Abstract: A ladder unit is slidably joined to an edge of or beneath a working surface by a mounting frame having a roller assembly or other slidable means. The ladder unit includes a stair assembly that is rotatably mounted to the mounting frame by a hinge, and configured to rotate between an open position, in which a support provided on the stair assembly does not contact the working surface, and a closed position, in which the support contacts the working surface. In this regard, the ladder unit may be slidably moved from location to location along the working surface when the stair assembly is in the open position with substantially low friction, and may be stabilized in a location for use when the stair assembly is in the closed position.

Abstract: A lightweight mobile robot includes a chassis less than 500 pounds and two independent tracked drives including a drive wheel assembly, four or more independently suspended bogie assemblies, an idler wheel assembly, a compliant front shoe fixedly coupled to an independently suspended bogie assembly positioned adjacent the idler wheel assembly, and a compliant elastomer track entraining the drive wheel, road wheels, idler wheel assembly and compliant front shoe. The bogie assembly includes a serpentine suspension arm having a corresponding road wheel rotatably mounted at a distal end thereof, the bogie arm swingable through a range entirely beneath the chassis. The serpentine suspension arm provides clearance for adjacent road wheels to swing past one another without making contact with any portion of the adjacent bogie assembly. The compliant elastomer track has center guides and peripheral drive features protruding therefrom for engaging the drive wheel, road wheels, and idler wheel.