Development of self balancing biped with inverse Dynamics

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Re: Development of self balancing biped with inverse Dynamic

Postby JoeJ » Wed Feb 12, 2020 12:16 pm

Sounds more you understand what i meant :) smelling the beer... :mrgreen:

Yeah, thinking about this single point is the right way to think about it. If we call this point Center Of Pressure, and we have ability to control its position, balancing becomes easy.
I did it by controlling ankle torque. But we could also just generate a virtual contact directly and ignore real feet contacts. This would be easy and precise, and if done right still no cheating.
(I considered this a plan B if problems, or as a LOD soluition at the distance - could be extended to procedural animation replacement for real physics at distance characters, etc.)

I your last posts i was wondering a bit why you pay so much attention to foot orientation and contacts.
Because i did not have to do this, and i had balancing ragdoll on two moving and rotating platforms non the less.
I only have this old video where they move very slowly, but worked also with much higher speed:

If you look at the feet, you see they do not care a lot about alignment, orientation even goes out of place sometimes.
But that's no big issue - it only changes the shape of the support polygon.
It is only important to control the single point that puts pressure from COM to ground.
We can do this with ankle torque and left / right foot pressure, and it does not even matter if the point is between the feet or in air.
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Re: Development of self balancing biped with inverse Dynamic

Postby Julio Jerez » Thu Feb 13, 2020 5:13 pm

ok Joe I am change the design, the leg control will not control the feel orientation.
Instead the feed will have it own joint that essentially will be kind of a sticky rolling Resistance joint using a down hinge joint with dry friction.
it will be this friction that that will make i possible for the model to be archive it balance

this reduce the legs to be 4 degree of freedom as opposed to 6 that was before.
then each feet now will have it own independent 2 dof that will can be control bu poses of by the environment. basically a pose will try to control the foot when on air, by the contact points will override the orient-ion when the hit an obstacle. The override action is natural because fhe dry friction. I like the method much better

I start the change but is broken now because the referent for calculation the support point is no long the same, but you can see that the model now rolls around it feet.
I will work on this this weekend.
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