Tri-Star Stair-Climbing Wheelchair

Assistive wheelchairs that climb ordinary stairs don't use legs or tracks — the most common mechanical solution is a tri-star (planetary) wheel cluster: three wheels mounted 120° apart on a rotating hub, sized so that the chord between successive step edges exactly matches one third of the cluster's own circle. This simulator builds that geometry from real step height and depth, drives the rigid three-wheel assembly through a genuine 120°-per-step pivoting climb, and lets you toggle the self-leveling seat linkage on and off — off, you can watch the seat frame tumble through the same rotation as the wheels, which is exactly why real designs like the iBOT wheelchair need a counter-rotating parallelogram linkage to keep the rider upright.