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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

|> Basic Anatomy
|> The Gaits
|> 4-Legged Speed
|> Dogs' Elbows
|> Climbing
|> Leg Mechanics
|> Simple Biomorphic Legs
|> Morphable Foot-Hand
|> Robot Leg Design
|> Timing Analysis
(including 6- and 8-leggers)
|> References
Gallery of Incredible
(mostly) Robot Walkers
[Biscuit the rock-climbing dog]
see also webpages on our walking robots:
- NEW - hexapod Nico-6- NEW -

- quadruped Nico-II -
- octopod Gimlee-U8 -
- quadruped Nico -
plus links page on Locomotion

<| Basics
[Basic Anatomy - loads 60 KB of images] 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 Basic Anatomy, 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.

[Comparative Leg Anatomy - loads 80 KB of images] 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
[Walk, Trot, Turn - loads 50KB of images]
Walk, Trot, Turn
[Running - loads 20 KB of images]
Running and Galloping
Animal gaits have been studied throughout history, at least as far back as Aristotle.

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 Biomotion.

Some helpful people have provided interesting animations of moving creatures:

  • Eadweard Muybridge [1] [2] (1830-1904) made extensive early studies on animal locomotion.
  • Canine sideshow, Gait of the Tiger, Java Horse, Quicktime Llamas, Treadmill Gecko
  • from the book Horse Gaits, Balance, and Movement
  • Kimura Lab has animations of several quadrupeds
  • McGill has animations of a number of multi-pedal creatures
  • MIT has some multi-megabyte animations, mainly of bipedal movement
  • also Etienne's Running Man, Mackenzie's 6-legged Twitchy, Ruffwear Shepherd, World's Best Running Dogs, and SANS simulation.
  • Do Elephants Run?: Hutchinson [1] [2], news [1] [2] [3]

    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. See also, slow-walk / creep of Nico-II

  • <| 4-Legged Speed
    [crusin'] How fast can a land animal go?
    See the 4-Legged Speed page.

    <| Dogs' Elbows
    [my left foot] What does a dog think about its "elbow"? Is it just another joint, or its most "expressive" joint? When a dog "points", does it know it's pointing? See The Dog's Elbow page. Includes some info on quadruped jumping.

    <| Climbing
    [my sole pads] Why are some quadrupeds, like mountain goats and big-horn sheep, such great climbers? We have been gathering info on Quadruped Climbing. One day, we'd like our robots to be able to climb stairs, at the very least.

    [Biscuit] Something new: Stanford robot rock climber, article.

    <=== Biscuit, the rock-climbing dog.

    <| Leg Mechanics
    [Leg Mechanics - loads 25 KB of images] 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 Leg Mechanics.

    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?

    [Leg Dynamics - loads 25 KB of images]

    R.J. Full 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 Leg Dynamics.

    <| 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 thoughts.

    <| 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
    The next page contains references to papers and sites discussing different possibilities for robot leg design.

    The next page presents some preliminary speculations on robot leg design, based upon material presented on these related pages.

    <| Timing Analysis of Quadruped and other Gaits
    [hex/octo timing] 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 multi-legged walkers: hexapods and octopods - including AVI files of spider walking.

    Vision in Quadrupeds. This doesn't specifically have to do with locomotion, but it's something interesting.

  • Dogs, rabbits, horses, buffalo, lions, cheetah, gazelle, and other animals have a "visual streak", rather than a fovea. [1] [2] [3]
  • "Vision in Animals - What do Dogs and Cats See?"
  • "The Ramp Retina - What is it and does it exist" - also image of horse visual field
  • "How Horses See"
  • <| References

  • "The Dog in Action", by McDowell Lyon, 1950, Howell Book House - excellent treatment of dog gaits.
  • "Dog Locomotion and Gait Analysis" by Curtis M. Brown, 1986, Hoflin pub - at Amazon.
  • "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.
  • Animal Gaits: bowlingsite.mcf.com - Muybridge pictures - walk, trot, gallop, jump
  • "Gait Adaptation in a Quadruped": iguana-robotics.com
  • "Stable Neural Control of Walking": ias.uwe.ac.uk
  • Gait Analysis: links list, UIUC, Curtin [history], Rush, Musculographics, Olshen, human gaits, Gaited Horses
  • Motion Analysis Videos: U.Mich, SMU
  • Shoes and gaits: unshod
  • Eadweard Muybridge (1830-1904) - Animal Locomotion: Gallery, posters [1] [2]
  • Dogs: dog breeds
  • Biomechanics: newsgroup, reference
  • Kinematics: running man, foot-ankle, Cavagna
  • Virtual Dog: gamasutra
  • Anatomy: animal, human
  • Amputee prosthetics: Ossur
  • High-speed photography, biomechanics: Dickinson, Lauder [1] [2], Ritzmann
  • Catalogs of Walking Bots: Berns, Kimura
  • Our Robotics Links Page: oricomtech.com
  • 4-Legged Robocup Competition: robocup.org and csc.liv.ac.uk

    <| TOP

    © Oricom Technologies, Sept 2001, updated Nov 2006