Differencedrives

Differencedrives, often called differential drives, refer to a mobile base configuration that uses two powered wheels placed on opposite sides of a rigid chassis. Each wheel is driven independently, typically by its own motor and sometimes paired with a fixed caster wheel for support. The arrangement enables steering by varying the relative wheel speeds rather than by steering a single front wheel.

The kinematics of a differential drive are straightforward. If the left and right wheels have linear velocities vL and vR, the instantaneous linear velocity of the chassis is v = (vR + vL) / 2, and the angular velocity about the vertical axis is ω = (vR − vL) / L, where L is the distance between the wheels (the track width). If the wheel angular speeds are used instead, vL = rωL and vR = rωR, with r the wheel radius. When vL equals vR, the vehicle moves straight; when they differ, it follows a circular arc around the instantaneous center of rotation.

Control and sensing for differencedrives typically rely on wheel encoders to measure rotation and estimate pose through odometry. Open-loop control may suffice for simple tasks, but most systems employ closed-loop feedback to correct drift. Additional sensors, such as IMUs or SLAM systems, help reduce odometry error and improve localization.

Advantages of differencedrives include mechanical simplicity, robustness, low cost, and good performance on flat indoor surfaces. Limitations include non-holonomic motion, potential wheel slip, articulated turning dynamics, and odometry drift over time. They are widely used in small robots, educational platforms, and service robots where compact, reliable, and easy-to-control motion is desired. See also: differential drive robot, odometry, non-holonomic steering.