sure! most of my publications were centered around how robots should climb vertically, but i am also familiar with horizontal and also on various substrates (sand, mesh, etc). we studied the animals "steady state" locomotion (such sprinting as fast as you can without thinking about your steps). this paper is the culmination of many hours spent with cockroaches, geckos, home-made 3d force sensors, high speed cameras, matlab, and c++ simulations :)
let me know if you have any questions or would like to talk about other animals, substrates, and/or differences between horizontal and vertical locomotion.
I'm wondering if modeling/simulating quadruped locomotion would help make this task a lot easier. Instead of trying some machine learning/computer vision on the pressure data, reason about what kind of walking pattern brought forth the results. Like a paw can't be in two places at the same time and other heuristics like that.
Any suggestions for literature I should read up on for horizontal locomotion? :-)
there's no substitute for the actual foot force data. i would collect this directly, in 3d (not just z-direction -- which it seems like you are currently doing), to understand the basics and then later involve simulations to iterate different designs that produce the desired motion and forces. i built a force plate that measures forces in 3d with piezoelectric sensors. it shouldn't be as hard with a feline because their feet have a reasonable distance between them (try getting only one of a cockroach's feet to be touching the plate at a given time to measure what forces it produces!). the reason why i have this opinion is that the most interesting part of comparing how animals run versus climb are the lateral forces. another interesting thing is that the number of legs is irrelevant (well except maybe monopod) because when studying two, four, six or 44 (centipede -- man those things are scary to handle!) legs, the forces reduce to a basic pattern we all share in common. when a centipede is sprinting, only three of its legs are on the ground at any time, so it's forces look identical to a cockroach or any other hexapod. when you have less than 6 legs, then you can observe the effective 6 legs by analyzing various portions of their phase. for example, when you walk (bipedal), when your foot is out in front of your center of mass, the forces generated are like the front feet of a hexapod (deceleration only). when you foot is near your CM, it generates forces like the middle legs of a hexapod (deceleration followed by acceleration). and when your foot is behind your CM, it generates forces like the rear feet of a hexapod (acceleration only).
there's more i want to say, but i'll save it for a subsequent comment :)
as for additional reading for you, i would take a look at Robert J. Full's research. there are a couple horizontal locomotion papers cited in the my paper linked in the prior comment that have phrases like "on the horizontal plane" or "on land" in the titles.
I'm helping veterinary scientists with their gait analysis, basically by porting the calculations used for pressure measurements (so no 3D forces) on humans and solving problems like detecting the paws along the way.
An example of what this gets used for are things like lameness detection or diagnosing disorders. Or it could be used to evaluate the effectiveness of the treatment.
While the pressure plate doesn't measure 3D forces, it does have the advantage of giving you information about the distribution, which I expect at least has strong correlations with 3D forces. Obviously you need animals of a certain size to get good data (or systems with very small sensors), so you wouldn't use it for gecko's or even really small dogs.
Perhaps I should try calculating the distance to the body's center of mass, to get an idea how well this distinguishes the different paws. The problem I'm having so far is that the quality of the measurements isn't always optimal and inferring which paws are making contact is difficult if you don't see paws from both sides (for quadrupeds at least).
I'll be sure to check out the research you pointed to!
http://www.roboticsproceedings.org/rss03/p02.html
let me know if you have any questions or would like to talk about other animals, substrates, and/or differences between horizontal and vertical locomotion.