A mini-sumo robot for competition
Ten centimetres square, 500 grams, and every gram spent on traction. The rules are fixed, so the design space is narrow and the trade-offs are clear.
IntermediateTarget budget €220.00From €59.77 with the cheapest option at every step
1.Gear motors chosen for torque× 2
Mini-sumo is a pushing contest, so top speed is worth little and stall torque is worth everything. A high reduction ratio on a small motor beats a fast motor every time. Check that the gearbox itself survives being stalled, since that is the normal operating point of this robot.
Assembly
- Target a reduction ratio above 50:1 and check the published stall torque, not the no-load speed.
- Prefer metal gearboxes, because a plastic final stage strips on the first hard push.
- Mount the motors as low as the rules allow, since the centre of gravity decides who gets flipped.
2.Wheels and tyres× 2
Grip is the whole match. Soft silicone tyres on a rigid hub hold better than moulded plastic wheels, and they need cleaning between rounds because dust from the ring kills the friction coefficient.
3.Edge and opponent sensors
Two sensor jobs with opposite requirements. Downward reflectance sensors find the white border of the ring and must react in a few milliseconds. Forward distance sensors find the opponent and need range rather than speed.
Assembly
- Put one edge sensor at each front corner, so a diagonal approach to the border is still caught.
- Poll the edge sensors in an interrupt, never in the main loop behind the opponent search.
- Test the forward sensors against a black opponent, which is the worst case for infrared reflectance.
4.Battery and driver
A two-cell lithium pack and an H-bridge rated well above the combined stall current. In this class the driver spends most of the match near stall, so its continuous rating is the one that counts and not its peak.
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