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Running Gaits

Galloping Dogs. The basic gallop is illustrated by Whisker, the pointer. This is a 4-step gait, shown here as LR, RR, LF, then RF. The leg ordering is very different from the walk and trot.

The RF leg is actually the "leading" leg here. The characteristic of this gait is that the leading leg bears the weight of the body over longer periods of time that any other leg, and is more prone to fatique and injury. The single suspension phase [positions 13-15] is initiated by catapaulting the entire body off the leading leg [positions 10-12]. The force comes from the back legs pushing off onto the non-leading front leg, and then onto the leading leg [positions 3-8]. Notice the length of time the back legs are suspended.

There is a postion where all 4 legs are under the body, and others where either the 2 front or 2 rear legs are extended away from the body, but none where both fronts and both rears are extended simultaneously (as for the next gallop shown below). This gives a degree of rocking to the body, as the relative position of the COG moves forward and backwards.

[touch-down] The figure at the left is of a real dog shown in the same position of the gallop as the schematic dog of position 11. Note how all of its weight bears down on its right-front paw, which is bent heavily to absorb the shock, and that the right-front elbow is locked in a straight extension [in both figures], so the leg doesn't collapse under the load.

For comparison purposes, this is similar to footfall in the running horse. The anatomy of the lower leg of the horse is heavy on tendon, with very little muscle, and with the tendon bending around the fetlock bone as a pivot point. In running animals, upwards to 70% the energy of each stride is stored in the muscles and stretching of the leg tendons, to be released during the following stride.

Galloping is too much to think about for a robot at this point.

Eadweard Muybridge (1830-1904) made early movies of running dogs and other animals:
Click here for a short animation sequence
of a dog doing a gallop (86 Kbytes).
Click here for a short animation sequence
of a dog doing a running jump (128 Kbytes).
Flying Dogs. Lastly, the full-tilt Double Suspension Gallop is illustrated by Sargent Flash, the Greyhound. [suspension is the phase where all feet are off the ground simultaneously].

The 3rd and 6th pictures illustrate well how the mirror image design of the legs produces symmetrical limb movement during running, and helps keep the COG of the animal at the same relative location during all aspects of the stride. From a stability viewpoint, this is clearly vital in preventing the dog's body from pitching nose over during the run.

Robots think about doing this only in their electric dreams.

[spinal flex] Check this site for horse and dog gallop pictures.

See here for incredible pictures of galloping crocodiles: U.Florida, Reptilis.

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© Oricom Technologies, Nov 2001, updated Nov 2004.