Walking Machine

A walker is a vehicle that moves on legs rather than wheels or tracks. Walkers have been constructed with anywhere from one to more than eight legs. They are classified according to the number of legs with common configurations being one leg (pogo stick or "hopper"), two legs (biped), four legs (quadruped), and six legs (hexapod). One of the first appearances of such machines in modern literature was the tripods of H. G. Wells' famous The War of the Worlds. The novel does not contain a fully-detailed description of the tripod's (or "fighting-machine", as they are known in the novel) mode of locomotion, however it is hinted at: "Can you imagine a milking stool tilted and bowled violently along the ground? That was the impression those instant flashes gave. But instead of a milking stool imagine it a great body of machinery on a tripod stand."

While the mobility of walkers is arguably higher than that of wheeled or tracked vehicles, their inherent complexity has limited their use mainly to experimental vehicles, primarily robots. Such difficulties have let them be primarily known in fictional works. Real life, larger manned walker vehicles have existed, however, with examples being General Electric's walking truck, the University of Duisburg-Essen's ALDURO, and John Deere's hexapod Walking Forest Machine. One-legged walkers, hoppers, have been built with some success, but currently the more common walkers are toys like the bipedal QRIO and ASIMO, and the quadruped AIBO. Some walkers such as the BigDog are designed for use in the military. The largest walking machine ever made is the Big Muskie dragliner.

A chicken walker is a fictional type of bipedal robot or mecha, distinguished by its rear-facing knee joint. This type of articulation resembles a bird's legs, hence the name. However, birds actually have forward facing knees; they are digitigrade, and what most call the "knee" is actually the ankle. They are usually less able to handle extremely rugged terrain than "man walkers". They are often shown to be faster than other robots, capable of road runner like movements. The best example of this contrast in film is the fast pursuits of the ED-209 versus the steady walking pace of RoboCop in the RoboCop franchise. Also, in the Star Wars franchise, the chicken-walking AT-ST was used as a light scout vehicle rather than the elephantine AT-AT, which were lumbering quadrupeds.

Walking is generally distinguished from running in that only one foot at a time leaves contact with the ground: for humans and other bipeds running begins when both feet are off the ground with each step. (This distinction has the status of a formal requirement in competitive walking events, resulting in disqualification at the Olympic level.) For horses and other quadrupedal species, the running gaits may be numerous, and while walking keep three feet at a time on the ground. The average human child achieves independent walking ability around 11 months old. While not strictly bipedal, several primarily bipedal human gaits (where the long bones of the arms support at most a small fraction of the body's weight) are generally regarded as variants of walking.