Abstract
An autonomous transport robot for transporting a payload, autonomous transport robot including, frame with integral payload support that has a payload seat surface defining a payload datum position that determines predetermined payload position relative to autonomous transport robot, transfer arm connected to the frame and configured for autonomous transfer of payload to and from the frame, one caster wheel mounted to frame, drive section with a pair of traction drive wheels astride the drive section, drive section being connected to the frame, wherein the one caster wheel and one traction drive wheel of the pair of traction drive wheels roll, on a rolling surface effecting autonomous transport robot traversal over the rolling surface, each having a fully independent suspension, and are disposed on the frame astride the integral payload support so that the payload seat surface at the payload datum position is disposed at minimum distance above the rolling surface.