tire
Power Supply: 1 x 9 VDC, 1 A, AC adapter
Dimensions: 6.75" x 7.5" x 6.75" (width x depth x height)
Weight: ~9.5 lbs.
Status: 2000/04 - competed in 2000 OCAD Sumo Robot Challenge
2002/05 - dismantled for parts

Purpose

Midget Black (MB) was designed as an autonomous platform for the 2000 OCAD Sumo Robot Challenge. However, due to time constraints, the autonomous circuit wasn't completed in time for the competition date, so a simple, tethered remote control was added and the robot was entered into the Lightweight Class.

MB and controller are shown below.

Body

MB's body is fashioned from 1/4" pressboard/panelling (?) that I found outside my apartment (!) supported by an internal frame of 1/2" x 1/2" pine strips.

Motors and Controller

MB is propelled by a pair of generic gearboxes stuffed with small DC motors, mounted forward-facing at the front of the platform for a differential drive. The wheels were removed from the front assembly of a small R/C car. A pair of casters support the rear of the platform.

The robot is controlled via a tethered remote control having a direction switch (DPDT slider) and power button (NO pushbutton) for each motor.

Taking advantage of the Lightweight Class rules, power is off-board, supplied by a 9 VDC, 1 A adapter.

The robot bottom and controller are shown in the (poor) picture below. The directional switches are on the face of the controller, the power buttons on the top, and the power input jack on the bottom.

Competition

The weight limit for OCAD's Lightweight Class was 10 lbs, so sandbags -- made from sandwich bags -- filled the space originally intended for the autonomous circuitry, bringing MB's weight up to approximately 9.5 lbs.

During the first round (of a best-of-three match), MB had traction problems and was defeated. Before the next round, elastic bands were added around the circumferance of the drive wheels for a quick fix of traction.

The added traction greatly aided MB in the following round against a well-matched opponent, and a slow pushing match ensued. Unfortunately, as MB was shoved sideways at one point during the round, the elastic bands on one wheel came free and entangled the drive axle, and I lost control of that side. MB was then slowly pushed from the ring.

Due to the large number of contestants, the Lightweight Class followed a single-elimination tree, so MB and I were done for the day.

Lessons Learned

  • Differential drive arrangements should have drive wheels positioned along the centre axis of the robot for tight turning and better manoeuvrability.
  • Test robot traction on playing surface, or similar, before competition and adjust tires and/or wheels as necessary.
  • Practice driving the robot before competition!
  • Start designing and building WELL in advance!

    • Acknowledgement

    Thanks to: Sham Dewan for project enthusiasm and working alongside me on a robot of his own; Jason Wright for the motor gearboxes; and Denis Pollic and Devin Ostrom for their advice.

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    © 2002 Andrew O'Malley