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Quadruped Locomotion - Musings About Running Dogs
and Other 4-Legged Creatures
"On the internet, nobody knows you're a dog" - from famous
New Yorker cartoon
This page represents some observations about the body design of 4-legged mammals, and how
this might relate to leg design of robots.
All mammals have the same basic body design, consisting of head, spine, legs,
and feet, and the next page presents some background material on their
as well as some of the similarities and differences between species.
Of special interest to the roboticist is how the "mirror-image" front-back
leg design gives stability to the frame, and some of the specializations
in horses, dogs, and cats that contributes to their great runnning ability.
The next page discusses some issues of Comparative Leg Anatomy
between animals higher and lower on the tree of life. Animals overall have an analogous leg
structure, but vastly different leg attachment and locomotion techniques.
<| The Gaits
Animal gaits have been studied throughout
at least as far back as
| Walk, Trot, Turn|
| Running and Galloping|
The next page gives some background material about the slower gaits, including
Walking and Trotting, as well as some basic
info about Turning. Trotting itself is not
actually that slow, and some race horses can trot almost as fast as others can
gallop. However, Trotting is similar enough to the Walk that one might think a
robot could be endowed with trotting ability as a natural extension of
implementing the Walk.
The next page gives some information about the faster gaits, such as
Running and Galloping.
We are not going to consider fast running as a viable means for robot mobility
at this time.
Robert Full has a wealth of background info on gaits on his course page in
Some helpful people have provided interesting animations of moving creatures:
Eadweard Muybridge 
(1830-1904) made extensive early studies on animal locomotion.
Gait of the Tiger,
from the book Horse Gaits, Balance, and Movement
Kimura Lab has animations of several
McGill has animations of a number of
MIT has some multi-megabyte animations, mainly of
Etienne's Running Man,
Mackenzie's 6-legged Twitchy,
World's Best Running Dogs,
and SANS simulation.
Do Elephants Run?:
Creep Gait Stability.
Based upon some earlier work on the Creep Gait in our quadruped Nico, we have done an
Analysis of the Creep Gait
to determine which step-sequences can produce a stable gait.
slow-walk / creep of Nico-II
Why are some quadrupeds, like mountain goats and big-horn sheep, such great climbers?
We have been gathering info on
One day, we'd like our robots to be able to climb stairs, at the very least.
Stanford robot rock climber,
<=== Biscuit, the rock-climbing dog.
<| Leg Mechanics
In order that a walking or running animal does not injure its body with each
dynamic maneuver, the joints and legs must have some mechanisms for absorbing
shocks built in. In addition, the legs must bend and extend as natural results
of stepping movements. The next page presents information related to
This information is of crucial importance to designing legs for a robot.
Animal legs have up to 5 segments and 5 joints, and many degrees of freedom,
and one question a roboticist must ask is how many joints and DOFs are
necessary for a mechanical creation?
of the Berkeley Polypedal Lab has done a series if investigations into the
dynamic aspects of locomotion across the animal kingdom. He concludes that force patterns
of the limbs are similar for many types of land, sea, and air locomotion, and presents
some expanatory models.
The following page describes some of the aspects of
<| A Simple Biomorphic Leg
We have been examining the mechanics of simplified leg designs, based upon the
mechanics of biological creatures - the next page presents some
<| Preliminary Design for a Morphable Foot-Hand
Follows is a preliminary idea for a 3-toed robotic foot that can dynamically morph into
a hand - preliminary thoughts.
<| Robot Leg Design
<| Timing Analysis of Quadruped and other Gaits
We have been examining the timing sequences of the various gaits of the dogs described above,
mainly with attention to simplified leg designs. This information is shown in the "gait section"
on our quadruped walker project page.
Timing diagrams are shown for a creep and
a basic diagonal walk.
In addition, the following page shows timing diagrams of typical gaits for some
hexapods and octopods
- including AVI files of spider walking.
"The Dog in Action", by McDowell Lyon, 1950, Howell Book House - excellent treatment of
"Dog Locomotion and Gait Analysis" by Curtis M. Brown, 1986, Hoflin pub - at
"Horse Gaits, Balance, and Movement", by S.E. Harris, 1993, Howell Book House.
"The Vertebrate Body", by A.S. Romer & T.S. Parsons, 1977, W.B.Saunders.
"Vertebrate Adaptations", readings from Scientific American, W.H. Freeman & Co, 1968.
"A Textbook of Entomology", by H.H. Ross et al, pub J.Wiley & Sons, 1982.
- Muybridge pictures - walk, trot, gallop, jump
"Gait Adaptation in a Quadruped":
"Stable Neural Control of Walking":
Motion Analysis Videos:
Shoes and gaits:
Eadweard Muybridge (1830-1904) - Animal Locomotion:
High-speed photography, biomechanics:
Catalogs of Walking Bots:
Our Robotics Links Page:
4-Legged Robocup Competition:
© Oricom Technologies, Sept 2001, updated Nov 2006