http://www.sharon-zarabi.com/web/image-segmentation-phd-thesis/ The Military carries heavy loads on skids capable of carrying as much as 5000 lbs. The problem with this is the skids are not capable of dealing with even the smallest of obstrucitons, such as a hose or a change in floor height.
source url At Intelligent Automation Inc. I developed a robotic system that had an innovative hinged wheel capable of traversing obstacles up to 8″ tall. Hybrid Hexapod Robotic Vehicle (HHRV) is used for heavy stable lifting of loads up to 5000 lbs. Using six legs, arranged asymmetrically to support the platform, the device can operate in an omni-directional fashion.
http://www.nahug.com/college-papers-purchase/ The unique hinged wheels can unlock in sequence when an obstacle is detected, allowing the wheel to simply ride over the obstruction while maintaining stability on the remaining wheels.