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kirtley24
12-07-2007, 10:40 AM
Thanks Victor and others who contributed to this interesting discussion!

So I guess we now have the answer from the horse's mouth.

What is fascinating, though, is to see how many hypotheses were generated
for the behaviour (apropulsive ankle, lower centre of mass, etc.). It turned
out to be none of these (though all were plausible). There's a lesson in
there somewhere for gait analyzers :-)

Chris


On 12/8/07, Ton van den Bogert wrote:
>
> I received the following reply from Victor Ng-Thow-Hing at Honda Research
> Institute.
>
> --
>
> Ton van den Bogert, Biomch-L co-moderator
>
> -----Original Message-----
> From: Victor Ng-Thow-Hing [mailto:victorngthowhing@yahoo.com]
> Sent: Friday, December 07, 2007 1:19 PM
> To: van den Bogert, Ton; BIOMCH-L@NIC.SURFNET.NL
> Subject: RE: [BIOMCH-L] Asimo robot gait
>
> Hi Ton,
>
> The short answer is I believe the joint kinematics were chosen to avoid
> singularities when computing the Jacobian during footstep planning -
> hence,
> the bent knee.
> In particular, the walking requires the solution of an inverse kinematics
> problem involving the waist and feet, and because of the lack of degrees
> of
> freedom in the leg, singularities can occur near the straight-knee
> configuration. However, there has recently been several straight-leg
> walking
> robots from Waseda university (WABIAN-2) in Tokyo that get around this
> problem
> by adding more degrees of freedom.
>
> There may be other factors, such as the choice of a ZMP-type controller
> for
> balance. ZMP control is somewhat more conservative than the way humans
> achieve
> balance.
> Also, the walk controller may be trying to stabilize the upper body center
> of
> gravity, and a more groucho-style, bent-knee gait can facilitate this in
> the
> absence of more degrees of freedom in the waist.
>
> Regards,
> Victor.
> Honda Research Institute
>
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