Let's Make Robots!

Gait design

Where can I find some practical information about designing and programming gaits for quadrupeds and hexapods? 

There's plenty of theoretical mathematics on the web but I'm looking for a straight forward practical basics. I'll look at the sophisticated methods later.

Did the majority of robot builders here use a "start from scratch" trial and error approach?


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You could do a lot worse than study the movement of insects and quadruped animals.  If you make a point of watching the legs, it's amazing how many widely varying leg movements there are in the animal kingdom.  Some time ago I found a really simple analysis of several four-leggged gaits in a robotics context but haven't been able to track it down since, despite a lot of looking.

One of my favourites is the komodo dragon and the chameleon is brilliant! (Needs to be in the trees for the camouflage to work, though #;¬)

Thanks, that really useful information to get started. I was looking at all thes robots and thinking,"how did they design their gaits?", but I see that it's often very much a "try and see" approach and depends obviously on the physical characteristics of each robot.

I think I'm finally going for a quaduped. I watched a few videos and it seems a good idea for the body to shift away from the leg that's going to be raised in order to shift the center of gravity.

I'm probably going to use an SSC-32 servo controller. I see it has some built in gait sequences for hexapods so I'm wondering if that can be adapted for quadrupeds

As for inverse kinematics, I will indeed leave that for later.

(Disclaimer - Observations only; I've never made a quadruped #;¬)

You're right about shifting body weight for a quadruped - For slow movement, especially if you're only using 4 servos, you need the 'bot to be stable on the other 3 legs while you bring the fourth leg forward clear of the ground.  I was thinking about a 4 servo robot with a 5th servo to twist the front of the body relative to the rear to help with this.  Big feet would be an advantage for stability but harder to handle in the 'recovery' stage.

For fast movement, it strikes me that the rhythm of movement relative to body-weight is important and is something animals do instinctively but would be extremely complex on a 'bot, requiring accelerometer feedback.

I'm considering using the following servos to keep cost to a minimum:

Coxa: hs-485hb,  Femur: hs-645mg , Tibia: hs-485hb

Does that sound a reasonable choice?

The chassis and legs will be in 2mm aluminium and designed to keep weight down to a minimun.  A Mega 2560 cpu and SSC-32 servo controller.