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hzhang24
12-07-2007, 05:39 AM
Hirai(1998) has shown a very good paper almost 10 year ago for describing the
development process of ASIMO. It was shown that in order to prevent the robot
rotate(fall), the tipping moment, a moment causing robot to fall, has to be
carefully controlled through ground reaction force control models. This
ground reaction force control models control the robot body trajectory by
shifting the robot positions from “ tip over” to the “equilibrium” positions.
Feet position has also to be changed following the body trajectory to maintain
the robot whole body equilibrium states. For both single and double support
phases, the ground reaction force control models were realized by
lowering/lifting the frontal section of the robot body by overcoming the tip
moment, which may lead to the phenomena called “leg flexion”. My guess is
based on the fact that in the paper, they used joint angles, ground reaction
force, and body inclination as feedbacks for joint angle determination. Since
joint angle controls the upper body and lower body angles as well as positions,
as a result, I think the very apparent leg flexion is a part of results from
ground reaction force control models. It was also found that the body
displacement errors and Zero moment point (ZMP) control were used as feedbacks
for feet position orientation calculation. Feet positions control play an
essential role not only in coordinating the body and feet positions but also
decelerating the upper body accelerating forces by the strategy named as “ feet
stride”. Feet stride may also partly contribute to the “leg flexion”.


References
Hirai et al (1998). The development of Honda humanoid robot, IEEE International
Conference on robotics and Automation

We may also sense the HONDA efforts to make ASIMO humanoid by these two papers:

Sakagami et al (2002). The intelligent ASIMO: system overview and integration,
IEEE/RSJ International Conference Intelligent Robots and System

Yoshitaka et al (2005). Development and psychological evaluation of Multimodal
Presentation Markup Language for Humanoid Robots, Proceedings of 2005 5th
IEEE-RAS International Conference on Humanoid Robots


Regards

Hongbo Zhang
Ph.D student in occupational biomechanics, Virginia Tech