Drivetrains
Choose tank, mecanum, omni, or swerve from field requirements, traction, packaging, and testing capacity.
A moves the and supports the carried by it. Test how reliably it reaches scoring positions with all mechanisms installed.
Drivetrain selection
| Type | Movement | Main tradeoff |
|---|---|---|
| Tank or skid-steer | Forward, reverse, and turning | Strong traction can also resist turning through scrub |
| Forward, sideways, and rotation | Roller geometry permits strafing but changes traction and efficiency | |
| Omni arrangement | Depends on wheel layout; some permit sideways motion | Wheel orientation, packaging, and control must agree |
| Swerve | Each driven wheel is steered | Extra steering hardware, sensing, , and repair work |
Choose from the needed approach angles, obstacles, scoring alignment, permitted interaction, and workshop capability. A complex drivetrain is useful only if its added movement helps the team's actual game tasks.
Traction and turning
For a simplified traction estimate, , where is an effective friction coefficient and is normal load on the driven contacts. cannot produce extra forward force once the wheels slip. Real contact, especially mecanum rollers, is more complicated than this model.
Tank wheels must slide sideways during a skid-steer turn. A long wheelbase with high-traction contacts can make that expensive in current and mechanical load. Wheel layout, center drop where appropriate, and omni wheels at selected positions can change turning behavior. Follow the chosen manufacturer's geometry rather than adding a center drop arbitrarily.
For mecanum, wheel handedness and roller orientation must match the intended layout and . Verify the vendor's diagram from the robot's top view. Turning a wheel over or placing it in the wrong corner changes the force direction even if motor commands are correct.
Robot mass
Select wheel diameter and gearing using motor and reduction calculations. Include the expected payload, mechanisms, and battery. A bare that accelerates well may be sluggish after a lift and are installed.
An extended arm moves the center of mass toward a tipping edge. With the robot stationary, check whether the point directly below its center of mass lies inside the area between its ground contacts. Acceleration and braking can still tip a robot that passes this stationary check.
Support wheel against weight and collisions. Check that structural flex does not alter belt alignment, gear mesh, or tracking-wheel contact. Reserve clean mounting surfaces for the localization hardware.
Direction testing
Start with wheels safely clear to verify each output, then test on the intended surface. Compare forward, reverse, turning, and strafing where supported. Record payload, battery state, surface, commanded action, measured motion, and faults.
Investigate drift by checking mechanical freedom, wheel installation, motor direction, and equal loading before tuning software. An can measure a spinning wheel even when that wheel slips against the floor.
Measure time to a scoring position as well as top speed. Include settling time, driver correction, and arrival heading. Repeat with the major mechanism extended where safe; that configuration often exposes flex, stability, and current demand hidden in the stowed robot.
Use a known working for comparisons. Follow the manufacturer's build guide for the selected drivetrain.